Study of Dry Photoresist Stripping Processes for Hydrogen Silsesquioxane Thin Films
- PDF / 366,877 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 219 Views
STUDY OF DRY PHOTORESIST STRIPPING PROCESSES FOR HYDROGEN SILSESQUIOXANE THIN FILMS HUEY-CHIANG LIOU1, JERRY DUEL1, VICTOR FINCH1, QINGYUAN HAN2, PALANI SAKTHIVEL2, AND RICKY RUFFIN2 1 Semiconductor Fabrication Materials, Dow Corning Corporation, Midland, Michigan 486860994; 2Fusion System Division, Semiconductor Equipment Operation, Eaton Corporation, Rockville, MD 20855-2798 ABSTRACT The impact of dry stripping process chemistries on the selective removal DUV photoresist (PR) in the presence of hydrogen silsesquioxane (HSQ) have been studied along with HSQ film properties in order to develop a new, effective process to minimize changes in HSQ during the PR stripping processes. The results show that oxygen-free gas mixtures, specifically H2/N2 gas mixtures, have the best combination of PR:HSQ ash selectivity and minimized changes in HSQ films. However, gas mixtures containing CF4 or O2 greatly reduce PR/HSQ ash selectivity. The process temperature is another parameter that strongly influences ash selectivity. While the higher ash temperature greatly enhances selectivity in oxygen-free gas mixtures, the ash selectivity is only marginally enhanced with increasing ash temperature in the presence of O2. Furthermore, the k-value of HSQ suffers in the presence of O2 due to the oxidization of HSQ films. The data also shows that lower pressure will help to increase ash selectivity. In this study, processes have been demonstrated, which yield a PR:HSQ selectivity greater than 150, while maintaining the dielectric constant of HSQ at 2.8. INTRODUCTION As the minimum geometry of ultra large scale integrated (ULSI) devices moves toward below 0.2 µm, implementation of low k dielectric materials in the fabrication of these devices is needed to reduce the intraline capacitance between metal lines and to increase the signal propagation speed [1]. Among all available low k materials, hydrogen silsesquioxane (HSQ) has attracted attention in the semiconductor industry due to its lower dielectric constant (k < 3.0, after cure), ease of processing, excellent gap fill and excellent planarization capabilities. In addition, HSQ has been used in production for 0.35-0.5 µm devices [2]. However, one of the challenges in applying HSQ in < 0.20 µm devices is the photoresist (PR) stripping step due to possible interactions between stripping chemistries and HSQ films and, therefore, change its dielectric properties. The general chemical composition of HSQ before curing is (HSiO3/2)n and a representative molecular structure is shown in Figure 1. From the infrared spectrum, it has been shown that HSQ consists of random network linkages based on the eight-corner H8Si8O12 structure [3]. When thermally processed, the bonds in HSQ break and its molecular structure is rearranged/redistributed into an amorphous film with more network bonding. It has been known that HSQ films are sensitive to the amine based PR stripper used in wet PR stripping processes and to O2 used in the traditional O2 downstream plasma stripping processes [4-5]. The HSQ film shrinkag
Data Loading...
