Patent Application
20110064545
1. Field of the Invention
Embodiments of the present invention relate to apparatus and methods for processing substrates. Particularly, embodiments of the present invention provide apparatus and methods for transferring substrates during processing.
2. Description of the Related Art
In manufacturing of semiconductor devices, substrates sometimes are processed at high temperatures. In existing systems, substrates generally remain in the processing chamber to cool off after processing at high temperatures to avoid breaking from thermal shock. Cooling off the substrates in the processing chamber takes away production time from the processing chamber causing cost of ownership to increase. Additionally, cooling off substrates in the processing chamber requires frequent cooling down and heating up of the processing chamber causing temperature swings in the processing chamber. The temperature swings in the processing chamber may cause deposits or films formed on internal surfaces of the processing chamber to flake off and increase particle contamination. Frequent cooling and heating of the processing chamber also increases energy cost.
Embodiments of the present invention provide methods and apparatus for substrate transferring before, after or between high temperature processing to avoid thermal shock, increase efficiency of processing chambers, and reduce energy consumption.
Embodiments of the present invention generally provide apparatus and methods for transferring substrate during processing. More particularly, embodiments of the present invention provide a substrate transfer mechanism for heating substrates and/or controlling temperature of substrates during transferring.
One embodiment of the present invention provides a robot blade assembly for supporting a substrate or a substrate carrier thereon. The robot blade assembly comprises a base plate, an induction heating assembly disposed on the base plate, and a top plate disposed above the induction heating assembly.
Another embodiment of the present invention provides a cluster tool. The cluster tool comprises a transfer chamber having a transfer volume, a load lock coupled to transfer chamber, and one or more processing chambers coupled to the transfer chamber. The one or more processing chambers are configured to processing substrates at elevated temperature. The cluster tool further comprises a substrate transfer mechanism disposed in the transfer volume and configured to transfer substrates among the load lock and the one or more processing chambers, and an induction heating assembly configured to heat substrates being transferred by the substrate transfer mechanism.
Yet another embodiment of the present invention provides a method for processing one or more substrates. The method comprises transferring the one or more substrates from a first chamber to a second chamber by a transfer mechanism while heating the one or more substrates using an induction heating element to a first temperature, and processing the one or more substrates in the second chamber at a second temperature. The first temperature is substantially close to and lower than second temperature.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Embodiments of the present invention generally provide apparatus and methods for transferring substrates during processing. More particularly, embodiments of the present invention provide a substrate transfer mechanism for heating substrates and/or controlling temperature of substrates during transferring.
Embodiments of the present invention provide apparatus and methods for transferring substrates at high temperature without thermal shock, therefore, improving throughput by eliminating cooling and heating periods during processing.
In one embodiment of the present invention, a substrate transfer mechanism comprises a transfer blade having an induction heating assembly configured to provide induction heating to substrates and/or substrate carriers being transferred. In one embodiment, the induction heating assembly comprises one or more planar spiral coils configured to heat substrates and/or a carrier of substrates with inductive energy. In one embodiment, the transfer blade further comprises a reflective foil configured to reflect the electromagnetic field towards the substrate and/or carrier being heated. In one embodiment, the transfer blade comprises an infrared reflective film to avoid heating of the transfer blade and the one or more spiral planar coils.
In another embodiment, heating elements are disposed in a transfer path of the substrates, for example, in a transfer chamber, to heat the substrates or maintain the substrates at a high temperature during transfer. In one embodiment, one or more induction heating elements are disposed over a chamber lid of a transfer chamber.
Substrate transfer mechanisms of the present invention can be used to rapidly heat substrates and/or maintain substrates at a high temperature while transferring the substrates. In one embodiment, a substrate transfer mechanism with induction heating elements is used to preheat substrates during transfer to a hot processing chamber to avoid thermal shock. In another embodiment, a substrate transfer mechanism with induction heating elements is used to retrieve substrates at a high temperature without thermal shock by maintaining the substrates at a high temperature using induction heating. In another embodiment, one or more portions of the substrate transfer path, such as a transfer chamber, are heated to prevent thermal shock to substrates during transfer.
The cluster tool 100 comprises a transfer chamber 106 having a transfer region 107. The cluster tool 100 comprises a first processing chamber 102 and a second processing chamber 104 coupled to the transfer chamber 106. In one embodiment, the processing chambers 102, 104 may be configured to deposit layers for a LED structure. The processing chambers 102, 104 may be a hydride vapor phase epitaxial (HVPE) chamber or a metal organic chemical vapor deposition (MOCVD) chamber.
A robot assembly 117 is disposed in the transfer region 107 and configured to transfer substrates to and from the first and second processing chambers 102, 104. In one embodiment, the robot assembly 117 comprises a heating element and is configured to transfer substrates while heating the substrates to a high temperature or maintaining the substrate at a high temperature.
The cluster tool 100 further comprises a load lock chamber 108 coupled with the transfer chamber 106 and a load station 110 coupled with the load lock chamber 108. The load lock chamber 108 and the load station 110 are configured to load substrates to the first processing chamber 102 and the second processing chamber 104 through the transfer chamber 106. In one embodiment, the cluster tool 100 further comprises a batch load lock chamber 109, configured for storing a plurality of substrate carriers, coupled with the transfer chamber 106.
The load station 110 is configured as an atmospheric interface to allow an operator to load a plurality of substrates for processing into the confined environment of the load lock chamber 108, and to unload a plurality of processed substrates from the load lock chamber 108. In one embodiment, substrates for processing may be grouped in batches and transported by a conveyor tray 111 on a carrier plate 112. In another embodiment, the load station 110 may be an automatic loading station configured to transfer substrates between carrier plates and transferring cassettes.
The load lock chamber 108 provides an interface between the atmospheric environment of the load station 110 and the controlled environment of the transfer chamber 106. Substrates are transferred between the load lock chamber 108 and the load station 110 via the slit valve and between the load lock chamber 108 and the transfer chamber 106 via another slit valve. In one embodiment, the load lock chamber 108 may comprise multiple carrier supports that are vertically stacked. The carrier supports may be vertically movable to facilitate loading and unloading of a carrier plate 112.
The load lock chamber 108 is coupled to a pressure control system (not shown) which pumps down and vents the load lock chamber 108 to facilitate passing the substrate between the vacuum environment of the transfer chamber 106 and the substantially ambient (e.g., atmospheric) environment of the load station 110. In addition, the load lock chamber 108 may also comprise features for temperature control.
The transfer chamber 106 is generally maintained at a vacuum state or a low pressure state. In one embodiment, the transfer chamber 106 may have a controlled environment maintained by an inert gas, such as helium gas and nitrogen gas, a reducing gas, such as ammonia, or combinations thereof.
The robot assembly 117 is operable to transfer substrates among the load lock chamber 108, the batch load lock chamber 109, the processing chamber 104 and the processing chamber 102. In one embodiment, the robot assembly 117 may comprise heated end effectors configured to keep the substrates at elevated temperature during transfer. In one embodiment, the robot assembly 117 is configured to keep substrates at a temperature higher than about 350° C. during transfer among the processing chambers. In one embodiment, the robot assembly 117 is configured to heat the substrates to higher than about 700° C. In another embodiment, the robot assembly 117 is configured to heat the substrates between about 700° C. and about 1100° C.
The batch load lock chamber 109 having a cavity for storing a plurality of substrates placed on the carrier plates 112 therein. A storage cassette may be moveably disposed within the cavity. The storage cassette may comprise a plurality of storage shelves supported by a frame. In one embodiment, the batch load lock chamber 109 may be configured to clean the substrates prior processing. In one embodiment, the batch load lock chamber 109 may have one or more heaters configured to heat the substrates disposed therein and may be connected to an inert gas source and/or a cleaning gas source to perform a thermal cleaning of the substrates prior to processing.
During an operation, for example manufacturing LED devices, a carrier plate 112 containing a batch of substrates is loaded on the conveyor tray 111 in the load station 110. The conveyor tray 111 is then moved through a slit valve into the load lock chamber 108, placing the carrier plate 112 onto the carrier support inside the load lock chamber 108, and the conveyor tray returns to the load station 110. While the carrier plate 112 is inside the load lock chamber 108, the load lock chamber 108 is pumped and purged with an inert gas, such as nitrogen, in order to remove any remaining oxygen, water vapor, and other types of contaminants.
After the batch of substrates have been conditioned in the batch load lock chamber 109, the robot assembly 117 may pick up the carrier plate 112 and transfer the carrier plate 112 to the processing chamber 102 for a MOCVD or HVPE process. In one embodiment, the robot assembly 117 heats the carrier plate 112 and the substrates thereon to a temperature close to the temperature in the processing chamber 102 during transfer so that the carrier plate 112 can be disposed on the heated processing chamber 102 without thermal shock. Induction heating may be used to achieve rapid heating and without heating up the robot assembly 117 itself. During processing, such as in HVPE processing, the substrates may be heated in the processing chamber 102 to a temperature up to about 1100° C.
After processing in the processing chamber 102, the robot assembly 117 picks up the carrier plate 112 from the processing chamber 102 without waiting for the carrier plate 112 to cool down. To avoid thermal shock to the carrier plate 112 and the substrates, the induction heating element in the robot assembly 117 is activated to maintain the high temperature of the carrier plate 112 and the substrates and to prevent dramatic temperature drop. In one embodiment, an RF power source is applied to the induction heating element in the robot assembly 117 and the current and/or duration of the RF power may be adjusted to maintain the carrier plate 112 at a desired temperature range.
The carrier plate 112 is transferred from the processing chamber 102 to the processing chamber 104 for another process, for example a MOCVD process. In one embodiment, the processing chamber 104 may be heated at a temperature about 800° C., and the carrier plate 112 may be maintained at a temperature between 700° C. to about 800° C. during transferring. Similarly, after processing in the processing chamber 104, the robot assembly 117 picks up the carrier plate 112 from the processing chamber 104 without waiting for the carrier plate 112 to cool down. The induction heating element in the robot assembly 117 is activated to maintain the high temperature of the carrier plate 112 and the substrates and to prevent dramatic temperature drop.
The base plate 241 may be formed from a dielectric material, or any material that is not responsive to induction heating. In one embodiment, the base plate 241 is formed from quartz material.
In an embodiment, the base plate 241 may comprise an infrared reflective coating 242 on surfaces facing the induction heating assembly 243. The infrared reflective coating 242 is configured to reflect infrared energy from the induction heating assembly 243 and the heated substrate 113/carrier plate 112 to prevent the base plate 241 from heating up by the infrared energy. In an embodiment, the infrared reflective coating 242 comprises a titanium nitride film. The titanium nitride film may be about 0.5 mm in thickness. In another embodiment, the infrared reflective coating 242 may comprise a gold film.
In one embodiment, the blade 204 further comprises a ferrite liner 244 disposed under the induction heating assembly 243. The ferrite liner 244 is configured to shield the inductive field of the induction heating assembly 243 from the base plate 241, therefore, preventing any induction heating of the base plate 241. In one embodiment, the ferrite line 244 is a foil made of ferrite material with a thickness about 2 mm.
The induction heating assembly 243 generally comprises one or more coils 255 disposed over the base plate 241. Each coil 255 is connected to a RF power source 248 which provides high frequency alternating current to the coil 255. The induction heating assembly 243 further comprises a capacitor 249 coupled to the RF power source 248 in a parallel manner. In one embodiment, the capacitor 249 may be cooled by a fluid coolant, such as water. In one embodiment, the capacitor 249 may be used to adjust the phase of the RF power applied to the one or more coils 255.
The induction heating assembly 243 is configured to rapidly heat a substrate or a substrate carrier made of electrically conducting material by applying a RF current to the one or more coils 255. During heating, the high frequency alternating current in the one or more coils 255 causes eddy currents within an electrically conducting object being heated. The resistance to the eddy current in the electrically conducting object leads to Joule heating of the object.
Embodiments of the present invention comprise controlling induction heating by controlling one or more of operating parameters, such as the frequency of the RF power source 248, duration of the RF power applied, power of the RF power source 248, spacing between the one or more coils 255 and the object being heated, such as the carrier plate 112, and spacing between neighboring wires of the coil 255. In one embodiment, the frequency of the RF power source is about 40 kHz to about 100 kHz. In another embodiment, the frequency of the RF power source is about 45 kHz to about 65 kHz. In another embodiment, the frequency of the RF power source is below about 50 kHz. In one embodiment, the power of the RF power source is about 10 kW. In one embodiment, a carrier plate 112 may be heated by the coils 255 to about 1000° C. in about 20 seconds.
The carrier plate 112 may be made from a material subject to induction heating. In one embodiment, the carrier plate 112 is made of graphite. In another embodiment, the carrier plate 112 is made of graphite coated with silicon carbide. In another embodiment, the carrier plate 112 is made of silicon carbide.
Each of the one or more coils 255 is a planar spiral coil wound from a cable having a plurality of wires individually wrapped in an insulator. In one embodiment, each planar spiral coil may have about 10 turns. In another embodiment, neighboring planar spiral coils may be wound along opposite directions so that, when RF power of the same phase is applied to the neighboring coils, the currents within outer portion of the neighboring planar spiral coils are of the same direction, therefore, do not cancel one another. Alternatively, neighboring planar spiral coils may be wound along the same direction, and a phase alternating capacitor may be used within the circuit of one of the coil to make sure that currents within wires of the neighboring coils are not off opposite directions.
The top plate 245 is generally fabricated from a dielectric material which is not subject to induction heating. In one embodiment, the top plate 245 is also made of an infrared transparent material. In one embodiment, the top plate 245 is made of quartz. In one embodiment, the top plate 245 is also coated with an infrared reflective coating, such as a titanium nitride film or a gold film.
As discussed above, one or more coils may be used in providing induction heating. The one or more coils may be arranged according to the heating needs. In one embodiment, as shown in
Embodiments of the present invention also provide methods and apparatus for inductively heating substrates and/or carriers using induction heating elements positioned along a transfer path, for example in transfer chambers and load locks. In one embodiment, one or more induction heating elements may be disposed outside a transfer chamber and configured to heat substrates or carriers while the substrates and carriers are within the transfer chamber. The one or more induction heating elements may be positioned on a lid of the transfer chamber.
The transfer chamber 500 comprises a chamber bottom 501, sidewalls 503 disposed over the chamber bottom 501, and a chamber lid 502 disposed over the sidewalls 503. The chamber bottom 501, sidewalls 503 and chamber lid 502 define a transfer volume 504. A robot 510 is disposed within the transfer volume 504. The robot 510 has a robot blade 511 configured to support and transfer a carrier plate 112. In one embodiment, the robot blade 511 comprises induction heating elements, similar to robot blades described above. In another embodiment, the robot blade 511 does not include any heaters.
A plurality of slit valve openings 505 are formed through the sidewalls 503. Each slit valve opening 505 provides an interface with other chambers, such as a processing chamber 102, and a load lock chamber 109. Slit valves 507 may be used to selectively open and close the slit valve openings 505 so that the transfer volume 504 can be selectively in fluid communication with the chambers connected to the transfer chamber 500. When the slit valve 507 is open, the robot blade 511 can extend through the slit valve opening 505 to pick up or drop off a carrier plate 112 in the chamber connected thereto.
In one embodiment, a vacuum pump 530 is connected to the transfer volume 504 so that the transfer chamber 500 can be maintained at a vacuum state or a low pressure state. In another embodiment, the transfer volume 504 has a controlled environment maintained by an inert gas, such as helium gas and nitrogen gas, a reducing gas, such as ammonia, or combinations thereof.
The transfer chamber 500 comprises an induction heating assembly 509 disposed outside the transfer chamber. In one embodiment, the induction heating assembly 509 is disposed adjacent the chamber lid 502. The chamber lid 502 has a window 512. The induction heating assembly 509 is configured to heat substrates on the carrier plate 112 in the transfer chamber 500 through the window 512.
The induction heating assembly 509 generally comprises one or more coils 520. The coils 520 may be planar spiral coils. In one embodiment, the coils 520 include two parallel rows as shown in
The coils 520 may comprise two or more coils for uniform heating. In one embodiment, the coils 520 comprises an inner heating element 522 and an outer heating element 521. The outer heating element 521 is coupled to a first power source 524 and a first heating station 523. The inner heating element 522 is coupled to a second power source 526 and a second heating station 525. Both the first power source 524 and the first heating station 523 are separate and distinct from the second power source 526 and the second heating station 525. The heating elements 522, 521 operate independently from each other so that collectively, a wide range of precise temperature tuning is possible. The heating elements 521, 522 may be spaced from the top of the substrate or the top of the carrier plate 112 by a distance of between about 0.2 inches and about 0.8 inches.
The outer heating element 521 may comprise an induction coil that has between about 8 turns and about 11 turns. In one embodiment, the outer heating element 521 may be arranged in two substantially parallel rows and have an outer diameter of between about 12 inches and about 15 inches. The inner heating element 522 may comprise an induction coil that has between about 6 turns and about 9 turns. In one embodiment, the inner heating element 522 may be arranged in two substantially parallel rows and have an outer diameter of between about 3 inches and about 6 inches. The number of turns and heating element 521, 522 size is not limited to those shown or described. For example, for heating a bigger carrier plate 112, the size and shape of the heating elements 521, 522 can be adjusted accordingly so the concept is not limited to the particular sizes discussed above.
The first heating station 523 and power source 524 may be arranged to supply between about 30 kW of power and about 45 kW of power while the second heating station 525 and power supply 526 may be configured to supply between about 10 kW and about 17 kW of power. In one embodiment, the frequency of the first power source 524 and second power supply 526 may be different.
The inner heating element 522 and the outer heating element 521 are disposed outside of the chamber lid 502 adjacent the window 512. The window 512 is optically transparent. In one embodiment, the window 512 is made of transparent or opaque quartz. In another embodiment, the window 512 may comprise a dielectric material that is electromagnetically transparent. In another embodiment, the window 512 may be a metallic window with slits to reduce eddy currents.
In one embodiment, a coating 508 may be present on the transparent window 512 to reflect heat back into the transfer chamber 500. In one embodiment, the coating 508 may comprise titanium nitride. In another embodiment, the coating 508 may comprise gold. In another embodiment, the coating 508 may comprise tungsten, or any other reflective material that has high reflectivity in the infrared region. In one embodiment, the coating 508 may be present inside of the transfer chamber 500 as shown in
In operation, the induction heating assembly 509 may be activated to heat substrates or maintaining hot substrates at high temperature while the substrate are in the transfer chamber 500 in transit. The induction heating assembly 509 may be used independently or in combination with induction heating in the robot blade 511.
The induction heating in the transfer chamber 500 are advantageous because they are induction heating elements rather than resistive heating elements. The induction heating elements are more efficient than resistive heating elements because they utilize less energy and are powered by an RF power source. The induction heating elements do not heat all of the material (such as the entire chamber), but rather, the heat is focused onto the predetermined area (such as the substrates and the carriers).
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/242,924 (Attorney Docket No. 13300L), filed Sep. 16, 2009, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61242924 | Sep 2009 | US |
