Method of controlling the uniformity of PECVD-deposited thin films

Abstract

We have discovered that controlling a combination of PECVD deposition process parameters during deposition of silicon-containing thin film provides improved control over surface standing wave effects. By minimizing surface standing wave effects, the uniformity of film properties (particularly film thickness) across a substrate surface onto which the films have been deposited is improved. The process parameters which have the greatest effect on surface standing wave effects include: the spacing between the upper and lower electrodes in the plasma reactor; the RF frequency of the plasma source; the amount RF power to the plasma source; the process chamber pressure; the relative concentrations of the various components in the precursor gas composition; and the precursor gas overall flow rate relative to the substrate processing volume.

Description

RELATED APPLICATIONS [0001] This application is a continuation-in-part of U.S. application Ser. No. 10 / 829,016, filed Apr. 20, 2004, which is currently pending.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention pertains to a method of controlling surface standing wave effects during PECVD deposition of a silicon-containing thin film. By controlling surface standing wave effects during film deposition, the uniformity of a silicon nitride film deposited by PECVD (plasma-enhanced chemical vapor deposition) can be tightly controlled over a large surface area. [0004] 2. Brief Description of the Background Art [0005] Current interest in thin film transistor (TFT) arrays is particularly high because these devices are used in liquid crystal active matrix displays of the kind often employed for computer and television flat panels. The liquid crystal active matrix displays may also contain light emitting diodes for back lighting. Further, organic light e...

AI Technical Summary

Benefits of technology

The patent text describes a method for depositing a-SiNx:H films that can be used in the manufacture of TFT structures, such as flat panel displays. The method allows for consistent film thickness and properties across a substrate, with a wet etch rate of less than 800 Å / min. The film has a low Si—H bonded content, meaning it has a low amount of hydrogen. The method also allows for a high deposition rate, typically greater than 1000 Å / min. The film has excellent performance capabilities, with a uniformity of the film thickness and properties across a substrate of less than 15% in terms of the 1500 mm×2200 mm dimension. The film has a low N2 content, meaning it has a low amount of nitrogen. The method also allows for a high NH3 content, meaning it has a high amount of hydrogen. The film has a low wet etch rate, meaning it can be easily removed using a specific etchant. The combination of these technical effects allows for the production of high-quality a-SiNx:H films suitable for use in TFT structures.

Problems solved by technology

However, we discovered that when the substrate size was increased to dimensions of 1500 mm to 1800 mm, this precursor source gas produced a non-uniform film thickness which varied by as much as about 25%; produced film structures where the Si—H bonded content exceeded 23 atomic %; and, produced films where the wet etch rate in HF solution (normalized to thermal oxide 1000 Å / min) exceeded 2400 Å / min in some instances.

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