WO2004102676A1

WO2004102676A1 - Photoelectric converting semiconductor device, method for manufacturing same, and processing apparatus used in such method

Info

Publication number: WO2004102676A1
Application number: PCT/JP2004/005950
Authority: WO
Inventors: Hikaru Kobayashi
Original assignee: Japan Science And Technology Agency
Priority date: 2003-05-14
Filing date: 2004-04-23
Publication date: 2004-11-25
Also published as: JP2004342723A; TW200428671A

Abstract

A photoelectric converting semiconductor device is disclosed wherein a semiconductor layer having a pn structure or a pin structure is processed with a solution containing a nonmetallic cyanogen compound or a solution containing a metallic cyanogen compound, so that defect level is eliminated and contaminant metal is removed from the photoelectric converting semiconductor device, thereby improving the photoelectric conversion efficiency.

Description

Description: Photoelectric conversion semiconductor device, method of manufacturing the same, and processing apparatus used in the method

The present invention relates to a photoelectric conversion semiconductor device such as a solar cell, a method for manufacturing the same, and a processing apparatus used in the method. Background art

Solar cells using semiconductors that utilize the photoelectric conversion function of the parent silicon for the photovoltaic layer have been put into practical use, and the photovoltaic layer of the parent silicon has a single-crystal, polycrystalline, or amorphous thin film. Implemented in layers or thin films. In particular, solar cells that have a single-crystal or polycrystalline matrix silicon photovoltaic layer with an output electrode formed on a semiconductor layer with a pn structure have an amorphous matrix silicon photovoltaic layer. Prospects are expected for its higher photoelectric conversion efficiency and less initial light degradation compared to solar cells. In a solar cell, the presence of a defect level in the band gap of a semiconductor lowers the photoelectric conversion efficiency, so it is important to take measures to eliminate the defect level. Such defect levels are also observed in photovoltaic layers made of polycrystalline silicon (polysilicon), microcrystalline silicon, single-crystal silicon, amorphous silicon, and the like. In particular, it is known that a large number of silicon dangling bonds (dangling pounds) exist in a boundary region such as a grain boundary in a polycrystalline silicon / microcrystalline silicon. When dangling bonds exist in a photovoltaic layer of a photoelectric conversion element such as a solar cell or a photosensor, there is a possibility that optical characteristics such as photoelectric conversion efficiency may be deteriorated.

The present invention is intended to suppress or reduce the decrease in photoelectric conversion efficiency due to such a defect level. The purpose is to provide an effective solution to the solution. Disclosure of the invention

The photoelectric conversion semiconductor device of the present invention is a photoelectric conversion semiconductor device comprising a semiconductor layer having a pn structure or a pin structure and an output electrode provided on the semiconductor layer, wherein a surface region or a particle of the semiconductor layer is provided. A boundary region such as a boundary is characterized in that metals or contaminants containing metals are removed and dangling bonds are terminated by cyano groups.

In the photoelectric conversion semiconductor device of the present invention, by removing attached substances such as contaminant metals from the semiconductor layer having a pn structure or a pin structure and terminating dangling bonds with a cyano group, a surface region or a grain boundary or the like can be obtained. The defect in the boundary region is suppressed or eliminated, and high efficiency of the photoelectric conversion semiconductor device is achieved. The method for manufacturing a photoelectric conversion semiconductor device according to the present invention includes a process of removing adhering substances such as contaminant metals from a semiconductor layer and terminating unbonded hands with a cyano group as described above. In other words, in at least one stage from a state before forming a pn structure or a pin structure on a semiconductor substrate to a state after forming an output electrode, a cyan treatment in which the semiconductor substrate is exposed to a solution or gas containing a cyanide compound. It is characterized by having a process. The cyan compound includes a non-metallic cyan compound and a metal cyan compound, and any of the cyan compounds can be used. Examples of the non-metallic cyanide include hydrogen cyanide, dicyan, and ammonium cyanide. Examples of the metal-based cyanide include lithium cyanide, sodium cyanide, rubidium cyanide, and cesium cyanide.

Examples of the cyan treatment process include a step of immersing a semiconductor substrate in an aqueous solution containing a non-metallic cyanide compound or an alcohol solution containing a metal-based cyanide compound This is the step of immersion in As the alcohol, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like can be used.

When the substrate or the like is silicon, the etching of the substrate can be prevented by using alcohol as the solvent. When water is used by adding water to the solvent, the water molecule acts as a solvate for the cyanide ion in the solution, and the activity of the cyanide ion can be controlled.

Preferably, the method further includes a rinsing step of rinsing the semiconductor substrate with a cleaning liquid after the cyan treatment process. Due to this rinsing, a cyanide compound of a metal such as copper, or a complex of a metal such as copper and a cyano group or a cyanide ion, which adheres to and remains in a surface region of the semiconductor layer or a boundary region including a grain boundary, etc. It is removed from the semiconductor layer. This rinsing can be performed using a solvent such as pure water or an alcohol solution. Thereafter, if necessary, a drying treatment for removing a solvent or the like from the surface region of the semiconductor layer or the like may be performed.

The semiconductor substrate processing apparatus of the present invention includes everything from cyan treatment of a semiconductor substrate to treatment of a rinsed waste liquid, and has a configuration in which a cyan component is not discharged into the environment. That is, the semiconductor substrate processing apparatus of the present invention includes: a cyan processing unit that exposes a semiconductor substrate to a solution or a gas containing a cyan compound; a rinsing unit that rinses the semiconductor substrate after the cyan processing with a cleaning liquid; A cleaning liquid processing unit for decomposing and removing the cyan component in the cleaning liquid after rinsing by ozone treatment or ozone treatment combined with ultraviolet light irradiation, or treatment with hypochlorous acid solution;

If this semiconductor substrate processing apparatus is used, a semiconductor substrate is treated from the surface with a solution or gas containing a cyanide compound, rinsed after the cyan treatment, and furthermore, a cyan component in a cleaning liquid (waste liquid) after the rinse is removed. Since it can be decomposed and removed, waste liquid containing cyan component is not released to the outside. According to the photoelectric conversion semiconductor device of the present invention, in the surface region or the boundary region of the semiconductor layer, the metal or the contaminant containing the metal is removed, and the dangling bonds are terminated with a cyano group. High efficiency can be realized.

According to the method for manufacturing a photoelectric conversion semiconductor device of the present invention, the semiconductor substrate is formed of a cyanide compound before, during, or after forming a semiconductor layer having a pn structure or a pin structure, or after forming an output electrode on the semiconductor layer. With the provision of a cyan treatment process in which the semiconductor layer is exposed to a solution or a gas containing nitrogen, the defects in the semiconductor layer also disappear due to the above-described termination of unbonded hands due to cyan, thereby increasing the efficiency of the photoelectric conversion semiconductor device. To achieve high performance.

Further, according to the processing apparatus of the present invention, before, during or after forming a semiconductor layer having a pn structure, or after forming an output electrode on the semiconductor layer, the surface is treated with a solution or gas containing a cyanide compound, The semiconductor layer or the output electrode is rinsed with a cleaning liquid, and the cleaning liquid (waste liquid) after the rinsing is treated with ozone treatment or ozone combined with ultraviolet light irradiation, or the cleaning liquid after the cleaning treatment is treated with a hypochlorous acid solution. By providing the functions of processing and processing, semiconductor photoelectric conversion devices can be made more efficient and achievable with higher performance using practicable manufacturing means. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing a cyan treatment step in one embodiment of the manufacturing method.

FIG. 2 is a flow sectional view showing one embodiment for manufacturing a photoelectric conversion semiconductor device.

FIG. 3 is a schematic diagram of a processing apparatus for manufacturing a photoelectric conversion semiconductor device. BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a description will be given of a case where a photovoltaic layer made of polycrystalline silicon is exposed to a compound having a cyanide component, whereby a remarkable improvement in conversion efficiency has been found.

FIG. 1 is a cross-sectional view of a processing device で in a step of processing a photoelectric conversion device having a photovoltaic layer of polycrystalline silicon as an embodiment of the present invention. A polycrystalline silicon layer body having a pn structure formed of a p-type polycrystalline silicon layer 11 as a photovoltaic layer and an n-type polycrystalline silicon layer 12 containing n-type impurities, for example, phosphorus (P); A transparent electrode 13 made of ITO (indium tin oxide) formed on a D-type polycrystalline silicon layer 11, which is a polycrystalline silicon layer, and an n-type, another polycrystalline silicon layer, The photoelectric conversion device including the aluminum electrode 14 formed on the polycrystalline silicon layer 12 is immersed in a processing tank 16 filled with the processing solution 15.

Here, the transparent electrode 13 may be formed on the n-type polycrystalline silicon layer 12, and the aluminum electrode 14 may be formed on the p-type polycrystalline silicon layer 11. Also, not limited to ITO as the transparent electrode 1 3, it is possible to use S N_〇 _2.

FIGS. 2A to 2D are flow cross-sectional views showing a process of forming the polycrystalline silicon layer in a photoelectric conversion device having a polycrystalline silicon photovoltaic layer according to an embodiment of the present invention. FIG.

First, in the process shown in Fig. 2 (a), the thickness is 100 to 600! ! ! Prepare a polycrystalline silicon substrate 11 of FIG.

Next, as shown in FIG. 2B, an n-type impurity is diffused to form an n-type diffusion layer 12 of about 0.5 μm. The n-type diffusion layer 12 may be formed by a thermal diffusion method, an ion implantation method, or the like. Phosphorus or arsenic can be used as n-type impurities Here, phosphorus is used.

Subsequently, in a step shown in FIG. 2 (c), an aluminum electrode 13 having a thickness of about 200 nm is formed by a sputtering method or a vapor deposition method.

Further, in the step shown in FIG. 2 (d), a transparent electrode (ITO) 14 having a thickness of about 100 nm was formed by a sputtering method or a vapor deposition method to manufacture a photoelectric conversion device.

Next, as shown in FIG. 1, the above photoelectric conversion device is placed in a processing tank 16 containing a hydrogen cyanide (HCN) aqueous solution 15 adjusted to a concentration of 1 mol and a temperature of 25 ° C. for about 2 minutes. Immerse in hydrogen cyanide aqueous solution 15.

Then, the cyan-treated photoelectric conversion device is washed with ultrapure water of 10 ° C.

In the present embodiment, the above-described photoelectric conversion device is described as a method of performing cyan processing in the state of the structure shown in FIG. 2 (d). However, the present invention is not limited to this. For example, FIGS. 2 (a) to 2 (c) In any of the substrate configurations at any stage, the process of immersing the substrate in the aqueous hydrogen cyanide solution 15 and the subsequent process of cleaning the substrate for processing with ultrapure water can be performed. Works effectively.

In a semiconductor layer such as a silicon substrate, dangling bonds existing in the silicon surface region and boundary regions such as grain boundaries are terminated by cyan ions (CN-I) and disappear when treated with the above-mentioned solution containing a cyanide compound. Has the effect of doing In particular, in the case of a polycrystalline semiconductor layer of silicon or a compound containing silicon, many unbonded bonds and their bonds are formed in a boundary region such as a surface region and a grain boundary to which a metal such as copper or a contaminant containing such a metal adheres. Although a defect level such as a complex is generated, the treatment with the cyan compound-containing solution removes the contaminants adhered to the surface region, and the defect also causes the above-mentioned dangling bonds due to cyan ions. Defect extinction function that disappears due to terminal action There is. ·

An improvement in photoconductivity was recognized by the defect annihilation action in the semiconductor layer, and therefore, the photoelectric conversion device obtained in this embodiment achieved high photoelectric conversion efficiency.

In the present embodiment, when manufacturing the above-mentioned photoelectric conversion device, for example, in any of the processing substrate configurations shown in FIGS. 2 (a) to 2 (c), an aqueous solution of hydrogen cyanide by a processing device as shown in FIG. Although the process of immersing in 15 and the subsequent process of cleaning the substrate for processing with ultrapure water were carried out, the photoelectric conversion devices obtained by the processes were all the cyanide according to the present embodiment. Compared to a photoelectric conversion device manufactured without performing the immersion process in a hydrogen aqueous solution 15 and the subsequent process of cleaning the processing substrate with ultrapure water, the performance of a significantly higher photoelectric conversion efficiency was realized.

Further, in the present embodiment, when the above-mentioned photoelectric conversion device is manufactured, for example, the substrate configuration at any one of the stages shown in FIGS. When performing the treatment step of immersing in a hydrogen cyanide aqueous solution 15, a positive voltage is applied to the substrate in the range of 0.1 V to 50 V, and the treatment temperature is heated in the range of room temperature to 100 ° C. In addition, the action of the cyan treatment was promoted, and the photoelectric conversion devices obtained by the above all realized much higher photoelectric conversion efficiency. According to the experimental results, the photoelectric conversion efficiency of the photoelectric conversion device according to the present embodiment is 12.3 at maximum when the processing substrate is subjected to a cyan treatment for 2 minutes at an applied voltage of 10 V and a processing temperature of 50 ° C. % Was achieved, and the photoelectric conversion efficiency of the photoelectric conversion device manufactured without performing the cyan treatment was 8.8%, which was a significant improvement in performance. When the cyan treatment was performed at a temperature of 50 ° C. without applying a voltage, 10.5% was obtained, and when the cyan treatment was performed at a room temperature by applying a voltage, 10.1% was obtained. • The same performance improvement can be obtained when a single crystal silicon substrate is used. Further, similar performance improvement can be obtained when a photoelectric conversion device having a pη structure or a pin structure is formed on a predetermined substrate, for example, a glass substrate by plasma CVD or the like.

In this embodiment mode, treatment with a solution or gas containing a cyanide compound is performed before, during, or after forming a semiconductor layer having a pn structure, or after forming an output electrode on the semiconductor layer. Prepare the process.

Next, a specific example of the removal of contaminants will be described.

In order to remove metals such as copper, which are contaminants, mainly from the surface region and boundary regions such as grain boundaries of the semiconductor layer, the semiconductor layer is subjected to a solution or gas containing a cyanide compound (for example, mist) in a cyan treatment process. (Hereinafter referred to as process I). Examples of the solution containing a cyanide compound include a solution in which a nonmetallic cyanide compound such as hydrogen cyanide, dicyan or ammonium cyanide is dissolved in a solvent, for example, pure water or an alcohol solution, or potassium cyanide, sodium cyanide, A solution in which a metal cyanide compound such as rubidium cyanide or cesium cyanide is dissolved in an alcoholic solution, and a solution having a concentration of about 1 mol is appropriate. In this step I, contaminants such as copper existing on the surface of the semiconductor layer or in a boundary region such as a grain boundary form a compound with cyanide, or form a complex with a cyano group or a cyanide ion. When solutions containing cyanide are used, those compounds or complexes elute in the solution.

Next, the semiconductor layer is rinsed (hereinafter, referred to as a process Π). That is, in this step II, the semiconductor layer is washed with a solvent such as pure water or an alcohol solution. By this rinsing, a cyanide compound of a metal such as copper or a complex of a metal such as copper with a cyano group or a cyanide ion, which adheres to and remains in a boundary region such as a surface region or a grain boundary of the semiconductor layer, is removed. Is removed from the semiconductor layer. Thereafter, if necessary, a drying treatment for removing a solvent or the like from the semiconductor layer is performed.

Thus, the semiconductor layer is in a state where metals such as copper have been removed. According to the measurement results, a metal such as copper remaining in the semiconductor layer, the measurement lower limit value of the metal atom by Ken查meter (3 X 1 0 ⁹ atoms / cm ²⁾ with the following is obtained Contact is, reliably It was found to have been removed.

In addition, when the semiconductor layer is treated with the above-mentioned cyanide-containing solution, the attached metal such as copper or a contaminant containing these metals is removed, and at the same time, the boundary such as the surface region and the grain boundary is removed. The effect of eliminating defects in the region due to termination of a dangling bond existing in the region with a cyano group or the like can be obtained. In particular, in the semiconductor layer of silicon-silicon compound, defects such as many dangling bonds and their composites occur on the surface where metals such as copper or contaminants containing these metals are adhered and in the boundary regions such as grain boundaries. However, by treating with the cyanide-containing solution, the contaminants are removed, and the defect is also eliminated by the above-mentioned dangling terminal action of the cyano group. is there. And, by the defect annihilation action in the semiconductor layer, improvement in photoconductivity and performance of high photoelectric conversion efficiency are realized.

Note that, in the present embodiment, the force verified for copper as an example of a contaminated metal The present invention is not limited to copper, and other metal elements, for example, metals such as iron, nickel, cobalt, silver, tungsten, and titanium The processing solution and the cleaning process used in this embodiment are also effective for removing elements from the surface of a substrate or the like.

In addition, in the step II of rinsing the substrate or the like, there is a possibility that a so-called cyan component such as a cyan compound or a cyano group or a cyanide ion may remain in the rinse solution after the treatment. Washing The purified liquid (rinse waste liquid) is treated in ozone or ozone combined with ultraviolet light irradiation to decompose and remove the cyan component remaining in the rinse waste liquid. As a result, the above-mentioned cyan component does not remain in the rinse waste liquid generated in step II.

Further, the cleaning liquid (rinse waste liquid) after the cleaning treatment is subjected to a chemical treatment with a so-called hypochlorous acid solution containing hypochlorite (for example, sodium hypochlorite), so that the rinse waste liquid is removed. It is also possible to decompose and remove the above-mentioned cyan component remaining in the image. In this case, the concentration of the hypochlorous acid solution and the treatment temperature may be appropriately set by estimating the remaining amount of the cyan component in the rinse waste liquid.

Steps I and II, and the function of decomposing the residual cyan component in the rinse waste liquid are provided, so that metals such as copper adhering to the substrate or the like or contaminants containing these metals can be removed. Along with the removal, the cyan component remaining in the rinse waste liquid after the cleaning treatment can also be completely decomposed and removed.

In the present embodiment, the photoelectric conversion device has a structure shown in FIG. 2 (d). The cyan treatment is not limited to the structure shown in FIG. 2 (d) .For example, in any of the steps shown in FIGS. 2 (a) to (c), the above-mentioned steps I and II are performed by the photoelectric conversion in the manufactured photoelectric conversion device. It was effective in improving the performance of efficiency.

FIG. 3 is a schematic diagram of the processing apparatus of the present embodiment. The processing apparatus main body 20 includes a processing unit 23 for immersing a semiconductor substrate 21 in a processing solution 22, and then takes out the substrate 21. Then, at room temperature, a washing section 24 for washing (rinsing) using a mixed solution of ultrapure water and methanol as a washing liquid, and a so-called rinse waste liquid after washing (rinsing) are introduced. It is equipped with a waste liquid treatment section 25 for ozone treatment. The processing section 23 has a processing solution supply section 26 having a function of supplying and discharging the processing solution 22, and a cleaning section 24. Has a cleaning liquid supply unit 27 '.

The waste liquid treatment section 25 includes an ultraviolet ray generation source and a poson generation source, and decomposes the cyan component (CN) remaining in the rinse waste liquid by irradiating the above-mentioned rinse waste liquid with ultraviolet rays and applying ozone. By discharging the rinse waste liquid together with the rinse waste liquid to the cleaning waste liquid recovery section 28, the waste liquid can be made into a rinse waste liquid containing no cyan component.

When a cyanide-containing aqueous solution formed from a non-metallic cyanide, for example, a cyanide such as hydrogen cyanide, dicyan or ammonium cyanide, is used as a treatment solution, a substrate or the like is immersed in the treatment solution, and then the substrate or the like is used. The so-called rinse waste liquid after taking out and washing (rinsing) it with ultrapure water at room temperature is a dilute aqueous solution having the above-mentioned cyanide content. Therefore, the rinse waste liquid is also introduced into the waste liquid treatment section 25, where ultraviolet light and ozone are applied to the rinse waste liquid to decompose the cyan component (CN) remaining in the rinse waste liquid. By discharging the rinse waste liquid together with the rinse waste liquid to the washing waste liquid recovery section 28, a rinse waste liquid containing no cyan component can be obtained.

In the processing apparatus of the present embodiment shown in FIG. 3, the transport mechanism and drying means for taking the substrate 21 into the processing apparatus and taking it out of the processing apparatus take into consideration the gas-phase shutoff inside and outside the processing apparatus. If this is the case, conventional technology can be used sufficiently, so it is omitted.

In the embodiment, a photoelectric conversion device having a pn structure is described as an example; however, a photoelectric conversion device having a pin structure can achieve the same effect.

In the present embodiment, the same effect can be expected for the semiconductor layer not only of silicon (S i) but also of a III-V compound or an organic semiconductor. Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be used for a photoelectric conversion semiconductor device such as a solar cell having a photovoltaic layer made of polycrystalline silicon, microcrystalline silicon, single crystal silicon, amorphous silicon, or the like.

Claims

The scope of the claims

1. In a photoelectric conversion semiconductor device including a semiconductor layer having a pn structure or a pin structure and an output electrode provided in the semiconductor layer,

A photoelectric conversion semiconductor device, wherein a metal or a contaminant containing a metal is removed from a surface region or a boundary region of the semiconductor layer, and dangling bonds are terminated by a cyano group.

2. The semiconductor device according to claim 1, wherein the semiconductor layer is made of at least one material selected from polycrystalline silicon, single-crystal silicon, and amorphous silicon.

2. The photoelectric conversion semiconductor device according to item 1.

3. A method for manufacturing a photoelectric conversion semiconductor device, comprising: forming a semiconductor layer having a pn structure or a pin structure on a semiconductor substrate; and forming output electrodes on the p-type semiconductor layer and the _n- type semiconductor layer of the semiconductor layer. ,

P n structure or! At least one stage from the state before forming the in-structure to the state after forming the output electrode includes a cyan treatment step of exposing the semiconductor substrate to a solution or gas containing a cyanide compound. Characteristic method of manufacturing a photoelectric conversion semiconductor device.

4. The method according to claim 3, wherein the cyan compound is at least one non-metallic cyan compound selected from the group consisting of hydrogen cyanide, dicyan, and ammonium cyanide.

5. The cyan treatment step according to claim 3, wherein the semiconductor substrate is a step of immersing the semiconductor substrate in an aqueous solution containing a nonmetallic cyanide. Manufacturing method.

6. The method according to claim 3, wherein the cyan compound is at least one metallic cyan compound selected from the group consisting of potassium cyanide, sodium cyanide, rubidium cyanide, and cesium cyanide. .

7. The manufacturing method according to claim 3, further comprising a rinsing step of rinsing the semiconductor substrate with a cleaning liquid after the cyan treatment process.

8. Expose the semiconductor substrate to a solution or gas containing cyanide.

With the department,

A rinsing section for rinsing the semiconductor substrate after the cyan treatment with a cleaning liquid; and a cleaning liquid after the rinsing after the rinsing cleaning liquid is treated with an ozone treatment or an ultraviolet light irradiation combined ozone treatment or a hypochlorous acid solution. A cleaning liquid processing section for decomposing and removing the cyan component of the semiconductor substrate processing apparatus.