JP2002343766A - Plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the selectivity in dry etching using fluorocarbon gas of >=0.5 in C/F ratio. SOLUTION: After a semiconductor substrate where a silicon oxide film is formed and a resist film is formed on the silicon oxide film is installed in the reaction chamber of a plasma processor, the fluorocarbon gas of >=0.5 in C/F ratio is introduced into the reaction chamber. In this case, a relational expression τ=P×V/Q (where τ is the staying time (sec) of the gas in the reaction chamber, P the pressure (Pa) of the gas, V the volume (L) of the reaction chamber, and Q the flow rate (Pa.L/sec)) is used to control the flow rate so that the staying time τ is >=0.1 (sec) and <=1 (sec). Then, plasma made of the fluorocarbon gas is generated and the resist film is used as a mask to etch the silicon oxide film with the plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma processing method used in a semiconductor device manufacturing process.
In particular, the present invention relates to a plasma processing method for performing etching or film formation using plasma made of a fluorocarbon gas.

[0002]

2. Description of the Related Art In recent years, the miniaturization of semiconductor devices has been accelerated, and processing at a level of 0.1 μm has finally been required.

However, the manufacturing process of a semiconductor device is basically performed without changing from the conventional one.
After depositing a thin film on a semiconductor substrate, a resist film composed of an organic film is formed on the thin film by lithography, and then the thin film is etched using the resist film.

However, in order to cope with miniaturization of semiconductor devices, the exposure light of lithography is changed to i-line, KrF excimer laser or ArF excimer laser.
Organic resist films corresponding to changes in exposure light have also been developed.

Further, introduction of an ArF excimer laser as exposure light for processing at a level of 0.1 μm has been considered, but in this case, it is pointed out that the etching resistance of the organic resist film is poor. .

Therefore, various techniques have been proposed to ensure the selectivity to the resist film. For example, a technique using a silicon material for a member in a reaction chamber and using a function of scavenging fluorine by the silicon material, that is, a technique of lowering the concentration of fluorine in an etching gas and improving selectivity to a resist is proposed. Have been.

Hereinafter, a conventional plasma processing method will be described.
This will be described with reference to FIG.

FIG. 1 shows a schematic structure of an inductively coupled plasma processing apparatus. As shown in FIG. 1, an inner wall of a reaction chamber 10 is covered with a quartz plate 11. An induction coil 12 is provided outside the reaction chamber 10, and the induction coil 1
One end of 2 is connected to the first high-frequency power supply 13, and the other end of the induction coil 12 is grounded.

A gas introduction unit 14 of the reaction chamber 10 is connected to a gas supply source (gas cylinder) via a mass flow controller 15.
16, the gas discharge part 17 of the reaction chamber 10 is connected to an exhaust pump 19 via a pressure control valve 18, and the gas pressure of the reaction chamber 10 is controlled by the mass flow controller 15 and the pressure control valve. 18 and the exhaust pump 19.

A sample stage 20 serving as a lower electrode is provided inside the reaction chamber 10, and the sample stage 20 is connected to a second high frequency power supply 22 via a matching circuit 21.

The control device 23 includes a first high-frequency power supply 13,
By transmitting control signals to the second high-frequency power supply 22, the mass flow controller 15, and the pressure control valve 18, the first high-frequency power supplied to the induction coil 12 from the first high-frequency power supply 13 and the second high-frequency power supply 22 Sample table 20
, The flow rate of the gas supplied from the gas supply source 16 to the reaction chamber 10, and the flow rate of the gas discharged from the reaction chamber 10.

Normally, the gas pressure in the reaction chamber 10 is controlled to a predetermined value within the range of 0.133 Pa to 1.33 Pa by controlling the pressure control valve 18 while driving the exhaust pump 19 continuously. .

A process gas is supplied from the gas introduction part 14 to the reaction chamber 10, and a gas pressure in the reaction chamber 10 is maintained at a predetermined value.
2 is supplied with a first high-frequency power to generate a plasma composed of a process gas.
Supplies the second high-frequency power to the sample stage 20 to draw the generated plasma into the semiconductor substrate placed on the sample stage 20. As a result, the thin film formed on the surface of the semiconductor substrate is etched or the thin film is deposited on the surface of the semiconductor substrate.

As described above, since the silicon material has a function of scavenging fluorine, when an etching gas containing fluorine is introduced into the reaction chamber 10, the sample table 20 and the silicon ring (shown in FIG. Is omitted) is bonded to fluorine to form SiF _x (x =
3, 4) are generated. Thereby, the concentration of fluorine in the etching gas is adjusted, and the etching rate is controlled. It is generally known that the concentration of fluorine affects the etching rate of a resist film.

Japanese Patent Application Laid-Open No. Hei 10-98024 discloses a method for improving the selectivity of a silicon oxide film to a resist film when dry etching (plasma etching) is performed on the silicon oxide film using the resist film as a mask. , The ratio of carbon to fluorine (hereinafter C
/ F ratio. It has been suggested that it is preferable to use a fluorocarbon gas having a relatively large amount, for example, a C ₅ F ₈ gas.

[0016]

However, the present inventors performed dry etching on a silicon oxide film using a C ₅ F ₈ gas having a large C / F ratio using a resist film as a mask. Conventionally used C
It was found that the selectivity was not improved as compared with the C ₂ F ₈ gas having a small / F ratio.

Hereinafter, an experiment performed by the present inventor will be described.

An ICP plasma dry etching apparatus is used as an etching apparatus, the magnitude of electric power supplied for generating plasma is set to 1600 W, and a mixed gas of C ₅ F ₈ gas and Ar gas is used as an etching gas. And the gas flow rate is C ₅ F ₈ gas: Ar gas = 4.7: 4.
0 (ml / min), gas pressure is 0.133P
a. Under such process conditions, the silicon oxide film was etched using the resist film as a mask.

As a result, a gas having a large C / F ratio (C ₅ F ₈
Despite the use of gas, the selectivity to the resist film was 1.81. This selectivity does not change so much as compared with a conventionally used gas having a small C / F ratio (C ₂ F ₆ gas).

In view of the above, the present invention provides a C / F ratio of 0.5
It is an object of the present invention to improve selectivity when dry etching is performed using the above fluorocarbon gas.

[0021]

The present inventors have found that when dry etching is performed on a silicon oxide film using a fluorocarbon gas having a large C / F ratio, the selectivity to a resist film is improved. I think it is due to the reason. That is, a polymer film is deposited on the surfaces of the silicon oxide film and the resist film, and the polymer film suppresses etching. For this reason, when the degree of decrease in the etching rate of the silicon oxide film is smaller than the degree of decrease in the etching rate of the resist film, the selectivity to the resist film is improved, while the degree of decrease in the etching rate of the silicon oxide film is reduced. However, when the etching rate of the resist film is larger than or equal to the degree of reduction, the selectivity to the resist film does not improve.

Therefore, when a fluorocarbon gas having a large C / F ratio is used, the selectivity to the resist film is not necessarily improved, but a fluorocarbon gas having a large C / F ratio is used, and the etching rate of the silicon oxide film is reduced. By making the degree smaller than the degree of decrease in the etching rate of the resist film, the selectivity to the resist film can be improved.

Further, the present inventor has found that the residence time τ of the fluorocarbon gas τ = P × V / Q (where P is the pressure (unit: Pa) of the fluorocarbon gas, and V is the volume (unit: L) of the reaction chamber. Focusing on the flow rate (unit: Pa · L / sec) of the fluorocarbon gas, and selecting the resist film by changing the pressure and the flow rate of the fluorocarbon gas in the reaction chamber having various volumes. The residence time τ at which the ratio was improved was determined. As a result, the C / F ratio is set to 0.1.
When using a fluorocarbon gas of 5 or more,
The stay time τ is larger than 0.1 (sec) and 1 (se
c) It was found that when the ratio was below, the selectivity to the resist film was improved. If the stay time τ is 0.1 (se
c) In the following cases, the fact that the selectivity to the resist film is not improved means that the deposition of the polymer is promoted, that is, the deposition rate of the organic film is improved.

Incidentally, as can be seen from the relational expression of stay time τ = P × V / Q, the stay time τ changes depending on the volume V of the reaction chamber.

Therefore, the stay time τ = P × V / Q and the power density Pi = P =
When the concept of P × W ₀ / Q, which is the product of W ₀ / V (where W ₀ is the magnitude of electric power and V is the volume of the reaction chamber), is introduced, the volume of the reaction chamber becomes Regardless, it has been found that the selectivity to the resist film can be improved or the deposition rate of the organic film can be improved.

The present invention has been made based on the above findings, and is specifically as follows.

[0027] The first plasma processing method according to the present invention comprises:
A step of installing a substrate having a silicon oxide film formed on a surface thereof inside a reaction chamber of a plasma processing apparatus, and a step containing carbon and fluorine and a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber. A step of introducing a fluorocarbon gas and a step of generating a plasma made of the fluorocarbon gas and etching the silicon oxide film using the plasma, wherein a residence time of the fluorocarbon gas in the reaction chamber is τ = P × V / Q (where P is the pressure (unit: Pa) of the fluorocarbon gas, V is the volume (unit: L) of the reaction chamber, and Q is the flow rate (unit: Pa · L / sec) of the fluorocarbon gas. ) To 0.1 (se
Control is made larger than c) and 1 (sec) or less.

According to the first plasma processing method, the residence time τ of the fluorocarbon gas in the reaction chamber is set to 0.1 (s).
Since etching is performed on the silicon oxide film while controlling it to be larger than (ec) and 1 (sec) or less, the selectivity to the resist film can be improved to 2 or more while the process is stabilized.

The second plasma processing method according to the present invention comprises:
A step of installing a substrate having a silicon oxide film formed on a surface thereof inside a reaction chamber of a plasma processing apparatus, and a step containing carbon and fluorine and a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber. A step of introducing a fluorocarbon gas and a step of generating a plasma made of the fluorocarbon gas and etching the silicon oxide film using the plasma, wherein a residence time of the fluorocarbon gas in the reaction chamber is τ = P × V / Q (where P is the pressure (unit: Pa) of the fluorocarbon gas, V is the volume (unit: L) of the reaction chamber, and Q is the flow rate (unit: Pa · L / sec) of the fluorocarbon gas. ) And the power density Pi = W ₀ of the power supplied to generate the plasma.
/ V (However, W ₀ is the magnitude of the power (unit: A W),
V is the volume (unit: L) of the reaction chamber. ) Controls the value of P × W ₀ / Q to ^{0.8 × 10 4 (sec · W} / m 3) greater than and ^{8 × 10 4 (sec · W} / m 3) or less is the product of.

According to the second plasma processing method, the value of P × W ₀ / Q which is the product of the residence time τ of the fluorocarbon gas in the reaction chamber and the power density Pi of the power supplied to generate the plasma is determined. 0.8 × 10 ⁴ (sec · W /
Since the silicon oxide film is etched while being controlled to be larger than m ³ ) and not more than 8 × 10 ⁴ (sec · W / m ³ ), the selectivity to the resist film is set to 2 while the process is stabilized. The above can be improved.

A third plasma processing method according to the present invention comprises:
A step of placing a substrate inside a reaction chamber of a plasma processing apparatus; a step of introducing a fluorocarbon gas containing carbon and fluorine and having a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber; Generating a plasma consisting of the following, and depositing an organic film on the substrate using the plasma: residence time τ = P × V / Q of the fluorocarbon gas (where P is the pressure (unit: Pa ), V is the volume (unit: L) of the reaction chamber, and Q is the flow rate of fluorocarbon gas (unit: Pa · L / sec).

According to the third plasma processing method, the residence time τ of the fluorocarbon gas in the reaction chamber is set to 0.1 (s).
ec) Since the organic film is deposited under the following control, the film formation rate of the organic film can be improved while the process is stabilized.

[0033] The fourth plasma processing method according to the present invention comprises:
A step of placing a substrate inside a reaction chamber of a plasma processing apparatus; a step of introducing a fluorocarbon gas containing carbon and fluorine and having a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber; Generating a plasma consisting of the following, and depositing an organic film on the substrate using the plasma: residence time τ = P × V / Q of the fluorocarbon gas (where P is the pressure (unit: Pa ), V is the volume (unit: L) of the reaction chamber, and Q is the flow rate (unit: Pa · L / sec) of the fluorocarbon gas) and the power supplied to generate the plasma. Power density Pi = W ₀ / V (however,
W ₀ is the magnitude of electric power (unit: W), and V is the volume of the reaction chamber (unit: L). ) And P × W ₀ / Q
Is controlled to 0.8 × 10 ⁴ (sec · W / m ³ ) or less.

According to the fourth plasma processing method, the value of P × W ₀ / Q, which is the product of the residence time τ of the fluorocarbon gas in the reaction chamber and the power density Pi of the power supplied to generate the plasma, 0.8 × 10 ⁴ (sec · W /
m ³ ) Since the organic film is deposited under the control described below, the film formation rate of the organic film can be improved while the process is stabilized.

In the first to fourth plasma processing methods,
Fluorocarbon gas is C ₄ F ₈ gas, C ₄ F ₆ gas, C
₃ F ₈ gas, is preferably a gas containing at least one of a C ₅ F ₈ gas and C ₆ F ₆ gas.

In the first to fourth plasma processing methods,
The stay time τ is preferably controlled by at least one of a mass flow controller provided in the plasma processing apparatus and a valve and a pump provided in the plasma processing apparatus.

A fifth plasma processing method according to the present invention comprises:
A step of installing a substrate having a silicon oxide film formed on a surface thereof inside a reaction chamber of a plasma processing apparatus, and a step containing carbon and fluorine and a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber. A step of introducing a first fluorocarbon gas, a step of generating a first plasma made of the first fluorocarbon gas, and etching the silicon oxide film using the first plasma; Introducing a second fluorocarbon gas containing carbon and fluorine and having a ratio of carbon to fluorine of 0.5 or more, and generating a second plasma composed of the second fluorocarbon gas; Depositing an organic film on the etched silicon oxide film using plasma, wherein the first fluorocarbon gas in the reaction chamber is 1 of the stay time _{τ 1 = P 1 × V /} Q 1
(Where P ₁ is the pressure (unit: Pa) of the first fluorocarbon gas, V is the volume (unit: L) of the reaction chamber, and Q ₁ is the flow rate (unit:
Pa · L / sec). ) Is controlled to be larger than 0.1 (sec) and equal to or smaller than 1 (sec), and the second residence time τ ₂ = P ₂ × V / Q ₂ of the second fluorocarbon gas in the reaction chamber is controlled.
(Where P ₂ is the pressure (unit: Pa) of the second fluorocarbon gas, V is the volume (unit: L ₂ ) of the reaction chamber, and Q ₂ is the flow rate (unit:
Pa · L / sec). ) Is controlled to 0.1 (sec) or less.

According to the fifth plasma processing method, the selectivity to the resist film is set to 2 while the process is stabilized.
It is possible to improve not only the above, but also to increase the deposition rate of the organic film.

According to a sixth plasma processing method of the present invention,
A step of installing a substrate having a silicon oxide film formed on a surface thereof inside a reaction chamber of a plasma processing apparatus, and a step containing carbon and fluorine and a ratio of carbon to fluorine of 0.5 or more inside the reaction chamber. A step of introducing a first fluorocarbon gas, a step of generating a first plasma made of the first fluorocarbon gas, and etching the silicon oxide film using the first plasma; Introducing a second fluorocarbon gas containing carbon and fluorine and having a ratio of carbon to fluorine of 0.5 or more, and generating a second plasma composed of the second fluorocarbon gas; Depositing an organic film on the etched silicon oxide film using plasma, wherein the first fluorocarbon gas in the reaction chamber is 1 of the stay time _{τ 1 = P 1 × V /} Q 1
(Where P ₁ is the pressure (unit: Pa) of the first fluorocarbon gas, V is the volume (unit: L) of the reaction chamber, and Q ₁ is the flow rate (unit:
Pa · L / sec). ) And the power density of the _first power supplied to generate the first plasma, Pi ₁ = W ₁ /
V (where W ₁ is the magnitude of the first electric power (unit: W) and V is the volume of the reaction chamber (unit: L)). ) Is the first product of P ₁ × W ₁ / Q ₁ .
Larger than 8 × 10 ⁴ (sec · W / m ³ ) and 8 × 10 ⁴
(Sec · W / m ³ ) or less, and the second stay time τ ₂ = P ₂ × V / of the second fluorocarbon gas in the reaction chamber.
Q ₂ (where, P ₂ is the pressure (unit: Pa) of the second fluorocarbon gas, V is the volume (unit: L) of the reaction chamber, and Q ₂ is the flow rate (unit: Pa · L / sec)), and the power density Pi ₂ = W of the _second power supplied to generate the second plasma.
₂ / V (where, W ₂ is the magnitude of the second power (unit: W)
And V is the volume (unit: L) of the reaction chamber. ) And the value of P ₂ × W ₂ / Q ₂ , which is the second product of 0.8 × 10 ⁴
(Sec · W / m ³ ) or less.

According to the sixth plasma processing method, the selectivity to the resist film is set to 2 while the process is stabilized.
It is possible to improve not only the above, but also to increase the deposition rate of the organic film.

In the fifth or sixth plasma processing method,
And the first fluorocarbon gas is C_FourF₈Gas, C_Three
F₈Gas, C_FiveF₈Gas and C₆F₆At least of the gas
Is also a gas containing one, and the second fluorocarbon gas
Is C_FourF₈Gas, C_FourF₆Gas, C _ThreeF₈Gas, C_FiveF₈gas
And C₆F₆A gas containing at least one of the gases
Preferably.

In the fifth or sixth plasma processing method, the first stay time τ ₁ and the second stay time τ ₂ are determined by the mass flow controller provided in the plasma processing apparatus and the valve provided in the plasma processing apparatus. And at least one of a pump and a pump.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma processing method according to each embodiment of the present invention will be described. As a premise, a principle of solution of the present invention will be described.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047] [Table 1], [Table 2] and [Table 3], in the plasma etching method using the C ₅ F ₈ as an etching gas, the volume of the reaction chamber, the C ₅ F ₈ gas flow rate and C ₅ F ₈ shows the results of an experiment in which plasma etching was performed while changing the gas pressure, and the residence time τ of the gas in the reaction chamber was determined.

[Table 1] shows the case where the volume of the reaction chamber is 25 liters, [Table 2] shows the case where the volume of the reaction chamber is 10 liters, and [Table 3] shows the case where the volume of the reaction chamber is 50 liters. It is the case of liter. In the experiment for determining the stay time τ, the flow rate (mL) per minute in the standard state was used as the gas flow rate, so that the gas flow rate per minute in the standard state was 79.05 (mL) = 133.3 (Pa).・ L
/ Sec), the flow rate of the C ₅ F ₈ gas is shown in units of (× 133.3 / 79.05 (Pa · L / sec)). Further, since mTorr was used as the gas pressure, the pressure of the C ₅ F ₈ gas is shown in the unit of (× 0.133 (Pa)) based on the conversion formula of 1 (mTorr) = 0.133 (Pa).

The data in [Table 1], [Table 2] and [Table 3] are based on the volume of the reaction chamber (unit: L) and the gas flow rate (unit: Pa ·
L / sec) and the gas pressure (unit: Pa) are given by τ = P × V
/ Q (where τ is the residence time of the gas in the reaction chamber (unit: sec), P is the gas pressure (unit: Pa), V is the volume of the reaction chamber (unit: L), Q Is the gas flow rate (unit: Pa · L / sec)) to determine the gas residence time τ. Further, in [Table 1], [Table 2] and [Table 3], a region surrounded by a thick line frame is:
The stay time at which the selectivity of the silicon oxide film to the resist film becomes 2 or more is shown.

Therefore, [Table 1], [Table 2] and [Table 3]
Therefore, in the plasma etching method using C ₅ F ₈ gas as the etching gas, the residence time τ is 0.1 (se).
It can be seen that when the value is larger than c) and 1 (sec) or less, a value of 2 or more can be obtained as the selectivity of the silicon oxide film to the resist film. In some regions other than the region surrounded by the thick frame, the staying time τ is in the range of 0.1 to 1 (sec). Experience has shown that the use of pressure stabilizes the process. In [Table 1], [Table 2] and [Table 3], the stay time τ is 0.01 (sec) to 39.
Although it is distributed in the range of 5.3 (sec), the present invention has a distribution of 0.3 (sec).
An extremely narrow region of 1 to 1 (sec) is selected. If this extremely short region is selected, the process becomes stable and the selectivity of the silicon oxide film to the resist film becomes 2 or more. It was found.

When the staying time τ is less than 0.1 (sec), the lower selectivity to the resist film means that the polymer deposition is promoted, that is, the organic film deposition rate Means better. Therefore, when the residence time τ of the gas is set to 0.1 (sec) or less, the deposition rate of the organic film is improved.

Incidentally, as can be seen from the above-mentioned relational expression of τ = P × V / Q, the stay time τ changes depending on the volume V of the reaction chamber.

Therefore, the power density Pi = W ₀ / V (where W ₀ is the magnitude of the power (unit: W)) and V is the volume of the reaction chamber (unit) : L)) and the stay time τ, E = P
The concept of × W ₀ / Q is introduced. This way,
Regardless of the volume of the reaction chamber, the selectivity to the resist film can be improved, or the deposition rate of the organic film can be improved.

If the stay time τ is smaller than 0.1 and 1 (s
ec) The following range means that the product E of the stay time τ and the power density Pi is larger than 0.8 × 10 ⁴ (sec · W / m ³ ) and 8 × 10 ⁴ (sec · W / m ³ ) or less.

Therefore, the product E of the stay time τ and the power density Pi is larger than 0.8 × 10 ⁴ (sec · W / m ³ ) and 8
If it is not more than × 10 ⁴ (sec · W / m ³ ), the process becomes stable and the selectivity of the silicon oxide film to the resist film becomes 2 or more.

When the product E of the stay time τ and the power density Pi is 0.
When it is not more than 8 × 10 ⁴ (sec · W / m ³ ), the deposition rate of the organic film is improved.

FIG. 2 shows the dwell time τ and BPSG when plasma etching was performed by changing the etching gas.
(Boro-phospho-silicate glass) and the relationship with the etching rate of the resist film. In FIG. 2, ★ represents the etching rate for the BPSG film when using C ₂ F ₆ gas, Δ represents the etching rate for the BPSG film when using C ₄ F ₈ gas, and ● represents the etching rate for the BPSG film.
Shows the etching rate for the BPSG film when using ₅ F ₈ gas, ☆ shows the etching rate for the resist film when using C ₂ F ₆ gas, and Δ shows the resist when using C ₄ F ₈ gas. The レ ー ト indicates the etching rate for the resist film when the C ₅ F ₈ gas is used.

FIG. 2 shows that when the C ₄ F ₈ gas and the C ₅ F ₈ gas are used, the etching rate of the BPSG film and the resist film decreases as the staying time decreases.
This is considered to be because a polymer film is deposited on each surface of the BPSG film and the resist film, and the polymer film functions to suppress etching. On the other hand, when the C ₂ F ₆ gas is used, it can be seen that the shorter the residence time, the higher the etching rate of the BPSG film and the resist film.

FIG. 3 shows the dependence of the ratio of the etching rate of the BPSG film to the etching rate of the resist film, that is, the dependency of the selectivity on the resist film on the residence time τ. In FIG. 3, ★ represents the selectivity when using C ₂ F ₆ gas, Δ represents the selectivity when using C ₄ F ₈ gas, and ● represents the use of C ₅ F ₈ gas. The selection ratio at the time is shown.

FIG. 3 shows that when C ₄ F ₈ gas and C ₅ F ₈ gas are used, the shorter the staying time, the higher the selectivity to the resist film. However, when C ₄ F ₈ gas is used, if the stay time is 0.2 (sec) or less,
The selectivity decreases. This is because the decrease in the etching rate of the BPSG film is larger than the decrease in the etching rate of the resist film. On the other hand, when C ₂ F ₆ gas is used, it can be seen that the selectivity hardly depends on the stay time.

From the above considerations, when a fluorocarbon gas having a carbon ratio of 0.5 or more, such as C ₄ F ₈ gas and C ₅ F ₈ gas, is used, the staying time is shorter than 0.1 (sec). It is confirmed that the etching selectivity is improved when it is controlled to a large value and 1 (sec) or less.

FIG. 4 shows an inductively coupled plasma processing apparatus.
To generate plasma consisting of fluorocarbon gas.
F^-Ion, CF^3-Ion, C_TwoF_Five ^-Io
N, C_FiveF₇ ^-Ion, C₇F₁₁ ^-Ion and C₈F₁₁ ^-I
Show the dependence of the amount of each ion on on the residence time.
This measurement was performed using electron attachment mass spectrometry.
It is. Therefore, F^-The ions are all C_xF_yFrom the molecule
Produced by the dissociative electron attachment process of
CF^3-Ion is CF_FourIn the process of attaching dissociative electrons from molecules
Generated by C_TwoF_Five ^-The ion is C_TwoF₆Solutions from molecules
It is produced by the process of attaching detached electrons. Also, C_Five
F₇ ^-Ion, C₇F₁₁ ^-Ion and C₈F ₁₁ ^-To ion
The similar dissociative electron attachment process and non-dissociative electron
It is produced in both the adhesion process and the adhesion process.

[0063] From FIG. 4, when a shorter stay time, F ^- ions, CF ^3- ions and C ₂ F ₅ ^- While low order ions is reduced, such as an ion, C ₅ F ₇ ^- ion, C ₇ F ₁₁ ^- ions and C ₈ F ₁₁ ^- higher ions such as ions can be seen to increase. That is, when the staying time is shortened, the lower-order molecules are decreased while the higher-order molecules are increased. Therefore, it is found that when the staying time is shortened, the selectivity to the resist film is improved.

FIG. 5 shows the residence time τ and the power density P when plasma etching is performed by changing the etching gas.
The relation between the product E with i and the etching rate of the BPSG and the resist film is shown. Note that, in FIG. 5, the calculation is performed on the assumption that the power density Pi is 1800 W. FIG.
In the formula, ★ represents the etching rate for the BPSG film when using C ₂ F ₆ gas, Δ represents the etching rate for the BPSG film when using C ₄ F ₈ gas,
● indicates the etching rate for the BPSG film when using C ₅ F ₈ gas, ☆ indicates the etching rate for the resist film when using C ₂ F ₆ gas, and Δ indicates C ₄ F _8.
The etching rate for the resist film when gas is used is shown, and ○ indicates the etching rate for the resist film when C ₅ F ₈ gas is used.

FIG. 5 shows that in the case of using C ₄ F ₈ gas and C ₅ F ₈ gas, the etching rate of the BPSG film and the resist film decreases when the product E of the stay time and the power density decreases. This is the stay time τ
And the same relationship as the relationship between the etching rate of the BPSG film and the resist film.

FIG. 6 shows the dependence of the selectivity for the resist film on the product E of the stay time and the power density. In FIG. 6, the power density Pi is calculated as 1800 W. In FIG. 6, ★ represents the selectivity when using C ₂ F ₆ gas, Δ represents the selectivity when using C ₄ F ₈ gas, and ● represents the use of C ₅ F ₈ gas. The selection ratio at the time is shown.

FIG. 6 shows that when C ₄ F ₈ gas and C ₅ F ₈ gas are used, when the product E of the stay time and the power density is reduced, the selectivity to the resist film is increased. This is because the same relationship as the relationship between the stay time and the selection ratio described above is established.

From the above considerations, when a fluorocarbon gas having a carbon ratio of 0.5 or more, such as C ₄ F ₈ gas and C ₅ F ₈ gas, is used, the product E of the residence time and the power density is obtained.
Is larger than 0.8 × 10 ⁴ (sec · W / m ³ ) and 8 ×
It is confirmed that the etching selectivity is improved when the control is performed at 10 ⁴ (sec · W / m ³ ) or less.

[0069] Figure 7, in inductively coupled plasma processing apparatus, in the case where plasma is generated consisting of fluorocarbon gases, F ^- ions, CF ^3- ions, C ₂ F ₅ ^- ions, C ₅ F ₇ ^- ions, C ₇ F ₁₁ ^- ions, and C ₈ F ₁₁ ^- shows the dependence on the product of the residence time and the power density of each ion of the ion.

From FIG. 7, the product E of the stay time and the power density is
If you make it smaller, F^-Ion, CF^3-Ion and C_TwoF_Five ^-
While low-order ions such as ions decrease, C_FiveF₇ ^-Io
N, C ₇F₁₁ ^-Ion and C₈F₁₁ ^-Higher order ions such as ions
It can be seen that the number increases. That is, stay time and power
If the product E with the density is reduced, the choice for the resist film
It can be seen that the property is improved.

[0071] FIG. 8 (a) ~ (c) is a residence time as a parameter, F ^- shows the result of measuring the intensity distribution of the electron energy of the ion, FIG. 8 (a) is the residence time 4.5 (Sec), FIG. 8 (b) shows the case where the stay time is 5.2 (sec), and FIG. 8 (c) shows the case where the stay time is 13.5 (sec). These intensity distributions
Dissociable fragments from each molecule can be observed and measurements can be made for those with known cross-sectional areas.

[0072] From FIG. 8 (a) ~ (c) , for the C ₂ F ₆ gas and C ₃ F ₈ gas, the residence time is prolonged, C ₂ F ₆
It can be seen that the gas and C ₃ F ₈ gas increase. This phenomenon is consistent with the result shown in FIG. FIG.
From (a) to (c), it can be seen that when the staying time is shortened, the regulated fluorocarbon gas such as C ₂ F ₆ gas or C ₃ F ₈ gas which adversely affects the environment can be reduced.

Incidentally, Japanese Patent Application Laid-Open No. Hei 5-259119 proposes a technique for shortening the staying time τ by using a high-speed exhaust pump, thereby improving the etching selectivity. JP-A-5-259119

The technique shown in FIG. 7 and the description thereof is apparently similar to the present invention.

However, the problem to be solved by the invention of JP-A-5-259119 is that the chemical formula: SiO ₂ +
By rapidly exhausting CO ₂ on the right side represented by CF _x → SiF _x + CO ₂ , a reaction product (C
O _2, etc.) is intended to influence try less of, the invention of JP-A-5-259119 Patent Publication not specified regarding the etching gas.

On the other hand, the present invention does not have the above-mentioned problem at all, and when etching using a gas having a large C / F ratio, it is necessary to make sure that the selectivity to the resist film is increased. It has been found that it is important to set the product E of the time τ or the stay time and the power density in a predetermined range. Therefore, the invention of JP-A-5-259119, in which the etching gas is not specified, and the present invention, in which the process gas is specified as a fluorocarbon gas having a C / F ratio of 0.5 or more, are technically different. It is completely different in terms of ideas, configurations and effects.

(First Embodiment) A plasma processing method according to a first embodiment will be described below with reference to FIGS.

First, in step SA 1, a semiconductor substrate is carried into the reaction chamber 10 of the plasma processing apparatus, and the semiconductor substrate is set on the sample table 20. In this case, a silicon oxide film is formed on the semiconductor substrate, and a patterned resist film is formed on the silicon oxide film.

Next, in step SA2, the reaction chamber 1
0, a fluorocarbon gas having a C / F ratio of 0.5 or more, for example, a C ₅ F ₈ gas is introduced. In this case, the gas pressure is controlled to be in a range of 0.665 Pa to 3.99 Pa, for example, 1.33 Pa.

Next, at step SA3, τ = P ×
V / Q (where τ is the residence time of the gas in the reaction chamber (unit: sec), P is the gas pressure (unit: Pa), V is the volume of the reaction chamber (unit: L), Q is a gas flow rate (unit: Pa · L / sec), and the residence time τ is larger than 0.1 (sec) and 1
(Sec) The mass flow controller 1
Adjust 5 to control the gas flow.

Next, in step SA4, a first high frequency power is applied from the first high frequency power supply 13 to the induction coil 12 to generate a plasma made of a fluorocarbon gas, for example, a C ₅ F ₈ gas. In this case, the stay time τ is 0.
When the gas flow rate is controlled to be greater than 1 (sec) and equal to or less than 1 (sec), the power density of the first high-frequency power supplied to generate plasma, Pi = W ₀ / V
(However, W ₀ is the magnitude of electric power (unit: W 2), and V is the volume of the reaction chamber (unit: L 2)) and E = P × W ₀ / Q is necessarily 0.8 × 10
⁴ (sec · W / m ³ ) and 8 × 10 ⁴ (sec · W /
m ³ ) It is set as follows.

Next, in step SA5, a second high-frequency power is applied from the second high-frequency power supply 22 to the sample stage 20, and the generated plasma is introduced onto the semiconductor substrate on the sample stage 20, In step SA6, plasma etching is performed on the silicon oxide film using the resist film as a mask.

According to the first embodiment, the residence time τ of the pafluorocarbon gas in the reaction chamber is set to 0.1 (sec).
And E (P × W ₀ / Q), which is the product of the power density Pi of the first high-frequency power and the stay time τ, is set to 0.8 × 10 ⁴ (sec · W / m ³ ) and 8 × 10 ⁴ (sec · W / m ³ ) or less, the selection ratio of the silicon oxide film to the resist film can be made 2 or more.

(Second Embodiment) Hereinafter, a plasma processing method according to a second embodiment will be described with reference to FIGS.

First, in step SB1, a semiconductor substrate is carried into the reaction chamber 10 of the plasma processing apparatus, and the semiconductor substrate is set on the sample stage 20.

Next, in step SB2, the reaction chamber 1
0, a fluorocarbon gas having a C / F ratio of 0.5 or more, for example, a C ₅ F ₈ gas is introduced. In this case, the gas pressure is controlled to be in a range of 0.665 Pa to 3.99 Pa, for example, 1.33 Pa.

Next, in step SB3, the stay time τ is set to 0.1 (sequence) using the above-mentioned relational expression τ = P × V / Q.
c) Adjust the mass flow controller 15 to control the gas flow rate as described below.

Next, in step SB4, a first high-frequency power is applied to the induction coil 12 from the first high-frequency power supply 13 to generate a plasma composed of a fluorocarbon gas, for example, a C ₅ F ₈ gas. In this case, the stay time τ is 0.
When the gas flow rate is controlled to be 1 (sec) or less, E = P × W ₀ /, which is the product of the power density Pi of the first high-frequency power supplied to generate plasma and the residence time τ.
Q is necessarily set to 0.8 × 10 ⁴ (sec · W / m ³ ) or less.

Next, in step SB5, a second high-frequency power is applied from the second high-frequency power supply 22 to the sample table 20, and the generated plasma is introduced onto the semiconductor substrate on the sample table 20, In Step SB6, an organic film is deposited on the semiconductor substrate.

According to the second embodiment, the residence time τ of the pafluorocarbon gas in the reaction chamber is set to 0.1 (sec).
The power density P of the first high-frequency power is set as follows.
E = P × W ₀ / Q which is the product of i and stay time τ is 0.8
Since it is set to 10 ⁴ (sec · W / m ³ ) or less, an organic film can be formed at an excellent deposition rate.

(Third Embodiment) Hereinafter, a plasma processing method according to a third embodiment will be described with reference to FIGS.

First, in step SC1, a semiconductor substrate is carried into the reaction chamber 10 of the plasma processing apparatus, and the semiconductor substrate is set on the sample stage 20.

Next, in step SC2, the reaction chamber 1
A first fluorocarbon gas having a C / F ratio of 0.5 or more, for example, a C ₅ F ₈ gas is introduced into the inside of 0. In this case, the gas pressure is 0.665 Pa to 3.99 Pa.
, For example, 1.33 Pa.

Next, in step SC3, using the above-mentioned relational expression τ = P × V / Q, the stay time τ is 0.1 (se
The mass flow controller 15 is adjusted to control the flow rate of the first gas so as to be larger than c) and equal to or less than 1 (sec).

Next, in step SC4, a first high frequency power is applied to the induction coil 12 from the first high frequency power supply 13 to generate a first plasma made of a first fluorocarbon gas, for example, a C ₅ F ₈ gas. I do. In this case, if the flow rate of the first gas is controlled so that the stay time τ is greater than 0.1 (sec) and equal to or less than 1 (sec), the first gas supplied to generate the first plasma is controlled. E = P × W ₀ which is the product of the power density Pi of the high-frequency power and the stay time τ
/ Q is necessarily set to be larger than 0.8 × 10 ⁴ (sec · W / m ³ ) and equal to or smaller than 8 × 10 ⁴ (sec · W / m ³ ).

Next, in step SC5, a second high-frequency power is applied from the second high-frequency power source 22 to the sample stage 20 to introduce the first plasma onto the semiconductor substrate on the sample stage 20, In step SC6, plasma etching is performed on the silicon oxide film using the resist film as a mask.

Next, when the plasma etching is completed,
In Step SC7, after the introduction of the first perfluorocarbon gas is stopped, an oxygen gas is introduced into the reaction chamber 10 and an oxygen plasma composed of the oxygen gas is generated to form a resist film on the silicon oxide film. Is removed by ashing.

Next, in Step SC8, the reaction chamber 1
Inside 0, a second fluorocarbon gas having a C / F ratio of 0.5 or more, for example, a C ₅ F ₈ gas is introduced. In this case, the gas pressure is 0.665 Pa to 3.99 Pa.
, For example, 1.33 Pa.

Next, in step SC9, the stay time τ is set to 0.1 (sequence) using the above-mentioned relational expression τ = P × V / Q.
c) Adjust the mass flow controller 15 to control the flow rate of the second gas as described below.

Next, in step SC10, a first high-frequency power is applied from the first high-frequency power supply 13 to the induction coil 12, and a second fluorocarbon gas, for example, C ₅ F _{8 is applied.}
A plasma composed of a gas is generated. In this case, if the gas flow rate is controlled such that the residence time τ of the second gas is 0.1 (sec) or less, the power density Pi of the first high-frequency power supplied to generate the second plasma And stay time τ
E = P × W ₀ / Q is necessarily 0.8 × 1
^{0 4 (sec · W / m} 3) is set below.

Next, in step SC11, a second high-frequency power is applied from the second high-frequency power supply 22 to the sample stage 20, and the generated plasma is introduced onto the semiconductor substrate on the sample stage 20, In Step SC12, an organic film is deposited on the silicon oxide film.

In the first to third embodiments, the C ₅ F ₈ gas is used alone as the fluorocarbon gas. However, the C ₄ F ₈ gas, the C ₄ F ₆ gas, the C ₄ F ₆ gas, ₃ F ₈ gas or C ₆ F ₆ gas may be used alone, or a mixed gas of these gases may be used.

Further, in the third embodiment, the first fluorocarbon gas and the second fluorocarbon gas are the same gas, but the first fluorocarbon gas and the second fluorocarbon gas are the same gas. Or different gases.

In the first to third embodiments,
Although an inductively coupled plasma processing apparatus was used as the plasma processing apparatus, an ECR plasma processing apparatus, a surface wave excitation type plasma processing apparatus, or the like can be used instead.

Further, in the first to third embodiments, the gas flow rate is controlled by adjusting the mass flow controller 15, but instead the gas flow is controlled by adjusting the mass flow controller 15, the pressure control valve 18 and the exhaust gas. The adjustment may be performed by adjusting at least one of the adjustment of the pump 19. The flow rate of the fluorocarbon gas may be adjusted by mixing an inert gas, a nitrogen gas, a carbon monoxide gas, or a carbon dioxide gas with the process gas, and adjusting the flow rates of these gases.

[0105]

According to the plasma processing method of the present invention, the selectivity to the resist film can be improved to 2 or more and the film formation rate of the organic film can be improved while the process is stabilized. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an inductively coupled plasma processing apparatus used in a plasma processing method according to a conventional example and each embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between residence time and BPSG and an etching rate of a resist film when plasma etching is performed by changing an etching gas.

FIG. 3 is a diagram showing a relationship between residence time and selectivity to a resist film when plasma etching is performed by changing an etching gas.

FIG. 4 is a diagram showing the dependence of various ions on the residence time when plasma made of a fluorocarbon gas is generated in an inductively coupled plasma processing apparatus.

FIG. 5 is a graph showing the relationship between the product of the residence time and the power density and the BPS when plasma etching is performed by changing the etching gas.
FIG. 4 is a diagram showing a relationship between G and an etching rate of a resist film.

FIG. 6 is a diagram showing a relationship between a product of a stay time and a power density and a selectivity to a resist film when plasma etching is performed by changing an etching gas.

FIG. 7 is a diagram showing the dependence of various ions on the product of the residence time and the power density when plasma composed of a fluorocarbon gas is generated in the inductively coupled plasma processing apparatus.

8A is a diagram showing a result of measuring the intensity distribution of electron energy of F ⁻ ions when the stay time is 4.5 (sec), and FIG. 2
(C) is a diagram showing the result of measuring the intensity distribution of electron energy of F ^- ions in the case of (c);
Is F when the stay time is 13.5 (sec)
^- is a graph showing the results of measuring the intensity distribution of the electron energy of the ions.

FIG. 9 is a flowchart showing a plasma processing method according to the first embodiment.

FIG. 10 is a flowchart illustrating a plasma processing method according to a second embodiment.

FIG. 11 is a flowchart illustrating a plasma processing method according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 10 reaction chamber 11 quartz plate 12 induction coil 13 first high-frequency power supply 14 gas introduction unit 15 mass flow controller 16 gas supply source 17 gas discharge unit 18 pressure control valve 19 exhaust pump 20 sample table 21 matching circuit 22 second high-frequency power supply 23 Control device

Claims (4)

[Claims] 1. A step of installing a substrate having a silicon oxide film formed on a surface thereof in a reaction chamber of a plasma processing apparatus, wherein the reaction chamber contains carbon and fluorine and the ratio of carbon to fluorine is A step of introducing a fluorocarbon gas of 0.5 or more, and generating a plasma comprising the fluorocarbon gas,
Etching the silicon oxide film using the plasma, wherein the residence time of the fluorocarbon gas in the reaction chamber τ = P × V / Q (where P is the pressure of the fluorocarbon gas (unit: Pa), V is the volume (unit: L) of the reaction chamber, and Q is the flow rate (unit: Pa · L / sec) of the fluorocarbon gas. And a plasma processing method characterized by controlling the temperature to 1 (sec) or less. 2. A step of installing a substrate in a reaction chamber of a plasma processing apparatus, and introducing a fluorocarbon gas containing carbon and fluorine and having a ratio of carbon to fluorine of 0.5 or more into the reaction chamber. Generating a plasma comprising the fluorocarbon gas,
Depositing an organic film on the substrate using the plasma, and the residence time of the fluorocarbon gas τ = P × V / Q
(Where P is the pressure of the fluorocarbon gas (unit:
Pa), V is the volume of the reaction chamber (unit: L), and Q is the flow rate of the fluorocarbon gas (unit: Pa ·
L / sec). ) Is controlled to 0.1 (sec) or less. 3. The fluorocarbon gas includes a C ₄ F ₈ gas, a C ₄ F ₆ gas, a C ₃ F ₈ gas, a C ₅ F ₈ gas and a C ₆ F ₆ gas.
3. The plasma processing method according to claim 1, wherein the gas contains at least one of the gases. 4. The residence time τ is controlled by at least one of a mass flow controller provided in the plasma processing apparatus and a valve and a pump provided in the plasma processing apparatus. The plasma processing method according to claim 1.