JPH02259535A - Temperature measuring method - Google Patents

Abstract

PURPOSE:To eliminate the need for the setting of emissivity and to accurately measure the temp. of a body in a non-contact state by respectively measuring the radiant quantities in the plural absorption peak wavelengths obtained from the absorptivity of the body to be measured. CONSTITUTION:IR detectors 11 and 12 for detecting the IR emitted from the photoresist 2a coating the surface of a semiconductor wafer 2 placed on a heating plate 3 are provided. The filters 11a and 12a selectively transmitting the wavelengths lambda1 and lambda2 different from each other are provided to the detectors. The outputs of the detectors 11 and 12 are inputted to a temp. calculator 13 through amplifiers 11c and 12c respectively having gains K1 and K2. The monochromatic emissivities Elambda1 and Elambda2 at the wavelengths lambda1 and lambda2 are obtained by the gains K1 and K2 from the previously measured absorption spectrum of the body to be measured, and the setting is controlled to K1/K2 Elambda2/Elambda1. Since the emissivity of a body is equal to the absorptivity, a measurement with a little effect of the IR radiation from the background of the body to be measured can be realized by measuring the high-absorptivity wavelength of the body.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a temperature measuring method.

(Prior Art) In general, there are two methods for measuring the temperature of an object: a method in which a temperature sensor such as a thermometer or a thermocouple is brought into contact with the object to be measured; There is a method of measuring the amount of radiation and calculating the temperature of the subject mj regular holiday from the amount of radiation.

Of these methods, the latter method utilizes the Stefan-Boltzmann law, and is expressed by the following equation, T-(E/σ0ε), which expresses the relationship between temperature T, injection power E, and emissivity ε.
1/4 is used to calculate the temperature of the object to be measured, but in actual measurements, these estimated values E゛ε' are used because there is no way to accurately know the emissivity E and emissivity ε. Then, estimate the temperature T- using the following equation.

T"-(E-/σ.ε-)1/4 In these equations, σ0 is the Stefan-Boltzmann constant [4,88X10-8(Kcal/m2hK
' ) ] is shown.

According to this method, the temperature can be filled without contacting the object to be measured.
can be determined.

(Problem to be Solved by the Invention) However, among the conventional temperature t-1 determination methods described above, in the method of measuring by bringing a temperature sensor such as a thermocouple into contact with the object to be measured, it is difficult to bring the temperature sensor into contact. There is a problem in that it is not possible to measure the temperature of areas that cannot be measured.

For example, in a baking device that places a semiconductor wafer on a heating plate and bakes a photoresist coated on the surface of the semiconductor wafer, it is preferable to control the heating temperature by detecting the temperature of the photoresist. However, since it is not possible to bring a temperature sensor into contact with the photoresist coated on the surface of a semiconductor wafer (this would damage the photoresist film), for example, a temperature sensor such as a thermocouple is buried inside the heating plate. Temperature is measured by estimating the temperature of the photoresist from the temperature, but this method has a problem in that it is not possible to accurately measure the temperature of the photoresist.

In addition, in the conventional temperature measurement method of determining the infrared rays emitted from the object to be measured and calculating the temperature of all the objects using the Stefan-Boltzmann law from the amount of radiation, there is no contact with the object to be measured. The temperature of the photoresist can be directly determined even in the case of the above-mentioned baking equipment because the temperature can be measured with Infrared rays from the heating plate are mainly measured to measure the temperature of the heating plate, and there is a problem in that the temperature of the silicon wafer and photoresist cannot be accurately measured. Another problem with this method is that it is necessary to set the emissivity, which cannot be accurately known.

The present invention has been made in response to such conventional circumstances, and aims to provide a temperature measurement method that does not require setting of emissivity and can accurately measure the temperature of a measured object without contact. It is something to do.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention measures radiation amounts at a plurality of absorption peak wavelengths obtained from the absorption characteristics of the Δ-1 regular holiday, and calculates the amount of radiation from these measured values. It is characterized by calculating the temperature of the measuring object.

(Function) In the temperature measurement method of the present invention, the amount of radiation at a plurality of absorption peak wavelengths determined from the absorption characteristics of the n1 constant is measured, and the temperature of the object is calculated from these aPj constant values. In other words, since the emissivity and absorption rate of the object to be measured are equal, by measuring the amount of radiation at the wavelength with high absorption rate (absorption peak wavelength), that is, the wavelength with high emissivity,
The temperature of the object to be measured can be accurately determined 3-1 without contact, and there is no need to set the emissivity.

(Example) Hereinafter, an example in which the temperature measurement method of the present invention is applied to temperature measurement in a baking process of semiconductor wafers will be described with reference to the drawings.

The baking apparatus 1 is provided with a heat generating plate 3 on which a semiconductor wafer 2 can be placed. This heating plate 3 is provided with a resistance heater 4 as a heating means, for example, and this resistance heater 4 is equipped with a temperature controller 5.
A power source 6 configured to be able to control the electric power supplied to the resistance heater 4 is connected thereto. Note that the surface of the heat generating plate 3 on which the semiconductor wafer 2 is placed is given a mirror finish by, for example, forming a metal thin film by sputtering or the like. This is to reduce the influence of infrared rays from the heat generating plate 3 on temperature measurement, which will be described later.

Even if the infrared rays emitted from the surface of the heat generating plate 3 are reduced in this way, the semiconductor wafer 2 has a high transmittance of infrared rays, and heating is primarily performed by thermal conduction rather than by radiation, so the heating efficiency is reduced. The decrease is slight.

The baking device 1 also includes a temperature constant device 10.
is provided. The temperature Δ-l determining device 10 is capable of detecting electromagnetic waves, such as infrared rays, emitted from the photoresist 2a deposited on the surface of the semiconductor wafer 2 placed on the heat generating plate 3 or from the semiconductor wafer 2 itself. A plurality of infrared detectors 11.12, for example, two infrared detectors 11.12, are provided, and each of these infrared detectors 11.12 has an infrared detector configured to selectively transmit infrared rays of different wavelengths (λ1 and λ2, which will be described later). A structured filter lla, 12a is provided. And these infrared detectors 11.
The outputs of 12 are sent to the temperature calculator 1 through amplifiers 11c and 12C, each of which has a gain of 1 and a gain of 1 and is configured to be able to adjust K2.
3.

Further, the temperature measurement result calculated by the temperature calculator 13 of the temperature measuring device 10 is configured to be fed back to the temperature controller 5, and this temperature
The power supply 6 is controlled by the temperature controller 5 based on the fixation, and the power supplied to the resistance heater 4 is adjusted so that the semiconductor wafer 2 or the photoresist 2a reaches a predetermined temperature.

In this baking apparatus 1 having the above configuration, in this embodiment, the temperature of the photoresist 2a or the semiconductor wafer 2 is measured by the temperature measuring device 10 in the following manner.

As is well known, according to Blank's law, the monochromatic emission power E of electromagnetic waves (mainly infrared rays) from a black body is b λ E −CI−λ−5/[exp (C2/λT
)-11b λ where λ: Wavelength (m) T: Kelvin temperature* (K) C1: Constant -3,2179X 10-" (Kcal
・m2/h)C2: Constant -1,438a XI
G-” (m IK).

Therefore, if we express the estimated monochromatic output power E' and λ 1 E ゛ at wavelengths λ1 and λ2 using Blank's law mentioned above, E - ε where η1 and η2 are the efficiencies of the light-receiving element λ2 and 11.12, respectively. 1 fist η1φC1・λ1−5λ1
λ1 / [exp (C2/λ1T) −11−ελ1・
K1 ・f (λ1.T) E −ε 2・η2φC1 λ2−5λ2
λ2/[exp (C2/λ2T)-1corελ2φ
becomes f(λ2.T) in 2. Here, 1 and K2 are calibrated for the gain of the amplifier 11 C% 12 c so that ε ・K1 ・η1 − ελ2 λ1 is 2・η2, and taking the ratio of both equations, E − /E − f λ1.T)λ1
λ2 /f(λ2.T).

The temperature calculator 13 is, for example, NEWTON-RAPII.
The temperature T is calculated from the above equation by numerical analysis such as the SON method.

Note that the above gain and the calibration of K2 can be easily achieved as follows.

For example, first of all, in practice, 71-1 constant is set to η1Φη2 in the target radiation wavelength range, that is, the light-receiving element 1
A light receiving element is selected such that efficiency η1 and η2 of 1.12 are equal with sufficient accuracy. Next, monochromatic emissivities ε17 and ελ2 at wavelengths λ1 and λ2 are determined from the previously measured absorption spectrum of the object to be measured. These ελ1
Using λ2, set the gain to 1 and 2 so that the ratio of 1 to 2 for ε becomes K+/2*ε/ε λ2 λ1. In this case, there is a great advantage that the ratio of 1 to 2 is determined only from the optical properties of the object to be measured, regardless of the type of light receiving element.

Furthermore, if both efficiencies η1 and η2 are known, then K1/
K1 and K1 may be set to 2, such as 2-ε η2/ελ, η1 λ2 .

On the other hand, according to Kirchhoff's law, the ratio of emission power and absorption rate of all objects is equal, and its value is equal to the emission power of a black body. That is, the ejection powers of various objects are expressed as E, , K2.
...Efi, absorption rate φ1φ2.・・・・・・
Let φ be the emission power of the black body, and let the absorption rate be φ, then the following equation holds true.

E, /φI-E2/φ2-・・・・・・・・・-E/φ
-EIf you transform this, you get El/E-φ, E2/E-φ2゜..., EO/E-φ.

However, E, /E-εa (emissivity) Because there is, ε1kakuφ1. C2””φ2. ......,εyu■φ.

Therefore, it is derived that the emissivity of every object is equal to the absorption rate of the same object. Therefore, when making temperature measurements,
The wavelength at which the measured object has a high emissivity, that is, a high absorption rate (
By measuring infrared rays at peak absorption wavelengths,
It is possible to realize a highly accurate temperature nj constant with little influence of infrared radiation from the background of a constant body.

Here, the graphs in Figure 2 and Figure 3, where the vertical axis is the transmittance and the horizontal axis is the wavelength, show the infrared rays when a silicon wafer and a photoresist film with a thickness of approximately 5 μm are formed on the silicon wafer, respectively. It shows the absorption characteristics for As shown in the graph of FIG. 2, the silicon wafer has absorption peaks at wavelengths of 9 μm and 16 μm, and as shown in the graph of FIG. has several absorption peaks at wavelengths of 3 μm and about 7 μm, for example.

Therefore, in this embodiment, when measuring the temperature of the semiconductor wafer (silicon wafer) 2, temperature measurement is performed with wavelengths λ1 and λ2 of 9 μm and 16 μm. Further, when measuring the temperature of the photoresist 2a, temperature measurement is performed with λ1 and λ2 set to 3 μm and 7 μm.

In addition, in the gain of the amplifier 11C%12C mentioned above, K
Calibration 2 needs to be performed separately when measuring the temperature of the semiconductor wafer 2 in advance and when determining the temperature of the photoresist 2a by δ-1.

That is, in this embodiment, the filters 11a,
The infrared detectors 11 and 12 equipped with 12a measure the amount of infrared radiation at two wavelengths λ1 and λ2 corresponding to the infrared absorption peak wavelength of the semiconductor wafer 2 or photoresist 2a, and calculate the temperature from these ill constant values. The temperature is calculated by the calculator 13. Therefore, by measuring the amount of radiation at wavelengths with high emissivity, the semiconductor wafer 2 and the photoresist 2a can be accurately measured without contact.
The temperature of n1 can be fixed. Further, there is no need to set the emissivity as in the conventional case.

Furthermore, since the heating plate 3 has a mirror finish, the amount of infrared rays incident on the infrared detectors 11 and 12 from the heating plate 3 can be reduced, and more accurate temperatures of the semiconductor wafer 2 and the photoresist 2a can be determined by n1. can be determined.

Therefore, based on the accurate temperature of the photoresist 2a or the semiconductor wafer 2, the resistance heater 4 is connected to the power source 6.
The temperature of the photoresist 2a can be maintained at a desired temperature and a good baking process can be performed.

In the above embodiments, examples of silicon wafers and photoresists were explained as the subject to be measured, but it can also be applied to temperature measurements of other objects to be measured, such as polyimide and silicon insulating films, insulating plates, It can be applied to any material that has an absorption peak wavelength, such as ion-sensitized polyvinyl chloride films, epoxy, acrylic, and polyurethane resins.

[Effects of the Invention] As described above, the temperature measuring method of the present invention does not require emissivity setting and can accurately measure the temperature of the object without contact.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a baking apparatus for explaining the temperature 13) I orthotropy of an embodiment of the present invention, and FIG. 2 is a graph showing the absorption characteristics of silicon wafers for infrared rays.
FIG. 3 is a graph showing the absorption characteristics for infrared rays when a photoresist film with a thickness of about 5 μm is formed on a silicon wafer. 1...Baking device, 2...Semiconductor wafer, 2a...Photoresist, 3...
...Heating plate, 4...Resistance heater, 5...
...Temperature controller, 6...Power supply, 10...
...Temperature measuring device, 11.12...Infrared detector, 11a112a...Filter, lie,
12C...Amplifier, 13...Temperature calculator. Applicant Chill Kyushu Co., Ltd. Applicant Kokusai Technological Development Co., Ltd. Agent Patent attorney Sa Suyama - (1 other person) Figure 1

Claims (1)

[Claims] (1) A temperature measurement method characterized by measuring the amount of radiation at a plurality of absorption peak wavelengths determined from the absorption characteristics of the object to be measured, and calculating the temperature of the object to be measured from these measured values.