JPS62193182A - Manufacture of photovoltaic device - Google Patents

Abstract

PURPOSE:To prevent residual matters from being left on interfaces and and to prevent underlaying layers from being damaged thermally, by applying approximately uniform energy beam to a semiconductor film arranged to cover continuously all of a plurality of electrode films on a substrate for removing portions of the semiconductor film so as to separate the semiconductor film into a plurality of photoelectric conversion elements. CONSTITUTION:A transparent electrode film 11 of tin oxide is adhered on a substrate 10. Portions 11' of the film 11 are removed by applying laser beams thereto for separating and forming individual transparent electrode film sections 11a, 11b. these portions 11a, 11b... provide spaces between adjacent transparent electrode film sections. An amorphous semiconductor film 12 of amorphous silicon or the like is adhered over the substrate 10, and portions 12' are removed by applying laser beams for separating and forming semiconductor film sections 12a, 12b.... A back electrode film 13 of a single aluminium layer or of a bi-layer structure consisting of aluminium and titanium or the like is adhered all over the substrate 10 including the exposed portions. In the final step, portions 13a, 13b... are removed by applying laser beams. Though some low-resistance layer is left on the surface, it does not raise substantial problem if an illuminance is ordinary. Thus, the present method can prevent residual matters from being left on the removal interface and can prevent underlaying layers from being damaged thermally.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method of manufacturing a photovoltaic device using an energy beam such as a laser beam.

(b) Conventional technology Figure 1 is disclosed in U.S. Pat. No. 4,281,208 and shows the basic structure of a photovoltaic device that has already been put into practical use. Insulating and translucent substrates such as (2a) (2b) (2c
)... are transparent electrode films deposited at regular intervals on the substrate (1), (3a) (3bH3c)... are amorphous silicon etc. that have been poorly deposited on each transparent electrode film. The amorphous semiconductor films (4a), (4b), (4c), etc. are formed by superimposing each amorphous material on a conductor film, and each transparent electrode film (2b) on the right
(2c) Each of the transparent electrode films (2a), (2b), (2c), and back electrode films (4a), (4b), (4c), etc. that can be partially overlapped with... A photoelectric conversion element (5a>(5b)(5c)...) is constituted by the laminate.

Each amorphous semiconductor film (3a) (3b) (3c)...
It contains, for example, a PIN junction parallel to the film surface, and therefore includes a transparent substrate (1) and a transparent electrode film (2a) (2b) (
2c) When light is incident sequentially through..., a photovoltaic force is generated. Each amorphous semiconductor film (3a) (3bH3c)
・The photovoltaic force generated inside the back surface N, the electrode film 4a) (4
bH4c)... are added in series by connection.

Usually, photolithographic techniques are used in photovoltaic devices having a similar structure or are excellent in precision processing. In the case of this technique, the process of depositing a transparent electrode film on the entire surface of the substrate (1) and the separation of each individual transparent electrode film (2a), (2b), and (2c) by photoresist and etching are performed. The step of removing the adjacent spaced parts of the transparent electrode films (2a), (2b, and 2c), and the step of removing the substrate (1
) A step of depositing an amorphous semiconductor film on the entire upper surface, and each individual amorphous semiconductor film by photoresist and etching (
The separation of the amorphous semiconductor films (3a), (3b), (3c), . . . , and the removal of adjacent spacing portions of the amorphous semiconductor films (3a, 3b, 3c), . . . are repeated in sequence.

However, although photo-etching technology is excellent in fine processing, it tends to cause defects in the amorphous semiconductor film due to pinholes or peeling at the periphery of the photoresist that defines the etching pattern.

The prior art disclosed in Japanese Unexamined Patent Publication No. 57-12568 provides the above-mentioned adjacent spacing by burning out the film by laser beam irradiation, and does not use the photoresist required in photolithography, or any wet process. This technique, which has excellent precision processing properties, is extremely effective in solving the above problems.

However, as mentioned above, while laser processing that does not use any wet process is extremely effective in terms of precision processing, it does have problems as shown in enlarged views of the main parts in Figures 2 (a) to (c). Contains. That is, each photoelectric conversion element (
5a) (5b)... Transparent electrode film divided into parts (
2a) (2b)... An amorphous semiconductor film is formed continuously over the top, and the adjacent semiconductor film is irradiated with a Lede beam (LB>) in order to divide the semiconductor film into each photoelectric transformer. When the semiconductor film located in the gap is removed, as shown in FIG. 2(a), the portion of the semiconductor film that has been completely irradiated with the peripheral edge of the laser beam (LB) is removed by the peripheral edge of the laser beam (LB). Because it does not have enough energy, it is annealed and microcrystallized, or crystallized, resulting in a low resistance Ji.
1 (6a) (6b), or residues of the molten semiconductor film (7) remain at the interface of the removed portion as shown in Figure 2(b), resulting in the formation of a predetermined pattern accurately. cannot be removed. The residue remaining at the interface of the removed part (
7) and low resistance layer (6a>(6b)), since the energy density distribution in the laser beam (LB) is a normal distribution, that is, a Gaussian distribution, it is necessary to irradiate both sides of the adjacent gap to be removed. This is thought to occur as a result of a lower energy distribution at the periphery than at the center.Furthermore, the irradiated laser beam (LB) has a Gaussian distribution in which the periphery has a lower energy distribution than at the center as described above. When the semiconductor film is removed, the photoelectric conversion elements (5a) (5b)
)・Not only are semiconductor films <3a) (3b)... divided into adjacent photoelectric conversion elements <5a) (5b)
・Transparent electrode film (2b
)..., and the exposed length cannot be reduced as much as possible without causing an increase in the series resistance component, thus requiring a wide laser beam.
As a result, the center becomes extremely high in energy, causing thermal damage (8) as shown in FIG. 2(c).

In particular, the formation of the low resistance layer (6a><6b) of the semiconductor film is performed by irradiating the semiconductor film (3a><6b) with a laser beam (LB).
Even if H3b) can be physically separated, the same photoelectric conversion element (5b) can be separated through this low resistance layer (6b).
transparent electrode film (2b)... and back side 1#i film (4b)...
This causes the photoelectric conversion element (5b) to be short-circuited.

(c) Problems to be Solved by the Invention The present invention solves the formation of a low resistance layer at the interface of the removed portion of the semiconductor film, which causes the short circuit accident as described above, and
This is intended to solve the problem of residual residue remaining at the interface of the removed portion and thermal damage to the underlying layer.

(d) Means for Solving the Problems In order to solve the above-mentioned problems, the present invention aims to solve the above-mentioned problems by using semiconductors arranged continuously over a plurality of substrates (II+electrode film-H) constituting a plurality of photoelectric conversion elements. Two characteristics are that the semiconductor film in the irradiated area is removed by irradiating the film with an energy beam whose energy distribution is substantially uniform over the irradiated area, and that the semiconductor film is divided into a plurality of photoelectric conversion elements.

(e) Effect As described above, by irradiating a predetermined location of the semiconductor film disposed on the substrate side electrode film with an energy beam whose energy distribution is substantially uniform over the irradiation area, the semiconductor film portion in the irradiation area is In addition, only the underlying substrate side T! is removed without substantially forming a low resistance layer. Thermal damage to the L electrode film can be reduced.

(f) Example FIGS. 3 to 8 show examples of the method of the present invention in the order of steps.

In the process shown in Figure 1, the thickness is 1m to 3mm and the surface is 10c.
A transparent electrode film (11) made of tin oxide (Sn02) with a thickness of 2,000 to 5,000 thick can be deposited on the entire surface of a substrate (10) of transparent glass or the like with a size of about Qcm to 1 m x 1 m.

In the process shown in FIG.
a) (llb>(llc)... is formed separately.The wavelength of the laser to be used is suitable so that it is hardly absorbed by the substrate (10), and the wavelength of the laser used is 0.
A preferred embodiment is a pulse oscillation type with a wavelength of 35 μm to 2.5 μm. A preferred embodiment is Nd with a wavelength of 1.06 μm, a metal density of 13 J/crr12, and a pulse frequency of 3 KHz:
It is a YAG laser, and the interval between adjacent interval parts (11') (
Ll) is set to approximately 1100u.

In the process shown in FIG.
b) The entire surface of the substrate (10) including the surface of (llc) has a thickness of 5,000 to 700 mm, which effectively contributes to photoelectric conversion.
An amorphous semiconductor film (12) such as 41-crystalline silicon (a-3i) is rejuvenated. The semiconductor film (12) contains a PIN junction parallel to the film surface, and therefore, more specifically, a P-type amorphous silicon carbide is first deposited, and then a 1-type and an N-type non-conductor are deposited. Crystalline silicon is deposited in successive layers.

In the process shown in FIG. 6, adjacent spacing parts <12') are removed by laser beam irradiation, and each individual amorphous semiconductor film (
12aH12bH12c)... are separated and formed.

A feature of this process is that the energy distribution of the usable laser beam has a substantially uniform distribution over the irradiation area. Figure 9 shows the temperature distribution on the irradiated surface when the irradiated area is irradiated with a circular laser beam with a substantially uniform energy distribution and the irradiated area has a radius of 40 μm. It is drawn in the radial direction starting from the center. As is clear from Fig. 9, the temperature distribution of a laser beam with an approximately uniform energy distribution results in an approximately constant high temperature distribution corresponding to the energy distribution for the irradiation area, and a slight temperature distribution at the interface of the irradiation area. Although a temperature gradient due to heat conduction of the irradiated medium is observed, the temperature drops sharply to the room temperature of the non-irradiated area, and the overall distribution is approximately rectangular.

-1, FIG. 10 depicts the temperature distribution on the irradiated surface when a conventional laser beam having a Gaussian distribution is used in the radial direction starting from the center, similar to FIG. 9. The temperature reached at the center of the process is the same in both Figures 9 and 10, and for example, by irradiating with such a laser beam, an amorphous semiconductor with a thickness of 5000 mm can be removed. , the lower transparent electrode film (lla
) (The absolute temperature is set at about 1400K to avoid thermal damage to the ILC).

Figure 11 shows the depth and thickness when the energy distribution is approximately uniform and the temperature distribution on the irradiated surface, that is, the surface of the amorphous semiconductor film (12), follows the approximately rectangular distribution shown in Figure 8. The directional temperature distribution is simulated using 100 isothermal lines. The sample targeted for simulation was a Sn film with a thickness of 1000 nm on a glass substrate (10).
It has a structure in which a transparent electrode film (11) consisting of ○2 and an amorphous silicon semiconductor film (12) with a film thickness of 5000 are laminated. As a result of this phenomenon, when a temperature of about 1400 K is applied to the surface of the semiconductor film (12), the isothermal distribution width in the thickness direction (the deep direction) of the semiconductor film (12) is wide, and the SnO2 transparent electrode Even at the interface with the film (11), the semiconductor film (12) is at a temperature of about 1200 F or below, which is sufficient to remove the semiconductor film (12). On the other hand, the isothermal distribution width in the radial direction, that is, in the surface direction, is extremely narrow because the interfacial temperature gradient at the irradiated surface falls steeply.

Incidentally, although the temperature at which the amorphous silicon semiconductor film (12) can be removed varies somewhat depending on the method and conditions for forming the semiconductor film (12), it is generally about (-120°C as described above).
0, while the temperature at which it is annealed and converted into a low resistance layer ranges from about 1000K to the removal temperature of about 1200K.
It is between the machining and machining rooms. Therefore, in the temperature range above 1200°C, the semiconductor film (
12) is removed and the semiconductor film in the temperature range of 1000I (~120OK) is converted into a low resistance layer.Assuming that the semiconductor film (12) is removed in a region with a radius of about 38 μm from the center, and the removed interface is However, only a negligible low resistance layer is formed.

On the other hand, when using a conventional laser beam with a Gaussian distribution, the temperature distribution on the irradiated surface exhibits a Gauss+7 Gauss distribution equivalent to the energy distribution, as shown in Figure 1O. When the temperature distribution in the depth direction is simulated using equal crosstalk every 100 times, it becomes as shown in FIG. 12. That is, although the m degree distribution in the depth direction at the center of the irradiated area is equal to the uniform distribution shown in Figure 11, the isothermal distribution width in the radial direction is due to the gentle temperature gradient on the irradiated surface. , 1200 to 100O
Approximately 8 μm on the surface in the K annealing temperature range
, has a width of about 11 m at the interface with the SnO2 transparent electrode film. Therefore, in processing using a conventional Gaussian Lely' beam, even if a semiconductor film in the temperature range of 1200 KLIJ or above is removed, the semiconductor film will be removed over a wide range of approximately 8 μm to 11 μm in the radial direction from the removed interface. It had been converted into a low resistance layer. Furthermore, in the conventional processing, the width of removal of the semiconductor film is less than 10 μm in radius, which is narrower than about 38 m in the processing shown in FIG. As a result, if we try to widen the removal width of the semiconductor film in order to electrically connect in series through the exposed portion of the transparent electrode film exposed by removing the semiconductor film that disconnects adjacent photoelectric conversion elements, ( a) A method of increasing the intensity of the laser beam and bringing the center into a high temperature state to widen the isothermal distribution width below 1200℃, and (b) increasing the number of scans of the laser beam instead of increasing the intensity of the laser beam. There are two possible methods.

However, in both of these methods, the formation of a low resistance layer cannot be avoided, and in method (a), the center of the laser beam is in an extremely high energy state, causing thermal damage to the underlying transparent electrode film. In the case of method (b), the number of scans increases, resulting in a decrease in work efficiency. On the other hand, in this embodiment, which uses a laser beam with a substantially uniform energy distribution over the irradiation area, there is no substantial formation of a low-resistance layer, and no thermal damage is caused to the underlying film.
Furthermore, the processing range can be expanded.

As shown in FIG. 15, the laser beam (LBt) having a substantially uniform energy distribution over the irradiation area is placed in the optical path of a normal laser beam <LBl) having a Gaussian energy distribution. An iris (21) having a square or round hole (20) having an open diameter of approximately 25% of the incident diameter starting from the center is arranged, and the round hole (20) of the iris (21) is The laser beam that passed (
LB2) is guided to a condensing lens 22), and the laser beam (LB1) condensed by the condensing lens (22) is irradiated onto the shipwreck surface under the following conditions. (21) Condensing lens (22)
If the distance to the center of is a, the distance from the center of the condenser lens (22) to the surface to be processed is b, and the focal length of the condenser lens (22) is r, - 10-'' - a b f' When the following is satisfied, the energy distribution of the laser beam (LB1) irradiated onto the surface to be processed becomes a substantially uniform distribution.

In the process shown in FIG.
2), the amorphous semiconductor film (1)
2) are individually separated into amorphous semiconductor films (12a) (1
2b) (12C)- and transparent electrode film (lla>(llb
) (llc)... including each exposed portion of the board <10)
On the upper surface, there is a single layer aluminum structure with a thickness of about 2000 Å or more, or a two-layer structure in which titanium or titanium-silver is stacked on the aluminum, or a back surface TL electrode film 13) in which a two-layer structure is stacked double. be made younger.

In the final step in FIG. 8, the back electrode film <13> is attached to the amorphous semiconductor film in FIG. As in the separation step (12), each individual back electrode film (1
3a) (13b>(13c)). As a result, each individually divided transparent electrode film (lla>(llb)
(llc)-・, amorphous semiconductor film (12a) (12b)
(12c) and back electrode film (13a) (13b) (
13c) Photoelectric transformer cable-T (14a) consisting of a laminate of
<14b) (14c). are electrically connected in series on the substrate (10>).

Figure 13 shows a laser beam starting from the center of the irradiated surface when irradiating the irradiated area with a laser beam having a substantially uniform energy distribution and a circular irradiated area as shown in Figure @9. The temperature distribution in the depth and thickness direction when dividing the back electrode film (13) using a laser beam whose temperature distribution in the radial direction exhibits a substantially rectangular distribution was simulated using equimixture lines every 200. This is what I did. The sample to be simulated was a S film with a thickness of 1000A on the glass substrate (10) used in the previous simulation.
n02 Transparent'! t [membrane (11),! :, film thickness 5000
The human amorphous material is made into a laminate with a conductive film (12), and the film thickness is 5.
000 aluminum single layer back electrode film (13)
was superimposed. As a result of this, the melting point of Aluminum 7 is approximately 930 at the insulation temperature.
Radial 38a from the center of the temperature distribution on this 930
However, the back electrode film part of the aluminum single layer structure was removed. On the other hand, according to Nyumireshin who refuses, 100
A slight temperature distribution above OK also exists on the amorphous silicon semiconductor film (12) side that is in contact with the back electrode film portion.

Although the temperature distribution above 1000°C means that the amorphous silicon semiconductor film (12) in the above region is microcrystallized or completely crystallized and converted into a low resistance layer, the formation of the low resistance layer is Since it remains in a very shallow region from the surface, it is of virtually negligible magnitude.

Figure 14 uses a conventional laser beam with a Gaussian distribution, and is almost the same as the laser processing shown in Figure 13 above.
This is a temperature distribution simulation in the depth direction using equimixture lines every 200 when trying to obtain the removal width of 3). As a result of the simulation, the removal width of the back electrode film (13) is approximately the same as that of the laser processing shown in FIG. 13, but because the temperature gradient is gentle, the temperature distribution width near the melting point of the back electrode film (13) is Melting and dripping of the electrode film forming material occurs widely at the removal interface of the back electrode film, and not only the region north of 1200 of the amorphous silicon semiconductor film (12) is removed, but also the removal interface 1200K-1O
It can be seen that the OQK region was converted into a low resistance layer.

Therefore, the back electrode films (+3a) (13b) (13c), which are divided in the final step of FIG. 8, are physically and electrically separated, and the adjacent photoelectric conversion elements (14a) (14
b) (14c)... are reliably connected in series.

In addition, in the final step shown in FIG. 8 above, the back electrode film (+3a
) (t3b) (13cm- is each amorphous semiconductor film (12a
) (12bH12c)...Since the removal has been completed by irradiation with a laser beam with a substantially uniform energy distribution, the surface portion of the amorphous semiconductor film exposed in such a removed area has the above-mentioned appearance. Although some low-resistance layer is formed, this low-resistance layer is usually (7) illuminance <400 L u even when the photovoltaic device is used up under sunlight or indoor light.
x or more), then ￥qualitatively! There is no A title. Only about 200
It is also said that under low illuminance below Lux, adverse effects such as leakage due to the low resistance layer occur. In such a case, the low-resistance layer may be removed by performing the backside etching (plasma etching), or the backside electrode film (13) may be removed in the process of removing the backside electrode film (13) as shown in FIG. Instead of selectively removing only the pole film, the underlying amorphous semiconductor film (12) may also be removed at the same time.

Furthermore, even in the final step shown in FIG. 8 in the above-described embodiment, the energy distribution of the usable laser beam was approximately uniform over the irradiation area as in the step shown in FIG. Laser beams with the same Gaussian distribution may also be used. However, in this case, a low-resistance layer is formed in the lower amorphous semiconductor film portion, which may cause a short circuit between adjacent charge conversion elements (14a) (14bH14c), so the low-resistance layer is divided. Because it has to be removed and removed, a slight loss of workability is inevitable.

(g) Effect of full sun and moon As is clear from the above explanation, the manufacturing method of the present invention produces an energy beam whose energy distribution is approximately uniform over the irradiation area.
Since the substrate side is irradiated to the predetermined location of the semi-41 film placed on the polar film, only the semiconductor film portion in the 5 irradiation area can be removed without substantially forming a low resistance layer, and the adjacent It is possible to prevent a short-circuit accident between the photoelectric conversion elements or one photoelectric conversion element, and also to avoid the occurrence of residual residue at the removed interface and thermal damage to the underlying layer.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the basic structure of a photovoltaic device, Figures 2 (a) to (c) are enlarged cross-sectional views of important parts to explain the drawbacks of the conventional method, and Figures 3 to 8 are 9 is a temperature distribution characteristic diagram illustrating the energy distribution of the laser beam used in the method of the present invention, and FIG. 10 is a temperature distribution characteristic diagram illustrating the energy distribution of the conventional method. ,
11 and 12 are isothermal distribution characteristic diagrams when an amorphous silicon semiconductor film is irradiated with a laser beam having the energy distribution shown in FIGS. 9 and 10, respectively. Figures 9 and 10 show isothermal distribution characteristics when the laser beam with the energy distribution is irradiated onto the aluminum back electrode film, and Figure 15 shows the fundamental method for creating the laser beam used in Method No. 5 of the present invention. FIG. 16 is a cross-sectional view showing another embodiment of the final step of the method of the present invention. (10)--Substrate, (11) (lla) (llb) (l
lc) --- Toru 81! Electrode film, (12) 12a) (1
2b) (12c)・Amorphous semi-tetrabody membrane, (13) (13a
)(13b)(13c)--Back electrode film, (14a)<
14b) (14c)...Photoelectric conversion element, (21)...Iris, (22)...Condensing lens.

Claims (1)

[Claims] (1) A method for manufacturing a photovoltaic device in which a plurality of photoelectric conversion elements are electrically connected in series on an insulating surface of a substrate, wherein the photovoltaic devices are connected in series on a plurality of substrate-side electrode films constituting the plurality of photoelectric conversion elements. The semiconductor film arranged across the irradiation area is irradiated with an energy beam whose energy distribution is approximately uniform over the irradiation area, the semiconductor film in the irradiation area is removed, and the semiconductor film is divided into a plurality of photoelectric conversion elements. A method for manufacturing a photovoltaic device characterized by: