The BCT solution is an automatic correction for systematic offset built into the PCS product based on calibration from 2-5 wafers. This paper explores the validity of a predictive model for process control for use by manufacturers of semiconductor devices with a multitude of products or part numbers. The proposed model defines the parameters of interests as a function of the film stack, tool attributes, and mask characteristics. The paper proposes a process for model development that dramatically reduces the cost of materials, tool time, and engineering effort.
The need for process control in the semiconductor industry has been established and the benefits have been demonstrated. In the past, process control applications in the semiconductor manufacturing have relied on univariable control schemes. In the case of poly gate etch control methods have manipulated trim time or O2 flow to maintain a target poly gate FI CD target as the input DI CD varies. This study focuses on the impact of process control on secondary output goals and compares the effect of univariable control with that of multivariable control. There are two important conclusions for semiconductor manufacturers: (i) univariable control schemes sacrifice secondary control goals when trying to achieve the primary control goal and (ii) manufacturers must adopt multi-input multi-output control schemes to actively control both secondary process goals and primary control goals.
Studies on photomask Cr and MoSi etch processes were carried out and etch kinetics and modeling were performed. The photomasks were etched using an AMAT Centura II DPS and compared with a Unaxis VLE 770 ICP etcher. Mask metrology to support theoretical suppositions was performed on several tools: a KLA-Tencor P-12 profiler was used for depth measurement, while the KLA-Tencor 8250XP-R SEM was used for CD metrology and process characterization. The Toshiba EBM3500 50KeV writing system on positive chemically amplified resist was used for pattern creation. Cr and MoSi loading - etch rate equations were theoretically proposed and experimentally tested. It was found that the calculated Cr and MoSi etch rates agreed well with the experimental results. The equations can be used for etch time calculations and endpoint determinations of extremely low Cr load photomasks. Cr and MoSi local etch rates versus local loading on one photomask were studied and kinetic equations were proposed, showing good agreement with experimental results. Cr and MoSi etch CD movements versus local load on one photomask were also investigated. It was found that load effects on Cr and MoSi etch CD movements could be controlled in opposite directions and then a compensation consideration was proposed in MoSi optimization instead of using a point-to-point 3σ as the optimization parameter. By using this compensation method, the final MoSi CD unformity of 100-110 nm technology node photomasks is in the range of 8.5 to 10.1 nm. This final CD uniformity is similar to those etched using VLR 770 ICP etcher.
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