A preparation method for P-type high-resistance and ultra-high-resistance Czochralski single-crystal silicon substrates

Abstract

The present invention relates to a method for preparing a P-type high-resistance and ultra-high-resistance Czochralski single-crystalline silicon substrate. The present invention controls the matching of the oxygen content and resistivity in the silicon wafer, so as to ensure that the conduction type of the silicon substrate does not change after device manufacturing is completed, and has a high resistivity; the oxygen content can be fixed to change the doping amount, or the resistivity can be fixed to change the oxygen content, or both can be changed simultaneously, with flexible operation, greatly improving the yield of high-resistance silicon crystals.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and particularly relates to a method for preparing a P-type high-resistance and ultra-high-resistance Czochralski single-crystal silicon substrate. Background Art

[0002] Single-crystal silicon wafers grown by the Czochralski method are widely used in the manufacture of semiconductor electronic devices. Different devices have different requirements for the oxygen content and resistivity in the silicon wafers. The demand for P-type high-resistance single-crystal silicon for radio frequency SOI is increasing day by day. Radio frequency SOI (RF-SOI) is a radio frequency device and integrated circuit fabricated using SOI process technology. SOI refers to a substrate structure with a SiO2 insulating layer inserted in a bulk silicon material. Fabricating low-voltage and low-power integrated circuits on an SOI substrate is one of the mainstream choices for deep sub-micron technology nodes. RF-SOI has the following advantages: (1) RF-SOI has a very high operating frequency; (2) RF-SOI can implement an integrated circuit stacked structure, while improving power and energy efficiency ratio; (3) The SOI substrate used in the RF-SOI process can reduce parasitic effects, making the quality factor of the radio frequency chip higher, the loss lower, the noise coefficient better, and at the same time improving the insulation level and linearity of the product.

[0003] In the Czochralski single-crystal silicon manufacturing process, polycrystalline silicon raw materials are transferred into a quartz crucible, heated and melted, a seed crystal is immersed in the silicon melt and rotated upward for pulling, and silicon solidifies and crystallizes at the interface between the seed crystal and the silicon melt. As the seed crystal is pulled upward, a single-crystal silicon ingot is formed.

[0004] The resistivity and conduction type of single-crystal silicon are determined by the type and content of the incorporated electroactive impurities (such as B, P, and As). During the growth of Czochralski single-crystal silicon, oxygen is transported into the silicon melt through the dissolution of the quartz crucible, and the silicon dioxide (SiO2) in the crucible becomes mobile silicon and oxygen atoms or loosely bonded silicon plus oxygen or SiO. Most of the oxygen incorporated into the silicon melt evaporates from the free surface of the melt, and the remaining oxygen segregates into the growing crystal through the solid-liquid interface between the melt and the crystal. Oxygen-related thermal donors generated during low-temperature heat treatment will seriously affect the resistivity and conduction type of the silicon wafer.

[0005] Impurity compensation can be used to change the conduction type of a certain region in a semiconductor by diffusion or ion implantation according to needs to fabricate various devices. However, when not controlled properly, the phenomenon of N D ≈N A will occur. At this time, the donor electrons can just fill the acceptor energy level. Although there are many impurities, they cannot provide electrons and holes to the conduction band and valence band. This material is easily mistaken for a high-purity semiconductor. In fact, there are many impurities and its performance is very poor, and it cannot be used in practice.

[0006] The prior art mainly reduces the amount of thermal donors generated by reducing the oxygen content in silicon crystals, thereby reducing the impact of thermal donors on resistivity. Due to the use of crucibles, it is difficult to reduce the oxygen in silicon crystals and there are requirements for doping technology. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing a P-type high-resistance and ultra-high-resistance Czochralski single-crystal silicon substrate, which controls the matching of the oxygen content and resistivity in the silicon wafer, realizes that the conductivity type of the silicon substrate does not change after device manufacturing, and has a high resistivity.

[0008] The present invention provides a method for preparing a P-type high-resistance and ultra-high-resistance Czochralski single-crystal silicon substrate, including the following steps:

[0009] (1) According to the conversion relationship between the boron impurity concentration and resistivity in the SEMI MF723-99 standard based on the change in resistivity of the silicon wafer before and after heat treatment, calculate the generated thermal donor concentration n TD ; convert the compensated acceptor concentration 2n TD into the P-type resistivity ρ0; wherein, the ρ0 is the resistivity critical value, and the initial resistivity of the P-type silicon wafer should not exceed ρ0, otherwise the conductivity type of the substrate will change to N-type after heat treatment;

[0010] (2) Take silicon wafers with different oxygen contents [O i 0 for heat treatment experiments, obtain the relationship between the thermal donor concentration n TD and the oxygen content, and then draw the relationship curve between the oxygen content and the resistivity critical value in the silicon crystal, and obtain the matching value of any oxygen content and resistivity according to the curve and fitting;

[0011] (3) According to the matching value of the oxygen content and resistivity, control the process parameters to prepare a single-crystal silicon substrate with a P-type and high-resistance and ultra-high-resistance.

[0012] The heat treatment temperature in the steps (1) and (2) is 250-550 °C, and the time is 0.5-5 h.

[0013] In the step (1), 2n TD and ρ0 refer to the conversion relationship between the boron impurity concentration and resistivity in the SEMI MF723-99 standard.

[0014] For the boron-doped silicon single crystal in the SEMI MF723-99 standard, the doping agent concentration value is calculated from the resistivity value, that is, the formula for P-type resistivity to concentration is as follows:

[0015]

[0016] In the formula: ρ - resistivity, Ω·cm; N - doping agent concentration, atoms / cm 3 .

[0017] The resistivity value of the boron-doped silicon single crystal is calculated from the dopant concentration value, that is, the formula from P-type concentration to resistivity is as follows:

[0018]

[0019] Where: ρ——resistivity, Ω·cm; N——dopant concentration, atoms / cm 3 。

[0020] The high resistivity refers to >1000 ohm-cm, and the ultra-high resistivity refers to >10000 ohm-cm.

[0021] The single-crystalline silicon substrate can have high or ultra-high resistivity within a relatively high oxygen content range, meeting the requirements of the RFSOI substrate.

[0022] Beneficial effects

[0023] The present invention controls the matching of the oxygen content and resistivity in the silicon wafer, realizes that the conductivity type of the silicon substrate does not change after device manufacturing, and has high resistivity; the oxygen content can be determined to change the doping amount, or the resistivity can be determined to change the oxygen content, or both can be changed simultaneously, with flexible operation, greatly improving the yield of high-resistivity silicon crystals and ultra-high-resistivity silicon crystals. Brief Description of the Drawings

[0024] Figure 1 It is a schematic diagram of crystal growth of the present invention.

[0025] Figure 2 It is the resistivity relationship that P-type high-resistivity silicon crystals with different oxygen contents need to satisfy.

[0026] Figure 3 It is the calculation process of oxygen content and resistivity. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0028] Example 1

[0029] Taking heat treatment at 450°C for 2h as an example:

[0030] (1) Calculate the concentration of thermal donors \(n_{TD}\) generated according to the conversion relationship between boron impurity concentration and resistivity based on the change in resistivity of the silicon wafer before and after heat treatment; since the thermal donors are double donors, that is, the donor concentration provided by the thermal donors is \(2n_{TD}\), convert the compensated acceptor concentration \(2n_{TD}\) into the P-type resistivity \(\rho_0\); where, the \(\rho_0\) is the resistivity critical value. To make the P-type silicon wafer with an oxygen content of \([O i _0\) not invert and have a high or ultra-high resistivity after device manufacturing, the initial resistivity of the P-type silicon wafer should not exceed \(\rho_0\);

[0031] (2) Take silicon wafers with different oxygen contents of \([O i _0\) for heat treatment experiments, obtain the relationship between the thermal donor concentration \(n_{TD}\) and the oxygen content, and then draw the relationship curve between the oxygen content in the silicon crystal and the resistivity critical value (as Figure 2 shown), and obtain the matching value of any oxygen content and resistivity by fitting according to the curve;

[0032] (3) Control the process parameters to prepare a P-type single crystal silicon substrate with a high resistance according to the matching value of oxygen content and resistivity.

[0033] According to the relationship between the oxygen content and the critical resistivity obtained in step (1) and step (2), if the oxygen content is constant (6 ppm), to obtain a high-resistance silicon wafer with a P-type substrate after device manufacturing, the target resistivity of single crystal silicon growth should not exceed 4096 ohm-cm. If the resistivity of the P-type silicon wafer is determined to be 16384 ohm-cm, the oxygen content in the silicon wafer should be controlled at 4 ppm.

Claims

1. A method for preparing a P-type high-resistance and ultra-high-resistance Czochralski single-crystal silicon substrate, comprising the following steps: (1) According to the conversion relationship between boron impurity concentration and resistivity, calculate the generated thermal donor concentration n based on the change in resistivity of the silicon wafer before and after heat treatment. TD Since the thermal donors are double donors, the compensated acceptor concentration is 2n. TD Convert it to the P-type resistivity ρ0; among them, where ρ0 is the resistivity critical value, and the initial resistivity of the P-type silicon wafer should not exceed ρ0; the heat treatment temperature is 250 - 550 °C, and the time is 0.1 - 8 h; (2)Take silicon wafers with different oxygen contents [O i 0 and conduct heat treatment experiments to obtain the relationship between the thermal donor concentration n TD and the oxygen content, and then draw the relationship curve between the oxygen content and the resistivity critical value in the silicon crystal. According to the curve, the matching value of any oxygen content and resistivity is obtained by fitting; wherein, the heat treatment temperature is 250-550 °C and the time is 0.1-8 h; (3) According to the matching value of the oxygen content and the resistivity, control the process parameters to prepare a substrate of P-type single-crystal silicon with high resistance and ultra-high resistance.

2. The preparation method according to claim 1, characterized in that: 2n in the step (1) TD and ρ0 refer to the conversion relationship between the boron impurity concentration and the resistivity in accordance with the SEMIMF723-99 standard.

3. The preparation method according to claim 1, characterized in that: The high resistance means > 1000 ohm-cm.

4. The preparation method according to claim 1, characterized in that: The ultra-high resistance means > 10000 ohm-cm.

Images