JPS583292A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To perform a high efficiency in a photoelectric converter under solar light or a fluorescent lamp by utilizing an absorbing effect to metal impurity by putting-in chlorine into a semiconductor and prticularly in a single crystal silicon semiconductor. CONSTITUTION:A semiconductor substrate 1 is oxidized, chlorine is added to the substrate, and an oxidized silicon 3 with chlorine is formed. Further, the oxidized film of the periphery is selectively retained, and an impurity layer 5 is formed in the other part. Subsequently, an N<+> type layer is thermally diffused in nitrogen. Further, a reflection preventive film 6 is formed on the upper surface of the layer 5. Thereafter, an electrode 10 of silver or nickel for N type impurity or of aluminum for P type impurity is formed. The reflection preventive film contains mainly titanium, tantalum, indium, tin or antimony oxide or nitride.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly efficient photoelectric conversion device having a conversion efficiency of 16 or more under mu M1 or 5 or more at 300 lux under fluorescent light, and a method for manufacturing the same.

The present invention is particularly effective for solar cell materials, especially low-purity single-crystal silicon semiconductors for low cost use. The present invention aims to: (1) contain chlorine in a semiconductor, especially a single-crystal silicon semiconductor, to increase the diffusion length in the semiconductor by 5 to 100 times compared to a non-additive; and (2) reduce defects such as scooking fall in the semiconductor. ■ By oxidizing the semiconductor material at high temperature, impurities, especially metal impurities, in the low-impurity semiconductor can be removed by using keratin (sucking out) into the oxide film on the surface. In addition, (4) this effect can be achieved by increasing the carrier mobility and (4) by providing a P+N, P-type, or Nt-type junction in a region smaller than 0.5μ, especially in a region smaller than 0.5μ. The purpose is to prevent carrier recombination at the bonding surface and reduce bonding leakage.

In the present invention, in order to obtain this suction effect, oxidation in an atmosphere containing chlorine is carried out at 1050°C or higher, preferably 4°C to 1°C.
Tickling of heavy metals is carried out at a high temperature of 250°C for 10 minutes or more, preferably 30 minutes to 6 hours (longer periods are also acceptable), and scooking faults in the semiconductor are also eliminated. The purpose is

The present invention is based on P1 process, P'NXN' process (1 layer is intrinsic or 1 layer is
0.5μ or less, preferably 50μ or less in order to make the bonding surface of the junction very short compared to the surface to which light is irradiated.
Since the chlorine is formed in a very thick layer of 0A to 0.3μ, a bonding impurity layer is formed after this process to prevent re-diffusion during the process of adding and sucking out chlorine.

The present invention leaves an oxide film formed on the semiconductor at the outer periphery of an impurity region on a semiconductor to which chlorine is added, and a parasitic channel is formed in the semiconductor layer below the region. In other words, for example, by applying a boron glass or silicon oxide film to the back surface of a P-type substrate, this substrate can be
050'Ajl is 120♂C Diffusion for 1 to 5 hours: → gettering by oxidation At the same time as adding chlorine, oxidize boron from boron glass into the substrate with a depth of 3 to 20μ, preferably 5μ or more, such as chloride. Temperatures above 1050°C, especially 11Y, together with a physical gas such as dry oxygen
Thermal oxidation was carried out at a temperature of 0 to 1250"C. For example, in chlorine, 0.1 to 10 grams of oxygen, especially 1 to 3 grams, and in hydrogen chloride, 0.5 to 20 grams, especially 2 to 7 grams of oxygen. In the case of a liquid such as triclene, it is bubbled with nitrogen or oxygen at a concentration of 3 to 30% of the oxygen, especially 6 to 15%, and the vapor gas is introduced. compounds, but they are 105
Temperatures above 0'C, especially 1100-1250'C! In this case, carbon reacts with oxygen to form carbon dioxide gas, which is stabilized and does not mix into the silicon semiconductor. As a result, only silicon can diffuse and mix into the silicon semiconductor at such high temperatures. Furthermore, at this time, heavy metals in semiconductors, especially Fe, N, etc. are oxidized at high temperatures.

It is possible to suck out islands, Ou, Zn, etc., as well as B, A1, etc., and some of them can be converted into chloride to promote outward diffusion, and as a result, the lifetime of electron/hole carriers can be increased by 10 to 100 times.

FIG. 1 shows an example of the manufacturing process of a conventional photoelectric conversion device.

In the drawing, an N-type impurity layer (5) of the opposite conductivity type is formed to a depth of 0.3 to 1 μm on the top of a semiconductor (1), for example, P-type 3Acm. Thereafter, an electrode material (10) was formed to make ohmic contact with this impurity layer. For example, in this P-type semiconductor, an aluminum film was formed to a thickness of 0.5 to 1 μm. Furthermore, a photo-etching process is applied to the resist (-
1) is used as a mask to selectively remove unnecessary material (10). After that, the anti-reflection film (6) is applied as shown in Figure 1 (0).
A film (referred to as ARP') having a refractive index of 1.8 to 2.2 is formed by covering the insulating film (5) on the semiconductor surface and the counter electrode (1o) by 1/4 of the thickness.

It is also known to form an oxide film over the entire structure by subjecting it to trichlene oxidation as in the present invention after the step shown in FIG. 1), and to use this oxide film as an ARP. However, in this case, since there is already a P'N junction, this junction is deeper, and the refractive index for ARP is only 1.3 to 1.5, and the film thickness at that time is 1/4λ. Therefore, there was not enough oxidation time necessary for extraction, and as a result, the photoelectric conversion efficiency decreased due to light absorption in the first layer (5) on the irradiated surface side. Therefore, even if the structure is as shown in Figure 1 (0), the efficiency is AM'1 (100 mw/c
The conversion efficiency was 8-11% at 300 lux under fluorescent light, and only 1-3% at 300 lux under fluorescent light.

In Fig. 1, this antireflection film (6) was formed by depositing SiO or the like using a vacuum evaporation method, but in this case, this electrode (
The side part (9) of 10) is difficult to be deposited and becomes extremely thin. Furthermore, when formed by the coating method, this side part (9
) instead of the original '700-1000A thickness.
000A to 1μ is formed, and thermal distortion between the applied antireflection film and the electrode (10) deteriorates reliability, making it extremely difficult to put it into practical use from an engineering perspective! It was bloody.

The present invention prevents such drawbacks and eliminates the problems shown in FIGS. 2 to 4.
An example of this is shown in the figure.
, N"P, etc., and an impurity layer having conductivity type, and an antireflection film having a refractive index of 1.7 to 2.2, particularly a film mainly composed of titanium or tantalum oxide, is formed on the upper surface of the impurity layer. Its thickness is also 1/4λ, and in sunlight it is 700
The thickness of the impurity layer (5) is 0.5 μm or less, especially 500 μm to 0.5 μm, in order to improve the conversion efficiency and improve the characteristics of the incident light, especially on the short wavelength side. It is characterized by being 3μ. □ Therefore, after sucking out heavy metals and removing scooking faults, the impurity layer is heated at a temperature lower than the temperature for this removal, that is, when the former is 1050'O,
-0'(!Hereinafter, for example, if the former is 1200°C for 20 minutes to 6 hours, 900'0 5 to 15 minutes to ensure that no re-diffusion of impurities occurs, and furthermore, the junction depth of this impurity layer is 0.5μ or less. It is characterized in that this joint surface is provided in a region to which chlorine has been added, since the suction is 1 μ or more, particularly 1 to 10 μ.' Examples thereof will be described below with reference to the drawings.

Embodiment 1 FIG. 2 shows a vertical sectional view of a photoelectric conversion device for implementing the present invention.

Pour the bubble mixture into the reactor and heat it to 1200'C! 3
The semiconductor was oxidized by heating for 0 minutes to 3 hours. Then, chlorine was added into the semiconductor substrate (2), and in addition, silicon oxide containing chlorine (3) was formed to a thickness of 15oO to 1μA. By raising the temperature to this high temperature, even low-grade single crystal silicon can be sucked out and the defects can be eliminated.
We were able to increase the size of holes and electrons to μ, and were able to obtain properties similar to those of high-purity silicon semiconductors.

Furthermore, in (B), the oxide film (3) of the peripheral seedlings on the main surface is selectively left, and the impurity layers (5), (4) are formed on other parts.
is formed to a depth of 500A to 0.5μ. That is, the upper surface of the semiconductor (2) is coated with phosphorus glass (pS) by a coating method.
G) or arsenic glass (A S G) 150
~3006C prebake was performed. Next, the N1 layer (sheet resistance 10-80"10) was heated and diffused in nitrogen at 700-1000@O to a thickness of 0.5 μ or less, especially 500
Diffused to a depth of A~0.3μ.

In drawing (C), an antireflection film (6) was further formed on the upper surface of this impurity layer (5). This was carried out by a coating method similar to the embodiment shown in FIG. This coated titanium oxide-based carbohydrate is heated to 100 to 200°C, for example 150°C.
After prebaking at C, the electrode (10) material of this embodiment is coated with silver, nickel for the N&' one and aluminum for the P impurity layer by screen printing method on the upper surface, and then the electrode (10) material is applied to the back side. A metal that makes ohmic contact, such as aluminum, was coated and formed, and prebaked for drying. After this, the contact on the back side is completed and the counter electrode material is applied on the front side through the anti-reflection film.
To provide electrical continuity to the layers, additional sintering was performed in air or nitrogen at a temperature of 400 to 400°C. Then, a part of this electrode material penetrates the pre-baked anti-reflection film (6) and is electrically continuous with the impurity layer (5) on the substrate (1) as shown in the figure 0, so that the ARP (6)
The cap does not require an etching process on the electrode section, making it an excellent low-cost product.

Furthermore, the method of the present invention is characterized in that the electrode on the front surface is formed with an ARP mixed surface metal structure, and at the same time, the electrode (8) and the impurity layer (4) are brought into ohmic contact on the back surface. In this way, the manufacturing process could be simplified. - When impregnating this electrode (10), the anti-reflection film (6) in the area that is irradiated with light is also sintered at the same time, and at the 0th point, these are integrated, so their thermal expansion coefficients match, and the impurity layer due to the stress The generation of recombination centers in (5) could be prevented.

In the example shown in FIG. 2, a conversion efficiency of 12 to 15 degrees could be obtained depending on the resistance of the electrode section under AMl. Furthermore, even under fluorescent light at 300 lux, we obtained an open circuit voltage of 0.38 V, a short circuit current of 45 pA/cm', and an efficiency of 6 to 10%, which is two to three times larger than the previously published values. there were. Furthermore, if the anti-reflection film is a conductive transparent film, the efficiency can be 13% or more even if the distance between the electrodes is 3 to 10 mm, and it has a large area feature that allows for a large area of 5 to 10 cm. have

Furthermore, in the present invention, this antireflection film is: - titanium oxide (TiOx), silicon oxide-titanium oxide mixture, tantalum oxide, transparent conductive film (tin oxide).

■ Oxides such as titanium nitride, nitride/tal, indium nitride, tin nitride, or mixtures thereof such as TN (mixture of indium nitride and tin nitride)
Nitride, especially conductive nitride, and the counter electrode can be made of aluminum, nickel, silver, indium, soot, lead (solder), or a multilayer or mixture of these by coating or printing. It is used as an electrode material. In other words, in the case of aluminum, the mixed layer below it is aluminum, aluminum oxide, and ARP'
It is made of wood and is excellent for use in weak light. Furthermore, add 0.0 Ni and Or under this person 1. -01 to 3μ is formed to improve reliability. Furthermore, aluminum is selectively coated with silver to make it a semiconductor. In the present invention, for these electrodes, a method combining a lift-off method and a vacuum evaporation method, and a method of printing and forming a stain electrode material on ARF by screen printing or coating method can also be used.

Embodiment 2 The steps of this embodiment are shown in FIG. 3 in a vertical sectional view. That is, in FIG. 3(A), the semiconductor substrate (
For example, 10 to 3000 n- of N type or type 1 to 1)
A phosphorus glass film (14) was formed on the back side of the semiconductor (2) by a coating method, and a phosphor glass film (150
After prebaking at 0°C, silicon oxide (6) was again applied to the top surface and formed by prebaking.

Thereafter, the semiconductor (1) was oxidized in the same manner as in the example, and the oxide film (
3) was formed to suck out heavy metals and eliminate stacking 2 ortho. In order to oxidize this surface for as long as 12000013 hours, BSIP was applied to the back surface.
(back surface hold) Nt 5 due to effect
In addition, the oxide film (3) was selectively removed and the P-type impurity layer (5) was replaced with titanium oxide. An anti-reflection film made of a mixture with boron glass was applied, and boron was diffused from this applied film and fired at the same time to form an ARP.The impurity layer should be 0.5μ or less, for example 0.2μ゜ (sheet resistance 10~ 901LA3) to 900”(:
! stomach. Thereafter, this A RP (a) was selectively removed, and aluminum, nickel, silver, or a multilayer film (10) of these was formed as a counter electrode on this portion by a printing method or an electroless plating method.

As a result, the efficiency is high (7 to 8 inches) under fluorescent light.
In addition to this, it was also possible to obtain 16 to 18% in AMl.

In this example, since the P''-I-Nti bond is used, there is a high breakdown voltage at the junction and a long lifetime, so it was possible to obtain a photoresponse and efficient high absorption on the long wavelength side.

Example 3 FIG. 4(A) shows another embodiment of the present invention.

This embodiment is a further simplification of the first embodiment.

For a P-type semiconductor, for example, 0.1 to 3 Acm (2), N1
The impurity layer (5) is set at a depth of 0.25p and the diffusion electrode (
10) is directly connected to the impurity layer (5) as in Example 1.

Maximum 17 at AMI for sunlight irradiation light (10),
It was possible to obtain t3% and 8.5 inches under fluorescent light at 300 lux.Other aspects were the same as in Example 1.

Example 4 This example is shown in FIG. 4(B), and is based on a P-type semiconductor (
2), an N1 impurity layer (5) is provided over the surface region. In this example, ARP (6
) is formed, the impurity layer (5) is ion-implanted to a high concentration of 10 to 1 ocm with a thickness of 0.5μ or less or 0.
．． Impurities are implanted to a depth of 1μ or less, and then -70
It was heated to a temperature of 0 to 1000''C to form an impurity layer (sheet resistance 10 to 200 j'L10).At the same time, ARP was also sintered to complete ARF.

Furthermore, the main surface of the ARF (6) is provided against the side surface of the semiconductor (2), to eliminate electrical short-circuiting with the semiconductor when the counter electrode (10) is externally connected.

Example 5 This embodiment is shown in FIG. 4(0).

An impurity layer (5) of N゛ is provided on the irradiated surface and part of the side and back surfaces of the intrinsic or substantially intrinsic semiconductor (2), so that no electrodes, etc. are present on the irradiated surface. .

In addition, a reverse P4 type impurity layer (4) is selectively formed on the back surface.
fN"-knee P" junction is formed.The electrodes are (8
) and (No) are provided on the back side.

As is clear from the above explanation, the present invention is inexpensive and easy to use.
This is a highly reliable photoelectric conversion device that requires high efficiency, especially when exposed to sunlight or household fluorescent light. By making the impurity layer extremely turbulent, the light absorption in that region is reduced, and furthermore, the generation of electron Φ-hole pairs of incident light is promoted,
Among these, heavy metals in joints with particularly large internal electric fields,
This prevents carrier failures due to defects, etc.

We believe that by combining these chemically and synergistically, the effect is extremely large in low-grade silicon semiconductors, especially single crystal semiconductors, and this will greatly contribute to the industrial world in times of engineering and energy crises.

Polycrystalline odor gas can also be expected to have the same effect, but in that case, the open circuit voltage is 50% higher than that of single crystal, especially in weak light.
The voltage was as low as ~100 mV, which is consistent with the present invention.

In the present invention, the semiconductor substrate is mainly made of P-type single crystal silicon. However, even if the conductivity type is N type, it is not N''-P--P'' structure from the irradiated surface side as in the present invention, but N'-
It is also possible to have one or several layers of junctions such as P-P', Pl-N", P'-N"N"-P, etc. (16). Also, as the material of the present invention, monocrystalline silicon gentrite type Needless to say, the idea of the present invention can be applied to silicon having a high-speed quenching process, other crystal structures, and other materials such as germanium and compound semiconductors.

Furthermore, in the present invention, N'-P in the vertical direction with respect to the substrate.
'-F' or N-P structure.However, while configuring one or more P-N or PN junctions in the lateral direction to the substrate, it is also possible to use a phototransistor or a phototransistor array for a photosensor array, etc. Needless to say, the present invention is applicable to any case.

In the present invention, only chlorine is used. However, other halogens such as fluorine, bromine, and iodine can also be expected to produce effects similar to those of the present invention.

[Brief explanation of drawings]

FIG. 1 shows a conventional photoelectric conversion device. FIGS. 2 and 3 are vertical sectional views showing the photoelectric conversion device of the present invention and its manufacturing process. FIG. 4 shows another embodiment of the invention. Patent applicant: Semiconductor Energy Research Institute, Inc. ￥1 Diagram

Claims (1)

[Claims] 1. A semiconductor containing chlorine, an impurity layer with a high impurity concentration and a depth of 0.5μ or less provided on the semiconductor on the light irradiation side, and a refractor provided on the region. Rate 1.7-2.2
A photoelectric conversion device comprising an antireflection film comprising: 2. Claim 1 is characterized in that a silicon oxide film containing chlorine is provided on the surface of a silicon semiconductor of one conductivity type containing chlorine and around the outer periphery of an impurity region of an opposite conductivity type. Photoelectric conversion device. 3. In claim 1, the antireflection film is mainly composed of titanium, tantalum, indium, tin, or antimony oxide or nitride, and has a thickness of about 1/4 of the wavelength of incident light. Photoelectric conversion device 0 characterized by having