JPH10189549A - Plasma treatment apparatus and etching method for metal wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment apparatus by which an etching residue is not generated in an etching operation making use of a photoresist and by which the photoresist can be etched with high selection. SOLUTION: The height of a cylindrical vacuum container (a bell jar) 1 at a source part used to generate a plasma is constituted to be 60mm or lower, or to be 35mm or lower from the upper end of an RF antenna, or of a flat plate. When the height of the bell jar 1 is reduced, the generation center of the plasma is situated at the lower part, the plasma is diffused easily to a process chamber 5 which is installed so as to be connected to the lower side, the density of the plasma in the process chamber is increased, an etching residue is reduced even under a pressure of 15 to 20mTorr, the high selection ratio of an etching operation is obtained with reference to a resist on a wafer 8 placed on a wafer placing electrode 7, and a high-performance etching apparatus can be constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for manufacturing a semiconductor device, and more particularly to a structure of a plasma processing apparatus and a method for etching metal wiring.

[0002]

2. Description of the Related Art A cylindrical vacuum vessel (hereinafter referred to as a bell jar) made of a dielectric material by applying a high frequency to an antenna coil.
As a typical example of a plasma processing apparatus that generates plasma therein, there is a helicon wave plasma processing apparatus.
For example, JP-A-3-68773. Helicon wave plasma is a type of plasma wave generated in a plasma medium when a static magnetic field is formed in the plasma, and the phase velocity of the plasma wave is as small as the thermal motion velocity of electrons. Electrons with a velocity about the same as the phase velocity of the helicon easily interact with the helicon wave. This is an interaction phenomenon commonly called landau damping.
The result of this interaction, the energy obtained from the helicon wave high-energy electrons are generated is converted into electron kinetic energy, by ionizing action of the high-energy electrons, 10 ^12-1
A high-density plasma having a plasma density of 0 ¹³ / cm ³ is obtained.

FIG. 13 shows a configuration diagram of a plasma processing apparatus using this helicon wave plasma. The plasma generator is
It comprises a bell jar 21, a loop-shaped antenna coil 22 made of a conductor arranged above and below the jar, and a magnetic coil 24 for generating a static magnetic field arranged so as to surround these. High frequency power is applied to the antenna coil 22 from a power supply 23, and a helicon wave plasma is generated by the generated electric field and static magnetic field. The size of the bell jar 21 is 100 mm in inner diameter and 200 mm in height. The plasma generated in the bell jar 21 diffuses into a process chamber 25 provided below the bell jar 21 and provided with a wafer mounting electrode 27. The electrode 27 is configured such that the ion energy in the plasma can be independently controlled by a magnetic field generated by a magnet 29 disposed around the electrode 27 and a high-frequency power applied from a power supply 26.
Desired plasma processing can be performed on the wafer 28 placed on the electrode 27.

[0004]

In the helicon wave plasma processing apparatus shown in FIG. 13, for example, an AlSiCu alloy film formed on a wafer is dried with a mixed gas of chlorine gas and boron trichloride gas using a resist mask. When the etching is performed, the following two problems occur. The first problem is that the process margin is narrow. As an example of this, a description will be given of the selectivity with respect to the resist when the AlSiCu alloy is etched using the helicon wave plasma etching apparatus, that is, the relationship between the etching rate ratio between the AlSiCu alloy and the photoresist and the etching residue.

FIG. 14 shows that the pressure is set between 4 mTorr and 15 mTo.
FIG. 9 is a diagram showing a relationship between a resist selectivity and an etching residue when the resistance is changed to rr. In addition, in order to show the relationship between the etching residue and the ion current density, the figure also shows the ion current density measured about 25 mm on the wafer with a Langmuir probe. As can be seen from the drawing, a pressure of 15 mTorr is required to obtain a high selectivity (to resist of 3.0 or more).
An area of up to 20 mTorr is effective, but as long as a conventional apparatus is used, an etching residue is generated and cannot be applied to an actual process. Looking at the pressure dependency of the ion current density at this time, it can be seen that as the pressure increases, it decreases significantly. As the pressure is increased, the generation of etching residues is caused by such an increase in pressure.
It is considered that one of the causes is the remarkably reduced ion current density.

FIG. 15 is a diagram similar to FIG. 14 and shows the source power dependency. Again, the lower the source power, the higher the selectivity tends to be,
As the source power decreases, the ion current density decreases, and an etching residue is generated. That is, when a conventional helicon wave plasma etching apparatus is used, it is extremely difficult to suppress residues and perform high-selectivity etching on a resist, and there is a high possibility that a problem will occur in the manufacture of a semiconductor device.

The second problem is that etching products are easily deposited on the ceiling of the bell jar of the helicon wave plasma processing apparatus, and it is difficult to clean the inside of the bell jar because of its elongated shape. The reason is that only the ceiling is particularly cooled by receiving the wind from the cooling fan arranged on the ceiling of the bell jar, and the top is projected about 60 mm above the loop antenna. And the like, there is almost no sputtering effect of the deposit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma processing apparatus in which no etching residue is generated during etching using a photoresist and the photoresist can be selectively etched. Another object of the present invention is to provide a plasma processing apparatus that makes it difficult for deposits to adhere to a bell jar and that makes it easy to remove the attached deposits. Another object of the present invention is to provide an etching method capable of etching a metal wiring with a high selectivity.

[0009]

The plasma processing apparatus of the present invention is characterized in that the height of the cylindrical vacuum vessel constituting the plasma source section is 60 mm or less. In particular, it is preferable that the height of the cylindrical vacuum vessel is 35 nm or less from the upper end of the antenna. Alternatively, the cylindrical vacuum vessel may be configured as a flat plate having a height of zero. Here, a process chamber is provided below the plasma source unit, and a means for generating a magnetic field, and an electrode on which a sample is mounted and to which high-frequency power is applied are arranged in the process chamber. The plasma generated in the section is configured to be introduced. Further, this plasma processing apparatus is applied as an etching apparatus for selectively etching a metal wiring using a resist as a mask.

Further, according to the etching method of the present invention, an ion saturation current density of 15 m
Dry etching is performed on aluminum and aluminum alloy used for metal wiring at A / cm ² or more. Furthermore, using a process gas containing chlorine, the ion saturation current density is 15 mA / cm ² or more, preferably 3 mA / cm ² or more.
TiN or T used for metal wiring at 5 mA / cm ² or more
A barrier metal such as iW is etched and over-etched.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a first embodiment of the present invention, in which the inner diameter is 100 mm, which is almost the same as the conventional one, but the height of the cylindrical quartz bell jar 1 is 30 mm, which is shorter than the conventional one. An antenna coil 2 connected to a power supply 3 is arranged around the unit, and two pairs of electromagnetic coils 4 for generating a magnetic field are installed therearound to form a plasma source unit. A process chamber 5 is continuously provided below the plasma source section as in the past. A wafer 8 can be placed on the upper surface of the process chamber 5 and high frequency power is applied from a power source 6. A wafer mounting electrode 7 is provided, and a magnet 9 for generating a magnetic field is provided around the wafer mounting electrode 7.

In the plasma processing apparatus configured as described above, the plasma characteristics and the etching characteristics were measured. FIG. 2 shows the result of the source power dependence of the ion saturation current density. For comparison, the results for a conventional helicon wave plasma source are also shown. The discharge conditions were as follows: gas flow rate: Cl ₂ / BCl ₃ = 80 sccm / 20
sccm, pressure 10 mTorr, magnetic field coil current: IN
/ OUT = 40A / 40A (10 near the antenna coil
0 G) and a bias power of 140 W. For the plasma diagnosis, a position about 180 mm (about 25 mm above the wafer) from the bottom of the bell jar was measured using a Langmuir probe. As shown by these results, at a pressure near 10 mTorr, a bell jar having a height of 30 mm provided a higher plasma density than the conventional helicon wave plasma source, and the difference became more pronounced as the source power increased.

Further, the relationship between the ion saturation current density and the state of generation of residues when etching was performed by the apparatus using the bell jar of this embodiment was examined. The result is shown in FIG. The discharge conditions and plasma analysis conditions at this time are the same as those in FIG. As is apparent from these results, the conventional helicon wave plasma source could not suppress the residue at all even when the source power of 2500 W was applied, whereas the bell jar of this embodiment having a height of 30 mm had a source power of at least 2000 W. Is applied, it is possible to suppress the residue on the entire surface of the 6-inch wafer.

Further, when the etching characteristics at a source power of 2500 W were examined, the Al etching rate was 1.08 μm / min, the Al etching uniformity within a 6-inch wafer plane was ± 3.3%, and the resist selectivity was 2%. .7
Met.

[0015] In order to investigate the state of devo- sion adhering to the inner wall of the bell jar 1 due to the plasma treatment,
The degree of contamination on the inner wall of the bell jar after continuous etching of about 5000 wafers was visually confirmed. The structure of the wafer used for continuous etching is PR (photoresist)
/ AlSiCu / base SiO ₂ , and the discharge conditions are the same as in FIG. As a result, no devotion was observed on the inner wall of the bell jar.

Next, a second embodiment will be described.
FIG. 4 is a schematic diagram of the second embodiment. 150m diameter
A flat plate 11 made of quartz having a thickness of 5 mm and a thickness of 5 mm is placed on the ceiling of the plasma processing chamber, an antenna coil 12 connected to a power supply 13 is placed 8 mm above the plate, and two pairs of electromagnetic coils 14 are placed around the antenna coil 12. A plasma processing apparatus having a plasma source unit was prepared. On the lower side of the plasma source section, as in the first embodiment, a wafer 18 is placed and an electrode 17 to which high-frequency power is applied, a power supply 16, and a magnet 19.
Is provided.

The plasma characteristics and the etching characteristics when using this apparatus were examined. FIG. 5 shows the result of the source power dependence of the ion saturation current density. For comparison, the results of a conventional helicon wave plasma source and an apparatus using a 30 mm bell jar are also shown. The discharge conditions were as follows: gas flow rate: Cl ₂ / BCl ₃ = 80 sccm / 20 scc
m, pressure 10 mTorr, magnetic field coil current: IN / OU
T = 40A / 40A (about 100G near the antenna coil) and bias power 140W. Using a Langmuir probe for plasma diagnosis, a position at about 180 mm (about 25 mm above the wafer) from the bottom of the bell jar was measured.
As shown by these results, at a pressure near 10 mTorr, a higher plasma density is obtained as the bell jar length is shortened, and the difference becomes more pronounced as the source power increases.

Further, three types of discharge parts, ie, a conventional type (a bell jar height of 200 mm) and a shortened type (a bell jar height of 3 mm).
0 mm) and a flat plate type (bell jar height: 0 mm) were examined for the relationship between the ion saturation current density and the state of generation of residues when etching was performed. FIG. 6 shows the result. The discharge conditions and plasma analysis conditions at this time are the same as those in FIG. As is evident from this result, by shortening the bell jar length, a high ion saturation current density region that could not be obtained with the conventional helicon wave plasma source was obtained, there was no residue, and the photoresist was etched with high selectivity. It becomes possible to do. In particular, when a metal wiring is etched with a program gas containing chlorine at an ion saturation current density of 15 mA / cm ² or more, the resist mask can be processed with high selectivity without generating a residue. It is possible.

Further, when the etching characteristics at a source power of 2500 W were examined, the Al etching rate was 1.05 μm / min, the Al etching uniformity within a 6-inch wafer surface was ± 3.9%, and the resist selectivity was 3%. .0
Met.

In order to investigate the state of deposition adhering to the surface of the quartz flat plate by the plasma treatment, 5
The degree of contamination on the surface of the quartz flat plate after continuous etching of about 000 sheets was visually checked. The structure of the wafer used for the continuous etching is PR / AlSiCu / SiO underlayer.
₂ and the discharge conditions are the same as in FIG. As a result, no deposition was observed on the surface of the quartz flat plate.

Here, a quartz bell jar is used in the first embodiment, but the same effect has been confirmed even when the material of the bell jar is alumina ceramic. Similarly, although a flat plate made of quartz is used in the second embodiment, the same effect has been confirmed even when the material of the flat plate is alumina ceramic.

As can be seen from the bell jar structure of the first and second embodiments as described above, the apparatus of each embodiment has a structure in which the height of the bell jar is reduced as compared with the conventional helicon wave plasma processing apparatus. As a result, the plasma generating section is located lower than in the prior art, and has a structure in which ions and radicals can be easily introduced into the process chamber. Therefore, diffusion loss to the inner wall of the bell jar is small, and the plasma density near the wafer is increased.

FIG. 7 shows a conventional helicon wave plasma, a plasma of a plasma processing apparatus using a bell jar having a low height shown in FIG. 1, and a plasma processing apparatus using a flat plate made of a dielectric shown in FIG. FIG. 6 compares the pressure dependence of the ion saturation current densities of the respective plasmas. As shown in the figure, a higher ion saturation current density is realized as the height of the bell jar is reduced. In particular, in the case of plasma of a plasma processing apparatus using a plate made of a dielectric,
Even in a pressure region such as 5 mTorr, the ion saturation current density hardly decreases. Therefore, an amount of ions sufficient to suppress the etching residue can be obtained. Further, since the height of the bell jar in the present apparatus is lower than that of the conventional one, the temperature uniformity of the entire bell jar is improved, and deposits are less likely to adhere to the bell jar ceiling. Even if the deposits adhere, they can be easily removed because they are easily cleaned.

Next, a third embodiment will be described. Here, ions obtained when the etching process is performed by respective devices using three types of discharge parts, that is, a conventional type (bell jar height 200 mm), a shortened type (bell jar height 30 mm), and a flat plate type (bell jar height 0 mm). The relationship between the saturation current density and the photoresist etching rate and the relationship between the ion saturation current density and the state of generation of the etching residue were examined, and the results are shown in FIG. The discharge conditions were as follows: gas flow rate: Cl ₂ /
BCl ₃ = 80 sccm / 20 sccm, pressure 10 mT
orr, magnetic field coil current: IN / OUT = 40A / 40
A (about 100 G near the antenna coil) and a bias power of 140 W. As shown in the figure, the ion saturation current density is up to 8 mA / cm ² with increasing the ion saturation current density, but also increase photoresist etch rate, ion saturation current density ion at 8 mA / cm ² or more regions As the saturation current density increases, the photoresist etching rate tends to decrease.

Next, the value of the ion saturation current density at which residues are generated in the AlSiCu alloy is examined. The value differs depending on the wafer temperature. The value is less than 15 mA / cm ² when the wafer temperature is 60 ° C. and less than 90 mA when the wafer temperature is 90 ° C. less than 8 mA / cm ^2, when the 110 ° C. had occurred less than 6 mA / cm ^2. From these results, in order to perform highly selective etching on the photoresist without generating residues, it is advantageous to have a high ion saturation current density, and the wafer temperature region normally used is about 60 ° C. or higher. Considering
It can be seen that the ion saturation current density is desirably 15 mA / cm ² or more. Similar results were obtained when the pressure was 4 mTorr. It has been confirmed that similar results can be obtained in the case of an aluminum alloy containing no Si.

Next, a fourth embodiment will be described. Here, ions obtained when the etching process is performed by respective devices using three types of discharge parts, that is, a conventional type (bell jar height 200 mm), a shortened type (bell jar height 30 mm), and a flat plate type (bell jar height 0 mm). Saturation current density and Al
The relationship between the Cu film, the TiN film, the SiO ₂ film, and the photoresist etching rate when each of the films was etched was examined, and the results are shown in FIG. The discharge conditions were as follows: gas flow rate: Cl ₂ / BCl ₃ = 80 sccm / 20 scc
m, pressure 10 mTorr, magnetic field coil current: IN / OU
T = 40A / 40A (about 100G near the antenna coil) and bias power 140W. As shown in the figure, the photoresist etching rate increases with an increase in the ion saturation current density up to an ion saturation current density of 10 mA / cm ^2, but increases in a region of 15 mA / cm ² or more. As a result, the photoresist etching rate tends to decrease significantly. Further, as the plasma density increases, the dependency on the etching material tends to decrease.

Further, as shown in FIG.
Looking at the ion saturation current density dependence of the etching rates of the Cu film, TiN film, and SiO ₂ film, it can be seen that the tendency of the decrease is slower than the etching rate of the photoresist. As a result, the selectivity to resist shown in FIG. 11 was improved from 0.7 to 1.5 and the selectivity to SiO ₂ was improved from 0.2 to 1.0 as the plasma density was increased. Is done. In particular, 35 mA / c
Above m ² , the selectivity of SiO ₂ to resist increases significantly. Similar results were obtained for the TiW film. This shows the effectiveness in barrier metal etching and over-etching when high-density plasma of 15 mA / cm ² or more containing chlorine processes a metal wiring having a laminated structure by dry etching.

Here, in order to find the optimum height of the bell jar in the present invention, the relationship between eight different heights of the bell jar and the obtained ion saturation current density was examined. FIG. 12 shows the result. The height of the bell jar was represented by the height from the upper end of the antenna. The etching conditions were almost the same as in the first embodiment, but the pressure was 7 mTorr. As a result, to obtain a high-density plasma, the height of the bell jar should be 60 m.
m or less, especially the height of the bell jar is 35 m from the top of the antenna.
It has been found that setting the value to m or less is extremely effective.

[0029]

As described above, according to the present invention, the height of the cylindrical vacuum vessel constituting the plasma source part is 60 mm or less, preferably 35 nm or less from the upper end of the antenna, or the cylindrical vacuum vessel is high. Since it is configured as a flat plate having a thickness of 0 m, the plasma density near the wafer can be increased in a pressure region of 10 mTorr to 20 mTorr, and the residue can be formed even at a pressure of 10 mTorr to 20 mTorr, which enables a highly selective process for photoresist. Can be suppressed. In particular, by performing treatment with a plasma having an ion saturation current density of 15 mA / cm ² or more, highly selective etching of a metal wiring with respect to a resist mask can be performed without generating a residue. The reason is that the adoption of a low-height bell jar or a flat plate made of a dielectric material causes the plasma source section to be located lower than before, and has a structure in which ions and radicals are easily introduced into the process chamber. This is because the diffusion loss is reduced, and a plasma with a higher density than before can be obtained. That is, in principle, this etching method can be performed by any apparatus that can obtain the same high-density plasma.

Further, according to the present invention, deposition is less likely to be deposited on the ceiling of the bell jar, and the deposited deposition can be easily removed, so that the problem of dust generated from the ceiling of the bell jar can be reduced. . The reason is,
This is because the temperature uniformity of the bell jar or the entire flat plate is improved by using a bell jar or a flat plate made of a dielectric material which is significantly lower than the conventional one.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the source power dependence of the ion saturation current density in the conventional and the helicon plasma sources of FIG. 1;

3 is a diagram showing a relationship between a resist selectivity and a residue generation region in the conventional and helicon plasma sources of FIG. 1;

FIG. 4 is a schematic configuration diagram of a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the source power dependence of the ion saturation current density in the conventional and helicon plasma sources of FIG. 4;

FIG. 6 is a diagram showing the relationship between the resist selectivity and the residue generation region in the conventional and the helicon plasma sources of FIGS. 1 and 4;

FIG. 7 is a diagram showing the pressure dependence of the ion saturation current density in the conventional and the helicon plasma sources of FIGS. 1 and 4;

FIG. 8 is a diagram showing a relationship between a photoresist etching rate and a residue generation region in the conventional and the helicon plasma sources of FIGS. 1 and 4;

FIG. 9 is a diagram showing the ion saturation current density dependence of the photoresist etching rate in the conventional and the helicon plasma sources of FIGS. 1 and 4;

FIG. 10 is a diagram showing the ion saturation current density dependence of the photoresist etching rates of AlCu, TiN, and SiO _{2 in} the conventional and the helicon plasma sources of FIGS. 1 and 4;

FIG. 11 is a diagram showing the ion saturation current density dependence of the resist selectivity ratio of AlCu, TiN, and SiO _{2 in} the conventional and helicon plasma sources of FIGS. 1 and 4;

FIG. 12 is a diagram showing a relationship between a height from an RF antenna upper end to a bell jar upper end and an obtained ion saturation current density.

FIG. 13 is a schematic configuration diagram of a conventional helicon plasma etching apparatus.

14 is a diagram showing the pressure dependence of the selectivity to resist and the ion saturation current density in the helicon plasma source of FIG. 13;

FIG. 15 is a diagram showing source power dependence of a resist selectivity and an ion saturation current density in the helicon plasma source of FIG. 13;

[Explanation of symbols]

 Reference Signs List 1 bell jar 2 antenna coil 4 magnetic coil 5 process chamber 7 wafer mounting electrode 8 wafer 9 magnet 11 flat plate 12 antenna coil 14 magnetic coil 15 process chamber 17 wafer mounting electrode 18 wafer 19 magnet

Claims (8)

[Claims] 1. A plasma generating apparatus comprising: a cylindrical vacuum vessel made of a dielectric; an antenna disposed around the vacuum vessel to which high-frequency power is applied; and an electromagnetic coil disposed around the vacuum vessel. A plasma processing apparatus having a plasma source unit to be operated, wherein the height of the cylindrical vacuum vessel is 60 mm or less. 2. The plasma processing apparatus according to claim 1, wherein the height of the cylindrical vacuum vessel is 35 mm or less from the upper end of the antenna. 3. The plasma processing apparatus according to claim 1, wherein the cylindrical vacuum vessel is configured as a flat plate having a height of 0 mm. 4. The plasma processing apparatus according to claim 1, wherein the cylindrical vacuum vessel or the flat plate is made of quartz or alumina ceramics. 5. A process chamber is connected to a lower portion of the plasma source section. In the process chamber, means for generating a magnetic field and an electrode on which a sample is placed and to which high-frequency power is applied are arranged. 5. The plasma processing apparatus according to claim 1, wherein plasma generated in the source section is introduced. 6. The plasma processing apparatus according to claim 5, wherein said apparatus is an etching apparatus for selectively etching a metal wiring using a resist as a mask. 7. A method for etching metal wiring, comprising dry-etching aluminum and an aluminum alloy used for metal wiring at an ion saturation current density of 15 mA / cm ² or more using a process gas containing chlorine. 8. An ion saturation current density of 15 mA / cm ² or more, preferably 35 mA, using a process gas containing chlorine.
TiN or Ti used for metal wiring at mA / cm ² or more
A method for etching a metal wiring, comprising etching a barrier metal such as W and over-etching.