JPH05295577A - Method for cleaning substrate - Google Patents

Abstract

PURPOSE:To clean a substrate at a low cost without having spotting on the surface by drying. CONSTITUTION:The contaminant on the surface of a substrate 4 is cleaned off as follows. (1) The contaminated substrate is dipped in an org. solvent 2, and the contaminant is washed away by the solvent 2 from the substrate 4. (2) The solvent 2 is heated to a temp. 1.5-10 deg.C lower than the b.p. to form a solvent vapor layer 3 on the solvent 2. (3) The substrate 4 in the solvent 2 is pulled up from the solvent 2 at the speed of 8.4 to 15.0mm/sec to volatilize the solvent on the substrate 4 into the solvent vapor layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a substrate on which a thin film is applied by a thin film forming technique.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic photosensitive member used in a copying machine, a printer or the like employs a thin film forming technique such as a plasma CVD method on the surface of a cylindrical aluminum base.
Amorphous silicon film (hereinafter a-
It is manufactured by depositing a Si film).

In such an electrophotographic photosensitive member, the film thickness of the a-Si film deposited on the surface of the substrate is extremely thin, and the adhesion of the a-Si film to the substrate surface, electrical characteristics, etc. are largely dependent on the surface condition of the substrate. Since it depends on the surface of the substrate, the outer peripheral surface of the substrate is usually subjected to smoothing treatment such as mirror polishing, and then dirt such as oil and processing debris adhering to the substrate surface is completely removed by washing with an organic solvent. Was.

In order to clean the substrate, first, C in the cleaning tank.
By injecting an organic solvent such as H ₂ Cl ₂ and immersing the substrate in the organic solvent, the dirt such as processing scraps and oil adhering to the surface of the substrate is washed out in the organic solvent. It is carried out by volatilizing the organic solvent adhering to the surface of the substrate while pulling it up from the solvent.

[0005]

However, according to this conventional method of cleaning a substrate, when the substrate is pulled up from the organic solvent, the organic solvent containing oil or the like adheres to the surface of the substrate, which becomes a dry stain. Remains on the surface of the substrate and a thin film such as an a-Si film is deposited on the surface of the substrate by a thin film forming technique such as plasma CVD, a film-forming defect occurs on the a-Si film due to the dry stain. Alternatively, the a-Si film has a drawback that the electrical characteristics of the film are not uniform as a whole.

Therefore, in order to solve the above-mentioned drawbacks, a freeboard (a layer of solvent vapor formed by a steam generator or the like) is provided on the organic solvent in the cleaning tank, and the freeboard adheres to the substrate surface in the freeboard. A method is known in which an organic solvent containing oil or the like is volatilized to effectively prevent the occurrence of dry stains on the surface of the substrate.

However, in the above cleaning method, a steam generator must be separately incorporated in the cleaning device in order to provide a freeboard, which makes the cleaning device expensive and makes the entire structure complicated, and at the same time generates steam. It has the drawback of requiring a very large amount of organic solvent with the use of a vessel.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to provide a method for cleaning a substrate which is low in cost and which does not cause drying stains on the surface of the substrate. is there.

[0009]

The method of cleaning a substrate according to the present invention is characterized in that dirt adhering to the surface of the substrate is cleaned by the following steps (1) to (3).

(1) A step of immersing a substrate having stains in an organic solvent and washing the stains from the substrate with the organic solvent.

(2) The organic solvent is added at a boiling point of 1.5 to 10 ° C.
Heating to a low temperature to form a solvent vapor layer on the organic solvent.

(3) The substrate immersed in the organic solvent is 8.4.
To a rate of 15.0 mm / sec, and a step of evaporating the organic solvent attached to the surface of the substrate from the organic solvent in the solvent vapor layer.

[0013]

EXAMPLES Examples of the present invention will be described below by taking the case of cleaning a cylindrical substrate used for an electrophotographic photoreceptor as an example.

FIG. 1 is a schematic view of a cleaning apparatus used for carrying out the cleaning method of the present invention. 1 is a cleaning tank, 2 is an organic solvent, 3 is a solvent vapor layer, 4 is a cylindrical substrate, 5 Is an ultrasonic oscillator, 6 is a heater, and 7 is a condenser tube.

The cleaning tank 1 is made of stainless steel or the like, and an organic solvent 2 such as dichloromethane (CH ₂ Cl ₂ ) or trichloroethane (CCl ₃ CH ₃ ) is injected into the cleaning tank 1.

The organic solvent 2 is used to wash away dirt such as oil and processing dust attached to the surface of the cylindrical substrate 4, and the surface of the cylindrical substrate 4 is put in a state suitable for depositing an a-Si film or the like. Make the action.

A cleaning tank 1 into which the organic solvent 2 is injected
An ultrasonic transducer 5 is provided on the inner wall surface and a heater 6 is provided on the bottom surface.
Are connected to and embedded in drive circuits (not shown).

When electric power is applied to the ultrasonic oscillator 5 as the drive circuit is driven, the ultrasonic oscillator 5 vibrates while emitting ultrasonic waves of a predetermined frequency in the organic solvent 2 injected into the cleaning tank 1,
As a result, the cleaning effect of the organic solvent 2 is enhanced.

On the other hand, the heater 6 generates Joule heat when electric power is applied as the drive circuit is driven, and heats the organic solvent 2 in the cleaning tank 1 to a temperature 1.5 to 10 ° C. lower than the boiling point. , Part of the organic solvent 2 is vaporized and the organic solvent 2
A thick solvent vapor layer 3 composed of the same organic substance vapor as the organic solvent 2 is generated on the upper part of.

When the cylindrical substrate 4 is pulled up from the organic solvent 2 at a predetermined speed, the solvent vapor layer 3 adheres to the surface of the cylindrical substrate 4 while exposing the cylindrical substrate 4 to the vapor of the organic substance forming the solvent vapor layer 3. The organic solvent 2 thus formed is uniformly vaporized and dried, which effectively prevents the generation of dry stains on the surface of the cylindrical substrate 4.

When the liquid temperature of the organic solvent 2 becomes higher than the above-mentioned heating temperature range, vapor condensation occurs due to the temperatures of the organic solvent 2 and the solvent vapor layer 3 becoming substantially equal. If a sufficient cleaning effect cannot be obtained, and if it falls below the above-mentioned heating temperature range,
The solvent vapor layer 3 having a sufficient thickness cannot be generated above the organic solvent 2. Therefore, it is necessary to heat the liquid temperature of the organic solvent 2 to a temperature lower than the boiling point by 1.5 to 10 ° C.

As the cylindrical substrate 4, a cylindrical body made of, for example, aluminum or glass, which has been subjected to smoothing treatment such as mirror polishing on the outer peripheral surface, is preferably used.

Further, a condensing pipe 7 is arranged on the inner wall of the upper portion of the cleaning tank 1, and the condensing pipe 7 cools and liquefies the vapor of the organic substance forming the solvent vapor layer 3 so that the vapor is washed. 1 It works to prevent leakage to the outside.

Next, a method of cleaning the cylindrical substrate 4 using the above cleaning device will be described.

First, while injecting an organic solvent 2 such as dichloromethane or trichloroethane into the cleaning tank 1,
The cylindrical substrate 4 is immersed in the organic solvent 2.

Next, the organic solvent 2 is heated by a heater 6 to a temperature lower than the boiling point by 1.5 to 10 ° C., and a thick solvent composed of the same organic vapor as the organic solvent 2 is formed on the liquid surface of the organic solvent 2. The vapor layer 3 is formed.

Next, the ultrasonic vibrator 5 embedded in the inner wall surface of the cleaning tank 1 is vibrated at a frequency of 28 kHz for about 2 minutes to remove dirt such as oil adhering to the surface of the cylindrical substrate 4. Wash out and wash in organic solvent 2.

Next, the cylindrical substrate 4 is pulled up from the organic solvent 2 at a speed of 8.4 to 15.0 mm / sec so that its outer peripheral surface forms a plane perpendicular to the liquid surface of the organic solvent 2.

In this case, since a thick solvent vapor layer 3 made of the same organic substance vapor as the organic solvent 2 is formed by the heating of the heater 6 above the liquid surface of the organic solvent 2, it is lifted from the organic solvent 2. The cylindrical substrate 4 is a solvent vapor layer 3
Since it is exposed to the inside for a long time, even if the organic solvent 2 containing oil or the like adheres to the surface of the cylindrical substrate 4, the adhering organic solvent 2 is evenly dried in the solvent vapor layer 3, and as a result, No dry spot is generated on the outer peripheral surface of the cylindrical substrate 4. Therefore, when an electrophotographic photosensitive member is manufactured by depositing an a-Si film on the outer peripheral surface of the cylindrical substrate 4 by a plasma CVD method or the like, the cylindrical substrate 4
Since there are no dry spots on the outer peripheral surface of the film, there are almost no film-forming defects on the surface, and the electrical characteristics are almost uniform over a-.
It becomes possible to deposit a Si film.

The solvent vapor layer 3 can be easily generated by heating the organic solvent 2 to a temperature lower than the boiling point by 1.5 to 10 ° C. by the heater 6 or the like to vaporize a part of the organic solvent 2. Therefore, there is no need to separately install an expensive steam generator or the like in the cleaning device, and the cleaning device can have a simple overall structure and a low cost, and as a result, a cylinder to be used with such a cleaning device. The cleaning of the substrate is inexpensive and has good workability. At the same time, in the method for cleaning a substrate according to the present invention, the amount of the organic solvent used can be minimized, whereby the cost of cleaning can be further suppressed.

When the cylindrical substrate 4 is pulled up from the organic solvent 2 at a speed of 8.4 mm / sec or less, the work efficiency of cleaning the cylindrical substrate 4 is greatly reduced, which is not suitable for a large amount of work. And when the cylindrical substrate 4 is pulled up at a speed of 15.0 mm / sec or more,
It cannot be exposed to the inside for a sufficient time, and a dry stain occurs on the surface of the cylindrical substrate 4. Therefore, the cylindrical substrate 4 must be pulled up from the organic solvent 2 at a speed in the range of 8.4 to 15.0 mm / sec.

(Experimental Example) Next, the operation and effect of the present invention will be described based on an experimental example.

First, dichloromethane was injected into the cleaning tank (internal volume: 30 liters) shown in FIG. 1 in which an ultrasonic vibrator and a heater were incorporated, and dichloromethane (boiling point: 39 ° C.) was adjusted to 36 ° C. by the heater. Heated to temperature,
A cylindrical substrate made of aluminum in the dichloromethane (outer diameter: 108 mm, length dimension: 358 mm, thickness: 5
mm).

Next, the ultrasonic vibrator is vibrated in CH ₂ Cl ₂ at a frequency of 28 kHz for 2 minutes to wash the surface of the cylindrical substrate, and thereafter, the outer surface of the cylindrical substrate is treated with an organic solvent. While maintaining the surface perpendicular to the liquid surface, the organic solvent adhering to the surface of the cylindrical substrate is volatilized while being pulled up from the organic solvent in the range of 3 to 20 mm / sec, and the cleaning of the cylindrical substrate is completed.

Dry stains generated on the outer peripheral surface of the cylindrical substrate were visually examined to confirm the occurrence of dry stains. The results are shown in Table 1.

[0036]

[Table 1]

As is clear from Table 1, the pulling speed when pulling up the cylindrical substrate from the organic solvent is 15 mm / se.
If the speed is less than or equal to c, the cylindrical substrate is exposed to a thick solvent vapor layer formed on the liquid surface of the organic solvent for a long time, and is uniformly dried from above in the solvent vapor layer. Therefore, it can be seen that the dry stain does not occur on the surface of the cylindrical substrate.

The present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the gist of the present invention.

[0039]

According to the substrate cleaning method of the present invention, since a thick solvent vapor layer composed of the vapor of the same organic material as the organic solvent is formed on the organic solvent, the substrate lifted from the organic solvent. Even if an organic solvent containing oil adheres to the surface of the substrate that is exposed to the solvent vapor layer for a long time, the organic solvent that adheres is evenly dried in the solvent vapor layer, and as a result, the surface of the substrate is No dry spots will be generated.

Further, according to the substrate cleaning method of the present invention, the solvent vapor layer has an organic solvent of 1.
Since it can be easily generated by heating to a temperature 5 to 10 ° C lower and vaporizing a part of the organic solvent, there is no need to separately incorporate an expensive steam generator into the cleaning device, and the cleaning device is completely eliminated. The overall structure can be simple and inexpensive, and as a result, the cleaning of the substrate using such a cleaning device can be inexpensive and easy to work with.

At the same time, in the substrate cleaning method of the present invention, the amount of the organic solvent used can be minimized, which can further reduce the cleaning cost.

[Brief description of drawings]

FIG. 1 is a schematic view of a cleaning device used in a cleaning method of the present invention.

[Explanation of symbols]

 1 ... Cleaning tank 2 ... Organic solvent 3 ... Solvent vapor layer 4 ... Cylindrical substrate 5 ... Ultrasonic transducer 6 ... Heater 7 ... Condensing tube

Claims (1)

[Claims] 1. The stain adhered to the surface of the substrate is described in (1) below.
A method of cleaning a substrate, which comprises cleaning in steps (3) to (3). (1) Dip a substrate with dirt in an organic solvent,
The process of washing dirt from the substrate with an organic solvent. (2) A step of heating the organic solvent to a temperature lower than the boiling point by 1.5 to 10 ° C. to form a solvent vapor layer on the organic solvent. (3) The substrate immersed in the organic solvent is 8.4 to 15.0.
A step of evaporating the organic solvent adhering to the surface of the substrate from the organic solvent at a speed of mm / sec in the solvent vapor layer.