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WO1996004534A1 - Appareil de surveillance de la temperature en des points multiples d'une plaquette de semi-conducteur pendant son traitement - Google Patents

Appareil de surveillance de la temperature en des points multiples d'une plaquette de semi-conducteur pendant son traitement Download PDF

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Publication number
WO1996004534A1
WO1996004534A1 PCT/US1995/008521 US9508521W WO9604534A1 WO 1996004534 A1 WO1996004534 A1 WO 1996004534A1 US 9508521 W US9508521 W US 9508521W WO 9604534 A1 WO9604534 A1 WO 9604534A1
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WO
WIPO (PCT)
Prior art keywords
wafer
temperature
emissivity
reflectivity
semiconductor wafer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1995/008521
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English (en)
Inventor
Dario Cabib
Robert A. Buckwald
Michael E. Adel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CI Systems Israel Ltd
Original Assignee
CI Systems Israel Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CI Systems Israel Ltd filed Critical CI Systems Israel Ltd
Priority to US08/604,997 priority Critical patent/US5823681A/en
Publication of WO1996004534A1 publication Critical patent/WO1996004534A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/0003—Radiation pyrometry, e.g. infrared or optical thermometry for sensing the radiant heat transfer of samples, e.g. emittance meter

Definitions

  • the present invention relates to methods and systems for monitoring the temperature of semiconductor wafers during processing.
  • the emissivity of the semiconductor wafer i.e., the wafer emission relative to the emission of a perfect blackbody at the same temperature, is generally not known and is dependent on wavelength, temperature and surface conditions, such as morphology and the presence of layers & other structure.
  • the semiconductor wafer is often transparent to radiation in the wavelength band in which the pyrometer operates, which precludes the use of conventional pyrometry. In some cases the wafer goes from transparent to opaque during the process as a result of the deposition of metallic or other materials.
  • collimated radiation is used to perform the reflection measurements from the wafer surface. While the use of collimated radiation has the advantage of allowing remote optical access it may result in erroneous reflectivity measurements and hence inaccurate emissivity estimates from surfaces which are not optically smooth in the wavelength band of interest.
  • Moslehi et al. have proposed a technique to overcome this shortcoming which entails the use of laser scatterometry to measure the wafer "scattering parameter" at one wavelength. Laser scatterometry is utilized to extract the scattering parameter at a different wavelength from that of the optical pyrometer. The emissivity may then be computed by combining this scattering parameter with the specular reflectivity measured in the pyrometer wavelength band.
  • this technique requires considerable hardware and various empirically derived relations.
  • Moslehi et al. have proposed a technique with a view toward application in rapid thermal processing and have therefore chosen in their detailed description a pyrometer wavelength band in the mid infrared (5.4 microns). Yomoto and Moslehi et al.
  • Crowley et. al also suggest the use of a two stage calibration technique in which a general pyrometer calibration table is determined with a thermocouple instrumented wafer.
  • the second stage involves utilizing an arbitrary wafer selected from a batch of a particular lot to obtain a specific correction factor to the pyrometer reading for the batch of wafers to be processed. This is an inherent disadvantage in that a specific calibration must be carried out for every different kind of batch wafer, a procedure which is unacceptable in a true production environment.
  • an emissivity compensating non-contact system for measuring the temperature of a semiconductor wafer, comprising: (a) a semiconductor wafer emissivity compensation station for measuring the reflectivity of said wafer at discrete wavelengths to yield wafer emissivity in specific wavelength bands; (b) a measurement probe which is optically coupled to a semiconductor process chamber, said probe sensing wafer self emission by means of at least one optical detector and a light modulator; (c) background temperature determining means for independently sensing the temperature of a source of background radiation; and (d) means for calculating the temperature of said semiconductor wafer based on said reflectivity, self-emission and background temperature.
  • FIG. 1 illustrates the major components of a system according to the present invention and the interconnections between them;
  • FIG. 2 illustrates a monochromator subassembly of the wafer emissivity compensation station (WECOMP) station of the system of Figure 1;
  • WECOMP wafer emissivity compensation station
  • FIG. 3 illustrates the coupling optics subassembly of the wecomp station of Figure 1;
  • FIG. 4 illustrates a spherical mirror assembly which is preferably mounted above the coupling optics on the wecomp station to facilitate improved emissivity compensation
  • FIGs. 5A and 5B illustrate, in side view and top view, respectively, a measurement probe assembly according to one embodiment of the present invention
  • FIG. 6 illustrates a cavity configuration in which the quartz rod couples between semiconductor wafer and heater according one embodiment of the present invention
  • FIG. 7 flow diagram of a calibration procedure
  • FIG. 8 flow diagram of a measurement procedure.
  • the present invention is of a non-contact semiconductor wafer temperature monitoring system and method which can be used to monitor the temperature of wafers during processing.
  • the current invention has at least two significant advantages over previously known configurations such as that disclosed by Crowley et al.
  • the optics used herein are convergent which allows both the specular and diffuse components of the reflected radiation to be collected and utilized.
  • the reflectivity measurement is carried out over a plurality of discrete wavelengths, which enhances the accuracy and precision of the measurements.
  • FIG. 1-3 illustrates the main components of a system according to the present invention.
  • a wafer emissivity compensation (hereinafter "WECOMP") station 10 is used to carry out reflectivity and transmission measurements on every wafer prior to its entering any one of several, for example, five, processing chambers
  • Probe 13 preferably operates in a specific optical band pass determined, on the long wavelength side, by the "cut-off behavior of the photoconductive or photovoltaic detector, i.e., the semiconductor optical abso ⁇ tion edge, and, on the short wavelength side, by the very sha ⁇ spectral drop off of the Planck function.
  • WECOMP station 10 and all probes 13 are electronically coupled to a controller unit 14 which controls acquisition and preliminary signal processing before downloading digital data from WECOMP station 10 and all probes 13 to a personal computer 16, or other microprocessor-based digital instrument.
  • personal computer 16 calculates wafer temperature in each of process chambers 12 and relays these data via other digital information channels or to a visual display unit.
  • WECOMP station 10 preferably includes a monochromator 11 which is shown in Figure 2. WECOMP station 10 further includes a source module 18 which generates polychromatic radiation over a continuous range of wavelengths.
  • optical fiber 20 at the bottom of Figure 2 is the same optical fiber 20 as at the bottom of Figure 3.
  • the coupling optics collimates the radiation emanating from optical fiber 20 using collimating lens 22 and refocuses the radiation on the wafer 24 using focusing lens 26.
  • the convergent beam of large angular acceptance coming out of focusing lens 26 leaves coupling optics 21 and optical window 28 and impinges on semiconductor wafer 24.
  • the large angular acceptance (low F number) of coupling optics 21 allows for the simultaneous measurement of both specular and diffuse reflectance, thereby improving emissivity estimation.
  • the reflected beam is then collected by the same optics and focussed back on the same optical fiber 20, through which it is conducted to monochromator 11 which accepts radiation only within a narrow acceptance angle.
  • monochromator 11 measures wafer emissivity in specific wavelength bands of from about 0.7 to about 2.4 microns.
  • the signal is detected by detector 30 and is then spectrally analyzed at consecutive discrete narrow wavelength bands within the spectral range of the measurement probe detectors.
  • detector 30 Any suitable detector 30 may be used, such as detectors which include one or more of Si, Ge or InAs.
  • monochromator 11 measure wafer emissivity in specific bands between about 0.7 and about 2.3 ⁇ m.
  • the signal from detector 30 is then processed and digitally transmitted to personal computer 16 as input to the calibration and measurement algorithms, which are described in more detail below.
  • the versatility and performance of WECOMP station 10 is preferably augmented by the inclusion of a spherical mirror 32, shown in Figure 4 which may be intermittently positioned, as by use of a suitable shutter 34, above the wafer at a distance equal to the radius of curvature of spherical mirror 32 in order to improve the emissivity compensation, especially when transparent wafers are measured.
  • Spherical mirror 32 performs two important functions. First, spherical mirror 32 simulates the reflectivity of semiconductor wafer 23 after a highly reflective layer has been deposited on the top surface of the wafer.
  • spherical mirror 32 allows measurement of the transmission of wafer 24 in order to facilitate estimation of the wafer emissivity in cases where the wafer is transparent in the spectral band of the detector in use.
  • Spherical mirror 32 may be positioned remotely from the wafer itself, that is, outside process chamber (as shown in Figure 4), beyond a window even in the case of convergent optics in the reflectivity measurement station.
  • Measurement probe 13 which is located at least partly within processing chambers 12, preferably includes a rod 36, preferably of quartz or sapphire, which couples the radiation from a wafer/rod cavity 38 to the radiation photoconductive or photovoltaic detector 40 via a radiation modulator 42 as shown in Figure 5.
  • Modulator 42 includes a chopper 43 which is a disk having an annular array of openings 45 which intersect the optical path between rod 36 and photovoltaic detector 40 and which act to modulate the incoming radiation.
  • the chopping of the incoming radiation acts to improve the performance of the detector and electronics system by increasing signal frequency from a dc signal to a signal in which the noise level of the detector and electronics system is considerably reduced, in the process also eliminating dc drift issues.
  • cavity 38 acts to enhance emissivity of wafers of low emissivity. The enhancement is achieved through multiple reflections between wafer 24 and the reflective surfaces of cavity 38.
  • the cavity configuration shown in Figure 6 is one of many alternatives which can be envisaged for optically coupling rod 36 to wafer 24.
  • the measurement probe optics are designed to have the same wide acceptance angle from rod 36 as the WECOMP station 10 coupling optics. This is achieved by the unique characteristic of the possible acceptance angle of rod 36 configuration of 90 degrees, which is only limited by the measurement probe coupling optics.
  • the large acceptance angles makes possible very efficient radiation collection of up to a few steradian compared to relative solid angles of conventional collimated optics of several millisteradian.
  • the large acceptance angles drop the lower limit of the measurable temperature measurement range well below that achievable with conventional collimated beam pyrometer techniques.
  • the solid angle of acceptance of the measurement probe optics is chosen to be equal to that of WECOMP station monochromator 11 which further reduces the error in the emissivity estimation algorithm.
  • a system according to the present invention further includes an embedded thermocouple 44 ( Figure 6) in the heater 46 of each process chamber 12 in which measurement probe 13 is installed.
  • Thermocouple 44 allows for the real time monitoring of heater temperature via a digital thermocouple reading device communicating with personal computer 16.
  • the availability of thermocouple 44 facilitates the calibration of, and accounting for, the radiation contributed by heater 46.
  • FIG. 1 schematically depicts the multiplicity of probes 13, with one probe 13 being provided for each processing chamber 12. Since each probe 13 has its own detector, the various signals can be processed simultaneously or can be handled sequentially by the electronic control unit.
  • a system according to the present invention can operate as follows. First, a calibration procedure is carried out, as outlined in Figure 7. For this pu ⁇ ose, a reference wafer is inserted into processing chamber 12. A vacuum is maintained in processing chamber 12 so as to keep wafer 24 cold. The temperature of heater 46 is then raised and is measured with thermocouple 44 at N points between temperatures of (T h ) between T, and T 2 , where, 5 T h is the set of temperatures between temperatures T, and T 2 at which the two steps of the full calibration are performed and is a vector of length N.
  • V ⁇ ld The output voltage (V ⁇ ld ) at these temperatures is measured, and the relation between V ⁇
  • ⁇ ⁇ u is the output voltage for each temperature of the vector T h measured when the wafer is cold and therefore not adding to the background radiation and is a vector of length N.
  • Output voltage (V h0 ,) is measured for the same temperatures points as before (T h ), where, V to is the output voltage for each temperature of the vector T b measured when the wafer is hot and is a vector of length N.
  • V w is the output voltage related to wafer contribution, after background reduction and is a vector of length N.
  • T 0 is the temperature at which the indirect calibration is performed.
  • Each wafer's reflectivity is averaged over the relevant band resulting in an element reflectivity vector R, v , where, R av is an M-sized vector wherein each element gives the average reflectivity of one of the M wafers used for the indirect calibration.
  • the average is performed over the relevant spectrum window.
  • the background radiation is then separated into direct and indirect components:
  • W ⁇ tta is the part of the background attributed to direct radiation from the heater at temperature T 0 and is calculated using a linear regression of the above relation; i n i r - d is the part of the background attributed to back-reflections of heater radiation by the wafer and into the system and is a vector of length M; and ⁇ is the indirect background factor which is calculated using linear regression of the above relation.
  • the cavity factor is calculated from the dependence of V w on Rstrich v , wherein V w is calculated from the previous step: and is then assumed to be proportional to e ⁇ while C f is determined using linear regression, where,
  • C f is the cavity factor
  • c' is the wafer emissivity for each of the M wafers including the cavity factor and is calculated by the expression: Data from the full calibration is reduced to two calibration functions, one relating the background contribution to the temperature and the other relating the wafer radiation to the temperature.
  • the calibration functions are normalized according to the indirect calibration results.
  • the background function is normalized using ⁇ and the reflectivity.
  • the wafer function is normalized using the cavity factor and the reflectivity.
  • the short calibration procedure is similar to that described above but for a single temperature T 0 and a single reference wafer.
  • the calibration functions determined in the full calibration procedure can then be re-normalized based on the new measurement results.
  • An alternative calibration can be used which inco ⁇ orates the spectral measurement of the wafer emissivity.
  • a theoretical calibration table can be created, leaving only a geometrical factor to be determined in the calibration process.
  • the background calibration and the indirect calibration remain as previously described.
  • the theoretical calibration table is created using three known spectral functions: (1) Plank's blackbody radiation equation W( ⁇ ); (2) the wafer emissivity (including the cavity factor) e'( ⁇ ); and (3) the detector responsivity 9t( ⁇ ).
  • T the theoretical voltage can be calculated from:
  • the factor A is then found by fitting the measured values of (V w ,T h )to the table values (V,T).
  • Wafer reflectivity is first measured in WECOMP station 10. Wafer
  • VJ voltage resulting from wafer and background radiation
  • TJ heater temperature
  • T m is then substituted into the background calibration function.
  • the factor ⁇ and the average wafer reflectivity are inco ⁇ orated into the calculation.
  • the result is the voltage emanating from the background (V b (TJ).
  • the voltage related to the wafer is calculated as
  • the wafer temperature T w is calculated using the wafer calibration function. The calculation includes the use of the cavity factor and the wafer average reflectivity.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Radiation Pyrometers (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

L'invention concerne un système de mesure à compensation d'émittance, permettant de mesurer sans contact la température d'une plaquette de semi-conducteur (24). Ce système comporte un poste (10) de compensation de l'émittance mesurant le pouvoir de réflexion de la plaquette (24) à des longueurs d'ondes différentes, pour déterminer l'émittance dans des bandes spécifiques de longueurs d'onde. Le système comprend en outre une sonde de mesure (13) qui est couplée optiquement à une chambre de traitement (12) pour semi-conducteurs. La sonde (13) détecte l'émission spontanée de la plaquette en utilisant un ou plusieurs détecteurs optiques (40) et un modulateur de lumière (42). Un dispositif (44) pour déterminer la température de fond détecte d'une manière indépendante la température d'une source (46) de rayonnement de fond. Finalement, un dispositif (16) calcule la température de la plaquette de semi-conducteur à partir du pouvoir de réflexion, de l'émission spontanée de la plaquette, et de la température de fond.
PCT/US1995/008521 1994-08-02 1995-07-12 Appareil de surveillance de la temperature en des points multiples d'une plaquette de semi-conducteur pendant son traitement Ceased WO1996004534A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US08/604,997 US5823681A (en) 1994-08-02 1995-07-12 Multipoint temperature monitoring apparatus for semiconductor wafers during processing

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IL110,549 1994-08-02
IL110549A IL110549A (en) 1994-08-02 1994-08-02 Multipoint temperature monitoring apparatus for semiconductor wafers during processing

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999010718A1 (fr) * 1997-08-27 1999-03-04 Steag Rtp Systems Gmbh Procede et dispositif servant a ameliorer la regulation de la temperature dans des systemes de traitement thermique rapide (rtp)
CN112771354A (zh) * 2018-09-28 2021-05-07 美特拉斯有限公司 用于控制半导体晶片温度的方法和设备
CN116472440A (zh) * 2020-10-27 2023-07-21 杰富意钢铁株式会社 表面温度测量方法、表面温度测量装置、热浸镀锌系钢板的制造方法和热浸镀锌系钢板的制造设备

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3796099A (en) * 1971-12-27 1974-03-12 Nippon Kokan Kk Method for measuring the surface temperature of a metal object
US4919542A (en) * 1988-04-27 1990-04-24 Ag Processing Technologies, Inc. Emissivity correction apparatus and method
US4956538A (en) * 1988-09-09 1990-09-11 Texas Instruments, Incorporated Method and apparatus for real-time wafer temperature measurement using infrared pyrometry in advanced lamp-heated rapid thermal processors
US4969748A (en) * 1989-04-13 1990-11-13 Peak Systems, Inc. Apparatus and method for compensating for errors in temperature measurement of semiconductor wafers during rapid thermal processing
US4979133A (en) * 1988-02-08 1990-12-18 Minolta Camera Kabushiki Kaisha Pyrometer
US4979134A (en) * 1988-07-15 1990-12-18 Minolta Camera Kabushiki Kaisha Method for measuring surface temperature of semiconductor wafer substrate, and heat-treating apparatus
US5029117A (en) * 1989-04-24 1991-07-02 Tektronix, Inc. Method and apparatus for active pyrometry
US5156461A (en) * 1991-05-17 1992-10-20 Texas Instruments Incorporated Multi-point pyrometry with real-time surface emissivity compensation
US5305416A (en) * 1993-04-02 1994-04-19 At&T Bell Laboratories Semiconductor processing technique, including pyrometric measurement of radiantly heated bodies
US5326173A (en) * 1993-01-11 1994-07-05 Alcan International Limited Apparatus and method for remote temperature measurement

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3796099A (en) * 1971-12-27 1974-03-12 Nippon Kokan Kk Method for measuring the surface temperature of a metal object
US4979133A (en) * 1988-02-08 1990-12-18 Minolta Camera Kabushiki Kaisha Pyrometer
US4919542A (en) * 1988-04-27 1990-04-24 Ag Processing Technologies, Inc. Emissivity correction apparatus and method
US4979134A (en) * 1988-07-15 1990-12-18 Minolta Camera Kabushiki Kaisha Method for measuring surface temperature of semiconductor wafer substrate, and heat-treating apparatus
US4956538A (en) * 1988-09-09 1990-09-11 Texas Instruments, Incorporated Method and apparatus for real-time wafer temperature measurement using infrared pyrometry in advanced lamp-heated rapid thermal processors
US4969748A (en) * 1989-04-13 1990-11-13 Peak Systems, Inc. Apparatus and method for compensating for errors in temperature measurement of semiconductor wafers during rapid thermal processing
US5029117A (en) * 1989-04-24 1991-07-02 Tektronix, Inc. Method and apparatus for active pyrometry
US5156461A (en) * 1991-05-17 1992-10-20 Texas Instruments Incorporated Multi-point pyrometry with real-time surface emissivity compensation
US5326173A (en) * 1993-01-11 1994-07-05 Alcan International Limited Apparatus and method for remote temperature measurement
US5305416A (en) * 1993-04-02 1994-04-19 At&T Bell Laboratories Semiconductor processing technique, including pyrometric measurement of radiantly heated bodies

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999010718A1 (fr) * 1997-08-27 1999-03-04 Steag Rtp Systems Gmbh Procede et dispositif servant a ameliorer la regulation de la temperature dans des systemes de traitement thermique rapide (rtp)
CN112771354A (zh) * 2018-09-28 2021-05-07 美特拉斯有限公司 用于控制半导体晶片温度的方法和设备
CN116472440A (zh) * 2020-10-27 2023-07-21 杰富意钢铁株式会社 表面温度测量方法、表面温度测量装置、热浸镀锌系钢板的制造方法和热浸镀锌系钢板的制造设备

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Publication number Publication date
IL110549A (en) 1998-02-08
IL110549A0 (en) 1994-11-11

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