300mm直径硅片湿洗槽出水口设计

Water motions influenced by an outlet of a batch-type 300-mm diameter silicon wafer wet cleaning bath were experimentally andnumerically studied in order to quickly remove the contaminants from the bath. The outlet consisting of a pinhole arrays (PA) nearthe top edge of the bath side wall was designed and evaluated along with an ordinary overfow (OF outlet, The experiment showedthat the amount of a blue-colored ink, used as a tracer, in the bath having both the OF- and the PA-outlets decreased faster than that inthe bath having only the 0F-outlet. Simultaneously the amount of the blue-colored ink that retumed to the bath bottom was reducedby using both the PA-outlet and the 0F-outlet. The numerical calculations also showed that particles in the bath quickly went outthrough the PA-outlet.

An advanced semiconductor material surface should be maintainecclean for the electronic device fabrication.1,2 The batch-type wetcleaning method, using ultrapure water and chemical reagents in a bath, hasbeen very popular for cleaning the surface of small and large diameterwafers3-i8 The water flow in the wet cleaning bath has been continuously studied16-19 in order to improve the productivity of the cleaningprocess. While the contaminants, such as small particles, were de-tached and transported away from the wafer surface, they frequentlyreturned to the wafers following the water recirculation. 

Thus, thewater flow in the bath should be further studied in detail.The water recirculation is considered to be formed by an asymmetric water injection and the insufficient cross section of the outlet.19,20In our previous study,19 the water injection nozzle consisting of dualtubes was designed taking into account the pressure distribution in thenozzle for injecting the water in the normal direction with the symmetric water velocity distribution. While the efficiency of contaminationremoval from wafers is dominated by the direct water injection to thewafers from the water nozzles, the recontamination is influenced bthe recirculation which may be caused by the outlet design. The wateroutlet design should be studied, next.The wet cleaning bath for the semiconductor materials processhas preferred the overflow outlet in order to effectively remove manyparticles floating on the water surface. 

The overflow outlet is equivalent to the outlet having a significantly thin cross section along thetop edge of the four side walls. In order to remove the contaminantsthrough the overflow outlet, a large and fast stream is necessary nealand toward the top edge of the bath side wall. Consequently, such afast stream requires large and fast recirculations which simultaneouslyand unfortunately take some contaminants back to the wafers. Thusa new water outlet design is expected for govering the entire waterow in the bath.

In this study, the water outlet of the wafer wet cleaning bath wasstudied both experimentally and numerically from the viewpoint ofexpanding the outlet cross section. For this purpose, pinhole arrayswere formed near the top edge of the bath side wall. The entire waterflow was studied by water flow observations and numerical calcula-tions taking into account the transport phenomena. The changes in thewater flow determined by the pinhole arrays were evaluated.

Figure 1

The water was introduced from the two water injection nozzlesplaced at the right and left bottom of the bath. The water was injectedin the normal direction from the nozzle body.19 Each nozzle suppliedwater at the flow rate of 85 L min-l. The total water flow rate was17 L min-1.

The water injected from the nozzle went through the spaces between and around the wafers. Finally, the water overflowed from thetop edge of the bath side wall. This bath had the function of ultrasonicwave irradiation from the entire bath bottom without any disturbance.The directions of the water injected from the nozzles were visualizedusing a tracer, such as blue-colored ink, and were captured by a VTRcamera.

Figure 2 shows the batch-type wetcleaning bath having the pinholearrays near the top edge of the bath side wall. The pinhole diameterwas 2 mm. The position of the pinholes was 20, 30 and 50 mmfrom the top of the bath side wall, taking into account the typicalhorizontal water flow along the water surface observed in this studyThe distance between the pinholes in the horizontal direction was30 mm; one horizontal array had 38 pinholes. The water filow ratesupplied from the water injection nozzle was exactly the same as thatfor the bath shown in Fig. 1. The water went out through the arranged pinholes. Simultaneously, the rest of water overflflowed from the top of the bath side wall.