JPH069020Y2 - Porous electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a porous electrode, and more particularly to a porous electrode used in a plasma etching apparatus.

[Prior art and problems to be solved]

Conventionally, a porous electrode used in a plasma etching apparatus uses a porous filter medium having a uniform thickness.

FIG. 5 shows a porous electrode 31 using a porous filter medium 33 having a uniform thickness.

That is, the porous electrode 31 has an inlet 34 for a small-diameter fluid 35 in the center of the upper surface and an outlet 32 of a large diameter in the lower surface, and a main body 36 made of a conductive material. A disk-shaped porous filter material 3 which is disposed at the outlet 32 of the main body 36 and has conductivity.
3 and 3.

In the above-mentioned porous electrode 31, the fluid 35 is filtered by the porous filter medium 33 and flows out. However, the flow velocity is high in the central portion facing the inflow port 34, and the flow velocity becomes slower toward the peripheral portion. There is a problem that the fluid becomes turbulent on the downstream side of the porous filter medium 33.

Therefore, in the plasma etching apparatus as shown in FIG. 6 which uses the porous electrode 31 having the plate-shaped porous filter material 33, the etching accuracy and the like are adversely affected.

The plasma etching apparatus shown in FIG. 6 includes an upper electrode 43, which is a porous electrode, inside a casing 41 in which an enching chamber 42 is formed, and a lower electrode 44 arranged so as to face the upper electrode 43. I am.

The upper electrode 43 is formed in a hollow shape with a small-diameter inlet 43a for introducing the reactive gas 45 in the upper center, and a plate-shaped porous filter material 43c at the lower outlet 43b.
Is provided.

The upper surface of the lower electrode 44 is the porous filter material 43.
A substrate 46 to be etched is placed on the opposite surface of the lower electrode 44.
Has become.

The lower electrode 44 is grounded for anode coupling connection, and a high frequency power supply 47 is connected between the lower electrode 44 and the upper electrode 43 to apply a high frequency voltage between the electrodes 43 and 44.

An exhaust port 48 is formed in the casing 41.

In the plasma etching apparatus including the upper electrode 43, which is a porous electrode, and the lower electrode 44 as described above,
On the upper surface of the lower electrode 44, polysilicon, SiO ₂ ,
A substrate 46 made of a thin film of PSG (phosphosilicate glass), aluminum alloy, refractory metal, silicide (silicide), etc. is placed.

Then, from the inflow port 43a of the upper electrode 43 to the reactive gas 4
5 is introduced into the hollow portion and flows out toward the lower electrode 44 from the porous filter material 43c arranged at the outlet 43b.

Then, the space between the electrodes 43 and 44 is filled with the reactive gas 45, and a high frequency voltage is applied from the high frequency power source 47 between the electrodes 43 and 44 to generate the reactive gas 45 between the electrodes 43 and 44. Is turned into plasma, and the substrate 46 placed on the upper surface of the lower electrode 44 is etched into a desired pattern.

However, as described above, the reactive gas 45 that flows in through the inflow port 43a, is filtered by the porous filter medium 43c and flows out, has a high flow velocity in the central portion of the porous filter medium 43c and a flow velocity as the distance from the central portion increases. Will be late.

Therefore, the porous filtering material 43 corresponding to the inflow port 43a
The amount of fluid flowing out from the portion c is too large, while
If the amount of outflow from this portion is made appropriate, there is a problem that the amount of outflow is too small in the peripheral portion.

Further, the reactive gas 45 becomes turbulent in the downstream portion after passing through the porous filter material 43c, the concentration of the reactive gas 45 becomes nonuniform in the space between the electrodes 43, 44, and the plasma density However, there is a problem in that the etching rate of the substrate 46 becomes non-uniform and accurate etching cannot be performed.

The present invention solves the above-mentioned problems of the conventional ones, and it is possible to supply a uniform flow rate of fluid to the downstream side of the porous filter medium, while the reaction gas is turbulent on the outflow side. It is an object of the present invention to provide a porous electrode that can prevent a situation.

[Means for Solving the Problems]

To achieve the above object, the present invention provides a porous electrode used as an electrode of a plasma etching apparatus,
With a small-diameter inlet in the upstream central portion, having a large-diameter outlet in the downstream, and a conductive main body, the outlet of the main body, provided in a closed state,
The central portion facing the inflow port is thick, and the thickness gradually decreases toward the peripheral portion, and the porous filter material having conductivity is provided, and the reactive gas flowing in from the inflow port is porous. It is configured such that it passes through the porous filter medium and flows out at a substantially uniform flow velocity over the entire lower surface of the porous filter medium.

[Action]

By adopting the above configuration, the present invention can secure a substantially uniform flow rate over the entire surface on the downstream side of the porous electrode, and can also secure a substantially uniform flow rate over the entire surface. It is possible to reliably prevent the downstream side from becoming a turbulent state.

〔Example〕

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

1 and 2 show a porous electrode according to the present invention.

The porous electrode 1 has an inlet 4 for a small-diameter fluid 5 in the center of the upper surface and an outlet 2 of a large diameter for the lower surface.
The main body portion 6 formed of a conductive material and the main body portion 6 are disposed at the outlet 2 of the main body portion 6, have conductivity, and have a thick central portion and a thinner portion toward the peripheral portion. And a porous filter material 3 in the shape of a convex lens.

In the porous electrode 1 having the above-described structure, the central portion of the porous filter medium 3 facing the small-diameter inlet 4 flows at a high flow velocity, and flows toward the peripheral portion at a low flow velocity, but at a high flow velocity. Since the central portion of the porous filter medium 3 that flows in has a large thickness and the peripheral portion that flows in at a slow speed has a small thickness, the downstream side of the porous filter medium 3 filters the fluid at a uniform flow velocity. It will be leaked.

Moreover, a uniform flow velocity of the fluid can be ensured on the downstream side without increasing the flow velocity of the fluid flowing out from the central portion of the porous filtration medium 3, and the entire lower surface of the porous filtration medium 3 is substantially uniform. A flow rate can be secured.

Here, the air permeability of the fluid 5 passing through the porous filter medium 3 is represented by the following formula.

k = (Q / A) (d / Δp) where k is air permeability, Q is flow rate, A is cross-sectional area, d is thickness, Δp is differential pressure, and (Q / A) is flow velocity v Is shown.

That is, in a porous body having a homogeneous composition, the thickness d of the porous body and the flow velocity v have an inversely proportional relationship,
The porous filter material 3 of the homogeneous composition used in the porous electrode 1 according to the present invention has a thick central portion facing the inlet 4 of the fluid 5 and gradually becomes thinner toward the peripheral portion away from the inlet 4. It is formed in a convex lens shape.

Therefore, since the porous filter medium 3 is formed thick in the portion facing the inflow port 4 and flowing in at a high flow rate, the flow velocity flowing out to the downstream side becomes slow, while the flow velocity of the fluid 5 moving away from the inflow port is small. Since the thickness of the porous filter medium 3 is thin in the peripheral portion flowing in, the flow velocity flowing out to the downstream side becomes faster, and the flow velocity is controlled as a whole, and the flow velocity is almost uniform over the entire surface of the porous filter medium 3. Therefore, it is possible to secure a substantially uniform flow rate over the entire lower surface.

FIG. 3 shows a plasma etching apparatus using the porous electrode 1 according to the present invention as the upper electrode 13.

This plasma etching apparatus includes an upper electrode 13 which is a porous electrode 1 inside a casing 11 in which an etching chamber 12 is formed, and a lower electrode 14 which is arranged so as to face the upper electrode 13.

The upper electrode 13 is formed in a hollow shape having a small-diameter inlet 13a for introducing the reactive gas 15 at the center of the upper portion thereof. The outlet 13b on the lower surface has a thick central portion and a thinner wall toward the peripheral portion. Convex lens-shaped porous filter material 13c
Is provided.

The upper surface of the lower electrode 14 is the porous filter material 13
The substrate 16 facing the c, the substrate 16 to be etched is placed on the facing surface, and the lower portion of the lower electrode 14 is the water-cooled portion 14a.
Has become.

The lower electrode 14 is grounded for anode coupling connection, and a high frequency power source 17 is connected between the lower electrode 14 and the upper electrode 13 to apply a high frequency voltage between the electrodes 13 and 14.

An exhaust port 18 is formed in the casing 11.

In the plasma etching apparatus including the upper electrode 13 and the lower electrode 14 which are porous electrodes as described above,
On the upper surface of the lower electrode 14, polysilicon, SiO ₂ ,
A substrate 16 made of a thin film of PSG (phosphosilicate glass), aluminum alloy, refractory metal, silicide (silicide) or the like is placed.

Then, from the inflow port 13a of the upper electrode 13, the reactive gas 1
5 is introduced into the hollow portion and flows out toward the lower electrode 14 from the porous filter material 13c arranged at the outlet 13b.

Then, the space between the electrodes 13 and 14 is filled with the reactive gas 15, and a high frequency voltage is applied from the high frequency power source 17 between the electrodes 13 and 14, so that the reactive gas 15 existing between the electrodes 13 and 14 is discharged. Is turned into plasma, and the substrate 16 placed on the upper surface of the lower electrode 14 is etched into a desired pattern.

Then, the reactive gas 15 which flows in from the inflow port 13a, is filtered by the porous filter medium 13c arranged at the outflow port 13b and flows out, has a high flow velocity in the central portion of the porous filter medium 13c, and the central portion thereof. Although the flow velocity becomes slower from the end to the peripheral portion, the flow velocity of the reactive gas 15 flowing out to the downstream side is as follows because the thickness of the porous filter material 13c is a convex lens shape.
It does not change much over all parts of the porous filter medium 13c, and the flow velocity is controlled as a whole.
Reactive gas 1 at a uniform flow rate over the entire downstream side of c
5 flows out.

Thereby, a substantially uniform flow rate can be secured over the entire lower surface of the porous filter medium 13c.

Moreover, the above can be achieved without increasing the flow rate of the fluid flowing out from the central portion.

And, in the plasma etching apparatus using the porous electrode 1 according to the present invention as the upper electrode 13, the reactive gas 1
5, the reactive gas 15 is discharged from the entire surface of the porous filter medium 13c disposed at the outflow port 13b of No. 5 into the space between the electrodes 13 and 14 in a laminar flow state with a uniform flow velocity, and the reactive gas 15 is discharged onto the substrate 16. It is possible to perform uniform and accurate etching with a constant etching rate on the upper surface of the substrate 16 without causing the concentration of 15 and the plasma density to be disturbed.

The convex lens-shaped porous filter material 13c made of a conductive material used in the present invention is, for example, silicon carbide (SiC).
70 parts by weight of the above powder and 30 parts by weight of water are mixed with a carbon source such as carbon or resin so as to be 3 to 5 parts by weight in terms of carbon, and the mixture is poured into a molding die for molding. Forming a body, and then calcining the compact at 1500 ° C., and further subjecting silicon (Si) equivalent to about 20% of the weight of the calcined body to a sintering reaction at a temperature of 1500 ° C. Can be manufactured by.

FIG. 4 shows another example of the porous electrode provided with the convex lens-shaped porous filter material according to the present invention.

This porous electrode has a plano-convex lens shape in which the outflow side surface of the porous filtering material used in the porous electrode shown in FIG. 1 is flat.

That is, the porous electrode 21 shown in this other example has an inlet 24 for a small-diameter fluid 25 at the upstream center and an outlet 22 with a large diameter downstream, and is made of a conductive material. In the main body 26 and the outlet 22 of the main body 26,
It is composed of a plano-convex lens-like porous filter material 23 having a planar outflow side, a convex inflow side, a central portion having a thickness, and a wall thickness gradually decreasing toward the peripheral portion.

For this reason, since the porous filter medium 23 is thick at the portion where the fluid 25 facing the inflow port 24 flows in at a high flow rate, the flow velocity flowing out to the downstream side becomes slow, and the fluid 25 moves away from the inflow port 24. Since the wall thickness is gradually thinned in the portion which flows in at a low flow velocity, the flow velocity flowing out to the downstream side does not change so much, the flow velocity is controlled as a whole, and the flow velocity is uniform over the entire downstream side of the porous filter medium 23. Become.

[Effect of device]

Since the present invention is configured as described above, the flow velocity of the fluid passing through the porous filter medium can be made substantially uniform over the entire surface, and a substantially uniform flow rate can be obtained over each part of the porous filter medium. Can be secured.

Moreover, the flow rate of the fluid passing through each part of the porous filter medium facing the inlet can be arbitrarily set according to the thickness of the central part of the porous filter medium, and is substantially equal to the set amount of this central part. The flow rate can be secured at each part of the porous filter medium.

Therefore, when used in the plasma etching apparatus, the reactive gas passing through the porous filter medium is discharged into the space between the upper and lower electrodes in a uniform laminar flow state, which causes disturbance in the concentration of the reactive gas and the plasma density. This has the effect that a uniform etching rate can be secured and accurate etching can be performed.

[Brief description of drawings]

1 is a schematic sectional view of a porous electrode according to the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a schematic sectional view showing a plasma etching apparatus using the porous electrode according to the present invention as an upper electrode. FIG. 4 is a schematic sectional view showing another example of the porous electrode according to the present invention, FIG. 5 is a schematic sectional view of a conventional porous electrode, and FIG. 6 uses a conventional porous electrode as an upper electrode. It is a schematic sectional drawing which shows a plasma etching apparatus. 1, 21, 31 ... Porous electrode 2, 22, 32 ... Outflow port 3, 23, 33 ... Porous filter material 4, 24, 34 ... Inflow port 5, 25, 35 ... Fluid 6, 26 , 36 ... Main body 11, 41 ... Casing 12, 42 ... Etching chamber 13, 43 ... Upper electrode (porous electrode) 13a, 43a ... Inflow port 13b, 43b ... Outflow port 13c, 43c ... Porous filter material 14,44 ...... Lower electrode 14a, 44a ...... Water cooling part 15,45 ...... Reactive gas 16,46 ...... Substrate 17,47 ...... High frequency power supply 18,48 ...... Exhaust port

Claims (1)

[Scope of utility model registration request] 1. A main body of a porous electrode used as an electrode of a plasma etching apparatus, which has a small-diameter inflow port in the upstream central part and a large-diameter outflow port in the downstream, and which is electrically conductive. Part and the outlet of the main body are provided in a closed state, the central part facing the inlet is thick, and the thickness gradually decreases toward the peripheral part, and the conductivity is improved. And a reactive gas flowing in from the inflow port, passing through the porous filter medium and flowing out at a substantially uniform flow rate over the entire lower surface of the porous filter medium. A porous electrode characterized by the above.