JPH0982686A - Plasma processing apparatus and method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a high-melting metal film to be easily and selectively etched to a polycrystalline silicon film by a method wherein a peripheral member formed of material which keeps the volume ratio of oxygen-containing gas to a mixed gas of halogen-containing gas and oxygen-containing gas staying in a prescribed range is provided in the vicinity of a substrate. SOLUTION: A silicon film and a high-melting metal film are successively formed on a substrate 11, the substrate 11 is introduced into a processing chamber 10, and plasma source gas comprising halogen-containing gas which contains at least either of fluorine and chlorine and oxygen-containing gas is turned into plasma in the processing chamber 10 to anisotropically etch the laminated film composed of the silicon film and the metal film. The volume ratio of the oxygen-containing gas to the mixed gas of the halogen-containing gas and the oxygen-containing gas is set to 50 to 80:100 when the oxygen-containing gas is calculated in terms of O2 gas. A peripheral member 19 formed of material selected out of silicon, aluminum, and high-melting metals is provided around the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a semiconductor device manufacturing method characterized by a method of etching a laminated film of a silicon film and a refractory metal film.

[0002]

2. Description of the Related Art Large-scale integrated circuits (LSIs) formed by connecting a large number of transistors, resistors, etc. to an electric circuit in important parts of a computer, communication equipment, etc. ) Is often used. For this reason, the performance of the entire device is greatly related to the performance of the LSI alone. The performance of the LSI alone can be improved by increasing the degree of integration, that is, by miniaturizing the elements.

However, with the high integration of semiconductor integrated circuits due to the miniaturization of elements in recent years, there is a problem that the operation speed of the element is limited by RC delay of electrodes such as gate electrodes and wiring such as gate wiring. It has turned into.

This type of delay can be suppressed by reducing the resistance of the electrodes and wiring. For example, in the case of a gate electrode of a MOS transistor or the like, it can be suppressed by adopting a polycide gate having a two-layer structure of a metal silicide film and a polycrystalline silicon film.

By the way, after the 0.25 μm generation, a gate electrode having a resistance lower than that of the polycide gate is required,
Recently, attention has been paid to a polymetal gate having a laminated structure of a refractory metal film and a polycrystalline silicon film.

[0006] The use of tungsten (W) as a high melting point metal, the resistivity of tungsten because about one order of magnitude smaller than the tungsten silicide (WSi _x), it is possible to significantly reduce the RC delay time.

Further, in the 0.25 μm generation and beyond, in addition to the technique for reducing the gate resistance, a highly precise pattern forming technique is essential. That is, in order to form a polymetal gate, an etching technique capable of anisotropically etching the refractory metal film and the polycrystalline silicon film and selectively etching the refractory metal film with respect to the underlying polycrystalline silicon film is used. Mandatory.

However, with the conventional etching technique, it is difficult to selectively etch the refractory metal film with respect to the polycrystalline silicon film. For this reason, in the step of etching the refractory metal film, there arises a problem that the polycrystalline silicon film is traversed up to the silicon substrate which is not necessary to be etched.

Such a problem becomes particularly noticeable in a laminated film of a polycrystalline silicon film and a refractory metal film, which have become thinner due to miniaturization, and therefore, in the conventional etching technique, a fine pattern of 2.25 μm generation or later is used. It is very difficult to form a unique gate pattern.

As a related technique, a molybdenum film or a molybdenum silicide film (M
A technique using a mixed gas of carbon tetrachloride (CCl ₄ ) and oxygen in order to selectively etch (oSi ₂ film) is known (J. Elctrochem. Soc., 131, 232).
5 (1984)). However, it does not mention that the refractory metal film is selectively etched with respect to the polycrystalline silicon film. In addition, although other etching methods have been proposed, none mentions the material structure in the etching apparatus.

[0011]

As described above, it is difficult to selectively etch the refractory metal film with respect to the polycrystalline silicon film by the conventional etching technique.
As the laminated film of the polycrystalline silicon film and the refractory metal film is made thinner due to the miniaturization, it is not necessary to go over the polycrystalline silicon film and etch the silicon substrate below it at the stage of etching the refractory metal film. There was a problem that it was etched.

The present invention has been made in consideration of the above circumstances, and an object thereof is to easily select a refractory metal film with respect to a silicon film such as a polycrystalline silicon film even if miniaturization progresses. It is an object of the present invention to provide a plasma processing apparatus and a semiconductor device manufacturing method that can be etched.

[0013]

In order to achieve the above object, a plasma processing apparatus according to the present invention (claim 1) includes a substrate having a laminated film in which a silicon film and a refractory metal film are sequentially laminated. A processing container that accommodates and performs anisotropic etching of the laminated film using plasma, and a halogen-containing gas containing at least one of fluorine and chlorine that becomes the plasma and an oxygen-containing gas are included in the processing container. Means for introducing a plasma source gas, a mounting table provided in the processing container for mounting the substrate, and a halogen base during the anisotropic etching provided on the periphery of the substrate in the processing container. And a peripheral member formed of a material that maintains a volume% of the oxygen-containing gas with respect to a mixed gas of the gas and the oxygen-containing gas within a predetermined range. To.

Further, another plasma processing apparatus (Claim 2) according to the present invention is the plasma processing apparatus (Claim 1), in which the mounting table on which the substrate is mounted is maintained within the predetermined range. It is characterized by being formed from.

Further, another plasma processing apparatus (Claim 3) according to the present invention is the plasma processing apparatus (Claim 1), wherein the predetermined range is the oxygen-containing gas converted to O ₂ gas. And 50 to 80% by volume.

Another plasma processing apparatus (claim 4) according to the present invention is the plasma processing apparatus (claim 1), wherein the material is one material selected from silicon, aluminum and refractory metals. Alternatively, it is a compound of two or more materials.

A method of manufacturing a semiconductor device according to the present invention (claim 5) includes a step of sequentially forming a silicon film and a refractory metal film on a substrate, and the step of introducing the substrate into a processing container, and thereafter, the processing chamber. By plasmaizing a plasma source gas containing a halogen-containing gas containing at least one of fluorine and chlorine and an oxygen-containing gas to anisotropically etch the laminated film, and the halogen-containing gas in the anisotropic etching And a step of maintaining the volume% of the oxygen-containing gas with respect to the mixed gas with the oxygen-containing gas at 50 to 80 volume% when the oxygen-containing gas is converted into O ₂ gas.

Another method of manufacturing a semiconductor device according to the present invention (claim 6) is the same as the method of manufacturing a semiconductor device (claim 5), wherein a peripheral member is provided around the substrate,
As a material of the peripheral member, one material selected from silicon, aluminum and refractory metals or a compound of two or more materials is used.

Further, in the above plasma processing apparatus and semiconductor device manufacturing method, the material may be oxide, nitride or carbide of silicon, aluminum and refractory metal.

At least one of the fluorine gas and the chlorine gas is, for example, SF ₆ gas, CF ₄ gas or C gas.
It is preferable to use l ₂ gas, CCl ₄ gas, or a mixed gas thereof.

The oxygen gas is not limited to O ₂ gas,
For example, nitric oxide (NO) gas, nitrous oxide (NO
₂ ) It may be supplied in the form of gas, ozone (O ₃ ) gas or the like. At this time, in the case of a gas other than the O ₂ gas, the predetermined range is 50 when converted to oxygen (O ₂ ) gas.
˜80% by volume.

The refractory metal film may be made of tungsten, molybdenum, or a nitride or carbide of these metals. [Operation] The present invention was made based on the following findings and experimental results.

When plasma etching (anisotropic etching) is performed on a polycrystalline silicon film using a mixed gas of a halogen gas and an oxygen gas as a reactive gas (plasma source gas), the surface of the polycrystalline silicon film is oxidized. At the same time, an etching product (for example, SiCl _x when chlorine gas is used as the halogen gas) generated by the halogen gas contained in the reactive gas reacts with oxygen contained in the reactive gas, Silicon oxide is produced.

Since such silicon oxide is deposited on the polycrystalline silicon film and suppresses the etching of the polycrystalline silicon film, the etching rate of the polycrystalline silicon film sharply decreases.

On the other hand, when a film made of tungsten, molybdenum or the like (high melting point metal film) is etched using the same reactive gas, these metal halogen oxides are produced as etching products. Since the oxide has a high vapor pressure, it does not deposit on the refractory metal film unlike the case of the polycrystalline silicon film.

Therefore, theoretically, in anisotropic etching of a laminated film formed by forming a refractory metal film on a polycrystalline silicon film, plasma etching is performed using the above-mentioned reactive gas, whereby the refractory metal film is theoretically formed. The film can be etched selectively with respect to the polycrystalline silicon film.

However, when the selective etching of the laminated film of the polycrystalline silicon film and the refractory metal film was actually carried out based on the above findings, the etching rate of the polycrystalline silicon film was lowered and the conditions for obtaining the selection ratio were: A fluorine or chlorine gas or a mixed gas of these two gases and an oxygen gas is used as the reactive gas, and the volume% of the oxygen gas with respect to the mixed gas during etching is within a predetermined range, that is, 50 to 80 volume%. It turned out to be limited to cases.

Therefore, if there is a member that consumes halogen gas or oxygen in the etching apparatus, the above volume% is likely to deviate from the predetermined range, making selective etching of the polycrystalline silicon film difficult. In particular, it becomes difficult when there is a member made of a material that consumes oxygen.

Therefore, in the plasma processing apparatus according to the present invention, the mounting table and its peripheral members (for example, peripheral ring), which are particularly consuming members, are selected as the members that consume the halogen gas and oxygen, and the above-mentioned predetermined materials are selected as the materials. Range is used during the etching. In addition,
When a part of the mounting table on which the substrate is mounted is exposed in the apparatus, it is preferable that the exposed portion or the whole is made of the above-mentioned material. Therefore, by using the semiconductor manufacturing apparatus according to the present invention, the refractory metal film can be easily and selectively etched with respect to the silicon film such as the polycrystalline silicon film.

On the other hand, in order to make the etching shape of the refractory metal film vertical, the lower the pressure and flow rate of the reactive gas, the better. The reason for this will be described below by taking the case of using a parallel plate type etching apparatus as an example.

The higher the pressure, the lower the energy of the ions incident on the substrate to be processed, and the weaker the vertical etching by the ions. On the other hand, the higher the pressure, the more radicals of fluorine and chlorine are generated in the plasma. This type of radical contributes to isotropic etching. Therefore, the higher the pressure is, the more the etching component in the horizontal direction is increased compared to the etching component in the vertical direction, and the etching shape is slightly tapered.

Further, as the flow rate increases, the residence time of the product in the etching apparatus (vacuum container) becomes shorter, and the amount of unreacted radicals relatively increases as compared with the reaction product, resulting in a reverse taper. It becomes the etching shape.

In order to obtain such a vertical etching shape, it is desirable to carry out etching under a low pressure and a low flow rate. Under such conditions, the amounts of halogen gas and oxygen gas in the etching apparatus are reduced. Therefore, if there is a member made of a material that consumes these gases in the etching apparatus, it becomes difficult to maintain the volume% within a predetermined range.

However, in the plasma processing apparatus according to the present invention, as described above, the above-mentioned volume% is predetermined as the material of the mounting table and its peripheral members (for example, peripheral ring) which are members that consume a lot of halogen gas and oxygen. Since the material maintained within the range is used, the refractory metal film can be easily etched into the vertical shape.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments (embodiments) of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a plasma etching apparatus according to an embodiment of the present invention.

This plasma etching apparatus is roughly divided into an etching chamber 10, an introduction preliminary chamber 20 and a discharge preliminary chamber 30, and an etching chamber 10, an introduction preliminary chamber 20 and a discharge preliminary chamber 30. The spaces are separated by gate valves 21 and 31, respectively.

The substrate 11 to be etched is introduced from the gate valve 22 provided in the introduction preliminary chamber 20 while the etching chamber 10 is kept in vacuum, and then the discharge preliminary chamber 30 is introduced.
From the gate valve 32 provided on the substrate to be etched 1
Since 1 is discharged, it is possible to avoid the adverse effect of the atmospheric atmosphere and dry-etch the substrates 11 to be etched one by one in a short time. In addition, mounting tables 23 and 33 are installed inside the introduction preliminary chamber 20 and inside the discharge preliminary chamber 30, respectively.

Inside the etching chamber 10, there is provided an electrode 12 which also serves as a mounting table on which the substrate 11 to be etched is placed. The electrode 12 is cooled for controlling the substrate 11 to be etched to a desired temperature. A tube 13 is provided. Also, the electrode 12 is 13.56 MH for plasma excitation.
It is connected to a high frequency power supply 16 via a blocking capacitor 14 and a matching device 15 so as to apply a high frequency power of z. In addition, a ring-shaped plate (peripheral ring) 19 for improving the uniformity of the electric field formed on the substrate 11 to be etched is disposed as a peripheral member around the electrode 12.

Here, in the case of the conventional device, the peripheral ring 1
Although 9 is formed of carbon, quartz (SiO ₂ ) is used in this embodiment. On the other hand, a reactive gas supply line 40 is provided above the etching chamber 10, and a predetermined reactive gas described later is introduced into the etching chamber 10 from the reactive gas supply line 40. There is. The reactive gas is adjusted to a desired flow rate value by the valve 41 and the flow rate controller 42, and is kept at a constant pressure in the etching chamber 11 by the control valve 43 provided in the lower portion of the etching chamber 10. Has become.

The inner wall (upper wall) of the etching chamber 10 is grounded, so that a high-frequency voltage can be applied between the inner wall and the electrode 12 and the reactive gas can be turned into plasma. . Above the etching chamber 10,
A permanent magnet 17 is installed, and the permanent magnet 17 is rotated around an axis of rotation 18 by an electromagnetic motor (not shown). This permanent magnet 17 generates about 200
The Gaussian magnetic field makes it possible to generate and maintain a high ion density plasma even in a high vacuum of 10 ⁻³ Torr or less. A large amount of ions are generated from the high-ion-density plasma generated in this manner, and the substrate 11 to be etched 11
And is etched to perform etching.

First, as a clue for improving the selection ratio of the refractory metal film to the polycrystalline silicon film, physical property data of halides of silicon, tungsten and molybdenum are shown in the following table.

[0042]

[Table 1]

Considering the etching product of tungsten, the vapor pressure of fluoride (WF ₆ ) is the highest, and the vapor pressure of chloride (WCl ₅ , WCl ₆ ) is not so high. On the other hand, in the case of silicon, fluoride (SiF _4), chloride (Si
Both Cl ₄ ) have a very high vapor pressure.

Therefore, pure sulfur hexafluoride (SF ₆ ) or C
When a fluorine-based gas such as F ₄ is selected as the etching gas, it is difficult to improve the selection ratio of the tungsten film selection with respect to the polycrystalline silicon film. Also, Cl ₂ and carbon tetrachloride (C
It is expected that chlorine-based gases such as Cl ₄ ) will be similarly difficult.

On the other hand, paying attention to halogen oxides, tungsten fluorine oxide (WOF ₄ ) and chlorine oxide (W
There are compounds with a relatively high vapor pressure, such as OCl ₂ ).
Therefore, it is expected that the use of halogen oxides as an etching product will improve the selectivity to silicon.

Therefore, using a conventional plasma etching apparatus (peripheral ring 19 made of carbon), a mixed gas of sulfur hexafluoride (SF ₆ ) gas and O ₂ gas is used, and a tungsten film and The laminated film with the crystalline silicon film was etched. The etching conditions are a high frequency applied power of 0.7 W / cm ₂ , a pressure of 8 mTorr, a total flow rate of 50 SCCM, and a temperature of the electrode 12 of 65 ° C. The following experiments were carried out using a conventional plasma etching apparatus unless otherwise specified.

FIG. 2 shows that SF ₆ was used in the above etching.
O for the flow rate (volume) of a mixed gas of gas and O ₂ gas
₂ Gas flow rate (volume) percentage (volume%) 0-100
It is a figure which shows the result at the time of etching by changing in the range up to%. FIG. 2A shows the dependency of the etching rate of the tungsten film and the etching rate of the polycrystalline silicon film on the volume% of O ₂ gas. In addition, FIG.
Shows the O ₂ gas volume% dependency of the selection ratio of the tungsten film to the polycrystalline silicon film.

As shown in FIG. 2A, the etching rate of the tungsten film does not depend so much on the volume% of O ₂ gas, but the etching rate of the polycrystalline silicon film decreases as the volume% of O ₂ gas increases. However, when the volume% of O ₂ gas is 60% or more, the selection ratio of the tungsten film to the polycrystalline silicon film becomes about 1.

Then, a mixed film of chlorine (Cl ₂ ) gas and O ₂ gas was used to etch the laminated film of the tungsten film and the polycrystalline silicon film. The etching conditions are a high frequency applied power of 0.7 W / cm ₂ and a pressure of 8 mTorr.
r, the total flow rate is 50 SCCM, and the temperature of the electrode 12 is 65 ° C.

FIG. 3 is a diagram showing the results of the above etching when the volume% of O ₂ gas was changed in the range of 0 to 100%. FIG.
(A) shows the O ₂ gas volume% dependence of the etching rate of the tungsten film and the etching rate of the polycrystalline silicon film. Further, FIG. 3B shows the O ₂ gas volume% dependency of the selection ratio of the tungsten film to the polycrystalline silicon film.

[0051] As shown in FIG. 3, the etching rate of the tungsten film increases with the volume% of O ₂ gas is increased, the volume% of O ₂ gas is not greater than 60%. On the other hand, the etching rate of the polycrystalline silicon film sharply decreases as the volume% of O ₂ gas increases, and deposition starts when the volume% of O ₂ gas is 60% or more.

Then, the surface of the polycrystalline silicon film exposed to the plasma was evaluated by the photoelectron spectroscopy (XPS) method, and as a result, the Ols spectrum showing the presence of oxygen was strongly observed, and it was found that the Si2p spectrum was chemically shifted. It was However, Cl as the etching gas was not detected.

From this result, it was found that the surface of the polycrystalline silicon film was in a state close to the silicon oxide film (SiO _x ). This is because when the polycrystalline silicon film is etched under the condition that the volume% of O ₂ gas is 60% or more, SiO _x removed from the polycrystalline silicon film is deposited (adhered) on the etching surface and the progress of etching is hindered. It is thought to be due to the cause.

In the field of chemical vapor deposition (CVD) of an insulating film, research on forming SiO ₂ by using a mixed gas of SiCl ₄ gas and O ₂ gas has been conducted for a long time, and is reported. According to this, Si ₂ OCl ₆ and Si ₄ O ₄ Cl ₈ are generated in addition to SiO ₂ at a film forming temperature of around 900 ° C.

On the other hand, in the case of CVD using plasma, there is an example in which a good SiO ₂ film is formed at a film forming temperature of 200 ° C. From the results of analyzing the film components, the film contains impurities such as Cl. I know it's not.

As described above, even in the Cl ₂ / O ₂ mixed gas system, it is possible that SiCl ₄ , which is the etching product of the polycrystalline silicon film, reacts with oxygen or oxygen radicals as shown in the reaction formula below. Is high and one can expect a situation similar to plasma CVD.

SiCl _x + O ₂ (or O ^* ) → SiO _y + Cl ₂ As described above, when the volume% of O ₂ gas is 60% or more, as shown in FIG. The selection ratio of the tungsten film is dramatically increased.

Further, the mixed film of SF ₆ gas, Cl ₂ gas and O ₂ gas was used to etch the laminated film of the tungsten film and the polycrystalline silicon film. The etching conditions are high frequency applied power 0.7 W / cm ₂ and pressure 20 mT.
orr, total gas flow rate 100 SCCM, electrode 12 temperature 6
5 ° C.

FIG. 4 shows that in the above etching, the flow rate of O ₂ gas was fixed at 60 SCCM, SF ₆ gas and Cl _{2 were used.}
Cl ₂ gas at a flow rate of a percentage of the flow rate of a gas mixture of gas (volume%) varied between 0 and 100 percent is a diagram showing the results of etching.

As shown in FIG. 4, volume% (SF ₆ flow rate /
When the (Cl ₂ flow rate) is around 50% (20/20), the etching rate of the polycrystalline silicon film sharply decreases, and when the volume% reaches 50% or more, deposition starts. This is a phenomenon similar to the case where a mixed gas of Cl ₂ gas and O ₂ gas is used, and the selection ratio of the tungsten film to the polycrystalline silicon film is dramatically improved.

Next, using a mixed gas of SF ₆ gas, O ₂ gas and N ₂ gas, the laminated film of the tungsten film and the polycrystalline silicon film was etched. The etching conditions are high-frequency applied power of 0.7 W / cm ² and pressure of 10 mTo.
rr, the temperature of the electrode 12 is 40 ° C. Of all the gases, the volume% of O ₂ gas with respect to the mixed gas of halogen gas (SF _{6 in} this case) and O ₂ gas was kept the same as before.

FIG. 5 shows that in the above etching, SF ₆
Gas flow rate is 10 SCCM, O ₂ gas flow rate is 15 SC
Fixed to CM, it is a diagram showing the results of etching the flow rate of N ₂ gas was changed in a range of 0～30SCCM.

As shown in FIG. 5, the etching rates of the tungsten film and the polycrystalline silicon film both decrease as the flow rate of the N ₂ gas increases, but the decreasing rates are the same. The selectivity of the tungsten film with respect to is unchanged. That is, the addition ratio is not affected by adding nitrogen.

In addition to this, the same result can be obtained by adding a rare gas such as Ar, and a gas which does not affect the etching products is a mixed gas of the above-mentioned fluorine or chlorine or a mixed gas thereof and oxygen. It was found that even when added to, the selectivity was not affected.

From the above results, the reactive gas supply line 4
The reactive gas (plasma source gas) supplied from 0 to the etching chamber 10 is composed of a mixed gas of fluorine or chlorine or a mixed gas thereof and an oxygen gas, and contains fluorine or chlorine or a mixed gas thereof and an oxygen gas. It was revealed that the refractory metal film can be selectively etched with respect to the polycrystalline silicon film by introducing a gas having a volume ratio of oxygen gas to the mixed gas of 50 to 80%.

As a result of further investigation on such a phenomenon, it was found that the following should be noted. First, the aspect ratio of the etching mask pattern affects its selectivity. This will be specifically described with reference to FIG.

FIG. 6A shows a state in which an etching mask pattern 51 is formed on the polycrystalline silicon film 50. The width of the etching mask pattern 51 is about 0.8 μ.
m, and the height is about 1.0 μm. The distance between two adjacent etching mask patterns 51 is about 0.
It was changed in the range of 4 to 10 μm.

The polycrystalline silicon film 50 was etched along the etching mask pattern 51. The etching conditions are high-frequency applied power 0.7 W / cm ² and pressure 20 mTo.
rr, gas flow rate SF ₆ / Cl ₂ / O ₂ = 10/30/6
The temperature is 0 SCCM and the temperature of the electrode 12 is 65 ° C.

FIG. 6B shows the result of SEM observation of the shape after the above etching when the distance between the etching mask patterns 51 is 10 μm. As shown in FIG. 6B, the distance between the etching mask patterns 51 is 1
In the case of 0 μm, the etching of the polycrystalline silicon film 50 between the patterns is stopped, which coincides with the experimental result of FIG.

However, it was found that the polycrystalline silicon film 50 between the patterns was etched when the distance between the etching mask patterns 51 was about 1 μm. That is, it has been found that the etching rate of the polycrystalline silicon film 50 has a pattern dependency, and the above-mentioned selection ratio is not satisfied on the entire surface of the substrate.

Further, as shown in FIG. 6B, it was found that deposits 52 were formed on the side walls of the etching mask pattern 51. The deposit 52 formed on the sidewall of the etching mask pattern 51 makes it difficult to reach the etching surface between the patterns, and the aspect ratio of the etching mask pattern greatly affects the selection ratio, resulting in pattern dependence of the etching shape. Conceivable.

Secondly, the etching mask pattern is made of a material that consumes oxygen such as an organic material,
For example, when a photoresist pattern is used, it has been found that the above-described selectivity cannot be obtained between the patterns, as shown below.

FIG. 7A shows a state in which an etching mask pattern 61 made of a silicon oxide film (a material that hardly consumes oxygen) is formed on the polycrystalline silicon film 60. FIG. 7B shows an etching shape when the polycrystalline silicon film 60 is etched using the etching mask pattern 61. The etching conditions are: high frequency applied power 0.7 W / cm ² , pressure 20 mTorr, gas flow rate SF ₆ / Cl ₂ / O ₂ = 10/30/60 SCC
M, the temperature of the electrode 12 is 65 ° C.

As shown in FIG. 7B, when a silicon oxide film is used as the etching mask pattern material, the etching rate of the polycrystalline silicon film 60 has no pattern dependence and the etching proceeds uniformly.

FIG. 7C shows a state in which an etching mask pattern 62 made of a carbon film (a material that consumes oxygen) is formed on the polycrystalline silicon film 60. The aspect ratio of the etching mask pattern 62 is the same as that of the etching mask pattern 61.

FIG. 7D shows an etching shape when the polycrystalline silicon film 60 is etched using the etching mask pattern 62 under the same conditions as the etching mask pattern 61.

As shown in FIG. 7D, when a carbon film is used as the etching mask pattern material, the polycrystalline silicon film 60 in the region of the etching mask pattern 62 is used.
Was found to be etched abnormally fast.

As shown in FIGS. 2 and 3, it can be seen that the etching rate of the polycrystalline silicon film sharply increases as the volume% of O ₂ gas decreases. Therefore, when a material that consumes oxygen is used for the etching mask pattern 62, the volume% of O ₂ gas in the region where the etching mask pattern 62 is present is smaller than that in the other regions, so that the polycrystalline silicon film is formed. The etching rate becomes faster and the etching shape becomes pattern-dependent as shown in FIG.

Therefore, in order to maintain the selection ratio of the tungsten film to the polycrystalline silicon film and prevent the pattern dependence, it is necessary to select a material for the etching mask pattern that does not change the volume% of O ₂ gas in the plasma atmosphere. There is.

Third, it is necessary to pay attention to the gas pressure and flow rate during etching. Etching technology for the 0.25 μm generation and beyond is required to form a pattern with an accuracy of 0.02 μm or less. Therefore, the difference between the mask size and the tungsten film size conversion must be controlled within the accuracy. Particularly in the etching of the tungsten film, it is important to suppress lateral retreat, so-called side etching.

Therefore, the amount of side etching of the tungsten film was examined. The etching conditions are as follows: high frequency applied power 1.0 W / cm ² , flow rate SF ₆ / Cl ₂ / O ₂ = 10 /
The temperature of the electrode 12 is 80 ° C.

FIG. 8 is a diagram showing the results of the above etching when the gas pressure was changed in the range of 10 to 30 mTorr. As shown in FIG. 8, it was found that the amount of side etching of the tungsten film sharply increased when the pressure was increased.

Further, in the above etching, the total gas flow rate during etching was changed from 50 to 100 SCCM, and the relationship between the side etching amount and the total gas flow rate introduced was investigated. The etching conditions are high frequency applied power 1.0 W /
cm ² , gas pressure 10 mTorr, gas flow rate ratio SF
₆ : Cl ₂ : O ₂ = 1: 1: 3, electrode 12 temperature 80 ° C.
It is.

FIG. 9 shows the resulting relationship between the total gas flow rate and the side etching amount. As shown in FIG. 9, the side etching amount is suppressed as the total gas flow rate is lower, and the shape after etching approaches a vertical shape.

From these results, it was found that the lower the gas pressure and the lower the flow rate of the etching conditions, the better the vertical processing of the tungsten film. Next, in order to investigate the selection ratio of the tungsten film to the polycrystalline silicon film at low gas pressure and low gas flow rate, the etching characteristics of the polycrystalline silicon film were investigated.

First, as shown in FIG. 10A, a silicon nitride film 71 having a thickness of 200 nm is formed on the polycrystalline silicon film 70 by the CVD method, and then the entire surface is spin-coated to a film thickness of about 1 μm. Photoresist was applied, exposed and developed to form a photoresist pattern 72. The width of the pattern was about 1 μm, and the interval between the patterns was about 0.4 μm.

Next, as shown in FIG. 10B, the silicon nitride film 71 is etched using the photoresist pattern 72 as an etching mask pattern and CF ₄ gas as an etching gas.

Next, as shown in FIG. 10C, the remaining photoresist pattern 72 is removed using a mixed solution of sulfuric acid and hydrogen peroxide. Next remaining silicon nitride film 71
As an etching mask pattern with SF ₆ gas and Cl
_The polycrystalline silicon film 70 is etched using a mixed gas of ₂ gas and O ₂ gas as an etching gas. The etching conditions are: high frequency applied power 1.0 W / cm ² , gas pressure 10 mTorr, flow rate SF ₆ / Cl ₂ / O ₂ = 5 /
The temperature of the electrode 12 is 80 ° C. with 5/15 SCCM.

As a result of SEM observation of the shape after etching, as shown in FIG. 10D, the region of the silicon nitride film 71 is satisfied although the conditions of the material of the mask and the aspect ratio thereof are satisfied. In, it was found that the etching of the polycrystalline silicon film 70 progressed abnormally fast and the pattern dependence of the selection ratio was observed.

Next, the total flow rate was 100 SCCM without changing the flow rate ratio among SF ₆ gas, Cl ₂ gas and O ₂ gas.
(Specifically gas flow rate SF ₆ / Cl ₂ / O ₂ =
20/20/60 SCCM) and the polycrystalline silicon film 70 was etched.

As a result, when the total flow rate is 100 SCCM,
As shown in FIG. 10E, it was found that the polycrystalline silicon film 70 could be uniformly etched at the etching rate obtained from the experimental results for the selection ratios of FIGS.

The reason why such a phenomenon occurs is that when the total flow rate is small, unreacted halogen and oxygen in the plasma are reduced, making it difficult to generate deposits and etching gas in the etching apparatus. There are two points that there are factors that change the ratio (O ₂ volume%).

Therefore, the inventor has paid attention to the material of the peripheral ring in the etching apparatus. As shown in FIG. 1, in the etching apparatus, a peripheral ring 19 is provided around the substrate 11 to be processed.
A ring-shaped plate referred to as is placed and is placed on the electrode 12 together with the substrate 11 to be processed. The peripheral ring 19 is used to improve the uniformity of the electric field formed on the substrate 11 to be processed. This is done by changing the material, shape and thickness of the peripheral ring 19.

When a plasma discharge is generated in the etching apparatus, an electric field is formed in the peripheral ring 19 as well as the substrate 11 to be processed.
9 is also etched.

In the experiments up to this point, the peripheral ring 19 has been etched by using the conventional etching apparatus in which carbon is used. Therefore, the polycrystalline silicon film 70 is etched again using the etching apparatus of this embodiment in which the peripheral ring 19 is made of quartz (SiO ₂ ).

For the etching, a sample was used in which a mask pattern made of a silicon nitride film 71 (film thickness 200 nm) was formed on the above-mentioned polycrystalline silicon film 70. The etching conditions are: high frequency applied power of 1.0 W / cm ² , gas pressure of 10 mTorr, total flow rate of 50 to 100 SCCM, gas flow rate ratio SF ₆ : Cl ₂ : O ₂ = 1: 1: 3, electrode 12
The temperature is 80 ° C.

As a result, even at the total gas flow rate of 50 SCCM, as shown in FIG.
The etching shape of No. 1 progressed uniformly regardless of the silicon nitride film (etching mask pattern) 71, and the tendency was not dependent on the flow rate.

From a series of experimental results, it was found that the material of the peripheral ring 19 affects the selective etching. FIG.
FIG. 4 is a diagram for explaining the influence of a peripheral ring on selective etching. Under this gas condition, an etching product (for example, SiCl ₄ ) reacts with oxygen in the plasma 80, and the reaction product (SiO ₂ ) is deposited on the surface of the polycrystalline silicon film 81 which is an etching surface. The deposition of this reaction product suppresses the etching of the polycrystalline silicon film thickness 81 and holds the key to the selective etching.

However, under the conditions of low pressure and low gas flow rate, the absolute amounts of halogen and oxygen existing in the etching apparatus are small. Therefore, the amount of oxygen consumed by etching the peripheral ring 19 affects the ratio of halogen (fluorine, chlorine) and oxygen in the plasma 80.

In the region of the etching mask pattern 82 where the contribution of the deposition to the surface of the polycrystalline silicon film 81 is originally small, the etching exceeds the deposition, and as a result, the pattern dependence becomes apparent.

Therefore, even after the 0.25 μm generation,
In order to selectively etch the refractory metal film with respect to the polycrystalline silicon film 80, which has an excellent processed shape, the reactive gas having the above-mentioned predetermined O ₂ gas volume% is used and the parts around the substrate are used. As the material of the peripheral ring 19 which is, it is necessary to select a substance that keeps the O ₂ gas volume% within the above-mentioned predetermined range.

Although quartz is used as the material of the peripheral ring 19 in the present embodiment, other materials satisfying the above conditions may be silicon, aluminum, refractory metals, their alloys or their nitrides or oxides. It can be a thing.

Further, as a result of conducting the above-mentioned experiment similarly using silicon carbide, it was found that the selectivity was not affected. The silicon carbide film naturally contains carbon atoms and is expected to consume oxygen in the etching apparatus.

Therefore, the etching characteristics of the silicon carbide film were examined by using a mixed gas of CF ₄ gas and oxygen (O ₂ ) gas as an etching gas. The etching conditions are a high frequency applied power of 1.5 W / cm ² , a gas pressure of 10 mTorr,
The total flow rate is 50 SCCM and the temperature of the electrode 12 is 80 ° C.

[0105] As shown in FIG. 12, the volume% ratio of O ₂ gas to the mixed gas of O ₂ gas and CF ₄ gas 0
When it is changed in the range of 0%, the etching rate of the silicon carbide film tends to decrease as the volume% of O ₂ gas increases. From this result, the silicon carbide film does not consume oxygen unlike the case of the carbon film. The etching product of the silicon carbide film is not mainly an oxide such as carbon monoxide but CF _x
Is considered to be a fluoride. From this, it is considered that the silicon carbide film is hard to react with oxygen and is hard to be etched even under the above-mentioned gas conditions (for example, mixed gas of SF ₆ gas, Cl ₂ gas, and O ₂ gas). Therefore, as the material of the peripheral ring, besides silicon carbide, aluminum or a carbide of a refractory metal can also be used.

Although the types of electrodes and wirings are not particularly limited in the above-described embodiment, the present invention is applicable to electrodes such as gate electrodes which are required to have low resistance and wirings such as word wirings in which RC delay is remarkable. Especially effective.

In the above embodiment, the peripheral ring is taken as an example of the peripheral component of the substrate. However, the peripheral component is not limited to this, and the peripheral component is the peripheral component of the substrate and is conventionally made of a material that consumes oxygen. The same effect can be obtained by using a material that does not consume oxygen as in the case of the above embodiment.

[0108]

As described in detail above, according to the present invention, the refractory metal film can be easily and selectively etched with respect to the silicon film.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing O ₂ gas volume% dependence of etching rate and selectivity when SF ₆ gas is used as fluorine gas.

FIG. 3 is a diagram showing O ₂ gas volume% dependence of etching rate and selectivity when Cl ₂ gas is used as chlorine gas.

FIG. 4 SF ₆ gas / C of etching rate and selectivity
Figure showing the l ₂ gas ratio dependence

FIG. 5 is a diagram showing the effect of adding nitrogen gas to the reactive gas.

FIG. 6 is a process cross-sectional view for explaining the influence of an etching mask pattern on etching of a polycrystalline silicon film.

FIG. 7 is a process cross-sectional view for explaining the influence of the material of the etching mask pattern on the etching of the polycrystalline silicon film.

FIG. 8 is a characteristic diagram showing the relationship between gas pressure and side etching amount.

FIG. 9 is a characteristic diagram showing the relationship between the total flow rate and the side etching amount.

FIG. 10 is a diagram for explaining a selection ratio of a tungsten film to a polycrystalline silicon film at a low gas pressure and a low gas flow rate.

FIG. 11 is a diagram for explaining the influence of a peripheral ring on selective etching.

FIG. 12 is a diagram showing the O ₂ gas volume% dependency of the side etching amount when Cl ₂ gas is used as chlorine gas.

[Explanation of symbols]

 10 ... Etching chamber 11 ... Substrate to be etched 12 ... Electrode (mounting table) 13 ... Cooling pipe 14 ... Blocking capacitor 15 ... Matching device 16 ... High frequency power supply 17 ... Permanent magnet 18 ... Rotating shaft 19 ... Peripheral ring 20 ... Preparatory chamber for introduction 21 ... Gate valve 22 ... Gate valve 23 ... Mounting table 30 ... Exhaust chamber 31 ... Gate valve 32 ... Gate valve 33 ... Mounting table 40 ... Reactive gas supply line 41 ... Valve 42 ... Flow controller 50 ... Polycrystalline silicon Film 51 ... Etching mask pattern 52 ... Deposit 60 ... Polycrystalline silicon film 61 ... Etching mask pattern 62 ... Etching mask pattern 70 ... Polycrystalline silicon film 71 ... Silicon nitride film 72 ... Photoresist pattern 80 ... Plasma 81 ... Polycrystalline silicon Film 82 ... Etching mask pattern

Claims (6)

[Claims] 1. A processing container for accommodating a substrate having a laminated film formed by sequentially laminating a silicon film and a refractory metal film, and performing anisotropic etching of the laminated film using plasma, and the processing container. A means for introducing a plasma source gas containing a halogen-containing gas containing at least one of fluorine and chlorine, which becomes the plasma, and an oxygen-containing gas, and a mounting table provided in the processing container for mounting the substrate. A material that is provided in the periphery of the substrate in the processing container and that keeps a volume% of the oxygen-containing gas with respect to a mixed gas of the halogen-containing gas and the oxygen-containing gas during the anisotropic etching within a predetermined range. And a peripheral member formed of the plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein the mounting table on which the substrate is mounted is made of a material that maintains the predetermined range. 3. The predetermined range is such that the oxygen-containing gas is O
The plasma processing apparatus according to claim 1, wherein the content is 50 to 80% by volume when converted to ₂ gases. 4. The plasma processing apparatus according to claim 1, wherein the material is one material selected from silicon, aluminum and refractory metals or a compound of two or more materials. 5. A step of sequentially forming a silicon film and a refractory metal film on a substrate; and after introducing the substrate into a processing chamber, a halogen-containing gas containing at least one of fluorine and chlorine and oxygen in the processing chamber. A plasma source gas containing a contained gas is plasmatized to anisotropically etch the laminated film, and the volume of the oxygen-containing gas relative to the mixed gas of the halogen-containing gas and the oxygen-containing gas during the anisotropic etching. %, When the oxygen-containing gas is converted to O ₂ gas, the step of maintaining 50% by volume to 80% by volume. 6. A peripheral member is provided around the substrate, and as the material of the peripheral member, one material selected from silicon, aluminum and refractory metals or a compound of two or more materials is used. The method of manufacturing a semiconductor device according to claim 5, wherein