Simulations of consecutive diffusion process
Process simulation based on virtual reality can comprehensively present the real process on the computer. It can play an important role in the development and manufacturing field of diffusion furnace. This paper researches the establishment of consecutive diffusion process and the key techniques of process simulation. In the process of creating process simulation, V code would be created to control motion of each part. A simulation that reflects on the real process could be acquired with this research. This process simulation not only shortens the development time of diffusion furnace, but also makes designer have a perspective to the defects of product in the design process. It promotes the effective of design, and reduces changes in later period of design.
Advanced process control for furnace systems in semiconductor manufacturing
Traditional semiconductor manufacturing relies on statistical process control and human intervention as the fundamental method to change the process parameters to generate desired output. With the increase in demand for quality, yield, throughput, and performance, Advanced Process Control (APC) is needed to improve the manufacturing processes using run-to-run, wafer-to-wafer, within wafer and real-time process control. In this paper, multivariate, model-based APC system is developed using feed-forward and feedback mechanisms to automatically determine the optimal recipe parameters for each batch based on both incoming wafers and tool state properties. The APC methodology discussed in this paper mostly concentrates on diffusion batch processes. Primarily, it is implemented on the depletion processes such as Low Pressure Chemical Vapor Deposition (LPCVD) nitride. In addition to the traditional LPCVD nitride, APC models have also been tested and deployed on advanced Atomic Layer Deposition (ALD) nitride batch furnace systems. Implementation of APC includes process characterization and understanding of the reaction mechanism of each process. Effects of temperature, time and number of ALD cycles govern the fundamental equations of the model that determine the inputs for subsequent batch. The integration of Equipment Interface (EI), Mathematical Model and the furnace Tokyo Electron Ltd. (TEL) was pivotal for the success of the project. Significant improvement in run to run, lot to lot and wafer to wafer variation in thickness is demonstrated by implementation of APC. In addition to the process parameters, batch size effect is also considered for the APC roll out.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.