CN113584585B

CN113584585B - Production method of heavily As-doped silicon single crystal capable of reducing head resistivity

Info

Publication number: CN113584585B
Application number: CN202110897832.8A
Authority: CN
Inventors: 张兴茂; 闫龙; 王忠保; 李小红; 伊冉
Original assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Current assignee: Ningxia Zhongxin Wafer Semiconductor Technology Co ltd
Priority date: 2021-08-05
Filing date: 2021-08-05
Publication date: 2022-09-27
Anticipated expiration: 2041-08-05
Also published as: CN113584585A

Abstract

The invention provides a method for producing heavily As-doped silicon single crystals capable of reducing the resistivity of heads, belonging to the technical field of production of doped silicon single crystals. The method comprises the following steps: in the pre-diameter-equaling process, adjusting the flow of argon gas to 120slm-130slm, and keeping the flow of the argon gas until the two-stage diameter-equaling process is finished; in addition, in the pre-equal diameter process, the furnace pressure of the single crystal furnace is adjusted to 12kPa-15 kPa; in the first-stage isometric procedure, gradually increasing the furnace pressure of the single crystal furnace to 18-20 kPa; in the second constant diameter process, the furnace pressure of the single crystal furnace is maintained at 18 kPa-20 kPa. The method for producing the heavily arsenic-doped silicon single crystal can obviously reduce the resistivity of the prepared heavily arsenic-doped silicon single crystal, particularly reduce the resistivity of the head of the heavily arsenic-doped silicon single crystal rod to be less than 0.0029 omega-cm, improve the comprehensive utilization rate of the heavily arsenic-doped silicon single crystal rod and reduce the production cost. Meanwhile, in the pulling process of the heavily arsenic-doped silicon single crystal bar, the probability of NG (tungsten nitride) caused by crystal change is obviously reduced, and the qualification rate of the heavily arsenic-doped silicon single crystal bar is further improved.

Description

Production method of heavily As-doped silicon single crystal capable of reducing head resistivity

Technical Field

The invention belongs to the technical field of doped silicon single crystal production, and particularly relates to a method for producing heavily-doped As silicon single crystal capable of reducing head resistivity.

Background

At present, the semiconductor power device has increasingly vigorous demand along with the rising of the industry in the fields of photovoltaic power generation and new energy electric automobiles, so that the resistivity characteristic of power devices such as IGBT (insulated gate bipolar translator) and the like on N-type wafers is more and more high in requirement. At present, the resistivity specification requirement of the N-type heavily doped As is generally below 0.003 omega-cm, and the extremely individual requirement is already below 0.002 omega-cm. However, the resistivity of the existing large-size (more than 8 inches) As-doped silicon single crystal is generally between 0.0035 and 0.0045 omega cm, and the requirement of low resistivity cannot be met.

In the existing production process for producing large-size heavily As-doped silicon single crystals by the Czochralski method, a gas phase doping mode is adopted for doping, and the main process comprises stabilizing, seeding, shouldering, shoulder rotating, diameter equalizing and ending, wherein before diameter equalizing, the furnace pressure of a single crystal furnace is maintained to be stable at a lower position (8kPa-10kPa), and when the diameter is equalized, the furnace pressure is gradually increased to a higher position (16kPa-18kPa) and maintained until ending. Before the constant diameter, the flow rate of argon gas is maintained at a high level (90slm to 100slm), and the flow rate of argon gas is gradually decreased until the end of the constant diameter. Taking a 2408-inch heavily As-doped silicon single crystal bar produced by a single crystal furnace SR As an example, when the silicon material inventory is 120kg, the appropriate inventory of As dopant is 900g-950g, the head resistivity of the produced heavily As-doped silicon single crystal is mostly concentrated on 0.0031-0.0035 omega.cm, and the usable part of the crystal bar is less. The resistivity of the medium-heavily doped As silicon single crystal can be reduced to a certain extent by increasing the feeding amount of the As dopant, but a large amount of As impurities which do not enter silicon melt remain in the single crystal furnace, so that the crystal is frequently changed in the crystal growth process, and the single crystal cannot be formed.

Disclosure of Invention

In view of the above, the present invention provides a method for producing a heavily As-doped silicon single crystal capable of reducing the head resistivity, so As to solve the technical problems of the prior art that the head resistivity of the heavily As-doped silicon single crystal is high and the usable part of the ingot is small.

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

a production method of heavily As-doped silicon single crystal capable of reducing resistivity of a head is used for producing 8 inches of heavily As-doped silicon single crystal by using a 2408SR single crystal furnace As a production device and adopting a Czochralski method, and comprises a pre-diameter-equaling process, a first-diameter-equaling process, a second-diameter-equaling process and a finishing process which are sequentially carried out;

in the pre-diameter-equaling process, the argon flow is adjusted to 120slm-130slm, and the argon flow is kept until the two-stage diameter-equaling process is finished; in addition, in the pre-equal diameter process, the furnace pressure of the single crystal furnace is adjusted to 12kPa-15 kPa; in the first-stage constant diameter process, gradually increasing the furnace pressure of the single crystal furnace to 17-20 kPa; in the second constant diameter process, the furnace pressure of the single crystal furnace is maintained at 17kPa-20 kPa.

Preferably, the pre-isodiametric step comprises a stabilizing step, a seeding step, a shouldering step and a shouldering step which are sequentially performed.

Preferably, in the one-stage constant diameter process, the constant diameter length is 200mm-500 mm.

Preferably, in the one-stage constant diameter process, the constant diameter length is 300 +/-10 mm.

According to the technical scheme, the invention provides the production method of the heavily As-doped silicon single crystal capable of reducing the resistivity of the head, and the production method has the beneficial effects that: the furnace pressure of the single crystal furnace in the processes of pre-isometric process, first-stage isometric process, second-stage isometric process and ending process is adjusted, the argon flow in the process is improved, the resistivity of the prepared heavily As-doped silicon single crystal is obviously reduced, particularly, the resistivity of the head of the heavily As-doped silicon single crystal rod is reduced to be less than 0.0029 omega. Meanwhile, the resistivity is reduced, and the probability of NG caused by crystal change in the drawing process of the heavily As-doped silicon single crystal rod is obviously reduced, so that the qualification rate of the heavily As-doped silicon single crystal rod is further improved, and the production cost is reduced.

Drawings

FIG. 1 is a schematic view of process adjustment of a method for producing a heavily As-doped silicon single crystal capable of reducing the head resistivity.

FIG. 2 is a graph comparing the resistivity and quality of the resulting single crystal ingots before and after process adjustments.

Detailed Description

The technical solutions and effects of the embodiments of the present invention are further described in detail below with reference to the drawings of the present invention.

Referring to FIG. 1, in one embodiment, a method for producing a heavily As-doped silicon single crystal capable of reducing the resistivity of the head portion is used for producing 8 inches of heavily As-doped silicon single crystal by using a 2408SR single crystal furnace As a production device and adopting a Czochralski method, and comprises a pre-isometric process, a first isometric process, a second isometric process and a final process which are sequentially carried out.

Specifically, the pre-isodiametric step comprises a stabilizing step, a seeding step, a shouldering step and a shouldering step which are sequentially carried out, wherein the first isodiametric step is a step of entering a section from isodiametric to isodiametric length of 200mm-500mm, and the second isodiametric step is a step of starting from the section from isodiametric length of 200mm-500mm and ending at isodiametric length. Preferably, the one-stage constant diameter step is a step of entering a zone from constant diameter to constant diameter with a length of 300 + -10 mm.

In this embodiment, in the pre-diameter-equalizing step, the flow rate of argon gas is adjusted to 120slm to 130slm, and the flow rate of argon gas is maintained until the second-stage diameter-equalizing step is completed. In addition, in the pre-equal diameter process, the furnace pressure of the single crystal furnace is adjusted to 12kPa-15 kPa; in the first-stage constant diameter process, gradually increasing the furnace pressure of the single crystal furnace to 17-20 kPa; in the second constant diameter process, the furnace pressure of the single crystal furnace is maintained at 17kPa-20 kPa.

Referring to fig. 2, the resistivity of the As-heavily doped silicon single crystal is significantly reduced by adjusting the furnace pressure of the single crystal furnace in the pre-isodiametric step, the first-stage isodiametric step, and the second-stage isodiametric step, and increasing the flow rate of argon gas in the process, especially by reducing the resistivity of the head of the As-heavily doped silicon single crystal ingot to below 0.0029 Ω. Meanwhile, the resistivity is reduced, and the probability of NG caused by crystal change in the drawing process of the heavily As-doped silicon single crystal rod is obviously reduced, so that the qualification rate of the heavily As-doped silicon single crystal rod is further improved, and the production cost is reduced.

The technical solutions and effects of the present invention are further described below by specific examples. It is worth to be noted that the following specific experimental examples all adopt a Hanhong 2408SR single crystal furnace to produce 8 inches of heavily As-doped silicon single crystal with low resistivity (the resistivity is 0.003 ohm. cm). In the experimental examples of the present invention, the process parameters which are not particularly limited are generally parameters which can be obtained by those skilled in the art.

When the adjustment is not enhanced, in the same process of the following experimental examples, 2 batches (i.e. 20 crystal rods pulled in total) are produced by using 10 hanhong 2408SR single crystal furnaces arranged in parallel as the statistical background base.

Comparative example 1

Producing the target heavily As-doped silicon single crystal by the following process flow: charging, melting, high-temperature treatment, stabilizing, doping, stabilizing, seeding, shoulder turning, shouldering, isometric and ending. Wherein, the processes of stabilizing, seeding, shoulder turning and shouldering are defined as the pre-equal diameter process, and the equal diameter process is divided into a first equal diameter process (from the beginning of equal diameter to the length of equal diameter of 300mm) and a second equal diameter process (from the length of equal diameter of 300mm to the end of equal diameter).

Argon flow parameters: in the pre-diameter-equalizing step, the argon flow is adjusted to be 100slm, in the first-stage diameter-equalizing step, the argon flow is gradually reduced until the first-stage diameter equalization is finished, the argon flow is reduced to 70slm, and the argon flow is maintained until the second-stage diameter-equalizing step is finished.

Furnace pressure parameters of the single crystal furnace: in the pre-diameter-equaling process, the furnace pressure of the single crystal furnace is kept at 8kPa, in the first diameter-equaling process, the furnace pressure is gradually increased until the first diameter-equaling process is finished, the furnace pressure is increased to 17kPa, and the furnace pressure is kept until the second diameter-equaling process is finished.

Wherein the dosage of the silicon is 120kg, and the dosage of the As dopant is 950 g. In the gas phase doping process, the seeding temperature, the seeding pot position, the seeding pressure and the argon flow during seeding are kept. Other process parameters (including furnace pressure, argon flow, temperature, crucible rotation speed, single crystal growth speed, etc.) are parameters of general significance that can be obtained by a person skilled in the art.

And (3) counting the crystal variation occurrence probability under the process, detecting the resistivity distribution of the obtained complete crystal bar, and referring to the table 1 for counting and detecting results.

Comparative example No. two

The dosage of As dopant is increased to 1000g, and other processes and parameters are the same As those of the first comparative example. And (3) counting the crystal variation occurrence probability under the process, detecting the resistivity distribution of the obtained complete crystal bar, and referring to the table 1 for counting and detecting results.

Comparative example No. three

The dosage of As dopant is reduced to 850g, and other processes and parameters are the same As those of the first comparative example. And (3) counting the crystal variation occurrence probability under the process, detecting the resistivity distribution of the obtained complete crystal bar, and referring to the table 1 for counting and detecting results.

Experimental example 1

Argon flow parameters: in the pre-diameter-equalizing step, the argon flow is adjusted to 110slm, in the first-stage diameter-equalizing step, the argon flow is gradually reduced until the first-stage diameter equalization is finished, the argon flow is reduced to 75slm, and the argon flow is maintained until the second-stage diameter-equalizing step is finished.

Furnace pressure parameters of the single crystal furnace: in the pre-diameter-equalizing step, the furnace pressure of the single crystal furnace is kept at 10kPa, in the first diameter-equalizing step, the furnace pressure is gradually increased until the first diameter-equalizing step is finished, the furnace pressure is increased to 17.5kPa, and the furnace pressure is kept until the second diameter-equalizing step is finished.

Other processes and parameters are the same as those of the first comparative example. And (3) counting the crystal variation occurrence probability under the process, detecting the resistivity distribution of the obtained complete crystal bar, and referring to the table 1 for counting and detecting results.

Experimental example two

Argon flow parameters: in the pre-diameter-equaling step, the argon flow is adjusted to 120slm, in the first-stage diameter-equaling step, the argon flow is gradually reduced until the first-stage diameter equaling is finished, the argon flow is reduced to 80slm, and the argon flow is kept until the second-stage diameter-equaling step is finished.

Furnace pressure parameters of the single crystal furnace: in the pre-diameter-equalizing step, the furnace pressure of the single crystal furnace is kept at 12kPa, in the first diameter-equalizing step, the furnace pressure is gradually increased until the first diameter-equalizing step is finished, the furnace pressure is increased to 18kPa, and the furnace pressure is kept until the second diameter-equalizing step is finished.

Experimental example III

Argon flow parameters: in the pre-diameter-equalizing step, the flow rate of argon gas was adjusted to 120slm, and the flow rate of argon gas was maintained until the second-stage diameter-equalizing step was completed.

Experimental example four

Argon flow parameters: in the pre-diameter-equalizing step, the flow rate of argon gas was adjusted to 125slm, and the flow rate of argon gas was maintained until the second-stage diameter-equalizing step was completed.

Furnace pressure parameters of the single crystal furnace: in the pre-diameter-equalizing step, the furnace pressure of the single crystal furnace is kept at 13kPa, in the first diameter-equalizing step, the furnace pressure is gradually increased until the first diameter-equalizing step is finished, the furnace pressure is increased to 18.8kPa, and the furnace pressure is kept until the second diameter-equalizing step is finished.

Experimental example five

Argon flow parameters: in the pre-diameter-equalizing step, the flow rate of argon gas was adjusted to 130slm, and the flow rate of argon gas was maintained until the second-stage diameter-equalizing step was completed.

Furnace pressure parameters of the single crystal furnace: in the pre-diameter-equalizing step, the furnace pressure of the single crystal furnace is kept at 15kPa, in the first diameter-equalizing step, the furnace pressure is gradually increased until the first diameter-equalizing step is finished, the furnace pressure is increased to 20kPa, and the furnace pressure is kept until the second diameter-equalizing step is finished.

TABLE 1 statistical results of comparative and experimental examples

Referring to table 1, comparative examples one to three disclose that doping by a gas phase doping method increases the amount of dopant added, which is beneficial to improving the resistivity of the As-heavily doped silicon single crystal, but increases the crystallization rate (the probability of converting the As-heavily doped silicon single crystal into polycrystal partially or completely) due to the presence of more dopant gas in the gas phase of the single crystal furnace, and decreases the amount of dopant added, which is beneficial to decreasing the crystallization rate, but the resistivity of the As-heavily doped silicon single crystal cannot be effectively guaranteed due to the less dopant amount of the dopant. This conclusion is consistent with current theory for heavily doped silicon single crystals.

The combination of the first experimental example and the second experimental example shows that the furnace pressure of the pre-diameter-equant process and the first-stage diameter-equant process is increased, and the argon flow in the pre-diameter-equant process and the first-stage diameter-equant process is increased, so that the resistivity of the prepared heavily As-doped silicon single crystal is improved. However, when the furnace pressure is increased to 12kPa and the argon flow rate reaches 120slm, if the argon flow rate is kept low in the one-stage constant diameter process, the NG rate of the single crystal ingot (the probability of crystal change or ingot pulling failure due to other reasons) is suddenly increased, and the reason may be that the APC valve angle of the single crystal furnace is closed due to the state of the blast furnace pressure and the low gas flow rate, and the argon circulation in the furnace body is not obtained.

And (3) keeping the furnace pressure of the pre-diameter-equalizing process and the first-stage diameter-equalizing process at a higher level and keeping the argon flow at a higher level in all the processes (namely, not reducing the argon flow in the first-stage diameter-equalizing process), so that the APC valve of the single crystal furnace is kept to operate at a low valve level. On the basis, the resistivity of the prepared heavily As-doped silicon single crystal bar can be effectively improved, the average level of the resistivity is reduced by 12.5%, and the head resistivity can be lower than a target value of 0.003 omega. Meanwhile, in the crystal bar drawing process, the probability of NG occurrence is remarkably reduced from about 45% before improvement to about 20%, and the reduction amplitude is more than 50%.

Combining the fourth experimental example and the fifth experimental example, on the premise that the working condition of the single crystal furnace is allowed (the design of the single crystal furnace can be improved to enable the single crystal furnace to meet the process requirements), the furnace pressure of the former process and the first-stage process of the equal diameter is continuously increased, the argon flow in all the processes is increased, the resistivity of the prepared heavily As-doped silicon single crystal rod is further reduced, and the trend of accelerated reduction is realized. And the probability of NG is kept at about 20% during the crystal bar drawing process.

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 production method of heavily As-doped silicon single crystal capable of reducing resistivity of a head is used for producing 8 inches of heavily As-doped silicon single crystal by using a 2408SR single crystal furnace As a production device and adopting a Czochralski method, and is characterized by comprising a pre-diameter-equalizing process, a first-section diameter-equalizing process, a second-section diameter-equalizing process and a final process which are sequentially carried out;

in the pre-diameter-equaling process, the argon flow is adjusted to 120slm-130slm, and the argon flow is kept until the two-stage diameter-equaling process is finished; in addition, in the pre-equal diameter process, the furnace pressure of the single crystal furnace is adjusted to 12kPa-15 kPa; in the first-stage isometric procedure, gradually increasing the furnace pressure of the single crystal furnace to 18-20 kPa; in the second constant diameter process, the furnace pressure of the single crystal furnace is maintained at 18 kPa-20 kPa.

2. The method for producing a heavily As-doped silicon single crystal capable of reducing the head resistivity As claimed in claim 1, wherein the pre-isodiametric step comprises a stabilizing step, a seeding step, a shouldering step and a shouldering step, which are performed in this order.

3. The method for producing a heavily As-doped silicon single crystal capable of reducing the head resistivity As claimed in claim 1, wherein the length of the constant diameter in the one-stage constant diameter process is 200mm to 500 mm.

4. The method for producing a heavily As-doped silicon single crystal capable of reducing the head resistivity As claimed in claim 3, wherein the length of the constant diameter in the one-stage constant diameter process is 300 ± 10 mm.