JPH1098021A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device, capable of selectively opening a precise microscopic hole for connection in a silicon oxide. SOLUTION: A microscopic connecting hole is formed in a silicon oxide film 102, through plasma etching with a mixture of a fluorocarbon compound expressed by a general formula CmFn (where m and n are natural numbers expressing atomicity and fulfil the requirement m>=2, n<=2m), oxygen, and an inert-gas such as Ar gas. The etching process of the silicon oxide film 102 is divided into two processes: a partial-etching process just prior to exposing an active substratum material layer and an over-etching process after that, a microscopic connecting hole is opened in a silicon oxide film by decreasing the content ratio of the inert gas to the composition of an etching gas in the over-etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for etching a silicon oxide film.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, especially in the drilling of a silicon oxide film, the junction depth of an impurity diffusion region becomes shallower in order to increase the speed and miniaturization of the device, and various material layers become thinner. Therefore, there is a demand for an etching technique which is excellent in selectivity with respect to the base and has little damage. Also, a slight dimensional conversion difference due to the receding of the resist is becoming unacceptable, and it is becoming important to improve the resist selectivity. As a conventional highly selective processing technique, there is JP-A-6-208974. this is,
The volume ratio of oxygen-containing gas to C4F8 gas is 1/8 to
By etching the mixed gas of 1 by ECR to perform plasma etching, the etching rate ratio of silicon oxide can be made sufficiently higher than the etching rate of photoresist and polycrystalline silicon, so that silicon oxide is selectively etched. It is possible.

[0003]

However, these methods provide good results with respect to the underlayer selectivity. However, when deep holes with a large aspect ratio are to be formed in the future,
The etching rate is as low as about 500 nm, and the selectivity with respect to the photoresist is about 3.8, so that the amount of retreat of the photoresist is large. In the case of etching a substrate having a silicon oxide film of 1500 nm, if the overetch amount is 50%, the etching time is about 270 seconds. As a result, as shown in FIG. .
For a photoresist dimension of 50 μm, the dimensions are 0.65 μm and about 0.15 μm larger. Therefore, there was a problem that it could not cope with future fine processing.

[0004]

According to the method of manufacturing a semiconductor device of the present invention, the general formula is CmFn (where m and n are natural numbers indicating the number of atoms, and satisfy the conditions of m ≧ 2 and n ≦ 2m). ), And etching the silicon compound layer using an etching gas containing oxygen and an inert gas.

In the method of manufacturing a semiconductor device of the present invention, a fluorocarbon represented by the general formula CmFn (where m and n are natural numbers indicating the number of atoms and satisfy the conditions of m ≧ 2 and n ≦ 2m). A partial etching step of etching the silicon compound layer to a depth substantially not exceeding its layer thickness using an etching gas containing a compound, oxygen and an inert gas, and reducing the inert gas as compared with the partial etching step. An over-etching step of etching the remaining portion of the silicon compound layer using an etching gas.

In the method of manufacturing a semiconductor device according to the present invention, the general formula described in claims 1 and 2 is CmFn (where m and n are natural numbers indicating the number of atoms, and satisfies the conditions of m ≧ 2 and n ≦ 2m). C) as a fluorocarbon compound represented by
8 is used.

[0007]

According to the method of the present invention, the general formula is CmFn (where m and n are natural numbers indicating the number of atoms, and m ≧ 2 and n ≦ 2m).
Satisfies the condition. ), And an inert gas such as Ar gas mixed with oxygen, and plasma etching is performed, so that the amount of etching in the direction perpendicular to the wafer is reduced by the sputtering effect of the inert gas ions. More. This has the effect of increasing the etching rate of the silicon oxide film and reducing the amount of photoresist retreat.

The present invention is based on the above concept, but also proposes a method aiming at higher selection, lower damage and lower contamination. It is a method of dividing the etching of the silicon oxide film into two steps of a partial etching step immediately before the base material layer is exposed and an over-etching step thereafter, and reducing the inert gas content ratio in the etching gas composition in the over-etching step. It is. According to this method, the sputtering effect of the inert gas in the vicinity of the interface with the base in the silicon oxide film is reduced as compared with the partial etching step, and therefore, there is an effect that further higher selectivity and lower damage can be realized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. This embodiment is an example in which a silicon oxide film is etched using a mixed gas of C4F8 / O2 / Ar by applying to drilling. FIG. 3 is a schematic sectional view showing an ECR type plasma etching apparatus used in this embodiment. In the figure, reference numeral 301 denotes a plasma generation chamber made of stainless steel, and a microwave introduction window 302 made of a quartz glass plate is provided in a closed state at the center of the upper wall of the plasma generation chamber 301. And this microwave introduction window 302
A waveguide 303 is disposed above the waveguide 30.
The other end of 3 is connected to a microwave oscillator 304.

On the other hand, a reaction chamber 305 is provided continuously below the plasma generation chamber 301, and a plasma extraction window 306 is provided between the plasma generation chamber 301 and the reaction chamber 305. A plasma extraction window 30 is provided at the bottom of the reaction chamber 305.
The sample stage 307 is disposed at a position facing the sample stage 6, and an electrode 308 is embedded on the upper surface of the sample stage 307.
The semiconductor substrate 30 as a sample is placed on the sample stage 307.
9 is detachably mounted by means such as electrostatic attraction. The electrode 308 is connected to a high-frequency power supply 310 to which a DC power supply 311 is connected. Further, a gas introduction pipe 312 and a vacuum pump 313 are provided in the reaction chamber 305.

The plasma generation chamber 301 and the waveguide 30
An excitation coil 314 is provided around a part of the outer periphery of the reaction chamber 3, and an excitation coil 315 is provided around the outer periphery of the upper part of the reaction chamber 305. Excitation coils 316 are provided around the outer periphery of the lower part of the sample stage 307.
Reference numerals 15 and 316 are connected to a DC power supply (not shown).

Next, the operation of the ECR type plasma etching apparatus configured as described above will be described. The microwave emitted by the microwave oscillator 304 is supplied to the introduction tube 303.
Through the microwave introduction window 302 and the plasma generation chamber 3
01 is introduced. In the plasma generation chamber 301 which functions as a cavity resonator for microwaves, electrons generated by microwave discharge perform spiral motion by a magnetic field generated by the exciting coil 314, and a magnetic field of 875 Gauss is generated for a microwave frequency (2.45 GHz). Once formed, the electrons undergo cyclotron resonance and many gas molecules are ionized to generate plasma. Reaction chamber 3 by exciting coils 314, 315, 316
A diverging magnetic field having a lower magnetic flux density is formed toward the direction 05, whereby the plasma is introduced into the reaction chamber 305. The reaction chamber 305 is evacuated by a vacuum pump 313 to a desired gas atmosphere from a gas introduction pipe 312.

On the other hand, the electrode 308 causes a bias electric field induced by the high-frequency power supply 310 to act on the surface of the semiconductor substrate 309 to control the kinetic energy and direction of the ions.
The DC power supply 311 causes the semiconductor substrate 309 to move the electrode 30
8 is electrostatically attracted.

Next, a first embodiment using this apparatus and its results will be described. As a semiconductor substrate as a sample, a silicon oxide film having a thickness of about 1500 nm formed on a substrate silicon and a photoresist film formed on a part thereof was used as shown in FIG. 1A. First, after the gas pressure in the reaction chamber 305 is reduced to 1 × 10 ⁻⁶ Torr or less by the vacuum pump 313,
Ar for C4F8 gas 45sccm and O2 gas 14sccm
Gases mixed with each other at a rate of 250 sccm were separately introduced from the gas introduction pipe 312, and in each case, the gas pressure was adjusted to about 5 mTorr. Next, a magnetic field was formed from the exciting coils 314, 315, and 316 as described above, and a microwave of about 1.75 kW was introduced from the microwave oscillator 304 into the plasma generation chamber 301 to convert the mixed gas into plasma. Further, about 700 W of high-frequency power was applied to the electrode 308 by the high-frequency power supply 310, and etching was performed by applying a bias electric field on the semiconductor substrate 309 fixed by electrostatic attraction.

As a result, the etching rate of the silicon oxide film was 830 nm, which was about 1.6 times higher than the etching rate of the prior art. Therefore, the selectivity with respect to the photoresist is about 6.4, and the retreat of the photoresist is reduced as shown in FIG. 1B. 02
It was only about μm larger. At this time, the underlayer selectivity was about 40.

Next, as a second embodiment, similarly, in the hole processing, the etching of the silicon oxide film using the C4F8 / O2 / Ar mixed gas is divided into two steps of a partial etching step and an over-etching step. A
This is an example in which the selectivity is further improved by relatively reducing the content ratio of r. This process is illustrated in FIGS. 2 (a), (b),
This will be described with reference to FIG.

First, the wafer shown in FIG.
08, C4F8 gas 45 sccm and O2 gas 14
Gases obtained by mixing Ar gas at a ratio of 250 sccm to sccm were separately introduced from the gas introduction pipe 312, and in each case, the gas pressure was adjusted to about 5 mTorr. Next, a magnetic field is generated from the exciting coils 314, 315 and 316 as described above, and about 1.75 from the microwave oscillator 304 is generated.
A microwave of kW was introduced into the plasma generation chamber 301 to convert the mixed gas into plasma. Further, about 700 W of high-frequency power was applied to the electrode 308 by the high-frequency power supply 310, and partial etching was performed by applying a bias electric field on the semiconductor substrate 309 fixed by electrostatic attraction. In the partial etching, as shown in FIG. 2B, the silicon oxide film has been etched at about 1200 nm, and the etching has been completed at an etching time of about 87 seconds.

Therefore, the etching conditions were as follows: 45 sccm of C4F8 gas and 14 sccm of O2 gas, and 0 sc of Ar gas.
cm, the gas pressure was 3 mTorr, the microwave power was about 1.75 kW, the high frequency power was about 500 W, and over-etching was performed for 95 seconds to remove the remaining part. In this over-etching step, the Ar ion was eliminated, and the high-frequency power supply was reduced to reduce the incident ion energy due to Ar ions. As a result, as shown in FIG.
Residual parts could be removed under the condition that the selectivity to No. 3 was increased and the damage was reduced. As a result, FIG.
As shown in FIG. 7, the regression of the photoresist was also reduced, and the dimensional conversion difference was only about 0.05 μm larger than the photoresist dimension of 0.50 μm. At this time, the underlayer selectivity was about 70. As described above, favorable high anisotropy and high selectivity etching could be performed by the two-step etching.

Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the etching conditions and apparatuses described above.

[0020]

According to the method of the present invention, the general formula is CmFn (where m and n are natural numbers indicating the number of atoms, and m ≧ 2 and n ≦
The condition of 2 m is satisfied. ), And an inert gas such as Ar gas mixed with oxygen, and plasma etching is performed, so that the amount of etching in the direction perpendicular to the wafer is reduced by the sputtering effect of the inert gas ions. More. This has the effect of increasing the etching rate of the silicon oxide film and reducing the amount of photoresist retreat.

The present invention is based on the above concept, but also proposes a method aiming at higher selection, lower damage and lower contamination. It is a method of dividing the etching of the silicon oxide film into two steps of a partial etching step immediately before the base material layer is exposed and an over-etching step thereafter, and reducing the inert gas content ratio in the etching gas composition in the over-etching step. It is. According to this method, the sputtering effect of the inert gas in the vicinity of the interface with the base in the silicon oxide film is reduced as compared with the partial etching step, and thus there is an effect that further higher selection and lower damage can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a process in a first embodiment of the present invention.

FIG. 2 is a sectional view of a process in a second embodiment of the present invention.

FIG. 3 is a schematic view of a dry etching apparatus used in the first and second embodiments of the present invention.

FIG. 4 is a cross-sectional view of a process in a conventional technique.

[Explanation of symbols]

 101 Photoresist 102 Silicon oxide film 103 Substrate silicon 201 Photoresist 202 Silicon oxide film 203 ... Substrate silicon 301... Plasma generation chamber 302... Microwave introduction window 303... Waveguide 304... Microwave oscillator 305. ... Reaction chamber 306... Plasma extraction window 307... Sample table 308... Electrode 309... Semiconductor substrate 310. Power supply 311 DC power supply 312 Gas inlet tube 313 Vacuum pump 314, 315, 316 Excitation coil 401 Photo Resist 402 ... oxidized silicon Con film 403 ...... substrate silicon

Claims (4)

[Claims] 1. A fluorocarbon compound represented by the general formula CmFn (where m and n are natural numbers indicating the number of atoms and satisfy the conditions of m ≧ 2 and n ≦ 2m), oxygen and an inert gas. A method of manufacturing a semiconductor device, comprising etching a silicon compound layer using an etching gas containing: 2. A fluorocarbon compound represented by the general formula CmFn (where m and n are natural numbers indicating the number of atoms and satisfy the conditions of m ≧ 2 and n ≦ 2m), oxygen and an inert gas. And a partial etching step of etching the silicon compound layer to a depth substantially not exceeding the layer thickness thereof using an etching gas containing the inert gas, and using an etching gas obtained by reducing the inert gas in the partial etching step. An over-etching step of etching a remaining portion of the silicon compound layer. 3. The general formula according to claim 1, wherein CmFn (where m and n are natural numbers indicating the number of atoms, and m ≧ 2, n ≦
The condition of 2 m is satisfied. A method for manufacturing a semiconductor device, comprising using C4F8 as the fluorocarbon compound represented by the formula (1). 4. A method of manufacturing a semiconductor device according to claim 1, wherein argon is used as the inert gas.