Method of treating active material

An active substance treating method is characterized in that an active substance is caused to react with an inactivating substance in an exhaust system for a thin film forming apparatus. A thin film forming apparatus includes a common chamber having a region where plasma CVD is carried out and a region where thermal CVD is carried out, a device provided in the chamber for pressing a substrate onto a holder, a lamp for illuminating light having a component of a wavelength of 1 .mu.m or above to heat the substrate, an introducing port for separately introducing two active substances to a vicinity of the substrate, a vaporizing device in which at least two bubblers are series-connected to vaporize the active substances, and an exhaust system which is divided into two systems each of which has a heater and which has a port for introducing an inactivating substance into an exhaust pump.

 

What is claimed is:

1. A method of forming a metal film whose main component is Al atoms comprising the steps of:

providing a film forming apparatus including a common region where plasma chemical vapor deposition (CVD) is performed and a region where thermal chemical vapor deposition (CVD) is performed;

pressing a substrate onto a holder in said chamber;

heating the substrate with a lamp for illuminating light having a component of a wavelength of 1 .mu.m or above;

separately introducing two active substances via introducing ports to a vicinity of the substrate;

vaporizing the active substances by at least two series connected bubblers;

forming the metal film and depositing on the substrate;

exhausting unreacted active substances into an exhaust system, said exhaust system being divided into two systems each of which has a heater.

2. The method according to claim 1, wherein the metal film forms an electrode for a Schottky diode.

3. The method according to claim 1, wherein a metal film whose main component is Cu is formed on the metal film.

4. A method of depositing an aluminum film on a surface of a substrate by introducing dimethyl-aluminum-hydride and hydrogen into a reaction chamber,

wherein said reaction chamber is composed of a metal having an interior surface coated with ceramic to prevent deposition of aluminum.

5. The method according to claim 4, further comprising introducing a gas containing silicon into said reaction chamber to form an aluminum film containing silicon.

6. The method according to claim 4, comprising the step of forming polycrystal aluminum on said substrate and forming a copper film on said polycrystal aluminum.

7. The method according to claim 6, comprising the steps of conveying said substrate in a vacuum or inactive atmosphere after forming said polycrystal aluminum thereon, and thereafter forming said copper film whereby oxidation of said polycrystal aluminum is inhibited.

8. The method according to claim 4, comprising the steps of depositing an insulating film on said substrate and thereafter depositing a single crystal aluminum film in an open portion of said insulating film.

9. A method of depositing an aluminum film on surface of a substrate by introducing dimethyl-aluminum-hydride and hydrogen into a reaction chamber, wherein said reaction chamber is composed of a metal having an interior surface coated with insulator to prevent deposition of aluminum.

10. The method according to claim 9, further comprising introducing a gas containing silicon into said reaction chamber to form an aluminum film containing silicon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of treating an active material, a vaporizing device which utilizes such a method, and a thin-film forming apparatus which utilizes such a device.

2. Description of the Related Art

As IC complexity has advanced, attention is being focused in recent years on the technologies of forming microstructures of submicron geometries on a semiconductor wafer with excellent controllability. Particularly, in the manufacturing process of, for example, ICs or LSI devices, miniaturization of transverse dimensions of the devices increases the irregularity of pattern formation in the microstructures. Hence, in the interconnect structure forming process, excellent coating of the irregular surface of a pattern formed at a high density and complexity with a conductive film, which is an interconnection material, and embedding of a fine opening for the interconnection, having a diameter of 1 .mu.m or less, (hereinafter, the opening being referred to as a contact hole) with an interconnection material, such as Al, are required.

Interconnection materials must be those which offer excellent ohmic contact to semiconductors, allow for formation of a film having low resistivity on an industrial basis, show excellent adhesion to a silicon or silicon oxide film, allow for fine patterning, have metallurgical properties suitable to bonding, and exhibit high reliability under normal operating conditions.

Conventionally, interconnect structures for an IC or LSI device are commonly formed by sputtering using Al or an Al alloy. To form an Al or Al alloy film, a chamber of a sputtering apparatus is evacuated to 10.sup.-5 to 10.sup.-6 Pa, Ar gas having a high purity is introduced into the chamber under a pressure of 1 to 10.sup.-1 Pa, and then a DC voltage is applied between electrodes to generate glow discharge. Sputtering involves bombardment by accelerated Ar.sup.+ of a cathode (target) and transformation of atoms near the surface of the target material as a vapor to a Si substrate on which an anode is placed. However, since the target material is sputtered to deposit the atoms thereof on the surface of a wafer as a source substrate, the shape of the deposited film varies depending on the irregularities of the wafer surface. Particularly, in the case of a contact hole having a diameter of 1 .mu.m or less and a depth of 1 .mu.m or more, it is difficult to completely embed the contact hole by sputtering.

Thin-film forming technologies which employ CVD involve decomposition of the material gas contained in the vapor phase which is in contact with the surface of a wafer by thermal energy in order to form a desired thin film. In CVD, since a film material can be uniformly distributed over the surface of the wafer and since a thin-film deposition occurs due to decomposition of the material gas on the wafer surface, step coverage is improved as compared with sputtering. Further, CVD enables a thin film to be selectively formed on a particular substance only by utilizing differences in the decomposition reaction mechanism of the material gas with the surface of various substances, such as Si, metals or insulating materials. It is therefore possible to selectively form a conductive film in a contact hole only by adequately selecting the type and deposition conditions of the material gas.

Thus, various studies have been made on the formation of interconnecting material films by CVD, and the possibility that the film of a metal, such as Al, W or Cu, can be formed by CVD has already been confirmed.

Most of the material gases for interconnecting films are liquid at ambient temperatures and generally have a low vapor pressure. For example, the saturated vapor pressure of dimethyl aluminum hydride, used as the material gas for an Al film, is about 2 Torr at ambient temperatures, and the saturated vapor pressure of triisobutyl aluminum is 0.5 Torr. Thus, in order to introduce a liquid material gas whose vapor pressure at ambient temperatures is low into a reaction chamber of a CVD apparatus, a vaporizing device must be provided.

Conventionally, a bubbling device is used as a vaporizing device for liquid material gases. FIG. 1 is a schematic view of a bubbling device. In the bubbling device shown in FIG. 1, a carrier gas is introduced into a liquid material 92 accommodated in a bubbling vessel 91 from a carrier gas introducing pipe 93, whereby the vapor of the liquid material 92 is taken into bubbles 95 of the carrier gas. The carrier gas which contains vapor of the liquid material is supplied from a gas discharge pipe 96.

However, organic metallic compounds used as CVD material gases are generally very active chemically and readily react with water or oxygen at ambient temperatures. Thus, when organic metallic compounds are vaporized by bubbling, water or oxygen contained in the carrier gas as impurities readily react with such an organic metallic compound and are thereby caught in the liquid. In addition, since the vapor pressure of such a reaction product is generally lower than the vapor pressure of an organic metallic compound, the reaction product accumulates in the organic metallic compound, gradually reducing the purity thereof as bubbling progresses.

When such an organic metallic compound with impurities contained therein is used in CVD, the quality and deposition rate of the CVD film formed on the substrate vary markedly, thus making the formed film unstable. Hence, deterioration in purity of the organic metal compound is conventionally prevented by increasing the purity of the carrier gas. However, since the carrier gas is generally transported to the thin-film forming apparatus via a pipe from a supply facility, even if the purity of the carrier gas supplied from the supply facility is high, the purity of the carrier gas may be reduced by leakage of a small amount of gas into the carrier gas, which would occur during transportation of the carrier gas to the thin-film forming apparatus, or when an external gas component enters the carrier gas from the inner surface of a pipe, thus reducing the purity of the organic metallic compound gas.

Thus, vaporization of a very reactive liquid compound by bubbling leads to a problematic reduction in the purity of the organic metallic compound with time.

Furthermore, in the CVD apparatus, since a film forming chamber is evacuated by a vacuum pump after the material gas has been introduced into the chamber, a flammable compound is sucked into the pump. In addition, because such a material gas has a low vapor pressure at ambient temperatures and is thus liquid, when it is sucked into the pump it is liquefied and remains therein. In that case, even if an inactive gas is introduced from a ballast valve, it is difficult to completely remove the material gas in the pump. Such a material gas may ignite when the pump is opened to the atmosphere for maintenance or the like.

Conventionally, when such a flammable substance is sucked into the pump, the interior of that pump must be purged slowly before maintenance using an inactive gas, and the portion of the interior of the pump where the flammable substance is considered to be lodged must be treated under an inactive gas atmosphere. Thus, safety of the pump is reduced, and the maintenance operation is troublesome.

In a conventional chemical vapor deposition apparatus which employs an organic aluminum gas, such as trimethyl aluminum (TMA) or dimethyl aluminum hydride (DMAH), a heater (hereinafter referred to as an after heater) is disposed in an exhaust mechanism to thermally decompose an unconverted gas into nontoxic substances in the following manner:

2Al(CH.sub.3).sub.3 +3H.sub.2 .fwdarw.2Al+6CH.sub.4 (1)

2AlH(CH.sub.3).sub.2 +H.sub.2 .fwdarw.2Al+4CH.sub.4 (2)

FIG. 2 schematically shows an exhaust system in which an after heater is disposed. In FIG. 2, reference numeral 4 denotes a reaction chamber, reference numeral 41 denotes a mechanical booster pump, reference numeral 42 denotes an after heater, and reference numeral 43 denotes a rotary pump. The final exhaust indicated by an arrow is connected to, for example, a local exhaust pipe which is lightly evacuated by, for example, a fan.

The exhaust mechanism shown in FIG. 2 has the following problems: since an unconverted gas is thermally decomposed into a metal and hydrocarbon gas, the metal attaches to the inner wall of the heater. Thus, the operation of the apparatus must be suspended periodically to remove the metal attached to the heater. When the apparatus is used for mass production, maintenance performed to remove the metal is considered to be wasteful down-time.

The chemical vapor deposition process, which employs an organic aluminum gas, uses his gas solely or in a state wherein it is mixed with a carrier gas or hydrogen serving as a reaction gas, as shown by formulas (1) and (2). When hydrogen is mixed excessively into an organic aluminum gas, it is impossible for the after heater to convert hydrogen into a safe substance, thus causing an explosive to flow into the exhaust pipe. Thus, the exhaust gas must be connected to a strong exhaust pipe completely shielded from the atmosphere, and a special diluting mechanism must be provided to discharge such an exhaust into the atmosphere.

Another problem encountered by the conventional after heater method shown in FIG. 2 is the presence of a small amount of organic metal which has not been thermally decomposed. Any gas not brought into contact with the heater surface is exhausted in the form of an organic metal. Although such a gas does not explode, it may be discharged into the atmosphere as powder of alumina.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a method of treating an active material, which method is capable of diminishing the danger which may be anticipated during maintenance of a pump into which an active material is sucked, and which method enhances the operability of maintenance.

A second object of the present invention is to provide a vaporizing device which is capable of supplying vapor of a very active organic metal compound having a high purity by preventing deterioration of the purity of that organic metal compound when the active organic metal compound is vaporized by bubbling.

To achieve the above-described objects, the present invention provides an active substance treating method which is characterized in that an active substance is caused to react with an inactivating substance in an exhaust system for a thin film forming apparatus.

The present invention further provides a thin film forming apparatus which comprises a common chamber having a region where plasma CVD is carried out and a region where thermal CVD is carried out, means provided in said chamber for pressing a substrate onto a holder, a lamp for illuminating light having a component of a wavelength of 1 .mu.m or above to heat the substrate, introducing means for separately introducing two active substances to a vicinity of the substrate, vaporizing means in which at least two bubblers are series-connected to vaporize the active substances, and an exhaust system which is divided into two systems, each of which has a heater and which has means for introducing an inactivating substance into an exhaust pump.

The above-described apparatus is used to form an electrode for a Schottky diode, a single crystal Al layer in a contact hole or a base layer for a Cu interconnection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a conventional bubbling device;

FIG. 2 is a schematic cross-sectional view of a conventional thin film depositing apparatus;

FIG. 3 is a schematic cross-sectional view of a device to which an active substance treating method according to the present invention is applied;

FIG. 4 is a schematic cross-sectional view of another embodiment of the device to which the active substance treating method according to the present invention is applied;

FIG. 5 is a schematic view of an embodiment of a thin film forming apparatus according to the present invention;

FIG. 6 is a schematic cross-sectional view showing a driving portion for driving a recording head according to the present invention;

FIG. 7 is an equivalent circuit diagram showing the circuit configuration of a single block of the driving portion for a semiconductor device shown in FIG. 6;

FIG. 8 is a schematic perspective view of an ink jet recording head according to the present invention;

FIG. 9 is a schematic cross-section taken along the line E-E' of FIG. 8;

FIG. 10 is a schematic view illustrating a driving method for the recording head shown in FIG. 9;

FIGS. 11a-f is a schematic cross-sectional view showing the manufacturing process of the recording head according to the present invention;

FIG. 12 is a schematic cross-sectional view showing another driving portion for driving the recording head according to the present invention;

FIG. 13 is a cross-sectional view of a contact hole portion of a semiconductor device according to the present invention;

FIGS. 14a-f shows the manufacturing processes of the manufacturing method according to the present invention;

FIG. 15 is a cross-sectional view of a multi-interconnection layer to which the present invention is applied;

FIG. 16 is a cross-sectional view of a contact formed by combining selective CVD and Cu;

FIGS. 17a and b is a cross-sectional view of an embodiment of a sample holding tool according to the present invention;

FIG. 18 is a schematic cross-sectional view of an embodiment of a thin film depositing apparatus according to the present invention;

FIG. 19 shows part of another embodiment of the thin film depositing apparatus according to the present invention;

FIG. 20 is a schematic cross-sectional view of a heating mechanism for the thin film depositing apparatus according to the present invention;

FIG. 21 is a schematic cross-sectional view of another embodiment of the thin film depositing apparatus according to the present invention;

FIG. 22 is a cross-sectional view showing a semiconductor device manufacturing process according to the present invention;

FIGS. 23a and b is a cross-sectional view showing a semiconductor device manufacturing process according to the present invention;

FIG. 24 is a schematic cross-sectional view of another embodiment of the thin film depositing apparatus according to the present invention;

FIG. 25 is a schematic cross-sectional view of still another embodiment of the thin film depositing apparatus according to the present invention; and

FIG. 26 is a cross-sectional view of a burning chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An active substance treating method according to the present invention is characterized in that an active substance is treated by making it react with an inactivating substance.

A vaporizing device employed in the present invention includes a first container, a first introducing port connected to the first container to introduce a carrier gas, a second introducing port connected to the first container to supply a liquid, a third introducing port connected to a second container to supply a liquid, and a connecting pipe for connecting the first and second containers. The liquid supplied from the second introducing port is bubbled by the carrier gas introduced from the first introducing port, and the gas generated by that bubbling is supplied to the second container via the connecting pipe to bubble the liquid supplied to the second container. A gaseous mixture of the vapor of the liquid and the carrier gas is discharged from a discharge port connected to the second container.

A thin-film deposition apparatus according to the present invention is characterized in that a plurality of heaters for treating an exhaust gas are disposed parallel to each other beyond a reaction chamber used for deposition of a thin film.

The thin-film deposition apparatus according to the present invention is characterized in that a burning chamber having an oxygen gas introducing device and a plurality of filters are disposed beyond means for exhausting a reaction chamber used for depositing a thin film.

According to the active substance treating method employed in the present invention, where an active substance which may ignite in the air, such as an organic metallic compound, is exhausted using a pump, the active substance can be inactivated in the pump by introducing an inactivating substance into the pump. Thus, even when the interior of the pump is opened to the atmosphere for, for example, maintenance, the active substance is not discharged into the atmosphere, greatly reducing the danger of, for example, ignition.

According to the vaporizing device employed in the present invention, bubbling devices for bubbling the carrier gas into the liquid to supply vapor of the liquid to an external device together with the carrier gas are series-connected. In this way, the impurities in the carrier gas which react with the liquid supplied to the first bubbling device are caught, and the liquid supplied to a subsequent bubbling device is bubbled by the gas discharged from the first bubbling device to increase the purity of vapor of the liquid.

Since the plurality of after heaters are disposed in parallel, the maintenance time required for valve operation, can be reduced to a minimum operation rate of the apparatus can thus be improved.

To remove an exhaust gas, thermal decomposition which employs an after heater is not utilized but oxidation by the burning of oxygen is utilized. In this method, complete removal of hydrogen and an organic metal is achieved.

In the oxidation method according to the present invention, unavoidably generated metal particles are not discharged into the atmosphere, and the down-time of the apparatus can be reduced to a minimum.

According to the present invention, it is possible to form a highly reliable electrode and interconnection by continuously forming an Al film by a single crystal selective growth of CVD, an Al film by polycrystalline non-selective growth of CVD and then a thin film Cu film. There is no limitation on the forming method.

The irregularities of the surface of an LSI device increase as the device miniaturization advances. That is, a contact hole or through hole becomes deeper and narrower (for example, depth of 0.8 .mu.m and width of 0.5 .mu.m). Further, a current density may increase up to 1.times.10.sup.5 to 10.sup.6 A/cm.sup.2. In the present invention, single crystal Al is selectively grown in the contact hole or through hole to completely bury the hole. At that time, an excellent flat surface of a wafer is obtained. Furthermore, since an Al/Si interface is formed by single crystal Al and single crystal Si, an alloy spike-free and low-resistance contact is obtained. Subsequently, an Al film is formed uniformly over the entire wafer surface (including an oxide film) to a thickness ranging from 100 to 300 .ANG. by non-selective growth. Control between selective growth and non-selective growth is conducted by switching over thermal CVD and plasma CVD. That thin Al film has the function of improving adhesion between a subsequently deposited Cu thin film and SiO.sub.2. Formation of a Cu film is conducted by either PVD (sputtering or EB deposition) or CVD. Alternatively, the Al thin film may be patterned before formation of the Cu film, Cu being formed on the Al only by the selective CVD process.

In brief, the manufacturing process sequence goes from selective Al film formation to non-selective Al film formation (patterning), then to Cu film formation and finally patterning. In this way, a high performance electrode or interconnection can be realized.

The selective Al film is preferably used as a Schottky electrode for a recording head, and the thin Cu film having the Al base layer is preferable as the interconnection for a recording head.

Examples of respective components will be described below. A thin film forming apparatus according to the present invention is provided by adequately combining the following embodiments.

First Embodiment

FIG. 3 is a schematic view of an apparatus to which the active substance treating method according to the present invention is applied.

In FIG. 3, reference numeral 111 denotes a bubbling container for bubbling an inactivating substance, reference numeral 116 denotes an inactivating substance accommodated in the bubbling container 111, reference numerals 112 and 113 denote reverse flow preventing containers for preventing reverse flow of the inactivating substance 116, reference numeral 114 denotes a flow meter for measuring the flow rate of a carrier gas, reference numeral 115 denotes an introducing port for introducing a carrier gas, reference numeral 121 denotes a rotary pump, reference numeral 122 denotes a suction port, reference numeral 123 denotes an exhaust port, reference numeral 124 denotes a ballast gas introducing port, reference numeral 125 denotes a ballast valve, and reference numeral 126 denotes a drain valve.

In this embodiment, the rotary pump 121 was used as an exhaust device for a CVD apparatus for forming an aluminum film, which will be described later. A gaseous mixture of dimethyl aluminum hydride (DMAH) and hydrogen was used as the material gas for the CVD method used to form an aluminum film. The gaseous mixture was introduced into a film forming chamber (not shown) at a flow rate of 500 sccm and at a flow rate ratio between DMAH and hydrogen of 1:100. After an aluminum film was formed on the surface of a semiconductor surface in the film forming chamber by CVD, generated reaction product or unreacted gas is exhausted using the rotary pump 121. At that time, ethanol was accommodated in the bubbling container 111 as the inactivating substance 116, and nitrogen gas was introduced from the carrier gas introducing port 115 via the flow meter as the carrier gas. Next, a gaseous mixture of ethanol vapor obtained by bubbling and nitrogen was introduced into the rotary pump 121 by opening the ballast valve 125. The flow rate of nitrogen was 2 liters/min.

After the CVD apparatus was used for a week to form an aluminum film in the manner described above, the discharge port 123 and the drain valve 126 of the rotary pump 121 were opened to replace oil. At that time, the oil which flowed out from the discharge port 123 and the drain valve 126 did not ignite or smolder at all, and safe oil replacement could thus be performed. It is considered from both the time required for film formation and the flow rate of the material gas that about 60 g of DMAH flowed into the rotary pump 121. It is thus estimated that several g of DMAH remained in the pump oil. This is an amount sufficient to ignite when the interior of the pump is opened to the atmosphere. Thus, it is considered that DMAH was converted into stable alcoholate by introducing ethanol vapor into the pump.

Since the flow rate of the carrier gas and the flow ratio between the inactivating substance and the carrier gas must be suitably selected according to the amount of material gas supplied to the CVD apparatus, the number of wafers on which aluminum is deposited and the film forming conditions, the carrier gas may be supplied via a bypass line (not shown) which bypasses the bubbling container 111 or the bubbling container 111 may be warmed or heated. However, it is not necessary for the amount of inactivating substance introduced into the pump to be strictly controlled; an amount of inactivating substance which is enough to inactivate the material gas introduced into the film forming chamber of the CVD apparatus may be introduced.

If an organic metallic compound is used as an active substance, an active hydride which mildly reacts with the organic metallic compound is desirably used as an inactivating substance.

When an inactivating substance is to be introduced into the pump, active hydride whose saturated vapor pressure at ambient temperatures is relatively high is used as an inactivating substance from the viewpoint of maintenance and ease of gas introduction. Active hydride is evaporated by bubbling using an inactive gas, and the thus-generated mixture gas of the inactive gas and the active hydride is introduced from the ballast valve of the vacuum pump.

If a highly reactive organic aluminum compound, for example, is used as the organic metallic compound, active hydride whose vapor pressure at ambient temperatures is high, such as methanol, ethanol or propanol, is desirably used.

Second Embodiment

FIG. 4 is a schematic cross-sectional view of a vaporizing device to which the active substance treating method according to the present invention is applied.

Reference numerals 1101 and 1201 denote a first bubbling container and a second bubbling container, respectively, reference numerals 1110 and 1212 denote introducing ports through which a carrier gas is introduced into the first and second bubbling containers 1101 and 1201, respectively, reference numerals 1121 and 1223 denote valves for stopping introduction of the carrier gas into the first and second bubbling containers 1101 and 1201, respectively, reference numerals 1111 and 1211 denote introducing ports through which a liquid material is introduced into the first and second bubbling containers 1101 and 1201, respectively, reference numerals 1122 and 1222 denote opening/closing valves for supplying the liquid material into the first and second bubbling containers 1101 and 1201, respectively, reference numerals 1123 and 1221 denote gas discharge valves for discharging gas from the first and second bubbling containers 1101 and 1201, respectively, reference numeral 1222 denotes a discharge port through which gas is discharged from the second bubbling container 1201, reference numeral 1113 denotes a pipe through which the gas in the first bubbling container 1101 is exhaust or discharged, reference numeral 1124 denotes a valve for opening and closing the pipe 1113, and reference numerals 1100 and 1200 denote liquid materials supplied into the first and second bubbling containers 1101 and 1201, respectively.

Vaporization conducted using the vaporizing device shown in FIG. 4 using, as a liquid material, dimethyl aluminum hydride, and, as a carrier gas, hydrogen gas will be described below in detail.

First, regarding the empty first and second bubbling containers 1101 and 1201, the valves 1121, 1122, 1222 and 1223 were closed, and the gas discharge valves 1123, 1221 and 1124 were opened. Next, the first and second bubbling containers 1101 and 1201 were evacuated to an order of 10.sup.-3 Torr from the pipe 1113. After the valve 1124 was closed, the valve 1121 was opened to introduce hydrogen gas from the carrier gas introducing port 1110 to substitute hydrogen for the contents of the first and second bubbling containers 1101 and 1201. Thereafter, the valve 1121 was closed. Such an operation of substituting hydrogen for the contents of the first and second bubbling containers 1101 and 1201 was repeated two more times, and then all the valves were closed once the first and second bubbling containers 1101 and 1201 were filled with hydrogen gas. At that time, the pressure in the first and second bubbling containers 1101 and 1201 was maintained slightly higher than atmospheric pressure in order to minimize entrance of the atmosphere.

Next, the valves 1121, 1123, 1221 and 1223 were opened in that order to supply hydrogen gas from the carrier gas introducing port 1110 at a flow rate of 100 sccm. After 500 ml of dimethyl aluminum hydride was introduced into the first bubbling container 1101 from the introducing port 1111 by opening the valve 1122 when hydrogen gas was flowing, the valve 1122 was closed. Subsequently, 500 ml of dimethyl aluminum hydride was similarly introduced into the second bubbling container 1201 from the introducing port 1211 by opening the valve 1122, and then the valve 1222 was closed. Thus, bubbling of liquid dimethyl aluminum hydride by hydrogen gas is smoothly conducted. In order to increase the divided pressure of the material gas, i.e., dimethyl aluminum hydride, contained in hydrogen gas which is the carrier gas and reduce the viscosity of liquid dimethyl aluminum hydride and thereby achieve smoother bubbling, the first and second bubbling containers 1101 and 1201 may be heated to about 80.degree. C.

Quartz was used as the material of the inner wall of the first and second bubbling containers 1101 and 1201 in order to prevent thermal decomposition of dimethyl aluminum hydride. Next, the flow rate of hydrogen gas was increased to 1000 sccm.

The thus-obtained hydrogen gas with dimethyl aluminum hydride contained therein was introduced into a container of a CVD apparatus from the discharge port 1212 via a pipe heated to 80.degree. C. to deposit Al on a silicon wafer by the CVD process. The temperature of the silicon wafer was 270.degree. C., and the gas pressure was 1.2 Torr. At that time, the deposition rate of the Al film on the surface of the silicon wafer was about 3000 .ANG./min. Al deposition was conducted under the above-described conditions for three months at a rate of 10 batches a day. When the Al film formed after three months was compared with the initially formed Al film, there was no difference between the two films in terms of film quality. As a comparative example, an Al film was formed similarly using the gas bubbled in the first bubbling container 1101. First, after the pipe 1113 was connected to the container of the CVD apparatus, hydrogen gas was introduced into the first bubbling container 1101 from the carrier gas introducing port 1110 at a flow rate of 1000 sccm by closing the valve 1221 and by opening the valves 1110, 1123 and 1124. The gas obtained by conducting bubbling only in the first bubbling container 1101 was supplied to the CVD apparatus from the purging pipe 1113. Next, Al film deposition was conducted under the same conditions as the above-mentioned. However, visual observation revealed that the surface of the obtained Al film was unclear, and SEM observation revealed that there were fine irregularities having a dimension of 0.1 .mu.m in the surface of the Al film.

It is apparent from the aforementioned results that film formation conditions can be stably maintained over a long time by using the bubbling device according to the present invention.

In the present invention, not only when a liquid material which readily reacts with the impurities contained in the carrier gas is used by also when the impurities are absorbed in the liquid material, the purity of the vapor of the supplied liquid material can be maintained at high level high over a long period of time by bubbling the liquid material using the carrier gas. Further, although two bubbling containers were series-connected in this embodiment, three or more bubbling devices may be used. The number of bubbling devices to be connected depends on the purity of the carrier gas or liquid material or the reactivity of the liquid material with the carrier gas.

Third Embodiment

A thin film forming apparatus for forming a thin film using the material gas obtained by the bubbling device shown in FIGS. 3 and 4 will now be described. This thin film forming device also includes the active substance treating device as an exhaust device.

FIG. 5 is a schematic view of such a thin film forming apparatus.

In a reaction furnace 303 evacuated by an exhaust device 301 and an exhaust adjusting valve 302, a semiconductor substrate 305 is placed on a substrate holder 304 with a heater incorporated therein. Silane gas, a material gas, is introduced into the reaction furnace 303 toward the outer periphery of the substrate 305 via introduction pipes 306 and 307 after it was diluted by argon gas.

Dimethyl aluminum hydride, which is introduced into the reaction furnace 303 via an introduction pipe 308 using Ar gas as the carrier gas, is sent to the surface of the substrate 305 via a branched pipe 309.

The pressure in the reaction furnace was set to 0.1 to 10 Torr, and the surface temperature of the substrate 305 was set to 250 to 400.degree. C. The concentration (divided pressure) of silane gas, which is diluted by argon gas and introduced into the reaction furnace 303, is varied according to the proportion of silicon contained in the aluminum film formed on the substrate 305.

Similarly, dimethyl aluminum hydride, which is introduced toward the surface of the substrate 305 using argon as the carrier gas, may be introduced in a state where it is mixed with hydrogen gas, if a desired aluminum film quality is obtained or selective growth is conducted.

In order to form an aluminum alloy film which contained 0.5 to 2% of silicone, the mole ratio of dimethyl aluminum to silane, which were introduced toward the surface of the substrate 305 heated to about 300.degree. C., was set between 20:1 and 6:1.

The gas between the surface of the substrate and the branched pipe 309 is from 3 to 30 mm, with preferably 10 mm.

Fourth Embodiment

FIG. 6 is a schematic cross-sectional view of a driving portion of a recording head manufactured using the thin film forming apparatus shown in FIG. 5.

In FIG. 6, a p-type isolation buried region 402 and an n-type isolation buried layer 403 are formed in an n-type silicon substrate 401. Reference numeral 404 denotes an n-type epitaxial region, reference numeral 405 denotes an n-type isolation region, and reference numeral 406 denotes a p-type isolation region.

An n-type isolation region 407 and a p-type isolation region 408 are formed on the n-type isolation region 405 and the p-type isolation region 406, respectively.

Reference numeral 409 denotes an n-type isolation region which is a cathode region of a Schottky barrier diode. Reference numeral 410 denotes a p-type guard ring layer which is formed to prevent generation of various influences caused by the surrounding portion of the diode, to limit concentration of an electric field and to prevent deterioration in the reverse withstanding voltage of the surrounding portion of the diode. Reference numeral 411 denotes an isolation electrode, reference numeral 412 denotes a cathode electrode for the Schottky barrier diode, and reference numeral 413 denotes an anode electrode for the Schottky barrier diode.

Metal/semiconductor contact between the n-type epitaxial region 404 and the anode electrode 413 forms a Schottky barrier diode. This Schottky barrier diode is surrounded by the p-type layers including the p-type isolation regions 408, the p-type isolation regions 406 and the p-type isolation buried region 402. The n-type layers, including the n-type isolation region 407, the n-type isolation region 405, the n-type epitaxial region 404 and the n-type isolation buried layer 403, form an isolation region. Thus, a device isolation type Schottky barrier diode is provided. A plurality of such cells are electrically connected in a matrix.

The operation of the driving portion of the semiconductor device shown in FIG. 6 will be described below.

In FIG. 6, a bias current flows between the cathode region 412 and the anode region 413 by applying a negative bias voltage (V.sub.H1) to the cathode region 412 of the Schottky barrier diode and by grounding the anode region 413 thereof. Flow of current to adjacent cells can be prevented by grounding the isolation electrode 411, thus preventing erroneous operation of other diodes.

FIG. 7 shows an equivalent circuit of the single block of the driving portion of the semiconductor device shown in FIG. 6.

In the semiconductor device shown in FIG. 6, a Schottky junction is formed by the anode region 412 and the n-type epitaxial region 404 by setting the concentration of the n-type epitaxial region 404 to 1.times.10.sup.17 cm.sup.-3 or less.

The current-voltage characteristics of the Schottky function are expressed as follows:

J=J.sub.0 {e.times.p(eV/nkt)-1}(A/cm.sup.2) (1)

where e is an electric charge of electrons and e=1.602.times.10.sup.-19 (coulomb), k is Boltzmann's constant and k=1.38.times.10.sup.-23 (J/K), n is an index which represents deviation from the ideal characteristics, and is called the ideal factor or diode factor. When Al is used for the cathode and anode electrodes to form a Schottky junction of Al or Si, n=1.05. T is the absolute temperature.

J.sub.0 is the saturation current density and is defined by Equation (2).

J.sub.0 =R*T.sup.2 exp(-e.phi..sub.MS /kT) (2)

where R* is the Richardson constant and R*=120 (A/K.sup.2 .multidot.cm.sup.2), and .phi..sub.MS is the barrier height between the metal and the semiconductor and .phi..sub.MS =0.5 to 0.77 (eV) in the case of Al and Si. In the experiments conducted to measure the C-V value for a Schottky junction of Al and n-type Si, .phi..sub.MS was 0.69 (eV).

Assuming that .phi..sub.MS =0.69 (eV) and that T=298 (K), the saturation current density J.sub.0 is given by

J.sub.0 3.2.times.10.sup.-5 (A/cm.sup.2) (3)

It can be seen from Equation (3) that a very large current can be made to flow in a Schottky diode as compared with the saturation current density of 1.times.10.sup.-12 to 1.times.10.sup.-10 (A/cm.sup.2) for a PN junction diode.

FIG. 8 is a schematic perspective view of an ink jet recording head according to the present invention.

In FIG. 8, reference numeral 500 denotes an ink discharge port, and reference numeral 501 denotes a liquid passage wall member made of a photosensitive resin to form a liquid passage which communicates with the discharge port 500.

Reference numeral 502 denotes a ceiling plate made of glass or resin, and reference numeral 503 denotes a liquid supply port.

FIG. 9 is a schematic cross-section taken along the line E-E' of FIG. 8 which shows the ink jet recording head having the aforementioned driving portion of the semiconductor device. Identical reference numerals in FIG. 9 to those in FIG. 6 represent similar or identical elements.

FIG. 10 schematically illustrates a method of driving a recording head shown in FIG. 9.

In a recording head 2100, an electrothermal energy conversion element is made up of an SiO.sub.2 film 2101 formed on the substrate having the aforementioned driving portion by thermal oxidation, a heat accumulating layer 2102, which may be an SiO.sub.2 film formed by sputtering, a heating resistor layer 2103, which may be an HfB.sub.2 formed on the heat accumulating layer 2102, and an electrode 2104 which may be made of Al. Also, a protective film 2105, which may be a SiO.sub.2 film, and a protective film 206, which may be made of Ta, are formed by sputtering on a heating portion 2110 of the electrothermal energy conversion element.

The SiO.sub.2 film which forms the heat accumulating layer 2102 also acts as an interlayer insulator between interconnections 2201 and 2203 of the driving portion.

Similarly, the protective film 2105 also acts as an interlayer insulator between interconnections 2201 and 2202.

Also, a protective film 2107 made of an organic material, such as photosensitive polyimide, as an insulating film exhibiting excellent resistance to a recording liquid is formed on the interconnection 2202 formed on the top of the driving portion.

Although not shown, a grooved ceiling plate or an orifice plate may be disposed as a component of the recording head to form a liquid passage or a discharge port. In this way, a recording head of the type in which a liquid is discharged in a direction which intersects the heating surface of the electrothermal energy conversion element can be formed, unlike the recording head of the type shown in FIG. 8, in which a liquid is discharged in a direction substantially parallel to the heating surface of the electrothermal energy conversion element.

The method of driving such a recording head will be described below. Although only two semiconductor devices (cells) are shown in FIG. 10, for example, 128 cells may be electrically connected in a matrix in the recording head.

Hereinafter, driving of electrothermal energy conversion elements RH1 and RH2, which are the two segments in the same group, will be described.

To drive the electrothermal energy conversion element RH1, the group to which the element RH1 belongs is selected by a switch G1 and at the same time the electrothermal energy conversion element RH1 is selected by a switch S1, whereby a diode cell SH1 is biased in a forward direction, supplying a current to the electrothermal energy conversion element RH1 to heat it. The thus-generated thermal energy changes the state of the liquid, thus generating a bubble and discharging the liquid from the discharge port.

The electrothermal energy conversion element RH2 is driven similarly by selectively turning on the switch G1 and a switch S2 to drive a diode cell SH2 and thereby supply a current to the electrothermal energy conversion element.

At that time, the substrate 401 is grounded via the isolation regions 403, 405 and 407. Erroneous operation due to an electrical interference between the adjacent semiconductor devices (cells) can be prevented by providing the isolation regions 403, 405 and 407 in the manner described above.

The manufacturing process of the recording head of this embodiment will be described below with reference to FIG. 11.

A silicon oxide film was formed to a thickness of 5000 to 20000 .ANG. on the surface of the n-type silicon substrate 401 doped with impurities at a concentration of 1.times.10.sup.12 to 10.sup.16 cm.sup.-3.

The portion of the silicon oxide film located at a position where the n-type isolation buried region 403 was to be formed was removed by the photolithographic process.

After a silicon oxide film was formed to a thickness of 100 to 3000 .ANG., n-type impurities, e.g., P or As ions, were implanted to form the n-type isolation buried region 403 doped with impurities at a concentration of 1.times.10.sup.17 to 1.times.10.sup.19 cm.sup.-3 by thermal diffusion.

After an oxide film was removed, a silicon oxide film was formed again to a thickness of 5000 to 20000 .ANG..

Subsequently, the portion of the silicon oxide film located at a position where the p-type isolation buried layer 402 was to be formed was removed. After a silicon oxide film was formed to a thickness of 100 to 3000 .ANG., p-type impurities, e.g., B ions, were implanted by thermal diffusion to form the p-type isolation region 402 doped with impurities at a concentration of 1.times.10.sup.17 to 1.times.10.sup.19 cm.sup.-3.

After the oxide film was removed from the entire surface, the n-type epitaxial region 404 doped with impurities at a concentration of 1.times.10.sup.12 to 1.times.10.sup.17 cm.sup.-3 was epitaxially grown to a thickness of 5 to 20 .mu.m (as shown in FIG. 11(a)).

Next, a silicon oxide film was formed to a thickness of 1000 to 10000 .ANG. on the surface of the n-type epitaxial region, and then the portion of the oxide film located at a position where the p-type isolation region 406 was to be formed was removed. Thereafter, a BSG film was deposited over the entire surface by CVD, and the p-type isolation region doped with impurities at a concentration of 1.times.1018 to 1020 cm-3 was formed by thermal diffusion to a thickness of 10 .mu.m so that it reached the p-type isolation buried region 402. After the BSG film and the silicon oxide film were removed, a silicon oxide film was formed to a thickness of 1000 to 10000 .ANG.. After the portion of the oxide film located at a position where the n-type isolation region 405 was to be formed was removed, a PSG film was formed, and the n-type isolation region 405 was formed by thermal diffusion so that it reached the n-type isolation buried region 403 (as shown in FIG. 11(b)).

Thereafter, the PSG film was removed and the portion of the oxide film corresponding to a cell region was removed, a silicon oxide film was formed to a thickness of 100 to 3000 .ANG.. After resist patterning was conducted, ion implantation of n-type impurities was conducted only on the region where the n-type isolation region 407 and the n-type isolation region 409 which was the cathode region of a Schottky barrier diode were to be formed.

After resist removal, resist patterning was conducted on the region where the p-type isolation region 408 and the p-type guard ring region 410 were to be formed, and then ion implantation of p-type impurities was conducted. Thereafter, heat treatment was conducted to perform activation. The thickness of the respective regions 407, 408 and 409 was 1.0 .mu.m or less, and the impurity concentration was 1.times.10.sup.19 to 10.sup.20.multidot. cm.sup.-3 (as shown in FIG. 11(c)).

After the portion of the silicon oxide film located on the connecting portions between the adjacent electrodes was removed, AL--Si was deposited in the contact holes by CVD.

Thereafter, an SiO.sub.2 film 4102 was formed over the entire surface to a thickness of about 1.0 .mu.m as the heat storing layer and the interlayer insulator by sputtering (as shown in FIG. 11(d)).

Next, an HfB.sub.2 film was deposited to a thickness of 1000 .ANG. as a heat resistor layer 4103. After an Al interconnection layer was deposited on the heat resistor layer 4103 as a pair of electrodes 4104 of the electrothermal energy conversion element and as an anode electrode interconnection 4201 and a cathode electrode interconnection 4202 of the diode, the layer was patterned.

Thereafter, an SiO.sub.2 film 4105 was deposited as the protective layer of the electrothermal energy conversion element and as the interlayer insulator, and contact holes were formed. After a cathode electrode interconnection 4202 was formed, Ta was deposited on the heating portion of the electrothermal energy conversion element as the protective layer against cavitation. Thereafter, photosensitive polyimide was formed on the SiO.sub.2 film 4105 and the cathode electrode interconnection 4202 as the protective layer (as shown in FIG. 11(f)).

A liquid passage wall member and a ceiling plate were deposited on the substrate having the thus-manufactured electrothermal energy conversion element and semiconductor device to manufacture a recording head.

A performance test was conducted on the recording head in which a plurality of thus-manufactured semiconductor devices were connected in a matrix. In this performance test, eight semiconductor diodes were connected in a single segment. When 300 mA (2.4 A in total) of current was supplied to each of the semiconductor diodes, the adjacent semiconductor diodes did not malfunction, and excellent discharge could be attained.

FIG. 12 is a schematic cross-sectional view of the driving portion for driving the above-described recording head.

The driving portion shown in FIG. 12 is a modification of the fourth embodiment. In this modification, no epitaxial layer is formed so that the recording head can be formed using five masks.

The manufacturing process of the driving portion of the above recording head will be described below.

After a silicon oxide film was formed to a thickness of 1000 to 10000 .ANG. on the surface of an n-type silicon substrate 4301 doped with impurities at a concentration of 1.times.10.sup.12 to 10.sup.17 cm.sup.-3, the portion of that oxide film located at a cell region was removed, and then a silicon oxide film was formed to a thickness of 100 to 3000 .ANG.. After resist patterning, n-type impurities, e.g., PH.sub.3 (phosphine) or As ions, were implanted only in the region where an n-type high-concentration region 4302 serving as the cathode region of the Schottky barrier diode was to be formed. After the resist was removed, resist patterning of the region where a p-type guard ring region 4303 was to be formed was conducted, and then p-type impurities, e.g., B or BF.sub.2 ions, were implanted. Next, heat treatment was conducted for activation. The impurity concentration of the n-type high-concentration region 4302 and that of the p-type guard ring region 4303 were 1.times.10.sup.19 to 10.sup.20 cm.sup.-3. Thereafter, the portion of the silicon oxide film located on the connecting portions between the electrodes was removed, and the Al was deposited by the aforementioned method.

The present invention offers excellent advantages, particularly when it is applied to an ink jet recording head of the type which includes means for generating heat energy (such as an electrothermal transducer or a laser) as the energy utilized for ink discharge to generate changes in the state of an ink, because such a recording head can achieve high-density and high-definition recording.

The typical structure and operational principle of such a recording head are disclosed in, for example, U.S. Pat. Nos. 4,723,129 and 4,740,796. This principle can be applied to both a so-called on-demand type recording system and a continuous type recording system. However, the principle is more suitably applied to an on-demand type recording system for the following reasons. In this on-demand type recording system, an electrothermal transducer is disposed for the sheet or the liquid passage at which liquid (ink) is retained. A heat energy is generated in the electrothermal transducer by applying at least a single driving signal which assures a rapid increase in the temperature exceeding nucleation boiling point to the electrothermal transducer in response to the recording data, generating film boiling on the heating portion of the recording head and forming a bubble in the liquid (ink) one-to-one correspondence to the driving signal. The liquid (ink) is ejected through an ejection outlet as a consequence of development and collapse of the bubble to form at least a single droplet. Development and collapse of a bubble can be adequately performed when a pulse-like driving signal is applied, thus achieving discharge of the liquid (ink) having excellent responsiveness. Pulse-like driving signals, disclosed in, for example, U.S. Pat. Nos. 4,463,359 and 4,345,262, are preferably used. In addition, superior recording can be performed by adopting the conditions described in U.S. Pat. No. 4,313,124, which relates to the temperature increasing rate of the heating surface.

In addition to the recording heads disclosed in the above-mentioned specifications, each including a combination of discharge ports, a liquid passage and an electrothermal transducer, (a straight line-like or right angle-like liquid flow passage), recording heads disclosed in U.S. Pat. Nos. 4,558,333 and 4,459,600 and constructed such that the heating portion is disposed in a curved area can also be used. In addition, a recording head disclosed in Japanese Patent Laid-Open No. 59-123670 and structured such that a common slit is provided for a plurality of electrothermal transducers as the discharge portions thereof or a recording head disclosed in Japanese Patent Laid-Open No. 59-138461 and structured such that the opening for absorbing the pressure wave of a heat energy opposes the discharge portion can also be employed in the present invention. In other words, whatever the structure of the recording head, it is possible according to the present invention to perform recording reliably and effectively.

A full line type recording head having a length corresponding to the width of the maximum recording medium that a recording apparatus can record can also be used. The full line type recording head may have a structure in which a plurality of recording heads are combined to fulfill the required length or may be constructed by a single recording head.

In addition to the above-described serial type recording head which is fixed to the apparatus body, a chip type recording head, which is replaceable and whose mounting on the apparatus body assures both the electrical connection with the apparatus body and ink supply from the apparatus body, or a cartridge type recording head with an ink tank formed therein can also be employed in the present invention.

To make the present invention more advantageous, the provision of discharge recovery means or auxiliary means for the recording head in the recording apparatus is preferable. Suitable examples of such additional means include capping means for the recording head, cleaning means, pressurization or suction means, a preliminary heating means made up of an electrothermal transducer, a heating element other than the electrothermal transducer or a combination of the electrothermal transducer and the heating element other than the electrothermal transducer, and preliminary discharge means which performs discharge other than recording.

In the present invention, there is no limitation to the type or number of recording heads mounted on a recording apparatus. For example, the present invention can be applied to either a recording apparatus which includes a single recording head for a single color ink or to a recording apparatus which includes a plurality of recording heads for a plurality of inks which differ in terms of the recording color or density. That is, the present invention can be applied to a recording apparatus which is capable of recording in a single color, such as in black, in a plurality of different colors or in a full color which are achieved by the use of a single recording head or a plurality of recording heads.

In the aforementioned examples, liquid ink has been described. However, an ink, which is solidified at room temperature or below, but which is softened or liquefied at room temperature can also be used. Also, an ink which is liquefied when a recording signal is applied thereto can also be used, because the temperature of the ink is generally adjusted between 30.degree. C. and 70.degree.0 C. in the aforementioned ink jet recording apparatus in order to set the viscosity thereof within a stable discharge range. In addition, an ink which is a solid when left unused but is liquefied by heating can also be used. In this way, an increase in the temperature due to heat energy can be prevented by utilizing that heat energy to change the phase state of the ink from a solid to a liquid, or evaporation of the ink can be prevented. In any enent, an ink which is normally a solid but liquefied when a thermal energy is applied thereto can also be used in the present invention. Such an ink includes one which is liquefied when a thermal energy is applied thereto in response to a recording signal and thus discharged in the form of a liquid and one w