EFFECTS OF PROCESS CHEMICAL PURITY ON MOS CAPACITOR ELECTRICAL PARAMETERS.

MOS grade chemicals are supplied with extensive specifications which mean little to the integrated circuit fabricator since there is no indication as to which impurities are important and what type of degradations may occur. The electrical effects of iron, chromium and calcium are assessed with MOS capacitors. The elements are added as trace quantities to 5% HF which is used as the final step in a pre-oxidation clean. It is shown that the addition of Ca has no measureable effect while Fe causes a high fixed oxide charge density and high level of mobile ions whereas Cr causes a lowering of minority carrier generation lifetime.