CN111270300A - Preparation method of gas-phase doped zone-melting silicon single crystal - Google Patents

Abstract

The invention discloses a preparation method of a gas-phase doped zone-melting silicon single crystal, which comprises the following steps: (1) pulling the primary polycrystal into a monocrystal or polycrystal according to a normal zone melting crystal pulling process; (2) grinding the drawn single crystal or polycrystal into cone, notching, cleaning and drying; (3) and (3) charging the treated single crystal or polycrystal into a furnace, setting the doping flow according to the target resistivity, and finishing the pulling of the single crystal according to the normal gas phase doping zone melting crystal pulling process. According to the method for preparing the gas phase doping zone melting silicon single crystal, impurities in the silicon core are uniformly distributed in the whole single crystal or polycrystal formed by drawing as much as possible through first drawing instead of being limited in the silicon core, so that the fluctuation of the central resistivity of the gas phase doping zone melting silicon single crystal caused by nonuniform stirring of the silicon core impurities is reduced, the nonuniformity of the axial resistivity and the radial resistivity of the single crystal is effectively reduced, and the target resistivity hit rate and the stability of the gas phase doping zone melting silicon single crystal are improved.

Description

Preparation method of gas-phase doped zone-melting silicon single crystal

Technical Field

The invention relates to a preparation method of a silicon single crystal, in particular to a preparation method of a gas-phase doped zone-melting silicon single crystal.

Background

In the process of pulling the zone-melting silicon single crystal, a certain amount of impurities are required to be doped in order to obtain certain electrical properties so as to improve the electrical activity of the zone-melting silicon single crystal. At present, the main doping methods of the zone-melting silicon single crystal are Neutron Transmutation Doping (NTD), gas phase doping, and the like. Among them, the single crystal obtained by Neutron Transmutation Doping (NTD) has the best nonuniformity of axial and radial resistivities, but is gradually replaced by the gas phase doping technology due to the defects of long production period, high production cost, limitation of neutron irradiation, and the like. However, with the development of integrated circuit technology, the requirement for the nonuniformity of the resistivity of the silicon wafer is higher and higher, and how to improve the nonuniformity of the resistivity of the gas-phase doped zone-melting silicon single crystal is very important.

At present, the high nonuniformity of the resistivity of the gas-phase doped zone-melting silicon single crystal is mainly reflected in large fluctuation of the resistivity of a central point. The polycrystalline rod used by the zone-melting silicon single crystal is prepared on a silicon core through chemical vapor deposition, the resistivity of the polycrystal mainly comes from the silicon core, the resistivity of the silicon core is generally 50-100 omega cm, the target resistance of the gas-phase doped silicon single crystal is generally within 100 omega cm, and if the impurities in the silicon core are not uniformly distributed in the single crystal drawing process, the fluctuation of the resistivity is inevitably caused. For this reason, those skilled in the art are constantly improving the doping process, including eccentric pulling, forward and reverse pulling, etc., but the results are very poor.

Disclosure of Invention

The invention aims to provide a preparation method of a gas-phase doped zone-melting silicon single crystal, which is used for improving the target resistivity hit rate and stability of the gas-phase doped zone-melting silicon single crystal.

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

a method for preparing a gas phase doped zone-melting silicon single crystal comprises the following steps:

(1) pulling the primary polycrystal into a monocrystal or polycrystal according to a normal zone melting crystal pulling process;

(2) grinding the drawn single crystal or polycrystal into cone, notching, cleaning and drying;

(3) and (3) charging the treated single crystal or polycrystal into a furnace, setting the doping flow according to the target resistivity, and finishing the pulling of the single crystal according to the normal gas phase doping zone melting crystal pulling process.

The invention has the advantages that:

according to the method for preparing the gas phase doping zone melting silicon single crystal, impurities in the silicon core are uniformly distributed in the whole single crystal or polycrystal formed by drawing as much as possible through first drawing instead of being limited in the silicon core, so that the fluctuation of the central resistivity of the gas phase doping zone melting silicon single crystal caused by nonuniform stirring of the silicon core impurities is reduced, the nonuniformity of the axial resistivity and the radial resistivity of the single crystal is effectively reduced, and the target resistivity hit rate and the stability of the gas phase doping zone melting silicon single crystal are improved.

Drawings

FIG. 1 is a schematic view of a process flow of a gas-phase doped float-zone silicon single crystal according to the present invention.

FIG. 2 is a result of measuring the resistivity at the axial center point of the gas phase doped zone-melting silicon single crystal prepared in comparative example 1.

FIG. 3 shows the results of measuring the resistivity at the axial center point of the gas phase doped zone-melting silicon single crystal produced in example 1.

Detailed Description

The present invention is further illustrated by the following figures and examples, which are not meant to limit the scope of the invention.

Example 1

By using the method, the primary polycrystalline silicon is pulled into the silicon single crystal, and then the silicon single crystal is grinded, grooved, corroded and dried to prepare the 5-inch N-type <111> air-doped silicon single crystal with the target resistivity of 65-85 omega cm. The flow rate of the doping gas (phosphine) is 30mL/min, the flow of the carrier gas argon is 1L/min, the flow rate of the mixed gas entering the furnace is 100mL/min, and the pressure entering the furnace is 3 bar.

Comparative example 1

The primary polysilicon was directly prepared into a 5-inch air-doped silicon single crystal under the same conditions as in example 1.

The stability of the resistivity of the axial center point and the nonuniformity of the radial resistivity of the gas-doped silicon single crystal prepared by the two methods are evaluated, and particularly as shown in fig. 2, fig. 3 and table 1, the axial and radial uniformity of the resistivity of the gas-phase doped zone-melting silicon single crystal prepared by the method are obviously improved.

TABLE 1

Preparation method	Target resistivity	Measured resistivity	Single crystal bulk non-uniformity (RRV)
				Example 1	65-85Ω·cm	68-80Ω·cm	11.6％
Comparative example 1	65-85Ω·cm	65-84Ω·cm	19.9％

Claims (1)

1. A preparation method of a gas-phase doped zone-melting silicon single crystal is characterized by comprising the following steps:

(1) pulling the primary polycrystal into a monocrystal or polycrystal according to a normal zone melting crystal pulling process;

(2) grinding the drawn single crystal or polycrystal into cone, notching, cleaning and drying;

(3) and (3) charging the treated single crystal or polycrystal into a furnace, setting the doping flow according to the target resistivity, and finishing the pulling of the single crystal according to the normal gas phase doping zone melting crystal pulling process.

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