JPH093623A - Method for forming thin film - Google Patents

Abstract

PURPOSE: To provide a thin-film forming method that suppresses generation of pinholes as little as possible and that easily performs quantitative production control. CONSTITUTION: First, a roll film 30 and a target object are loaded in a sputtering device 20, and then a sputtering tank 27 is evacuated inside so as to fill with argon. While drawing out film 30 and being applied with a sputtering part 23, a brushing roller 25 is rotated for brushing, so that a first sputtering is performed. Next, while the film taken up on a winding roller 22 is rewound to a film feeding part 21 and brushed with the brushing roller, a second sputtering is performed. After the completion of the second sputtering, while the film is again drawn out from the film feeding part 21 and rewound on the winding roller 22, a third sputtering is performed without using the brushing rollers 25, 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film of metal or its compound on a substrate.

[0002]

2. Description of the Related Art Generally, a vacuum deposition method, an ion plating method, a sputtering method or the like is used as a thin film forming technique for forming a thin film of a metal or its compound on a substrate such as plastics, glass or ceramics. Among them, the sputtering method is widely used in the field of electronic industry and the like because it can easily and efficiently form a thin film of high quality by using a wide range of simple metals having a relatively high melting point or alloys and compounds thereof.

By the way, although thin film forming technology has advanced, high quality thin films can be easily formed.
Since the demand for quality performance in the electronic industry field is extremely strict, various improvements have been attempted in thin film forming technology in order to improve quality performance. Above all, pinholes are required to be completely absent.Therefore, when forming a thin film, first create a clean environment, thoroughly wash the substrate itself and wear dust-proof clothing as little as possible. Every measure is taken, such as wrapping.

[0004]

However, such measures are still trial-and-error, and are not the definitive solutions for reducing pinholes. Furthermore, in the conventional thin film forming method, since the pinholes do not always occur in the same state, but the generation state of the pinholes varies, there is also a problem that quantitative production control cannot be performed for thin film formation. Remaining.

The occurrence of such a pinhole is absolute with respect to the function of the thin film (for example, electric resistance performance in the case of an ITO thin film and electric insulation performance in the case of a TiO ₂ thin film) as well as appearance quality. Will cause defects,
A solution that can avoid this is desired. The present invention has been made in view of such problems, and an object thereof is to provide a thin film forming method capable of suppressing the occurrence of pinholes as much as possible and easily performing quantitative production control.

[0006]

In order to achieve the above object, the invention according to claim 1 is a thin film forming method for forming a thin film of a metal or a compound thereof on a substrate. A first thin layer forming step of forming a layer, a cleaning step of cleaning the surface of the formed thin layer by a physical means, and a thin layer of a metal or a compound thereof formed on the cleaned thin layer. 2 thin layer forming step.

The invention according to claim 2 is characterized in that, in contrast to the invention according to claim 1, the physical means brushes the surface of the thin layer with fibers. Claim 3
The described invention is characterized in that, in contrast to the invention described in claim 1, the physical means cleans the surface of the thin layer with ultrasonic waves.

[0008]

The inventors of the present invention have made earnest studies on pinholes that occur when a thin film of a metal or its compound is formed on a substrate, and as a result, form a thin layer on the substrate and brush its surface with fibers. By cleaning by physical means such as ultrasonic cleaning, and forming thin layers further, pinholes in the thin film formed are extremely reduced,
Moreover, I discovered the surprising fact that the occurrence rate of pinholes is small.

This is because at the stage of forming a thin film on the substrate, impurities causing pinholes are generated from the substrate itself or the metal or its compound itself, and therefore pinholes can be formed even if a thin layer is further formed. While it is impossible to prevent the occurrence of the above, the impurities are removed by cleaning by a physical means, and it is presumed that pinholes are extremely reduced if a thin layer is further formed thereon.

According to the first aspect of the invention, in the first thin layer forming step, a thin layer of metal or its compound is formed on the substrate, and in the cleaning step, the surface of the formed thin layer is physically formed. It is cleaned by means. Then, in the second thin layer forming step, a thin layer of metal or its compound is formed on the cleaned thin layer in an overlapping manner. Therefore, a thin film with few pinholes is formed.

By repeating the cleaning step and the second thin layer forming step, a thin film with fewer pinholes can be formed. Further, according to the invention of claim 2, in the cleaning step, the surface of the thin layer is brushed with fibers, and according to the invention of claim 3, the surface of the thin layer is cleaned with ultrasonic waves.

By using these means among the physical means, the effect of reducing pinholes in the thin film becomes particularly large.

[0013]

EXAMPLES The thin film forming method of the present invention will be specifically described below. The substrate used in the thin film forming method of the present invention is an electrical insulator having a fixed shape made of plastics, glass, ceramics or the like as a material, and a thin film is formed on one surface thereof. Generally, the shape is a film shape. ，
Although it is a sheet or plate, it may have a curved structure depending on the application.

The metal or metal compound used in the thin film forming method of the present invention is a thin film forming technique, that is, a vacuum deposition method, an ion plating method, a chemical vapor deposition method (CV).
D), all metals or compounds capable of forming a thin film on the substrate by the sputtering method or the like are applicable. Therefore, the present invention can be applied to thin films having various functions used for various applications.

For example, Cu, C for electronic industry use
A thin film of an alloy such as r, Ni, Au, Pt, Al / Si, Ti / Si is used as an electrode / wiring film for Cr, Ta, Sn.
O ₂ , ITO (Indium Tin Oxide), etc. are used for the resistance film and Al
N, AlO ₂ , TiO ₂ , SiO ₂ , BaTiO ₃ , PbT
iO ₃ etc. in the dielectric _{film, Si 3 N 4, TiO 2} , Si 2 , etc. are electrically insulating film, Fe, Co, Ni-Fe or the like to the magnetic film,
SiC, Ge, etc. are used for the sensor film, and Te-C, Te-Se, etc. are used for the optical recording film.

Further, for optical industry use, SiO ₂ ,
TiO ₂ , ZrO _{2 and the} like are used for anti-reflection wear-resistant coating films, and for precision machine decoration applications, Cr, Ti
N, TiC, WC, etc. are used as the surface hardened film, Zn, Cd, T
i, Ta, TiN, SiC, etc. are used for the corrosion resistant heat resistant film, Ag, A
u, TiC, etc. are used for the decorative film. Here, the present invention can be applied to a thin film formed by using two or more different metals and metal compounds.

In the present invention, the physical means for cleaning means various kinds of substances which do not change the surface condition of the thin layer itself and remove dust or the like that causes pinholes on the thin layer. Means means chemical means such as modifying the surface of the thin layer, physicochemical such as dissolving and removing the surface of the thin layer with a solvent, or treating the surface of the thin layer with light (corona, plasma, ultraviolet). It is different from means.

Specifically, a cloth-like article made of fibers, a brush-like article, or the fibers themselves (for example, cotton-like fibers) are used for brushing on a thin layer, or together with these, distilled water, alcohols, etc. Brushing, ultrasonically cleaning the thin layer surface with ultrasonic waves, rolling the thin layer surface with an adhesive roller, squeezing the thin layer surface with a rubber sheet, spraying high pressure water on the thin layer surface Among them, the method of brushing with fibers and the method of ultrasonic cleaning are preferable, and the former is particularly preferable.

When using fibers for brushing, it is desirable to devise the shape of the fibers and the brushing method so as not to damage the thin layer surface. The number of times of cleaning by physical means needs to be performed at least once during the formation of the thin film. That is, the thin film forming method of the present invention includes a step of forming a thin layer on a substrate, a step of cleaning, and a step of further forming a thin layer on the cleaned thin layer. Therefore, since the thin layer forming step is performed at least twice, it is easy to adjust the film thickness, and it is possible to form a thick film.

Further, by increasing the number of cleanings and repeating the cleaning step and the step of forming a thin layer, the effect of reducing the pinholes is further enhanced, but substantially only one cleaning is required. Therefore, most pinholes can be prevented, and the number of cleanings is substantially 3 or less. The cleaning step and the second thin layer forming step are basically performed as one unit, but the final step may end with the cleaning step.

Further, the first and second thin layer forming steps are usually carried out once for a predetermined time continuously, but when the predetermined thin layer thickness cannot be obtained, the second thin layer is formed. It is possible to obtain a predetermined thickness by repeating the same thin layer forming step without performing the cleaning step after the layer forming step.
The thin film forming method of the present invention can also be performed using a discontinuous apparatus. For example, in the case of the sputtering method, a step of forming a thin layer on a substrate by sputtering in a vacuum chamber, once removing the substrate from the vacuum chamber, cleaning it, and again placing it in the vacuum chamber for sputtering can be performed. .

However, a thin film of higher quality can be obtained by continuously performing thin layer formation and cleaning treatment in a vacuum chamber using a continuous apparatus. For example,
Set a roll-shaped film (eg PET film, polyimide film) in the vacuum chamber and sputter it to form a thin layer, and then wind it while cleaning and reversely unwind it to form a thin layer by sputtering. By taking the step of forming, a high-quality thin film having almost no pinholes can be formed.

The present invention will be described in more detail with reference to Examples 1 to 4 and Comparative Examples, but the present invention is not limited to the contents described here. (Embodiment 1) FIG. 1 is a schematic configuration diagram of a sputtering apparatus used in one embodiment of the present invention.

As shown in the figure, the sputtering apparatus 1
Is a sputtering tank 4 in which a substrate holder 2 for mounting a substrate 11 and a target electrode 3 for mounting a target object 12 are stored, a vacuum pump 5 capable of evacuating the sputtering tank 4 to a high vacuum, and a sputtering tank 4
And a direct current glow discharge device 7 for applying a direct current voltage between the base 11 and the target object 12, and the like.

In the thin film forming method of the present embodiment, a polyimide film having a thickness of 25 μm and a size of 100 mm × 500 mm (manufactured by Toray DuPont, trade name: Kapton) is used as the substrate 11, and copper is used as the target object 12. I set this. After activating the vacuum pump 5 to evacuate the sputtering tank 4, argon gas is enclosed in the rare gas enclosure 6 to adjust the pressure to 2.0 × 10 ⁻³ Torr.
Sputtering was performed by discharging with a DC glow discharge device 7 at an applied power of 2.0 kw for 10 seconds. The sputtering tank 4 was returned to atmospheric pressure, the substrate 11 was taken out, and the film thickness of the formed thin copper layer was measured and found to be 0.15 μm.

Next, the copper thin layer surface was slowly brushed back and forth three times with a gauze containing methanol.
Then, the thin film 13 was formed on the substrate 11 again by setting the substrate 11 in the sputtering tank 4 and performing sputtering under the same conditions as above. The thickness of the thin film thus formed was 0.31 μm, and when pinholes were counted with a microscope, it was 100 mm × 50.
Two of them were confirmed in the size of 0 mm.

Comparative Example 1 In the thin film forming method of this comparative example, the sputtering apparatus 1 was used in the same manner as in Example 1, but the sputtering was performed twice without performing the step of brushing with gauze in the middle. went. The polyimide film used as the substrate was one that had been subjected to careful ultrasonic cleaning in advance to obtain a surface state free of dust and the like.

The copper thin film thus formed on the substrate had a film thickness of 0.33 μm, and when pinholes were counted with a microscope, 290 pieces were confirmed in a size of 100 mm × 500 mm. . (Example 2) In this example, the same sputtering apparatus 1 as in Example 1 was used.
A polyethylene terephthalate film with a size of 180 mm x 500 mm is used, and ITO is used as a target object.
(Indium tin oxide) was used.

In the thin film forming method of this embodiment, first, in the sputtering tank 4, under the same conditions as in Embodiment 1, I was formed on the substrate.
A TO thin layer was formed. Then, the substrate was taken out from the sputtering tank 4, and the thickness of the formed ITO thin layer was measured and found to be 0.12 μm. Next, ultrasonic cleaning was performed for 1 minute in distilled water. Then, the substrate was set again in the sputtering tank 4 and sputtering was performed under the same conditions as above.

The ITO thus formed on the substrate
The thin film had a film thickness of 0.23 μm, and when pinholes were counted with a microscope, five pinholes were confirmed in a size of 180 mm × 500 mm. (Comparative Example 2) In the thin film forming method of this comparative example, the sputtering apparatus 1 was used in the same manner as in Example 3, but the sputtering was performed twice without performing the ultrasonic cleaning on the way.

The ITO thus formed on the substrate
The thin film of No. 2 had a film thickness of 0.24 μm, and when pinholes were counted with a microscope, 20 of them were confirmed in a size of 100 mm × 500 mm. (Embodiment 3) This embodiment is an example of forming a thin film by an ion plating method.

A circular silicon wafer (N type) having a diameter of 3 inches, which has not been washed in advance, is used as a substrate, SiO ₂ is used as a film material, and an insulating thin layer of SiO ₂ is formed on the wafer surface in an ion plating tank. Formed. Then, the substrate was taken out from the ion plating tank, and the thickness of the thin layer was measured and found to be 0.11 μm. Immediately, the thin layer surface was manually brushed back and forth three times with a light touch using a cloth made of ultrafine fibers.

Then, again, the substrate was set in the ion plating tank, and ion plating was performed under the same conditions as above. Si formed on the substrate in this way
The O2 thin film has a uniform and beautiful appearance and its thickness is 0.2μ.
When the thin film was observed with a differential interference microscope, there were no pinholes.

The following check was performed on the further formed thin film. Aluminum was sputtered on both surfaces (that is, the surface of the SiO ₂ thin film and the surface opposite thereto) of the silicon wafer on which the SiO ₂ thin film was formed to form an electrode layer having a thickness of 1 μm. Then, in vacuum at 300 ℃ 3
Annealing treatment was performed by leaving it for 0 minutes.
The annealing process is a process that is performed as necessary to form ohmic contact.

When a lead wire was connected to the formed electrode layer via an ammeter and a voltage of 200 V (DC) was applied between the electrodes, only a current of 1 μA or less flowed through the ammeter. This result is almost completely pinhole free S
It proves that an iO ₂ thin film is formed. (Comparative Example 3) A circular silicon wafer (N type) having a diameter of 3 inches similar to that used in Example 3 was used as a substrate except that ultrasonic cleaning was performed in advance, and SiO 2 was used as a film material under the same conditions as in Example 3. ₂ was used to form an insulating thin layer of SiO _{2 on} the wafer surface in an ion plating tank. The film thickness was measured and found to be 0.1 μm.

Then, after waiting for 3 minutes, again under the same conditions as above.
Ion plating was performed. On the substrate in this way
SiO formed on_TwoThe thin film has a thickness of 0.21 μm
And when observing the thin film with a differential interference microscope, 1.3
Pieces / cm^TwoPinholes are detected at a ratio of
Were evenly distributed over almost the entire surface. Also formed thin film
The aluminum electrode layer was formed in the same manner as in Example 3.
Formed, annealed, and 200 V (D
When the check of applying the voltage of C) was performed, the ammeter
A current of 20 mA was applied to the device. The result is SiO _TwoThin
The current is flowing through the pinholes formed in the film.
Is shown.

By comparing with the results of Example 3 above, even if the silicon wafer itself is sufficiently cleaned in advance and the thin film is not taken out from the ion plating tank during the thin film formation by ion plating, the thin film formation It can be seen that the pinholes cannot be extremely reduced as in the case where cleaning is performed by physical means during the process.

(Embodiment 4) FIG. 2 is a schematic configuration diagram of a continuous sputtering apparatus used in this embodiment. This sputtering device 20 is equipped with a film feeding section 21 for mounting a roll film 30 serving as a base and feeding the roll film 30, a winding roller 22 for winding the fed film 31, and a target object mounted and applied thereto. A sputtering unit 23 for performing sputtering, a pair of guide rollers 24 for guiding the fed film 31, a pair of brushing rollers 25, 26 for brushing a thin layer formed on the film by sputtering, and these units are housed. The sputtering chamber 27 includes a sputtering chamber 27, a vacuum pump 28 for evacuating the chamber, and a rare gas enclosure 29 for enclosing a rare gas in the chamber.

The pair of guide rollers 24 are arranged on both sides of the sputtering unit 23 with the sputtering unit 23 interposed therebetween, so that the film 31 can be sputtered by the sputtering unit 23.
Guide. In addition, the brushing rollers 25, 2
Numeral 6 is a cloth-like ultrafine fiber wound seamlessly around the entire roller having an extremely high cushioning property. The brushing roller 25 is on the take-up roller 22 side and the brushing roller 26 is on the film mounting portion 21 side. It is installed in.

Although not shown, the film feeding section 2
1, the take-up roller 22, and the guide roller 24 are each connected to a drive motor so that the rotation speed can be controlled from the outside. In addition, the brushing rollers 25, 2
Each of 6 is also connected to a drive motor and can be controlled from the outside by another circuit. Film 3
Auxiliary rollers for adjusting the traveling position and tension of No. 1 are also appropriately installed.

The roll film 30 used in this embodiment is
A polyimide film made of the same material as in Example 1 and having a width of 200 mm and a length of 10 m is wound in a roll shape. Also, the target object is the same as in the example.
Use copper. In the thin film forming method of the present embodiment, first, the roll film 30 and the target object were mounted on the sputtering apparatus 20, the inside of the sputtering tank 27 was evacuated, and argon was sealed to adjust the internal pressure to 2 × 10 ⁻³ Torr.

The feeding speed of the roll film 30 is 1.0
m / min, rotation speed of brushing roller 25 300 times /
Minute, the applied power at the sputtering unit 23 is 2.0 kw
It was set to (DC) and the first sputtering was started. At this time, a thin layer of copper is formed on the film 31 fed from the roll film 30 when passing through the sputtering unit 23, the thin layer surface formed is brushed by a brushing roller 25, and the film 31 is wound by a take-up roller. It was wound up at 22. The brushing roller 25
The pressure for brushing was adjusted so that an appropriate pressure was obtained in advance so that the thin film would not be scratched, and that pressure was reached.

By performing sputtering while winding the film in this manner, a film having a thickness of 9 m was wound on the winding roller 22. Next, the film wound on the winding roller 22 is fed to the film feeding unit 21.
The second sputtering was performed while rewinding the film into the film. The conditions here are the same as those for the first sputtering, but without using the brushing roller 25, the brushing roller 2
Brushed with # 6.

After the second sputtering was completed in this way, the film was unwound from the film unwinding portion 21 again, and the third time sputtering was performed while winding the film around the winding roller 22. The third sputtering was performed under the same conditions as the first sputtering, except that the brushing roller 25,
26 was not used. In this way, the winding roller 22
The film wound on the film has a thickness of 0.3
A copper thin film of 2 μm was formed, and when the number of pinholes was counted with a microscope, only 5 pinholes were confirmed in the whole.

Table 1 summarizes the thin film forming conditions and effects of Examples 1 to 4 and Comparative Examples 1 to 3 described above.

[0046]

[Table 1] Comparing the pinhole generation results of Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the thin film forming methods of Examples 1 to 3 have extremely reduced thin film pinholes. In addition, the values of the film thickness and the number of generated pinholes measured in Examples 1 to 3 and Comparative Examples 1 to 3 are average values of several tests, and in Examples 1 to 3, the occurrence of pinholes was measured. It was also confirmed that there was almost no variation in the number, and in Comparative Examples 1 to 3, there were many variations in the pinhole generation rate.

(Other Matters) It was also confirmed that the present invention can be applied regardless of the type of material of the base material, and that there is no difference in effect depending on the material. Further, when the surface of the thin film is cleaned by chemical or physicochemical means during the formation of the thin film, a remarkable effect can be obtained as in the case of cleaning by the physical means as in the above embodiment. I also confirmed that it was not there.

As described above, the major effect of reducing the pinholes during the formation of the thin film and only by the cleaning by the physical means is that the cause of the pinholes is the occurrence of the thin film from the substrate or the like. It is speculated that it is removed by cleaning by physical means. However, it is needless to say that it is preferable to carry out the thin film forming method according to the present invention in a clean environment and to clean the substrate itself.

[0049]

According to the thin film forming method of the present invention, during the thin film formation, the surface of the thin layer is cleaned at least once by physical means such as brushing with fibers or ultrasonic cleaning. , A remarkable pin which cannot be achieved by cleaning the substrate itself or cleaning the environment by the conventional physical, physicochemical or chemical means performed before thin layer formation. The hole reduction effect can be achieved, which greatly contributes to the formation of a high-quality and high-performance thin film.

Moreover, the number of pinhole defects in the thin film substrate, which can be finally obtained under any thin film forming conditions, does not vary, and the quality is always maintained in a controlled state, so that quantitative production control becomes possible. This thin film forming technology can meet the demand for quality performance in the electronic industry field, especially the strict requirement for pinholes, and therefore has a great practical effect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sputtering apparatus used in an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a continuous sputtering apparatus used in Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sputtering apparatus 4 Sputtering tank 7 DC glow discharge device 20 Continuous sputtering apparatus 23 Sputtering section 25, 26 Brushing roller 27 Sputtering tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication H05K 3/16 6921-4E H05K 3/16 (72) Inventor Kenichi Nishi Nishi 163 Morikawahara-cho, Moriyama-shi Bunch Gunze Co., Ltd. Shiga Research Institute

Claims (3)

[Claims] 1. A thin film forming method for forming a thin film of a metal or a compound thereof on a substrate, comprising: a first thin layer forming step of forming a thin layer of a metal or a compound thereof on a substrate; A thin film forming method comprising: a cleaning step of cleaning the surface by physical means; and a second thin layer forming step of forming a thin layer of a metal or a compound thereof on the cleaned thin layer. 2. The method of forming a thin film according to claim 1, wherein the physical means brushes the surface of the thin layer with fibers. 3. The method for forming a thin film according to claim 1, wherein the physical means cleans the surface of the thin layer with ultrasonic waves.