JP5172008B1 - Inspection method and manufacturing method of polycrystalline silicon wafer and use thereof - Google Patents

Abstract

An inspection method for efficiently selecting only defective products of a polycrystalline silicon wafer, in particular, defective products in which SiC filaments that cause Id defects of solar cells are present at crystal grain boundaries, and the multi-layer obtained thereby. Provide crystalline silicon wafer applications.
A series of polycrystalline silicon wafer groups (a-h) obtained by slicing a polycrystalline silicon block based on a standard physical property value for selecting defective or non-defective polycrystalline silicon wafers. An inspection method for selecting defective or non-defective products from the physical property values corresponding to the reference physical property values of one polycrystalline silicon wafer, and the polycrystalline silicon in which the polycrystalline silicon wafer was adjacent at the time of slicing Relative comparison of physical property values corresponding to the reference physical property values possessed by the wafer, and based on the tendency of each physical property value possessed by each polycrystalline silicon wafer of the series of polycrystalline silicon wafer groups, a defective product of the polycrystalline silicon wafer Or select non-defective products.
[Selection] Figure 1

Description

The present invention relates to a method for inspecting and manufacturing a polycrystalline silicon wafer, and an application of the polycrystalline silicon wafer obtained thereby.

The use of natural energy is attracting attention as an alternative to oil, which is causing various problems in the global environment. Among them, the solar cell does not require a large facility and does not generate noise during operation, and thus has been particularly actively introduced in Japan and Europe.
Solar cells using compound semiconductors such as cadmium tellurium have also been put into practical use. However, in terms of the safety of the material itself, past achievements, and cost performance, the solar cell using a crystalline silicon wafer (substrate) Batteries (crystalline silicon solar cells) occupy a large share.

Crystalline silicon solar cells are broadly classified into two types, single crystal silicon solar cells and polycrystalline silicon solar cells, depending on the wafer used. The former has high photoelectric conversion efficiency, but the latter is frequently used because of high cost. .
A polycrystalline silicon wafer, which is generally widely used as a substrate for polycrystalline silicon solar cells, is obtained by unidirectionally solidifying molten silicon in a crucible by a casting method or electromagnetic casting method to obtain a large polycrystalline silicon ingot. Then, it is cut into a prismatic silicon block using a band saw or the like, and further sliced using a wire saw or the like into a wafer.

In polycrystalline silicon solar cells, dark reverse leakage current (Id) defects often occur in succession in battery characteristic inspection.
Dark reverse leakage current (Id) is, as the name suggests, a current that flows when a reverse bias is applied to the pn junction of a polycrystalline silicon solar cell without light irradiation. Generally, a value larger than a certain value is regarded as defective.
As the cause of Id failure, there are various causes such as those caused by the manufacturing process of the solar cell, those caused by the specific resistance (low resistance) of the wafer, and those caused by foreign matters such as SiC.

For example, Non-Patent Document 1 shows a nitrogen-doped N-type SiC filament having a diameter of several μm as one of the causes of Id failure of a polycrystalline silicon solar cell manufactured using a polycrystalline silicon ingot by a casting method. Has been.
Since SiC filaments precipitate along grain boundaries during unidirectional solidification and are distributed over a range in height, i.e., direction of unidirectional solidification, this type of Id failure is the height of the block. There is a tendency to occur continuously in the direction. Usually, when a SiC filament precipitates, a SiN filament also precipitates at the same time, so that any one of them or a mixture of both is confirmed at the crystal grain boundary. The SiN filament itself does not cause the Id defect, but since the SiC filament is usually deposited in the vicinity, the SiC filament including both of them is used as the SiC filament.

J. Bauer et al., `` INVESTIGATIONS ON DIFFERENT TYPES OF FILAMENTS IN MULTI-CRYSTALLINE SILICON FOR SOLAR CELLS '', Proceedings 22nd European Photovoltaic Solar Conference and Exhibition, Milan, Italy, 2007, p.994-997

As a result of various evaluations of a polycrystalline silicon wafer and a solar cell manufactured using the same, the present inventors have found that nitrogen-doped N-type SiC filaments occupy a large part of Id defects. There may be a continuous occurrence of Id defects due to the specific resistance of the wafer, but this is simply caused by the silicon raw material when the silicon ingot is manufactured by the casting method, and can be dealt with by adjusting the raw material.
Thus, in order to further reduce the cost of the polycrystalline silicon solar cell, it is necessary to avoid Id defects due to the SiC filament. However, the countermeasures are not shown in Non-Patent Document 1 described above.

In an ordinary method for inspecting a polycrystalline silicon wafer, the appearance of the wafer is inspected to determine whether there is a foreign substance in the surface, whether there is a step exceeding a reference value, and whether the crystal grain size is fine.
Recently, a transmission type inspection apparatus using infrared rays has begun to be adopted. Since the inside of the wafer can be inspected with infrared rays, for example, if the size is larger than the resolution of the camera provided in the inspection apparatus, foreign matter existing in the bulk that cannot be confirmed from the surface can be confirmed. However, basically, it is necessary to inspect whether each item has passed each wafer as in the conventional appearance inspection.

  Therefore, the present invention is an inspection of a polycrystalline silicon wafer for efficiently sorting out only defective products of a polycrystalline silicon wafer, in particular, only defective products in which SiC filaments that cause Id defects of solar cells are present at grain boundaries. It is an object of the present invention to provide a method and use of a polycrystalline silicon wafer obtained thereby.

  As a result of intensive studies to solve the above problems, the present inventors succeeded in identifying the problems in the conventional method for inspecting a polycrystalline silicon wafer as described above. The present inventors have found an inspection method for efficiently selecting only defective products, particularly defective products in which SiC filaments are present at crystal grain boundaries, and have reached the present invention.

Thus, according to the present invention, a series of polycrystalline silicon wafer groups obtained by slicing a polycrystalline silicon block based on reference physical property values for selecting defective or good polycrystalline silicon wafers. This is an inspection method for selecting defective or good products from
A physical property value corresponding to the reference physical property value of one polycrystalline silicon wafer, and a physical property value corresponding to the reference physical property value of the polycrystalline silicon wafer adjacent to the polycrystalline silicon wafer at the time of slicing A polycrystalline silicon wafer characterized by selecting a defective or non-defective product of the polycrystalline silicon wafer based on a relative comparison and a tendency of each physical property value of each polycrystalline silicon wafer of the series of polycrystalline silicon wafer groups An inspection method is provided.

The present invention also provides a polycrystalline silicon wafer selected as a non-defective product by the method for inspecting a polycrystalline silicon wafer and a polycrystalline silicon solar cell manufactured using the polycrystalline silicon wafer.
Furthermore, according to the present invention, there is provided a method for manufacturing a polycrystalline silicon wafer using the above-described inspection method for a polycrystalline silicon wafer,
A step of slicing a polycrystalline silicon block to obtain a polycrystalline silicon wafer;
A step of selecting defective or non-defective products by using the inspection method on the sliced polycrystalline silicon wafer to obtain non-defective products;
A method for producing a polycrystalline silicon wafer is provided.

According to the present invention, inspection of a polycrystalline silicon wafer for efficiently sorting out only defective products of a polycrystalline silicon wafer, in particular, defective products in which SiC filaments that cause Id failures of solar cells are present at the grain boundaries. The method and use of the resulting polycrystalline silicon wafer can be provided.
That is, the method for inspecting a polycrystalline silicon wafer of the present invention is generally suitable as a method for inspecting a polycrystalline silicon wafer obtained by processing a polycrystalline silicon ingot manufactured by a casting method or an electromagnetic casting method. According to the present invention, it is possible to efficiently select a polycrystalline silicon wafer having a low Id defect occurrence rate, and a low-cost polycrystalline silicon solar cell and a solar cell module can be obtained by reducing the defect rate of the wafer. It can be supplied to the market and can contribute to further dissemination of them.

In addition, the polycrystalline silicon wafer inspection method includes the following steps:
(1) As a standard physical property value for selecting defective or non-defective polycrystalline silicon wafers on a slice plane from a series of polycrystalline silicon wafer groups obtained by slicing the polycrystalline silicon block A step of confirming a polycrystalline silicon wafer having a maximum aggregate region of crystal grains of a reference crystal grain size or less,
(2) a step of setting the maximum gathering area as a reference area, a polycrystalline silicon wafer having the reference area as a reference wafer, and selecting the reference wafer as a defective product;
(3) If there are more than a predetermined allowable number of crystal grains below the reference crystal grain size in a region corresponding to the reference region in the polycrystalline silicon wafer adjacent to the reference wafer, the polycrystalline silicon wafer is defective. And if the non-existent polycrystalline silicon wafer is selected as a non-defective product and the inspection is terminated, and (4) if the polycrystalline silicon wafer is selected as a defective product in step (3), the polycrystalline silicon wafer The above effect is further exhibited when the process includes the step of repeating the step (3) until an uninspected polycrystalline silicon wafer adjacent to the wafer is not sorted out.

In addition, the inspection method of the polycrystalline silicon wafer is performed when the reference crystal grain size is 5 mm or less, particularly 2 mm or less, when the reference area is 100 mm ² or more, and when the predetermined allowable number is 1. The above effects are further exhibited.
Furthermore, the method for inspecting a polycrystalline silicon wafer is when the polycrystalline silicon wafer is for a solar cell and the defective product is a polycrystalline silicon wafer that causes a reverse leakage current failure in the dark when the solar cell is manufactured. It can be carried out suitably, and the above effects are further exhibited.
In evaluating the crystal grain size, the Σ3 grain boundary often found on the surface of the polycrystalline silicon wafer is not regarded as a grain boundary here. This is because the Σ3 grain boundary is a grain boundary introduced due to stacking faults during crystal growth or stress after crystal growth, and the origin is clearly different from the crystal grain boundary caused by compositional supercooling. Here, the Σ3 grain boundary means a grain boundary in which the crystals on both sides of the grain boundary are mirror-symmetric with respect to the (111) plane, and can be confirmed as a linear characteristic grain boundary on the wafer. Sometimes the Σ3 grain boundaries are packed in parallel.

It is the schematic which shows an example of the inspection method of the polycrystalline silicon wafer of this invention. It is a schematic sectional drawing (a)-(c) which shows the presence pattern of the crystal grain in a polycrystal silicon ingot.

  The method for inspecting a polycrystalline silicon wafer according to the present invention is a series of polycrystalline silicon wafers obtained by slicing a polycrystalline silicon block based on standard physical property values for selecting defective or non-defective polycrystalline silicon wafers. An inspection method for selecting defective or non-defective products from a wafer group, wherein a physical property value corresponding to the reference physical property value of one polycrystalline silicon wafer and the polycrystalline silicon wafer were adjacent at the time of slicing A relative comparison is made with a physical property value corresponding to the reference physical property value possessed by the polycrystalline silicon wafer, and based on the tendency of each physical property value possessed by each polycrystalline silicon wafer in the series of polycrystalline silicon wafer groups. It is characterized by sorting out defective or non-defective products.

The background of the present invention will be described.
First, the inventors evaluated a solar cell in which an Id defect due to a SiC filament occurred, and a wafer having a SiC filament at a crystal grain boundary has many fine crystal grains having a crystal grain size of about 1 mm or less. Further, since the SiC filament has a high conductivity, it has been found that if there is even one of the fine crystal grains as described above in the wafer surface, an Id defect is caused by a leak in the SiC filament portion (however, an Id defect determination is made). This is not limited to the case where the standard is loose, and an allowable value (predetermined allowable value) in the wafer having the fine crystal grain number is evaluated with respect to the standard).

Therefore, the present inventors selected a wafer having one or more crystals having a crystal grain size of 1 mm or less as a defective wafer in a polycrystalline silicon wafer inspection process, and produced a solar cell using a non-defective wafer other than those. As a result, the incidence of Id defects could be greatly reduced.
However, when solar cells were produced using defective wafers selected in the inspection process, Id defects did not occur in most wafers. This means that the above inspection standard is not appropriate, and a large number of non-defective non-defective wafers are determined to be defective. That is, only defective wafers in which SiC filaments that cause Id defects of solar cells are present at grain boundaries. Means that it cannot be sorted efficiently.

  That is, in the above inspection method, only the fact that “a wafer having SiC filaments at the crystal grain boundary has many fine crystal grains having a crystal grain size of about 1 mm or less” is inspected for all wafers, Wafers having one or more crystals of 1 mm or less were selected as defective wafers. From the above results, the criterion of “crystal grain size of 1 mm or less” is a sufficient condition for “wafers having SiC filaments at crystal grain boundaries”. It turns out that this is not a necessary condition.

  The reason why fine crystal grains having a crystal grain size of 1 mm or less exist in the polycrystalline silicon wafer is that the SiC filament which is a problem in the present invention is present at the crystal grain boundaries, and the crystal grains are merely stochastic. Examples include the presence of fine crystal grains having a small particle diameter, and the presence of fine crystal grains generated by entering a dual phase or slip in a single crystal grain during crystal growth. In the above inspection process, it is considered that a wafer having fine crystal grains having a crystal grain diameter of 1 mm or less is selected as a defective wafer due to the latter two causes.

  2A to 2C are schematic cross-sectional views showing the existence patterns of crystal grains in the polycrystalline silicon ingot. Each drawing shows a cross section along the longitudinal direction of the polycrystalline silicon ingot, that is, the crystal growth direction. Therefore, the arrow GO in the figure represents the “crystal growth direction” of unidirectional solidification, and the arrow SO perpendicular to GO represents the “slice direction” for slicing the ingot into the wafer.

FIG. 2A is a schematic cross-sectional view of a polycrystalline silicon ingot in which fine crystal grains 3 exist because SiC filaments exist at the crystal grain boundaries.
Fine crystal grains 3 are compositionally supercooled at the portion where SiC filaments are precipitated at the crystal grain boundaries during crystal growth by unidirectional solidification, and silicon, SiC, and SiN crystal nuclei are formed in the melt. It is thought that it was generated. This compositional supercooled state is considered to spread in the plane and continue over time, and crystal nuclei generated in the melt fall on the crystal and adhere to it, so that a region having a crystal grain size of 1 mm or less is formed. It is thought that it was formed.

  2 (b) and 2 (c) show that a polycrystalline silicon ingot in which fine crystal grains 4 are generated only in a stochastic manner and a single crystal grain during crystal growth are generated by multiple twin phases and slips. 2 is a schematic cross-sectional view of a polycrystalline silicon ingot in which fine crystal grains 5 exist.

  Therefore, when the wafers obtained by slicing the polycrystalline silicon ingots of FIGS. 2A to 2C along the AA ′, BB ′, and CC ′ sections are compared, all the wafers have fine crystals. There are grains. Therefore, in the conventional inspection method in which a good or defective product is selected by setting an appearance inspection standard for one wafer, all wafers are selected as defective products. However, the present inventors have confirmed that even if a solar cell is fabricated using a wafer sliced from the polycrystalline silicon ingot of FIGS. 2B and 2C, the probability of Id failure is extremely low. Yes.

Therefore, there is an inspection method that can efficiently sort a defective wafer (wafer A) as shown in FIG. 2A and non-defective wafers (wafers B and C, respectively) as shown in FIGS. 2B and 2C. I need it.
In comparison with the ingots of FIGS. 2B and 2C that include the wafers B and C, the inventors of the ingot of FIG. It was found that the existing region has a continuous spread in the crystal growth direction and the slice direction.
In other words, since fine crystal grains with SiC filaments exist in a specific region of the ingot, a specific inspection standard is set instead of inspecting wafers obtained by slicing from one ingot one by one. It was found that the non-defective product or the defective product can be efficiently sorted by inspecting as a series (set) of wafers arranged in the sliced order.

The conventional inspection method is a method in which each wafer is individually inspected (selected) according to a specific appearance inspection standard, and a series (set) of wafers arranged in the sliced order are relatively inspected adjacent to each other. The inspection method of the present invention in which inspection (selection) is performed based on a standard is a completely new idea.
Here, as a specific inspection standard, the above-described crystal grain size (reference crystal grain size) and a region where a crystal grain having a fine crystal grain size exists (reference region) are mentioned, and these are examples, There is no particular limitation as long as it is a standard that can be used to determine whether the wafer is good or bad. Examples of such inspection standards include minority carrier lifetime, specific resistance, wafer size, wafer thickness, angle formed by each side of the wafer, defect density, photoluminescence emission intensity, carrier mobility, and the like.
A specific inspection standard such as “reference crystal grain size” for comparing one wafer with its adjacent wafer is particularly referred to as “reference physical property value”.

  A method for inspecting a polycrystalline silicon wafer of the present invention using the reference crystal grain size and the reference region as specific inspection standards will be specifically described.

A polycrystalline silicon wafer to be inspected in the present invention is obtained by a known method such as a casting method or an electromagnetic casting method, and after a molten silicon is unidirectionally solidified in a crucible to obtain a large polycrystalline silicon ingot, It is cut into a prismatic polycrystalline silicon block using a known apparatus, and further sliced to a desired thickness using a known apparatus such as a wire saw to form a wafer.
The prismatic polycrystalline silicon block has its surface polished as necessary for the purpose of preventing the occurrence of cracks during slicing.
In addition, it is preferable that the surface of the polycrystalline silicon wafer be cleaned by a known method before the inspection in order to remove dirt adhering to the surface during slicing.

At present, the thickness of the polycrystalline silicon wafer is generally about 170 to 200 μm, but the tendency is to reduce the thickness for cost reduction.
In the inspection method of the present invention, the order (arrangement) of a series (set) of polycrystalline silicon wafers obtained by slicing one polycrystalline silicon block is important, and the order of polycrystalline silicon blocks before slicing is determined. Are arranged to be retained or retained as much as possible, or identified so that their order is fully recognized.

Next, a series (set) of polycrystalline silicon wafers are inspected by the inspection method of the present invention.
Although the inspection method of the present invention will be described with reference to FIG. 1, the present invention is not limited thereby. Here, an example in which the predetermined allowable number is 1 will be described.
FIG. 1 is a schematic view showing an example of an inspection method for a polycrystalline silicon wafer according to the present invention.
1A to 1H are schematic cross-sectional views of a wafer sliced in a direction perpendicular to the crystal growth direction GO of the polycrystalline silicon ingot. That is, the wafers (a) to (h) are arranged in the crystal growth direction of the polycrystalline silicon ingot.

Step (1): Reference physical property values for selecting defective or non-defective products of the polycrystalline silicon wafer on the slice surface from a series of polycrystalline silicon wafer groups obtained by slicing the polycrystalline silicon block. As shown in FIG. 1, a polycrystalline silicon wafer having a maximum aggregate region of crystal grains having a reference crystal grain size equal to or smaller than the reference crystal grain size is determined as (e ).

Step (2): The maximum gathering area is set as a reference area, a polycrystalline silicon wafer having the reference area is set as a reference wafer, and the reference wafer is selected as a defective product.
That is, in FIG. 1, the reference wafer selected as a defective product corresponds to (e), and the drawing number 2 corresponds to the reference region.

Step (3): When there are more than a predetermined allowable number (here, 1) of crystal grains below the reference crystal grain size in the region corresponding to the reference area in the polycrystalline silicon wafer adjacent to the reference wafer, The polycrystalline silicon wafer is selected as a defective product. If it does not exist, the polycrystalline silicon wafer is selected as a non-defective product and the inspection is completed.
That is, in FIG. 1, adjacent uninspected polycrystalline silicon wafers correspond to (d) and (f), and in the region corresponding to the reference region, crystal grains having a reference crystal grain size equal to or smaller than a predetermined allowable number are obtained. Since (1 here) or more exist, it is selected as a defective product.

Step (4): When the polycrystalline silicon wafer is selected as a defective product in the step (3), the non-inspected polycrystalline silicon wafer adjacent to the polycrystalline silicon wafer is selected until the defective product is not selected. repeat.
That is, in FIG. 1, adjacent uninspected polycrystalline silicon wafers correspond to (c) and (g), and then (b), which are crystals having a crystal grain size equal to or smaller than the reference crystal grain size in a region corresponding to the reference region. Since there are more than a predetermined allowable number of grains (here 1), the grains are selected as defective.
1 (a) and 1 (h) show that there are no crystal grains smaller than the reference crystal grain size in the region corresponding to the reference region (less than a predetermined allowable number (here, 1)). As screened.

Here, the figure number 1 in FIG. 1 is a crystal grain, but it is outside the reference region and has no connection with the crystal grain in the reference region. Not sorted as defective.
The physical properties and inspection (selection) results of the polycrystalline silicon wafers of FIGS.

  The means for confirming and selecting the polycrystalline silicon wafer in each of the above steps is not particularly limited, and visual observation is particularly preferable because an instrument such as an optical microscope may be used.

The reference crystal grain size may be set according to specifications required for a polycrystalline silicon wafer. For example, the polycrystalline silicon wafer is for a solar cell, and in order to avoid Id defects of the solar cell, it is 5 mm or less. Preferably, it is 2 mm or less, more preferably 1 mm or less.
When the reference crystal grain size exceeds 5 mm, the proportion of the polycrystalline silicon wafer selected as defective does not have SiC filaments at the crystal grain boundary tends to increase, and the efficiency of the inspection method of the present invention decreases. Sometimes.

Further, the reference region is preferably 100 mm ² or more, more preferably 200 mm ² or more, and more preferably 400 mm ² or more in order to avoid the Id defect of the solar cell, similarly to the above-mentioned reference crystal grain size. Is particularly preferred.
If the reference area is less than 100 mm ² , an area where a large number of phenomena occur suddenly as shown in FIGS. 2B and 2C may be determined as the reference area.

  As described above, the method for inspecting a polycrystalline silicon wafer according to the present invention is such that the polycrystalline silicon wafer is for solar cells, and the defective product has a reverse leakage current failure in the dark when a solar cell is produced. It is suitable when it is a wafer.

(Polycrystalline silicon wafer)
The polycrystalline silicon wafer of the present invention is obtained by sorting out the non-defective product by the polycrystalline silicon wafer inspection method of the present invention.
If necessary, the surface of the polycrystalline silicon wafer may be polished by a known method.
That is, the method for producing a polycrystalline silicon wafer according to the present invention includes a step of slicing a polycrystalline silicon block to obtain a polycrystalline silicon wafer, and the polycrystalline silicon wafer according to the present invention for the sliced polycrystalline silicon wafer. And a step of selecting a defective product or a good product by using a wafer inspection method to obtain a good product.

(Polycrystalline silicon solar cell)
The polycrystalline silicon solar cell of the present invention is manufactured using the polycrystalline silicon wafer of the present invention.
A polycrystalline silicon solar cell can be manufactured, for example, by a known solar cell process using the polycrystalline silicon wafer of the present invention. That is, in the case of a silicon wafer doped with a p-type impurity by a known method using a known material, an n-type impurity is doped to form an n-type layer to form a pn junction, and the surface electrode And a back surface electrode is formed and a polycrystalline silicon solar cell is obtained. Similarly, in the case of a silicon wafer doped with n-type impurities, a p-type impurity is doped to form a p-type layer to form a pn junction, and a surface electrode and a back electrode are formed to form a polycrystalline silicon solar A battery cell is obtained. Alternatively, in addition to those using pn junctions between silicon, MIS type solar cells in which a metal is vapor-deposited with a thin insulating layer interposed therebetween, for example, a silicon thin film of amorphous type having a conductivity type opposite to that of a polycrystalline wafer is formed. There are films that use p-type and n-type silicon heterojunctions with different structures. Further, a plurality of them are electrically connected to obtain a polycrystalline silicon solar cell module.

  In the present specification, the concept including “solar battery cell” and “solar battery module” is simply referred to as “solar battery”. Therefore, for example, what is described as “polycrystalline silicon solar cell” is meant to include “polycrystalline silicon solar cell” and “polycrystalline silicon solar cell module”.

  The present invention will be specifically described below with reference to test examples, but the present invention is not limited to these test examples. In addition, the reference numerical value can be appropriately changed according to the situation.

(Test example)
A polycrystalline silicon ingot produced by the cast method is processed into 25 blocks of 156 mm x 156 mm x 250 mm size using a band saw, and further sliced into a size of 156 mm x 156 mm x thickness 0.18 mm using a wire saw About 17,000 polycrystalline silicon wafers were obtained and cleaned.
Subsequently, the obtained polycrystalline silicon wafer was classified into non-defective products and defective products by the inspection method of the present invention and the conventional inspection method, and the defect occurrence rate (%) in each inspection was obtained.
The inspection method of the present invention is as described above. The reference crystal grain size in the inspection is 1 mm, the reference region is 4 cm ² (400 mm ² ), and the predetermined allowable number is 1.
Further, in the conventional inspection method, the reference crystal grain size is set to 1 mm as in the inspection method of the present invention, and wafers having crystal grains smaller than the reference crystal grain size are selected as defective products.

Moreover, the obtained polycrystalline silicon wafer was put into a normal solar battery cell process to produce a solar battery, and the dark reverse leakage current (Id) of each solar battery was measured.
Next, the Id defect occurrence rate (%) when a solar cell is manufactured from a wafer selected as a non-defective product in each inspection and the Id defect occurrence rate when a solar cell is manufactured from a wafer selected as a defective product in each inspection ( %).
In the case of uninspected, the Id defect occurrence rate (%) of all wafers was determined on the assumption that all wafers were selected as non-defective products.
The obtained results are shown in Table 2.

The following can be seen from the results in Table 2.
Of the 1.4% of wafers selected as defective by the inspection method of the present invention, the actually produced solar cell has an Id defect occurrence rate of 96.0%, while it is selected as defective by the conventional inspection method. Of the 21.0% of the wafers produced, the actually produced solar cell has an Id defect occurrence rate of 6.1%, and the inspection method of the present invention has higher accuracy of sorting defective products than the conventional inspection method. .
Further, among the wafers (98.6%) selected as non-defective products by the inspection method of the present invention, the actually produced solar cell has an Id defect occurrence rate of 0.3%, while the conventional inspection method is non-defective. Among the wafers selected (79.0%), the actually produced solar cell has an Id defect occurrence rate of 0.3%, and there is no difference between the two inspection methods.

In other words, in the wafer inspection, the ratio of selecting a non-defective product as a defective product is 0.056% in the inspection method of the present invention with respect to the total number of wafers, while 19% in the conventional inspection method. The inspection method of the present invention has a higher accuracy of sorting defective products than the conventional inspection method.
Therefore, according to the inspection method of the present invention, wafers that have Id defects before the production of solar cells can be selected with higher accuracy than conventional inspection methods, so that the production yield of solar cells can be increased. It is possible to improve the cost of solar cells and contribute to the spread.

1 Fine crystal grains without SiC filaments 2 Reference region 3 Fine crystal grains with SiC filaments 4 Fine crystal grains just generated stochastically 5 Double phase and slip are included in a single crystal grain during crystal growth Generated fine crystal grains SO Slice direction GO Crystal growth direction AA 'Slice cross section BB' Slice cross section CC 'Slice cross section

Claims (8)

It is an inspection method for selecting defective or good products from a series of polycrystalline silicon wafer groups obtained by slicing a polycrystalline silicon block.
(1) As a standard physical property value for selecting defective or non-defective polycrystalline silicon wafers on a slice plane from a series of polycrystalline silicon wafer groups obtained by slicing the polycrystalline silicon block Confirming a polycrystalline silicon wafer having a maximum aggregate region of crystal grains of a reference crystal grain size or less;
(2) a step of setting the maximum gathering region as a reference region, a polycrystalline silicon wafer having the reference region as a reference wafer, and selecting the reference wafer as a defective product;
(3) If there are more than a predetermined allowable number of crystal grains below the reference crystal grain size in a region corresponding to the reference region in the polycrystalline silicon wafer adjacent to the reference wafer, the polycrystalline silicon wafer is defective. A process of screening the polycrystalline silicon wafer as a non-defective product when it does not exist and terminating the inspection,
(4) When the polycrystalline silicon wafer is selected as a defective product in the step (3), the reference crystal grains in the region corresponding to the reference region of the uninspected polycrystalline silicon wafer adjacent to the polycrystalline silicon wafer The process of selecting the polycrystalline silicon wafer as a defective product when the number of crystal grains having a diameter equal to or larger than a predetermined allowable number is present, and selecting the polycrystalline silicon wafer as a non-defective product when it does not exist, and ending the inspection. Repeat the process until no more
A method for inspecting a polycrystalline silicon wafer, comprising: The method for inspecting a polycrystalline silicon wafer according to claim 1 , wherein the reference crystal grain size is 5 mm or less. The method for inspecting a polycrystalline silicon wafer according to claim 2 , wherein the reference crystal grain size is 2 mm or less. The method for inspecting a polycrystalline silicon wafer according to claim 1, wherein the reference region is 100 mm ² or more. Wherein the predetermined acceptable number, the inspection method of the polycrystalline silicon wafer according to a any one of claims 1 to 4, 1. The polycrystalline silicon wafer is a solar cell, according to the defective products any one of claims 1 to 5 is a polycrystalline silicon wafer as a dark state reverse leakage current failure when producing a solar cell Inspection method for polycrystalline silicon wafers. A method for producing a polycrystalline silicon wafer using the method for inspecting a polycrystalline silicon wafer according to any one of claims 1 to 6 ,
A step of slicing a polycrystalline silicon block to obtain a polycrystalline silicon wafer;
A method of producing a non-defective product by sorting out defective products or non-defective products from the sliced polycrystalline silicon wafer using the inspection method. A method for producing a polycrystalline silicon solar cell, wherein an electrode is formed on the polycrystalline silicon wafer produced by the method for producing a polycrystalline silicon wafer according to claim 7 to obtain a polycrystalline silicon solar cell.