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外延生长时需要高纯氢气,要求露点至少为-70℃,含氧等气体总量<1ppm,含尽可能少的灰尘。为此,需要净化氢。可以通过各种方法达到净化目的。目前国内一般方法还是用分子筛和105型催化剂来净化氢。这个方法是简易的但有不足之处,有些杂质气体不能去除,如氮、一氧化碳和碳氢化合物等。105型催化剂与氢气中杂质氧气作用生成水,水分子附在105型催化剂的表面上逐渐地使催化剂表面钝化,如果不及时再生处理则对氢净化是极不利的。有人以无机化合物进行脱水净化氢,但这些化合物在硅器件生产中是有害的。例如:用NaOH和P_2O_5进行脱水,其中Na~+等杂质对沾污硅半导体材料方面是极其有害的。鉴于这种情况,我们一直采用钯合金扩散法来净化氢。
High-purity hydrogen is required for epitaxial growth and requires a dew point of at least -70 ° C. The total amount of oxygen-containing gas <1 ppm contains as little dust as possible. For this purpose, hydrogen needs to be purified. Purification can be achieved through various methods. At present, the general method is to use molecular sieve and type 105 catalyst to purify hydrogen. This method is simple but has some drawbacks, some impurities can not be removed gas, such as nitrogen, carbon monoxide and hydrocarbons. Type 105 catalyst reacts with oxygen in hydrogen to form water. Water molecules attach to the surface of Type 105 catalyst gradually passivating the catalyst surface, which is very detrimental to hydrogen purification if not regenerated in time. Hydrogen is dehydrated and purified by inorganic compounds, but these compounds are detrimental to the production of silicon devices. For example: dehydration with NaOH and P 2 O 5, in which impurities such as Na ~ + are extremely detrimental to the contamination of silicon semiconductor materials. In view of this situation, we have been using the palladium alloy diffusion method to purify hydrogen.