Temperature calibration with band gap absorption method

A method and apparatus for calibration non-contact temperature sensors within a process chamber are described herein. The calibration of the non-contact temperature sensors includes the utilization of a band edge detector to determine the band edge absorption wavelength of a substrate. The band edge detector is configured to measure the intensity of a range of wavelengths and determines the actual temperature of a substrate based off the band edge absorption wavelength and the material of the substrate. The calibration method is automated and does not require human intervention or disassembly of a process chamber for each calibration.

FIELD

Embodiments of the present disclosure generally relate to apparatus and methods for semiconductor processing. More particularly, the apparatus and methods disclosed relate to the calibration of temperature sensors within a thermal process chamber.

DESCRIPTION OF THE RELATED ART

Semiconductor substrates are processed for a wide variety of applications, including the fabrication of integrated devices and microdevices. During processing, the substrate is positioned on a susceptor within a process chamber. The susceptor is supported by a support shaft, which is rotatable about a central axis. Precise control over a heating source, such as a plurality of heating lamps disposed below and above the substrate, allows the substrate to be heated within very strict tolerances. The temperature of the substrate can affect the uniformity of the material deposited on the substrate.

The temperature of the substrate is measured throughout the deposition process using non-contact temperature sensors. The non-contact temperature sensors are disposed on/through a lid of the thermal process chamber. Over time, the temperature readings of the non-contact temperature sensors drifts due to changes of the conditions of the hardware within the process chamber. Aging of the heating lamps, window coatings, and susceptor affect the temperature measurements over time. Previous calibration methods have used calibration kits which utilize opening of the process chamber and significant down time.

Therefore, a need exists for improved methods and apparatus for calibrating non-contact temperature sensors within thermal process chambers.

SUMMARY

The present disclosure generally relates to apparatus and methods for calibrating pyrometers within an epitaxial deposition chamber. More specifically, the present disclosure relates to the use of band gap edge detectors to determine the temperature of a substrate. A measurement assembly for calibrating pyrometers within a processing chamber according to one embodiment of the present disclosure includes a band edge calibration assembly. The band edge calibration assembly includes a light source positioned to emit a light and a band edge detector disposed adjacent to the light source and positioned to receive the light emitted by the light source. The measurement assembly for calibrating pyrometers within a processing chamber further includes a first pyrometer disposed adjacent to the band edge calibration assembly and positioned to receive a radiation measurement, and a controller connected to each of the light source, the band edge detector, and the first pyrometer. The controller is configured to determine a band edge absorption wavelength from the light received by the band edge detector.

In another embodiment, the an apparatus for substrate processing includes a chamber body, a substrate support disposed within the chamber body, a first transmission member disposed over the substrate support and within the chamber body, a second transmission member disposed below the substrate support and within the chamber body, a lid disposed above the first transmission member, a plurality of lamps disposed between the first transmission member and the lid, a calibration substrate disposed on the substrate support, a radiation source positioned to direct radiation onto or through the calibration substrate; and a band edge calibration assembly disposed on the lid. The band edge calibration assembly includes a band edge detector positioned to receive the radiation from the radiation source after being reflected off of or passing through the calibration substrate. The apparatus for substrate processing further includes a first pyrometer is disposed adjacent to the band edge calibration assembly, and a controller. The controller is configured to irradiate a portion of the calibration substrate using the radiation source, measure a band edge absorption wavelength, measure a first temperature of the calibration substrate using the first pyrometer, determine an actual temperature of the calibration substrate using the band edge absorption wavelength, and calibrate the first pyrometer by comparing the first temperature of the calibration substrate and the actual temperature of the calibration substrate.

In yet another embodiment, a method of calibrating a pyrometer within a process chamber is disclosed. The method of calibrating the pyrometer includes transferring a calibration substrate onto a substrate support within a chamber body, irradiating a portion of the calibration substrate using a light source, measuring a band edge absorption wavelength using a band edge detector, measuring a first temperature of the calibration substrate using a first pyrometer, and determining an actual temperature of the calibration substrate using the band edge absorption wavelength. The first pyrometer is calibrated by comparing the first temperature of the calibration substrate and the actual temperature of the calibration substrate. The calibration substrate is then transferred out of the chamber body.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally relate to apparatus and methods for semiconductor processing, more particularly, to a thermal process chamber. The thermal process chamber includes a substrate support, a first plurality of heating elements disposed over the substrate support, and a measurement assembly disposed within the thermal process chamber to calibrate non-contact temperature sensors. The calibration apparatus and method utilizes a band edge detector to determine the actual temperature of a calibration substrate. The calibration substrate has a known band gap over a range of temperatures. Absorption edge frequency is only dependent upon the material band gap of the calibration substrate and therefore is not affected by changes within the hardware of a process chamber, such as the aging of heat lamps, window coatings, or susceptor. The measurement of the band gap of the calibration substrate is correlated to a temperature measurement and used to calibrate non-contact temperature sensors, such as pyrometers, within the process chamber.

Using the methods described herein, the non-contact temperature sensors is calibrated using an automatic process, which does not use human intervention or the removal of chamber components. The automation of the calibration process reduces downtime, reduces human error, and improves the consistency of the calibration.

A “substrate” or “substrate surface,” as described herein, generally refers to any substrate surface upon which processing is performed. Processing includes deposition, etching, and other methods utilized during semiconductor processing. For example, a substrate surface which may be processed includes silicon, silicon oxide, doped silicon, silicon germanium, germanium, gallium arsenide, glass, sapphire, and any other materials, such as metals, metal nitrides, metal alloys, and other conductive or semi-conductive materials, depending on the application. A substrate or substrate surface which may be processed also includes dielectric materials such as silicon dioxide, silicon nitride, organosilicates, and carbon dopes silicon oxide or nitride materials. The substrate itself is not limited to any particular size or shape. Although the embodiments described herein are made with generally made with reference to a round 200 mm or 300 mm substrate, other shapes, such as polygonal, squared, rectangular, curved, or otherwise non-circular workpieces may be utilized according to the embodiments described herein.

FIG. 1is a schematic plan view of a substrate processing system100which includes the process chamber130a-ddescribed herein, according to one embodiment. The substrate processing system100is used to process semiconductor substrates by performing a variety of processes on the substrates. The substrate processing system100described herein includes a transfer chamber110, a plurality of process chambers130a-130d, load lock chambers120a,120b, a factory interface (FI)140, and front opening universal pods (FOUPs)150a,b. The process chambers130a-dand the load lock chambers120a,120bare coupled to the transfer chamber110. The load lock chambers120a,120bare additionally coupled to the FI140. The FI140accepts the FOUPS150a,bcoupled thereto opposite the load lock chambers120a,120b. The load lock chambers120a,120binclude cassettes135disposed therein, which are used to store substrates between processing operations. The transfer chamber110includes a transfer robot115disposed therein. The transfer robot115is used to transfer substrates between the process chambers130a-dand the load lock chambers120a,120b.

Each of the process chambers130a-dincludes a loading port125disposed adjacent to the transfer chamber110through which substrates enter or leave the process chambers130a-d. The process chambers130a-dare described in greater detail inFIG. 2. In some embodiments there are four process chambers130a-d, such that there is a first processing chamber130a, a second processing chamber130b, a third processing chamber130c, and a fourth processing chamber130d. The transfer chamber110is a central chamber, which is configured to transfer substrates within a controlled environment. The transfer chamber110is maintained at a constant temperature and pressure. The transfer chamber110may be vacuum isolated from each the process chambers130a-dwhile substrates are being processed within the process chambers130a-d.

The load lock chambers120a,120binclude a first load lock chamber120a, and a second load lock chamber120b. The load lock chambers120a,120bare disposed between and coupled to both the transfer chamber110and the FI140. Each of the load lock chambers120a,120binclude a cassette135. The cassette135is shown in greater detail inFIG. 3and described herein. The cassette135holds a plurality of substrates. The substrates are stored in the cassette135between processing operations and may be moved by the transfer robot115.

The FI140includes one or more robots (not shown) disposed therein. Substrates are transferred within the FI140between the FOUPs150a,band the load lock chambers120a,120b. The FI140is a clean environment and may be held at a constant temperature and pressure different from the transfer chamber110.

The FOUPs150a,binclude a first FOUP150a, and a second FOUP150b. There may be additional FOUPs not shown. The FOUPs150a,bare used for storing substrates either before or after processing within the process chambers130a-d.

FIG. 2is a schematic sectional view of a process chamber130a, which includes a measurement assembly270described herein, according to one embodiment. The process chamber130ais the first process chamber, but the second process chamber130b, the third process chamber130c, and the fourth process chamber130dmay be similar or the same as the first process chamber130a. The process chamber130amay be used as an epitaxial deposition chamber, a rapid thermal process chamber, or other thermal treatment chamber. The process chamber130amay be used to process one or more substrates, including the deposition of a material on an upper surface of a substrate202, heating of a substrate202, etching of a substrate202, or combinations thereof. The substrate202is a device substrate and includes a plurality of partially formed semiconductor devices formed thereon. The substrate202may be similar to a calibration substrate350, which is used in place of the substrate202.

The process chamber130agenerally includes a chamber body248, an array of radiant heating lamps204for heating, and a susceptor206disposed within the process chamber130a. As shown inFIG. 2, an array of radiant heating lamps204may be disposed below the susceptor206, above the susceptor206, or both above and below the susceptor206. The radiant heating lamps204may provide a total lamp power of between about 2 KW and about 150 KW. The radiant heating lamps204may heat the substrate202to a temperature of between about 350 degrees Celsius and about 1150 degrees Celsius. The susceptor206may be a disk-like substrate support as shown, or may include a ring-like substrate support (not shown), which supports the substrate from the edge of the substrate, which exposes a backside of the substrate202to heat from the radiant heating lamps204. The susceptor206may be formed from silicon carbide or graphite coated with silicon carbide to absorb radiant energy from the lamps204and conduct the radiant energy to the substrate202, thus heating the substrate202. In some embodiments, the susceptor206serves as a radiation source after being heated to an elevated temperature. In such an example, the susceptor206serves as a broad-band radiation source and emits a broad range of wavelengths. The susceptor206may be at a temperature greater than 350° C., such as between about 350° C. and about 1200° C.

The susceptor206is located within the process chamber130abetween a first transmission member208, which may be a dome, and a second transmission member210, which may be a dome. The first transmission member208and the second transmission member210, along with a base ring212that is disposed between the first transmission member208and second transmission member210, generally define an internal region211of the process chamber130a. Each of the first transmission member208and/or the second transmission member210may be convex and/or concave and/or planar. In some embodiments, each of the first transmission member208and/or the second transmission member210are transparent. The first transmission member208is disposed between the chamber lid254and the susceptor206. In some embodiments, an array of radiant heating lamps204may be disposed outside of the internal region211of the process chamber130aand/or above the first transmission member208, for example, a region201defined between the first transmission member208and a chamber lid254). The substrate202can be transferred into the process chamber130aand positioned onto the susceptor206through a loading port125formed in the base ring212. A process gas inlet214and a gas outlet216are provided in the base ring212.

The susceptor206includes a shaft or stem218that is coupled to a motion assembly220. The motion assembly220includes one or more actuators and/or adjustment devices that provide movement and/or adjustment of the stem218and/or the susceptor206within the internal region211. For example, the motion assembly220may include a rotary actuator222that rotates the susceptor206about a longitudinal axis A of the process chamber130a. The longitudinal axis A may include a center of an X-Y plane of the process chamber130a. The motion assembly220may include a vertical actuator224to lift and lower the susceptor206in the Z direction. The motion assembly220may include a tilt adjustment device226that is used to adjust a planar orientation of the susceptor206in the internal region211. The motion assembly220may also include a lateral adjustment device228that is utilized to adjust the positioning of the stem218and/or the susceptor206side to side within the internal region211. In embodiments including a lateral adjustment device228and a tilt adjustment device226, the lateral adjustment device228is utilized to adjust positioning of the stem218and/or the susceptor206in the X and/or Y direction while the tilt adjustment device226adjusts an angular orientation (a) of the stem218and/or the susceptor206. In one embodiment, the motion assembly220includes a pivot mechanism230. As the second transmission member210is attached to the process chamber130aby the base ring212, the pivot mechanism230is utilized to allow the motion assembly220to move the stem218and/or the susceptor206at least in the angular orientation (a) to reduce stresses on the second transmission member210.

The susceptor206is shown in an elevated processing position but may be lifted or lowered vertically by the motion assembly220as described above. The susceptor206may be lowered to a transfer position (below the processing position) to allow lift pins232to contact the second transmission member210. The lift pins232extend through holes207in the susceptor206as the susceptor206is lowered, and the lift pins232raise the substrate202from the susceptor206. A robot, such as the robot115, may then enter the process chamber130ato engage and remove the substrate therefrom though the loading port125. A new substrate202may be loaded onto the lift pins232by the robot, and the susceptor206may then be actuated up to the processing position to place the substrate202, with its device side258facing up. The lift pins232include an enlarged head allowing the lift pins232to be suspended in openings by the susceptor206in the processing position. In one embodiment, stand-offs234coupled to the second transmission member210are utilized to provide a flat surface for the lift pins232to contact. The stand-offs provide one or more surfaces parallel to the X-Y plane of the process chamber130aand may be used to prevent binding of the lift pins232that may occur if the end thereof is allowed to contact the curved surface of the second transmission member210. The stand-offs234may be made of an optically transparent material, such as quartz, to allow energy from the lamps204to pass therethrough.

The susceptor206, while located in the processing position, divides the internal volume of the process chamber130ainto a process gas region236that is above the susceptor206, and a purge gas region238below the susceptor206. The susceptor206is rotated during processing by the rotary actuator222to minimize the effect of thermal and process gas flow spatial anomalies within the process chamber130aand thus facilitates uniform processing of the substrate202. The susceptor206may rotate at between about 5 RPM and about 100 RPM, for example, between about 10 RPM and about 50 RPM. The susceptor206is supported by the stem218, which is generally centered on the susceptor206and facilitates movement of the susceptor206substrate202in a vertical direction (Z direction) during substrate transfer, and in some instances, processing of the substrate202.

In general, the central portion of the first transmission member208and the central portion of the second transmission member210are formed from an optically transparent material such as quartz. The thickness and the degree of curvature of the first transmission member208may be selected to provide a flatter geometry for uniform flow in the process chamber.

One or more lamps, such as an array of the radiant heating lamps204, can be disposed adjacent to and beneath the second transmission member210in a specified manner around the stem218. The radiant heating lamps204may be independently controlled in zones in order to control the temperature of various regions of the substrate202as the process gas passes thereover, thus facilitating the deposition of a material onto the upper surface of the substrate202. While not discussed here in detail, the deposited material may include silicon, doped silicon, germanium, doped germanium, silicon germanium, doped silicon germanium, gallium arsenide, gallium nitride, or aluminum gallium nitride.

The radiant heating lamps204may include a radiant heat source, depicted here as a lamp bulb241, and may be configured to heat the substrate202to a temperature within a range of about 200 degrees Celsius to about 1,600 degrees Celsius. Each lamp bulb241can be coupled to a controller250. The controller250includes power distribution board, such as printed circuit board (PCB)252, memory255, and support circuits257. The controller250may supply power to each lamp bulb241, control the process gas source251, control the purge gas source262, control the vacuum pump257, and control the measurement assembly270. A standoff may be used to couple the lamp bulb241to the power distribution board, if desired, to change the arrangement of lamps. In one embodiment, the radiant heating lamps204are positioned within a lamphead245which may be cooled during or after processing by, for example, a cooling fluid introduced into channels249located between the radiant heating lamps204.

In some embodiments, a liner263is disposed within the base ring212and surrounding the susceptor206. The liner263is coupled to the base ring212and protects the inside surface of the base ring212during substrate processing. The process gas inlet214, the gas outlet216, and the purge gas inlet264are all disposed through the liner263. In some embodiments, the liner263is a reflective liner.

Process gas supplied from a process gas supply source251is introduced into the process gas region236through the process gas inlet214formed in the sidewall of the base ring212. The process gas inlet214is configured to direct the process gas in a generally radially inward direction. As such, in some embodiments, the process gas inlet214may be a cross-flow gas injector. The cross-flow gas injector is positioned to direct the process gas across a surface of the susceptor206and/or the substrate202. During a film formation process, the susceptor206is located in the processing position, which is adjacent to and at about the same elevation as the process gas inlet214, thus allowing the process gas to flow generally across the upper surface of the susceptor206and/or substrate202. The process gas exits the process gas region236through the gas outlet216located on the opposite side of the process chamber130aas the process gas inlet214. Removal of the process gas through the gas outlet216may be facilitated by a vacuum pump257coupled thereto. In some embodiments, there are multiple process gas inlets214and multiple gas outlets216. In some embodiments, there are five or more process gas inlets214disposed along the inner circumference of the base ring212and three or more gas outlets216disposed along the inner circumference of the base ring212. Each of the process gas inlets214and the gas outlets216are parallel to one another and are configured to direct or receive process gas which flows along different portions of the substrate202.

Purge gas supplied from a purge gas source262is introduced to the purge gas region238through the purge gas inlet264formed in the sidewall of the base ring212. The purge gas inlet264is disposed at an elevation below the process gas inlet214. The purge gas inlet264is configured to direct the purge gas in a generally radially inward direction. The purge gas inlet264may be configured to direct the purge gas in an upward direction. During a film formation process, the susceptor206is located at a position such that the purge gas flows generally across a back side of the susceptor206. The purge gas exits the purge gas region238and is exhausted out of the process chamber130athrough the gas outlet216located on the opposite side of the process chamber130aas the purge gas inlet264.

The measurement assembly270enables accurate measurement of the temperature of the substrate202. Substrate temperature is measured by non-contact temperature sensors272,278configured to measure temperature at the device side258of the substrate202and the bottom side253of the substrate202. The measurement assembly270further includes light source274and the band edge detector276. Each of a first non-contact temperature sensor272, the light source274, and the band edge detector276are disposed above the substrate202. A second non-contact temperature sensor278is disposed below the substrate202and within the lamphead245. The non-contact temperature sensors272,278may be pyrometers disposed in ports formed in the chamber lid254or the lamphead245.

The light source274is a laser light source with a controlled intensity and wavelength range. In some embodiments, a broad band light source is utilized. The light source274may be a diode laser or an optical cable. When the light source274is an optical cable, the optical cable is connected to an independent light source, which may be disposed near the process chamber. The light source274may alternatively be a bundle of lasers or optical cables, such that a plurality of light beams are focused into a first calibration light beam286. In some embodiments, the light source274can emit radiation at a varying wavelength range. The varying wavelength range allows the light source274to emit wavelengths which would be within about 200 nm of the expected absorption edge wavelength of the calibration substrate. The use of a varying wavelength range eliminates noise which may be caused by the use of a wider wavelength spectrum and allows for an increase in the strength of emission of the narrower range from the light source274to increase the signal strength received by the band edge detector276. In some embodiments, one or more of the radiant heating lamps204are utilized as the light source274, and the light source274is disposed between the chamber lid254and the first transmission member208. In some embodiments, the light source274may be classified as a radiation source, such as a thermal radiation source or a broad band radiation source. The radiation source may be a laser diode or an optical assembly. The optical assembly may include a laser, a lamp, or a bulb as well as a plurality of lenses, mirrors, or a combination of lenses and mirrors.

The band edge detector276measures the intensity of different wavelengths of light within a second calibration light beam284, which is reflected off the calibration substrate350. The band edge detector276is configured to find a wavelength at which the calibration substrate350transitions from absorbing a wavelength of radiation to reflecting nearly all of a wavelength of radiation. The band edge detector276may include several optical components disposed therein in order to separate and measure the second calibration light beam284. In some embodiments, the band edge detector276is a scanning band edge detector and scans through a range of wavelengths to determine the transition wavelength at which the calibration substrate350transitions from absorbing to reflecting radiation. In some embodiments, the band edge detector276measures the intensity of wavelengths of light transmitted through a calibration substrate350(described below) from the susceptor206. As described above, in some instances the susceptor206serves as a radiation source. The intensity of wavelengths of the radiation emitted by the susceptor206and transmitted through the calibrations substrate350or a substrate202may be measured by the band edge detector276. The band edge detector276then determines a wavelength at which the calibration substrate350transitions from absorbing wavelengths to transmitting wavelengths. An optional filter may be placed between the band edge detector276and the susceptor and configured to filter out radiation emitted by the lamp bulbs241.

In some embodiments, a second band edge detector is disposed below the susceptor206. The second band edge detector may be in a similar position as the second non-contact temperature sensor278and/or may replace or be combined with the second non-contact temperature sensor278. The second band edge detector is similar in structure to the first band edge detector276, but calibrates the second non-contact temperature sensor278by measuring the intensity of the wavelengths transmitted through the calibration substrate350through a lower window disposed within the susceptor206. The second non-contact temperature sensor278and the second band edge detector are both represented herein by the second non-contact temperature sensor278, but it is generally understood that the second band edge detector and the second non-contact temperature sensor28may have a similar spatial relationship as that shown between the band edge detector276and the first non-contact temperature sensor278.

During the calibration methods disclosed herein, the substrate202is replaced with a calibration substrate350. The calibration substrate350is similar in size and shape as the substrate202. The calibration substrate350includes a top side358and a bottom side353. The top side358is similar to the device side258of the substrate202and the bottom side353is similar to the bottom side253of the substrate202. The calibration substrate350may be made of a variety of crystal structure materials. Exemplary materials and compounds which may form the calibration substrate350include Si, Ge, SiC, GaN, GaAs, AlN, InN, 3C—SiC, or InP material. Different materials with different crystal structures are known to have different band gaps with different temperature ranges. In embodiments described herein, a calibration substrate350formed from a crystalline SiC material is beneficial as the crystalline SiC material has an absorption edge wavelength which is easily measured using current band edge detection technology for temperatures between about 300° C. and about 1200° C. The band gap can be measured by determining the wavelength at which radiation transitions from being absorbed by the material to reflected by the material.

The calibration substrate350is formed from a single material or compound, as introducing additional materials/compounds may cause multiple band gaps to be measured by the band edge detector276. In some embodiments, the calibration substrate350has a concentration of a single compound or material greater than about 95%, such as greater than 98%, such as greater than 99%, such as greater than 99.9%, such as greater than 99.99%, such as greater than 99.999%. The calibration substrate350is a crystalline material and non-crystalline material is minimized to improve band gap edge detection. Using a calibration wavelength with a high percentage of a single material also increases thermal uniformity within the calibration substrate350. Thermal uniformity improved the accuracy of a comparison between the temperature measurements of the first and second non-contact temperature sensors272,278and the band edge detector276when each of the measured temperatures are from slightly different positions along the surface of the calibration substrate350.

During calibration of the first and second non-contact temperature sensors272,278, a first measurement radiation path282of the first non-contact temperature sensor272is disposed between the first non-contact temperature sensor272and the device side358of the calibration substrate350. A second measurement radiation path288of the second non-contact temperature sensor278is disposed between the second non-contact temperature sensor278and the bottom side353of the calibration substrate350. The first calibration light beam286is emitted by the light source274and strikes the top side358of the calibration substrate350before being reflected as the second calibration light beam284and received by the band edge detector276. The band edge detector276analyzes the wavelengths of the second calibration light beam284and determines an actual temperature of the calibration substrate350. The method in which the actual temperature of the calibration substrate350is determined is described herein (FIGS. 5 and 6). The actual temperature of the calibration substrate350is compared to the temperatures measured by the first and second non-contact temperature sensors272,278to facilitate calibration of the first and second non-contact temperature sensors272,278.

The chamber lid254may be a reflector and optionally placed outside the first transmission member208to reflect infrared (IR) light that is radiating off the substrate202and redirect the energy back onto the substrate202. The chamber lid254may be secured above the first transmission member208using a clamp ring256. The chamber lid254can be made of a metal such as aluminum or stainless steel. The measurement assembly270is disposed through the chamber lid254to receive radiation from the device side250of the substrate202.

FIG. 3is a schematic side view of a cassette135used within a load lock chamber120a,120bof the substrate processing system100ofFIG. 1, according to one embodiment. The cassette135is used to store substrates, such as the substrates202while the substrates are not being processed within the process chambers130a-d. The cassette135includes an upper member304, a lower member302, and a plurality of support members306.

The upper member304and the lower member302are disk shaped and have the same diameter. The diameters of the upper member304and the lower member302are about 305 mm to about 325 mm when a 300 mm substrate is stored within the cassette135. The diameters of the upper member304and the lower member302are about 10 mm to about 25 mm, such as about 10 mm to about 15 mm larger than the outer diameter of the substrates202.

The plurality of support members306are vertically disposed and configured to hold substrates, such as the substrate202, as well as the calibration substrate350. The support members306are disposed between the upper member304and the lower member302. The support members306are coupled to each of the upper member304and the lower member302. The support members306include a first support member308, a second support member310, and a third support member312. Each of the first, second, and third support members308,310,312include a plurality of ledges320disposed therein. The ledges320within each of the first, second, and third support members308,310,312face radially inward towards a central axis325of the cassette135.

Each of the first, second, and third support members308,310,312have 20 to 50 ledges, such as about 25 to 40 ledges for supporting substrates, such as substrate202and calibration substrate350. In some embodiments, the cassette135has 28 ledges disposed in each of the first, second, and third support members308,310,312, so that at least one calibration substrate350can be stored within the cassette135along with25device substrates202. The substrates202and the calibration substrate350are held in a horizontal position while stored in the cassette135and are contacted at an outer edge by the ledges320from each of the first, second, and third support members308,310,312.

FIG. 4is a schematic sectional view of the measurement assembly270used within the process chamber130aofFIG. 2, according to one embodiment. In addition to the components described with regard toFIG. 2, the measurement assembly270ofFIG. 4further includes a first window403, a second window408, a third window404, a fourth window407, and a cover420.

The first window403is disposed within a first opening402. The first window403is disposed between the first non-contact temperature sensor272and the first transmission member208. Therefore, the first window403is disposed between the first non-contact temperature sensor272and the calibration substrate350. The first window403is a quartz window and allows for radiation from within the process chamber130ato pass therethrough. The first window403may filter radiation emitted by the calibration substrate350to allow only wavelengths which the first non-contact temperature sensor272measures. The radiation traveling along the first measurement radiation path282travels between the top side358of the calibration substrate350and the first non-contact temperature sensor272. The first measurement radiation path282intersects both the first transmission member208and the first window403. In some embodiments, which may be combined with other embodiments, the first measurement radiation path282may intersect the top side358of the calibration substrate350at any radial position along the calibration substrate350. In some embodiments, the first measurement radiation path282intersects the top side358of the calibration substrate350at a specific location, such as either less than 15 mm from the center of the substrate, such as less than 10 mm from the center of the substrate, such as less than 5 mm from the center of the substrate or the first measurement radiation path282intersects the top side258of the calibration substrate350at a radius of about 110 mm to about 130 mm, such as about 115 mm to about 125 mm, such as about 120 mm.

The second window408is disposed within a second opening409. The second window408is disposed between the second non-contact temperature sensor278and the second transmission member210. Therefore, the second window408is disposed between the second non-contact temperature sensor278and the calibration substrate350. The second window408is a quartz window and allows for radiation from within the process chamber130ato pass there through. The second window408may filter radiation emitted by the calibration substrate350to allow only wavelengths which the second non-contact temperature sensor278measures. The radiation traveling along the second measurement radiation path288travels between the bottom side of the susceptor206and the second non-contact temperature sensor278. The second measurement radiation path288intersects both the second transmission member210and the second window408. In some examples, the second measurement radiation path288may intersect the bottom side of the susceptor206at any radial position along the calibration substrate350. In other examples, the second measurement radiation path288intersects the bottom side of the susceptor206at a specific radial position, such as a radial position directly below the calibration substrate350and either less than 15 mm from the center of the substrate, such as less than 10 mm from the center of the substrate, such as less than 5 mm from the center of the substrate or the second measurement radiation path288intersects the bottom side of the susceptor206at a radial position directly below the calibration substrate350at a radius of about 110 mm to about 130 mm, such as about 115 mm to about 125 mm, such as about 120 mm.

The third window404is disposed within a third opening405. The third window404is disposed between the light source274and the first transmission member208. Therefore, the third window404is disposed between the light source274and the calibration substrate350. The third window404allows light emitted by the light source274to pass there through. The light emitted by the light source274and traveling along the first calibration light beam286is disposed between the light source274and the top side358of the calibration substrate350. The first calibration light beam286passes through both of the first transmission member208and the third window404. The first calibration light beam286may intersect the top side358of the calibration substrate350at any radial position along the calibration substrate350. In some examples, the first calibration light beam286intersects the top side358of the calibration substrate350either less than 15 mm from the center of the substrate, such as less than 10 mm from the center of the substrate, such as less than 5 mm from the center of the substrate or the first calibration light beam286intersects the top side258of the calibration substrate350at a radius of about 110 mm to about 130 mm, such as about 115 mm to about 125 mm, such as about 120 mm.

The first calibration light beam286intersects the top side258of the calibration substrate350within less than 5 mm, such as less than 2 mm, such as less than 1 mm from the location in which the first measurement radiation path282intersects the radiation path. In some embodiments, the first calibration light beam286intersects the top side258of the calibration substrate350at the same radial position as the first measurement radiation path282. Measuring the calibration substrate350at the same location allows for a direct comparison between temperature measurements and reduces error when compared to measurements made at different radial distances from the center of the calibration substrate350.

The fourth window407is disposed within a fourth opening406formed through the chamber lid254. The fourth window407is disposed between the band edge detector276and the first transmission member208. Therefore, the fourth window407is also disposed between the band edge detector276and the calibration substrate350.

The light received by the band edge detector276and traveling along the second calibration light beam284is disposed between the band edge detector276and the top side358of the calibration substrate350. The second calibration light beam284passes through both of the first transmission member208and the fourth window407. The second calibration light beam284intersects the top side358of the calibration substrate350at the same location as the first calibration light beam286. The second calibration light beam284is a reflection of the first calibration light beam286off the top side258of the calibration substrate350. The second calibration light beam286is altered by intersecting the calibration substrate350and has a reduced wavelength range that is measured by the band edge detector276.

The cover420is disposed above the chamber lid254and surrounds the first non-contact temperature sensor272, the light source274, and the band edge detector276. The cover420may alternatively be disposed around each of the first non-contact temperature sensor272, the light source274, and the band edge detector276individually, such that there are a plurality of covers420. The cover420may serve as a support to hold each of the first non-contact temperature sensor272, the light source274, and the band edge detector276in place. The cover420prevents radiant energy from escaping the process chamber130aand interfering with other equipment.

The temperature of a portion of the susceptor206is measured using the second non-contact temperature sensor278. The temperature of a portion of the susceptor206measured using the second non-contact temperature sensor278is a bottom surface and disposed opposite the location at which the calibration substrate350is measured by the first non-contact temperature sensor.

FIG. 5is a method500of utilizing the measurement assembly270within the process chamber130aofFIG. 2, according to one embodiment. The method500includes a first operation502, a second operation504, a third operation506, a fourth operation508, a fifth operation510, a sixth operation512, and a seventh operation514. Each of the operations502,504,506,508,510,512, and514are performed sequentially as shown inFIG. 5and described herein.

The method500includes a first operation502of transferring a calibration substrate, such as the calibration substrate350from a cassette, such as the cassette135(FIG. 3). The calibration substrate350is stored within the cassette between each calibration of the first and second non-contact temperature sensors272,278(FIG. 4). The calibration substrate350is removed from the cassette by the transfer robot115within the transfer chamber110(FIG. 1).

During the second operation504, the transfer robot transfers the calibration substrate into the processing chamber, such as the processing chamber130aor any of the other processing chambers130b,130c,130d(FIGS. 1 and 2). The calibration substrate passes through the transfer chamber110before being inserted into the processing chamber through a loading port, such as the loading port125(FIG. 2). The calibration substrate is placed onto a susceptor and the transfer robot is retracted from the process chamber.

During the third operation506, a calibration process is performed. The calibration process includes utilizing the calibration substrate and the measurement assembly270. The calibration process of the third operation506is described in greater detail with reference to the method600of calibrating the non-contact temperature sensors.

After the third operation506, the temperature calibration process is stopped in a fourth operation508. Stopping the temperature calibration process includes stopping the flow of any process gases introduced into the process chamber, stopping of any heating of the calibration substrate, and ceasing of the measurement of the temperature of the calibration substrate.

After the temperature calibration process is ceased, the calibration substrate is removed from the process chamber during a fifth operation510. The calibration substrate is removed by the transfer robot through the loading port. The calibration substrate is inserted back into the cassette subsequent to being removed from the process chamber.

After removal of the calibration substrate from the process chamber, a semiconductor substrate may be transferred into the process chamber during the sixth operation512. The semiconductor substrate may be similar to the substrate202(FIG. 1). The semiconductor substrate may have partially formed semiconductor devices disposed thereon. The semiconductor substrate is transferred into the process chamber by the transfer robot and may have been stored within the cassette during the temperature calibration process or may have been stored in a separate process chamber.

Subsequent to the sixth operation512of transferring a semiconductor substrate into the process chamber, a substrate processing operation is performed during the seventh operation514. The substrate processing operation may include a deposition process on the top surface of the substrate. The substrate processing operation may further include heating the substrate, introducing at least one process gas, introducing a purge gas, and evacuating the process and purge gases. A plurality of substrates are processed during the substrate processing operation.

The sixth and seventh operations512,514are repeated so that between each calibration process multiple substrates are processed. The sixth and seventh operations512,514may be repeated, such that more than 50 substrates are processed within the processing chamber between each calibration process. In some embodiments, the calibration process is only performed once every several days and several hundred substrates are processed within the processing chamber between each calibration process.

The method500is repeated automatically after a preset amount of substrates have been processed within the processing chamber or after the processing chamber has reached a preset run time. The method500is automated and programmed into a controller, such as the controller250. The method500does not use human intervention and is completed without disassembly of the process chambers. The calibration of the non-contact temperature sensors using the method500requires minimum downtime of the system by only pausing processing operations for the length of time it takes to perform operations504,506,508, and510.

FIG. 6is a method600of calibrating non-contact temperature sensors, such as the non-contact temperature sensors272,278, within the process chamber ofFIG. 2, according to one embodiment. The method600is part of the third operation506of the method500described herein. Calibrating the non-contact temperature sensors includes a first operation602, a second operation604, a third operation606, a fourth operation608, and a fifth operation610. The operations602,604,606,608,610described with regard to the method600are performed subsequently as shown inFIG. 6and described herein.

The first operation602includes performing a calibration processing operation. The calibration processing operation may be similar to the substrate processing operation514performed on the regular substrate. The calibration processing operation includes heating the substrate, introducing a process gas, introducing a purge gas, and evacuating the process and purge gases. The process gas may be different from the process gas utilized in the substrate processing operation of the seventh operation514of the method500. A process gas may be a carrier gas, such as a H2gas. The carrier gas assists in matching process conditions with those found in the substrate processing operation514. The carrier gas assists in matching the pressure and gas flow which would be found during the substrate processing operation514. However, the process gas does not include reactant gases or deposition/etch gases, which may alter the surface of the calibration wafer. The process chamber and calibration substrate may be heated using the radiant heating lamps204(FIG. 2) and/or a susceptor heater (not shown). The heating of the process chamber and the calibration substrate is performed gradually and the temperature increases over time.

The second operation604includes measuring a wavelength of absorption of the calibration substrate using the band edge detector276(FIG. 4). During the second operation604a first calibration light beam286is emitted by the light source274or one of the radiant heating lamps204. When the first calibration light beam286strikes the top side358of the calibration substrate350at a first location, a first wavelength range of the first calibration light beam286is absorbed by the calibration substrate350while a second wavelength range of the first calibration light beam286is reflected as the second calibration light beam284. The second calibration light beam284enters the band edge detector276. The band edge detector276measures the intensity of a variety of wavelengths within the wavelength spectrum of the second calibration light beam284. The band edge detector276maps the intensity of the wavelength measurements over the wavelength range measured by the band edge detector276. Either a broad band light source, such as the light source274is utilized to form the first calibration light beam286, or one or more radiant heating lamps204is used to form the first calibration light beam286. The light source274may be beneficially utilized in order to improve the accuracy of the measurement. The light source274may emit a precise range of wavelengths at a set intensity and direction. This makes the light source274highly adjustable and may provide for improved measurement precision. The radiant heating lamps204may be used to reduce the number of components disposed on a lid of the process chamber. The radiant heating lamps204emit a range of light which may be similar to the range emitted by the light source274. The radiant heating lamps204have a controlled intensity. The radiant heating lamps204may be used to emit light which is absorbed and reflected by the calibration substrate350.

In some embodiments, which may be combined with other embodiments, radiation is transmitted through the calibration substrate and measured by the band edge detector276on the opposite side of the calibration substrate350from the radiation light source. This may occur when a susceptor on which the calibration substrate350is disposed is transparent to the light emitted by the light source at a wavelength detected by the band edge detector276or when the susceptor itself emits radiation after heating.

The band edge detector276may measure the intensity of wavelengths between about 250 nanometers (nm) to about 1350 nm, such as about 300 nm to about 1300 nm. The light sources (either the light source274or the radiant heating lamps204) may emit light at a wavelength of about 250 nm to about 1350 nm, such as about 300 nm to about 1300 nm.

An exemplary map of the intensity of the wavelength measurements if found inFIG. 7.FIG. 7shows the measurement of the intensity708of wavelengths over a range of wavelengths706. The range of wavelengths706measured by the band edge detector276may be the same range of wavelengths emitted by the light source274as the first calibration light beam286. The intensity708of the wavelengths over the range of wavelengths706is mapped to form an intensity curve702. The intensity curve702shows a sharp change between the wavelength range which is absorbed by the calibration substrate350, the wavelength range having a low or near zero measured intensity, and the wavelength range which is reflected by the calibration substrate350, the wavelength range having a high or near 1 measured intensity. The intensity is measured as a fraction of the intensity of the wavelength emitted by the light source274. The absorption edge wavelength is disposed in the midpoint704of the transition between low measured intensity and high measured intensity of the wavelength range. The absorption edge wavelength is the wavelength at which the wavelengths transition from being absorbed to being reflected by a material. The absorption edge wavelength is directly correlated to the band gap of a material and the band gap of a material is dependent upon the temperature of the material. As temperature changes within an object, such as the calibration substrate350, the band gap and thus the absorption edge wavelength also changes. Therefore, a temperature of a material can be measured by measuring the absorption edge wavelength.

Returning toFIG. 6, in the third operation606, the band edge detector276determines the temperature of the calibration substrate based off of the absorption edge wavelength found in the second operation604. A graph such as the correlated temperature graph800is utilized to equate the absorption edge wavelength with a temperature. The correlation curve802of the correlated temperature graph800may be found experimentally and correlates temperature806to the measured absorption edge wavelength804. The temperature determined by the band edge detector276using the absorption edge wavelength is beneficial in that the determined temperature is not influenced by the aging of any components within the process chamber, such as the process chamber130aofFIG. 2. The absorption edge wavelength is dependent upon temperature and the material of the calibration substrate350, but is minimally influenced by the state of the components within the process chamber. Therefore, since the same calibration substrate350is utilized and stored between each of the calibration processes, an accurate and repeatable actual temperature is able to be performed using the measurement assembly270and the band edge detector276. The actual temperature is the temperature measured by the band edge detector276.

In the fourth operation608the temperature of the calibration substrate350is determined using the first and second non-contact temperature sensors described herein. The temperature of the first and second non-contact temperature sensors is determined by measuring the radiation emitted by the calibration substrate350. In some embodiments, the non-contact temperature sensors are pyrometers. The temperature measured by the first non-contact temperature sensor is a first temperature, or a first measured temperature. The temperature measured by the second non-contact temperature sensor is a second temperature, or a second measured temperature. The areas of the calibration substrate350which are measured by the first and second non-contact temperature sensors are within about 5 mm of the radial position of the area measured by the band edge detector. In some embodiments, each of the first and second non-contact temperature sensors measure an area with the same radius as the area measured by the band edge detector. In some embodiments, the area is also called a measurement point.

In some embodiments, the second and fourth operations604,608are performed simultaneously to ensure the temperatures measured are equivalent. In some embodiments, all of the second, third, and fourth operations604,606, and608are performed simultaneously.

Over time, the temperature measurements of the first and second non-contact temperature sensors drifts due to aging and wear of components within the process chamber. Therefore, the temperature measurements of the non-contact temperature sensors should be calibrated periodically. In the fifth operation610, the non-contact temperature sensors are calibrated using the actual temperature determined by the band edge detector. The non-contact temperature sensors may be adjusted to a temperature matching or near (within a predetermined degree of accuracy) the temperature measured by the band edge detector.

In some embodiments, the method600of calibrating non-contact temperature sensors described herein is performed multiple times at a variety of temperatures so that the first and second non-contact temperature sensors may be calibrated to a wide range of temperatures. In some embodiments an adjustment algorithm can determine an optimum calibration amount for the non-contact temperature sensors after the method600has been repeated over a range of calibration substrate temperatures. The non-contact temperature sensors may be calibrated by adjusting each measurement by the same amount, or the non-contact temperature sensors may be adjusted on a curve determined by the controller.

The embodiments disclosed herein relate to the calibration of non-contact temperature sensors within a thermal processing chamber, such as an epitaxial processing chamber, using a band edge detector and absorption edge wavelengths. A calibration substrate is utilized to better enable consistent calibration results and provide an expected absorption edge wavelength for the material from which the calibration substrate is formed.