JP3158612B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus and a dry etching method, and more particularly to a dry etching apparatus and a dry etching method suitable for performing high anisotropy and high speed etching at a high throughput.

[0002]

2. Description of the Related Art In a conventional dry etching apparatus, etching is performed by switching an etching gas in order to perform anisotropic processing. For example, Japanese Patent Application Laid-Open No. 61-61423 and
In JP-A-63-65628, anisotropic etching is performed in a first step, a sidewall protective film is formed in a second step, isotropic etching is performed in a third step, and etching is performed by switching a gas in each step. do. JP-A-60-50923 and JP-A-2-105
In Japanese Patent No. 413, anisotropic processing is realized by time modulation etching in which an etching gas and a deposition gas are switched at intervals of several seconds. Also, JP-A-2-270
In Japanese Patent Publication No. 320, a wafer is fixed by electrostatic suction in order to improve temperature controllability in low-temperature etching and increase anisotropy. In order to fix a wafer by electrostatic attraction or to remove a fixed wafer, plasma discharge is necessary. In order to perform accurate etching, it is better to switch the gas to an inert gas before discharging. As described above, when performing anisotropic etching, gas switching is essential.

In order to switch gas efficiently,
Higher exhaust capacity is better. The configuration of the pumping system of the conventional dry etching apparatus has a pump capacity of 1000 l / s, the conductance of the pumping system is 200 to 1000 l / s, and the effective pumping speed of the entire apparatus is 100 to 500 l / s.
Met. The volume of the conventional dry etching apparatus is 2
It was 00-300 l.

[0004] One measure of the exhaust capacity is the time that the gas stays in the vessel from the time the gas flows in until the gas is exhausted. The gas residence time is obtained by the following equation: gas residence time = volume of apparatus / effective pumping speed. With conventional equipment, the gas residence time is 0.4 ~
3s. Since the time required for gas switching is longer than the gas residence time, the conventional dry etching apparatus and dry etching method required 1 s or more to switch the gas.

[0005] A dry etching apparatus having a short gas residence time of 25 ms has been developed by Journal of Vacuum Scientific Technology B8 (1990) 118.
Page 5 (J. Vac. Sci. Technol. B8 (1990) p. 1)
185). In this device, the volume between the electrodes is
It is about 2 l, and the effective pumping speed of the apparatus is about 80 l / s.

[0006]

At the time of gas switching,
The gas in the container must be exhausted in order to suppress the deterioration of the etching characteristics due to the gas mixture before and after the switching.
At the time of gas switching, the effective exhaust efficiency decreases as the partial pressure of the exhaust gas decreases. Therefore, the time required for the discharge is several times the residence time of the gas.

In the conventional dry etching apparatus, the stay time was about 0.4 to 3 s. That is, gas switching requires a time of one second or more. Therefore, in the time modulation etching, one step has a step time of several seconds in both the etching step and the deposition step.

In the prior art as described above, when the step time is several seconds, a side structure during the etching step causes a step structure on the side wall, and it takes time to switch the gas, so that the etching throughput decreases. In order to observe the shape during etching by providing a sample observing means in the etching apparatus, the gas had to be stopped and the pressure had to be reduced.Therefore, if etching was performed while observing the shape, there was a problem that the throughput was reduced. Was.

[0009]

According to the present invention, the exhaust system of the dry etching apparatus has a pumping speed of 2500 l / s, desirably 4000 l / s.
The conductance of the exhaust system is 2000 l / s, preferably 3000 l / s, and the effective exhaust speed of the entire apparatus is 13 l / s.
00 l / s or more.

In addition, the volume of the conventional dry etching apparatus is designed so that the residence time of the gas is 100 ms or less. That is, the volume was made smaller than the value of effective pumping speed × 100 ms (2).

[0011] Further, at least one gas introduction system is provided,
As a gas flow controller provided therein, a gas flow controller capable of maintaining a constant flow rate for a minimum time of 50 ms or less was used. In addition, the gas flow controller, the discharging means, and the means for controlling the pumping speed are controlled by a collective controller. A means for observing the sample was provided.

[0012]

[Effect] During the etching, the gas B is changed from the gas A to the gas B.
When the etching is switched to the above, if the gas B is not etched after sufficiently exhausting the gas A, the gases before and after the switching are mixed and the etching characteristics are deteriorated.

[0013] The pressure changes as shown in FIG. If the air is evacuated for a sufficiently long time, the pressure drops to the ultimate vacuum. However, in that case, the throughput becomes extremely poor. Therefore, in practice, the next gas is introduced at the time when the gas discharge is completed at about 95%.

The pressure change from the stop of the gas to the end of the discharge follows the differential equation of dP / dt = -SP / V, where P is the pressure, S is the effective pumping speed, and V is the volume of the apparatus. As shown in FIG. 2, when the above equation is solved with the gas stop time set to t = 0, the time until the gas pressure reaches the pressure after discharge (discharge time) is: discharge time = (V / S) ln (before discharge) (Pressure / pressure after discharge) (4) Here, (V / S) is the residence time of the gas, so discharge time = residence time × ln (pressure before discharge / pressure after discharge) (5).

FIG. 4 shows the relationship between the ratio of the gas discharged outside the container and ln (pressure before discharge / pressure after discharge). Even if the gas is stopped and then exhausted for the duration of the gas, only 60% of the total gas is exhausted. For example, 95% of gas
Is discharged, ln (pressure before discharge / pressure after discharge)
Is 4. That is, 95% of the gas cannot be discharged unless the gas is evacuated for four times the stay time.

In the conventional dry etching apparatus, the residence time is about 1 s, so that the discharge time is several seconds. In the present invention, the effective pumping speed is 1300 l / s, and the staying time is
Since the discharge time is set to 100 ms or less, the discharge time can be shortened by about 1/10 compared to the related art. As a result, the gas switching time was shortened and the throughput was improved.

Further, since the minimum time during which the gas flow controller can maintain a constant flow rate is set to 50 ms or less, the gas switching time is shortened, and the gas introduction can be performed in a pulsed manner. As a result, the time for one step can be reduced to 100 ms or less in etching that frequently switches gases such as time modulation etching. 1200n etching rate
m / min etching for one step time of, for example, 10
ms, the etching amount in one step is 0.2 nm.
And about one atomic layer. That is, since the gas introduction and the gas switching time can be shortened, and the gas can be introduced in a pulsed manner, it is possible to perform etching capable of controlling about several atomic layers.

Further, since the discharging means and the means for changing the pumping speed are collectively controlled together with the gas flow controller, highly accurate etching can be performed with high throughput.

Further, since the observation means for the sample is provided,
High-precision etching can be performed while monitoring the etching shape. At that time, the time required for stopping the gas and lowering the pressure was reduced to 100 ms or less, so that etching could be performed without lowering the throughput.

[0020]

【Example】

<Embodiment 1> One embodiment of a dry etching apparatus according to the present invention is shown in FIG. In this apparatus, an etching gas is introduced into a vacuum processing chamber 1, and 2.
A high frequency of 45 GHz is generated, and this high frequency is
To transport to the discharge part 4 to generate gas plasma 5. A solenoid coil 6 for generating a magnetic field is arranged around the discharge part for high-efficiency discharge, and an electron cyclotron resonance (Electron Cyclotron Resonanc) with a magnetic field of 875 Gauss is used.
e: also called ECR) to generate high density plasma. The discharge unit 4 has a sample stage 7 on which a wafer 8 is placed.
Is installed and an etching process is performed by the gas plasma 5.

The etching gas is supplied from the gas inlet 9 to the discharge unit 4 through the vacuum processing chamber 1 through the exhaust pipe 10 to the exhaust pump 1.
1 discharges out of the vacuum processing chamber 1. At this time, the exhaust speed can be changed by the conductance valve 12.

A cooling mechanism 1 is provided on a sample stage 7 on which a wafer is placed.
6 to cool the wafer to 0 ° C. or lower.
Furthermore, 13.56M from 400kHz by RF power supply 17.
Hz RF bias can be applied.

A heater 18 is provided in the vacuum processing chamber 1 so that a baking process for heating the vacuum processing chamber 1 to 50 ° C. or more can be performed. As a result, residual gas components on the wall surface of the vacuum processing chamber 1 and deposits of reaction products having a relatively low vapor pressure are removed, so that the ultimate pressure can be reduced to 0.5 μtorr or less, 1/10 or less of the conventional pressure. Was. Therefore, even when low-pressure etching is performed at an etching operation pressure of 0.5 mtorr, clean etching can be performed with impurity gas components suppressed to 1/1000 or less.

The pump 11 has a pumping speed of 2000 l.
/ S two turbo molecular pumps and a total pumping speed of 40
The discharge section 4 was arranged symmetrically with respect to the central axis of the discharge section 4 at 00 l / s. The discharge section 4, the vacuum processing chamber 1, the exhaust pipe 10, and the total exhaust conductance of the conductance valve 12 which are gas passages were designed to be 4000 l / s.
The effective pumping speed can be obtained by 1 / effective pumping speed = 1 / pump pumping speed + 1 / total pumping conductance (6). In this embodiment, the effective pumping speed is 20.
00 l / s. The total volume of the discharge part 4, the vacuum processing chamber 1, and the exhaust pipe 10 was designed as small as 100 l so that the residence time of the gas in the vacuum processing chamber 1 was 50 msec.
As a result, the discharge time can be reduced, for example, the time required for 95% discharge is about 200 ms. The conventional device is 95
The discharge time could be reduced to 1/5 to 1/30 as compared with the case where the% discharge took about 1 to 6 s. Therefore, the time required for gas switching was shortened, and the etching throughput was improved.

The processing gas is supplied to a gas flow controller 13a,
The gas was introduced from the gas inlet 9 to the discharge section through the buffer chamber 15 having a small hole in the form of a mesh through the gas pipes 14a, 14b and 14c. By providing the buffer chamber 15 and widening the gas opening area by mesh-shaped small holes, the gas flow rate at the time of gas introduction can be reduced to 1/3 of the sound speed.
The results were as follows, and a uniform flow was obtained. Further, when gas is introduced from each of the gas pipes 14a, b, and c into the discharge unit 4, two or more gas inlets 9 are arranged symmetrically with respect to the central axis of the discharge unit. As a result, deviation of the gas distribution in the gas plasma 5 can be suppressed.

A plurality of gas flow controllers 13 and a plurality of gas pipes 14 are provided for switching the processing gas to flow to the discharge section 4. A different kind of gas source was connected to each piping system. Of course, a gas mixing device may be attached to the piping system so that the mixed gas can flow.

In this embodiment, three piping systems are provided. The minimum time in which the gas flow controllers 13a, b, and c of the piping system can maintain a constant flow rate is the same as the gas discharge time. As a result, the gas type can be exchanged immediately upon completion of discharge. Regarding the effect that the shortest time in which the gas flow controller 13 can maintain a constant flow rate is almost equal to the gas discharge time, for example, the gas flow controllers 13a and 13b
Are alternately switched to flow to the discharge unit 4.

If the minimum time during which the gas flow controller 13 can maintain a constant flow rate is 200 ms, it is possible to flow gas in a pulsed manner at the timing shown in FIG.
If the shortest time during which the gas flow controller 13 can maintain the constant flow rate is as slow as about 1 s, the flow control cannot be switched in 1 s or less, and FIG.
The pulse length and interval cannot be made 1 s or less as in If the gas flow controller 13a has a performance different from the shortest time 200ms in which the gas flow rate controller 13a can maintain a constant flow rate and the gas flow rate controller 13b has a performance different from the minimum time 1s in which the gas flow rate controller 13b can maintain a constant flow rate, as shown in FIG. Although A is sufficiently exhausted, the gas B cannot be flowed, resulting in a non-operation time.

If a gas flow controller is used in which the shortest time capable of maintaining a constant flow rate is the same as the discharge time, the effect of the present invention, that is, the reduction of the discharge time, can be maximized. Of course, by installing a large number of gas piping systems, it is possible to reduce the time such as the non-operation time. However, in this case, since the gas cannot be flowed in a pulsed manner, the effects inherent in pulse etching such as digital etching cannot be expected.

In the present invention, gas exposure time of 10 Langmuir or less can be achieved at a normal etching operation pressure by using a piezo valve having a gas residence time of 10 ms or less and a response time of 10 ms or less for a gas introduction controller. Here, 1 Langmuir is a unit indicating the amount of gas exposure to the solid surface, and is an amount defined by 1 s × 1 μtorr. Under a gas atmosphere of 1 μtorr, gas particles of the same number as the number of atoms in one layer of the solid surface enter in 1 s.
A gas exposure of one Langmuir means that gas particles of the same degree as one solid surface are incident. The fact that the gas exposure amount can be reduced to 10 Langmuir or less means that the gas particles can be controlled to be incident on the sample to an amount of 10 atomic layers or less on the surface by one pulsed gas introduction. For example, at an operating pressure of 1 mtorr, 10
ms is equivalent to 10 Langmuir. In the conventional dry etching equipment, the gas residence time was about 1 s,
Pressure control could not be performed with such short time pulses.
Further, since the shortest time during which the gas introduction controller can maintain a constant flow rate is about 1 s, gas introduction with a short pulse time of 10 ms cannot be performed.

In the present invention, the introduction of the pulse gas enables the etching gas to be introduced to the surface of the sample with an accuracy of one atomic layer or less, so that high-precision etching can be performed. Of course, the minimum time required to maintain a constant flow rate required for the gas introduction controller varies depending on the operating pressure. In addition, another type of gas introduction controller may be used as long as the shortest time that can maintain a required constant flow rate is obtained.

The gas flow rate of the gas flow controllers 13a, 13b, 13c and the timing of the gas inflow can be controlled by the gas switching controller 22. In order to further control the gas inflow timing, a stop valve may be provided in the gas pipe 14 so that the opening and closing thereof can be controlled by the gas switching controller 22.

The gas switching controller 22 is replaced by a batch controller 23
The operation timing of the gas switching controller 22 can be controlled by a control signal from the collective controller 23. Further, the collective controller 23 is connected to the microwave generators 2 and R
These operation conditions and operation timings can be collectively controlled without connecting to the F power supply 17 and the conductance valve 12. Thus, the gas switching controller 22,
By attaching the collective controller 23, gas switching can be performed efficiently. Further, since microwaves, RF bias, and the like can be simultaneously controlled, time modulation etching and multi-step etching can be performed with high throughput and high accuracy.

If the storage means is attached to the collective controller 23 and the relationship between the opening degree of the conductance valve 12 and the effective pumping speed is stored, the discharge time can be obtained. When switching gas while controlling the conductance valve 13 for pressure control, gas switching can be performed with high accuracy by using a discharge time stored in advance. For example, as shown in FIG. 3, unless the gas flow is interrupted at the time of gas switching, the end of discharge cannot be monitored due to a change in pressure. If the discharge time is known in advance, the influence of gas mixing can be suppressed by stopping the microwave only during that time.

<Embodiment 2> In the conventional time modulation etching, the time of one step was long.
Side etching occurs during the etching step. Although a deposition film is formed to suppress the side etching, side etching and deposition occur alternately, and a step is formed on the side wall. If a capacitor film or the like is grown on this step, problems such as an uneven film thickness and a large leak current occur. Therefore, in the present embodiment, a description will be given of time modulation etching using an ultra-high-speed pulse for gas introduction without causing a step on the side wall. In the present embodiment, time modulation etching with vertical and flat side walls can be performed by performing gas introduction with an ultrahigh-speed pulse of 100 ms or less, preferably about 10 ms.

It takes four times as long as the gas stay time to discharge 95% of the gas after stopping the gas introduction, as described in the operation section. In order to enable gas introduction even with a pulse of 10 ms, the gas residence time is 1/4 of that of 2.5 m.
s. Therefore, in the present embodiment, the apparatus configuration is the same as that of the first embodiment shown in FIG. 1, but the volume of the vacuum processing chamber 1 is 10 l, the pumping speed of the pump is 10000 l / s, 1 conductance
0000 l / s. The effective pumping speed is 5000 l / s,
The gas stay time is 2 ms.

As an example of time modulation etching using an ultrahigh-speed pulse for gas introduction, etching at the atomic layer level by Cl ₂ gas plasma and O ₂
The trench etching of Si for forming a side wall protective film at an atomic layer level by gas plasma will be described.

As shown in FIG. 11 (a), the sample used in this embodiment was obtained by patterning a SiO ₂ mask 24 on a Si substrate 25. The pattern width is 0.1 μm, S
The thickness of the iO ₂ mask 24 is 500 nm.

First of Time Modulation Etching
The step is Si etching by Cl ₂ gas plasma. The pressure at the time of etching was 0.5 mtorr. At this time, the gas flow rate was 200 sccm, and the conditions for high vacuum and high pumping speed etching were used. The microwave power was 500 W, the RF bias was 20 W at 2 MHz, and the wafer temperature was 10 ° C.
At this time, the etching rate of Si is 1400 nm / min.
The etching selectivity with respect to SiO ₂ (Si / SiO ₂ ) is 5
It was 0. However, immediately after the start of the etching, an extremely thin oxide film 26 exists on the Si surface. This film is hardly etched unless an RF bias is applied, but the etching rate under this condition of applying an RF bias of 20 W at 2 MHz is only reduced by about 10%.

When the wafer temperature is 10 ° C., side etching occurs in Si etching using Cl ₂ gas plasma. However, the etching rate in the vertical direction is sufficiently higher than the side etching rate,
Side etching hardly occurs during etching for several atomic layers. Since the thickness of the Si1 atomic layer is about 0.2 nm, if etching is performed for only 10 ms, FIG.
As shown in FIG. 1 (b), etching can be performed only for one atomic layer of Si.

Here, C is controlled by the gas flow controller 13.
Stop l ₂ gas and let O ₂ gas flow. 8 ms for Cl ₂ gas
Later, 95% is emitted. If the microwave is stopped before stopping the Cl ₂ gas, the discharge stops and only the etching of one atomic layer proceeds. At this time, even if the microwave is not stopped, the discharge stops due to the pressure drop after 8 ms, so that it is not necessary to stop the microwave. However, the Cl ₂ gas must be sufficiently exhausted before the O ₂ gas flows.

The next step is a process using O ₂ gas plasma, and an extremely thin oxide film 26 is formed on the surface.
1 (c)). The discharge conditions at this time were a pressure of 0.5 mtorr,
The gas flow rate was 200 sccm and the microwave power was 500 W. The oxide film 26 on the side wall surface suppresses side etching. The processing time is from 10 ms to 1
It may be about 00 ms. However, when an RF bias is applied during this process, oxygen ions enter the bottom surface with high energy, and a thick oxide film with an advanced oxidation state is formed on the bottom surface. Therefore, the etching reaction is hindered. O
_{In the two-} gas plasma process, the RF bias is preferably set to zero.

After the O ₂ gas plasma treatment, the introduction of the O ₂ gas is stopped, and the Cl ₂ gas is flown. After 8 ms, 95% of the O ₂ gas has been exhausted and the process can proceed to the next step. The above steps are one cycle of the present embodiment.

The next step is the etching of one atomic layer of Si by Cl ₂ gas plasma as described above. At this time, as shown in FIG. 11D, the oxide film 26 on the side wall becomes a side wall protective film. Since the newly etched portion has an etching amount of about an atomic layer, side etching does not occur.

By repeating the above steps, a thin oxide film is formed on the side wall to suppress side etching. Further, since the etching amount in one etching step using Cl ₂ gas plasma is set to one Si atomic layer, side etching does not occur even in the etching step.
By the above effects, trench etching in which side etching was not performed and the side wall was flat could be performed. S
The selectivity to the iO ₂ mask 24 is 50, the etching rate during the etching step is 1200 nm / min, 1 μm.
A trench with a depth of m could be formed by etching for 3 minutes.

In this embodiment, in order to control the etching amount in one etching step to about one atomic layer,
The gas pulse width was controlled to about 10 ms. Even if the amount of etching in one step is increased to about 10 atomic layers, the side etching can be only about 1 to 2 layers at most. Therefore, a similar effect can be obtained even if the etching step is set to about 100 ms. Oxidation treatment by O ₂ gas plasma is also 1
Up to about 00 ms, the inhibition of the etching of the bottom surface by the oxide film is such that the etching rate is reduced by several percent. That is, even if the gas pulse width is about 100 ms, the same effect as in the present embodiment can be obtained. In this case, since the apparatus can be designed so that the gas stay time is about 20 ms, a pump with a low exhaust speed can be used.

Conventionally, Cl ₂ /
A mixed gas of O ₂ was used. In this conventional method, the reaction product reacted with O ₂ and the oxide was deposited on the wafer as a deposit. This deposit acts as a sidewall protective film,
Enables anisotropic etching. However, this deposit also caused a reduction in pattern width and particle contamination. In the present embodiment, the amount of etching in one step is several atomic layers, and the formation of deposits is suppressed because O ₂ does not act on the reaction product.
There is no influence of the deposit.

In this embodiment, the Si trench etching by Cl ₂ gas and O ₂ gas has been described.
It is also effective for gate etching of i. The same effect can be obtained if the combination of gases is a combination of an etching gas and a gas for forming a film (deposition property).

Embodiment 3 As one embodiment of the dry etching method of the present invention, time modulation etching will be described.

In the time modulation etching, an etching process is performed by alternately switching an etching gas and a deposition gas. As a result, the microloading effect can be suppressed.

FIG. 8 shows a time chart of the conventional time modulation etching. This example is disclosed in
This is an embodiment of Japanese Patent Publication No. 05413. In this example, etching is performed by alternately switching the etching gas and the deposition gas. The purpose of flowing the deposition gas is to cause deposition on the wafer. However, since the etching gas remains immediately after the gas switching, if a microwave discharge occurs immediately after the switching, the effect of the etching gas appears,
There is a problem that etching occurs instead of deposition. For example, when etching polycrystalline Si using SF6 gas as an etching gas and CCl4 gas as a deposition gas, if the deposition gas contains 5% or more of an etching gas,
The characteristics of the time modulation etching deteriorate.
Therefore, deposition must be performed after exhausting 95% of the etching gas.

As shown in FIG. 4, exhausting 95% of the gas requires four times the residence time of the gas. In conventional dry etching equipment, the residence time of gas is 1.
It was about 5 seconds. So the discharge time is at least 6s
Was needed. In the example shown in FIG. 8, the microwave discharge is stopped for 9 seconds.

In the present invention, the effective pumping speed is set to 2000 l /
s, and the gas residence time was shortened to 50 ms, so that the discharge time could be shortened. The effect is shown in FIG.
It was shown to.

In the conventional dry etching apparatus, the residence time of the gas was about 1 second or more.
% Evacuation time required several seconds. On the other hand, in the present invention, since the stay time is set to 100 ms or less,
The discharge time could be about 0.2 s or less. FIG. 1 shows the performance of Japanese Patent Application Laid-Open No. 2-105413 as an example of a conventional dry etching apparatus and the performance of this embodiment. In this example, the discharge time is 1/100
Could be shortened.

FIG. 9 shows a time chart of one embodiment of the time modulation according to the present invention. Conventionally, the microwave discharge was stopped for 9 s after the deposition gas was flowed, whereas the discharge time could be set to about 0.2 s in the present embodiment, so that the microwave discharge stop period was about 0.2 s. It will be good. Therefore, as shown in the enlarged view, a time interval of 0.2 s was provided when switching between the etching gas and the deposition gas. During this time, the gas is quickly exhausted out of the container,
The gas discharge stops in a short time (about 0.2 s) without stopping the microwave. Since one etching step is 3 s, there is almost no effect even if the discharge is stopped by gas exhaust without stopping the microwave. Immediately after turning on / off the microwave generator, the power system is unstable.
Deterioration of the etching characteristics due to the instability can be prevented.

As described above, the time for stopping the 9 s discharge in the related art can be reduced to 0.2 s. Conventionally, 52 in 4 cycles
Although it took s, the total etching time was reduced by 70% to 16 s in this embodiment. In this embodiment, polycrystalline Si etching has been described, but the same effect can be obtained for all etching materials for which time-modulated etching is effective.

In this embodiment, since the stop of the discharge is as short as 0.2 s in 4 s, there is a problem that the wafer temperature becomes higher than in the conventional example due to heating by the discharge. But,
If electrostatic attraction is used as a means for fixing the wafer to the sample stage, the cooling efficiency is increased and there is no practical problem. Of course, the non-discharge time between cycles may be extended so that the wafer temperature does not rise.

<Embodiment 4> Multi-step etching which is another embodiment of the dry etching method of the present invention will be described.

The multi-step etching is an etching in which a gas is switched during one etching. For example, in the first step, a gas for anisotropic etching is passed,
In the second step, the sidewall is protected by a deposition gas, and in the third step, the etching residue on the step is removed by an isotropic etching gas.

When the wafer is fixed using electrostatic attraction, the gas is switched. When the wafer is electrostatically attracted to the sample stage and when the wafer is released from the electrostatic attraction, charges must be accumulated or released on the wafer. One way to accomplish this charge transfer is to generate a plasma above the wafer.

When the wafer is electrostatically attracted to the sample stage, the adhesion between the wafer and the sample stage is still poor. Therefore, heat conduction is poor, and the wafer temperature rises due to heat from the plasma.
Therefore, when plasma of an etching gas is used for electrostatic attraction, side etching or the like may occur.
In addition, when plasma of an etching gas is used to remove electrostatic attraction, problems such as over-etching progressing too much occur. Therefore, it is desirable to use an inert gas plasma when attaching and detaching the electrostatic chuck.

When performing three-step multi-step etching using electrostatic attraction, gas switching is performed four times. In the conventional dry etching, an exhaust time of about 6 s was required for one gas switching. That is, 24 s per wafer was necessary for gas discharge accompanying gas switching. The etching time for one wafer was about 30 s, and the switching of gas required the same degree of etching.

In this embodiment, since the gas discharge time is set to 0.2 s or less, one gas switching time can be set to 0.2 s or less. As a result, gas switching can be performed in 0.8 s per wafer. The total etching time can be shortened by 43% from the conventional 54s to 31s, and the throughput is improved.

<Embodiment 5> An embodiment of the dry etching method according to the present invention will be described. In this embodiment, the etching shape and the like are simultaneously observed during the etching. Conventionally, the etched shape has been observed using an electron microscope after the completion of the etching. If an electron microscope is attached to the etching apparatus, the shape can be observed even during the etching. However, electron microscopy requires that the plasma be turned off and that the pressure be reduced to 10 μtorr or less, preferably 1 μtorr or less. When the etching pressure is 1 mtorr, the time required to stop the gas and discharge it to 1 μtorr takes about 7 times the gas residence time as shown in FIG. 10, since the pressure ratio before and after discharge is 1000. . In a conventional dry etching apparatus, the gas staying time is about 1 s, so that it takes about 10 s to discharge the gas. Therefore, if the observation with an electron microscope is performed during the etching, the throughput is deteriorated by the time of the gas discharge.

In the present embodiment, the gas residence time was set to 50 ms, so that the gas discharge time for observation with an electron microscope was 0.4.
s or less. As described above, in the present embodiment, since the time required for gas discharge was shortened, it was possible to minimize a decrease in throughput due to observation with an electron microscope during etching. As a result, it is possible to perform etching while monitoring the etching shape and the etching residue,
High-precision etching can be performed.

The effect of the present invention has the same effect when etching while performing observation such as surface analysis performed under high vacuum, in addition to observation with an electron microscope during etching.

[0067]

According to the present invention, etching with high anisotropy and flat side wall shape can be performed by time modulation etching using an ultra-high-speed gas pulse. Further, according to the present invention, the time required for gas switching can be reduced to 1/100 or less of that of the related art, so that highly anisotropic etching such as time-modulated etching multi-step etching can be performed at high throughput. . According to the present invention, etching can be performed with high throughput while performing analysis requiring high vacuum, and thus etching control can be performed with high accuracy. Further, the effects of the present invention are not limited to the above-described etching apparatus. For example, RIE, magnetron type RIE,
Other devices such as a helicon resonance type RIE have similar effects.

[Brief description of the drawings]

FIG. 1 is a sectional view of a dry etching apparatus according to an embodiment of the present invention.

FIG. 2 is a time chart at the time of gas switching.

FIG. 3 is a time chart of gas switching.

FIG. 4 is a characteristic diagram showing a relationship between a ratio of exhaust gas and a natural logarithm of a pressure ratio.

FIG. 5 is a time chart of gas switching.

FIG. 6 is a time chart of gas switching.

FIG. 7 is a time chart showing a relationship between a gas stay time and a discharge time.

FIG. 8 is a time chart of conventional time-modulated etching.

FIG. 9 is a time chart of time modulation etching according to the present invention.

FIG. 10 is an explanatory diagram showing a relationship between a pressure ratio before and after discharge and its natural logarithm.

FIG. 11 is a process chart of one embodiment of ultra-high-speed gas pulse time modulation etching.

[Explanation of symbols]

1: vacuum processing chamber, 2: microwave generator, 3: waveguide,
4 ... discharge part, 5 ... gas plasma, 6 ... solenoid coil, 7 ... sample stand, 8 ... wafer, 9 ... gas inlet, 10 ...
Exhaust pipe, 11: Exhaust pump, 12: Conductance valve, 13a, b, c: Gas flow controller, 14a,
b, c: gas pipe, 15: buffer chamber, 16: cooling mechanism, 17: RF power supply, 18: heater, 19: butterfly valve, 20: gas flow, 21: microwave introduction window.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-126835 (JP, A) JP-A-63-304631 (JP, A) JP-A-63-199978 (JP, A) 218013 (JP, A) Hikaru Hei 2-93578 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/3065

Claims (7)

(57) [Claims] In a dry etching method, an etching gas is introduced into a container, the etching gas is turned into plasma, and a workpiece placed in the container is dry-etched by the plasma. The introduction of the deposition gas together with the etching gas is switched in a pulse shape, and the switching of the gases is performed so that the etching cycle and the deposition cycle do not overlap with each other. A dry etching method, wherein the gas is introduced into the container through a gas flow controller, the exhaust conductance of the container is set to 2000 l / s or more, and the effective exhaust speed in the container is set to 1300 l / s or more. 2. The method according to claim 1, wherein the residence time of the etching gas in the container is 100 ms or less.
The dry etching method described. 3. The etching gas is intermittently introduced.
The amount of the etching gas when introduced is 10
2. The dry etching method according to claim 1, wherein the dry etching is not more than Langmuir. 4. A container, a table provided in the container for mounting a workpiece, gas introducing means for introducing gas into the container, and discharging means for discharging gas from the container. The gas introducing means is provided with a flow rate adjusting means having a minimum time of 10 ms or less which can maintain a constant flow rate of the gas.
A dry etching method for selectively etching a workpiece using a dry etching apparatus provided with an exhaust pump having a pressure of at least 00 / s, wherein the step of placing the workpiece in a container; An etching gas is supplied into the workpiece surface 10.
A step of introducing an amount equal to or less than the atomic layer amount, converting the workpiece into a plasma, and dry-etching the workpiece placed in the container; and introducing a deposition gas into the container, converting the workpiece into plasma, and converting the workpiece into a plasma. A process of forming the film, and a process of processing the workpiece while repeating the dry etching process and the film forming process. 5. The dry etching method according to claim 4, wherein the introduction of said etching gas is 100 ms or less. 6. The introduction of the deposition gas is 100 m.
The dry etching method according to claim 4 or 5, wherein the value is not more than s. 7. The dry etching method according to claim 4, wherein said workpiece is a Si wafer.