Charles R. Spinner

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.

Effect of lens aberrations as a function of illumination condition on full-field process windows

The effect of lens aberrations on the process windows of a 248 nm stepper is presented for multiple locations within the exposure field and for various illumination conditions. It is shown that the effect on the process window depends on the field location and the illumination condition. The common process window for multiple field locations is significantly reduced from the single location result. Process window data obtained with one illumination condition is shown to be useful in predicting results with other illumination conditions.

Minimizing photoresist dispense volumes on organic antireflective layers: the effects of chemistry and coating methodology on defect size and density

Preventing the formation of defects at the interface between an organic bottom-side anti-reflective coating and a photoresist is problematic with the use of these films. These defects have been attributed to different sources, such as mismatch of surface free energies, trapped water, etc., and have been shown to be highly dependent on the rotational speed of the wafer during the photoresist dispense step. Extensive work has also been done by most semiconductor manufacturers to reduce photoresist dispense volumes during wafer processing. Due to significant increases in photoresist cost for 248 nm lithography, this issue has become increasingly important. This paper shows that defect prevention and resist volume reduction can be accomplished with a fast, high pressure dispense of the photoresist.

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.

Monitoring process-induced oxide breakdown and its correlation to interface traps

In-line testing methods of thin gate oxide integrity are compared based on oxide breakdown characteristics. The results were obtained on test structures with plasma induced oxide degradation due to the different plasma based deposition and etch processes used in the five metal CMOS fabrication. Voltage ramp technique has been identified as the most sensitive and universal technique to investigate breakdown characteristics. In order to find out about the possible correlation between the degradation of oxide bulk and the Si/SiO2 interface, trap density in MOSFETs was also monitored using transconductance and charge pumping measurements. It was found that while interface degradation was indeed more severe in the structures showing lower breakdown voltages, no quantitative relationship with breakdown voltage could be established. Process-induced defect distribution across the wafers will also be discussed.

Effects of absorptive dye loading and substrate reflectivity on a 0.5-micron i-line photoresists process

The effects of an increasing amount of absorptive dye contained in a positive i-line photoresist were studied for a 0.5 micrometers process on two substrates with substantially different reflectivities. Parameters such as dissolution rates, focus latitudes, and resistance to reflective notching were simulated and compared to experimental results. Reductions in resist profile and focus latitude were observed as the photoresist non-bleachable absorbance was increased, and as the substrate reflectivity was decreased. It was also found that a reduction in substrate reflectivity was more effective than increasing the resist dye loading in suppressing reflective notching of the photoresist.

Characterization and performance of advanced i-line photoresists for 0.5-micron CMOS technology

ABSTRACT An evaluation procedure for advanced I-line photoresists is presented. The evaluation is compre-hensive in nature, including manufacturing and quality requirements as well as the usual patterningperformance tests. The evaluation is divided into three general categories: Performance, Manufac- turability, and Materials. These categories include a total of 23 individual performance tests and 15 evaluation criteria. A scoring method is described which assigns a numerical rating to the resistperformance. Weighting constants contained in this procedure can be adjusted to vary the emphasison particular measures of the photoresist performance. 1. INTRODUCTION The use of I-line illumination systems for production of devices with a critical dimension of <0.5zm is assured as the immediate future of the semiconductor industry. However, if one examines thegeneral equation relating the minimum feature size to wavelength and numerical aperture (NA):Minimum Feature = k1 * it is clear that a k1 factor of <0.7 is required for numerical apertures of 0.5 or less. A k1 factor of 0.8is often assumed for production systems. Key to the development of production-worthy systems arematerial and process improvements which make the use of a k1 factor of less than 0.7 more appropriate.Recent papers comparing photoresists typically concentrate on the patterning performance of theindividual resists.13 While this is a primary concern, it does not take into account factors which areimportant in a manufacturing environment. It is clear that if two photoresists have comparable resolu-tion and process latitudes, but one is 30% faster, the faster photoresist is preferred for manufacturing.Thus, a photoresist selection process should include additional criteria.We have developed a photoresist/developer evaluation procedure which combines the usual mea-sures of photoresist performance with two additional evaluation categories: Manufacturability andMaterials. In the following sections we describe the objectives and the structure of each of the cate-gories and discuss the quantitative scoring procedure for the evaluation.