TWI449930B - Method of determining quality of silicon brick - Google Patents

Description

Quality determination method of twin rod

The present invention relates to a quality determination method, and more particularly to a method for determining the quality of a twin rod.

Solar energy is a clean, pollution-free and inexhaustible source of energy. Solar energy is the focus of attention in the face of the current shortage of petrochemical energy and pollution. Since solar cells can directly convert solar energy into electrical energy, it has become one of the most important research topics in the industry.

Most solar cells are made from germanium wafers. The tantalum wafer is an ingot formed from a tantalum raw material, which is formed by sawing to form a plurality of twin rods, and then cutting the twin rods. At present, the value of the carrier lifetime measurement is measured for the whole of the twin rod, and the quality of the twin rod is directly determined. However, since the life measurement of the carrier is easily affected by external factors such as the surface roughness of the crystal and the condition of the probe of the machine, it is easy to cause errors between the measurement data of the carrier life of the batch, and the quality determination is not accurate.

Therefore, there is a need for an improved method for accurately determining the quality of a twin rod.

The present invention provides a method for determining the quality of a twin rod, which can accurately determine the quality of the twin rod before the cutting step.

The invention provides a method for determining the quality of a twin rod. The method first measures the multi-point carrier lifetime of at least one crystal rod, and sorts the data of the carrier lifetime from large to small. Next, find the first lowest carrier lifetime LD _x in the pre-X% group, where X = any value of 10-20; and find the second lowest carrier lifetime LD _Y in the pre-Y% group , where Y = 40~90. Then, the ratio of LD _x to LD _Y is calculated, and it is judged whether or not the ratio is smaller than a predetermined value.

In an embodiment of the invention, X is 10 and Y is any one of 50 to 80.

In an embodiment of the invention, the predetermined value is less than or equal to 1.5.

In an embodiment of the invention, the predetermined value varies in proportion to Y.

In an embodiment of the invention, the above-mentioned twin rod has an average carrier lifetime of greater than or equal to 3 μs.

In an embodiment of the present invention, after the step of calculating the ratio, the method for determining the quality of the twin rod further comprises performing a cutting step on the twin rod to separate the used material of the twin rod from the recycled material.

In an embodiment of the invention, after performing the cutting step, the method for determining the quality of the twin rod further comprises a step of slicing the twin rod to form a plurality of tantalum wafers.

In one embodiment of the invention, the above-described twin rods are used to make solar cells.

In an embodiment of the invention, the ratio is related to the conversion efficiency of the solar cell.

The coefficient of determination (R ²⁾ in one embodiment of the invention, the coefficient of determination of the ratio of the conversion efficiency of each of the silicon rod (R ²⁾ greater than the minimum carrier lifetime and the conversion efficiency of each single group of the silicon rod .

Based on the above, the present invention provides a basis for determining the ratio of the carrier lifetime measurement data distribution associated with the conversion efficiency to accurately determine the quality of the crystallizing rod prior to the cutting step of the twin rod.

The above described features and advantages of the present invention will be more apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing a method for determining the quality of a twin rod in accordance with an embodiment of the present invention. 2 is a diagram showing the carrier lifetime distribution of a twin rod in accordance with an embodiment of the present invention.

Referring to FIG. 1, step S100 is performed to measure the multi-point carrier lifetime of at least one of the crystal rods, and the data of the obtained carrier lifetimes are arranged from large to small. As shown in Fig. 2, the data of the measured carrier lifetimes are ranked from large to small to obtain a curve.

Next, proceeding to step S102, in the data arrangement, the first lowest carrier lifetime LD _X in the previous X% group is found. In an embodiment, X is any one of 10 to 20. Therefore, as shown in FIG. 2, when X is 10, the LD ₁₀ is about 9.54 μs. However, the invention is not limited thereto.

Thereafter, step S104 is performed to find the second lowest carrier lifetime LD _Y in the previous Y% group in the same data arrangement. In an embodiment, Y is any one of 40 to 90. In another embodiment, Y is any one of 50 to 80. In one embodiment, when Y is 60, the LD ₆₀ is about 6.45 μs, as shown in FIG.

Then, in step S106, the ratio (LD _X /LD _Y ) of LD _X to LD _Y is calculated, and it is judged whether the ratio is less than a predetermined value to determine the quality of the twin rod. In an embodiment, the predetermined value is, for example, 1.5 or less. Additionally, the predetermined value may vary in proportion to Y. In an embodiment, the predetermined value may vary, for example, in the range of 1.3 to 1.5 as a function of Y. As shown in Fig. 2, LD ₁₀ /LD ₆₀ is about 1.48 (=9.54 μs / 6.45 μs), and this value is less than 1.5, that is, falls within the predetermined range set. In the above embodiment, the LD _X /LD _Y ratio is exemplified by LD ₁₀ /LD ₆₀ , but the invention is not limited thereto. In other embodiments, LD _X /LD _{Y is,} for example, LD ₁₀ /LD ₄₀ , LD ₁₀ /LD ₄₅ , LD ₁₀ /LD ₅₀ , LD ₁₀ /LD ₅₅ , LD ₁₀ /LD ₆₅ ,LD ₁₀ /LD ₇₀ ,LD ₁₀ / LD ₇₅ , LD ₁₀ / LD ₈₀ , LD ₁₀ / LD ₈₅ or LD ₁₀ / LD ₉₀ .

Therefore, the present invention utilizes the ratio of the two groups of carrier lifetime measurement data as a basis for determining the quality of the twin rod by means of relative values rather than absolute values.

In addition to the determination basis of the present invention, the calculation of the average carrier lifetime of the twin rod can also be used as one of the basis for determination. In one embodiment, the average carrier lifetime of the twin rod is, for example, greater than or equal to about 3 μs. In addition, other determinations known to those of ordinary skill in the art can be used.

In addition, the LD _X /LD _Y ratio calculated by the method of the present invention is related to the conversion efficiency of the solar cell and will be further illustrated in Example 1. Therefore, the LD _X /LD _Y ratio calculated by the method of the present invention can be used to determine the quality of the twin rod.

After calculating the LD _X /LD _Y ratio, the dicing bar can be subjected to a dicing step to separate the strontium rod from the regrind. Next, after the cutting step, the twinning bar can be further subjected to a slicing step to form a plurality of tantalum wafers that can be used to fabricate solar cells. The cutting step and the slicing step are well known in the art to those skilled in the art and will not be described again.

Based on the above, the present invention can grasp the advantages and disadvantages of the twin rod by the ratio of LD _X /LD _Y related to the conversion efficiency of the solar cell before performing the slicing step or even the cutting step.

Hereinafter, the features and effects of the embodiment will be described in detail by way of specific examples. However, these examples are not intended to limit the invention.

Example 1

Figure 3a is a graph showing the relationship between the lowest carrier lifetime and the conversion efficiency of a single crystal of a single group of crystals, wherein the lowest carrier lifetime of a single group is, for example, LD ₆₀ in Figure 3a, but not Limited. In addition, FIG. 3b is a graph showing the relationship between the LD _X /LD _Y ratio of each twin rod and the conversion efficiency of the twin rod, wherein the LD _X /LD _Y ratio is, for example, LD ₁₀ /LD ₆₀ in FIG. 3b, but not This is limited.

Referring to FIG. 3a and FIG. 3b simultaneously, the coefficient of determination (R ² ) of the regression analysis obtained in the graph can be found that the LD _X /LD _Y ratio of each crystal rod and the coefficient of determination of conversion efficiency are larger than each 矽. The coefficient of determination of the lowest carrier lifetime and conversion efficiency for a single group of ingots. In other words, in Figures 3a and 3b, it shows that the LD _X /LD _Y ratio is a more decisive factor, and the LD _X /LD _Y ratio is more related to the conversion efficiency than the single group measurement. high.

Therefore, the conversion efficiency range of the solar cell produced by the twin rod can be known using the LD _X /LD _Y ratio, and the quality of the twin rod can be determined.

Example 2

Figure 4 shows a comparison of the error values of two measurements between LD ₆₀ and LD ₁₀ /LD ₆₀ .

First, a first bar of the first LD ₁₀ , the first LD _60, and the LD ₁₀ /LD ₆₀ is obtained by passing a crystal bar through steps S100 to S104 as shown in FIG. Next, steps S100 to S104 are performed again on the same twin rod, and second ratios of the second LD ₁₀ , the second LD _60, and the LD ₁₀ /LD ₆₀ are obtained. Then, the first LD ₆₀ is subtracted from the second LD ₆₀ to obtain an error value between the two measurements of the LD ₆₀ . Similarly, the first ratio LD ₁₀ / LD ₆₀ and the second ratio LD ₁₀ / LD ₆₀ is subtracted, to obtain an error value between LD ₁₀ / LD ₆₀ measured twice. The above steps were repeated, and the error values of the two measurements of LD ₆₀ and LD ₁₀ /LD ₆₀ were measured for each of the twin rods, and the obtained error values were plotted to obtain FIG.

Referring to FIG. 4, it is shown that the distribution range of the error of the LD ₁₀ /LD ₆₀ ratio is smaller than the distribution range of the error of the LD ₆₀ . In other words, it is better to perform experiments using the LD ₁₀ /LD ₆₀ ratio which is a relative value than the experiment using the LD ₆₀ which is an absolute value. Therefore, by using the ratio of LD ₁₀ /LD ₆₀ as the basis for determining the quality, it is possible to reduce the degree of influence of, for example, crystal defects, surface roughness, enthalpy retraction, and machine error, thereby greatly improving the quality of the twin rod. accuracy.

Example 3

FIG. 5 illustrates a comparison of error values between two measurements between LD ₄₀ and LD ₁₀ /LD ₄₀ . In this example, the error values between the two measurements were calculated and plotted in the same procedure as in Example 2 except that LD ₄₀ was used instead of LD ₆₀ .

Similarly, it can be seen from Fig. 5 that the distribution of the error of the LD ₁₀ /LD ₄₀ ratio is smaller than the distribution of the error of the LD ₄₀ . Therefore, the experiment using the ratio of LD ₁₀ /LD ₄₀ has better reproducibility, thereby more accurately reflecting the quality of the twin rod.

Example 4

Figure 6 shows a comparison of the error values of the two measurements between LD ₉₀ and LD ₁₀ /LD ₉₀ . In this example, the error values between the two measurements were calculated and plotted in the same procedure as in Example 2 except that LD ₉₀ was used instead of LD ₆₀ .

Similarly, it can be seen from Fig. 6 that the distribution range of the error of the LD ₁₀ /LD ₉₀ ratio is smaller than the distribution range of the error of the LD ₉₀ . Therefore, the experiment using the ratio of LD ₁₀ /LD ₉₀ has better reproducibility, thereby more accurately reflecting the quality of the twin rod.

In summary, the present invention provides a method for determining the quality of a twin rod by using a ratio of the distribution of the carrier lifetime measurement data as a basis for determination. This method uses a relative value, so that the degree of error between the batch measurement data can be reduced, and the LD _X /LD _Y ratio calculated by this method is related to the conversion efficiency, so before the crystallization rod performs the cutting step That is, the quality of the twin rod can be accurately determined. In other words, the method of the present invention can determine the range of conversion efficiency of the solar cell earlier than conventional methods that require solar cell fabrication to achieve conversion efficiency.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

S100~S106‧‧‧Steps

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing a method for determining the quality of a twin rod in accordance with an embodiment of the present invention.

2 is a diagram showing the carrier lifetime distribution of a twin rod in accordance with an embodiment of the present invention.

Figure 3a is a graph showing the relationship between the lowest carrier lifetime and the conversion efficiency of a twin rod for a single group of individual crystal rods.

Fig. 3b is a graph showing the relationship between the LD _X /LD _Y ratio of each twin rod and the conversion efficiency of the twin rod.

Figure 4 shows a comparison of the error values of two measurements between LD ₆₀ and LD ₁₀ /LD ₆₀ .

FIG. 5 illustrates a comparison of error values between two measurements between LD ₄₀ and LD ₁₀ /LD ₄₀ .

Figure 6 shows a comparison of the error values of the two measurements between LD ₉₀ and LD ₁₀ /LD ₉₀ .

S100~S106‧‧‧Steps

Claims (9)

A method for determining the quality of a twin rod includes: measuring a multi-point carrier lifetime of at least one crystal rod, and sorting the data of the carrier lifetimes from large to small; finding the front X% group a first lowest carrier lifetime LD _x , where X = 10 to 20; find a second lowest carrier lifetime LD _{Y of the} previous Y% group, where Y = 40 to 90 a value; and calculating a ratio of LD _x to LD _Y and determining whether the ratio is less than a predetermined value, wherein the predetermined value varies in proportion to Y. The method for determining the quality of a twin rod as described in claim 1, wherein X=10, Y=50-80. The method for determining the quality of a twin rod as described in claim 1, wherein the predetermined value is 1.5 or less. The method for determining the quality of a twin rod as described in claim 1, wherein the average lifetime of the twin rod is greater than or equal to 3 μs. The method for determining the quality of the twin rod according to the first aspect of the patent application, after the step of calculating the ratio, further comprises performing all the steps on the twin rod to make the used material and the recycled material of the twin rod separate. The method for determining the quality of a twin rod as described in claim 5, after performing the cutting step, further comprises performing a slicing step on the twin rod to form a plurality of tantalum wafers. The method for determining the quality of a twin rod as described in claim 1, wherein the twin rod is used for fabricating a solar cell. The method for determining the quality of a twin rod as described in claim 7, wherein the ratio is related to a conversion efficiency of the solar cell. The method for determining the quality of a twin rod as described in claim 1, wherein the ratio of the ratio of each of the twin rods to the conversion efficiency (R ² ) is greater than the minimum carrier lifetime of a single group of the respective twin rods. The coefficient of determination of conversion efficiency (R ² ).