JPH10125654A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Problem] To surely remove carbon-based deposits adhering to a resist or a side wall during dry etching. SOLUTION: In a method of dry-etching an insulating film made of SiO _{2 in a} plasma using a photoresist pattern as a mask, a mixed gas obtained by adding a nitrogen-based gas to a fluorine-based gas, a fluorine-based gas, a nitrogen-based gas, and a Penning effect A method for manufacturing a semiconductor device, wherein dry etching is performed using an excited plasma of a mixed gas of an inert gas which causes the etching to etch the insulating film and to remove carbon-based deposits generated during the dry etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to an etching step capable of removing carbon-based deposits generated when dry-etching an insulating film made of SiO _2. The present invention relates to a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, in a resist ashing method for removing a resist constituting an etching mask in the process of manufacturing a semiconductor device, a method of mixing an oxygen gas and a chlorofluorocarbon-based gas is first used. A first step of using a gas at a relatively high pressure, for example, 3 × 10 ⁻² Torr, and a relatively low pressure of, for example, 1 ×, using a mixed gas of an oxygen gas and a chlorofluorocarbon-based gas similar to the aforementioned gas.
A method comprising a second step performed at 10 ^-2 Torr is disclosed in
No. 119724.

This method includes the following steps. FIG.
As shown in FIG. 1A, a SiO ₂ film 11 is laminated on a semiconductor substrate 10 to form a resist pattern 12 having a desired shape. Next, as shown in FIG. 2B, using this resist pattern 12 as a mask, sulfur hexafluoride, methane tetrafluoride, ethane hexafluoride, etc. are used as a reaction gas, and the reaction ion etching method is used. Perform isotropic etching. Thereby, the deposit 13 is formed on the side wall of the SiO ₂ film 11.
Will be deposited. After that, the resist pattern 12
First, one of oxygen and sulfur hexafluoride is removed.
0: 1 mixed gas or 8 to 1 of oxygen and Freon gas
Using a 2: 1 mixed gas, the first etching is performed for about 3 minutes by a parallel plate type ion etching apparatus under a pressure of about 3 × 10 ⁻² Torr. Subsequently, while the reaction gas is kept as it is, the pressure is reduced to 1 × 10 ⁻² Torr, and the second etching is further performed for about 3 minutes. As a result, FIG.
As shown in (c), the resist 12 is removed, and Si
The O ₂ film 11 is patterned into a desired shape, and only a small amount of the deposit 13 remains on the side wall.

Japanese Patent Application Laid-Open No. 4-337633 discloses a method of removing a deposit by introducing an N ₂ gas after dry etching of a SiO ₂ film using a resist, and then removing the resist by an O ₂ gas. Proposed.

Further, Japanese Patent Application Laid-Open No. 5-275326 discloses a process of removing a hardened resist by using a plasma of a mixed gas of oxygen and fluorine, and a method of removing a remaining unhardened resist by using an oxygen plasma. And a removing step. Here, a gas containing fluorine such as CF ₄ , NF ₃ , SF ₆ and C ₄ F ₈ is disclosed as a fluorine-based gas. When oxygen plasma is used, only oxygen is used, and oxygen and N ₂ , He, and Ar are used. Are disclosed.

On the other hand, with the recent increase in the degree of integration of semiconductor integrated circuits, finer processing is required. In particular, dry etching of an insulator composed of a SiO ₂ film or the like is a base material for S.
A high selection ratio with i is required. Generally, a plasma of a fluorine-based gas containing a large amount of carbon atoms is used as an etching gas in order to realize dry etching with a high selectivity. However, in dry etching in such plasma, carbon-based deposits generated during etching tend to contain a large amount of carbon (the C / F ratio increases).

Under these circumstances, a conventional resist removal method using O ₂ plasma, a resist removal method using plasma of oxygen gas and fluorine-based gas, or wet etching with an organic solvent or the like is added. It is impossible to completely remove the carbon-based deposit containing a large amount of carbon by the conventional resist removing method. This is a carbon deposit - (CF) - Although To easily decomposed or disassembled polymerization film must be changed to stable binding than CF bonds, utilized in the prior art O ₂ plasma or O ₂
This is considered to be because it is difficult to change the bond into a more stable bond than the CF bond in the / CF ₄ plasma, and the solubility of the-(CF) -polymer film is low in the organic solvent.

However, the carbon-based deposits described above cause short-circuiting, cause deterioration of the film quality such as an oxide film deposited in the next step, or cause contamination of a semiconductor device used in the next step. In other words, for example, as shown in FIG. 3, the carbon-based deposit 22 generated on the upper surface or the side surface of the SiO ₂ film 21 formed on the semiconductor substrate 20 is removed from the wiring layer 23 formed in a later step. The separation is hindered (A in FIG. 3), and the occurrence of a short circuit is promoted. Further, for example, Japanese Patent Laid-Open No. 4-3
Japanese Patent No. 37633 describes a method of removing deposits after dry etching. However, the increase in deposits during dry etching causes a dimensional shift, making it impossible to precisely process the SiO ₂ film. There is also.

[0009]

According to the present invention, SiO 2 is used.
_In a method of dry-etching an insulating film composed of _{2 in a} plasma using a photoresist pattern as a mask, a mixed gas obtained by adding a nitrogen-based gas to a fluorine-based gas or a fluorine-based gas, a nitrogen-based gas, and an inert gas that causes a Penning effect The present invention provides a method for manufacturing a semiconductor device, in which dry etching is performed using an excited plasma of a mixed gas comprising: etching the insulating film and removing carbon-based deposits generated during the dry etching.

[0010]

In the method of manufacturing a semiconductor device of the embodiment of the present invention, an insulating film made of SiO _2, a method for removing carbon-based deposits generated during dry etching with etching the insulating film, which In order to realize the above, a dry etching step under a condition in which a carbon-based deposit is not easily formed, or a dry etching step for removing the carbon-based deposit can be further combined with this step.

[0011] In the present invention, the insulating film made of SiO ₂ means a predominantly composed of SiO ₂ insulating film, and the insulating film to which an impurity is mixed or diffused from the underlying or the upper base film, other insulating films, for example, SiN or the like It may be an insulating film made of SiO _{2 which is} partially contained. For example, P-TEOS, HTO,
PECVD (Plasma Enhanced Chemical Vaper Deposit
ion), LP (Low Pressure) CVD, CV such as normal pressure CVD
D method, PVD (Physical Vaper Deposi
NSG, PS formed by the coating method
G, BPSG or a thermal oxide film. The thickness of the insulating film in this case is not particularly limited as long as it can function as an insulating film, but in the present invention, when the insulating film made of SiO ₂ is thick, Great effect. In the present invention, the insulating film may be formed directly on the semiconductor substrate, or may be formed on a wiring layer, an element such as a transistor or a capacitor, or on a different insulating film.

The photoresist pattern used as a mask is formed of a resist usually used in a photolithography process, has a desired film thickness, and is patterned into a desired shape. In the present invention, as described above, the excited plasma dry etching method of a mixed gas obtained by adding a nitrogen-based gas to a fluorine-based gas or a mixed gas of a fluorine-based gas, a nitrogen-based gas, and an inert gas that causes a Penning effect is used. The first step includes a dry etching step mainly under a condition in which a carbon-based deposit is hardly formed or not, and / or a second step includes a dry etching step for removing a carbon-based deposit. In the first step, dry etching is performed using the photoresist pattern as a mask.
A carbon-based deposit formed by polymerization of CF _X (X = 1 to 3) may slightly adhere to the pattern or the side surface. In this case, the second step is further performed to bond the CF. (Bonding energy: 5.72 eV / mol) to form a CN bond (binding energy:
(7.98 eV / mol), vaporized, and discharged to completely remove carbon-based deposits.

For example, as the mixed gas in the present invention,
Is CF_Four, CHF_Three, C_TwoF₆, C_FourF ₈At least one of
Species of fluorine gas, N_Two, N_TwoO, NH_ThreeAt least one of
A gas to which a kind of nitrogen-based gas is added is exemplified. Specifically
Is CF_Four/ CHF_ThreeAnd N_Two, CF_FourAnd N_Two, CF_Four/ C
HF_ThreeAnd N_TwoO, CF_FourAnd N_TwoO, CF_Four/ CHF_ThreeAnd N
H_Three, CF_FourAnd NH_Three, CF_Four/ C_TwoF₆And N_Two, CF_FourAnd N
_Two, CF_Four/ C_TwoF₆And N_TwoO, CF_FourAnd N_TwoO, CF_Four/
C_TwoF₆And NH_Three, CF_FourAnd NH_ThreeEtc., among which
Also CF_Four/ CHF_ThreeAnd N_TwoIt is preferable to use
In addition, these mixed gases cause a Penning effect.
Mixed gas containing inert gas such as Ar, He, etc.
Is preferred. This is due to the penning effect of the inert gas.
The amount of plasma increases and each gas is easily dissociated.
Because it can be made. As an example of this combination
For example, CF_Four/ CHF_Three/ Ar and N_Two, CF_Four/ CHF_Three/
He and N_TwoIs mentioned. The ratio of the mixed gas at this time is
Fluorine gas: Nitrogen gas = 10 to 200: 10 to 20
0 SCCM is preferable and further contains an inert gas.
In the case, fluorine-based gas: inert gas: nitrogen-based gas = 10
~ 200: 10 ~ 600: 10 ~ 200 SCCM
preferable. Specifically, CF_Four: CHF_Three: Ar: N_Two=
10 to 100: 0 to 100: 10 to 600: 10 to 20
0 SCCM, more preferably 20: 30: 150: 30
It is about SCCM.

The RF power for exciting the mixed gas into plasma is about 500 to 1500 W, preferably 1 to
It is about 300W. The pressure at this time is 100 to 1
About 000 mTorr, more preferably about 400 mTorr
r. Further, the etching time depends on the gas flow rate,
Depending on RF power etc., for example, about 1 to 5 minutes,
More preferably, it is about 2 to 3 minutes.

When the step performed under the above-mentioned conditions is the first step, and when the second step is performed, the same mixed gas as described above can be used as the mixed gas.
For example, CF ₄ / Ar and N ₂ , and CF ₄ / He and N ₂ can be mentioned. The mixed gas at this time can be used in the same ratio as described above. Specifically, when CF ₄ / Ar and N ₂ are used, CF ₄ : Ar: N ₂ = 50 to 200: 3
It is about 00: 800: 50-200 SCCM, more preferably about 90: 300: 60 SCCM.

In the second step, it was confirmed that the higher the pressure and the lower the RF power, the more selectively the carbon-based deposit can be etched by the plasma and the better the result can be obtained. I have. In other words, the sputtering effect by plasma is reduced,
This is because the base is hardly etched. Therefore, the RF power for exciting the mixed gas into plasma is about 50 to 400 W, preferably about 200 W. At this time, the pressure is 800 to 1500 mTo.
It is about rr, more preferably about 1000 mTorr. Further, the etching time varies depending on the gas flow rate, RF power, and the like, but is, for example, about 0.5 to 4 minutes, and more preferably about 1 minute.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to the present invention will be described with reference to the drawings. As shown in FIG.
A 1.4 μm P-TEOS film 2 was deposited on the AlSiO ₂ film 1 and a 1.3 μm resist film 3 was applied thereon. Next, a via hole having a diameter of 0.6 μm was formed in the resist film 3 by ordinary photolithography.

Thereafter, as shown in FIG.
The P-TEOS film 2 was opened using the strike film 3 as a mask.
First, in the first stage etching, CF_Four/ CHF_Three/ Ar
/ N _TwoPerform mixed gas excited plasma etch for about 2.5 minutes
Was. The conditions at this time are as follows: pressure: 400 mTorr, RF power.
ー: 1300W, gas flow rate: CF_Four/ CHF_Three/ Ar / N
_Two= 20/30/150/30 SCCM. Subsequently, FIG.
As shown, the second stage etching was performed with CF_Four/ A
r / N_TwoPerform for about 1 minute with mixed gas excited plasma
The carbon-based deposit 4 attached to the surface of the strike film 3 is removed.
Was. The conditions at this time are as follows: pressure: 1000 mTorr, RF power.
ー: 200W, gas flow rate: CF_Four/ Ar / N_Two= 90/300/6
It was 0SCCM.

[0019] Then, as shown in FIG. 1 (d), O ₂
Resist ashing was performed using plasma or O ₂ / CF ₄ plasma, and the resist was removed using an organic solvent. P-TEO formed by the above method
When the surface of the via hole in the S film 2 was confirmed by SEM (scanning electron microscope), there was no resist residue on the surface, and the carbon-based deposit was completely removed.

[0020]

According to the present invention, it is possible to reliably remove carbon-based deposits adhering to a resist or a side wall during dry etching. And then,
Even when a step for removing the resist is performed, the resist residue can be completely removed after removing the resist. In addition, the method of the present invention was used under different conditions,
When the step is performed in a step process, the generation of carbon-based deposits can be further reduced, and the carbon-based deposits can be more reliably removed in a shorter time.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional process drawing of a main part showing one embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a schematic cross-sectional process diagram of a main part showing one embodiment of a conventional method for manufacturing a semiconductor device.

FIG. 3 is a schematic cross-sectional view of a main part of a semiconductor device for describing a problem of the related art.

Claims (5)

[Claims] 1. A method of dry-etching an insulating film made of SiO _{2 in a} plasma using a photoresist pattern as a mask, wherein a mixed gas obtained by adding a nitrogen-based gas to a fluorine-based gas or a fluorine-based gas, a nitrogen-based gas, and Penning Manufacturing a semiconductor device, wherein dry etching is performed using an excited plasma of a mixed gas of an inert gas causing an effect to etch the insulating film and to remove carbon-based deposits generated during the dry etching. Method. 2. The method according to claim 1, wherein the fluorine-based gas is CF ₄ , CHF ₃ , C ₂
At least one of F ₆ and C ₄ F ₈ and the nitrogen-based gas are N ₂ , N
_{2. The} method according to claim 1, wherein the method is at least one of ₂ O and NH ₃ . 3. The mixing ratio of a fluorine-based gas to a nitrogen-based gas is 10 to 200: 10 to 200, and the mixing ratio of a fluorine-based gas, a nitrogen-based gas, and an inert gas causing a Penning effect is 10 to 200: 10 to 10. 2. The method according to claim 1, wherein the ratio is 200: 10 to 600. 4. A dry etching is performed as a first step by using C
After etching with F ₄ / CHF ₃ / Ar (or He) / N ₂ gas, CF ₄ / Ar (or He) /
_{2. The method according} to claim 1, comprising a two-step process of etching with N ₂ gas.
The manufacturing method of the semiconductor device described in the above. 5. The etching of the second step is performed at 800 mTo.
^{2. The} method for manufacturing a semiconductor device according to claim 1, wherein the method is performed under an RF power having an electron density of 2 W / cm ² or less under a pressure of rr or more.