JP2003037140A - Film thickness measuring instrument and method, and method for manufacturing film thickness reference wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To repeatably measure and manage a thickness of a very thin insulating film whose increase of thickness cannot be neglected. SOLUTION: The film thickness measuring instrument measures a single layer or a plurality of layers of the very thin insulating films formed on a wafer 11, by using optical technique of a single wavelength ellipsometry, spectro- ellipsometry, or reflection and interference of a single wavelength or a plurality of wavelengths. The instrument has a pre-process mechanism for exposing the wafer to be measured 11 to corona discharge by transmitting the wafer beneath a corona discharging wire 12 under air or an atmosphere, including oxygen and nitrogen, just before measuring the thickness of the insulating film by using optical technique. The corona discharge ionizes the oxygen in the air and generates ozone and oxygen ions. Since an organic material for changing an optical characteristic is removed by the ozone and the oxygen ions, an intrinsic thickness of the insulating film formed on a surface of the wafer can be accurately and repeatably measured and managed when the thickness of the insulating film is measured by the optical technique.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrathin insulating film thickness measuring device used in a semiconductor integrated circuit, a film thickness measuring method and a film thickness reference wafer manufacturing method.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have been rapidly miniaturized and highly integrated, and accordingly, the gate insulating film thickness of transistors has been reduced to 5 nm or less. The gate insulating film is an important film that determines the transistor performance / reliability, and it is essential to properly manage the film thickness and its uniformity / reproducibility. The conventional method for controlling the film thickness measuring device will be described below.

In FIG. 14, 1 is a semiconductor substrate, and 2 is an insulating film formed on the main surface of the semiconductor substrate. An optical film thickness measuring method using an ellipsometer has been conventionally used for in-line monitoring of the insulating film thickness. Generally, as an optical film thickness measuring device such as an ellipsometer, in order to compensate for stability of the laser (gas or semiconductor) and aging, and for aging and deterioration of the optical mirror, lens, phase compensator, detector, etc., Calibration is performed by using a wafer, which is generally called a reference wafer, in which a thin film whose film thickness is known and whose material and optical characteristics are known is formed on a semiconductor, mainly a silicon substrate. That is, the film thickness of a reference wafer of known optical characteristics and film thickness is periodically measured at regular intervals, and if the measured value is within a certain fixed range with respect to the film thickness of a known reference wafer, the film It can be said that the measurement result by the thickness measuring device is certain within a certain range. Generally, this operation is called film thickness calibration and is performed once a day or once a week.

Originally, film thickness measurement by ellipsometry is a measurement method based on the first principle, and it is a reference wafer if the wavelength and intensity of its light source and the optical characteristics and positions of various optical parts are stable. Is one of the absolute measurements that you do not need. However, in practice, the instability of the light source, the optical characteristics of the optical components, and the positional accuracy are not absolute, so when precise film thickness measurement is required,
It is usual to confirm the accuracy of the measurement with a reference wafer of known optical properties. Generally, in the case of the conventionally used film thickness measurement of about 100 nm, a deviation of 1 nm is allowed even if the measurement accuracy is 1%. This deviation of 1 nm is a sufficiently achievable accuracy for an ellipsometer, and when measuring a film thickness at this level, the film thickness calibration using such a reference wafer is performed unless there is a significant obstacle to the optical system or optical parts. Is not necessary.

However, in order to grasp the state of the device, the film thickness 1
It is usual that the accuracy of the film thickness measuring device is confirmed using a reference wafer of about 00 nm. Further, in recent years, an ultrathin film having a film thickness of about 10 nm may be measured, and therefore a film thickness reference wafer having a film thickness of about 10 nm may be used. In that case, the range for compensating the reliability of the film thickness is ± 0. .3 to 0.5 nm is adopted.

[0006]

However, due to the recent miniaturization of semiconductor devices, especially MOS transistors, the gate insulating film has been thinned to a thickness of 3 to 1
Ultra-thin insulating films having a thickness of nm have come to be used. For the gate insulating film having such a film thickness range, the control value of the film thickness is required to be ± 0.2 to 0.1 nm. That is, the atomic step of the silicon atom is 0.3.
Even though it is 14 nm, the film thickness range to be controlled is ±
It is as small as 0.1 nm. In order to measure such a thin film with high accuracy, the ellipsometer enhances the stability of the laser that is the light source, and controls the environment of the optical parts (humidity, temperature), and repeats the measurement accuracy within ± 0.000.
It is raised to about 3 nm. Therefore, its accuracy is several tens of minutes compared with the film thickness accuracy to be controlled, and there is no problem in stability and accuracy as a measuring device.

However, considering the absolute measurement, although the repeatability is sufficient, it is doubtful whether or not the measurement is an absolute value measurement. Therefore, it goes without saying that film thickness calibration with a reference wafer having known film thickness and optical characteristics is essential for film thickness measurement of film thickness 3 to 1 nm. However, in the case of film thickness standard wafers, the problems that could be ignored in the past for thin films cannot be ignored.

When an insulating film having a thickness of 5 nm or less is formed and measured by an ellipsometer, it is confirmed that the film thickness increases with time. This can be observed for the first time with an optical film thickness measuring device having an extremely stable measuring system. In a conventional film thickness measuring device with an accuracy of about ± 0.3 nm, the phenomenon is observed. Difficult to say, this phenomenon is not a general observation. This is due to the fact that substances in the atmosphere, especially those mainly organic substances, adhere to the surface of the insulating film over time. It is considered that since the film became a film, its optical properties changed and it was observed as an increase in optical film thickness. If the film thickness is thicker than 5 nm, such an increase in the film thickness is sufficiently smaller than the total film thickness, so that it is not a big problem in film thickness measurement. However, when the total film thickness becomes 5 nm or less, the increased film thickness cannot be ignored. Therefore, in order to measure the thickness of the ultrathin insulating film with good reproducibility, there is a problem that the phenomenon of increasing the thickness must be overcome.

Here, the first conceivable idea is to remove the deposits on the surface of the insulating film by cleaning. Generally, cleaning such as known RCA cleaning is used for cleaning semiconductor wafers. The RCA cleaning is composed of a combination of cleaning with sulfuric acid and hydrogen peroxide, then cleaning with ammonia, hydrogen peroxide, dilute hydrofluoric acid etching, and cleaning with hydrochloric acid and hydrogen peroxide. At this time, the mixing ratio of ammonia, hydrogen peroxide solution, and water is 1: 1: 5, and the temperature is about 80 ° C. In such cleaning, the purpose is to remove particles, organic substances, and heavy metals in the first place, but in order to achieve the purpose, the purpose is achieved by etching the underlying object to be cleaned.

In the cleaning of ammonia, hydrogen peroxide and water (hereinafter referred to as APM cleaning) generally used as a modification of RCA cleaning, for example, the mixing ratio is 1: 1: 5 and 80 ° C.
In the case of using this cleaning for the ultra-thin insulating film thickness reference wafer, if the reference wafer is a silicon dioxide film,
If the film thickness is 3 nm, the APM cleaning reduces the film thickness to 1.2 nm after 10 minutes of cleaning. This is APM
The etching rate of the cleaning silicon dioxide film is 0.18
This is because it is nm / min. Therefore, in this case, when the control range of the film thickness is 3.0 ± 0.1 nm,
If PM cleaning is performed, it may be possible to remove the adhered organic substances on the surface, but at the same time, the insulating film itself is also etched, and is no longer useful as a film thickness standard. In other words, in order to remove the deposits on the surface and not change the film thickness of the insulating film having a film thickness of 3 nm or less, the idea of simply cleaning when the film becomes dirty cannot be dealt with anymore. Therefore, at present, a traceable film thickness standard wafer having a film thickness of 5 nm or less is not in the market. This is because it is not possible to prevent an increase in film thickness after film formation, and it is not possible to grasp the amount of increase.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a film thickness measuring device and film thickness measuring device capable of measuring and controlling the film thickness of an ultrathin insulating film with a film thickness measuring device with good reproducibility. A measuring method and a method for manufacturing a film thickness reference wafer are provided.

[0012]

In order to solve the above-mentioned problems, a film thickness measuring apparatus according to claim 1 of the present invention is a single-wavelength ellipsometry, a spectroscopic ellipsometry, or a single-wavelength or plural-wavelength reflection / interference optics. Is a film thickness measuring device for measuring a single-layer or multi-layer ultra-thin insulating film formed on a wafer by an optical method. It has a pretreatment mechanism for exposing it to corona discharge by passing it just below the corona discharge wire in an atmosphere containing.

As described above, before exposure to corona discharge by passing the wafer to be measured just under the corona discharge wire in the air or in the atmosphere containing oxygen and nitrogen immediately before the measurement of the insulating film thickness by the optical method. Since it has a treatment mechanism, corona discharge ionizes oxygen in the atmosphere to generate ozone and oxygen ions, and the generated ozone and oxygen ions are active and can remove organic substances adhering to the wafer surface. As a result, organic substances that change the optical characteristics are removed, so when the thickness of the insulating film is measured by an optical method, the original thickness of the insulating film formed on the wafer surface can be accurately and reproducibly reproduced. Can be measured and managed.

A film thickness measuring apparatus according to a second aspect is a single-layer or multi-layer ultra-thin insulation formed on a wafer by single-wavelength ellipsometry, spectroscopic ellipsometry, or a single-wavelength or multiple-wavelength reflection / interference optical method. A film thickness measuring device for measuring a film, which has a wavelength of 150 to 3 on a surface of a wafer to be measured immediately before an insulating film thickness is measured by an optical method.
It has a pretreatment mechanism for irradiating the entire surface with 50 nm ultraviolet light.

As described above, the wavelengths of 150 to 3 are formed on the surface of the wafer to be measured immediately before the measurement of the insulating film thickness by the optical method.
Since it has a pretreatment mechanism that irradiates the entire surface with 50 nm ultraviolet light, the ultraviolet light ionizes oxygen in the atmosphere to generate ozone and oxygen ions, and the generated ozone and oxygen ions are active and adhere to the wafer surface. It is possible to remove the organic substances that are present. As a result, organic substances that change the optical characteristics are removed, so when the thickness of the insulating film is measured by an optical method, the original thickness of the insulating film formed on the wafer surface can be accurately and reproducibly reproduced. Can be measured and managed.

The film thickness measuring device according to claim 3 is the same as that according to claim 1.
In the film thickness measuring apparatus described above, a wafer to be measured is held on a stage in a reduced pressure atmosphere from 15 ° C. to 50 ° C.
It has a mechanism for heating to 0 ° C. In this way, with the wafer to be measured held on the stage, 1
Since it has a mechanism for heating from 5 ° C. to 500 ° C., organic substances and water on the heated wafer surface are removed by evaporating due to vapor pressure. Further, the reduced pressure makes it easier for organic substances on the wafer surface to be desorbed.

A film thickness measuring device according to a fourth aspect is the first aspect.
The film thickness measuring apparatus described above has a mechanism for irradiating the entire surface of the wafer to be measured with ultraviolet light having a wavelength of 150 to 350 nm when the wafer to be measured is passed directly under the corona discharge wire. As described above, when the wafer to be measured is passed directly under the corona discharge wire, the surface of the wafer to be measured is irradiated with ultraviolet light having a wavelength of 150 to 350 nm over the entire surface. Therefore, ozone is generated by corona discharge and UV irradiation. By combining the above, a higher concentration of ozone can be generated and the organic substances on the surface can be efficiently removed.

A film thickness measuring apparatus according to a fifth aspect is the film thickness measuring apparatus according to the first, second, third or fourth aspect, wherein a stage for holding a wafer for measuring an insulating film thickness by an optical method, The stage that holds the wafer by the pretreatment mechanism is independent. In this way, since the stage that holds the wafer for measuring the insulating film thickness by the optical method and the stage that holds the wafer by the pretreatment mechanism are independent, reproducibility is achieved even with an extremely thin insulating film. The film thickness can be measured well.

According to a sixth aspect of the film thickness measuring method, a step of holding a wafer having an ultrathin insulating film on a stage and a wafer temperature of 1 in air or in an oxygen and nitrogen atmosphere.
Exposing the corona discharge to the entire surface of the wafer by passing the corona discharge wire directly under the corona discharge wire while maintaining the temperature in the range of 5 ° C. to 500 ° C .; And measuring the film thickness of the insulating film by an optical method.

As described above, the step of holding the wafer having the ultrathin insulating film on the stage, and the corona discharge in the state where the temperature of the wafer is kept in the range of 15 ° C. to 500 ° C. in the air or the atmosphere of oxygen and nitrogen. A step of exposing the entire surface of the wafer to corona discharge by passing the stage directly under the wire, and a step of moving the wafer and the stage to predetermined positions after each step and measuring the thickness of the insulating film by an optical method. Since it contains ozone and oxygen ions generated by corona discharge, it is possible to remove organic substances adhering to the wafer surface, and the organic substances and water on the heated wafer surface evaporate due to vapor pressure. To be removed. Therefore, it is possible to remove the organic substances on the surface of the insulating film by the pretreatment and measure the film thickness of the ultrathin insulating film itself accurately and with good reproducibility.

According to a seventh aspect of the present invention, there is provided a method for manufacturing a film thickness reference wafer, wherein the film thickness of a film thickness reference wafer having a known film thickness of an ultrathin insulating film formed on a semiconductor substrate is periodically measured, and the measurement is performed. A method of manufacturing a film thickness reference wafer used when controlling measurement accuracy by having a value within a predetermined range with respect to the film thickness of a known reference wafer, which is a film forming means for thermal oxidation, thermal nitriding, or thermal oxynitriding. A step of forming an insulating film having a predetermined film thickness by means of, and a predetermined time after the insulating film is formed, the insulating film is exposed to a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water.
Including a step of treating at 0 to 150 ° C. for a predetermined time and a step of replacing the chemical solution with warm pure water or ultrapure water and drying.
Each process has at least 3 before use as a reference wafer
Complete from 0 minutes before to just before.

As described above, a step of forming an insulating film having a predetermined thickness by means of film forming means such as thermal oxidation, thermal nitriding and thermal oxynitriding,
After a predetermined time has passed after forming the insulating film, the insulating film is treated with a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water to 80%.
Since the reference wafer does not remove all the deposits, it includes a part of the deposits instead of removing the chemicals with warm pure water or ultrapure water and drying the treatment. By solidifying and leaving, it becomes possible to serve as a stable film thickness standard. In addition, since each process is completed at least 30 minutes before and immediately before the use as the reference wafer, the influence of redeposition of organic substances can be eliminated.

In the method of manufacturing a film thickness reference wafer according to claim 8, the film thickness of a film thickness reference wafer having a known film thickness of an ultrathin insulating film formed on a semiconductor substrate is regularly measured, and the measurement is performed. A method of manufacturing a film thickness reference wafer used when controlling measurement accuracy by having a value within a predetermined range with respect to the film thickness of a known reference wafer, which is a film forming means for thermal oxidation, thermal nitriding, or thermal oxynitriding. A step of forming an insulating film having a predetermined film thickness by the following steps, and a predetermined time after the insulating film is formed, the mixing ratio of ammonia water and hydrogen peroxide water or ammonia water and ozone water is 1: 1 to the insulating film. 1 with a mixture that is 1: 500
It includes a step of treating at 5 ° C. to 40 ° C. for a predetermined time, and a step of substituting the chemical solution with warm pure water or ultrapure water and drying, and each treatment is completed at least 30 minutes before and immediately before use as a reference wafer. .

As described above, a step of forming an insulating film having a predetermined thickness by means of film forming means such as thermal oxidation, thermal nitriding and thermal oxynitriding,
After a predetermined time from the formation of the insulating film, the mixture of ammonia water and hydrogen peroxide solution or ammonia water and ozone water having a mixing ratio of 1: 1 to 1: 500 is applied to the insulating film.
Since the process includes a step of treating at 40 ° C. to 40 ° C. for a predetermined time and a step of substituting the chemical solution with hot pure water or ultrapure water and drying, the organic matter is removed from the reference wafer having an increased film thickness due to the organic matter attached to the surface, The film thickness almost returns to that at the time of film formation, and it becomes possible to serve as a film thickness reference. Also,
Since each treatment is completed at least 30 minutes before and immediately before use as a reference wafer, the influence of redeposition of organic substances can be eliminated.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram showing a film thickness measuring device according to a first embodiment of the present invention.
Indicates a pretreatment position, and (b) indicates a film thickness measurement position.

This film thickness measuring device has a structure in which a single-layer or multi-layer ultrathin insulating film formed on a wafer is measured by an optical method. It has a pretreatment mechanism for exposing it to corona discharge by passing it directly under a corona discharge wire in air or in an atmosphere containing oxygen and nitrogen.

In FIG. 1, 11 is a semiconductor substrate (wafer) made of silicon, on the surface of which an insulating film having a film thickness of 5 nm or less is formed. Here, an oxynitride film having a thickness of 2.8 nm formed at 1000 ° C. in a mixed gas atmosphere of nitric oxide and oxygen is used. 12 is a corona discharge wire, 13
Is a single-wavelength ellipsometer with a wavelength of 63
With a 2.8 nm He-Ne laser, the angle of incidence of the laser on the wafer is 70 degrees. In the present embodiment, the single-wavelength ellipsometer, which is the optical film thickness measuring device, cannot be touched further. This optical film thickness measuring device
This is because the same applies to other principles such as spectroscopic ellipsometry or optical methods of single-wavelength or multiple-wavelength reflection / interference other than single-wavelength ellipsometry.

As shown in FIG. 1A, the wafer 11 is set on the stage 15 by a transfer system. In this embodiment, the stage 15 is kept at room temperature and has no heating device. Wafer 11 placed on stage 15
Moves to the pretreatment position. At this time, the corona discharge wire 12 is placed at a position approximately 2 cm above the wafer 11 at the pretreatment position.
The corona discharge wire 12 has about 2
A voltage of 000V is applied. At the pretreatment position, the wafer 11 placed on the stage 15 passes directly under the corona discharge wire 12 while being exposed to the corona discharge generated by the corona discharge wire 12.

At this time, the corona discharge ionizes oxygen in the atmosphere to generate ozone and oxygen ions. The generated ozone and oxygen ions are active and can remove the organic substances adhering to the wafer surface. However, the stage 15 is kept at room temperature, the ozone generated directly under the corona discharge wire 12 has a low concentration, and the ozone extinction life is short. Most of the ozone generated by the corona discharge wire 12 disappears on the wafer surface, but at that time, the organic substances on the wafer surface are decomposed. If ozone gas or the like is used here, on the contrary, the optical system and drive system of the measuring device will be deteriorated by oxidation, and unreacted ozone is harmful, so that a processing device such as an ozone destroyer is required to render it harmless. At this time, the entire surface of the wafer can be exposed to corona discharge by fixing the corona discharge wire 12 and moving the stage 15 in a constant horizontal direction, or by fixing the stage 15 and scanning the corona discharge wire 12 in a constant horizontal direction. As a result, the organic substances attached to the entire surface of the wafer can be removed.

When the processing at the pre-processing position is completed, FIG.
As shown in (b), the stage 15 is moved to the film thickness measurement position, and the film thickness is measured by the single wavelength ellipsometer 13. Since organic substances that change the optical characteristics are removed by pretreatment, when measuring the film thickness with an ellipsometer, etc.
The original film thickness of the insulating film formed on the wafer surface can be measured accurately and with good reproducibility.

A second embodiment of the present invention will be described with reference to FIG. 2A and 2B are conceptual diagrams showing a film thickness measuring device according to a second embodiment of the present invention, where FIG. 2A shows a pretreatment position and FIG. 2B shows a film thickness measuring position.

This film thickness measuring device has a structure in which a single-layer or multi-layer ultrathin insulating film formed on a wafer is measured by an optical method, and the film thickness of the wafer to be measured is measured immediately before the measurement of the insulating film thickness by the optical method. Wavelength 150-350 on the surface
It has a pretreatment mechanism for irradiating the entire surface with nm ultraviolet light.

In FIG. 2, reference numeral 11 denotes a semiconductor substrate (wafer) made of silicon, on the surface of which an insulating film having a film thickness of 5 nm or less is formed. In this embodiment mode, a 2.6 nm silicon dioxide film is formed at 1000 ° C. in an oxygen atmosphere. Reference numeral 13 is a single wavelength ellipsometer, and 14 is a UV lamp.

As shown in FIG. 2A, the wafer 11 is first transferred onto the stage 15 and then transferred to the pretreatment position. About 5c above the wafer 11 at the pretreatment position
The Xe arc lamp 14 is installed at the position m.
The lamp 14 can emit ultraviolet light having a wavelength of 150 to 350 nm. There is no particular limitation on the power of the lamp 14, but it should be limited to such a level that the temperature of the wafer 11 is not significantly increased by being absorbed by the wafer 11 upon exposure to the wafer 11. Specifically, the temperature of the wafer 11 should be such that it can be maintained at 300 ° C. or lower. Wafer 1 placed on stage 15
1 is exposed to the ultraviolet light produced by the UV lamp 14.
Ultraviolet light ionizes oxygen in the atmosphere to generate ozone and oxygen ions. The generated ozone and oxygen ions can remove organic substances adhering to the wafer surface. At this time, by fixing the UV lamp 14 and moving the stage 15 in a fixed horizontal direction, or by fixing the stage 15 and scanning the UV lamp 14 in a fixed horizontal direction, the entire surface of the wafer can be exposed to ultraviolet light. As a result, organic substances attached to the entire surface of the wafer can be removed. In the case of this embodiment, the UV lamp 1 is used as a source for generating ozone.
Although No. 4 was used, the purpose of this case is also to generate ozone to the extent that only the organic substances on the surface can be removed without oxidizing the wafer itself.

When the processing at the pre-processing position is completed, FIG.
As shown in (b), the stage 15 is moved to the film thickness measurement position, and the film thickness is measured by the single wavelength ellipsometer 13. Since organic substances that change the optical characteristics are removed by pretreatment, when measuring the film thickness with an ellipsometer, etc.
The original film thickness of the insulating film formed on the wafer surface can be measured accurately and with good reproducibility.

As described above, the structures of the first embodiment and the second embodiment are generally effective in removing the organic substances attached to the wafer surface. Moreover, since the organic substances can be removed during wafer loading, it is possible to remove the organic deposits on the surface without sacrificing the throughput of film thickness measurement. However, depending on the form of adhesion of the organic matter, it may not be possible to remove it only by corona discharge wire or UV light irradiation. This is because ozone generated by these methods does not necessarily have a high concentration. However, it can be a sufficiently effective removal method for general organic matter adhesion.

A third embodiment of the present invention will be described with reference to FIG. 3A and 3B are conceptual diagrams showing a film thickness measuring device according to a third embodiment of the present invention. FIG. 3A shows a pretreatment position and FIG. 3B shows a film thickness measuring position.

This film thickness measuring apparatus has a mechanism for heating from a room temperature to 500 ° C. in a reduced pressure atmosphere while holding the wafer to be measured on the stage in the film thickness measuring apparatus of the first embodiment. In FIG. 3, 11 is a semiconductor substrate (wafer) made of silicon, and an insulating film having a film thickness of 5 nm or less is formed on the surface. 13 is an ellipsometer,
Reference numeral 15 is a heating stage, 16 is an exhaust pipe connected to a vacuum pump, and 17 is an introduction pipe of an atmosphere containing air or oxygen and / or nitrogen. Stage 1 at pretreatment position
The wafer 11 placed on the substrate 5 can be heated by the heating stage 15 from room temperature to about 500 ° C. Reference numeral 18 is a measuring stage, and 19 is a gate valve for loading and unloading the wafer 11.

As shown in FIG. 3A, the wafer 11 is placed on the stage 15 in the pretreatment chamber at atmospheric pressure by the transfer system. At this time, the stage 15 is resistance-heated and is about 3
It is kept at 00 ° C. This is because the stage itself can be heated up to 500 ° C., but if the temperature of the wafer 11 is overheated, the oxidation of the silicon substrate due to ozone proceeds and the film thickness measurement in the next step is affected. The method for heating the wafer 11 is not limited. For example, it is possible to attach a quartz glass window above the pretreatment chamber and directly heat the wafer 11 from above by an infrared lamp (halogen lamp or the like). Organic substances and moisture on the heated wafer surface are removed by evaporating due to vapor pressure. Also, at this time, the pretreatment chamber is set to 1 to
By reducing the pressure to about rr, organic substances on the wafer surface are more easily desorbed. Since the pressure is not limited, the pressure may be determined in the range of normal pressure to about 1 torr in consideration of the throughput. At this time, the corona discharge wire 12 installed in the vicinity of 2 cm above the wafer in the pretreatment chamber
Even if ozone is generated by corona discharge due to, it is even more effective in removing organic substances. At this time, when using together with corona discharge, the temperature of the stage is 200
Better results may be obtained at a low temperature of about ℃. Needless to say, at this time, if the wafer 11 can be rotated together with the stage 15, the removal uniformity of organic substances by corona discharge can be improved.

When the treatment at the pretreatment position is completed, the pressure is restored to normal pressure, the wafer 11 is taken out from the gate valve 19, and another stage 1 for measurement is used as shown in FIG. 3B.
The wafer 11 is placed on the wafer 8, the wafer 11 is moved to the measurement position, and the film pressure is measured by the single-wavelength ellipsometer 13. Since the organic substances that change the optical characteristics are removed by the pretreatment, when the film thickness is measured by an ellipsometer or the like, the original film thickness of the insulating film formed on the wafer surface can be accurately and reproducibly measured.

In the case of the film thickness measuring apparatus according to the present embodiment, since the time from film formation to film thickness measurement is relatively short (several hours at the longest) in normal film thickness measurement, corona discharge As a matter of course, it is efficient to perform corona discharge, reduced pressure, and substrate heating only when measuring a wafer that has been stored for a long time, such as a film thickness reference sample, as pretreatment at atmospheric pressure and room temperature. Nor. This is because the amount of organic substances attached to the surface of the wafer immediately after film formation is small, and thus large-scale removal of organic substances is not effective, but rather causes a decrease in throughput.

A fourth embodiment of the present invention will be described with reference to FIG. 4A and 4B are conceptual views showing a film thickness measuring device according to a fourth embodiment of the present invention, where FIG. 4A shows a pretreatment position and FIG. 4B shows a film thickness measuring position.

This film thickness measuring device is the same as the film thickness measuring device of the first embodiment, but when the wafer to be measured is passed directly under the corona discharge wire, the surface of the wafer to be measured is irradiated with ultraviolet light having a wavelength of 150 to 350 nm. It has a mechanism that illuminates the entire surface. In FIG. 4, 11 is a semiconductor substrate (wafer) made of silicon, and an insulating film having a film thickness of 5 nm or less is formed on the surface. The insulating film is formed by processing a silicon substrate in a 206 ° C. perchloric acid solution for 30 minutes and has a film thickness of 3.5 nm.
The chemical oxide film of was used. 12 is a corona discharge wire, 13
Is an ellipsometer, and 14 is a UV lamp.

As shown in FIG. 4A, the wafer 11 is placed on the stage 15 by the transfer mechanism. At the pretreatment position, the wafer 11 placed on the stage 15 is exposed to the UV light from the UV lamp 14 and the corona discharge generated by the corona discharge wire 12 at the same time. Ultraviolet light and corona discharge ionize oxygen in the atmosphere to generate ozone and oxygen ions. The generated ozone and oxygen ions can remove organic substances adhering to the wafer surface.

When the processing at the pre-processing position is completed, FIG.
As shown in (b), the stage 15 is moved to the film thickness measurement position, and the film thickness is measured by the ellipsometer 13. Since the organic substances that change the optical characteristics are removed by the pretreatment, when the film thickness is measured by an ellipsometer or the like, the original film thickness of the insulating film formed on the wafer surface can be accurately and reproducibly measured. In the present embodiment, by combining corona discharge and ozone generation by UV irradiation, a higher concentration of ozone is generated and organic substances on the surface are efficiently removed.

The fifth embodiment of the present invention will be described with reference to FIG. 5A and 5B are conceptual diagrams showing a film thickness measuring device according to a fifth embodiment of the present invention. FIG. 5A shows a pretreatment position and FIG. 5B shows a film thickness measuring position.

This film thickness measuring device is the same as the film thickness measuring device according to the first to fourth embodiments, in which a stage for holding a wafer for measuring an insulating film thickness by an optical method and a wafer for pretreatment are used. The holding stage is independent. In FIG. 5, 11 is a semiconductor substrate (wafer) made of silicon, on the surface of which an insulating film having a film thickness of 5 nm or less is formed. 12 is a corona discharge wire, 13 is an ellipsometer, 14 is a UV lamp, 15 is a heating stage, 16
Is an exhaust pipe connected to a vacuum pump, and 17 is an intake pipe for introducing air or an atmosphere containing oxygen and / or nitrogen. Reference numeral 18 is a measuring stage, and 19 is a gate valve for loading and unloading the wafer 11.

As shown in FIGS. 5A and 5B, the stage 15 for pretreatment is independent of the stage 18 for film thickness measurement, and the film thickness measurement is first performed on the wafer to be measured. 11 is transferred to the pretreatment stage 15 and pretreatment is performed. The pretreatment conditions at this time are a stage temperature of 300 ° C.,
Pressure 1 torr, applied voltage 20 to the corona discharge wire 12
The emission wavelength band of the 00V, UV lamp 14 is 150 to 35
Pretreatment was carried out at 0 nm for 1 minute. After that, the pressure in the chamber is returned to the pretreatment stage 15 to the film thickness measurement stage 1
The wafer 11 is transferred to No. 8 and the film thickness is measured by the ellipsometer 13. This allows the film thickness to be measured with good reproducibility even with an extremely thin insulating film.

A sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a process diagram showing a film thickness measuring method according to a sixth embodiment of the present invention.

This film thickness measuring method comprises a step of holding a wafer having an ultrathin insulating film on a stage, and a temperature of the wafer from room temperature to 50 in air or an atmosphere of oxygen and nitrogen.
The process of exposing the corona discharge to the entire surface of the wafer by passing the stage directly under the corona discharge wire while keeping it in the range of 0 ° C., and after each process, the wafer and the stage are moved to a predetermined position, and the optical And a step of measuring the film thickness of the insulating film by a method. Moreover, these steps can be performed using the film thickness measuring apparatus of the first or third embodiment.

As shown in FIG. 6A, in the film thickness measurement of the ultrathin insulating film, first, the semiconductor substrate 11 having the ultrathin insulating film is held on the stage 15. In this embodiment, a 2.20 nm-thickness silicon dioxide film formed in oxygen at 1000 ° C. by an RTP apparatus is used as the insulating film. By leaving this wafer in a clean room for 3 months in advance, the film thickness value by ellipsometer is 2.5n.
It was increasing with m. As shown in FIGS. 6 (b) and 6 (c), the wafer 11 and the insulating film surface held were placed 2 cm directly below the corona discharge wire 12 to which 2000 V was applied in the air or in the atmosphere of oxygen and nitrogen, and the stage 15 was set to 1 c.
Corona discharge is exposed on the entire surface of the wafer by moving at a speed of m / sec.
The wafer 11 was placed on the stage 15 at 300 ° C. when it was passed directly below. Although the accurate temperature of the wafer 11 is not measured, it is 28 seconds after about 30 seconds after being placed on the stage 15.
The temperature was raised to 0 ° C or higher. After that, the wafer 11 and the stage 15 were moved to predetermined positions, and the film thickness was measured by an optical method using the ellipsometer 13 as shown in FIG. The measured value obtained by the single-wavelength ellipsometer 13 having a wavelength of 632.8 nm was 2.23 nm. Therefore, the organic substance on the surface of the insulating film was removed by the above-mentioned pretreatment, and the film thickness of the ultrathin insulating film itself was accurately and reproducible. It can be measured well. According to the present embodiment, it was possible to almost remove the 0.3 nm-equivalent organic matter attached to the wafer surface in three months. However, after the measurement, the adhesion to the surface started anew, and the film thickness became 2.28 nm 2 hours after the measurement. Therefore, it goes without saying that the process immediately before the measurement is important.

A seventh embodiment of the present invention will be described with reference to FIGS.
A description will be given based on 0. FIG. 7 is a process diagram showing a pretreatment method for a film thickness reference wafer according to a seventh embodiment of the present invention.

The film thickness of the film thickness reference wafer is periodically measured, and the measured value is within a predetermined range with respect to the known film thickness of the reference wafer. In the manufacturing method, a step of forming an insulating film having a predetermined thickness and a predetermined time after the insulating film is formed, the insulating film is heated to 80 to 80% with a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water. It includes a step of treating at 150 ° C. for a predetermined time and a step of substituting a chemical solution with warm pure water or ultrapure water and drying, and each treatment is completed from at least 30 minutes before to immediately before use as a reference wafer.

As shown in FIG. 7A, the semiconductor substrate 11
When the ultrathin insulating film formed above is used as a film thickness reference wafer with a known film thickness, first, the insulating film having a predetermined film thickness is formed by a known film forming means such as thermal oxidation, thermal nitriding, or thermal oxynitriding. The film 2 is formed. After an arbitrary time has elapsed after the formation of the insulating film, organic substances contained in the atmosphere adhere to the surface of the insulating film.

In FIG. 8, data was obtained up to 3 months due to the time dependence of the thickness of a 2.6 nm thick silicon dioxide film formed at 1000 ° C. in an oxygen atmosphere. Immediately after the film formation, the film thickness starts to increase rapidly due to the adhesion of organic substances and water on the surface.
It increases by about 0.5 nm after 2 hours. After that, the film thickness continues to increase, and the amount of increase tends to saturate, but it gradually increases until about 1 year. Since the present embodiment is applied to the sample according to the present embodiment for three months, the increase amount of the film thickness is about 0.2 nm. However, if it is actually left as it is, the increase amount reaches 0.3 to 0.5 nm.

Therefore, as shown in FIGS. 7B and 7C, the insulating film is heated to 95 ° C. with a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water (mixing ratio 4: 1). After spraying for 7 minutes, the chemical solution was replaced by spraying hot pure water and ultrapure water and dried. Thereafter, the result of measurement within 30 minutes after washing is also shown in FIG. The film thickness measured after washing was 2.63 nm. Here, in order to eliminate the effect of redeposition of organic substances, the pretreatment must be completed at least 30 minutes before and immediately before the use as a reference wafer. This makes it possible to obtain a film thickness reference wafer that can be used for controlling the film thickness measuring device (FIG. 7D). In the case of a film thickness reference wafer, if the film thickness can be measured accurately on a regular basis, it can fulfill its role, and may be carried out each time the film thickness calibration is carried out.

In order to remove the organic substances and the like adhering to the wafer surface, it suffices to dissolve and remove only the adhering substances without etching the silicon, but in reality it is not possible to identify the adhering organic substances one by one. It is possible, and even if it can be specified, it is a plurality of substances, so it is extremely difficult to find an etching solution that can selectively remove only those substances.
On the other hand, the role of the film thickness reference wafer is that the film thickness is stable during film thickness calibration. The film thickness does not have to be equal to the film thickness immediately after film formation. Any stable film may be used as a reference for the film thickness. Focusing on that point, it is not necessary to remove all the deposits attached to the wafer surface.

As shown in FIG. 9, deposits (surface attachment layer 2
Of 0), only those that are easy to remove are removed, and conversely, those that are difficult to remove are solidified and transformed into stronger adherents, so that the film thickness will always be the same as that of the insulating film 2 formed. It becomes two layers of the layer (surface solidified layer 20a). Since this strong adhesion layer 20a cannot be removed by the cleaning of the present embodiment,
According to the pretreatment method of the present embodiment, only the newly attached organic material layer can be removed, and the solidified strong attachment layer 20a can always be retained. In this case, although it is thicker than the film thickness at the time of film formation, it can stably serve as a film thickness reference.

FIG. 10 is a graph schematically showing this state. Although the film thickness after film formation increases with time, the film thickness after cleaning becomes stable at the film thickness obtained by adding a certain film thickness to the film thickness during film formation by the cleaning of this embodiment. That is,
The present embodiment does not remove all the adhered substances, but rather solidifies and leaves a part of the adhered substances to serve as a stable film thickness standard.

Although a mixed solution of sulfuric acid and hydrogen peroxide solution is used as the cleaning solution in the present embodiment, a mixed solution of sulfuric acid and ozone water may be used.

An eighth embodiment of the present invention will be described with reference to FIGS. 11 to 13. FIG. 11 is a process diagram showing a pretreatment method for a film thickness reference wafer according to the eighth embodiment of the present invention.

The film thickness reference wafer is regularly measured, and the measured value is within a predetermined range with respect to the known film thickness of the reference wafer. In the manufacturing method, a step of forming an insulating film having a predetermined thickness and a predetermined time after the insulating film is formed, a mixing ratio of ammonia water and hydrogen peroxide water or ammonia water and ozone water to the insulating film is changed. Use as a reference wafer, including a step of treating with a mixed solution of 1: 1 to 1: 500 at room temperature to 40 ° C. for a predetermined time and a step of substituting a chemical solution with warm pure water or ultrapure water and drying. Complete at least 30 minutes before and just before.

As shown in FIG. 11A, the semiconductor substrate 1
When the ultrathin insulating film formed on 1 is used as a film thickness reference wafer having a known film thickness, first, a known film forming means such as thermal oxidation, thermal nitriding, thermal oxynitriding, etc. The insulating film 2 is formed. A 1.8 nm-thickness silicon dioxide film was grown at 900 ° C. in an oxygen atmosphere on a semiconductor substrate, especially on a P-type (100) 10 to 15 Ωcm silicon substrate. Then, the wafer was stored for 3 months in a clean room in order to adhere organic substances and the like to the surface. The film thickness measured by an ellipsometer immediately after film formation was 1.82 nm. After that, the film thickness is 1.
It increased to 88 nm, and continued to increase gradually to 2.05 nm after 3 months.

As shown in FIGS. 11 (b) and 11 (c), ammonia water, hydrogen peroxide solution, and water (hereinafter referred to as APM) are used in a ratio of 1: 1: 100 to the wafer left for three months.
The liquid mixed in 1. was immersed in the solution kept at 30 ° C. for 10 minutes. Subsequently, the chemical solution was replaced with ultrapure water and dried. The pretreatment is at least 3 before use as a reference wafer.
The process was completed from 0 minutes before immediately before. The result is shown in FIG. By subjecting the diluted and low-temperature APM cleaning as in the present embodiment, the organic substances are removed by the APM from the wafer having the increased film thickness due to the organic substances attached to the surface. It can be seen that the film thickness almost returns to that at the time of film formation. On the other hand, although the dilution and low temperature APM as in the present embodiment has a capability of etching a silicon dioxide film in a strict sense, its etching rate is 0.05 nm / min or less, and practically no insulating film is formed. It will not be etched. However, strictly speaking, if the cleaning of the present embodiment is repeated infinitely, the film thickness will be gradually reduced from that at the time of film formation (FIG. 13). Also in this embodiment, it is necessary to carry out the measurement within 30 minutes after cleaning (FIG. 11).
(D)).

[0065]

According to the film thickness measuring apparatus of the first aspect of the present invention, the wafer to be measured is subjected to corona discharge in the air or in the atmosphere containing oxygen and nitrogen immediately before the measurement of the insulating film thickness by the optical method. Since it has a pretreatment mechanism that exposes it to corona discharge by passing it directly under the wire, corona discharge ionizes oxygen in the atmosphere to generate ozone and oxygen ions, and the generated ozone and oxygen ions are active,
Organic substances adhering to the wafer surface can be removed. As a result, organic substances that change the optical characteristics are removed, so when the thickness of the insulating film is measured by an optical method, the original thickness of the insulating film formed on the wafer surface can be accurately and reproducibly reproduced. Can be measured and managed.

According to the film thickness measuring apparatus of the second aspect of the present invention, before the entire surface is irradiated with the ultraviolet light having the wavelength of 150 to 350 nm immediately before the measurement of the insulating film thickness by the optical method. Since it has a processing mechanism, ultraviolet light ionizes oxygen in the atmosphere to generate ozone and oxygen ions, and the generated ozone and oxygen ions are active and can remove organic substances adhering to the wafer surface. As a result, the organic substances that change the optical characteristics are removed, so when the thickness of the insulating film is measured by an optical method,
The original film thickness of the insulating film formed on the wafer surface can be measured and managed accurately and with good reproducibility.

According to a third aspect of the present invention, the wafer to be measured is held on the stage in a reduced pressure atmosphere from 15 ° C. to 500 ° C.
Since it has a mechanism of heating to ℃, the organic substances and water on the heated wafer surface are removed by evaporating by the vapor pressure. Further, the reduced pressure makes it easier for organic substances on the wafer surface to be desorbed.

According to the present invention, when the wafer to be measured is passed directly under the corona discharge wire, the surface of the wafer to be measured is irradiated with ultraviolet light having a wavelength of 150 to 350 nm over the entire surface. By combining ozone generation by irradiation, higher concentration ozone can be generated and organic substances on the surface can be efficiently removed.

According to the present invention, since the stage for holding the wafer for measuring the insulating film thickness by the optical method and the stage for holding the wafer by the pretreatment mechanism are independent, it is an extremely thin insulating film. However, the film thickness can be measured with good reproducibility.

According to the film thickness measuring method of the sixth aspect of the present invention, the step of holding the wafer having the ultrathin insulating film on the stage, and the temperature of the wafer at 15 ° C. in the air or the oxygen and nitrogen atmosphere. To 500 ° C., exposing the corona discharge to the entire surface of the wafer by passing the stage directly under the corona discharge wire, and moving the wafer and stage to predetermined positions after each step, Since it includes a step of measuring the film thickness of the insulating film by a static method, ozone and oxygen ions generated by corona discharge can remove organic substances adhering to the wafer surface as well as heating of the wafer surface. Organic substances and water are removed by evaporating due to vapor pressure. Therefore, it is possible to remove the organic substances on the surface of the insulating film by the pretreatment and measure the film thickness of the ultrathin insulating film itself accurately and with good reproducibility.

According to the method of manufacturing a film thickness reference wafer according to claim 7 of the present invention, a step of forming an insulating film having a predetermined film thickness by means of film forming means such as thermal oxidation, thermal nitriding and thermal oxynitriding; After a predetermined time after the film formation, the insulating film is heated to 80 to 80% with a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water.
Since it includes a step of treating at 150 ° C. for a predetermined time and a step of replacing the chemical solution with warm pure water or ultrapure water and drying the solution,
The reference wafer can serve as a stable film thickness reference by solidifying and leaving a part of the adhered substance instead of removing all the adhered substance. In addition, each process requires at least 3 before use as a reference wafer.
Since the process is completed from 0 minutes before to immediately before, the influence of redeposition of organic substances can be eliminated.

According to the method of manufacturing a film thickness reference wafer according to claim 8 of the present invention, a step of forming an insulating film having a predetermined film thickness by means of film forming means such as thermal oxidation, thermal nitriding and thermal oxynitriding; After a lapse of a predetermined time after forming the film, the insulating film is heated to 15 ° C. with a mixed solution having a mixing ratio of ammonia water and hydrogen peroxide water or ammonia water and ozone water of 1: 1 to 1: 500.
To 40 ° C. for a predetermined time, and a step of substituting the chemical solution with warm pure water or ultrapure water and drying, the organic matter is removed from the reference wafer whose film thickness has increased due to the adhesion of the organic matter to the surface, and It becomes possible to return to the film thickness at the time of film formation and serve as a film thickness reference. Also,
Since each treatment is completed at least 30 minutes before and immediately before use as a reference wafer, the influence of redeposition of organic substances can be eliminated.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a film thickness measuring device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a film thickness measuring device according to a second embodiment of the present invention.

FIG. 3 is a conceptual diagram showing a film thickness measuring device according to a third embodiment of the present invention.

FIG. 4 is a conceptual diagram showing a film thickness measuring device according to a fourth embodiment of the present invention.

FIG. 5 is a conceptual diagram showing a film thickness measuring device according to a fifth embodiment of the present invention.

FIG. 6 is a process drawing showing a film thickness measuring method according to a sixth embodiment of the present invention.

FIG. 7 is a process chart showing a method of manufacturing a film thickness reference wafer according to a seventh embodiment of the present invention.

FIG. 8 is a graph showing the change with time in film thickness immediately after film formation in the seventh embodiment of the present invention.

FIG. 9 is a schematic diagram of changes in film thickness after surface attachment and pretreatment in the seventh embodiment of the present invention.

FIG. 10 is a graph showing changes over time in film thickness and changes in film thickness after cleaning in the seventh embodiment of the present invention.

FIG. 11 is a process drawing showing a method of manufacturing a film thickness reference wafer according to an eighth embodiment of the present invention.

FIG. 12 is a graph showing a change over time in the film thickness immediately after film formation in the eighth embodiment of the present invention.

FIG. 13 is a graph showing changes with time in film thickness and changes in film thickness after cleaning in the eighth embodiment of the present invention.

FIG. 14 is an explanatory diagram of a conventional film thickness measuring device management method.

[Explanation of symbols]

1 Semiconductor substrate 2 Ultra-thin insulating film 3 attached matter 11 Semiconductor substrate 12 Corona discharge wire 13 Ellipsometer 14 UV lamp 15 stages 16 Exhaust pipe 17 Introducing piping

Continued front page    F term (reference) 2F065 AA30 BB03 BB22 CC19 CC31                       FF50 FF51 FF61 LL32 RR07                       TT07 UU00                 2G052 AA13 AD32 AD52 EB11 FC02                       FC03 GA11                 4M106 AA01 AA13 AB02 BA07 BA20                       CA48 CA70 DH03 DH04 DH32                       DJ32

Claims (8)

[Claims] 1. A film thickness measuring device for measuring a single-layer or multi-layer ultra-thin insulating film formed on a wafer by single-wavelength ellipsometry, spectroscopic ellipsometry, or optical technique of single-wavelength or multiple-wavelength reflection / interference. There is a pretreatment mechanism that exposes the wafer to be measured to corona discharge by passing it directly under the corona discharge wire in air or in an atmosphere containing oxygen and nitrogen immediately before measuring the insulation film thickness by an optical method. A film thickness measuring device characterized by the above. 2. A film thickness measuring device for measuring a single-layer or multi-layer ultra-thin insulating film formed on a wafer by single-wavelength ellipsometry, spectroscopic ellipsometry, or a single-wavelength or multiple-wavelength reflection / interference optical method. A film thickness measuring device having a pretreatment mechanism for irradiating the entire surface of the wafer to be measured with ultraviolet light having a wavelength of 150 to 350 nm immediately before the measurement of the insulating film thickness by an optical method. 3. The film thickness measuring apparatus according to claim 1, further comprising a mechanism for heating the wafer to be measured on a stage to 15 ° C. to 500 ° C. in a reduced pressure atmosphere. 4. When the wafer to be measured is passed directly under the corona discharge wire, a wavelength of 15 is measured on the surface of the wafer to be measured.
The film thickness measuring device according to claim 1, further comprising a mechanism for irradiating the entire surface with ultraviolet light of 0 to 350 nm. 5. A stage for holding a wafer for measuring an insulating film thickness by an optical method and a stage for holding a wafer by a pretreatment mechanism are independent.
The film thickness measuring device according to 2, 3, or 4. 6. A step of holding a wafer having an ultrathin insulating film on a stage, and a step of holding the wafer temperature in the range of 15 ° C. to 500 ° C. in air or in an atmosphere of oxygen and nitrogen, A step of exposing corona discharge to the entire surface of the wafer by passing the stage directly below and moving the wafer and the stage to predetermined positions after each of the steps, and measuring the thickness of the insulating film by an optical method. A method for measuring film thickness, which comprises a step. 7. An ultrathin insulating film formed on a semiconductor substrate has a known film thickness, and a film thickness of a reference wafer is regularly measured, and the measured value is predetermined with respect to the known film thickness of the reference wafer. A method of manufacturing a film thickness reference wafer used when controlling the measurement accuracy by being within the range, which is a step of forming an insulating film having a predetermined film thickness by a film forming means of thermal oxidation, thermal nitriding, or thermal oxynitriding. A step of treating the insulating film with a mixed solution of sulfuric acid and hydrogen peroxide solution or sulfuric acid and ozone water at a temperature of 80 to 150 ° C. for a predetermined period of time after forming the insulating film; A method for manufacturing a film thickness reference wafer, comprising the steps of substituting a chemical solution and drying, wherein each of the processes is completed at least 30 minutes before and immediately before use as a reference wafer. 8. An ultrathin insulating film formed on a semiconductor substrate has a known film thickness, the film thickness of a reference wafer is regularly measured, and the measured value is predetermined with respect to the known film thickness of the reference wafer. A method of manufacturing a film thickness reference wafer used when controlling the measurement accuracy by being within the range, which is a step of forming an insulating film having a predetermined film thickness by a film forming means of thermal oxidation, thermal nitriding, or thermal oxynitriding. After a predetermined time from the formation of the insulating film, a mixed solution having a mixing ratio of ammonia water and hydrogen peroxide solution or ammonia water and ozone water of 1: 1 to 1: 500 is applied to the insulating film at 15 ° C. to 40 ° C. A step of treating at ℃ for a predetermined time,
A method of manufacturing a film thickness reference wafer, comprising the steps of substituting a chemical solution with warm pure water or ultrapure water, and drying, wherein each of the processes is completed at least 30 minutes before and immediately before use as a reference wafer.