JP2001068456A - Reactive ion etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow stable and fast etching continuously by allowing a reactive product which suppresses disappearance of etching seed on the inside wall surface of a reactive device to stick to the inside wall surface. SOLUTION: A material 3 which is to be etched and a single crystal silicon substrate are carried into a load lock chamber 11. When a vacuum chamber 1 and the load lock chamber 11 reach a specified vacuum level, a gate valve 13 is opened. Then the single crystal silicon substrate in the load lock chamber 11 is transferred over a lower electrode 2 in the vacuum chamber 1, and the gate valve 13 is closed. Then a gas guiding valve 10 is opened for introducing an etching gas. After etching with HBr gas and O2 gas introduced, only the flow rate of O2 gas is reduced for etching. Thus, a substance produced at etching of the single crystal silicon substrate sticks to the inside wall surface of reactive device, and increases the amount of etching seed on the inside wall surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive ion etching method for etching a semiconductor substrate, a thin film, a wiring material and the like in accordance with a mask pattern in a manufacturing process of a semiconductor device.

[0002]

2. Description of the Related Art The reactive ion etching method is a dry etching method in which the surface of a material to be etched is anisotropically processed in the direction of incidence of ions by a reactive gas and directional ion bombardment. For example, using a halogen element or a reaction gas containing a halogen element, as a material containing silicon such as single crystal silicon, polysilicon, amorphous silicon, silicon dioxide, silicon nitride, or aluminum, titanium, tungsten, molybdenum, copper, or an impurity, Anisotropic etching of a metal such as aluminum to which copper is added or a metal compound such as gallium arsenide, indium phosphide, tungsten silicide, or titanium silicide is possible.

In such a reactive ion etching method, the etching rate often depends on the concentration of an etching species contributing to the reaction. That is, the higher the concentration of the etching species in the reactor, the higher the etching rate in many cases. Therefore, in order to control the etching rate with good reproducibility, it is necessary to control the concentration of the etching species in the reactor.

[0004] The concentration of the etching species varies depending on the balance between generation and extinction. The generation of the etching species is determined by the distribution of electron density and its kinetic energy, and is determined by the reaction gas pressure and the input power introduced into the device.
Controllability is very high. On the other hand, the disappearance of the etching species may be caused by consumption by etching, evacuation by a vacuum pump, or disappearance by recombination on the inner wall surface of the reactor, and it is very difficult to control the disappearance rate. In particular, the disappearance due to recombination on the inner wall surface of the reactor is easily affected by the state of the inner wall surface, and changes during the etching. For this reason, the disappearance rate of the etching species is not stable, which causes a variation in the etching rate.

[0005]

Therefore, if it is possible to suppress the change in the disappearance rate due to recombination on the inner wall of the reactor, which is considered to be the cause of the variation in the etching rate,
High-speed etching can be stably realized.
An object of the present invention is to provide a reactive ion etching method capable of solving the above problems and performing high-speed etching stably.

[0006]

According to the present invention, in order to achieve the above object, a reaction gas is excited by plasma in a reaction apparatus.
In a reactive ion etching method for etching a material to be etched, a reaction product capable of suppressing the disappearance of etching species on the inner wall surface of the reaction device is attached to the inner wall surface, and the reaction product is substantially continuously etched. It is characterized by performing etching.

In particular, silicon can be etched at a high speed by using any one of single crystal silicon, polycrystalline silicon, and amorphous silicon as the material to be etched and the material containing silicon.

Further, when the material to be etched and the material containing silicon are any of single crystal silicon, polycrystal silicon and amorphous silicon, HBr,
Alternatively, any one of a mixed gas of HBr and SiF ₄ and O ₂ ,
By etching with a mixed gas containing at least one of H ₂ O, N ₂ O, and NH ₃ , it is possible to etch a deep groove structure in which a side wall is vertical.

[0009]

Embodiments of the present invention will be described below. FIG. 1 shows an example of a reaction apparatus used in the present invention. As shown in the figure, a lower electrode 2 connected to a high-frequency power supply 14 is arranged in a vacuum chamber 1 formed of stainless steel also serving as a ground, and a single crystal silicon substrate or a desired An etching target material 3 made of a single crystal silicon substrate on which a pattern is formed is placed. The lower electrode 2 has a structure in which a coolant flows inside, and can keep the temperature of the material 3 to be etched or the like constant. In addition, in order to improve thermal contact between the material 3 to be etched and the lower electrode 2, it is fixed by a quartz clamp (not shown). The lower electrode surface is covered with Kapton tape (manufactured by DuPont).

The multi-spiral coil 5 formed through the quartz glass 4 forms an upper electrode. The multi-spiral coil 5 is connected to a high-frequency power supply 14,
A high frequency of 3.56 MHz is applied to the vacuum chamber 1
A plasma can be generated inside. An inner chamber 6 made of stainless steel is inserted into the vacuum chamber 1. This inner chamber 6
And the quartz glass 4 is heated to 30 to 150 by a heater.
It has a structure that can be heated to ℃.

The inside of the vacuum chamber 1 is evacuated by a vacuum pump 7, and the pressure in the vacuum chamber 1 is kept constant by a slot valve 8. The reaction gas is mixed after being adjusted in flow rate by a mass flow controller in the gas introduction unit 9, and is introduced into the vacuum chamber 1 through the gas introduction valve 10.

A load lock chamber 11 is provided so that the degree of vacuum in the vacuum chamber 1 does not deteriorate when a material to be etched or the like is loaded or unloaded.
Carry in and out of the material to be etched and the like.

On the other hand, a material to be etched on which a desired mask pattern is formed is prepared. As an example, as shown in FIG. 2, a 220 angstrom silicon dioxide film 22, a 1500 angstrom nitride film 23, and a 5000 angstrom silicon dioxide film 24 are laminated on a single crystal silicon substrate 21 and then formed by ordinary photolithography. Was performed to perform patterning. Further, another single crystal silicon substrate having no mask pattern formed on its surface is prepared.

The etching is performed as follows. First,
The inside of the vacuum chamber 1 of the reactor shown in FIG. 1 is evacuated to 10 ⁻⁴ Pa or less by the vacuum pump 7. The material 3 to be etched and a single-crystal silicon substrate (not shown) previously prepared are carried into the load lock chamber 11.

When the inside of the vacuum chamber 1 and the load lock chamber 11 reach a predetermined degree of vacuum, the gate valve 1
3, the single crystal silicon substrate in the load lock chamber 11 is carried on the lower electrode 2 in the vacuum chamber 1, and the gate valve 13 is closed.

The lower electrode 2 is heated at a constant temperature by a heat exchanger.
For example, it is maintained at 50 ° C. The gas introduction valve 10 is opened, and a gas for performing etching is introduced. As an example, in order to remove the natural oxide film on the surface, Cl ₂ gas is 70 SCCM, the pressure in the vacuum chamber is 2 Pa, the applied power of the upper electrode is 3.0 W / cm ² , and the applied power of the lower electrode is 1.0 W / cm ² and etching for 10 seconds. Thereafter, HBr gas was supplied at 70 SCCM and O ₂ gas was supplied at ₂ SCCM.
Introduced by SCCM, pressure in vacuum chamber 1 was 3P
a, Etching was performed for 1 minute with the applied power to the upper electrode being 3.0 W / cm ² and the applied power to the lower electrode being 2.0 W / cm ^2, and then only the flow rate of the O ₂ gas was changed to 1.5 SCCM. Etching was performed for 6 minutes.

As a result of the etching of the single crystal silicon substrate, an etching product adheres to the inner wall surface in the reactor.

Next, the gate valve 13 is opened, and the single crystal silicon substrate in the vacuum chamber 1 is carried out from above the lower electrode 2. Next, the material 3 to be etched on which a desired mask pattern is formed is transferred from the load lock chamber 11 to the vacuum chamber 1.
It is carried onto the lower electrode 2 in the inside, and the gate valve 13 is closed.

The gas introduction valve 10 is opened to introduce a gas for performing etching. As an example, in order to remove the natural oxide film on the surface, Cl ₂ gas is 70 SCCM, the pressure in the vacuum chamber is 2 Pa, the applied power of the upper electrode is 3.0 W / cm ² , and the applied power of the lower electrode is 1.0 W / c
m ² and etching for 10 seconds. Then HB
The r gas was introduced at 70 SCCM and the O ₂ gas at ₂ SCCM, the pressure in the vacuum chamber 1 was 3 Pa, the power applied to the upper electrode was 3.0 W / cm ² , and the power applied to the lower electrode was 2.
After performing etching for 1 minute at 0 W / cm ² , etching was performed for 6 minutes while changing only the flow rate of the O ₂ gas to 1.5 SCCM.

As a result, a pattern having an opening width of 0.8 μm could be etched to a depth of 5.2 μm. For comparison, before etching the material to be etched, without etching the single crystal silicon substrate,
The material to be etched on which the same mask pattern was formed was carried onto the lower electrode 2 in the vacuum chamber 1 and was etched. The etching conditions were the same as above. As a result, the etching depth was 4.1 microns, and it was confirmed that the etching rate was reduced.

It was confirmed from the analysis of the emission spectrum of the plasma during the etching that the difference in the etching rate was caused by the difference in the concentration of the etching species. That is, when the material to be etched is etched without etching the single crystal silicon substrate, the emission intensity of the emission spectrum (wavelength: 750.74 nm) derived from bromine is 37.
It was 3.5 counts. On the other hand, when the single crystal silicon substrate was etched, the count increased to 606.0 counts.

As described above, according to the present invention, the substance generated during the etching of a single crystal silicon substrate adheres to the inner wall surface of the reactor, reduces the recombination coefficient of the etching species on the inner wall surface, The amount of etching species in the apparatus can be increased, and the etching rate can be increased.

The etching for reducing the recombination coefficient of the etching species does not need to be performed every time the material to be etched is etched. Under the above conditions, after etching the single-crystal silicon substrate once, etching was continuously performed on 25 materials to be etched, but it was confirmed that no significant change was observed in the etching shape and the etching rate. However, when a substance adhering to the inner wall surface of the device is etched by the etching of the material to be etched, it is necessary to perform etching for appropriately reducing the recombination coefficient of the etching species. Further, when the vacuum in the apparatus is broken, it is preferable to clean the inside of the apparatus and perform etching for reducing the recombination coefficient of the etching species.

The case where HBr is used as the etching gas has been described above. However, if a substance capable of reducing the recombination coefficient of the etching species can be attached to the inner wall surface of the reactor, the etching conditions may be variously changed. Is possible. To change the etching gas, use HBr
HBr gas and SiF ₄ gas may be used in place of the gas. For example, when the inside of the vacuum chamber 1 and the load lock chamber 11 shown in FIG. 1 reach a predetermined degree of vacuum, the gate valve 13 is opened, and the single crystal silicon substrate in the load lock chamber 11 is moved to the lower electrode 2 in the vacuum chamber 1. The gate valve 13 is closed.

The lower electrode 2 is heated at a constant temperature by a heat exchanger.
For example, it is maintained at 50 ° C. After the gas introduction valve 10 is opened to perform etching for removing the natural oxide film, a gas for etching the material to be etched is introduced. As an example, HBr gas is 50 SCCM, SiF ₄
Gas was introduced at 4.5 SCCN and O ₂ gas was introduced at 3.7 SCCM, the pressure in the vacuum chamber 1 was 3 Pa, the applied power to the upper electrode was 3.0 W / cm ² , and the applied power to the lower electrode was 0.5 W / cm. ² and after etching for 1 minute,
6 minutes 15 by changing only the flow rate of O ₂ gas to 3.0 SCCM
Etching for 2 seconds was performed.

Next, the gate valve 13 is opened, and the single crystal silicon substrate in the vacuum chamber 1 is carried out from above the lower electrode 2. Next, the material to be etched having the desired mask pattern formed thereon is carried from the load lock chamber 11 onto the lower electrode 2 in the vacuum chamber 1 and the gate valve 13 is closed.

After the gas introduction valve 10 is opened to perform etching for removing the natural oxide film, a gas for etching the material to be etched is introduced. As an example, H
50 SCCM of Br gas and 4.5 SCC of SiF ₄ gas
M, O ₂ gas was introduced at 3.7 SCCM, the pressure in the vacuum chamber 1 was 3 Pa, and the power applied to the upper electrode was 3.0 W.
/ Cm ² , the power applied to the lower electrode is 0.5 W / cm ² ,
After etching for 1 minute, the etching was performed for 6 minutes and 15 seconds while changing only the flow rate of the O ₂ gas to 3.0 SCCM.

As a result, a pattern having an opening width of 0.8 μm can be etched to a depth of 5.5 μm. For comparison, without etching the single crystal silicon substrate, the material to be etched having the same mask pattern was carried on the lower electrode 2 in the vacuum chamber 1 and etched. The etching conditions were the same as above, HBr gas was 50 SCCM, and SiF ₄ gas was 4.5.
SCCM and O ₂ gas were introduced at 3.7 SCCM, the pressure in the vacuum chamber 1 was 3 Pa, the applied power to the upper electrode was 3.0 W / cm ² , and the applied power to the lower electrode was 0.5 W / c.
After performing etching for 1 minute at m ² , etching was performed for 6 minutes and 15 seconds while changing only the flow rate of the O ₂ gas to 3.0 SCCM. As a result, the depth became 4.1 microns.

As described above, even when the kind of the etching gas is changed, the etching rate can be increased by etching the single crystal silicon substrate before etching the material to be etched. In order to confirm the increase in etching species, the emission spectrum of plasma during the etching of the material to be etched was analyzed. FIG. 3 shows the results of measuring the emission intensity of the emission spectrum (wavelength 750.74 nm) derived from bromine plasma as an etching species while changing the etching time of the single crystal silicon substrate, and the etching depth per minute. The calculation results of are shown.
As shown in the figure, when the single crystal silicon substrate is etched, the light emission intensity increases and the etching depth per minute also increases when the single crystal silicon substrate is etched. I understand.

The results shown in FIG. 3 indicate that the HBr gas
0 SCCM, 4.5 SCCM of SiF ₄ gas and 3.7 SCCM of O ₂ gas were introduced, the pressure in the vacuum chamber 1 was 3 Pa, the power applied to the upper electrode was 3.0 W / cm ² , and the power applied to the lower electrode was 0. The results of etching performed at a power of 0.5 W / cm ² for one minute and then changing the flow rate of the O ₂ gas only to 3.0 SCCM for a predetermined time are shown. That is, when the etching time is 5 minutes, the etching is performed for 1 minute under the condition that the flow rate of the O ₂ gas is 3.7 SCCM.
The etching depth was measured for 4 minutes while changing only the flow rate of the oxygen gas to 3.0 SCCM, and the result of conversion of the etching depth per minute is shown. Here, the fact that the etching rate does not significantly change by changing the flow rate of the O ₂ gas is as follows.
Has been confirmed.

In the above-described embodiment, the O ₂ gas is added as an etching gas. However, this is added to prevent abnormal etching of the side wall of the groove when etching a deep groove. This is not always necessary when etching a single crystal silicon substrate.

However, in the etching for forming a trench having a large aspect ratio such as a trench structure, in order to prevent the occurrence of side etching or the like, in addition to the O ₂ gas, a gas for promoting the growth of the sidewall protective film, specifically, a gas for promoting the growth. H ₂ O, N ₂ , N
_It is preferable to add at least one of ₂ O and NH ₃ . Needless to say, the addition of these gases does not impair the effects of the present invention.

In addition to the above-mentioned etching gas, Cl ₂ gas, HCl gas, BBr ₃ gas, BCl ₃ gas, SiCl
The same effect can be obtained by using a gas containing at least one of the _four gases.

Further, the same effect can be obtained when an amorphous silicon or polycrystalline silicon film is used instead of a single crystal silicon substrate, as long as the material contains at least silicon.

The material to be etched is not limited to a single crystal silicon substrate, but may be other semiconductor materials or metals, for example, a polycrystalline silicon film, an amorphous silicon film, an aluminum film, or an aluminum alloy film containing silicon or copper. , Copper film, tungsten film, tungsten nitride film, molybdenum film, titanium film, titanium nitride film, tungsten titanium film, tungsten silicide film, titanium silicide film, compound semiconductor film such as silicon carbide, gallium arsenide, indium phosphide, etc. Can obtain the same effect.

[0036]

As described above, according to the present invention, etching at a high etching rate can be realized by etching a material containing silicon before the step of etching the material to be etched.

The present invention has the advantage that the etching can be performed at a high etching rate and the shape can be controlled at the same time even if a reaction gas for promoting the growth of the sidewall protective film is added to the etching gas.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a reaction apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram illustrating a material to be etched used in an embodiment of the present invention.

FIG. 3 is a table illustrating an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Lower electrode 3 Material to be etched 4 Quartz glass 5 Multi spiral coil 6 Inner chamber 7 Vacuum pump 8 Slot valve 9 Gas introduction unit 10 Gas introduction valve 11 Load lock chamber 12 Transfer robot 13 Gate valve 14 High frequency power supply 21 Single crystal Silicon substrate 22 silicon dioxide film 23 nitride film 24 silicon dioxide film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K057 DA12 DB06 DC10 DD03 DE11 DE20 DM02 DN01 5F004 AA01 AA03 BA20 BB11 BB13 BB18 BB21 BC08 DA01 DA04 DA26 DB00 DB01 DB02 EA06 EA07 EB04 EB05

Claims (3)

[Claims] 1. A reactive ion etching method in which a reaction gas is plasma-excited in a reactor to etch a material to be etched, wherein a material containing silicon is etched in the reactor, and an inner wall surface of the reactor is etched. A reactive ion etching method, characterized in that a reaction product capable of suppressing the disappearance of an etching species in the above step is attached to the inner wall surface, and the material to be etched is etched substantially continuously. 2. The reactive ion etching method according to claim 1, wherein the material to be etched and the material containing silicon are any of single crystal silicon, polycrystalline silicon, and amorphous silicon. Ionic etching method. 3. The reactive ion etching method according to claim 2, wherein said etching material and said silicon-containing material are mixed with HBr or a mixed gas of HBr and SiF ₄ with O ₂ , H ₂ O, N A reactive ion etching method characterized by etching with a mixed gas containing at least one of ₂ O and NH ₃ .