Heat treatment apparatus equipped with a radiation thermometer and method for measuring temperature using a radiation thermometer

Abstract

The present invention provides a heat treatment apparatus and a temperature measurement method that more accurately measure the temperature of a wafer. [Solution] A heat treatment apparatus 1 comprises a support for supporting a wafer W, a heating device for heating the wafer, and a radiation thermometer for measuring the temperature of the wafer's side surface, wherein the heating device is a laser beam irradiation device 14. The support includes a plurality of arms 13 that support the outer periphery of the wafer. The laser beam irradiation device irradiates the lower surface of the wafer with polygonal laser light L, with the vertices of the polygon located on the lower surface of the arms. The temperature measurement method involves measuring the temperature of the wafer's side surface using a radiation thermometer 15.

Description

Technical Field

[0001] The present invention relates to a heat treatment apparatus for heat-treating a wafer, and to a heat treatment apparatus provided with a radiation thermometer and a temperature measurement method using the radiation thermometer.

Background Art

[0002] In semiconductor manufacturing processes, there are many heat treatment processes performed while heating a wafer. In the heat treatment process, although the temperature is controlled, usually, the temperature of the wafer itself during the heat treatment is not measured or controlled, and the temperature (output) of the heating device is measured and controlled. For example, when heating a wafer placed on a hot plate, the hot plate incorporates a thermocouple, and the temperature of the hot plate is measured and controlled. Since there is a temperature difference between the temperature of the hot plate and the temperature of the wafer, a wafer with a pre-attached thermocouple (TC wafer) is heated on the hot plate, and a calibration curve is created for the temperature of the hot plate and the TC wafer. Based on this calibration curve, for example, when the hot plate is at 410 °C, the wafer reaches 400 °C, and temperature control is performed based on this relationship. When sensors such as heating devices and thermocouples deteriorate, there is a deviation between the set temperature and the actual temperature, so the calibration curve needs to be calibrated regularly, and this calibration work is very laborious. Also, during the calibration work, the heat treatment apparatus cannot be used for manufacturing, and there are cases where the processes upstream and downstream of the heat treatment also stop, resulting in a problem of a significant decrease in productivity.

[0003] As a method for measuring the temperature of the heated wafer itself, a method using a non-contact radiation thermometer can be considered. For example, the present applicants have proposed a laser heat treatment apparatus provided with a radiation thermometer in Patent Documents 1 and 2. Patent Document 1 describes an apparatus that irradiates an infrared laser beam with a beam diameter greater than or equal to the diameter of the wafer onto the back surface of the wafer. Patent Document 2 describes a laser heat treatment apparatus having a plurality of arms that support the outer peripheral portion of the wafer and a laser beam irradiation device that irradiates a polygonal laser beam onto the lower surface of the wafer, where the vertices of the polygon of the laser beam are located on the lower surface of the arm.

[0004] Patent Document 1 describes that wafer temperature measurement using a radiation thermometer should be performed on the back (bottom) surface of the wafer (see Claim 3, paragraph 0013, Figure 1, etc., of Patent Document 1). This is because, during the semiconductor manufacturing process, other materials such as metal films are laminated onto the top surface of the wafer, or oxidation reactions are carried out. As a result, the intensity of infrared radiation emitted from the wafer fluctuates due to the influence of these other materials with different emissivity, making it impossible to accurately measure the temperature.

[0005] On the other hand, since no processing is performed on the back surface of the wafer, the exposed material (wafer substrate) remains constant. However, it was found that there are cases where a discrepancy occurs between the measured temperature on the back surface of the wafer and the actual temperature of the wafer. The inventors investigated and found that this is because infrared radiation emitted from materials other than the wafer, such as electrodes formed on the surface of the wafer and the stage supporting the wafer, is added to the infrared radiation emitted from the wafer after passing through it, causing the radiation thermometer measuring the back surface of the wafer to detect more infrared radiation. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-001642 [Patent Document 2] Japanese Patent Publication No. 2022-037414 [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective is to provide a heat treatment apparatus and a temperature measurement method that can more accurately measure the temperature of a wafer. [Means for solving the problem]

[0008] The means for solving the problems of the present invention are as follows. 1. A support that supports the wafer, A heating device for heating the wafer, A radiation thermometer for measuring the temperature of the side surface of the wafer, A heat treatment apparatus characterized by having 2. The heating apparatus according to 1, characterized in that the heating device is a laser light irradiation device. 3. The heating apparatus according to 2., characterized in that the support comprises a plurality of arms that support the outer periphery of the wafer. 4. The laser irradiation device irradiates the lower surface of the wafer with a polygonal laser beam. The heating apparatus according to claim 3, characterized in that the polygon has its vertices located on the lower surface of the arm. 5. A method for measuring the temperature of a heated wafer, A method for measuring temperature, characterized by measuring the temperature of the side surface of a wafer using a radiation thermometer. [Effects of the Invention]

[0009] The heat treatment apparatus of the present invention measures the temperature of the side surface of a wafer using a radiation thermometer. The heat treatment apparatus of the present invention can accurately measure the wafer temperature because it is not affected by infrared radiation emitted from other materials, even if other materials with different emissivity from the wafer substrate are laminated on the wafer surface, formed as an intermediate layer, or supporting the wafer. This invention allows for the measurement of the temperature of the heated wafer itself. By adjusting the heating conditions while measuring the actual wafer temperature, more accurate temperature control becomes possible. With this invention, even if the heating device deteriorates or otherwise, the wafer heating temperature can be maintained at the set temperature by adjusting the heating conditions, thereby significantly reducing the time and cost required for maintenance of the heating device. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram of a heat treatment apparatus 1, which is an embodiment of the present invention. [Figure 2]Schematic diagram of a heat treatment apparatus 1 according to an embodiment of the present invention, in which a radiation thermometer 15 measures the temperature of the side surface of a wafer W. **Embodiments for Carrying Out the Invention**

[0011] The heat treatment apparatus of the present invention includes a support for supporting a wafer, a heating device for heating this wafer, and a radiation thermometer for measuring the temperature of the side surface of this wafer. In this specification, a numerical range expressed as "A to B" means A or more and B or less, including both ends thereof.

[0012] The heat treatment apparatus of the present invention can perform known heat treatments on a wafer. For example, activation annealing of impurities, oxidation, nitridation, diffusion, CVD treatment, hydrogen annealing, argon annealing, drying, curing, drive-in, reflow, silicidation, activation, interface stabilization, sintering, etc. of a coating film such as a resist can be performed. Also, conditions such as temperature and time during the treatment can adopt known conditions. In the heat treatment apparatus of the present invention, the type of the heating device is not particularly limited, and a known heating device can be used. For example, laser heating, condensing heating, resistance heating (hot plate, hot wall), heat radiation, an electric furnace, etc. can be used. However, in order to measure the wafer temperature more accurately, it is preferable that, in addition to the wafer and the heating device, particularly the chamber is not heated in the heat treatment apparatus of the present invention. Therefore, as the heating device, laser heating, condensing heating, and resistance heating (hot plate) from the bottom surface are preferable.

[0013] FIG. 1 shows a schematic diagram of a heat treatment apparatus 1 according to an embodiment of the present invention. Note that the heat treatment apparatus 1 is merely an embodiment example of the present invention, and the heat treatment apparatus of the present invention is not limited thereto. For example, although the heat treatment apparatus 1 supports the wafer W only by the arm 13, the wafer W can also be placed on a stage. The heat treatment apparatus 1 is a laser heat treatment apparatus. The heat treatment apparatus 1 has a chamber 11 for performing heat treatment, and a holder 12 is fixed in this chamber 11. The holder 12 includes six arms 13 provided at equal intervals as a support, and the wafer W is supported by these arms 13. In the heat treatment apparatus 1, the wafer W is supported only by the arms 13, and most of the lower surface of the wafer W is not in contact with other substances.

[0014] A metal film M is formed on the wafer W. For the metal film M, materials known in the field of semiconductor manufacturing can be used, such as copper, aluminum, etc. The wafer W is not particularly limited as long as it is a circular wafer made of various known materials such as silicon, SiC, and III-V group compounds, and it may be a wafer for known applications such as integrated circuits and MEMS. Also, the wafer may be unprocessed, in the process of being processed, or may be one in which a layer made of a substance different from the substrate, such as SOI (Silicon On Insulator) or SiC on Si, is laminated on the surface and formed as an intermediate layer. The heat treatment apparatus of the present invention can accurately measure the temperature even if a region made of a substance different from the substrate is provided on the wafer W, for example, a wafer in the process of being processed or a wafer such as SOI or SiC on Si.

[0015] The size of the wafer W is not particularly limited, and it can be targeted from those with a diameter of 10 mm to 450 mm or more. Since a small-diameter wafer has a small volume, local temperature drop due to heat dissipation is likely to occur. The heat treatment apparatus of the present invention can suppress heat dissipation to the arms, so it can be preferably used for small-diameter wafers. For example, the diameter of the wafer W is preferably 4 inches or less, more preferably 3 inches or less, and even more preferably 2 inches or less. Also, the diameter of the wafer W is preferably 0.5 inches (12.5 mm) or more. The present invention measures the temperature of the side surface of a wafer W, where the side surface of the wafer W refers to the surface connecting the upper and lower surfaces, which are parallel to each other. Furthermore, the shape of the wafer edge (the cross-sectional shape of the wafer side surface in the wafer thickness direction) is not particularly limited in the present invention.

[0016] Chamber 11 can be selected from known chambers depending on the type of heat treatment, the material and size of the wafer W, and other conditions. Chamber 11 has a gate (not shown) for inserting and removing the wafer W. Chamber 11 is provided with a laser light irradiation window 111 and a temperature measurement window 112. The laser light L irradiated from the laser light irradiation device 14 passes through the laser light irradiation window 111 and is irradiated onto the lower surface of the wafer W as a regular hexagon with its vertices positioned on the lower surface of the arm 13.

[0017] In addition to the laser light irradiation window 111 and the temperature measurement window 112, the chamber 11 can also be connected to windows for visually inspecting or photographing the state of the wafer W, and, depending on the processing to be performed, to piping such as hydrogen gas supply lines, oxygen gas supply lines, inert gas supply lines such as argon or nitrogen, exhaust lines, and pressure measurement sensors. The laser light irradiation window 111, the temperature measurement window 112, and any other windows must be made of materials with high light transmittance appropriate to their purpose. For example, the temperature measurement window 112 must be made of a material with high infrared transmittance, such as quartz, BaF2, MgF2, CaF2, sapphire, ZnSe, or glass. Furthermore, if the chamber is subjected to reduced pressure, a material with sufficient mechanical strength should be selected.

[0018] The laser beam irradiation device 14 includes at least a semiconductor laser oscillator and an optical system for adjusting the shape of the laser beam. The laser beam generated by the semiconductor laser oscillator is adjusted by the optical system, which includes various lenses such as aspherical lenses and rod lenses, a homogenizer, an expander, and other optical elements, to form a uniform laser beam L shaped like a regular hexagon with its vertex located on the lower surface of the arm 13, and then emitted. The semiconductor laser oscillator can be a continuous-oscillation high-power semiconductor laser oscillator or a known pulsed-oscillation semiconductor laser oscillator. In the present invention, the wavelength of the irradiated laser light is not particularly limited as long as it is a wavelength that can heat the wafer. For example, 400 nm to 1600 nm (visible light to infrared) is preferred, 780 nm to 1200 nm (infrared) is more preferred, and 800 nm to 1000 nm is even more preferred. Furthermore, the infrared laser light irradiated onto the lower surface of the wafer may be a polygon whose vertices are located on the lower surface of the arm. It is preferably an n-sided polygon (where n is 4 or more and 8 or less), and more preferably a hexagon. It is also preferable that it be a regular polygon. It is preferable to irradiate the lower surface of the wafer W perpendicularly with the laser light L, but it is also possible to irradiate it obliquely to the lower surface of the wafer W within a range where uniform irradiation is possible.

[0019] Figure 2 shows a schematic diagram of how the radiation thermometer 15 measures the temperature of the wafer side surface in the heat treatment apparatus 1. When wafer W is heated, infrared IR is emitted from wafer W. W Infrared radiation is emitted. For example, in silicon, the material of a typical wafer W, when the effective wavelength of the radiation thermometer is 1.95 μm to 2.6 μm, the reflectance is almost constant at slightly less than 0.4 regardless of temperature, the emissivity is constant at slightly less than 0.7 above 600°C but decreases below that temperature, and the transmittance is almost 0 above 600°C but increases below that temperature. For example, at an effective wavelength of 1.95 μm to 2.6 μm for a radiation thermometer, the emissivity of silicon at 400°C is about 0.15, the reflectivity is about 0.4, and the transmittance is about 0.45. A silicon wafer at 400°C transmits about 45% of the infrared radiation in the 1.95 μm to 2.6 μm range. When a silicon wafer W with a metal film M formed on it is heated to 400°C, infrared radiation IR is also emitted from the heated metal film M. M Of these, approximately 45% of infrared radiation in the 1.95 μm to 2.6 μm range passes through the wafer. Therefore, when the temperature of the back surface of wafer W is measured with a radiation thermometer, IR W Furthermore, IR M Because it also detects other factors, it is not possible to accurately measure the temperature of wafer W.

[0020] In contrast, in the heat treatment apparatus 1 of the present invention, the radiation thermometer 15 measures the temperature of the wafer side surface W through the temperature measurement transmission window 112. Measuring the temperature of the wafer side surface W with the radiation thermometer 15 means that the focal point of the radiation thermometer 15 is located on the side surface of the wafer W. In the heat treatment apparatus 1 of the present invention, the radiation thermometer 15 detects only the infrared radiation IRw emitted from the wafer W, and not the infrared radiation IRw emitted from the metal film M. M It does not detect [something]. Therefore, the heat treatment apparatus 1 of the present invention can accurately measure the temperature of the wafer W.

[0021] The placement of the radiation thermometer 15 is not particularly limited as long as it can measure the temperature of the wafer W side. However, in cases where a wafer W having another substance such as a metal film M on its upper surface is supported only by the arm 13, as in the heat treatment apparatus 1, and no other substance is located below the wafer W, it is preferable that the optical axis of the radiation thermometer 15 is within a range of 5° below to 45° above the horizontal (hereinafter, upward is positive and downward is negative with respect to the horizontal, and will be indicated as -5 to 45°) in order to prevent detection of infrared radiation emitted by the other substance located on the upper surface of the wafer. The optical axis of the radiation thermometer is more preferably 0 to 45°, even more preferably 5 to 45°, even more preferably 10 to 45°, and even more preferably 15 to 45°. Furthermore, if no other substance such as a metal film M is formed on the upper surface of the wafer W supported by the arm 13, the optical axis of the radiation thermometer 15 can be in the range of -45 to 45°, and -30 to 30° is preferred.

[0022] When another substance is present beneath the wafer W, such as when the wafer W is placed on a stage, the optical axis of the radiation thermometer 15 is preferably 0 to 45° in order to prevent infrared radiation emitted by the other substance, such as a stage located below the wafer, from passing through the wafer W and being detected by the radiation thermometer. The optical axis of the radiation thermometer is more preferably 0 to 30°, even more preferably 0 to 20°, even more preferably 0 to 15°, even more preferably 0 to 10°, even more preferably 0 to 5°, even more preferably 0 to 3°, even more preferably 0 to 1°, and most preferably horizontal (0°).

[0023] A known radiation thermometer 15 can be used. However, since the focal point of the radiation thermometer 15 of the present invention is located on the side of the wafer W, the size of the target size 151 must be less than or equal to the thickness of the wafer W. The thickness of the wafer W is defined by SEMI standards, etc., along with the diameter of the wafer. For example, a 300 mm wafer has a thickness of 0.775 mm, an 8-inch wafer has a thickness of 0.725 mm, a 4-inch wafer has a thickness of 0.52 mm, a 2-inch wafer has a thickness of 0.279 mm, and a half-inch wafer has a thickness of 0.25 mm (minimum standard). The target size of the radiation thermometer 15 is preferably 95% or less of the thickness of the wafer W, more preferably 90% or less, even more preferably 85% or less, even more preferably 80% or less, even more preferably 75% or less, and even more preferably 70% or less. The target size 151 of the radiation thermometer 15 is preferably 0.5 mm or less, more preferably 0.4 mm or less, even more preferably 0.3 mm or less, even more preferably 0.25 mm or less, even more preferably 0.2 mm or less, and even more preferably 0.15 mm or less. The angle of light path spread after the focal point of the radiation thermometer 15 is preferably 45 degrees or less, more preferably 35 degrees or less, even more preferably 30 degrees or less, and even more preferably 25 degrees or less. If the wafer W includes layers made of materials other than the substrate, such as SOI (active layer Si / BOX layer SiO2 / substrate Si), the radiation thermometer is positioned to measure the temperature of one of the layers. Any layer can be measured, but it is preferable to measure the temperature of the substrate. [Examples]

[0024] Using the minimal laser heating device described in Patent Document 2, a wafer was supported by six arms placed at equal intervals, and the wafer was heated by irradiating it from below with a hexagonal infrared laser whose vertices were located on the underside of the arms. For the wafers used, we employed an untreated half-inch silicon wafer (250 μm thick) and a silicon wafer with a 300 nm thick aluminum film deposited on its upper surface. For each different laser power setting, the temperature of the bottom center and side of the wafer was measured using a radiation thermometer (Japan Sensor Co., Ltd., FLHX-TNE0220, sensor head: 0025BZ15, target size diameter 0.15 mm). To prevent interference with the holder, temperature measurements from the wafer side were taken from a 30° angle above the horizontal. The results are shown in Table 1.

[0025] [Table 1]

[0026] The temperature measured on the side of the wafer was lower than the temperature measured on the bottom (center) of the wafer due to heat dissipation from the wafer edges. The temperature measured on the underside of the wafer showed a significant temperature difference between the Si wafer and the Si wafer with Al electrodes; for example, the difference was as much as 20°C at a laser output of 10W. In contrast, the temperature measured on the side of the wafer showed a small temperature difference between the Si wafer and the Si wafer with the Al electrode; for example, it was only 2°C when the laser output was 10W. [Explanation of symbols]

[0027] W wafer M Metal film 1 Heat treatment apparatus 11 chambers 111 Laser irradiation transparent window 112 Temperature measurement transparent window 12 holders 13 Arms 14. Laser beam irradiation device L Regular hexagonal laser beam 15 Radiation thermometer 151 Target Size

Claims

1. A support that supports the wafer, A heating device for heating the wafer, A radiation thermometer for measuring the temperature of the side surface of the wafer, A heat treatment apparatus characterized by having

2. The heating apparatus according to claim 1, characterized in that the heating device is a laser light irradiation device.

3. The heating apparatus according to claim 2, characterized in that the support comprises a plurality of arms that support the outer periphery of the wafer.

4. The laser irradiation device irradiates the lower surface of the wafer with a polygonal laser beam. The heating apparatus according to claim 3, characterized in that the vertices of the polygon are located on the lower surface of the arm.

5. A method for measuring the temperature of a heated wafer, A method for measuring temperature, characterized by measuring the temperature of the side surface of a wafer using a radiation thermometer.

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