Marina V. Plat

Application of ion chromatography to failure analysis of electronics packaging

Abstract Ionic contamination is a frequent cause of corrosion failures in electronics packaging. Ionic Cl − , SO 2− 4 , Na + and K + are the species most frequently associated with corrosion and are easily detected by ion chromatography (IC) or other surface analysis techniques (XRF, EDX, etc). This paper will describe a corrosion problem, involving gold-plated copper wires and an automated wire bonding operation, and its solution using IC and Fourier transform infrared (FT-IR) analysis, which showed that the corrosion was caused by ionic NO 2 − and NO 3 − , species which are not easily detected by other surface analysis techniques.

Lithography using ultrathin resist films

The industry trend toward higher numerical apertures and lower k1 factors is severely constraining the manufacturing process margin for current and future lithography technologies. Ultrathin resist (UTR) films and other thin layer imaging techniques offer the promise of improved process margin as compared to conventional single layer resist schemes. In this study, an UTR over hard mask process was used to pattern the transistor gates of a high performance microprocessor using 248 nm lithography while focusing on four key areas of concern for UTR films: resist film defectivity, response of thin resist to device topography, quality of pattern transfer on device wafers, and device yield comparable to a baseline process. The intrinsic defectivity of resist films as thin as 65 nm is found to be no greater than that of a >500 nm resist film on flat silicon wafers. No pinhole defects are observed during scanning electronic microscopy review of defects on as-coated UTR films. As expected, the UTR process is sensi...

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.

Shot-size reduction of photoresist formulations

The cost of expendable chemicals in the resist process is increasing and with this the economic impetus to conserve usage. The volume of liquid resist dispensed (shot size) determines the consumption rate and disposal volumes of liquid resist. The choice of resist solvent can influence the shot volume. Three formulation factors influence the shot size: (1) the surface tension of the resist and the interfacial energy of the coating surface, (2) the viscosity of the resist formulation, and (3) the evaporation rate of the solvent. The suitable resist formulation and subsequent solvent choice should be of the lowest surface tension and lowest viscosity and be balanced by an evaporation rate which allows a minimum shot volume to be spread on the surface without significant solvent loss. Of all the solvents examined, ethyl 3-ethoxy propionate (EEP) gave the lowest shot size relative to the old resist solvent standard of 2- ethoxy ethyl acetate (ECA).

TAR processing for CD control in I-line and 248-nm lithography

The combination of dyed photoresist and top antireflection (TAR) coatings was applied to I- line and deep-UV lithography on polysilicon. Optimization of the resist layers absorption and application of the TAR process significantly improves CD control of submicron gate level lithography.

Formulation and modeling of dyed positive i-line resist for control of the reflective notching and CD variation

This study evaluates the effect of dyes, including photosensitive dyes, on resist performance such as: swing curve reduction, resist dissolution rate, resolution, dose and focus latitude, scumming, etc. The paper demonstrates good correlation between modeling of the dyed resist performance and experimental results.

Characterization Enhancements in Resist Photospeed

Current photospeed testing methods are based on dose to clear (E 0 ) or resist contrast (γ 10 ). Either method is inadequate for controlling sensitivity to within ±1.5%. We investigated various methods for improving these photospeed tests. Ranked in order of decreasing importance are: (i) controlling standing waves (reflectivity); (ii) choice of developer, (iii) develop time; and (iv) exposure pattern. Reflectiuty can be controlled by careful attention to resist thickness, addition of a bottom antireflective layer, addition of a low refractive index layer (AquaTar), or by using a thick photoresist. Moreover, we can utilize the whole dissolution curve rather than the one-point determination of the E 0 test