Environment-friendly boron diffusion source formula

Abstract

The invention discloses a formula of an environment-friendly boron diffusion source. The formula comprises the following raw materials in parts by weight: glycol ether; diboron trioxide; the preparation method comprises the following steps: preparing a diboron trioxide / glycol ether solution from diboron trioxide and glycol ether, preparing an aluminum nitrate / glycol ether solution from aluminum nitrate and glycol ether, and preparing a boron diffusion liquid source from the diboron trioxide / glycol ether solution, the aluminum nitrate / glycol ether solution and alumina powder. According to the environment-friendly boron diffusion source formula, a silicon wafer is sequentially subjected to surface corrosion, surface oxidation, drying and polishing procedures, the silicon wafer is put into an etching solution of a hydrofluoric acid / nitric acid / water mixed solution system to react and then put into an alkaline solution to react at normal temperature, so that the surface concentration of the silicon wafer after diffusion is relatively high; the problem that the surface concentration is low due to the boron absorption effect of silicon dioxide after boron diffusion is solved, the uniformity of a silicon wafer after boron diffusion is good, and the problem that the boron diffusion source at a single position is low is solved.

Description

technical field [0001] The invention relates to the technical field of boron diffusion, in particular to an environment-friendly boron diffusion source formula. Background technique [0002] The boron diffusion process is to dope a certain amount of boron impurities into the silicon wafer crystal to change the original electrical properties of the silicon wafer. In the field of silicon-based semiconductor device manufacturing, boron diffusion is an important doping process. In terms of material form, the sources used to realize boron diffusion include gaseous sources, liquid sources and solid sources. [0003] The gaseous source generally chooses boron chloride with strong gettering performance, which can ensure that the silicon wafer has a high minority carrier lifetime, but the bond strength of boron chloride is relatively strong, requiring high decomposition energy, and the temperature for boron diffusion is as high as 960 Above ℃, it is easy to cause heat loss to the d...

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Problems solved by technology

[0003] The gaseous source generally chooses boron chloride with strong gettering performance, which can ensure that the silicon wafer has a high minority carrier lifetime, but the bond strength of boron chloride is relatively strong, requiring high decomposition energy, and the temperature for boron diffusion is as high as 960 Above ℃, it is easy to cause heat loss to the device, and the low-pressure condition requires an auxiliary vacuum pump, and the preparation cost is high; boron bromide is mostly used as a liquid source. In order to obtain a diffusion thin layer resistance of 150Ω / sq in a conventional method, the temperature needs to be 950°C Above, gaseous BCl 3 with liquid BBr 3 Reacts with oxygen at high temperature to form boron oxide (B 2 o 3 ) deposited on the wafer surface, due to B 2 o 3 It is liquid at the diffusion temperature, its uniformity is poor, and the surface concentration is low due to boron absorption by silica after boron diffusion