Method of forming pre-metal dielectric film on a semiconductor substrate including first layer of undoped oxide of high ozone:TEOS volume ratio and second layer of low ozone doped BPSG

Abstract

A method of forming a pre-metal dielectric film having good as deposited gapfill characteristics, as well as good mobile-ion gettering capability. The method involves first depositing a layer of high-ozone undoped silicon dioxide film having a high ozone/TEOS volume ratio. Then, a low-ozone doped BPSG film is deposited over the high-ozone undoped silicon dioxide layer. The film layers are heat treated to densify the film, and then the top layer is planarized using known planarization techniques to a thickness that allows for adequate mobile-ion gettering.

Description

TECHNICAL FIELD[0001]This invention relates to semiconductor processing and, more particularly, to a method of forming a dielectric film on a semiconductor substrate and to a method of forming a semiconductor device having this dielectric film.BACKGROUND ART[0002]In the formation of semiconductor integrated circuit devices, a frequent practice in the planar process is to form subsurface diffusion layers and polysilicon conductors on a silicon substrate surface. One or more dielectric films are deposited over the silicon substrate surface and metal wiring conductors are formed on or in the dielectric film to interconnect the various components formed on the silicon substrate surface to achieve the desired integrated circuit.[0003]It is desirable that the dielectric films which are deposited on the substrate prior to the metallization process have a good mobile-ion gettering property, as well as a good reflow or gapfill property. A type of insulating film that has been widely used in ...

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Benefits of technology

[0010]The above objects have been achieved by a method of forming a pre-metal dielectric film having good as-deposited gapfill characteristics, as well as good gettering capability. The method involves first depositing a layer of high-ozone undoped silicon dioxide film that provides the void-free gapfill characteristic and then depositing a low-ozone doped BPSG film that provides the gettering capability. This two layer insulating film provides the ability to have the gaps adequately filled between small or narrow lines without sacrificing good mobile-ion gettering properties. Prior art insulating films tend to provide either good gapfill or good gettering but not both, or the prior art films require several layers to achieve the desired properties.

[0011]The undoped silicon dioxide film has a high ozone / TEOS volume ratio of at least 15 to 1, as compared to the prior art doped BPSG film which generally have lower ozone / TEOS ratios, such as 10 to 1. By forming a film with a high ozone / TEOS ratio, the surface mobility of the TEOS-dimer is increased, causing the film to have better flow characteristics. The reactants can diffuse readily on the surface, thus finding the regions having the lowest energy. This results in a void-free dielectric film surface.

[0012]A heat treatment is then applied to densify the film, rather than to soften and flow the film as is done in the prior art. This allows the best treatment to be conducted at a lower temperature, which prevents the diffusion problems described above that are associated with high temperature heat treatment in smaller device geometries. Finally, the top of the second BPSG layer is planarized using chemical mechanical planarization. The method of the present invention can be used in the formation of semiconductor devices and can be also used in the formation of other structures requiring a good gapfill or step coverage, such as the formation of polysilicon bus structures.

Problems solved by technology

This results in a void-free dielectric film surface.

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