JP2006294964A - Boron diffusing material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boron diffusing material which further extends a diffusible time after an oxidation treatment. <P>SOLUTION: The boron diffusing material is constituted by a ceramic sintered body in which there are contained Al<SB>2</SB>O<SB>3</SB>component, SiO<SB>2</SB>component and BN component. A total percentage content of the Al<SB>2</SB>O<SB>3</SB>component and the SiO<SB>2</SB>component is 20 to 80 mass%, a percentage content of the BN component is 20 to 80 mass%, a mole ratio of Al<SB>2</SB>O<SB>3</SB>/SiO<SB>2</SB>is 1.0 to 2.4, and an open pore ratio is 13 to 43%. Moreover, a method of manufacturing the boron diffusing material comprises the steps of carrying out a CIP forming of mixed powder including a mixture and/or a compound of 20 to 80 mass% containing the Al<SB>2</SB>O<SB>3</SB>component and the SiO<SB>2</SB>component in which the mole ratio of Al<SB>2</SB>O<SB>3</SB>/SiO<SB>2</SB>is 1.0 to 2.4, and a boron nitride of 20 to 80 mass%; and carrying out a sintering in non-oxidizing atmosphere. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a boron diffusing material and a method for producing the same.

  Conventionally, when boron is thermally diffused into, for example, germanium, silicon, or the like to form a p-type semiconductor, a boron nitride sintered body is used as a boron diffusion material. The boron diffusing material is formed by utilizing boron oxide on the surface in advance and using it. When the boron oxide is consumed, the oxidation treatment is performed again to replenish the boron oxide. Since such re-oxidation treatment takes a lot of work, in recent years it has been developed to use a boron nitride composite sintered body containing boron oxide as a boron diffusion material (hereinafter referred to as “boron oxide composite”). It is called "diffusing material.") Even when this boron oxide composite diffusion material is used, boron oxide is formed on the surface thereof, but the diffusion time after the oxidation treatment has an advantage that it is longer than that of a boron diffusion material made of a boron nitride sintered body. is there.

The boron oxide composite diffusion material is manufactured by sintering boron nitride powder containing a large amount of boron oxide or sintering a mixed powder of boron oxide powder and boron nitride powder. The problem in this case is that since a large amount of boron oxide is contained in the structure of the sintered body, warping or the like occurs during use, which hinders uniform boron diffusion. Therefore, it has been proposed to use a hot pressed sintered body of a mixed powder containing boron nitride powder, alumina powder, high silicate glass powder and / or silica powder as a boron diffusion material (Patent Document 1). However, the diffusion time after the oxidation treatment is about 40 hours, and there is still room for improvement.
JP-A-10-303137

  An object of the present invention is to provide a boron diffusing material in which the diffusible time after the oxidation treatment is further extended.

  The present invention includes an Al2O3 component, a SiO2 component, and a BN component, the total content of the Al2O3 component and the SiO2 component is 20 to 80% by mass, the content of the BN component is 20 to 80% by mass, and Al2O3 / SiO2 The boron diffusion material is characterized by being composed of a ceramic sintered body having a molar ratio of 2.4 to 1.0 and an open porosity of 13 to 43%. The present invention also provides a mixture and / or compound containing Al2O3 and SiO2 components having a molar ratio of Al2O3 / SiO2 of 1.0 to 2.4, and 20% by mass of boron nitride. After the CIP molding of the mixed powder containing ˜80 mass%, it is sintered in a non-oxidizing atmosphere.

  According to the present invention, there is provided a boron diffusion material that further extends the diffusible time after the oxidation treatment.

  If the amount of boron oxide generated on the surface of the boron diffusing material by the oxidation treatment is small, the diffusible time until the next oxidation treatment is shortened. Therefore, the larger the amount of boron oxide produced, the better. However, it adheres to a jig such as quartz glass, and it becomes difficult to use it repeatedly. In the present invention, this problem is solved by setting the open porosity of the boron diffusion material to 13 to 43%. With this open porosity, boron oxide is generated up to the inside of the open pores, so the amount of generation increases, and since it is a porous body, the contact area with the jig is reduced and adhesion is reduced. When the open porosity is less than 13%, the amount of boron oxide produced decreases, and when it exceeds 43%, the deformation of the boron diffusing material during diffusion increases. The pore diameter is preferably 0.5 mm or less, particularly preferably 0.1 mm or less.

  The open pores in the present invention are pores in which one or both ends of the pores are open to the outside. The open porosity can be expressed by (saturated mass−dry mass) × 100 / (saturated mass−mass in water), and can be measured by Archimedes method.

  The boron diffusion material of the present invention contains 20 to 80% by mass of a BN component. Many of the BN components exist as BN. If the content of the BN component is less than 20% by mass, the amount of boron oxide produced by the oxidation treatment decreases, and if it exceeds 80% by mass, the amount of boron oxide produced becomes excessive and adhesion to silicon and jigs increases. Become. The preferred BN component content is 30 to 70% by mass.

  The Al2O3 component and the SiO2 component are contained in a total amount of 20 to 80% by mass. If this ratio is less than 20% by mass, the amount of boron oxide produced during the oxidation treatment will be excessive and the above-mentioned problems will occur, and if it exceeds 80% by mass, the amount of boron oxide produced by the oxidation treatment will decrease and diffusion will be possible. Time is shortened. The Al2O3 component and the SiO2 component are contained at a molar ratio of Al2O3 / SiO2 of 1.0 to 2.4. If this molar ratio exceeds 2.4, deformation during diffusion increases, and if it is less than 1.0, the diffusable time decreases. Particularly preferable contents of the Al2O3 component and the SiO2 component are 30 to 70% by mass in total, and the molar ratio of Al2O3 / SiO2 is 1.2 to 2.0. Al2O3 component and SiO2 component exist as 3Al2O3 · 2SiO2 and the like.

  The method for producing a boron diffusing material of the present invention includes a mixture containing Al2O3 and SiO2 components and / or a compound containing 20 to 80% by mass of Al2O3 / SiO2 molar ratio of 2.4 to 1.0, and nitriding. A CIP-molded mixed powder containing 20 to 80% by mass of boron is sintered in a non-oxidizing atmosphere. As the mixture containing the Al2O3 component and the SiO2 component, for example, a mixture of an Al2O3 component such as γ-alumina or α-alumina and an SiO2 component such as Aerosil or borosilicate glass is used, and a compound containing the Al2O3 component and the SiO2 component For example, mullite or the like is used. The contents of the Al2O3 component, the SiO2 component and the BN component of the boron diffusing material can be controlled by the ratio of the raw material blend. The open porosity can be controlled by the density of the CIP molded body. Since the conventional boron diffusing material is manufactured by a hot press method, a density distribution is generated, so that it is difficult to control the open porosity as in the present invention. Sintering of the CIP molded body is performed by holding at a temperature of 1400 to 1900 ° C. in a non-oxidizing atmosphere such as nitrogen, argon, or helium.

Examples 1-7 Comparative Examples 1-5
Boron nitride powder (BN purity: 99 mass% or more, average particle size: 7 μm), alumina powder (Al 2 O 3 purity: 99 mass% or more, average particle size: 0.2 μm), and borosilicate glass powder (purity: 99 mass) % Or more, composition: 90% by mass of SiO 2, 10% by mass of B 2 O 3, and average particle size: 2.1 μm) were mixed in the ceramic sintered body composition shown in Table 1 and mixed for 3 hours by a ball mill. This mixed material was subjected to CIP molding (molded body dimensions: outer diameter: about 150 mm, height: about 60 mm) using a rubber mold and sintered in a nitrogen gas atmosphere at a temperature of 1700 ° C.

Comparative Example 6
The mixed raw material was filled in a graphite die having an inner diameter of 150 mm, and hot press sintered at a temperature of 1600 ° C., a holding time of 4 hours, and a pressure of 12 MPa.

  A disk having a diameter of 125 mm and a thickness of 1.5 mm was processed from the obtained ceramic sintered body to form a boron diffusing material, and the open porosity, deformation amount, and diffusible time were measured. The results are shown in Table 1.

(1) Open porosity: measured by Archimedes method.
(2) Deformation amount: After the boron diffusion material was heated in an oxygen atmosphere at a temperature of 1100 ° C. for 1 hour, the deformation after heating in a nitrogen stream at a temperature of 1200 ° C. for 10 hours was measured with a gap gauge.
(3) Diffusion time: after heating the boron diffusing material in an oxygen atmosphere at a temperature of 1100 ° C. for 1 hour, the boron diffusing material and silicon are alternately arranged at an interval of 3.5 mm. Repeated diffusion tests were performed under the conditions of time, and after treatment with hydrofluoric acid, the layer resistance of silicon was measured by a four-probe method. The cumulative time before the layer resistance value changed to high was defined as the diffusion cumulative time.

The boron diffusion material of the present invention can be used for p ⁺ n junction, p ⁺ p junction devices, such as solar cells, inverters, and photodiodes.

Claims (2)

The Al2O3 component, the SiO2 component and the BN component are included, the total content of the Al2O3 component and the SiO2 component is 20 to 80% by mass, the content of the BN component is 20 to 80% by mass, and the molar ratio of Al2O3 / SiO2 is A boron diffusing material characterized by comprising a ceramic sintered body having 1.0 to 2.4 and an open porosity of 13 to 43%. The molar ratio of Al2O3 / SiO2 is 2.4 to 1.0, the mixture and / or compound containing the Al2O3 component and the SiO2 component is 20 to 80% by mass, and boron nitride is 20 to 80% by mass. The method for producing a boron diffusing material according to claim 1, wherein the mixed powder is sintered in a non-oxidizing atmosphere after CIP molding.