Microloading effect in ultrafine SiO2 hole/trench etching

In the search of new etchant gas combinations which address the earth's env ironmental concerns, a new C3F6-based plasma etch chemistry is investigated and evaluated for patterning fine SiO2 structures. Trimethylsilane and O-2 are added first separately to C3F6 to investigate their respective influen ce. It is shown that both trimethylsilane and O-2 additive gases have benef icial effects on the hole etching process but also result in undesired effe cts such as enhancement of the microloading effect upon trimethylsilane add ition, and poor BPSG/resist selectivity upon O-2 addition. When trimethylsi lane and O-2 are combined and mixed with C3F6, the opening of fine deep hol es are achieved. For example, 0.15 mu m holes with an aspect ratio of 15 ar e fabricated using C3F6/8% trimethylsilane/20% O-2. The plasma conditions e mployed are a pressure of 10 mTorr, an rf source power of 500 W, a total fl ow rate of 30 seem, and a bias power of 150 W. These plasma conditions allo w good control of the hole size, practical resist selectivity for deep hole processing, and microloading-free etching of holes down to 0.15 mu m. The C3F6-based plasma etch performance is further evaluated for nanometer-scale patterns using the simpler C3F6/O-2 gas system. Line and space and mesh ho le patterns delineated by electron lithography are fabricated with dimensio ns as small as 20 and 70 nm, respectively. (C) 1999 American Vacuum Society . [S0734-2101(99)20804-4].