Hydrogen-Blocking Film for Ferroelectric Capacitors

Abstract

An ammonia-free method of depositing silicon nitride by way of plasma-enhanced chemical vapor deposition (PECVD). Source gases of silane (SiH4) and nitrogen (N2) are provided to a parallel-plate plasma reactor, in which energy is capacitively coupled to the plasma, and in which the wafer being processed has been placed at a support electrode. Low-frequency RF energy (e.g., 360 kHz) is applied to the support electrode; high-frequency RF energy (e.g., 13.56 MHz) is optionally provided to the parallel electrode. Process temperature is above 350° C., at a pressure of about 2.5 torr. Any hydrogen present in the resulting silicon nitride film is bound by N—H bonds rather than Si—H bonds, and is thus more strongly bound to the film. The silicon nitride can serve as passivation for ferroelectric material that may degrade electrically if contaminated by hydrogen.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority, under 35 U.S.C. §119(e), of Provisional Application No. 61 / 530,281, filed Sep. 1, 2011, incorporated herein by this reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.BACKGROUND OF THE INVENTION[0003]This invention is in the field of integrated circuit manufacture. Embodiments of this invention are more specifically directed to the formation of a silicon nitride film formed over a ferroelectric capacitor structure in an integrated circuit.[0004]Conventional metal-oxide-semiconductor (MOS) and complementary MOS (CMOS) logic and memory devices are prevalent in modern electronic devices and systems, as they provide an excellent combination of fast switching times and low power dissipation, along with their high density and suitability for large-scale integration. As is fundamental in the art, however, those devices are essentially volatile, in that logic and memory ...

AI Technical Summary

Benefits of technology

This patent is about a way to make a silicon nitride film using plasma enhanced chemical vapor deposition (PECVD). The process involves using ammonia-free chemistry with silane and nitrogen gases. The plasma is created using low ratio of high frequency to low frequency applied power in a capacitively-coupled plasma reactor. The resulting film has a low ratio of H-Si bonds to H-N bonds, suggesting that the hydrogen in the film is tightly bound and less likely to contaminate nearby ferroelectric material. This is important because it can improve the quality of the film and reduce contamination risks during subsequent processing.

Problems solved by technology

As is fundamental in the art, however, those devices are essentially volatile, in that logic and memory circuits constructed according to these technologies do not retain their data states upon removal of bias power.

In contrast, conventional MOS capacitors lose their stored charge on power-down of the device.

However, the use of HDP CVD to form the first nitride layer (nitride film 25 in FIG. 3) is a costly and complicating process step in the overall manufacturing flow of the integrated circuit including the ferroelectric capacitor.

As known by those in the industry, HDP (i.e., inductively-coupled plasma) reactors are relatively expensive.

If HDP CVD is required for a specific purpose, use of the HDP reactor is generally limited to those specific processes, to minimize the cost of adding additional HDP capacity.

Even so, the insertion of an HDP CVD process into the manufacturing flow can result in bottlenecks, and limits the extent to which multiple processes are performed in situ in a single reactor.

Images