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Method of Determining Critical Thickness of Silicon Nitride Layers

IP.com Disclosure Number: IPCOM000034556D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Faix, W: AUTHOR [+4]

Abstract

The completeness and with it the critical thickness of CVD (Chemical Vapor Deposition) silicon nitride (Si3N4) layers is determined by measuring the breakdown voltage. The nucleation and growth of a CVD silicon nitride layer is a statistical process. Influential on the growth are the substrate, the gas composition in the reaction tube and the process parameters, such as the deposition rate, the temperature and whether or not LPCVD (Low- Pressure Chemical Vapor Deposition) or PECVD (Plasma-Enhanced Chemical Vapor Deposition) is used. At the start of the growth cycle, stable nuclei are generated on the substrate consisting, for example, of SiO2 . These nuclei are statistically distributed on the substrate surface. As deposition continues, the nuclei grow into islands.

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Method of Determining Critical Thickness of Silicon Nitride Layers

The completeness and with it the critical thickness of CVD (Chemical Vapor Deposition) silicon nitride (Si3N4) layers is determined by measuring the breakdown voltage. The nucleation and growth of a CVD silicon nitride layer is a statistical process. Influential on the growth are the substrate, the gas composition in the reaction tube and the process parameters, such as the deposition rate, the temperature and whether or not LPCVD (Low- Pressure Chemical Vapor Deposition) or PECVD (Plasma-Enhanced Chemical Vapor Deposition) is used. At the start of the growth cycle, stable nuclei are generated on the substrate consisting, for example, of SiO2 . These nuclei are statistically distributed on the substrate surface. As deposition continues, the nuclei grow into islands. Subsequently, these islands interconnect, finally forming a complete layer. At this point, the critical thickness of the layer is reached. The following example shows how the method works. On silicon wafers, covered with an SiO2 layer, Si3N4 was deposited by means of LPCVD, using ammonia (NH3) and dichlorosilane (SiH2Cl2) as reactive gases. The conditions were such that the composition of the growing silicon nitride was stoichiometric. After deposition had started, wafers were taken from the reaction tube at regular intervals, e.g., every minute. On the wafers, aluminum dots were evaporated, and the breakdown voltage was subsequently m...