JP3318409B2 - Plasma processing apparatus and ashing method using this plasma processing apparatus - Google Patents

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 for processing an object to be processed (hereinafter simply referred to as a "wafer") such as a semiconductor wafer in a plasma atmosphere, and an ashing method using the plasma processing apparatus.

[0002]

2. Description of the Related Art As a plasma processing apparatus for performing etching and ashing using plasma, an apparatus called a downstream type is known. In this downstream type plasma processing apparatus, a chamber above the stage of an object to be processed is covered by a chamber, and a pair of sheet-like electrodes are arranged above the chamber to make the upper part of the chamber a plasma generation space, while the lower space facing the stage Is a processing space, an object to be processed is avoided far from a plasma generation space in which a large amount of charged particles or the like that adversely affect the processing are present, and only radicals effective for the reaction flow down to the processing space.

[0003]

In the above-mentioned downstream type plasma processing apparatus, plasma is mainly generated at the narrowest portion of the opposed sheet-like electrodes, and all of the space between the sheet-like electrodes is generated. Does not occur uniformly in the space. For this reason, sufficient radicals cannot be obtained, and the etching rate and the ashing rate decrease.
When the high frequency power applied to increase the etching rate or ashing rate is increased or the degree of vacuum is changed, plasma is drawn to the stage or exhaust port, and as a result, the plasma approaches the wafer and the wafer is charged up by charged particles. Or abnormal discharge occurs.

[0004]

In order to solve the above-mentioned problems, a plasma processing apparatus according to the present invention comprises a so-called plasma generation space.
Vertical bell-shaped upper half and processing dome lower half
In a downstream type plasma processing apparatus comprising a first portion and a second portion, the upper electrode is constituted by first and second sheet electrodes, and the first sheet electrode and the second sheet electrode are combs having convex portions and concave portions. With a tooth shape, the convex portion of one sheet-like electrode meshes with the concave portion of the other sheet-like electrode at a substantially constant interval, and furthermore, the
The lower end of the vertical bell-shaped upper half is connected to the ground.
That surrounds the second sheet electrode, further wherein dounce
A ground electrode was provided around the outer periphery of the lower half of the dome shape of the trim type chamber.

The ashing method according to the present invention uses the plasma processing apparatus, uses oxygen gas as a reaction gas, sets a flow rate of the reaction gas to 300 to 5000 sccm, and applies a high-frequency applied power of 300 to 3000 W or more.
Further, the temperature of the object was set to 250 ° C. or less.

[0006]

The first and second sheet-like electrodes are formed in a comb-like shape, and these are meshed at regular intervals, so that plasma is uniformly generated along the circumferential direction of the chamber, and charged particles are generated downward. Even if it flows down, it is removed by the ground electrode surrounding the lower periphery of the chamber.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a partially cutaway front view of a plasma processing apparatus according to the present invention. In the plasma processing apparatus, an opening 2 is formed in a base 1, and a chamber 3 made of quartz is formed so as to cover the opening 2. Attachment, the shape consists of a dome-shaped lower half 3a and a vertical bell-shaped upper half 3b,
A reaction gas inlet 4 is provided in the upper half 3b, and a first sheet electrode 5 connected to a high frequency power supply and a second sheet electrode 6 connected to ground are provided on the outer periphery of the upper half 3b. Are arranged facing each other with a left and right separation with respect to the axis of.

[0008] The first sheet-like electrode 5 and the second sheet-like electrode 6 are convex portions 5 extending in the circumferential direction of the upper half portion 3b of the chamber.
a, 6a and the concave portions 5b, 6b are continuously formed in the vertical direction to form a comb-like shape, and the convex portions 5a,
6a is engaged with the recesses 6b, 5b of the other sheet-like electrode at a substantially constant interval g. As described above, by making the interval g between the pair of sheet electrodes 5 and 6 substantially constant in the circumferential direction and the axial direction, plasma is uniformly generated along the inner periphery of the upper half portion 3b of the chamber.

The lower end 6c of the second sheet electrode 6 surrounds the chamber 3 at a position lower than the first sheet electrode 5. By surrounding the lowermost end of the plasma generation space with the sheet-like electrode 6 connected to the ground, charged particles can be prevented from flowing toward the wafer W.

On the other hand, a stage 7 for setting a wafer W faces the opening 2 of the base 1 from below, and an exhaust passage 8 connected to a vacuum pump is formed in the base 1. Has a ground electrode 9 surrounding it. With such a configuration, the charged particles fly to the ground electrode 9 before flying to the exhaust hole or the like at the time of discharge, so that abnormal discharge can be prevented and the radical concentration on the surface of the wafer W to be processed can be increased. . The ground electrode 9 surrounding the outer periphery of the lower portion of the chamber may have a ring shape, or the same effect can be obtained even if the ground electrode 9 is divided into a plurality of ring shapes.

FIG. 2 is a front view of a plasma processing apparatus according to another embodiment. In this embodiment, the first sheet electrode 5 and the second sheet electrode 6 are connected to the upper half 3b of the chamber. Convex portions 5a, 6a and concave portions 5b, 6b extending in the axial direction of
Are formed continuously in the circumferential direction, and the protrusions 5a, 6a of one sheet-like electrode mesh with the recesses 6b, 5b of the other sheet-like electrode at a substantially constant interval g. . Also in this plasma processing apparatus, plasma is uniformly generated on the inner peripheral surface of the upper half part 3b of the chamber along the space g as in the above case.

Next, if the above-described plasma processing apparatus is used, ashing can be performed under the following conditions. Reaction gas: Oxygen gas + argon gas or nitrogen gas or mixed gas to which CHF3 or the like is added as required Reactant gas flow rate: 300 to 5000 sccm Pressure: 0.3 to 2.0 Torr Temperature of object to be treated: 250 ° C. or less High frequency power: 300 to 3000 W or more

The present invention will be described more specifically. FIG. 3 shows a change in emission spectrum in the case of using the device of the present invention and in a conventional device, both of which use oxygen gas as a reaction gas. As is clear from this figure, according to the present invention, there are many active species participating in the reaction, and the amount of charged particles causing damage is extremely small.

Here, in the conventional apparatus, since the discharge was non-uniform, the gas flow rate could not be increased more than about 500 sccm, and the high frequency power was less than 1 kW at most. According to the present invention, since the discharge becomes uniform, it is possible to increase the gas flow rate and the high-frequency power. Therefore, it is possible to increase the ashing rate by adding CHF ₃ gas in addition to oxygen gas as a reaction gas. Become. Even with oxygen gas alone, a high ashing rate can be obtained. However, if this is done, the temperature of the object to be processed increases, and the object is damaged. If CHF ₃ gas is added to oxygen gas at a volume ratio of 5 to 10% with respect to oxygen gas, Since the reaction proceeds by confining the active species, the temperature rise is suppressed and damage is less likely to occur as compared with the case of using oxygen gas alone.

FIG. 4 is a graph comparing the emission spectrum change between the case where the ring-shaped ground electrode 9 is provided and the case where the ring-shaped ground electrode 9 is not provided. As is clear from this graph, the provision of the ground electrode 9 increases the number of active species participating in the reaction and reduces the number of charged particles that cause damage.

Although ashing has been described as a mode of use of the plasma processing apparatus according to the present invention, the plasma processing apparatus according to the present invention can also be used for etching or the like by appropriately selecting and using a reaction gas. it can.

[0017]

As described above, according to the plasma processing apparatus of the present invention, the first and second sheet-like electrodes are formed in a comb-like shape, and these are meshed at regular intervals. In addition, since plasma is uniformly generated in the circumferential direction of the chamber, the stability of discharge is improved. If the stability of the discharge is improved, the flow rate of the gas can be increased, and the power of the applied high frequency can be increased. Incidentally, conventionally, the gas flow rate was about 500 sccm and the power was less than 1 kW, but the gas flow rate can be 1800 sccm or more and the power can be 2 kW or more. When the gas flow rate increases, radicals effective for the reaction increase as shown in FIG. 3, the number of charged particles causing charge-up and the like decreases, and even when a ring-shaped ground electrode is provided. As shown in FIG. 4, a similar tendency is observed. Therefore, if these structures are adopted, the ashing rate and the etching rate can be increased while maintaining low damage. Incidentally, the ashing rate was conventionally 2.5 to 2.7 μm / min.
0 μm / min or more, and regarding the damage, the flat band voltage shift 0.0
2 V or less was achieved, and the uniformity was ± 8% or less for an 8-inch wafer and ± 5% or less for a 6-inch wafer.

Further, according to the ashing method of the present invention, since the above-described plasma processing apparatus is used, the concentration of radicals (active species) on the surface of the object to be processed can be increased.
F ₃ gas is mixed with oxygen gas, whereby the temperature of the object to be treated is 250 ° C. or less (about 300 ° C. in a conventional microwave method).
C.) and ashing can be prevented as a result.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a plasma processing apparatus according to the present invention.

FIG. 2 is a front view of a plasma processing apparatus according to another embodiment.

FIG. 3 is a graph showing a relationship between a reaction gas flow rate and a change in emission spectrum.

FIG. 4 is a graph showing a relationship between the presence or absence of a ring-shaped ground electrode and a change in emission spectrum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 3 ... Chamber, 5 ... 1st sheet electrode, 6 ... 2nd sheet electrode, 5a, 6a ... convex part, 5
b, 6b recess, 9 ring-shaped ground electrode, W wafer.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Matsushita 150 Nakamaruko, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Tokyo Oka Kogyo Co., Ltd. (72) Inventor Kaoru Sakamoto 150 Nakamaruko, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Tokyo Oka Kogyo Co., Ltd. (56) References JP-A-63-260030 (JP, A) JP-A-63-156533 (JP, A) JP-A-58-204526 (JP, A) JP-A-4-160163 (JP, A) JP-A-62-105996 (JP, A) JP-A-59-126500 (JP, U) Patent 3266163 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 1/46 C23F 4/00 H01L 21/3065

Claims (2)

(57) [Claims] 1. A plasma generator is provided above a stage of an object to be processed.
Vertical bell-shaped upper half of raw space and dome of processing space
While covering with a downstream type chamber consisting of a lower half of the shape, and providing an exhaust port around the stage,
Vertical bell-shaped upper half of the downstream chamber
A plasma processing apparatus in which a first sheet-like electrode connected to a high-frequency power supply and a second sheet-like electrode connected to the ground are arranged on the outer peripheral surface of the first sheet-like electrode;
The form a comb shape having a second sheet electrode, respectively convex and concave portions, meshes open the further substantially regular intervals in the recess of the sheet-shaped electrode protruding portions and the other of one of the sheet-shaped electrode Vertical fishing that is the plasma generation space
The lowermost end of the bell-shaped upper half is connected to a second shell connected to the ground.
Surrounds at over preparative shaped electrodes, the plasma processing apparatus characterized by being provided with a ground electrode surrounding this further on the outer periphery of the dome-shaped lower half portion of the downstream-type <br/> chamber. 2. An ashing method using a plasma processing apparatus according to claim 1, wherein an oxygen gas is used as a reaction gas, and a flow rate of the reaction gas is 300 to 5000 sccm.
An ashing method, wherein the high-frequency applied power is 300 to 3000 W or more and the temperature of the object to be processed is 250 ° C. or less.