JPH081076A - Formation of thin film by coating - Google Patents

Abstract

PURPOSE:To form an excellent thin film at a low cost by vibrating either a substrate or an applied pasty material with an acoustic device with noncontact during or after the coating stage of the pasty material. CONSTITUTION:The fine powder of cadmium sulfide(CdS) is admixed with propylene glycol as a binding agent to prepare pasty CdS. The CdS paste is screen-printed on a borosilicate glass substrate 10 to form a CdS coating film 11. The coating film 11 is then ultrasonically vibrated by the acoustic device 12 at a distance of about 10mm from the substrate 10 and simultaneously vibrated horizontally by a vibrator 14 with a contact process. Consequently, the ruggednesses marked on the CdS printed film disappear, and an excellent smooth face is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a paste-like material, which is widely used in the production of various electronic parts, semiconductor elements, magnetic recording materials, etc., in which a fine powdery material and a binder are mixed, on various substrates. The present invention relates to a coating film forming method of forming a thin film by coating on.

[0002]

2. Description of the Related Art As an existing technique, when a powdery material and a binder are mixed to form a paste material, which is applied to various substrates, vibration is applied to the substrates to improve the surface smoothness. There is known a method of improving, reducing fine holes in the film, and improving the adhesion between the substrate and the coating film.

[0003]

When a vibrating object is brought into contact with a substrate coated with the pasty material to give vibration, in order to cause a preferable change in the smoothness of the surface or the like in the coating film, the pasty material is used. Depending on the type, high energy vibration may be required. In such a case, the applied vibration may deteriorate the substrate, reduce its mechanical strength, and cause cracks and the like. Also, when applying vibration using a general ultrasonic vibrator, the frequency of vibration cannot be continuously changed,
It is difficult to give the vibration of the optimum frequency depending on the conditions of the applied film.

Further, when vibration having a constant frequency is continuously applied to the substrate, a two-dimensional standing wave (a wave in which a vibrating position and a non-vibrating position are constant) is generated in the substrate, and the vibration is caused for a long time. The film applied by gathers in the part with less vibration,
On the contrary, the film thickness becomes thin in the portion where the vibration is large, and the film thickness may be uneven as a whole. Therefore, the present invention is to solve such a conventional problem, to effectively utilize the characteristics of the thin film forming method by applying a paste-like material, and to provide a good thin film coating film forming method at low cost. To aim.

[0005]

A method for coating a thin film according to the present invention comprises a step of applying a paste-like material in which a fine powder and a binder are mixed onto a substrate, and a step of applying the paste-like material or After the applying step, there is a step of applying non-contact vibration to at least one of the substrate and the applied paste-like material by using an acoustic device.

Further, according to the present invention, a step of applying a paste-like material in which fine powder and a binder are mixed onto a substrate, and the substrate and the applied paste-like material during or after the applying step of the paste-like material. On at least one of the materials,
The method has a step of applying non-contact vibration using an acoustic device and simultaneously applying vibration to the substrate in a contact method using another vibration device.

Further, the present invention changes the output frequency of the acoustic device during the application of the above vibration. Here, as a coating method, any of a screen printing method, a drawing printing method, a relief printing method, an intaglio printing method, and a spray method can be used.

[0008]

[Function] A method of vibrating along with thin film coating is to apply vibrations of various frequencies when a thin film is formed by coating a paste prepared by mixing fine particles of various materials and a binder. As a result, the unevenness of the surface of the film is eliminated and smoothed, pinholes in the film are reduced, bubbles and the like caught in the paste-like material are removed, and the adhesion between the applied film and the substrate is increased and the material particles Increase the packing density and orientation. As a result, it has characteristics that the optical characteristics and the electromagnetic characteristics at the time of forming a thin film are improved, and the mechanical strength is also improved, and a good functional thin film can be easily prepared.

The present invention provides, as a method of applying the vibration,
In particular, by directly vibrating the coating film in a non-contact manner using a speaker or a whistle-like structure, which is a method in which vibration propagates in the air, and at the same time, a weak vibration in a contact manner with respect to the substrate. By applying the above, the above effect can be obtained without causing adverse effects such as damage and deterioration of the coated substrate due to vibration. At the same time, in the case of an acoustic device, it is easy to continuously change the frequency, and the optimum frequency can be selected according to the conditions of the coated film. Furthermore, by changing the frequency while applying vibration, it is possible to continuously change the wavelength of the standing wave and prevent unevenness in the coating film.

[0010]

The present invention will be described below with reference to examples. FIG.
Shows a schematic cross-sectional view of a general CdS / CdTe-based sintered thin film solar cell. In the figure, 1 is a glass substrate, and a CdS sintered film 2, a CdTe sintered film 3, and a carbon film 4 are sequentially formed on the substrate 1. 5 is AgI formed on the CdS film
n electrode, 6 is an AgIn electrode formed on a carbon film, 7
And 8 show lead wires. This solar cell has a light receiving surface on the glass substrate side. Arrows in the figure indicate incident light.

The film forming method of the present invention will be described below. First, cadmium sulfide (CdS) with a particle size of 2-3 μm
A mixture obtained by adding 35 g of propylene glycol as a binder to 100 g of the fine powder of was mixed for about 2 hours in a mixer (grinding machine) to prepare paste CdS. The CdS paste obtained in this way was measured in a size of 350 mm × 4.
A CdS printing coating film having a thickness of about 60 μm was formed by a screen printing method on a borosilicate glass substrate having a thickness of 50 mm and a thickness of 1.1 mm. Then, from a distance of 10 mm or less on the glass substrate, ultrasonic vibration having a frequency of 10 to 50 kHz was applied to the coating film by an acoustic device for 1 to 30 seconds, and simultaneously vibration having a frequency of 1 to 10 kHz was applied in the horizontal direction. As a result, during screen printing, the unevenness on the CdS print film, which had been caused by marking the mesh of the warp yarns and the weft yarns forming the screen on the print film, disappeared, and a good smooth surface was obtained.

FIG. 2 shows the configuration of the vibration device used here. In the figure, 9 is a stage (stand) for supporting the substrate and each member,
Reference numeral 10 is a substrate, 11 is a coated thin film, 12 is an acoustic device that emits sound waves, 13 is a spring that supports the substrate, 14 is a contact-type vibrating device, and 15 is a sound wave generated by the acoustic device. After that, the binder in the printed film was removed by drying in air at 120 ° C. for 120 minutes and then inserted into an electric furnace at 700 ° C. having a nitrogen atmosphere for 160 minutes to form a CdS sintered film. .

Conventional C film-formed without vibration after printing
dS film, CdS sintered film which was formed by applying vibration by a conventional contact method immediately after printing immediately before printing, CdS sintered film which was formed by applying vibration by a non-contact method, and simultaneously applying vibration by a non-contact method CdS that gives weak vibration to substrate by contact method
A comparison of the surface roughness of the sintered film is shown in FIG. As is clear from FIG. 3, according to the coating method in which three kinds of vibrations are applied, as compared with the film formed by the conventional screen printing,
It can be seen that the undulations on the film surface are reduced to 1/2 or less, and the smoothness is improved.

Next, 100 g of fine powder of Cd and Te in equimolar ratios was formed on the CdS sintered film thus obtained.
On the other hand, a mixture in which 48 g of propylene glycol was added as a binder was mixed in a mixer (grinding machine) for about 10 hours to prepare paste CdTe. The obtained CdTe paste is printed on the above CdS sintered film by a screen printing method to form a CdTe film having a thickness of about 30 μm, and then a frequency of 10 to 50 kHz is applied to the coating film from a distance of 10 mm or less on the glass substrate using an acoustic device. Ultrasonic vibration for 1 to 30 seconds was applied. As a result, the irregularities generated on the surface of the CdTe film during screen printing disappeared, a very good smooth surface was obtained, and pinholes disappeared, and the adhesion with the CdS sintered film 2 was improved.

After that, the CdTe sintered film 3 was formed by the drying and firing steps. Then, on the CdTe sintered film,
After printing the carbon electrode film 4 and the AgIn electrode films 5 and 6, before drying, ultrasonic vibration of a frequency of 10 to 50 kHz was applied to the coating film from a distance of 10 mm or less on the glass substrate for 10 to 30 seconds using an acoustic device. After being applied, the carbon film 4 and the AgIn electrode films 5 and 6 are dried and heat-treated, respectively.
Was formed. Through the above steps, the CdS / CdTe solar cell shown in the schematic sectional view of FIG. 1 was obtained.

Next, when the frequency was changed from 10 kHz to 50 kHz while applying vibration to the CdS film immediately after printing for 30 seconds, and when the frequency was changed to 3 at a constant frequency (28 kHz).
A comparison of surface roughness when vibration is applied for 0 seconds is shown in FIG. It can be seen that when vibration is applied at a constant frequency, a periodic change in the film thickness, which is considered to be caused by the standing wave generated on the substrate, occurs. On the other hand, it can be seen that the one in which the frequency is changed is very flat.
It is considered that this is because the wavelength of the standing wave generated on the substrate changes according to the change in frequency.

Table 1 shows a comparison between the conventional contact method and the non-contact method of the present invention. This table shows the products manufactured by each method (CdS
In the case of the conventional contact method, the chipping of the substrate during vibration and the damage to the substrate during heat treatment are 3% and 1.5%, respectively, whereas In the case of the contact method, it can be seen that the influence on the substrate is significantly reduced to 0% and 0.5%, respectively. Further, when the non-contact type vibration and the weak contact type vibration were used together, they were 1% and 0.8%, respectively. In addition, the number of pinholes after sintering was 5.2 cm ^{-2 in the} conventional contact method and 6.1 cm ^-2 in the non-contact method. 1.8cm ^{- 2} to have been significantly reduced.

[0018]

[Table 1]

It should be noted that the effect of smoothing the film surface, removing pinholes, improving light transmittance, etc. obtained by printing and applying these paste-like materials on the substrate and then applying vibration before the drying thereof is achieved. In the embodiments, the material is applied to the semiconductor material and the conductive material, but it is also applicable to the magnetic recording material, the dielectric material, the insulator material and the like by changing the frequency and the amplitude. Further, similar effects were obtained even in the case of a printing / coating film prepared by applying an intaglio printing, a letterpress printing, a spraying method, a drawing printing method or the like instead of the screen printing method.

[0020]

As described above, according to the present invention, the substrate coated with a thin film is smoothed by removing the unevenness of the film surface without damaging the pinholes in the film,
Bubbles and the like caught in the pasty material are removed, the adhesion between the applied film and the substrate is enhanced, and the packing density and orientation of the material particles are enhanced. As a result, it is possible to improve optical characteristics and electromagnetic characteristics when forming a thin film, improve mechanical strength, and easily produce a good functional thin film.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a CdS / CdTe based sintered thin film solar cell obtained according to an example of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an acoustic vibration device used in an example of the present invention.

FIG. 3 is a diagram comparing the surface roughness of CdS films obtained by various methods.

FIG. 4 is a diagram comparing the presence or absence of a frequency change of a sound wave giving vibration and the surface roughness of the obtained CdS film.

[Explanation of symbols]

 1 Glass Substrate 2 CdS Film 3 CdTe Film 4 Carbon Film 5 AgIn Electrode 6 AgIn Electrode 7 Lead Wire 8 Lead Wire 9 Stage 10 Substrate 11 Coating Film 12 Acoustic Device 13 Spring 14 Vibration Device 15 Sound Wave

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Murozono 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A step of applying a paste-like material in which fine powder and a binder are mixed onto a substrate, and at least one of the substrate and the applied paste-like material during or after the step of applying the paste-like material. And a step of applying vibration in a non-contact manner using an acoustic device. 2. A step of applying a paste-like material obtained by mixing fine powder and a binder onto a substrate, and at least one of the substrate and the applied paste-like material during or after the step of applying the paste-like material. 1. A method for coating and forming a thin film, which further comprises the step of vibrating in a non-contact manner using an acoustic device and simultaneously vibrating the substrate in a contact method using another vibrating device. 3. The thin film coating method according to claim 1, wherein the output frequency of the acoustic device is changed while the vibration is being applied.