In this paper, we will demonstrate a novel approach to improve process window prediction capability. The new method, Lithography Manufacturability Check (LMC), will be shown to be capable of predicting wafer level CDs across an entire chip and the lithography process window with a CD accuracy of better than 10nm. The impact of reticle CD error on the weak points also will be discussed. The advantages of LMC for full chip process window analysis as well as the MEEF check to catch process weak points will be shown and the application to real designs will be demonstrated in this paper. LMC and MEEF checks are based on a new lithography model referred to as the Focus Exposure Matrix Model (FEM Model). Using this approach, a single model capable of simulating a complete range of focus and exposure conditions can be generated with minimal effort. Such models will be shown to achieve a predictive accuracy of less than 5nm for device patterns at nominal conditions and less than 10nm across the entire range of process conditions which define the nominal process window. Based on the inspection results of the full chip LMC check, we identify process weak points (with limited process window or excessive sensitivity to mask error) and provide feedback to the front end design stage for pattern correction to maximize the overall process window and increase production manufacturability. The performance and full function of LMC will also be described in this paper.
We have developed an 80nm poly gate patterning process for 0.13 micrometers VLSI manufacturing using 248nm lithography with double-exposure phase-shifting technique. We show that: Systematic intra-field line width variation can be controlled within 6nm (3(sigma) ), and total wafer variation across the wafer held to within 10nm (3(sigma) ), with good line-end shortening control for gate endcaps. The k1 factor is < 0.2 (80nm target gate length in 320nm pitch).
Manufacturing of reticles, which combine both OPC and PSM, is becoming more and more challenge. Materials cost is high, several accurate writing processes are needed and repair is almost impossible. This makes inspection a critical and very complicated process. This study describes an inspection of a test vehicle consisting of 55 cells targeted for sub- wavelength design rule technology. This study describes an inspection of the 55 cells test plate targeted for 0.17 micrometer design rule technology. The plate is written on a MoSi layer with 18% transmission for 248 nm lithography. The MoSi has higher transmittance in I-line and G-line that reduces the contrast between the MoSi and the glass (relative to the usual contrast in binary plates). The technique for inspection by Applied Materials RT8000ES 436nm die-to-database is described. The technique is based on expansion of the reduced dynamic range of gray level that results from the lower contracts, re-gaining the inspection capability. This paper reviews the results of G-line versus I-line inspection of high transmission PSM and describes the method of the sensitivity verification including CD defects analysis.
Off-axis illumination (OAI) has been shown as one of the most practical resolution enhancement techniques (RET) available for optical lithography. A customized off-axis illumination aperture filter (CIF) was designed to gain the benefits of OAI and keep the optical proximity effect (OPE) in a manage-able range for sub-0.18micrometers line and space patterns. The performance of the filter comparing with conventional, annular and quadruple illuminations in term of depth of focus, OPE, throughput, dose and power uniformity for both 0.18micrometers and 0.15micrometers NA Nikon KrF excimer laser stepper with a maximum partial coherence factor of 0.8 is presented in the paper. A brief description of the design principle of the filter is also given. A summarized conclusion on the weakness of the filter and possible improvements is also presented in the paper.
Finding high performance and low cost anti-reflection strategies is a common goal for all photolithographers. This task is getting tough for dual damascene process than the metal-etch process because the oxide thickness variation enhances the thin film interference effect. In this paper, different ARC strategies using organic and inorganic material were examined to compare their CD control performance in sub-0.81micrometers dual damascene structure for KrF 248nm lithography. The organic bottom ARC (BARC) achieves reflectivity control through modulation its thickness. The first and second minimal points in BARC swing curve were chosen as the film thickness to be evaluated. The inorganic ARC, which referred to dielectric ARC (DARC) using PECVD silicon oxynitride in this article, was investigated with single layer and double layers structures. The double- layer DARC structure consists of two layers with different extinction coefficient K values. The optimal refractive index and thickness of each ARC structure were calculated from some available photolithography simulators. A PECVD process for DARC growth that provides easily tunable range of refractive index and thickness was established to meet the DUV process requirement from simulation. The performances of each ARC structure were evaluated on patterning 0.18 micrometers trench and 0.20 micrometers via in back-end- of-line dual damascene process. It showed that the double- layer DARC provided the most effective CD control ability among these ARC structures. The double-layer DARC should be one of the most potential candidates for sub-0.18 micrometers dual damascene process.
It is very easy to manipulate the optical proximity effect (OPE), when the new concept of the post-exposure bake (PEB) processing is suggested. By changing the temperature of the PEB, the bias of the line width between the packed lines and the isolated line varies drastically. The OPE is thus faithfully controllable through the PEB processing. On the other hand, by putting the experimental data in contrast with the theoretical simulation, the OPE is resolved into the resist effect and the optical effect. The resist effect could be eliminated by lowering the PEB temperature, while the optical effect is reduced from choosing a proper stepper illumination setting, NA & (sigma) . Moreover, the linearity and the line-end shortening also get benefits from this new process.