Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2001-01-04
2003-05-13
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S709000, C438S714000, C438S723000, C438S724000, C438S725000
Reexamination Certificate
active
06562721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dry etching method and method of manufacturing a semiconductor device, and more particularly to a dry etching method for forming a semiconductor device structure on a semiconductor wafer.
2. Description of the Related Art
In a semiconductor device, a silicon oxide (hereinafter referred to SiO
2
) layer is widely used as an interlayer layer where a contact hole (via hole), a wiring groove, and the like is formed by a dry etching process.
In the dry etching process, as a etching stopper film (film for selectively stopping the progress of etching in a position thereof) used for an etching depth to be uniform, a silicon nitride (hereinafter referred to Si
3
N
4
) film is most frequently used. This is because the film is the most superior film as the etching stopper film of the insulating layer in view of stability as the film, compatibility with the SiO
2
layer, heat resistance, insulating property, and other general properties.
Moreover, a gas for general use in SiO
2
etching at present is a gas mainly comprising C
x
F
y
(x and y are positive integers). In addition, argon (Ar), oxygen (O
2
), carbon monoxide (CO) and the like may be added to this main gas as occasion demands.
As described above, Si
3
N
4
is most frequently used as the etching stopper of the insulating layer, but sufficiently high selection property can not be obtained in an SiO
2
etching process which is generally performed at present.
There are two reasons for this with regard to a semiconductor device structure. The first reason is that the contact hole used in recent years is remarkably high in aspect ratio, a deposition component does not easily enter a hole bottom part, and sufficient protection effect is not obtained. The second reason is that Si
3
N
4
has the insulating property, but dielectric constant of Si
3
N
4
is higher than that of SiO
2
, and therefore, Si
3
N
4
remaining outside the contact hole as a part of the insulating layer must be as thin as possible (about 50 nm). Consequently, the film thickness of the Si
3
N
4
as a etching stopper film becomes inevitably thin as about 50 nm, and therefore, the required selection property is a remarkably high value such as the order of 50 to 100. By these reasons, as a selection ratio to Si
3
N
4
in insulation layer etching, a substantially infinite selection ratio is required, but it is remarkably difficult to achieve the ratio in a current etching method.
A reason why the high selection property cannot be obtained with respect to Si
3
N
4
in the conventional etching method in which the C
x
F
y
gas is used as the main gas is as follows. When an active species of the gas contacts Si
3
N
4
, first C extracts N on a surface, F attacks freed Si and the etching supposedly proceeds in this pattern. Since both (CN)x and SiF
4
are high vapor pressure materials, on occurrence of a reaction the etching proceeds.
SUMMARY OF THE INVENTION
Wherefore, one object of the present invention is to provide an effective dry etching method, which solves the aforementioned related-art problems.
Another object of the present invention is to provide a method of manufacturing a semiconductor device using the effective dry etching method.
According to the present invention, there is provided a dry etching method which comprises a step of etching an insulating layer of a semiconductor device structure using a silicon nitride represented by Si
3
N
4
as an etching stopper under an etching gas atmosphere. The etching gas includes a gas containing iodine in a molecule. The insulating layer may be a silicon oxide represented by SiO
2
layer, a fluorine-containing silicon oxide layer, or an organic SOG layer or another silicon oxide insulating layer. Additionally, a mixing ratio (I/C) of iodine to carbon in the etching gas, that is, a ratio of number (quantity) of iodine atoms to number (quantity) of carbon atoms in the etching gas is 0.3≦(I/C)≦1.5, that is, the ratio (I/C) is 0.3 or more, and 1.5 or less. Here, the iodine-containing gas can be an HI gas or a gas having a constitution of C
x
H
y
I
z
(x, y and z are positive integers).
According to another aspect of the present invention, there is provided a dry etching method which comprises a step of etching an insulating layer of a semiconductor device structure using a silicon nitride film represented by Si
3
N
4
as an etching stopper under an etching gas atmosphere. The etching gas includes a gas containing chlorine or bromine in a molecule. The insulating layer may be a silicon oxide represented by SiO
2
layer, a fluorine-containing silicon oxide layer, or an organic SOG layer or another silicon oxide insulating layer. Additionally, a mixing ratio (Cl (or Br)/C) of chlorine or bromine to carbon in the etching gas is 0.3≦(Cl (or Br)/C)≦1.5. That is, a ratio of number (quantity) of chlorine atoms or bromine atoms to number (quantity) of carbon atoms in the etching gas is 0.3 or more, and 1.5 or less. Here, the gas containing chlorine or bromine can be a Cl
2
gas, an HCl gas, a gas having a constitution of C
x
H
y
Cl
z
(x, y and z are positive integers), a gas having a constitution of C
x
Cl
z
(x, and z are positive integers), for example, CCl
4
, a Br
2
gas, an HBr gas, or a gas having a constitution of C
x
H
y
Br
z
(x, y and z are positive integers)
According to further aspect of the present invention, there is provided a method of manufacturing a semiconductor device which comprises steps of forming a wiring layer on a semiconductor substrate via an insulator, forming a silicon nitride film represented by Si
3
N
4
on the wiring layer, forming an insulating layer on the silicon nitride film, and forming a contact hole in the insulating layer by a dry etching method. The dry etching method includes a step of etching the insulating layer by using the silicon nitride film as an etching stopper under an etching gas atmosphere. The etching gas includes a gas containing iodine, chlorine or bromine in a molecule, and a mixing ratio ((I, Cl or Br)/C) of iodine, chlorine or bromine to carbon in the etching gas is 0.3 or more, and 1.5 or less.
According to yet further aspect of the present invention, there is provided a method of manufacturing a semiconductor device which comprises steps of forming a pair of gate electrode structures on a semiconductor substrate via gate insulating films, covering the gate electrode structures and a space between the gate electrode structures with a silicon nitride film represented by Si
3
N
4
continuously, forming an insulating layer on the silicon nitride film, and forming a contact hole in the insulating layer between the gate electrode structures by a dry etching method. The dry etching method includes a step of etching the insulating layer by using the silicon nitride represented by Si
3
N
4
film as an etching stopper under an etching gas atmosphere. The etching gas includes a gas containing iodine, chlorine or bromine in a molecule, and a mixing ratio ((I, Cl or Br)/C) of iodine, chlorine or bromine to carbon in the etching gas is 0.3 or more, and 1.5 or less.
Furthermore, the aforementioned etching method is preferably used when a contact hole with an aspect ratio of 20 or less is formed in the insulating layer.
In this case, etching is performed by the etching gas from the surface of the insulating layer to reach Si
3
N
4
so that the contact hole can be formed in the insulating layer. Alternatively, in a two-step etching method which comprises performing etching from the surface of the insulating layer with a first etching gas to form an upper part of the contact hole, and subsequently performing the etching with a second etching gas until Si
3
N
4
is reached to form a lower part of the contact hole; the aforementioned etching gas including iodine, chlorine or bromine can be used as the second etching gas.
According to the dry etching method of the present invention, iodine contained in the etching gas forms CNI, which is a low vapor pressure material on Si
3
N
4
, and inhibits
Katten Muchin Zavis & Rosenman
NEC Electronics Corporation
Tran Binh X.
Utech Benjamin L.
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