阅读说明：本技术 一种直拉法生产单晶中收尾阶段单晶收放趋势的判断方法 (Method for judging single crystal winding and unwinding trend in ending stage in single crystal production by Czochralski method ) 是由 张欢 连庆伟 李超 王雅楠 吴志强 崔彬 姜舰 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种直拉硅单晶收尾阶段单晶收放趋势的判断方法,包括以下步骤：(1)按照所生产单晶直径的1-1.3倍预算出收尾长度,结合勾股定理算出收尾的两个角度为63°和69°,根据两个角度分别计算不同长度段内的重量随长度变化斜率,绘制出理论重量随长度变化曲线图；(2)通过单晶炉客户端获得收尾部分任意位置A和重量B；通过单晶炉客户端获得收尾部分位置A下的位置C和重量D；计算位置A到位置C的重量随着长度的变化斜率α＝(D-B)/(C-A)；(3)将理论重量随长度变化曲线图划分成提高拉速区、拉速维持区、降低拉速区,将α放入理论重量随长度变化曲线图中,实时调节拉速。采用本发明能够及时有效的判断出单晶收放趋势,正确的调节拉速,提高单晶的完好率。(The invention discloses a method for judging the monocrystal winding and unwinding trend in the ending stage of Czochralski silicon monocrystal, which comprises the following steps: (1) estimating the ending length according to 1-1.3 times of the diameter of the produced single crystal, calculating two angles of ending as 63 degrees and 69 degrees by combining the pythagorean theorem, respectively calculating the slope of the change of the weight in different length sections along with the length according to the two angles, and drawing a curve graph of the change of the theoretical weight along with the length; (2) acquiring any position A and weight B of the ending part through a single crystal furnace client; obtaining a position C and a weight D below a position A of the ending part through a client of the single crystal furnace; calculating the change slope alpha of the weight from the position A to the position C along the length as (D-B)/(C-A); (3) dividing the curve graph of the theoretical weight changing along with the length into a pulling speed increasing area, a pulling speed maintaining area and a pulling speed reducing area, putting alpha into the curve graph of the theoretical weight changing along with the length, and adjusting the pulling speed in real time. The method can effectively judge the monocrystal winding and unwinding trend in time, correctly adjust the pulling speed and improve the perfectness rate of the monocrystal.)

1. A method for judging the single crystal collecting and releasing trend in the ending stage of the single crystal production by the Czochralski method is characterized by comprising the following steps:

(1) budgeting the ending length of the same heat according to 1-1.3 times of the diameter of the produced single crystal, calculating two ending angles of 63 degrees and 69 degrees by combining the pythagorean theorem, respectively calculating the slope of the change of the weight in different length sections along with the length according to the two angles, and drawing a curve graph of the change of the theoretical weight along with the length;

(2) acquiring any position A and weight B of the ending part through a single crystal furnace client; then, obtaining a position C and a weight D below the position A of the ending part through a single crystal furnace client; calculating the change slope alpha of the weight from the position A to the position C along the length as (D-B)/(C-A);

(3) dividing a curve graph of the theoretical weight changing along with the length into a pulling speed increasing area, a pulling speed maintaining area and a pulling speed reducing area, putting alpha into the curve graph of the theoretical weight changing along with the length, and if the slope alpha falls into the pulling speed increasing area, increasing the pulling speed in time; if the slope alpha falls in the pulling speed maintaining area, the pulling speed is not adjusted; and if the slope falls in the pull-down speed area, the pull-down speed is timely reduced.

2. The method for judging a tendency of taking up and paying off a single crystal at an end stage in the production of a single crystal by the Czochralski method as set forth in claim 1, wherein a distance C-A between the position A and the position C in the step (2) is 5 to 10 mm.

3. The method for judging the crystal pulling and releasing tendency in the final stage of the production of the single crystal by the Czochralski method as set forth in claim 1, wherein in the step (1), the process of plotting a graph of the theoretical weight as a function of length is as follows:

1) theoretically calculating the ending weight W1 ═ 1/3 ═ π ═ R12+ R1 × (1 + R1) of single crystal in h length²) H rho, wherein R1 and R1 are the upper and lower diameters of the ending part in the ending length section respectively, h is the ending length, and rho is the density of the monocrystalline silicon;

2) theoretically calculating the final weight W2 ═ 1/3 ═ π · (R2) in the next h segment²+R2*r2+r2²) H ρ; wherein R2 and R2 are the upper and lower diameters of the ending part in the ending length segment, h is the ending length, and rho is the density of the monocrystalline silicon;

3) theoretically calculating the weight change delta W in two h sections as W2-W1;

4) calculating the slope l of the weight of two h sections changing along with the length as delta W/h; calculating the slope of the change of the weight along with the length in different length sections by analogy;

5) and drawing a theoretical weight change curve graph along with the length according to the obtained weight change slopes along with the length in the two sections with different ending angles and different lengths.

4. The method for judging the crystal pulling and releasing tendency at the end stage in the production of a single crystal by the Czochralski method as set forth in claim 1, wherein in the step (3), the temperature compensation is changed simultaneously to assist the adjustment in the process of adjusting the pulling rate.

5. The method for judging the crystal pulling and releasing tendency at the ending stage in the production of the single crystal by the Czochralski method as claimed in claim 1, wherein the ending slope is kept oscillating around a curve of theoretical weight change with length during ending to ensure the beauty of the tail of the single crystal.

Technical Field

The invention relates to a method for judging the monocrystal winding and unwinding trend in the ending stage of monocrystal production by a Czochralski method, and belongs to the field of semiconductor silicon material production.

Background

With the advent of the information age, it is becoming more important to effectively master information resources, and so the performance requirements for computer processing, storage, and transmission of information are also increasing. The advent of large scale integrated circuits has provided a developmental foundation for improving the performance of computers. SiO with highly stable silicon material surface structure₂The advantages of the passivation layer, such as large critical shear stress and no toxicity, determine that the silicon material is the basic material for manufacturing the integrated circuit. As integrated circuit technology advances, the silicon chip size for integrated circuits is becoming larger and larger to control cost, and currently 8 inch and 12 inch polished wafers are the mainstream in the market. The application of large-size silicon wafers has higher and higher requirements on the production technology of monocrystalline silicon. The existing methods for producing the silicon single crystal rod mainly comprise a Czochralski silicon crystal method (CZ), a suspension zone melting method (FZ) and an epitaxial method. Compared with the FZ method and the epitaxial method, the CZ method is more popular and widely applied to the semiconductor production industry. The CZ method is a process of melting polycrystalline silicon in a quartz crucible, and obtaining single crystals through processes of seeding, shouldering, shoulder rotating, constant diameter, ending, furnace blowing and the like. Diameter signals are obtained by a CCD optical system in the growing process, so that the size of the monocrystalline silicon is controlled to be the target size.

For large-diameter single crystals, as the furnace cylinder of the single crystal furnace is fixed in size, the ending part can be blocked by the equal-diameter part in the previous stage along with the increase of the growth length of the single crystal. On-site workers cannot visually judge the section of the retraction and the release of the single crystal at the ending part by naked eyes, and adjust the ending pulling speed only by personal experience. The pulling speed of the single crystal ending can not be accurately adjusted, the pulling speed is not lifted in time, the ending blockage/breakage or poor shape is caused, the perfectness rate of the single crystal production is seriously influenced, and the production cost is increased. In addition, from the single crystal end-up process, dislocations may be generated if the end-up length is insufficient, so many manufacturers require end-up lengths of 1 to 1.3 times the diameter. Not only ensures that the length of the single crystal ending is enough and no dislocation exists, but also ensures that the length of the ending is not too long and the resource is not consumed. Therefore, the improvement of the ending process to ensure the appearance of the single crystal and the completeness of the ending result has important significance for improving the profit of manufacturers.

The method has certain limitation, accurate analysis cannot be performed on the tail part of the single crystal during short-time collection and release, and the real-time change trend of the tail part of the single crystal cannot be judged.

For the production sector, the aesthetic appearance of the end shape of the single crystal and the integrity of the single crystal are of great importance to the company's income. How to quickly judge the retraction state of the ending part of the single crystal and timely and effectively adjust the ending pulling speed has important significance for saving the production cost and improving the perfectness rate of the single crystal.

Disclosure of Invention

Based on the problems in the prior art, the invention aims to provide the method for judging the single crystal collecting and releasing trend in the ending stage of the single crystal production by the Czochralski method, the method can effectively judge the single crystal collecting and releasing trend in time, help operators to correctly adjust the pulling speed and improve the perfectness rate of the single crystal.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for judging the single crystal collecting and releasing trend in the ending stage in the production of single crystals by a Czochralski method comprises the following steps:

(1) budgeting the ending length of the same heat according to 1-1.3 times of the diameter of the produced single crystal, calculating two ending angles (namely the angle formed by the ending growth surface and the single crystal inclined surface) of 63 degrees and 69 degrees by combining the pythagorean theorem, respectively calculating the change slope of the weight in different length sections along with the length according to the two angles, and drawing a curve graph of the theoretical weight along with the change of the length;

(2) acquiring any position A and weight B of the ending part through a single crystal furnace client; then, obtaining a position C and a weight D below the position A of the ending part through a single crystal furnace client; calculating the change slope alpha of the weight from the position A to the position C along the length as (D-B)/(C-A);

(3) dividing a curve graph of the theoretical weight changing along with the length into a pulling speed increasing area, a pulling speed maintaining area and a pulling speed reducing area, putting alpha into the curve graph of the theoretical weight changing along with the length, and if the slope alpha falls into the pulling speed increasing area, increasing the pulling speed in time; if the slope alpha falls in the pulling speed maintaining area, the pulling speed is not adjusted; and if the slope falls in the pull-down speed area, the pull-down speed is timely reduced.

Wherein, the distance C-A between the position A and the position C in the step (2) is preferably 5-10 mm.

In the step (1), the process of drawing a curve chart of the theoretical weight along with the change of the length is as follows:

1) theoretically calculating the ending weight W1 ═ 1/3 ═ π ═ R1 of the single crystal in h length²+R1*r1+r1²) H rho, wherein R1 and R1 are the upper and lower diameters of the ending part in the ending length section respectively, h is the ending length, and rho is the density of the monocrystalline silicon;

2) theoretically calculating the final weight W2 ═ 1/3 ═ π · (R2) in the next h segment²+R2*r2+r2²) H ρ; wherein R2 and R2 are the upper and lower diameters of the ending part in the ending length segment, h is the ending length, and rho is the density of the monocrystalline silicon;

3) theoretically calculating the weight change delta W in two h sections as W2-W1;

4) calculating the slope l of the weight of two h sections changing along with the length as delta W/h; calculating the slope of the change of the weight along with the length in different length sections by analogy;

5) and drawing a theoretical weight change curve graph along with the length according to the obtained weight change slopes along with the length in the two sections with different ending angles and different lengths.

Preferably, in the step (3), the temperature compensation is changed simultaneously during the adjustment of the pulling speed to assist the adjustment.

Preferably, the ending slope is kept oscillating around the curve of theoretical weight change with length during ending to ensure the beauty of the single crystal tail.

The invention has the beneficial effects that:

the invention provides a theoretical reference for adjusting the tail pulling speed by providing a slope diagram of the change of the theoretical weight along with the length, and solves the problem that the tail folding and unfolding state of the large-diameter single crystal cannot be observed by naked eyes.

The invention can basically realize fixed-angle ending by controlling the fluctuation of the change slope of the weight along with the length around the change slope of the theoretical weight along with the length, so that the ending angle fluctuates between 63-69 degrees, and the attractiveness of the ending shape is ensured.

Drawings

FIG. 1 is a flow chart of the method of the present invention.

FIG. 2 is a graph of the slope of theoretical weight as a function of length for example 1, wherein the locations of the pull-up region, pull-up maintenance region, and pull-down region are identified.

FIG. 3 is a graph showing the distribution of the actual ending weight as a function of length in a graph showing the slope of the theoretical weight as a function of length in example 1.

FIG. 4 is a full view of the shape of the tail of the single crystal in example 1.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples. The examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention.

The method of the invention is implemented as follows:

a: the ending length of the same heat is estimated according to 1-1.3 times of the diameter of the produced single crystal, and two angles of ending are calculated to be 63 degrees and 69 degrees by combining the pythagorean theorem. And respectively calculating the change slope of the weight along with the length in each length section according to the two angles.

b: theoretically calculating the ending weight W1 ═ 1/3 ═ π ═ R1 of the single crystal in h length²+R1*r1+r1²) H rho, wherein R1 and R1 are the upper and lower diameters of the ending part in the ending length section respectively, h is the ending length, and rho isThe density of the monocrystalline silicon;

c: theoretically calculating the final weight W2 ═ 1/3 ═ π · (R2) in the next h segment²+R2*r2+r2²) H ρ; wherein R2 and R2 are the upper and lower diameters of the ending part in the ending length segment, h is the ending length, and rho is the density of the monocrystalline silicon;

d: theoretically calculating the weight change delta W in two h sections as W2-W1;

e: calculating the slope l of the weight of two h sections changing along with the length as delta W/h; calculating the slope of the change of the weight along with the length in different length sections by analogy;

f: drawing a theoretical weight change curve graph along with the length according to the obtained weight change slopes along with the length in the two sections with different ending angles;

g: acquiring any position A and weight B of the ending part through a single crystal furnace client;

h: obtaining a position C and a weight D below a position A of the ending part through a client of the single crystal furnace;

i: the distance delta d between the position A and the position C of the ending part is made as small as possible, namely the value of C-A is made as small as possible;

j: calculating the change slope alpha of the weight from the position A to the position C along the length as (D-B)/(C-A);

k: dividing the theoretical weight change curve graph with the length into a pulling speed increasing area according to the fact that the actual ending weight slope falls in different areas of the theoretical weight change curve graph with the length, wherein the area is considered to be in an ending release state, and if the slope falls in the range, the pulling speed is required to be increased in time; a pull-up speed maintaining area, which is considered as a normal ending, no ending and no releasing state, and if the slope falls in the range, the pull-up speed can not be adjusted; and reducing the pulling speed in a pulling speed reducing area, wherein the area is considered to be in a state that the tail is in a receiving state, and if the slope falls within the range, the pulling speed is reduced in time.

l: with the increase of the tail length of the single crystal, the pulling speed is timely adjusted according to the steps a-k, and the temperature compensation can be changed to assist adjustment in the process of adjusting the pulling speed;

m: in the ending process, the ending slope is kept to oscillate near a curve of the theoretical weight changing along with the length as much as possible so as to ensure the attractiveness of the tail of the single crystal.

Example 1

The experimental ending is carried out on a silicon single crystal with the diameter of 208mm by using the method of the invention. First, a graph of the change slope of the theoretical weight with the length is obtained through theoretical calculation, as shown in fig. 2.

The initial tail weight B was recorded as 0.784012kg at 10mm position A as per step g.

Δ d was taken to be 10 mm.

And d, according to the step h, setting the position C at the position with the length of 10mm below the ending position A. Position C was 10mm and the tail weight D at this time was recorded as 0.815994 kg.

According to step j, α ═ D-B)/(C-a). The slope a of the change in the weight of the AC segment tail with length was found to be 0.031982.

The theoretical calculation results in weight change slopes of-0.06898 and-0.05682 at 63 ° and 69 ° at 20mm, respectively. 0.031982 was brought into a graph of the slope of theoretical weight as a function of length and was found to fall within the pull rate region of the lift, so the pull rate was increased incrementally at fixed increments of 3mm/hr and the temperature was supplemented by 2 sp/hr.

Repeat step g-1, i.e. position E at 10mm length at the trailing portion position C, position E being 30mm, and record the weight F of the tail at this point as 0.651001 kg. The slope beta of the change of the tail weight of the CE section along with the length is-0.164993.

The theoretical calculation results in weight change slopes of-0.07032 and-0.05463 at 63 ° and 69 ° at 30mm, respectively. By bringing-0.164993 into a graph of the slope of theoretical weight as a function of length, it was found that the slope falls within the region of decreasing pull rate, so that the pull rate was gradually decreased at fixed increments of 2mm/hr, and the temperature was decreased by 2 sD/hr.

Repeating the step g-1 along with the increase of the length of the ending, wherein the shape of the ending is continuously close to 63-69 degrees along with the continuous adjustment of the pulling speed.

In order to verify the reliability of the invention, the change slope of each section of weight along with the length after adjustment in the ending process is recorded, the distribution condition of the actual ending weight along with the length in a graph of the change slope of the theoretical weight along with the length is drawn, and Origin is used for fitting into a line, as shown in fig. 3. And the change of the slope of the crystal of each section and the folding and unfolding trend are judged by analyzing the fluctuation of the curve.

And after the experimental single crystal growth is finished, taking out the experimental single crystal after the furnace is stopped and cooled. The tail retraction variation trend (as shown in fig. 4) is visually observed and compared with the retraction trend judged by the slope curve of the weight variation along with the length in fig. 3. The curve is found to judge that the retraction and extension trend of the tail of the single crystal is well consistent with the actual retraction and extension trend of the growth of the single crystal. The method can accurately judge the tail-in and tail-out trend, can make timely adjustment, and ensures the completeness of the tail-in and the perfect shape of the tail-in. The method is stable, reliable, timely and effective.