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Method for sequential high-density plasma deposition and sputter etching for gap filling using low-mass sputtering agents

IP.com Disclosure Number: IPCOM000011847D
Publication Date: 2003-Mar-19
Document File: 5 page(s) / 220K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for sequential high-density plasma deposition and sputter etching for gap filling using low-mass sputtering agents (such as hydrogen and helium). Benefits include improved gap filling performance, minimal incorporation of impurities, and improved ease of manufacturing.

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Method for sequential high-density plasma deposition and sputter etching for gap filling using low-mass sputtering agents

Disclosed is a method for sequential high-density plasma deposition and sputter etching for gap filling using low-mass sputtering agents (such as hydrogen and helium). Benefits include improved gap filling performance, minimal incorporation of impurities, and improved ease of manufacturing.

Background

              Voids occur within trenches and vias after gap filling using chemical vapor deposition (CVD) processes in structures with high aspect ratios and/or aggressive critical dimensions. Examples include shallow trench isolation and inter-metal dielectric deposition. CVD processes include low-pressure (LPCVD), plasma etched (PECVD), and high-density plasma (HDPCVD).

              Conventionally, PECVD is used for relatively less aggressive structures (aspect ratio <3.5 and minimum space ~200 nm). The voiding problem is solved by the sequential deposition of sputter etch using Ar and/or O2. Deposition is performed multiple times for aggressive structures. Even in the best case, the process is inferior to single step high-density plasma (HDP) deposition processes.

              HDPCVD is conventionally used for aspect ratio <~4.0 and minimum space >~150 nm structures. In these geometries, single step HDP deposition suffices. For more aggressive structures (aspect ratio >4, space <150 nm), an addition of elements other than SiH4/O2/Ar (such as Helium, Hydrogen, PH3, NF3, and SiF4) to deposition chemistry improves gap-fill capabilities.

              Aggressively scaled trenches and vias in ULSI fabrication include shallow trench isolation and nondamascene inter-metal dielectrics (IMD). The HDPCVD process is the leading conventional solution for high-volume manufacturing. As the critical dimensions and aspect ratio become increasingly aggressive, voids cannot be eliminated from the trenches or vias. Voids result from the pinching-off effect that results from “bread-loafing” in the high deposition-to-sputter (D/S) ratio limit (see Figure 1) or cross sputtering in the low D/S ratio limit (see Figure 2). In certain cases, voids can be eliminated in the low D/S ratio limit but result in sputter erosion of the underlying layer (for example, silicon nitride erosion in shallow trench isolation).

              As the critical dimension shrinks, neither of the two limiting process regimes in HDPCVD (high D/S, low D/S) nor any combination (such as the multi-step approach) utilizing conventional hi-mass sputtering agents is sufficient for void-free fill without introducing other process gases in the deposition process (see Figure 3). High-mass sputter agents include O2, Ar, and Kr. The introduction of other process gases is not optimal as they may result in the incorporation of impurities in the deposited dielectric film (such as Hydrogen, SiF4, or NF4) that might cause the degradation of gate leakage or dielectric breakdown.

General description

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