JPH03101126A - Electrode for plasma etching apparatus use - Google Patents

Abstract

PURPOSE:To reduce the irregularity in the supply amount of a reactive gas and to execute a uniform etching operation by a method wherein a conductive porous body whose gas transmission is specific is arranged and installed at an outflow port of the reactive gas. CONSTITUTION:A disk-shaped conductive porous body 9 whose gas transmission in terms of nitrogen gas is 20X10<-2> to 800X10<-2> (cc.cm/cm<2>.sec.cmH2O) is arranged and installed at an outflow port 8 of an upper-part electrode 3. Thereby, it is easy to limit the irregularity in the supply amount of a reactive gas 5 within two times over the hole face between electrodes 3, 4; a substrate 10 placed on the lower-part electrode 4 can be etched nearly uniformly. the operation to attach the electrodes to a plasma etching apparatus and the operation to set the etching condition can be completed easily in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrode for a plasma etching device, and in particular,
The present invention relates to an electrode for a parallel plate type plasma etching apparatus used in a plasma etching apparatus used for manufacturing semiconductor integrated circuits and the like.

[Prior art and problems to be solved] Conventionally, wet etching has been used in the production of semiconductor integrated circuits, but in recent years dry etching has become mainstream due to the miniaturization of circuit patterns and improved productivity. It becomes.

Among these, plasma etching apparatuses using parallel plate electrodes are widely used.

FIG. 3 shows a conventional plasma etching apparatus using parallel plate type electrodes, and this plasma etching apparatus consists of upper parts arranged parallel to each other and facing each other in a casing 21 forming an etching chamber 22. It includes an electrode 23 and a lower electrode 24.

The upper electrode 23 has an inlet 26 for the reactive gas 25, has a hollow interior so that the reactive gas 25 can pass through the hollow part 27, and has a reactive gas inlet 26 on the surface opposite the inlet 26. A plurality of small holes 28 serving as outflow ports for releasing the sexual gas 25 are provided, and the whole is made of a conductive material, and the lower electrode 24 has a surface facing the small holes 28,
It is made of a plate-shaped conductive material on which a substrate 29 is placed.

The lower electrode 24 is connected to the ground potential by anode coupling, and a high frequency power source 30 is connected between the upper electrode 23 and a high frequency voltage can be applied between the picture electrodes 23 and 24. Furthermore, an exhaust port 31 is formed in the casing 21 .

In the plasma etching apparatus equipped with the upper electrode 23 configured as described above, a substrate 29 on which a thin film to be a sample is formed is placed on the lower electrode 24, and the substrate 29 is placed on the upper electrode 23. The reactive gas 25 is introduced from the inlet 26 and released from the small hole 28 toward the lower electrode 24 through the hollow part 27, so that the reactive gas 25 is spread between the picture electrodes 23 and 24. At the same time, the picture electrode 23.
A high frequency voltage is applied between the picture electrodes 23 and 24 to turn the reactive gas 25 present between the picture electrodes 23 and 24 into plasma, and the plasma etches the thin film on the substrate 29 placed on the lower electrode 24 into a desired pattern. It is something.

However, in the case of using the electrode for a plasma etching apparatus as described above, since the outlet of the reactive gas 25 provided in the upper electrode 23 is the small hole 28, the reactive gas 25 is discharged toward the lower electrode 24. The concentration of the reactive gas 25 becomes non-uniform on the surface of the substrate 29, and the picture electrodes 23, 24
There is a problem in that the electric field is disturbed during etching, and the etching rate on the surface of the substrate 29 becomes non-uniform, making it impossible to perform accurate etching.

In order to solve the above problems, the present inventors first made the upper electrode part facing the lower electrode an open outlet, and arranged a porous body made of a conductive material in the outlet. electrode for plasma etching equipment (patent application 1986)
-25668).

That is, in the conventional upper electrode shown in FIG.
Instead of the upper electrode having small holes at the outlet, a porous body made of a conductive material having fine communicating holes is disposed at the outlet to serve as the upper electrode.

However, even with the electrode for plasma etching equipment using the above-mentioned porous material, although there is no large disturbance in the flow rate of the reactive gas and the etching rate as in the small hole part, When the entire surface of a porous body is examined in detail, it is found that the permeability varies more than twice over the surface of the electrode, and as a result, there are large variations in the flow rate of the reactive gas and its etching rate. It was something.

In this case, the variation in etching becomes particularly large in the case of a narrow gap type in which the distance between the upper electrode and the lower electrode is small.

In addition, when installing the above-mentioned porous body in the plasma etching apparatus, it is necessary to adjust the supply pressure of the reactive gas to find conditions that minimize the variation in the flow rate of the reactive gas described in O11. That is, although the etching condition setting work is performed, there is a problem in that this etching condition setting work takes a lot of time and causes a decrease in etching productivity.

The present invention solves the problems of the conventional methods as described above, and it is possible to easily reduce the variation in the amount of reactive gas supplied over the entire surface of the electrode to within twice, and to achieve uniform etching. It is an object of the present invention to provide an electrode for a plasma etching apparatus, which can easily attach the electrode to the plasma etching apparatus and set etching conditions, and improve etching productivity.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an upper electrode that is disposed inside a casing, has a hollow shape, and from which a reactive gas flows out, and this upper electrode. A lower electrode is placed facing the lower electrode and a substrate is placed on the surface of the lower electrode, and a double frequency voltage is applied between the two electrodes to etch the substrate placed on the lower electrode. This is an electrode for a plasma etching device for use in an etching device, and the upper electrode of this plasma etching electrode has an air permeability of 20×10-2 to 800×10-” equivalent to nitrogen gas at the outlet of the reactive gas. cc-cm/
It has a structure in which a conductive porous body of c+ff-5ec-cmH,O) is disposed.

[Effect]

By adopting the above configuration, the present invention makes it easy to reduce the variation in the amount of reactive gas supplied over the entire electrode surface to within twice that of the sample placed on the lower electrode surface. Uniform etching can be performed, and electrodes can be attached to the plasma etching apparatus and etching conditions can be set in a short time.

〔Example〕

Embodiments of the present invention shown in the drawings will be described below.

FIG. 1 shows a plasma etching apparatus using electrodes for a plasma etching apparatus according to the present invention, which are arranged in parallel to each other in a casing 1 forming an etching chamber 2. Ru,
The upper electrode 3 includes an upper electrode 3 and a lower electrode 4, each of which is entirely made of a conductive material. A reactive gas 5 such as nitrogen gas can pass through the interior, and an outlet 8 is provided on the opposite surface of the inlet 6, and the outlet 8 has an air permeability equivalent to nitrogen gas of 20X10-2 to 80.
0X10-”(cc-cm/ctM-5ee-c
A disc-shaped conductive porous body 9 of m H, O) is disposed.

Further, a substrate 10 is placed on the surface of the lower electrode 4 facing the porous body 9 provided at the outlet 8 of the upper electrode 3, and the lower electrode 4 is grounded and connected by anode coupling. A high frequency power source 11 is connected between the upper electrode 3 and the picture electrodes 3 and 4, so that a high frequency voltage can be applied between the picture electrodes 3 and 4. Furthermore, an exhaust port 12 is formed in the casing 1.

In the plasma etching apparatus equipped with the upper electrode 3 configured as described above, the substrate 10 on which the F# film serving as a sample is formed is placed on the surface of the lower electrode 4, and the substrate 10 is placed on the upper electrode 3. , the reactive gas 5 is introduced from the inlet 6 and discharged from the porous body 9 toward the lower electrode 4 through the hollow part 7, into the space between the picture electrodes 3 and 4. While filling the reactive gas 5, a high frequency voltage is applied between the picture electrodes 3 and 4 to turn the reactive gas 5 present between the picture electrodes 3 and 4 into plasma, and this plasma causes the lower electrode 4 to
A thin film of substrate 10 placed on a surface can be etched into a desired pattern.

In the present invention, the air permeability equivalent to nitrogen gas at the outlet 8 of the upper electrode 3 is 20X 10-'' as described above.
~800X 10-” (cc-cta/d-sec
Since the disc-shaped conductive porous body 9 of -cmH,O) is disposed, the reactive gas 5
It becomes easy to reduce the variation in the supply amount to within twice the amount of etching, and it becomes possible to perform substantially uniform etching on the substrate 10 placed on the surface of the lower electrode 4.

In addition, the work of attaching the electrode to the plasma etching apparatus and setting the etching conditions is extremely easy and can be completed in a short time if the porous body 9 has the above-mentioned air permeability. We were able to.

For reference, the permeability of the porous material used in conventional electrodes for plasma etching equipment, equivalent to nitrogen gas, is 0.
lX10-'~8x10(cc-c+++/c+1-s
ec °cmHtO).

Then, the air permeability mentioned above, that is, 0.0% in terms of nitrogen gas equivalent.
I X 10-" ~ 8 X 10-" (cc-
ell/d-sec -, craHz O), it is extremely difficult to keep the variation in the amount of reactive gas supplied over the entire surface of the electrode within twice, and it is difficult to set the etching conditions. It took a long time.

Generally, the relationship between the thickness of a porous body and the flow rate of a fluid such as a reactive gas is expressed by the following equation.

Q=(k-A・Δp/L) ・・・・・・(1) Here, Q is the fluid flow rate, k is the air permeability specific to the porous body, Δ is the ventilation area, and Δp is the flow rate through the porous body. The pressure difference between the fluid before and after the process, and L represents the thickness of the porous body.

That is, when the air permeability is different, the pressure difference Δp between the fluid before and after passing through the porous body must be changed in order to maintain the same fluid flow rate.

Further, as the air permeability k increases, the pressure difference Δp can be made smaller.

Further, the relationship between the air permeability and the magnitude of the variation in the air permeability is as follows.

That is, assuming that the bore of the porous body is a circular pipe1, and from the Hagen-Poiseuille equation, u-(gc/32μ ri・d2・Δp where U is the flow velocity, gc is the gravity conversion coefficient, and μ is the fluid viscosity, ! is the thickness of the porous body, d is the diameter of the circular tube, and Δp is the pressure drop.

The air permeability corresponds to (gc/32μ)·d2.

Therefore, k−α・(gc/32μ), d! However, α is a constant.

Let us perform a sensitivity analysis of k with respect to d.

In other words, when finding the relationship between k'/ and d, k'/ = [2, α・(gc/32μ)・dl/[α・(gc/
32μ)・d"1 -2/d, and it can be seen that the larger d is, the smaller the change in air permeability is.

That is, the larger the air permeability (d is larger), the smaller the variation in air permeability (k''/k) becomes.

Therefore, when the air permeability is high, the variation in the amount of reactive gas flow 2 becomes small, and it becomes easy to set conditions for electrode attachment and etching.

On the other hand, the upper limit of the permeability of the porous body is regulated in relation to the etching conditions, and the permeability of the porous body in the present invention equivalent to nitrogen gas is 20XIO-2 to 800X1.
0-” (cc-c+n/c+II ・sec・cmH
, 0), the object of the present invention can be achieved, but preferably 20X10-2 to 400X10 (cc-cm'/c+
fl·sec −cmH,O).

The above porous body can be manufactured by appropriately selecting the particle size of the sintered material particles serving as the raw material of the porous body, sintering conditions, and the like.

Note that the material of the above porous body may be a ceramic material, a metal material, etc., which are usually used as a porous body made of an electrically conductive material.

The present invention will be explained in more detail below using experimental examples.

Experimental example Silicon carbide particles with an average particle size of 20 Q/7 m are used as a raw material and molded, and silicon metal is added to this material in a vacuum for 1500 m.
Infiltrated with C at 22%, diameter 140mm, thickness 3.4
A conductive porous body in the shape of a disc of mm was prepared.

The material obtained above has an air permeability equivalent to nitrogen gas of 30
X 10-” (cc-cm/cnl-sec-
cmH.

0), and the variation in air permeability over the entire surface of the porous body was within 1.2 times.

The porous material described above was attached to the outlet of an electrode for a plasma etching device, and conditions were set to allow proper etching by actually etching, but the time required for this was measured and was 15 minutes.

On the other hand, a disc-shaped conductive porous body having a diameter of 1140 mm and a thickness of 3.4 mm was prepared in the same manner as described above by using silicon carbide particles having an average particle size of 50 .mu.m as a raw material.

The one obtained above has an air permeability equivalent to nitrogen gas of 3
10-2(cc-cm/cl-sec-cmH
z ○), and the variation in air permeability over the entire surface of the porous body was 2.8 times.

The above porous body was attached to the outlet of an electrode for a plasma etching apparatus, and the time required to set the same etching conditions as above when actually etching was measured by the same operator, and it took 4 hours.

From the above results, the air permeability equivalent to nitrogen gas according to the present invention is 20X10-2 to 800X10-" (cc・cm/
In a plasma etching device using an electrode in which a porous material with a temperature of , it is possible to perform uniform etching, and when installing it in an etching device, the time required to obtain suitable conditions can be greatly shortened, and etching productivity can be greatly improved.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to easily reduce the variation in air permeability on the electrode surface to within twice.
Uniform etching can be achieved5, and the time required to establish suitable conditions for installation in an etching device can be greatly shortened, greatly improving the productivity of plasma etching processing. It has excellent effects such as:

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a plasma etching device equipped with an electrode for a plasma etching device according to the present invention, FIG. 2 is a perspective view of a porous body used in the electrode for a plasma etching device according to the present invention, and FIG. 1 is a schematic explanatory diagram of a plasma etching apparatus equipped with a conventional plasma etching apparatus electrode; FIG. 1, 2 2, 2 3, 2 4, 2 5, 2 6, 2 1...Casing 2...Etching chamber 3...Upper electrode 4...・Lower electrode 5...Reactive gas 6...Inlet 6 7.27...Hollow section 8...Flow outlet 9...・Porous body 10.29... Substrate 11.30... High frequency power supply 12.31... Exhaust D 28... Small hole

Claims (1)

[Claims] (1) An upper electrode that is arranged inside the casing and has a hollow shape and from which reactive gas flows out, and a lower part that is arranged opposite to the upper electrode and on which the substrate is placed. an electrode for use in a plasma etching apparatus for etching a substrate placed on the lower electrode by applying a high frequency voltage between the two electrodes, the electrode for plasma etching The upper electrode has an air permeability equivalent to nitrogen gas of 20 x 10^-^2 to 800 x 10^- at the reactive gas outlet.
＾2 (cc・cm/cm＾2・sec・cmH_2O)
1. An electrode for a plasma etching device, characterized by disposing a conductive porous body.