CN115810543A - Silicon wafer rapid heat treatment method for improving denuded zone and oxygen precipitation density - Google Patents

Abstract

The invention relates to a silicon wafer rapid heat treatment method for improving a clean area and oxygen precipitation density, which belongs to the technical field of semiconductor processing and comprises the following operation steps: the first step is as follows: heating the silicon wafer to 1230-1270 ℃ in a mixed atmosphere of inert gas and H2, wherein the concentration ratio of the inert gas to the H2 is 3-1. The second step: the silicon wafer is kept at 1270 ℃ for 30 seconds or more. The third step: when the temperature is reduced, the temperature reduction rate of the high-temperature stage is kept stable, the temperature is reduced to 650-700 ℃, and then the temperature is continuously reduced to the normal temperature. By controlling the thickness of the denuded zone, the oxygen precipitation density of the gettering region is increased while the COP density of the surface is reduced.

Description

Silicon wafer rapid heat treatment method for improving denuded zone and oxygen precipitation density

Technical Field

The invention relates to the technical field of semiconductor processing, in particular to a rapid heat treatment method for a silicon wafer for improving a clean area and oxygen precipitation density.

Background

The silicon wafer is the main material for preparing the super large scale integrated circuit, generally obtains monocrystalline silicon by a Czochralski method, and then is made into a semiconductor silicon wafer for the integrated circuit by the technical processes of slicing, lapping, corroding, polishing and the like. The melting point of silicon is 1420 deg.c, and during pulling, part of the quartz crucible material enters the silicon melt at high temperature, so that the silicon melt is contaminated with contaminating substances, mainly oxygen, and oxygen impurities are present in the silicon single crystal at a certain concentration. The oxygen atoms serve as impurity centers, which causes generation of different types of defects such as COP, oxidation induced stacking fault OISF and the like, and the defects bring various influences on the use of subsequent silicon wafers.

The heat treatment process carried out in the device manufacturing process can lead oxygen in the silicon wafer to be gathered to generate oxygen precipitation, and the oxygen precipitation has double functions: oxygen precipitates in the device operating region can cause device failure; the oxygen precipitates in the non-working region act as gettering sites, trapping unwanted transition metal impurities introduced during device fabrication. Integrated circuit fabrication requires a reduction in metal contamination introduced during processing.

The intrinsic gettering technique is a technique that can effectively remove a transition metal from a device region. The method utilizes the dual function of oxygen precipitation and the characteristic of high metal diffusion speed, forms oxygen precipitation with enough density in a silicon wafer body through a heat treatment process to be used as a capture center of metal impurities, forms a clean area without the oxygen precipitation in a device working area by inhibiting the nucleation and growth of the oxygen precipitation, and quickly diffuses metal contamination into the silicon wafer body through high-temperature annealing (about 1000 ℃) treatment after the device process is finished so as to be captured near the oxygen precipitation.

The key parameters for measuring the internal impurity absorption process are as follows: the thickness of the denuded zone and the oxygen precipitate density. It is generally desirable that the denuded zone be of a relatively high thickness while the oxygen precipitates beneath the denuded zone be sufficiently high. The denuded zone and the oxygen precipitation density obtained by the traditional annealing method are generally lower, and the gettering effect cannot be achieved.

Disclosure of Invention

The invention mainly solves the defects in the prior art and provides a silicon wafer rapid heat treatment method for improving the denuded zone and the oxygen precipitation density.

The technical problem of the invention is mainly solved by the following technical scheme:

a rapid thermal processing method for silicon wafers to increase denuded zone and oxygen precipitate density includes the following operational steps:

the first step is as follows: in the mixed atmosphere of inert gas and H2, the silicon wafer is heated to 1230-1270 ℃, and the heating rate of the silicon wafer is 80-90 ℃/S. And the concentration ratio of the inert gas to H2 is 3-1.

The second step is that: the silicon wafer is kept at 1270 ℃ for 30 seconds or more.

The third step: when the temperature is reduced, the temperature reduction rate of the high-temperature stage is kept stable, the temperature is reduced to 650-700 ℃, and then the temperature is continuously reduced to the normal temperature.

Preferably, the inert gas is Ar or N2. By using the mixed gas of the inert gas and the H2 as the protective atmosphere of the rapid thermal treatment, more ideal denuded zone thickness and high oxygen precipitation density are obtained, and the inert gas and the H2 have certain concentration ratio.

Preferably, the rapid annealing heat preservation time is not less than 30s, experiments prove that the reduction of COP density is closely related to the heat preservation time, and the COP density at the beginning is rapidly reduced along with the extension of the heat preservation time; along with the extension of the heat preservation time, the COP density can reach a constant value and is not changed, and the reduction of the COP density is not obviously changed by continuously extending the heat preservation time.

Preferably, the cooling rate in the high-temperature stage is 40-60 ℃/S, then the cooling rate when the temperature is reduced to the normal temperature is 70-75 ℃/S, the cooling rate is increased, the oxygen precipitation density is increased, and the thickness of the clean area is increased.

The silicon wafer is subjected to a special high-temperature annealing process in the mixed atmosphere of inert gas and hydrogen, so that the surface COP can be eliminated; obtaining a clean area of 100-110 microns; the obtained oxygen precipitation density is 5E 9-2E 10atoms/cm < 3 >, and the method has great effect on the subsequent preparation of integrated circuit devices by silicon wafers.

The invention can achieve the following effects:

compared with the prior art, the silicon wafer rapid heat treatment method for improving the denuded zone and the oxygen precipitation density improves the oxygen precipitation density of the gettering region and reduces the COP density of the surface simultaneously by controlling the thickness of the denuded zone.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments.

Example (b): a rapid thermal processing method for silicon wafers to increase denuded zone and oxygen precipitate density includes the following operational steps:

the first step is as follows: the silicon wafer was heated to 1270 ℃ in a mixed atmosphere of an inert gas and H2 with a concentration ratio of inert gas to H2 of 2. The inert gas is Ar or N2. The heating speed of the silicon chip is 85 ℃/S.

The second step is that: the silicon wafer is kept at 1270 ℃ for 30 seconds or more. The rapid annealing heat preservation time is not less than 30s, experiments prove that the reduction of COP density is closely related to the heat preservation time, and the COP density is rapidly reduced along with the extension of the heat preservation time at the beginning; along with the extension of the heat preservation time, the COP density can reach a constant value and is not changed any more, and the reduction of the COP density is not obviously changed by continuously extending the heat preservation time.

The third step: when the temperature is reduced, the temperature reduction rate of the high-temperature stage is kept stable, the temperature is reduced to 650-700 ℃, and then the temperature is continuously reduced to the normal temperature. The cooling rate of the high-temperature stage is 40-60 ℃/S, then the cooling rate of the high-temperature stage to the normal temperature is 70-75 ℃/S, the cooling speed is increased, the oxygen precipitation density is increased, and the thickness of the clean area is increased.

In conclusion, the rapid thermal processing method for silicon wafers capable of improving the denuded zone and the oxygen precipitation density improves the oxygen precipitation density of the gettering region and simultaneously reduces the COP density of the surface by controlling the thickness of the denuded zone.

The above description is only an embodiment of the present invention, but the structural features of the present invention are not limited thereto, and any changes or modifications within the scope of the present invention by those skilled in the art are covered by the present invention.

Claims (4)

1. A rapid thermal processing method for silicon wafers for increasing the denuded zone and oxygen precipitate density is characterized by comprising the following operating steps:

the first step is as follows: heating the silicon wafer to 1230-1270 ℃ in a mixed atmosphere of inert gas and H2, wherein the concentration ratio of the inert gas to the H2 is 3-1;

the second step: keeping the temperature of the silicon wafer at 1270 ℃ for 30 seconds or more;

the third step: when the temperature is reduced, the temperature reduction rate of the high-temperature stage is kept stable, the temperature is reduced to 650-700 ℃, and then the temperature is continuously reduced to the normal temperature.

2. The rapid thermal processing method for silicon wafers to enhance denuded zone and oxygen precipitate density as claimed in claim 1 wherein: the inert gas is Ar or N2.

3. The process according to claim 1 for rapid thermal processing of silicon wafers to increase denuded zone and oxygen precipitate density wherein: the rapid annealing heat preservation time is not less than 30s, experiments prove that the reduction of COP density is closely related to the heat preservation time, and the COP density is rapidly reduced along with the extension of the heat preservation time at the beginning; along with the extension of the heat preservation time, the COP density can reach a constant value and is not changed any more, and the reduction of the COP density is not obviously changed by continuously extending the heat preservation time.

4. The rapid thermal processing method for silicon wafers to enhance denuded zone and oxygen precipitate density as claimed in claim 1 wherein: the cooling rate at the high temperature stage is 40-60 ℃/S, then the cooling rate when the temperature is reduced to the normal temperature is 70-75 ℃/S, the cooling speed is increased, the oxygen precipitation density is increased, and the thickness of a clean area is increased.