JPH0978225A - Formation of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form thin films having excellent film quality with a good adhesion property by irradiating a substrate surface with electromagnetic waves while evacuating the inside of a predischarge chamber to a high vacuum, removing the materials adsorbed on the substrate surface, then forming the thin films on the substrate surface. SOLUTION: The substrate 102a is carried into the predischarge chamber 101 and is installed therein. While the inside of the chamber is evacuated to the high vacuum by a pump 105a, the substrate 102a is irradiated with the electromagnetic waves (UV rays, IR rays, microwaves) which are absorbed in the materials adsorbed on the substrate surface but are not absorbed in the substrate itself from an electromagnetic wave irradiation means 103, by which the materials adsorbed on the surface are removed. The substrate 102b is carried via a gate valve 106b into a film forming chamber 107 evacuated to the high vacuum and is installed on a substrate holder 108 when the irradiation with the electromagnetic waves ends. A sputtering gas is then introduced from gas introducing means 111 into the chamber and electric power is supplied to a target 109 from an electric power supplying means 110 to generate plasma 112, by which the target 109 is sputtered and the thin films are formed on the surface of the substrate 102b.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a thin film by sputtering or the like.

[0002]

2. Description of the Related Art Conventionally, in a process of forming various optical thin films such as oxide thin films on a substrate surface by a sputtering method, it is not possible to remove impurities (hereinafter referred to as "adsorbed substances") adsorbed or attached to the substrate surface. Very important.

The adsorbed substance on the surface of the substrate not only deteriorates the adhesion strength between the thin film and the substrate, but is also taken into the film to cause problems such as changing the refractive index of the thin film and increasing absorption. In addition, H generated by desorption of adsorbate
A gas such as ₂ O changes the sputtering rate and causes a film thickness variation in the process of controlling the film thickness by the film formation time.

For this reason, the substrate is usually placed in a preliminary exhaust chamber, and the adsorbate is removed by maintaining the chamber in a high vacuum, and then introduced into the film forming chamber. Note that the preliminary evacuation chamber can carry the substrate into the film formation chamber while always maintaining a vacuum without opening the film formation chamber to the atmosphere, so that the amount of impurity gas in the film formation chamber can be kept low. It also has a function.

However, since organic impurities such as H ₂ O and an organic substance (n is a natural number) composed of — (CH ₂ ) _n — have a large adsorbing power with respect to the optical glass or the like, the preliminary exhaust chamber is made high. These cannot be easily removed even if a vacuum is maintained.

In order to remove the adsorbate having a large adsorption force as described above, conventionally, the substrate is heated to a high temperature by a heater or the like in a preliminary exhaust chamber kept in a high vacuum, so that the adsorbate is desorbed from the substrate. Was adopted and the method of removing this was adopted.

[0007]

However, a plastic substrate, an optical glass substrate or a substrate having a color filter for which surface accuracy is very important is deformed or the surface accuracy cannot be ensured when the substrate temperature is increased. Such problems occur. For this reason, it is necessary to keep the substrate temperature low (usually 100 ° C. or lower), and at this low temperature, it takes a very long time to remove the substrate. I was doing sputtering. During sputtering, the substrate is exposed to plasma, impacted by high-energy particles such as ions and electrons and sputtered particles, and the temperature of the substrate also rises. Desorb. Since the sputtering rate fluctuates due to the influence of the impurities, the film thickness was not constant even when the film was formed for the same time, and the film thickness could not be controlled with high accuracy. Further, since a thin film is formed in a state where impurities are adsorbed on the surface of the substrate, the adhesion between the thin film and the substrate is low, and further, since a thin film containing a large amount of impurities is formed, the refractive index may change. ,
There were also problems such as increased absorption of light in the ultraviolet and visible regions.

Therefore, an object of the present invention is to remove adsorbed substances on the surface of a substrate sufficiently in a short time without raising the temperature of the substrate more than necessary, and to control the film thickness with high precision. A thin film forming method capable of forming a thin film having high adhesiveness with and having excellent film quality.

[0009]

Means for Solving the Problems The present inventors have conducted various studies to achieve the above object, and as a result, completed the present invention.

A first aspect of the present invention is a thin film forming method using a thin film forming apparatus having a preliminary evacuation chamber, wherein while the preliminary evacuation chamber is evacuated to a high vacuum, it is absorbed by an adsorbed substance on the surface of the substrate but is absorbed by the substrate itself. Relates to a method for forming a thin film, characterized in that the adsorbed substance is removed by irradiating at least the surface of the substrate with an electromagnetic wave that is not absorbed, and then a thin film is formed on the surface of the substrate.

A second aspect of the present invention is a thin film forming method using a thin film forming apparatus having a preliminary evacuation chamber, while purging the preliminary evacuation chamber with a gas that has a small adsorption energy with respect to a substrate and does not affect film formation and film quality. , The electromagnetic waves that are absorbed by the adsorbed substance on the substrate surface but not absorbed by the substrate itself are irradiated to at least the substrate surface in the preliminary exhaust chamber, and then the adsorbed substance is removed by evacuating the preliminary exhaust chamber to a high vacuum. Then, the present invention relates to a method for forming a thin film, which comprises forming a thin film on the surface of the substrate.

According to a third aspect of the invention, the gas having a small adsorption energy to the substrate and having no influence on the film formation and film quality is a gas comprising at least one selected from O ₂ , N ₂ , He, Ne and Ar. The present invention relates to a thin film forming method.

A fourth aspect of the present invention relates to a method of forming a thin film according to the first, second or third aspect of the present invention, wherein an electromagnetic wave diffusing means is provided in the preliminary exhaust chamber so that the inner wall surface of the preliminary exhaust chamber is also irradiated with the electromagnetic wave.

A fifth invention is that the electromagnetic wave is ultraviolet light.
4 to a method for forming a thin film of the invention.

In a sixth aspect of the invention, the electromagnetic wave is 140 to 320 nm.
The method for forming a thin film according to any one of the first to fourth aspects of the present invention, which is ultraviolet light in the wavelength region of.

A seventh invention is that the electromagnetic wave is infrared rays.
~ A method for forming a thin film according to any one of the fourth invention.

In the eighth invention, the electromagnetic wave is 2.0 to 3.6 μm.
The present invention relates to a method for forming a thin film according to any one of the first to fourth aspects of the invention, which is infrared light in the wavelength region of m.

The ninth invention relates to the method for forming a thin film according to any one of the first to fourth inventions, wherein the electromagnetic wave is a microwave.

In a tenth aspect of the invention, the electromagnetic wave is 1 to 30 GHz.
The method for forming a thin film according to any one of the first to fourth aspects of the present invention, which is a microwave in the frequency range.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

First, the method according to the first invention will be described. FIG. 1 shows a schematic view of a thin film forming apparatus used in the method according to the first invention. In FIG. 1, the thin film forming apparatus is roughly divided into a preliminary exhaust chamber (101) and a film forming chamber (107), which are connected by a gate valve (106b).

In the preliminary exhaust chamber (101), the substrate (102
An electromagnetic wave irradiating means (103) for irradiating an electromagnetic wave to a) is provided. The electromagnetic wave irradiating means may be provided outside the preliminary exhaust chamber, in which case the electromagnetic wave is applied to the substrate from outside the preliminary exhaust chamber through the transmission window.

Further, if necessary, the preliminary exhaust chamber (101) is provided with an electromagnetic wave diffusing means (104) so that the inner wall surface of the preliminary exhaust chamber is also irradiated with the electromagnetic wave. By this magnetic wave diffusing means, it is possible to remove adsorbed substances on the inner wall surface of the preliminary exhaust chamber and prevent contamination of the substrate surface. Further, the electromagnetic wave diffusion means can adjust the irradiation amount to the wall surface of the preliminary exhaust chamber according to the situation so that the substrate surface is not contaminated when the exhaust takes a long time due to the large amount of adsorbed substances on the wall surface of the preliminary exhaust chamber. ing.

When ultraviolet rays are irradiated in the method of the present invention, the electromagnetic wave irradiation means (103) includes the following. Lamps such as Xe resonance line lamp, Hg lamp, Xe lamp, Xe-Hg lamp, D ₂ lamp, metal halide lamp, rare gas resonance line lamp, excimer lamp, excimer laser, YAG laser, Ar ion laser, N ₂ laser, A laser generator such as a dye laser is used. When using lamps, install an infrared filter, infrared reflection mirror, cold mirror, etc.
It is desirable to cut the wavelength that heats the substrate. Particularly when a substrate having absorption in the visible light region is used, or when it is desired to particularly suppress the heating of the substrate, it is preferable to use a mirror or a filter capable of reflecting / cutting not only infrared rays but also visible rays. Also, an optical filter can be used together to control the wavelength region.

In the case of irradiating infrared rays in the method of the present invention, lamps such as a halogen lamp and a laser generator such as a CO ₂ laser are used as the electromagnetic wave irradiation means (103). Also, an optical filter may be used together to control the wavelength region.

In the above-mentioned optical filter for controlling the wavelength region, when the electromagnetic wave is emitted from the outside of the preliminary exhaust chamber, the transmission window of the preliminary exhaust chamber can be used as the optical filter.

When irradiating with microwaves in the method of the present invention, an apparatus capable of generating microwaves in a frequency range of at least 1 to 30 GHz is used.

A pump (105a) is connected to the preliminary evacuation chamber (101) in order to create a high vacuum inside the chamber. This pump (105a) is preferably a vacuum pump that has a high exhaust rate when making a high vacuum. Examples of such a vacuum pump include a turbo molecular pump, a cryopump, an ion pump, an ion sublimation pump, and the like. A cryopump is particularly preferable when the adsorbing substance is H ₂ O. In addition, a dry pump, a rotary pump, etc. may be used together.

Further, a gate valve (106a) for loading the substrate (102a) from the outside of the apparatus into the preliminary exhaust chamber (101), and a gate valve (for loading the substrate from the preliminary exhaust chamber to the film forming chamber ( 106b) is provided. By loading the substrate through these gate valves, the film formation chamber (107) is not opened to the atmosphere,
Further, since the substrate can be carried into the film formation chamber while always maintaining a vacuum, the amount of the impurity gas in the film formation chamber can be suppressed low.

In the film forming chamber (107), a substrate holder (1
08) is provided, and the substrate (102b) is installed there. Sputter target (109) on top
, And this sputter target is electrically connected to the sputter power supply means (110) outside the film formation chamber. The film forming chamber is connected to the pump (105b) and the sputtering gas introducing means (111). The pump (105b) is the same as the pump (105a).

A method for forming a first thin film of the present invention using the above apparatus will be described below.

First, the substrate (102a) is loaded from the gate valve (106a) into the preliminary exhaust chamber (101) and set.

Next, the pump (105b) starts the exhaust of the preliminary exhaust chamber (101). This exhaust irradiates the substrate (102a) with a predetermined electromagnetic wave until the inside of the preliminary exhaust chamber has a predetermined vacuum degree. Irradiation may be carried out for a desired time if necessary. After reaching a predetermined degree of vacuum, the electromagnetic wave irradiation is stopped.

As the electromagnetic wave for irradiation, ultraviolet rays, infrared rays or microwaves are desirable.

The ultraviolet rays to be applied are preferably ultraviolet rays in the wavelength range of 140 to 320 nm, especially when an optical glass substrate such as a quartz substrate is used. Especially the adsorbate is H ₂ O
When it is, ultraviolet rays in the wavelength region of 140 to 170 nm are preferable. Ultraviolet rays with a wavelength of less than 140 nm are effective in removing the adsorbed gas, but deteriorate the quartz substrate and increase absorption in the ultraviolet region, which is not preferable. On the other hand, 32
Electromagnetic waves in the visible region with a wavelength longer than 0 nm do not electronically excite the adsorbed gas so that the adsorbed gas is not removed, and the inner wall surface of the preliminary exhaust chamber may be heated, and the radiation may heat the substrate. Absent. In addition, 140-1
When using an electromagnetic wave that includes ultraviolet light in the wavelength range of 70 nm but also in the wavelength range longer than 320 nm, it can be irradiated from outside the preliminary exhaust chamber through the transmission window of the optical filter that cuts the wavelength range longer than 320 nm. desirable.

The infrared ray to be irradiated is 2.0 to 3.6 μm, especially when an optical glass substrate such as a quartz substrate is used.
Infrared light in the wavelength region of is preferable. Especially when the adsorbate is H ₂
When it is O, infrared rays having a wavelength near 3 μm are preferable.

The microwave used for irradiation is, in particular, a quartz substrate.
When an optical glass substrate such as a plate is used, 1 to 30 GHz
Microwaves in the frequency region of are preferred. Especially adsorbed material
Is H ₂If it is O, it has a frequency near 20 GHz.
Microwaves are preferred.

Two or more kinds of these electromagnetic waves such as ultraviolet rays, infrared rays and microwaves may be simultaneously irradiated.

After the completion of the electromagnetic wave irradiation, the substrate is carried into the film forming chamber (107) through the gate valve (106b) and placed in the substrate holder (108). Since the film forming chamber (107) has been evacuated to a high vacuum by the pump (105b) in advance, the film forming chamber is not opened to the atmosphere during this loading operation. Next, oxygen, a rare gas or the like is introduced into the film forming chamber from the sputtering gas introducing means (111) so as to have a predetermined pressure. After the above preparations are completed, power is supplied from the sputtering power supply means (110) to the sputtering target (109) to generate plasma (112) and sputtering is performed to form a thin film on the surface of the substrate (102b). .

Next, the method according to the second invention will be described. FIG. 2 shows a schematic diagram of a preliminary exhaust chamber of a thin film forming apparatus used in the method according to the second invention. 2, the basic structure of the preliminary exhaust chamber (201) is the same as that of the preliminary exhaust chamber (101) of FIG.
1) is connected to the film forming chamber (107) as in FIG.

The characteristic structure of the preliminary exhaust chamber (201) of FIG. 2 different from that of FIG. 1 is that the vacuum valves (215a, 215b),
And a gas cylinder (21) equipped with a gas purification means (214)
3) is provided. In addition, a gas flow rate control means, a gas flow meter, etc. may be provided.

As the gas purifying means (214), it is desirable that it has an excellent ability to remove a substance having a large adsorption energy with respect to the substrate or the wall surface of the preliminary exhaust chamber. Examples of the removal method include an adsorption method, a getter method, and a method using a chemical reaction.

The method of forming a thin film using the above-mentioned thin film forming apparatus is as follows.

First, the substrate (202) is carried into the preliminary exhaust chamber from the outside of the apparatus, and then the vacuum valves (215a, 215b) are opened before exhausting the preliminary exhaust chamber. Then, a purging gas (described later) is supplied from the gas cylinder (213) through the gas purifying means (214) to the preliminary exhaust chamber (201).
It is introduced into the inside and purged. At this time, the vacuum valve (2
15a) and the vacuum valve (215b) may be alternately opened and closed to replace the air in the preliminary exhaust chamber with the purging gas, and then the above purging may be performed.

Simultaneously with the start of purging, electromagnetic waves are radiated. The adsorbed substance desorbed by the irradiation of the electromagnetic wave is discharged from the vacuum valve (215b) to the outside of the preliminary exhaust chamber together with the purging gas.

After sufficiently irradiating the electromagnetic wave, the introduction of the purging gas is stopped and the vacuum valves (215a, 215b) are closed. Then, pump (205) until a predetermined pressure is reached.
Exhaust by. Subsequent operations are performed in the same manner as in the method according to the first aspect of the invention.

The above-mentioned purging gas needs to have a small adsorption energy with respect to the substrate. In addition, it is desirable that the adsorption energy is small with respect to the inner wall surface of the preliminary exhaust chamber. Further, it is desirable that the gas has little or no effect on the film formation and film quality even if mixed into the film forming chamber.

As such a purging gas, O ₂ ,
N ₂ , He, Ne, Ar and the like can be mentioned. These are 1
One kind may be used alone, or two or more kinds may be mixed and used.

Further, it is necessary that these purging gases contain as little gas as possible that affects film formation and film quality. Particularly, it is desirable to remove a gas having a large adsorption energy, such as H ₂ O, as much as possible.
It is preferably ppb or less. Therefore, before introducing the purge gas into the preliminary exhaust chamber, it is desirable to remove impurities that affect the film formation and film quality by the gas purification means.

In the above method of the present invention, the substrate itself is not heated by the irradiation of the specific electromagnetic wave, but only the adsorbed substance on the substrate surface is selectively excited to promote desorption. The gas component of the desorbed adsorbate is exhausted by a pump in the method according to the first aspect of the invention and is discharged by a purging gas in the method of the second aspect. As a result, the adsorbate is removed without increasing the temperature of the substrate.

[0051]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Example 1 Using the thin film forming apparatus shown in FIG. 1, a thin film was produced by the method according to the first invention.

In FIG. 1, substrates (102a, 102b)
Is a quartz substrate, the electromagnetic wave irradiation means (103) is an ultraviolet irradiation device, 104 is an ultraviolet diffusion plate, and the pump (105a) is 10
Cryo pump with exhaust capacity of 00 (l / s) and 50
(L / s) exhaust capacity dry pump, pump (10
5b) is a turbo molecular pump having an exhaust capacity of 1000 (l / s) and a rotary pump having an exhaust capacity of 100 (l / s).

An Xe resonance line lamp (luminous line emission of 147 nm) is used as the ultraviolet irradiation device (103), a cold mirror is provided on the back surface of the lamp, and an infrared reflection mirror for avoiding heating of the substrate between the lamp and the substrate. , And an optical filter were installed. With these, the wavelength of the ultraviolet light applied to the quartz substrate was controlled to 140 to 320 nm. Further, the ultraviolet diffusion plate (204) was set so that the ultraviolet rays were irradiated to the wall surface of the preliminary exhaust chamber.

After the above setting was completed, first, the quartz substrate (102a) was loaded into the preliminary exhaust chamber (101) from the gate valve (106a) and set.

Next, the pump (105b) was started to evacuate the preliminary exhaust chamber (101). The substrate (102a) was irradiated with the above-mentioned ultraviolet rays until the inside of the preliminary exhaust chamber became a predetermined vacuum degree by this exhaust. After reaching a predetermined degree of vacuum, the irradiation with the ultraviolet rays was stopped.

After the irradiation of ultraviolet rays, the quartz substrate is carried into the film forming chamber (107) through the gate valve (106b),
It was installed in the substrate holder (108). Film forming chamber (107)
Is evacuated to a high vacuum by the pump (105b) in advance, the film forming chamber is not opened to the atmosphere during this loading operation. Next, oxygen and Ar gas were introduced into the film forming chamber (107) from the sputtering gas introducing means (111) so as to have a predetermined pressure. After the above preparations were completed, electric power was supplied from the sputtering power supply means (110) to the sputtering target (109) to generate plasma and perform sputtering, thereby forming a thin film on the surface of the substrate (102b).

Table 1 shows the temperature change of the substrate with respect to the ultraviolet irradiation time, and the gas component amounts (desorption amount of the adsorbed substance) of the mass numbers 17, 72 and 85. Gas component with mass number 17 is H
Corresponding to ₂ O, the components with mass numbers 72 and 85 are-
It corresponds to an organic substance having (CH ₂ ) _n − (n is a natural number). Here, the temperature of the substrate was measured by a thermocouple installed on the substrate so as not to be directly irradiated with ultraviolet rays. The desorption amount of the adsorbed substance was determined by measuring the gas component in the preliminary exhaust chamber using a quadrupole partial pressure gas monitor capable of quantitatively measuring the gas component by ionizing it. This desorption amount is the ion current value (A)
Indicated by The ion current value indicating the desorption amount is obtained by subtracting the value of the desorbed gas component from the inner wall surface of the preliminary exhaust chamber.

From this table, H ₂ O and organic substances adsorbed on the surface of the substrate are sufficiently desorbed in a short irradiation time of 20 minutes or less and at a relatively low substrate temperature of 40 ° C. or less. I understand.

Example 2 A thin film was produced by the method according to the second invention, using the thin film forming apparatus having the preliminary exhaust chamber shown in FIG.

In FIG. 2, the substrate (202) is a quartz substrate, the electromagnetic wave irradiation means (203) is an ultraviolet irradiation device, and 20
4 is an ultraviolet diffusion plate, and the pump (205) is 1000 (l /
It is a cryopump with an exhaust capacity of s) and a dry pump with an exhaust capacity of 50 (l / s).

An Xe resonance line lamp (luminous line emission of 147 nm) is used for the ultraviolet irradiation device (203), a cold mirror is provided on the back surface of the lamp, and an infrared reflection mirror for avoiding heating of the substrate between the lamp and the substrate. , And an optical filter were installed. With these, the wavelength of the ultraviolet light applied to the quartz substrate was controlled to 140 to 320 nm. Further, the ultraviolet diffusion plate (204) was set so that the ultraviolet rays were irradiated to the wall surface of the preliminary exhaust chamber.

After completing the above setting, first, the quartz substrate
The plate (202) is carried into the preliminary exhaust chamber, and this preliminary exhaust chamber is
Open the vacuum valves (215a, 215b) before exhausting.
Was. Then, use nitrogen gas (purging gas) in the gas cylinder.
Preliminary discharge from (213) through gas purification means (214)
It was introduced into the air chamber (201) and purged. In addition,
Composition other than nitrogen component of nitrogen gas that has passed through the purification means
Is CO, CO₂, O₂, H ₂Each O is 10 ppb
Below, the other components were below the detection limit.

At the same time when the purging was started, the above ultraviolet rays were irradiated. The adsorbed substance desorbed by the irradiation of the ultraviolet rays is discharged to the outside of the preliminary exhaust chamber through the vacuum valve (215b) together with the nitrogen gas.

After sufficiently irradiating the ultraviolet rays, the introduction of nitrogen gas was stopped and the vacuum valves (215a, 215b) were closed. Then, evacuation was performed by the pump (205) until a predetermined pressure was reached. With respect to the subsequent operations, a thin film was formed in the same manner as the operation of Example 1.

Although a slight amount of nitrogen gas was adsorbed on the surface of the substrate, it was immediately removed by heating with plasma, and this slight amount of nitrogen gas did not affect the film quality or adhesion.

Example 3 Using the thin film forming apparatus shown in FIG. 1, a thin film was produced by the method according to the first invention. The electromagnetic wave irradiating means (103) is an infrared irradiating device, and was carried out in the same manner as in Example 1 except that a 2 kW halogen lamp and an optical filter were used to irradiate infrared rays in the wavelength region of 2.0 to 3.6 μm. .

Table 1 shows the temperature change of the substrate with respect to the irradiation time of infrared rays and the amount of gas component having a mass number of 17 (desorption amount of adsorbed substance). This gas component having a mass number of 17 corresponds to H ₂ O. Here, the temperature of the substrate was measured by a thermocouple installed on the substrate so as not to be directly irradiated with ultraviolet rays. The desorption amount of the adsorbed substance was determined by measuring the gas component in the preliminary exhaust chamber using a quadrupole partial pressure gas monitor capable of quantitatively measuring the gas component by ionizing it. This desorption amount is shown by the ion current value (A). The ion current value indicating the desorption amount is obtained by subtracting the value of the desorbed gas component from the inner wall surface of the preliminary exhaust chamber.

From this table, it can be seen that H ₂ O adsorbed on the surface of the substrate is sufficiently desorbed in a short irradiation time of 20 minutes or less and at a relatively low substrate temperature of 45 ° C. or less. Recognize.

Example 4 Using the thin film forming apparatus shown in FIG. 1, a thin film was produced by the method according to the first invention. At that time, the electromagnetic wave irradiation means (1
03) is provided outside the preliminary exhaust chamber, and
The same procedure as in Example 1 was performed except that the microwave of 30 GHz was irradiated.

Table 1 shows the temperature change of the substrate with respect to the microwave irradiation time and the amount of the gas component having a mass number of 17 (desorption amount of the adsorbed substance). The gas component having a mass number of 17 is H ₂ O.
Corresponding to. Here, the temperature of the substrate was measured by a radiation thermometer. The desorption amount of the adsorbed substance was determined by measuring the gas component in the preliminary exhaust chamber using a quadrupole partial pressure gas monitor capable of quantitatively measuring the gas component by ionizing it. This desorption amount is shown by the ion current value (A). The ion current value indicating the desorption amount is obtained by subtracting the value of the desorbed gas component from the inner wall surface of the preliminary exhaust chamber.

From this table, it can be seen that H ₂ O adsorbed on the surface of the substrate is sufficiently desorbed in a short irradiation time of 20 minutes or less and at a relatively low substrate temperature of 46 ° C. or less. Recognize.

[0073]

[Table 1]

Example 5 A thin film was formed by the method according to the second invention by using the thin film forming apparatus having the preliminary exhaust chamber shown in FIG.

While purging the preliminary exhaust chamber with high-purity nitrogen gas, the quartz substrate was irradiated with infrared rays in the wavelength range of 2.0 to 3.6 μm using a halogen lamp of 2 kW and an optical filter. The procedure was as in Example 2. The infrared irradiation was performed for 10 minutes. During this time, when the substrate temperature was measured by a radiation thermometer, it was about 50 ° C.

After the irradiation of infrared rays, the quartz substrate is carried into the film forming chamber.
The gas released during the sputtering is analyzed by a gas analyzer.
I monitored it at. Figure 3 shows the deposition chamber during sputtering.
H ₂O partial pressure (H₂Shows the change over time of the O ion current value)
You. In FIG. 3, H₂Where the O partial pressure is rising,
Detached from the substrate when the discharge power was applied.
H₂Due to O. Do not irradiate the quartz substrate with infrared rays
H compared to the case₂Ion current with mass number 17 corresponding to O
It can be seen that the value has decreased by one digit or more. Similarly, organic
Ion current values of mass numbers 72, 85, etc. corresponding to the molecule are also
It was decreasing by more than one digit. That is, the substrate is irradiated with infrared rays.
As a result, the substrate temperature is raised only by about 50 ° C.
H adsorbed on the surface of the plate₂O and organics could be removed.

[0077]

As is apparent from the above description, according to the method of the present invention, the adsorbed substances on the substrate surface can be sufficiently removed in a short time without raising the temperature of the substrate more than necessary.

As a result, even after removing the adsorbate on the surface of the plastic substrate or the optical glass substrate such as a lens having a highly precise surface shape, which could not be subjected to the treatment for removing the adsorbate due to its weakness against heat. Film formation such as sputtering can be performed.

As a result, the impurities in the formed film are reduced, so that the film quality is improved (refractive index is stable, absorption of light in the ultraviolet / visible region is small, etc.) and the adhesion between the substrate and the film is high. Become. Further, in the film formation, the desorbed gas released during sputtering is reduced, so that the sputtering rate is stable, the film thickness can be controlled with high accuracy, and the reproducibility of the film formation is improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a thin film forming apparatus used in the method of the present invention.

FIG. 2 is a schematic view of a preliminary exhaust chamber of a thin film forming apparatus used in the method of the present invention.

FIG. 3 is an explanatory diagram showing changes over time in the H ₂ O partial pressure (ion current value of H ₂ O) in the film forming chamber during sputtering in the method of the present invention.

[Explanation of symbols]

 101, 201 preliminary evacuation chambers 102a, 102b, 202 substrates 103, 203 electromagnetic wave irradiation means 104, 204 electromagnetic wave diffusion means 105a, 105b, 205 pumps 106a, 106b, 206a, 206b gate valves 107 film formation chambers 108 substrate holders 109 sputter targets 110 Sputtering power supply means 111 Sputtering gas introduction means 112 Plasma 213 Gas cylinder 214 Gas purification means 215a, 215b Vacuum valve

Claims (10)

[Claims] 1. A method for forming a thin film by a thin film forming apparatus having a preliminary exhaust chamber, wherein while the preliminary exhaust chamber is being evacuated to a high vacuum, an electromagnetic wave that is absorbed by an adsorbed substance on the substrate surface but not absorbed by the substrate itself. Is applied to at least the surface of the substrate in the preliminary exhaust chamber to remove the adsorbed substance, and then a thin film is formed on the surface of the substrate. 2. A method for forming a thin film by a thin film forming apparatus having a preliminary exhaust chamber, wherein while the preliminary exhaust chamber is being purged by a gas that has a small adsorption energy to a substrate and does not affect film formation and film quality, At least the surface of the substrate is irradiated with an electromagnetic wave that is absorbed by the adsorbed substance but is not absorbed by the substrate itself, and then the adsorbed substance is removed by evacuating the pre-evacuated chamber to a high vacuum. A method for forming a thin film, which comprises forming a thin film on the surface of a substrate. 3. Gases which have a small adsorption energy to the substrate and which do not affect the film formation and film quality are O ₂ , N ₂ ,
The method for forming a thin film according to claim 2, wherein the gas is at least one selected from He, Ne, and Ar. 4. The method for forming a thin film according to claim 1, 2 or 3, wherein the electromagnetic wave is irradiated onto the inner wall surface of the preliminary exhaust chamber by providing an electromagnetic wave diffusion means in the preliminary exhaust chamber. 5. The method for forming a thin film according to claim 1, wherein the electromagnetic wave is ultraviolet light. 6. The method for forming a thin film according to claim 1, wherein the electromagnetic waves are ultraviolet rays in a wavelength range of 140 to 320 nm. 7. The method for forming a thin film according to claim 1, wherein the electromagnetic waves are infrared rays. 8. The method for forming a thin film according to claim 1, wherein the electromagnetic waves are infrared rays in a wavelength range of 2.0 to 3.6 μm. 9. The electromagnetic wave is a microwave.
The method for forming a thin film according to any one of 1. 10. The method for forming a thin film according to claim 1, wherein the electromagnetic wave is a microwave in the frequency range of 1 to 30 GHz.