Overcoming the limitations of Al metal line patterning technology without damascene process
Etch patterning process using Al wiring is technical challenging in sub-280 nm pitch devices especially when Cu damascene process is not available in 8 inch wafer semiconductor fabrication facilities. However, some of the CMOS image sensors (CIS) at our company are designed to meet back end of layers (BEOL) minimum design rule (DR) of 200 nm pitch (Bar/Space 100/100nm) without damascene process. In addition to meeting the pitch requirement, the vertical profile of the metal 1 should be suitable for the characteristics of its optical sensor. If we cannot perform the metal 1 layer module process and patterning implementation, the optical attribute called Brightness(Y) Signal to Noise Ratio (YSNR) will decline, which is the most important part of the product. Moreover, electrical attributes and yield requirements cannot be achieved. Fig. 1. and 2. show the top and vertical view of the present CIS metal 1 profiles. In this paper, we optimized etch module process to realize fine metal pattern of CIS products which are based on Al wiring in 200nm pitch without using damascene process.
Effects of BCl3 gas on physical damage and Al residues in oxide hard-mask-based Al etching
This paper presents the effects of BCl3 additive gas on physical damage and the prevention against damage in oxide hard-mask-based Al etching. The BCl3 addition in the TiN/Ti break-through step effectively passivated the sidewall against the upper TiN/Ti notching damage; however, the TiN/Ti profile was easily distorted under excessive BCl3 added. The Al bottom notching depth decreased with decreasing BCl3/Cl2 ratio in the Al over-etch step. As the BCl3/Cl2 ratio is less than or equal to 0.625, the Al bottom notching was eliminated. Nevertheless, the low BCl3 addition in the Al over-etch step would result in increasing Al residues because insufficient passivation at low BCl3 flow cannot effectively protect the semi-iso Al sidewall from attack of Cl atoms, and insufficient ion bombardment at this low BCl3 cannot remove those residues around the damaged sidewall. An optimized condition achieves both notching-free and residue-free profiles.
Development of an Analytical Method for Explosive Residues in Soil
Abstract : An analytical method was developed to determine the concentrations of HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT in soil. The method involves extracting a 2-g sample with 50 mL of acetonitrile using an ultrasonic bath procedure for 18 hr. A 10-mL portion of the extract is diluted with 10 mL of water, filtered through a 0.45-micrometer Millex SR filter, and analyzed by RP-HPLC using a fixed 254-nm UV detector. Separations were obtained on an LC-18 column eluted with 50:50 water-methanol. Retention times were 2.55, 3.82, 5.16, 6.25, 7.04, 8.47 and 10.15 min for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT, respectively. Confirmation of analyte identities is recommended by RP-HPLC on an LC-CN column using 50:50 water-methanol. Kinetic studies using naturally contaminated soil indicated that equilibrium was achieved within 24 hr for the majority of soils and analytes studied. The method provides linear calibration curves over a wide range of concentrations. Reporting limits were conservatively estimated at 1.6, 1.8, 1.5, 0.5, 5.5, 0.8 and 0.8 micro grams/g for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT. Analytical precision was estimated at + or - 0.44, 0.51, 0.43, 0.13, 1.24, 0.27 and 0.20 micro grams/g, respectively, in the range of homogeneous variance near the detection limits. At higher concentrations the relative standard deviation was constant at 2% for HMX, RDX, DNB and TNB, 3% for TNT and 2,4-DNT, and 6% for Tetryl.