Polycrystalline Si1-xGex thin film deposition by rapid thermal chemical vapor deposition

Thin film vapor deposition processes, e.g., chemical vapor deposition, are widely used in high-volume manufacturing of electronic and optoelectronic devices. Ensuring desired film properties and maximizing process yields require control of the chemical precursor flux to the deposition surface. However, achieving the desired control can be difficult due to numerous factors, including delivery system design, ampoule configuration, and precursor properties. This report describes an apparatus designed to investigate such factors. The apparatus simulates a single precursor delivery line, e.g., in a chemical vapor deposition tool, with flow control, pressure monitoring, and a precursor-containing ampoule. It also incorporates an optical flow cell downstream of the ampoule to permit optical measurements of precursor density in the gas stream. From such measurements, the precursor flow rate can be determined, and, for selected conditions, the precursor partial pressure in the headspace can be estimated. These capabilities permit this apparatus to be used for investigating a variety of factors that affect delivery processes. The methods of determining the pressure to (1) calculate the precursor flow rate and (2) estimate the headspace pressure are discussed, as are some of the errors associated with these methods. While this apparatus can be used under a variety of conditions and configurations relevant to deposition processes, the emphasis here is on low-volatility precursors that are delivered at total pressures less than about 13 kPa downstream of the ampoule. An important goal of this work is to provide data that could facilitate both deposition process optimization and ampoule design refinement.

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Application of Constant Absorptivity Ring (Car) to Improve Polysilicon Thickness Uniformity In A Rapid Thermal Chemical Vapor Deposition Reactor

MRS Proceedings ◽

10.1557/proc-303-19 ◽

1993 ◽

Vol 303 ◽

Author(s):

Mahesh K. Sanganeria ◽

Mehmet C. ÖztÖrk

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Silicon Oxide ◽

Chemical Vapor ◽

Thin Film Deposition ◽

Film Deposition ◽

Excessive Heat ◽

Thermal Chemical Vapor Deposition ◽

Novel Approach ◽

Cooling Effects

ABSTRACTRapid Thermal Chemical Vapor Deposition (RTCVD) is a promising technology for thin film deposition in advanced cluster tool systems. It is well known that, if left uncompensated, excessive heat losses that occur around the wafer edge can lead to temperature and deposition non-uniformities. Using polysilicon deposition on SiO2 as an example we have shown that deposition non-uniformity can be aggravated by absorptivity variations across the wafer. In this paper, we propose a novel approach to alleviate this problem. In this technique, the edge cooling effect is compensated by increasing the absorptivity of the substrate around its perimeter. This is achieved by etching a thin (width≈200μm) ring from the isolation oxide around the wafer perimeter prior to polysilicon deposition. During polysilicon deposition, the absorptivity of the silicon-oxide-polysilicon structure continually changes resulting in positive and negative feedback mechanisms in certain polysilicon thickness ranges determined by both modeling and experiments. However, this absorptivity always remains less than the constant absorptivity of the silicon-polysilicon ring along the perimeter which is referred to here as the Constant Absorptivity Ring (CAR). The higher absorptivity of CAR shields edge cooling effects from the rest of the wafer. In this paper, we present the results of our experiments conducted to demonstrate the effectiveness of CAR in improving uniformity of polysilicon. We show that by using CAR uniform films can be obtained in a reactor which otherwise delivers a polysilicon non-uniformity of 30-40%.

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