Novel method of filling mixture gas for TFT LCD and LED MOCVD doping process

Summary form only given. As scientific technology makes progress, there are more and more applications of mixture gas in semiconductor, flat panel display, LED MOCVD and solar manufacturing process. The request of mixture gas criteria is more critical than before, especial on precise concentration control, impurity control and high volume gas supply under safe condition. In order to meet customer´s request, Praxair (PX) has developed the novel method of filling mixture gas for TFT LCD and LED MOCVD doping process. It includes two kinds of filling method for different applications in TFTLCD and LED MOCVD doping process. For TFT LCD process, PX has developed on-site high volume blending system of 1% PH3/H2 mixture gas for TFT LCD n+ a-Si doping process & it has been qualified by Taiwan customer. The on-site blending system can provide high volume, more tighten concentration control, more reliable on gas supply, reduces gas cylinder change frequency and lowest cost of ownership. PX on-site blending system uses pure PH3 cylinder and H2 gas (customer supply) to form 1% PH3/H2 mixture by dynamic MFC control through in-situ concentration sensor feedback. The blending system has excellent performance of PH3 concentration control & has reached mean value 1.0002%, stdev 0.0128% performance by customer on-site demo. The performance is 6X better than customer target. The blending system has been proved and qualified by small, middle and large batches mass production and shows comparable result on process, device, yield, RA performance in comparison with current supplier (gas cylinder or toner package). The other method of filling SiH4 or Si2H6 mixture is for LED MOCVD nGaN doping process. PX has developed the concentration analysis system and it can analyze the concentration from two digital percentage levels until ppm level. In general, it uses traditional gravimetric method for filling SiH4 or SiH4 mixture and needs 4 ~ 6 filling steps(depend on balance gas) to re- ch ppm level. Due to lots of filling steps, it causes propagation error in filling steps and can´t control mixture gas concentration precisely. It also causes lots of cost and working labor on filling process. PX has developed the novel method for concentration analysis and reduces filling steps from 4~6 steps to 2~3 steps for ppm concentration level. Due to less filling steps, it reduces the propagation error and gets better concentration control products. For example, 200 ppm Si2H6/H2 mixture gas cylinder concentration spec. is +/- 10% by using traditional gravimetric method, PX can reach gas cylinder concentration spec. +/- 5% by using new method. The tighten concentration spec. cylinders can reduce or skip test-run time after cylinder change & provide more consistent concentration control within batch to batch cylinders. The new method is not only for SiH4 or Si2H6 mixture in LED MOCVD process & it can extend to others process gas like GeH4/H2 mixture in advance semiconductor EPI process or other applications.