JPH04127012A - Thickness sensor and measuring method of thickness of adhering layer - Google Patents

Abstract

PURPOSE:To correctly measure the thickness by heating or cooling a substrate, and detecting the temperature which is changed corresponding to the thickness of an adhering substance to the substrate. CONSTITUTION:A heating thin film heater 21 and temperature detecting thermocouples 31a, 31b of thin films are provided on a substrate 1 which is poor in thermal conduction. The material of the substrate 1 is glass, ceramic, quartz, acrylic resin or the like. Moreover, for a cooling means to cool a predetermined position of the substrate 1, such one that uses the Peltier effect or the like with use of a compound of bismuth, tellurium etc. is employed. The thermocouples 31a, 31b and an ohmic electrode 8 which detects the potential difference of the thermocouples are used to detect the temperature of a target position on the substrate 1. The substrate 1 thermally connected to a heat sink is heated or cooled, and the thermoelectromotive force as a detecting signal of the temperature of the target position is detected. Accordingly, the thickness of an adhering layer 4 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to measurement of film thickness such as deposits deposited by vacuum evaporation equipment, plasma CVD equipment, sputtering equipment, etc. and plating thickness during Au plating.

[Conventional technology]

BACKGROUND ART Quartz crystal film thickness detectors have been used to measure the thickness of deposits deposited in vacuum evaporation equipment, plasma CVD equipment, sputtering equipment, and the like.

The crystal film thickness detector utilizes the phenomenon that the resonance frequency of a crystal resonator changes depending on the thickness of the deposited film, and is characterized by high detection accuracy and fast response speed.

In addition, recently, electron impact excitation spectroscopy, which applies excitation light caused by electron bombardment of evaporated metals, has been used. This method utilizes the phenomenon that the substance is excited and emits light with a wavelength spectrum unique to the substance, and the intensity of the light at this time is proportional to the density of the vapor flow, that is, the evaporation rate.In particular, by installing an optical filter in the detection part, It has the feature of being able to detect the first place in two sources at the same time.

In addition, as another conventional technology, an amorphous semiconductor thin film having a large Seebeck coefficient has been reported (Japanese Patent Publication No. 2-0
27826), (Japanese Unexamined Patent Publication No. 186900/1983).

[Problem to be solved by the invention]

However, the crystal resonant frequency method requires a stable frequency oscillator and a frequency counter, and the shape of the crystal oscillator cannot be miniaturized, making it difficult to miniaturize and integrate the film thickness detector. There are also problems in that it is easily affected by high frequency noise and measurement is complicated.

In addition, electron impact excitation spectroscopy requires a highly sensitive photoreceiver and a thermionic emitter, which is extremely expensive, and the detection unit consists of an emitter and a photoreceiver, making it difficult to miniaturize and integrate. Another problem was that the measurement method was complicated.

As for amorphous semiconductor thin films having large Seebeck coefficients, there has been no specific disclosure of a thickness sensor that utilizes changes in thermal resistance.

Therefore, it is an object of the present invention to solve these conventional problems, such as being easily affected by high frequency noise, difficult to miniaturize/downsize, expensive, and complicated to measure.

[Means to solve the problem]

In order to solve the above problems, the present invention comprises means for heating or cooling a thermally poor conductor substrate (hereinafter also simply referred to as the substrate) using semiconductor thin film technology, and means for detecting temperature. Ru.

In this way, the present invention is not affected by high frequency noise.
This invention was created based on the inventor's discovery that it is possible to obtain a thickness sensor that is compact, integrated, inexpensive, and has a structure that does not require complicated measurement methods.

Taking advantage of this fact, the present invention provides a means 2 or stage for heating or cooling a predetermined location on a substrate 1 of a thermally poor conductor, and a means 2 or step for heating or cooling a predetermined location on the substrate 1 of the thermally poor conductor, and the temperature of the heated or cooled desired location on the substrate. By providing the means 3 or step for detecting, a thickness sensor and a method for measuring the thickness of an adhered layer that are not subject to high frequency noise, are miniaturized, integrated, inexpensive, and have a simple measuring method are realized. .

[Effect]

The operation of the present invention will be explained using FIGS. 3 and 6.

When a substance is attached to this thickness sensor, such as by vapor deposition, the thermal resistance decreases. At this time, if a predetermined position of the substrate 1 is being heated, the temperature at that desired position will decrease, and conversely, if it is being cooled, the temperature at that desired position will be increased. this,
The decrease or increase in temperature corresponds to the thickness of the adhesion layer 4, and by detecting the decrease or increase in temperature,
The thickness of the adhesion layer 4 can be measured.

FIG. 3 is a diagram showing the relationship between the thickness tf of the AU adhesion layer 4 of the thickness sensor of the present invention shown in FIG. 1 and the thermoelectromotive force VO for detecting temperature changes. Here, the Au adhesion layer 4 is deposited on the entire opposing surfaces of the surfaces on which the thin film heater 21 and the thin film thermocouples 31a and 31b are formed. As can be seen from FIG. 3, the detected thermoelectromotive force V has good linearity with respect to the thickness tf of the Au adhesion layer 4.

is obtained. Next, Fig. 6 is a diagram showing the relationship between the thickness of the Au adhesion layer 4 of the thickness sensor shown in Fig. 5 and the detected thermoelectromotive force, where the open triangles (△) represent experimental values and the straight lines represent calculated values. It shows the value. As can be seen in Figure 6, the experimental value △ and the calculated value shown by the straight line almost match, indicating that the theory has been verified. Furthermore, it can be seen that there is a nearly linear relationship between the thickness of the Au adhesion layer 4 and the output thermoelectromotive force.

〔Example〕

The thickness sensor according to the present invention includes a substrate 1 of a thermally poor conductor that is thermally connected to a heat sink 5, a means 2 for heating or cooling a predetermined position of the substrate 1, and a means 2 for heating or cooling the substrate 1. and means 3 for detecting the temperature at a desired position on the substrate heated or cooled by the substrate. FIG. 1 is a diagram showing an embodiment of the thickness sensor according to the present invention, in which a thin film heater 21 for heating and a thin film heater 21 for temperature detection are placed on a substrate 1 of a thermally poor conductor that is thermally connected to a heat sink 5. Thin film thermocouples 31a and 31b are constructed.

As for the material of the substrate 1 which is a thermally poor conductor, it is preferable that the thermal resistance changes greatly with respect to a small thickness of the adhesive layer 4, so a material that has a small thermal conductivity with respect to the thermal conductivity of the adhesive layer 4 is suitable. . Therefore, the material for the substrate 1, which is a thermally poor conductor, is as follows:
Glass, ceramic, crystal, quartz, acrylic, or organic films such as epoxy and bolimide are used.

The means 2 for heating or cooling a predetermined position of the substrate 1 includes electric resistance heating, absorption heating of a light absorption film, and the like. FIG. 1 shows an example in which heating is performed using a thin film heater 21.

On the other hand, as means 2 for cooling a predetermined position of the substrate, there is cooling by the Bertier effect using a compound of ha, hismuth, tellurium, or the like. In short, in the thickness sensor according to the present invention, it is only necessary to heat or cool a predetermined position of the substrate 1.

As the means 3 for detecting the temperature at a desired position on the substrate 1,
There are thermocouples, radiation thermometers, etc. In FIG. 1, temperature is detected using thin film thermocouples 31a and 31b and an ohmic electrode 8 (hereinafter simply referred to as an electrode) that detects the potential difference between the thin film thermocouples 31a and 31b.

In the embodiment shown in FIG. 1, a portion of the thermally poor conductor substrate 1 is thermally connected to a heat sink 5. In the embodiment shown in FIG. The heat sink 5 can be a block-shaped object with a large heat capacity, or it can be connected to a thin conductive wire that conducts heat well to the outside. By connecting it to the heat sink 5, a part of the substrate 1, which is a thermally poor conductor, is kept at a constant temperature. will be maintained (
(hereinafter, this part is also referred to as a constant temperature section), this constant temperature section 6 is
This is the position opposite to the thin film heater 21, that is, the peripheral part of the substrate 1 on the right side in Fig. 1 (the part indicated by B in Fig. 1). Since the thin film heater 21 is installed, the ON-OFF state of the thin film heater 21
A constant temperature is always maintained regardless of the This constant temperature section 6
is necessary not only for the cold junction of the thin film thermocouples 31a and 31b, but also for creating a temperature gradient within the substrate 1 when the means 2 for heating or cooling is provided at a predetermined position on the substrate 1. It is essential. In addition, in FIG. 1, in order to reduce the escape of heat from the thin film heater 21 through the heater electrode, that is, to improve heating efficiency, the thin film heater 21 is
The electrode 8 for this purpose has a thin pattern of wiring.

Here, an example of a manufacturing method of the embodiment shown in FIG. 1 of the thickness sensor according to the present invention will be briefly described.

As the thermally poor conductor substrate 1, as described above, glass, ceramic, crystal, quartz, acrylic, or an organic film such as uboxy or borimide is used.

After thoroughly cleaning this substrate 1 with an S-containing solvent or the like, it is dried in a clean environment.

Next, thin film thermocouples 31a and 31b are formed. The thin film thermocouples 31a and 31b preferably have a large thermal resistance, and are made of amorphous semiconductor thin film such as a-Si or a-Ge. These amorphous semiconductors are SiH
4. Deposit by plasma CVD using a gas such as GeHa or Hz. At this time, the n-type semiconductor has PH3, 'A
Doping gases such as SH, and B2H for P-type semiconductors are supplied in varying amounts.

Unnecessary parts of the deposited amorphous semiconductor are removed using photoetching technology, and a predetermined 1HIl thermocouple 31a is formed.
, 31b. Note that '7R film thermocouples 31a, 3
1b may be composed of an amorphous thin film or the like having a large Seebe coefficient and a small metal thin film or the like.

Subsequently, the thin film heater 21 is formed. As this thin film resistor, a metal thin film such as nichrome or tantalum is used.

These thin films are deposited by sputtering or vacuum evaporation. Unnecessary portions of this thin film are similarly removed to form a thin film heater 21 of a desired shape.

Further, a metal thin film such as gold for electrodes is deposited, and unnecessary parts are similarly removed to form electrodes 8 for the thin film thermocouples 31a and 31b and the thin film heater 21.

In addition, as a surface protective film, Sin, thin film, S l 3N4
A thin film or the like may also be provided.

The measurement principle of the present invention and the role of the constant temperature section 6 will be explained using FIG. 2.

FIG. 2 is a diagram of the temperature gradient at the stage when a predetermined position of the substrate I is heated (in this case, it is only heated because it is a 'fit film heater) in the embodiment described in FIG. 1. In the figure, constant temperature section 6 (
The inner peripheral part B) of the substrate indicated by diagonal lines on the right side of the figure always maintains a constant temperature regardless of whether the thin film heater 21 is ON or OFF because it is directly installed on the Cu block or the like.

On the other hand, the desired position W of the heating section 7 (the peripheral area A in the substrate indicated by diagonal lines on the left side in the figure) is located at the i-film heater 21.
When the thin film heater 21 is OFF, the temperature is the same as that of the constant temperature section 6, but when the thin film heater 21 is ON, the temperature is higher than that of the constant temperature section 6.

Therefore, when the thin film heater 21 is ON, the heating section 7 and the constant temperature section 6
A temperature difference T1 occurs between the two.

This temperature difference T1 is determined by the product of the heat generation amount Q of the thin film heater 21 and the thermal resistance Rs, and is expressed by the following equation (1).

△T 1 = Q x Rs −−−−−−−−−
(1) In this case, the thermal resistance Rs depends almost only on the thermal resistance of the substrate 1. Therefore, assuming that the thermal conductivity of the substrate 1 is λS, the length is Ls, the width is Ws, and the thickness is US, the thermal resistance Rs is expressed by the following equation (2).

λ s W s

Subsequently, a step begins in which a first temperature after heating a desired position of the substrate 1 is detected. In Figure 2, this temperature difference T1
YT membrane mature thermocouples 31a and 31b are used for the detection method. At this time, the thermoelectromotive force V1 of the thin film thermocouple 3I is obtained by multiplying the Seebeck coefficient of the thin film thermocouples 31a and 31b by S and the temperature difference by T1 (2(3)).

V1=SxΔT1−−−−−・−−−−−−−−−1−
--- (3) Since there is no adhesion layer 4 at this point,
The thermoelectromotive force Vl generated is constant.

From this stage, a stage begins in which an adhesion layer 4 is formed on at least a portion of the surface of the substrate 1.

The deposits 4 that can be measured according to the present invention include Au, Pt, and Ti.
Any material may be used, including metals such as , Cr, semiconductors such as Si, GaAs, and ZnTe, and insulators such as Sin, SiN4, and Alt03. This is because the thickness measurement of the adhesion layer 4 according to the present invention utilizes changes in thermal resistance.

In the embodiment shown in FIG. 1, the adhesion layer 4 is formed on the surface opposite to the surface on which the thin film heater 21 and thin film thermocouples 31a and 31b are formed. Before the adhesion layer 4 is formed, heat flows only within the substrate 1 and is transmitted from the heating section 7 to the constant temperature section 6. On the other hand, when the adhesive layer 4 is formed, part of the heat that was flowing only within the substrate 1 flows through the adhesive layer 4 and is transmitted from the heating section 7 to the constant temperature section 6. Therefore, the thermal resistance between the heating section 7 and the constant temperature section 6 is reduced. If the thermal conductivity of the adhesive layer 4 is Sf, the length is Lf, the width is Wf, and the thickness is tf, then the thermal resistance of only the adhesive layer 4, Rf, is expressed by the following 2(4).

λ f Wfxtf Also, the composite thermal resistance R of the thermal resistance Rs and Rf of the substrate 1 is
It is calculated by the following formula (5).

Rs Rf Similarly to formula (1), the temperature difference T2 between the heating section 7 and the constant temperature section 6 after the adhesion layer 4 is formed is expressed by the following 2(6).

△T 2 = Q X R−−−−−−−−−−−−−
--- (6) As seen from equation (6), the temperature difference T2
is smaller than the temperature difference ΔT1 before the adhesion layer 4 is formed.

Subsequently, a step of detecting a second temperature at a predetermined position after the adhesion layer 4 is formed begins. That is, in this embodiment, the temperature difference ΔT2 is measured. The second temperature detection method is the same as the first temperature detection method, and in the case of the embodiment shown in FIG. 1, it is detected by thermoelectromotive force generated by thin film thermocouples 31a and 31b. At this time, the thermoelectromotive force V2 is obtained in the same manner as the above-mentioned equation (3), and is obtained using the following equation (7).

V2=Sx△T2 −−−−−−・・・−・−−−−−
−111−−−−・−−−−−−・−・−・・−(7)
In this way, the thermoelectromotive force V1 which is the first temperature detection signal
and thermoelectromotive force v2, which is the second temperature detection signal, is obtained.

Subsequently, the adhesive layer 4 is heated by the difference between the first temperature and the second temperature.
Now we move on to the step of finding the thickness.

From equations (3) and (7), the difference between 8T1 and ΔT2 is expressed by the following equation (8).

l Also, from 2(1) and (6), the difference between 8T1 and 8T2 is expressed by the following equation (9).

△T1-ΔT 2 = Q X (Rs -R) --
-----------(9) The following formula aω is obtained from formulas (8] and (9).

By substituting equations (2), (3), (4), and (5) into 2〇〇 and rearranging, ⑐〇〇 representing the thickness tf of the adhesion layer 4 is obtained.

λ fLsWf V2 (It) In the formula OD, λs, , Ls, Ws, t s, and Sf, Lf, and Wf are known.

Therefore, the thickness tf of the adhesion layer 4 is determined by detecting the thermoelectromotive force Vl, 2, which is a temperature detection signal.

Note that even when measuring the thickness in a liquid during plating, etc., the thickness of the adhesion layer 4 can be measured by correcting the heat radiation into the liquid.

FIG. 3 shows that in the embodiment shown in FIG. 1, L s =10 (ms) W s = 2 on the substrate l of the thermally poor conductor.
(ms) using a ceramic substrate with ts=150Cμ11), the Seebeck coefficient of the thin film thermocouples 31a and 31b is 0.
．． 25-(mV/K), the amount of heat generated by the thin film heater 21 is 4
00 (@W) is a diagram showing the relationship between the thickness tf of the Au adhesion layer 4 and the detected thermoelectromotive voltage Vo. The voltage Vo is plotted on the N-axis, and the thickness tf of one deposited layer is plotted on the horizontal axis. In this case, the Au adhesion layer 4 is attached to the thin film heater 21 and the thin film thermocouple 31.
It adheres to the entire opposing surfaces of the surfaces where a and 31b are formed. A detected thermal electromotive voltage Vo with good linearity is obtained with respect to the thickness tf of the Au adhesion layer 4.

FIG. 4 is a diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 4, the constant temperature section 6 includes:
An electrode 8 extending in a circular shape around the periphery is used as a heating means, a thin film heater 21 at the center in the figure is used as a heating means, and two pairs of thin film thermocouples 31a and 31b extending in a fan shape are used as a temperature detecting means. The thermal resistance in this case is from the thin film heater 2 at the center to the electrode 8 that extends circularly around the periphery. In addition, the thin film thermocouple 31
Two pairs of thermoelectromotive voltages caused by a and 31b are wired in series, and the thermoelectromotive voltage for detecting temperature is doubled.

FIG. 5 shows a combination of the embodiments shown in FIG. 4, in which the output directions of the thermoelectromotive voltages of the thin film thermocouples 31a and 31b have opposite characteristics. Each central thin film heater 21 has an equal amount of heat generation Q, and before the adhesion layer 4 is formed, the thermoelectromotive voltages from the thin film thermocouples 31a and 31b are balanced, and the heat generated by the entire thickness sensor is No electromotive force is output. On the other hand, if the adhesive layer 4 is formed only on one of the circular thermal resistance parts (for example, the left side is the part, and the right side is the part ), the electromotive force is not output. Only the thermal resistance of the circular part on the left decreases. Therefore, the thermoelectromotive voltage of only one part decreases, the balance of both thermoelectromotive voltages is disrupted, and the thermoelectromotive voltage corresponding to the adhesion layer 4 is output as a whole of the thickness sensor.

FIG. 6 shows the Au adhesion layer 4 in the embodiment shown in FIG.
The vertical axis shows the voltage due to the relationship between the thickness of the
o, the thickness tf of the adhesion layer is plotted on the horizontal axis. Also, Δ
As shown in Figure 0, where 0 indicates the experimental value and the straight line indicates the calculated value, the experimental value and the calculated value show good agreement, and the thickness of the Au adhesion layer 4 and the output thermoelectromotive voltage It can be seen that there is an almost linear relationship between them.

In FIG. 7, a thermistor thin film resistor 32 is used for temperature detection, and a bridge circuit is integrated on the thickness sensor. Note that a thin film heater 21 is used for heating, and the constant temperature section 6 is located on the opposite side of the thin film heater 21. In FIG. 7, assuming that the thin film resistor 33 which is close to the thin film heater 21 is a thermistor, if a bias voltage is applied to this bridge circuit, a voltage corresponding to the temperature will be output from the bridge circuit. Output.

FIG. 8 shows an example in which light is used for heating. Light is introduced from outside the thickness sensor, absorbed by the light absorption film 9 in the center, and converted into heat. A plurality of pairs of thin film thermocouples 31a and 31b are used to detect the temperature, and the constant temperature section 6 is an electrode 8 on the circular periphery. In the embodiment shown in FIG. 8, since light introduced from the outside is used for heating, there is an advantage that the number of wiring lines can be reduced when thickness is measured in a vacuum apparatus or the like.

Figure 9 shows a radiation film 3 such as a black body formed in a circular shape in the center.
4, and the radiant heat from the radiant film 34 is utilized for temperature detection. A thin film heater 21 is used for heating, and the constant temperature section 6 has one pole 8 around a circular portion.

The embodiment shown in FIG. 9 also does not require wiring for temperature detection, so it has the advantage that the number of wiring can be reduced when measuring thickness in a vacuum apparatus or the like.

Similarly to the embodiment shown in FIG. 9, FIG. 1υ uses radiant heat for temperature detection. Similarly, the constant temperature section 6 is located at the electrode 8 at the circular periphery.

However, in the embodiment shown in FIG.
is formed to surround the periphery of the radiant film 34 in the center, so the radiant film 34 is
The advantage is that the temperature becomes uniform and more accurate temperature measurement is possible.

In the examples shown in FIGS. 1 to 10 so far,
In each case, an example has been described in which a predetermined position of the substrate is heated, but it can also be carried out without heating (or cooling).

In this cooled embodiment, instead of the heater, N
A Peltier element composed of a P-type semiconductor, a metal, and a P-type semiconductor causes a current to flow from the N-type semiconductor to the P-type semiconductor. The effect is cooling (or heating if the current is reversed). In addition, there is no problem in cooling the predetermined position by a method other than the Peltier effect, for example, by spraying cooled gas within a range that does not affect the degree of vacuum.

Thickness measurement using cooling exhibits its advantages in cases where measurement accompanied by heat generation in a cooling atmosphere is undesirable, or in cases where measurement is performed near a high temperature limit.

〔Effect of the invention〕

First, the thickness sensor of the present invention measures the thickness by heating or cooling the substrate and detecting changes in temperature that depend on the thickness of deposits on the substrate. Naturally, the problem that the thickness detector generates noise due to the oscillation frequency of the crystal and the frequency for vapor deposition is solved, and accurate measurement becomes possible.

Next, since the present invention consists of a heating or cooling means and a temperature detecting means, it can be easily miniaturized by using semiconductor allll technology, etc., and the sensor can be set in a wide range of locations, allowing multiple points during vacuum evaporation. Measurement is possible, and more materials can be deposited.

Furthermore, by using semiconductor thin film technology, etc., it can be manufactured at a very low cost compared to its performance.

Furthermore, since the measurement principle is not complicated, various troubles are less likely to occur.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an implementation of a thickness sensor according to the present invention, FIG. 2 is a diagram showing a temperature gradient within the substrate of the thickness sensor shown in FIG. 1, and FIG. 3 is a diagram similar to that shown in FIG. FIGS. 4 and 5 are diagrams showing the relationship between the thickness of the Au adhesion layer and the detected thermoelectromotive force of the thickness sensor shown in FIG. FIG. 6 is a diagram showing the relationship between the thickness of the Au adhesion layer and the detected thermoelectromotive voltage of the thickness sensor shown in FIG. 5, and also a diagram showing the effect of the present invention. FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are diagrams showing other embodiments of the thickness sensor of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate of thermally poor conductor, 2... Means for heating or cooling, 3... Means for detecting temperature, 4... Adhesive layer, 5... Heat sink, 6, 8, 21, 1a 32. 33. - Constant temperature section, 7... Heating section, - Electrode, 9... Light absorption film, - Thin film heater, 31b... Thin film thermocouple, - Thermistor Ei# resistor, - Thin film resistor, 34...Radiation film. Patent Applicant Anritsu Co., Ltd. Agent Patent Attorney Kowa Ryutabe Diagram x - x' Cross Section Diagram (Seal

Claims (1)

[Claims] 1) A substrate (1) of a thermally poor conductor that has a surface for forming an adhesion layer on at least a portion thereof and is thermally connected to a heat sink, and a predetermined position of the substrate. means (2) for heating or cooling the substrate; and means (3) for detecting the temperature at a desired position on the substrate heated or cooled by the heating or cooling means; A thickness sensor for measuring the thickness of the deposited layer by detecting a temperature that varies accordingly. 2) heating or cooling a predetermined position on the substrate of a thermally poor conductor that is thermally connected to a heat sink; and detecting a first temperature after heating or cooling the predetermined position on the substrate. , forming an adhesion layer on at least a portion of the surface of the substrate; and detecting a second temperature at a desired position of the substrate after forming the adhesion layer;
A method for measuring the thickness of an adhesion layer, including the step of determining the thickness of the adhesion based on the difference between the first temperature and the second temperature.