JPS6126366Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a plasma etching apparatus that can etch an etching sample with good uniformity in the production of semiconductor integrated circuits and the like.

A conventional plasma etching apparatus will be explained with reference to FIG. In FIG. 1, an upper electrode 2 and a lower electrode 1 are placed facing each other with an appropriate distance in an etched chamber 4 made of aluminum or stainless steel, and the output from a high frequency power source 7 is connected to a matching circuit. 6 to either the upper electrode 2 or the lower electrode 1, and the other one is grounded. Note that 5 is an insulator.

In the plasma etching apparatus shown in FIG. 1, after the etching chamber 4 is evacuated to a certain degree of vacuum, a fluorine-based and chlorine-based etching gas such as CF ₄ or CCI ₄ is introduced, and 1×
A high frequency power of about 10 ^to 2 KW is applied between the upper electrode 2 and the lower electrode 1 at a pressure of 10 -2 to 10 torr to generate plasma and remove the sample on the lower electrode 1, for example.
A semiconductor wafer as an etching sample 3 having Si, SiO ₂ , Si ₃ N ₄ , chromium, etc. formed on its surface is etched.

This plasma etching apparatus is called a parallel plate type plasma etching apparatus, and compared to plasma etching apparatuses with cylindrical electrodes that were mainstream before this, an electric field of the same intensity is applied perpendicularly to the etching sample at any position. Because of this, it is easy to obtain etching with a relatively uniform distribution of etching speed within the lower electrode, and an etching pattern with less undercuts (side etching) can be obtained, so it is widely used in the fabrication of patterns for semiconductor integrated circuits.

However, in the conventional structure described above, the etching speed generally slows down or speeds up concentrically in the radial distance direction from the center of the etching sample 3, that is, the circular lower electrode 1, as shown in FIG. This results in non-uniformity as indicated by H.

Therefore, when used for etching semiconductor integrated circuits, if etching is carried out until the entire surface of the etching sample 3 is etched, the dimensions of the pattern obtained after etching will be larger depending on the part where etching is completed quickly and the part where etching is completed later. It makes a difference〓〓〓〓〓
There was a drawback that it was difficult to use.

Generally, as a measure to improve the above, conditions with good uniformity are set by changing the type and flow rate of etching gas, uniformity of the flow of etching gas (air supply port, exhaust port), etching pressure, high frequency power, etc. However, in this case, by changing the above items, the etching characteristics, that is, the etching rate, the amount of side etching (undercut), and the selectivity of the etching rate relative to other films (the underlying film of the sample and the resist used as a mask) can be changed. membrane or
Important properties such as SiO 2 films (e.g. SiO ₂ films) also change. The conditions for uniform etching rate distribution and the conditions for obtaining the necessary etching characteristics are not necessarily the same, and the current situation is to find conditions that are a compromise between the two.

This idea was made to solve the above-mentioned drawbacks of the conventional etching properties.It maintains optimal conditions such as pressure, etching gas, and high-frequency power to obtain the necessary etching characteristics, while achieving a uniform in-plane etching rate distribution. It is an object of the present invention to provide a plasma etching apparatus capable of obtaining the following characteristics.

An embodiment of the plasma etching apparatus of this invention will be described below with reference to FIG. FIG. 3 shows the configuration of its main parts, and is an enlarged cross-sectional view of the upper electrode and lower electrode. This third
In the figure, the same parts as in FIG. 1 will be described with the same reference numerals. 1 is the lower electrode (sample stage), 2 is the upper electrode, 3 is the etching sample 3
These conductor wafers are placed in an etching gas at a certain degree of vacuum, and high frequency power is applied between the upper electrode 2 and the lower electrode 1 to generate plasma and etch the etching sample 3.

In this example, in the conventional case where both the upper electrode 2 and the lower electrode 1 shown in FIG. If the etching rate decreases concentrically in the distance direction, this is corrected in order to make the etching rate distribution uniform.

Flat circular lower electrode 1 and etching sample 3
On the other hand, the upper electrode 2 is installed so as to have a concave curved surface facing each other at an appropriate distance from each other on the same central axis.

When high-frequency power is applied between the upper electrode 2 and the lower electrode 1 to generate plasma, the plasma intensity and the electric field intensity are concentric with the surfaces of the lower electrode 1 and the etching sample 3 in a radial distance direction from the central axis. The distribution becomes stronger.

As a result, the etching rate increases in this direction, and as a result, it is possible to obtain a highly uniform in-plane etching rate distribution as shown in FIG. 5.

As explained above, in the first embodiment, the in-plane distribution of the etching rate is made uniform by the curvature of the concave surface of the upper electrode 2, which has a concave surface disposed opposite to the surfaces of the lower electrode 1 and the etching sample 3. This is achieved by taking the appropriate values.

In this case, as the curvature of the concave surface becomes steeper, that is, in the radial distance direction from the central axis, and as the distance between the upper and lower electrodes becomes shorter, the etching rate increases concentrically in this direction.

Therefore, a uniform in-plane distribution of etching rate can be obtained by appropriately adjusting the curvature of the concave surface of the upper electrode 2.
Etching conditions such as etching vacuum and high frequency power do not need to be set in order to obtain a uniform in-plane distribution of etching speed, but the required etching characteristics, that is, etching speed, side etching amount (undercut amount), selectivity (with respect to the underlying layer), etc. , mask layer), etc. can be set.

In the first embodiment, when the etching rate decreases concentrically as the circular lower electrode 1 and the etching sample 3 move in the radial distance direction from the central axis, in order to correct this, a circular lower electrode 1 is used as the circular upper electrode 2. The case where a circular upper electrode 2 having a concave surface with a certain curvature is installed on the surface of the electrode 1 has been described, but as a second embodiment, as shown in FIG. Contrary to the first embodiment, by adopting the structure of the circular upper electrode 2 having a convex surface with an appropriate curvature and facing the surface of the sample 3 at an appropriate distance. When the etching rate increases concentrically as the circular lower electrode 1 and the etching sample 3 move in the radial distance direction from the central axis, that is, in the etching apparatus with the conventional structure shown in FIG. 1, the etching rate shown in the H curve in FIG. In the case of such an etching rate distribution, a uniform in-plane etching rate distribution as shown in FIG. 5 can be obtained due to the opposite effect of the first embodiment.

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In this case as well, as in the first embodiment, the curvature of the convex surface of the circular upper electrode 2 is set to an appropriate value depending on the degree of correction of the in-plane distribution of etching rate, thereby obtaining a uniform etching rate distribution. be able to.

As third and fourth embodiments, examples of etching apparatuses used for etching actual semiconductor integrated circuits are shown in FIGS. 6 and 7. This is an example of an etching apparatus for simultaneously processing a large number of etching samples (wafers).

Starting from the third embodiment shown in FIG. 6, FIG. 6a is a cross-sectional view, and FIG. 6b is a plan view of the lower electrode 1 in FIG. 6a. This Figure 6a, 6th
In both figures in Figure b, 1 is a circular lower electrode (sample stage), 2 is a circular upper electrode, 3 is an etching sample (conductor wafer), 4 is an etching chamber, 5 is an insulator, and 6 is a high-frequency power matching. The circuit includes a high frequency power supply 7 and a high frequency power supply connection electrode and ground electrode switching circuit 8.

These are performed by evacuating the inside of the etching chamber 4 with a vacuum pump, introducing etching gas, applying high frequency power between the upper electrode 2 and the lower electrode 1 under a certain pressure, generating plasma, and forming a circular lower part. A large number of etching samples (conductor wafers) 3 placed on an electrode 1 are etched simultaneously.

FIGS. 6a and 6b show that in the case of the conventional parallel plate circular upper and lower electrode structure, the etching rate decreases concentrically in the radial distance direction from the central axis of the circular lower electrode 1. To correct this, a circular upper electrode 2 having the same central axis and a suitable concave surface is placed at an appropriate distance from the circular lower electrode 1 and the surface of the etching sample 3.

Thereby, a large number of etching samples 3 can be processed simultaneously with good uniformity.

FIG. 7a is a sectional view showing the structure of a fourth embodiment of the invention, and FIG. 7b is a plane view of the lower electrode in FIG. 7a. In the case of the embodiment shown in FIGS. 7a and 7b, contrary to the case of FIGS. 6a and 6b, in the conventional electrode structure, the direction is radial from the central axis of the circular lower electrode 1 In the past, when the etching rate increased concentrically, in order to correct this, a circular upper electrode 2 with a convex surface of an appropriate curvature on the same central axis was installed with respect to the circular lower electrode 1 and the surface of the etching sample 3. are installed at an appropriate distance.

As a result, the plasma and electric field strength decrease concentrically in this direction, so that the in-plane distribution of the etching rate is corrected and a uniform distribution is obtained.

As a fifth embodiment of this invention, as shown in FIG. 8a (cross-sectional view) and FIG. 8b (plan view of the lower electrode in FIG. 8a), etching gas is introduced from one etching gas inlet 9. When the etching gas flow passes through the etching sample surface 3 and the circular lower electrode 1 in a certain direction, such as when the etching gas is introduced and evacuated from the vacuum exhaust port 10 on the opposite side, the conventional parallel In the flat electrode structure, the etching rate changes concentrically in the radial distance direction from the center axis of the circular lower electrode 1, and the etching rate also changes along the flow direction of the etching gas.

To correct this, Figure 8a and Figure 8b
As shown in FIG. 2, a circular upper electrode 2 having a convex or concave surface with respect to the surface of the circular lower electrode 1 is installed so as to be inclined in the direction of the flow of etching gas. This makes it possible to simultaneously make uniform the concentric etching rate distribution in the radial distance direction from the central axis of the surface of the circular lower electrode 1 and the etching rate distribution in the flow direction of the etching gas.

Note that the shape of the circular upper electrode 2 may be a cone with an appropriate inclination angle to simplify processing.

As described above, according to the plasma etching apparatus of this invention, the upper electrode, which is disposed opposite to the circular lower electrode on which the etching sample is placed, has a convex or concave surface with respect to the lower electrode. Since the electrode is circular in shape, the in-plane distribution of the etching rate can be made uniform.

For this reason, etching gas conditions, high frequency power,
Etching conditions such as the degree of etching vacuum have almost no restrictions in terms of uniformity of the etching rate distribution, so settings such as etching rate, selectivity (to resist, underlayer), side etching amount, etc. should be set to obtain the best values. Can be done.

[Brief explanation of the drawing]

Figure 1 shows the configuration of a conventional plasma generator.
2 is a diagram showing the relationship between the position of the etching sample on the lower electrode and the etching rate in the plasma etching apparatus of FIG. 1, and FIG. 3 is a diagram showing the upper part of an embodiment of the plasma etching apparatus of this invention. FIG. 4 is an enlarged sectional view of the upper electrode and lower electrode of the second embodiment of the plasma etching apparatus of this invention, and FIG. 5 is an enlarged sectional view of the plasma etching apparatus of this invention. Characteristic diagram showing the relationship between the position of the etching sample on the lower electrode and the etching speed in the etching device, Fig. 6a
is a sectional view showing the configuration of a third embodiment of the plasma etching apparatus of this invention, and FIG.
FIG. 7a is a sectional view showing the structure of the fourth embodiment of the plasma etching apparatus of this invention, FIG. 7b is a plan view of the lower electrode in FIG. 7a, and FIG. FIG. 8a is a sectional view showing the structure of a fifth embodiment of the plasma etching apparatus of this invention, and FIG. 8b is a plan view of the lower electrode in FIG. 8a. 1... Lower electrode, 2... Upper electrode, 3... Etching sample, 4... Etching chamber, 5...
Insulator, 6...High frequency power matching circuit, 7...
...High frequency power supply, 8...High frequency power supply connection electrode and ground electrode switching circuit, 9...Etching gas inlet, 10...Vacuum exhaust port. 〓〓〓〓〓

Claims (1)

[Scope of utility model registration request] A lower electrode with a circular plane on which an etching sample is placed, an upper circular electrode placed opposite to this lower electrode, and an etching chamber that accommodates these and into which etching gas is introduced under a certain reduced pressure. In the plasma etching apparatus comprising means for generating plasma by applying high frequency power between the upper electrode and the lower electrode, the upper electrode may have a convex or concave surface having an arbitrary curvature relative to the lower electrode. Characteristic plasma etching equipment.