Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-12-03
2001-10-16
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S355000, C438S359000
Reexamination Certificate
active
06303487
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, in order to reduce a capacitance between the adjacent interconnection conductors.
In a semiconductor device, when a plurality of interconnection conductors are formed adjacent to each other at the same level in an insulating film, it is known to form an air gap between the adjacent interconnection conductors in order to reduce a capacitance between the adjacent interconnection conductors. This technology is disclosed by, for example, Japanese Patent Application Pre-examination Publication No.
JP-A-57-190331 (an English abstract of JP-A-57-190331 is available from the Japanese Patent Office and the content of the English abstract of JP-A-57-190331 is incorporated by reference in its entirety into this application), Japanese Patent Application Pre-examination Publication No. JP-A-09-055431 (an English abstract of JP-A-09-055431 is available from the Japanese Patent Office and the content of the English abstract of JP-A-09-055431 is incorporated by reference in its entirety into this application), Japanese Patent Application Pre-examination Publication No. JP-A-10-150103 (which corresponds to U.S. patent application Ser. No. 08/975,046 filed Nov. 20, 1997, the content of which is incorporated by reference in its entirety into this application, and an English abstract of JP-A-10-150103 is available from the Japanese Patent Office and the content of the English abstract of JP-A-10-150103 is incorporated by reference in its entirety into this application), and Japanese Patent Application Pre-examination Publication No. JP-A-10-229121 (an English abstract of JP-A-10-229121 is available from the Japanese Patent Office and the content of the English abstract of JP-A-10-229121 is incorporated by reference in its entirety into this application).
With an increased integration density of the semiconductor device, a spacing between adjacent interconnection conductors is decreasing more and more. When the spacing between adjacent interconnection conductors becomes small, however, the prior art process cannot satisfactorily or surely form between adjacent interconnection conductors an air gap which is effective in reducing the capacitance between the adjacent interconnection conductors.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, which has overcome the above mentioned problem of the prior art process.
Another object of the present invention is to provide a method for forming between adjacent interconnection conductors an air gap which is effective in reducing the capacitance between the adjacent interconnection conductors, even if the spacing between adjacent interconnection conductors becomes small.
Still another object of the present invention is to provide a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, in a simple and certain process in comparison with the prior art process.
The above and other objects of the present invention are achieved in accordance with the present invention by a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, comprising the steps of:
preparing a substrate having a first insulator film and a plurality of lower level interconnection conductors formed separately from each other on the first insulator film;
depositing a second insulator film to completely cover the plurality of lower level interconnection conductors and the first insulator film in a chemical vapor process under the condition that a growth speed in a vertical direction perpendicular to a principal surface of the substrate is lower than a growth speed in a horizontal direction in parallel to the principal surface of the substrate, until the second insulator film has such a thickness that an air gap is formed within the second insulator film between the adjacent interconnection conductors;
further continuing to deposit the second insulator film in the chemical vapor process under the condition that the growth speed in the vertical direction perpendicular to the principal surface of the substrate is not lower tan the growth speed in the horizontal direction in parallel to the principal surface of the substrate, until the second insulator film reaches a necessary thickness.
In one embodiment, the above mentioned two-step deposition of the second insulator film is carried out by:
setting the substrate on a lower electrode in a chemical vapor deposition machine;
depositing the second insulator film to completely cover the plurality of lower level interconnection conductors and the first insulator film in an atmosphere pressure chemical vapor deposition process while supplying a low bias voltage to the lower electrode and supplying a voltage supply voltage to an upper electrode located to oppose the substrate put on the lower electrode within the chemical vapor deposition machine, until the second insulator film has such a thickness that the air gap is formed within the second insulator film between the adjacent interconnection conductors; and
further continuing to deposit the second insulator film in the atmosphere pressure chemical vapor deposition process by supplying an elevated bias voltage to the lower electrode until the second insulator film reaches the necessary thickness.
In another embodiment, the above mentioned two-step deposition of the second insulator film is carried out by:
setting the substrate in a bias electron cyclotron resonance chemical vapor deposition machine,
depositing the second insulator film to completely cover the plurality of lower level interconnection conductors and the first insulator film in a bias electron cyclotron resonance chemical vapor deposition process while supplying a small RF power, until the second insulator film has such a thickness that the air gap is formed within the second insulator film between the adjacent interconnection conductors; and
further continuing to deposit the second insulator film in the bias electron cyclotron resonance chemical vapor deposition process by supplying an RE power larger than the small RF power, until the second insulator film reaches the necessary thickness.
According to another aspect of the present invention, there is provided a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, comprising the steps of:
preparing a substrate having a first insulator film and a plurality of lower level interconnection conductors formed separately from each other on the first insulator film, and setting the substrate on a lower electrode in a chemical vapor deposition machine;
depositing a second insulator film to completely cover the plurality of lower level interconnection conductors and the first insulator film in an atmosphere pressure chemical vapor deposition process while supplying a low bias voltage to the lower electrode and supplying a voltage supply voltage to an upper electrode located to oppose the substrate put on the lower electrode within the chemical vapor deposition machine so that a growth speed in a vertical direction perpendicular to a principal surface of the substrate is lower than a growth speed in a horizontal direction in parallel to the principal surface of the substrate, until the second insulator film has such a thickness that an air gap is formed within the second insulator film between the adjacent interconnection conductors;
further continuing to deposit the second insulator film in the atmosphere pressure chemical vapor deposition process until the second insulator film reaches a necessary thickness.
The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred
Gurley Lynne A.
Hayes Soloway Hennessey Grossman & Hage PC
NEC Corporation
Tsai Jey
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