A Mark

Properties and performance of near-UV reflectivity control layers (RCL)

To overcome the limitations of two-component formulations, we have synthesized polymeric dyes which offer no or low bake processing and have suitable I line absorbance in films less than 100 nm thick. The polymeric RCL films are synthesized from absorbing dyes which are grafted onto polymers which are insoluble in the resist casting solvents. We have utilized amine dyes which are imidized onto polymeric backbones by a one step synthesis. The peak absorbance of the grafted dye after imidization undergoes a blue shift of about 30 nm and thus appropriate H line dyes are used to achieve I line peak absorbance.

Enhanced i-line lithography using AZ BARLi coating

A combined wet/dry develop process using AZR 7800 resist is described which achieves final resolution of 0.25 micrometer lines and spaces after transfer into the semiconductor substrate. The process utilizes AZR BARLiTM bottom coating both as an antireflective and as an etch enhancement layer. Features which are not resolved after the wet development step can be transferred linearly in the dry development step, which allows the introduction and removal of lithographic bias in a feature-size independent way. The resist process used employs very short bake times at high temperatures to achieve improved resist densification, which leads to substantial gains in thermal stability.

Process effects resulting from an increased BARC thickness

Process improvements attributed to the use of bottom anti- reflective coatings (B.A.R.C.s) are well documented. As our experience with these materials improves, so does our understanding of additional optimization. Recent supplier experiments suggest an increase in the thickness of AZR BARLiTM (bottom anti-reflective layer i-line) solution to reduce photoresist swing curve ratios. Also, changes in thin film stack on common substrates can adversely affect the degree of photoresist reflective notching. It is therefore of extreme importance to determine optimum thickness(es) of a B.A.R.C. material to ensure maximum process potential. We document several process effects in the conversion of a SRAM test device (0.38 - 0.45 micrometers) from a 650 angstrom to a 2000 angstrom BARLiTM film thickness using conventional i-line photolithography. Critical dimension (CD) uniformity and depth of focus (DOF) are evaluated. Defect density between the two processes are compared before and after etch employing optical metrology and electrical test structures. Sensitivity of overlay as a function of BARLiTM film thickness is investigated as well.

Sub-half-micron i-line photolithography process using AZ BARLi

A process using a bottom-side antireflective coating, AZ BARLi, has been studied for 0.50 micrometers and sub-0.5 micrometers features using I-line photolithography. Significant improvements were demonstrated for such process parameters as CD swing curve ratio, exposure latitude, and reflective notching of the photoresist. Extensive characterization was done on defects observed between the BARLi and photoresist coatings, and a process developed for their elimination. Factors which had significant effects on the observed number of defects, and their distribution, were the type of photoresist coat program used, solvent treatment of the BARLi surface, and a high temperature bake after photoresist coat. Data is presented for a complete process, which includes plasma etching the BARLi antireflective coating.

Planarizing BARC 0.32-μm i-line lithography process for the reduction of intradie CD variation

The effects of increasing bottom-side anti-reflective coating (BARC) thickness on the CD distribution within a device are presented. In conjunction with the increasing BARC thickness, reductions in the photoresist thickness are shown to be beneficial. Significant reductions in CD variability and increases in the depth of focus versus CD spread are achieved with increased BARC and reduced photoresist thickness. Although significant improvements are seen with a thicker BARC film for the photolithography process, the importance of optimizing the etch process for the thicker films is shown. The effects of CD distribution on important electrical device parameters are also presented.