The oxidation on nickel silicide (NiSix) during plasma etching and oxygen ashing is investigated for stable contact resistance on NiSix. NiSix exposed by various processes is observed by X-ray photoelectron spectroscopy. The oxidation on NiSix is promoted by the fluorine that remains during etching and the oxide thickness on n+ NiSix is greater than that on p+ NiSix. The remaining fluorine after etching can be decreased by in-situ nitrogen plasma treatment during the post-etching process. Therefore, the oxidation progress with exposure to air and the difference in oxidation on NiSix between n+ and p+ can be suppressed.

Profile and dimension control mechanism in polysilicon gate etching is studied systematically by the use of two-dimensional (2-D) etching topography simulator, Reaction rates are calculated by taking into account interactions between incoming ion/radical fluxes and an ever-changing macroscopic adsorbed particle layer on the film surface. A qualitative guideline is presented for achieving both anisotropic etched-profile formation and the dimension difference minimization between the inner line pattern width w(i) and the outermost line pattern width w(e) in repeated line and space configuration, When w(e) > w(i) > w(m) (resist mask width), following two possible measures are necessay, One is to make gas pumping speed large for shortening the residence time of depositive radicals, The other is to make cathode temperature high for lowering sticking coefficient of depositive radicals, These are effective in-reducing the amount of deposited film especially at the Sidewall of external part of the outermost line pattern (SEP), Higher gas pressure is also effective in sputtering the deposited film especially at SEP.

The anisotropic etching of organic films such as anti reflective coating (ARC) and resist for dry development using inductively coupled plasma (ICP) was studied. In ARC etching, the controllability of critical dimension (CD) and the selectivity to underlayers were investigated for O-2 based gas chemistries by adding N-2, He, CHF3, Cl-2, HBr and SO2. The SO2/O-2 chemistry has the advantage of both the CD controllability and the selectivity to underlayers. Field emission Auger electron spectroscopy (FE-AES) analysis revealed that the SO2 gas is useful for sidewall protection due to the sulfur deposition. In dry development etching, the controllability of the etched profile was investigated. It was discovered that the Vpp (peak to peak voltage of RF bias) increases with increasing SO2 flow ratio to O-2 so that a recession occurs in the silylated layer due to high ion energy. A vertical profile was obtained for a 0.13 mu m pattern of resist and poly-Si optimizing SO2/O-2 gas chemistry.

We have studied what determines the silylation contrast for the liquid-phase silylation process in ArF excimer laser lithography. In the liquid-phase silylation, the diffusion kinetics is dependent on the concentration of the diffusion promoter, which acts as the relaxation of the polymer film. The silylating condition of a proper concentration induces the equilibrium state of relaxation and diffusion: Case II diffusion. It was found that the Case II diffusion condition resulted in a higher silylation contrast. Next, attention was paid to the photo-crosslinking density for improving the silylation contrast. The soft-baking temperature had an influence on the crosslinking density. The densification of the polymer film by soft-baking increases the photo-crosslinking density, but an extreme densification decreases it, when the soft-baking temperature is near glass transition temperature (T g). It is considered that the arrangement of the polymer chains is closely linked with the efficiency of photo-crosslinking.

Profile and dimension control mechanisms in poly-silicon gate etching are studied systematically by the use of a two-dimensional etching topography simulator. Reaction rates are calculated by taking into account interactions between incoming ion/radical fluxes and an ever-changing macroscopic adsorbed particle layer on the film surface. A qualitative guideline is presented for achieving both anisotropic etched-profile formation and the dimension difference minimization between the inner line pattern and the outermost line pattern in L&S

In this paper, we propose the use of Lissajous Electron Plasma (LEP)4) which is a low pressure, non-magnetic plasma generation process. LEP is fundamentally different from conventional triode plasmas in its unique use of a rotating electric field to produce cycloid-like electron trajectories. This paper describes the characterization of the plasma and demonstrates its usefulness to sub-half micron etching in comparison with a magnetron enhanced RIE (MERIE) process.

Requirements for metal etching in sub-half micron devices include precise profile and dimension control along with low charge related damage for gate oxides thinner than 10 nm. Lissajous Electron Plasma (LEP) is a new plasma generation method which provides a uniform low pressure plasma using a rotating electric field. Due to its low operating pressure, LEP achieves excellent profile control and high selectivity without using polymer forming gases. In addition, generation of a low pressure plasma with a non-magnetic configuration, which is a distinctive feature of LEP, results in damage-free etching in CMOS devices.<>

A new concept for plasma generation which enhances plasma density at low pressures through the use of a high-frequency rotating electric field is introduced. A 50-MHz electric power was applied to three electrodes which are positioned with a triangular symmetry. A phase shift of 120° between the electrodes brought about uniform and high plasma density at a pressure of 1 Pa. The nonuniformity of Ar gas plasma generated was within 10% over a 6” wafer using a tuned Langmuir probe electron density measurement. Polysilicon etchings were made by both SF6/O2 and Cl2/O2 plasmas. The achieved polysilicon etch-rate was over 200 nm/min for both kinds of plasmas at an electric power of 90 W along with a 13.56 MHz RF bias power of 30 W applied to the substrate. High etch-rate selectivity between polysilicon and oxide of 45 for SF6/O2 and 152 for Cl2/O2 was realized. A very low etch-rate nonuniformity of 1.5% was attained for Cl2/O2.