The invention relates generally to an apparatus and a method for cooling a substrate, such as a semiconductor wafer.
A semiconductor device is generally fabricated by repetitively performing a series of processes, such as photolithography, diffusion, etching, ion implantation, deposition, and metallization processes, on a substrate (e.g., a wafer). The manufacturing equipment for fabricating a semiconductor device includes apparatus for performing each of these processes, such as a process chamber into which a substrate is loaded to perform each process. Further, semiconductor device manufacturing equipment can also include at least one load lock chamber connected to a process chamber, a cassette or carrier that can hold a number of substrates, and a mechanical transfer mechanism for moving substrates among different equipment, including the process chamber and the load lock chamber.
In a typical semiconductor fabrication operation, at least one substrate is loaded onto a cassette and moved from an input stage into the load lock chamber while the load lock chamber is vented to atmosphere. The load lock chamber is then pumped down to a desired high vacuum pressure. Thereafter, the substrate in the load lock chamber is mechanically transferred to a process chamber for processing, where the substrate is subjected to high processing temperature. When processing is completed, the substrate is moved from the process chamber and placed into a cooling station prior to returning the substrate to the load lock chamber. Cooling of a substrate is necessary to avoid damaging temperature-sensitive apparatus associated with handling post-process wafers. Exemplary temperature-sensitive apparatus include, but are not limited to, the atmosphere robot arm and its associated components, as well as plastic wafer storage cassettes. After cooling, the substrate is transferred back to the original cassette located in the load lock chamber. Subsequent to the other substrates in the load lock chamber being processed in a similar manner, the load lock chamber is vented to atmospheric pressure.
A load lock chamber thus functions as a transition chamber between the process chamber, which is maintained under vacuum, and the input stage, which is under atmospheric pressure. A load lock chamber allows substrates to be transferred into the process chamber without venting the process chamber to atmosphere, thereby reducing processing times in the process chamber and minimizing exposure of the process chamber to atmospheric contamination.
The present invention provides a load lock chamber with integrated cooling capability. Specifically, the cooling systems and methods of the present invention is implemented in a load lock chamber to take advantage of the mechanisms that are already in place (e.g., the existing gas delivery system) and can be adapted for cooling a substrate. This integrated apparatus increases system throughput and decreases physical footprint because processed substrates can be transferred from a process chamber into a load lock chamber without the need for separate cooling. Further, the systems and methods of the present invention facilitates uniform cooling of a substrate in the load lock chamber.
In one aspect, the invention features an apparatus for cooling a substrate having (i) a top surface and a bottom surface and (i) at least one vertical side surface corresponding to a substrate thickness. The apparatus comprises a chamber configured to receive the substrate. The chamber comprises a plurality of sidewall sections surrounding the substrate and oriented in a vertical direction substantially parallel to the vertical side surface of the substrate. The apparatus also includes at least one gas inlet port on a first side wall section of the chamber. The gas inlet port is configured to introduce a cooling gas into the chamber in a lateral direction parallel to the top and bottom surfaces of the substrate. The apparatus further includes at least one gas outlet port on a second side wall section of the chamber located substantially opposite of the first side wall section of the chamber with the substrate disposed therebetween. The gas outlet port is configured to conduct at least a portion of the cooling gas out of the chamber along the lateral direction. The gas inlet port and the gas outlet port, in combination, are adapted to cause the cooling gas to cooperatively flow across the top and bottom surfaces of the substrate in the lateral direction to cool the substrate.
In another aspect, a method is provided for cooling a substrate having (i) a top surface and a bottom surface and (i) at least one vertical side surface corresponding to a substrate thickness. The method includes securing the substrate in a chamber. The chamber comprises a plurality of sidewall sections surrounding the substrate and oriented in a vertical direction substantially parallel to the vertical side surface of the substrate. The method also includes introducing, via at least one gas inlet port, a cooling gas into the chamber in a lateral direction parallel to the top and bottom surfaces of the substrate. The gas inlet port is located on a first side wall section of the chamber. The method further includes conducting, via at least one gas outlet port, at least a portion of the cooling gas out of the chamber along the lateral direction. The gas outlet port is located on a second side wall section of the chamber substantially opposite of the first side wall section of the chamber with the substrate disposed therebetween. The method also includes cooling, by a flow of the cooling gas from the gas inlet port to the gas outlet port, the top and bottom surfaces of the substrate along the lateral direction.
Any of the above aspects can include one or more of the following features. In some embodiments, the at least one gas outlet port is substantially aligned with the substrate in the vertical direction to facilitate cooling of the top and bottom surfaces of the substrate. In some embodiments, the at least one gas inlet port is substantially aligned with the substrate in the vertical direction.
In some embodiments, at least one bumper is provided that is located in the chamber. The bumper is raised in the vertical direction to prevent lateral movement of the substrate caused by the cooling gas flow. In some embodiments, the bumper is integrated with a pad in the chamber on which the substrate is placed.
In some embodiments, a clamping pin is provided that is located in the chamber. The clamping pin is adapted to exert a physical pressure on the substrate in the vertical direction to prevent at least one of a vertical or lateral movement of the substrate caused by the cooling gas flow. In some embodiments, the clamping pin is retractable in the vertical direction.
In some embodiments, at least one second gas inlet port is provided that is located on a top wall of the chamber. The second gas inlet port is configured to introduce a second gas into the chamber in the vertical direction. In some embodiments, the second gas inlet port is adapted to conduct the second gas to exert a gas pressure on the substrate in the vertical direction to prevent at least one of a vertical or lateral movement of the substrate in the chamber.
In some embodiments, the chamber is a load lock chamber. In some embodiments, one or more valves are included in a gas delivery system and are in fluid communication with the gas inlet port. The valves are adjustable to provide variable flow rate of the cooling gas via the gas inlet port to control a cooling rate of the substrate.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating the principles of the invention by way of example only.
The advantages of the technology described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the technology.
Generally, the load lock chamber 100 is defined by multiple sidewall sections 112, a top wall 114 and a bottom wall 116 that substantially encase the substrate 108 in the holder 106. The sidewall sections 112 can be oriented in a vertical direction 118 substantially parallel to the vertical side surface of the substrate 108. The top and bottom walls 114, 116 of the chamber 100 are positioned relative to the top and bottom surfaces 108a, 108b, respectively, of the substrate 108, such as parallel to the top and bottom surfaces of the substrate 108.
The one or more gas inlet ports 104 are located on a first side wall section 112a of the chamber 100 and are configured to introduce a cooling gas, such as a nitrogen (N2) gas, into the chamber 100 in a lateral direction 120 substantially parallel to the top surface 108a and the bottom surface 108b of the substrate 108 and perpendicular to the vertical direction 118. In general, directing a cooling gas to flow across the top and bottom surfaces 108a, b of the substrate 108 facilitates heat transfer from the substrate 108 to the gas, thereby reducing the temperature of the substrate 108.
The one or more gas outlet ports 110 are located on a second side wall section 112b of the chamber 100 and are configured to conduct at least a portion of the cooling gas out of the chamber 100 along the lateral direction 120. The second side wall section 112b is located substantially opposite of the first sidewall section 112a with the substrate 108 and the holder 106 disposed between the two sections 112a,b. This opposite-wall arrangement of the gas inlet ports 104 and gas outlet ports 110 allows at least a portion of the nitrogen gas to cooperatively flow across the top and/or bottom surfaces 108a,b of the substrate 108 to cool the substrate 108 before exiting from the chamber 100.
In some embodiments, the gas manifold 102 is configured to deliver a cooling gas to the chamber 100 to cool the substrate 108. Specifically, the gas manifold 102 can be configured to introduce as well as control the introduction of a cooling gas from at least one gas source (not shown) into the chamber 100 via one or more of the inlet ports 104 fluidly coupled to the first side wall section 112a. In some embodiments, the gas manifold 102 is connected to the same gas source (not shown) and/or delivery system (not shown) that are traditionally used by the load lock chamber 100 to deliver a gas to the chamber 100 for adjusting the internal pressure of the chamber 100. That is, the gas (e.g., nitrogen) that is typically used for restoring the internal pressure in the load lock chamber 100 from vacuum to atmospheric pressure may be used by the manifold 102 to cool the substrate 108 in the chamber 100. In some embodiments, the same gas is used for both cooling and pressure adjustment. In some embodiments, the gas manifold 102 also includes one or more valves 122 in fluid communication with one or more of the gas inlet ports 104 to control the flow rate of the gas delivered therethrough. The valves 122 are adjustable, either manually by an operator or automatically by a computer numerical controller, to provide adjustable flow rate of the cooling gas delivered via one or more of the gas inlet ports 104. This enables control of the velocity of the cooling gas, thereby providing variable cooling rate for cooling the substrate 108 in the chamber 100. In some embodiments, the substrate 108 can be cooled at different cooling rates over time in response to variable system throughput requirements by selectively manipulating the valves 122 of the manifold 102. In some embodiments, the valves 122 are adjusted to achieve turbulence in the cooling gas flow for the purpose of enhanced thermal transfer. For example, if two valves 122 are included in the manifold 102, one valve 122 can be adjusted to offer slow venting by restricting the gas flow to minimize the pressure burst into the evacuated volume, while the other valve 122 can be adjusted to offer a variable flow rate, which provides an adjustable cooling rate. The resultant gas flow can be turbulent in nature.
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In some embodiments, the one or more gas inlet ports 104 and/or the one or more gas outlet ports 110 are suitably arranged on their respective sidewall sections to enhance the uniform distribution of the cooling gas across the top and bottom surfaces 108a, 108b of the substrate 108. For example, at least one gas inlet port 104 can be substantially aligned with the substrate 108 in the vertical direction 118, such as at about the same vertical height as the substrate 108 in the chamber 100, to facilitate cooling of the top and bottom surfaces 108a, 108b of the substrate 108. Likewise, at least one gas outlet port 110 can be substantially aligned with the substrate 108 in the vertical direction 118 to further enhance uniform cooling.
In another aspect, the present invention features various mechanisms for securing the substrate 108 to the load lock chamber 100. In cases where the cooling gas flow across the substrate 108 has a high velocity, the cooling gas flow can potentially disturb and move the substrate 108. Therefore, it may be desirable to secure the substrate 108 within the chamber 100 to prevent substrate movement. However, when the velocity of the cooling gas is low, the substrate 108 is unlikely to move, thus may not need to be secured.
In some embodiments, the clamping pin 502 is attached to an actuator 600.
At step 804, a cooling gas, such as nitrogen gas, is introduced into the chamber 100 via at least one gas inlet port 104 that is configured to conduct the gas in the lateral direction 120 substantially parallel to the top and bottom surfaces 108a, 108b of the substrate 108. The gas inlet port 104 is located on the first side wall section 112a of the chamber 100. In some embodiments, an operator can manipulate one or more valves coupled to the gas inlet port 104 to achieve a variable flow rate of the cooling gas. In some embodiments, the flow rate of the cooling gas is adjusted to create laminar or turbulent flow conditions.
At step 806, the cooling gas is adapted to exit from the chamber 100 via at least one gas outlet port 110 along the lateral direction 120. The gas outlet port 110 is located on a second side wall section 112b of the chamber 100 substantially opposite of the first side wall section 112a of the chamber 100 with the substrate 108 disposed therebetween.
Such lateral flow of the cooling gas from the inlet port 104 to the outlet port 110 is adapted to cool both the top and bottom surfaces 108a, 108b of the substrate 108 at step 808. Specifically, the gas inlet port 104 and/or the gas outlet port 110 are positioned on their respective side wall sections 112 to allow substantially uniform flow of the cooling gas across the top and bottom surfaces 108a, 108b of the substrate 108. For example, at least one of the gas inlet port 104 or the gas outlet port 110 can be positioned along its corresponding side wall section at about the same vertical height as the substrate 108 in chamber 100.
One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.