CN108290694B

CN108290694B - Wafer plate and mask apparatus for substrate fabrication

Info

Publication number: CN108290694B
Application number: CN201680070352.1A
Authority: CN
Inventors: T·布卢克; A·扎内托; T·佩德森; W·E·小伦斯塔得雷
Original assignee: Intevac Inc
Current assignee: Intevac Inc
Priority date: 2015-10-01
Filing date: 2016-09-30
Publication date: 2021-05-04
Anticipated expiration: 2036-09-30
Also published as: MY190638A; SG10201906641WA; CN108290694A; TW201722822A; WO2017059373A1; PH12018500685A1; KR102447219B1; TWI611998B; JP6816132B2; KR20180059804A; JP2018531510A

Abstract

A system for processing wafers in a vacuum processing chamber. The carrier includes a frame having a plurality of openings, each opening configured to receive one wafer. The transport mechanism is configured to transport a plurality of carriers throughout the system. The plurality of wafer plates are configured to support wafers. An attachment mechanism for attaching a plurality of wafer plates to each carrier, wherein each wafer plate is attached to a respective location at the underside of a respective carrier such that each of the wafers positioned on one of the wafer carriers is positioned within one of the plurality of openings in the carrier. The mask is attached over a front side of one of the plurality of openings in the carrier. An alignment stage supports the wafer plate under the opening in the carrier. The camera is positioned to simultaneously image the mask and the wafer.

Description

Wafer plate and mask apparatus for substrate fabrication

Technical Field

The present application relates to systems for vacuum processing, such as systems used in the manufacture of solar cells, flat panel displays, touch screens, and the like.

Background

Various systems for manufacturing semiconductor ICs, solar cells, touch screens, and the like are known in the art. The processes of these systems are performed in vacuum and include, for example, Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), ion implantation, etching, and the like. There are two basic approaches to such systems: single substrate processing or batch processing. In single wafer processing, only a single substrate is present within the chamber during processing. In a batch process, there are several substrates within the chamber during processing. Single substrate processing enables a high level of control over the processes within the chamber and the resulting films or structures fabricated on the substrate, but results in relatively low throughput. In contrast, batch processing results in lower control over processing conditions and the resulting film or structure, but provides much higher throughput.

In general, batch processing (such as that employed in a system for manufacturing solar cells, touch panels, and the like) is carried out by conveying and manufacturing substrates in the form of a two-dimensional array of n × m substrates. For example, a PECVD system developed by Roth & Rau for solar fabrication utilizes a tray of 5 × 5 wafers to achieve a throughput of 1200 wafers/hour reported in 2005. However, other systems utilize trays having two-dimensional arrays of 6 x 6, 7 x 7, 8 x 8, or even greater numbers of wafers. While the use of trays in a two-dimensional array of wafers increases throughput, the handling and loading and unloading operations of such large trays become complicated.

In some processes, it is desirable to apply a bias (bias), such as an RF (radio frequency) or DC (direct current) potential, to the substrate being processed. However, since batch systems utilize a moving tray with substrates, it is difficult to apply the bias.

Also, some processes may be performed while held horizontally, while some can benefit from a substrate being held vertically. However, vertical loading and unloading of substrates is more complicated than horizontal loading and unloading.

Some processes may require the use of a mask to shield a portion of the substrate from a particular manufacturing process. For example, the mask may be used for contact formation or for edge rejection to prevent shunting (blanking) of the cell. That is, for cells having contacts on the front and back sides, the material used to make the contacts may deposit on the edge of the wafer and form a shunt between the front and back contacts. Therefore, it is desirable to use a mask to discard the edges of the cell during the fabrication of at least the front or back contacts.

As another illustration, for the manufacture of silicon solar cells, it is desirable to deposit blanket metal (blanket) on the back surface to act as a light reflector and electrical conductor. The metal is typically aluminum, but the blanket metal may be any metal used for a variety of reasons, such as cost, conductivity, solderability, etc. The deposited film thickness can range from very thin (e.g., about 10nm) to very thick (e.g., 2-3 um). However, the blanket metal must be prevented from wrapping around the edges of the silicon wafer as this forms a resistive connection, i.e., shunt, between the front and back surfaces of the solar cell. To prevent such connection, a reject area may be formed on the back-side edge of the wafer. The general dimension of the discard area is less than 2mm wide, but it is preferred to make the discard as thin as possible.

One method of forming such a discard region is by using a mask; however, the use of masks has many challenges. Due to the high competitiveness of the solar industry, the production of masks must be very cheap. Moreover, due to the high throughput of solar energy manufacturing equipment (typically 1500-. Also, since the mask is used to prevent film deposition on certain portions of the wafer, the mask must be able to absorb and accommodate the deposition build-up. In addition, since film deposition is done at elevated temperatures, the mask must be able to function properly at elevated temperatures (e.g., up to 350 ℃) while still accurately maintaining the width of the drop out region while accommodating substrate warpage due to thermal stress.

Disclosure of Invention

The following summary is included to provide a basic understanding of some aspects and features of the invention. This summary is not an extensive overview of the invention, and it is therefore intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Embodiments of the present invention provide a modular system architecture in that the system is capable of using different processes and process steps, and is versatile in that the system is adaptable to the fabrication of a variety of devices including, for example, solar cells, flat panel displays, touch screens, and the like. In addition, the system can handle different types and sizes of substrates by simply changing the carrier used without reconfiguration.

The system architecture enables substrate handling separate from vacuum processing, such as loading and unloading in an atmospheric environment. Furthermore, various embodiments enable manual loading and unloading with or without automation, i.e., the system may be implemented without a loading/unloading robot. The system implements stationary or pass-by processing of substrates within a vacuum environment. In certain embodiments, vacuum isolation is provided between each process chamber using an actuated valve. Various embodiments provide electrostatic clamping of the substrate to achieve effective cooling and prevent accidental movement of the substrate. In other embodiments, mechanical clamping is achieved using, for example, a spring-loaded clamp with a release mechanism for loading/unloading the substrate. Various embodiments are also capable of biasing the substrate, or floating the substrate, using, for example, RF or DC bias power.

Various embodiments enable simplified substrate handling by performing handling on linear array carriers and processing on a two-dimensional array of n x m substrates by processing several linear array carriers simultaneously. Other embodiments provide a transport mechanism in which the substrates are processed in a vertical orientation, but loading and unloading is performed while the substrates are manipulated horizontally.

Embodiments of the present invention also use masks to achieve substrate processing, which can be implemented using a dual mask arrangement. A two-piece masking system is configured to mask a substrate and includes: an inner mask consisting of a flat metal sheet having apertures exposing portions of the wafer to be processed; and an outer mask configured to be disposed over and mask the inner mask, the outer mask having an opening cutout of a size and shape similar to those of the substrate, the outer mask having a thickness greater than that of the inner mask. The mask frame may be configured to support the inner mask and the outer mask such that the outer mask is sandwiched between the mask frame and the inner mask. In one example where a dual mask arrangement is used for edge isolation, the size of the open cut in the inner mask is slightly smaller than the size of the solar wafer, such that when the inner mask is placed on the wafer, the inner mask covers the peripheral edge of the wafer, and the open cut in the outer mask is slightly larger than the open cut in the inner mask. A top frame carrier may be used to hold and secure the inner and outer masks to the wafer carrier.

A load and unload mechanism is provided that simultaneously handles four rows of substrates. The loading/unloading mechanism is configured for vertical movement, having a lowered position and a raised position. In its lowered position, the mechanism is configured to simultaneously: the method includes removing a row of processed substrates from a carrier, placing a new row of substrates on an empty carrier, placing the row of processed substrates on a substrate removal mechanism, and retrieving the new row of substrates from a substrate delivery mechanism. The substrate removal mechanism and the substrate delivery mechanism may be conveyor belts that travel in the same or opposite directions. In its raised position, the mechanism is configured to rotate 180 degrees.

In some embodiments an arrangement is utilized wherein the wafer plate is attached to the carrier from the bottom side, while the mask arrangement is attached to the carrier from above. One of the wafer plate or the mask arrangement is attached to the carrier in a fixed orientation while the other can be realigned as each new wafer is loaded. In an exemplary embodiment, the mask arrangement is arranged on the carrier in a fixed orientation. When a new wafer is loaded onto the wafer plate, the wafer plate is brought into its position under the carrier. Subsequently, the alignment of the wafer with respect to the mask arrangement is verified using the camera. Subsequently, the wafer plate may be translated and/or rotated to achieve proper alignment with the mask arrangement. When the correct orientation is reached, the wafer plate is lifted and attached to the carrier by, for example, a series of magnets. In one embodiment, the wafer plate includes suction holes such that a vacuum is applied to the suction holes during the alignment process in order to hold and press the wafer against the wafer plate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain and illustrate the principles of the invention. The drawings are intended to show the major features of exemplary embodiments in a diagrammatic manner. The drawings are not intended to depict every feature of actual embodiments nor relative dimensions of the depicted elements, and are not drawn to scale.

Fig. 1 illustrates an embodiment of a multi-substrate processing system in which a transport carrier supports a linear array of substrates, but processing is performed on a two-dimensional array of substrates.

FIG. 1A shows an example of a system in which the carrier is held in a horizontal orientation during transport and processing; while figure 1B shows an example where the carrier is horizontal during transport and loading/unloading but vertical during processing.

FIG. 2 shows a polycrystalline round carrier according to one embodiment, while FIG. 2A shows a partial cross-section.

Fig. 2B shows an example of a carrier for processing a silicon wafer, and fig. 2C shows an example of a carrier for processing a glass substrate.

Fig. 3A is a top view and fig. 3B is a side view of a loading/unloading mechanism according to one embodiment. Fig. 3C illustrates an embodiment of a substrate alignment mechanism.

Fig. 4 illustrates an embodiment of a vacuum processing chamber 400 that may be used with the disclosed system.

Fig. 5 shows an embodiment of a mask and carrier assembly.

Fig. 6A-6C show three embodiments demonstrating how a vacuum chamber can be equipped with different processing resources of various sizes and configurations.

Fig. 7A-7E show views of a polycrystalline round carrier with an apparatus for dual masks according to various embodiments.

Fig. 8 is a cross section of an enlarged portion of a frame, an outer mask and an inner mask according to one embodiment, and fig. 8A is a cross section of an enlarged portion of a frame, an outer mask and an inner mask according to another embodiment.

FIG. 9 illustrates an embodiment of an outer mask with an inner mask embedded therein.

FIG. 10 illustrates an embodiment of an inner mask for edge isolation.

Fig. 11 shows an embodiment of a single wafer carrier.

Fig. 12 shows an embodiment of the outer mask from a lower side perspective.

FIG. 13 illustrates an embodiment of a top frame supporting an inner mask and an outer mask.

FIG. 14 illustrates an embodiment of an inner mask for forming a plurality of holes in a wafer.

Figure 15 shows an embodiment of a carrier for use with the mask of figure 9.

Fig. 16A-16D illustrate an embodiment in which the wafer plate is attached to the carrier from the bottom side and the dual mask is attached to the carrier from the top side.

FIG. 16E illustrates a dual mask arrangement according to one embodiment.

Fig. 16F is a cross section of a portion of a system according to an embodiment, with the enlarged portion shown in the inset.

Figure 16G illustrates a wafer plate having a vacuum table and a peripheral buffer in accordance with another embodiment.

FIG. 16H illustrates a top portion of the load alignment station according to one embodiment.

Fig. 16I shows a top portion of an unloading station according to one embodiment.

Detailed Description

The following detailed description provides examples that emphasize certain features and aspects of the inventive processing systems claimed herein. Various disclosed embodiments provide a system in which multiple substrates (e.g., semiconductor or glass substrates) are simultaneously processed within a vacuum processing chamber, such as a plasma processing chamber. Although glass substrates, such as those used for touch screens, are not generally considered wafers, it should be understood that references to wafers are used in this disclosure for convenience and ease of understanding, and that glass substrates may be substituted for all of these references.

Fig. 1 is a top view of an embodiment of a multi-substrate processing system in which a transport carrier supports a linear array of substrates, but processing is performed on a two-dimensional array of substrates. In the system 100 shown in fig. 1, substrates are loaded and unloaded at the load/unload station 105, i.e., from the same side of the system. However, it should be understood that the system may also be designed such that the loading station is disposed on one side of the system and the unloading station is disposed on the opposite side of the system. In some embodiments, the loading of the substrate onto the carrier and/or the unloading of the substrate from the carrier may be performed manually, while in other embodiments, automation is provided to perform one or both of these tasks.

The substrates are loaded onto a carrier positioned in the load/unload station 105 and transported from the carrier return station 110. Each carrier supports a linear array of substrates (i.e., two or more substrates arranged in a single row) in a direction perpendicular to the direction of travel within the system. The carrier moves from the load/unload station 105 to the buffer station 115 via the carrier return station 110. The carriers are stopped in the buffer station 115 until a low vacuum lock chamber (LVLL)120 is ready to receive them. In some embodiments, which will be described later, the buffer station also acts as a tilting station, in which horizontally oriented carriers are tilted by 90 ° to assume a vertical orientation. In such embodiments, clips (clips) are used to hold the substrate in place when the substrate is in a vertical orientation.

At the appropriate time, the valve 112 is opened and the carrier positioned in the buffer station 115 is transferred into the LVLL 120. Valve 112 is then closed and the LVLL 120 is evacuated to a rough vacuum level. Thereafter, the valve 113 is opened and the carrier is transferred from the LVLL 120 into a high vacuum lock (HVLL) 125. When the HVLL is pumped to its vacuum level, the valve 114 is opened and the carrier is transferred from the HVLL 125 into the process chamber 130. The system may have any number of process chambers 130 linearly aligned such that a carrier may be transferred from one chamber to the next via a valve positioned between each two process chambers. At the end of the last process chamber, a valve is arranged to open to the vacuum lock opposite to the one in the system inlet, i.e. first the HVLL and then the LVLL. Thereafter, the carrier exits via valve 116 to carrier return module 135. The carriers are returned from the return module 135 to the carrier return station 110 using, for example, a conveyor (not shown) positioned above or below the process chamber 130.

As mentioned above, each carrier supports a linear array of substrates, which makes it easier to load and unload substrates, and makes it easier to process, manipulate and transport the carrier. However, in order for the system to have a high throughput, each process chamber 130 is configured to accommodate and simultaneously process a two-dimensional array of substrates positioned on several (i.e., two or more) carriers arranged in a one-by-one fashion. For greater efficiency, in the particular embodiment of fig. 1, the buffer station 115, the LVLL 120 and the HVLL 125 are each configured to simultaneously receive the same number of carriers as are simultaneously received within the process chamber 130. For example, each carrier may support three glass substrates in a row, but each process chamber is configured to process two carriers simultaneously, thereby processing a two-dimensional array of 3 × 2 substrates.

According to other embodiments, the vacuum lock chamber and buffer chamber are sized to operate on multiple carriers (e.g., two carriers) to provide increased pump/vent and pressure stabilization times. Furthermore, the buffer chamber may be used to transition the carrier motion from a station-to-station motion to a continuous pass-through motion within the processing chamber. For example, if one processing chamber processes the carrier in a stationary mode and the next chamber processes in a traveling mode, a buffer chamber may be provided between the two chambers. The carriers in the system form a continuous stream of carriers in the process chambers or modules, and each process chamber/module may have 5 to 10 carriers that are continuously moved through the process source (e.g., heat source, PVD, etch, etc.) in a head to foot fashion.

As shown in fig. 1, the portion of the system dedicated to the transfer, loading, and unloading of substrates is positioned in an atmospheric environment. On the other hand, all processing is performed in a vacuum environment. Transfer, loading and unloading are much easier in an atmospheric environment than in a vacuum.

Fig. 1A shows one example of a system (such as the system shown in fig. 1) in which the carrier 200 is held in a horizontal orientation during transport and processing. The carrier is returned to the starting point via a linear conveyor 140 positioned above the process chamber. The linear conveyor 140 may be a conveyor belt or a series of motorized wheels. As shown in fig. 1A, each carrier 200 supports four substrates 220 linearly arranged in a row. Also, for illustrative purposes, the top of the chamber 120 is removed so as to expose an arrangement of six carriers that are simultaneously positioned in the chamber 120. Thus, according to this embodiment, twenty-four substrates are processed simultaneously per chamber while four substrates are supported per carrier.

Fig. 1B shows an example where the carrier is horizontal during transport and loading/unloading but vertical during processing. The apparatus of FIG. 1B is very similar to the apparatus of FIG. 1A, except that the vacuum lock chamber and the processing chamber are vertically inverted in order to process substrates in a vertical orientation. The configurations of the vacuum lock chamber and the process chamber in both embodiments of fig. 1A and 1B may be identical, except that they are mounted horizontally in fig. 1A, and vertically with respect to their sides in fig. 1B. Thus, the buffer station 115 and the buffer station 145 located on the other end of the system are modified to include a lift that changes the orientation of the carrier by 90 °, as shown in the buffer station 145.

Fig. 2 illustrates a linear array carrier that may be configured for processing silicon wafers, glass substrates, and the like, according to one embodiment. As shown in fig. 2, the structure of the linear array carrier according to this embodiment is rather simple and inexpensive. It should be understood that the carrier may be configured for different numbers of substrates and substrate sizes simply by mounting different clamps (chuck) on top of the carrier. Also, it should be understood that each process chamber may be configured to receive several carriers simultaneously, thereby simultaneously processing multiple wafers on multiple carriers.

The carrier 200 of fig. 2 is constructed from a simple frame 205, which frame 205 is formed by two transport rails 215 and two ceramic rods 210. The ceramic rods 210 improve thermal insulation between the carrier (not shown) attached thereto and the rest of the chamber. As shown in the inset, at least one side of each ceramic rod 210 forms a fork arrangement 235 with the transfer rail 215. Cavities 245 are formed in the fork arrangement 235 in order to allow the ceramic rods 210 to move freely under thermal expansion (illustrated by the double-headed arrows) without exerting pressure on the transport rails 215.

A magnetic drive bar 240 is provided on each transport track 225 to enable transport of the carriers throughout the system. Magnetic drive rods ride on magnetized wheels to transport the carrier. To improve the cleanliness of the system, the drive rod 240 may be nickel plated. Such magnetic means ensure accurate transport, so that the carrier does not slip due to high accelerations. Also, such magnetic means enable a large spacing of the wheels, so that the carrier is attached to the wheels by magnetic force and can cantilever outward (cantilever) over a large range to span a large gap. In addition, such magnetic means enable the transport of the carrier in a vertical or horizontal orientation, since the carrier is attached to the wheels by magnetic force.

The carrier contact assembly 250 is attached to the transfer rail 225 and mates with a chamber contact assembly 252 (see inset) attached to the chamber. The chamber contact assembly has an insulating rod 260 having contact brushes 262 embedded therein. The contact assembly 250 has a conductive extension 251 (fig. 2A), which conductive extension 251 is interposed between an insulating spring 264 and an insulating rod 260, thereby being pressed against a brush contact 264 to receive a bias voltage from a mating contact. Biasing may be used, for example, for substrate biasing, substrate clamping (for electrostatic clamps), and the like. The bias may be RF or DC (continuous or pulsed). The carrier contact assembly 250 may be disposed on one or both sides of the carrier.

Fig. 2A is a partial cross-section showing how the carrier is transmitted and how the carrier receives bias power. Specifically, fig. 2A shows the drive rod 240 riding on three magnetized wheels 267 attached to the shaft 268. The shaft 268 extends beyond the chamber walls 269 such that the shaft 268 can be rotated by devices outside the internal vacuum environment of the chamber. The shaft 268 is coupled to the motor via a flexible band, such as an O-ring, to accommodate changes in shaft diameter.

Fig. 2B shows an example of a carrier for processing a silicon wafer (e.g., for fabricating a solar cell). In fig. 2B, wafer 220 may be clamped to carrier 223 using, for example, a clamping potential. A lifter (lifter)215 may be used to lift and lower the wafer for loading and unloading. Fig. 2C shows an embodiment where the carrier may be used to process a glass substrate such as a touch screen. In this embodiment, a mechanical spring-loaded clamp or clip 227 may be used to hold the substrate in place. The carrier 224 may be a simple tray (pallet) with means for spring-loaded clips.

Fig. 3A and 3B illustrate an embodiment of a substrate loading and unloading mechanism in conjunction with carrier return. Fig. 3A is a top view and fig. 3B is a side view of the loading/unloading mechanism. As shown in fig. 1A, the conveyor returns the carrier after processing is complete. Subsequently, the carrier is lowered by the elevator 107 and horizontally transferred to the loading/unloading station 105. As shown in fig. 3A and 3B, dual conveyors (i.e., conveyors 301 and 303) are used to bring new substrates for processing and remove processed wafers. Since the system will work exactly the same anyway, it is not important which conveyor brings in new wafers and which removes processed wafers. Also, in this embodiment,

conveyors

301 and 303 are shown conveying substrates in opposite directions, but the same result may be achieved when both conveyors travel in the same direction.

The apparatus of fig. 3A and 3B supports simultaneous manipulation of two carriers. Specifically, in this embodiment, the processed substrates are unloaded from one carrier while new substrates are loaded onto another carrier. In addition, at the same time, the processed substrate is placed on the processed substrate conveyor, and a new substrate is picked up from the new substrate conveyor to be delivered to the carrier in the next round (round). This operation is performed as follows.

The substrate pick-up mechanism is configured to have two motions: rotational movement and vertical movement. Four rows of grippers 307 are attached to the substrate pick-up mechanism 305. The clamp 307 may be, for example, a vacuum clamp, an electrostatic clamp, or the like. In this particular example, four rows of Bernoulli (Bernoulli) grippers are used, i.e., grippers that can hold a substrate using Bernoulli suction. The four rows of grippers are positioned two on each side so that when two rows of grippers are aligned with the carrier, the other two rows of grippers are aligned with the conveyor. Thus, when the pick-up mechanism 305 is in its lowered position, one row of grippers picks up a processed substrate from a carrier and the other row of grippers places a new substrate on the other carrier, while on the other side, one row of grippers places a processed substrate on one conveyor and the other row of grippers picks up a new substrate from the other conveyor. Subsequently, the pick-up mechanism 305 is in its raised position and turned 180 degrees, wherein at the same time the carrier is moved one pitch, i.e. the carrier with the new substrate is moved one step, the carrier from which the processed substrate is removed is moved to a new substrate loading position, and the other carrier with the processed substrate is moved into an unloading position. The pick-up mechanism 305 is then in its lowered position and the process is repeated.

To provide a specific example, in the snapshot of fig. 3A, carrier 311 has processed substrates that are being picked up by a row of grippers on pick-up device 305. Carrier 313 is loading a new substrate from another row of grippers of pick-up device 305. On the other side of pick-up device 305, one row of grippers is placing processed substrates on conveyor 303 while the other row of grippers is picking up new substrates from conveyor 301. When these actions are completed, the pick-up device 305 is lifted to its raised position and turned 180 degrees as indicated by the curved arrow. At the same time, the entire carrier is moved one step, i.e. the carrier 316 is moved to the position previously occupied by the carrier 317, at which time the carrier 313 loaded with new substrates is moved to the position previously occupied by the carrier 316, the empty carrier 311 is moved to the position previously occupied by the carrier 313, and the carrier 318 loaded with processed substrates is moved to the position previously occupied by the carrier 311. The pick-up device is now lowered so that carrier 311 is loaded with new substrates, the processed substrates are removed from carrier 318, the substrates removed from carrier 311 are placed on conveyor 303, and new substrates are picked from conveyor 301. Subsequently, the pickup 305 is raised, and the process is repeated.

The embodiment of fig. 3A and 3B also utilizes an optional mask lifter 321. In this embodiment, a mask is used to create the desired pattern on the surface of the substrate, i.e., to expose certain areas of the substrate for processing while covering other areas to prevent processing. The carrier travels through the system with the mask positioned over the substrate until the carrier reaches the mask lifter 321. When the carrier with the processed substrate reaches the mask lifter (carrier 318 in fig. 3A and 3B), the mask lifter 321 is in its raised position and lifts the mask from the carrier. The carrier may then proceed to an unload station to unload its processed substrate. At the same time, the carrier with the new substrate (carrier 319 in fig. 3B) is moved into the mask lifter, and the mask lifter 321 is in its lowered position, so that the mask is placed onto the new substrate for processing.

As can be appreciated, in the embodiment of fig. 3A and 3B, the mask lifter removes the mask from one carrier and places the mask on a different carrier. That is, the mask does not return to the carrier from which it was removed, but is instead placed on a different carrier. Depending on the design and number of carriers in the system, it will be possible for the mask to return to the same carrier after several turns, but only after being lifted from another carrier. Vice versa, i.e. depending on the design and number of carriers and masks in use, it is possible that each mask is used by all carriers in the system. That is, each carrier in the system will be used with each mask in the system, where the carrier will be moved through the system using a different mask in each process cycle.

As shown in the inset, the carrier elevator can be implemented by providing two vertical transport devices (one on each side of the carrier). Each conveyor consists of one or more conveyor belts 333 actuated by rollers 336. The lift pins 331 are attached to the conveyor belt 333 such that when the conveyor belt 333 moves, the lift pins 331 engage the carrier and move the carrier in a vertical direction (i.e., up or down, depending on which side of the system the elevator is positioned on and the carrier return conveyor is positioned above or below the processing chamber).

Fig. 3C illustrates an embodiment of a substrate alignment mechanism. According to this embodiment, the clamp 345 has a spring-loaded alignment pin 329 on one side and a notch 312 on the opposite side. As shown by the dashed lines and the rotational arrows, the rotational push pin 341 is configured to enter the notch 312 to push the substrate 320 against the alignment pin 329, and then retract. Note that the rotating push pin 341 is not part of the clamp 345 or carrier and does not travel within the system, but is stationary. If a mask is used, the spring loaded alignment pins are pressed to a lower position. Accordingly, a substrate alignment mechanism is provided comprising a clamp having a first side configured with alignment pins, a second side orthogonal to the first side and configured with two alignment pins, a third side opposite the first side and configured with a first notch, and a fourth side opposite the second side and configured with a second notch; the alignment mechanism further includes a first push pin configured to enter the first recess to push the substrate against the first alignment pin, and a second push pin configured to enter the second recess and push the substrate against the two alignment pins.

Fig. 4 illustrates an embodiment of a vacuum processing chamber 400 that may be used with the disclosed system. In the illustration of fig. 4, the lid of the chamber is removed to expose its internal construction. The chamber 400 may be mounted in a horizontal or vertical orientation without any modification to its composition or its configuration. The chamber is constructed of a simple box frame with openings 422 for evacuation. An inlet opening 412 is cut in one side wall while an outlet opening 413 is cut in the opposite side wall to enable the carrier 424 to enter the chamber, traverse the entire chamber and exit the chamber from the other side. A gate valve is provided at each of the

openings

412 and 413, although only the gate valve 414 is shown for clarity of illustration in fig. 4.

To achieve efficient and accurate transfer of the carrier 424 in both horizontal and vertical orientations, the magnetic wheels 402 are disposed on opposite sidewalls of the chamber. The carrier has magnetic bars that ride on magnetic wheels 402. The shaft on which the wheel 402 is mounted extends into the atmosphere outside the chamber, where the shaft is actuated by a motor 401. Specifically, several motors 401 are provided, each motor actuating several shafts with belts (e.g., O-rings). Also, an idler 404 is provided to laterally restrain the carrier.

A feature of the embodiment of fig. 4 is that the diameter of the magnetic wheel is less than the sidewall thickness of the chamber. This enables the magnetic wheels to be positioned within the inlet opening 412 and the outlet opening 413 as shown by the

wheels

406 and 407. Since the positioning of the

wheels

406 and 407 within the inlet and

outlet openings

412 and 413 minimizes the gap that the carrier must span without support from the wheels, the carrier can be transferred more smoothly into and out of the chamber.

Fig. 5 shows an embodiment of a mask and carrier assembly. Proceeding from left to right along a curved arrow, a single substrate mask assembly 501 is mounted on a mask carrier 503 that supports several mask assemblies; and the mask carrier 503 is mounted to the substrate carrier 505. In one embodiment, springs located between floating mask assemblies 501 hold the mask assemblies in place to engage guide pins 507 disposed on the substrate carrier 505 so that each mask is aligned with its corresponding substrate. Each single substrate mask assembly is constructed from an inner foil mask that is inexpensive and capable of multiple reuse. The foil mask is made of a flat sheet of magnetic material with perforations, according to the desired design. The outer mask covers and protects the inner mask by being subjected to a thermal load so that the foil mask does not deform. An aperture in the outer mask exposes an inner mask region having a perforation. The frame holds the inner and outer masks on the mask carrier 503. Magnets embedded in the substrate carrier 505 pull the inner foil mask into contact with the substrate.

Each substrate support (e.g., mechanical or electrostatic chuck) 517 supports a single substrate. Each fixture 517 can be varied to support different types and/or sizes of substrates so that the same system can be used to process different sizes and types of substrates. In this embodiment, the clamp 517 has retractable substrate alignment pins 519 and a means of aligning the substrate over the clamp (provision). In this embodiment, the means for achieving alignment consists of a slot 512 that receives a retractable pin that urges the substrate against the alignment pin 519 and then retracts out of the slot 512. This enables the substrate and the mask to be aligned with the substrate carrier so that the mask is aligned with the substrate.

As can be appreciated, the systems described thus far are inexpensive to manufacture and provide efficient vacuum processing of various substrates (such as solar cells, touch screens, etc.). The system can be configured with two-ended (double end) or single ended loading and unloading, i.e., substrate loading and unloading from one side, or loading from one side and unloading from the opposite side. The substrate is not manipulated in a vacuum. The system is modular in that as many vacuum processing chambers as needed can be installed between the input and output vacuum lock chambers. The vacuum chamber has a simple design with few parts in vacuum. The vacuum chamber may be mounted in a horizontal or vertical orientation. For example, for solar cell processing, the system may process the substrate in a horizontal orientation, while for a touch screen, the substrate may be processed in a vertical orientation. In any event, loading, unloading and transfer in the atmospheric environment is accomplished with the substrate in a horizontal orientation. A process source (e.g., a sputtering source) can be mounted above and/or below the substrate. The system is capable of through-type processing or static processing, even if the substrate is stationary or moving during vacuum processing. The chamber may house a sputtering source, a heater, an implantation beam source, an ion etching source, and the like.

For solar applications, the vacuum chamber may include a low energy injector (e.g., less than 15 KV). For a particular solar cell design (e.g., PERC, IBC, or SE), a mask arrangement may be used to perform the implantation that applies the mask. Also, texture etching may be performed using an ion etching source or laser assisted etching with or without a mask. For point contact cells, a mask with a number of holes aligned with the contacts may be used. Also, a thick metal layer may be formed by successively aligning several PVD chambers and successively forming one layer over another.

For touch panel applications, the chamber may be used to deposit cold and/or hot ITO layers using PVD sources. This process is performed in such a manner that several (e.g., three) touch pads are arranged on each carrier in the width direction and several (e.g., two) carriers are positioned simultaneously within each chamber, to achieve higher throughput and simpler manipulation. The same system can manipulate a touch screen of a tablet computer or a cell phone sized glass without any internal reconfiguration. Briefly, a suitable carrier is constructed while the entire system remains unchanged. Further, the substrate is not manipulated in vacuum.

Handling and processing operations may be the same for all types and sizes of substrates. The empty carrier moves to be loaded from the carrier back to the elevator. If a mask is used, the mask is removed and left at the elevator. The substrate is loaded onto the carrier in an atmospheric environment. The carrier is moved back to the elevator and the mask is placed over the substrate. Subsequently, the carrier is moved into the vacuum lock chamber. In a vacuum, the transport of the carrier is via a simple magnetic wheel positioned in the chamber wall and actuated (energized) from the atmosphere or vacuum environment outside the chamber. The chamber may have valves for isolation and may have a source above or in the drawer (drawer) to process the substrate below. The substrate may be removed at the unload end of the system or may rest on a carrier to return to the load end (i.e., the inlet side of the system). The carriers are returned from the processing end of the system to the loading end of the system on a simple conveyor belt. A simple pin conveyor lifts or lowers the carrier to or from the transfer and unloading station.

Fig. 6A to 6C show three embodiments, showing how a vacuum chamber can be equipped with different process sources of different sizes and configurations. In the example of fig. 6A to 6C, three substrates arranged along the width are presented, but it is of course possible to arrange more or less substrates in the width direction on the carrier. Also, in fig. 6A to 6C, it is presented that the process chamber can accommodate several (e.g., two or three) carriers to perform the process simultaneously. The source shown in fig. 6A-6C may be any process source such as PVD, etching, implantation, etc.

Fig. 6A shows an embodiment in which a single source 601 is disposed on the chamber 600. The single source is used to process all substrates positioned within the chamber 600. The source 601 may have a length and/or width that covers all substrates simultaneously. For some sources, it may be too complex or too expensive to fabricate a single source of such a large size. For example, if the source 601 is a sputtering source, the target body must be made very large, which is expensive, complex, and results in inefficient utilization. Thus, according to the embodiment of fig. 6B and 6C, several smaller sources are used. In the embodiment of FIG. 6B, each of the sources 603A-603C is wide enough to cover only a single substrate, but it may also cover more than one substrate along the length direction (i.e., in the direction of substrate travel). By staggering the sources so that each source covers only one of the substrates in each carrier, all of the substrates can be processed. This arrangement is particularly suitable for pass-through processing. In contrast, in the embodiment of FIG. 6C, each of the sources 606A-606C is wide enough, i.e., covers all of the substrates in one carrier in a direction perpendicular to the direction of substrate travel, but they are too narrow to cover all of the substrates positioned within the chamber. In fact, in some embodiments, each of the sources 606A-606C is even narrower than one substrate. This arrangement is equally applicable to pass-through or stationary processing.

The above-described embodiments provide a vacuum processing chamber having a vacuum enclosure sized to receive and process several substrate carriers simultaneously. The housing is also configured to simultaneously support a plurality of processing sources. The processing source may be, for example, a sputtering source, which may be a narrow source of sufficient length to span all of the substrates held by the substrate carrier, but of a width that may be narrower than the width of the substrates positioned on the carrier. Several such sources may be positioned in a back-to-back manner (back-to-back) over the entire length or part of the length of the chamber in the direction of carrier travel. The chamber has several shafts positioned on two opposite sides to transport the carrier within the chamber. Each shaft is rotated by a flexible belt actuated by a motor. Each axle has several magnetic wheels positioned thereon in alternating pole order (pole order), i.e., when the outer periphery of one wheel is magnetized south and the inner diameter is magnetized north, the outer periphery of an adjacent wheel is magnetized north and the inner diameter is magnetized south. The chamber further having an inlet sidewall with an inlet opening and an outlet sidewall opposite the inlet sidewall and having an outlet opening; wherein the magnetized wheel device is positioned within the inlet sidewall and protrudes into the inlet opening, and the magnetized wheel device is positioned within the outlet sidewall and protrudes into the outlet opening so as to drive the substrate carrier through the inlet opening and the outlet opening.

The disclosed system is a linear system, wherein the chambers are arranged linearly in such a way that one chamber is coupled to the next, so that the substrate carriers enter the system from one side, traverse all chambers in a linear manner, and exit the system on the opposite side. The carrier is moved directly from one chamber to the next via a gate valve separating the chambers. Once the carrier exits the vacuum environment of the system, the carrier enters a lift and moves vertically to a return conveyor that transfers the carrier horizontally back to the entry side of the system where it enters another lift and is moved vertically to load a new substrate and again enters the vacuum environment of the system. The carrier is maintained in a horizontal orientation while being transported in an atmospheric environment. However, in one embodiment, when the carrier enters a vacuum environment, it is rotated to a vertical orientation such that the substrate is processed while being held in the vertical orientation.

The system may have a loading and unloading station positioned on the inlet side of the system. The loading and unloading system has a rotating structure on which four rows of grippers are positioned, two on each side of the axis of rotation. On each side of the axis of rotation, a row of grippers is configured for unloading the processed substrate and a row of grippers is configured for loading a new substrate. The rotating structure is configured for vertical movement wherein the structure picks up a substrate when the rotating structure is in its lowered position and rotates 180 degrees when the rotating structure is in its raised position. And, when the structure is in its lowered position, one row of grippers picks up a substrate while the other row of grippers positions (i.e., releases) its substrate on each side of the axis of rotation. In one embodiment, two conveyors are provided across the entrance of the system, with one conveyor delivering new substrates and the other conveyor removing processed substrates. The rotary structure is configured such that in its lowered position one row of grippers is aligned with the conveyor delivering new substrates and the other row of grippers is aligned with the conveyor removing processed substrates. At the same time, on the other side of the axis of rotation, one row of grippers is aligned with the empty carrier, while the other row of grippers is aligned with the carrier holding the processed substrates.

In some embodiments, means are provided for applying an electrical potential to the substrate. Specifically, each carrier includes a conductive strip that is inserted into a slider that includes an elongated contact brush and a compliant (compliant) insulating spring configured to press the conductive strip against the elongated contact brush as the carrier enters the process chamber. An insulating strip (such as a Kapton strip) may be used to attach the conductive strips to the carrier.

When the processing of the substrates requires the use of masks, the masks may be individually disposed on each substrate, or one mask may be formed to cover all the substrates of one carrier at the same time. The mask may be held in place using, for example, magnets. However, for precise processing, the mask must be made very thin, and thus may be deformed by thermal stress during processing. In addition, thin masks can collect deposits quickly, and these deposits can interfere with the accurate placement and masking of the mask. Therefore, it would be advantageous to use a dual mask arrangement according to embodiments disclosed below.

Fig. 7A to 7E show views of a polycrystalline round carrier with an apparatus for dual masks according to various embodiments. FIG. 7A shows a polycrystalline circular carrier having a dual mask arrangement, wherein the mask arrangement is in a lowered position such that the inner mask is in intimate physical contact with the wafer; FIG. 7B shows a multi-wafer carrier with a dual mask arrangement, wherein the mask arrangement is in a raised position, thereby enabling replacement of the wafer; FIG. 7C illustrates a multi-wafer carrier with a dual mask arrangement, including a wafer lifter for loading/unloading wafers; FIG. 7D shows a partial cross-section of a polycrystalline circular carrier with a dual mask arrangement, wherein the mask arrangement and wafer lifter are in a raised position; and FIG. 7E shows a partial cross-sectional view of a polycrystalline circular carrier with a dual mask arrangement, wherein the mask arrangement and the wafer lifter are in a lowered position.

Referring to fig. 7A, a polycrystalline circular carrier, also referred to as a carrier support 700, has three individual single circular carriers or carriers 705 supported by a carrier frame or bar 710, the carrier frame or bar 710 being made of, for example, ceramic. Each single wafer carrier 705 is configured to hold a single wafer with a dual mask arrangement. In fig. 7A, the dual mask arrangement is in the lowered position, but no wafer is in any carrier so as to expose the configuration of the carrier. In fig. 7B, the dual mask arrangement is shown in a raised position, again with no wafer in any carrier. In the embodiment of fig. 7A-7E, lifter 715 is used to raise and lower the dual mask device; however, to reduce cost and complexity, lifter 715 may be eliminated and the dual mask arrangement may be lifted manually. A transfer rail 725 is provided on each side of the frame 710 to enable transfer of the carrier 700 throughout the system.

Each single wafer carrier 705 has a base 730 (visible in fig. 7B), the base 730 having a raised frame 732 with recesses 735 to support wafers suspended by their periphery. The base 730 with the frame 732 forms a pocket 740 under the suspended wafer, the pocket 740 being beneficial for capturing broken wafer fragments. In some embodiments, the frame 732 may be separate from the base 730. The outer mask 745 is configured to be mounted on the frame 732 so as to cover the frame 732 and to cover the periphery of the inner mask, but to expose a central portion of the inner mask corresponding to the wafer. This is illustrated by the cross-sectional view in the embodiment of fig. 8.

In fig. 8, the base or carrier 805 has a raised frame 830 with recesses 832 that support the wafer 820 at its periphery. The base 805 with the frame 830 forms a pocket 840 and the wafer is suspended over the pocket. A series of magnets 834 are positioned within the raised frame 830 so as to surround the perimeter of the wafer 820. In some embodiments, particularly for high temperature operations, the magnet 834 may be made of samarium cobalt (SmCo). An inner mask 850 is positioned over the raised frame 830 and wafer 820 and held in place by magnets 834 such that the inner mask physically contacts the wafer. The outer mask 845 is positioned over and physically contacts the inner mask 850 such that the outer mask covers the perimeter of the inner mask 850 except for the areas where the inner mask is designed to impart processing to the wafer. Fig. 9 shows an example of an outer mask 945 in this example made of a folded sheet of aluminum, wherein the outer mask covers the inner mask except for a small perimeter edge 952 since this example is used for edge shunt isolation processing. Fig. 10 shows an example of an inner mask 750 for edge shunt isolation, which is a substantially flat piece of metal with an aperture that is the same size and shape as the wafer except that it is slightly smaller than the size of the wafer (e.g., 1-2mm smaller than the size of the wafer). In the embodiment of fig. 8, a mask frame 836 is provided to enable supporting and lifting the inner and outer masks off of the carrier. In this configuration, the outer mask 845 is sandwiched between the mask frame 836 and the inner mask 850.

Fig. 8A shows another embodiment, which may be used, for example, to form a contact pattern on the backside of a wafer. In this embodiment, the carrier forms a top platform to support the wafer over its entire surface. The magnets 834 are embedded throughout the area of the carrier below the top surface of the carrier. The inner mask 850 covers the entire surface of the wafer 820 and has a plurality of holes depending on the contact design.

Returning to fig. 7A-7E, lifters 715 may be used to lift the outer and inner masks together. Also, a wafer lifter 752 may be used to lift the wafer off of the frame 730 so that the wafer may be replaced with a new wafer for processing using the robot. However, the

lifters

715 and 752 may be eliminated and the operations of lifting the mask and replacing the wafer may be accomplished in a manual manner instead.

In the embodiment described above with reference to fig. 8, the carrier supports the wafer on its peripheral edge such that the wafer is suspended. Pockets formed beneath the wafer capture broken wafer fragments and prevent entrapment of the deposited material. On the other hand, in the embodiment of fig. 8A, the wafer is supported over its entire surface. The mask assembly is lowered to a position for sputtering or other forms of processing and is manually or mechanically lifted for loading and unloading of the wafer. A series of magnets on the carrier help hold the inner mask in place and bring the inner mask into intimate contact with the wafer. After repeated use, the inner and outer masks may be replaced while the rest of the carrier assembly may be reused. The frame 810, also referred to as the sidebar of the mask assembly, may be made of a low thermal expansion material such as aluminum oxide or titanium.

According to the above embodiments, the inner mask establishes a close and gapless contact with the substrate. The outer mask protects the inner mask, carrier and carrier frame from the deposited material. In the illustrated embodiment, the outer mask opening and the inner mask opening are in a quasi-square shape, suitable for application to a single crystal solar cell during an edge shunt isolation process. During other processes, the inner mask has certain aperture arrangements, while the outer mask has quasi-square shaped apertures. The quasi-square shape is a square whose corners are cut according to a round ingot from which a wafer is cut. Of course, if a polycrystalline square wafer is used, the outer and inner mask openings are also square.

Fig. 11 shows an embodiment of a single wafer carrier 1105. The wafer rests on the recess 1132 at its periphery. Magnets 1134, shown in phantom, are disposed entirely around the wafer inside the carrier. Alignment pins 1160 are used to align the external module to carrier 1105. Fig. 12 shows an embodiment of the outer mask from a lower perspective. The outer mask 1245 has alignment holes or recesses 1262 corresponding to the alignment pins 1260 of the carrier 1205.

Fig. 13 illustrates an embodiment of a top frame 1336 for holding the outer and inner masks and securing the masks to the carrier. Top frame 1336 may be comprised of, for example, two longitudinal bars 1362, which two longitudinal bars 1362 are held together by two transverse bars 1364. The outer mask is held within pocket 1366. Alignment holes 1368 are provided to align the top frame with the carrier.

Fig. 14 shows an example of an inner mask having a hole pattern designed, for example, for making a plurality of contacts on a wafer. Such an inner mask may be used with the carrier shown in fig. 15, where the magnets 1534 are distributed over the entire area below the wafer surface. The magnets are oriented in alternating polarizations.

The upper or outer mask may be made of thin (e.g., about 0.03 inch) aluminum, steel, or other similar material and configured to mate with the substrate carrier. The inner mask is made of a very thin (e.g., about 0.001 to 0.003 inch) flat steel sheet or other magnetic material and is configured to nest within the outer mask.

According to other embodiments, there is provided an apparatus for supporting a wafer during processing, the apparatus comprising: a wafer carrier or carrier having a raised frame with recesses for supporting a wafer around its periphery and confining the wafer to a predetermined position; an inner mask configured to be disposed over the raised frame, the inner mask having an aperture arrangement configured to mask a portion of the wafer and expose a remaining portion of the wafer; and an outer mask configured to be positioned over the raised frame over the inner mask, the outer mask having a single opening configured to partially cover the inner mask. A top frame carrier may be used to hold and secure the inner and outer masks to the wafer carrier.

The magnets are positioned in the carrier and alternate either completely around the frame in the form of N-S-N or completely under the entire surface of the carrier and directly under the wafer. The outer mask and the inner mask are designed to be held to the frame only by magnetic force, so that the substrate can be conveniently and rapidly loaded and unloaded.

The mask assembly can be removed from the wafer carrier and support frame to load the substrate into the carrier. The outer and inner masks are raised as part of the mask assembly. Once the wafer is positioned on the carrier in the wafer pocket, the mask assembly is lowered back down onto the carrier. The inner mask overlaps the top surface of the wafer. Magnets in the carrier frame pull the inner mask down into intimate contact with the substrate. This forms a tight compliant seal against the edge of the wafer. The outer mask is designed to prevent deposition on the thin, compliant inner mask. As described above, the deposition process may cause the inner mask to heat up, causing the mask to warp and loose contact with the wafer. If the mask loses contact with the wafer, a metal film may be deposited in the exclusion area on the surface of the substrate wafer. The pocket and the frictional force generated by the magnet prevent the substrate and the mask from moving relative to each other during conveyance and deposition, and the outer mask prevents film deposition from occurring on the inner mask and prevents the inner mask from warping.

The mask assembly may be periodically removed from the system with the carrier by using a vacuum carrier exchanger. The carrier exchanger is a portable vacuum housing with a carrier transport mechanism. It enables carriers to be exchanged "on the fly" without stopping the continuous operation of the system.

Fig. 16A-16D illustrate embodiments that may be implemented within a loading station, such as loading station 105. In this embodiment, a wafer plate is used to support the wafer, wherein the wafer plate is removably attached to the carrier from the bottom side while the dual mask is attached from the top side. Fig. 16A to 16D show only relevant portions of the system to simplify the explanation. Also, some elements have been removed in order to enable visualization of features of the embodiments.

In fig. 16A-16D, a carrier 1600 includes a simple frame 1605 having a plurality of openings 1602 having the shape of a substrate (e.g., a semiconductor wafer) to be processed, but may be slightly larger to enable passage of the substrate therethrough. A plurality of wafer plates 1610 are attached to the bottom of each carrier 1600. Wafer plate 1610 is typically a simple form of aluminum plate and may include an attachment mechanism that attaches the wafer plate to the bottom side of carrier 1600. When wafer board 1610 is attached to carrier 1600, substrate 1620 positioned on the front side of wafer board 1610 is aligned with opening 1602 and exposed through opening 1602. The attachment mechanism may include mechanical clips, springs, magnets, and the like. In the example shown, a plurality of magnets 1612 (fig. 16C) are used as the attachment mechanism.

Masking devices 1649 are positioned on the top side of each carrier 1600 such that each masking device 1649 covers one substrate exposed through the opening 1602. The mask arrangement 1645 may be a dual mask arrangement similar to the arrangement shown in fig. 9 and 10, but other arrangements may be used depending on the process to be performed. For example, fig. 16E shows a dual mask device in which the inner mask 1650 is a simple stamped flat piece of metal, which in this example is made of a paramagnetic material. The outer mask 1645 is a simple aluminum plate with an opening similar in shape to the opening of the inner mask but slightly larger. Note that in such a dual mask arrangement, only the inner dimension of the opening of the inner mask is critical, while all other dimensions do not require high manufacturing tolerances, thus reducing the complexity and cost of manufacturing the mask. And in this device the mask is attached to the carrier 1600 in a fixed orientation such that the opening of the inner mask 1650 is aligned with the opening 1602 in the carrier.

For clarity, the carrier 1600 is shown in some figures as if suspended, but of course, the carrier is supported and transported by a transport mechanism such as that shown in fig. 1A. On the other hand, the wafer plates travel independently on dedicated conveyor belts 1632 until they are delivered to stage 1664 and then attached to the carrier 1600. The operation of the mechanism is as follows. The lift mechanism 1662 is configured to load the wafer plate 1610 onto a wafer plate linear conveyor (such as a conveyor belt) 1633. A stage mechanism 1664 is provided to align each wafer plate 1610 so that the wafer positioned thereon is aligned with the opening of the inner mask 1650 (using the camera 1670) and then lift the wafer plate so that it attaches to the carrier 1600. In this embodiment, when the wafer plate is positioned on the stage 1662, a vacuum is applied through the holes 1614 in the wafer plate 1610 to hold the wafer and prevent it from moving during the alignment process. Since clamping the wafer plate to the carrier prevents the wafer from moving, the vacuum may be terminated once the wafer plate is attached to the carrier 1600.

In addition, a loading mechanism 1605 (fig. 16D) may be used to load the substrate onto the wafer plate 1610. Note that the wafer plate 1610 may be loaded with substrates prior to loading the wafer plate 1610 onto the carrier. For example, at the time shown in fig. 16A, the following procedure is shown: two wafer plates (identified as a and B) have no wafers, one wafer plate (identified as C) has wafers seated thereon but the wafer plate has not yet been attached to carrier 1600, and one wafer plate (identified as D) has wafers seated thereon and is raised and attached to carrier 1600.

An advantage of the embodiment shown in fig. 16A to 16D is that the transfer of the wafer plate for loading and unloading wafers is done separately from the transfer of the carrier and mask. In this way, the wafer plate can be removed from the system for cleaning. Furthermore, since the wafer plates are made of relatively inexpensive aluminum slabs (slab), they can be easily replaced with new wafer plates without affecting the operation of the system.

As shown more clearly in fig. 16B and 16D, the empty carrier 1600 is delivered to the workstation by a lift 1635 and then positioned onto a conveyor (e.g., conveyor belt 1633). In this example, each carrier is configured to accommodate two wafer plates for processing two wafers simultaneously, but the carrier may be made to accommodate other numbers of wafer plates. Another conveyor (e.g., conveyor belt 1632) conveys the wafer plate 1610 below the conveyor 1633. A wafer loading mechanism (e.g., robot 1605) places the wafers onto the wafer plate 1610. As the wafers are placed onto the wafer plate 1610, the conveyor 1632 moves the wafer plate 1610 to an alignment station above the alignment stage 1664. A vacuum pump 1647 is then used to deliver suction to the wafer plate to hold the wafer on the wafer plate and to hold the wafer plate on the alignment stage. Specifically, the wafer plate has vacuum holes 1614 below the wafer. When suction is applied through these holes 1614, the wafer is held on the wafer plate and seals the holes. Thus, the same suction force blocked by the wafer causes the wafer plate to be held against the alignment stage by vacuum. Simultaneously, conveyor 1633 delivers the empty carrier 1600 to an alignment station directly above stage 1664. The carrier in the alignment station has a mask arrangement 1649 attached to the carrier over the opening 1602. To perform the alignment, actuator 1667 lifts the carrier 1600 off the conveyor so that the carrier is mechanically held in a stationary position. The stage 1664 then lifts the wafer plate and performs a rotation or translation as necessary to align the wafer to the opening of the mask 1645 as determined by the controller 1671 through the image obtained by the camera 1670. Once proper alignment is achieved, the stage further raises the wafer plate until the wafer plate contacts the underside of the carrier. The vacuum is then terminated such that the wafer plate is attached to the carrier via mechanical or magnetic means. Subsequently, stage 1664 is lowered to accept another wafer plate while conveyor 1633 moves the loaded carrier out of the alignment station and brings an unloaded carrier to repeat the process.

In one embodiment, the procedure for loading and processing a substrate proceeds as follows: the carrier without wafers is returned from the unload station. In embodiments where the wafer plates are delivered by attachment to a carrier, the wafer plates are removed from the carrier and lowered to a conveyor, for example, by a lift mechanism 1662. Alternatively, the wafer plate 1610 may be delivered independently of the carrier. The loading mechanism positions a plurality of wafers, one wafer per wafer plate, onto a respective wafer plate. Subsequently, the wafer plate and carrier are independently moved to an alignment station where a camera 1670 images the wafer and mask. These images are provided to a controller 1671, which controller 1617 checks the alignment of the mask opening with respect to the wafer. That is, in this particular example, the mask 1645 is attached to the carrier in a fixed orientation. The wafer carrier is positioned on an x-y-z-theta stage 1664 located below the camera. The position/orientation of the wafer relative to the mask opening is calculated by the controller using the image provided by the camera 1670, and the controller 1671 sends a signal to the stage 1664 to correct the orientation by translating or rotating the x-y-z-theta stage 1664 as necessary. Subsequently, the wafer plate is lifted by the stage and attached to the carrier, wherein the wafer is positioned in contact with the inner mask. In this position, the magnetic force holds the wafer plate in the carrier so that the wafer cannot move, and the vacuum can then be released. Also, the same magnetic force keeps the dual mask device pressed against the wafer. Thus, the wafer is prevented from moving relative to its alignment position. That is, in one embodiment, when the wafer plate is in the alignment station and the wafer has been positioned in the alignment position, a vacuum is applied to the wafer via the wafer plate to prevent the wafer from moving. However, once the wafer plate is attached to the carrier and the mask contacts the wafer, the vacuum suction may be terminated. The carrier is then moved through the system for processing, and the process is repeated when the processing is complete.

In one embodiment, after processing is complete, the wafer is removed from the wafer plate in an unloading station, and then the wafer plate is tilted into a vertical orientation. This enables the debris to be dumped before the wafer plate is returned for further processing if any of the wafers are broken during processing.

Fig. 16F is a cross-section of a portion of the system, with the enlarged portion shown in the inset. It can be seen that a dual mask arrangement is used in this embodiment, where the inner mask 1650 is covered by the outer mask 1645. Magnets 1612 are disposed around the perimeter of wafer plate 1610 to hold wafer plate 1610 to the bottom side of carrier 1605.

In a specific embodiment, the following procedure is performed, wherein each carrier is capable of supporting five wafer plates. Five wafers are loaded onto five separate wafer plates. The five loaded wafer plates are then moved to the alignment station. In this particular embodiment, each wafer plate has a shim with magnets disposed around the edge. The gasket may be made of a fluoroelastomer of the type designated FKM under ASTM D1418 and ISO 1629 standards. In the alignment station, the alignment stage lifts five wafer plates off the conveyor (where five separate alignment stages are provided to align five wafer plates simultaneously). When the wafer plate is lifted off the conveyor, the vacuum holds the wafer plate firmly on the lifter and the wafer firmly on the wafer plate. At this time, five cameras respectively image five wafers. The conveyor then moves the carrier into an alignment station directly above the wafer plates so that each opening in the carrier is above one of the wafer plates. The carrier is then lifted off the conveyor belt to position the carrier in a mechanically fixed stationary position. Subsequently, the camera is activated to image five openings on the carrier. The system then calculates the x-axis and y-axis for each mask opening and for each of the five wafers. Subsequently, the five X/Y/theta stages move each wafer so that the X-axis and Y-axis of each wafer coincide with the X-axis and Y-axis of each corresponding mask. Subsequently, the five wafer plates are lifted upward until the wafer plates contact and are attached to the carrier such that the wafers on each wafer plate are positioned within the respective openings in the carrier and contact the respective inner masks. Subsequently, the vacuum is released, so that the wafer plate is now mechanically or magnetically attached to the carrier. Subsequently, the carrier and table are lowered and the procedure is repeated for the second row.

Fig. 16G shows an alternative embodiment of a wafer plate 1610. In this embodiment, the wafer plate 1610 is still made of an aluminum slab. Three vacuum mesas (mesas) 1613 are disposed on the front side of the wafer plate 1610, each mesa having vacuum holes 1614. In one embodiment, the mesas are made of a soft material and each mesa includes a seal 1611 around each aperture 1614. Thus, when a wafer is placed over the wafer plate 1610 and vacuum is applied to the mesas, the wafer is held over the three mesas by the vacuum so that the wafer does not contact the surface of the wafer plate 1610. Since only three mesas are provided, no force is applied to the wafer to bend or break it. Also, a buffer ring 1618 is disposed around the periphery of the wafer plate 1610. Magnets 1612 are embedded in bumper ring 1618. In this embodiment, the buffer ring does not provide a hermetic seal to the wafer to avoid pumping the wafer toward the surface of the wafer plate 1610. This is accomplished by, for example, using a porous material to fabricate the buffer ring 1618 or providing air channels 1619 to provide fluid communication from the environment to the space between the wafer and the top surface of the wafer plate 1610.

FIG. 16H illustrates a top surface of a bed plate 1672, according to one embodiment, which plate 1672 may be mounted to a loader table 1669 or an alignment table 1664, or to both. A pedestal 1672 is secured to the top of the loader table 1669 and the alignment table 1664, and the wafer plate 1610 is seated on the pedestal 1672. As shown in fig. 16H, two sets of vacuum holes are provided through the top surface of bed plate 1672: the first set of holes 1668 align with and form vacuum paths to corresponding vacuum holes 1614 of the wafer plate 1610 to deliver suction to the wafer in order to hold the wafer to the wafer plate 1610. The second set of holes 1667 provide suction to hold the wafer plate 1610 to the seat of the alignment stage 1664. Thus, in one embodiment, when the carrier is delivered to the loading station, the loading stations are raised and suction is activated to at least the second set of holes 1667 such that each loading station attaches a respective wafer plate by vacuum force. When the load station is lowered, the wafer plate 1610 is separated from the carrier by the vacuum force holding the wafer plate to the seat plate 1672. Since in one embodiment the carrier is returned without a wafer (which is unloaded at the unload station), there is no need to deliver vacuum to the bore 1668 during the process. In fact, these holes may be plugged or the loading station provided with a bed plate 1672 with only vacuum holes 1667.

Fig. 16I shows the top surface of a bed plate 1674, which bed plate 1674 may be mounted to an unloading station, such as at the carrier return chamber 135 shown in fig. 1, 1A, and 1B. A pedestal plate 1674 is fixed to the top of the unloading station, and the wafer plate 1610 is mounted on the pedestal plate 1674. As shown in fig. 16I, the first set of holes 1668 are blocked or the first set of holes 1668 are not provided such that there is no vacuum access to the corresponding vacuum holes 1614 of the wafer plate 1610. That is, there is no suction applied to the wafer in the unload station to hold the wafer to the wafer plate 1610. The second set of holes 1667 provide suction to hold the wafer plate 1610 to the seat of the alignment stage 1664. Thus, in one embodiment, when a carrier is delivered to the unload station, suction to holes 1667 is initiated to hold the respective wafer plates by vacuum force. Subsequently, as indicated by the curved arrow, the unload station tilts seat plate 1674 so that if there is any broken wafer debris on wafer table 1610, the debris will slide off wafer plate 1610 and into collection slot 1682.

As can be appreciated from the above disclosure, there is provided a system for processing wafers, the system comprising: a loading station having a loading table movable in a vertical direction and having a loading seat plate having a first set of suction holes; an alignment station having an alignment stage movable in an x-y-z direction and a rotational direction and having an alignment shoe with a second set of suction holes and a third set of suction holes; an unloading station having an unloading table movable in a vertical direction and an inclined direction and having an unloading seat plate having a fourth set of suction holes, the unloading seat plate assuming a vertical orientation when the unloading table is moved in the inclined direction; at least one vacuum processing chamber located between the alignment station and the unloading station; a plurality of wafer plates, each wafer plate configured to support one wafer and having a fifth set of suction holes configured to apply vacuum to wafers positioned on the wafer plate; a transfer mechanism configured to transfer the plurality of wafer plates sequentially from the loading station to the alignment station, the vacuum processing chamber, the unloading station, and back to the loading station; wherein the first, second, and fourth sets of suction holes are configured to apply a vacuum to the wafer plate, the third set of vacuum holes being aligned with and providing fluid communication to the fifth set of suction holes. The system may further include a plurality of carriers, each carrier configured to support a plurality of wafer plates from an underside of the carrier; and a plurality of masks, each mask attached over a top surface of one of the carriers.

Each wafer plate may include three mesas, each mesa receiving one of the suction holes. Each land may further include a seal around the suction aperture. Each wafer plate may also include a cushion ring and a plurality of magnets attached to the cushion ring. The system may include a container configured to receive wafer fragments from the wafer plate when the unloading station is moved in the tilted direction. The alignment station may also include a camera aligned to image the wafer on the wafer plate and to image the mask attached to the carrier, the wafer plate being mounted on the alignment stage. Also, the controller receives the image from the camera and sends an alignment signal to the alignment stage in order to align the wafer to the mask. The transport mechanism may include a first transport belt configured to transport the carrier and a second transport belt configured to transport the wafer plate.

While the present invention has been discussed in terms of exemplary embodiments of specific materials and specific steps, it will be appreciated by those skilled in the art that variations to these specific examples may be made and/or used, and that such structures and methods will be derived from the understanding afforded by the described and illustrated practices and the description of operation, to facilitate modifications that may be made without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A system for processing a wafer in a vacuum processing chamber, comprising:

a plurality of carriers, each of the carriers comprising a frame having a plurality of openings, each of the openings configured to receive one wafer;

a plurality of wafer plates, each wafer plate configured to support a wafer;

a transport mechanism configured to transport the plurality of wafer plates and to transport the plurality of carriers throughout the system;

an attachment mechanism for attaching the plurality of wafer plates to each of the carriers, wherein each wafer plate is attached to a respective location at the underside of a respective carrier such that the one wafer positioned on each wafer plate is positioned within one of the plurality of openings in the carrier;

a plurality of masks, each of the masks attached over a top side of one of the plurality of openings in the carrier;

an alignment stage configured to support one of the wafer plates below one of the plurality of openings of the carrier, the alignment stage configured to perform translational, rotational, and lifting motions;

a camera positioned to image one of the plurality of masks and to image a wafer positioned on one of the wafer plates when the wafer plate is positioned on the alignment stage;

a controller to receive the image from the camera and send a correction signal to the alignment stage.

2. The system of claim 1, wherein the plurality of masks comprises:

a plurality of inner masks, each inner mask configured to be disposed over one of the plurality of openings in the carrier, the inner masks having a pattern of openings that mask a portion of the wafer and expose a remaining portion of the wafer; and

a plurality of outer masks, each outer mask configured to be placed over a respective inner mask, the outer masks having openings configured to partially cover the inner masks.

3. The system of claim 1, wherein each wafer plate comprises a flat plate made of aluminum.

4. The system of claim 3, wherein the attachment mechanism comprises a plurality of magnets attached to each wafer plate of the plurality of wafer plates.

5. The system of claim 4, wherein each wafer plate of the plurality of wafer plates further comprises a vacuum hole.

6. The system of claim 1, further comprising a conveyor belt configured to convey the wafer plate to a location within a field of view of the camera.

7. The system of claim 1, wherein the transfer mechanism comprises a first linear conveyor configured to transfer the carrier throughout the system and a second linear conveyor configured to transfer the wafer plate when the wafer plate is unloaded from the carrier.

8. The system of claim 5, wherein the alignment stage comprises a bed plate having a first set of vacuum holes aligned with the vacuum holes of the wafer plate and a second set of vacuum holes configured to deliver suction to hold the wafer plate to the bed plate.

9. The system of claim 5, further comprising an unload table comprising an unload seat plate configured to block the vacuum holes of the wafer plate to prevent fluid communication to the vacuum holes, the unload seat plate comprising a set of vacuum holes configured to deliver suction to hold the wafer plate to the unload seat plate.

10. The system of claim 1, further comprising a container configured for collecting substrate debris from the wafer plate and a substrate unloading station having a tilt mechanism for tilting the wafer plate to a vertical orientation above the container for collecting any substrate debris from the wafer plate.

11. A system for processing wafers, comprising:

a loading station having a loading table movable in a vertical direction and having a loading bed plate having a first set of suction holes;

an alignment station having an alignment stage movable in an x-y-z direction and a rotational direction about the z direction and having an alignment shoe with a second set of suction holes and a third set of suction holes;

an unloading station having an unloading table movable in a vertical direction and an inclined direction and having an unloading seat plate having a fourth set of suction holes, the unloading seat plate assuming a vertical orientation when the unloading table is moved in the inclined direction;

at least one vacuum processing chamber located between the alignment station and the unloading station;

a plurality of wafer plates, each wafer plate configured to support one wafer and having a fifth set of suction holes configured to apply vacuum to wafers positioned on the wafer plate;

a transfer mechanism configured to transfer the plurality of wafer plates from the loading station to the alignment station, the vacuum processing chamber, the unloading station, and return the plurality of wafer plates to the loading station in succession;

wherein the first, second, and fourth sets of suction holes are configured to apply a vacuum to the wafer plate, the third set of suction holes being aligned with and providing fluid communication to the fifth set of suction holes.

12. The system of claim 11, further comprising a plurality of carriers, each carrier configured to support a plurality of wafer plates from an underside of the carrier.

13. The system of claim 12, further comprising a plurality of masks, each mask attached over a top surface of one of the carriers.

14. The system of claim 11, wherein each wafer plate includes three mesas, each mesa receiving one of the fifth set of suction holes.

15. The system of claim 14, wherein each of the mesas further comprises a seal around a respective one of the fifth set of suction holes.

16. The system of claim 14, wherein each wafer plate further comprises a buffer ring and a plurality of magnets attached to the buffer ring.

17. The system of claim 11, further comprising a container configured to accept wafer fragments from a wafer plate as the unload station moves in the oblique direction.

18. The system of claim 13, wherein the alignment station further comprises a camera aligned to image wafers positioned on a wafer plate seated on the alignment stage and to image masks attached to a carrier.

19. The system of claim 18, further comprising a controller that receives the image from the camera and sends an alignment signal to the alignment stage to align the wafer to the mask.

20. The system of claim 12, wherein the transport mechanism comprises a first conveyor belt configured to transport the carrier and a second conveyor belt configured to transport the wafer plate.

21. A method for processing a wafer in a vacuum processing chamber, comprising:

securing a mask on a top surface of a carrier, the mask overlapping an opening in the carrier;

loading a wafer onto a top surface of a wafer plate;

transferring the wafer plate with the wafers to an alignment station and placing the wafer plate onto an alignment table;

starting a camera to image the wafer on the alignment stage;

transferring the carrier with the mask to the alignment station;

activating the camera to image the mask;

calculating a degree of misalignment using the images of the wafer and the mask, and actuating the alignment stage to align the wafer to the mask;

once the wafer is aligned with the mask, raising the alignment stage so as to attach the wafer plate to the bottom side of the carrier such that the wafer is positioned within the opening in the carrier;

lowering the alignment stage;

transferring the carrier into the vacuum processing chamber to process the wafer.

22. The method of claim 21, further comprising applying suction to the wafer while the wafer plate is positioned on the alignment stage.

23. The method of claim 21, wherein securing the mask comprises attaching an inner mask to the carrier and attaching an outer mask over the inner mask.

24. The method of claim 21, wherein attaching the wafer plate to the bottom side of the carrier comprises applying a magnetic force between the wafer plate and the carrier.

25. The method of claim 24, further comprising applying the magnetic force to the mask.

26. A method for processing a wafer in a vacuum processing chamber, comprising:

conveying a wafer plate to a loading position, and loading a wafer onto the wafer plate;

moving the wafer plate to an alignment station and placing the wafer plate on an alignment stage;

applying suction to hold the wafer on the wafer plate;

imaging the wafer by using a camera, and calculating an x axis and a y axis of the wafer according to the image;

transferring a carrier into the alignment station and positioning the carrier over the wafer plate such that an opening in the carrier is over the wafer plate, wherein a mask having a mask opening is positioned over the carrier;

lifting the carrier to position the carrier in a mechanically fixed rest position;

activating the camera to image the mask opening on the carrier and calculating an x-axis and a y-axis of the mask opening;

actuating the alignment stage to move the wafer plate such that the x-axis and the y-axis of the wafer coincide with the x-axis and the y-axis of the mask opening;

lifting the wafer plate upward until the wafer plate contacts and is attached to the carrier such that the wafer is positioned within the opening in the carrier;

releasing the suction force; and the number of the first and second groups,

transferring the carrier with the wafer plate into the vacuum processing chamber.

27. The method of claim 26, wherein the applying suction comprises applying suction to hold the wafer to the wafer plate and to hold the wafer plate to the alignment stage.

28. A method as claimed in claim 26 further comprising transporting the carrier out of the vacuum processing chamber and loading the wafer plate onto an unload station, and actuating the unload station to tilt the wafer plate to remove any wafer fragments located on the wafer plate.