Tunable dielectric constant oxide and method of manufacture

Details Tunable dielectric constant oxide and method of manufacture Tunable dielectric constant oxide and method of manufacture

1997-03-21

2001-04-03

Bowers, Charles (Department: 2823)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

Insulative material deposited upon semiconductive substrate

C438S783000, C438S784000, C257S310000, C257S532000

Reexamination Certificate

active

06211096

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to a method of manufacturing semiconductor devices and, specifically, to a method of forming films such as silicon oxide films used in the manufacture of such devices, the films having a tunable dielectric constant.
2. Description of the Related Art
Chemical vapor deposition (CVD) is a commonly used technique for forming thin films and has been widely used as a manufacturing technique in the semiconductor device industry. CVD methods using an organic or inorganic silicon compound gas and an oxidizing gas are well known as methods for forming thin films of silicon oxide. In such semiconductor devices, an insulating film is typically utilized for electrically isolating element wiring. The typical insulating film used in the past was a SiO
2
film formed by the thermal oxidation of a silicon substrate or a SiO
2
film formed by chemical vapor deposition under a reduced pressure or atmospheric pressure using gaseous materials such as silane and tetraethoxy silicate (TEOS). Particularly in the case of aluminum wirings, SiO
2
films are preferred for insulation and are formed by CVD techniques using either TEOS or silane and O
2
because such SiO
2
films can be formed under temperatures as low as about 400° C.
As transistors are scaled into the submicron regions in such semiconductor devices, the interconnect spacing between wiring is reduced so that electromagnetic coupling of adjacent metal lines is possible causing errors, noise and, in the extreme case, a non-functioning device. As the space between two adjacent metal lines is shortened in accordance with the miniaturization of the semiconductor circuitry, increased capacitance occurs between the metal lines tending to obstruct the higher operating speed of the semiconductor device, thereby inhibiting the performance improvement offered by the miniaturization of the device.
As a result of these shortcomings, it is often important to decrease the dielectric constant of the insulating film which is interposed between two adjacent lines in a semiconductor device. The SiO
2
film formed by conventional plasma CVD methods typically has a dielectric constant in the range from about 4.0 to 5.0. The higher the dielectric constant of the oxide film, the further the electromagnetic field can penetrate into the dielectric media. By reducing the dielectric constant of the oxide, two interconnect lines can be placed closer in proximity, thus lowering the operating voltage of the transistor because the noise margin thereof can be reduced. It is desirable, therefore, in some instances to reduce the dielectric constant of such films from approximately 4.5 to about 3.0 or lower.
Contrarily, it is sometimes desirable to increase the dielectric constant of the oxide film being formed in semiconductor devices such as capacitors. The higher dielectric constant materials can be used to form regions of capacitance within the integrated circuit. The higher the dielectric constant of the material, the smaller the capacitance region required, resulting in a smaller capacitor, thereby equating to an area savings.
The dielectric constant of oxides can be lowered by the addition of carbon or fluorine into the oxide. While this general principle has been stated in the prior art, the previous attempts to provide a film having a lowered dielectric constant have exhibited various deficiencies. For example, in Japanese Patent Application No. 2-77127, fluorine is introduced into SiO
2
by means of ion implantation. However, it is necessary to apply a heat treatment at a temperature of at least about 600° C. within the SiO
2
layer. Thus, the SiO
2
layer formed by this method cannot be used for isolation of aluminum wirings within semiconductor devices.
In U.S. Pat. No. 5,429,995, issued Jul. 4, 1995 and assigned to Kabushiki Kaisha Toshiba, a method is shown for manufacturing a semiconductor device with a film which exhibits a low dielectric constant which uses FSi (OC
2
H
5
)
3
as the silicon source gas. A particular object of the invention was to provide an insulating film having low hygroscopicity. It would be desirable, however, to use as the organic silicon source gas a conventional TEOS to allow conformal coverage and to provide a process which can be run on any of the conventional PECVD type deposition systems.
Additionally, in certain of the prior art techniques, it has been difficult to control accurately the fluorine concentration in the SiO
2
film.
Accordingly, it is an object of the present invention to provide a method for forming a SiO
2
film which has a tunable dielectric constant and which is formed by conventional plasma CVD methods using TEOS as the silicon source gas or which is formed by either HDP (high density plasma) or atmospheric pressure chemical vapor deposition (APCVD) methods using a silane as the source gas.
Another object of the invention is to provide a method for manufacturing a semiconductor device in which a silicon oxide film containing fluorine and carbon is produced, the film acting as an insulating film for electrically isolating conductive layers included in the semiconductor device, the film being formed by plasma CVD technique using an organic silicon gas as a starting material.
Another object of the invention is to provide basic nitrogen incorporation to act as a moisture and OH barrier for the activating film.
Another object of the invention is to provide a lower dielectric constant film which is stable with higher concentrations of fluorine incorporated into the film.
Another object of the invention is to provide a method of manufacturing semiconductor devices in which the conductive layers on the silicon oxide films so produced have improved reliability.
SUMMARY OF THE INVENTION
A method for manufacturing a semiconductor device is shown in which a silicon oxide film acts as an insulating film for electrically isolating conductive layers included in the semiconductor device. A silicon oxide film is formed containing fluorine and having a given dielectric constant by CVD method using a source gas containing at least silicon, nitrogen, carbon, oxygen and fluorine contributors. The ratio of nitrogen to oxygen in the source gases used in the CVD method is controlled in order to control the ultimate carbon and fluorine concentrations and hence the dielectric constant of the silicon oxide film so produced. The addition of nitrogen to the film also acts as a barrier to the diffusion of H
2
O or OH into the film in subsequent processing steps. Preferably, the source gases, in addition to a silicon contributor include N
2
O, O
2
and C
2
F
6
. The given dielectric constant and moisture barrier properties of the silicon oxide film are determined by controlling the relative ratios of N
2
O:O
2
:C
2
F
6
and high frequency to low frequency power applied, with silane SH
x
or NH
x
as the source gases in the CVD method.
The silicon source can be a conventional TEOS. N
2
O can be used as the nitrogen contributor in the source gas to add nitrogen to the silicon oxide film which is formed in order to improve reliability of the film when used in a semiconductor device.
A method is also shown for manufacturing a semiconductor device in which a silicon oxide film is formed with regions having a relatively high dielectric constant, the regions of relatively high dielectric constant being used to form capacitors within the semiconductor device. In this aspect of the invention, a silicon oxide film can be formed containing fluorine and having a given dielectric constant value by plasma CVD method using a source gas containing at least silicon, nitrogen, carbon, oxygen and fluorine contributors introduced within a reaction chamber. A high dielectric compound can also be introduced into the reaction chamber to form the relatively high dielectric constant silicon oxide film. The high dielectric compound is preferably selected from the group consisting of either a single source or mixtures of alkoxy compounds of the general formula MOR, or titanate comp

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