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As the semiconductor industry moves into deeper sub -quarter micron regime, minimization of post develop process defects is of paramount significance in manufacturing environments. Reduced defect levels can significantly increase the yield in production, resulting in substantial cost savings and also reduce time to market of new devices. Typical approaches to reduce defect levels include extension of the DI (De-lonized water) rinse time immediately after completion of photoresist development, use of multiple rinse steps and variable rinse spin speed. However, many of these penalize the process throughput. The uniqueness of this project was the use of enhanced rinse hardware with a mechanistic understanding and characterization of defect generation for an advanced DUV resist.Numerous studies have identified the development step as the source of the majority of the post-development particles and residues. Thus improving the development-and-rinse step can potentially reduce particle contamination. Defect reduction was accomplished thorough process characterization of defect sources and also through implementation of enhanced rinse hardware. Our enhanced hardware provides an improved rinsing action and a more uniform coverage and reduces the impact forces near each orifice through its optimized geometry. A partial-six factor DOE (Design of Experiment) was implemented with a resolution of first order terms and 2nd factor interactions. Factors examined included rinse spin speed, rinse time, acceleration during dry cycle, nozzle type, rinse time algorithm and chemical injection time The processing system was an advanced SVG Track clustered with a Micrascan II system. This project successfully characterized defect density performance and located the lowest defect level and shortest rinse time from a develop process standpoint, without any impact on CD's. The defect density levels were reduced by a factor of 7 and the develop process time was reduced by 23 %. This was qualified for 0.2-micron defect sizes and larger which is applicable to .25 micron lithography. The yield impact of this defect reduction for killer defects is significant cost savings. In addition, the reduced develop process time can significantly increase the throughput because the develop process is the rate limiting step in a Track system.

The effect of varying time and temperature profile at the PEB step on a 250 nm isolated line is studied for an Acetal and an ESCAP type Deep UV (DUV) resist. Experimental studies on the Acetal resist resulted in very non-linear Critical Dimension (CD) sensitivities with CD variation largest for low Post Expose Bake (PEB) temperature and short PEB time. A global CD model was created by fitting experimental data to a first order kinetics equation. An effective activation energy of 50 Kcal/mole was obtained for the Acetal resist whereas PROLITH simulations for an ESCAP type resist gave 69 Kcal/mole. These results are consistent with the well-documented diffusion-controlled deprotection reaction taking place during the PEB process. The global CD model was then used to investigate the impact of transient and steady-state temperature profiles on CD control. In order to achieve this goal, actual 2 dimensional wafer temperature profiles were input to the global CD model and PEB-induced CD variation was calculated during each sampling period of the 1 7 temperature readings across the wafer as a function of time. The resultant time-evolution of the PEB-induced CD variation was used to infer the relative importance of the transient and steady-state component of temperature profiles.At the low PEB temperature of 90°C for the Acetal resist, transient effects dominate for a nominal 90 second process. Slower deprotection reaction yields large CD's at 356 nm and predicted PEB-induced CD variation of 6.9 nm. At 100°C, transient effects are less prevalent but still present. Tight steady-state and transient temperature uniformity along with wafer-wafer temperature profile repeatability and stringent control of process timing and delays are important. At I 10°C, transient effects are dominant early in the process and they are completed within about 50seconds in this model. However as photoacid is lost to competing reactions and the time necessary for deprotection is extended, even in this case transients could still play a part in final CD results. In general, both mean CD and CD variation results improve with increasing PEB temperature for a 90 second PEB time. PROLITH simulations using ESCAP resist parameters and actual measured CD profiles both support these model predictions. Improved resist formulations along with advanced photoresist processing tool layout, wafer-handler scheduler and PEB module designs are all necessary ingredients for minimum PEB-induced CD variation.

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