JPH08203999A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To obtain a semiconductor device capable of simplifying and easily performing a manufacturing process of a semiconductor device having a contact hole having a stepped shape. [Structure] A temporary contact hole 14 is formed in the interlayer insulating film 12 by anisotropic etching, and a second contact hole 14 is formed on the interlayer insulating film 12.
Of the resist film 15 is applied to fill the inside of the temporary contact hole 14 with the second resist film 15, and the second resist film 15 is anisotropically etched back to a position where a step is formed in the temporary contact hole 14. Then, the interlayer insulating film 12 above the position where the part 15a of the second resist film of the temporary contact hole 14 is embedded is isotropically etched to remove the part 15a of the second resist film of the temporary contact hole 14. A part 16 of the contact hole having a diameter larger than that of the temporary contact hole 14 is formed above the embedded position, and a part 15a of the second resist film is removed to form a contact hole 17 formed. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device for improving the step coverage of wiring in a contact hole.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have been highly integrated,
The circuit patterns formed therein are also becoming finer. Accordingly, the aspect ratio of the contact hole is increasing, and the step coverage when forming a wiring material in the contact hole is becoming a problem. Therefore, a semiconductor device has been proposed in which the shape of the contact hole has a step to improve the step coverage of film formation of the wiring in the contact hole. Hereinafter, a method for manufacturing a semiconductor device having a contact hole having a step will be described.

FIG. 4 is a sectional view showing a conventional manufacturing process of a semiconductor device. In the figure, 1 is a semiconductor substrate, 2 is an element isolation region formed on the upper surface of the semiconductor substrate 1, 3 is a first interlayer insulating film laminated on the semiconductor substrate 1, and 4 is this first
Is a second interlayer insulating film laminated on the interlayer insulating film 3 and is made of a material having an etching rate higher than that of the first interlayer insulating film 3. 5 is a resist film patterned and formed on the second interlayer insulating film 4, 6 is a temporary contact hole formed through the first and second interlayer insulating films 3 and 4 with the same diameter, and 7 is The contact hole has a step at the boundary between the first and second interlayer insulating films 3 and 4, and the second interlayer insulating film 4 has a diameter larger than that of the first interlayer insulating film 3.

Next, a manufacturing process of the conventional semiconductor device configured as described above will be described. First, the element isolation region 2
First and second interlayer insulating films 3 and 4 are sequentially formed on the semiconductor substrate 1 on which is formed by, for example, a CVD method (FIG. 4).
(A)). Next, a resist is applied on the second interlayer insulating film 4 and patterned to form a resist film 5 (FIG. 4).
(B)). Next, the first and second interlayer insulating films 3 and 4 are anisotropically etched using the resist film 5 as a mask to form a temporary contact hole 6, and then the resist film 5 is removed (FIG. 4C). .

Next, the temporary contact hole 6 is isotropically etched by, for example, wet etching to form a contact hole 7. At this time, the shape of the contact hole 7 is such that the etching rate of the second interlayer insulation 4 is the first.
Is larger than that of the interlayer insulating film 3 of
Has a step at the boundary between the interlayer insulating films 3 and 4 of
The second interlayer insulating film 4 has a hole having a larger diameter than the first interlayer insulating film 3 (FIG. 4 (d)). Therefore, the contact hole 7 is formed to have a step, and the step coverage is improved by forming a wiring through the contact hole 7.

Further, unlike the above-mentioned conventional example, a conventional example in which a contact hole having a step is formed by one kind of interlayer insulating film will be described below. FIG. 5 shows, for example, Japanese Patent Laid-Open No. 63-12215.
FIG. 7 is a cross-sectional view showing another manufacturing process of the conventional semiconductor device shown in Japanese Patent Laid-Open No. 2 publication. In the figure, the same parts as those in the above-mentioned conventional example are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 8 is an interlayer insulating film formed on the semiconductor substrate 1, 9 is a resist film patterned on the interlayer insulating film 8, 9a is a modified resist film in which the opening of the resist film 9 is enlarged, and 10 is interlayer insulating film. Temporary contact hole opened part way through the film 8, 1
Reference numeral 1 is a contact hole formed through the interlayer insulating film 8 and having a step.

Next, a manufacturing process of the conventional semiconductor device configured as described above will be described. First, the interlayer insulating film 8 is formed on the semiconductor substrate 1 in which the element isolation region 2 is formed, and a resist is applied and patterned on the interlayer insulating film 8 to form a resist film 9 (FIG. 5A). Next, using the resist film 9 as a mask, the interlayer insulating film 8 is dry-etched for a predetermined time to open the interlayer insulating film 8 up to the middle thereof to form a temporary contact hole 10 (FIG. 5B).

Next, for example, plasma ashing is performed for a predetermined time to retreat and enlarge the opening of the resist film 9 to form a corrected resist film 9a (FIG. 5).
(C)). Next, the interlayer insulating film 8 is dry-etched again for a predetermined time by using the modified resist film 9a as a mask, and the portion of the temporary contact hole 10 formed previously with the diameter of the temporary contact hole 10 and the opening of the modified resist film 9a are opened. A portion having a diameter is formed, and a contact hole 11 having a step is formed at this boundary (FIG. 5D).

Next, the modified resist film 9a is removed (FIG. 5 (e)). Therefore, the contact hole 11 is formed to have a step, and if the wiring is formed through the contact hole 11, the step coverage is improved.

[0010]

The conventional semiconductor device is constructed as described above, and the shape of each contact hole 7 and 11 has a step.
Although the step coverage can be improved by forming the wiring through the wirings 11 and 11, in the above-described conventional example, the two types of interlayer insulating films 3 and 4 must be formed, which complicates the process and Although the conventional example can be formed by forming only one type of interlayer insulating film 8, it is very difficult to adjust the plasma ashing for retracting the resist film 9 and forming the modified resist film 9a with good controllability. It is difficult to form a desired step, and the conventional manufacturing method has various problems.

The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a method of manufacturing a semiconductor device which can simplify and simplify the process and can improve the step coverage of wiring in a contact hole. To aim.

[0012]

Means for Solving the Problems Claim 1 according to the present invention.
In the method of manufacturing a semiconductor device described above, in forming a contact hole having a stepped shape in an interlayer insulating film on a semiconductor substrate, the interlayer insulating film is formed on the semiconductor substrate, and a temporary contact is made to the interlayer insulating film by anisotropic etching. A hole is formed, a resist is applied on the interlayer insulating film, and the temporary contact hole is filled with the resist. Then, the resist is anisotropically etched back to the position where a step is formed in the temporary contact hole, and the interlayer insulating film above the position where the resist is buried in the temporary contact hole is isotropically etched to make a temporary contact. A hole having a diameter larger than the diameter of the temporary contact hole is formed above the position where the resist is embedded in the hole, and the resist is removed to form the contact hole.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device, an interlayer insulating film is formed on a semiconductor substrate, a resist is applied on the interlayer insulating film and patterned, and the interlayer insulating film is used as a mask. Etching is performed by gradually reducing the content of trifluoromethane using a gas system containing trifluoromethane to form a temporary contact hole.
Then, the contact hole is formed by removing the resist and the side wall protective film which is a reaction product of the resist and trifluoromethane formed on the inner wall of the temporary contact hole during etching.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein the etching includes the step of adjusting the trifluoromethane content to 40% or more and less than 40%. .

[0015]

In the method for manufacturing a semiconductor device according to the first aspect of the present invention, in forming a contact hole having a step in the interlayer insulating film on the semiconductor substrate, the interlayer insulating film is formed on the semiconductor substrate, A temporary contact hole is formed in the interlayer insulating film by etching, a resist is applied on the interlayer insulating film, and the inside of the temporary contact hole is filled with the resist. Then, the resist is anisotropically etched back to the position where a step is formed in the temporary contact hole, and the interlayer insulating film above the position where the resist is buried in the temporary contact hole is isotropically etched to make a temporary contact. Since a hole having a diameter larger than the diameter of the temporary contact hole is formed above the position where the resist is embedded in the hole and the contact hole is formed by removing the resist, a contact hole having a stepped shape can be easily formed. be able to.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein an interlayer insulating film is formed on a semiconductor substrate,
A resist is applied on the inter-layer insulation film and patterned, and the inter-layer insulation film is etched using the resist as a mask to reduce the trifluoromethane content stepwise using a gas system containing trifluoromethane to form a temporary contact hole. To do. Then, the contact hole is formed by removing the resist and the side wall protective film which is a reaction product of trifluoromethane with the resist formed on the inner wall of the temporary contact hole at the time of etching, so that the contact hole having a step shape can be easily formed can do.

Further, in the method for manufacturing a semiconductor device according to the third aspect of the present invention, since the etching including the step of setting the content of trifluoromethane to be 40% or more and less than 40% is performed, the contact hole is surely removed. A step portion can be formed in

[0018]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a manufacturing process of a semiconductor device according to a first embodiment of the present invention. In the figure, the same parts as those in the conventional case are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 12 is an interlayer insulating film formed on the semiconductor substrate 1, 13 is a first resist film patterned and formed on the interlayer insulating film 12, and 14 is a temporary contact hole formed through the interlayer insulating film 12. , 15 is a second resist film coated on the interlayer insulating film 12, and 15a is a temporary contact hole 1
4 is a part of the second resist film whose upper surface is buried lower than the upper surface of the interlayer insulating film 12, 16 is a part of a contact hole described later, and 17 is a contact hole formed in the interlayer insulating film 12 and having a step. is there.

Next, a manufacturing process of the semiconductor device of the first embodiment constructed as described above will be described. First, for example, CVD is performed on the semiconductor substrate 1 on which the element isolation region 2 is formed.
An interlayer insulating film 12 is formed by a method, a resist is applied on the interlayer insulating film 12, and patterning is performed to form a first resist film 13. Then, using the first resist film 13 as a mask, the interlayer insulating film 12 is anisotropically etched to form a temporary contact hole 14 (FIG. 1A). Next, the first resist film 13 is removed, and the second resist film 15 is applied on the interlayer insulating film 12 to fill the inside of the temporary contact hole 14 (FIG. 1B).

Next, the second resist film 15 is etched back by anisotropic etching to obtain a temporary contact hole 1.
The second resist film 15 is removed up to a position where the upper surface is lower than the upper surface of the interlayer insulating film in 4 (this position is the position of the step portion of the contact hole 13 described later), and the second
A part of the resist film 15a is left (FIG. 1C). Next, the interlayer insulating film 12 at the opening of the temporary contact hole 14
Is subjected to isotropic etching, for example, by wet etching to form a part 16 of the contact hole having a diameter larger than that of the temporary contact hole 14 (FIG. 1D). Next, a part of the second resist film 15a is removed by oxygen plasma, for example, to form a contact hole 17 (FIG. 1).
(E)).

In the method of manufacturing the semiconductor device of Example 1 manufactured as described above, since the contact hole 17 is formed so as to have a step, the contact hole 1
If the wiring is formed through the step 7, the step coverage can be improved, and the interlayer insulating film 12 can be formed by one type, and the step can be easily formed by wet etching. The process can also be simplified as compared with the conventional one.

The step forming position of the contact hole is
It is possible to easily form the second resist film 11 at a desired position by controlling the etch back.

Embodiment 2 FIG. In the first embodiment, the case where the step portion of the contact hole 17 has one step has been described, but the present invention is not limited to this, and the step of the contact hole is repeated to form two or more step portions. It goes without saying that you can do it.

Example 3. FIG. 2 is a sectional view showing a manufacturing process of a semiconductor device according to a third embodiment of the present invention. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 18 is an interlayer insulating film formed on the semiconductor substrate 1, 19 is a resist film patterned and formed on the interlayer insulating film 18, and 20 is, for example, CF and CF ₃ formed on an upper wall surface of a temporary contact hole described later.
Such as a carbon-based sidewall protection film, 21 a part of the temporary contact hole, 22 a temporary contact hole in which the interlayer insulation film 18 is penetrated and the sidewall protection film 20 remains on the upper part, and 23 is an interlayer insulation film. The contact hole has a step portion while penetrating the film 18.

Next, a manufacturing process of the semiconductor device of the third embodiment constructed as described above will be described. First, for example, CVD is performed on the semiconductor substrate 1 on which the element isolation region 2 is formed.
An interlayer insulating film 18 is formed by a method, and a resist is applied on the interlayer insulating film 18 and patterned to form a resist film 19. Then, using the resist film 19 as a mask, the interlayer insulating film 1
Etching of 8 is performed. At this time, the etching conditions are, for example, CHF ₃ (chemical formula of trifluoromethane), CF ₄ and Ar.
And the gas ratio of CHF _{3 is} , for example, 8
Perform at 0%. Then, the resist film 18 and CHF are formed on the side wall.
The reaction product with ₃ is deposited, and a part 21 of the temporary contact hole where the side wall protective film 20 is formed is formed (FIG. 2).
(A)).

Next, the gas ratio of CHF ₃ which is an etching condition is gradually reduced to, for example, 20%, and the interlayer insulating film 18 is formed.
When the etching is continuously performed, since the reaction product of the resist film 19 and CHF ₃ is not deposited on the side wall, the side wall protective film 20 is etched with a smaller diameter than the patterning of the resist film 19 to form the temporary contact hole 21. (FIG. 2 (b)). Next, the resist film 19 and the sidewall protection film 20 are removed by oxygen plasma, for example, to form a contact hole 23 (FIG. 2C).

In the method of manufacturing the semiconductor device of the third embodiment manufactured as described above, since the contact hole 23 is formed so as to have a step, it is possible to form a wiring through the contact hole 23. For example, not only the step coverage is improved, but also the step coverage can be formed only by changing the etching conditions, so that the manufacturing process can be further simplified and facilitated.

The step forming position of the contact hole 23 can be easily formed at a desired position by controlling the switching time of the etching conditions.

Example 4. In the third embodiment, the case where the stepped portion of the contact hole 23 is one step has been described, but the present invention is not limited to this, and the etching condition C of the third embodiment is used.
By increasing the number of steps for changing the gas ratio of HF ₃ , it is possible to form two or more stepped portions of the contact hole.

An example of forming a contact hole having two step portions will be described with reference to FIG. First, after the formation as shown in FIG. 2A through the same steps as those in the above-mentioned Example 3, the gas ratio of CHF ₃ is set to, for example, 50%, and then the interlayer insulating film 18 is etched. At this time, the reaction product of the resist film 19 and CHF ₃ is deposited on the side wall to form the second side wall protective film 24, but the content of CHF ₃ is gradually reduced from 80% to 50%. Therefore, it is formed thinner than the side wall protection film 20.

Next, when the interlayer insulating film 18 is etched under the etching conditions of a CHF ₃ gas ratio of, for example, 20%, the reaction product of the resist film 19 and CHF ₃ is not deposited on the side wall. The side wall protective films 20 and 24 are etched to have a smaller diameter than the patterning of the resist film 19 to form a temporary contact hole 25 (FIG. 3).
(A)). Next, the resist film 1 is formed by oxygen plasma, for example.
9 and both side wall protective films 20 and 24 are removed to form contact holes 26 (FIG. 3B).

In the method of manufacturing the semiconductor device of the fourth embodiment manufactured as described above, since the contact hole 26 is formed so as to have a step, it has the same effect as that of the third embodiment.

Example 5. In Examples 3 and 4 above, CH
While showing a variety of examples of gas ratio of F _3, these not limited, CHF ₃ and the resist and is a boundary 40% ratio gas CHF ₃ become unresponsive, CHF ₃ gas ratio of 40% or more If the etching is performed so as to include steps of less than 40%, it is possible to surely form a contact hole having a step.

[0034]

As described above, according to claim 1 of the present invention, in forming a contact hole having a step difference in the interlayer insulating film on the semiconductor substrate, the interlayer insulating film is formed on the semiconductor substrate, A temporary contact hole is formed in the interlayer insulating film by anisotropic etching, a resist is applied on the interlayer insulating film, and the inside of the temporary contact hole is filled with the resist.
Then, the resist is anisotropically etched back to the position where a step is formed in the temporary contact hole, and the interlayer insulating film above the position where the resist is buried in the temporary contact hole is isotropically etched to make a temporary contact. A hole having a diameter larger than the diameter of the temporary contact hole is formed above the position where the resist of the hole is embedded,
Since the resist is removed to form the contact hole,
It is possible to provide a method of manufacturing a semiconductor device that can simplify and facilitate the formation of a contact hole having a stepped shape and can improve the step coverage of wiring or the like in the contact hole.

According to a second aspect of the present invention, an interlayer insulating film is formed on a semiconductor substrate, a resist is applied on the interlayer insulating film and patterned, and the interlayer insulating film is trifluoromethane using the resist as a mask. Etching is performed by gradually reducing the content of trifluoromethane by using a gas system containing TiO2 to form a temporary contact hole. Then, the side wall protective film, which is a reaction product of the resist and the trifluoromethane formed on the inner wall of the temporary contact hole at the time of etching, is removed to form the contact hole, so that the contact hole having a stepped shape can be formed more easily. It is possible to provide a method of manufacturing a semiconductor device which is simpler and easier, and which can improve step coverage such as wiring into the contact hole.

According to the third aspect of the present invention, since the etching is performed in the second aspect including the step of setting the content of trifluoromethane to be 40% or more and less than 40%, the step difference is surely achieved. It is possible to provide a method for manufacturing a semiconductor device which can form a contact hole having a shape having a shape and can more surely improve the step coverage such as wiring into the contact hole.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of a semiconductor device according to a third embodiment of the invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of a semiconductor device according to a fourth embodiment of the invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of a conventional semiconductor device.

FIG. 5 is a cross-sectional view showing another conventional manufacturing process of a semiconductor device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 semiconductor substrate, 12 interlayer insulation film, 14 temporary contact hole, 15 2nd resist film, 15a 2nd resist film part, 16 contact hole part, 17
Contact hole, 18 interlayer insulating film, 19 resist film, 20 sidewall protection film, 21 part of temporary contact hole, 22 temporary contact hole, 23 contact hole.

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device for forming a contact hole having a stepped shape in an interlayer insulating film on a semiconductor substrate, comprising the steps of forming the interlayer insulating film on the semiconductor substrate and anisotropic etching. To form a temporary contact hole in the interlayer insulating film, a step of applying a resist on the interlayer insulating film and filling the inside of the temporary contact hole with the resist, and the temporary etching of the resist by anisotropic etching. A step of etching back to the position where the step is formed in the contact hole, and isotropic etching of the interlayer insulating film above the position where the resist is embedded in the temporary contact hole to perform the resist in the temporary contact hole. Step of forming a hole having a diameter larger than the diameter of the temporary contact hole above the embedded position of And a step of removing the resist to form the contact hole, the method of manufacturing a semiconductor device. 2. A step of forming an interlayer insulating film on a semiconductor substrate, a step of coating and patterning a resist on the interlayer insulating film, a step of coating the interlayer insulating film with the resist as a mask, and a gas containing trifluoromethane. System to reduce the trifluoromethane content stepwise to form a temporary contact hole by etching, and the resist and the resist and the trifluoromethane formed on the inner wall of the temporary contact hole during the etching. And a step of forming a contact hole by removing a side wall protective film which is a reaction product of the semiconductor device. 3. The method of manufacturing a semiconductor device according to claim 2, further comprising an etching step including a step of setting the content of trifluoromethane to 40% or more and less than 40%.