JP2003234337A - Plasma etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the defect that an SiN film is concurrently etched together with an organic SiO<SB>2</SB>film when the organic SiO<SB>2</SB>film is etched, because a correlation between contents of carbon and hydrogen contained in the organic SiO<SB>2</SB>film and the selective rate of the organic SiO<SB>2</SB>film to the SiN film of a ground is unknown, and the SiN film is low even if the organic SiO<SB>2</SB>film having a low relative dielectric constant and proper electrical characteristics is employed. <P>SOLUTION: In the plasma etching method, treatment gas containing fluorocarbon, etc., is introduced from a gas inlet port 11C into a treatment vessel 11, and an organic and low dielectric constant film on a silicon nitride film in a substrate W to be etched is plasma-etched. The silicon nitride film wherein the C/Si of its surface is more than 0.285 is used, and thereby, the organic and low dielectric constant film can be selectively etched for the silicon nitride film. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma etching method.

[0002]

2. Description of the Related Art Conventionally, as an interlayer insulating film in a semiconductor device, a SiN film (silicon nitride film) is used as a barrier layer of Si.
An O ₂ film was used. However, the silicon oxide film (S
Since the relative dielectric constant of the (iO ₂ film) is relatively high, there has been a problem in terms of electrical characteristics in recent semiconductor devices that require a finer wiring structure. To solve the problem, a relatively low dielectric constant organic SiO ₂ film, i.e. SiO ₂
A film that incorporates carbon and hydrogen is used.

[0003]

However [0007] Conventionally, unknown correlation between the content of carbon and hydrogen in the SiO ₂ film of organic, and SiO ₂ film selection ratio of the organic system to SiN film underlying Therefore, even if an organic SiO ₂ film having a low relative dielectric constant and good electrical characteristics is adopted, since the selection ratio of the organic SiO ₂ film to the SiN film is low, the organic Si ₂ film is
There is a problem that the SiN film is also etched when the O ₂ film is etched.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a plasma etching method capable of increasing the selection ratio of an organic SiO ₂ film to a SiN film.

[0005]

The present inventors have found that the SiN film
Organic SiO against_TwoVarious studies on membrane selection ratio
As a result, the organic-based SiO for the SiN film_TwoMembrane selection
The ratio is based on organic SiO _TwoSi, not the composition and structure of the film
The amount ratio of carbon to silicon on the surface of the N film (hereinafter,
It describes as "C / Si". ) Depends on
It was

The present invention has been made on the basis of the above-mentioned findings, and the plasma etching method according to claim 1 of the present invention converts the processing gas introduced into the processing container into plasma, and treats the processing target in the processing container. In a method of plasma etching a material film containing carbon and silicon formed on a silicon nitride film in a body, C / Si on the surface of the silicon nitride film is 0.285 or more. is there.

The plasma etching method according to a second aspect of the present invention is the plasma etching method according to the first aspect, wherein C / Si on the surface of the silicon nitride film is 0.285-1.
It is characterized by being 0.

According to a third aspect of the present invention, in the plasma etching method according to the first aspect, the surface of the silicon nitride film has C / Si of 0.285 to 0.
It is characterized by being 470.

The plasma etching method according to a fourth aspect of the present invention is characterized in that, in the invention according to any one of the first to third aspects, the material film contains oxygen. It is a thing.

The plasma etching method according to a fifth aspect of the present invention is the plasma etching method according to any one of the first to fourth aspects, wherein the processing gas is a substance containing carbon and fluorine. It is characterized by including.

According to a sixth aspect of the present invention, in the plasma etching method according to the fifth aspect, the processing gas contains at least one of nitrogen, carbon monoxide and oxygen. It is a feature.

Further, the plasma according to claim 7 of the present invention
The etching method is the method according to claim 5 or 6.
In the light, the gas containing carbon and fluorine is C
F_Four, CHF_Three, CH_TwoF_Two, CH_ThreeF, C_TwoF_Four, C
_TwoF₆, C_ThreeF₆, C_ThreeF₈, C _FourF₆, C_FourF₈as well as
C₅F₈Characterized by including at least one of
According to claim 5 or claim 6,

Further, in the plasma etching method according to the eighth aspect of the present invention, the processing gas introduced into the processing container is turned into plasma, the processing gas introduced into the processing container is turned into plasma, and the target gas present in the processing container is converted into plasma. In the method of plasma etching a substance film containing carbon, silicon and oxygen on a silicon nitride film in a treated body, as the treatment gas, a substance containing carbon and fluorine, a substance containing nitrogen, and a substance containing carbon and oxygen. It is characterized in that a mixed gas containing and is used, and the amount of the nitrogen-containing substance in the processing gas introduced into the processing container is reduced as the plasma etching progresses.

Further, in the plasma etching method according to claim 9 of the present invention, the processing gas introduced into the processing container is turned into plasma, and carbon and silicon on the silicon nitride film in the object in the processing container are processed. In the method of plasma etching a material film containing oxygen and oxygen, a plasma etching method using a mixed gas containing a material containing carbon and fluorine, a material containing nitrogen, and a material containing carbon and oxygen as the processing gas. The amount of introduction of the substance containing carbon and oxygen in the processing gas into the processing container is increased as the process proceeds.

The plasm according to claim 10 of the present invention
The etching method is the method according to claim 8 or 9.
In the invention, CF_Four, CHF_Three, CH_TwoF_Two, CH_Three
F, C_TwoF_Four, C_TwoF₆, C_ThreeF₆, C_ThreeF₈, C_FourF
₆, C_FourF₈, C₅F₈From at least one of
And the substance having nitrogen is N_Two, N_TwoO, NO _Two
Consisting of at least one of the above and having carbon and oxygen
Substances are CO, CO _TwoFrom at least one of
It is characterized by becoming.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below based on the embodiments shown in FIGS. First, an etching apparatus preferably used in the plasma etching method of this embodiment will be described. As shown in FIG. 1, the etching apparatus 10 used in this embodiment forms a processing container 11 made of metal (for example, aluminum whose surface is oxidized) and grounded for safety, and an upper wall of the processing container 11. The upper electrode 13 is supported on the side wall 11A via the insulator 12, and the lower electrode 15 is provided below the upper electrode 13 with the insulator 14 on the bottom surface 11B.

A first high frequency power supply 17 is connected to the upper electrode 13 via a matcher 16, and a second high frequency power supply 19 is connected to the lower electrode 15 via a matcher 18. An electrostatic chuck 20 is arranged on the lower electrode 15. The electrode 20A interposed in the electrostatic chuck 20 is connected to a DC power supply 21, and DC power is applied from the DC power supply 21 to the electrode 20A to electrostatically attract the wafer W on the electrostatic chuck 20. Further, the side wall 1 of the processing container 11
A gas inlet 11C connected to a processing gas source (not shown) is formed in the upper portion of 1A, and the processing gas is introduced into the processing container 11 through the gas inlet 11C. A gas exhaust port 11D connected to an exhaust device (not shown) is formed in the lower portion of the side wall 11A of the process container 11, and the inside of the process container 11 is evacuated from the gas exhaust port 11D via the exhaust device.

Next, an embodiment of the plasma etching method of the present invention using the etching apparatus 10 will be described. First, the wafer W is placed on the electrostatic chuck 30 in the processing container 11 via the carry-in port (not shown). Then
While exhausting the inside of the processing container 11 from the gas exhaust port 11D,
The processing gas is introduced into the processing container 11 through the gas introduction port 11C. At this time, the first and second high-frequency power supplies 17 and 19 apply the first and second high-frequency powers to the upper electrode 13 and the lower electrode 15, respectively. Further, DC power is also applied to the electrostatic chuck 20 at the same time as or before or after the first and second high-frequency power is applied. By these operations, the electrostatic chuck 2
The wafer W is adsorbed on the surface of the wafer W, the process gas is turned into plasma between the upper electrode 13 and the lower electrode 15, and the etching target portion of the wafer W is plasma etched.

In this embodiment, the material film containing carbon (C) and silicon (Si) on the silicon nitride film formed on the wafer W is targeted for etching. C / Si on the surface of the silicon nitride film is 0.285 or more, and 0.2
85-1.0 are preferable and 0.285-0.470 are more preferable. The substance film containing carbon (C) and silicon (Si) may contain oxygen (O) or hydrogen (H).

In the plasma etching of this embodiment,
The processing gas used is carbon (C) and fluorine (F)
A gas containing a substance having a is preferably used. carbon
As a gas containing a substance having (C) and fluorine (F)
Is, for example, CF_Four, C_TwoF _Four, C_TwoF₆, C_ThreeF₆,
C_ThreeF₈, C_FourF₆, C_FourF₈, C₅F₈Floroka, etc.
Carbon containing gas, CHF_Three, CH_TwoF_Two, CH_ThreeF
And other gas containing hydrofluorocarbon.
The processing gas contains at least one of these gases.
I'm out. Therefore, select two or more of these gases as appropriate.
The mixed gas described above can be used as appropriate. For processing gas
Is oxygen (O_Two), Nitrogen (N_Two), Carbon monoxide (CO)
And inert gas such as argon (Ar) and helium (He)
Can be appropriately selected and added. Oxygen (O_Two),
Nitrogen (N_Two) Is added, carbon (C) and silica
Increasing the etching rate of substances containing elemental (Si)
be able to.

When C / Si on the surface of the above-mentioned silicon nitride film is larger than 0.285, fluorine radicals (F ^* ) which are reaction active species and carbon (C) on the surface of the silicon nitride film are bonded to each other, and CF. _{An X-} based polymer is formed on the surface of the silicon nitride film, and silicon (S
The action of inhibiting the withdrawal of i) works greatly. As a result, the etching rate of the silicon nitride film is reduced and the selectivity of the material film containing carbon and silicon to the silicon nitride film is increased, and the material film containing carbon and silicon is selectively etched with respect to the silicon nitride film. can do. However, when C / Si on the surface of the silicon nitride film exceeds 1.0, the surface resistance value of the silicon nitride film is excessively lowered, which may impair the function as a barrier layer, which is not preferable. Therefore, according to the present embodiment, the material film containing carbon and silicon can be selectively plasma-etched with respect to the silicon nitride film by setting the C / Si on the surface of the silicon nitride film to 0.285 or more. .

In another embodiment of the present invention, the processing gas introduced into the processing container 11 is turned into plasma, and carbon (C) formed on the silicon nitride film in the wafer W in the processing container 11 is converted into plasma. When a material film containing silicon, silicon (Si), and oxygen (O) is plasma-etched, a processing gas includes carbon (C), a material containing fluorine (F), a material containing nitrogen (N), and carbon (C). ) And a substance containing oxygen (O). Then, when the processing gas is introduced into the processing container 11, the introduction amount of the substance having nitrogen in the processing gas is reduced as the plasma etching progresses, and then introduced into the processing container 11. Reducing the amount of introduction does not mean only the case where the amount is continuously reduced as shown in FIG. 2 (a). For example, as shown in (b) to (d) of FIG. Although it may partially increase in the decreasing process of, the case where the plasma etching time as a whole tends to decrease is also included. The same applies to the case where the introduction amount of the processing gas is increased as described above.
(A) to (d) of the above. Of course, the introduction mode of the processing gas is not limited to the examples shown in FIGS.

As the substance having carbon and fluorine in the processing gas, the same gas as in the above embodiment can be used. Further, as the substance having nitrogen in the process gas, at least one of N ₂ , N ₂ O and NO ₂ can be selected and used, and as the substance having carbon and oxygen, CO can be used. , CO ₂ can be selected and used. Although the substance film containing carbon, silicon, and oxygen may contain hydrogen, this embodiment can also be applied to this case.
Further, by reducing the introduction amount of the substance containing nitrogen into the processing container 11, it is possible to reduce the abrasion of the resist which is the etching mask of the substance film containing carbon, silicon and oxygen as the etching progresses.

In still another embodiment of the present invention, the processing gas introduced into the processing container 11 is turned into plasma and carbon (C) formed on the silicon nitride film in the wafer W in the processing container 11 is converted into plasma. ), A substance film containing silicon (Si) and oxygen (O), and a substance containing carbon (C) and fluorine (F), a substance containing nitrogen (N), and carbon A mixed gas containing (C) and a substance containing oxygen (O) is used. Then, when the processing gas is introduced into the processing container 11, the substances containing carbon and oxygen in the processing gas are increased as shown in FIGS. 3A to 3D as the plasma etching progresses. It is introduced into the processing container 11. By increasing the amount of the substance having carbon and oxygen introduced into the processing container, the fluorine radical (F ^* ), which is a reactive species, reacts with the substance having carbon and oxygen and is chemically inactive. become. Therefore,
The reaction between silicon (Si) and fluorine (F) in the silicon nitride film can be suppressed, and the etching rate of the silicon nitride film can be reduced. Further, since the substance containing carbon and oxygen also has the effect of protecting the resist, it is possible to reduce the amount of abrasion of the resist as the plasma etching progresses. The plasma etching method of this embodiment and the other embodiments may be performed together. That is, when the processing gas is introduced into the processing container 11, the nitrogen-containing substances in the processing gas tend to be reduced as the plasma etching progresses, and the carbon- and oxygen-containing substances in the processing gas tend to be reduced. And then each is introduced into the processing container 11.

[0025]

EXAMPLES Specific examples will be described below. [Preparation of Samples] In this example, the following three kinds of samples were prepared by using the plasma CVD method and the spin coating method. Sample A: Using a plasma CVD apparatus, the pressure inside the reaction vessel was kept at 900 mTorr, the susceptor temperature was kept at 375 ° C., and hexamethyldisilane (HMDS) was added at 50 scc.
At a flow rate of m, N ₂ O was introduced into the reaction vessel at a flow rate of 200 sccm, and the frequency of the high frequency power source for plasma generation was set to 1
A material film containing carbon and silicon was formed on the silicon nitride film of the wafer by setting 3.56 MHz and the power thereof to 250 W. Sample B: LKD-S2010 manufactured by JSR was spin-coated on the silicon nitride film of the wafer to form a material film containing carbon and silicon. Sample C: KSR-5109 manufactured by JSR was spin-coated on the silicon nitride film of the wafer to form a material film containing carbon and silicon.

[Calculation of C / Si] By XPS (X-ray photoelectron spectroscopy) analysis of the surface of the silicon nitride film, the peak intensity due to each element on the surface of the silicon nitride film is measured to determine the substance on the surface of the silicon nitride film. The quantitative ratio was calculated. That is, the peak intensity due to carbon (C) and the peak intensity due to silicon (Si) are obtained, and the ratio of these peak intensities (peak intensity due to C / peak intensity due to Si) is
/ Si. C / Si on the surface of silicon nitride film
Was calculated by immersing the material film containing carbon and silicon on the silicon nitride film of each sample by immersing it in hydrogen fluoride to expose the silicon nitride film, and by XPS analysis of the exposed surface. VG as an XPS device
ESCALAB 2001-Q from SCIENTIFIC
N was used. When the silicon nitride film itself was immersed in hydrogen fluoride (the immersion time is about the same as the above), carbon (C), silicon (Si), nitrogen (N ), The ratio of peak intensities due to fluorine (F) hardly changed. Therefore, it is considered that C / Si does not change by being immersed in hydrogen fluoride.

Next, using the etching apparatus 10 shown in FIG. 1, each sample is etched under the following etching conditions to etch the target portion, and the following Table 1 shows each sample.
The results shown in are obtained. [Etching conditions] First high frequency power source frequency: 500 MHz First high frequency power source: 1000 W Second high frequency power source frequency: 1.6 MHz Second high frequency power source: 600 W Pressure in processing chamber: 2 Pa Wafer temperature: 0 ° C. Etching gas flow rate: C ₄ F ₈ = 10 sccm, A
r = 190 sccm

[0028]

[Table 1] However, E / R: etching rate (nm / min) selection ratio: etching rate of material film / etching rate of SiN film

According to the results shown in Table 1, when the C / Si on the surface of the silicon nitride film is set to 0.285 or more, the selection ratio of the substance film containing carbon and silicon to the silicon nitride film is significantly increased. I found out that As shown in Table 1, there seems to be no correlation between C / Si on the surface of the silicon nitride film and C / Si on the surface of the substance film containing carbon and silicon (the sample surface in the table). is there.

Therefore, according to the present embodiment, the material film containing carbon and silicon on the silicon nitride film having C / Si of at least 0.285 on the surface of the silicon nitride film is C ₄ F ₈
It was possible to selectively etch the material film containing carbon and silicon with respect to the silicon nitride film by performing the plasma etching with.

The present invention is not limited to the above embodiments. For example, as the processing gas, a mixed gas in which two or more kinds of gases are appropriately selected can be used for each gas as necessary.

[0032]

According to the inventions of claims 1 to 10, there is provided a plasma etching method capable of increasing the selection ratio of an organic SiO ₂ film to a silicon nitride film (SiN film). Can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of an etching apparatus applicable to a plasma etching method of the present invention.

FIG. 2 is a graph conceptually showing a mode in which the amount of introduction of a substance having nitrogen in the processing gas is tended to decrease with the progress of plasma etching.

FIG. 3 is a graph conceptually showing a mode in which the introduction amount of a substance having carbon and oxygen in the processing gas is tended to increase with the progress of plasma etching.

[Explanation of symbols]

W wafer (object to be processed) 10 Etching equipment 11 Processing container 13 Upper electrode 15 Lower electrode

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Claims (10)

[Claims] 1. A method of plasma-etching a processing gas introduced into a processing container to plasma-etch a material film containing carbon and silicon formed on a silicon nitride film in a target object in the processing container. The material amount ratio of carbon to silicon on the surface of the silicon nitride film is 0.285.
A plasma etching method characterized by the above. 2. The plasma etching method according to claim 1, wherein the ratio of carbon to silicon on the surface of the silicon nitride film is 0.285 to 1.0. 3. The plasma etching method according to claim 1, wherein the material amount ratio of carbon to silicon on the surface of the silicon nitride film is 0.285 to 0.470. 4. The plasma etching method according to claim 1, wherein the material film contains oxygen. 5. The plasma etching method according to claim 1, wherein the processing gas contains a substance containing carbon and fluorine. 6. The plasma etching method according to claim 5, wherein the processing gas contains at least one of nitrogen, carbon monoxide, and oxygen. 7. The gas containing carbon and fluorine is CF
_Four, CHF_Three, CH _TwoF_Two, CH_ThreeF, C_TwoF_Four, C_Two
F₆, C_ThreeF₆, C_ThreeF₈, C_FourF₆, C_FourF₈And C
₅F₈At least any one of
The plasma etching according to claim 5 or 6,
Method. 8. A method of plasma-etching a processing gas introduced into a processing container to plasma-etch a material film containing carbon, silicon and oxygen on a silicon nitride film in an object to be processed in the processing container, As the processing gas, a mixed gas containing a substance having carbon and fluorine, a substance having nitrogen, and a substance having carbon and oxygen is used, and the substance having nitrogen in the processing gas as the plasma etching progresses. 2. A plasma etching method, characterized in that the amount of the gas introduced into the processing container is reduced. 9. A method of plasma-etching a processing gas introduced into a processing container to plasma-etch a material film containing carbon, silicon and oxygen on a silicon nitride film in an object to be processed in the processing container, As the processing gas, a mixed gas containing a substance having carbon and fluorine, a substance having nitrogen, and a substance having carbon and oxygen is used, and carbon and oxygen in the treatment gas are removed as the plasma etching progresses. A plasma etching method comprising increasing the amount of a substance contained in the processing container. 10. The substance containing carbon and fluorine is C
F_Four, CHF_Three, CH_TwoF_Two, CH_ThreeF, C_TwoF_Four, C
_TwoF₆, C_ThreeF₆, C_ThreeF₈, C_FourF₆, C _FourF₈, C
₅F₈Of at least one of
The substance possessed is N_Two, N_TwoO, NO_TwoAt least
A substance consisting of one of them and having carbon and oxygen is CO,
CO_TwoCharacterized by comprising at least one of
The plasma etch according to claim 8 or 9,
How to go.