阅读说明：本技术 一种半导体级硅粉的纯化方法 (Purification method of semiconductor grade silicon powder ) 是由 张辰宇 赵丽霞 魏汝省 马康夫 方芃博 陈琪 李刚 许正 靳霄曦 张馨丹 于 2021-11-12 设计创作，主要内容包括：本发明公开了一种半导体级硅粉的纯化方法,属于半导体材料加工技术领域；该方法是先将待纯化的硅粉置于感应加热炉内,在真空状态下升温至1000-1300℃；真空度为4.5-5.5×10～(-)～(6)mbar；之后在炉腔中注入高纯H-(2)至700-900mbar；随后再抽真空至原始真空度；将氯化氢与氩气以流量比7-9:1.5-2.5通入腔体内,通气至压力为700-900 mbar,保持4-6 h,之后将炉体内压力降至＜10 mbar；本发明有效提高硅粉的纯度,纯化后的硅粉满足生产高纯碳化硅粉料的纯度要求；同时也降低了整个纯化过程的危险性。(The invention discloses a purification method of semiconductor grade silicon powder, belonging to the technical field of semiconductor material processing; firstly, putting silicon powder to be purified in an induction heating furnace, and heating to 1000-1300 ℃ in a vacuum state; the vacuum degree is 4.5-5.5 multiplied by 10 ‑ 6 mbar; then high-purity H is injected into the furnace chamber 2 To 700 and 900 mbar; then vacuumizing to the original vacuum degree; introducing hydrogen chloride and argon into the cavity at a flow ratio of 7-9:1.5-2.5, introducing the gas to a pressure of 700-; the invention effectively improves the purity of the silicon powder, and the purified silicon powder meets the purity requirement of producing high-purity silicon carbide powder; and simultaneously, the danger of the whole purification process is reduced.)

1. The method for purifying the semiconductor grade silicon powder is characterized by comprising the following steps of:

a) putting the silicon powder to be purified in an induction heating furnace, and heating to 1000-1300 ℃ in a vacuum state; vacuum degree of 4.5X 10^-6-5.5×10^-6mbar; then in the furnace chamberInjecting high purity H₂To 700 and 900 mbar; maintaining for 10-20min, and vacuumizing to 4.5 × 10^-6-5.5×10^-6mbar；

b) The temperature in the furnace is continuously increased to 1600-2000 ℃, hydrogen chloride and argon are introduced into the cavity according to the flow ratio of 7-9:1.5-2.5, the gas is introduced until the pressure is 700-900mbar, the gas is kept for 4-6 h, and then the pressure in the furnace is reduced to less than 10 mbar.

2. The method for purifying semiconductor grade silicon powder according to claim 1, wherein in the step a, the furnace body is slowly heated to 1200 ℃ in the induction heating furnace at a heating rate of 10 ℃/min in a vacuum state.

3. The method for purifying semiconductor grade silicon powder according to claim 1, wherein in the step a, high purity H is injected₂The aeration speed of (2) is 1.5-2.5L/min.

4. The method according to claim 1, wherein in step b, the pressure in the furnace body is reduced to < 10 mbar at a pumping rate of 10 mbar/min.

5. The method for purifying semiconductor grade silicon powder according to claim 1, wherein the operation of step b is performed after the operation of step a is repeated 5-6 times, and the operation of step b is also repeated 5-6 times.

6. The method according to claim 1, wherein the silicon powder to be purified is placed in a graphite crucible and then placed in an induction furnace.

7. The method for purifying semiconductor grade silicon powder according to claim 1, wherein after step b is finished, under the protection of Ar, the induction heating furnace is slowly cooled to room temperature, opened, and the purified silicon powder is taken out and packaged.

Technical Field

The invention belongs to the technical field of semiconductor material processing, and particularly relates to a purification method of semiconductor grade silicon powder.

Background

With the rapid development of semiconductors and the progress of microelectronic technology, the requirements of high voltage resistance, high temperature resistance, radiation resistance, high frequency and high reliability are provided for core components, and the traditional silicon and gallium arsenide devices are close to the working limit and cannot meet the requirements. The third generation semiconductor silicon carbide has the properties of wide forbidden band, high thermal conductivity, high electron saturation migration rate, high breakdown electric field and the like, and the characteristics determine that the third generation semiconductor silicon carbide has great potential in overcoming the contradiction between power and frequency of power electronic devices and improving the high temperature resistance and the radiation resistance of semiconductor devices, and is considered as an ideal semiconductor material for manufacturing optoelectronic devices, high-frequency high-power devices and high-temperature electronic devices. Wherein the high-purity semi-insulating silicon carbide single crystal substrate is a key substrate material of the GaN power device. The high-purity silicon carbide powder is a raw material for growing the high-purity semi-insulating silicon carbide single crystal substrate, and the purity of the powder directly influences the growth quality, resistivity and other electrical properties of the silicon carbide single crystal.

At present, graphite powder and silicon powder are generally used as raw materials to synthesize high-purity silicon carbide powder, so the purity of the raw material silicon for synthesizing the powder needs to be controlled in order to control the purity of the powder. However, at present, silicon powder is generally prepared by mechanically crushing and cleaning a large silicon material, although metal impurities contained in the silicon powder are greatly reduced, the purity of the silicon powder still cannot meet the requirement of preparing high-purity silicon carbide powder, and meanwhile, because the silicon powder has small granularity, large surface energy and easy nitrogen adsorption, the metal impurities and the nitrogen content in the silicon carbide powder prepared by directly using the silicon powder are high, and various defects in crystals can be induced to generate and influence the electrical properties of the crystals when single crystal growth is carried out.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a purification method of semiconductor grade silicon powder to improve the purity of the silicon powder, so that the purified silicon powder meets the purity requirement of producing high-purity silicon carbide powder.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a purification method of semiconductor grade silicon powder comprises the following steps:

a) putting the silicon powder to be purified in an induction heating furnace, and heating to 1000-1300 ℃ in a vacuum state; vacuum degree of 4.5X 10^-6-5.5×10^-6mbar; then high-purity H is injected into the furnace chamber₂To 700 and 900 mbar; maintaining for 10-20min, and vacuumizing to 4.5 × 10^-6-5.5×10^-6mbar。

b) The temperature in the furnace is continuously increased to 1600-2000 ℃, hydrogen chloride and argon are introduced into the cavity according to the flow ratio of 7-9:1.5-2.5, the gas is introduced until the pressure is 700-900mbar, the gas is kept for 4-6 h, and then the pressure in the furnace is reduced to less than 10 mbar.

Preferably, in the step a, the furnace body is slowly heated to 1200 ℃ at a heating rate of 10 ℃/min in a vacuum state in the induction heating furnace.

Preferably, in step a, high purity H is injected₂The aeration speed of (2) is 1.5-2.5L/min.

Preferably, in step b, the pressure in the furnace is reduced to < 10 mbar with a gas evacuation rate of 10 mbar/min.

Preferably, the operation of step b is performed after repeating the operation of step a 5-6 times, and the operation of step b is also repeated 5-6 times.

Preferably, the silicon powder to be purified is placed in a graphite crucible and then placed in an induction heating furnace.

Preferably, after the step b is finished, under the protection of Ar, the induction heating furnace is slowly cooled to room temperature, the furnace is opened, and the purified silicon powder is taken out and packaged.

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

the invention utilizes the small molecular size of hydrogen, can be fully diffused in the gaps of the raw materials, and is beneficial to discharging nitrogen in the gaps of the silicon powder. At the same time H₂High thermal conductivity, H₂Can be sufficiently diffused in the gaps of the silicon powder, and therefore, passes through H₂The heat conduction can fully heat the silicon powder, fully desorb the gas adsorbed on the surface, and can follow H in the air extraction process₂Viscous airflow escapes from the crucible, so that the nitrogen removal effect is further improved. And (3) reacting the hydrogen chloride with the metal simple substance and the compound impurities thereof in the silicon powder at a high temperature to remove the metal impurities. Meanwhile, the dried hydrogen chloride gas has low price, no toxicity, no flammability and no explosion, has high safety and can be continuously applied for a long time.

According to the invention, silicon powder is further purified, and the purified silicon powder meets the purity requirement of producing high-purity silicon carbide powder; the purified silicon powder growing powder is white and transparent; the wafer obtained after crystal processing has uniform resistivity which is larger than 1E10 omega cm, and meets the requirement of a high-purity semi-insulating silicon carbide single crystal substrate; the temperature required in the whole purification process is lower, so that the energy consumption is further reduced, and the risk of the whole purification process is also reduced.

Drawings

FIG. 1 is a silicon carbide powder prepared using the silicon powder purified in example 1;

FIG. 2 is a resistivity profile of a wafer made from the silicon carbide powder of FIG. 1.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solution of the present invention is described in detail below with reference to the embodiments and the drawings, but the scope of protection is not limited thereto.

Example 1

1. Putting the silicon powder to be purified in a graphite crucible, putting the graphite crucible in an induction heating hearth, sealing, and vacuumizing the furnace chamber to 5 multiplied by 10 when the heating is not started^-6mbar, then slowly heating the furnace body to 1200 deg.C at a heating rate of 10 deg.C/min under vacuum, maintaining the temperature, and injecting high purity H into the furnace chamber at an aeration rate of 2L/min₂To 800mbar, held for 15 minutes and then evacuated to 5X 10^-6mbar, which is a pump cycle, followed by a second injection of high purity H₂To 800mbar, for 15 minutes, and subsequently to 5X 10^-6mbar, which was repeated 5 times in cycles such that the vacuum in the apparatus was maintained at 5X 10^-6mbar. The purpose of the step is to mainly utilize the small molecular size of hydrogen, which can be fully diffused in the gap of the raw material and is beneficial to discharging nitrogen in the gap of the silicon powder. At the same time H₂High thermal conductivity, and from the above, H₂Can be sufficiently diffused in the gaps of the silicon powder, and therefore, passes through H₂The heat conduction can fully heat the silicon powder, fully desorb the gas adsorbed on the surface, and can follow H in the air extraction process₂Viscous airflow escapes from the crucible, so that the nitrogen removal effect is further improved.

2. And continuously heating the temperature in the furnace to 1600 ℃, introducing hydrogen chloride and argon into the cavity according to the flow ratio of 8:2, introducing the gas until the pressure is 800mbar, stopping introducing the gas, maintaining the gas for 5 hours, fully reacting the hydrogen chloride gas in the cavity with metal impurities, then reducing the pressure of the furnace body from 800mbar to a near vacuum state (< 10 mbar) at a pumping speed of 10 mbar/min, so as to perform a hydrogen chloride introducing pumping and filling cycle, and repeating the cycle for 5 times to finish the process. The aim of the step is to remove metal impurities by reacting hydrogen chloride with metal simple substances and compound impurities thereof in silicon powder at high temperature.

3. And finally, slowly cooling to room temperature under the protection of Ar, opening the furnace, taking out the purified silicon powder, packaging and finishing the experiment.

In this embodiment, a "halogen gas purification" process is added after the high-temperature purification process, that is, hydrogen chloride gas is introduced at a high-temperature stage, and the dried hydrogen chloride gas is dissociated into chlorine radicals and hydrogen radicals at a temperature above 1600 ℃.

Wherein the chlorine free radical can react with the high boiling point metal simple substance and the metal compound to generate the low boiling point metal chloride impurity. Thus, high boiling point impurities can be removed by repeatedly pumping air, and the purity of the silicon powder is further improved.

Example 2

1. Putting the silicon powder to be purified in a graphite crucible, putting the graphite crucible in an induction heating hearth, sealing, and vacuumizing the furnace chamber to 4.5 multiplied by 10 when the heating is not started^-6mbar, then slowly heating the furnace body to 1000 deg.C at a heating rate of 10 deg.C/min under vacuum, maintaining the temperature, and injecting high purity H into the furnace chamber at an aeration rate of 2.5L/min₂To 700mbar, for 20 minutes, and then to 4.5X 10^-6mbar, which is a pump cycle, followed by a second injection of high purity H₂To 700mbar for 15 minutes, and subsequently to 4.5X 10^-6mbar, which was repeated 6 times in cycles such that the vacuum in the apparatus was maintained at 4.5X 10^-6mbar。

2. And continuously heating the temperature in the furnace to 2000 ℃, introducing hydrogen chloride and argon into the cavity according to the flow ratio of 9:2.5, introducing the gas until the pressure is 700mbar, stopping introducing the gas, maintaining the gas for 5 hours, fully reacting the hydrogen chloride gas in the cavity with metal impurities, then reducing the pressure of the furnace body from 700mbar to a near vacuum state at a pumping speed of 10 mbar/min, and performing hydrogen chloride introduction pumping and filling circulation repeatedly for 5 times to finish the process. The aim of the step is to remove metal impurities by reacting hydrogen chloride with metal simple substances and compound impurities thereof in silicon powder at high temperature.

3. And finally, slowly cooling to room temperature under the protection of Ar, opening the furnace, taking out the purified silicon powder, packaging and finishing the experiment.

Example 3

1. Putting the silicon powder to be purified into a graphite crucible, putting the graphite crucible into an induction heating hearth, and sealingThe furnace chamber is vacuumized to 5.5 x 10 when heating is not started^-6mbar, then slowly heating the furnace body to 1300 deg.C under vacuum at a heating rate of 10 deg.C/min, maintaining the temperature, and injecting high purity H into the furnace chamber at an aeration rate of 1.5L/min₂To 900mbar, for 20 minutes and then to 5.5X 10^-6mbar, which is a pump cycle, followed by a second injection of high purity H₂To 900mbar for 15 minutes, and subsequently to 5.5X 10^-6mbar, which was repeated 6 times in cycles such that the vacuum in the apparatus was maintained at 5.5X 10^-6mbar。

2. And continuously heating the temperature in the furnace to 1800 ℃, introducing hydrogen chloride and argon into the cavity according to the flow ratio of 7:1.5, introducing the gas until the pressure is 900mbar, stopping introducing the gas, maintaining the gas for 5 hours, fully reacting the hydrogen chloride gas in the cavity with metal impurities, then reducing the pressure of the furnace body from 900mbar to a near vacuum state at a pumping speed of 10 mbar/min, and performing hydrogen chloride introduction pumping and filling circulation repeatedly for 5 times to finish the process. The aim of the step is to remove metal impurities by reacting hydrogen chloride with metal simple substances and compound impurities thereof in silicon powder at high temperature.

3. And finally, slowly cooling to room temperature under the protection of Ar, opening the furnace, taking out the purified silicon powder, packaging and finishing the experiment.

While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.