JP2019175950A - Semiconductor substrate with passivation layer, solar battery element and solar battery - Google Patents

Abstract

To provide a semiconductor substrate with passivation layer excellent in a passivation effect, and a solar battery element with passivation layer excellent in passivation effect and excellent in power generation performance and a solar battery.SOLUTION: The semiconductor substrate with passivation layer includes: a semiconductor substrate 1; a passivation layer 5 which is provided at least a part of at least one surface of the semiconductor substrate 1 and contains Bi; and a silicon nitride film formed on the passivation layer 5. An average thickness of all of the passivation layer 5 and the silicon nitride film is 10 nm to 1000 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor substrate with a passivation layer, a solar cell element, and a solar cell.

An example of the manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a textured structure is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen, A process for several tens of minutes is performed at 900 ° C. to uniformly form an n-type diffusion layer on the surface of the p-type silicon substrate.

In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the light-receiving surface of the p-type silicon substrate but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. Further, the n-type diffusion layer formed on the back surface needs to be converted into a p ⁺ -type diffusion layer. For this reason, an aluminum paste containing aluminum powder, a binder, etc. is applied to the whole or a part of the back surface, and this is heat-treated (fired) to form an aluminum electrode, and an n-type diffusion layer is formed as a p ⁺ -type diffusion. Ohmic contact is obtained by converting into layers.

  However, the electrical conductivity of the aluminum electrode formed from the aluminum paste is low. Therefore, in order to reduce the sheet resistance of the aluminum electrode, the aluminum electrode generally formed on the entire back surface must have a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since the thermal expansion coefficient differs greatly between silicon and aluminum, a large internal stress is generated in the silicon substrate during the heat treatment (firing) and cooling for forming the aluminum electrode on the silicon substrate. This large internal stress causes crystal grain boundary damage, crystal defect growth and warpage.

In order to solve this problem, there is a method of reducing the amount of aluminum paste applied and reducing the thickness of the aluminum electrode. However, when the amount of aluminum paste applied is reduced, the amount of aluminum diffusing from the surface of the p-type silicon semiconductor substrate becomes insufficient. As a result, a desired BSF (Back Surface Field) effect (an effect of improving the collection efficiency of generated carriers due to the presence of the p ⁺ -type diffusion layer) cannot be achieved, and there may be a problem that the characteristics of the solar cell deteriorate. .

In relation to the above, an aluminum paste is applied to a part of the surface opposite to the light receiving surface of the silicon substrate (hereinafter also referred to as “back surface”) to partially form a p ⁺ -type diffusion layer and an aluminum electrode. A point contact technique has been proposed (see, for example, Patent Document 1).
In the case of a solar cell having a point contact structure on the back surface, it is necessary to suppress the recombination rate of minority carriers on the surface of the silicon substrate on which no aluminum electrode is formed.
For this purpose, it has been proposed to provide a SiO ₂ film or the like as a back surface passivation layer (see, for example, Patent Document 2). The passivation effect by providing such a SiO ₂ film is exhibited by the action of terminating the dangling bonds of silicon atoms in the back surface layer portion of the silicon substrate and reducing the surface state density that causes recombination.

As another method for suppressing recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field that generates a fixed charge in the passivation layer. Such a passivation effect is generally called a field effect, and an aluminum oxide (Al ₂ O ₃ ) film or the like has been proposed as a material having a negative fixed charge (see, for example, Patent Document 3). Such a passivation layer is generally formed by a method such as an ALD (Atomic Layer Deposition) method or a CVD (Chemical Vapor Deposition) method (for example, see Non-Patent Document 1).

Japanese Patent No. 3107287 Japanese Patent Laid-Open No. 2004-6565 Japanese Patent No. 4767110

Journal of Applied Physics, 104 (2008), 113703-1〜113703-7

  The passivation layer described in Non-Patent Document 1 is intended to suppress minority carrier recombination in the solar cell substrate by an electric field effect due to negative fixed charges. In order to suppress carrier recombination, a passivation layer having a larger negative fixed charge is required.

  One embodiment of the present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor substrate with a passivation layer having a passivation layer that has an excellent passivation effect. Another object of one embodiment of the present invention is to provide a solar cell element and a solar cell that have a passivation layer that has an excellent passivation effect and that have excellent power generation performance.

  Specific means for solving the above problems include the following embodiments.

<1> a semiconductor substrate;
A passivation layer provided on at least part of at least one surface of the semiconductor substrate and containing Bi;
A silicon nitride film provided on the passivation layer,
A semiconductor substrate with a passivation layer, wherein the total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm.
<2> The semiconductor substrate with a passivation layer according to <1>, wherein the passivation layer further contains Al.
<3> The semiconductor substrate with a passivation layer according to <1> or <2>, wherein the Bi content in the passivation layer is 1% by mass to 90% by mass.
<4> a semiconductor substrate having a pn junction in which a p-type layer and an n-type layer are pn-junction;
A passivation layer provided on at least part of at least one surface of the semiconductor substrate and containing Bi;
A silicon nitride film provided on the passivation layer;
An electrode disposed on at least one of the p-type layer and the n-type layer,
The solar cell element whose total average thickness of the said passivation layer and the said silicon nitride film is 10 nm-1000 nm.
<5> A solar cell having the solar cell element according to <4> and a wiring material disposed on an electrode of the solar cell element.

  According to one embodiment of the present invention, it is possible to provide a semiconductor substrate with a passivation layer including a passivation layer that has an excellent passivation effect. Further, according to one embodiment of the present invention, it is possible to provide a solar cell element and a solar cell that have a passivation layer that is excellent in a passivation effect and that are excellent in power generation performance.

It is sectional drawing which shows typically an example of the manufacturing method of the solar cell element which has a passivation layer. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element which has a passivation layer. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element which has a passivation layer. It is a schematic plan view which shows an example of the light-receiving surface of a solar cell element. It is a schematic plan view which shows an example of the formation pattern of the passivation layer in a back surface. It is a schematic plan view which shows another example of the formation pattern of the passivation layer in a back surface. It is the schematic plan view to which the A section of FIG. 5 was expanded. It is the schematic plan view to which the B section of FIG. 5 was expanded. It is the schematic plan view to which the A section of FIG. 5 was expanded. It is the schematic plan view to which the B section of FIG. 5 was expanded. It is a schematic plan view which shows an example of the back surface of a solar cell element.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and the present invention is not limited thereto.

In the present specification, the numerical ranges indicated by using “to” include numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. Good. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.
In the present specification, the content rate or content of each component in the composition is such that when there are a plurality of substances corresponding to each component in the composition, the plurality of kinds present in the composition unless otherwise specified. It means the total content or content of substances.
In the present specification, the particle diameter of each component in the composition is a mixture of the plurality of types of particles present in the composition unless there is a specific indication when there are a plurality of types of particles corresponding to each component in the composition. Means the value of.
In this specification, the term “layer” includes a configuration formed in a part in addition to a configuration formed in the entire surface when observed as a plan view. Further, in this specification, “layer” may be referred to as “film”.
In this specification, the term “process” includes a process that is independent of other processes and includes the process if the purpose of the process is achieved even if it cannot be clearly distinguished from the other processes. It is.

The passivation layer in this specification refers to a layer having an effect of suppressing recombination of carriers generated in a semiconductor substrate (hereinafter sometimes referred to as a passivation effect). The passivation effect may be caused by any method such as a method of terminating a defect (dangling bond) on a semiconductor surface, a method of bending a band by a fixed charge, or the like.
In this specification, “the total average thickness of the passivation layer and the silicon nitride film” refers to the total average thickness of the passivation layer and the silicon nitride film on one surface of the semiconductor substrate. When the passivation layer and the silicon nitride film are provided on both surfaces of the semiconductor substrate, the total average thickness of the passivation layer and the silicon nitride film is calculated for each surface of the semiconductor substrate.

<Semiconductor substrate with passivation layer>
The semiconductor substrate with a passivation layer of the present embodiment includes a semiconductor substrate, a passivation layer containing Bi provided on at least a part of at least one surface of the semiconductor substrate, and a silicon nitride film provided on the passivation layer. The total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm. Hereinafter, each component will be described.

(Passivation layer)
The passivation layer is provided on at least a part of at least one surface of the semiconductor substrate. The passivation layer contains Bi.
Since the semiconductor substrate with a passivation layer has a passivation layer containing Bi, the lifetime of the carrier is increased, and an excellent passivation effect is exhibited. The reason for this can be considered as follows. The passivation layer containing Bi can have a negative fixed charge, whereby an electric field is generated in the vicinity of the interface with the semiconductor substrate, and the concentration of minority carriers can be reduced. As a result, it is considered that carrier recombination at the interface with the semiconductor substrate is suppressed, the lifetime of carriers is increased, and an excellent passivation effect is obtained.

  In this specification, the passivation effect of a semiconductor substrate is obtained by reflecting the effective lifetime of minority carriers in a semiconductor substrate on which a passivation layer is formed using a reflection microwave photoconductive device using a device such as WT-2000PVN (Nihon Semi-Lab Co., Ltd.). It can be evaluated by measuring by the attenuation method.

Here, the effective lifetime τ is expressed by the following equation (A) by the bulk lifetime τ _b inside the semiconductor substrate and the surface lifetime τ _s of the semiconductor substrate surface. When the surface state density on the surface of the semiconductor substrate is small, τ _s becomes long, resulting in a long effective lifetime τ. Further, even if defects such as dangling bonds in the semiconductor substrate are reduced, the bulk lifetime τ _b is increased and the effective lifetime τ is increased. That is, by measuring the effective lifetime τ, the interface characteristics between the passivation layer and the semiconductor substrate and the internal characteristics of the semiconductor substrate such as dangling bonds can be evaluated.

1 / τ = 1 / τ _b + 1 / τ _s (A)

  Note that a longer effective lifetime indicates that the minority carrier recombination rate is slower. In addition, power generation performance tends to be improved by configuring a solar cell element using a semiconductor substrate having a long effective lifetime.

  In addition, since the passivation layer-containing semiconductor substrate according to the present embodiment includes Bi, the passivation effect is easily maintained even when the semiconductor substrate is placed in an environment such as high temperature and vacuum in the subsequent manufacturing process. The reason for this can be considered as follows. The passivation layer containing Bi is considered to be in a state in which the structure is difficult to change even under an environment such as high temperature and vacuum. Therefore, even if a solar cell is manufactured using the semiconductor substrate with a passivation layer of this embodiment, for example, it is considered that a state having a desired passivation effect is maintained.

The content of Bi in the passivation layer can be appropriately selected as necessary.
From the viewpoint of maintaining the passivation effect and the passivation effect, the Bi content in the passivation layer is, for example, preferably 1% by mass to 90% by mass, more preferably 10% by mass to 85% by mass, More preferably, it is 15 mass%-80 mass%.

  The passivation layer may further contain other metal elements other than Bi. Examples of other metal elements include Al. When the passivation layer further contains Al, the passivation effect tends to be further improved. The reason for this can be considered as follows. The passivation layer containing Al can have a negative fixed charge. Thereby, an electric field is generated in the vicinity of the interface with the semiconductor substrate, and the concentration of minority carriers can be reduced. As a result, it is considered that carrier recombination at the interface with the semiconductor substrate is suppressed and an excellent passivation effect is obtained. Furthermore, when the passivation layer contains Al together with Bi, the passivation effect tends to be maintained even when placed in an environment such as high temperature or vacuum.

  When the passivation layer contains Al, the content of Al in the passivation layer is, for example, preferably 1% by mass to 90% by mass and preferably 5% by mass to 85% by mass from the viewpoint of the passivation effect. More preferably, it is more preferably 10% by mass to 80% by mass.

  Further, when the passivation layer contains Al, the content of Bi with respect to the total mass of Bi and Al is preferably 30% by mass to 99% by mass, for example, from the viewpoint of maintaining the passivation effect and the passivation effect. It is more preferably 40% by mass to 95% by mass, further preferably 50% by mass to 90% by mass, and particularly preferably 60% by mass to 90% by mass.

In addition, as the other metal element, at least one element selected from the group consisting of Nb, Ta, V, Y, and Hf (hereinafter, also referred to as “element M ¹ ”) can be given.
As the element M ^1, passivation effect, workability in preparing the later-described passivation layer forming composition, and from the viewpoint of pattern formability of the passivation layer forming composition, Nb, Ta, and from the group consisting of Y It is preferably at least one selected, and more preferably Nb.

If the passivation layer comprises an element M ^1, the content of the element M ¹ can be selected as needed. From the viewpoint of the passivation effect, the content of the element M ¹ in the passivation layer is, for example, preferably 0.1% by mass to 80% by mass, and more preferably 0.5% by mass to 75% by mass. More preferably, it is 1 mass%-70 mass%.

Further, when containing at least one passivation layer is selected from the group consisting of Al and the element M ^1, from the viewpoint of retention of the passivation effect and passivation effect, containing Bi to the total mass of Bi and Al and the element M ¹ The rate is, for example, preferably 30% by mass to 99% by mass, more preferably 40% by mass to 95% by mass, further preferably 50% by mass to 90% by mass, and 60% by mass to 90% by mass is particularly preferred.
By setting the Bi content in the above range, the passivation effect and the retention of the passivation effect tend to be improved.

Passivation layer, Bi, may contain other metal elements other than Al and the element M ^1.
Examples of other metal elements other than Bi, Al, and element M ¹ include, for example, Li, Na, K, Mg, Ca, Sr, Ba, La, Ti, B, Zr, Cr, Mo, W, Mn, Fe, And at least one element selected from the group consisting of Co, Ni, Cu, Zn, and Pb (hereinafter also referred to as “element M ² ”). As the element ^{M 2,} from the viewpoint of the power generation performance of the case where the solar cell element, Li, Na, K, Mg , Ca, Sr, Ba, La, Ti, B, Zr, Mo, Co, Zn, and Pb It is preferably at least one selected from the group consisting of, more preferably at least one metal element selected from the group consisting of Ti and Zr, and even more preferably Zr.

If the passivation layer comprises an element M ^2, the content of the element M ² may be selected as needed. From the viewpoint of the passivation effect, the content of the element M ² in the passivation layer is preferably, for example, 0.1% by mass to 80% by mass, and more preferably 0.5% by mass to 75% by mass. More preferably, it is 1 mass%-70 mass%.

From the viewpoint of the passivation effect, the content of the element M ² with respect to the mass of Bi is, for example, preferably 90% by mass or less, more preferably 85% by mass or less, and 80% by mass or less. Is more preferable.

  In addition, the content of Bi in the passivation layer and other metal elements included as necessary is determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), or high frequency inductively coupled plasma. It can be measured by mass spectrometry (ICP-MS). For example, the content of each element can be measured by the following measurement method. First, the passivation layer is dissolved in an acid or alkaline aqueous solution, and this solution is atomized and introduced into Ar plasma. Next, the wavelength and intensity are measured by dispersing light emitted when the excited element returns to the ground state. Then, the element is qualitatively determined from the obtained wavelength, and quantified from the obtained intensity.

  Further, from the viewpoint of the passivation effect, the passivation layer may contain Si. When the passivation layer contains Si, reduction of the passivation effect tends to be suppressed. The reason is not clear, but can be considered as follows.

  In the passivation layer, Si is usually present in the form of an oxide. At this time, the oxide exists as a plurality of phases due to differences in crystallinity, generation direction, and the like, and an interface may be formed between adjacent phases. The phase in the passivation layer may be observable from a transmission electron microscope image.

  Thus, there are cases where a plurality of phases exist in the passivation layer and an interface between the phases exists. At this interface, it is assumed that the penetration rate of substances (such as hydrogen atoms) that inhibit the passivation effect existing outside is faster than that in the phase. This phenomenon occurs because the diffusion rate of the substance depends on the density in the moving medium. Since the inside of the phase is filled with the substance, the penetration rate of hydrogen atoms and the like from the outside is slow. On the other hand, it can be said that hydrogen atoms and the like easily enter since there are voids, defects and the like in atomic size with the change of material at the phase interface. For this reason, hydrogen atoms and the like existing outside may be diffused by reaching the substrate through the interface, and as a result, the passivation effect may be reduced.

  Here, in the passivation layer containing Si, it is guessed that Si tends to be unevenly distributed at the interface between phases. This is considered to be due to the fact that the atomic radius of the silicon atom is a size that is easy to move in the phase and that it is suitable for existing at the interface. The silicon atoms present at the interface are considered to fill the voids, defects, etc. at the interface, and the penetration rate of hydrogen atoms and the like from the outside is reduced, and as a result, it is assumed that a sufficient passivation effect is obtained.

  In general, when a silicon nitride film is formed on a passivation layer, hydrogen atoms contained in the silicon nitride film are likely to enter the passivation layer by heat treatment (firing), and it is difficult to obtain a sufficient passivation effect. This is presumably because the charge disappears or the interface state increases due to the invading hydrogen atom. However, even when a silicon nitride film is formed on the passivation layer, if the passivation layer contains Si, a sufficient passivation effect can be obtained by the above effect.

  When the passivation layer contains Si, the Si content can be selected as appropriate. From the viewpoint of the passivation effect, the Si content in the passivation layer is, for example, preferably 0.01% by mass to 40% by mass, more preferably 0.1% by mass to 35% by mass, and 0 More preferably, the content is 5% by mass to 30% by mass.

  The Si content in the passivation layer is determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), or high frequency inductively coupled plasma mass spectrometry (ICP). -MS).

  The thickness of the passivation layer is not particularly limited and can be appropriately selected according to the purpose. For example, the average thickness of the passivation layer can be 500 nm or less, preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, still more preferably 10 nm to 250 nm, and more preferably 15 nm to 200 nm. It is particularly preferred.

  The average thickness of the passivation layer is calculated as an arithmetic average value obtained by measuring the thickness of nine points by an ordinary method using an automatic ellipsometer (for example, FIBRabo Inc., MARY-102).

  In addition to the passivation effect, the passivation layer may have other effects. Specifically, other effects include an effect as a protective layer for protecting the surface of the semiconductor, an effect as an antireflection film having a desired refractive index, and the like.

(Semiconductor substrate)
It does not restrict | limit especially as a semiconductor substrate, According to the objective, it can select suitably from what is normally used. As the semiconductor substrate, for example, a substrate made of silicon, germanium, or the like, doped (diffused) with p-type impurities or n-type impurities can be used. Among these, a silicon substrate is preferable. The semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate. Among these, from the viewpoint of the passivation effect, a semiconductor substrate in which the surface on which the passivation layer is formed is a p-type layer is preferable. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, the p-type layer is formed on the n-type semiconductor substrate or the p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer. It may be a thing.

  The thickness in particular of a semiconductor substrate is not restrict | limited, According to the objective, it can select suitably. The average thickness of the semiconductor substrate can be, for example, 50 μm to 1000 μm, and preferably 75 μm to 750 μm.

When the semiconductor substrate with a passivation layer is applied to a solar cell element, the passivation layer may be provided on either the light receiving surface side or the back surface side of the solar cell element.
Moreover, the passivation layer containing Bi is suitable for a passivation layer on the back surface side of the p-type semiconductor substrate and the light-receiving surface side of the n-type semiconductor substrate, which are p-type layers. This is because the passivation layer containing Bi has a negative fixed charge.

(Silicon nitride film)
The semiconductor substrate with a passivation layer of this embodiment has a silicon nitride film provided on the passivation layer. By providing a silicon nitride film on the passivation layer, even when an aluminum electrode is formed on the silicon nitride film using an aluminum electrode paste, aluminum atoms are prevented from entering the passivation layer, and a sufficient passivation effect is obtained. Tends to be obtained.

  The thickness of the silicon nitride film is not particularly limited and can be appropriately selected according to the purpose. The average thickness of the silicon nitride film is, for example, preferably 500 nm or less, more preferably 10 nm to 400 nm, still more preferably 15 nm to 300 nm, and particularly preferably 20 nm to 250 nm. The average thickness of the silicon nitride film is calculated in the same manner as the passivation layer.

  In addition, the semiconductor substrate with a passivation layer of the present embodiment is formed, for example, after a composition layer is formed by applying a composition for forming a passivation layer to at least a part of at least one surface of the semiconductor substrate as described later. The composition layer can be heat-treated to form a passivation layer, and after forming the passivation layer, a silicon nitride film can be formed on the passivation layer by plasma CVD (PECVD) or the like.

(Relationship between passivation layer and silicon nitride film)
In this embodiment, the total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm. When the average thickness of the passivation layer and the silicon nitride film is less than 10 nm, the aluminum layer penetrates into the passivation layer using the aluminum electrode paste on the passivation layer, and the passivation effect is reduced. There is. In addition, when the total average thickness of the passivation layer and the silicon nitride film is larger than 1000 nm, at least one of the passivation layer and the silicon nitride film is liable to generate fine cracks, resulting in a decrease in the passivation effect and warping of the wafer. It may be easier.
The total average thickness of the passivation layer and the silicon nitride film is preferably 25 nm to 800 nm, more preferably 50 nm to 600 nm, and even more preferably 75 nm to 500 nm.
The ratio of the average thickness of the passivation layer to the average thickness of the silicon nitride film (passivation layer / silicon nitride film) is preferably 0.01 to 100, more preferably 0.02 to 50, and More preferably, it is 05-10. In the case where a silicon nitride film is provided as an antireflection film or the like on the surface of the semiconductor substrate where the passivation layer is not provided, the silicon nitride film provided on the surface where the passivation layer is not provided is provided. The thickness is not considered when calculating the ratio between the average thickness of the passivation layer and the average thickness of the silicon nitride film.

<Composition for forming a passivation layer>
The composition for forming a passivation layer is not particularly limited as long as it can form a passivation layer containing Bi by heat treatment. Among these, from the viewpoints of impartability, the denseness of the formed passivation layer and the passivation effect, a bismuth compound represented by the following general formula (I) (hereinafter also referred to as “compound of formula (I)”) is contained. It is preferable to use a composition for forming a passivation layer (hereinafter also referred to as “specific composition for forming a passivation layer”). The composition for forming a specific passivation layer may further contain other components as necessary.

Bi (OR ¹ ) _m (I)

In general formula (I), each R ¹ independently represents an alkyl group, an aryl group, or an acyl group. m represents 3 or 5.

(Compound of formula (I))
The composition for specific passivation layer formation contains the compound (formula (I) compound) represented by general formula (I). The composition for specific passivation layer formation may contain 1 type of compounds of a formula (I), and may contain 2 or more types.
When the composition for forming a specific passivation layer contains the compound of formula (I), a passivation layer having an excellent passivation effect can be formed by a simple technique. The reason can be considered as follows.

Bismuth oxide (Bi ₂ O ₃ or Bi ₂ O ₅ ) formed by heat-treating (firing) the composition for forming a specific passivation layer containing the compound of formula (I) has defects of bismuth atoms or oxygen atoms. However, it is considered that a large negative fixed charge is likely to be generated. This fixed charge generates an electric field in the vicinity of the interface of the semiconductor substrate, so that the concentration of minority carriers can be reduced. As a result, the carrier recombination rate at the interface is suppressed, and an excellent passivation effect is obtained. It is done.

  Here, regarding the state of the passivation layer that generates a fixed charge on the semiconductor substrate, a cross section of the semiconductor substrate is observed with a scanning transmission electron microscope (STEM), and electron energy loss spectroscopy (EELS, Electron) is observed. This can be confirmed by examining the binding mode in the analysis of Energy Loss Spectroscopy. Further, by measuring an X-ray diffraction spectrum (XRD, X-ray diffraction), the crystal phase near the interface of the passivation layer can be confirmed. Furthermore, the fixed charge of the passivation layer can be evaluated by the CV method (Capacitance Voltage measurement).

In addition, the passivation layer formed from the composition for forming a passivation layer may have a larger surface state density obtained by the CV method than the aluminum oxide layer formed by the ALD method or the CVD method. is there. However, since the passivation layer formed from the composition for forming the specific passivation layer has a large electric field effect, the minority carrier concentration decreases and the surface lifetime τ _s increases. Therefore, the surface state density is not a relative problem.

  In addition, the passivation layer formed by heat-treating (firing) the composition for forming a specific passivation layer containing the compound of formula (I) can easily maintain the passivation effect even when placed in an environment such as high temperature and vacuum. There is a tendency.

In the general formula (I), each R ¹ independently represents an alkyl group, an aryl group, or an acyl group. m represents 3 or 5, and m is preferably 3.

R ¹ is preferably independently an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an acyl group having 1 to 10 carbon atoms. The alkyl group represented by R ¹ may be linear or branched.

Each of the alkyl group and aryl group represented by R ¹ may have a substituent or may be unsubstituted, and is preferably unsubstituted.
Examples of the substituent for the alkyl group include an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Examples of the substituent for the aryl group include a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group.

The acyl group represented by R ¹ includes a carbonyl group moiety and a hydrogen atom directly bonded to a carbon atom of the alkyl group moiety, aryl group moiety or carbonyl group moiety. The alkyl group moiety in the acyl group represented by R ¹ may be linear or branched. The alkyl group part and the aryl group part in the acyl group represented by R ¹ may have a substituent, may be unsubstituted, and are preferably unsubstituted. Examples of the substituent of the alkyl group moiety in the acyl group represented by R ¹ include a phenyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Examples of the substituent of the aryl group moiety in the acyl group represented by R ¹ include a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group.
The carbon number of the alkyl group and aryl group represented by R ¹ does not include the carbon number of the substituent.

Specific examples of the alkyl group represented by R ¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and n-hexyl group. N-octyl group, 2-ethylhexyl group, 3-ethylhexyl group and the like.
Specific examples of the aryl group represented by R ¹ include a phenyl group.
Specific examples of the acyl group represented by R ¹ include a formyl group, an acetyl group, a benzoyl group, and a 2-ethylhexanoyl group.
Among these, R ¹ is preferably an acyl group from the viewpoint of storage stability.

  The state of the compound of formula (I) may be solid or liquid at 25 ° C. From the viewpoint of the storage stability of the composition for forming a passivation layer and the miscibility with water, an aluminum oxide precursor or a compound represented by the general formula (III) contained as necessary, the compound of the formula (I) is: It is preferably liquid at 25 ° C.

  The compound of formula (I) is specifically bismuth acetate (III), bismuth trishexanoate, bismuth tris (2-ethylhexanoate), bismuth trisoctanoate, bismuth tris (2,2-dimethyloctanoate), Examples thereof include bismuth trisneodecanoate and bismuth isopropoxide. Among them, as the compound of formula (I), tris (2-ethylhexanoic acid) bismuth is preferable.

  The compound of formula (I) may be prepared or commercially available. As a commercial item, the tris (2-ethylhexanoic acid) bismuth etc. of an AMAX Co., Ltd. can be mentioned, for example.

  The compound of formula (I) is prepared by reacting a bismuth halide with an alcohol in the presence of an inert organic solvent, and further adding ammonia or amines to extract the halogen (Japanese Patent Laid-Open No. 63-227593). Known manufacturing methods such as Japanese Patent Laid-Open No. 3-291247 and Japanese Patent Laid-Open No. 3-291247) can be used.

  The compound of formula (I) may form a chelate structure by mixing with a compound having a specific structure having two carbonyl groups described later. Examples of the compound having a chelate structure include tris (hexafluoroacetylacetonato) bismuth and bismuth tris (2,2,6,6-tetramethyl-3,5-heptanedionate).

  The presence of the alkoxide structure in the compound of formula (I) can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  The content rate of the compound of Formula (I) contained in the composition for specific passivation layer formation can be suitably selected as needed. From the viewpoint of the passivation effect, the content of the compound of formula (I) is, for example, preferably 1% by mass to 80% by mass with respect to the total mass of the specific passivation layer forming composition, and 3% by mass to 50%. More preferably, it is more preferably 5% by mass to 30% by mass, and particularly preferably 7% by mass to 20% by mass.

  The composition for forming the specific passivation layer may contain a Bi oxide in addition to the compound of formula (I) as a Bi source. The content of the compound of formula (I) with respect to the total mass of the bismuth compound as the Bi source is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. It is preferably 98% by mass or more.

When the composition for specific passivation layer formation contains the aluminum oxide precursor mentioned later, the content rate of a formula (I) compound is not restrict | limited in particular. Among them, the content of the compound of the formula (I) with respect to the total mass of the compound of the formula (I) and the aluminum oxide precursor is, for example, preferably 0.5% by mass to 90% by mass, and 1% by mass to 75%. More preferably, it is more preferably 2% by mass to 70% by mass, and particularly preferably 3% by mass to 70% by mass.
By setting the content of the compound of formula (I) to 0.5% by mass or more, the passivation effect tends to be improved. Moreover, it exists in the tendency for the storage stability of the composition for passivation layer formation to improve by making content rate of a compound of Formula (I) into 90 mass% or less.

(water)
The composition for forming a specific passivation layer may contain water. Moreover, the composition for specific passivation layer formation may contain the hydrolyzate of the compound of formula (I). It has been found that the action of water on the compound of formula (I) improves the thixotropy of the composition. Although the mechanism is not clear, it can be considered as follows.

  By allowing water to act on the compound of formula (I), a hydrolyzate of the compound of formula (I) is formed, and the hydrolyzate of the compound of formula (I) is considered to form a network between metal compounds. Further, it is considered that this network is easily broken when the composition for forming a passivation layer is flowing, and is re-formed when the composition becomes stationary again. This network increases the viscosity when the composition for forming a passivation layer is stationary, and decreases the viscosity when the composition is flowing. As a result, it is considered that the viscosity ratio at the high shear rate and the low shear rate of the composition for forming a passivation layer, that is, the thixotropy, is improved, and the thixotropy necessary for pattern formation is expressed.

  In the composition for forming a passivation layer, the thixotropy is improved by allowing water to act on the compound of formula (I), and the composition for forming a passivation layer is applied to a semiconductor substrate. Shape stability is further improved, and a passivation layer can be selectively formed at a desired position in a desired shape. Therefore, in the composition for forming a passivation layer containing water, in order to express desired thixotropy, at least one of a thixotropic agent and a resin to be described later (hereinafter, at least one of the thixotropic agent and the resin may be referred to as a thixotropic agent). Even if a thixotropic agent or the like is used, the amount added can be reduced as compared with the conventional passivation layer-forming composition.

  When forming a passivation layer using a composition for forming a passivation layer containing a thixotropic agent composed of organic matter, the thixotropic agent may be thermally decomposed and volatilized from the passivation layer through a degreasing process. is there. Further, a thermal decomposition product such as a thixotropic agent may remain in the passivation layer as an impurity even after the degreasing process, and the remaining thermal decomposition product such as a thixotropic agent may cause deterioration of the characteristics of the passivation layer. On the other hand, when forming a passivation layer using a composition for forming a passivation layer containing a thixotropic agent composed of an inorganic substance, the thixotropic agent may not be volatilized and remain in the passivation layer even after a heat treatment (firing) step. . The remaining thixotropic agent may cause deterioration of the properties of the passivation layer.

  On the other hand, in the composition for forming a passivation layer containing water, it is considered that water or a hydrolyzate of the compound of formula (I) behaves as a thixotropic agent when water acts on the compound of formula (I). Water is more easily volatilized from the passivation layer than a conventional thixotropic agent or the like in a heat treatment (firing) step or the like performed when the passivation layer is formed using the composition for forming a passivation layer. For this reason, there is a tendency that the passivation effect of the passivation layer is less likely to be lowered due to the presence of the residue in the passivation layer.

  As described above, when the composition for forming a passivation layer contains water, it is possible to form a passivation layer having excellent pattern forming properties and excellent passivation effect by a simple method. Moreover, a passivation layer having a desired shape can be formed by using a composition for forming a passivation layer having excellent pattern formability. This makes it possible to manufacture an excellent semiconductor substrate with a passivation layer, a solar cell element, and a solar cell.

  The water state may be solid or liquid. From the viewpoint of miscibility with the compound of formula (I), water is preferably a liquid.

The content of water contained in the composition for forming a passivation layer can be appropriately selected as necessary.
From the viewpoint of imparting thixotropy to the composition for forming a passivation layer, the water content is preferably, for example, 0.01% by mass or more with respect to the total mass of the composition for forming a passivation layer. The content is more preferably 03% by mass or more, further preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more.
Moreover, it is preferable that the content rate of water is 80 mass% or less with respect to the total mass of the composition for passivation layer formation from a viewpoint of pattern formation property and a passivation effect, for example, and it is 70 mass% or less. Is more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

  The amount of water acting on the compound of formula (I) in the composition for forming a passivation layer can be calculated from the amount of alcohol or carboxylic acid liberated from the compound of formula (I). When water acts on the compound of formula (I), alcohol or carboxylic acid is liberated from the compound of formula (I). The amount of this free alcohol or carboxylic acid is proportional to the number of functional groups of the compound of formula (I) to which water has acted. Therefore, by measuring the amount of the liberated alcohol or carboxylic acid, the amount of water acting on the compound of formula (I) can be calculated. Measurement of the amount of liberated alcohol or carboxylic acid can be confirmed using, for example, gas chromatography mass spectrometry (GC-MS).

  The content of the alcohol or carboxylic acid contained in the composition for forming a passivation layer is, for example, preferably 0.5% by mass to 70% by mass, more preferably 1% by mass to 60% by mass. It is further more preferable that it is mass%-50 mass%.

The composition for forming a passivation layer may contain at least one hydrolyzate of the compound of formula (I), and if necessary, contains at least one hydrolyzate of an aluminum oxide precursor described later. It may contain, and may contain at least 1 sort (s) of hydrolyzate of the formula (III) compound mentioned later.
The hydrolyzate of the compound of formula (I) may contain a dehydration condensate of the hydrolyzate of the compound of formula (I), and the hydrolyzate of the aluminum oxide precursor includes an aluminum oxide precursor. The hydrolyzate of the hydrolyzate of formula (III) may be contained, and the hydrolyzate of the compound of formula (III) may contain the dehydration condensate of the hydrolyzate of the compound of formula (III).

  In the composition for forming a passivation layer containing water, the content of the compound of formula (I) is the total content of the compound of formula (I) and the hydrolyzate of the compound of formula (I) in the composition for forming a passivation layer. is there. Further, in the composition for forming a passivation layer containing water, the content of the aluminum oxide precursor described later is the total content of the aluminum oxide precursor and the hydrolyzate of the aluminum oxide precursor in the composition for forming the passivation layer. It is. Furthermore, in the composition for forming a passivation layer containing water, the content of the compound of formula (III) described later is the sum of the compound of formula (III) and the hydrolyzate of the compound of formula (III) in the composition for forming a passivation layer. It is the content rate of. Furthermore, in the composition for forming a passivation layer containing water, the content of the silicon compound is the total content of the silicon compound and the hydrolyzate of the silicon compound in the composition for forming the passivation layer.

(Aluminum oxide precursor)
The composition for forming a passivation layer may contain an aluminum oxide precursor. The aluminum oxide precursor is not particularly limited as long as it can produce aluminum oxide by heat treatment (firing). The composition for forming a passivation layer may contain one type of aluminum oxide precursor or two or more types.

The aluminum oxide precursor becomes aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing). At this time, the formed aluminum oxide tends to be in an amorphous state, and a four-coordinate aluminum oxide layer is easily formed in the vicinity of the interface with the semiconductor substrate. It is considered that due to the four-coordinate aluminum oxide layer, a large negative fixed charge can be provided in the vicinity of the interface with the semiconductor substrate. Thereby, an electric field is generated in the vicinity of the interface with the semiconductor substrate, and the concentration of minority carriers can be reduced. As a result, it is considered that the carrier recombination rate at the interface with the semiconductor substrate is suppressed, and an excellent passivation effect is obtained.

In addition to the above, by combining the compound of formula (I) and the aluminum oxide precursor, it is considered that the passivation effect becomes higher due to the respective effects in the passivation layer. Further, the composite metal alkoxide of bismuth (Bi) and aluminum (Al) contained in the compound of formula (I) is formed by heat treatment (firing) in the state where the compound of formula (I) and the aluminum oxide precursor coexist. Generate. Thereby, the physical properties such as the reactivity and vapor pressure of the composition for forming a passivation layer are improved, the denseness of the passivation layer as a heat-treated product (baked product) is improved, and as a result, the passivation effect is considered to be higher. .
In this specification, the denseness of the passivation layer can be evaluated by visually confirming the occurrence of unevenness and voids from the contrast of the observed image using a transmission electron microscope. It can be said that the smaller the occurrence of unevenness and voids in the passivation layer, the higher the density.

Here, the presence or absence of tetracoordinated aluminum oxide is determined by observing the cross section of the semiconductor substrate with a scanning transmission electron microscope (STEM) and coupling with electron energy loss spectroscopy (EELS). Can be confirmed by analyzing. Tetracoordinated aluminum oxide is considered to be a structure in which the center of silicon dioxide (SiO ₂ ) is isomorphously substituted from silicon to aluminum, and is formed as a negative charge source at the interface between silicon dioxide and aluminum oxide like zeolite and clay. It is known.

  In addition, the state of the formed aluminum oxide can be confirmed by measuring an X-ray diffraction spectrum (XRD, X-ray diffraction). For example, it can be confirmed that the XRD has an amorphous structure by not showing a specific reflection pattern.

  The aluminum oxide precursor may be liquid or solid. From the viewpoint of the passivation effect and storage stability, it is desirable to use an aluminum oxide precursor that has good stability at room temperature (for example, 25 ° C.). Moreover, when using a solvent, it is desirable to use an aluminum oxide precursor having good solubility or dispersibility in the solvent. By using such an aluminum oxide precursor, the homogeneity of the formed passivation layer is further improved, and a desired passivation effect tends to be stably obtained.

  As the aluminum oxide precursor, an organic aluminum oxide precursor is preferably used, and examples thereof include a compound represented by the following general formula (II) (hereinafter also referred to as “specific aluminum compound”).

In general formula (II), each R ² independently represents an alkyl group. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represents a hydrogen atom or an alkyl group. Here, when any one of R ^{2 to} R ⁵ , X ² and X ³ is present in plural, groups represented by the same plural symbols may be the same or different from each other.

In formula (II), R ² represents an alkyl group independently, preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. The alkyl group represented by R ² may be linear or branched. The alkyl group represented by R ² may have a substituent or may be unsubstituted, and is preferably unsubstituted. Examples of the substituent for the alkyl group include an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Note that the carbon number of the alkyl group represented by R ² does not include the carbon number of the substituent.

The alkyl group represented by R ² is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms and is an unsubstituted alkyl group having 1 to 4 carbon atoms from the viewpoint of storage stability and a passivation effect. It is more preferable.

Specific examples of the alkyl group represented by R ² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and n-hexyl group. N-octyl group, 2-ethylhexyl group, 3-ethylhexyl group and the like.

  In general formula (II), n represents the integer of 0-3. From the viewpoint of suppressing the occurrence of defects such as gelation and ensuring storage stability over time, it is preferably an integer of 1 to 3, more preferably 1 or 3, and 1 from the viewpoint of solubility. More preferably it is.

X ² and X ³ in the general formula (II) each independently represent an oxygen atom or a methylene group. From the viewpoint of storage stability, at least one of X ² and X ³ is preferably an oxygen atom.

R ³ , R ⁴ and R ⁵ in the general formula (II) each independently represent a hydrogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and preferably a hydrogen atom or carbon number 1 More preferably, it is an alkyl group of ˜4. The alkyl group represented by R ³ , R ⁴ and R ⁵ may be linear or branched. The alkyl group represented by R ³ , R ⁴ and R ⁵ may have a substituent or may be unsubstituted, and is preferably unsubstituted. Examples of the substituent for the alkyl group include an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Note that the carbon number of the alkyl group represented by R ³ , R ^4, and R ⁵ does not include the carbon number of the substituent.

Among these, from the viewpoints of storage stability and a passivation effect, R ³ and R ⁴ in the general formula (II) are each independently preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms. Or it is more preferable that it is a C1-C4 unsubstituted alkyl group.
In addition, R ⁵ in the general formula (II) is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and a passivation effect, and is a hydrogen atom or 1 to 4 carbon atoms. It is more preferably an unsubstituted alkyl group.

Specific examples of the alkyl group represented by R ³ , R ⁴ and R ⁵ in the general formula (II) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group. , T-butyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, 3-ethylhexyl group and the like.

The specific aluminum compound is a compound in which n in the general formula (II) is 0 and R ² is each independently an alkyl group having 1 to 4 carbon atoms, from the viewpoint of storage stability and a passivation effect, N in the formula (II) is an integer of 1 to 3, R ² is independently an alkyl group having 1 to 4 carbon atoms, and at least one of X ² and X ³ is an oxygen atom, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁵ is each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. It is preferable that at least one selected.
More preferably, the specific aluminum compound is a compound in which n in the general formula (II) is 0 and R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and the general formula (II) N is an integer of 1 to 3, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and at least one of X ² and X ³ is an oxygen atom, When R ³ or R ⁴ bonded to the oxygen atom is an alkyl group having 1 to ⁴ carbon atoms and X ² or X ³ is a methylene group, R ³ or R ⁴ bonded to the methylene group is a hydrogen atom, , R ⁵ is at least one selected from the group consisting of compounds each having a hydrogen atom.

In the specific aluminum compound, from the viewpoint of storage stability by chelation, n in the general formula (II) is an integer of 1 to 3, and R ⁵ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A certain compound is preferable.

  Specific examples of the specific aluminum compound (aluminum trialkoxide) represented by the general formula (II) where n is 0 include trimethoxyaluminum, triethoxyaluminum, triisopropoxyaluminum, trisec-butoxyaluminum, monosec- Examples include butoxy-diisopropoxyaluminum, tritert-butoxyaluminum, and tri-n-butoxyaluminum.

  Specific examples of the specific aluminum compound represented by the general formula (II), where n is an integer of 1 to 3, include aluminum ethyl acetoacetate diisopropylate, aluminum methyl acetoacetate diisopropylate, aluminum tris (ethyl acetoacetate). ), Aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum tris (acetylacetonate), and the like.

  The specific aluminum compound represented by the general formula (II) and n is an integer of 1 to 3 may be prepared or commercially available. Commercially available products include, for example, trade names of Kawaken Fine Chemical Co., Ltd., ALCH, ALCH-50F, ALCH-75, ALCH-TR, ALCH-TR-20, aluminum chelate M, aluminum chelate D, and aluminum chelate A (W). Can be mentioned.

The specific aluminum compound represented by the general formula (II) and n is an integer of 1 to 3 is prepared by mixing an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups described later. Can do. A commercially available aluminum chelate compound may also be used.
When an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups are mixed, at least a part of the alkoxy group of the aluminum trialkoxide is substituted with a compound having a specific structure to form an aluminum chelate structure. At this time, if necessary, a liquid medium may be present, and heat treatment, addition of a catalyst, and the like may be performed. By replacing at least part of the aluminum alkoxide structure with the aluminum chelate structure, the stability of the specific aluminum compound to hydrolysis and polymerization reaction is improved, and the storage stability of the composition for forming a passivation layer containing this is further improved. To do.

  The compound having a specific structure having two carbonyl groups is preferably at least one selected from the group consisting of a β-diketone compound, a β-ketoester compound, and a malonic acid diester from the viewpoint of reactivity and storage stability. . Specific examples of the compound having a specific structure having two carbonyl groups include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl. -2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione, etc. Β-diketone compound; methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, isobutyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, n-pentyl acetoacetate, isopentyl acetoacetate, N-hexyl acetoacetate, n-octyl acetoacetate, n-heptyl acetoacetate, 3-pentyl acetoacetate, 2-acetate Ethyl luheptanoate, ethyl 2-methylacetoacetate, ethyl 2-butylacetoacetate, ethyl hexylacetoacetate, ethyl 4,4-dimethyl-3-oxovalerate, ethyl 4-methyl-3-oxovalerate, ethyl 2-ethylacetoacetate Methyl 4-methyl-3-oxovalerate, ethyl 3-oxohexanoate, ethyl 3-oxovalerate, methyl 3-oxovalerate, methyl 3-oxohexanoate, ethyl 3-oxoheptanoate, 3-oxo Β-ketoester compounds such as methyl heptanoate and methyl 4,4-dimethyl-3-oxovalerate; dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate Di-t-butyl malonate, di-n-hexyl malonate, t-butylethyl malonate, methylmalonate And malonic acid diesters such as diethyl acetate, diethyl ethylmalonate, diethyl isopropylmalonate, diethyl n-butylmalonate, diethyl sec-butylmalonate, diethyl isobutylmalonate, diethyl 1-methylbutylmalonate, etc. it can.

  When the specific aluminum compound has an aluminum chelate structure, the number of aluminum chelate structures is not particularly limited as long as it is 1 to 3. Among these, 1 or 3 is preferable from the viewpoint of storage stability, and 1 is more preferable from the viewpoint of solubility. The number of aluminum chelate structures can be controlled, for example, by appropriately adjusting the ratio of mixing aluminum trialkoxide and a compound having a specific structure having two carbonyl groups. Moreover, you may select suitably the compound which has a desired structure from a commercially available aluminum chelate compound.

  The specific aluminum compound is at least one selected from the group consisting of aluminum ethyl acetoacetate diisopropylate and triisopropoxyaluminum from the viewpoint of the passivation effect and compatibility with the solvent contained as necessary. Preferably, it contains aluminum ethyl acetoacetate diisopropylate, and more preferably.

  The presence of the aluminum chelate structure and the presence of the alkoxide structure in the specific aluminum compound can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  When the aluminum oxide precursor contains a specific aluminum compound, the content of the specific aluminum compound in the aluminum oxide precursor is, for example, preferably 80% by mass or more, more preferably 90% by mass or more, and 95 More preferably, it is at least mass%.

  When the composition for forming a passivation layer contains an aluminum oxide precursor, the content of the aluminum oxide precursor in the composition for forming a passivation layer can be appropriately selected as necessary. The content of the aluminum oxide precursor is preferably, for example, 0.1% by mass to 60% by mass with respect to the total mass of the composition for forming a passivation layer from the viewpoint of storage stability and a passivation effect. More preferably, it is 5 mass%-55 mass%, It is more preferable that it is 1 mass%-50 mass%, It is especially preferable that it is 1 mass%-45 mass%.

When the composition for forming a passivation layer contains an aluminum oxide precursor, the content of the aluminum oxide precursor is not particularly limited. Especially, it is preferable that the content rate of the aluminum oxide precursor with respect to the total mass of a compound of a formula (I) and an aluminum oxide precursor is 10 mass%-99.5 mass%, for example, 25 mass%-99 mass%. %, More preferably 30% by mass to 98% by mass, and particularly preferably 30% by mass to 97% by mass.
By setting the content of the aluminum oxide precursor to 10% by mass or more, the passivation effect tends to be improved. Moreover, it exists in the tendency for the storage stability of the composition for passivation layer formation to improve because the content rate of an aluminum oxide precursor shall be 99.5 mass% or less.

(Compound represented by formula (III))
The composition for forming a passivation layer may contain a compound represented by the following general formula (III) (hereinafter also referred to as “compound of formula (III)”). When the composition for forming a passivation layer contains the compound of formula (III), a passivation layer having an excellent passivation effect can be formed. In addition, the composition for formation of a passivation layer may contain 1 type of compounds of Formula (III), and may contain 2 or more types. When the composition for forming a passivation layer contains the compound of the formula (III), a larger negative fixed charge is developed, and the passivation effect tends to be further improved. Moreover, when the composition for forming a passivation layer containing the compound of formula (III) is heat-treated (fired), a composite oxide having a large refractive index tends to be generated. When a solar cell element using a composite oxide having a large refractive index as a passivation layer is created, sunlight tends to re-enter the back surface of the passivation layer and the semiconductor substrate without improving the power generation performance. .

M ¹ (OR ⁶ ) _l (III)

In the general formula (III), M ¹ is at least one selected from the group consisting of Nb, Ta, VO, Y and Hf, and provides a passivation effect, a pattern forming property of the composition for forming a passivation layer, and a passivation layer. From the viewpoint of workability in preparing the composition for forming, M ¹ is preferably at least one selected from the group consisting of Nb, Ta and Y, and the thixotropic property of the composition for forming a passivation layer From the viewpoint, Nb is more preferable.

In General Formula (III), each R ⁶ independently represents an alkyl group, an aryl group, or an acyl group, and is an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. An acyl group is preferable, an alkyl group having 1 to 8 carbon atoms is more preferable, and an alkyl group having 1 to 4 carbon atoms is more preferable. The alkyl group represented by R ⁶ may be linear or branched.

The alkyl group and aryl group represented by R ⁶ may have a substituent or may be unsubstituted, and is preferably unsubstituted. Examples of the substituent of the alkyl group include an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group. Examples of the substituent of the aryl group include a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxy group, A carboxy group, a sulfo group, a nitro group, etc. are mentioned.

The acyl group represented by R ⁶ includes a carbonyl group portion and at least one of an alkyl group portion and an aryl group portion. The alkyl group moiety in the acyl group represented by R ⁶ may be linear or branched. The alkyl group part and the aryl group part in the acyl group represented by R ⁶ may have a substituent, may be unsubstituted, or are preferably unsubstituted. Examples of the substituent of the alkyl group moiety in the acyl group represented by R ⁶ include a phenyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group, and an aryl group in the acyl group represented by R ^6. Examples of the substituent of the group part include a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxy group, a carboxy group, a sulfo group, and a nitro group.
The number of carbon atoms of the substituent is not included in the number of carbon atoms of the alkyl group, aryl group, and acyl group represented by R ⁶ .

Specific examples of the alkyl group represented by R ⁶ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and n-hexyl group. N-octyl group, 2-ethylhexyl group, 3-ethylhexyl group and the like.
Specific examples of the aryl group represented by R ⁶ include a phenyl group.
Specific examples of the acyl group represented by R ⁶ include formyl group, acetyl group, benzoyl group, and 2-ethylhexanoyl group.
Among these, R ⁶ is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, from the viewpoint of the passivation effect.

In the general formula (III), l represents the valence of ^{M 1.} L is preferably 5 when M ¹ is Nb, l is preferably 5 when M ¹ is Ta, and l is 3 when M ¹ is VO. Preferably, when M ¹ is Y, l is preferably 3, and when M ¹ is Hf, l is preferably 4.

As the compound of formula (III), M ¹ is at least one selected from the group consisting of Nb, Ta and Y, and R ⁶ is preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, A compound in which M ¹ is Nb and R ⁵ is an unsubstituted alkyl group having 1 to 4 carbon atoms is more preferable.

  The compound of formula (III) may be solid or liquid at normal temperature (25 ° C.). From the viewpoint of the storage stability of the composition for forming a passivation layer and the miscibility between the compound of formula (I) and the aluminum oxide precursor, the compound of formula (III) is preferably liquid at room temperature (25 ° C.).

Specific examples of the compound of formula (III) in which R ⁶ is an alkyl group include niobium methoxide, niobium ethoxide, niobium isopropoxide, niobium n-propoxide, niobium n-butoxide, niobium t-butoxide, niobium iso Butoxide, Tantalum methoxide, Tantalum ethoxide, Tantalum isopropoxide, Tantalum n-propoxide, Tantalum n-butoxide, Tantalum t-butoxide, Tantalum isobutoxide, Yttrium methoxide, Yttrium ethoxide, Yttrium isopropoxide, Yttrium n -Propoxide, yttrium n-butoxide, yttrium t-butoxide, yttrium isobutoxide, vanadium oxymethoxide, vanadium oxyethoxide, vanadium oxyisopropoxide, vanadium oxy Si-propoxide, vanadium oxy n-butoxide, vanadium oxy t-butoxide, vanadium oxyisobutoxide, hafnium methoxide, hafnium ethoxide, hafnium isopropoxide, hafnium n-propoxide, hafnium n-butoxide, hafnium t- Butoxide, hafnium isobutoxide, and the like, among which niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, yttrium isopropoxide, and yttrium n-Butoxide is preferred.

Specific examples of the compound of formula (III) in which R ⁶ is an aryl group include niobium phenoxide, tantalum phenoxide, yttrium phenoxide, hafnium phenoxide and the like.

Compounds of formula (III) in which R ⁶ is an acyl group are niobium formate, niobium acetate, niobium 2-ethylhexanoate, tantalum acetate, tantalum 2-ethylhexanoate, yttrium formate, yttrium acetate, yttrium 2-ethylhexanoate, Examples include hafnium formate, hafnium acetate, and hafnium 2-ethylhexanoate.

  The compound of formula (III) may be prepared or commercially available. Commercially available products include, for example, pentamethoxyniobium, pentaethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, penta-i-butoxyniobium, penta-n-butoxyniobium from High Purity Chemical Laboratory Co., Ltd. , Penta-sec-butoxy niobium, pentamethoxy tantalum, pentaethoxy tantalum, penta-i-propoxy tantalum, penta-n-propoxy tantalum, penta-i-butoxy tantalum, penta-n-butoxy tantalum, penta-sec-butoxy tantalum Penta-t-butoxytantalum, vanadium (V) trimethoxide oxide, vanadium (V) triethoxide oxide, vanadium (V) tri-i-propoxide oxide, vanadium (V) tri-n-propoxide oxide, vanadium( ) Tri-i-butoxide oxide, vanadium (V) tri-n-butoxide oxide, vanadium (V) tri-sec-butoxide oxide, vanadium (V) tri-t-butoxide oxide, tri-i-propoxy yttrium, tri- n-butoxy yttrium, tetramethoxy hafnium, tetraethoxy hafnium, tetra-i-propoxy hafnium, tetra-t-butoxy hafnium, pentaethoxyniobium, pentaethoxy tantalum, pentaboxy tantalum, yttrium-n-butoxide from Hokuko Chemical Co., Ltd. , Hafnium-tert-butoxide, vanadium oxytriethoxide, vanadium oxytrinormal propoxide, vanadium oxytrinormal butoxide, vanadium oxy from Nichia Corporation Triisobutoxide include vanadium oxy-tri secondary butoxide and the like.

In the preparation of the compound of formula (III), a halide of a specific metal (M ¹ ) and an alcohol are reacted in the presence of an inert organic solvent, and ammonia or amines are added in order to further extract halogen ( Known manufacturing methods such as JP-A-63-227593 and JP-A-3-291247) can be used.

  The compound of formula (III) may be contained in the composition for forming a passivation layer as a compound in which a chelate structure is formed by mixing with a compound having a specific structure having two carbonyl groups in the same manner as the compound of formula (I). .

  The presence of the alkoxide structure in the compound of formula (III) can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  The content of the compound of formula (III) contained in the composition for forming a passivation layer can be appropriately selected as necessary. From the viewpoint of the passivation effect, the content of the compound of formula (III) is preferably, for example, 0.1% by mass to 50% by mass with respect to the total mass of the composition for forming a passivation layer, and 0.5% by mass. % To 30% by mass is more preferable, 1% to 20% by mass is further preferable, and 1% to 10% by mass is particularly preferable.

(Silicon compound)
The composition for forming a passivation layer may contain a silicon compound. The silicon compound is physically or chemically interacted or chemically bonded with the compound of formula (I), the aluminum oxide precursor, the compound of formula (III), the resin, the liquid medium, etc. in the composition for forming a passivation layer, The surface tension of the composition for forming a passivation layer can be controlled. Thereby, the thickness nonuniformity of the composition layer which is a coating film is suppressed, and the variation in the thickness of the passivation layer formed is suppressed. In addition, the generation of voids in the heat-treated product layer (baked product layer) of the passivation layer forming composition is suppressed, the density of the passivation layer is improved, and a uniform passivation layer is formed. Is obtained.

The silicon compound is not particularly limited as long as it contains a silicon atom in the molecule. The silicon compound is preferably a compound in which an oxygen atom is bonded to a silicon atom from the viewpoint of easy preparation of the composition for forming a passivation layer. The compound in which an oxygen atom is bonded to a silicon atom may form a complex with at least one selected from the group consisting of an organic compound and an inorganic compound.
Specific examples of the silicon compound include silicon alkoxides, silicate compounds, and silicone oils and siloxane resins that are compounds having a siloxane bond. Among these, silicon alkoxides, silicate compounds, and silicone oils are preferable. The silicone oil may be a copolymer of a compound having a siloxane bond and another compound. The silicon alkoxide and silicate compound may be oligomers.

Examples of the oligomer of the silicate compound include compounds represented by the following general formula (IV).
Si _k O _k-1 (R ⁷ O) _{2 (k + 1)} (IV)
In general formula (IV), R ⁷ represents an alkyl group having 1 to 8 carbon atoms or an acyl group having 1 to 8 carbon atoms. k represents an integer of 1 to 10. Examples of the silicate compound include methyl silicate, ethyl silicate, isopropyl silicate, n-propyl silicate, n-butyl silicate, n-pentyl silicate, acetyl silicate and the like.

Moreover, as a commercial item of a silicate compound, what is marketed from Fuso Chemical Industry Co., Ltd., Tama Chemical Industry Co., Ltd., Colcoat Co., Ltd., etc. is mentioned.
Specific examples of methyl silicate and its oligomer include methyl silicate 51 from Fuso Chemical Industry Co., Ltd. or Colcoat Corporation, methyl silicate 53A from Colcoat Corporation, and the like. Specific examples of ethyl silicate and its oligomer include silicate 40 of Tama Chemical Co., Ltd. or Colcoat Co., Ltd., ethyl silicate 45 of Tama Chemical Industry Co., Ltd., ethyl silicate 28 of Colcoat Co., Ltd., ethyl silicate 48 and the like. Specific examples of other silicates and oligomers thereof include N-propyl silicate and N-butyl silicate manufactured by Colcoat Co., Ltd.

  From the viewpoint of suppressing generation of voids in the heat-treated product layer (baked product layer) and improving the denseness of the passivation layer, the silicon compound preferably contains a compound represented by the general formula (IV). Compared to silicon alkoxide, the compound represented by the general formula (IV) has a gentle reaction with the compound of the formula (I) in the heat treatment (firing), and the reaction can be suppressed to a specific temperature state. Thus, it is assumed that the reaction occurs uniformly, the generation of voids in the heat-treated product layer (baked product layer) is suppressed, and the denseness of the passivation layer is improved.

  From the viewpoint of reducing the surface tension of the composition for forming a passivation layer and improving the printability, the silicate compound is preferably an ethyl silicate compound or an oligomer of an ethyl silicate compound.

The plurality of R ⁷ O groups possessed by the silicate compound may be the same or different. The R ⁷ O group preferably contains a methoxy group and an ethoxy group. When the silicate compound has a methoxy group and an ethoxy group, the ratio of the equivalent number of methoxy groups to the equivalent number of ethoxy groups (methoxy group / ethoxy group) is preferably, for example, 30/70 to 70/30, It is more preferably 40/60 to 60/40, further preferably 45/55 to 55/45, and the number of equivalents of methoxy group and the number of equivalents of ethoxy group are particularly preferably close to equivalent. Examples of the silicate compound having methoxy group and ethoxy group in approximately equal amounts include EMS-485 manufactured by Colcoat Co., Ltd.

  A silicate compound may be used individually by 1 type, and may use 2 or more types together. The silicate compound may be used in combination with water, a catalyst, a liquid medium, or the like, if necessary.

  The silicon alkoxide is not particularly limited as long as it has a silicon atom and an alkoxy group bonded to the silicon atom. Specific examples of the silicon alkoxide include compounds represented by the following general formula (V).

R ^8A _n Si (OR ^8B ) _4-n (V)

In the general formula (V), R ^8A represents an alkyl group or an aryl group, the alkyl group and the aryl group may have a substituent, and R ^8B is a saturated or unsaturated group having 1 to 6 carbon atoms. A hydrocarbon group or a hydrocarbon group having 1 to 6 carbon atoms substituted with an alkoxy group having 1 to 6 carbon atoms is shown. n represents 1-3 and 1 or 2 is preferable.

The alkyl group represented by R ^8A in the general formula (V) preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 to 3 carbon atoms. The aryl group represented by R ^8A in formula (V) preferably has 6 to 14 carbon atoms, and more preferably a phenyl group.

In the general formula (V), ^examples of the substituent that the alkyl group or aryl group represented by R ^8A may have include a fluorine atom, a (meth) acryloxy group, a vinyl group, an epoxy group, a styryl group, and an amino group. Etc. The amino group may further have a substituent, and examples of the alkyl group having an amino group having a substituent include N- (2-aminoethyl) -3-aminopropyl group and N-phenyl-3-aminopropyl. Groups and the like.

R ^8B in General Formula (V) represents a C 1-6 hydrocarbon group substituted with a C 1-6 saturated or unsaturated hydrocarbon group or a C 1-6 alkoxy group.
Examples of the saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms represented by R ^8B in the general formula (V) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and isobutyl. Group, t-butyl group, amyl group, cyclohexyl group and the like.

Moreover, as a C1-C6 hydrocarbon group substituted by the C1-C6 alkoxy group represented by R ^<8B> in general formula (V), a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group Ethoxyethyl group, methoxypropyl group, ethoxypropyl group, propoxypropyl group and the like.

From the viewpoint of improving the printability and the denseness of the passivation layer, the silicon alkoxide preferably contains a silane coupling agent. The silane coupling agent is not particularly limited as long as it is a compound having a silicon atom, an alkoxy group, and an organic functional group other than the alkoxy group in one molecule. A silane coupling agent may be used individually by 1 type, and may use 2 or more types together. Examples of the silicon alkoxide include the following compounds (a) to (g) containing a silane coupling agent.
(A) 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. Silicon alkoxide having (meth) acryloxy group (b) Epoxy group such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Or a silicon alkoxide having a glycidoxy group (c) N-2- (aminoethyl) 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopro Silicon alkoxide having amino group such as rutriethoxysilane (d) Silicon alkoxide having mercapto group such as 3-mercaptopropyltrimethoxysilane (e) Methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane Alkyl groups such as n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis (trimethoxysilyl) hexane (F) Silicon alkoxide having a phenyl group such as phenyltrimethoxysilane, phenyltriethoxysilane, etc. (g) Trifluoropropyltrimethoxysila Silicon alkoxide having a trifluoroalkyl group such

The silicon alkoxide preferably includes a silicon alkoxide having an acryloxy group, a methacryloxy group, an epoxy group, an alkyl group, or a trifluoroalkyl group.
Silicon alkoxide may be used in combination with water, a catalyst, a liquid medium, or the like, if necessary.

  The silicone oil is not particularly limited. Specific examples of the silicone oil include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, amino-modified silicone oil, and mercapto. Modified silicone oil, epoxy modified silicone oil, carboxy modified silicone oil, higher fatty acid modified silicone oil, carnauba modified silicone oil, amide modified silicone oil, radical reactive group containing silicone oil, terminal reactive silicone oil, ionic group containing silicone oil Etc.

  When the composition for forming a passivation layer contains a silicon compound, the content of the silicon compound is preferably, for example, 0.01% by mass or more with respect to the total mass of the composition for forming a passivation layer. The content is more preferably at least 05 mass%, further preferably at least 0.1 mass%. When the content of the silicon compound is 0.01% by mass or more, the surface tension of the passivation layer forming composition is lowered, and the coatability and printability tend to be improved.

  When the composition for forming a passivation layer contains a silicon compound, the content of the silicon compound is preferably 35% by mass or less, for example, with respect to the total mass of the composition for forming a passivation layer, 30% by mass. % Or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less. It exists in the tendency for the passivation effect to be more fully acquired as the content rate of a silicon compound is 35 mass% or less.

  When the composition for forming a passivation layer contains a silicon compound, the content of silicon atoms in the composition for forming a passivation layer is preferably 0.001% by mass to 15% by mass, and 0.01% by mass to It is more preferably 10% by mass, and further preferably 0.05% by mass to 5% by mass.

(resin)
The composition for forming a passivation layer may further contain a resin. When the composition for forming a passivation layer contains a resin, the shape stability of the composition layer formed by applying the composition for forming a passivation layer on a semiconductor substrate is further improved, and the passivation layer is formed in a desired shape. It can be selectively formed at a desired position.

The type of resin is not particularly limited. The resin is preferably a resin whose viscosity can be adjusted within a range in which a satisfactory pattern can be formed when the composition for forming a passivation layer is applied onto a semiconductor substrate. Specific examples of the resin include polyvinyl alcohol, polyacrylamide, polyacrylamide derivatives, polyvinylamide, polyvinylamide derivatives, polyvinylpyrrolidone, polyethylene oxide, polyethylene oxide derivatives, polysulfonic acid, polyacrylamide alkylsulfonic acid, cellulose, and cellulose derivatives (carboxymethylcellulose). , Cellulose ethers such as hydroxyethyl cellulose and ethyl cellulose), gelatin, gelatin derivatives, starch, starch derivatives, sodium alginate, sodium alginate derivatives, xanthan, xanthan derivatives, guar gum, guar gum derivatives, scleroglucan, scleroglucan derivatives, tragacanth, Tragacanth derivative, dextrin, dextrin derivative, (meta) Examples include crylic acid resin, (meth) acrylic acid ester resin (alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resin, styrene resin, siloxane resin, and copolymers thereof. . These resins may be used alone or in combination of two or more.
In this specification, “(meth) acryl” means at least one of acryl and methacryl, and “(meth) acrylate” means at least one of acrylate and methacrylate.

  From the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group, from the viewpoint of easily adjusting viscosity and thixotropy even when the content is small. It is more preferable to use a cellulose derivative.

  The molecular weight of these resins is not particularly limited, and is preferably adjusted appropriately in view of the desired viscosity as the composition for forming a passivation layer. The weight average molecular weight of the resin is preferably, for example, 1,000 to 10,000,000, more preferably 1,000 to 5,000,000, from the viewpoints of storage stability and pattern formability. . In addition, the weight average molecular weight of resin is calculated | required by converting using the analytical curve of a standard polystyrene from the molecular weight distribution measured using GPC (gel permeation chromatography).

  When the composition for forming a passivation layer contains a resin, the content of the resin in the composition for forming a passivation layer can be appropriately selected as necessary. For example, the resin content is preferably 0.1% by mass to 50% by mass with respect to the total mass of the composition for forming a passivation layer. From the viewpoint of expressing thixotropy that facilitates pattern formation, the resin content is more preferably 0.2% by mass to 25% by mass, and 0.5% by mass to 20% by mass. Is more preferable, and it is particularly preferably 0.5% by mass to 15% by mass.

  In addition, when the composition for formation of a passivation layer contains water, since thixotropy improves, it is not necessary to contain resin. Therefore, when the composition for forming a passivation layer contains water, the content of the resin contained in the composition for forming a passivation layer is preferably 0.5% by mass or less, and 0.2% by mass or less. More preferably, it is more preferably 0.1% by mass or less, and it is particularly preferable that the resin is substantially not contained.

(High boiling point material)
The composition for forming a passivation layer may use a high boiling point material together with the resin or as a material replacing the resin. The high boiling point material is preferably a compound that is easily vaporized when heated and does not need to be degreased. Moreover, it is preferable that the high boiling point material has a high viscosity so that the shape can be maintained after the composition for forming a passivation layer is applied to the semiconductor substrate. An example of a material that satisfies these conditions is isobornylcyclohexanol.

  Isobornylcyclohexanol is commercially available, for example, as “Telsolve MTPH” (Nippon Terpene Chemical Co., Ltd., trade name). Isobornylcyclohexanol has a high boiling point of 308 ° C. to 318 ° C. When it is removed from the composition layer, it does not need to be degreased by heat treatment (firing) like a resin, but is vaporized by heating. Can be eliminated. For this reason, most of the solvent and isobornyl cyclohexanol contained in the composition for forming a passivation layer as necessary can be removed in the drying step after application on the semiconductor substrate.

  When the composition for forming a passivation layer contains a high-boiling material, the content of the high-boiling material is preferably, for example, 3% by mass to 95% by mass with respect to the total mass of the composition for forming a passivation layer. More preferably, it is 5 mass%-90 mass%, and it is further more preferable that it is 7 mass%-80 mass%.

(Liquid medium)
The composition for forming a passivation layer may contain a liquid medium (solvent or dispersion medium).
When the composition for forming a passivation layer contains a liquid medium, the viscosity can be easily adjusted, the impartability is further improved, and a more uniform passivation layer tends to be formed.
It does not restrict | limit especially as a liquid medium, It can select suitably as needed. The liquid medium preferably includes a liquid medium capable of dissolving the compound of formula (I), an aluminum oxide precursor added if necessary, and the compound of formula (III) to form a uniform solution, and at least one of the organic solvents. More preferably it contains a seed. In this specification, a liquid medium means a medium in a liquid state at room temperature (25 ° C.), except for water.

  Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as di-n-propyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl Ether, diisopropyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene Recall di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, Diethylene glycol di-n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether , Triethylene Recall methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol methyl n-hexyl ether, tetraethylene glycol di- n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol di-n-butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, dipropylene Glycol methyl-n-butyl ether, dip Lopylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl -N-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl-n-butyl ether Tetrapropylene glycol methyl-n-hexyl A Ether solvents such as tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-acetate Pentyl, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, Ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate, glycol diacetate, methoxytrie acetate Lenglycol, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol Methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ- Ester solvents such as valerolactone; acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, Nn-propylpyrrolidinone Aprotic polar solvents such as N, Nn-butylpyrrolidinone, Nn-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide; methylene chloride, chloroform, Hydrophobic organic solvents such as dichloroethane, benzene, toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol N-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2 -Ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl Alcohol solvents such as alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; Phenol solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, Examples include glycol monoether solvents such as dipropylene glycol monoethyl ether and tripropylene glycol monomethyl ether; terpene solvents such as terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, oximene, and ferrandolene. These liquid media may be used individually by 1 type, and may use 2 or more types together.

  Among these, the liquid medium preferably contains at least one selected from the group consisting of a terpene solvent, an ester solvent, and an alcohol solvent, and is selected from the group consisting of a terpene solvent, from the viewpoint of impartability to a semiconductor substrate and pattern formation. More preferably, at least one kind is included.

  When the composition for forming a passivation layer includes a liquid medium, the content of the liquid medium is determined in consideration of the imparting property, the pattern forming property, and the storage stability. For example, the content rate of the liquid medium may be 5% by mass to 98% by mass with respect to the total mass of the composition for forming a passivation layer, from the viewpoint of impartability of the composition for forming a passivation layer and pattern forming properties. Preferably, it is 10 mass%-95 mass%.

(Acid compounds and basic compounds)
The specific passivation layer forming composition may further contain at least one of an acidic compound and a basic compound. When the composition for forming a passivation layer contains an acidic compound or a basic compound, from the viewpoint of storage stability, the content of the acidic compound or the basic compound is, for example, relative to the total mass of the composition for forming a passivation layer Each of them is preferably 1% by mass or less, and more preferably 0.1% by mass or less.
Examples of acidic compounds include Bronsted acid and Lewis acid. Specific examples include inorganic acids such as hydrochloric acid and nitric acid; organic acids such as acetic acid. Examples of basic compounds include Bronsted bases and Lewis bases. Specifically, examples of the basic compound include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides, and organic bases such as trialkylamine and pyridine.

(Other metal compounds)
The specific passivation layer-forming composition comprises Bi, Al, Nb, Ta, V, Y in addition to the compound of formula (I), an aluminum oxide precursor contained as necessary, a compound of formula (III), and a silicon compound. , And other metal compounds containing metal elements other than Hf may be further contained. Examples of other metal compounds include metal alkoxides containing metal elements other than Bi, Al, Nb, Ta, V, Y, and Hf, metal complexes such as chelate complexes, and organometallic compounds. Another metal compound may be used individually by 1 type, or may use 2 or more types together. When the composition for forming a specific passivation layer contains another metal compound, a larger negative fixed charge is developed, and the passivation effect tends to be further improved. Moreover, when the composition for forming a passivation layer containing another metal compound is heat-treated (fired), a composite oxide having a large refractive index tends to be generated. When a solar cell element using a composite oxide having a large refractive index as a passivation layer is created, sunlight tends to re-enter the back surface of the passivation layer and the semiconductor substrate without improving the power generation performance. .

The other metal compound preferably contains a metal alkoxide from the viewpoint of the reactivity of the compound of formula (I), the aluminum oxide precursor contained as necessary, the compound of formula (III) and the silicon compound. The metal alkoxide is not particularly limited as long as it is a compound obtained by reacting a metal atom with an alcohol. Specific examples of the metal alkoxide include compounds represented by the following general formula (VI).
M ² (OR ⁹ ) _t (VI)

In the general formula (VI), M ² represents a metal element having a valence of 1 to 7 (excluding Bi, Al, Nb, Ta, V, Y, and Hf). Specifically, as the ^{M 2, Li, Na, K} , Mg, Ca, Sr, Ba, La, Ti, B, Zr, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, and Examples thereof include at least one metal element selected from the group consisting of Pb. Among these, from the viewpoint of power generation performance when a solar cell element is configured, M ² is Li, Na, K, Mg, Ca, Sr, Ba, La, Ti, B, Zr, Mo, Co, Zn, and It is preferably at least one metal element selected from the group consisting of Pb, more preferably at least one metal element selected from the group consisting of Ti and Zr, and even more preferably Zr.

In the above general formula (VI), R ⁹ represents a saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 6 carbon atoms substituted with an alkoxy group having 1 to 6 carbon atoms. . t represents the valence of ^{M 2.}

Examples of the group represented by R ⁹ in the general formula (VI) include the same groups as those represented by R ^8B in the general formula (V).

  The composition for forming a specific passivation layer comprises a reaction between a compound of formula (I) and at least one of an aluminum oxide precursor, a compound of formula (III), a silicon compound, and another metal compound, which is included as necessary. You may include things. In order to obtain such a reactant, water may be added to the specific passivation layer forming composition. For example, when the aluminum oxide precursor, the compound of formula (III), the silicon compound and other metal compounds, which are included as required, are alkoxides, hydrolysis proceeds by adding water, and thixotropy increases. The printability of the composition for forming a passivation layer can be improved.

(Other ingredients)
The composition for forming a passivation layer may further contain other components usually used in the field as necessary, in addition to the components described above.
Other components include, for example, thixotropic agents (excluding water, hydrolyzate of compound of formula (I), hydrolyzate of aluminum oxide precursor and hydrolyzate of compound of formula (III)), wettability improver, Examples include leveling agents, surfactants, plasticizers, fillers, antifoaming agents, stabilizers, antioxidants, and perfumes.
When the composition for forming a passivation layer contains other components, the content of the other components is not particularly limited. For example, each component may be added in an amount of 0.1% relative to 100 parts by mass of the total composition for forming a passivation layer. You may use by about 01 mass part-20 mass parts. Other components may be used individually by 1 type, and may use 2 or more types together.

  Further, as other components, it is preferable to include at least one thixotropic agent. By including at least one kind of thixotropic agent, the shape stability of the composition layer formed by applying the composition for forming a passivation layer on a semiconductor substrate was further improved, and the composition layer was formed as a passivation layer. The region can be selectively formed at a desired position in a desired shape.

  Examples of thixotropic agents include fatty acid amides, polyalkylene glycol compounds, organic fillers, and inorganic fillers. Specific examples of the polyalkylene glycol compound include compounds represented by the following general formula (VII).

R _< ¹⁰ _> -(O-R _< ¹¹ _> ) _n- O-R _< ¹² _> ... (VII)

In general formula (VII), R ¹⁰ and R ¹² each independently represent a hydrogen atom or an alkyl group, and R ¹¹ represents an alkylene group. n is an arbitrary integer of 3 or more. Incidentally, ^{R 11} may be different even with the same in the presence of a plurality of ^{(O-R 11).}

  Specific examples of the fatty acid amide include compounds represented by the following general formulas (VIII), (IX), (X) and (XI).

R ¹³ CONH ₂ ... (VIII)
R ¹³ CONH—R ¹⁴ —NHCOR ¹³ ... (IX)
R ¹³ NHCO—R ¹⁴ —CONHR ¹³ ... (X)
R ¹³ CONH—R ¹⁴ —N (R ¹⁵ ) ₂ ... (XI)

In the general formulas (VIII), (IX), (X) and (XI), R ¹³ and R ¹⁵ each independently represent an alkyl group or alkenyl group having 1 to 30 carbon atoms, and R ¹⁴ represents 1 to 10 carbon atoms. Represents an alkylene group. R ¹³ and R ¹⁵ may be the same or different.

  Examples of the organic filler include acrylic resin, cellulose resin, and polystyrene resin.

  Examples of the inorganic filler include particles such as silicon dioxide, aluminum hydroxide, aluminum nitride, silicon nitride, aluminum oxide, zirconium oxide, silicon carbide, and glass.

The volume average particle diameter of the organic filler or inorganic filler is preferably 0.01 μm to 50 μm.
In this embodiment, the volume average particle diameter of the filler can be measured by a laser diffraction scattering method.

(Physical property value)
The viscosity of the composition for forming a specific passivation layer is not particularly limited, and can be appropriately selected depending on a method for applying the composition to a semiconductor substrate. For example, the viscosity of the composition for forming a specific passivation layer can be 0.01 Pa · s to 10000 Pa · s. Especially, it is preferable that the viscosity of the composition for specific passivation layer formation shall be 0.1 Pa.s-1000 Pa.s from a viewpoint of pattern formation.
In the present specification, the viscosity is measured using a rotary shear viscometer under conditions of 25 ° C. and a shear rate of 1.0 s ⁻¹ .

The shear viscosity of the composition for forming a specific passivation layer is not particularly limited, and the composition for forming a specific passivation layer preferably has thixotropy. Among them, from the viewpoint of pattern formability, shear viscosity eta ₁ at a shear rate of 1.0 s ^-1, thixotropic index is calculated by dividing the shear viscosity eta ₂ at a shear rate of ^{_{10s -1 (η 1 / η 2}} ) is For example, it is preferably 1.05 to 100, and more preferably 1.1 to 50.
Also, if a particular passivation layer forming composition containing high-boiling material in place of the resin, from the viewpoint of pattern formability, shear viscosity eta ₁ at a shear rate of 1.0 s ^-1, shear at a shear rate of 1000 s ^-1 The thixo ratio (η ₁ / η ₃ ) calculated by dividing by the viscosity η ₃ is, for example, preferably 1.05 to 100, and more preferably 1.1 to 50.
In this specification, the shear viscosity is measured at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 50 mm, cone angle 1 °).

(Method for preparing composition for forming specific passivation layer)
The method for preparing the composition for forming the specific passivation layer is not particularly limited. For example, the compound of the formula (I) and other components such as water, an aluminum oxide precursor, a compound of the formula (III), a silicon compound, a resin, a liquid medium, etc., contained as necessary are mixed by a commonly used mixing method. Can be prepared. Moreover, after dissolving resin in a liquid medium, you may prepare the composition for specific passivation layer formation by mixing this, a compound (I), etc.

  Furthermore, the specific aluminum compound may be prepared by mixing an aluminum alkoxide and a compound capable of forming a chelate with aluminum. At that time, a liquid medium may be used as appropriate, and heat treatment may be performed. A composition for forming a specific passivation layer is prepared by mixing the specific aluminum compound thus prepared, the compound of formula (I), and, if necessary, a solution containing the compound of formula (III), a silicon compound, a resin and the like. May be prepared.

  In addition, the component contained in the composition for specific passivation layer formation, and content of each component are thermal analysis, such as a differential thermal-thermogravimetry simultaneous measurement apparatus (TG / DTA), nuclear magnetic resonance (NMR), infrared. It can be confirmed using spectral analysis such as spectroscopy (IR), chromatographic analysis such as high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and the like.

<Method for manufacturing semiconductor substrate with passivation layer>
The method for manufacturing a semiconductor substrate with a passivation layer according to this embodiment includes a step of forming a composition layer by applying a composition for forming a passivation layer to at least a part of at least one surface of the semiconductor substrate, A step of forming a passivation layer by heat treatment (firing), and a step of forming a silicon nitride film on the passivation layer.
The manufacturing method of the semiconductor substrate with a passivation layer may further include other steps as necessary.
As the composition for forming a passivation layer, the above-mentioned composition for forming a specific passivation layer is preferable. By using the composition for forming a specific passivation layer, a passivation layer having a high density and an excellent passivation effect can be formed in a desired shape by a simple method.

  As the semiconductor substrate to which the composition for forming a passivation layer is applied, those described in the above-described semiconductor substrate with a passivation layer can be used.

It is preferable that the manufacturing method of the semiconductor substrate with a passivation layer further has the process of providing alkaline aqueous solution on a semiconductor substrate before the process of forming a composition layer. That is, it is preferable to wash the surface of the semiconductor substrate with an alkaline aqueous solution before applying the composition for forming a passivation layer on the semiconductor substrate. By washing with an alkaline aqueous solution, organic substances, particles and the like present on the surface of the semiconductor substrate can be removed, and the passivation effect tends to be further improved.
As a method for cleaning with an alkaline aqueous solution, generally known RCA cleaning and the like can be exemplified. For example, the semiconductor substrate can be cleaned by immersing the semiconductor substrate in a mixed solution of ammonia water and hydrogen peroxide water and treating at 60 ° C. to 80 ° C. to remove organic substances and particles. The washing time is preferably, for example, 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

  The method for forming the composition layer by applying the composition for forming a passivation layer on the semiconductor substrate is not particularly limited. For example, the method of providing the composition for forming a passivation layer on a semiconductor substrate can be mentioned using a known application method. Specific examples include an immersion method, a printing method, a spin coating method, a dispenser method, a brush coating method, a spray method, a doctor blade method, a roll coating method, and an ink jet method. Among these, from the viewpoint of pattern formation, a printing method such as a screen printing method and an ink jet method are preferable, and a screen printing method is more preferable.

The application amount of the composition for forming a passivation layer can be appropriately selected according to the purpose. For example, the thickness of the passivation layer to be formed can be appropriately adjusted so as to be a desired thickness described later. For example, the average thickness of the passivation layer can be adjusted by adjusting the liquid medium content of the composition for forming a passivation layer. By increasing the liquid medium content, the average thickness of the passivation layer tends to be reduced. By reducing the liquid medium content, the average thickness of the passivation layer tends to increase.
In addition, when the composition for forming a passivation layer is applied by screen printing, it is possible to adjust the film thickness by changing the number of meshes, the wire diameter, the thickness, the opening, etc. of the screen plate. Furthermore, the film thickness can be adjusted by adjusting both the liquid medium content and the forming method of the composition for forming a passivation layer.

  A passivation layer can be formed on a semiconductor substrate by heat-treating (baking) the composition layer formed with the composition for forming a passivation layer to form a heat-treated product (baked product) derived from the composition layer. it can.

When the above-mentioned composition for forming a specific passivation layer is used as the composition for forming a passivation layer, the heat treatment (firing) conditions of the composition layer include, for example, the compound of formula (I) contained in the composition layer, if necessary Examples of the conditions include the aluminum oxide precursor, the compound of formula (III), and the like that can be converted into bismuth oxide (Bi ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), and the like that are heat-treated products (baked products). .

Especially, when the composition for forming a passivation layer contains an aluminum oxide precursor, it is preferable that the heat treatment (firing) conditions are such that a layer containing amorphous Al ₂ O ₃ having no specific crystal structure can be formed. When the passivation layer is composed of a layer containing amorphous Al ₂ O ₃ , the passivation layer can effectively have a negative charge, and a more excellent passivation effect can be obtained.

  From the viewpoint of effectively giving a fixed charge to the passivation layer and obtaining a more excellent passivation effect, the heat treatment (firing) temperature is preferably 300 ° C. to 900 ° C., for example, 400 ° C. to 900 ° C. Is preferable, and it is more preferable that it is 450 to 800 degreeC. The heat treatment (firing) time can be appropriately selected according to the heat treatment (firing) temperature and the like. The heat treatment (firing) time is, for example, preferably 30 seconds to 10 hours, and more preferably 1 minute to 5 hours.

  The thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer can be 500 nm or less, preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, still more preferably 10 nm to 250 nm, and more preferably 15 nm to 200 nm. It is particularly preferred.

  A method for manufacturing a semiconductor substrate with a passivation layer is obtained by applying a composition for forming a passivation layer to a semiconductor substrate to form a composition layer, and then forming the composition layer before the step of forming the passivation layer by heat treatment (firing). You may have further the process of drying. By having a process of drying the composition layer, a passivation layer having a more uniform thickness tends to be formed.

  The step of drying the composition layer is not particularly limited as long as at least a part of water and the liquid medium that can be contained in the composition for forming a passivation layer can be removed. The drying treatment can be, for example, a heat treatment at 30 ° C. to 600 ° C. for 5 seconds to 60 minutes, and is preferably a heat treatment at 40 ° C. to 450 ° C. for 30 seconds to 40 minutes. The drying treatment may be performed under normal pressure or under reduced pressure.

  In the case where the composition for forming a passivation layer contains a resin, the method for producing a semiconductor substrate with a passivation layer includes the step of forming a passivation layer by applying a composition for forming a passivation layer and then forming a passivation layer by heat treatment (firing). You may further have the process of degreasing the composition layer formed from the composition for layer formation. By having a step of degreasing the composition layer, a passivation layer having a more uniform passivation effect can be formed.

  The step of degreasing the composition layer is not particularly limited as long as at least a part of the resin that can be contained in the composition for forming a passivation layer can be removed. The degreasing treatment can be, for example, a heat treatment at 30 ° C. to 600 ° C. for 5 seconds to 60 minutes, and is preferably a heat treatment at 40 ° C. to 450 ° C. for 30 seconds to 40 minutes. The degreasing treatment is preferably performed in the presence of oxygen, and more preferably performed in the atmosphere.

The method for manufacturing a semiconductor substrate with a passivation layer includes a step of forming a silicon nitride film on the passivation layer after a step of forming the passivation layer by heat treatment (firing) after applying the composition for forming a passivation layer. .
The method for forming the silicon nitride film is not particularly limited, and a known method such as plasma CVD (PECVD) can be used.

In the plasma CVD method, a semiconductor substrate on which a passivation layer is formed is placed in a plasma reaction chamber, a silicon nitride film forming gas atmosphere is placed in the reaction chamber, and a silicon nitride film is grown on the surface of the passivation layer in the semiconductor substrate by discharging. Let The plasma CVD method includes a high frequency plasma CVD method, a microwave plasma CVD method, a direct current plasma CVD method, and the like, and is not particularly limited.
The silicon nitride film forming gas includes an atmospheric gas and a reaction gas as a film forming raw material gas. As the atmospheric gas, a general atmospheric gas such as hydrogen (H ₂ ) or argon (Ar) can be used. The reaction gas includes a silicon compound gas and a nitrogen compound gas. Examples of the silicon compound gas include silicon hydride (silane), silicon tetrachloride (SiCl ₄ ), silicon tetrafluoride (SiF ₄ ), trichlorosilicon (SiHCl ₃ ), tetramethyl silicon (TMS, Si (CH ₃ ) _{4, and the} like. In addition, nitrogen gas, ammonia, or the like is used as the nitrogen compound gas.

The thickness of the silicon nitride film formed on the passivation layer is not particularly limited and can be appropriately selected depending on the purpose. The average thickness of the silicon nitride film is, for example, preferably 500 nm or less, more preferably 10 nm to 400 nm, still more preferably 15 nm to 300 nm, and particularly preferably 20 nm to 250 nm.
The average thickness of the silicon nitride film is calculated in the same manner as the passivation layer.

The total average thickness of the passivation layer and the silicon nitride film is preferably 25 nm to 800 nm, more preferably 50 nm to 600 nm, and even more preferably 75 nm to 500 nm.
The ratio of the average thickness of the passivation layer to the average thickness of the silicon nitride film (passivation layer / silicon nitride film) is preferably 0.01 to 100, more preferably 0.02 to 50, and More preferably, it is 05-10.

<Solar cell element>
The solar cell element of the present embodiment includes a semiconductor substrate having a pn junction formed by pn junction of a p-type layer and an n-type layer, and at least part of at least one surface of the semiconductor substrate, and contains Bi A passivation layer, a silicon nitride film provided on the passivation layer, and an electrode disposed on at least one of the p-type layer and the n-type layer, and the passivation layer and the silicon nitride The total average thickness of the film is 10 nm to 1000 nm. The solar cell element may further include other components as necessary.
The solar cell element of this embodiment is excellent in power generation performance by having a passivation layer containing Bi.

It does not restrict | limit especially as a semiconductor substrate, According to the objective, it can select suitably from what is normally used. As a semiconductor substrate, what was demonstrated by the semiconductor substrate with a passivation layer mentioned above can be used, and what can be used conveniently is also the same. The surface of the semiconductor substrate on which the passivation layer is provided may be a p-type layer or an n-type layer. Among these, a p-type layer is preferable from the viewpoint of power generation performance. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, the p-type layer is formed on the n-type semiconductor substrate or the p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer. It may be a thing. The surface of the semiconductor substrate on which the passivation layer is provided is preferably a light receiving surface in the solar cell element.

  The thickness in particular of a semiconductor substrate is not restrict | limited, According to the objective, it can select suitably. The average thickness of the semiconductor substrate can be, for example, 50 μm to 1000 μm, and preferably 75 μm to 750 μm.

  Further, the thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. The average thickness of the passivation layer can be, for example, 500 nm or less, preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, still more preferably 10 nm to 250 nm, and more preferably 15 nm to 200 nm. It is particularly preferred.

  The solar cell element of this embodiment has a silicon nitride film on the passivation layer. The thickness of the silicon nitride film is not particularly limited and can be appropriately selected according to the purpose. The average thickness of the silicon nitride film is, for example, preferably 500 nm or less, more preferably 10 nm to 400 nm, still more preferably 15 nm to 300 nm, and particularly preferably 20 nm to 250 nm.

The total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm, preferably 25 nm to 800 nm, more preferably 50 nm to 600 nm, and still more preferably 75 nm to 500 nm.
The ratio of the average thickness of the passivation layer to the average thickness of the silicon nitride film (passivation layer / silicon nitride film) is preferably 0.01 to 100, more preferably 0.02 to 50, and More preferably, it is 05-10.

  The shape and size of the solar cell element are not particularly limited. The shape and size of the solar cell element is preferably a square having a side of 125 mm to 156 mm, for example.

<Method for producing solar cell element>
The method for manufacturing a solar cell element of this embodiment is for forming a passivation layer of this embodiment on at least a part of at least one surface of a semiconductor substrate having a pn junction part formed by joining a p-type layer and an n-type layer. Applying a composition to form a composition layer, heat-treating (sintering) the composition layer to form a passivation layer, forming a silicon nitride film on the passivation layer, and disposing an electrode on at least one of the p-type layer and the n-type layer. And the total average thickness of a passivation layer and a silicon nitride film shall be 10 nm-1000 nm. The method for manufacturing a solar cell element may further include other steps as necessary.

  The step of disposing the electrode on at least one of the p-type layer and the n-type layer may be before the step of forming the passivation layer by heat treatment (firing) after applying the composition for forming a passivation layer. It may be after the step of forming the silicon nitride film.

  As the composition for forming a passivation layer, the above-mentioned composition for forming a specific passivation layer is preferable. By using the composition for forming a specific passivation layer, a solar cell element having a high density and a passivation layer having an excellent passivation effect and having excellent power generation performance can be produced by a simple method. Moreover, by using the composition for forming a specific passivation layer, the passivation layer can be formed on the semiconductor substrate on which the electrode is formed so as to have a desired shape, and the productivity of the solar cell element is excellent.

  As a method for disposing the electrode on at least one of the p-type layer and the n-type layer in the semiconductor substrate, a commonly used method can be employed. For example, an electrode can be manufactured by applying a paste for forming an electrode such as a silver paste or an aluminum paste to a desired region of a semiconductor substrate and performing a heat treatment (firing) as necessary.

The surface of the semiconductor substrate on which the passivation layer is provided may be a p-type layer or an n-type layer. From the viewpoint of power generation performance, the surface of the semiconductor substrate is preferably a p-type layer.
The details of the method for forming a passivation layer using the composition for forming a specific passivation layer are the same as the method for manufacturing a semiconductor substrate with a passivation layer described above, and the preferred embodiments are also the same.

  The thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. The average thickness of the passivation layer can be, for example, 500 nm or less, preferably 1 nm to 500 nm, more preferably 5 nm to 300 nm, still more preferably 10 nm to 250 nm, and more preferably 15 nm to 200 nm. It is particularly preferred.

  The method for manufacturing a solar cell element according to this embodiment includes a step of forming a silicon nitride film on the passivation layer. The method for forming the silicon nitride film is not particularly limited, and a known method such as plasma CVD (PECVD) can be used, and details thereof are as described above.

  The thickness of the silicon nitride film can be appropriately selected according to the purpose. The average thickness of the silicon nitride film is, for example, preferably 500 nm or less, more preferably 10 nm to 400 nm, still more preferably 15 nm to 300 nm, and particularly preferably 20 nm to 250 nm.

The total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm, preferably 25 nm to 800 nm, more preferably 50 nm to 600 nm, and still more preferably 75 nm to 500 nm.
The ratio of the average thickness of the passivation layer to the average thickness of the silicon nitride film (passivation layer / silicon nitride film) is preferably 0.01 to 100, more preferably 0.02 to 50, and More preferably, it is 05-10.

  Hereinafter, although the manufacturing method of the solar cell element of this embodiment is demonstrated, referring drawings, this invention is not limited to these examples. In addition, the magnitude | size of the member in each figure is notional, The relative relationship of the magnitude | size between members is not limited to this. Moreover, the same code | symbol is attached | subjected to the member which has the substantially same function through all the drawings, and the overlapping description may be abbreviate | omitted.

  FIG. 1 is a cross-sectional view schematically showing an example of a method for producing a solar cell element having a passivation layer. However, this process diagram does not limit the present invention at all.

  In FIG. 1A, the p-type semiconductor substrate 1 is washed with an alkaline aqueous solution to remove organic substances, particles, and the like on the surface of the p-type semiconductor substrate 1. Thereby, the passivation effect improves more. As a cleaning method using an alkaline aqueous solution, a method using generally known RCA cleaning and the like can be mentioned.

  Thereafter, as shown in FIG. 1 (2), the surface of the p-type semiconductor substrate 1 is subjected to alkali etching or the like to form irregularities (also referred to as a texture structure) on the surface. Thereby, reflection of sunlight can be suppressed on the light receiving surface side. For alkali etching, an etching solution composed of NaOH and IPA (isopropyl alcohol) can be used.

Next, as shown in FIG. 1 (3), by thermally diffusing phosphorus or the like on the surface of the p-type semiconductor substrate 1, an n ⁺ -type diffusion layer 2 is formed with a thickness on the order of submicrons, and p A pn junction is formed at the boundary with the mold bulk portion.

As a method for diffusing phosphorus, for example, a method of performing treatment for several tens of minutes at 800 ° C. to 1000 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen can be cited. In this method, since phosphorus is diffused using a mixed gas, as shown in FIG. 1 (3), in addition to the light receiving surface (front surface), n ⁺ type is also applied to the back surface and side surfaces (not shown). A diffusion layer 2 is formed. A PSG (phosphosilicate glass) layer 3 is formed on the n ⁺ -type diffusion layer 2. Therefore, side etching is performed to remove the side PSG layer 3 and the n ⁺ -type diffusion layer 2.

Thereafter, as shown in FIG. 1 (4), the PSG layer 3 on the light receiving surface and the back surface is removed using an etching solution such as hydrofluoric acid. Further, as shown in FIG. 1 (5), the back surface is separately etched to remove the n ⁺ -type diffusion layer 2 on the back surface.

Then, as shown in FIG. 1 (6), an antireflection film 4 made of silicon nitride or the like is provided on the n ⁺ -type diffusion layer 2 on the light-receiving surface by a plasma CVD (PECVD) method or the like with a thickness of about 90 nm.

  Moreover, about the back surface, you may planarize the unevenness | corrugation of a back surface using alkaline aqueous solutions, such as NaOH.

  Next, as shown in FIG. 1 (7), after a passivation layer forming composition is applied to a part of the back surface by a screen printing method or the like, heat treatment (baking) is performed at 300 ° C. to 900 ° C. after drying. Layer 5 is formed. Further, thereafter, a silicon nitride film (not shown) is provided on the passivation layer 5 by a plasma CVD (PECVD) method or the like.

  In FIG. 5, an example of the formation pattern of the passivation layer in the back surface is shown as a schematic plan view. FIG. 7 is an enlarged schematic plan view of a portion A in FIG. FIG. 8 is an enlarged schematic plan view of a portion B in FIG. In the case of the formation pattern of the passivation layer shown in FIG. 5, as can be seen from FIGS. 7 and 8, the passivation layer 5 on the back surface is a dot-like pattern except for the portion where the back surface output extraction electrode 7 is formed in a later step. Formed with. The pattern of the dot-shaped openings is defined by the dot diameter (La) and the dot interval (Lb), and is preferably arranged regularly. The dot diameter (La) and dot interval (Lb) can be arbitrarily set, and from the viewpoint of suppressing the passivation effect and recombination of minority carriers, it is preferable that La is 5 μm to 2 mm and Lb is 10 μm to 3 mm. It is more preferable that Lb is 10 μm to 1.5 mm and Lb is 20 μm to 2.5 mm, and it is more preferable that La is 20 μm to 1.3 mm and Lb is 30 μm to 2 mm.

  In the case where the composition for forming a passivation layer has an excellent pattern forming property, the dot diameter (La) and the dot interval (Lb) are more regularly arranged in the pattern of the dot-like openings. For this reason, recombination of minority carriers is effectively suppressed, and the power generation performance of the solar cell element is improved.

  Moreover, another example of the formation pattern of the passivation layer in the back surface is shown as a schematic plan view. FIG. 9 is an enlarged schematic plan view of a portion A in FIG. FIG. 10 is an enlarged schematic plan view of a portion B in FIG. In the case of the formation pattern of the passivation layer shown in FIG. 5, as shown in FIGS. 9 and 10, the passivation layer 5 on the back surface is p-type in a line shape except for a portion where the back surface output extraction electrode 7 is formed in a later step. The semiconductor substrate 1 is formed with an exposed pattern. The pattern of the line openings is defined by the line width (Lc) and the line interval (Ld), and is preferably arranged regularly. The line width (Lc) and the line interval (Ld) can be arbitrarily set, but from the viewpoint of suppressing the passivation effect and minority carrier recombination, for example, it is preferable that Lc is 1 μm to 300 μm and Ld is 500 μm to 5000 μm. More preferably, Lc is 10 μm to 200 μm and Ld is 600 μm to 3000 μm, and Lc is 30 μm to 150 μm and Ld is 700 μm to 2500 μm.

  When the composition for forming a passivation layer has an excellent pattern forming property, the line width (Lc) and the line interval (Ld) are more regularly arranged in the pattern of the line-shaped openings. For this reason, recombination of minority carriers is effectively suppressed, and the power generation performance of the solar cell element is improved.

  Here, the passivation layer having a desired shape is formed by applying the composition for forming a passivation layer to a portion where the passivation layer is to be formed (portion other than the opening) and heat-treating (sintering). On the other hand, the passivation layer forming composition is applied to the entire surface, and after heat treatment (firing), the passivation layer in the opening can be selectively removed by laser, photolithography, or the like to form the opening. . Further, the passivation layer forming composition can be selectively applied to a desired position by masking with a mask material in advance on a portion where the composition for forming the passivation layer is not applied, such as an opening.

  The formation pattern of the silicon nitride film is the same as the formation pattern of the passivation layer 5. A method for making the formation pattern of the silicon nitride film the same as the formation pattern of the passivation layer 5 is not particularly limited. For example, after the silicon nitride film is formed on the entire surface of the passivation layer 5, the silicon nitride film is selectively removed by laser, photolithography or the like according to the formation pattern of the passivation layer 5.

  Next, as shown in FIG. 1 (8), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like. FIG. 4 is a schematic plan view showing an example of the light receiving surface of the solar cell element. As shown in FIG. 4, the light receiving surface electrode includes a light receiving surface collecting electrode 8 and a light receiving surface output extraction electrode 9. In order to secure a light receiving area, it is necessary to suppress the formation area of these light receiving surface electrodes. In addition, from the viewpoint of resistivity and productivity of the light receiving surface electrode, the width of the light receiving surface current collecting electrode 8 is preferably 10 μm to 250 μm, and the width of the light receiving surface output extraction electrode 9 is preferably 100 μm to 2 mm. In FIG. 4, two light receiving surface output extraction electrodes 9 are provided. However, from the viewpoint of minority carrier extraction efficiency (power generation performance), the number of light receiving surface output extraction electrodes 9 may be three or more.

  On the other hand, as shown in FIG. 1 (8), an aluminum electrode paste containing glass particles and a silver electrode paste containing glass particles are applied to the back surface by screen printing or the like. FIG. 11 is a schematic plan view showing an example of the back surface of the solar cell element. Although the width | variety of the back surface output extraction electrode 7 is not restrict | limited in particular, From viewpoints, such as connectivity of the wiring material in the manufacturing process of a later solar cell, it is preferable that the width | variety of the back surface output extraction electrode 7 is 100 micrometers-10 mm.

  After applying the electrode paste to each of the light receiving surface and the back surface, after drying, the light receiving surface and the back surface are heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the air, and the light receiving surface collecting electrode is applied to the light receiving surface. 8 and the light receiving surface output extraction electrode 9, and the back surface collecting aluminum electrode 6 and the back surface output extraction electrode 7 are formed on the back surface, respectively.

After heat treatment (firing), as shown in FIG. 1 (9), on the light receiving surface, the glass particles contained in the silver electrode paste forming the light receiving surface electrode react with the antireflection film 4 (fire through), The light-receiving surface electrode (light-receiving surface current collecting electrode 8, light-receiving surface output extraction electrode 9) and the n ⁺ -type diffusion layer 2 are electrically connected (ohmic contact). On the other hand, the rear surface, the portion where the passivation layer 5 of the dot-like or line-like is not formed, by heat treatment (sintering), that the aluminum in the aluminum electrode paste diffuses into the p-type semiconductor substrate 1, p ⁺ -type A diffusion layer 10 is formed. In particular, by using the above-mentioned composition for forming a specific passivation layer, a passivation layer having an excellent passivation effect can be formed by a simple method, and a solar cell element having excellent power generation performance can be manufactured.

FIG. 2 is a cross-sectional view schematically showing another example of a method for manufacturing a solar cell element. After the n ⁺ -type diffusion layer 2 on the back surface is removed by etching treatment, the back surface is further removed. The solar cell element can be manufactured in the same manner as in FIG. 1 except that is flattened. For planarization, a technique such as immersing the back surface of the semiconductor substrate in a mixed solution of nitric acid, hydrofluoric acid, and acetic acid or a potassium hydroxide solution can be used.

FIG. 3 is a cross-sectional view schematically showing another example of a method for manufacturing a solar cell element. In this method, the process up to the step of forming the texture structure, the n ⁺ -type diffusion layer 2 and the antireflection film 4 on the p-type semiconductor substrate 1 (FIGS. 3 (19) to (24)) is the same as the method of FIG. is there.

After forming the antireflection film 4, as shown in FIG. 3 (25), the composition for forming a passivation layer is applied, and after drying, heat treatment (baking) is performed at 300 to 900 ° C. to form the passivation layer 5 To do. Further, thereafter, a silicon nitride film (not shown) is provided on the passivation layer 5 by a plasma CVD (PECVD) method or the like. The formation pattern of the silicon nitride film is the same as the formation pattern of the passivation layer 5.
FIG. 6 shows a schematic plan view of another example of the formation pattern of the passivation layer on the back surface. In the formation pattern of the passivation layer shown in FIG. 6, openings are arranged on the entire back surface, and openings are also arranged on the portion where the back surface output extraction electrode is formed in a later step.

Thereafter, as shown in FIG. 3 (26), boron or aluminum is diffused from the portion where the dot-like or line-like passivation layer 5 is not formed on the back surface, and the p ⁺ -type diffusion layer 10 is formed. When boron is diffused when forming the p ⁺ -type diffusion layer 10, a method of treating at a temperature around 1000 ° C. in a gas containing boron trichloride (BCl ₃ ) can be used. However, since the gas diffusion method is the same as in the case of using phosphorus oxychloride, the p ⁺ -type diffusion layer 10 is formed on the light-receiving surface, the back surface, and the side surface of the p-type semiconductor substrate 1. Therefore, it is necessary to take measures such as masking the portions other than the openings to prevent boron from diffusing into unnecessary portions of the p-type semiconductor substrate 1.

In addition, when aluminum is diffused when forming the p ⁺ -type diffusion layer 10, an aluminum paste is applied to the entire back surface or the opening, and this is heat-treated (fired) at 450 ° C. to 900 ° C., and aluminum is formed from the opening. The p ⁺ -type diffusion layer 10 can be formed by diffusing, and then a heat-treated product layer (baked product layer) made of an aluminum paste on the p ⁺ -type diffusion layer 10 can be etched with hydrochloric acid or the like.

  Next, as shown in FIG. 3 (27), aluminum is physically vapor-deposited on the entire back surface to form the back surface collecting aluminum electrode 11.

  Thereafter, as shown in FIG. 3 (28), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like, and a silver electrode paste containing glass particles is applied to the back surface by a screen printing method or the like. To do. The silver electrode paste on the light receiving surface is applied in a pattern according to the shape of the light receiving surface electrode shown in FIG. 4, and the silver electrode paste on the back surface is applied in a pattern according to the shape of the back electrode shown in FIG.

After applying the electrode paste to each of the light receiving surface and the back surface, after drying, the light receiving surface and the back surface are both heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the atmosphere, and as shown in FIG. A light receiving surface collecting electrode 8 and a light receiving surface output extraction electrode 9 are formed on the light receiving surface, and a back surface output extraction electrode 7 is formed on the back surface. At this time, on the light receiving surface, the light receiving surface electrode and the n ⁺ -type diffusion layer 2 are electrically connected, and on the back surface, the back surface collecting aluminum electrode 11 and the back surface output extraction electrode 7 formed by vapor deposition are electrically connected. Connected.

  1 to 3 show a method of forming the back surface collecting aluminum electrode 6 or 11 after forming the passivation layer 5 and the silicon nitride film (not shown) on the back surface, the back surface collecting aluminum electrode 6 is shown. Alternatively, the passivation layer 5 and a silicon nitride film (not shown) may be formed after the formation of 11.

1 to 3 show the method of forming the passivation layer 5 on the back surface, the above-described composition for forming the specific passivation layer is also applied to the side surface in addition to the back surface of the p-type semiconductor substrate 1. The passivation layer 5 may be further formed on the side surface (edge) of the p-type semiconductor substrate 1 by heat-treating (sintering) (not shown). Thereby, the solar cell element which is more excellent in power generation performance can be manufactured.
Alternatively, the passivation layer 5 may be formed by applying the above-mentioned composition for forming a specific passivation layer only to the side surface and forming a heat treatment (firing) without forming the passivation layer 5 on the back surface. In this case, thereafter, a silicon nitride film (not shown) is provided on the passivation layer 5 by a plasma CVD (PECVD) method or the like. When the composition for forming a specific passivation layer is used in a place with many crystal defects such as side surfaces, the effect is particularly great.

  Although FIGS. 1-3 showed the example using the p-type semiconductor substrate 1 as a semiconductor substrate, also when using an n-type semiconductor substrate, the solar cell element excellent in electric power generation performance can be manufactured according to the above. .

<Solar cell>
The solar cell of this embodiment has the solar cell element of this embodiment, and the wiring material arrange | positioned on the electrode of the said solar cell element. The solar cell may be configured by connecting a plurality of solar cell elements via a wiring material and sealing with a sealing material as necessary. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the industry. The size of the solar cell is not particularly limited. The size of the solar cell, for example, is preferably 0.5m ² ~3m ^2.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

<Example 1>
(Preparation of composition 1 for forming a passivation layer)
Tris (2-ethylhexanoic acid) bismuth (Amax Co., Ltd., structural formula: Bi (OCOCH (C ₂ H ₅ ) C ₄ H ₉ ) ₃ , molecular weight: 638.6), aluminum ethyl acetoacetate diisopropylate (Kawaken) Fine Chemical Co., Ltd., trade name: ALCH), silicate agent (Tama Chemical Co., Ltd., trade name: silicate 40, sometimes abbreviated as Si40), terpineol (Nippon Terpene Chemical Co., Ltd., sometimes abbreviated as TPO) And isobornylcyclohexanol (may be abbreviated as Nippon Terpene Chemical Co., Ltd., tersolve or MTPH) and kneaded for 5 minutes, and then added with pure water and further kneaded for 5 minutes to form a passivation layer forming composition. Product 1 was prepared. The content of each component in the composition 1 for forming a passivation layer was as shown in Table 1. In Table 1, “tris (2-ethylhexanoic acid) bismuth” is referred to as “bisethyl 2-ethylhexanoate”.

(Production of solar cell element)
A single crystal p-type semiconductor substrate (156 mm square, 180 μm thick) was prepared, and texture structures were formed on the light receiving surface and the back surface by alkali etching. Next, in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen, treatment was performed at a temperature of 900 ° C. for 20 minutes to form n ⁺ -type diffusion layers on the light receiving surface, the back surface, and the side surface. Thereafter, side etching was performed to remove the side silicate glass (PSG) layer and the n ⁺ -type diffusion layer, and the PSG layer on the light-receiving surface and the back surface was removed using an etching solution containing hydrofluoric acid. Further, the back surface was separately etched to remove the n ⁺ -type diffusion layer on the back surface. Thereafter, an antireflection film made of silicon nitride was formed on the n ⁺ -type diffusion layer on the light receiving surface so as to have a thickness of 90 nm by plasma CVD (PECVD).

After applying the prepared composition 1 for forming a passivation layer to the entire back surface of the p-type semiconductor substrate with a screen plate having a mesh number of 500 using a screen printer (Neurong Seimitsu Kogyo Co., Ltd., LZ-0913), 400 The mixture was heated at a temperature of 5 ° C. for 5 minutes and dried.
Next, using a tube furnace (MT-12x43-A type, Koyo Thermo System Co., Ltd.), the p-type semiconductor substrate was blown with nitrogen gas 4 L / min, oxygen gas 4 L / min, maximum temperature 800 ° C., holding time 10 minutes. Heat treatment (firing) was performed under the conditions to form the passivation layer 1. Moreover, the lifetime 1 (LT1) of the p-type semiconductor substrate before forming a silicon nitride film on a passivation layer was measured using the lifetime measuring device (WCT-120 by Sinton Instrument).

Thereafter, a silicon nitride film was formed on the passivation layer by plasma CVD (PECVD) to a thickness of 100 nm. Thereafter, the lifetime 2 (LT2) of the p-type semiconductor substrate after the silicon nitride film is formed on the passivation layer is measured using a lifetime measuring device (Sinton Instrument, WCT-120), and the life before and after the CVD process is measured. Time retention was calculated from the following formula.
LT retention ratio = (LT2 / LT1) × 100
The measured value of Example 4 described later was set to 100.0, and the lifetime measured value of the fabricated p-type semiconductor substrate was converted into a relative value for comparison. The results are shown in Table 1.

The pattern of the opening was formed so as to have the pattern shown in FIG. 5, FIG. 9, and FIG. Specifically, a line-shaped opening was opened with a laser so as to remove the passivation layer and the silicon nitride film in the region where the back surface output extraction electrode (reference numeral 7 in FIG. 11) was formed. This line-shaped opening pattern had a line width (Lc) of 100 μm and a line interval (Ld) of 2.0 mm.
The line interval (Ld) is the distance between the centers of the lines.

  Next, a commercially available silver electrode paste (PV-17F, DuPont) was applied to the light-receiving surface of the p-type semiconductor substrate so as to have the electrode pattern shown in FIG. 4 by screen printing. The electrode pattern is composed of a light receiving surface collecting electrode having a width of 120 μm and a light receiving surface output extraction electrode having a width of 1.5 mm, and printing conditions (screen plate) so that the thickness after heat treatment (firing) is 20 μm. , Mesh, printing speed, and printing pressure) were appropriately adjusted. This was heated at 150 ° C. for 1 minute to dry the solvent by evaporating.

  On the other hand, on the back side, a commercially available aluminum electrode paste (PVG-AD-02, PVG Solutions, Inc.) and a commercially available silver electrode paste (PV-505, DuPont) and the electrode pattern shown in FIG. It was given to become. The pattern of the back surface output extraction electrode made of silver electrode paste was constituted by 123 mm × 4 mm.

  The printing conditions (screen plate mesh, printing speed, and printing pressure) of the silver electrode paste and the aluminum electrode paste were as follows: the back surface output extraction electrode (silver electrode, symbol 7 in FIG. 11) and the back surface collection after heat treatment (firing). The thickness of the electric electrode (aluminum electrode, symbol 6 in FIG. 11) was adjusted as appropriate so as to be 20 μm. After application of each electrode paste, drying was performed by heating at 150 ° C. for 1 minute to evaporate the solvent.

  Subsequently, heat treatment (firing) was performed using a tunnel furnace (single-line transport W / B tunnel furnace, Noritake Co., Ltd.) under atmospheric conditions at a maximum temperature of 820 ° C. and a holding time of 10 seconds. The solar cell element 1 in which the electrode was formed was produced.

(Evaluation of power generation performance)
Evaluation of the power generation performance of the produced solar cell element 1 includes pseudo-sunlight (WXS-155S-10, Wacom Denso Co., Ltd.) and a voltage-current (IV) evaluation measuring instrument (IV CURVE TRACER MP- 180, Hidehiro Seiki Co., Ltd.). Jsc (short-circuit current), Voc (open voltage), F. F. (Curve factor) and η (conversion efficiency) are obtained by measuring in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005), respectively. The obtained measured value was converted into a relative value with the measured value of the solar cell element 4 produced in Example 4 described later as 100.0. The results are shown in Table 1.

<Example 2>
A solar cell element 2 was produced and the power generation performance was evaluated in the same manner as in Example 1 except that the silicon nitride film was formed to a thickness of 10 nm by plasma CVD (PECVD). The results are shown in Table 1.

<Example 3>
In Example 1, tris (2-ethylhexanoic acid) bismuth, ALCH, Si40, TPO, and tersolve were mixed and kneaded for 5 minutes, and then pure water was added and further kneaded for 5 minutes to form a passivation layer forming composition. 2 was prepared. In composition 2 for forming a passivation layer, the content of each component was as shown in Table 1.
And the solar cell element 3 was produced similarly to Example 1 except having used the composition 2 for formation of a passivation layer instead of the composition 1 for formation of a passivation layer, and the power generation performance was evaluated. The results are shown in Table 1.

<Example 4>
In Example 1, composition 1 for forming a passivation layer 1 was applied to the back surface of the substrate using a screen plate having a mesh number of 250 instead of a screen plate having a mesh number of 500, and then heated at a temperature of 400 ° C. for 5 minutes for drying treatment. After that, the solar cell was applied in the same manner as in Example 1 except that the composition 1 for forming a passivation layer was applied again and then dried, and the composition 1 for forming a passivation layer 1 was applied twice in total. Element 4 was fabricated and power generation performance was evaluated. The results are shown in Table 1.

<Comparative Example 1>
In Example 1, tris (2-ethylhexanoic acid) bismuth, ALCH, Si40, TPO, and tersolve were mixed and kneaded for 5 minutes, and then pure water was added and further kneaded for 5 minutes to form a passivation layer forming composition. 3 was prepared. The content rate of each component in the composition 3 for forming a passivation layer was as shown in Table 1.
A solar cell element C1 was produced in the same manner as in Example 1 except that the passivation layer forming composition 3 was used and a silicon nitride film was formed to a thickness of 3 nm by plasma CVD (PECVD), and the power generation performance was evaluated. went. The results are shown in Table 1.

<Comparative example 2>
After applying the passivation layer forming composition 1 to the back surface of the substrate, heating it at a temperature of 400 ° C. for 5 minutes for drying treatment, applying the passivation layer forming composition 1 again and then applying drying treatment, the passivation treatment is performed. A solar cell element C2 was produced in the same manner as in Example 4 except that the layer forming composition 1 was applied four times in total and the silicon nitride film was formed to a thickness of 500 nm by plasma CVD (PECVD). Then, the power generation performance was evaluated. The results are shown in Table 1.

  The lifetimes of the p-type semiconductor substrates produced in Examples 1 to 4 and before and after the CVD treatment were higher than those of Comparative Examples 1 and 2. In Examples 1 to 4, it is considered that the passivation layer by the CVD process was not damaged, the passivation layer and the silicon nitride film were not cracked, and the passivation effect was maintained.

  The performance of the solar cell elements 1 to 4 produced in Examples 1 to 4 was higher than that of the solar cell elements C1 to C2 produced in Comparative Examples 1 to 2. This is considered to be because a passivation layer having sufficient passivation characteristics was obtained because damage to the passivation layer due to CVD treatment and aluminum electrode formation did not occur.

1: p-type semiconductor substrate, 2: n ⁺ -type diffusion layer, 3: PSG (phosphorus silicate glass) layer, 4: antireflection film, 5: passivation layer, 6: aluminum electrode paste, or heat-treated (fired) Back surface collecting aluminum electrode, 7: Back surface output extraction electrode paste, or back surface output extraction electrode obtained by heat treatment (baking), 8: Light receiving surface current collection electrode paste, or light receiving surface current collection obtained by heat treatment (firing) Electrode: 9: light receiving surface output extraction electrode paste, or light receiving surface output extraction electrode obtained by heat treatment (baking), 10: p ⁺ type diffusion layer, 11: aluminum electrode for backside current collection

Claims (5)

A semiconductor substrate;
A passivation layer provided on at least part of at least one surface of the semiconductor substrate and containing Bi;
A silicon nitride film provided on the passivation layer,
A semiconductor substrate with a passivation layer, wherein the total average thickness of the passivation layer and the silicon nitride film is 10 nm to 1000 nm.   The semiconductor substrate with a passivation layer according to claim 1, wherein the passivation layer further contains Al.   The semiconductor substrate with a passivation layer according to claim 1 or 2, wherein a Bi content in the passivation layer is 1 mass% to 90 mass%. a semiconductor substrate having a pn junction formed by p-type junction of a p-type layer and an n-type layer;
A passivation layer provided on at least part of at least one surface of the semiconductor substrate and containing Bi;
A silicon nitride film provided on the passivation layer;
An electrode disposed on at least one of the p-type layer and the n-type layer,
The solar cell element whose total average thickness of the said passivation layer and the said silicon nitride film is 10 nm-1000 nm.   The solar cell which has a solar cell element of Claim 4, and the wiring material arrange | positioned on the electrode of the said solar cell element.