Detection of substrate warping during rapid thermal processing

Apparatus and methods for detecting substrate warping during RTP processing are provided. In one embodiment, one or more beams of light are provided above and across the substrate being processed. In this embodiment, the amount of beam blockage correlates to the amount of substrate warping. In another embodiment, a beam of light is reflected off of a substrate during processing. In this embodiment, the amount of movement of the beam correlates to the amount of substrate warping. In yet another embodiment, a region of a substrate is illuminated during processing. In this embodiment, images of the illuminated region are analyzed to determine the amount of substrate warping.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to apparatus and methods for detection of substrate warping during rapid thermal processing.

2. Description of the Related Art

Although annealing in early stages of silicon technology typically involved heating multiple wafers for long periods in an annealing oven, rapid thermal processing (RTP) has been increasingly used to satisfy the increasingly stringent requirements for increasingly smaller circuit features. RTP is typically performed in single-substrate chambers by irradiating a substrate with light from an array of high intensity lamps. The radiation is absorbed by the substrate and quickly heats it to a desired temperature, such as above 600 degrees Celsius. The radiant heating can be quickly turned on and off to controllably heat the substrate over a relatively short period of time, e.g., a few seconds.

During RTP processing, particularly during initial recipe setup processes, non-uniform substrate heating may occur. Rapid, non-uniform heating of the substrate results in warping of the substrate. In addition, due to the typically narrow gap between the substrate and a reflector plate situated above (or below) the substrate, the warped substrate may contact the reflector plate while the substrate is rotating. Force from this contact may lead to a number of undesirable results, such as moving the substrate from its support, scratching the substrate, or breaking the substrate.

Therefore, there is a need for effective methods and apparatus for detecting substrate warping during RTP to reduce the risk of substrate and/or equipment damage.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a chamber comprises one or more chamber walls, a chamber bottom, and a chamber lid enclosing a processing volume. The chamber further comprises a substrate support disposed within the processing volume, a laser device positioned to emit a beam of light substantially parallel to an upper surface of the substrate support, and a detection device coupled to the chamber above the substrate support.

In another embodiment, a rapid thermal processing chamber comprises one or more chamber walls, a chamber bottom, and a chamber lid enclosing a processing volume. The chamber further comprises a substrate support disposed within the processing volume, a laser device coupled to the chamber above the substrate support, and a detection device. The laser device is positioned to emit a first beam of light toward an upper surface of the substrate support. The detection device determines an amount of change in a position of a second beam of light, wherein the second beam of light is a reflection of the first beam.

In yet another embodiment, a rapid thermal processing chamber comprises one or more chamber walls, a chamber bottom, and a chamber lid enclosing a processing volume. The chamber further comprises a substrate support disposed within the processing volume, a laser device coupled to the chamber above the substrate support, and a detection device coupled to the chamber above the substrate support. The laser device is positioned to emit light onto a region of substrate positioned on a substrate supporting surface of the substrate support. The detection device is positioned to capture images of the illuminated region.

DETAILED DESCRIPTION

Embodiments of the present invention generally provide apparatus and methods for detecting substrate warping during RTP processes. In one embodiment, a laser beam is directed above and substantially parallel to an upper surface of a substrate disposed in an RTP chamber prior to heating. The beam is provided by a laser device disposed in one side wall of the chamber and detected by a detection device in an opposite side wall of the chamber. If the substrate warps during processing, at least a portion of the beam is blocked by the substrate, indicating that an undesirable amount of substrate warping has occurred.

In another embodiment, a laser beam is directed onto an edge region of a substrate disposed in an RTP chamber. The beam is provided by a laser device disposed in a chamber lid. The beam is reflected off of the substrate and detected by a detection device disposed in the chamber lid. If the substrate warps during processing, the reflected beam moves, and the detection device indicates the amount of movement, and thus, the amount of warping of the substrate.

In yet another embodiment, a laser beam is scanned across an upper surface of an edge region of a substrate disposed in an RTP chamber. The beam is provided by a laser device disposed in one side wall of the chamber, and a camera is disposed in an opposite side wall of the chamber. The beam illuminates the edge region, and the camera is focused on the edge region. If the substrate warps during processing, the angle of light scattered by the edge region and captured by the camera changes, indicating warping of the substrate.

FIG. 1is a schematic, cross-sectional view of an RTP chamber100according to one embodiment of the present invention. The RTP chamber100includes a chamber body102having a cylindrical side wall104, a bottom wall106, and a chamber lid108defining an interior volume110. The chamber100further includes a substrate support112having an edge ring113for supporting a substrate101. Below the substrate support112is a radiant heat source114that may include a plurality of high intensity lamps116, such as tungsten-halogen lamps. The radiant heat source also has a window118made from a material that is transparent to heat and light, such as quartz. The RTP chamber100further includes a lid108with a reflector plate121attached thereto.

The substrate support112shown is adapted to magnetically levitate and rotate within the interior volume110. To provide the magnetic levitation and rotation, a stator assembly120circumscribes the wall104of the chamber body102. The stator assembly120is magnetically coupled to a rotor assembly122disposed in the substrate support112.

An atmosphere control system124is also coupled to the interior volume110of the chamber body102. The atmosphere control system124generally includes one or more throttle valves and one or more vacuum pumps for controlling chamber pressure. The atmosphere control system124may additionally include gas sources for providing gases into the interior volume110.

The chamber100also includes a controller126, which generally includes a central processing unit (CPU)128, support circuits130, and memory132. The CPU128may be one of any form of computer processor that can be used in an industrial setting for controlling various actions and subprocessors. The memory132, or computer-readable medium, may be one or more of readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote, and is typically coupled to the CPU128. The support circuits130are coupled to the CPU128for supporting the control system124in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystem, and the like.

A laser device140is coupled to the side wall104in one region of the chamber body102, and a detection device150is coupled to the side wall104in an opposite region of the chamber body102. The laser device140is positioned to provide a beam of light (e.g., 1-3 mm diameter beam) through a window103in the chamber wall104and at a height of about 1 mm to about 10 mm above the surface of the substrate101positioned on the substrate support112at ambient temperature. The laser device140is positioned to provide the beam substantially parallel to a supporting surface134of the edge ring113(i.e., upper surface), and is thus, substantially parallel to the upper surface of the substrate101positioned on the substrate support112at ambient temperature. The beam provided from the laser device140is transmitted substantially parallel to the substrate supporting surface134of the edge ring113at a height of between about 1 mm and about 10 mm above the substrate101supported thereon at ambient temperature. In one embodiment, substantially parallel means less than three degrees from parallel. Preferably, the beam is emitted at less than 1.0 degrees from parallel. The laser device140may be any laser device capable of generating a beam of light at less than about 1000 nm (e.g., 632 nm, 810 nm, 925 nm). These wavelengths are selected so that the laser light is not transmitted through the silicon substrate101either at ambient or at elevated temperatures (e.g., greater than about 600 degrees Celsius). Other longer wavelength lasers can also be used, but at a lesser sensitivity at a lower temperature range (e.g., <500 degrees Celsius).

The detection device150is positioned to receive the beam through an aperture105and window107in the chamber wall104. The aperture105may be configured in the shape of a tube in order to define a direction relative to the detection device150along which light is permitted to pass in order to filter much of the light emitted from the radiant heat source114prior to reaching the detection device150. For example, the aperture105may be provided at a diameter of between about 3 mm and about 7 mm with a length to diameter ratio of between about 5:1 and about 10:1. Alternatively, a separate tube aperture (not shown) may be disposed through the chamber wall104to provide the light filtering.

The detection device150may be any suitable sensor for detecting the presence of a beam of light, such as a photodiode or the like. The detection device150provides a signal indicative of the presence or absence of light received from the laser device140. In addition, a filter152is provided to further ensure that only desired wavelengths of light reach the detection device150. The filter152may be a band pass filter, e.g., 10 nm to 20 nm band pass filter.

In operation, the controller126provides instructions to the laser device140to emit a beam (e.g., 3 mm beam) in the RTP chamber100with the substrate101at ambient temperature. In one embodiment, a continuous beam is emitted in an operation in which radiant heat is provided from the radiant heat source114in a continuous manner. In another embodiment, in which radiant heat is provided in a non-continuous manner, the intensity of the beam is modulated. The beam passes across the substrate101, through the aperture105and the filter152, before impinging on the detection device150. The detection device150, in turn, provides a signal to the controller126that the full beam is being received, thus, no substrate warping is detected. In the embodiment in which a modulated beam is provided, the detector signal is amplified and only the modulated signal is used as the sense signal. This scheme further acts as a filter to remove the “noise” of the light emitted from the radiant heat source114.

As the RTP chamber100heats the rotating substrate101, if the substrate101begins to warp (shown by dotted line inFIG. 1), a portion of the substrate101blocks a portion of the beam. When a portion of the beam is blocked, the detection device150receives less light, and its signal to the controller126is weaker. Once a programmed threshold is reached (e.g., indicating that half of the beam is blocked), the controller126may take action, such as sending instructions for shutting down the process or signaling the operator that undesirable substrate warping has occurred. Thus, damage to the substrate101and/or the chamber100components may be averted.

FIG. 2Ais a schematic, cross-sectional view of the RTP chamber100according to another embodiment. The RTP chamber100depicted inFIG. 2Ais similar to that depicted inFIG. 1except that the laser device140and the detection device150are disposed adjacent one another in the chamber wall104. In the example shown inFIG. 2A, the laser device140is above the detection device150; however, the detection device150could be provided above the laser device140without departing from the scope of the invention. A mirror160is disposed on the chamber wall104on a side of the chamber body102opposite the laser device140and detection device150. The mirror160is coupled to the chamber wall104adjacent a window109.

FIGS. 2B and 2Care schematic, top, cross-sectional views of the RTP chamber100according to other embodiments. The configuration depicted inFIG. 2Bis substantially similar to that ofFIG. 2Aexcept that the laser device140and the detection device150are positioned side-by-side rather than one above the other. In this configuration, as in the configuration ofFIG. 1, the beam provided from the laser device140is transmitted substantially parallel to the substrate supporting surface134of the edge ring113at a height of between about 1 mm and about 10 mm above the substrate101supported thereon at ambient temperature. The beam is reflected by the mirror160projected to the detection device150substantially parallel and at about the same height as the beam projected from the laser device140. Thus, more robust substrate warping detection is provided by the configuration ofFIG. 2Bthan that ofFIGS. 1 and 2Abecause the beam is passed over the substrate101in two regions rather than just one region.

The configuration depicted inFIG. 2Cis substantially similar to that ofFIG. 2Bexcept that the laser device140and the detection device150are spread apart and angled such that the beam projected from the laser device140is reflected by a plurality of mirrors160and passed over a plurality of regions of the substrate101prior to impinging on the detection device150. Thus, more robust substrate warping detection is provided by the configuration ofFIG. 2Cthan the configuration ofFIGS. 1,2A, and2B.

The operation of the configurations depicted inFIGS. 2A-2Cis substantially the same as for the configuration depicted inFIG. 1. For example, as the RTP chamber100heats the rotating substrate101, if the substrate101begins to warp (shown by dotted line inFIG. 2A), a portion of the substrate101blocks a portion of the beam. When a portion of the beam is blocked, the detection device150receives less light, and its signal to the controller126is weaker. Once a programmed threshold is reached (e.g., indicating that half of the beam is blocked), the controller126may take action, such as sending instructions for shutting down the process or signaling the operator that undesirable substrate warping has occurred.

FIGS. 3A and 3Bare schematic, partial, cross-sectional views of the RTP chamber100according to further embodiments of the present invention. InFIG. 3A, the laser device140is substantially the same as that of the previously described configurations, but it is coupled to the chamber lid108rather than the chamber wall104. Accordingly, the chamber lid108and the reflector plate has an aperture111disposed therethrough covered by a window115. In addition, the detection device150and filter152are coupled to the chamber lid108as well. In the configuration depicted inFIG. 3A, the detection device150is a detector capable of detecting the position/movement of a beam of light across its field of view rather than just the presence of a beam of light impinging upon it. For example, the detection device150may be a position sensitive detector (PSD) or a camera (e.g., CCD camera).

In operation, the controller126provides instructions to the laser device140, which projects a beam of light toward an edge region of the rotating substrate101. The beam is reflected by the substrate101toward the detection device150. The angle of the beam projected by the laser device140is calibrated so that the beam reflected from the planar substrate101at ambient temperature impinges substantially on the center of the detection device150. For example, the laser device140may be positioned to emit a beam that is reflected at an angle of between 0 and 45 degrees, and the reflected beam is directed onto the center of the detection device150. As the RTP chamber100heats the rotating substrate101, if the substrate101begins to warp (shown by dotted line inFIG. 3A), the angle of the reflected beam changes, and the beam impinges on the detection device150at a different location. Signals from the detection device150indicating the location of the beam, and thus, the amount of warping of the substrate101are provided to the controller126. The controller126may provide feedback to an operator indicating the amount of substrate101warping. Additionally, the controller126and detection device150may be calibrated to take action if a programmed threshold is reached. For example, the detection device may be able to detect up to a one degree movement of the reflected beam from the center of the detection device. However, an unacceptable amount of warping may correlate to a 0.5 degree deviation in the reflected angle. When the detection device140detects an amount of movement in the position of the reflected beam that is 0.5 degrees on greater, the controller126may send instructions for shutting down the process or signal the operator that undesirable substrate warping has occurred.

FIG. 3Bshows an alternate configuration, which is substantially similar to that ofFIG. 3A, except that rather than a single PSD or camera, the detection device150is made up of a plurality of stacked photodetectors, such as a plurality of stacked photodiodes. In the configuration shown, a lower photodetector155has a first diameter, and is positioned adjacent the filter152. Above the lower photodetector155is an intermediate photodetector156having a second diameter greater than the first diameter of the lower photodetector155. Above the intermediate photodetector is an upper photodetector157having a third diameter greater than the second diameter of the intermediate photodetector156. The photodetectors155-157are sized and arranged such that as the reflected beam moves, the beam transitions from the lower photodetector155to the intermediate photodetector156to the upper photodetector157. Thus, in operation the plurality of photodetectors155-157function similarly to the single detection device150described with respect to the configuration ofFIG. 3A. Although three photodetectors are depicted and described with respect toFIG. 3B, two or more photodetectors may be used to accomplish the same scheme without departing from the scope of the present invention.

In operation, the controller126provides instructions to the laser device140, which projects a beam of light toward an edge region of the rotating substrate101. The beam is reflected by the substrate101toward the detection device150. The angle of the beam projected by the laser device140is calibrated so that the beam reflected from the planar substrate101at ambient temperature impinges on the lower photodetector155. As the RTP chamber100heats the rotating substrate101, if the substrate101begins to warp (shown by dotted line inFIG. 3B), the angle of the reflected beam changes, and the beam impinges on the intermediate photodetector156. If the substrate101continues to warp, the angle of the reflected beam changes, and the beam impinges on the upper photodetector157. Signals from the detection device150indicating the location of the beam (i.e., which photodetector the beam is impinging on), and thus, the amount of warping of the substrate101are provided to the controller126. The controller126may provide feedback to an operator indicating the amount of substrate101warping. Additionally, the controller126and detection device150may be calibrated to take action if a programmed threshold is reached. For instance, the controller126may send instructions for shutting down the process or signal the operator that undesirable substrate warping has occurred upon detecting beam movement beyond the programmed threshold.

FIG. 4Ais a schematic, cross-sectional view of the RTP chamber100according to another embodiment of the present invention, andFIG. 4Bis a schematic, top, cross-sectional view of the RTP chamber depicted inFIG. 4Ataken along the section line B-B. Similar to the embodiment depicted inFIG. 1, the laser device140and the detection device150are coupled to the chamber wall104on opposite sides of the chamber body102. In the embodiment ofFIGS. 4A and 4b, the laser device140is configured to provide a wider scan of light, rather than a small beam, in order to illuminate an edge region of the substrate101. The detection device150is a camera (e.g., CCD camera) directed toward the illuminated region of the substrate101.

In operation, the controller126provides instructions to the laser device140, which projects a wide scan of light toward an edge region of the rotating substrate101. The light impinging on the substrate101, at ambient temperature, from the laser device140is scattered, and images are captured by the detection device150of the illuminated region of the substrate101showing the pattern of scattered light. As the RTP chamber100heats the rotating substrate101, if the substrate begins to warp, the pattern of scattered light of the illuminated region of the substrate101changes, and images of the illuminated region are captured by the detection device150showing the changed pattern of light. These images are sent to the controller126. The controller126may provide the images to an operator for monitoring the condition of the substrate101during processing. The controller126may be programmed to compare the images to stored images and determine when substrate101has exceeded a threshold amount of warping. At that point, the controller126may shut down the process or signal the operator that an undesirable amount of substrate warping has occurred in order to prevent substrate and/or equipment damage.

Therefore, a number of alternatives are described for detecting substrate warping during RTP processing. In one embodiment, one or more beams of light are provided above and across the substrate being processed. In this embodiment, the amount of beam blockage correlates to the amount of substrate warping. In another embodiment, a beam of light is reflected off of a substrate during processing. In this embodiment, the amount of movement of the beam correlates to the amount of substrate warping. In yet another embodiment, a region of a substrate is illuminated during processing. In this embodiment, images of the illuminated region are analyzed to determine the amount of substrate warping.

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. For example, although the chamber body102is depicted and described as being cylindrical, the chamber body102may configured differently, such as having multiple side walls (e.g., square, hexagonal, octagonal).