JP2001332510A - Semiconductor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a junction leakage from occurring by decreasing over- etching on the surface of an underlying diffusion layer in amount so as to prevent damage and erosion when a contact hole with a high aspect ratio is provided by etching. SOLUTION: An Si-rich insulating film 16 (SiOx: 1<=x<=2) and a BPSG interlayer dielectric 13 are formed on a semiconductor substrate 11 and a diffusion layer 12, a resist pattern is formed, and, when an anisotropic etching process is carried out with a C2F6 gas with a high C/F ratio, a fluorocarbon film is deposited on an interface between the interlayer dielectric 13 and the Si-rich insulating film 16 to stop etching. After the deposited film is removed once, the film 16 is etched with C2F6 with the low C/F ratio and O2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit device, when an electrode is formed on a diffusion layer formed on a semiconductor substrate, a contact hole is formed in an insulating film on the diffusion layer by dry etching. With the miniaturization of circuit patterns, the need to form contact holes with a large aspect ratio has increased. Hereinafter, a conventional contact forming method for a semiconductor device will be described.

FIG. 3 is a sectional view of a contact portion of a conventional semiconductor integrated circuit device, wherein 1 is a semiconductor substrate, 2 is a diffusion layer formed on the surface of the semiconductor substrate 1, and 3 is a semiconductor substrate 1 and a diffusion layer 2. The interlayer insulating film 4 formed thereon is a contact hole formed in the interlayer insulating film 3, and 5 is a contact hole resist pattern in which a portion where the contact hole 4 is formed is opened. The manufacturing process of the semiconductor device configured as described above will be described below with reference to FIG.

First, a diffusion layer 2 is formed by doping an impurity on a semiconductor substrate 1 as shown in FIG.
Then, an interlayer insulating film 3 is formed on the semiconductor substrate 1 and the diffusion layer 2, and a contact hole resist pattern 5 is formed on the interlayer insulating film 3 to obtain a resist pattern shape shown in FIG. Then, a portion not covered with the contact hole resist pattern 5 is etched by anisotropic dry etching to form a contact hole 4 as shown in FIG.

Here, in the process of forming the contact hole 4, there are various variations in manufacturing process parameters.
30% to 50% of the etching time calculated when (i) the representative value of the etching rate, (ii) the representative value of the thickness of the interlayer insulating film 3, and (iii) the representative value of the contact hole resist size are used. %, Over-etching is performed to set the contact hole completely open by absorbing the above three process variations. Therefore, when the interlayer insulating film is, for example, 1000 nm, the film thickness is converted to 300.
The over-etching amount was about 500 nm.

[0006]

However, in the above-described conventional structure, the etching rate is higher than the typical value, (ii) the interlayer insulating film 3 is thinner, and (iii) the size of the contact hole resist 5 is larger. In some cases,
Since over-etching is excessively applied on the diffusion layer 2 of the semiconductor substrate 1 and damages or erodes the diffusion layer, there is a problem that junction leakage between the diffusion layer 2 and the semiconductor substrate 1 increases. In particular, with the recent miniaturization, the shallow junction of the diffusion layer 2 has progressed, and the above problem has become serious.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device in which a contact hole can be formed without performing excessive over-etching on a diffusion layer. .

[0008]

According to a first aspect of the present invention, there is provided a semiconductor device, comprising: a semiconductor substrate; an insulating film having stoichiometry formed on the semiconductor substrate; and an insulating film between the semiconductor substrate and the insulating film. And a Si-rich insulating film containing more Si than the structure having the stoichiometry, and a contact hole exposing the semiconductor substrate formed by etching the insulating film and the Si-rich insulating film. is there.

According to the semiconductor device of the first aspect, for example, the etching can be stopped once by forming the Si-rich insulating film between the semiconductor substrate having the diffusion layer on the surface and the interlayer insulating film. Etching process variations such as film thickness variations of the insulating film, etching speed variations, and etching uniformity can be absorbed, and the amount of over-etching of the diffusion layer on the bottom surface of the contact hole can be reduced.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
Forming a Si-rich insulating film containing more Si on the semiconductor substrate than the structure having stoichiometry; forming an insulating film having stoichiometry on the Si-rich insulating film; Selectively etching the film with a first gas containing C and F to form an opening;
Depositing a fluorocarbon-based material on the exposed Si-rich insulating film, removing the fluorocarbon-based material, and selectively etching the Si-rich insulating film with a second gas containing C and F And

According to the method of manufacturing a semiconductor device of the present invention, a Si-rich insulating film containing more Si than a structure having stoichiometry and an insulating film having a stoichiometry on the Si-rich insulating film are formed. Then, when the insulating film is etched with a gas containing C and F, the etching stops at the interface with the Si-rich insulating film.
Only an overetch with a small etching amount on the i-rich insulating film acts on the semiconductor substrate. Therefore, (i) variations in the etching rate, (ii) variations in the thickness of the interlayer insulating film, and (iii) variations in the contact hole size, the processing variations absorbed by over-etching the normal diffusion layer once. It can be absorbed by stopping the etching. For this reason, the amount of over-etching applied to the diffusion layer is made smaller than the conventional amount of over-etching by setting the thickness of the Si-rich insulating film to a value corresponding to the minimum necessary thickness for the etching stop. Therefore, damage and erosion to the diffusion layer can be reduced.

As described above, when a contact is formed in a semiconductor device, overetching of the semiconductor substrate due to dry etching is reduced, whereby damage and erosion to the semiconductor substrate are suppressed, and the junction between the diffusion layer and the semiconductor substrate is reduced. Leakage can be reduced.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
Forming, on a semiconductor substrate, a Si-rich insulating film containing more Si than the structure having stoichiometry; forming an insulating film having stoichiometry on the Si-rich insulating film; The film is made of a first gas having a C / F atomic number composition ratio of 1/3 or more,
Forming an opening by selectively etching to the surface of the Si-rich insulating film; treating the inside of the opening with oxygen or a gas containing oxygen; Less than 1/3, C and F
Selectively etching with a second gas having a configuration including:

According to the method of manufacturing a semiconductor device of the third aspect, the same effect as that of the second aspect can be obtained.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
The stoichiometry according to claim 2 or claim 3.
The Si-rich insulating film containing more Si than the structure having
iO _x(1 ≦ x ≦ 2) with stoichiometry
The insulating film having the structure shown in FIG._TwoIt is.

According to the method of manufacturing a semiconductor device of the fourth aspect, the same effects as those of the second or third aspect can be obtained.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
In claim 2, claim 3 or claim 4, the film thickness ratio of the insulating film having stoichiometry to the film thickness of the Si-rich insulating film containing more Si than that of the structure having stoichiometry is 60 or less. is there.

According to the method of manufacturing a semiconductor device according to the fifth aspect, the same effects as those of the second, third, or fourth aspect are obtained.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a completed sectional view of a contact portion of a semiconductor integrated circuit device according to an embodiment of the present invention. In FIG. 1, 11 is a semiconductor substrate, 12 is a diffusion layer formed on the surface of the semiconductor substrate 11, 16 is a Si-rich insulating film formed on the semiconductor substrate 11 and the diffusion layer 12, and 13 is a Si-rich insulating film. Is a contact hole formed in the interlayer insulating film 13. In the present invention, S
i-rich insulating film 16, an insulating film that includes many Si than a configuration having a stoichiometry, i.e. in SiO _x refers to what a 1 ≦ x ≦ 2. At this time, the interlayer insulating film 1
Reference numeral 3 specifically denotes an insulating material having stoichiometry whose physical properties are substantially SiO ₂ , which may contain impurities such as P and B, and is configured as described above. Hereinafter, a method of manufacturing the semiconductor device of the present embodiment will be described with reference to FIGS. First, a diffusion layer 12 is formed by doping an impurity on the semiconductor substrate 11, and a Si-rich insulating film (SiO _x ) 16 is formed on the semiconductor substrate 11 and the diffusion layer 12 by, for example, SiH ₄ and O _2.
2A is obtained by a plasma CVD method using a gas obtained by mixing 2: 1 with a gas having a shape shown in FIG. Next, on the Si-rich insulating film 16, the interlayer insulating film 13,
For example, a BPSG film formed by a normal CVD method is 800 to 1
By forming the layer 200 nm and covering it with the contact hole resist pattern 15, the shape shown in FIG. 2B is obtained.

[0020] Then, although performing anisotropic etching using an etchant of, for example, fluorocarbon systems consisting larger configuration of the C / F ratio (etching gas), for example, C ₂
Inductively coupled plasma (ICP) type etching apparatus using F ₆ gas (C / F atomic ratio = 1/3), pressure of 5 mTorr, induction coil applied source power of 2300-2
When etching is performed at 500 W and a bias power of 1000 to 1200 W applied to the electrode on the side where the semiconductor substrate 11 is provided, the interlayer insulating film 13 obtains a vertically etched high aspect ratio shape.

At the interface between the interlayer insulating film 13 and the Si-rich insulating film 16, a reaction product film having a component of fluorocarbon is deposited, and the etching is almost completely stopped here. At this time, overetching is performed for about 50% of the thickness of the interlayer insulating film 13 with respect to the thickness of the interlayer insulating film 13, but further etching does not proceed from the interface where the etching has been stopped, so that the shape of FIG. 2C is obtained. In this step, since the Si-rich insulating film 16 is hardly etched, the over-etching is
%. Conversely, even if the film thickness of the Si-rich insulating film 16 is further reduced to several tens of nm, it can withstand the overetching of the interlayer insulating film 13. Si-rich insulating film 1
6 is sufficient if it is 20 nm or more, and the film thickness ratio with the interlayer insulating film 13 used in the present embodiment is 40 to 60, but basically it is sufficient to be 60 or less and 15 or more.

When the interlayer insulating film 13 is made of SiO ₂ ,
Efficiently volatile Si is ₂ F ₆ etch process gas
And F ₄ and CO ₂ is generated and etched. on the other hand,
SiF ₄ and CO ₂ are also generated in the oxygen-deficient film such as the underlying Si-rich insulating film 16, but C atoms that do not bond with oxygen increase due to the lack of oxygen, which is caused by SiO ₂ or etching gas. Reacts with the F component and becomes a fluorocarbon-based reaction product that is no longer etched and is deposited on the bottom surface of the contact hole (the surface of the film 16). This is considered to be the reason that etching does not proceed.

Next, the fluorocarbon-based reaction product once deposited in the contact hole 14 and the contact hole resist pattern 15 are subjected to ashing by plasma of oxygen or a gas containing oxygen and cleaning / removal by a mixed solution of sulfuric acid and hydrogen peroxide. As shown in FIG.

Finally, etching is performed with an etchant in which the amount of C contributing to the etching process is reduced as compared with the etchant used for etching the interlayer insulating film 13 in FIG. In this etching, the Si-rich insulating film 1
6 and the interlayer insulating film 13 are simultaneously etched at different etching rates. For example, oxygen is added to C ₂ F ₆
By adding 10%, a part of C of C ₂ F ₆ is combined with oxygen and discharged from the exhaust system of the dry etching apparatus in the form of CO ₂ , so the amount of C contributing to etching is apparently reduced. Can be done. The etchant used in the step of FIG. 2C is such that the ratio of the number of C atoms to the total number of C ₂ F ₆ + O ₂ gas is C / F atoms of C ₂ F ₆ used for etching the interlayer insulating film 13. It can be seen that the ratio is smaller than 1/3.

The etching conditions are as follows: ICP type etching apparatus, pressure: 5 mTorr, source power: 2500-27.
When etching is performed at 00 W and a bias power of 1100 to 1300 W, the etching of the Si-rich insulating film 16 on the surface of the interlayer insulating film 13 and the bottom of the contact hole 14 proceeds, and the contact hole 14 shown in FIG.
Is formed. At this time, the etching time is about 50% with respect to the film thickness of the Si-rich insulating film 16 of 30 to 50 nm, that is, 15 to 25 in terms of film thickness.
Etching equivalent to nm is sufficient.

As described above, according to the present invention, the thick interlayer insulating film 13 occupying a large part of the etching amount of the contact hole 14 and the large variation of the overetching are caused by the etching stop once on the surface of the Si-rich insulating film 16. The amount of over-etching of the diffusion layer 12 is not 30 to 50% of the conventional thickness of the interlayer insulating film 13 but is 30 to 50% of the thin Si-rich insulating film 16. In addition, over-etching of the diffusion layer 12 can be greatly reduced. Therefore, etching damage and erosion to the diffusion layer 12 can be reduced, and occurrence of junction leak and the like can be suppressed.

When the insulating film 13 is etched, the atomic composition ratio of C / F is 1/3 or more and the upper limit is 1/2.
Further, when etching the Si-rich insulating film, the number of C atoms with respect to the total gas is smaller than 1/3 and the lower limit thereof is 1/4.

[0028]

According to the semiconductor device of the first aspect, for example, etching can be stopped once by forming a Si-rich insulating film between a semiconductor substrate having a diffusion layer on the surface and an interlayer insulating film. In addition, variations in the thickness of the interlayer insulating film, variations in the etching rate, and variations in the etching process such as the uniformity of the etching can be absorbed, and the amount of over-etching of the diffusion layer on the bottom surface of the contact hole can be reduced.

According to the method of manufacturing a semiconductor device according to the second aspect, an Si-rich insulating film containing more Si than a structure having stoichiometry and an insulating film having stoichiometry on the Si-rich insulating film are formed. Then, when the insulating film is etched with a gas containing C and F, the etching stops at the interface with the Si-rich insulating film.
Only an overetch with a small etching amount on the i-rich insulating film acts on the semiconductor substrate. Therefore, (i) variations in the etching rate, (ii) variations in the thickness of the interlayer insulating film, and (iii) variations in the contact hole size, the processing variations absorbed by over-etching the normal diffusion layer once. It can be absorbed by stopping the etching. For this reason, the amount of over-etching applied to the diffusion layer is made smaller than the conventional amount of over-etching by setting the thickness of the Si-rich insulating film to a value corresponding to the minimum necessary thickness for the etching stop. Therefore, damage and erosion to the diffusion layer can be reduced.

As described above, when a contact is formed in a semiconductor device, overetching of the semiconductor substrate due to dry etching is reduced, whereby damage and erosion to the semiconductor substrate are suppressed, and the junction between the diffusion layer and the semiconductor substrate is reduced. Leakage can be reduced.

According to the method of manufacturing a semiconductor device of the third aspect, the same effect as that of the second aspect can be obtained.

According to the method of manufacturing a semiconductor device of the fourth aspect, the same effects as those of the second or third aspect can be obtained.

According to the method of manufacturing a semiconductor device according to the fifth aspect, the same effects as those of the second, third, or fourth aspect are obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a contact hole structure according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a process for manufacturing a contact hole according to an embodiment of the present invention.

FIG. 3 is a process chart showing a conventional method for manufacturing a contact hole.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 diffusion layer 3 interlayer insulating film 4 contact hole 5 contact hole resist pattern 11 semiconductor substrate 12 diffusion layer 13 interlayer insulating film 14 contact hole 15 contact hole resist pattern 16 Si-rich insulating film

Claims (5)

[Claims] 1. A semiconductor substrate, an insulating film having stoichiometry formed on the semiconductor substrate, and Si having a stoichiometric structure formed between the semiconductor substrate and the insulating film. And a contact hole exposing the semiconductor substrate by etching the insulating film and the Si-rich insulating film. 2. A step of forming a Si-rich insulating film containing more Si than a structure having stoichiometry on a semiconductor substrate, and forming an insulating film having a stoichiometry on the Si-rich insulating film. A step of selectively etching the insulating film with a first gas containing C and F to form an opening, and depositing a fluorocarbon-based material on the exposed Si-rich insulating film; And a step of selectively etching the Si-rich insulating film with a second gas containing C and F. 3. A step of forming a Si-rich insulating film containing more Si than a structure having stoichiometry on a semiconductor substrate, and forming an insulating film having stoichiometry on the Si-rich insulating film. Forming an opening by selectively etching the insulating film to the surface of the Si-rich insulating film with a first gas having a C / F atomic number composition ratio of 1/3 or more; Treating the inside of the opening with oxygen or a gas containing oxygen, and selecting the Si-rich insulating film with a second gas containing C and F, in which the number of C atoms is less than 1/3 of all gas atoms. A method of manufacturing a semiconductor device, comprising: 4. The configuration having stoichiometry has
The Si-rich insulating film containing much i is SiO _x (1 ≦ x ≦
4. The method for manufacturing a semiconductor device according to claim ₂ , wherein the insulating film having the structure having stoichiometry is substantially SiO2. 5. The configuration having stoichiometry has a higher S
5. The method of manufacturing a semiconductor device according to claim 2, wherein the ratio of the thickness of the insulating film having stoichiometry to the thickness of the Si-rich insulating film containing a large amount of i is 60 or less.