Processing apparatus for wafers

A high pressure processing apparatus and method which is compatible with a system wherein wafers are largely transported and processed under vacuum. The pressure vessel can be extremely small, i.e. has a total pressurized volume of which almost all interior points are within one or two centimeters of one of the workpieces which may be loaded into the chamber.

 

What is claimed is:

1. An apparatus for processing of wafers, comprising:

(a) a process chamber capable of operating at low pressure;

(b) one or more wafer support members within said process chamber, said wafer support members being capable of stably supporting a plurality of wafers in substantially face down positions with substantially no damage to structures on the face of said wafer; and

(c) a wafer transfer mechanism positioned to transfer wafers under control through an openable port into said process chamber, said wafer transfer mechanism being capable of operation under high vacuum.

2. The apparatus of claim 1 wherein wafer transfer mechanism has sufficient controllable vertical movement to selectably place and/or remove wafers from selectable positions in said wafer support members.

3. The apparatus of claim 1 wherein said apparatus is capable of performing chemical vapor deposition.

4. The apparatus of claim 1 wherein said apparatus is capable of performing slow low pressure processes.

5. The apparatus of claim 4 wherein said apparatus is capable of performing gaseous oxide deposition.

6. An apparatus for processing of a wafer comprising:

(a) a process chamber of a process module capable of operating at high and low pressure;

(b) one or more wafer support members within said process chamber capable of supporting said wafers substantially face down; and

(c) a wafer transfer mechanism positioned to transfer wafers under control through a port moveable between an open and closed positions into said process chamber at low pressure.

7. The apparatus as set forth in claim 6 wherein the interior walls of said chamber are adjacent said wafers when said port is in the closed position.

8. The apparatus as set forth in claim 6 wherein said chamber has an interior wall of quartz.

9. The apparatus as set forth in claim 6 wherein said chamber has an exterior wall of stainless steel.

10. An apparatus for processing of wafers, comprising:

(a) a process chamber;

(b) a wafer support member within said process chamber for stably supporting a plurality of wafers, face down, with substantially no damage to structures on the face of said wafer; and

(c) a wafer transfer mechanism positioned to transfer wafers to and from the wafer support member.

11. The apparatus as set forth in claim 10 further including a movable

port which allows access into the process chamber.

12. The apparatus as set forth in claim 10 further including a movable port which allows access to the process chamber wherein the interior walls of said chamber are adjacent said wafers when said port is in a closed position.

13. The apparatus as set forth in claim 10 wherein said chamber has an interior wall of quartz.

14. The apparatus as set forth in claim 10 wherein said chamber has an exterior wall of stainless steel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the accompanying drawings, wherein:

FIG. 1 shows a sample embodiment of a load lock which is compatible with vacuum processing and transport of semiconductor integrated circuit wafers.

FIG. 2 shows a graph of the time required to fall through air at various pressures for particulates of various sizes.

FIG. 3 shows a sample wafer transfer structure, in a process station, wherein the wafer is placed onto three pins by the transfer arm 28 reaching through the inter-chamber transfer port 30 from the adjacent vacuum load lock chamber 12.

FIG. 4 shows a closer view of a sample embodiment of a multi-wafer vacuum wafer carrier 10, docked onto the position registration platform 18 inside a load lock like that of FIG. 1.

FIGS. 5A and 5B show a plan view of a sample process stations including process modules and wafer transfer stages, and a load locks.

FIG. 6 shows a configuration for a process module, which can be used as one of the process modules inside the process station shown in Figures 5A and 5B.

FIG. 7 shows the plasma reactor of FIG. 6 in the closed position, as it would be during the actual etch process.

FIG. 8 shows a plan view of the reactor of FIG. 6.

FIG. 9 shows an improved version of the process module of FIG. 6, in a sample embodiment which includes the capability for process enhancement by ultraviolet light generated in situ and also the capability is also provided for providing activated species (generated by gas flows through an additional plasma discharge which is remote from the wafer face) to the wafer face. The module is shown in a process station which includes one module and one load lock, but can also be used in embodiments like that of FIGS. 5A and 5B.

FIG. 10 shows a physical configuration for a process station which can be used for implementing some of the embodiments described herein.

FIG. 11 shows a flow chart for a load lock control system which provides particulate protection in a vacuum process system.

FIG. 12 is a detailed view of the structure realize the capability for process enhancement by ultraviolet light generated in situ, in embodiments such as that of FIG. 9.

FIG. 13 shows an alternative version of the structure of FIG. 12, without the isolator window which (in the embodiment of FIG. 12) helps separate the gas flows of the ultraviolet source plasma from the process gas flows near the wafer face.

FIG. 14 shows a further alternative version of the structure of Figure 12, wherein the plasma which provides the ultraviolet source is generated between the electrodes which are approximately cylindrical, and wherein capability is also provided for providing activated species (generated by gas flows through an additional plasma discharge which is remote from the wafer face) to the wafer face.

FIG. 15 shows an example of a structure which generates activated species by gas flows through a plasma discharge which is remote from the wafer face, in embodiments like that of FIG. 14.

FIG. 16 shows an example of a module which provides the combined capability of plasma bombardment from a plasma in close proximity to the wafer face, and provision of activated species from a remote discharge, and illumination of the wafer face with intense ultraviolet light.

FIG. 17 shows an example of a process module which provides two separate gas feed distributors, and which is particularly advantageous for chemical vapor deposition operations using two source species.

FIG. 18 shows a portion of a process module whish permits rapid thermal processing to be performed with reduced risk of wafer damage, and FIGS. 19A, 19B and 19C schematically show how the operation of the heat source of FIG. 18 can alter the the distribution of heating across the wafer, and FIG. 20 shows sample plots of heating across a wafer diameter under the conditions of FIG. 19B and 19C.

FIGS. 21A and 21B show two structures for reducing conductive heat transfer between a wafer and a transparent vacuum window in rapid thermal processing embodiments, including sample gas flow connections to supply a purge gas to the void between the wafer and the transparent vacuum wall, and FIG. 21C shows a third way to minimize this conductive heat transfer, and FIG. 21D shows a sample vacuum seal which may be used with a transparent vacuum wall which is subject to wide temperature variations in a rapid thermal processing environment.

FIG. 22 shows another configuration of a heat source for rapid thermal processing, in which the overall width of the heat source is minimal.

FIG. 23 shows the details of a process module, which provides combined capabilities for high-temperature processing (and cleanup), plasma bombardment, and provision of remotely generated activated species to the wafer face.

FIG. 24 shows a process module, which provides combined capabilities for high-temperature processing (and cleanup), plasma bombardment, provision of remotely generated activated species to the wafer face, and illumination of the wafer face by intense ultraviolet light generated in situ.

FIGS. 25A and 25B show a process module with capability for edgepreferential processing (and specifically for photoresist bake and/or edge bead removal).

FIG. 26A shows a process module which permits cleanup and sputter deposition, and FIG. 26B and 26C show details of the module of Figure 26A, including a system for wafer transport within the module.

FIG. 27 shows a process module, compatible with a vacuum processing system, wherein multiple wafers are simultaneously processed under high pressure (or optionally under low pressure).

FIG. 28 shows a sample embodiment of an ion implanter process module which is compatible with a vacuum processing system.

FIGS. 29A through 29G are magnified sectional views of the inner walls of process gas piping, in several sample embodiments which provide advantages in a semiconductor process modules.

FIGS. 30A through 30E show a distributor structure, and show the improved results achieved with this structure in a descum process.

FIG. 31 is a block diagram of a computer control system.

FIG. 32 shows a process module with remote and in situ plasma.

FIGS. 33 and 34 show load lock chamber adapted to transfer wafers between a vacuum carrier and ambient.

FIGS. 35 and 36, which are similar, respectively to FIGS. 33 and 34, a load lock chamber adapted to trasnfer wafers between a vacuum carrier and a transfer mechanism to a vacuum processing system.

FIGS. 37 through 40 shoe details of a vacuum processor which has two rings of lamps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides major new concepts in semiconductor process methods and apparatus. The presently preferred embodiments will now be discussed in great detail, but it must be appreciated that the concepts which are included in these embodiments could also be used in many other embodiments, and the scope of the invention is not delimited by the particular examples shown.

FIG. 1 shows a sample embodiment of a vacuum wafer carrier 10 inside a vacuum load lock chamber 12. The vacuum wafer carrier 10 is also shown, in slightly greater detail, in FIG. 4.

The vacuum wafer carrier 10 is shown with its door 14 open. The door 14 is mounted in a pivotal manner to one side (the left side as shown in FIGS. 1 and 4) of the main body of carrier 10 by, for example, hinges (not shown). The door 14 has a vacuum seal 13 (FIG. 4) where it mates with the body of the vacuum wafer carrier, so that the interior of vacuum wafer carrier 10 can be maintained for several days and possibly for several tens of days, without enough leakage to raise the internal pressure above 10.sup.-3 Torr, for example, while the exterior of carrier 10 is subjected to the atmosphere.

The vacuum wafer carrier 10 is adapted to dock with a position registration platform 18. The position registration platform 18 is only partially visible in FIG. 1, but is shown in more detail in FIG. 4. When a vacuum wafer carrier 10 is placed inside the vacuum load lock chamber 12, the position of the vacuum wafer carrier 10 will, therefore, be accurately known. The vacuum wafer carrier 10 has ears 16 which engage vertical slots 17 fixed to the position registration platform 18. The vacuum wafer carrier 10 can be slid into these slots until it rests on the position registration platform 18, and thereby assure that the position of the vacuum wafer carrier 10 is definitely known. It is also useful for the position registration platform 18 to include two tapered pins 21. As shown in FIG. 4, the pins 21 are both conical shaped but they can be of different shapes, for example, one conical and one wedge-shaped. The pins 21 are positioned to engage tapered holes 23 in the underside of the vacuum wafer carrier 10 when it is lowered with ears 16 engaged with slots 17. A wide variety of other arrangements could be used to assure mechanical registration. Thus, the use of slots 17, ears 16, and pins 21 bring carrier 10 and chamber 12 into alignment (or mechanical registration).

The vacuum wafer carrier 10 also has a safety catch 15 on it which secures the door 14 from opening due to external forces being accidentally applied. An ear 500 extends from the side of the door 14 away from the hinges (not shown) which attach it to the main body of carrier 10. The safety catch 15 can also be used to hold the door 14 closed if the carrier 10 is used as a non-vacuum carrier. The ear is adapted to engage with a safety catch 15 rotatably mounted on the side (the right side as shown in FIG. 4) of carrier 10. However, under normal conditions of transport, this safety catch is not needed, since atmospheric pressure holds the door 14 shut against the internal vacuum of the vacuum wafer carrier 10. When the vacuum wafer carrier 10 is placed inside the vacuum load lock chamber 12 by engaging ears 16 with slots 17, a fixed finger 19 will engage the safety catch 15 and rotate it (upward as shown in FIG. 4) away from ear 500 to release it, so that the door 14 can be opened. Fixed finger 19 extends upward from platform 18 as shown in FIG. 4.

When the vacuum wafer carrier 10 is docked with the position registration platform 18, the door 14 will also be engaged with the top of door opening shaft 24. The door 14 can be provided with a shallow groove (not shown) in its underside, which mates with a finger and arm 25 on the top of the door opening shaft 24. The arm 25 is located to engage the door 14 near its attachment to the main body of carrier 10 in order to rotate the door 14 as desired. Thus, after the load lock has been pumped down so that differential pressure no longer holds the door 14 closed, the door can be opened by rotating (clockwise as shown in FIG. 4) door opening shaft 24. The door can be closed by rotating shaft 24 counterclockwise as shown in FIG. 4.

After the vacuum wafer carrier 10 is placed in the vacuum load lock chamber 12 (FIG. 1) and closed the load lock lid 20, a purge (with dry nitrogen or other clean gas), which can be at high pressure, is usefully applied through the manifold 22 (FIG. 1) inside the load lock lid 20. The manifold 22 includes holes in lid 20, a connection with a source of the gas into the holes in lid 20, and openings from the holes in the bottom of lid 20. The gas flows from the source through the holes in lid 20 and exits downward from lid 20 through the openings. The gas from the manifold 22 provides vertical flow which tends to transport particles downward. The gas flow from the manifold 22 also helps to remove some of the large particles which may have collected on the vacuum wafer carrier 10 during its exposure to atmospheric conditions.

After this initial purge stage (e.g. for 30 seconds or more), the chamber is then slowly pumped down to 10.sup.-3 Torr or less. This stage of the pump down should be relatively slow, in order not to stir up random particulates. That is, while low pressures do permit particles to fall from the air, those particles will still be available on the bottom of the chamber, and must not be stirred up if this can avoided.

In order to make sure that the airborne particulates have actually fallen out of the chamber air, the interior of the vacuum load lock can then be allowed to stay at 10.sup.-3 or 10.sup.-4 Torr for a few seconds, to make sure that all of the particles which are able to fall out of the air will do so.

The use of the carrier 10 and chamber 12 in the manner described above greatly reduce the problems of airborne particulates, which have always been the dominant type of particulate transport, so that the problem of ballistically transported particulates can now be usefully addressed.

A sloped bottom and polished sidewalls for the load lock may be used as a modification of chamber 12. This would reduce the population of particulates sticking to the sidewalls and bottom which can be sent disturbed by mechanical vibration.

Note that vacuum gauges 62 (FIG. 1) are connected to the interior of the vacuum load lock chamber 12. The vacuum gauges 62 include a high-pressure gauge (such as a thermocouple), a low pressure gauge (such as an ionization gauge), and a differential sensor which accurately senses when the load lock interior pressure has been equalized with the atmosphere. The door of a vacuum wafer carrier 10 is not opened until these gauges indicate that desired vacuum has been achieved inside the load lock.

After a roughing pump and its isolation valve 702 (FIG. 31) has brought the chamber down to a soft vacuum, the gate or isolation valve 39 can be opened to connect the pump 38 to the interior of the load lock, and the pump 38 can then be operated to bring the pressure down to 10 to the -3 Torr or less.

At this point, the pressures inside the vacuum wafer carrier 10 and the vacuum load lock chamber 12 are more or less equalized, and the door 14 can be opened by activating by an door drive motor 26 (FIG. 4), which is connected to door opening shaft 24 through a vacuum feedthrough 33. Motor 26 rotates shaft 24 in a clockwise direction as shown in FIGS. 1 and 4 to open the door 14 and in a counterclockwise direction to close the door 14. Two sensor switches 708 (FIG. 31) are also included inside the vacuum load lock chamber 12, to ascertain when the door 14 is in its fully opened position, and when the door 14 is fully shut. Thus, after the load lock chamber 12 has been pumped down and allowed to sit for a few seconds, the door opening shaft 24 is rotated in a clockwise direction to open the door 14, until one sensor switch detects that the door is fully open.

During this time, the transfer arm 28 is kept in its home position at an elevation below the bottom of the door, so that the door 14 has clearance to open. After the sensor switch detects that the door 14 is fully open, the transfer arm 27 can begin to operate. In order to close the door 14, shaft 24 is rotated in a counterclockwise direction until the other sensor switch detects that the door 14 is closed.

The transfer arm 28 has two degrees of freedom. The arm is capable of both vertical and horizontal movement. One direction of motion permits the transfer arm 28 to reach into vacuum wafer carrier 10 or through interchamber transfer port 30 into the adjacent process module, for example, process module 570 (FIG. 9). The other degree of freedom corresponds to vertical motion of the transfer arm 28, which permits selection of a wafer inside the vacuum wafer carrier 10 to remove, or which slot a wafer is placed into during a transfer operation.

An elevator drive motor 32 provides the elevation of the transfer arm 28, and the arm drive motor 34 provides the extension and retraction of the transfer arm 28. Neither of these motors requires a vacuum feedthrough since they are housed inside the exhaust manifold 36. The manifold 36, as shown in FIG. 1, has a cylindrical shape and extends from the bottom of chamber 12 downward. The manifold also extends through and is attached to the bottom of chamber 12 a short distance into chamber 12. The pump 38 is at the end of manifold 36 away from its attachment to chamber 12. The motor 26 also extends downward from chamber 12. Pump 38 can be, for example, a turbomolecular pump. The exhaust manifold 36 does not open directly into the vacuum load lock chamber 12, but instead has apertures 40 around its top (the end of manifold 36 extending into chamber 12). Thus, the exhaust manifold 36 is configured so that there is not a line of sight path from the elevator drive motor 32, the arm drive motor 34, or from the pump 38 to the vacuum load lock chamber 12. This reduces ballistic transport of particulates from these moving elements into the load lock chamber. The arrangement shown in FIG. 1 has been found useful but other arrangements are possible to provide the necessity transportation of the wafer 48.

The elevator drive motor 32 is connected to drive a sub-platform 42 up and down, and the arm drive motor 34 is mounted on this sub-platform 42 within the manifold 36. Motor 34 is fixed within manifold 36. The drive shaft of motor 32 drives a screw 510. Screw 510 passes through threads in sub-platform 42 to drive sub-platform 42 up or down dependent on the direction of rotation of the drive shaft of motor 32. Three rods 520, 521, and 522 pass through and are capable of sliding engagement with sub-platform 42. The rods are affixed to the top of manifold 36. Also affixed to subplatform 42 is a tubular support 46. This linkage within the manifold 36 allows the transfer 28 to easily move vertically.

Another linkage is provided inside the rotatable transfer arm support 44 which permits the transfer arm 28 to move very compactly. The tubular support 46 extends form sub-platform 42 up through the top of manifold 36. The rotatable transfer arm support 44 is connected to to be driven by a rotating rod (not shown) within tubular support 46. The tubular support 46 is fixed to arm support 44. Thus, the rotating rod is driven by the arm drive motor 34 and in turn drives arm support 44 and the rotatable transfer arm support 44 is mounted on a tubular support 46 which does not rotate but moves up and down. An internal chain and sprocket linkage is used so that the joint between rotatable transfer arm support 44 and transfer arm 28 moves with twice the angular velocity of the joint between rotatable transfer arm support 44 and tubular support 46. Of course, many other mechanical linkages could alternatively be used to accomplish this. This means that, when the rotatable transfer arm support 44 is in its home position, a wafer 48 will be supported approximately above the tubular support 46, but when the rotatable transfer arm support 44 is rotated 90 degrees with respect to the tubular support 46, the transfer arm 28 will have been rotated 180 degrees with respect to the rotatable tranfer arm support 44, so the transfer arm can either extend straight into the vacuum wafer carrier 10 or else straight through the inter-chamber transfer port 30 into the adjacent processing chamber. This linkage is described in greater detail in U.S. Pat. No. 4,659,413 issued to Davis et al on Apr. 21, 1987, which is hereby incorporated by reference.

The transfer arm 28 is a thin piece of spring steel, e.g., 0.030 inch thick. The transfer arm 28 has 3 pins 50 (FIGS. 1 and 3) on it to support the wafer 48. Each of the 3 pins 50 includes a small cone 5 (FIG. 3) on small shoulder 1900 (FIG. 3). The small cones 52 and small shoulders 1900 can be made of a material which is soft enough to not scratch silicon. For example, these portions, which are the only portions of transfer arm 28 which actually touch the wafers being transported, can be made of a high-temperature plastic (i.e. a plastic with a relatively low propensity to outgas under vacuum) such as Ardel (a thermoplastic phenyl acrylate, made by Union Carbide) or Delrin. Note that the use of a small cone 52 at the center or each of the 3 pins 50 permits very slight misalignments of the wafer to the transfer arm 28 to be corrected. In other words the system of wafer transport described here is a stable mechanical system, wherein small misalignments during successive operations will not accumulate, but will be damped out. The contact with the wafer 48 and the pins 50 are only at the edge of the wafer.

Note that, in the positioning of the wafer 48 as shown, one of the 3 pins 50 rests against the flat portion 56 (FIG. 4) on the circumference 49 (FIG. 4) of wafer 48. This means that, in this embodiment, the 3 pins 50 on the transfer arm 28 do not define a circle of the same diameter as the diameter of the wafer 48 to be handled.

To assure that the flat portion 56 (FIG. 4) of each wafer does not interfere with accurate handling of the wafers, the vacuum wafer carrier 10 has a flat contact surface 29 on its interior back side which the flat portion 56 of each wfer 48 will rest against. Elastic elements 27 (FIG. 4) on the inside surface of the door 14 pushes each wafer against this flat surface when the door 14 is closed, so that relative movement of the wafers and the carrier during transit is minimized, that is the wafers do not rub against the ledges 60. This also assures that, when the door 14 is opened, the location of the flat portion 56 on each wafer 48 is accurately known. That is the wafer is in a known predetermined alignment.

In operation, after the vacuum wafer carrier 10 is in the vacuum load lock chamber 12 with its door 14 open, the elevator drive motor 32 is operated to bring the transfer arm 28 to just below the height of the first wafer 48 which it is desired to remove, and the arm drive motor 34 is then operated to extend the transfer arm 28 into the interior of the carrier 10. This is the leftmost position of the three positions of arm 28 shown in FIG. 1. By operating the elevator drive motor 32 briefly, the transfer arm 28 is raised slightly until the 3 pins 50 around its circumference 49 lift the desired wafer off of the ledges 60 (FIG. 4) on which it has been resting inside the vacuum wafer carrier 10.

Note that the ledges 60, as shown in FIG. 4, are tapered surfaces rather than flat surfaces, so that contact between the ledges 60 and the wafer 48 resting on them is a line contact rather than an area contact, and is limited to the edge of the wafer. This prevents contact between carrier and wafer over a substantial area, possibly of many square millimeters, but the "line contact" used is over a much smaller area, typically of a few square millimeters or less. An alternative definition of the "line contact" used in this embodiment is that the wafer support contacts the surface of the wafer only at points which are less than one millimeter from its edge. Thus, by raising the transfer arm 28, a wafer 48 will be picked up, and will be resting on the small cones or small shoulders 1900 of the 3 pins 50 on the transfer arm 28.

The ledges 60 can have a center-to-center spacing of 0.187 inches inside the vacuum wafer carrier 10. This center-to-center spacing, less the thickness of the wafers 48, must allow clearance enough for the height of the transfer arm 28 plus the 3 pins 50, but need not be much more. For example, the transfer arm is about 0.080 inch thick, including the height of the small cones 52 on the 3 pins 50. The wafer 48 can be, for example, about 0.021 inch thick so that about 0.085 inch clearance is available. The thickness and diameters of the wafers can vary widely. Generally, larger diameter wafers will have greater thicknesses, but vacuum wafer carrier 10 of this kind is suited to use with such larger diameter wafers, since the size of the vacuum wafer carrier 10 and the center spacing of the ledges 60 inside the vacuum wafer carrier 10 can simply be adjusted appropriately. The carrier 10 can also be adapted to carry thinner wafers, for example, GaAs as desired.

After the transfer arm 28 has picked up the wafer 48, the arm drive motor 34 is operated to bring the transfer arm 28 to the home position (which is the middle position as shown in FIG. 1). This is the middle position of arms 28 as shown in FIG. 1. The elevator drive motor 32 is then operated to bring the transfer arm 28 to a height where it can reach through the inter-chamber transfer port 30 (FIG. 3).

The inter-chamber transfer port 30 is covered by an isolation gate 31. Although the gate 31 as shown in FIG. 3 seals the inter-chamber transfer port 30 by making sliding contact. When shaft 580 is rotated (as shown in FIG. 3), the linkage provided drives gate 31 upward (as shown in Figure 3) and covers the port 30. To open the port 30 the shaft 580 is rotated in the opposite direction. If desired the sealing can be performed by a rotated movement. (Again, the absence of sliding contact may be advantageous to reduce internally generated particulates.) The isolation gate 31 over the inter-chamber transfer port 30 can operated by an air cylinder, but a stepper motor could be used in the alternative. Thus, a total of four motors can be used: two which use vacuum feedthroughs, and two which are contained inside the exhaust manifold 36. The arm drive motor is now operated again, to extend transfer arm 28 through inter-chamber transfer port 30 into the adjacent processing chamber. This is the rightmost position of arm 28 as shown in FIG. 1. The adjacent processing chamber may be any one of many different kinds of process modules, for example, any processing module disclosed herein such as an implanter, a plasma etch, and a deposition module or any other type of process module.

The transfer arm reaching through the inter-chamber transfer port 30 will place the wafer 48 on wafer support pins 53 as shown in FIG. 3, like those used in the transfer arm 28 itself. (Note that the inter-chamber transfer port 30 should have enough vertical height to permit some vertical travel while the transfer arm 28 is extended through inter-chamber transfer port 30, so that transfer arm 28 can move vertically to lift a wafer from or deposit a wafer onto the wafer support, for example, wafer support pins 53 inside the processing chamber.) The wafer 28 is deposited by arm 28 on the tops of pins 53.

Alternatively, the processing chamber may include a fixture having spaced sloped ledges like the ledges 60 inside the transfer box, or may have other mechanical arrangements to receive the wafer. However, in any case, the arrangement used to receive the transferred wafer 48 must have clearance on the underside of the wafer (at least at the time of transfer), so that the transfer arm 28 can reach in on the underside of the wafer to emplace or remove it. If the wafer support pins 53 are used to receive the transferred wfer, it may be desirable to provide a bellows motion or a vacuum feedthrough in order to provide a vertical motion of the wafer support pins 53 inside the processing chamber. Thus, for example, where the processing chamber is a plasma etch or RIE (reactive ion etch) module, a bellows may be provided to move the wafer 48 vertically, for example, onto a susceptor after the transfer arm 28 has been withdrawn out of the way of the wafer 48.

Of course, the processing chamber may be an engineering inspection module or deposition module, for example. A vacuum-isolated microscope objective lens will permit inspection of wafers in vacuum and (using an appropriately folded optical path) in a face-down position. This means that heavy use of engineer inspection can be made where appropriate, without the loss of engineer time and clean-room quality which can be caused by heavy traffic through a clean room. The inspection module could be combined with other modules if desired.

In any case, the transfer arm 28 is withdrawn, and the gate 31 is moved to the closed position to close port 30, if desired. The process of wafer 48 then proceeds. After processing is finished, the isolation gate over the interchamber transfer port 30 is opened again, the transfer arm 28 is extended again, the elevator drive motor 32 is operated briefly so that the transfer arm 28 picks up the wafer 48, and the arm drive motor 34 is again operated to bring the transfer arm 28 back into the home position. The elevator drive motor 32 is then operated to bring the transfer arm 28 to the correct height to align the wafer 48 with the desired slot inside the vaccum wafer carrier. The arm drive motor 34 is then operated to extend the transfer arm 28 into the vacuum wafer carrier 10, so that the wafer 48 which has just been processed is sitting above its pair of ledges 60. The elevator drive motor 32 is then briefly operated to lower the transfer arm 28, so that the wafer is resting on its own ledges 60, and the arm drive motor 34 is then operated to retract the transfer arm 28 to home position. The sequence of steps described above is then repeated, and the transfer arm 28 selects another wafer for processing.

Note that, with the mechanical linkage of the transfer arm 28 and rotatable transfer arm support 44 described above, the wafers being transferred will move in exactly a straight line if the center to center lengths of transfer arm 28 and transfer arm support 44 are equal. This is advantageous because it means that the side of the wafer being transferred will not bump or scrape against the sides of the vacuum wafer carrier 10 when the wafer is being pulled out of or pushed into the box. That is, the clearances of the vacuum wafer carrier 10 can be relatively small (which helps to reduce particulate generation by rattling of the wafers during transport in the carrier) without risking particulate generation due to abrasion of the wafers against the metal box sides.

Processing continues in this fashion, wafer by wafer, until all the wafers inside the vacuum wafer carrier 10 (or at least as many of them as desired) have been processed. At that point the transfer arm 28 is returned empty to its home position and lowered below the lower edge of the door 14, and the isolation gate 31 over inter-chamber transfer port 30 is closed. Shaft 24 is rotated to close door 14 and provide initial contact for the vacuum seals between door 14 and the flat front surface of vacuum wafer carrier 10, so that the vacuum wafer carrier 10 is ready to be sealed (by pressure differential) as the pressure inside the load lock is increased. The vacuum load lock chamber 12 can now be pressurized again. When the differential sensor of the vacuum gauges 62 determines that the pressure has come up to atmospheric, the load lid 20 can be opened and the vacuum wafer carrier 10 (which is now sealed by differential pressure) can be manually removed. A folding handle 11 is usefully provided on the top side of the carrier, to assist in this manual removal without substantially increasing the volume required for the vacuum wafer carrier 10 inside the load lock.

After the vacuum wafer carrier 10 has been removed, it can be carried around or stored as desired. The vacuum seal 13 will maintain a high vacuum in the vacuum wafer carrier 10 so that particulate transport to the wafer surfaces (and also adsorption of vapor-phase contaminants) is minimized. The surface of wafers within the carrier 10 have the surface which is being processed to construct devices are facing downward to prevent particulates from settling on that surface.

Note that the vacuum wafer carrier 10 also includes elastic elements 27 mounted in its door. These elastic elements 27 exert light pressure against the wafers 48 when the door 48 is closed, and thus restrain them from rattling around and generating particulates. The elastic elements 27 are configured as a set of springs in the embodiment shown, but other mechanical structures (e.g. a protruding bead of an elastic polymer) could alternatively be used to configure this. Where the wafers used have flats, a flat contact surface 29 is provided on the inner back surface of the vacuum wafer carrier 10 for the wafer flats to be pressed against.

Note also that the ledges 60 on the sidewalls of the vacuum wafer carrier 10 are tapered. This helps to assure that contact with the supported surface of the wafer is made over a line only, rather than over any substantial area. This reduces wafer damage and particulate generation during transport. This also assists in damping out the accumulation of positioning errors, as discussed. The load lock lid 20 can have a window (not shown), to permit inspection of any possible mechanical jams.

An advantage of such embodiments is that, in the case of many possible mechanical malfunctions, the door of the vacuum wafer carrier 10 can be closed before attempts are made to correct the problem. For example, if somehow the transfer arm 28 picks up a wafer so that the wafer is not sitting properly on all three of the 3 pins 50, the door drive motor 26 can be operated to close the door 14 before any attempts are made to correct the problem. Similarly, the inter-chamber transfer port 30 can be closed if the transfer arm 28 can be retracted into home position. It may be possible to correct some such mechanical misalignment problems simply by deviating from the normal contact sequence. For example, the position of a wafer 48 on the transfer arm 28 may in some cases by adjusted by partially extending the transfer arm 28, so that the edge of the wafer 48 just touches the outside of the door 14, or of the isolation gate over the inter-chamber transfer port 30. If this does not work, the vacuum load lock chamber 12 can be brought back up to atmospheric pressure (with the door 14 of vacuum wafer carrier 10 closed) and the load lock lid 20 opened so that the problem can be manually corrected.

FIGS. 6, 7, and 8 show a single wafer reactor which can be used for reactive ion etching. Many of the process modules described in the present application incorporate at least some of the ideas and advantages of this embodiment, together with additional ideas and additional advantages derived therefrom. (A very similar reactor design can be used for plasma etching, i.e. etching at pressure higher than 100 m Torr. The terms "plasmas etching"and "reactive ion etching" (or "RIE") are sometimes kept distinct in the art, with RIE being used to refer to etching under conditions where plasma bombardment is large, i.e. at lower pressure and with the wafer mounted on the powered electrode. This distinction will not be rigorously observed in the present application. The teachings of the present application are applicable to both plasma and RIE etching as conventionally distinguished, although some of the several features taught by the present application are more advantageous in the context of RIE etching processes.

FIG. 6 shows a process module 104, which can be used in a processing system such as is shown in FIGS. 5A and 5B, as discussed below.

FIG. 6 shows a single wafer reactor which can be used for reactive ion etching or for plasma etching. As discussed above, the transfer arm 28 places a wafer onto the wafer support pins 53 (FIG. 4) and then retracts. At this point the whole lower assembly, including the chamber 112, ground electrode 110, process gas distributor 120, base plate 138, and quartz cylinder 114 are moved upward, using, e.g., an air cylinder or a vacuum feed through (not shown). A bellows 124 permits this vertical motion to occur while maintaining a vacuum-tight interface to the interior of the module 104. This vertical motion causes the backside of the wafer resting on the wafer support pins 53 to make contact with the powered electrode 118, and at this point the sliding pin supports 130 which are attached to the underside of the wafer support pins 53 retract slightly against a leaf spring 132. (Other elastic elements could be used in place of leaf spring 132, to assure a small amount of give in the sliding pin supports 130, so that the wafer is not pressed against the powered electrode 118 with too much force.)

The last portion of the upward travel of this assembly causes the seal 135 (FIG. 7) to make closure between the quartz cylinder 114 at the top of the chamber 112 and the quartz piece 116 which surrounds the powered electrode 118. Thus, when the seal is made, the interior of this process chamber is vacuum-sealed from the remainder of the interior of process module 104.

A helium bleed port 134 is provided to connect a helium supply to the back of the wafer. This helium space means that the space between the low points of the powered electrode 118 and the wafer will be filled with helium, rather than vacuum, and this assure a reasonably low-thermal-resistance and highly repeatable thermal contact between the wafer and the powered electrode 118. The powered electrode 118 can include coolant manifold spaces 136, to which coolant can be supplied.

In an alternative embodiment, the pins 53 are not mounted on sliding pin supports 130 supported by leaf spring 132, but are fixed. Since the helium bleed port 134 assures good thermal contact between the back side of the wafer and the surface of the powered electrode 118, a tolerance of several thousandths of an inch will still permit good RF coupling of the powered electrode 118 to the wafer 48, and still permit good thermal contact between the powered electrode 118 and the wafer 48. A tolerance of this magnitude should provide enough allowance for thermal expansions of chamber walls, variations in seal thickness, variation in wafer thickness, etc., to still permit reliable sealing of the lower chamber portion to the upper portion. Note that, in this embodiment, the quartz cylinder 114 and quartz piece 116 would usefully be shaped slightly differently, to minimize the lateral spread of the plasma adjacent to the face of the wafer. However, it has been found that utilizing sliding pin supports 130 permits the quartz cylinder 114 to confine the plasma closely near the wfaer face 54 as shown in FIG. 7.

FIG. 7 shows the upper portion of the process module of FIG. 6, in the closed position, with a wafer 48 held therein for processing. After the reactor has been closed, the helium bleed can be started through helium bleed port 134 (FIG. 6). At the same time, desired process gases can be provided through a process gas distributor 120.

The process gas distributor 120 is made of quartz, so that it does not pick up eddy currents from the RF power present. Moreover, since the surface of the quartz is highly insulating, the plasme boundary near the quartz will not have as much voltage nor as much current across it as the plasma boundary near a grounded conductive element would. This means that plasma-assisted reactions near the quartz will not occur at as high a rate as they would near a grounded conductive element, so that deposition is reduced. It should also be noted that quartz is a fairly good thermal insulator, and the temperature of the susceptor may therefore be raised (by radiation from the plasma) to 100 or 200 degrees C. This is advantageous for some processes, since raising the temperature of the distributor will further reduce deposition on it.

Under typical RIE operating conditions (10 to 200 microns of pressure, and 100 to 800 watts of applied power) the generated plasma will fill the chamber between the powered electrode 118 and the ground electrode 110 fairly uniformly. Thus, the process gas distributor 120 protrudes into the densest part of the plasma. The process gas distributor 120 is a ring, of perhaps one-half of the diameter of the wafer being processed, with hollow supports which lead down to gas connections 140 (FIG. 6) mounted in the base plate 138. A quick-connect mounting is provided for the quartz process gas distributor 120, so it can rapidly and easily be changed out as desired.

The process gas distributor 120 is usefully spaced away from the surface of the wafer by only four centimeters, for example. This spacing, and the exact shape of the process gas distributor 120, and the spacing of the gas feed ports 122 on the gas distributor, are not critical. These parameters can be changed if desired, but, if modified, they should be selected so that diffusion of process gases and process gas products from the gas feed ports 122 in the process gas distributors 120 provides: (1) diffusion-dominated transport of the process gases and process gas products to the plasma boundary at the face of the wafer 48; and (2) a fairly uniform concentration of the process gases and process gas products at the plasma boundary next to the face of wafer 48. For example, the spacing of the process gas distributor 120 away from the wafer face could be anywhere in the range from one to fifteen centimeters.

Under these low pressure conditions, and given the high area ratio between the area of the powered electrode 118 in contact with the plasma (which, in this embodiment, is essentially the same as the area of wafer 48), and the grounded electrode area (which in this embodiment is essentially the area of ground electrode 110, plus the interior area of chamber 112 and the exposed upper area of base plate 138), a high density of plasma bombardment will occur at the face wafer face 54. As is well-known to those skilled in the art, this plasma bombardment assists in achieving desirable anisotropy effects during etching.

The ground electrode 110 can be cooled, using coolant lines 150 (Figure 6) connected to manifold cavities inside the ground electrode 110. If additional cooling is needed, the chamber 112 may also be cooled. Note that coolant lines 150 are flexible hoses, to accommodate the vertical travel of the whole lower etching chamber 138 as described above. The gas supply tube 152, which supplies process gases through gas connections 140 to the process gas distributor 120, is also flexible for the same reason. If flexure of these hoses is found to generate excess particulates, a gas feed outside the bellows 124, through the side of the base plate 138, could be used instead.

FIG. 8 shows a plan view of the reactor of FIG. 6. The shape of the process gas distributor 120 can be seen more clearly in this plan view. It can also be seen that the base plate 138 includes substantial spaces around the edge of the ground electrode 110, which provide a passage from the gas feed ports 122 (FIG. 6) to a vacuum pump below. The overall gas flow in this reactor is downward, away from the face of the wafer, which assists in reducing particulates. An optional modification is the use of an in situ vacuum particle counter in the chamber 112, so that any increase in particle population in the critical volume can be detected and the opening of chamber 112 delayed until the particle count reaches selected level.

After the desired etching operation is finished, the gas supplied through process gas distributor 120 is cut off, and the process module 104 is pumped down to the same pressure as the rest of the process module (10 to the -3 Torr or less). A holding time may then be interposed, for thermal stabilization of the process module or for release of possible suspended particulates, and then the process module 104 is opened and arm 28 operates as described above to remove the wafer from chamber 12. The position of the arm 28 with the chamber 12 would be the rightmost position of arm 28 shown in FIG. 1.

Note that all of the operations described above can be very easily controlled. No servos or complex negative feedback mechanisms are needed. All the motors described are simple stepper motors, so that multiple modules of this type can be controlled by a single computer control system 206 (FIG. 10). The mechanical stability of the system as a whole--i.e. the inherent correction of minor positioning errors provided by the tapering of the wafer support pins 53, by the slope of the ledges 60 in the wafer carrier, and by the flat contact surface 29 on the backwall of the vacuum wafer carrier 10--helps to prevent accumulation of minor errors, and facilitates easy control.

This advantage of simple control is achieved in part because good control of mechanical registration is achieved. As noted, the docking of the vacuum wafer carrier 10 with position registration platform 18 provides one element of mechanical registration, since the location of the position registration platform 18 with respect to the transfer arm 28 can be accurately and permanently calibrated. Similarly, the vacuum wafer carriers 10 do not need to be controlled on each dimension, but merely need to be controlled so that the location and orientation of the ledges 60 are accurately known with respect to the bottom (or other portion) of the vacuum wafer carrier 10 which mates with position registration platform 18. As described above, this is accomplished by having channels which the vacuum wafer carrier 10 slides into until it rests on the position registration platform 15, but many other mechanical arrangements could be used instead. Various types of electronic and mechanical sensors could provide information about the position and operation of the system for further control and corrective action by the computer control system 206.

Similarly, mechanical registration must be achieved between the home position of the transfer arm 28 and the 3 pins 50 (or other support configuration) which the wafer will be docked to inside the processing chamber. However, this mechanical registration should be a simple one-time setup calibration. Note that angular positioning will be preserved by the vacuum wafer carrier itself, as was noted, whenever the door 14 is closed, spring elements inside it will press each wafer 48 against the flat contact surface 29 of the vacuum wafer carrier 10. Optionally, the vacuum wafer carrier 10 could be provided with a quick-connect vacuum fitting, to permit separate pumpdown on the vacuum wafer carrier 10.

It should be noted that the load lock mechanism described need not be used solely with vacuum wafer carriers 10, although that has been could to be useful. This load lock can also be used with wafer carriers which carry atmospheric pressure inside. Although this is an alternative embodiment, it still carries substantialy advantages, as is discussed above, over prior art load lock operations such as that shown in U.S. Pat. No. 4,609,103, by Bimer et al, issued on Aug. 27, 1984, which is incorporated by reference hereinto.

It should be noted that a vacuum wafer carrier 10 as described can be made in different sizes, to carry any dsired number of wafers. Moreover, a vacuum wafer carrier 10 of this kind can be used to carry or store any desired number of wafers, up to its maximum. This provides additional flexibility in scheduling and process equipment logistics.

FIG. 5A show a sample further alternative embodiment wherein two load locks, each containing a vacuum wafer carrier 10, are both connected to a process station 102 which contains four process modules one or more of which can be a process module 104 or the other process modules disclosed herein or any other suitable module. Unlike the embodiment described above, when the transfer arm 28 reaches through the inter-chamber transfer port 30 from a vacuum load lock chamber 12 into the process station 102, it places the wafer 48 onto one of two wafer stages 105. These wafer stages 105 can be three pin supports similar to pins 53 or two ledge supports, or may have other mechanical configurations as long as there is space underneath the supported wafer for the transfer arm 28 to lower free of the wafer and retract after it has placed the wafer on the supports. The wafer support used should be such as to make the line contact, rather than contact over any substantial area, with the under surface or edge of the wafer.

Another transfer arm assembly 106 is provided inside the process station 102. This transfer arm assembly is generally similar to the transfer arm 28, rotatable transfer arm support 44 and tubular support 46 as used inside the chamber 12, but there are some differences. First, the transfer arm 28 used inside the load lock only needs to move wafers in a straight line. By contrast, the transfer arm assembly 106 must also be able to move radially, to select any one of the process modules 104. Thus, an additional degree of freedom is needed. Second, the reach of the transfer arm assembly 106 need not be the same as the transfer arm 28, the rotatable transfer arm support 44, and tubular support 46 used inside the load lock, and in fact the reach of transfer arm assembly 106 can be larger, to permit adequate spacing of the process modules 104. Third, the transfer arm assembly 106 does not need as much travel in elevation as the transfer arm 28 used in the load locks. Fourth, in the configuration shown, the transfer arm assembly 106 will not have one of its 3 pins 50 resting on a wafer flat, so that the diameter of the circle defined by 3 pins 60 is not the same for transfer arms 28 and 128, even though they are handling wafers of the same diameter.

The tubular support of assembly 106 can be made rotatable and providing a third motor to drive this rotation. Thus, a third degree of freedom for the transfer arm is provided. Similarly, the dimensions of the transfer arm 128 of assembly 106 can simply be scaled as desired. Thus, transfer arm assembly 106 usefully includes a transfer arm rotatably mounted on a transfer arm support 144. The transfer arm support 114 is pivotably mounted to a tubular support (not shown), and an internal shaft, fixed to the transfer arm support 144, extends down through the tubular support. An internal chain drive with two to one gearing translates any differential rotation between tubular support 146 and transfer arm support 144 into a further differential rotation, i.e., over twice as many degrees between transfer arm support 144 and transfer arm 128. An arm drive motor, mounted below the transfer arm assembly 106, is connected to rotate the shaft which is fixed to transfer arm support 144. An arm rotation motor is connected to rotate the tubular support 146. Finally, an elevator mechanism provides vertical motion of the transfer arm assembly 106.

Note that the vertical motion required of transfer arm assembly 106 is not typically as much as that required of the transfer arm 28 in the vacuum load lock chamber 12, since the transfer arm 128 will typically not need to select one of several vertically separated wafer positions like those in the vacuum wafer carrier 10, but wi