JP2587971B2 - Thin film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for patterning thin films used for solar cells and liquid crystal display devices using inexpensive soda glass without using a photoresist. The groove is formed directly by laser beam drawing (pattern formation). The present invention also relates to a method for selectively processing a thin film in which a residue generated for direct writing is removed to remove a swelling of the residue in the groove.

[Prior Art] A method of using a photoresist in patterning a thin film is known. In this method, a conductive film such as a transparent conductive film is patterned on a soda glass substrate without damaging a blocking layer made of silicon oxide, phosphorus glass, or the like that prevents intrusion of an alkali metal element or the like provided on the outside. It has the feature that it can be performed. However, this method has a complicated process of coating a photoresist in a predetermined shape, using the resist as a mask, performing patterning, and then removing the photoresist. Therefore, there is a demand for a method of patterning at low cost.

As this inexpensive method, a method of directly drawing (pattern formation) by a laser processing method is known. As this laser processing method, a method using a YAG laser (wavelength 1.06 μm) is generally considered to be effective. In the method using this infrared light, the optical energy of the laser light is 1.23
There is only eV (1.06μm). On the other hand, a workpiece formed on a glass substrate, for example, a light-transmitting conductive film (hereinafter referred to as CTF) has an optical energy bandwidth of 3 to 4 eV. Therefore, tin oxide, indium oxide (including ITO),
CTFs such as zinc oxide (ZnO) do not have sufficient light absorption for the YAG laser light, and do not effectively use the energy of the laser light. In the laser processing method using the Q-switch oscillation of a YAG laser, the pulse light averages 0.5 to 1 W (light diameter 50 μm, focal length 40 mm, pulse frequency 3
Intense light energy (in the case of KHz, pulse width of 60 ns) must be applied at a scanning speed of 30 to 60 cm / min. As a result, the CTF can be processed by this laser beam, but at the same time, micro-cracks are generated at a depth of 10 to 50 μm in the soda glass having a blocking layer provided thereunder, causing damage. Was.

In addition, as irradiation light other than the YAG laser, a pulse laser having an ultraviolet light wavelength of 400 nm or less (energy of 3.1 eV or more) is irradiated, and a beam spot of 20 to 50 μφ is used instead of a beam spot of 20 to 50 μφ (for example, 10μm), length 10-60cm
For example, there has been known a method of irradiating a linear pattern of 30 cm with one or several pulses to the same location to form a linear groove and pattern processing a thin film. Pulse light with a wavelength of 400 nm or less (ultra short pulse width of 5 to 30 ns)
Irradiates light linearly, thereby increasing the light energy absorption efficiency of transparent materials such as CTF to more than 100 times that of using a YAG laser (1.06 μm), and consequently increasing the processing speed to more than 10 times. be able to.

In this case, an excimer laser beam is generally used as an initial light source. For this reason, the initial light irradiation surface has a rectangular shape, and its intensity is substantially uniform within the irradiation surface. For this reason, a rectangular area is increased by a so-called beam expander for expanding the width of light. After that, the laser light is focused in a slit shape by a cylindrical rod-shaped lens, that is, a cylindrical lens, along one of the X or Y directions.

Thus, a linear groove having a width of 2 to 200 μm, for example, 10 μm is formed.

These methods using laser light have a feature that the manufacturing process is easy because no photoresist is used. However, the groove portion formed by processing with the laser beam has a disadvantage that unprocessed portions, that is, a large amount of residues are likely to remain.

Due to this laser processing, the residue of the processed portion remains on the conductive film in the non-processed region, forming a convex portion. The mixture and compound of the soda glass and the conductive film remaining in the groove portion of the processed portion have a small amount of conductivity, so that it is not possible to sufficiently insulate the conductive film between the patterned adjacent conductive films. .

The height of the swelling of this mixture is 0.5 to 1
μm.

When a solar cell, a liquid crystal display device, and other electronic components are manufactured using the substrate in such a state, short-circuiting between the electrodes, disconnection, color unevenness, and the like due to the unevenness occur, and the production yield of the electronic components is reduced. I was copying.

[Object of the invention] The present invention is a laser light having a wavelength of 400μm or less, a buffer layer having flatness on a glass substrate, particularly glass, that is, a thin film on a substrate provided with a blocking layer for impurities such as alkali ions, The target material is a laminate, particularly a light-transmitting conductive film or a conductive film such as a metal film, or an insulating film such as a color filter below the conductive film, or a laminated body formed of a non-single-crystal semiconductor or the like thereon. It is an object of the present invention to realize a good surface to be processed without any residue near a groove of a processed portion when a conductive film or a laminated body is laser-processed and patterned.

[Structure of the Invention] In order to achieve the above object, a blocking layer (such as silicon oxide doped with phosphorous, sodium, and boron in a sufficiently small amount) is formed between a base substrate such as soda glass and a thin film to be processed. A first blocking layer), on which a thin film, particularly ITO, tin oxide, zinc oxide or a laminate thereof, and a metal conductive film such as chromium and molybdenum are laminated. If necessary, a laminate having an insulator or a semiconductor provided on its lower surface or upper surface may be used.
By irradiating the conductive film with laser light having a wavelength of 400 μm or less, the blocking layer in addition to the conductive film is simultaneously irradiated and removed to form a groove.
For this reason, a part of the mixture causes swelling due to the residue of the workpiece at the end of the processing groove, and also oozes out impurities such as sodium from the substrate material.

Therefore, these residues are stripped off with an acid (an acid capable of selectively stripping off the residues using a mixed solution of fluorides such as hydrofluoric acid and acidic ammonium fluoride diluted with water), and then the whole is removed. Form a second blocking layer. The second blocking layer is made of a liquid material, and is applied, printed or coated, and the whole is heated and cured. Then, since the groove of the laser processing part constitutes a concave part,
This part can be relatively thicker than on a thin film. And preferably 50-300 mm thick on the thin film, for example 200 mm, 100-600 mm thick (50 mm thick corresponds to 100 mm, 300 mm thick corresponds to 600 mm), for example 400 mm. It can be made more than 30% thicker. This thickness makes it possible to prevent the effect of oozing out alkali ions such as sodium in the substrate to the outside.

Furthermore, after forming a laminated body together with other semiconductors, insulators, and the like previously formed above or below the conductive film, all of them are patterned by laser light, and the upper surface and side surfaces of the resulting laminated body are formed. It is also possible to fill the second blocking layer and form the grooves.
At this time, since the thickness of the laminate is larger, the groove is formed to be thicker than the thickness of the second blocking layer on the laminate, so that the effect of shielding impurity ions such as sodium is more remarkable. can do.

 Examples will be described below.

Embodiment 1 FIG. 2 shows a system diagram of laser processing of the present invention using an excimer laser. An excimer laser (14) (wavelength 248 nm, Eg = 5.0 eV) was used as a processing laser. As shown in FIG. 3 (A), this laser has an initial light beam (21) of 16
It has 350 mm (millijoules) because it has a size of mm x 20 mm and an efficiency of 3%. Further, this beam was extended or enlarged in area by a beam expander (15). That is, 16
It was enlarged to mm x 300 mm (Fig. 3 (22)). At this time 5.6 ×
An energy density of 10 ^-2 mJ / mm ² was obtained.

Next, a laser beam is transmitted through a slit (16) having an interval of 2 mm × 300 mm to transmit a laser beam (22 mm × 300 mm).
3) get (FIG. 3 (C)) Further, the light was condensed (24) with a synthetic quartz cylindrical lens (17) so that the groove width on the processed surface became 10 μm. (FIG. 3 (D)) The width of the slit used at this time is not particularly determined, but it is necessary to narrow the laser beam to such an extent that the spherical aberration of the cylindrical lens does not influence.
The groove width of the workpiece is arbitrarily selected depending on the performance of the cylindrical lens.

FIG. 1 irradiates a slit-like pulse light onto a substrate,
A plurality of open grooves (6-1, 6-2, 6-3,... N) are formed. That is, as shown in FIG. 1 (A), a substrate having a blocking layer (2) (thickness of 100 to 1500 °), for example, silicon oxide with a thickness of 200 ° on soda glass (also called blue plate glass) is used. Further, a conductive film (4), for example, indium tin oxide or chromium,
Formed to a thickness of 3000 mm. As shown in FIG. 1 (B), these were irradiated with laser light using the optical system shown in FIGS. 2 and 3.

The pulse light was 248 nm light by a KrF excimer laser. Because the optical energy bandwidth of the light is 5.0e
Because V, the workpiece absorbs light sufficiently and only the conductive film can be selectively processed.

Pulse width 20 ns, repetition frequency 1-100 Hz, e.g. 10
Light irradiation was performed at Hz.

Then, the groove (6-1), (6-2), (6-3)
・ Get At this time, the residue (5-1) and the projection (5-2) are formed on the patterned conductive film (4) inside the groove.
Having. These are dissolved away with diluted hydrofluoric acid (diluted with water to 1/10), and then subjected to sufficient ultrasonic cleaning with acetone and pure water.

Then, as shown in FIG. 1 (C), the grooves (6-1), (6-
2) and (6-3) had only a groove, and all of the residue could be removed.

However, in the groove, the blocking layer (2) is also removed at the same time, and the upper part of the soda glass substrate is partially excavated (to a depth of 0.3 to 1 μm) and exposed. Therefore, when a liquid crystal display device or the like is made using only the structure shown in FIG. 1C, a liquid crystal requiring ultra-high purity comes into direct contact with the substrate material, and sodium is contained in the liquid crystal for a long time. There is a risk of seepage.

Further, if used as it is for an image sensor, a solar cell, or the like, sodium bleeds into the amorphous semiconductor from this portion, which promotes a photodegradation effect and an N-type semiconductor.

Therefore, in the present invention, a second blocking layer was formed on these upper surfaces as shown in FIG. 1 (D).

The blocking layer is preferably made of an organic resin such as polyimide which blocks sodium, or an inorganic material such as silicon oxide. These have a liquid state in a raw material state (non-polymerized state or liquid state of an organic silicide liquid such as silazane),
The raw material is applied and coated to a thickness of 50 to 2500 mm on the whole, for example, 300 mm on the conductive film and about 500 mm on the groove. This coating can be applied using a spinner, printing method,
A coater method or a spray method may be used.

Then, because these have a surface coated with liquid,
The grooves (6-1), (6-2),... Forming the concave portions are applied more and can be formed thicker.

Further, these liquid raw materials were thermally cured. For example, in the case of a polyimide solution, heat baking is performed at 230 ° C. for 2 hours. Also in the method using a liquid organic silicon compound, thermal oxidation was performed in air or oxygen to transform into a solid silicon oxide blocking layer.

Thus, as shown in FIG. 1 (D), the solvent was vaporized and the volume shrunk and became dense due to the heating reaction, so that the exudation of alkali ions and the like to the outside could be completely prevented.
The exudation of the organic substance from the lower side into the conductive film was blocked by the blocking layer (2) (first blocking layer). The infiltration of impurities into the conductive film or the laminate (7) from the side periphery and the upper surface was blocked by the second blocking layer (8).

Further, in the liquid crystal display device, it is effective that the second blocking layer functions as an alignment film by subjecting the surface to rubbing or the like as necessary.

Ideally, the second blocking layer should fill all of the recesses so that the upper surface of the second blocking layer approximately matches the upper surface of the conductive film, and should prevent local electric field concentration at the end of the conductive film. Can be For this reason, it is more preferable to apply and form a liquid raw material and to cure it.

In particular, the width of this groove is 50μ 20μm, 10μm, 5μ
In order to make the inside of the groove thicker in addition to making it possible to make the inside of this groove thicker, in addition to making it smaller as m and 3 μm, it is preferable to apply a liquid raw material capable of using surface tension and to carry out this curing step.

Thus, for example, the substrates in the longitudinal sectional view shown in FIG. 1 (D) are spaced apart from each other by a width of 2 μm, arranged in a matrix configuration, and filled with a liquid crystal material therebetween, whereby a liquid crystal capable of performing a matrix display can be obtained. A display device could be made.

In this case, one substrate was made of silicon oxide to form a second blocking layer, and the other substrate was made of polyimide organic resin to form a second blocking layer. Then, a rubbing treatment was performed on the organic resin side. Thus, even when the alignment film was treated at a high temperature of 50 ° C. for 1000 hours, the display section had a contrast of 20 and its value was not deteriorated at all.

In FIG. 1 (D), IT separated by this groove
Apply a 50V DC voltage between O (4-1) and (4-2) and apply ITO
When the current flowing between 100 points was measured,
２2 × 10 ⁻⁹ A (leakage current between grooves having a length of 30 cm and a width of 10 μm). These values are obtained because the second blocking layer also prevents surface leakage. Showed a constant value, and there was no problem in practical use.

[Effect] According to the present invention, since the entire outer periphery of the conductive film and the laminate is covered with the blocking layer in the laser processing, leakage between adjacent conductors can be further reduced.

According to the present invention, a good surface to be processed was obtained without generating a residue or the like remaining around the processing groove existing in the conventional method.

As a result, there is no short circuit or disconnection between the electrodes, and the ITO
Insulation between them was sufficient.

In the present invention, the conductive film may be made of ITO, SiO ₂ , ZnO or a multilayer film thereof, or may be a metal such as chromium or molybdenum.

It is effective to form an insulating film having a function of a color filter on the upper or lower side of these conductive films so that these conductive films have the same shape.

Further, a non-single-crystal semiconductor is laminated on the upper side of the conductive film,
It is effective to form another conductive film thereon and use it for an image sensor.

In the present invention, a second blocking layer is provided to cover all of these laminates to improve reliability.
High reliability was obtained even when an inexpensive soda glass substrate was used.

In the present invention, the case where the width between grooves (the area left without processing) is large is described. However, by connecting the light irradiation side by side, conversely, for example, the remaining area is 20 μm,
The part to be removed can be 400 μm.

[Brief description of the drawings]

FIG. 1 shows a method for manufacturing a substrate having a conductive film of the present invention. FIG. 2 shows an outline of a laser processing system used in the present invention. FIG. 3 shows the beam shape of the laser light.

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01L 31/04 H01L 21/76 Z

Claims (6)

(57) [Claims] A step of forming a first blocking film on a glass substrate; a step of forming the conductive film on the first blocking film; Removing the substrate surface selectively according to the following pattern; and forming a second on the conductive film so as to cover the exposed substrate surface.
Forming a blocking film according to the above. 2. The method according to claim 1, wherein
Removing the blocking film and the conductive film in a pattern suitable for a liquid crystal element. 3. A thin film forming method according to claim 1, wherein the first blocking film and the conductive film are removed by laser scribing. 4. A thin film forming method according to claim 3, wherein the laser scribe uses an excimer laser. 5. The thin film forming method according to claim 3, wherein the residue is removed after removing the first blocking film and the conductive film by laser scribing. 6. A thin film forming method according to claim 5, wherein said residue is removed with hydrofluoric acid.