Atsushi Saiki

Advanced planar metallization with polymer for VLSI

An advanced planar metallization technology has been developed that makes use of PIQ®(a polyimide type resin from Hitachi Chemical Co.). This technology employs a novel taper control etching approach for fine via holes, a sputter cleaning for low via hole contact resistance, and an A1 RIE for fine metallization patterning. Taper-controlled via holes in thick PIQ film satisfy demands for both minimizing via hole area and maintaining reliable step coverage in overlapping metallization at via hole steps. Appropriate sputter cleaning conditions accomplish low via hole contact resistance, eliminating undesirable influences on the polymer surface. Full use of RIE for both first and second metallization, in combination with taper control etching, provides 5\microm pitch metallization. This technology, because of its excellent planarization and newly developed techniques, is shown to be applicable to highly packed multi-level interconnections for future VLSIs.

Quantitative Analysis of Trace Hydrogen in Highly Purified Nitrogen Gas Using Rapid Reactions in Atmospheric Pressure Ionization Mass Spectrometer

Quantitative analysis of trace hydrogen in highly purified nitrogen gas for the semiconductor fabrication process was investigated using an atmospheric pressure ionization mass spectrometer (APIMS). A previous method wherein the sample gas is directly introduced into the APIMS is not capable of providing high-sensitivity measurements for hydrogen in nitrogen gas. By mixing 20% argon gas with the sample gas, the sensitivity was increased to ten times that of the previous method. This is due to the occurrence of a previously unreported rapid reaction through which the quantity of hydrogen ions is increased: (N2Ar)++H2→N2H++H+Ar. The detection limit in this method and the rate constant for this reaction were estimated to be 40 ppt and 1.4×10-10 molecule-1 cm3 s-1, respectively.

High packing linear integrated circuits using planar metallization with polymer

A linear IC for the TV chroma systems has been packed on a 2.34×2.36mm2chip using a two-level interconnection with Planar Metallization with Polymer (PMP) technology, and is packaged by plastic direct molding. The chip area of this device is reduced about 40% as compared to the conventional device with the sam function. Advanced PMF technique makes it possible to realize this linear IC with high yields and high reliability. In this technique; (1) Purified PIQ (a high heat resisting polyimide, Na 0.5ppm) is used for insulating layers. (2) A special solution of hydrazine-hydrate has been developed to etch the PIQ layer to form via-holes down to 3×3µm. Yield of via-hole contact proved to be over 99.9998%. (3) PMP makes it possible to place the pads for thermo-compression bonding on the active region of the device. (4) Pinhole density of the PIQ layer is less than 0.05/cm2. Failure of interconnection has not been observed in the reliability test.