TWM459985U - Silicon seed - Google Patents

Abstract

The invention discloses a silicon seed including a silicon crystal body and a protection layer. The protection layer is formed to overlay an external surface of the silicon crystal body. The met point of the silicon crystal body is higher than that of the silicon crystal body.

Description

矽 seed

The present invention relates to a silicon seed for producing a crystalline silicon ingot, and in particular, to a seed crystal which can reduce an impurity-contaminated area in a twinned ingot.

Most solar cells absorb sunlight and produce a photovoltaic effect. At present, most of the materials of solar cells are mainly coffins, mainly because coffins are the second most easily available elements on the earth, and they have the advantages of low material cost, no toxicity, and high stability. And it has a solid foundation in the application of semiconductors.

The solar cells based on coffins include three types: single crystal germanium, polycrystalline germanium and amorphous germanium. The use of polycrystalline germanium as a raw material for solar cells is mainly based on cost considerations because its price is comparable to that of the conventional Czochralski method (CZ method) and the floating zone method (FZ method). The single crystal crucible is relatively cheaper.

The use of polycrystalline germanium in the manufacture of solar cells has traditionally been produced using conventional casting processes. The use of a casting process to prepare polycrystalline germanium, which is then applied to solar cells, is a prior art in the art. Briefly, high purity germanium is melted in a mold (e.g., quartz crucible) and cooled under controlled solidification to form a polycrystalline germanium ingot. Then, the polycrystalline germanium ingot is cut into a wafer close to the size of the solar cell, and then applied to manufacture a solar cell. on. The polycrystalline tantalum ingot produced in this way is an aggregate of ruthenium crystal grains in which crystal orientations of crystal grains with each other are actually random.

In the existing polysilicon, it is difficult to perform a texturing process on the surface of the wafer to be formed because of the random crystal orientation of the crystal grains. The roughening of the surface can reduce the light reflection and increase the absorption of light energy through the surface of the battery to improve the efficiency of the photovoltaic cell. Further, "kneading/difference/defect" formed in the grain boundaries between the existing polycrystalline germanium grains tends to form clusters of nucleation-difference rows or structural defects in the form of a plurality of line-difference rows. These rows and the impurities they tend to attract cause a rapid recombination of charge carriers in photovoltaic cells made from existing polycrystalline germanium. This can result in a decrease in the efficiency of the battery. Photovoltaic cells made from such polycrystalline germanium are generally less efficient than equivalent photovoltaic cells made from single crystal germanium, even considering the radial distribution of defects present in single crystal germanium fabricated by the prior art. However, since the fabrication of existing polysilicon is relatively simple and less costly, as well as defect passivation that is effective in battery processing, polysilicon has become a widely used form of tantalum material for the fabrication of photovoltaic cells.

It has been disclosed in the prior art to lay a single-grain seed layer on the bottom of the crucible and to make a twinned ingot based on directional solidification. In this way, it is possible to cast an ingot having a high-performance single crystal germanium and/or a bi-crystal or a mono-like crystal block, and a subsequent load of a wafer. Life can be maximized and wafers are used to make efficient solar cells. Here, the term "single crystal germanium" means a main body of a single crystal germanium having a uniform crystal crystal orientation over the entire range. The term "bimorph" refers to a body of ruthenium having a uniform crystal orientation in a range of greater than or equal to 50% of the volume of the body, and having another uniform crystal orientation within the remaining volume of the body. . For example, such a twin germanium may comprise a single crystal germanium body having a crystal crystal orientation, which is adjacent to another single crystal germanium body having a different crystal crystal orientation in the immediate vicinity of the remaining volume of the crystalline germanium. The term "monocrystalline single crystal" refers to a host of crystalline germanium having a uniform crystal orientation in a range exceeding 75% of the volume of the body. In addition, now Some polycrystalline yttrium refers to a crystalline yttrium having a fine distribution of a centimeter scale, and having a plurality of crystals having a random crystal orientation in the main body of the ruthenium.

The prior art also has a nucleation promoting layer composed of polycrystalline germanium or single crystal granules at the bottom of the crucible to assist the nucleation of the ruthenium and to form a nucleation based on directional solidification, and finally grow into a small size 矽 grain at the bottom, and the overall defect density. The low-temperature twinning ingots, the photoelectric conversion efficiency of the solar cells produced by the twin-crystal ingots are also quite high.

However, in the prior art, a nucleation promoting layer composed of a single crystal seed layer, a polycrystalline germanium or a single crystal crumb is laid at the bottom of the crucible to form a twin ingot, and in the manufacturing process of the twin ingot, the impurities in the crucible Metals (eg, iron, aluminum, etc.) are mainly dissolved in bismuth melt, diffused into single-grain seed crystals, multi-grain or single-grain granules, along with smelting soup in single-grain seed crystals, Multi-grain or single-grain nucleation, long-crystal, single-crystal seed, multi-grain or single-grain granules will re-expand into the ruthenium crystal solidified in the casting process, resulting in twinning The impurity contamination area in the ingot is large.

Therefore, one of the technical problems to be solved by the present invention is to provide a seed crystal for producing a twinned ingot and reducing the impurity-contaminated area in the twin-shaped ingot.

One of the preferred embodiments of the present invention is a seed crystal for the production of twinned ingots. The seed crystal of this creation consists of a germanium crystal body and a protective layer. The protective layer is coated on the outer surface of the germanium crystal body. Also, the protective layer has a melting point higher than the melting point of the ruthenium crystal body.

In a specific embodiment, the protective layer may be made of SiO ₂ , Si ₃ N ₄ , BaO, AlN, BN, Al ₂ O ₃ or other melting point higher than the melting point of cerium and can effectively hinder the diffusion of impurities into the cerium crystal. The material of the body is formed.

In a specific embodiment, the germanium crystal body can be formed into a cube, Cuboid, spherical particles or irregularly shaped particles.

In one embodiment, the thickness of the protective layer ranges from 100 nm to 2500 nm.

Different from the prior art, the seed crystal of the present invention can effectively hinder the diffusion of impurities in the smelting soup into the ruthenium crystal body and then re-expand into the solidified ruthenium crystal in the process of manufacturing the twin crystal ingot, thereby It can reduce the impurity contamination area in the twin crystal ingot.

The advantages and spirit of the present invention can be further understood by the following embodiments and the drawings.

1‧‧‧矽 seed

10‧‧‧矽crystal body

102‧‧‧ outer surface

12‧‧‧Protective layer

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a seed crystal of one preferred embodiment of the present invention.

Figure 2 is a cross-sectional view of a seed crystal of another embodiment of the present invention.

Figure 3 is a cross-sectional view of a seed crystal of another embodiment of the present invention.

Figure 4 is a cross-sectional view of a seed crystal of another embodiment of the present invention.

Referring to FIG. 1, a seed crystal 1 of a preferred embodiment of the present invention is schematically illustrated in a cross-sectional view. The seed crystal 1 of this creation is used to manufacture twin crystal ingots.

As shown in FIG. 1, the seed crystal 1 of the present invention comprises a germanium crystal body 10 and a protective layer 12. The germanium crystal body 10 is composed of at least one crystal grain. The protective layer 12 is coated on the outer surface 102 of the germanium crystal body 10. Also, the protective layer 12 has a melting point higher than the melting point of the ruthenium crystal body 10.

In a specific embodiment, the protective layer 12 may be made of SiO ₂ , Si ₃ N ₄ , BaO, AlN, BN, Al ₂ O ₃ or other melting point higher than the melting point of the crucible and can effectively hinder the diffusion of impurities into the crucible soup into the crucible. The material of the crystal body 10 is formed.

In practical applications, the appearance of the crystal body 10 of the present invention may be a large-sized (centimeter-scale) cube, as shown in FIG. Please refer to FIG. 2, FIG. 3 and FIG. 4, which are schematic cross-sectional views showing the seed crystal 1 of other specific embodiments of the present invention. As shown in FIG. 2, the appearance of the crystal body 10 of the present invention may also be a rectangular parallelepiped having a large size (cm scale). As shown in Fig. 2, the appearance of the crystal body 10 of the present invention may also be a spherical particle of a small size (millimeter grade). As shown in Fig. 2, the appearance of the crystal body 10 of the present invention may also be a small-sized (millimeter-scale) irregularly shaped particle (so-called scrap).

In a specific embodiment, the thickness of the protective layer 12 ranges from 100 nm to 2500 nm, and the thickness of the protective layer 10 ranges from 100 nm to 500 nm. In practical application, in the process of manufacturing the twin crystal ingot, the time of contact between the seed crystal 1 and the smelting soup of the present invention is about 1 to 5 hours, and the protective layer 12 having a thickness ranging from 100 nm to 500 nm is in contact with the smelting soup. 1~5 hours is not completely dissolved, which is enough to protect the seed body 10, which can effectively prevent the impurities in the smelting soup from diffusing into the 矽 crystal seed body 10 and then re-expanding into the solidified yttrium crystal, thereby It can reduce the impurity contamination area in the twin crystal ingot.

In addition, the prior art uses a seed crystal to produce a twine ingot, and in order to prevent the seed crystal from completely melting when the tantalum melt has not begun to solidify, the seed layer is generally thickened. However, thickening the seed layer or increasing the manufacturing cost. As described above, the seed crystal 1 of the present invention is in contact with the enamel soup and the protective layer 12 is not completely melted, so that the thickness of the enamel seed layer composed of the enamel seed crystal 1 of the present invention can be reduced.

The above-mentioned various impurity diffusion barrier layers 12 have the effect of avoiding premature melting of the crystal 10 during the manufacturing process of the twinned ingot, and can shorten the manufacturing time of the twinned ingot and reduce the thickness of the seed layer.

With the above detailed description of the preferred embodiments, it is intended to more clearly describe the features and spirit of the present invention, and is not preferred as disclosed above. Specific embodiments are intended to limit the scope of this creation. On the contrary, the purpose is to cover all kinds of changes and equivalence arrangements within the scope of the patent application to which the present invention is intended. Therefore, the scope of the patent application filed by this creator should be interpreted broadly based on the above description so that it covers all possible changes and equivalent arrangements.

1‧‧‧矽 seed

10‧‧‧矽crystal body

102‧‧‧ outer surface

12‧‧‧Protective layer

Claims (4)

A seed crystal comprising: a germanium crystal body; and a protective layer coated on an outer surface of the germanium crystal body. The seed crystal of claim 1, wherein the system of the germanium crystal forms a cube, a cuboid, a spherical particle or an irregularly shaped particle. The seed crystal of claim 2, wherein the protective layer has a thickness ranging from 100 nm to 2500 nm. The seed crystal of claim 3, wherein the protective layer has a thickness ranging from 100 nm to 500 nm.