JPH0892769A - Dry etching method - Google Patents

Abstract

PURPOSE: To dry-etch a film consisting essentially of group VIA elements in periodic table at a high rate and selectivity by using a gas contg. a compd. of nitrogen and oxygen and a compd. of oxygen and hydrogen. CONSTITUTION: A film consisting essentially of group VIA elements in periodic table, especially Cr, Mo and W, is formed on a substrate. The film is dry-etched by using a gas contg. a compd. of nitrogen and oxygen such as NO2 formed by converting a gaseous mixture of O2 and N2 to plasma and a compd. of oxygen and hydrogen such as H2 O. By this method, since the film consisting essentially of Cr, Mo and W is etched with high slectivity to the silicon oxide film, a highly reliable wiring is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method, and more particularly to a dry etching method for chromium, molybdenum and tungsten films.

[0002]

2. Description of the Related Art Conventionally, a chromium-based film is deposited on a transparent glass substrate or a quartz substrate, and this is patterned.
A trained photomask is used. Chromium-based films are known to have excellent properties such as high durability against light when used as a mask material because they have high light-shielding properties, are hard, and have good adhesion to substrates, and can be repeatedly washed. ing. However, pattern formation by dry etching is difficult, and pattern formation by wet etching has been mainly used.

Next, this method and problems will be described.
A resist film having a desired pattern is formed on the chromium-based film by using an ordinary lithography technique, and a pattern of the chromium-based film is formed by using the resist as a mask and an etching solution such as diammonium cerium nitrate solution. Form. However, in the case of pattern formation by wet etching, there is a problem that the pattern is lost due to bubbles adhering to the substrate, and because the etching proceeds isotropically, the resist pattern and the finished chromium-based film pattern are formed. There is a problem that it is very difficult to form a fine pattern of sub-micron or less because of a conversion difference between the patterns. Further, there is a problem that the corners of the pattern are rounded.

Therefore, a pattern is formed by dry etching using a chlorine-based gas (JP-A-58-168235,
JP-A-58-153333 and JP-A-3-33848) have been tried, but there is a problem that a sufficient etching rate cannot be obtained. In addition, since gases such as chlorine, nitrogen dioxide, and carbon monoxide are corrosive and toxic, there is a problem in that handling these gases is difficult. Further, there is a problem that the chromium film cannot be selectively etched with a sufficient selection ratio.

Further, regarding the dry etching of molybdenum, tungsten, etc. deposited on the silicon oxide film,
Dry etching using chlorine-based or fluorine-based gas has been studied, but there is a problem that the etching selection ratio of molybdenum and tungsten to silicon oxide is small.

[0006]

As described above, in the conventional pattern formation method by wet etching, the problem of pattern defect due to the adhesion of bubbles and the pattern conversion difference occur. Moreover, there is a problem that it is difficult to form a fine pattern of submicron or less.

Further, in the conventional pattern forming method by dry etching, there is a problem that a sufficient etching rate and etching selection ratio cannot be obtained, and chlorine, nitrogen dioxide,
There is a problem that handling is difficult because a gas that is corrosive such as carbon monoxide and is toxic is used.

The present invention has been made in view of the above circumstances, and provides a dry etching method for a film containing a Group 6A element of the periodic table as a main component, which solves the problems such as the etching rate and the etching selection ratio. The purpose is to provide.

[0009]

In order to solve the above problems, the present invention provides a step of forming a film containing an element of Group 6A of the periodic table as a main component on a substrate, a compound of nitrogen and oxygen, and There is provided a dry etching method characterized in that a film containing an element of Group 6A of the periodic table as a main component is dry-etched using a gas containing a compound of oxygen and hydrogen.

The present invention further comprises the steps of forming a film containing an element of Group 6A of the periodic table as a main component on a substrate and using a gas containing nitrogen, oxygen and hydrogen and containing no halogen. Provided is a dry etching method characterized by dry etching a film containing an element of Group 6A of the periodic table as a main component.

The present invention also provides a step of forming a film containing a group 6A element of the periodic table as a main component on a substrate, and a gas containing nitrogen and oxygen as a main component of the group 6A element of the periodic table. To form a compound consisting of the elements of Group 6A of the Periodic Table, nitrogen, and oxygen,
Provided is a dry etching method characterized by dry-etching a film containing a group element as a main component.

The preferred embodiments of the present invention described above are as follows. (1) The compound of nitrogen and oxygen is NO ₂ . (2) The compound of nitrogen and oxygen is formed by converting a mixed gas of O ₂ and N ₂ into plasma.

(3) The compound of oxygen and hydrogen is water (H ₂
O). (4) Adding hydrogen to the gas containing nitrogen and oxygen and not containing halogen.

(5) Hydrogen is further added to the gas containing nitrogen and oxygen to form a compound consisting of the elements of Group 6A of the periodic table, nitrogen and oxygen as a hydrate. (6) The film containing an element of Group 6A of the periodic table as a main component is a chromium film or a chromium oxide film.

(7) The film containing an element of Group 6A of the periodic table as a main component is a tungsten film or a molybdenum film. (8) The gas containing nitrogen and oxygen and containing no halogen is a gas containing a compound of nitrogen and oxygen and a compound of oxygen and hydrogen. (9) The gas containing hydrogen in addition to the gas containing nitrogen and oxygen is a gas containing a compound of nitrogen and oxygen and a compound of oxygen and hydrogen.

[0016]

In the past, a film containing an element of Group 6A of the periodic table as a main component, particularly a chromium-based film, had a problem of low etching rate in dry etching because it was difficult to form a compound having a high vapor pressure. As a result of intensive investigations by the researchers, nitrogen oxides of films mainly containing the above-mentioned group of elements, especially chromium-based films, have a high vapor pressure and a sufficiently high etching rate without using chlorine-based gas. It was found that

Therefore, according to the dry etching method of the present invention, a gas containing nitrogen and oxygen is supplied to a film containing an element of the above group as a main component, particularly a chromium-based film, and the elements of the above group, nitrogen and oxygen are added. The film can be dry-etched by forming a compound consisting of This allows
It is possible to form a pattern such as a chromium-based film having a high etching rate and no defects.

When the dry etching method according to the present invention is used for etching a film containing an element of Group 6A of the periodic table other than a chromium-based film as a main component, such as a molybdenum or tungsten-based film, a base film, For example, the etching selection ratio between the silicon oxide film and the molybdenum or tungsten film can be made very large.

Furthermore, by adding hydrogen to the above-mentioned gas containing nitrogen and oxygen, a compound consisting of the elements of Group 6A of the periodic table, nitrogen and oxygen can be formed as a hydrate. By further increasing the etching rate, it becomes possible to pattern the film containing the element of Group 6A of the periodic table as a main component.

[0020]

Embodiments of the dry etching method according to the present invention will be described below with reference to the drawings. (Embodiment 1) First, as shown in FIG. 1A, a chromium film 12 is formed on a quartz substrate 11 by sputtering to a thickness of 500 A (angstrom; the same applies below), a target such as chromium, and O _2. A chromium oxide film 13 of 500 A is formed by a reactive sputtering method using a gas. An ordinary resist 14 having a thickness of about 1 μm is formed thereon, and the resist is selectively exposed and developed to form a resist pattern 14 shown in FIG.
Here, the chromium oxide film 12 serves as an antireflection film for suppressing the reflected light from the chromium film 11 and performing highly accurate patterning when exposing the resist.

Next, the substrate 11 is set in the etching apparatus shown in FIG. 2, and the chromium film 12 and the chromium oxide film 1 are set.
Etching 3 is performed. As shown in FIG. 2, a sample table 21 is installed inside a reaction container (etching chamber) 20 of the etching apparatus, and a sample 22 is placed on the sample table 21.
(Here, the quartz substrate 11) is set.

Reference numeral 23 is an ozonizer (gas excitation section).
When a high voltage is applied to an electrode (not shown) in the ozonizer 23, oxygen gas and nitrogen gas are excited to generate ozone and nitrogen oxides. Two
Reference numerals 4a and 24b denote gas introduction pipes. Oxygen gas and nitrogen gas flow in the gas introduction pipes 24a and 24b, respectively, and are mixed in the ozonizer-23.

A gas introducing pipe 25 is provided between the ozonizer 23 and the reaction container 20, and ozone and nitrogen oxides generated in the ozonizer 23 pass through the gas introducing pipe 25 and from the shower head 26 to the reaction container. 20 is supplied inside. An exhaust pipe 27 exhausts the gas inside the reaction vessel 20.

FIG. 3 is a characteristic diagram showing the etching rates of the chromium film and the chromium oxide film when the mixing ratio of oxygen and nitrogen as the source gas is changed by using the above etching apparatus. The pressure in the reaction vessel 20 is 101.3 × 10 ³ Pa
Then, the power applied to the electrodes of the ozonizer-23 was adjusted so that the ozone gas concentration became 8 vol%. The nitrogen oxide concentration at this time was quantified by ion chromatography. Regarding the etching rate of the chromium film and the chromium oxide film, etching does not occur when the amount of nitrogen mixed is 0, but when the amount of nitrogen mixed is 0.6% or more, the etching rate of 500 A / min can be used for etching. It was Further, at this time, by bubbling nitrogen gas in water and directly supplying the reaction gas to the reaction vessel 20 without exciting the bubbling gas, when 500 ppm of water is supplied, the amount of nitrogen mixed is 0.6.
%, The etching rate of the chromium film and the chromium oxide film became 700 A / min.

Although the mechanism of such etching is not clear, it is considered that chromium and chromium oxide are etched as chromium nitrate, hydrate of chromium nitrate (eg, 9 hydrate), and the like.

By the above-described etching method, the chromium film 12 and the chromium oxide film 13 are isotropically etched,
It is processed into a shape as shown in FIG. After that, when the resist pattern 14 is removed, there is a pattern conversion difference, but as shown in FIG. 1D, it is possible to form a highly reliable chromium-based film pattern without pattern defects. did it.

As described above, when water is supplied into the reaction vessel 20 together with ozone and nitrogen oxide, the etching rate of the chromium film 12 and the chromium oxide film 13 is improved, and higher speed patterning is possible. Becomes

In the above embodiment, the ozonizer
The same applies when a plasma generator using microwaves or the like is used instead of 23, and oxygen gas and nitrogen gas are used as raw material gases, and these gases are excited by the plasma generator and supplied into the reaction vessel 20. It was possible to etch chromium and chromium oxide.

Example 2 First, as shown in FIG. 4A, a chromium film 12 and a chromium oxide film 1 are formed on a quartz substrate 11.
3. A resist 14 is sequentially formed, and the resist 14 is patterned by using a lithography technique. So far,
These are the same steps as those shown in FIGS. 1A and 1B of the first embodiment.

Next, the substrate 11 is set in the parallel plate type etching apparatus shown in FIG.
The chromium film 12 and the chromium oxide film 13 are etched by using 4 as a mask.

As shown in FIG. 5, a sample stage 31 also serving as a cathode is installed inside a reaction container (etching chamber) 30 of this etching apparatus, and a sample 34 is placed on the sample stage 31.
(Here, the quartz substrate 11) is set.

Reference numeral 32 is a 13.56 MHz high frequency power source, which is electrically connected to the sample stage 31 also serving as a cathode so that high frequency power can be applied to the sample stage 31. On the other hand, the reaction container 30 is grounded, and the shower head 37 that also serves as an anode, which will be described later, is also grounded. 33 is a sample table 3 also serving as a cathode
1 is a spacer provided to insulate between 1 and the reaction container 30.

Reference numerals 35a and 35b denote gas introduction pipes for passing nitrogen dioxide (NO ₂ ) gas ₂ and nitrogen (N ₂ ) gas, respectively, and these gas introduction pipes 35a and 35b are joined to each other to form a gas introduction pipe 36. It is connected to the reaction container 30 via. The gas supplied from the gas introduction pipe 36 is supplied to the inside of the reaction container 30 through the shower head 37. Three
Reference numeral 8 denotes an exhaust pipe for exhausting the gas inside the reaction container 20.

In the etching apparatus configured as described above, the NO ₂ gas ₂ and the N ₂ gas are supplied into the reaction vessel 30, and these gases are turned into plasma by discharge by the high frequency power from the high frequency power supply 32. The chromium film and the chromium oxide film are etched by the gas thus converted into plasma.

In this embodiment, the etching condition is NO.
₂ gas flow rate 100 sccm, N ₂ gas flow rate 100 s
The chrome film 12 and the chrome oxide film 13 were etched under the conditions of ccm, pressure of 1 Pa and high frequency applied power of 500 watts. The etching rates of the chromium film 12 and the chromium oxide film 13 are 1500 A / min and 1700 A / min, respectively.
It was min. As a result, the chromium film 12 and the chromium oxide film 13 were etched into the shape shown in FIG. After that, when the resist pattern 14 was removed, a fine chromium-based film pattern having no pattern conversion difference could be formed (FIG. 4B).

Although the etching using the NO ₂ gas and the N ₂ gas has been described here, the same effect can be obtained by using the N ₂ gas and the O ₂ gas. Further, in the above example, the chromium-based film was etched using the resist as a mask,
The etching selectivity between the chromium-based film and the resist by the above etching method is small, and therefore it is more preferable to use a silicon oxide film as an etching mask instead of the resist. In this case, a silicon oxide film is deposited on the chromium film and the chromium oxide film by a sputtering method, a resist pattern is provided on the silicon oxide film, and the resist pattern is formed.
It is preferable that the silicon oxide film is etched with a fluorine-based gas by using the silicon oxide as a mask, and then the chromium-based film is etched by the method using the silicon oxide film as a mask.

Example 3 First, as shown in FIG. 6A, a diffusion layer 61a serving as a source and a drain is formed on the surface of a Si substrate 61, and the Si substrate 6 including the diffusion layer 61a is formed.
A silicon oxide film 62 is formed on the substrate 1 by the plasma CVD method. Next, on the silicon oxide film 52, the source,
A contact hole 63 communicating with the drain diffusion layer 61a is formed, and a titanium silicide film 64 is selectively formed on the surface of the diffusion layer 61a at the bottom of the contact hole 63. The titanium silicide film 64 is formed by a known sputtering method or C
It is formed by the VD method or the like.

Next, as shown in FIG. 6B, a tungsten film 65 is selectively grown inside the contact hole 63. WF ₆ and SiH ₄ were used as the source gas, and the deposition conditions were set to a deposition temperature of 200 ° C. and a pressure of 20 Pa. At this time, the tungsten particles 65a were partially grown on the silicon oxide film 62 other than the contact holes 63.

Subsequently, as shown in FIG. 6C, as a result of etching this sample using the etching apparatus shown in FIG. 2, the tungsten grains 65a partially grown on the silicon oxide film 62 are removed by etching. I was able to.
Oxygen gas with a nitrogen content of 1% was used as the source gas, and the etching conditions were set to a pressure of 101.3 × 10 ³ Pa. Further, the power applied to the electrodes of the ozonizer-23 was adjusted so that the ozone gas concentration was 8 vol%.
This condition was performed for 1 minute. The selection ratio between the tungsten grains 65a and the silicon oxide film 62 was 100 or more.

As a comparative example, a conventional fluorine-based gas (SF ₆
Alternatively, FIG. 7A shows a state when plasma etching is performed using CF ₄ ). Since the selection ratio between the tungsten particles 65a and the silicon oxide film 62 is as small as 1, the tungsten particles 65a can be removed by etching, but the silicon oxide film 62 around the tungsten particles 65a is scooped out, resulting in an uneven portion 62a on the surface. . Therefore, when an Al film to be the wiring of the first layer is formed on the Al film and the Al film is patterned into a wiring shape, there is a problem that an Al etching residue is generated in the uneven portion 62a.

Finally, an Al film to be the wiring of the first layer is formed on the tungsten film 65 left in the step of FIG. 6C, and this Al film is patterned into a wiring shape. As shown in FIG. 7B, a first-layer Al wiring 66 is formed.

As described above, when the dry etching method according to the present invention is used, since the tungsten particles can be etched with a high selection ratio with respect to the silicon oxide film, a highly reliable wiring can be formed.

In this embodiment, the method of selectively forming the tungsten film inside the contact hole leading to the source / drain diffusion layer has been described, but the first layer Al wiring and the second layer are used. Via hole for connecting the Al wiring of the second layer
Even if a tungsten film is selectively formed inside the
It goes without saying that the present invention can be applied.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, the etching of chromium, chromium oxide, and tungsten is described, but the present invention is not limited to this, and the present invention has the same effect when etching tungsten oxide, molybdenum, or molybdenum oxide. .

As a compound of nitrogen and oxygen, NO ₂
Besides, NO, N ₂ O, N ₂ O _{5 and the} like can be used. Further, the method of forming the compound of nitrogen and oxygen is
The present invention is not limited to the above embodiment, but other plasma sources such as E
CR, helicon, etc. can be used. Furthermore,
An excitation method using light or an electron beam can also be used.

Further, as a compound of oxygen and hydrogen, H ₂
In addition to O, H ₂ O ₂ or the like can be used. Also,
These compounds can also be formed by reacting a mixed gas of H ₂ and O ₂ . Furthermore, in the above example, the gas was directly introduced into the reaction vessel without being excited,
It is also possible to excite by the excitation method shown in each of the above-mentioned examples and introduce the excited gas into the reaction vessel. In addition, various modifications can be made without departing from the scope of the present invention.

[0047]

According to the dry etching method of the present invention, a film containing an element of Group 6A of the periodic table as a main component can be etched at a high etching rate and a high etching selection ratio, and defects of It becomes possible to easily form a non-pattern.

[Brief description of drawings]

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

FIG. 2 is a schematic cross-sectional view of an etching apparatus used in the method of the embodiment according to FIG.

FIG. 3 is a characteristic diagram showing the etching rates of a chromium film and a chromium oxide film when the mixing ratio of oxygen and nitrogen is changed.

FIG. 4 is a process sectional view showing another embodiment of the dry etching method according to the present invention.

5 is a schematic cross-sectional view of an etching apparatus used in the method of the example according to FIG.

FIG. 6 is a process sectional view showing still another embodiment of the dry etching method according to the present invention.

7A and 7B are sectional views showing a comparative example for the example method according to FIG. 6 and process steps following FIG.

[Explanation of symbols]

 11: Quartz substrate 12: Chromium film 13: Chromium oxide film 14: Resist 20: Reaction container (etching chamber) 21: Sample stage 22: Sample 23: Ozonizer 24a, 24b, 25: Gas introduction pipe 26: Shower head 27 : Exhaust pipe 30: Reaction container (etching chamber) 31: Sample stand (cathode) 32: High frequency power supply 33: Spacer 34: Samples 35a, 35b, 36: Gas introduction pipe 37: Shower head (anode) 38: Exhaust pipe 61 : Si substrate 61a: Diffusion layer serving as source and drain 62: Silicon oxide film 62a: Concavo-convex portion 63: Contact hole 64: Titanium silicide film 65: Tungsten film 65a: Tungsten grain 66: Al wiring

Claims (10)

[Claims] 1. A method of forming a film containing an element of Group 6A of the periodic table on a substrate as a main component, and using a gas containing a compound of nitrogen and oxygen and a compound of oxygen and hydrogen, the periodic table. A dry etching method comprising dry etching a film containing a Group 6A element as a main component. 2. The dry etching method according to claim 1, wherein the compound of nitrogen and oxygen is NO ₂ . 3. The compound of nitrogen and oxygen is replaced by O ₂ and N ₂
The dry etching method according to claim 1, wherein the mixed gas is formed into plasma. 4. The compound of oxygen and hydrogen is water (H ₂ O).
The dry etching method according to claim 1, wherein 5. The process of forming a film containing an element of Group 6A of the periodic table on the substrate as a main component, and a gas containing nitrogen and oxygen and containing no halogen, wherein the periodic table 6A is used.
A dry etching method comprising dry-etching a film containing a group element as a main component. 6. The dry etching method according to claim 5, wherein hydrogen is further contained in the gas containing nitrogen and oxygen and containing no halogen. 7. A step of forming a film containing an element of Group 6A of the periodic table on the substrate as a main component, and a film containing a gas containing nitrogen and oxygen as the main component of the element of Group 6A of the periodic table. To form a compound consisting of the element of Group 6A of the periodic table, nitrogen, and oxygen, and dry-etch the film containing the element of Group 6A of the periodic table as a main component. Dry etching method. 8. The gas containing nitrogen and oxygen is further allowed to contain hydrogen, and an element of Group 6A of the periodic table, nitrogen,
8. The dry etching method according to claim 7, wherein a compound consisting of oxygen and oxygen is formed as a hydrate. 9. The dry etching method according to claim 1, wherein the film containing an element of Group 6A of the periodic table as a main component is a chromium film or a chromium oxide film. 10. The dry etching method according to claim 1, wherein the film containing an element of Group 6A of the periodic table as a main component is a tungsten film or a molybdenum film.