JPH11317396A - Etching system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress decrease in etching rate in wafer margin and improve the uniformity of etching within wafer surface. SOLUTION: In a chamber 2 of an etching system, an upper electrode 3 and a lower electrode 4 are set facing opposite, and a work to be treated on a wafer 10 supported on an upper face 4a of the lower electrode 4 is etched under plasma generated between the upper electrode 3 and the lower electrode 4. In this case, a lower surface 3a of the upper electrode 3 is structured concave, so that a gap h1 between the upper electrode 3 and the lower electrode 4 in the margin of the lower surface 3a is smaller than a gap h2 between the upper electrode 3 and the lower electrode 4 at about central part of the beneath 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching apparatus used for an etching technique for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art A conventional etching apparatus having a narrow-gap parallel plate type chamber structure as shown in FIG. 4 is known. That is, in this etching apparatus 20, the upper electrode 22 and the lower electrode 23 are provided in the chamber 21 so as to face each other.
A high frequency voltage is applied between the second electrode 2 and the lower electrode 23. The lower surface of the upper electrode 22 is a flat surface, and is arranged such that the gap (hereinafter, referred to as a gap) with the upper surface of the lower electrode 23 is constant. An etching gas outlet (not shown) is formed on the lower surface of the upper electrode 22, and the lower electrode 23 also serves as a holding table for the wafer 10.

In the above-described etching apparatus 20, the inside of the chamber 21 is maintained in a predetermined vacuum state, and an etching gas is blown from the lower surface of the upper electrode 22 toward the lower electrode 23, so that the upper electrode 22 and the lower electrode 23 By applying a high frequency voltage during the period, a plasma in which the etching gas is discharged during the period is generated. Then, the object to be processed of the wafer 10 held on the upper surface of the lower electrode 23 is etched by the generated plasma.

[0004]

However, in recent years, as the density of semiconductor devices has increased, the wiring forming process has further advanced in the direction of miniaturization and multilayering. As a result, the manufacturing cost of the wafer increases, so that the diameter of the wafer has been increased in order to increase the number of chips obtained from one wafer and to suppress the cost per chip. However, even if the diameter of the wafer is increased, the uniformity of etching in the wafer surface of the technology used for manufacturing the semiconductor device, such as the etching technology, is the same as in the past in order to make the quality of the manufactured semiconductor device uniform. More than a certain level of performance is required.

However, in the above-described conventional etching apparatus, convection of the etching gas easily occurs at the peripheral portion of the wafer held on the upper surface of the lower electrode, and the exhaust state deteriorates. As a result, a reaction product of the plasma and the object to be processed on the wafer is easily deposited on the peripheral portion of the wafer, and the etching rate of the peripheral portion is reduced as compared with the central portion of the wafer, so that the in-plane surface of the wafer is reduced. Has a problem in that the etching uniformity is deteriorated.

For example, a silicon oxide (SiO ₂ ) film formed on a wafer 10 is etched using an etching apparatus 20 having a chamber structure shown in FIG.
F ₄ / CHF ₃ / Ar / N ₂ = 70 sccm / 60 sc
cm / 200 sccm / 20 sccm, power: 1000
W, atmosphere pressure: 53.3 Pa, when etching was performed under the condition that the gap h between the upper electrode 22 and the lower electrode 23 was 9 nm, the X direction of the wafer 10 shown in FIG.
In any of the Y directions, the result that the etching rate is reduced at the peripheral portion of the wafer 10 as shown in FIG. 5B is obtained.

When the diameter of the wafer is increased, the etching rate at the peripheral portion of the wafer is more remarkably reduced, and the etching uniformity in the wafer surface may be further deteriorated. The development of an etching apparatus capable of improving the quality is strongly desired.

[0008]

It is known that the etching rate changes when the gap h between the upper electrode and the lower electrode, which are opposed to each other in the chamber, is changed. Specifically, as shown in FIG. 6, when the gap h is reduced, the etching rate increases, and when the gap h is increased, the etching rate decreases. For example, in the etching apparatus 20 shown in FIG.
When the gap h between 3 and 9 is changed from 9 nm to 10 nm, the etching rate decreases by about 500 nm / min.

The reason why the etching rate is increased when the gap h between the upper electrode and the lower electrode is reduced is as follows.
By reducing the gap h, the density per unit area of plasma generated between the upper electrode and the lower electrode is increased, and per unit time of the plasma reacting with the object to be processed of the wafer held on the upper surface of the lower electrode. Is considered to be substantially increased. Conversely, when the gap h is increased, the etching rate is reduced because the gap h
Is increased, the density of plasma generated between the upper electrode and the lower electrode per unit area is reduced, and the number of plasmas reacting with the object to be processed on the wafer per unit time is substantially reduced. It is believed that there is.

Therefore, the inventor of the present invention makes the gap h between the upper electrode and the lower electrode small at the peripheral portion of the wafer and increases the gap h at the central portion of the wafer, so that the etching rate at the peripheral portion of the wafer can be improved. The present invention has been completed on the idea that the etching rate can be increased and the etching rate can be reduced at the center of the wafer.

That is, in the etching apparatus according to the present invention, an upper electrode and a lower electrode are provided in a chamber so as to face each other, and plasma is generated between the upper electrode and the lower electrode to be held on the upper surface of the lower electrode. The lower surface of the upper electrode is formed in a concavely curved shape such that a gap between the upper electrode and the lower electrode is smaller at a peripheral portion than at a substantially central portion of the lower surface. It is the configuration that was done.

In the above invention, the lower surface of the upper electrode is formed in a concavely curved shape so that the gap between the upper electrode and the lower electrode becomes smaller at the peripheral portion than at the substantially central portion. When plasma is generated between the lower electrode and the lower electrode, the density of the plasma per unit area becomes higher at the peripheral portion than at the substantially central portion of the lower surface of the upper electrode, and the peripheral portion of the wafer held on the upper surface of the lower electrode Substantially increases the number of plasmas reacting with the object to be processed per unit time. Therefore, even if convection of the etching gas occurs at the peripheral portion of the wafer and reaction products are easily deposited on the peripheral portion of the wafer, a decrease in the etching rate at the peripheral portion of the wafer is suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an etching apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of an etching apparatus according to the present invention, and FIG. 2 is an enlarged sectional view of a main part of FIG. 1 and 2 show a state where the wafer is held on the upper surface of the lower electrode.

As shown in FIG. 1, this etching apparatus 1
Is a narrow-gap parallel plate type, and includes a chamber 2 formed of a closed container, and an upper electrode 3 and a lower electrode 4 arranged in the chamber 2 so as to face each other.
The lower surface 3a of the upper electrode 3 is, as shown in FIG.
In a concave shape such that the gap h ₁ between the upper electrode 3 and the lower electrode 4 in the approximate center portion is larger than the gap h ₂ between the upper electrode 3 and the lower electrode 4 in the peripheral portion of the lower surface 3a. Is formed.

In the present embodiment, the upper electrode 3 has a substantially circular shape in plan view having a diameter substantially equal to that of the wafer 10 to be processed, and is formed so as to increase in thickness from a substantially central portion to a peripheral portion of the upper electrode 3. . Further, the curved state of the lower surface 3a is set in consideration of a state where the etching rate is lowered, a dimension of the gap, and the like.

The upper electrode 3 has a lower surface 3 of the upper electrode 3.
a, a large number of etching gas introduction pipes 5 for blowing out an etching gas from the upper electrode 4 toward the upper surface 4a of the lower electrode 4 are buried. It is in a state of being left. In FIG. 2, the illustration of the etching gas introduction pipe 5 and the ejection port 5a is omitted. Further, an etching gas supply pipe 6 is connected to the upper electrode 3 so as to communicate with the introduction pipe 5. Further, in the present embodiment, a high frequency power supply (RF power supply) 7 is connected to the upper electrode 3.

On the other hand, the lower electrode 4 also serves as a holding table for the wafer 10, and in the present embodiment, like the upper electrode 3, has a substantially circular shape in plan view having substantially the same diameter as the wafer 10 to be processed. The upper surface 4a for holding 10 is formed substantially flat. Although not shown, for example, inside,
A heater for heating the wafer 10 to a predetermined temperature, a cooling water circulation mechanism for cooling to a predetermined temperature, and the like are embedded. The upper surface of the lower electrode 4 may be provided with a groove or a hole for ejecting an inert gas such as a helium (He) gas or a nitrogen (N ₂ ) gas as a cooling gas. In this embodiment, the lower electrode 4 is grounded.

At the bottom of the chamber 2 provided with the upper electrode 3 and the lower electrode 4, for example, a gas exhaust port 8 for exhausting gas in the chamber 2 is formed. For example, a negative pressure source (not shown) composed of a turbo pump is connected. Therefore, the inside of the chamber 2 is evacuated by the negative pressure source and maintained at a predetermined vacuum state.

In the etching apparatus 1 configured as described above, the inside of the chamber 2 is maintained at a predetermined vacuum state, and an etching gas is blown out from the blowout port 5a of the upper electrode 3, and the upper electrode 3 and the lower electrode 4 are connected to each other. During this time, an RF voltage is applied to generate an etching gas plasma. Then, the wafer 10 held on the upper surface of the lower electrode 4
Is etched.

At this time, the lower surface 3a of the upper electrode 3 is positioned at the periphery of the gap h ₁ between the upper electrode 3 and the lower electrode 4.
But because it is formed is concavely curved so as to be larger than the gap h ₂ between the upper electrode 3 and the lower electrode 4 in the substantially central portion of the lower surface 3a, between the upper electrode 3 and the bottom electrode 4 The density of the generated plasma per unit area is higher at the peripheral portion than at the substantially central portion of the upper electrode 3. That is, since the density of the plasma per unit area on the peripheral portion of the wafer 10 held on the upper surface of the lower electrode 4 is increased, the number of plasmas reacting with the object to be processed on the peripheral portion of the wafer 10 per unit time is substantially reduced. Will increase.

As a result, even if convection of the etching gas occurs at the peripheral portion of the wafer 10 and reaction products are easily deposited on the peripheral portion of the wafer 10,
Since the decrease in the etching rate at the peripheral portion of 0 can be suppressed and the etching rate at the central portion of the wafer 10 can be made substantially equal, the etching uniformity in the plane of the wafer 10 can be improved. Therefore,
By using the etching apparatus 1, a highly reliable and high quality semiconductor device can be manufactured with a high yield.

In addition, it is not necessary to add a new member, and the etching uniformity can be improved without a significant change only by changing the shape of the lower surface 3a of the upper electrode 3, thereby increasing the manufacturing cost of the etching apparatus 1. Can be suppressed.

In this embodiment, the upper electrode and the lower electrode have a substantially circular shape in plan view having a diameter substantially equal to the diameter of the wafer. Can be formed in a concavely curved state.

Also, as shown in FIGS. 1 and 2, the lower surface of the upper electrode is concavely curved so that the gap h _{1 at} the peripheral portion of the wafer 10 is smaller than the gap h _{2 at} the central portion of the wafer 10. If formed
The shape of the lower surface of the upper electrode is not limited to this example.

[0025] When the upper electrode 3 of larger diameter than the diameter of the wafer 10, for example, extends from the portion 3a ₁ which is curved in the concave lower surface 3a of the upper electrode 3 as shown in the modification of FIG. 3 outwardly The projected portion 3a ₂ is replaced with a concavely curved portion 3a ₁
Periphery from extending horizontally flat surface (hereinafter, this surface a referred to as 3a ₂₎ it can be formed on. In this modification, when the upper electrode 3 and the lower electrode 4 are arranged to face each other, the upper electrode 3 and the lower electrode 4 are positioned with reference to the flat surface 3a ₂ of the lower surface 3a of the upper electrode 3 and the upper surface 4a of the lower electrode 4. Electrode 4
There is an advantage that positioning is easy.

[0026]

As described above, according to the etching apparatus of the present invention, the lower surface of the upper electrode has a concave shape such that the gap between the upper electrode and the lower electrode is smaller at the peripheral portion than at the substantially central portion of the lower surface. When plasma is generated between the upper electrode and the lower electrode, the density per unit area of the plasma is higher at the peripheral portion than at the substantially central portion of the lower surface of the upper electrode because the configuration is formed in a curved shape. can do. Therefore, even if convection of the etching gas occurs at the peripheral portion of the wafer and reaction products are easily deposited on the peripheral portion of the wafer, a decrease in the etching rate at the peripheral portion of the wafer can be suppressed, and Can be made substantially equal to the etching rate at the central portion of the wafer, so that the etching uniformity in the wafer plane can be improved. Therefore, with the use of the etching apparatus of the present invention, a highly reliable and high quality semiconductor device can be manufactured with high yield.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an etching apparatus according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a sectional view showing a modification of the main part of FIG. 1;

FIG. 4 is a schematic configuration diagram showing an example of a conventional etching apparatus.

FIGS. 5A and 5B are diagrams for explaining the problem of the present invention.

FIG. 6 is a diagram showing a relationship between an etching rate and a gap h between an upper electrode and a lower electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Etching apparatus, 2 ... Chamber, 3 ... Upper electrode, 3
a: lower surface, 4: lower electrode, 4a: upper surface, 10: wafer,
h _1, h ₂ ... gap

Claims (1)

[Claims] An upper electrode and a lower electrode are provided in a chamber so as to face each other, and a plasma is generated between the upper electrode and the lower electrode so that an object to be processed on a wafer held on the upper surface of the lower electrode is removed. In an etching apparatus for performing etching, a lower surface of the upper electrode is formed in a concavely curved shape so that a gap between the upper electrode and the lower electrode is smaller at a peripheral portion than at a substantially central portion of the lower surface. An etching apparatus characterized by the above-mentioned.