JP2000311888A - Parallel flat-plate dry etching device and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrode component for a wafer from being contaminated in etching and eliminate chip failure caused by the adhesion of dust to the wafer by forming a carbon compound film on the entire surface of the opposing surfaces of at least upper and lower electrodes and a surface for mounting a film to be etched of the lower electrode. SOLUTION: When a wafer 3 is placed on a lower electrode 2 and gas containing fluorine is introduced into a reaction chamber, a high-frequency voltage is applied to a high-frequency application coil 6 that is wound around an upper electrode 1, and a uniform magnetic and electric field is generated in the introduced gas containing fluorine, the gas containing fluorine is subjected to plasma decomposition. In this state, when a high-frequency voltage is applied from a high-frequency power supply 5 to the lower electrode 2 where the upper electrode 1 and the wafer 3 are placed, active radical or the like in plasma is supplied onto the wafer 3 and etching advances. The upper and lower electrodes 1 and 2 are covered with carbon compound such as silicon carbide. When a high-frequency power is supplied to both electrodes in etching, a silicon ion or the like is generated in plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure of a parallel plate type dry etching apparatus and a dry etching method using the apparatus.

[0002]

2. Description of the Related Art As an example of covering the surface of an electrode of a conventional parallel plate type dry etching apparatus with another substance, for example, covering the surface of an upper electrode with a sintered body of silicon carbide, see JP-A-62-10.
Japanese Patent No. 9317 discloses a first conventional parallel plate type dry etching apparatus, as shown in FIG. 3, in which a gas introduced from a sintered body of silicon carbide is introduced between opposed electrodes. The portion 14a is attached to the upper electrode via a conductive electrode ring 16. As a result, even when the gas introduction part 14a is exposed to the etching plasma, metal contamination on the workpiece to be etched does not occur, which occurs when a metal electrode is used, and etching using a fluorine-based gas is not performed. States that the etching reaction products are mostly volatile and can be removed by evacuation.

Further, when etching a silicon oxide film, a gas introduction portion 14a made of a sintered body of silicon carbide also has corrosion resistance to plasma of fluorine gas such as CF ₄ and CHF ₃ .

The diameter of the gas outlet of the gas introducing portion 14a can be formed in the range of about 0.2 nm to about 0.5 nm by using a sintered body, and by using this, a gas stream with good uniformity can be ejected. In addition, clogging due to a reaction product at the time of etching can be prevented.

The gas inlet is fixed to the upper electrode 11 by a conductive electrode ring 15, so that plasma can be generated stably, the plasma density can be increased, and the etching rate can be increased.

As an example of covering an electrode with carbon, Japanese Patent Laid-Open Publication No. 64-89518 discloses a parallel plate type dry etching apparatus as shown in FIG. In some cases, the opposite surface of the flat electrode other than the sample mounting portion of the mold dry etching apparatus is covered with carbon 14b.

In this case, a gas containing halogen, for example,
Also in the case of etching polysilicon with a gas composition of CCl ₂ F ₂ + N ₂ or in the etching of silicon using a CBrF ₃ gas, carbon is sufficiently supplied with respect to the amount of halogen, so that excess The halogen becomes a low-molecular halogen carbide and is efficiently exhausted.
As a result, it is described that polymerization does not occur, contamination in the etching chamber does not occur, the cleaning frequency of the chamber is reduced, and the reproducibility of etching can be improved.

Japanese Patent Application Laid-Open No. 8-250480 discloses that CF ₄ (etching gas) is used as an etching gas when forming a contact hole in a silicon oxide film.
And CHF ₃ or C ₂ F ₆ (gas for forming polymer) and Ar
(Banlas gas) is introduced. In this case, it is possible to form a contact hole having an inclined side wall pattern by adjusting the amount of Ar. 3 and 4, reference numeral 12 denotes a lower electrode, 13 denotes a wafer, 15 denotes a high-frequency power supply, and 17 denotes a processing chamber.

[0009]

However, in a dry etching apparatus disclosed in Japanese Patent Application Laid-Open No. 62-109317, in which only the upper electrode is covered by a gas introduction part whose main component is silicon carbide, as shown in FIG. At the time of dry etching, the lower electrode on which the workpiece is mounted is not particularly covered with a film or the like, and it is inevitable that the surface of the wafer is metal-contaminated by the components of the electrode material.

In a dry etching apparatus disclosed in Japanese Patent Application Laid-Open No. 64-89518 as an example of covering both electrode surfaces with carbon, as shown in FIG. It is covered with carbon. In this case, if a gas containing halogen is used,
During etching, polymerization does not occur, dirt in the etching chamber is eliminated, cleaning frequency is reduced, etching reproducibility is improved, but during dry etching, the surface of the carbon electrode is sputtered by high frequency voltage, The micro-crystals of carbon generated by the thermal shock of the particles become dusty particles and adhere to the wafer, causing a problem of causing contamination.

Japanese Patent Application Laid-Open No. 8-250480 uses CF ₄ as an etching gas. However, when CF ₄ is decomposed by plasma, the amount of a polymer film (polymer) generated is small. In this gas system, the formation amount of the polymer film (polymer) that covers the silicon surface at the bottom of the contact hole during etching is small, the etching amount of silicon increases, and the etching selectivity of the silicon oxide film to silicon cannot be increased. There is a problem.

[0012]

According to the first aspect of the present invention, there is provided a parallel plate type dry etching apparatus according to the present invention, wherein a high frequency voltage is applied between a plate upper electrode and a plate lower electrode, and the upper electrode and the lower electrode are applied. By the plasma generated between
In a parallel plate dry etching apparatus for etching a predetermined portion of a film to be etched mounted on the lower electrode, at least a surface of the upper electrode facing the lower electrode and a surface of the lower electrode on which the film to be etched is mounted. It is characterized in that a carbon compound film is formed on the entire surface.

According to a second aspect of the present invention, in the parallel plate type dry etching apparatus, the carbon compound film is formed on the side surface of the upper electrode and / or the side surface of the lower electrode. A parallel plate type dry etching apparatus according to claim 1.

According to a third aspect of the present invention, there is provided a parallel plate type dry etching apparatus according to the present invention, wherein the carbon compound film is silicon carbide. It is a dry etching device.

According to a fourth aspect of the present invention, there is provided a dry etching method according to the first aspect of the present invention, wherein a gas containing fluorine and carbon is plasma-treated using the parallel plate type dry etching apparatus according to any one of the first to third aspects. Decomposition generates fluorine radicals and first carbon fluoride, and carbon generated by sputtering a carbon compound film covering the upper electrode and the lower electrode by a high-frequency voltage applied to the upper electrode and the lower electrode. Reacts with the fluorine radicals to generate second carbon fluoride, and plasma-etches the silicon oxide film on the silicon substrate with the first carbon fluoride, the second carbon fluoride, and the fluorine radicals. It is characterized by the following.

In the dry etching method according to the present invention, the gas containing fluorine and carbon may be C ₂ F ₆ or C ₄ F ₈ or a mixture of C ₂ F ₆ and C ₄ F _8. The dry etching method according to claim 4, wherein a gas is used.

Further, the dry etching method according to the present invention according to claim 6 is characterized in that argon is used as a balance gas for the gas containing fluorine and carbon. This is an etching method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, based on one embodiment,
The parallel plate type dry etching apparatus and dry etching method of the present invention will be described in detail.

FIG. 1 is a block diagram of a parallel plate type dry etching apparatus according to a first embodiment of the present invention, and FIG. 2 is a block diagram of a parallel plate type dry etching apparatus of a second embodiment of the present invention. And FIG. 5 is a sectional view of a contact hole when the present invention is used. 1, 2 and 5, 1 is an upper electrode, 2 is a lower electrode, 3 is a wafer, 4a is a carbon compound, 5 is a high frequency power supply, 6 is a high frequency application coil, 7 is an upper electrode sealing material, and 8 is a reaction. The lower part of the room, 9 is a shielding part, 10 is a lower electrode sealing material, 18 is a matching circuit, 19 is a silicon substrate, 20 is a diffusion layer, 21 is a silicon oxide film, and 22 is BPSG.

In the structure of the apparatus according to the present invention, in FIG. 1, a cylindrical upper electrode 1 is provided concentrically with the reaction chamber and connected to the upper part of the reaction chamber. An airtight reaction chamber is formed. The material of the upper electrode 1 is formed by processing any of carbon, stainless steel, aluminum alloy and the like.

A high-frequency application coil 6 is wound around the outer wall surface of the upper electrode 1 at a uniform winding density, and is applied to a reaction chamber containing fluorine by the action of an electric field and a magnetic field generated by high-frequency power applied to the high-frequency application coil 6. The lower electrode 2 is housed opposite the cylindrical upper electrode 1 and is connected to a high frequency power supply 5 for applying a high frequency voltage to the lower electrode 2.

The lower reaction chamber 8 is formed of any one of alumina, stainless steel, aluminum alloy and the like, and has a cup-shaped quartz shielding portion 9 which slides along the inner surface of the lower reaction chamber 8. It is configured as follows. A gas introduction hole and a gas exhaust hole are disposed on the bottom surface of the lower portion of the reaction chamber 8. Gas in the reaction chamber is exhausted from the gas exhaust hole, and the pressure in the reaction chamber is maintained at a predetermined pressure by a pressure control device (not shown). While etching, a reactive gas is introduced from a gas introduction hole to perform etching.

As a feature of the present invention, as shown in FIGS. 1 and 2, at least the opposing surfaces of the upper electrode 1 and the lower electrode 2 are coated with a carbon compound. For example, as the carbon compound, silicon carbide (SiC)
Or boron carbide (B ₄ C). As the method for forming the coating layer, a method using a chemical vapor deposition method, a physical vapor deposition method, a sintered material of silicon carbide, or the like can be used. And
It is desirable that the side surface of the lower electrode 2 is also covered with a carbon compound. Further, it is desirable to form a carbon compound instead of the shielding portion 9 formed on the side surface of the upper electrode 1 in FIG.

The shielding portion 9 of FIG. 1 of the present invention is made of quartz in order to protect the surface of the lower reaction chamber 8 formed of a material such as alumina, stainless steel or an aluminum alloy from corrosive gas for etching. It is formed in a cup shape, and is fixed by screws (not shown) in the lower portion 8 of the reaction chamber.
Further, the shielding portion 9 of FIG. 2 of the present invention has the same specification as that of FIG. 1 except that it is provided in the lower portion 8 of the reaction chamber. The cylindrical quartz shield 9 is screwed with a screw (not shown) in order to prevent the occurrence of such a problem and to avoid contact with a corrosive gas for etching.

A description will be given of a case where a contact hole is formed in an insulating film (silicon oxide film) on a silicon substrate by using a gas containing fluorine in the dry etching apparatus thus configured.

First, the wafer 3 is placed on the lower electrode 2, a gas containing fluorine is introduced into the reaction chamber, and a high-frequency voltage is applied to the high-frequency application coil 6 wound around the upper electrode 1 to introduce the gas. In a gas containing fluorine, a uniform magnetic field,
When an electric field is generated, a gas containing fluorine is plasma-decomposed.

In this state, when a high-frequency voltage is applied from the high-frequency power supply 5 to the upper electrode 1 and the lower electrode 2 on which the wafer 3 is placed, active radicals and the like in the plasma are supplied onto the wafer, and the etching proceeds. According to the present invention, since the upper electrode 1 and the lower electrode 2 are covered with a carbon compound such as silicon carbide, when high-frequency power is applied to both electrodes during etching, the upper electrode 1 and the lower electrode 2 serve as covers for the upper electrode 1 and the lower electrode 2. The provided silicon carbide is sputtered to generate silicon ions and carbon ions in the plasma.

On the other hand, the gas containing fluorine used in the etching of the present invention is octafluorocyclobutane C ₄ F ₈ and hexafluoroethane C ₂ F ₆ , which easily forms a polymer film (polymer) and does not lower the etching rate. Is used as the balance gas, or argon is used as the balance gas, or one of C ₄ F _{8 and} C ₂ F ₆ is used as the balance gas.

The etching in the case where a mixture of C ₄ F ₈ and C ₂ F _{6 at} a fixed ratio and argon is used as a balance gas will be described below.

C ₄ F ₈ and C ₂ F ₆ are plasma-decomposed to generate fluorine ions (F radicals) as active species contributing to etching, and at the same time to generate first carbon fluoride (CFn) and the like. Further, the sputtered carbon ions work together with fluorine ions (F radicals) of active species generated by plasma decomposition of C ₂ F ₆ and C ₄ F ₈ so as to etch the silicon oxide film on the silicon substrate. The underlying silicon substrate is etched by fluorine ions (F radicals). However, there are silicon ions generated by sputtering silicon carbide in the plasma,
SiF which reacts with fluorine ion (F radical) and is volatile
_Since it becomes ₄ and is exhausted, silicon ions do not remain as dust in the reaction chamber. Thus, silicon ions have the effect of reducing the concentration of fluorine ions (F radicals) generated by excessive decomposition. On the other hand, the first
The carbon fluoride and the second carbon fluoride etch the silicon oxide film.

When the wafer on the lower electrode is negatively biased by the high frequency power supply, positive ions are attracted to the wafer surface. When plasma-decomposed reaction products such as first and second carbon fluorides containing carbon atoms charged to positive ions reach the silicon oxide film on the wafer surface,
Reacts with the oxygen element in the silicon oxide film to produce carbon monoxide (C
O), the silicon oxide film is etched, gasified and exhausted. On the silicon oxide film, the reaction product is consumed by the etching, so that a polymer film (polymer) does not deposit on the silicon oxide film.

On the other hand, in the case of the underlying silicon surface of the contact hole, since it does not contain oxygen atoms, it is charged with positive ions, and the polymerization reaction of the reaction product containing carbon atoms proceeds. The surface is covered with a polymer film (polymer). As a result, fluorine ions (F radicals) as etching active species are prevented from entering the silicon surface by the polymer film (polymer) formed on the silicon surface, and etching of the silicon surface becomes difficult to progress.

Thus, by using C ₂ F ₆ and C ₄ F ₈ gases which can easily form a polymer and do not lower the etching rate, a high etching selectivity of silicon oxide film to silicon can be obtained. Etching can be performed.

[0034] FIG. 5 shows a cross-sectional view of a result of forming the contact holes in the laminated film of BPSG22 / SiO ₂ 21 / silicon substrate 19. A contact hole with a smooth forward taper was formed in the etched portion of the laminated film. The silicon etching amount of the diffusion layer 20 is also small,
There was no increase in the contact resistance between the metal and the metal wiring. The etching conditions and results of the present invention are as follows.

First, as the RF power, the source power (power applied to the coil) is 1900 W, and the bias power is 1
400 W, pressure 5 mTorr, temperature 2
00 to 210 ° C, 0 to 10 ° C for lower electrode part, gas amount is C
₂ F _{6 10} sccm, C ₄ F _{8 6} sccm, Ar 90
sccm.

As a result of the etching, under the above conditions, the etching rate of the silicon oxide film is 6000.
Å / min, a selectivity of about 30 and an etching shift of 0.1.
02 μm, and the etching amount of silicon was about 0.06 μm.

[0037]

As described above in detail, by using the present invention, carbon fluoride covering the electrode portion is sputtered during dry etching to produce carbon fluoride;
When etching a silicon oxide film with carbon fluoride and fluorine radicals generated by plasma decomposition of an etching gas, the carbon fluoride and fluorine radicals are reactive species for etching the silicon oxide film. Since carbon fluoride forms a polymer film on the underlying silicon and suppresses etching of the underlying silicon by fluorine radicals, a high etching selectivity of the silicon oxide film with respect to silicon is obtained, and the reproducibility is improved. .

On the other hand, the use of silicon carbide can prevent electrode components from being contaminated on the wafer during etching, and can cause chip defects such as dust adhering to the wafer as in the case of carbon electrodes. Is also improved. Since silicon carbide is dense and strong, chemically stable and resistant to acids, it is inexpensive. Therefore, as in the present invention, it can be effectively used for semiconductor manufacturing equipment.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a parallel plate type dry etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a parallel plate type dry etching apparatus according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a first conventional parallel plate type dry etching apparatus.

FIG. 4 is a configuration diagram of a second conventional parallel plate type dry etching apparatus.

FIG. 5 is a sectional view of a contact hole portion when the present invention is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper electrode 2 Lower electrode 3 Wafer 4a Carbon compound 4b Carbon 5 High frequency power supply 6 High frequency application coil 7 Upper electrode sealing material 8 Lower reaction chamber 9 Shielding part 10 Lower electrode sealing material 18 Matching circuit 19 Silicon substrate 20 Diffusion layer 21 Silicon oxide film 22 BPSG

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4K057 DA13 DA20 DB17 DD01 DE06 DE07 DE08 DM02 DM03 DM06 DM08 DM09 DM10 DM28 DM29 DM31 DM33 DN01 5F004 AA00 AA02 BA04 BA09 BB11 BB18 BB28 BB29 BB30 DA00 DA01 DA02 DA03 DA06 DA10 DA23 DA25 DB02 DB03 DB06 EB01 EB03

Claims (6)

[Claims] 1. A high frequency voltage is applied between a flat plate upper electrode and a flat plate lower electrode, and plasma generated between the upper electrode and the lower electrode is used to apply a predetermined voltage to a film to be etched mounted on the lower electrode. In a parallel plate dry etching apparatus for etching a portion, at least a surface of the upper electrode facing the lower electrode,
A parallel plate dry etching apparatus, wherein a carbon compound film is formed on the entire surface of the lower electrode and the surface on which the film to be etched is mounted. 2. The parallel plate type dry etching apparatus according to claim 1, wherein the carbon compound film is also formed on a side surface of the upper electrode and / or a side surface of the lower electrode. 3. The parallel plate type dry etching apparatus according to claim 1, wherein the carbon compound film is silicon carbide. 4. A fluorine-containing gas and a first carbon fluoride are generated by plasma decomposition of a gas containing fluorine and carbon by using the parallel plate type dry etching apparatus according to any one of claims 1 to 3. A carbon compound film covering the upper electrode and the lower electrode is sputtered by a high-frequency voltage applied to the upper electrode and the lower electrode, so that carbon generated by the sputtering reacts with the fluorine radical to form a second carbon fluoride. And etching the silicon oxide film on the silicon substrate with the first carbon fluoride, the second carbon fluoride, and the fluorine radicals. 5. The gas containing fluorine and carbon,
5. The dry etching method according to claim 4, wherein C ₂ F ₆ or C ₄ F ₈ or a mixed gas of C ₂ F ₆ and C ₄ F ₈ is used. 6. The dry etching method according to claim 4, wherein argon is used as the balance gas in the gas containing fluorine and carbon.