CN114717648A

CN114717648A - Shoulder-laying method for improving survival rate of <100> single crystal

Info

Publication number: CN114717648A
Application number: CN202210403758.4A
Authority: CN
Inventors: 闫龙; 周文辉; 王忠保
Original assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Current assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Priority date: 2022-04-18
Filing date: 2022-04-18
Publication date: 2022-07-08
Anticipated expiration: 2042-04-18
Also published as: CN114717648B

Abstract

The invention provides a shouldering method for improving the survival rate of a <100> single crystal, which belongs to the technical field of single crystal growing by a single crystal furnace pulling method, wherein a crystal bar is drawn according to a preset drawing speed curve to obtain a target inch crystal bar with a shouldered shoulder shape of an isosceles triangle.

Description

Shoulder-laying method for improving survival rate of <100> single crystal

Technical Field

The invention relates to the technical field of single crystal growing by a single crystal pulling method in a single crystal furnace, in particular to a shouldering method for improving the survival rate of a single crystal by less than 100.

Background

Single crystal production is a process of melting a silicon material and then converting polycrystal into dislocation-free single crystal by pulling, but when dislocation is generated for some reason in the process of converting polycrystal into single crystal, the crystal loses single crystal property and is converted into polycrystal, and then crystal growth fails (referred to as NG).

In the prior art, when a single crystal with a crystal orientation of less than 100 is prepared, generally in a shouldering method with the crystal orientation of less than 100, four raised ridge bands formed by facet can be seen on the shoulder part, so that the NG rate of shouldering the single crystal with the crystal orientation of less than 100 is high, and particularly the pulling performance of heavily doped single crystal with extremely low resistivity is obvious.

Disclosure of Invention

In view of this, the invention provides a shouldering method for improving the survival rate of a single crystal to be less than 100, so as to solve the technical problem that the shouldering NG rate is caused by four ridge belts formed by facet generated by the shouldering method in the crystal direction to be less than 100 in the prior art.

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

a shouldering method for increasing the survival rate of single crystal to be less than 100 degrees is characterized by drawing a crystal rod according to a preset drawing speed curve to obtain a target inch crystal rod with an isosceles triangle shouldering shape.

Preferably, the predetermined pull rate curve is obtained by the following steps:

the method comprises the following steps: obtaining a shouldering height H according to the diameter D of the target inch of single crystal and the shouldering included angle alpha;

step two: shouldering according to the diameter D and the shouldering height H of the target inch of single crystal, and adjusting the shouldering shape to enable the shouldering shape to be an isosceles triangle, so that the corrected shouldering height H' is obtained;

step three: and (4) shouldering according to the diameter D of the target inch single crystal and the corrected shouldering height H' to obtain a preset pulling speed curve.

Preferably, the third step further comprises the following steps:

s1: shouldering according to the diameter D of the target inch single crystal and the corrected shouldering height H' to obtain an upper limit curve of a preset pulling speed and a lower limit curve of the preset pulling speed;

s2: and fitting to obtain a preset pulling speed curve according to the upper limit curve of the preset pulling speed and the lower limit curve of the preset pulling speed.

Preferably, in the first step, the included angle α between the shoulder-placing shapes is less than or equal to 72.32 °.

Preferably, in the second step, doping is not performed during seeding before shouldering.

Preferably, in the third step, the doping is normally carried out during seeding before shouldering.

Preferably, the step two: the shouldering height H is obtained by the following formula:

H＝D/2tan(α/2)。

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

according to the invention, the crystal bar is drawn through the preset drawing speed curve, so that the shouldered shoulder shapes are unified, and the isosceles triangle shoulder shapes can avoid the probability of four ridge belts appearing in the shoulder shapes in the shouldering process, thereby reducing the NG rate of shouldering.

Drawings

FIG. 1 is a graph illustrating the upper limit of a target pull rate and the lower limit of the target pull rate, according to one embodiment.

FIG. 2 is a graph of a target pull rate for one embodiment.

Figure 3 is a shouldering type drawing of the embodiment.

FIG. 4 is a shoulder-on view of a comparative example.

Fig. 5 graph comparing the average DIP of example one and comparative example one.

Detailed Description

The technical scheme and the technical effect of the invention are further elaborated in the following by combining the drawings of the invention.

A shouldering method for increasing the survival rate of single crystal to be less than 100 is characterized by drawing a crystal bar according to a preset drawing speed curve to obtain a target inch crystal bar with an isosceles triangle shouldered shape.

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

Further, the preset pulling speed curve is obtained through the following steps:

step two: shouldering according to the diameter D and the shouldering height H of the target inch single crystal, and adjusting the shouldering shape to enable the shouldering shape to be an isosceles triangle, so as to obtain an experimental pull speed curve and obtain a corrected shouldering height H'; in the shouldering process, according to the diameter D of the target inch single crystal, a preset shouldering diameter variation value D ' in the shouldering process enables the final D ' to be equal to D, then the shouldering height H corresponding to the shoulder diameter variation value D ' is obtained, the final H is equal to H, if the shouldering height is not corrected, an isosceles triangle shoulder shape cannot be obtained in the shouldering process only through theoretical calculation, and further the generation of ridge ridges cannot be avoided;

Specifically, the diameter pulling speed and temperature of each stage are set by adopting ADC1 (pulling speed control diameter) control according to the change value D' of the shouldering diameter and the shouldering height h, the camera reads the shouldering diameter and feeds back the shouldering diameter to the system, the system compares the difference between the diameter measured by the camera and the set diameter, and the diameter is adjusted by automatically adjusting the pulling speed so as to obtain an experiment pulling speed curve.

Specifically, the shouldering height is uniformly changed along with the shouldering diameter by fixing the shouldering included angle alpha, so that an experimental pull rate curve and a corrected shouldering height H 'are obtained, shouldering is performed according to the diameter D of the target inch single crystal and the corrected shouldering height H' to obtain a preset pull rate curve, shouldering is performed through the preset pull rate curve, so that shouldering shapes are unified, a raised ridge is formed due to the intersection of a {111} plane and the peripheral surface of the crystal, the directions < 110 > on the {111} plane are atomic closest stacking and are planes with the most easy slippage of dislocation, NG is easily generated, and the corrected shouldering height H is uniformly changed along with the shouldering diameter by fixing the shouldering included angle alpha, so that the occurrence of the {111} plane is avoided, the probability of 4 raised ridges in the shouldering shape is reduced, and the NG rate of the shouldering is reduced.

Further, the third step further includes the following steps:

Specifically, when the shoulder is put on the shoulder according to the change value D 'of the shoulder-putting diameter and the corrected shoulder-putting height H', the camera reads the shoulder-putting diameter and feeds back the shoulder-putting diameter to the system, the system compares the difference between the measured diameter and the set diameter of the camera, the pulling speed is automatically adjusted to adjust the diameter, the pulling speed slightly fluctuates, an upper limit curve of the preset pulling speed and a lower limit curve of the preset pulling speed are obtained through multiple experiments, and then fitting is carried out, so that the diameter in the shoulder-putting process is the same as the preset diameter, and the pulling speed curve does not fluctuate any more. If the shouldering height is not controlled by the diameter, the shouldering shape is square or flat when the predetermined pulling rate curve is obtained by controlling the pulling rate only, so that the NG rate cannot be controlled.

Further, in the first step, the included angle α of the shoulder-placing type is less than or equal to 72.32 °.

Furthermore, in the second step, doping is not carried out during seeding before shouldering, so that polycrystal is changed into single crystal better, and the probability of generating NG is reduced.

Further, in the third step, the doping is normally carried out during seeding before shouldering.

Further, the second step: the shouldering height H is obtained by the following formula:

H＝D/2tan(α/2)。

specifically, alpha/2 is less than 100 and is larger than the included angle between the crystal orientation growth direction and the shouldering-shaped bus, and the diameter of the crystal bar is controlled to control shouldering by controlling the included angle less than 100 and is larger than the included angle between the crystal orientation growth direction and the shouldering-shaped bus, so that shouldering shapes are unified and the NG rate is low.

After the preset pulling rate curve of the target-inch crystal bar is obtained by the method, when the target-inch crystal bar is produced in the future under the same condition, the preset pulling rate curve of the target-inch crystal bar is directly used for crystal bar drawing, the shoulder shapes of the obtained crystal bars are consistent, and the NG rate is low.

In the prior art, the diameter cannot be set in the shouldering process, the shoulder shape is usually a flat shoulder through the pulling speed adjustment, the method is suitable for simple products with the resistivity of more than 0.003 and the arsenic doping concentration of 750g, but when the products with the resistivity of less than 0.002 and the arsenic doping concentration of 900g-1000g are pulled, the NG rate is high by adopting the method in the prior art, the crystal bar cannot be pulled out within 100h, because when the doping concentration is high, various conditions such as undercooling of components and the like are easy to occur in the products, so that the single crystal is changed into polycrystal, the yield is influenced, and under a long time, the temperature in a furnace is high above 1400 ℃, silicon leakage is easy to occur, so that a thermal field is scrapped, and more serious explosion is possible.

The shoulder-laying method overcomes the technical bias that the shoulder shape of the shoulder-laying is an isosceles triangle steep shoulder, although the shoulder shape is higher than that of the shoulder shape in the prior art and the raw materials of the shoulder shape are wasted, the NG rate of the shoulder-laying is low for products with extremely low resistivity and high doping concentration, so that the waste of the raw materials is reduced, and huge economic benefits are brought.

Specifically, the contents of the present invention are illustrated by the following examples and comparative examples.

The following examples and comparative examples are exemplified by pulling 8-inch single crystals.

The first embodiment is as follows:

in the system (FT-CZ2408S2-3212SE-PCE-Ver4.209), ADC1 is modified to control shouldering; in ADC1, a diameter gradient of an 8-inch single crystal is set according to H ═ D/2tan α (α/2), D ' is 0 to 210mm in diameter and corresponding shouldering height gradient, H is 0 to 240mm, then shouldering is performed to obtain the corrected shouldering height H ' in ADC2, shouldering is performed a plurality of times according to the diameter D of the target-inch single crystal and the corrected shouldering height H ', the setting is performed in system ADCLMT to obtain an upper limit curve of a predetermined pulling rate and a lower limit curve of the predetermined pulling rate as shown in fig. 1, and the predetermined pulling rate curve as shown in fig. 2 is fitted according to the upper limit curve of the predetermined pulling rate and the lower limit curve of the predetermined pulling rate. Set up in ADC2 according to a predetermined pull rate curve and then shoulder-down, the shoulder-down version is shown in fig. 3, and the data set-up is shown in table 1.

Among them, the raised ridge zone is most likely to occur at the position marked in fig. 1, because it is that the {111} plane is likely to have a slip line and NG is likely to occur, and the isosceles triangle can grow away from the {111} plane, so that the ridge zone does not occur and the occurrence probability of NG is reduced.

TABLE 1

Note: ADC1 INI-ABS mm is shoulder height H, ADC1 INI-ABS mm is diameter D 'of target inch single crystal, ADC2 INI-ABS mm is corrected shoulder height H', ADC2 INI-ABS mm/min is pulling speed corresponding to diameter, ADCLMT ACT-ABS mm/min is upper limit value of pulling speed corresponding to diameter, ADCLMT ACT-ABS mm/min is lower limit value of pulling speed corresponding to diameter, TEMP INI-ABS min is time corresponding to temperature, TEMP INI-ABS deg is temperature.

The above examples were performed on different benches and the DIP number is shown in Table 2.

Watch 2 (steep shoulder)

Comparative example one:

in the prior art, when the shoulder is placed on the shoulder, the pulling speed and the temperature are manually adjusted according to the shoulder shape, and the shoulder shape is obtained by setting according to the data in the table 3 and is shown in fig. 4.

TABLE 3

Note: S/L INI-ABS (min) is the time corresponding to the pulling rate, S/L ACT-ABS (mm/min) is the pulling rate, TEMP INI-ABS (min) is the time corresponding to the temperature, and TEMP INI-INC (deg) is the temperature.

The shouldering was carried out on various benches in accordance with the above comparative examples, and the DIP number of the shouldering results is shown in Table 4.

Watch 4 (Flat shoulder)

Furnace platform number	LOT NO	DIP number
			N55	N5521022
	1
		N55	N5521023	2
N55	N5521024				10
		N55	N5521025	10
N56	N5621023				5
		N56	N5621024	2
N56	N5621025				3
		N56	N5621026	7
N58	N5821020				13
		N58	N5821021	5
N60	N6021020				7
		N60	N6021021	2
N60	N6021022				4
		N60	N6021023	4
N60	N6021024				3
		N63	N6321023	5
N63	N6321024				7
		N63	N6321025	3

The data in table 2 of example one and table 4 of comparative example one were averaged for DIP numbers for different furnace stations and plotted in the graph of fig. 5.

As can be seen from fig. 3, 4 and 5, compared with the comparative example i, when the shoulder is shouldered by the preset pull rate curve fitted by the invention, the shoulder shapes after shouldering are unified, no ridge belt is generated, and the shoulder is shouldered on different furnace platforms, DIP average values of different furnace platforms are all less than 3, so that the single crystal crystallization rate is improved by more than 70%, the probability of NG is greatly reduced, although the shoulder shape of the invention is higher, the NG rate of the invention is greatly reduced, and the waste of materials is avoided.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. A shouldering method for improving the survival rate of a <100> single crystal is characterized in that a crystal bar is drawn according to a preset drawing speed curve to obtain a target inch crystal bar with an isosceles triangle shouldered shape.

2. The shouldering method for improving the survival rate of a <100> single crystal according to claim 1, wherein the predetermined pull rate curve is obtained by the following steps:

3. The shoulder rest method for increasing the survival rate of a <100> single crystal according to claim 2, wherein the third step further comprises the steps of:

s2: and fitting to obtain a preset pulling rate curve according to the upper limit curve of the preset pulling rate and the lower limit curve of the preset pulling rate.

4. The shoulder-laying method for improving survival rate of <100> single crystal according to claim 2, wherein in the first step, the included angle α between shoulder-laying shapes is smaller than or equal to 72.32 °.

5. The shouldering method for improving the survival rate of the <100> single crystal according to claim 2, wherein in the second step, no doping is performed during seeding before shouldering.

6. The shouldering method for improving the survival rate of the <100> single crystal according to claim 2, wherein in the third step, the normal doping is performed during seeding before shouldering.

7. The shoulder rest method for increasing the survival rate of a <100> single crystal according to claim 1, wherein the second step: the shouldering height H is obtained by the following formula:

H=D/2tanα（α/2）。