JPH09162173A - Method and system for ashing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and a system for ashing in which a deteriorated layer formed on a resist through the use of a high dosage ion implantation mask can be removed through dry ashing in one chamber while protecting the substrate against damage, suppressing adhesion of particles and enhancing the throughput. SOLUTION: A wafer 30 having surface with a deposited deterioration film and covered with a resist is mounted on a wafer table 28 in a chamber 21 of an ashing system and kept at a low temperature. A high frequency plasma is generated in then generated in the chamber 21 and the deterioration film is removed from the surface of the resist. Subsequently, the wafer 30 is kept at a high temperature in the chamber 21 and the resist is removed by down flow using a microwave plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing method and an ashing apparatus suitable for removing a resist film having an altered film formed on its surface since it is used as a mask when performing ion implantation.

At present, miniaturization and high integration of semiconductor integrated circuits are rapidly progressing, and the diameter of wafers used is also increasing.

When manufacturing a semiconductor integrated circuit, a lithographic technique is indispensable, and a dry ashing technique capable of coping with the above-mentioned progress is required for removing the resist film used therein. There is a demand for high selectivity due to thinning, low damage to substrates, cleanliness, and high throughput.

According to the present invention, it is possible to provide one means capable of meeting the above-mentioned various demands.

[0005]

2. Description of the Related Art Generally, when a high-dose ion implantation is performed, an altered layer is formed on the surface of a resist film used, and the altered layer is removed by a non-altered layer located below it. However, it is difficult to remove the resist film from the normal resist film unless another means is adopted.

The wet ashing process is a preferable means in that respect because it is less likely to damage the substrate, but the chemical solution tank is contaminated every time the process is performed, and reattachment of particles to the substrate becomes a problem. There is.

By performing a dry ashing process, for example, a dry ashing process in which the substrate is directly exposed to plasma, the altered layer caused by the high dose ion implantation can be removed.

FIG. 2 is a principal part explanatory view showing a dry ashing device having a structure in which a substrate is directly exposed to plasma.

In the figure, 1 is a chamber, 2A is a reaction gas supply pipe for supplying, for example, H ₂ + H ₂ O, 2B is an exhaust port, 3 is a cooling stage, 4 is a high frequency source, and 9 is a wafer. ing.

When the resist film is ashed by using this dry etching apparatus, the deteriorated layer generated by the high dose ion implantation can be removed, so that the entire resist film can be easily formed. Although ashing can be performed, there is a problem in that the substrate is damaged.

Further, after removing the deteriorated layer by the dry ashing apparatus shown in FIG. 2, the normal resist film which is the non-altered layer is removed by the down flow ashing.

FIG. 3 is a main part explanatory view showing a dry ashing device for performing down flow ashing.
The same symbols as those used in the above denote the same parts or have the same meanings.

In the figure, 5 is a microwave waveguide and 6
Is a microwave transmitting window, 7 is a plasma generating chamber, 8 is a shower head, and 10 is a high temperature stage.

When the resist film is ashed by using this dry ashing apparatus, the plasma generated in the plasma generation chamber 7 does not directly contact the wafer 9 on the high temperature stage 10, so that the substrate is not damaged. Although it is small, of course, it is not possible to remove the deteriorated layer generated by the high dose ion implantation.

When the altered layer and the non-altered layer are removed by using the dry ashing apparatus described with reference to FIGS. 2 and 3, the object can be achieved without damaging the substrate.

However, since the substrate must be moved from the first dry ashing device to the second dry ashing device during the processing, the through-put is naturally lowered, and There is a drawback that particles are often attached.

A structure in which the first dry ashing device and the second dry ashing device are connected has also been proposed (see, for example, Japanese Patent Laid-Open No. 6-349786, if necessary). In terms of through-put and particle adhesion, it is possible to reduce the effect, and it is not a fundamental solution.

[0018]

In the present invention, since it is used as a mask for ion implantation with a high dose, a resist film having an altered layer formed on its surface is dry-ashed in one chamber. It is possible to remove it, and the substrate is not damaged,
In addition, the adhesion of particles is reduced, and the throughput can be improved.

[0019]

SUMMARY OF THE INVENTION According to the present invention, a high frequency plasma is generated in the same chamber in a dry ashing apparatus to generate reactive ion etching.
The basic principle is to make it possible to carry out down flow ashing by generating microwave plasma.

From the above, in the ashing method and the ashing apparatus according to the present invention, (1) the surface of the wafer mounting table (eg, wafer mounting table 28) in the chamber (eg, chamber 21) of the ashing apparatus is A step of placing a wafer (for example, the wafer 30) covered with a resist film having an altered film formed on it to maintain it at a low temperature, and then,
A step of generating high frequency plasma in the chamber to remove the deteriorated layer on the surface of the resist film, and then a high temperature plasma of the wafer in the same chamber and down flow using microwave plasma And a step of removing the film, or

(2) In above (1), the wafer is supported only by the cooling stage of the wafer mounting table (eg, wafer mounting table 28) in order to keep the wafer (eg, wafer 30) at a low temperature or a high temperature, or Is it characterized by switching depending on whether the wafer is supported only by the high temperature stage?

(3) A wafer (for example, the wafer 30) which is provided in the chamber (for example, the chamber 21) can be independently supported, and a high frequency source (for example, the high frequency source 2) is provided.
9) a cooling stage (for example, cooling stage 28) connected to
A) and a wafer mounting table (for example, wafer mounting table 28) having a high temperature stage (for example, high temperature stage 28B) capable of independently supporting the wafer, and a shower unit above the chamber.
In order to supply high-frequency energy to a plasma generation chamber (for example, plasma generation chamber 26) separated by a head (for example, shower head 27) and supplied with a reaction gas and a microwave, and a cooling stage on the wafer mounting table. Or a connected high-frequency source, or

(4) In the above (3), one of the cooling stage and the high temperature stage is inside and the other is outside, forming a double structure, and one of them is higher than the other. It is characterized in that it is movable in one direction and can separate a mounted wafer from the other.

According to the ashing method and the ashing apparatus of the present invention by adopting the above-mentioned means, the resist film having the altered layer formed on the surface is removed because it is used as a mask for ion implantation with a high dose amount. In this case, the RIE method using high-frequency plasma is used to remove the deteriorated layer, and the downflow ashing that is not exposed to plasma is used to remove the normal resist film after the deteriorated layer is removed. Since it is done, it does not damage the substrate, and since ashing is performed in the same chamber, adhesion of particles is suppressed to a small level,
In addition, it is possible to remove with high efficiency.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential parts of an ashing device for explaining an embodiment of the present invention.

In the figure, 21 is a chamber, 22 is a reaction gas inlet pipe, 23 is an exhaust port, 24 is a microwave waveguide,
25 is a microwave transparent window, 26 is a plasma generating chamber, 27
Is a shower head, 28 is a wafer mounting table, 28A is a cooling stage, 28B is a high temperature stage, 29 is a high frequency generation source, and 30 is a wafer.

In the illustrated ashing apparatus, the wafer mounting table 28 has a cooling stage 28A and a high temperature stage 28B.
The high temperature stage 2 has a double structure divided into
8B is movable up and down, for example, high temperature stage 28B
When the temperature of the wafer 3 is lowered below the cooling stage 28A, the wafer 3
0 can be supported only by the cooling stage 28A.

The high temperature stage 28B is replaced with the cooling stage 28A.
If the wafer 30 is raised above the
It can be separated from A and can be supported only by the high temperature stage 28B.

When the reaction gas is sent from the reaction gas inlet pipe 22 into the chamber 21 through the plasma generation chamber 26 and the shower head 27 and the high frequency energy is supplied from the high frequency generation source 29, the high frequency plasma enters the chamber 21. Can be generated.

A reaction gas is fed into the plasma generation chamber 26 from the reaction gas inlet pipe 22, and microwaves are supplied to the plasma generation chamber 26 through the microwave waveguide 24 and the microwave transmission window 25 to generate plasma. Then, only the active species in the plasma are transferred to the wafer 3 through the shower head 27.
0 can be supplied.

A case will be described in which dry ashing for removing the resist film having the altered layer is performed using the ashing apparatus described above.

(1) A wafer 30 having a resist film having an altered layer formed on its surface is set on the wafer mounting table 28.
Here, since the deteriorated layer is first removed, the high temperature stage 28B is lowered and the wafer 30 is supported only by the cooling stage 28A.

(2) The inside of the chamber 21 is evacuated from the exhaust port 23 to create a vacuum.

(3) The reaction gas is introduced into the chamber 21 through the reaction gas inlet pipe 22, and the internal gas pressure is adjusted to 0.5 [To.
rr]. To remove the deteriorated layer, H ₂ + H ₂ O is used as a reaction gas.

(4) The cooling stage 28A supporting the wafer 30 is water-cooled to a temperature of 10 ° C. When a high frequency is supplied from the high frequency generation source 29 to this cooling stage 28A, plasma is generated and RIE is performed. Therefore, the deteriorated layer on the surface of the resist film can be ashed at high speed.
The altered layer cannot be ashed by the down flow which is not directly exposed to the plasma.

During the RIE, it is necessary to keep the temperature of the wafer 30 at about 10 [° C.], and at a high temperature, for example, 100 [° C.] or higher, a phenomenon called resist pumping occurs, The resist film explodes.

(5) After removing the deteriorated layer, RIE is performed.
Then, the high temperature stage 28B is raised and the wafer 30 is separated from the cooling stage 28A as the next step.

By doing so, the wafer 30 is supported only by the high temperature stage 28B having a temperature of 200 ° C.

(6) The reaction gas is introduced into the plasma generation chamber 26 through the reaction gas inlet pipe 22, and the gas pressure is set to 1.0 [T
orr]. To remove the usual resist layer, O ₂ + H ₂ O is used as a reaction gas.

(7) Microwaves sent from the microwave waveguide 24 are introduced into the plasma generation chamber 26 through the microwave transmission window 25 to generate plasma, and ashing by down flow is performed.

At this time, the resist film is the shower head 2
It is ashed only by the active species passing through 7,
Ions and electrons generated in the plasma generation chamber 26 are trapped by the shower head 27, so that the plasma does not act directly, but the wafer 30 has a temperature of 200.
Since the temperature is as high as [° C.], the resist film is ashed at a high speed. In addition, down flow of O ₂ + H ₂ O
If the ashing is performed at room temperature, the ashing rate will be too low to be practical.

As described above, when the resist film having the deteriorated layer is removed by performing the two-step ashing, the ashing rate of the deteriorated layer is 1 [μm / min], and after the deteriorated layer is removed. Resist film ashing
It was confirmed that the rate was 4 [μm / min],
I was able to perform high-speed ashing.

The second step of ashing is O ₂
Since it is + H ₂ O down flow ashing, the selection ratio when the underlying layer is an oxide film is infinite.
There is no damage given to the wafer 30.

Further, since it is a two-step ashing process in the same chamber, particle adhesion due to movement between chambers and particle re-adhesion during steps in the process are extremely small, 0.2 [μm] or more. The number of particles was 10 or less. By the way, when RIE is performed in the first chamber and down flow ashing is performed in the second chamber, the number of particles of 0.2 [μm] or more is 50 or more.

Similarly, the through-put in the two-step ashing process in the same chamber was 60 wafers / hour. By the way, RIE in the first chamber
And when down-flow ashing is performed in the second chamber, 30 wafers / hour. this is,
An in-line method in which a wafer that has undergone down flow ashing in the second chamber is taken out, then a wafer that has undergone RIE in the first chamber is set in the second chamber, and then a new wafer is set in the first chamber. This is due to the fact that the throughput is inevitably low because it is processing.

The present invention is not limited to the embodiment described above, and many other modifications can be realized.

For example, in the above-described embodiment, the cooling stage and the high temperature stage are arranged inside and outside the wafer mounting table having a double structure, respectively. Further, it is optional to dispose a cooling stage on the outer side, or to move the inner stage up and down and fix the outer stage.

[0048]

In the ashing method and the ashing apparatus according to the present invention, the wafer covered with the resist film having the altered film formed on the surface thereof is placed on the wafer mounting table in the chamber of the ashing apparatus. Temperature is maintained at a low temperature, high-frequency plasma is generated in the chamber to remove the deteriorated layer on the resist film surface, the wafer is maintained at a high temperature in the same chamber, and a down flow using microwave plasma is performed. To remove the resist film.

According to the ashing method and the ashing apparatus of the present invention by adopting the above structure, the resist film having the altered layer formed on the surface thereof is removed because it is used as a mask for ion implantation with a high dose amount. In this case, the RIE method using high frequency plasma is used to remove the deteriorated layer, and the normal resist film is removed after the deteriorated layer is removed by down flow ashing that is not exposed to plasma. Since it is done, it does not damage the substrate, and since ashing is performed in the same chamber, adhesion of particles is suppressed to a small level,
Moreover, it can be removed with high efficiency.

[Brief description of the drawings]

FIG. 1 is a principal part explanatory view showing an ashing device for explaining an embodiment of the present invention.

FIG. 2 is an explanatory view of a main part of a dry ashing device configured to directly expose a substrate to plasma.

FIG. 3 is a principal part explanatory view showing a dry ashing device for performing down flow ashing.

[Explanation of symbols]

 Reference Signs List 21 chamber 22 reaction gas inlet pipe 23 exhaust port 24 microwave waveguide 25 microwave transmission window 26 plasma generation chamber 27 shower head 28 wafer mounting table 28A cooling stage 28B high temperature stage 29 high frequency generation source 30 wafer

Claims (4)

[Claims] 1. A step of placing a wafer covered with a resist film having an altered film formed on its surface on a wafer mounting table in a chamber of an ashing apparatus to maintain the wafer at a low temperature, and then, in the chamber. A step of generating high-frequency plasma to remove the deteriorated layer on the surface of the resist film, and then removing the resist film by a down flow using microwave plasma while keeping the wafer at a high temperature in the same chamber An ashing method comprising the steps of: 2. The method according to claim 1, wherein in order to keep the wafer at a low temperature or a high temperature, the switching is performed depending on whether the wafer is supported only by the cooling stage of the wafer mounting table or the wafer is supported only by the high temperature stage. Ashing method. 3. A wafer mounting table provided in a chamber, capable of independently supporting a wafer, having a cooling stage connected to a high-frequency generation source, and a high temperature stage capable of independently supporting the wafer, and the chamber. A plasma generation chamber which is isolated by a shower head and to which a reaction gas and a microwave are supplied, and a high frequency generation source connected to supply high frequency energy to a cooling stage on the wafer mounting table. An ashing device characterized by the following. 4. A cooling stage and a high-temperature stage, one of which is inside and the other of which is outside so as to form a double structure, and one of them is mounted so as to be movable in the height direction with respect to the other. 4. The ashing device according to claim 3, wherein the other wafer can be separated from the other wafer.