半导体晶圆清洗站多化学品供应系统的讨论

Abstract: A multi-chemical supply system is developed and applied to a wet station, which uses the multi-chemical process in one  bath. To control the concentration of two chemicals, control logic of a supply pump is programmed using the programable logic  controller (PLC). By using the multi-chemical supply system, wet station with single bath is applied to cleaning process using multi chemicals such as buffed oxide etchant (BOE) and standard clean 1 (SC-1). The concentration of each chemical is measured in the bath to verify the multi-chemical supply system. The control range in the each chemical concentration is measured to 1.33weight% in NH4OH and 0.23weight% in H2O2. The multi-chemical supply system can be movable and usable as an independent module of fixed wet station. By simply midifying the PLC, a multi-chemical supply system can be developed for a wet station.

Wet clean/etch process in the semiconductor manufacturing industry is used to remove the particle or defect on the wafer by cleaning or etching using high pure chemicasl. There  are pre-cleaning before diffusion, photo, and chemical vapor deposition (CVD), strip, etching, polymer treatment, cleaning  and spin scrubbing as the wet clean/etch process. Cleaning process is conducted before or after the main technologies of semiconductor wafer process. The particles and defects on the  wafer are generated during the super large scale integration (LSI) manufacturing process. The control of particles and defects on the silicon wafer is a main target to increase the packaging yield. In semiconductor manufacturing process,  removal of particle is only possible by the cleaning process.  From this perspective, cleaning process is repeatedly appeared in the main manufacturing process flow. With a smaller pitch of circuit patterns and higher density of large-scale integration (LSI), effect of particle and micro-contamination on the wafer  has been studied to increase the packaging yield . Wet station for wet clean/etch process is configured with wafer loader/un-loader, chemical bath, over flow rinse bath and dryer. Depending on the purpose of cleaning process, chemical and rinse bath has multi configuration to supply  several chemicals. The cleaning process in a multi-bath wet station is conducted sequentially according to combination of each chemical at each bath for removal of cleaning object. By combination of multi-bath layout, the station has large footprint. By an increase in the wafer size from 8inch to 12inch, the space occupied by the station is dramatically increasing. Therefore, a single bath systems using multi-chemical in one bath is increasingly demanded.

In this paper, multi-chemical supply system is developed and applied to wet station, which is using the multi-chemical  process in one bath. The multi-chemical supply system has  two chemical bottles, pneumatic system, two supply pumps,  capacitance sensor, chemical analyzer, and programmable logic controller (PLC) unit. To control the concentration of two chemicals, supply pump control logic is programmed using the PLC.

Fig1

A wet clean process using multi-chemical in one bath is  required according to an increase in the wafer size. A  multi-chemical supply system is developed for wet clean process in one bath of Sankyo wet system. The operation procedure of multi-chemical supply system is shown in Fig. 3. By a power switch operation signal, the chemical supply system is checked. By a chemical supply start signal, a supply  pump is operated to supply chemical to the chemical bath. The chemical supply is completed by a feedback signal from a  flow meter and a chemical analyzer. The PLC ladder diagram following the operation procedure was constructed with given tool. This diagram uses simple scheme for sensing of  concentration and controlling of supply pump.

Fig. 6 shows the concentration transient trend of SC-1 chemical as a fuction of chemical supplying time. From Fig. 6, NH4OH and H2O2 are settled in 10minutes with a  concentration deviation of 1.33wt% and 0.23wt%, respectively. In the bath using SC-1 chemical, chemical supply is conducted in the sequence of DIW, NH4OH, and H2O2. The concentration deviation is dependent on the chemical analyzer resolution and spike pump flow rate. The measured data are sufficient for required specification of bath concentration control value, which is recomended as less than 10minutes  with 5wt% of concentration deviation.