METHOD OF ANODIZING SILICON SUBSTRATE AND METHOD OF PRODUCING ACCELERATION SENSOR

摘要

A method of anodizing a silicon substrate includes a step of forming an n-type silicon buried layer (21) of n-type silicon in a predetermined region in a first surface of a p-type monocrystalline silicon substrate (2). The n-type silicon buried layer (21) has at its central portion an opening (21a) for a current to flow. N-type silicon layers (4, 6) are formed on the surface of the p-type monocrystalline silicon substrate (2) and on the n-type silicon buried layer (21). Silicon diffusion layers (5, 7) containing p-type impurities at a high concentration are formed in predetermined regions of the n-type silicon layers (4, 6) and are in contact with the n-type silicon buried layer (21). An electrode layer (13) is formed on the back surface of the p-type silicon substrate (2). The anode of a DC power source (15) is connected to the electrode layer (13), and the cathode is connected to an electrode (23) opposed to the p-type silicon substrate (2). A current is made to flow concentratedly into a region corresponding to the opening (21a) of the n-type silicon layer (4) in the direction from the back surface toward the front surface of the p-type monocrystalline silicon substrate (2) immersed in a hydrofluoric acid solution, so that the region is turned porous.