Making Sub-atmospheric Delivery Work for Compound Semiconductor Growth

Rodstein, Jay*; Dietz, Jim*
(Honeywell Labs, Plymouth, MN and ATMI, Danbury, CT)

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Sub-atmospheric pressure delivery of highly toxic gases, e.g., arsine & phosphine, has been in practice for implant applications since 1995. In these applications, small volumes (sccm) of dopant gas are delivered with increased safety and minor modification to the on-board delivery system. The appeal of a similar solution for MOCVD systems is highly desirable because of the larger volumes of highly toxic gases used in these processes. Hence, even greater safety benefits can be realized due to potential events that correspond to larger volume use. The primary barrier for migrating the sub-atmospheric pressure technology to CVD systems was the requirement for greater delivery rates for growth, typically liters per minute, which is two orders of magnitude greater than ion implant flows. ATMI has developed sub-atmospheric delivery systems for MOCVD applications. Honeywell Labs Plymouth was the second location to evaluate ATMI’s system. During the equipment selection process, a variety of issues needed to be resolved. The paper discusses key issues in the development and installation of this technology; and the resolutions and tradeoffs that were made. Key issues include: Gas quality, consistent delivery rate and system complexity, i.e., a drop in system is most desirable: Increased volume of gas on site: Selection of high quality parts, e.g., pumps, to satisfy customer needs for varying delivery rates and reliability: Authority Having Jurisdiction issues including fitting a development system into the Code and classification of sub-atmospheric pressure sources. Hazards and Operability Analysis and consideration of SEMI S2 standard were used to sort through the design and installation processes. Where there was no precedent, evaluation of acceptable components and equivalent methods were used.

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