Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/48—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation
  • C23C16/481—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating by irradiation, e.g. photolysis, radiolysis, particle radiation by radiant heating of the substrate
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/52—Controlling or regulating the coating process

Definitions

• Embodiments of the invention generally relate to reaction chambers and film formation apparatus and methods.
• ⁇ is a statistical term that is used to denote the standard deviation of the data.
• Film thickness is typically measured at a number of points, and ⁇ indicates the way in which a probability function, or a probability density function, is centered around its mean.
• a typical selective epitaxial film may be about 3O ⁇ A thick, with a required uniformity of about 1.0% for 1 ⁇ , and this value gets smaller with each new device generation. In this regime, every degree Celsius of temperature variation produces about 3 A of film thickness variation. A uniformity of 1% for 1 ⁇ in uniformity translates into about 1°C for 1 ⁇ of temperature control. Thus, a factor of six in improvement over the current generation of epitaxial deposition equipment is required for such process control.
• a second factor that affects equipment performance for these new processes is the need to account and correct for wafer emissivity, which affects both the accuracy of the temperature measurements as well as the rate and manner in which the wafer is heated by radiation lamps, radiation lamps being the technology of choice for these reactors.
• the current generation of epitaxial chambers was designed mainly to process blanket silicon wafers, which have constant and uniform emissivity characteristics across the entire substrate surface. Because of this, emissivity effects could simply be calibrated into the equipment.
• the emerging selective low temperature processes are targeted towards device wafers (wafers with integrated circuits partially printed on them), which means that emissivity is neither a known factor nor is this property constant across the wafer.
• One aspect of the invention includes a processing chamber.
• the processing chamber is bounded by a sidewall, and a first peripheral member, having an inner peripheral edge that extends into the processing chamber, is disposed around at least a portion of the sidewall.
• a substrate support such as a susceptor, is disposed within the system.
• a top cover is provided for covering the processing chamber. According to this embodiment, the top cover is disposed above the substrate support, and comprises a reflective surface that reflects light back towards the substrate support.
• the reflective surface is designed to reflect light emanating from the substrate back onto the substrate so as to increase the effective emissivity of the substrate.
• a plurality of optical probes may be provided to collect light emanating from the substrate to measure the temperature at various locations.
• the reflective surface may have a plurality of openings, each of which provides a field of view for a respective optical probe.
• the field of view for the optical probes does not extend beyond the substrate.
• all of the optical probes are substantially equidistantly spaced along the radial direction of the substrate.
• the optical probes may comprise optical pyrometers and fiber optics for carrying signals to signal processing equipment.
• an emissometer for measuring the active emissivity of the substrate may be provided. The temperature of the substrate may then be determined utilizing the output from the emissometer and one or more of the temperature probes.
• the emissometer comprises an opening in the reflective surface that is wide enough to substantially eliminate, within the area of the opening, the increased effective emissivity caused by the reflective surface; a hot mirror may be provided to cover this opening, which may reflect off-axis light back onto the substrate.
• An optical probe is provided to collect light emanating from the substrate that passes through the hot mirror.
• an outer edge portion of the substrate support overlaps with the inner peripheral edge of the peripheral member, thereby blocking light that emanates from below the substrate.
• the substrate support may be rotatably mounted within the system, and the inner peripheral edge of the peripheral member does not touch the outer edge of the substrate support.
• either of the overlapping surfaces may be roughened, or grooved, to enhance light-scattering or light-absorbing effects; optically active thin films may also be used to enhance the absorptivity of the overlapped surfaces.
• a second peripheral member or light shield may be disposed adjacent to the sidewall that extends into the processing chamber to overlap above the inner and outer ends of the peripheral member and substrate support.
• a heating system that exclusively provides the heating required for the film-formation process is disposed below the substrate.
• the substrate support is a susceptor that heats the substrate through conduction and radiation.
• the bottom portion of the susceptor entirely covers the bottom surface of the substrate.
• the bottom portion of the susceptor is designed to be highly absorbent of light emitted by the heating system.
• the susceptor may be made from a uniform material that is a good thermal conductor, such as graphite.
• the heating system comprises a plurality of lamps, with each lamp heating a predefined, specific zone across the substrate. The zones may overlap each other to provide a substantially uniform heating distribution across the substrate.
• FIG. 1A is a cross-sectional view of an embodiment of a film formation system
• FIG. 1 B is a partial cross-sectional view of the film formation system depicted in FIG. 1A;
• FIG. 2 is a graph illustrating temperature measurement errors as a function of substrate temperature for substrates with different emissivity values
• FIG. 3 illustrates enhanced emissivity effects according to one embodiment
• FIG. 4 is a graph of average pyrometric temperature measurement errors as a function of mean wafer temperature as measured by thermocouples
• FIG. 5 is a perspective view of a test wafer with thermocouples
• FIG. 6 is a graph illustrating pyrometric temperature measurement errors caused by stray lamp radiation
• FIG. 7 is a partial cross-sectional view of another embodiment of a film formation system
• FIG. 8 is an enlarged partial perspective view of the embodiment depicted in
• FIG. 7; [0022] FIG. 9 is a cross-sectional view of another embodiment of a film formation system
• FIG. 10 is a graph illustrating experimental results of pyrometer temperature data and thermocouple temperature data versus time for the embodiment depicted in
• FIG. 9 is a graph of calculated average pyrometric temperature measurement error as a function of actual temperature of a processing chamber shown in FIG. 9;
• FIG. 12 is a cross-sectional view of yet another embodiment of a film formation system
• FIG. 13 is a cross-sectional view of an embodiment of an emissometer depicted in FIG. 12;
• FIG. 14 is a cross-sectional view of another embodiment of a film formation system.
• FIG. 15 is a graph of heating distributions for heating zones of a heating system depicted in FIG. 14.
• FIGS. 1A and 1 B A schematic view of a film formation system 10 is shown in FIGS. 1A and 1 B.
• the system 10 which may be, for example, a CVD epitaxial system, a poly silicon or silicon nitride deposition system, or any other film deposition system for hot CVD processes, i.e., CVD processes that are around 400 0 C or greater.
• the system 10 includes a processing chamber 15 bounded by sidewalls 18. Examples of such systems are disclosed in commonly assigned United States Patent Nos. 5,108,792; 5,258,824; and 6,083,323, each of which is incorporated herein by reference.
• the sidewalls 18 may be made from quartz to protect equipment from the flammable and corrosive process gases used in silicon deposition.
• a substrate support shaft 17 is rotatably disposed within the processing chamber 15, and includes a substrate support 16 upon which may be placed a substrate 19 that is to be processed.
• the term substrate support may include any device that is used to support the substrate 19 within the chamber 15, and may include, for example, a susceptor that supports the substrate 19 across the entire bottom surface of the substrate 19, a ring-shaped support that supports the substrate 19 only along the peripheral edges of the substrate 19, a tripod-like configuration that supports the substrate 19 at three or more points on the bottom of the substrate 19, a configuration that supports the substrate 19 at three or more points along the edge of the substrate 19, etc.
• the substrate support 16 may rotate, thus rotating the substrate 19.
• the substrate support 16, in the form of a susceptor may be made from a material with uniform properties, good thermal conductivity (100 Watts/(meter °C) or better) and a low mass, such as graphite, silicon carbide coated graphite, solid silicon carbide, alumina and other suitable ceramic materials.
• the top of the processing chamber 15 may be sealed by top cover 11. Top cover 11 is disposed above the substrate support 16, and hence above the substrate 19.
• Top cover 11 includes an outer cover 12, an inner cover 14 and a reflective surface 13 abutting the inner cover 14.
• the inner cover 14 may be made of quartz, and the outer cover 12 may be made of steel to protect the relatively fragile inner cover 14 and sidewalls 18.
• the reflective surface 13 may be made from a gold film, or any other highly reflective material, sandwiched between the outer cover 12 and inner cover 14. Several different optical stacks may also form the reflective surface 13, including nickel covered with silicon dioxide; a simple aluminum surface polished to a mirror finish may also be used.
• the reflective surface 13 is designed to reflect light emanating from the substrate 19 back onto the substrate 19. As discussed in more detail later, the reflective surface 13 creates an enhanced emissivity effect for the substrate 19.
• a housing 30 envelopes and supports the chamber 15.
• the susceptor support shaft 17 extends through a bottom aperture 32 of the chamber 15. Such an extension enables a drive assembly (not shown) to rotate the susceptor support shaft 17, and thus the substrate 19, during processing. Such rotation is accomplished to enhance process uniformity.
• gases enter the chamber 15 through an entry port 34 and are removed through an exhaust port 36.
• heat is provided by radiation bulbs 38.
• the radiation bulbs 38 are mounted, proximate the chamber 15, on a support assembly 40 connected to a housing 30.
• the sidewalls 18 of the chamber 15 are transparent, allowing infrared radiation from the radiation bulbs 38 to freely enter the reaction chamber 15 for heating of the substrate 19.
• the quartz windows e.g., accessible portions of the transparent chamber sidewalls
• a coolant flow for cooling the chamber sidewalls 18 is supplied to the housing 30 from a blower 42 via inlet conduit 44, directed past the outside surface of the sidewalls 18 and exhausted through outlet conduit 46. More specifically, the coolant flow is supplied via conduit 44 to housing 30 through upper and lower inlet ports 48 and 50. The coolant flow exits the housing 30 through upper and lower exhaust ports 52 and 54.
• the housing 30 forms a shroud that channels the coolant past the chamber sidewalls 18. Typically, the coolant is air.
• An air vane 56 or other coolant flow control device located in the inlet conduit 44, controls the amount of air flow to the housing 30 and, in turn, controls the temperature of the sidewalls 18 of the chamber 15.
• other devices for controlling the coolant flow may be used, such as an adjustable iris, a valve, blower speed control circuitry and the like.
• the temperature of the quartz chamber sidewalls 18 may be monitored using a conventional optical pyrometer 58.
• the optical pyrometer 58 should be capable of measuring temperatures in the range of 100 degrees centigrade to 800 degrees centigrade, and of detecting a wavelength of between 4.8 and 5.2 microns. Such an optical pyrometer is available from Ircon, Inc.
• Optical pyrometer 58 may be used to measure the temperature of the substrate support 16, and in one embodiment is capable of measuring temperatures in the range of 350 degrees centigrade to 1300 degrees centigrade, detecting at a wavelength of about 905 nanometers. Such a pyrometer is available, for example, from Sekidenko. Selection of the 905 nanometer wavelength provides good signal discrimination, and reduces changes of substrate 19 emissivity with substrate 19 temperature. [0036] Referring now to FIG.
• the film formation system 10 further includes a plurality of optical probes 20 for collecting light emanating from the substrate 19.
• the optical probes 20 are located above the substrate 19, and may be disposed along the radius of the substrate 19 at substantially equal radial distances.
• the optical probes 20 may be mounted on, or in, the outer cover 12. In certain embodiments, at least four optical probes 20 are provided, but the number of optical probes 20 can be increased or decreased as needed to improve performance or reduce costs.
• Each optical probe 20 is directed towards the top surface of the substrate 19, through a respective opening 21 in the reflective surface 13 and openings 22 in outer cover 12, to directly measure the temperature of the substrate 19.
• Each optical probe 20 has an enlarged field of view, indicated by dashed lines 23, engineered to collect as much radiation from the substrate 19 as possible, but without monitoring radiation beyond the edge of the substrate 19. Hence, in the depicted embodiment, the field of view 23 of every optical probe 20 is confined within the substrate 19 and does not extend outside the substrate 19.
• Each optical probe 20 may comprise, for example, a 2mm sapphire light pipe 33 disposed within the openings 21 , 22 and optically connected to a 905nm optical filter 24. The light pipe 33 may end flush with the reflective surface 13.
• the optical probes 20 may be connected to signal-processing electronics using fiber optic cables, and the signal collected by the optical probes 20 can be converted to a t corresponding temperature by the signal-processing electronics, which then reports the temperature to a control system that uses the temperature information to adjust heating power as needed to maintain a uniform temperature across the substrate 19.
• the signal processing circuitry may be mounted with the optical filter 24, which may be desirable in some situations as such a configuration reduces signal loss associated with fiber optic cable.
• the optical probes 20 function as pyrometers that measure the top surface temperatures within their respective fields of view 23 of the substrate 19.
• the energy to heat the substrate 19 comes from an irradiative heating system located underneath the substrate 19.
• the design of the irradiative heating system is discussed in more detail later herein.
• ⁇ is the radiative power, which is the actual quantity measured by the pyrometers 20; Ci and C 2 are constants; ⁇ is the radiation wavelength (which may be, for example, 905 nm in the embodiment described above); T is the temperature of the substrate 19 and ⁇ is the emissivity of the substrate 19. If the emissivity is known, Planck's law can be used to calculate the temperature of the substrate 19 very precisely. If this emissivity is not known, then it is not possible to perform an accurate temperature calculation, and the error incurred can be large depending on the difference between the assumed emissivity and the actual emissivity. FIG.
• one embodiment provides a highly reflective surface 13 situated right above the substrate 19.
• the reflective surface 13 traps the light radiation emitted by the substrate 19 and reflects this light radiation back and forth between itself and the substrate 19, creating an emissivity enhancement effect.
• the mechanism involved may be explained with reference to FIG. 3.
• An optical probe 20 disposed above the reflective surface 13 will receive not only the direct emission from the substrate 19, indicated by ⁇ in FIG. 3, but also a number of reflections between the two surfaces 13, 19.
• the total radiative power reaching the optical probe 20 with the reflective surface 13 would be:
• a pparent 4 + (l - S)R + (l - sf R 2 + .8)
• FIG. 4 shows the measured magnitude of the temperature error caused by emissivity effects.
• a test substrate 100 with a very low emissivity top surface (a polysilicon film with an emissivity of about 0.35) was fitted with thermocouples 101.
• the thermocouples 101 were located at the same radii as the optical probes 20 so that temperature measurements taken by the two techniques could be compared.
• FIG. 4 is a graph of
• the error due to emissivity is less that 5 0 C for temperatures up to 85O 0 C.
• the measurement error for a substrate 19 with an emissivity of 0.35 would instead be in excess of 70 0 C at a temperature of 850 0 C.
• the reflective surface 13 thus reduces emissivity-induced errors by over 90%.
• Another problem encountered when using pyrometry for radiantly heated processing chambers is stray radiation. With reference to FIG.
• the substrate 19 may be heated using an irradiative heating system.
• the irradiative heating system uses one or more lamps 38 to heat the substrate 19. Consequently, the chamber 15 tends to be flooded with light.
• One problem with this arrangement is that the light produced by the irradiative heating system is almost indistinguishable from the light radiated by the substrate 19.
• the pyrometers 20 will collect both of these components, radiation from the substrate 19 and radiation from the heating system, and interpret all of this radiation as having been produced by the substrate 19. This results in a direct measurement error that can easily reach hundreds of degrees Celsius in magnitude.
• FIG. 6 is a graph providing comparative data of pyrometer temperature readings when little or no stray radiation blocking features are utilized. In FIG.
• FIGS. 7 and 8 A system is shown including a processing chamber 200 that is enclosed by sidewalls 201 , which may be made from quartz. Rotatably disposed within the system, as described above with respect to FIG. 1, is a substrate support 202 that is used to hold a substrate 204 during the film formation process. All of the
• 11 process heating that is required for the film formation process is provided by an irradiative heating system, which is disposed below the substrate support 202 , and hence below the substrate 204.
• the film formation system may be thought of as being divided into two regions: an upper region 206 above the substrate 204, and a lower region 207 that is below the substrate support 202. Since the irradiative heating system may be located exclusively in the lower region 207, it is desirable to prevent light from the irradiative heating system from entering the upper region 204, as this is where the pyrometers (or optical probes) are located for measuring the temperature of the substrate 204. [0045] Disposed around at least a portion of the sidewalls 201 is a peripheral member 205.
• Ledges and pockets may be designed in the sidewalls 201 and peripheral member 205 to keep these two components from moving with respect to each other, and an outer peripheral edge of peripheral member 205 contacts a retaining edge 203 of the sidewall 201.
• the peripheral member 205 may be, for example, a pre- heat ring.
• the peripheral member 205 may be made of graphite, and keeps light from transmitting through the sidewalls 201 into the processing chamber, which may be made of quartz and which may therefore be transparent or translucent.
• the peripheral member 205 comprises an inner end 208 that extends into the processing chamber 200. This inner end 208 overlaps with an outer end 209 of the substrate support 202. Hence, the peripheral member 205 and the substrate support 202 have respective overlapping inner and outer edge portions 208, 209.
• a gap 210 may be provided between the rotating substrate support 202 and the stationary peripheral member 205.
• the width of the gap 210, which separates the overlapping ends 208, 209 may be made as small as possible to keep the amount of light passing through the gap 210 down to a minimum, and in one embodiment is 0.075 inches wide.
• the overlapping surfaces 208, 209 may include a stepped feature at the outer peripheral edge of substrate support 202 and at the inner peripheral edge of peripheral member 205.
• the stepped features of the substrate support 202 and peripheral member 205 are shown as being complementary. It is noted that by providing a complementary stepped design between the outer peripheral edge 209 of substrate support 202 and inner peripheral edge 208
• the overlapping surfaces 208, 209 may be provided optically rough finishes that are designed to scatter and absorb light.
• the top surface of the outer end 209 of the substrate support 202 may be machined to provide a series of narrow grooves 211.
• the bottom surface of the inner end 208 of the peripheral member 205 may be similarly provided a grooved surface.
• grooves are used, it should be understood that any suitable surface that absorbs light may be used for the overlapping surfaces 208, 209, such as other types of angled surfaces, or optical films designed to absorb the radiation emitted by the irradiative heating system.
• FIGS. 7 and 8 further provides an upper peripheral member, or light shield 212.
• the upper light shield 212 may be made from graphite, and is disposed above the overlapping ends 208, 209 of the peripheral member 205 and susceptor 202.
• the upper light shield 212 may be disposed on, or adjacent to, upper sidewall 213.
• the upper sidewall 213 may be made from quartz. Ledges and pockets may be designed in the upper sidewall 213 and light shield 212 to keep these two components from moving with respect to each other.
• a gap 215 may separate the lower surface 214 of the upper light shield 212 from the top surfaces of the substrate support 202 and peripheral member 205 so as not to interfere with the rotation of the susceptor 202.
• the lower surface 214 of the upper light shield 212 may similarly be provided an optically rough or absorbent surface, such as a series of fine grooves or optically active films, to absorb light emanating from the gap 210.
• the upper light shield 212 may follow the entire perimeter of the sidewalls 201 , 213. Although depicted as discrete elements, upper sidewall 213 and lower sidewall 201 may be made from a monolithic element, manufactured with appropriate grooves or the like to accept the peripheral member 205.
• FIG.9 illustrates another film formation system 300, which comprises a processing chamber 301 bounded by quartz sidewalls 302, and a top cover 303.
• a substrate support shaft 304 is rotatably disposed within the processing chamber 301 , and comprises a susceptor 305 that holds a substrate 306.
• the susceptor 305 is made from a light, uniform and thermally conductive material having a thermal
• the top cover 303 comprises a reflective surface 307 sandwiched between a quartz inner layer 308 and a steel outer layer 309.
• the reflective surface 307 reflects radiation emanating from the substrate 306 back towards the top surface of the substrate 306 to increase the effective emissivity of the substrate 306.
• the reflective surface 307 constantly reflects energy back to the substrate 306 until the substrate 306 reaches a uniform and isothermal condition regardless of the emissivity value or pattern on the surface of the substrate 306.
• a plurality of optical probes 310 sample light emanating from the substrate 306, each optical probe 310 having a respective field of view 311 that does not extend beyond the substrate 306. Openings 312 in the reflective surface 307 may provide the respective fields of view 311 to the optical probes 310.
• the film formation system 300 comprises a heating system 313 that is disposed below the substrate support 305.
• the heating system 313 comprises one or more lamps 314, which radiate light up into the chamber 301 to heat the bottom portion of the substrate support 305. All process heating is provided by the heating system 313.
• the system 300 further comprises a graphite peripheral member 315, which may be a preheat ring that overlaps with the susceptor 305. There thus exists a region of overlap 316 between the susceptor 305 and the peripheral member 315, as disclosed in the above embodiment.
• the film formation system 300 is designed to prevent defects in the film formation process that are typically brought on by pattern loading and emissivity variations of the substrate 306.
• the susceptor 305 provides a constant absortivity
• FIG. 10 is a graph illustrating experimental results of pyrometer temperature data against thermocouple temperature data for the film formation system 300.
• thermocouples welded to its top surface were utilized. Those thermocouples were located directly underneath the optical probes 310 so that the pyrometric readings of the optical probes 310 could be directly compared.
• a high emissivity film (of about 0.95) was grown on the surface of the wafer prior to attaching the thermocouples. With this, the accuracy and repeatability of the optical probes 310 was tested by heating up the wafer through arbitrary thermal cycles and comparing the thermocouple readings with those taken by the optical probes 310.
• FIG. 10 which graphs a thermocouple and optical probe located near the center of the substrate, the system 300 provides tight correlation between the temperatures as measured by thermocouples versus temperature as measured through pyrometry via the optical probes 310.
• FIG. 11 shows a summary of the calculated average measurement error across all optical probes 310 as a function of actual chamber 301 temperature obtained during these tests. As shown, for the temperature range of interest (> 550 0 C), the error due to stray light is on the order of 2°C.
• FIG. 12 Another embodiment of a film formation system 400 which further provides for emissivity-effect corrections for pyrometric measurements, is shown in FIG. 12.
• the film formation system 400 is similar to the system 300 of FIG. 9; however, the system 400 further includes an emissometer 410 for measuring the actual emissivity of the substrate 420.
• the principle of operation of the emissometer 410 involves positioning an optical probe 403 in the chamber 402, but for this optical probe 403 the enhanced
• the optical probe 403 only sees the direct radiation from the substrate 420, without any reflected radiation. That is, the radiative power the optical probe 403 measures is:
• the emissivity of the substrate 420 may be calculated as:
• Tmeas is the measured wafer temperature
• delta is the difference in temperature measured by the temperature probe 404 and the emissometer probe 403
• R3 is the reflectivity of the reflective surface 401
• RE is the reflectivity of the cavity around the emissometer 410.
• the other constants are given as in Equation 1.
• several substrates 420 of known emissivity from 0.3 to about 0.95 may be run in the chamber 402, and the temperature delta between the emissometer 410 and regular pyrometer 404 may be measured to construct a calibration curve.
• This calibration curve may be fit with an exponential function, and subsequently used to determine the emissivity of an unknown substrate 420.
• This emissivity value is then used to perform a correction to the temperature reported by the pyrometric optical probes 405.
• FIG. 13 illustrates an embodiment of the emissometer 410.
• the optical probe 403 is located in an area of the reflective surface 401 where a relatively large diameter hole 406 is drilled or etched.
• the diameter of hole 406 may correlate with the field of view of the optical probe 403 and the distance to the substrate 420. It is desired that the optical probe 403 collects light that comes directly from the substrate 420 without having reflected off of the reflective surface 401 , and thus that the optical probe 403 receives none of the emissivity enhancement provided by the reflective surface 401. Hence, it is desirable for the diameter of the hole 406 to be as wide as possible.
• the optical probe 403 will almost always collect some emissivity enhancement radiation unless the hole 406 is made very large. Making the hold 406 very large may be undesirable, though, as this tends to create a cold spot on the substrate 420. Since the substrate 420 may rotate, this cold spot will create a cold ring on the substrate 420.
• a suitable compromise may be provided by making the diameter of the hole 406 the same size as the field of view on the surface of the substrate 420 of the optical probe 403. In one embodiment, the diameter of hole 406 may range from 0.5 inches to 2 inches. In another embodiment, the diameter may be about 0.75 inches.
• the diameter may be a function of the angle of view of the optical probe 403 and the distance from the optical probe 403 and the substrate 420.
• the width of the hole 406 effectively eliminates the emissivity enhancement effect of the reflective surface 401 for the radiation reaching this probe 403.
• a hot mirror 407 is positioned to cover the hole 406.
• the hot mirror 407 is designed to reflect off-axis light back to the substrate 420, which minimizes the amount of heat lost through the hole 406.
• Such a hot mirror may be obtained, for example, from Sekidenko.
• the emissometer 410 Because of hot mirror 407, only radiation emitted directly underneath the probe 403 reaches the emissometer 410. This radiation is not enhanced by the reflective surface 401 , and can then be compared to a regular pyrometric probe 404, 405 to compute the emissivity of the substrate 420, as described above. When the emissivity of the substrate 420 is known, the temperature of the substrate 420 can be accurately determine using Eqn. 1 , and the radiative power detected by the optical probes 404, 405. [0057] Of course, any suitable emissometer may be used. For example, a reflectometer may be used to obtain the emissivity of the substrate.
• a reflectometer sends a beam of light to the substrate and measures the intensity of the reflection.
• the substrate will not transmit any of the light, and will reflect back some of the light.
• emissometers each with its respective field of view of the substrate, to determine the emissivity of the substrate over a corresponding plurality of regions.
• the emissivity of the substrate in one region as measured by the emissometer for that region may then be used to accurately compute the temperature of that region for a corresponding pyrometer with a field of view that encompasses the region. In this manner, the temperature distribution across the substrate may be more accurately measured, and hence more accurately controlled.
• an adjustable source of energy is provided to control the temperature within a film formation chamber.
• system 500 includes a four-zone irradiative heating system 510, with each zone 501 capable of being independently adjusted based on temperature feedback received from a corresponding radial distribution of pyrometric optical probes 502.
• the irradiative heating system 510 is disposed beneath susceptor 505, and comprises a plurality of lamps 503 and reflectors 504. Adjustment to the angles and orientations of the lamps 503 and reflectors 504 creates the independently adjustable heating zones 501.
• the heating zones 501 combine to produce a heating pattern that can be adjusted to be uniform across the bottom surface of the susceptor 505.
• the bottom surface of the susceptor 505 may be engineered to be maximally absorbing of the radiation emitted by the lamps 503, such as by making use of optical films, grooves, etc.
• a graph of the heating pattern generated by the heating system 510 is presented in FIG. 15, and shows the heat distribution measured across the susceptor 505 for each individual heating zone 501 when turned on independently.
• Each heating zone 501 heats the substrate 507 at a specific radius on the susceptor 505 (i.e., the heating distribution of each zone 501 is symmetric about the rotational center of the susceptor 505), and hence at a specific radius on the substrate 507, and all heating zones 501 overlap just enough to create a uniform heating distribution. It is expected that the heating zones 501 of the heating pattern indicated in FIG. 15 superimpose to produce a temperature distribution across the substrate 507 with better than 1°C for 1 ⁇ .

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• 2005
  • 2005-09-30 US US11/242,298 patent/US7691204B2/en not_active Expired - Fee Related
• 2006
  • 2006-09-11 WO PCT/US2006/035031 patent/WO2007040908A2/en not_active Ceased
  • 2006-09-11 KR KR1020087010501A patent/KR101047089B1/ko not_active Expired - Fee Related
  • 2006-09-11 JP JP2008533387A patent/JP5686952B2/ja not_active Expired - Fee Related
  • 2006-09-19 TW TW095134661A patent/TWI367958B/zh not_active IP Right Cessation

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