Wafer surface high-precision temperature measurement method and device based on photoluminescence principle

Abstract

The invention discloses a wafer surface high-precision temperature measurement method and device based on a photoluminescence principle, the surface of a wafer is coated with a fluorescent or phosphorescent material, the material can emit fluorescence or phosphorescence after being excited by an external light source, and calibration of the coated wafer is completed in combination with a temperature sensor arranged at a key point location; and calculating the high-temporal-spatial-resolution temperature response characteristic of the whole wafer surface, thereby realizing high-precision and high-temporal-spatial-resolution wafer temperature measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer surface temperature measurement, and in particular to a high-precision wafer surface temperature measurement method and device based on the photoluminescence principle. Background Art

[0002] Wafer surface temperature measurement refers to the process of measuring the surface temperature of semiconductor wafers through specific methods or equipment. With the increasing sophistication of semiconductor processes, temperature control on the wafer surface has become critical. The impact of temperature on yield runs through the entire process of integrated circuit chip production, including wafer manufacturing, etching, and deposition. Inaccurate or uneven temperature may cause wafer warping, thermal stress, and even microcracks, seriously affecting the yield and performance of the chip. Therefore, the temperature field distribution on the wafer surface needs to be monitored and controlled with high precision during the process.

[0003] At present, there are usually two types of temperature measurement methods for wafer surface: contact and non-contact. Contact temperature measurement is to integrate tiny sensors at specific locations on the wafer surface to achieve temperature monitoring. During the wafer processing process, the sensor measures the temperature information of different position coordinates, and encodes the temperature information into digital signals and writes them into the storage circuit; then, the main control chip sends the stored data through wireless signals. This method is mature in technology, has high measurement accuracy and low cost. However, since the sensor can only perform point measurements, its spatial resolution is limited and cannot meet the high-precision time and space requirements. Non-contact temperature measurement mainly uses radiation temperature measurement, which does not contact the wafer. By measuring the radiation heat, the temperature of the wafer surface is calculated using the radiation formula. Non-contact temperature measurement has a large temperature measurement range, can be monitored in real time, and has a fast response speed. However, since it uses radiation heat measurement, it is easily affected by the environment. When it is at a low temperature, the measurement accuracy is low.

[0004] In summary, new technologies and methods are urgently needed to achieve high-precision, high-temporal and high-spatial resolution large-scale wafer surface temperature measurement. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method and device for high-precision temperature measurement of a wafer surface based on the principle of photoluminescence.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: The present invention provides a high-precision wafer surface temperature measurement method based on the photoluminescence principle, comprising the following steps: S1. Arranging a temperature sensor at a set point on the surface of a wafer coated with a fluorescent or phosphorescent material; S2. Perform the following wafer surface temperature measurement process at different standard temperature points: The tunable laser source emits an excitation light of a specific wavelength, and the excitation light is reflected to the surface of the wafer through a reflective lens. The fluorescent or phosphorescent material coated on the surface of the wafer is excited by the excitation light to generate an optical signal of a specific wavelength. The convex lens converges the light signal emitted from the wafer surface; the light signal converged by the convex lens further passes through the filter group, which filters out the noise components in the light signal and only retains the light signal generated by the fluorescent or phosphorescent material; the pure light signal obtained after filtering by the filter group finally reaches the detector, which converts the captured pure light signal into a corresponding electrical signal and transmits the electrical signal to the computer; S3, each temperature sensor simultaneously transmits the temperature value obtained at the point to the computer; S4, through steps S2 and S3, the computer obtains the corresponding relationship between the electrical signal at different standard temperature points and the temperature data measured by the temperature sensor, and further obtains the quantitative relationship between the electrical signal and the temperature through a mathematical algorithm fitting equation; S5. When performing actual temperature measurement, a calibrated fluorescent or phosphorescent material is coated on the surface of the wafer that needs to be measured, and then the wafer surface temperature measurement process is performed according to step S2. The computer uses the equation fitted by the mathematical algorithm in step S4 to infer the temperature data of the wafer surface based on the received electrical signal.

[0007] Furthermore, the timing controller coordinates the working time of the tunable laser source and the signal acquisition time of the detector through a time control mechanism, controls the tunable laser source to emit stable excitation light within a set time interval, and controls the detector to acquire signals within a set optimal time window.

[0008] The present invention also provides a high-precision wafer surface temperature measurement device for implementing the above method, comprising a detector, a computer, a filter set, a convex lens, a tunable laser source, a reflective lens, a fluorescent or phosphorescent material, a wafer and a temperature sensor; The tunable laser source is used to emit excitation light of a specific wavelength, the reflective lens is used to receive the excitation light and reflect the excitation light to the surface of the wafer; the surface of the wafer is coated with fluorescent or phosphorescent materials; the convex lens is used to receive the light signal emitted from the surface of the wafer and converge the light signal; the filter group is used to filter the light signal after convergence by the convex lens, filter out the noise component in the light signal, and only retain the light signal generated by the fluorescent or phosphorescent material; the detector is used to receive the pure light signal filtered by the filter group and convert the pure light signal into an electrical signal, and transmit the electrical signal to the computer; The temperature sensor includes a plurality of temperature sensors, each of which is arranged at a set point on the surface of the wafer during calibration, and is used to obtain the temperature value of the point at the current standard temperature point and transmit it to the computer; The computer is used to obtain the quantitative relationship between the electrical signal and the temperature by fitting the equation through a mathematical algorithm according to the correspondence between the electrical signal at different standard temperature points and the temperature data measured by the temperature sensor during calibration; and is used to calculate the temperature data of the wafer surface according to the received electrical signal by fitting the equation through the mathematical algorithm during actual temperature measurement.

[0009] Furthermore, the above-mentioned device also includes a timing controller, which is communicatively connected to the tunable laser source and the detector respectively, and is used to coordinate the working time of the tunable laser source and the signal acquisition time of the detector, control the tunable laser source to emit stable excitation light within a set time interval, and control the detector to perform signal acquisition within a set optimal time window.

[0010] The beneficial effects of the present invention are: 1. The present invention uses the intrinsic temperature-sensitive properties of fluorescent or phosphorescent materials to calibrate a temperature response characteristic equation, thereby achieving high-precision temperature measurement on the wafer surface. The method is suitable for measuring a wide range of temperature changes, and solves the problem of weak signals and poor measurement accuracy of traditional thermometers in low-temperature environments, thereby ensuring the accuracy of the measured wafer surface temperature data.

[0011] 2. The present invention combines in-situ calibration with photoluminescence temperature measurement to achieve temperature measurement with high temporal and spatial resolution. It is suitable for high-precision measurement under the requirements of planar high resolution, solves the problem of discontinuous spatial measurement of traditional thermometers, and can provide important support for monitoring the surface temperature source of integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of a device used to implement the method of Example 1 of the present invention; Figure 2 A schematic diagram of the position of the wafer surface temperature sensor during calibration in Example 1 of the present invention; Figure numerals: 1. detector; 2. timing controller; 3. computer; 4. filter set; 5. convex lens; 6. tunable laser source; 7. reflective lens; 8. fluorescent or phosphorescent material; 9. wafer; 10. laboratory table; 11. temperature sensor. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment. Example 1

[0014] This embodiment provides a high-precision temperature measurement method for a wafer surface based on the principle of photoluminescence. Figure 1-2 As shown, the following steps are included: S1, arranging temperature sensors 11 at set points on the surface of the wafer 9 coated with the fluorescent or phosphorescent material 8 (the number of arranged sensors in this embodiment is 5); S2. Perform the following wafer surface temperature measurement process at different standard temperature points: The tunable laser source 6 emits an excitation light of a specific wavelength, and the excitation light is reflected to the surface of the wafer 9 through the reflective lens 7. The fluorescent or phosphorescent material 8 coated on the surface of the wafer 9 is excited by the excitation light to generate an optical signal of a specific wavelength. It should be noted that the wavelength, intensity and lifetime of the optical signal emitted by the fluorescent or phosphorescent material 8 are determined by the characteristics of the fluorescent or phosphorescent material 8, and are the result of the interaction between the fluorescent or phosphorescent material 8 and the excitation light.

[0015] The convex lens 5 converges the light signal emitted from the surface of the wafer 9, focusing the scattered light signal into a light signal with concentrated intensity, which is convenient for subsequent signal collection and processing. The light signal converged by the convex lens 5 further passes through the filter group 4, and the filter group 4 filters out the reflected light from the excitation light, the ambient background light, and other noise components that may interfere with the signal in the light signal, and only retains the light signal generated by the fluorescent or phosphorescent material 8. This process can ensure the purity of the light signal and the accuracy of the detection. The pure light signal obtained after filtering by the filter group 4 finally reaches the detector 1, and the detector 1 converts the captured pure light signal into a corresponding electrical signal, and transmits the electrical signal to the computer 3; S3, each temperature sensor 11 simultaneously transmits the temperature value of the point at which it is located at the current standard temperature point to the computer 3; S4, through step S2 and step S3, the computer 3 can obtain the corresponding relationship between the electrical signal at different standard temperature points and the temperature value measured by the temperature sensor, and the accurate quantitative relationship between the electrical signal and the temperature can be obtained through the mathematical algorithm fitting equation; S5. When performing actual temperature measurement, a calibrated fluorescent or phosphorescent material 8 is coated on the surface of the wafer that needs to be measured, and then the wafer surface temperature measurement process is performed according to step S2. The computer 3 uses the equation fitted by the mathematical algorithm in step S4 to infer the temperature data of the wafer surface according to the received electrical signal.

[0016] In this embodiment, the timing controller 2 coordinates the working time of the tunable laser source 6 and the signal acquisition time of the detector 1 with a high-precision time control mechanism. The timing controller 2 controls the tunable laser source 6 to emit stable excitation light within a set time interval through precise timing matching, and at the same time controls the detector 1 to acquire signals within the set optimal time window to avoid signal omissions or time dislocations.

[0017] It should be noted that, since the characteristic emission spectra of fluorescent or phosphorescent materials are usually distributed in a narrow band, and the stray light of the excitation light source (such as ultraviolet LED or laser), environmental background radiation (such as infrared thermal radiation or visible light interference) and dark current noise of the photodetector often cover a wider band, this embodiment uses a high-performance bandpass filter to accurately match the target wavelength window and only retains the light signal generated by the fluorescent or phosphorescent material.

[0018] It should be noted that when fluorescent or phosphorescent materials are excited, there are four stages: excited period, fully excited period, decay period and unexcited period. When temperature detection is based on the lifetime principle, the time window should include part of the fully excited period and the entire decay period; when temperature detection is based on the intensity ratio, the time window should only include part or the entire fully excited period. Example 2

[0019] This embodiment provides a high-precision wafer surface temperature measurement device for implementing the method described in Embodiment 1, including a detector 1, a computer 3, a filter group 4, a convex lens 5, a tunable laser source 6, a reflective lens 7, a fluorescent or phosphorescent material 8, a wafer 9 and a temperature sensor 11.

[0020] The tunable laser source 6 is used to emit excitation light of a specific wavelength, and the reflective lens 7 is used to receive the excitation light and reflect the excitation light to the surface of the wafer 9; the surface of the wafer 9 is coated with a fluorescent or phosphorescent material 8; the convex lens 5 is used to receive the light signal emitted from the surface of the wafer 9 and converge the light signal; the filter group 4 is used to filter the light signal converged by the convex lens 5, filter out the noise component in the light signal, and only retain the light signal generated by the fluorescent or phosphorescent material; the detector 1 is used to receive the pure light signal filtered by the filter group 4 and convert the pure light signal into an electrical signal, and transmit the electrical signal to the computer 3; The temperature sensor 11 includes a plurality of temperature sensors. During calibration, each temperature sensor 11 is arranged at a set point on the surface of the wafer 9 to obtain a temperature value at the point at the current standard temperature point and transmit it to the computer 3. The computer 3 is used to obtain the quantitative relationship between the electrical signal and the temperature by fitting the equation through a mathematical algorithm according to the correspondence between the electrical signal at different standard temperature points and the temperature data measured by the temperature sensor during calibration; and is used to calculate the temperature data of the wafer surface according to the received electrical signal by fitting the equation through the mathematical algorithm during actual temperature measurement.

[0021] In this embodiment, the wafer 9 is placed on a laboratory table 10 .

[0022] In this embodiment, the device also includes a timing controller 2, which is communicatively connected to the tunable laser source 6 and the detector 1, and is used to coordinate the working time of the tunable laser source 6 and the signal acquisition time of the detector 1, control the tunable laser source 6 to emit stable excitation light within a set time interval, and control the detector 1 to perform signal acquisition within a set optimal time window.

[0023] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A high-precision temperature measurement method for wafer surface based on the principle of photoluminescence, characterized in that: The steps include: S1, arranging a temperature sensor (11) at a set point on the surface of a wafer (9) coated with a fluorescent or phosphorescent material (8); S2. Perform the following wafer surface temperature measurement process at different standard temperature points: The tunable laser source (6) emits excitation light of a specific wavelength, and the excitation light is reflected to the surface of the wafer (9) through the reflective lens (7), and the fluorescent or phosphorescent material (8) coated on the surface of the wafer (9) is excited by the excitation light to generate an optical signal of a specific wavelength; The convex lens (5) performs convergence processing on the light signal emitted from the surface of the wafer (9); the light signal converged by the convex lens (5) further passes through the filter group (4), and the filter group (4) filters out the noise components in the light signal, and only retains the light signal generated by the fluorescent or phosphorescent material (8); the pure light signal obtained after filtering by the filter group (4) finally reaches the detector (1), and the detector (1) converts the captured pure light signal into a corresponding electrical signal, and transmits the electrical signal to the computer (3); S3, each temperature sensor (11) simultaneously transmits the temperature value obtained at the point where it is located to the computer (3); S4, through steps S2 and S3, the computer (3) obtains the corresponding relationship between the electrical signal at different standard temperature points and the temperature data measured by the temperature sensor, and further obtains the quantitative relationship between the electrical signal and the temperature through a mathematical algorithm fitting equation; S5. When performing actual temperature measurement, a calibrated fluorescent or phosphorescent material (8) is coated on the surface of the wafer to be measured, and then the wafer surface temperature measurement process is performed according to step S2. The computer (3) uses the equation obtained by fitting the mathematical algorithm in step S4 to infer the temperature data of the wafer surface according to the received electrical signal.

2. The method for high-precision temperature measurement of a wafer surface according to claim 1, characterized in that: The timing controller (2) coordinates the working time of the tunable laser source (6) and the signal collection time of the detector (1) through a time control mechanism, controls the tunable laser source (6) to emit stable excitation light within a set time interval, and controls the detector (1) to collect signals within a set optimal time window.

3. A high-precision wafer surface temperature measuring device for implementing the method described in any one of claims 1-2, characterized in that: It comprises a detector (1), a computer (3), a filter set (4), a convex lens (5), a tunable laser source (6), a reflective lens (7), a fluorescent or phosphorescent material (8), a wafer (9) and a temperature sensor (11); The tunable laser source (6) is used to emit excitation light of a specific wavelength, and the reflective lens (7) is used to receive the excitation light and reflect the excitation light to the surface of the wafer (9); the surface of the wafer (9) is coated with a fluorescent or phosphorescent material (8); the convex lens (5) is used to receive the light signal emitted from the surface of the wafer (9) and to converge the light signal; the filter group (4) is used to filter the light signal after convergence by the convex lens (5), filter out the noise component in the light signal, and only retain the light signal generated by the fluorescent or phosphorescent material (8); the detector (1) is used to receive the pure light signal filtered by the filter group (4), convert the pure light signal into an electrical signal, and transmit the electrical signal to the computer (3); The temperature sensors (11) include a plurality of them. During calibration, each temperature sensor (11) is arranged at a set point on the surface of the wafer (9) to obtain a temperature value at the point at the current standard temperature point and transmit it to the computer (3); The computer (3) is used to obtain the quantitative relationship between the electrical signal and the temperature by fitting the equation through a mathematical algorithm according to the corresponding relationship between the electrical signal at different standard temperature points and the temperature data measured by the temperature sensor during calibration; It is also used in actual temperature measurement to calculate the temperature data of the wafer surface based on the received electrical signal through the equation fitted by the mathematical algorithm.

4. The device according to claim 3, characterized in that The device also includes a timing controller (2), wherein the timing controller (2) is communicatively connected to the tunable laser source (6) and the detector (1), and is used to coordinate the working time of the tunable laser source (6) and the signal collection time of the detector (1), control the tunable laser source (6) to emit stable excitation light within a set time interval, and control the detector (1) to collect signals within a set optimal time window.

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