晶圓儲存與傳送之汙染控制

Contamination Control for Wafers During Storage and Transport Processes

古震維(Chen-Wei Ku)

指導教授 ： 胡石政

國立臺北科技大學/機電學院/機電科技研究所/博士(2010年)

摘要

半導體製程中，汙染控制的議題扮演著重要的角色，本研究主要探討晶圓傳送儲存與傳送過程中的微污染防治。FOUP為半導體製程間輸送及儲存的載具設備之一，因此對於其內部的潔淨程度要求嚴格，而內部若有微小微粒以及氧化物存在，會污染到內部的晶圓，因此將惰性氣體氮氣填充於載具內，在晶圓輸送及儲存過程中將污染源排出。
1. 450mm 晶圓傳送盒
本研究以數值與實驗方法進行450mm FOUP氮氣充填效率作分析，並研究450mm FOUP內部氧氣與水氣排除情形。 填充不同流量的氮氣進入450mm FOUP內，流量最佳化之經濟性分析。並改變填充入口之分佈，包括在450mm FOUP內使用不同的開口位置均一流的多孔管(置於)作氮氣填充之清淨效率研究。討論開孔孔管噴流之特性，比較是否使用多孔管之水蒸氣排除效率。分析450mm FOUP內在低濕度水氣吸附濃度方程式吸附(ka)與脫附係數(kd)。由於450mm wafer FOUP內表面積約300mm wafer FOUP的3倍，在低濕度狀態下將導致會有較大的分子脫附行為，kd值約300mmFOUP的2倍。
2. 300mm 晶圓傳送盒
在FOUP門載出完畢至定點時，FOUP內因門的開啟會有負壓的產生，導致微環境外較高的微粒濃度容易將污染物捲入影響晶圓，研究晶圓載出過程，流場變化分析。利用數值與實驗方法，僅作一次開門過程的動態模擬，觀察潔淨室的微粒污染濃度對FOUP影響。比較不同晶圓傳送盒開門移動速度對FOUP內微粒汙染情形。 FOUP門移動速度與壓力差微粒平均濃度的影響方程式如：
Cave = 4.56 x10-1 ( ) – 4.6 x 10-4 dP + 4.96 x 10-3.
3. 300 mm 晶圓微粒沉降速度的影響
晶圓在流動的流體中運動流場分析。晶圓移動時，晶圓會擠壓流體，同時流體也會填補因晶圓移動所產生的空洞，流體與晶圓交互作用所誘導流場的變化機制較為複雜。本研究以數值分析晶圓移動過程中，因晶圓的移動對於微粒沉降晶圓表面的污染，比較不同的晶圓移動速度探討污染微粒的沉降速度。模擬結果得到微粒沉降速度與晶圓移動速度之間係數關係(移動網格法)方程式：Vd/Vds=0.098Vb1/2+1.22 。

關鍵字

晶圓傳送盒 ； 氮氣充填 ； 數值分析

並列摘要

The issue of contamination control plays an important role in semiconductor manufacturing processes. This study evaluated the influences of micro-comtamination control on the transportation and purging performance in 450mm and 300mm-wafer front opening unified pods (FOUPs) and reticle pods, which must provide wafer and reticle protection, keeping isolated from contamination. In this study, we conducted a parametric study of purging a box for handling 450mm, 300mm wafers and reticle, with nitrogen experimentally, analytically and numerically.
1. 450mm-wafer FOUP
Since larger wafers surface have more circuit elements, where the crystal in a 450mm wafer exceeds two times greater than that in a 300mm wafer, and the cost in the production of integrated circuits is reduced, a FOUP containing large size wafers (450mm) was used in the present study. This study conducted experimental woks to investigate the effects of arrangements of purging locations and types of purging plenums on the extraction of moisture from the FOUP with 450mm wafers inside. Besides, a technology of computational fluid dynamic (CFD) was employed in this study. Langmuir adsorption models were used to construct physical models of contamination in the FOUP. Theoretical equations of the adsorption and desorption were derived and compared with the results of experiments. The constants of adsorption and desorption calculated from the measured data of the 450mm-wafer FOUP are -0.0038 and 15, respectively, which are 0.375 and 1.187 times the ones of the 300mm-wafer FOUP, respectively.
2. 300mm-wafer FOUP
This study experimentally and numerically investigated the influences of a FOUP’s door opening speed (Vdoor) and the pressure difference (dP) between the mini-environment and the cleanroom on the dynamic distributions of the averaged non-dimensional concentration of particles in the FOUP (Cave), which is defined as the averaged particle concentration in the FOUP (Cave) divided by the particle concentration in a cleanroom (CCR). Results show that the Cave is proportional to 1/2ρVdoor2 and inversely proportional to the dP, when the Vdoor and the dP is at 0.05~0.15 m/s and 0.3~12.7 Pa, respectively. The result of the present study can be expressed by a stepwise multiple regression equation: Cave = 4.56 × 10-1 (1/2ρVdoor2) – 4.6 × 10-4 dP + 4.96 × 10-3.
3. Particle deposition velocity of 300 mm wafers
An investigation of the particle deposition velocity (vd ) onto an upward moving 300 mm (dw) wafer in a cleanroom with a 0.3m/s downward velocity (vo) was performed by the dynamic mesh model of FLUENT CFD code. The results show that the air simultaneously replenishes the vacant space induced by the movement of the wafer and new recirculation zones were formed around the wafer. The results of the upward moving wafer are apparently different from those of the wafer fixed (free-standing) in the flowing fluids. Compared with a free-standing wafer, the particle deposition velocity on a moving wafer is increased significantly. The deposition velocity increases with the increase of wafer moving velocity (vb). The time averaged particle deposition velocity of particles with diameter of 0.1μm, over the dimensionless time τ ( τ=tvo/dw ) from 0 to 1.0, at the dimensionless moving velocity of the wafer Vb ( Vb=vb/vo ) of 0.3, 1.0, and 3.3 is 11.4%, 20.8% and 37.8% greater than the one of a free-standing wafer (vfs), respectively. In the computing range, the mean vd can be estimated by an equation of Vd = Vfs (0.208 Vb1/2 +1.0).

並列關鍵字

FOUP ； nitrogen purge ； CFD

參考文獻

吳文欽 (2008). 450mm 晶圓世代之決策分析. 高階經營管理碩士在職專班. 新竹, 國立清華大學. 碩士.

A. Licciardello, O. P., and S. Pignataro (1986). "Effect of organic contaminants on the oxidation kinetics of silicon at room temperature." Appl. Phys. Lett 48: 41–43.

Benjamin Y. H. Liu, K.-h. A. (1987). "Particle Deposition on Semiconductor Wafers." Aerosol Science and Technology 6: 215-224.

Budde K. J. , W. J. H., and M. M. Beyer (1995). "Application of ionmobility spectrometry to semiconductor technology: Outgassing of advanced polymers under thermal stress." Electrochem. Soc. 142: 888–897.

C. K. Alvin, W. W. a. N. (2000). "Modeling indoor particle deposition from turbulent flow onto smooth surface." Aerosol Science 31: 463-476.