JP2585503B2 - Laser processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a groove or a hole in a metal film using laser light.

[Conventional technology]

2. Description of the Related Art Conventionally, when forming an electrode of an integrated photoelectric conversion device, a method of processing a metal film forming the electrode by laser light is known.

It is common to use chromium alone (purity of 99.9% or more) as a metal film for performing laser processing.

However, this metal chromium becomes a so-called black chrome having a small reflection coefficient. In addition, because of its high hardness, when formed on an insulating film and subjected to heat treatment (200 ° C., 2 hours), minute cracks occur.

For this reason, it is required that the electrode coating has a certain degree of softness. In addition, it is important that the residue is not scattered around the groove where the laser beam is irradiated.

An example of the electrode material having a certain degree of softness is aluminum. However, aluminum has a high thermal conductivity (organic film 0.22W / mK, chromium 9
(0.3W / mK, glass 1.4W / mK, aluminum 237W / mK) and does not have sublimability (does not completely vaporize by laser light irradiation).

For these reasons, aluminum was considered to be unsuitable as a material to be processed for laser processing.
In particular, when forming a groove in an aluminum film formed on an inorganic insulator such as a glass substrate, a residue of aluminum oxide remains in and around the groove.

[Problems to be solved by the invention]

An object of the present invention is to obtain a technique for forming grooves or holes by laser light in aluminum or an aluminum alloy, which is a metal having a high thermal conductivity, which has been considered unsuitable for processing by laser light. I do.

Another object is to manufacture a photoelectric conversion device using a non-single-crystal semiconductor such as an amorphous semiconductor using the above technology.

[Means for solving the problem]

The present invention includes a step of forming a metal film on a substrate coated with an organic resin film having a thermal conductivity of 6.9 × 10 ⁻⁴ (cal / sec / cm / ° C.) or less; Forming a conductive film, and irradiating a pulsed laser beam to form a groove or a hole in the metal film and the light transmitting conductive film.

Further, the semiconductor device includes a first electrode provided over the substrate, a non-single-crystal semiconductor which generates photovoltaic power by light irradiation provided over the electrode, and a second electrode provided over the semiconductor. When manufacturing a photoelectric conversion device in which a plurality of photoelectric conversion elements are connected in series, a metal film is formed on a substrate coated with an organic resin film having a thermal conductivity of 6.9 × 10 ⁻⁴ (cal / sec / cm / ° C.) or less. Forming a light-transmitting conductive film on the metal film; and irradiating the metal film and the light-transmitting conductive film with a pulse laser beam to form a first groove to form a plurality of first grooves. Forming an electrode.

In the above invention, the metal film is preferably made of aluminum or an aluminum alloy containing aluminum as a main component.

The present invention, on an organic resin film having a very small thermal conductivity,
Forming a metal film having a relatively large thermal conductivity, further forming a translucent conductive film on the metal film, which has a sublimation property upon irradiation with laser light, and serves as an antireflection film for laser light,
Thereafter, by irradiating a laser beam, a groove is formed only in the translucent conductive film and the metal film.

[Action]

By using an organic resin film with a thermal conductivity of 6.9 × 10 ^-4 (cal / sec / cm / ° C) or less under the metal film, heat can escape from the metal film toward the substrate during laser irradiation. Prevent
The metal film can be sublimated.

In addition, a light-transmitting conductive film that does not have high thermal conductivity, has sublimation property when irradiated with laser light, and serves as an anti-reflection film for laser light is formed on a metal film, and is irradiated with laser light. Thus, the heating by the laser light can be concentrated on the metal film without releasing the heat, and as a result, the sublimation of the metal film by the laser light can be promoted.

By the above-described operation, only the portion irradiated with the laser beam can be selectively removed, and a groove or a hole without a residue can be formed.

The light-transmitting conductive film also has an effect of preventing a reaction between the metal film and a semiconductor provided over the metal film.

[Example 1] In this example, a metal film has a thickness of 300 to 3000 mm to prevent the thermal energy of laser light from being conducted and dissipated in the lateral direction, and has a very low thermal conductivity on the lower side. The present invention relates to a method of arranging an organic resin film and irradiating a laser beam (Q switch pulse) to the workpiece to form a groove or a hole.

In this embodiment, a non-single-crystal semiconductor including an amorphous semiconductor having at least one junction capable of generating a photovoltaic force by light irradiation is provided on a substrate having an insulating surface of an organic resin, particularly a substrate having flexibility. The present invention relates to a method for manufacturing a photoelectric conversion device capable of generating a high voltage, in which a plurality of photoelectric conversion elements (also simply referred to as elements) are electrically connected in series.

In this embodiment, grooves or holes are formed by arranging aluminum or a metal mainly composed of aluminum on the surface of the organic resin, and scribe this conductive film with a laser beam (hereinafter simply referred to as LS). The conductive film is divided into a plurality of regions to form electrodes.

As the electrode material to be processed by the laser beam, it is necessary to have reflectivity, to have sublimation property to facilitate laser processing, to have a low thermal conductivity, and to be used in a process of laminating semiconductors, etc. It is very important to have a so-called heat resistance that does not form an alloy.

The Al film has a high reflectivity (90% or more in the range of 400 to 800 nm) and a low sheet resistance (thickness of 0.5 to 1 Ω / □ / 1000 mm). It can be used for non-reactivity and for anti-reflection films, and is one of the most suitable electrodes for semiconductor devices if the difficulties in laser processing can be solved.

In this embodiment, an aluminum film or a metal film containing aluminum as a main component (hereinafter referred to as an aluminum film or an aluminum film) having reflectivity and excellent electrical conductivity is processed by a laser beam. A translucent conductive film (hereinafter referred to as CTF) composed mainly of indium oxide and tin oxide is laminated on top of it, and the insulating material in the upper layer of the substrate is compared with the thermal conductivity under this Al film. And 1/5 to 1/10
By providing an organic resin insulator having the above thermal conductivity, the Al film has laser workability.

The thermal conductivity of this organic resin is as follows when compared with other materials.

From the above data, it can be seen that all organic resins have low thermal conductivity and have only 1/5 that of glass, which is a typical example of an inorganic insulator. Therefore, in general, if the thickness is 0.1 μm or more, the thermal energy of the laser beam can be stored without being transmitted to the lower metal foil.

The shape of the photoelectric conversion device of this embodiment is determined by design specifications. However, for the sake of simplicity, in the following detailed description, the first electrode on the lower side (substrate side) of the first element and the second electrode ( It is described based on a pattern in the case where a semiconductor (that is, a side remote from the substrate) is electrically connected in series. Note that an element is a photoelectric conversion element, which indicates a photoelectric conversion device in a minimum unit. The photoelectric conversion device is configured by integrating a plurality of the photoelectric conversion elements.

FIG. 1 shows a reference example for showing the effect of the organic resin film.

In FIG. 1, a substrate (1) is composed of a metal white (6) and an organic resin film (7), and an Al film is formed on the film (7).

In the above configuration, when the metal film is irradiated with the laser beam (60), the heat loss in the downward direction (61) and the heat loss in the lateral direction (6
2), (62 ') and upward heat loss (63).

In FIG. 1, when chromium is used as the metal film (2), since the lateral heat conduction (62), (62 ') is small and has sublimability, the downward heat conduction (61) is low. Even with a glass substrate, a sufficient groove can be obtained. That is, a clean groove without any residue can be obtained.

However, when the metal film is aluminum and the substrate (1) is a glass substrate, heat cannot be sufficiently applied to the aluminum due to downward heat conduction, and a satisfactory groove cannot be obtained.

This is presumed to be because the irradiated portion cannot be heated to a temperature higher than the evaporation temperature by the light energy of the laser beam, and the melted state is maintained to some extent.

However, if the surface of the substrate is an organic resin film (7),
Since the heat conduction in the downward direction (61) is 1/5 that of glass, heat conduction in the horizontal direction like aluminum (62) (62 ')
Laser processing can be performed even on a material having a large value.

Further, in this case, a light-transmitting conductive film (68), that is, a light-transmitting conductive film (68) is further formed on the aluminum (67) as compared with the structure of FIG.
In the case of FIG. 1B, which has sublimability and does not have a very high thermal conductivity and is particularly formed of a material which becomes an antireflection film for laser light, the processability was further improved.

As a material of the light-transmitting conductive film, a non-oxide light-transmitting conductive film such as ITO, SnO ₂ , titanium oxide, chromium silicide, and nickel silicide can be used.

 FIG. 2 is a longitudinal sectional view showing the manufacturing process of this embodiment.

In the drawing, a flexible substrate (6) of a metal foil which has been subjected to an insulating surface treatment (6), for example, a stainless steel foil having a thickness of 10 to 200 μm, generally 20 to 50 μm, and a polyimide resin (7) of 0.1 to 5 μm
μm Generally, a substrate (1) formed to a thickness of about 1.5 μm, which is 60 cm long (left and right in the drawing) and 20 cm wide.
It is also in cm.

Thereafter, a first conductive film (2) was formed over the entire upper surface of the substrate (1). That is, 300 aluminum
Thickness of ~ 3000mm, and a further 1000mm of tin oxide film on top
The thickness was formed by a sputtering method, particularly a magnetron DC sputtering method. Furthermore, as the light-transmitting conductive film, a light-transmitting conductive film containing tin oxide to which a halogen element such as fluorine is added as a main component or ITO (tin oxide indium) (15)
(50-2000〜, typically 500-1500Å) was formed by magnetron sputtering.

For this reason, by using a target such as a metal such as aluminum and SnO _{2 as a} target in the same sputtering apparatus, it is possible to continuously form the target without setting the atmospheric pressure.

The aluminum as the first conductive film prevents the metal film from being back-diffused in the semiconductor by the subsequent heat treatment at 250 ° C. for 3 hours. Therefore, the tin oxide (3) blocking layer is effective. there were. Further, the tin oxide is effective because it has excellent ohmic contact with the P-type semiconductor layer on the upper surface. When this is made of ITO, the ohmic contact is excellent when an N-type semiconductor layer is formed on the upper surface thereof. In addition, it is effective to improve the reflection effect when the substantial optical path length is increased by the reflection of the long wavelength light of the incident light on the back electrode (first electrode).

Thereafter, an average output of 0.3 to 3 W (focal length: 40 mm) is applied from above the substrate by a YAG laser processing machine (manufactured by NEC), and a spot diameter of 20 to 70 μm φ, typically 40 μm φ, is controlled by a microcomputer to control the upper side. A laser beam was further irradiated, and a first groove (13) for a scribe line was formed by scanning, and a first electrode (37) was formed in each of the inter-element regions (31) and (11).

The groove (13) formed by LS has a width of about 50 μm and a length of 20
cm, and the depth was completely cut and separated to form the first electrode.

Thus, the width of the region constituting the first element (31) and the second element (11) was formed to be 5 to 40 mm, for example, 15 mm.

Thereafter, a non-single-crystal semiconductor layer to which a photovoltaic force is generated by irradiation with light by plasma CVD, photo-CVD or LPCVD, that is, a non-single-crystal semiconductor to which hydrogen or a halogen element having a PN or PIN junction is added, (3) to 0.3
.About.1.0 .mu.m, typically 0.7 .mu.m.

A typical example is a P-type (SixC _1-x 0 <x <1) semiconductor (about 3
00Å) (42) -one type of amorphous semiconductor or semi-amorphous silicon semiconductor (approximately 0.7 μm);
Non-single-crystal semiconductor having IN junction, or N-type microcrystalline silicon (about 300 °) semiconductor-I-type semiconductor (about 0.7 μm) -P-type microcrystalline Si semiconductor (about 200 °) -P-type Si _x C _1-x (About 50Å x
= 0.2-0.3) Semiconductor.

The non-single-crystal semiconductor (3) was formed with a uniform thickness over the entire surface.

Further, as shown in FIG. 2B, a second groove (18) was formed by a second LS process on the left side (first element side) of the first groove (13). .

Thus, the second groove (18) exposed the side surface or the side surface and the upper end surfaces (8) and (9) of the first electrode.

Further, in this embodiment, only the surface of the light-transmitting conductive film (15) of the first electrode (37) and the surface of the metal film (5) may be exposed. However, in order to improve the production yield, laser light is required. 0.1-1W
For example, all of the first electrode (37) in the depth direction was removed so that the voltage may be slightly varied at 0.8 W. as a result,
First on side (8) (side only or edge of side and top)
In FIG. (C), even if the ITO of the second electrode (38) is connected to the ITO by the connector (30), the contact resistance becomes an oxide-oxide contact (tin oxide-ITO contact) and an insulator barrier (insulation) is provided at the interface. ) Was not formed, so that there was no abnormality such as an increase in resistance during long-term use, which was practically preferable.

In FIG. 2, a second conductive film (5) and a connector (30) on the surface were further formed on the upper surface as shown in FIG. 1 (C).

Thereafter, a plurality of second electrodes (39) and (38) were isolated and formed by cutting and separating using a third LS, and a third groove (20) was obtained.

The second conductive film (4) is a light-transmitting conductive film (CTF) (4
5) was used.

As the CTF, ITO (a mixture mainly composed of indium oxide tin oxide) (45), which makes good ohmic contact with the N-type semiconductor, was formed to a thickness of 900 to 1500 °.
The light-transmitting conductive film (CTF) could be formed mainly of tin oxide. As a result, the second electrodes (38) and (39) were provided close to the semiconductor. this
As the CTF, a light-transmitting conductive film made of a non-oxide conductive film such as a chromium-silicon compound may be used.

These include electron beam evaporation or sputtering,
Using a CVD method including a CVD method and a photo-plasma CVD method, the semiconductor layer was formed at a temperature of 250 ° C. or less so as not to deteriorate the semiconductor layer.

Further, by removing the depth of the third groove not only by removing only the second electrode but also including the semiconductor layer (3) thereunder, and exposing the first electrode to a part thereof. , And isolation (20). This is because the laser light has a Gaussian distribution, and due to the variation in the irradiation intensity (power density) of the LS when forming the groove, a part of the second electrode remains and the two elements cannot be electrically separated. It was effective to prevent that.

Thus, as shown in FIG. 2 (C), a photoelectric conversion device in which a plurality of elements (31) and (11) are connected in series at the connecting portion (4) could be produced.

FIG. 2 (D) further shows that this embodiment is completed as a photoelectric conversion device. That is, a silicon nitride film (21) is uniformly formed to a thickness of 500 to 2000 mm as a passivation film by a plasma vapor deposition method or a photo-plasma vapor deposition method, and leakage current between the elements is generated by adsorption of moisture or the like. Further prevented.

 Further, an external lead-out terminal (23) is provided in a peripheral portion.

Thus, on the substrate (60 cm × 20 cm) as in this embodiment, each element is provided on a strip having a width of 14.35 mm × 192 mm in response to the irradiation light (10). 10mm, 4mm on the periphery, practically 580mm x 192mm
It has 40 steps inside and the effective area (192mm x 14.35mm 40 steps 1102cm
² or 91.8%).

As a result, when the segment has a conversion efficiency of 10.8% (1.05 cm ² ), the panel has a conversion efficiency of 5.8% (theoretically 7.3%), but the effective conversion efficiency is reduced due to the resistance of 40 stages connected in series (AM1 [100 mW / cm ² ]), the output power was 38.0 W.

And furthermore this panel e.g.
By combining 20cm in 3 or 4 series in a solid frame of aluminum sash or in a flexible frame made of carbon black, it is possible to package and install a 120cm x 40cm NEDO standard high power panel. is there.

In addition, for the NEDO standard panel, the upper surface of the photoelectric conversion device of this embodiment is bonded to the back surface of the glass substrate (the opposite side of the irradiation surface) by Seaflex to increase the mechanical strength against wind pressure, rain, etc. It is also effective.

Further, the details of this embodiment will be described below with reference to embodiments.

Embodiment 2 Another embodiment will be described with reference to the drawing of FIG.

That is, a metal foil substrate (1) having an insulating film
PI polyimide resin on the surface of a stainless steel foil with a thickness of μm
Substrate length 60cm, width coated with 1.5μm thickness using Q
20 cm was used.

Aluminum was further formed thereon to a thickness of 1200 mm by magnetron DC sputtering, and SnO ₂ was formed on the upper surface to a thickness of 1050 mm by magnetron DC sputtering using the same apparatus.

Next, after this, the first groove was formed with a spot diameter of 50 μm and an output of 0.
A 5 W YAG laser was controlled by a microcomputer at a scanning speed of 0.3 / min.

 The element regions (31) and (11) were 15 mm wide.

Thereafter, a non-single-crystal semiconductor having one PIN junction shown in FIG. 2 was manufactured by a known PCVD method, photo CVD method or photo plasma CVD method.

 Its total thickness was about 0.7 μm.

After this, the first groove was monitored on a television and shifted to the first element (31) side by 50 μm, spot diameter 50 μm, average output 0.5 W, room temperature, frequency 3 KHz, operation speed 60 cm / min. Then, a second groove (14) was formed by LS.

On the entire semiconductor thus obtained, ITO as a CTF was formed to an average film thickness of 700 ° by a sputtering method to form a second conductive film (5) and a connector (30).

Further, a third groove (20) is similarly formed by shifting to a depth of 50 μm from the second groove (14) toward the first element (31) side by LS, and FIG. Obtained.

At this time, as shown in the drawing, the depth of the third groove had reached the surface of the first electrode.

For this reason, the CTF and the semiconductor layer were completely removed.

The average output of the laser beam was 0.5 W, and the other conditions were the same as those for forming the second groove.

 Thus, FIG. 2 (C) was produced.

After the step of FIG. 2 (C), the edge of the panel is scanned with a laser beam output of 1 W to scan all of the first electrode, the semiconductor, and the second electrode in a rectangle 4 mm inside the glass edge, and the panel frame is formed. Electrical short circuit was prevented.

Thereafter, a passivation film (21) was formed at a temperature of 250 ° C. to a thickness of 1000 ° by a PCVD method or a photo-plasma CVD method.

As a result, 40 steps of 15 mm wide elements were made on a 20 cm x 60 cm panel.

The effective efficiency of the panel is 6.7 at AM1 (100 mW / cm ² )
%, Output 58.2W.

The effective area was 1102 cm ² , and 91.8% of the entire panel could be used effectively.

Example 3 In this example, a substrate having a size of 20 cm × 60 cm obtained by performing PIQ coating on a stainless steel foil having a thickness of 30 μm was used as a substrate. Further, five photoelectric conversion devices for a calculator having a size of 5 cm × 1 cm were connected in series on the same substrate.

The first electrode was aluminum. ITO was formed by the same sputtering method, and the lower second electrode was formed by LS.

Further, a non-single-crystal semiconductor having a NIP junction was laminated from the lower side in the same manner as in Example 1. Thereafter, light irradiation was performed on the back surface with a mercury lamp to polycrystallize the vicinity of the surface having a depth of 1000 mm or less. Further, a second electrode is formed on a P-type semiconductor by tin oxide (500
Å). Others are the same as the first embodiment.

The connecting part is 100 μm, and the external electrode is shown in Fig. 1 (A)
The left end and the right end of (B) are provided as an external lead electrode structure.

I was able to make 250 calculators at once.

500lx under fluorescent light as a good product with an effective conversion efficiency of 5.6% or more
Tested.

 As a result, a final production yield of 76% was obtained.

This was extremely effective in view of the fact that only 40 to 50% was obtained in the conventional method and the required area of the connecting portion was large.

 Others are the same as the first embodiment.

Furthermore, when cutting from this sheet, automatic cutting became possible by LS using strong pulse light of 10 to 15 W.

In this embodiment, a light-transmitting protective organic resin (22), for example, 2P (a resin that is cured by ultraviolet irradiation) is superposed on the upper light irradiation side, so that a photoelectric conversion device is formed between the metal layer and the organic resin. , And it has flexibility, and is extremely inexpensive for mass production.

In this embodiment, aluminum is mainly shown as a metal film having a thickness of 300 to 3000 mm. However, even when an aluminum alloy obtained by adding an additive to aluminum, for example, an aluminum alloy to which duralumin, copper, or silicon is added, when forming the organic resin film of the present embodiment, laser processing is performed similarly. Had the nature. Further, if it is not necessary to consider the reflectivity and the electric conductivity, laser processing was possible even with materials such as chromium, stainless steel, nickel, molybdenum, titanium and the like in the structure of this embodiment. In addition, even if this metal film is a multilayer film with aluminum formed on top of titanium and 10 to 300 mm (average), laser processing can be performed with little residue if the thickness is 3000 mm or less. Met.

〔The invention's effect〕

A metal film having a high thermal conductivity such as aluminum or an aluminum alloy is provided on an organic resin film having a thermal conductivity of 6.9 × 10 ⁻⁴ (cal / sec / cm / ° C.) or less, which is a configuration of the present invention, When a light-transmitting conductive film is provided over the metal to form a groove or a hole by laser light, a residue is formed on the metal film and the light-transmitting conductive film without damaging the organic resin film. Without forming a groove or a hole, it was possible to apply to the production of a photoelectric conversion device.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the principle of laser processing of this embodiment. FIG. 2 is a longitudinal sectional view showing a manufacturing process of the photoelectric conversion device of this embodiment.

Claims (4)

(57) [Claims] A step of forming a relatively conductive metal film on a substrate coated with an organic resin film having a thermal conductivity of 6.9 × 10 ⁻⁴ (cal / sec / cm / ° C.) or less; Forming a translucent conductive film having a sublimation property and a relatively low thermal conductivity on the metal film, and irradiating a pulse laser beam to form a groove in the metal film and the translucent conductive film; Or a step of forming an opening. 2. The laser processing method according to claim 1, wherein aluminum or an aluminum alloy mainly composed of aluminum is used as the metal film. 3. A first electrode provided on a substrate, a non-single-crystal semiconductor which generates photovoltaic power by light irradiation provided on the electrode, and a second electrode provided on the semiconductor When producing a photoelectric conversion device in which a plurality of photoelectric conversion elements having the following are connected in series, a substrate coated with an organic resin film having a thermal conductivity of 6.9 × 10 ⁻⁴ (cal / sec / cm / ° C.) or less A step of forming a metal film having relatively high conductivity, and has a sublimation property on the metal film,
Forming a light-transmitting conductive film having a relatively low thermal conductivity;
Irradiating the metal film and the translucent conductive film with pulsed laser light to form first grooves and form a plurality of first electrodes. 4. The laser processing method according to claim 3, wherein aluminum or an aluminum alloy containing aluminum as a main component is used as the metal film.