JPH11186238A - Plasma processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scale up more a plasma producing region in a parallel plate plasma processor, wherein an etching treatment of a semiconductor wafer is performed, than the surface of the wafer and to stabilize the production of a plasma. SOLUTION: The specific resistance of plasma correction members 4-1, which are arranged on the direct peripheral part of a wafer 8 and consist of a semiconductor material, is stipulated within a constant range and the structure of the members 4-1 is stipulated. The specific resistance of the members 4-1 consisting the semiconductor material is reduced along with a plasma treating time by heat, which is given from a plasma, but the members 4-1 can keep a constant specific resistance or higher until the end of plasma processing if the members 4-1 have a constant specific resistance or higher at normal temperatures and if the members 4-1 have a constant specific resistance or lower, a plasma is produced on an area larger than the wafer 8 because the electric field from a lower electrode 6 penetrates the materials 4-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a parallel plate type plasma processing apparatus used for plasma etching of a semiconductor wafer.

[0002]

2. Description of the Related Art In a parallel plate type (plane electrode type) plasma processing apparatus, when an outer peripheral portion of a peripheral edge of a wafer to be processed is an insulator (ceramic, quartz, etc.), an inner diameter portion of the insulator becomes a plasma edge portion. The state of plasma generation differs between the central portion and the peripheral portion of the wafer, and the plasma processing performance at the peripheral portion of the wafer was inferior to the processing performance at the central portion of the wafer.
Therefore, a device for obtaining uniformity of the plasma processing performance has been devised by placing a plasma compensating member made of the same material as the wafer on the outer peripheral portion of the wafer.

FIG. 5 is an explanatory sectional view showing a conventional parallel plate type plasma processing apparatus. The plasma processing chamber 1 is arranged in parallel with the grounded upper electrode 3, the upper electrode insulating material 2 surrounding the upper electrode, and the upper electrode, becomes a wafer stage on which the wafer 8 is mounted, and is supplied with power from the high frequency power supply 7. A lower electrode 6, a lower electrode insulating material 5 surrounding the lower electrode, and a ring-shaped semiconductor material which is disposed on the outer periphery of the wafer 8 on the lower electrode 6 and is used for the purpose of improving the plasma processing uniformity on the surface of the wafer 8. And a plasma correction member 4 composed of When the wafer 8 is set on the surface of the lower electrode 6, a plasma processing gas is introduced into the plasma processing chamber 1, and after the plasma processing gas pressure in the plasma processing chamber 1 is stabilized, high-frequency power is supplied from the high-frequency power source 7 to the lower electrode 6. , A plasma is generated between the lower electrode 6 and the upper electrode 3. The surface of the wafer 8 is plasma-etched by this plasma.

[0004]

FIGS. 3 and 4 are cross-sectional views of a plasma processing apparatus (FIG. 5) showing the distribution of the electric field intensity in the ion sheath of plasma in the wafer etching process.
, And plasma correction members are indicated by 4-3 and 4-4, respectively.

FIG. 3 shows an electric field intensity distribution when the resistance value of the plasma correction member 4-3 is large and close to an insulator.
The plasma generation region does not extend to the periphery of the wafer, and a uniform electric field cannot be obtained at the periphery of the wafer. Therefore, the etching performance at the wafer periphery is inferior to the etching performance at the center of the wafer.

FIG. 4 shows an electric field intensity distribution when the conductivity of the plasma correction member 4-4 is high, and the plasma generation region extends on the correction member outward from the periphery of the wafer. The electric field intensity decreases at the central portion of the wafer, and the processing capability at the peripheral portion of the wafer improves, but the processing capability at the central portion of the wafer decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a uniform plasma intensity distribution over the entire surface of a wafer, to generate a stable plasma whose generation region does not change during the etching process, and to have a good and uniform etching process performance over the entire wafer. An object of the present invention is to provide a plasma processing apparatus.

[0008]

According to the plasma processing apparatus of the present invention, the semiconductor material of the plasma compensating member provided on the outer peripheral portion of the wafer surrounding the peripheral edge of the lower electrode serving as the wafer stage has a constant specific resistance.

[0009] The plasma correction member is arranged in a ring shape surrounding a circular wafer.

The upper surface of the ring-shaped plasma compensating member has a constant width extending outward from the periphery of the wafer at the same level as the surface of the wafer.

The fixed width of the ring-shaped plasma compensating member is determined in accordance with the enlarged width of the plasma generation region.

The inner portion of the ring-shaped plasma compensating member extends inside the lower surface of the wafer and has a structure in which the lower electrode is not exposed to plasma.

The specific resistance of the semiconductor material serving as the base material of the plasma correction member is 1 Ωcm or more and 15 Ωcm or less.

The semiconductor material serving as the base material of the plasma correction member may be silicon.

Although the specific resistance of the semiconductor compensating member, which is a semiconductor, decreases with the plasma processing time due to the heat given by the plasma, if the specific resistance at room temperature is equal to or higher than a certain value, the specific resistance is higher than a certain value until the end of the plasma processing. In addition, if the plasma correction member has a specific resistance equal to or less than a certain value, the electric field from the lower electrode is transmitted, so that plasma is generated in a larger area than the wafer. The correction member has a specific resistance in a certain range, and a uniform and stable plasma can be generated over the entire surface of the wafer by modifying the shape and structure.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a parallel plate type plasma processing apparatus having a structure similar to that of the plasma processing apparatus shown in FIG. 3. Unlike FIG. 4 and FIG. 4, the plasma generation region is appropriately enlarged from the surface of the wafer to the surface of the plasma correction member, indicating that the plasma is uniformly and stably generated over the entire surface of the wafer.

In the plasma processing apparatus whose cross section is shown in FIG. 1, the semiconductor material of the base material of the plasma correcting member 4-1 is
It is a silicon material whose specific resistance value is between 1 Ωcm and 15 Ωcm, and the range of this specific resistance value is obtained from the result of an experiment. When the specific resistance value is less than 1 Ωcm, the plasma generation region does not sufficiently extend to the periphery of the wafer as shown in FIG. 3, and when the specific resistance value exceeds 15 Ωcm, the plasma generation region is formed as shown in FIG. In this case, it was impossible to obtain a uniform electric field intensity distribution from the center of the wafer to the periphery as shown in FIG. The plasma compensating member 4-1 is arranged in a ring shape surrounding the periphery of the circular wafer 8, the surface thereof extends outward at the same level as the surface of the wafer 8, and the width of the ring is 2
0 mm. The correction member 4-1 may be integrally formed in a ring shape, or a configuration in which a plurality of members are arranged in a ring shape.

In another embodiment shown in FIG. 2, a plasma compensating member 4-2 having the same specific resistance value is provided.
Is thinned in a stepwise manner by the thickness of the wafer 8, and this portion extends below the wafer 8. Accordingly, even when a gap is formed between the peripheral edge of the wafer 8 and the portion where the plasma correction member 4-2 contacts, there is no possibility that the surface of the lower electrode 6 is exposed to plasma.

This plasma processing apparatus is composed of a lower electrode 6 covered with a lower electrode insulating material 5, the surface of which is formed of aluminum cathode-oxidized, and an upper electrode insulating material 2 which is formed of silicon, and which is formed of silicon. A wafer 8 having an upper electrode 3 arranged in parallel with the electrode 6 and subjected to plasma processing is placed on the lower electrode 6, and CF ₄ or CH is used as a plasma generating gas.
F ₃ was introduced into the plasma processing chamber 1 by 30 sccm and 70 sccm respectively, and after the pressure in the plasma processing chamber 1 was stabilized, the oscillation frequency was 13.56 MH from the high frequency power supply 7.
When a high frequency power of z and an output of 1500 w is applied to the lower electrode 6, plasma is generated in a space formed by the lower electrode 6 and the upper electrode 3. At this time, the plasma is generated up to the surface of the plasma correction member 4.

There are various types of high-frequency power application systems, such as a system for applying high-frequency power not only to the lower electrode but also to the upper electrode. There is no change in that the members can be applied.

[0021]

According to the present invention, the specific resistance of the semiconductor material of the plasma compensating member is set within a certain range, and by modifying the shape thereof, uniform and stable plasma is generated over the entire surface of the wafer and uniform and excellent over the entire wafer. There is an effect that a high etching processing performance can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram in which a distribution of an electric field intensity in an ion sheath of plasma generated during processing is superimposed on a cross-sectional view illustrating an embodiment of a plasma processing apparatus of the present invention.

FIG. 2 is a sectional view showing another embodiment of the plasma processing apparatus of the present invention.

FIG. 3 is an explanatory diagram showing an example of a distribution of electric field intensity in a plasma ion sheath overlaid on a cross-sectional view of a conventional plasma processing apparatus.

FIG. 4 is an explanatory diagram showing an example of a distribution of electric field intensity in a plasma ion sheath overlaid on a cross-sectional view of a conventional plasma processing apparatus.

FIG. 5 is an explanatory view illustrating a cross-sectional view of a conventional parallel plate type plasma processing apparatus.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 plasma processing chamber 2 upper electrode insulator 3 upper electrode 4, 4-1, 4-2, 4-3, 4-4 plasma correction member 5 lower electrode insulator 6 lower electrode 7 high-frequency power supply 8 wafer

Claims (7)

[Claims] In a parallel plate type plasma processing apparatus having a plasma correction member made of a semiconductor material at an outer periphery of a wafer surrounding a wafer periphery of a lower electrode serving as a wafer stage, the semiconductor material has a constant specific resistance. Characteristic plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein the plasma correction member is arranged in a ring shape surrounding a peripheral edge of a circular wafer. 3. The plasma processing apparatus according to claim 2, wherein an upper surface of the ring-shaped plasma compensating member has a constant width extending outward from a peripheral edge of the wafer at the same level as the wafer surface. 4. The plasma processing apparatus according to claim 3, wherein the predetermined width is determined in accordance with an enlarged width of a plasma generation region. 5. The plasma processing apparatus according to claim 4, wherein an inner portion of the ring-shaped plasma compensating member extends inside the lower surface of the wafer and the lower electrode is not exposed to plasma. 6. The semiconductor material according to claim 2, wherein the semiconductor material has a specific resistance of 1 Ωcm or more and 15 Ωcm or less.
Item 6. The plasma processing apparatus according to Item 1. 7. The plasma processing apparatus according to claim 1, wherein the semiconductor material is silicon.