JP2001007087A - Single-wafer processing plasma ashing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly strip a resist on a wafer surface, while keeping the wafer temp. uniform at a low temp. in a single-wafer processing plasma ashing developing apparatus. SOLUTION: Protrusions 1 point-contacted to a central part of a wafer 10 and arcuate protrusions 2 line-contacted to the periphery of the wafer 10 are provided on a stage 3, the wafer 10 is mounted on these protrusions, a heating block 4 having a much higher heat capacity and held at a constant temp. is fixed to the stage 3, to transfer the heat of the block 4 to the wafer 10 via the arcuate protrusions 2, thereby uniformly heating the wafer 10 to keep desired temp. inside the wafer 10 surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-wafer plasma ashing apparatus for removing a patterned resist film formed on the surface of a single semiconductor substrate by plasma ashing, and more particularly, to mounting a semiconductor substrate thereon. Stay
About di.

[0002]

2. Description of the Related Art Usually, when a desired pattern is formed on a semiconductor substrate (hereinafter, referred to as a wafer) in the manufacture of a semiconductor device, a resist is applied to the entire surface of the wafer to form a resist film, and this resist film is selected. And remove the desired pattern
Ion is selectively implanted with the removed pattern film to inject impurities into the wafer,
Alternatively, the wiring, the circuit, and the element are formed by selective etching.

In any of the steps, the unnecessary resist left after these steps must be removed. The method of removing the resist is a method by plasma ashing which is currently most used.

In this method, a wafer is placed on a stage, which is one electrode of a container under reduced pressure, and glow discharge is caused by the introduced oxygen gas to generate plasma. Then, the resist containing a hydrocarbon compound as a main component is ashed by the activated oxygen atoms, and the ash separated from the wafer is discharged from the container.

Further, the peeling rate by the plasma ashing method varies depending on the temperature of the wafer. In other words, the higher the temperature, the higher the release rate, and the lower the temperature, the lower the release rate. However, when the temperature of the wafer is raised to 200 ° C. or more to increase the peeling rate, for example, a popping phenomenon occurs in which the hardened outer layer of the resist layer hardened by ion implantation or the like is generated by gas generation of the inner layer resist. Occurs, and the hardened outer layer is broken by the gas explosion inside, and the ash is scattered and adheres to the semiconductor element forming surface to generate a defective semiconductor device.

However, when the temperature is set to a low temperature of about 100 degrees, the above-mentioned popping phenomenon does not occur, although the peeling rate is lowered. However, the lower the peeling rate, the longer the time required for peeling, and the lower the total productivity. A resist stripping method and apparatus for solving such a problem is disclosed in Japanese Patent Laid-Open No. 10-32160.
No. 3 discloses this.

In the method and the apparatus for removing the resist, when the resist is removed from the cured layer on the surface of the resist,
An auxiliary stage is provided to be in contact with the central portion of the wafer or the outer edge of the wafer, and the wafer is lifted by the auxiliary stage in a state of being separated from the heater built-in stage to reduce the contact area. By suppressing the heat transfer from the wafer and lowering the temperature of the wafer, the occurrence of the pumping phenomenon is suppressed, and the cured layer of the resist is peeled off at a low speed. Then, after the cured layer is peeled off, the auxiliary stage is lowered so that the mounting surface of the stage that has been in contact with the outer peripheral surface of the wafer and the mounting surface of the wafer of the auxiliary stage coincide with each other. The wafer is brought into contact with the entire back surface, the temperature of the wafer is increased by heat transfer from the heater, and the wafer is peeled off at a high peeling rate, thereby shortening the total peeling time and improving productivity.

[0008]

In the above-described conventional resist stripping method and apparatus, the auxiliary stage having a small contact area supports the wafer at the center or outer edge of the wafer, but the large resist is removed. The more it becomes
A temperature difference occurs between the auxiliary stage and a portion that is in contact with the wafer and a portion that is not in contact with the wafer.

Further, the temperature of the wafer pushed up by the auxiliary stage, which is separated from the stage containing the heater, depends on the radiant heat of the plasma. Relying on unstable radiant heat makes it difficult to keep the temperature of the wafer constant, resulting in more and more temperature differences. This partial difference in the peeling rate may cause the resist to remain partially, and it takes much time. This means that even when the etching end point detection mechanism is provided, it is difficult to reliably determine when the hardened skin layer has been removed.

Certainly, if the separation is carried out in two stages of a low temperature and a high temperature, the processing speed is improved, but as long as this switching cannot be carried out reliably, is it possible to completely remove the resist without causing a pumping phenomenon and remaining? It is questionable. In addition, since the auxiliary stage is pushed up by the rod of the lifting mechanism during the peeling operation, there is a concern that the peeled ash adheres to the rod and hinders the operation of the lifting mechanism.

Accordingly, an object of the present invention is to provide a plasma etching apparatus capable of maintaining a uniform wafer temperature at a low temperature and uniformly removing a resist on a wafer surface.

[0012]

A feature of the present invention is that a gas such as oxygen is introduced into a container under reduced pressure, atoms of the gas are activated by glow discharge, and a resist coated on one semiconductor substrate is used. In a single-wafer plasma ashing apparatus for removing a semiconductor substrate, a plurality of projection members supporting a central portion of one semiconductor substrate at point contact and a plurality of arc-shaped projection members supporting a peripheral portion of the semiconductor substrate at line contact are provided. This is a single-wafer plasma ashing apparatus including a stage formed on the surface and a block with a built-in heater for maintaining the temperature of the stage constant. Further, it is desirable that the stage on which the projection member and the arc-shaped projection member are formed can be attached to and detached from the block. Further, the projection member is 3
It is desirable that there are three and the three protrusion members are arranged at the apex angle of an equilateral triangle.

On the other hand, a ring-shaped member arranged to surround the outer periphery of the stage and supporting and holding a peripheral portion of the semiconductor substrate, and the semiconductor substrate is lifted together with the ring-shaped member above the stage. It is preferable that the semiconductor device further comprises an elevating rod for placing the semiconductor substrate on the projection member and the arc-shaped projection member. Further, it is preferable to provide a sleeve for covering the lifting rod during the removal of the resist.

[0014]

Next, the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are a plan view and a sectional view taken along the line AA, respectively, showing a stage of a single-wafer plasma ashing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the stage is projected from the surface of the stage 3, is in point contact with the vicinity of the center of the wafer 10, and is in line contact with the projection 1 supporting the wafer 10, and is in line contact with the periphery of the wafer 10. Has an arc-shaped projection 2 for supporting the same.

Further, it is desirable that the projections 1 supporting the central portion of the wafer 10 by point contact are arranged at the positions of the apex angles of an equilateral triangle and support the wafer 10 at three points. With such a three-point support, even a large wafer of 10 inches can be stably supported by the three protrusions 1 contacting the wafer 10.

On the other hand, the arc-shaped projection 2 which is in line contact with the peripheral edge of the wafer 10 projects from the stage 3 at the same height as the projection 1. Then, it comes into contact with the peripheral portion of the wafer 10 placed on the three projections 1. However, the wafer 10 is not necessarily a flat substrate, and is often curved to swell upward or conversely, to swell downward. The manner of this curve differs depending on the previous process, but if the same lot, all wafers are curved with the same tendency, so the height of the arc-shaped protrusion 2 is changed to the height of the protrusion 1. It is not necessary to set the height of the arc-shaped protrusion 2 according to the state of curvature of the wafer 10.

The area where the wafer 10 contacts the entire area of the arc-shaped projection 2 must exceed 50 percent even if the deformation of the wafer is poor. For this reason, the arc-shaped projection 2 is manufactured beforehand so as to be higher than the projection 1, and the wafer, the arc-shaped projection 2 and the contact surface are checked to adjust the height of the arc-shaped projection 2 by shaving or the like. .

As described above, if the line contact area of the arc-shaped protrusion 2 is secured, the protrusion 1 that makes point contact with the center of the wafer 10 is formed.
The line contact area of the arc-shaped protrusion 2 that comes into contact with the peripheral portion of the wafer 10 is much larger than the contact area. In other words, the central portion of the wafer 10 is supported by the projection 1 having a large thermal resistance, and the peripheral portion of the wafer 10 is supported by the arc-shaped projection 2 having a small thermal resistance. Therefore, the heat from the block 4 having a large heat capacity is smoothly transmitted to the wafer 10 having a small heat capacity via the arc-shaped projections 2, and the same temperature as that of the block 4 can be reached in a short time.

In consideration of this, in FIG. 1, three arc-shaped projections 2 are provided. However, if the length of the arc-shaped projections is reduced and the number thereof is increased, the degree of curvature of the wafer 10 is reduced. Even if it is large, the total line contact area between the arc-shaped projection 2 and the wafer 10 can be secured. Also, as the total line contact area increases, the time to reach the saturation temperature decreases.

Normally, a fine pattern is formed from the central portion to the peripheral portion of the wafer, whereas the peripheral portion of the wafer often has no portion where the pattern is formed. Therefore, the resist coated on the wafer is more widely applied to the peripheral portion than to the central portion of the wafer 10. For this reason, as described above, if a temperature gradient is generated by transferring heat from the peripheral portion of the wafer 10 to the central portion, and the temperature of the peripheral portion of the wafer 10 is slightly higher than the temperature of the central portion of the wafer 10, The peeling rate at the peripheral portion is higher than that at the central portion, and the resist over the entire area of the wafer 10 can be uniformly peeled.

For example, if the heater 5 is controlled so as to keep the block 4 constant at 120 degrees Celsius, the peripheral portion of the wafer 10 is heated to 120 degrees, and there is a slight difference depending on the size of the wafer 10. However, the central portion of the wafer 10 can be maintained at 100 to 110 degrees by the heat transfer of the peripheral portion. Providing the temperature gradient at the peripheral portion and the central portion of the wafer 10 in this way suggests that the resist remaining on the entire surface of the wafer 10 can be uniformly stripped.

The stage 3 made of the same aluminum as the block 4 has a projection 1 and an arc-shaped projection 2 formed by forging, but does not damage the surface of the wafer 10. The hardness of the protrusions is
Lower than the surface hardness. Therefore, the wafer 10 is worn while the transfer of the wafer 10 is repeated many times, and the wafer 10 and the protrusion 1 are worn.
Are not in contact with each other, and the stage itself has a life.

Therefore, the stage which has been integrated with the block can be cut off, and the stage 3 can be easily replaced with the stage 4 so that the stage 3 can be easily replaced.
J3 can be removed. Of course, the stage 3 is fixed to the block 4 with screws (not shown) so as to easily mount the stage, and to secure heat transfer.

FIGS. 2A and 2B are a partial plan view and a sectional view showing a modification of the stage of FIG. As described above, each time the wafer is repeatedly mounted on the stage, the projections on the stage are worn, and the life of the stage is shortened. Therefore, in this embodiment, when the wafer is placed on the protrusion, horizontal movement (slip) that promotes abrasion is suppressed, and the wafer can be placed on the protrusion by movement in the direction perpendicular to the protrusion. That is, a mechanism is provided.

As shown in FIG. 2, the wafer mounting mechanism includes a ring 6 having a mounting surface on which a peripheral portion of the wafer 10 is mounted, and the ring 6 is moved up to a fixed position or is moved up to the stage 3 surface. An elevating rod 7 to be lowered and a sleeve 8 for covering the elevating rod 7 so that ash does not adhere to the elevating rod 7 during resist stripping.

Next, the operation of mounting the wafer on the projection and taking out the wafer from the stage in this stage will be described. First, when a wafer is placed on the projection 1 of the stage 3, the wafer is placed on a fork from a cassette stored in a chamber connected to the container via a gate valve.
The fork moves to position the wafer 10 on the stage 3 on which nothing is placed.

Next, the lifting rod 7 is raised, and the fork 9
Then, the wafer 10 is transferred to the ring 6. Then, the fork 9 on which the wafer 10 has been transferred moves in a direction perpendicular to the plane of the paper and stops at a position retracted from the stage 3. The wafer 10 transferred to the ring 6 is lowered together with the lifting rod 7 which is gently lowered by driving the motor, and the wafer 10
The peripheral portion of the wafer 10 is brought into contact with the arc-shaped projection 2. The lifting rod 7 is housed in the sleeve 8.

During the peeling of the resist from the wafer 10, the lifting rod 7 is covered by the sleeve 8, so that the scattered resist ash does not adhere. When the resist peeling is completed, the lifting rod 7 is raised, and the wafer 10 placed on the projection 1 is transferred to the ring 6. And the lifting rod 7
When the ring 6 on which the wafer 10 is loaded reaches a predetermined height due to the rise, the fork 9 moves from the retracted position, passes between the two lifting rods 7, and stops at the predetermined position. This state is shown in FIG.

Next, when the lifting rod 7 descends,
The mask 9 contacts the wafer 10. Then, the wafer 10 is transferred to the fork 9 by slightly raising the fork 9.
The fork 9 on which the wafer 10 is placed is retracted, and the lifting rod 7 is moved.
And the ring 6 is lowered to the surface of the stage 3.

By mounting the wafer 10 statically so as not to cause slippage or the like, abrasion of the projections 1 is reduced as compared with the conventional mounting of a wafer such as a manipulator, and the life of the stage 3 is extended. It could be stretched several times.

[0032]

As described above, according to the present invention, a projection having a point contact with the central portion of the wafer and an arc-shaped projection having a line contact with the peripheral portion of the wafer are provided on the stage. The heating block, which has a much larger heat capacity than the wafer and is maintained at a constant temperature, is fixed to the stage, and the heat of the heating block is transferred to the wafer through the arc-shaped projections. In addition, the wafer surface is uniformly heated and maintained at a desired temperature, the resist peeling rate in the wafer surface becomes uniform, and the effect of reducing the remaining resist which causes a quality defect, which has conventionally occurred, can be obtained. Was done.

[Brief description of the drawings]

FIG. 1 is a plan view showing a stage of a single-wafer plasma ashing apparatus according to an embodiment of the present invention, and is a sectional view taken along the line AA of FIG.

FIG. 2 is a partial plan view and a sectional view showing a modification of the stage of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection part 2 Arc-shaped protrusion part 3 Stage 4 Block 5 Heater 6 Ring 7 Elevating rod 8 Sleeve 9 Fork 10 Wafer

Claims (6)

[Claims] A single-wafer plasma ashing apparatus for introducing a gas such as oxygen into a container under reduced pressure, activating atoms of the gas by glow discharge, and removing a resist applied to one semiconductor substrate. A stage having a plurality of projecting members supporting a central portion of the semiconductor substrate at a point contact and a plurality of arc-shaped projecting members supporting a peripheral portion of the semiconductor substrate at a line contact; A single-wafer type plasma ashing apparatus comprising: a block with a built-in heater for maintaining a constant temperature of the stage. 2. The single-wafer plasma ashing apparatus according to claim 1, wherein the stage on which the projecting member and the arc-shaped projecting member are formed can be attached to and detached from the block. 3. The single-wafer plasma ashing apparatus according to claim 1, wherein the number of the protrusion members is three. 4. The single-wafer plasma ashing apparatus according to claim 3, wherein the three projection members are arranged at the apex of an equilateral triangle. 5. A ring-shaped member arranged to surround an outer periphery of the stage and supporting and holding a peripheral edge of the semiconductor substrate; and lifting the semiconductor substrate together with the ring-shaped member above the stage. 2. The single-wafer plasma ashing apparatus according to claim 1, further comprising an elevating rod for mounting the semiconductor substrate on the projection member and the arc-shaped projection member. 6. A single-wafer plasma ashing apparatus according to claim 5, further comprising a sleeve for covering said lifting rod during peeling of said resist.