Steve Seiichi Miura

Reduction of linewidth variation over reflective topography

As device dimensions have shrunk well below the one micron level, linewidth control particularly over reflective topography has become a major problem in optical lithography. Other than reflective notching caused by light reflected into unwanted areas, thin-film interference is the major contributor to linewidth variations. Small changes in film thickness over steps cause significant changes in the amount of energy deposited into photoresist films. Various methods used to solve this problem are investigated to measure their relative effectiveness. Conventional photoresist, dyed-resist, bottom layer ARCs (antireflcctivc coatings; both inorganic and organic), TAR (top-antircflcctivc layer) and CEL (contrast enhancement layer) as a special case of TAR arc compared for their relative effectiveness as well as their advantages and disadvantages for use in manufacturing. Simulations and functional evaluation of film thickness effects on exposure requirement and on linewidths as well as imaging over topography are used as a means of comparison. The use of TAR is a relatively new approach to solving this problem in a simple, effective manner. Material choice depends on film refractive index and ease of processing. Several TAR materials have been investigated and will be discussed.

Design of a bottom antireflective layer for optical lithography

The advent of deep-UV(DUV), chemically amplified, acid catalyzed photoresists as successors to positive diazoquinones photoresists has brought about a new set of process environment concerns directed towards all materials in contact or absorbed by the photoresists. In addition to the application of DUV bottom anti-reflective coatings (BARCs) to suppress optical reflection and subsequent linewidth distortion, we must consider the properties and interaction of the BARC layer with the labile photoacid of the latent image. In this regard, we have examined the physico-chemical aspects of the DUV BARC with regards to acting as a barrier layer to substrate poisoning, and as an optical absorbing layer that does not interact and/or distort the deep-UV profile. Various single component polymeric BARCs were synthesized and examined. Considerations will be discussed of the optical absorbance, the coating quality, dry etch rate, and the impermeability of the BARC layer to photoacid diffusion to fulfill the performance requirements of BARCs for DUV lithography.

New negative tone resists for subhalf micron lithography

Abstract New crosslinking type resist systems are described which use benzylic carbocation precursors carrying phenolic hydroxy group. The special feature of the new resists is the versatility of applications, ease of synthesis, high sensitivity, high contrast and a large process window. One such resist system has been used successfully in the back-end-of-the-line personalization for manufacturing advanced bipolar devices which required an exceptionally large process window. The new resist system is a promising candidate for surface imaging as well as for I-line, DUV and X-Ray applications.

Novel DNQ PACs for high-resolution i-line lithography

The use of i-line lithography for the 16 to 64 Mbit DRAM device generations calls for increased performance of i-line resists. This paper reports on investigations on novel sensitizers for advanced i-line lithography, starting out with a discussion of general design criteria, then discussing methodology and results of a screening phase, and examining in greater detail a small number of selected candidates for which resolution, exposure latitude, and depth-of-focus data were obtained. Finally, a new advanced resist for i-line lithography, AZR 7500, is presented, and its performance is evaluated in terms of the above criteria as well as thermal flow resistance.

Efficient numerical simulation of high-NA i-line lithography processes

Numerical algorithms employing the ID imaging model and the 2D wave-guide scattering model were implemented to achieve high speed in simulating high NA i-line processes. The CPU consumption and the range of validity of the models used were discussed. The simulator was applied to study the possibility of imaging 0.35/mi lines and spaces(L/S) utilizing lenses of NA=0.55, 0.60 and 0.65 and single layer resist (SLR) processes.