CN118007229A

CN118007229A - Crystal pulling method for heavily doped single crystal seeding and shoulder removal

Info

Publication number: CN118007229A
Application number: CN202410347030.3A
Authority: CN
Inventors: 魏兴彤; 芮阳; 白园; 王黎光; 曹启刚; 伊冉; 王忠保; 马成; 赵延祥
Original assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Current assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Priority date: 2024-03-26
Filing date: 2024-03-26
Publication date: 2024-05-10
Anticipated expiration: 2044-03-26
Also published as: CN118007229B

Abstract

The invention provides a crystal pulling method of heavily doped single crystal seeding and shouldering, which belongs to the technical field of single crystal growth by a single crystal furnace pulling method, wherein during seeding, seeding is performed according to a first preset seeding diameter, a first preset seeding temperature curve and a first preset pulling speed curve, so that the seeding diameter, the pulling speed and the temperature are mutually matched, the seeding quantity is improved, the seeding times are reduced, and after seeding is finished, the shouldering diameter D is obtained according to angle setting values of shoulder-to-shoulder included angles of preset different shoulder-to-shoulder heights; and shouldering is carried out according to the shouldering diameter D, a second preset shouldering power curve, a second preset pull speed upper limit curve and a second preset pull speed curve lower limit curve so as to draw shoulder types with different shouldering shoulder type included angles at different stages, so that the temperature difference caused by seeding is eliminated, the shouldering process grows in a preset growth state, the monocrystal structure is not damaged, and the NG rate is obviously reduced in the seeding and shouldering processes.

Description

Crystal pulling method for heavily doped single crystal seeding shoulder

Technical Field

The invention relates to the technical field of growing single crystals by a single crystal furnace pulling method, in particular to a method for pulling a heavily doped single crystal by seeding and shouldering.

Background

Because the doping concentration of the N-type heavily doped single crystal is high, when the impurity concentration is higher or the furnace internal pressure and argon gas are higher, the single crystal structure is easily damaged (the single crystal structure is damaged and replaced by NG), the damaged single crystal cannot be used as a product, the back melting and re-pulling must be carried out, each back melting action is called one-time pull, the time for pulling is longer and longer due to repeated back melting and re-pulling, oxide accumulation in the furnace is more and more serious, and the probability of survival of the grown crystal is also smaller and smaller.

The NG location is generally around: 1: seeding; 2: shoulder placement; 3: an equal diameter earlier stage; 4: the reasons of NG at each position in the middle and later stages of the equal diameter are different, wherein the first three NG reasons are influenced for the first time, the seeding difference can influence the seeding, the shouldering and the earlier stages of the equal diameter, and the shouldering difference can influence the shouldering and the earlier stages of the equal diameter, so that how to reduce the seeding times under high doping concentration becomes a difficulty which must be overcome.

Disclosure of Invention

In view of this, the present invention provides a method for pulling a heavily doped monocrystalline seed shoulder to reduce the number of seed steps.

The technical scheme adopted for solving the technical problems is as follows:

A crystal pulling method for heavily doped single crystal seeding shoulder comprises the following steps

S1: seeding according to the first preset seeding diameter, the first preset seeding temperature curve and the first preset pulling rate curve so as to improve the seeding quality;

S2: obtaining a shoulder diameter D according to preset angle setting values of shoulder included angles of different shoulder heights;

S3: shoulder putting is carried out according to the shoulder putting diameter D, a second preset shoulder putting power curve, a second preset pull speed upper limit curve and a second preset pull speed curve lower limit curve, so that the number of times of leading and putting is reduced;

S4: and (5) carrying out shoulder turning, constant diameter and ending drawing after the shoulder placement is finished to obtain the shoulder placement type symmetrical stepped crystal bar.

Preferably, in the step S1: after the first preset distance is reserved from seeding, the diameter of the first preset seeding is 5-7 mm;

the first preset seeding temperature curve continuously descends after seeding for a second preset distance, and the difference value between the temperature value of the second preset distance and the temperature value after seeding is positioned in a first preset range;

The first predetermined pull rate curve fluctuation is located within the second predetermined range by at least a third predetermined distance that directs a continuous length before the end of the crystallization.

Preferably, the first predetermined distance is 90 mm-100 mm, the second predetermined distance is 48 mm-52 mm, the first predetermined pulling speed range is-4 ℃ to-6 ℃, the second predetermined range is 2 mm/min-6 mm/min, and the third predetermined distance is 148 mm-150 mm

Preferably, in the step S1, the method further includes an upper limit and a lower limit of the first predetermined seeding diameter, where the upper limit and the lower limit of the first predetermined seeding diameter are ±0.5mm of the first predetermined seeding diameter.

Preferably, in the step S2, the shoulder diameter D is obtained by the following formula:

D=2Htan（α/2）

Wherein: d is a shoulder diameter set value, H is a shoulder height, and alpha is an angle set value of a shoulder included angle.

Preferably, in the step S3, the preset angle setting values of the shoulder-to-shoulder included angles with different shoulder-to-shoulder heights are specifically:

Dividing the shouldering process into an initial stage, a growing stage and an ending stage according to the shouldering height, wherein the angle set value of the shouldering type included angle of the initial stage is a first angle value, the angle set value of the shouldering type included angle of the growing stage is a second angle value, and the angle set value of the shouldering type included angle of the ending stage is a third angle value; the first angle value, the second angle value and the third angle value are sequentially increased.

Preferably, the shoulder height of the initial stage is 0mm to 80mm, the shoulder height of the growth stage is 85mm to 210mm, and the shoulder height of the final stage is 215mm to 280mm.

Preferably, the first angle value is 35-40 degrees, the second angle value is 40-45 degrees, and the third angle value is 45-55 degrees.

Preferably, in the step S3, the second predetermined pull speed upper limit curve and the second predetermined pull speed lower limit curve are ±0.3mm/min of the second predetermined pull speed curve.

Preferably, in the step S3, the second predetermined shoulder power curve continuously decreases from 0 to-12 kw with the shoulder height.

Compared with the prior art, the invention has the beneficial effects that:

According to the invention, when seeding, seeding is performed according to a first preset seeding diameter, a first preset seeding temperature curve and a first preset pulling speed curve, so that the seeding diameter, pulling speed and temperature are mutually matched, the seeding quality is improved, the seeding times are reduced, and after seeding is finished, the shoulder diameter D is obtained according to preset angle setting values of shoulder included angles of different shoulder heights; and shouldering is carried out according to the shouldering diameter D, a second preset shouldering power curve, a second preset pull speed upper limit curve and a second preset pull speed curve lower limit curve so as to draw shoulder types with different shouldering shoulder type included angles at different stages, so that the temperature difference caused by seeding is eliminated, the shouldering process grows in a preset growth state, the monocrystal structure is not damaged, and the NG rate is obviously reduced in the seeding and shouldering processes.

Drawings

Fig. 1 is a drawing showing the seeding diameters of the first and third embodiments.

Fig. 2 is a first predetermined pull rate graph of the first and third embodiments.

Fig. 3 is a first predetermined seeding temperature curve of the first and third embodiments.

Fig. 4 is a graph showing the results of the seeding quality of the first embodiment.

Fig. 5 is a graph showing a second predetermined pull rate curve, a second predetermined pull rate upper limit curve, and a second predetermined pull rate lower limit curve according to the second and third embodiments.

Fig. 6 is a second predetermined shouldered power plot.

Fig. 7 is a shoulder-shoulder view of the second and third embodiments.

Fig. 8 is a graph showing the results of the seeding quality of the third example.

Fig. 9 is a shoulder-to-shoulder diagram of the comparative example.

Figure 10 is a graph comparing the average number of shoulder positions for example two with comparative example one.

Wherein: the abscissa of FIGS. 1 to 3 is seeding length/mm, the ordinate of FIG. 1 is seeding diameter/mm, the ordinate of FIG. 2 is seeding pull rate/mm/min, and the ordinate of FIG. 3 is temperature/. Degree.C.

Detailed Description

The technical scheme and technical effects of the present invention are further elaborated below in conjunction with the drawings of the present invention.

Compared with the prior art, the invention has the beneficial effects that:

Further, in the step S1: after the first preset distance is reserved from seeding, the diameter of the first preset seeding is 5-7 mm;

The fluctuation of the first preset pulling speed curve is at least a third preset distance within the second preset range, the third preset distance guides the continuous length before the crystallization is finished, and the crystallization quantity is improved by determining the first preset crystallization diameter, adjusting the first preset crystallization temperature curve and the first preset pulling speed curve to enable the crystallization diameter, the crystallization pulling speed and the crystallization temperature to be matched with each other; and by controlling the fluctuation amplitude of the first preset pull rate curve and matching the cooling amplitude of the first preset temperature curve, the method can prevent the pull rate from suddenly changing and from being mismatched with the shouldering process when the temperature change difference is large, so that the shouldering process is caused to carry out middle-stage and early-stage NG.

Further, the first preset distance is 90 mm-100 mm, the second preset distance is 48 mm-52 mm, the first preset pulling speed range is-4 ℃ to-6 ℃, the second preset range is 2 mm/min-6 ℃ mm/min, and the third preset distance is 148 mm-150 mm

Further, in the step S1, the method further includes an upper limit and a lower limit of the first predetermined seeding diameter, where the upper limit and the lower limit of the first predetermined seeding diameter are ±0.5mm of the first predetermined seeding diameter.

Further, in the step S2, the shoulder diameter D is obtained by the following formula:

D=2Htan（α/2）

Further, in the step S3, the preset angle setting values of the shoulder-to-shoulder included angles with different shoulder-to-shoulder heights are specifically:

Further, the pull rate of the initial stage is greater than the pull rate of the growth stage, and the pull rate of the growth stage is greater than the pull rate of the end stage; the shouldering process is divided into three stages, crystal rod diameters corresponding to the three stages are obtained according to angle set values of shouldering shoulder included angles of the three stages, and shouldering is carried out according to the crystal rod diameters corresponding to the three stages, a second preset shouldering power curve, a second preset pull speed upper limit curve and a second preset pull speed curve lower limit curve; in the initial stage, the seeding enters the shoulder placement stage from the seeding, the difference caused by the seeding temperature difference exists, the longitudinal growth is mainly used in the initial stage, the shoulder type included angle is small, the growth pulling speed is high, the next stage is entered after the influence caused by the seeding temperature difference is eliminated through the growth of a certain shoulder placement height, the shoulder type included angle is reduced compared with the initial stage when the next stage is entered, the pulling speed is reduced compared with the initial stage, the smaller shoulder placement angle is more beneficial to the growth of the heavily doped shoulder placement, and the stability is higher; finally, when the ending stage is carried out, as the liquid mouth distance is insufficient, molten soup is more, the longitudinal temperature gradient is increased, the cooling rate is increased, so that the diameter of the stage grows fast and mainly grows transversely, the shoulder turning is carried out after the ending of the stage, the pulling speed of the shoulder turning is not required to be too high, and a larger shoulder angle and a lower shoulder pulling speed are set at the ending stage to match the shoulder pulling characteristics of the stage, so that the stability is improved, and the NG rate of the whole shoulder pulling process is reduced.

Further, the shoulder height of the initial stage is 0mm to 80mm, the shoulder height of the growth stage is 85mm to 210mm, and the shoulder height of the final stage is 215mm to 280mm.

Further, the first angle value is 35-40 degrees, the second angle value is 40-45 degrees, and the third angle value is 45-55 degrees.

Further, in the step S3, the second predetermined pull speed upper limit curve and the second predetermined pull speed lower limit curve are ±0.3mm/min of the second predetermined pull speed curve.

Further, in the step S3, the second predetermined shoulder power curve continuously decreases from 0 to-12 kw with the shoulder height.

Specifically, the content of the present invention is illustrated by the following examples and comparative examples.

The following examples and comparative examples were conducted with single crystals having a resistivity of not more than 0.002. Omega. Cm, a doping ratio of > 8 times the charge amount, and a furnace pressure of > 33 Kpa.

Embodiment one:

Through PID control, in a system (FT-CZ 2408S2-3212 SE-PCE-Ver4.209), a first preset seeding is 5mm, after seeding is started by 100mm, the diameter fluctuation range is 4.5 mm-5.5 mm, as shown in figure 1, and according to a first preset pulling rate curve as shown in figure 2, the pulling rate fluctuation range is 3 mm/min-5 mm/min, as shown in figure 3, the seeding is performed according to a first preset seeding temperature curve.

The experiment was performed according to the protocol of example one for 2 months, with the NG rate reduced to 9.1%, as shown in fig. 4.

Embodiment two:

In the system (FT-CZ 2408S2-3212 SE-PCE-Ver4.209), by PID control, among parameters, the system is divided into three stages according to the shouldering height, the corresponding shouldering height of each stage is provided with different angle setting values of the shouldering shoulder included angles, as shown in table 1, and shouldering is performed according to a second preset pull rate curve, a second preset pull rate upper limit curve, a second preset pull rate curve and a second preset shouldering power curve as shown in fig. 6, which are shown in fig. 5. Shoulder-on-shoulder is shown in fig. 7.

TABLE 1

The experiment was performed according to the protocol of example two for 1 month, and the NG rate was reduced to 21.4%, as shown in fig. 10.

Embodiment III:

In a system (FT-CZ 2408S2-3212 SE-PCE-Ver4.209), carrying out seeding in a first preset seeding temperature curve shown in figure 3 according to a first preset pulling speed curve shown in figure 2, wherein the first preset seeding temperature curve is 5mm, and the diameter fluctuation range is 4.5 mm-5.5 mm, as shown in figure 1; the method is divided into three stages according to the shouldering heights, the corresponding shouldering heights of each stage are provided with different angle setting values of shouldering shoulder included angles, as shown in table 1, the shouldering is performed according to a second preset pull speed curve, a second preset pull speed upper limit curve, a second preset pull speed curve and a second preset shouldering power curve shown in fig. 6, which are shown in fig. 7.

The experiment was performed according to the protocol of example three for 2 months, with the NG rate reduced to 16.7%, as shown in fig. 8.

Comparative example one

The shouldering is performed using a scheme such as that in example one of the embodiments of the shouldering method for increasing the survival rate of <100> single crystals disclosed in the grant publication No. CN114717648B, and the shouldering type is as shown in FIG. 9, and the parameters not mentioned are the same as those in the examples.

The experiment was performed according to the protocol of comparative example one, with a period of one month, and the number of shoulder placements obtained is shown in fig. 10.

It can be seen from the first, second and third embodiments that the invention can greatly reduce the NG rate in the seeding stage and the shoulder stage by setting the diameter, controlling the pulling speed and the temperature under the conditions of high doping ratio and high furnace pressure,

And as can be seen from fig. 10, for the conditions of high doping proportion and high furnace pressure, the proportion of the single shouldering NG of the invention is obviously reduced compared with that of the comparative example, so that the invention has wide application range and is more beneficial to large-size crystallization.

The foregoing disclosure is illustrative of the preferred embodiments of the present invention, and is not to be construed as limiting the scope of the invention, as it is understood by those skilled in the art that all or part of the above-described embodiments may be practiced with equivalents thereof, which fall within the scope of the invention as defined by the appended claims.

Claims

1. A method for pulling a heavily doped single crystal by seeding and shouldering, characterized in that it comprises the following steps:

S1: seeding according to a first predetermined seeding diameter, a first predetermined seeding temperature curve, and a first predetermined pulling speed curve to improve seeding quality;

S2: The shoulder diameter D is obtained according to the preset shoulder angle setting values of different shoulder heights;

S3: shoulder release is performed according to the shoulder release diameter D, the second predetermined shoulder release power curve, the second predetermined pulling speed curve, the second predetermined pulling speed upper limit curve, and the second predetermined pulling speed lower limit curve, thereby reducing the number of lead-in releases;

S4: After the shoulder is released, the shoulder is turned, the diameter is equalized, and the tail is pulled to obtain a crystal rod with a symmetrical stepped shoulder shape.

2. The method for pulling a heavily doped single crystal seeded crystal with shoulder release according to claim 1, characterized in that in the step S1: after a first predetermined distance from seeding, the first predetermined seeding diameter is 5-7 mm;

The first predetermined seeding temperature curve continues to decrease after the seeding second predetermined distance, and the difference between the temperature value of the second predetermined distance and the temperature value at the end of seeding is within the first predetermined range;

The fluctuation of the first predetermined pulling speed curve is located within the second predetermined range by at least a third predetermined distance, and the third predetermined distance refers to a continuous length before the end of wafer cutting.

3. The crystal pulling method for heavily doped single crystal seeding and shoulder release as described in claim 2 is characterized in that the first predetermined distance is 90mm~100mm, the second predetermined distance is 48mm~52mm, the first predetermined pulling speed range is -4℃~-6℃, the second predetermined range is 2mm/min~6mm/min, and the third predetermined distance is 148mm~150mm.

4. The crystal pulling method for shouldering of heavily doped single crystal seeding as claimed in claim 1 is characterized in that, in the step S1, it also includes the upper and lower limits of the first predetermined seeding diameter, and the upper and lower limits of the first predetermined seeding diameter are ±0.5 mm of the first predetermined seeding diameter.

5. The method for pulling a heavily doped single crystal seeded crystal with shoulder release according to claim 1, characterized in that in the step S2, the shoulder release diameter D is obtained by the following formula:

D = 2Htan (α/2)

Where: D is the setting value of the shoulder diameter, H is the shoulder height, and α is the setting value of the shoulder angle.

6. The method for pulling a heavily doped single crystal seeded crystal with shouldering according to claim 1, characterized in that in the step S3, the angle setting values of the shoulder angles of the preset shouldering heights are specifically:

The shoulder release process is divided into a starting stage, a growth stage, and an ending stage according to the shoulder release height. The angle setting value of the shoulder release angle in the starting stage is a first angle value, the angle setting value of the shoulder release angle in the growth stage is a second angle value, and the angle setting value of the shoulder release angle in the ending stage is a third angle value; the first angle value, the second angle value, and the third angle value increase sequentially.

7. The crystal pulling method for heavily doped single crystal seeding and shouldering as described in claim 6 is characterized in that the shoulder height in the initial stage is 0 mm to 80 mm, the shoulder height in the growth stage is 85 mm to 210 mm, and the shoulder height in the ending stage is 215 mm to 280 mm.

8. The crystal pulling method for heavily doped single crystal seeding and shoulder release as described in claim 6 is characterized in that the first angle value is 35°~40°, the second angle value is 40°~45°, and the third angle value is 45°~55°.

9. The crystal pulling method for heavily doped single crystal seeding and shouldering according to claim 1, characterized in that, in the step S3, the second predetermined upper limit curve of pulling speed and the second predetermined lower limit curve of pulling speed are ±0.3 mm/min of the second predetermined pulling speed curve.

10. The crystal pulling method for heavily doped single crystal seeding and shouldering according to claim 1, characterized in that in the step S3, the second predetermined shouldering power curve continuously decreases as the shouldering height decreases from 0 to -12kw.