Methods and apparatuses that decouple wafer temperature from pre-heat station residence time, thereby improving wafer-to-wafer temperature uniformity, are provided. The methods involve maintaining a desired temperature by varying the distance between the wafer and a heater. In certain embodiments, the methods involve rapidly approaching a predetermined initial distance and then obtaining and maintaining a desired final temperature using closed loop temperature control. In certain embodiments, a heated pedestal supplies the heat. The wafer-pedestal gap may be modulated by moving the heated pedestal and/or moving the wafer, e.g., via a movable wafer support. Also in certain embodiments, the closed loop control system includes a real time wafer temperature sensor and a servo controlled linear motor for moving the pedestal or wafer support.
In the following detailed description of the present invention, numerous specific embodiments are set forth in order to provide a thorough understanding of the invention. However, as will be apparent to those skilled in the art, the present invention may be practiced without these specific details or by using alternate elements or processes. In other instances, which utilize well-known processes, procedures and components have not been described in detail so as not to unnecessarily obscure aspects of the present invention.
In this application, the terms “semiconductor wafer”, “wafer” and “partially fabricated integrated circuit” will be used interchangeably. One skilled in the art would understand that the term “partially fabricated integrated circuit” can refer to a silicon wafer during any of many stages of integrated circuit fabrication thereon. The following detailed description assumes the invention is implemented on a wafer. However, the invention is not so limited. The work piece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other work pieces that may take advantage of this invention include various articles such as printed circuit boards and the like.
Prior to being placed in a processing chamber, wafers are often preheated. Preheating to a temperature at or near the process temperature increases process chamber throughput, as well reducing thermal stress to the wafer, improving temperature consistency across the wafer and improving deposited film quality and uniformity. With many apparatuses, a wafer is preheated while waiting for the processing station to be available. Once the processing station becomes available, the wafer is transferred from the preheat station to the available process module. In some processing stations, the wafer is preheated in a loadlock. The loadlock serves as a buffer between a room temperature, atmospheric-pressure environment and an elevated temperature, evacuated environment. Loadlock (or other preheat station) residence time may vary widely from wafer to wafer, however, because processing requirements and maximizing throughput necessitate that the processing chamber availability dictates the wafer transfer timing.
Wafer heating prior to processing is typically performed open loop with no control of final temperature. This can lead to poor wafer to wafer temperature uniformity, since the residence time at the pre-heat station may vary and the wafer temperature will continue to rise as the wafer waits for the process chamber to be ready for transfer.
According to various embodiments, the methods and systems described herein involve closed loop feedback control for rapid wafer heating and maintaining target wafer temperature in a preheat station. In certain embodiments, the temperature control systems use wafer temperature sensor and a servo controlled actuator for controlling the rate of heat transfer by varying the gap between the heater and the wafer.
In many embodiments, a heated pedestal supplies the heat to heat the wafer. Heated pedestals generally have embedded electrically powered heating elements. The wafer may rest slightly above the pedestal on a wafer support, with heat transfer from the pedestal to the wafer facilitated by using a gas with high thermal conductivity (e.g., helium) to provide for efficient thermal coupling between the wafer and the pedestal or other support to the wafer. As indicated above, the methods and systems described herein control heat transfer from the heater to the wafer, and thus wafer temperature, by modulating the gap between the heater and wafer. For the purposes of discussion, the description refers to such heated pedestals; however the scope of the invention is not so limited and includes other heat sources wherein the rate of heat transfer can be controlled by modulating the gap between the heat source and the wafer, e.g. radiation-type heat sources, as well as those heat sources embedded within pedestals. Internal and external heat sources include, but are not limited to, resistance-type and circulating-type heat sources.
The two stages of wafer temperature control are illustrated in
The initial approach parameters typically include a set velocity or set acceleration and the predetermined initial gap. The feedback control stage parameters include a max velocity, a max acceleration and a minimum gap. The predetermined initial gap may be experimentally determined for each type of wafer/desired temperature/pedestal temperature. In addition to constraining the predetermined initial gap to distances above that of the thermal distortion threshold gap, the gap should be big enough so that any variation in wafer-pedestal gap across the wafer (due to, for example, variations in the pedestal surface) is insignificant compared to the gap. In certain embodiments, this initial gap may also be set to be the minimum gap during the feedback control stage. In certain embodiments the minimum gap used during the feedback control stage differs from the predetermined initial gap. For example, because the thermal distortion threshold gap is dependent on the temperature differential between the wafer and the pedestal, becoming smaller as the temperature differential becomes smaller, this minimum gap may be smaller than the predetermined initial gap.
The initial approach stage described above is just one example of a stage prior to a feedback control stage. For example, the initial approach stage may be broken up into two or more stages, having different gaps, approach velocities, etc. As mentioned, in certain embodiments, there may be no initial approach, with the feedback control stage beginning immediately after introducing the wafer to the station.
Temperature measurement may be performed by any suitable device including a thermocouple, as in
As indicated, the temperature sensing device sends wafer temperature information to a controller, generally in the form of an output voltage. The controller analyzes the data and in turn sends instructions to a linear motor to modulate the wafer-pedestal gap and keep the temperature at the desired level. In general, accurate feedback control with small overshoot is necessary. In certain embodiments, the controller is programmed with Proportional Integral Derivative (PID) algorithms for stable and accurate control. In certain embodiments, the motor used to move the pedestal and/or wafer support is a servo controlled linear actuator motor, which receives instructions for a prescribed motion based on input from the thermometry equipment. The motor may have embedded logic circuitry to support the PID closed loop algorithms for gap variance.
As indicated above, the wafer-pedestal gap may be modulated by moving the pedestal or a wafer support holding the wafer in relation to each other. In certain embodiments, both may be capable of moving in response to modulate the gap. Any type of pedestal may be used including convex, concave or flat pedestals in various shapes and sizes. The pedestal typically has a heating element and has a thermocouple to control its temperature. In certain embodiments, the temperature is constant and the rate at which heat transfers to the wafer is controlled primarily by modulating the wafer-pedestal gap. However, in some embodiments, the pedestal heater power may also be varied.
The closed loop temperature control using gap variance to control the temperature as discussed above provides easier to implement and low cost alternatives to other closed loop wafer control systems that would use variance in light source, plasma intensity or power supplied to the heater.
A bare silicon wafer was introduced to a chamber having a heated pedestal capable of moving with respect to the wafer to modulate the wafer-pedestal gap. The pedestal temperature was 400 C. Wafer temperature was measured using a pyrometer. Initial approach and closed loop control stages were performed to maintain temperature at about 30° C. as follows:
Initial Approach Stage:
Wafer temperature at beginning of initial approach: 280 C
Wafer-Pedestal gap at beginning of initial approach: 0.4 inch
Predetermined initial gap (wafer-pedestal gap at end of initial approach): 0.10 inch
Pedestal velocity during initial approach: 0.04 inch per second
Pedestal acceleration during initial approach: 0.19 inch per s2
Closed-Loop Temperature Control Stage: (values below are typical values used during the optimization of the process)
Minimum allowable gap: 0.07 inch
Maximum pedestal velocity: 0.60 inch per second
Maximum pedestal acceleration: 3.9 inch per s2
The resulting wafer temperature profile is shown in
This application is a continuation of and claims priority from U.S. patent application Ser. No. 11/937,364, filed Nov. 8, 2007, titled “CLOSED LOOP TEMPERATURE HEAT UP AND CONTROL UTILIZING WAFER-TO-HEATER PEDESTAL GAP MODULATION,” all of which is incorporated herein by this reference.
Number | Name | Date | Kind |
---|---|---|---|
3612825 | Chase et al. | Oct 1971 | A |
4457359 | Holden | Jul 1984 | A |
4535835 | Holden | Aug 1985 | A |
4563589 | Scheffer | Jan 1986 | A |
4615755 | Tracy et al. | Oct 1986 | A |
5113929 | Nakagawa et al. | May 1992 | A |
5178682 | Tsukamoto et al. | Jan 1993 | A |
5228208 | White et al. | Jul 1993 | A |
5282121 | Bornhorst et al. | Jan 1994 | A |
5447431 | Muka | Sep 1995 | A |
5558717 | Zhao et al. | Sep 1996 | A |
5588827 | Muka | Dec 1996 | A |
5811762 | Tseng | Sep 1998 | A |
6072163 | Armstrong et al. | Jun 2000 | A |
6087632 | Mizosaki et al. | Jul 2000 | A |
6200634 | Johnsgard et al. | Mar 2001 | B1 |
6214184 | Chien et al. | Apr 2001 | B1 |
6228438 | Schmitt | May 2001 | B1 |
6307184 | Womack et al. | Oct 2001 | B1 |
6320736 | Shamouilian et al. | Nov 2001 | B1 |
6394797 | Sugaya et al. | May 2002 | B1 |
6413321 | Kim et al. | Jul 2002 | B1 |
6435869 | Kitamura | Aug 2002 | B2 |
6467491 | Sugiura et al. | Oct 2002 | B1 |
6559424 | O'Carroll et al. | May 2003 | B2 |
6561796 | Barrera et al. | May 2003 | B1 |
6563092 | Shrinivasan et al. | May 2003 | B1 |
6639189 | Ramanan et al. | Oct 2003 | B2 |
6753508 | Shirakawa | Jun 2004 | B2 |
6768084 | Liu et al. | Jul 2004 | B2 |
6800173 | Chiang et al. | Oct 2004 | B2 |
6860965 | Stevens | Mar 2005 | B1 |
6895179 | Kanno | May 2005 | B2 |
6899765 | Krivts et al. | May 2005 | B2 |
7024105 | Fodor et al. | Apr 2006 | B2 |
7105463 | Kurita et al. | Sep 2006 | B2 |
7138606 | Kanno et al. | Nov 2006 | B2 |
7189432 | Chiang et al. | Mar 2007 | B2 |
7194199 | Yoo | Mar 2007 | B2 |
7253125 | Bandyopadhyay et al. | Aug 2007 | B1 |
7265061 | Cho et al. | Sep 2007 | B1 |
7311782 | Strang et al. | Dec 2007 | B2 |
7318869 | Chiang et al. | Jan 2008 | B2 |
7327948 | Shrinivasan et al. | Feb 2008 | B1 |
7410355 | Granneman et al. | Aug 2008 | B2 |
7576303 | Natsuhara et al. | Aug 2009 | B2 |
7665951 | Kurita et al. | Feb 2010 | B2 |
7845891 | Lee et al. | Dec 2010 | B2 |
7941039 | Shrinivasan et al. | May 2011 | B1 |
7960297 | Rivkin et al. | Jun 2011 | B1 |
7981763 | Van Schravendijk et al. | Jul 2011 | B1 |
8033771 | Gage et al. | Oct 2011 | B1 |
8047706 | Goodman et al. | Nov 2011 | B2 |
8052419 | Nordin et al. | Nov 2011 | B1 |
8371567 | Angelov et al. | Feb 2013 | B2 |
8454294 | Gage et al. | Jun 2013 | B2 |
20020117109 | Hazelton et al. | Aug 2002 | A1 |
20020162630 | Satoh et al. | Nov 2002 | A1 |
20030013280 | Yamanaka | Jan 2003 | A1 |
20030113187 | Lei et al. | Jun 2003 | A1 |
20040018751 | Kusuda | Jan 2004 | A1 |
20040023513 | Aoyama et al. | Feb 2004 | A1 |
20040060917 | Liu et al. | Apr 2004 | A1 |
20040183226 | Newell et al. | Sep 2004 | A1 |
20040187790 | Bader et al. | Sep 2004 | A1 |
20050006230 | Narushima et al. | Jan 2005 | A1 |
20050045616 | Ishihara | Mar 2005 | A1 |
20050226793 | Sakakura et al. | Oct 2005 | A1 |
20050258164 | Hiramatsu et al. | Nov 2005 | A1 |
20060018639 | Ramamurthy et al. | Jan 2006 | A1 |
20060075960 | Borgini et al. | Apr 2006 | A1 |
20060081186 | Shinriki et al. | Apr 2006 | A1 |
20070029046 | Li et al. | Feb 2007 | A1 |
20070107845 | Ishizawa et al. | May 2007 | A1 |
20070205788 | Natsuhara et al. | Sep 2007 | A1 |
20070243057 | Shimada et al. | Oct 2007 | A1 |
20070283709 | Luse et al. | Dec 2007 | A1 |
20080102644 | Goto et al. | May 2008 | A1 |
20080134820 | Bjorck et al. | Jun 2008 | A1 |
20080169282 | Sorabji et al. | Jul 2008 | A1 |
20080217319 | Saule et al. | Sep 2008 | A1 |
20080237214 | Scheer et al. | Oct 2008 | A1 |
20090060480 | Herchen | Mar 2009 | A1 |
20090142167 | Gage et al. | Jun 2009 | A1 |
20090147819 | Goodman et al. | Jun 2009 | A1 |
20090277472 | Rivkin et al. | Nov 2009 | A1 |
20100163183 | Tanaka et al. | Jul 2010 | A1 |
20100270004 | Landess et al. | Oct 2010 | A1 |
20110207245 | Koshimizu et al. | Aug 2011 | A1 |
20110318142 | Gage et al. | Dec 2011 | A1 |
20120264051 | Angelov et al. | Oct 2012 | A1 |
20130122431 | Angelov et al. | May 2013 | A1 |
20130175005 | Gowdaru et al. | Jul 2013 | A1 |
Number | Date | Country |
---|---|---|
0 746 009 | Dec 1996 | EP |
62-229833 | Oct 1987 | JP |
01-107519 | Apr 1989 | JP |
06037054 | Feb 1994 | JP |
07-090582 | Apr 1995 | JP |
07147274 | Jun 1995 | JP |
08-316215 | Nov 1996 | JP |
09-092615 | Apr 1997 | JP |
2000-286243 | Oct 2000 | JP |
2002-246375 | Aug 2002 | JP |
2003-324048 | Nov 2003 | JP |
2005116655 | Apr 2005 | JP |
2006-210372 | Aug 2006 | JP |
2007-158074 | Jun 2007 | JP |
2009-218536 | Sep 2009 | JP |
20030096732 | Dec 2003 | KR |
0211911 | Feb 2002 | WO |
WO 2009001866 | Dec 2008 | WO |
WO 2010068598 | Jun 2010 | WO |
WO 2010101191 | Sep 2010 | WO |
WO 2012141722 | Oct 2012 | WO |
WO 2013103594 | Jul 2013 | WO |
Entry |
---|
Shrinivasan et al., “Single-Chamber Sequential Curing of Semiconductor Wafers,” Novellus Systems, Inc., U.S. Appl. No. 11/115,576, filed Apr. 26, 2005. |
U.S. Office Action mailed Oct. 3, 2007, from U.S Appl. No. 11/115,576. |
U.S. Final Office Action mailed May 2, 2008, from U.S Appl. No. 11/115,576. |
U.S. Office Action mailed Oct. 17, 2008, from U.S Appl. No. 11/115,576. |
Doble et al., “Concave Pedestal for Uniform Heating of Silicon Wafers,” Novellus Systems, Inc., U.S. Appl. No. 11/546,189, filed Oct. 10, 2006. |
U.S. Office Action mailed Jun. 16, 2008, from U.S. Appl. No. 11/546,189. |
U.S.Final Office Action mailed Oct. 16, 2008, from U.S Appl. No. 11/546,189. |
U.S. Office Action mailed Jul. 18, 2006, from U.S Appl. No. 11/184,101. |
Notice of Allowance and Fee Due mailed Jan. 25, 2007, from U.S Appl. No. 11/184,101. |
Nordin et al., “Closed Loop Temperature Heat Up and Control Utilizing Wafer-To-Heater Pedestal Gap Modulation,” Novellus Systems, Inc., U.S. Appl. No. 11/937,364, filed Nov. 8, 2007. |
Gage et al., “Transferring Heat in Loadlocks,” Novellus Systems, Inc., U.S. Appl. No. 12/140,196, filed Jun. 16, 2008. |
Rivkin et al., “Photoresist Stripping Method and Apparatus,” Novellus Systems, Inc., U.S. Appl. No. 61/050,880, filed May 6, 2008. |
U.S. Appl. No. 11/937,364, Office Action mailed Apr. 9, 2010. |
U.S. Appl. No. 11/115,576, Office Action mailed Apr. 22, 2009. |
U.S. Appl. No. 11/115,576, Office Action mailed Apr. 15, 2010. |
U.S. Appl. No. 11/129,266, “Tailored profile pedestal for thermo-elastically stable cooling for heating of substrates”, Landess et al., filed May 12, 2005. |
U.S. Appl. No. 11/129,266, Office Action mailed Feb. 20, 2009. |
U.S. Appl. No. 11/129,266, Office Action mailed Oct. 28, 2009. |
U.S. Appl. No. 11/608,185, Office Action mailed Apr. 26, 2010. |
U.S. Appl. No. 11/751,584, “Cast pedestal with heating element on coaxial heat exchanger”, Shrinivasan et al., filed May 21, 2007. |
U.S. Appl. No. 11/851,310, Office Action mailed Jun. 8, 2010. |
U.S. Appl. No. 61/122,308, “Conductively cooled process for wide temperature range processes”, Nieh et al., filed Dec. 12, 2008. |
U.S. Appl. No. 12/333,239, “Minimum contact area wafer clamping with gas flow for rapid wafer cooling”, Gage et al., filed Dec. 11, 2008. |
International Search Report and Written Opinion for application No. PCT/US2009/067040, mailed Aug. 2, 2010. |
U.S. Appl. No. 11/608,185, Office Action mailed Nov. 26, 2010. |
U.S. Appl. No. 12/333,239, Final Office Action mailed Dec. 27, 2010. |
Notice of Allowance for U.S. Appl. No. 11/851,310, mailed Jan. 5, 2011. |
U.S. Appl. No. 11/937,364, Office Action mailed Dec. 27, 2010. |
U.S. Appl. No. 12/333,239, Office Action mailed Mar. 9, 2011. |
U.S. Appl. No. 12/333,239, Notice of Allowance mailed Jun. 27, 2011. |
U.S. Appl. No. 12/333,239, Allowed Claims, Jun. 27, 2011. |
Notice of Allowance for U.S. Appl. No. 11/608,185, mailed Mar. 22, 2011. |
U.S. Appl. No. 13/086,010, “High Temperature Pedestal Overlay for Stable & Uniform Heat Transfer”, Angelov et al., filed Apr. 13, 2011. |
U.S. Appl. No. 13/102,858, “Load Lock Design for Rapid Wafer Heating”, Rivkin et al., filed May 6, 2011. |
U.S. Appl. No. 13/102,858, Office Action mailed Aug. 8, 2011. |
U.S. Appl. No. 13/227,160, “Minimum contact area wafer clamping with gas flow for rapid wafer cooling”, Gage et al., filed Sep. 7, 2011. |
U.S. Appl. No. 11/937,364, Notice of Allowance mailed Sep. 19, 2011. |
Allowed Claims for U.S. Appl. No. 11/937,364, as of Sep. 19, 2011. |
U.S. Appl. No. 12/435,890, Office Action mailed Dec. 28, 2011. |
U.S. Appl. No. 12/140,196, Office Action mailed Jan. 4, 2012. |
U.S. Appl. No. 13/102,858, Office Action mailed Jan. 23, 2012. |
U.S. Appl. No. 12/749,170, Office Action mailed Feb. 6, 2012. |
U.S. Appl. No. 13/621,060, filed Sep. 15, 2012, entitled “Transferring Heat in Loadlocks”. |
US Office Action, dated Feb. 28, 2013, issued in U.S. Appl. No. 12/435,890. |
US Office Action, dated Oct. 22, 2012, issued in U.S. Appl. No. 13/227,160. |
US Office Action, dated Jan. 3, 2014, issued in U.S. Appl. No. 13/736,410. |
PCT International Report on Patentability and Written Opinion, dated Jun. 3, 2011, issued in PCT/US2009/067040. |
Chinese First Office Action dated Jan. 23, 2013 issued in CN 200980149339.5. |
Chinese Second Office Action dated Sep. 11, 2013 issued in CN 200980149339.5. |
PCT International Preliminary Report on Patentability and Written Opinion, dated Oct. 24, 2013, issued in PCT/US2011/034819. |
JP Notice of Reasons for Rejection dated Apr. 9, 2013 issued in JP 2013510129. |
PCT International Search Report and Written Opinion, dated Apr. 12, 2013 issued in PCT/US2012/071976. |
Number | Date | Country | |
---|---|---|---|
Parent | 11937364 | Nov 2007 | US |
Child | 13276202 | US |