Preparation of SiC thin film from polyamic acid by the reaction with SiO gas and its shape and property control

制备方法：均苯四甲酸二酸酐与等摩尔芳香二胺、4，4‘-氧基二苯胺反应得到聚酰胺酸溶液，浇铸在玻璃板上，然后亚胺化。将得到的聚酰亚胺薄膜从平板上取下，在氩气或真空中与二氧化硅气体反应1h。亚胺化后的反应温度、反应时间和起始膜的厚度不同，β-碳化硅的形成依赖于该方法。在厚度为8μm的聚酰亚胺薄膜中，薄膜被完全硅化。形状控制：将聚丙烯酸酯溶液涂覆在几种不同形状的衬底上，并与二氧化硅气体反应制备出形状可控的碳化硅。由于亚胺化过程中收缩产生的应力，使得到的聚酰亚胺薄膜断裂。因此，虽然得到的碳化硅的形状继承了碳源的形状，但并不能得到形状可控的理想碳化硅。性能控制：在制备聚酰亚胺的过程中加入硼或镧，可以得到含杂元素的聚酰亚胺。将含杂元素聚酰亚胺薄膜与SiO_2气体反应，也可得到含杂元素的碳化硅薄膜。当温度达到400℃时，含镧碳化硅薄膜的电阻率随温度的升高而增加。

Preparation method : Polyamic acid (PAA) solution was obtained by reacting pyromellitic dianhydride with equimolar aromatic diamine, 4, 4' -oxydianiline, cast on a glass plate, and then imidized. Polyimide film obtained was removed from the plate and was reacted with SiO gas for 1 hour under Argon or in vacuo. By this method, beta-SiC was formed depending on thickness of the starting film, reaction time and heat treatment temperature after imidization. In the case of 8 μm thickness polyimide film, the film was silicidized completely.Shape control : PAA solution was painted on several substrates with different shapes and was reacted with SiO gas to prepare SiC with controlled shape. Due to the stress caused by shrinkage during imidization, polyimide film obtained was broken. Therefore, although shape of the SiC obtained succeed the shape of the carbon source, we can't obtained desired SiC with controlled shape.Property control : By adding boron or lanthanum during PAA preparation, we could obtained foreign element bearing polyimide. By reacting foreign element bearing polyimide film with SiO gas, we also could obtained foreign element bearing SiC film. Electrical resistivity of lanthanum bearing SiC film increases with an increase of temperature up to 400℃.