JP4608827B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and a plasma processing method for performing plasma processing such as plasma etching, and more particularly to improvement of a method for introducing a gas into a chamber.
[0002]
[Prior art]
With the high integration of semiconductor devices, high-precision microfabrication technology is required, while productivity is also being emphasized from the viewpoint of economic efficiency. Therefore, for example, in the dry etching process, which is one of the manufacturing processes of semiconductor devices, a high etching selectivity and a high etching rate are realized by adopting a dry etching method using high-density plasma, and a high-precision fine pattern is realized. Attempts have been made to achieve both processing and high productivity.
[0003]
In recent years, for the purpose of improving productivity, the wafer size has been increased from 200 mm to 300 mm, and further to 400 mm, and the area to be etched has gradually increased. Therefore, the dry etching method using high-density plasma is It tends to be used more and more. As an etching apparatus for performing dry etching using high-density plasma, for example, an RF bias application type ECR plasma etching apparatus, an inductively coupled (ICP) type plasma etching apparatus, a helicon wave type plasma etching apparatus, and the like have been developed. It is used in various areas.
[0004]
[Problems to be solved by the invention]
By the way, important points in the etching process are high-speed processing and high selectivity between the mask material and the base, and that the etching rate and etching profile are uniform over the entire wafer surface.
[0005]
In order to realize high-speed processing, it is necessary that the number of etchants such as radicals and ions is large. For this purpose, high-density plasma as described above is required. However, in the high-density plasma, the etchant dissociates excessively, and as a result, etching different from the original etching proceeds and the selectivity is lowered. For example, in the etching of an oxide film, it is difficult to ensure a sufficient selection ratio with the mask material resist and the underlying Si and SiN.
[0006]
With respect to uniformity, the key is how to introduce the etching gas into the chamber, and in general, it is advantageous to improve the uniformity by installing a shower head provided with a number of gas ejection holes above the wafer. It is considered to be. This shower head is desirably located as close as possible to the wafer. However, for example, in a large-diameter wafer, the ratio of highly depositable gas tends to be high in the center portion of the wafer, and etching is uniform. There is concern that sex will deteriorate. In particular, in the case of an inductively coupled (ICP) plasma source, when the plasma source is close to the wafer, the shape depending on the antenna shape is deteriorated, and the portion near the antenna has a high electron temperature and there is a concern about excessive dissociation or damage. Is done.
[0007]
The present invention has been proposed in view of such conventional circumstances, and provides a plasma processing apparatus and a plasma processing method capable of performing plasma processing with excellent uniformity and capable of dealing with various processes. With the goal. It is another object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of realizing highly selective etching without excessive dissociation of the introduced gas and simultaneously realizing high-speed processing.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the plasma processing apparatus of the present invention, a plasma source electrode and a substrate to be processed are disposed opposite to each other in a chamber, and an etching gas is introduced between the plasma source electrode and the substrate to be processed. The gas supply means for this is arrange | positioned, It is characterized by the above-mentioned. Further, the plasma processing method of the present invention has a gas supply means for introducing an etching gas between the plasma source electrode and the substrate to be processed while the plasma source electrode and the substrate to be processed are disposed opposite to each other in the chamber. It arrange | positions and the said to-be-processed substrate is plasma-processed, It is characterized by the above-mentioned.
[0009]
In the above configuration, the gas supply means can be installed at a close distance of the substrate to be processed, and uniform plasma processing is realized. At this time, since the plasma source electrode does not need to be close to the substrate to be processed, the shape is not deteriorated, and excessive dissociation and damage are avoided. In addition, by designing the gas supply means, a process with good uniformity can be easily obtained corresponding to various processes.
[0010]
In particular, when the gas supply means introduces a bulk gas to the plasma source electrode side and introduces an etching gas containing a gas acting as an etchant to the substrate to be processed, and plasma treatment is performed, excessive dissociation of the etching gas is caused. Highly selective plasma processing (etching) is realized. At this time, high-speed processing using high-density plasma is also realized at the same time.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plasma processing apparatus and a plasma processing method to which the present invention is applied will be described in detail with reference to the drawings. In the following description, the configuration of the plasma etching apparatus and the plasma etching method will be described as an example.
[0012]
In the plasma etching apparatus of this example, as shown in FIG. 1, a wafer 3 that is a substrate to be processed is placed in a vacuum chamber 1 while being supported by a wafer support member 2, and is opposed to the wafer 3. A plasma source electrode 4 is provided on the vacuum chamber 1. Further, a process gas introduction jig 5 serving as a gas supply means is installed between the wafer 3 and the plasma source electrode 4, and the process gas is supplied therefrom.
[0013]
Examples of applicable plasma etching apparatuses include an RF bias application type ECR plasma etching apparatus, an inductively coupled (ICP) type plasma etching apparatus, and a helicon wave type plasma etching apparatus. For example, in an ICP type plasma etching apparatus, UHF band electromagnetic waves are introduced into the vacuum chamber 1 using a microstrip type electromagnetic radiation antenna to generate plasma, and the silicon on the surface of the wafer 3 installed in the vacuum chamber 1 An oxide film is etched. Therefore, the plasma source electrode 4 is an upper plate provided with an antenna. Needless to say, the present invention is not limited to this and can be applied to various plasma etching apparatuses.
[0014]
A characteristic of the present invention is that a process gas introduction jig 5 as a gas supply means is installed between the wafer 3 and the plasma source electrode 4. Process gas is introduced from below. Until now, there has been no example of introducing process gas from such a position.
[0015]
Here, the gas blown upward from the process gas introduction jig 5, that is, toward the plasma source electrode 4 is a bulk gas such as Ar. Although this bulk gas is necessary for generating plasma, it is not necessary to consider dissociation, and even if it is excessively dissociated, it does not affect the selectivity of etching.
[0016]
On the other hand, the gas blown downward from the process gas introduction jig 5, that is, toward the wafer 3 is an etching gas containing a gas acting as a so-called etchant. Examples of the gas that acts as an etchant include fluorocarbon gases such as C ₄ F ₈ . These fluorocarbon gases are dissociated excessively when exposed to plasma having a high molecular weight and a high electron temperature, for example, CF ₂ and fluorine. The dissociated CF ₂ and fluorine radicals and ions exhibit etching characteristics different from those of C ₄ F ₈ radicals and ions that originally function as an etchant. For example, in oxide film etching, the mask material resist, the underlying Si, SiN, etc. It is difficult to obtain a selection ratio of
[0017]
As described above, if the etching gas containing the etchant is blown out from the process gas introduction jig 5 toward the opposite side of the plasma source electrode 4, the etching gas is introduced into the low electron temperature region below the vacuum chamber 1. The excessive dissociation of the gas acting as the etchant is suppressed. Further, since the distance between the process gas introduction jig 5 and the wafer 3 is short, the etching gas reaches the wafer 3 before the progress of dissociation proceeds excessively. Therefore, for example, in the oxide film etching, it is possible to obtain a high selection ratio with respect to the mask material and the base.
[0018]
The process gas introduction jig 5 is installed between the wafer 3 and the plasma source electrode 4, and the position (particularly, the height h with respect to the wafer 3) can be set arbitrarily. Therefore, only the process gas introduction jig 5 can be brought close to the closest distance of the wafer 3 without bringing the plasma source electrode 4 close to the wafer 3. As a result, uniform etching characteristics can be obtained by uniform gas introduction with the same effect as the shower head while avoiding the influence due to the plasma non-uniformity depending on the antenna shape, which is a problem in the ICP type plasma etching apparatus, for example. Can do. In particular, even in a large-diameter wafer having a diameter of 300 mm or more, which is likely to cause non-uniformity due to gas introduction at the center and the edge, uniform etching characteristics can be obtained, and the effect is great.
[0019]
The process gas introduction jig 5 is supplied with two kinds of gases, a bulk gas blown toward the plasma source electrode 4 and an etching gas blown toward the wafer 3. Each gas is controlled by a mass flow controller, and its composition and flow rate are set. For example, in the etching apparatus shown in FIG. 1, the bulk gas blown toward the plasma source electrode 4 is mixed and introduced by the mass flow controllers 6a and 6b. Similarly, as the etching gas blown toward the wafer 3, four types of gases are mixed and introduced by the mass flow controllers 7a, 7b, 7c, and 7d.
[0020]
Here, by adjusting each mass flow controller and controlling the composition and flow rate of the bulk gas flowing upward and the composition and flow rate of the etching gas flowing downward according to a predetermined setting (recipe), various processes can be handled. Is possible. Also, various processes can be handled by changing the height h of the process gas introduction jig 5. Furthermore, the process gas introduction jig 5 is provided with a plurality of gas blowing directions and speeds which are constantly changed, and by using the optimum one according to the processing process, it is easy to obtain uniform uniformity for various processes. Process can be realized.
[0021]
In the plasma etching apparatus having the above-described configuration, it is necessary to introduce two kinds of gases from the process gas introduction jig 5, and it is necessary to devise the structure of the process gas introduction jig 5 correspondingly. Therefore, a structural example of the process gas introduction jig 5 will be described below.
[0022]
As shown in FIG. 2, the process gas introduction jig 5 includes linear main paths 11 and 12 for supplying the respective gases and an annular branch path 13. The main path 11 and the main path 12 are arranged so as to be orthogonal to each other, and communicate with the branch path 13 so as to penetrate the branch path 13.
[0023]
In the branch path 13, a plurality of annular gas blowing pipes 13 a, 13 b, 13 c, and 13 d having different diameters are concentrically arranged so that gas is evenly supplied to the large-diameter wafer 3. It has been devised. Here, the number of the gas blowing pipes 13a, 13b, 13c, and 13d is preferably larger from the viewpoint of uniformity of gas introduction. Further, when it is desired to positively separate the upper and lower plasmas of the process gas introduction pipe 5, it is preferable that the number of the gas blowing pipes 13a, 13b, 13c, 13d is large. Conversely, when it is desired to reduce the influence on the plasma, it is preferable that the number of the gas blowing pipes 13a, 13b, 13c, and 13d is small. In this example, the number of gas blowing pipes 13a, 13b, 13c, and 13d is four.
[0024]
Each of the gas blowing pipes 13a, 13b, 13c, and 13d has a double structure and adopts a structure in which a bulk gas and an etching gas can be separately introduced. FIG. 3 shows the structure of each gas blowing tube 13a, 13b, 13c, 13d. As shown in FIG. 3, each gas blowing tube 13a, 13b, 13c, 13d is formed with a first semi-tubular member 21 in which a groove 21a serving as a bulk gas passage is formed and a groove 22a serving as an etching gas passage. The second semi-tubular member 22 is joined via a partition plate 23, and the space formed by the groove 21a and the space formed by the groove 22a are The partition plates 23 form independent gas introduction paths. The first semi-tubular member 21 and the second semi-tubular member 22 have gas blowing holes 21b and 22b arranged in an array along substantially the center of the grooves 21a and 22a.
[0025]
Therefore, for example, bulk gas is introduced from the main path 11 and passes upward from the gas blowing holes 21b through the upper grooves 21a in the two-story structure of the gas blowing pipes 13a, 13b, 13c, and 13d (plasma). Blowing out (toward the source electrode 4). The etching gas is introduced from the main path 12 and blown downward (toward the wafer 3) from the gas blowing holes 22b through the lower grooves 22a of the gas blowing pipes 13a, 13b, 13c, and 13d.
[0026]
The material of the annular gas blowing pipes 13a, 13b, 13c, and 13d constituting the branch path 13 is preferably Si, SiC, or the like for the purpose of actively trapping F radicals and the like. For example, if the material of the gas blowing pipes 13a, 13b, 13c and 13d is Si and is provided in the immediate vicinity of the wafer 3, the gas blowing pipes 13a, 13b, 13c and 13d are sputtered by F, and F is SiF. It is scavenged. As a result, even if F radicals and F ions are generated due to excessive dissociation, the original etching is not adversely affected. Further, since it is not necessary to impose such a role on the plasma source electrode 4 (upper plate provided with an antenna), the material of the upper plate can be a non-consumable material. In the above, the gas blowing pipes 13a, 13b, 13c, and 13d may be made of a consumable material such as Si or SiC, or only the lower semi-tubular member 22 may be a consumable material such as Si, The tubular member 21 can also be a non-consumable material such as quartz, aluminum alumite, or ceramic.
[0027]
Next, an actual usage example of the process gas introduction jig will be described. This example is a usage example when an oxide film is etched in an ICP type plasma etching apparatus. Settings in the ICP type plasma etching apparatus are as follows.
Source antenna power: frequency 13.56 MHz, power 2 kW
Lower electrode bias power: frequency 800 kHz, power 500 kW
Pressure: 100mTorr
Upper stage introduction (upward ejection) Bulk gas flow rate: CO 200 sccm, Ar 500 sccm
Lower stage introduction (downward ejection) Etching gas flow rate: CHF ₃ 5 sccm, C ₄ F _{8 10} sccm, CO 100 sccm
[0028]
In this example, CHF ₃ and C ₄ F ₈ gases for which dissociation is to be suppressed are introduced into the lower region of the electron temperature, and Ar (bulk gas) for plasma generation is ejected toward the upper plate. As a result, uniform etching could be realized without deteriorating the selection ratio due to excessive dissociation of CHF ₃ and C ₄ F ₈ gases.
[0029]
The plasma processing apparatus and the plasma processing method to which the present invention is applied have been described above, but the present invention is not limited to these examples, and various modifications can be made without departing from the scope of the present invention. Needless to say. For example, in the above description, the plasma etching apparatus and the plasma etching method have been mainly described. However, the present invention can be applied to plasma processing apparatuses and plasma processing methods in general, such as a plasma CVD apparatus and a plasma CVD method. Further, the gas introduced from the process gas introduction jig does not necessarily need to be divided into upper and lower parts, but simply supply the process gas from between the upper plate and the wafer, for example, adjusting the position of the process gas introduction jig. A certain effect can be obtained.
[0030]
【The invention's effect】
As is clear from the above description, according to the plasma processing apparatus and the plasma processing method of the present invention, the bulk gas is introduced directly under the upper plate (plasma source electrode) having a high electron temperature, and the process gas is excessively dissociated. In order to reach a position just above the wafer (substrate to be processed) before proceeding to (5), for example, when performing plasma etching, a high selection ratio can be obtained with respect to the mask material and the stop material.
[0031]
In addition, since the introduction of gas can be installed directly on the wafer without bringing the upper plate close to the wafer, the influence of plasma non-uniformity depending on the antenna shape of the upper plate, for example, is small and uniform due to the same effect as the shower head. Uniform treatment can be realized by introducing gas. In particular, even in a large diameter wafer having a diameter of 300 mm or more, which tends to deteriorate uniformity due to the influence of gas introduction at the center and the edge, uniform processing characteristics can be realized.
[0032]
Furthermore, in the present invention, it is possible to cope with various processes by controlling the composition and flow rate of the gas flowing upward and the composition and flow rate of the gas flowing downward according to the recipe. Also, various processes can be handled by changing the installation position (installation height) of the process gas introduction jig as the gas supply means.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration example of a plasma etching apparatus to which the present invention is applied.
FIG. 2 is a schematic perspective view showing an example of a process gas introduction jig.
FIG. 3 is a schematic perspective view of a main part of a structure example of an annular gas blow-out pipe, partially broken away.
[Explanation of symbols]
1 vacuum chamber, 3 wafer, 4 plasma source electrode, 5 process gas introduction jig, 11, 12 main path, 13 branch path, 13a, 13b, 13c, 13d gas blowing pipe, 21, 22 semi-tubular member, 21b, 22b Gas blowout hole

Claims (5)

A plasma source electrode and a substrate to be processed are disposed opposite to each other in the chamber, gas supply means for introducing an etching gas is disposed between the plasma source electrode and the substrate to be processed, and the gas supply means includes the plasma A gas introduction hole for blowing gas to the source electrode side; and a gas introduction hole for blowing gas to the substrate to be processed; the composition of the gas blown from the gas introduction hole on the plasma source electrode side; The gas blown out from the gas introduction hole on the plasma source electrode side is different from the composition of the gas blown out from the gas introduction hole on the substrate side, and is a bulk gas for generating plasma. The plasma processing apparatus characterized in that the gas blown out from the introduction hole contains a gas acting as an etchant . The plasma processing apparatus according to claim 1, wherein gas acting as the etchant characterized in that it is a fluorocarbon-based gas. With the plasma source electrode and the target substrate to face disposed in the chamber, a gas supply means for introducing an etching gas between these plasma source electrode and the substrate to be processed placed, by the gas supply means, the plasma A plasma processing method, wherein a bulk gas is introduced into a source electrode side and an etching gas containing a gas acting as an etchant is introduced into a substrate to be processed, and the substrate to be processed is subjected to plasma treatment. 4. The plasma processing method according to claim 3 , wherein a fluorocarbon gas is used as the gas acting as the etchant. The plasma processing method according to claim 3 , wherein the plasma processing is plasma etching.

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