JPS60140881A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the formation of a metal film by plating at the same time with a uniform p<+> layer by a method wherein a paste substance mainly made of Al powder, a kind or more of metals of Sn, In, and Sb, and a metal forming a high melting point alloy with Al is printed on a substrate and calcined. CONSTITUTION:Al paste compounded with at least a kind of metal selected out of Sn, In, and Sb is printed on the substrate 1 of silicon or the like and calcined, when a uniform p<+> layer 3 is formed, and the metal film by plating can be formed on the Al layer formed at the same time. The addition of the metal forming a high melting point alloy with Al into this Al paste eliminates the cohesion liable to generate in the Al layer during calcination or the generation of cracks. Particularly Co, Cr, Mn, Mo, Ti, Zr, B, or W is effective as the metal forming a high melting point alloy with Al that is very effective to form a smooth Al layer and a uniform p<+> layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device.
) and a method for manufacturing an electrode.

[Background of the invention]

An example of a semiconductor element and an example of an alternative photovoltaic configuration of a solar cell are shown in the figure.A light-receiving surface electrode is provided on the light-receiving surface of the 81-substrate having an n+/p/p+ junction formed thereon, and a light-receiving surface electrode on the back surface. 4. Back electrode 5
'(r-formed structure. Furthermore, an anti-reflection film or the like is generally not provided.

An important issue in this solar cell IC is to reduce manufacturing costs, and the method for forming the light-receiving surface electrode 4 and back surface electrode 5 is also low-cost plating or printing methods instead of the conventional vacuum deposition method. I'm starting to think about it. In particular, printing methods are being widely studied because they are easy to automate and have high productivity.

This printing method is also widely used to form P"l@3.
In this method, a paste-like substance (hereinafter referred to as AfiIn paste) made by kneading Aβ powder, an organic binder, and an organic solvent is applied by screen printing or the like, and then baked. Many H2 pastes for this purpose are commercially available for forming the P+ layer of solar cells.

However, when the P+ layer 3 and the back electrode 4 were formed using a commercially available In paste, the following problem occurred.

That is, when fired in the air (in an oxidizing atmosphere), the crane layer is oxidized and becomes an insulator (Afi20x), so the lever in the post-process is removed and the back side is made into a polar 4 using Ag paste or the like again.
This has the drawback that the process is complicated and the cost of the solar cell increases because it has to be completely formed. To prevent this,
The paste was fired in an inert atmosphere (N2.Ar+He
However, in the case of pre-market 2 pastes, agglomerations and cracks occur in the first layer after firing, resulting in a uniform P paste.
There was also the drawback that the solar cells could not be formed and the efficiency of the solar cell would decrease due to the formation of the pores.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an inexpensive and highly effective method for manufacturing semiconductor devices such as solar cells.

[Summary of the invention]

In the method for manufacturing a semiconductor device of the present invention, in forming an impurity layer of the same conductivity type and a dielectric layer on one main surface of a P-type silicon substrate, at least one type of metal selected from A2 powder and zsn+In+sb, It is characterized by applying a paste-like substance whose main components are A13 . and a metal forming a high melting point alloy, and then firing.

The present invention differs from conventional methods in that a paste-like material having the above composition (hereinafter abbreviated as He2 paste) is used to form the same conductive impurity layer and electrode. This technique is based on the fact that when this Aβ paste is printed on a substrate such as silicon and fired, a uniform P+ layer can be formed, and furthermore, an AR and paste fired layer (hereinafter referred to as A) can be formed at the same time.
This is due to the discovery that a metal film can be formed by plating on the lt layer), which was impossible with conventional commercially available products. That is, by plating one layer on this layer with Ushida wettability (metal (e.g., C'n rNj, +Pl) +Sn, etc.), etching of the Afi layer, printing of Ag paste, which was previously necessary, The process of forming electrodes for soldering by firing is completely unnecessary.

AI used in the present invention! , about the ingredients of the paste.

Further details are provided below. It is preferable that the Alt powder, which is the main component, has an average particle size of less than 10 μm J′,L.

When screen printing is performed using a material larger than 10 μm, clogging tends to occur and there is a problem in continuous printing.

I cut it. The powder-like shape of AIt powder is most preferably scaly.

When a single-piece AiV powder is used, a uniform AIt layer can be formed.

σ) AIt powder contains stearic acid and
Preferably, the material is coated with aluminum stearate or zinc stearate.

Adding at least one type of metal selected from Sn+IrzSb to this paste is very effective when using the AIt layer as it is as an electrode. Blending these metals 7
When the tAg paste is printed on a substrate such as all-silicon and fired, a uniform P+ layer is formed.At the same time, a covering A2 layer is formed.Secondly, a metal film is formed by plating, which was conventionally difficult to achieve. can.

By this process, the electrical resistance of the back electrode 5 can be reduced, and when gold FA with good solder wettability (for example, Cu + Ni + Pb + Sn, etc.) is used as the plating metal film, the soldering becomes a corner layer.

Selected from Sn+In+Sb 71. The blending ratio of at least one metal is (10 to 150 vofi%)/A1, preferably (25 to 100 voR%)/A! with respect to 100 vojlt of Ait powder. It is necessary that 10Won%/k11.11. ．． ! If the amount is less than 11, the above-mentioned effect of adding Sn+In+Sb will hardly be obtained. On the other hand, if it exceeds 150 voβ%/A,9, the electrical resistance of the formed A1 layer increases, leading to a decrease in cell efficiency.

In addition, adding a metal that forms a high melting point alloy with Al to this Al paste eliminates agglomeration and cracking that easily occur in the Au layer during firing, and creates a smooth AIt layer and uniform P conductivity. Very effective for forming layers.

In particular, Go+ is a metal that forms a high melting point alloy with A1.
Cr+Mn+MO+Ti+Zr+El+W is effective.

The blending ratio is (5 to 5
ovon%) AIt. If the blending ratio is 5v02%/d, l-9 less, the A2 mentioned earlier
There is almost no effect of adding metals that form high melting point alloys. Furthermore, if the value increases by 30 vofi%/AIJ, f), the electrical resistance of the formed A2 layer increases, resulting in a decrease in one cell compared to other vehicles.

Next, the other constituent components, the organic binder and organic solvent, will be described. These may be similar to those used in conventional thick film screen printing pastes. The organic binder is preferably a cellulose compound or a polymethacrylate compound, and the organic solvent is particularly preferably a polyhydric alcohol.

Next, the process of firing the Al paste will be described.

Firing temperature is 660-900℃, preferably 700-80℃
0℃ is strange. Since Au does not melt at temperatures lower than 660° C., a uniform P conductive layer and A2 layer are formed.

At temperatures higher than fC900° C., the junction depth of the n-junction layer formed on the light-receiving surface side changes, resulting in a decrease in cell efficiency.

The firing time is preferably 2 to 60 minutes, preferably 3 to 30 minutes.

If it is shorter than 2 minutes, the formation of the He1 layer and the P conductive layer will be incomplete, making it impossible to obtain a highly efficient cell. Also, if you bake for longer than 60 minutes, it will be the same as firing at a higher temperature than 900℃.
Cell efficiency decreases after 1 tsubo.

The melting atmosphere has an oxygen concentration of 500 ppm or less, preferably 5
An inert gas atmosphere of 0 ppm or less is preferable. 300PPn
When the concentration is higher than n, the oxidation of the A2 layer progresses and the electrical resistance increases, resulting in a decrease in cell mobility.

Inert gases include N2+ArTHe, but N2 is preferred because it is industrially easily obtainable and inexpensive.

Hereinafter, the present invention will be explained by examples.

Example 1 A P-type silicon substrate 1 (specific resistance: 19 m) was used as a junction-forming silicon substrate for solar cells, as shown in the figure.

A round wafer with a diameter of 3 inches was formed with a layer of 0.2 to 0.4 μm Q,')n+10 layers (surface sheet resistance 50JJ/mouth) by ion implantation on the surface.

The 8R paste contains scaly AJ with an average particle size of 2 μm or less coated with stearic acid on one surface, and 10 cp.
95 parts by weight of α-terpineol and 5 parts by weight of L cellulose of S
Thoroughly knead while adding the viscous liquid dissolved in the weight part to obtain a total viscosity of 15 pa-s (zυ speed 1f101] sθc-1
), and this d paste contains Sn+In+S
Various combinations of at least one kind of metal powder (average particle size of 5 μm or less) selected from b.
15 Volt%/Afl of CO was used.

The stiff Al paste was screen printed on the back side of the silicon substrate mentioned above, and after drying at 150°C for 10 minutes, the substrate was placed in a nitrogen gas atmosphere (oxygen concentration 2.6 ppm).
) for 5 minutes at 750°C. After this, a light-receiving surface electrode 4 was formed.

From the current-voltage characteristics of the solar cell produced in this way,
The open circuit voltage (Voa) and fill factor (F-1t')' were investigated.

In addition, we evaluated the appearance of the back electrode 4 (agglomeration of the Al layer, presence or absence of Kravuk), and electrolytic nickel plating (liquid composition: nickel sulfamate 150g/β, nickel chloride 10g/β).
Plating precipitation properties were evaluated using boric acid (4 og/A).

3-8 in Table 1. As shown in Nα9-14.

According to the method of the present invention, high Vocr, high F'P'' cell band properties were obtained, and furthermore, an AQ layer with good plating precipitation without cracks or agglomerations was obtained.

When the metal of In + Sn + S b and the metal C0 that forms a high melting point alloy with AJ2 are not added at all, such as Na1 in the first group, agglomeration and cracks occur in the A1 layer,
Plating precipitation properties were also poor. Furthermore, a P soil layer with uniform agglomeration and cracking was formed, and the %VOOIFF' was also low, resulting in a decrease in efficiency.

Like Na2 in Table 1, I n + S n + S
In the case of b without adding gold ingots, the plating precipitation was poor, and a decrease in FF due to this was observed.

Also, as in Nl19 in Table 1, no matter how many n metals Sn+In+SbO are used, the amount added is 150vofi%/An
, as Jniji increased, Voc+F'F decreased.

In addition, as a result of conducting a solder wettability test on the N14 to N14 plating with good plating precipitation properties, it was found that the solder wettability test was very good.
showed his sexuality.

Example Z The same substrate as in Example 1 was used as a silicon substrate for forming a junction for a solar cell.

The paste was thoroughly kneaded while adding scaly A-tan with an average particle size of 2 μm or less and a viscous liquid prepared by dissolving 20 parts by weight of polyisobutyl methacrylate in 80 parts by weight of α-terpineol, until the viscosity was approximately Particle size 1
Add a Sn powder bed of 0 μm or less 75voji%/4fi,
Furthermore, a blade with a metal forming a high melting point alloy with hft was used.

This A1 paste was printed in the same manner as in Example 1.

After drying and baking, a light-receiving surface electrode 4 was formed.

Characteristics of the produced solar cell and appearance of the A1 layer.

Plating precipitation? +7 lol It was investigated in the same manner as in Example 1. The plating solution is electrical steel plating solution (liquid composition: birophosphate steel 90g
zl, potassium pyrophosphate 350g/J1. Ammonia 3m
Wabe) was used.

Nα17-20 in Table 2. As shown in Sou 22-33.

By using the method of the present invention, cell characteristics of high VOO+high FF can be obtained, and furthermore, an A1 layer with good plating precipitation properties without cracks or agglomerations can be obtained.

If a metal that forms a high melting point alloy with Afi is not added or added in a small amount, such as Na15 and 16 in Table 2, agglomeration and cracks will occur in the A2 layer, and furthermore, Vo
c+FF' also decreased.

As shown in Table 2, Na21, the cutting edge amount is 30vofi%/
In the case of d or more, the precipitation property of the Cu plating film decreased, and Voo+FF' also decreased accordingly. In addition, among the samples with good plating precipitation properties in Table 2, similar to Example 1, the solder wettability was good.

Examples & The same silicon substrate as in Example 1 was used as a junction-forming silicon substrate for solar cells. The paste was prepared by thoroughly kneading a scaly A2 surface coated with zinc stearate and having an average particle diameter of 2 μm or less while adding a viscous solution prepared by dissolving 5 parts by weight of ethyl cellulose (%10 cps) in 95 parts by weight of α-terpineol. When the viscosity f' was approximately 15 Pa-s (speed 1i100 sec'), the average particle size was 10 μ.
m or less sb powder wood 75VOR%/An1MO powder song 15v
o1%/A1711] was used as A2 paste.

After printing and drying this 0 paste in the same manner as in Example 1,
q in the N2 atmosphere! Firing was performed using a combination of r types of conditions.

After this, the light-receiving surface electrode 4 was formed. The plating film deposition property is
Evaluation was performed using the same electrolytic N1 plating solution as in Example 1.

Na35, Na37-40 in Table 3. Na42~4
5. As shown in Nos. 1145 to 46, by using the method of the present invention, cell characteristics of high V o a + high F l' can be obtained, and furthermore, an A2 layer with good plating precipitation without cracks or agglomerations can be obtained. I found out that I can get it.

In addition, as in Na34 in Table 6, at a firing temperature below the melting point of An, the A1 layer is not formed and the precipitation of the Ni plating film is poor. Furthermore, r and Voa+FP have also become lower.

In addition, when the firing time was shorter than 2 minutes, such as Na36 in Table 3, the firing of the A1 layer was insufficient, resulting in the same results as N[L34 in Table 356.

Magnet 41 in Table 3 whose firing time is not long, N in Table 3
If the firing temperature is too high like A47, the bottle 2 becomes thicker and the short circuit current decreases, resulting in Voc +
F'F' decreases.

Oxygen like Na44 in Table 3! If 1 degree is too high, Af
The i-layer is oxidized, leading to a decrease in AFF and the precipitation of the Ni plating film.

In addition, the solder wettability was good for all of the samples with good plating precipitation properties in Table 3.

〔Effect of the invention〕

As described above, the method of manufacturing semiconductor devices, especially solar cells, using the method of the present invention is performed in an inert atmosphere, which is essential for preventing oxidation of the A1 layer, which has been difficult in the past when forming the P soil layer and the back electrode. It is now possible to bake in

It is also possible to perform plating on the first and second layers. This LV
? -The removal of one layer and the process of forming electrodes for soldering, which were required in the past, are no longer necessary, making it possible to significantly reduce the number of processes and manufacturing costs.

[Brief explanation of drawings]

The figure is a cross-sectional view showing a typical configuration of a solar cell. 1...Silicon substrate 2...N soil layer 6...P soil layer 4...Light receiving surface electrode 5...Back surface electrode Patent attorney Akio Takahashi

Claims (1)

[Claims] 1. In forming an impurity layer and an electrode of the same conductivity type on one main surface of a P-type silicon substrate, AL powder and S
Manufacturing a semiconductor device characterized by applying a paste-like substance mainly consisting of at least one metal selected from n, In+Sb, and a metal forming a high melting point alloy with A1, and then firing. Method. 2. The semiconductor device according to claim 1, wherein the Aμ powder is scaly and optionally surface coated with stearic acid, aluminum stearate, or zinc stearate. manufacturing method. l The blending ratio of at least one metal selected from Sn+In and Sb is 10 to 150 VoJ with respect to A2 powder.
2. The method of manufacturing a semiconductor device according to claim 1, wherein the ratio is 1%/AfA. 4.8! The metal that forms a high melting point alloy is G o + C
2. The method of manufacturing a semiconductor device according to claim 1, wherein n9 is at least one metal selected from r1Mn+Mo*Ti+zr+B+W. 5. The mixing ratio of An and the metal forming the high melting point alloy is A
5. The method for manufacturing a semiconductor device according to claim 1, wherein yAfl is 5 to 30 vofi% with respect to L powder. The method of manufacturing a semiconductor device according to claim 1, wherein the firing temperature is 660 to 900°C. Z. The method for manufacturing a semiconductor device according to claims 1 and 6, wherein the firing time is 2 to 60 minutes. (a) The method for manufacturing a semiconductor device according to claim 1, wherein the firing atmosphere is an inert gas atmosphere with an oxygen concentration of ipppm or less.