JPH01111334A - Method and apparatus for removal - Google Patents

Abstract

PURPOSE:To accurately detect the ending point of decomposing reaction by detecting the quantity of a light to be absorbed to a decomposing gas generated by the decomposing reaction of organic matter coated on the surface of a material to be treated, thereby detecting the ending point of the reaction. CONSTITUTION:When an organic matter coated on the surface of an object 4 to be treated is removed by decomposing with predetermined processing gas, the quantity of the light to be absorbed to the decomposing gas generated by the decomposing reaction of the organic matter is detected thereby to detect the ending point of the reaction. That is, when the light irradiated from a light emission body 11 is absorbed, the quantity of the light which arrives at photodetecting means 12 from the L.E. body 11 is reduced as compared with that before the decomposing reaction is started. Thus, the quantity of generated decomposed gas and hence the ending point of the reaction can be accurately detected on the basis of the variation in the quantity of the light without depending upon the quantity of the organic matter being coated in advance on the surface of the object to be processed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technique for removing organic substances adhered to the surface of a workpiece, and relates to a technique that is particularly effective when applied to resist removal from semiconductor wafers. be.

[Conventional technology]

Regarding resist removal technology in the semiconductor wafer manufacturing process, for example, see "Cleaning Design 1" published by Kindai Editorial Company.
It is described in the 981 autumn issue JPI-PIO.

The present inventor studied the structure of an apparatus for removing the above-mentioned resist. The following are the techniques studied by the present inventor, and the outline thereof is as follows.

Resist removal is performed on semiconductor wafers (hereinafter referred to as wafers).
A resist pattern made of photoresist is formed on the surface of the wafer, and after etching the insulating film and metal film using this as a mask, a processing gas such as an oxygen/ozone mixed gas is applied to the surface while heating the wafer in a resist removal device. The photoresist that is no longer needed after being supplied is decomposed and removed.

As a method for removing the resist, a method can be considered in which a wafer mounting table equipped with a heating source is provided in the chamber, and the processing gas is supplied to the surface of the wafer placed thereon while heating the wafer.

Further, at that time, a method of irradiating the processing gas in the chamber with ultraviolet light to quickly generate excited oxygen molecules to promote the decomposition reaction of the photoresist can be considered.

[Problem that the invention seeks to solve]

The inventors of the present invention have discovered that the following problems occur when a photoresist decomposition reaction is carried out in the chamber of the resist removal apparatus.

That is, in order to quickly remove unnecessary photoresist and efficiently transport the wafer to the next step after a predetermined etching step is completed, it is necessary to accurately detect the end point of the photoresist decomposition reaction.

However, since there is no known method for effectively detecting the end point of the photoresist decomposition reaction, the time required for the decomposition reaction is experimentally determined in advance, and the end point of the decomposition reaction is estimated based on this experimental value and the resist is removed. The current situation is that

However, this method has the problem that the throughput of the resist removal process is reduced because it is necessary to calculate the experimental value of the end point of the decomposition reaction for each of the many etching steps performed in the wafer manufacturing process.

In addition, it is not possible to take into account variations in photoresist film thickness from wafer to wafer or loft to loft, and variations in decomposition reaction time due to deterioration of the ultraviolet light source installed in the resist removal equipment. There are cases where the remaining wafers are transferred to the next process, which is one of the causes of lowering the yield of the wafer manufacturing process.

The present invention has been made focusing on the above problems,
The purpose is to provide a technique that can accurately detect the end point of a decomposition reaction of an organic substance adhered to the surface of an object to be treated.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, when organic matter deposited on the surface of a workpiece is decomposed and removed using a predetermined processing gas, the decomposition reaction is detected by detecting the amount of light absorbed by the decomposed gas generated by the decomposition reaction of the organic matter. This is a removal method that detects the end point.

In addition, in order to carry out the above-mentioned removal method, a part of the chamber where the decomposition reaction of organic matter is carried out by a predetermined processing gas is installed.
The removal device has a structure including a light emitter that emits light of a wavelength that is absorbed by the decomposed gas generated by the decomposition reaction of the organic substance, and a photodetector that detects the amount of light absorbed by the decomposed gas. be.

[Effect]

According to the above-mentioned means, when the light emitted from the luminescent material is absorbed by the decomposed gas generated from the organic substance, the amount of light reaching the light detection means from the luminescent material decreases compared to before the decomposition reaction starts. Therefore, based on the change in the amount of light, it is possible to accurately detect the amount of decomposed gas generated and, by extension, the end point of the decomposition reaction, without depending on the amount of organic matter previously deposited on the surface of the object to be treated.

〔Example〕

FIG. 1 is a cross-sectional view of a main part of a resist removal apparatus that is an embodiment of the present invention, and FIG. 2 is a graph showing changes in the intensity of light reaching the light detecting means from the light emitter during the photoresist decomposition reaction. It is.

In the resist removing apparatus 1 of this embodiment, a wafer mounting table 3 equipped with a built-in heater (not shown) is installed in the center of a chamber 2, and a wafer 4 placed horizontally on the upper surface of the wafer mounting table 3 is heated to a predetermined temperature. and the motor 5 below the chamber 2.
is rotated at a predetermined speed.

A transparent glass plate 7 made of a heat-resistant material such as quartz is installed horizontally at the lower end of the gas introduction pipe 6 installed at the center of the upper wall surface of the chamber 2.
A processing gas such as an oxygen/ozone mixed gas that is sprayed at the center of the wafer 4 is uniformly diffused over the entire surface of the wafer 4.

A large number of low-pressure mercury lamps 8 are arranged above the glass plate 7 at predetermined intervals, and when the processing gas is irradiated with ultraviolet light emitted from the low-pressure mercury lamps 8, the processing gas is immediately excited. Oxygen molecules are being generated.

Note that a reflector plate 9 that efficiently reflects ultraviolet light is installed on the upper wall surface of the chamber 2, so that the ultraviolet light is evenly irradiated onto the upper surface of the wafer mounting table 3.

Further, an exhaust pipe 10 is installed on the lower side wall of the chamber 2, so that decomposed gas generated by the decomposition reaction of the photoresist and excess processing gas are exhausted to the outside of the chamber 2.

A phosphor (light-emitting body) 11 is formed in a ring shape around the entire periphery of the upper surface of the wafer mounting table 3 so as to absorb ultraviolet light emitted from the low-pressure mercury lamp 8 and emit light. It has become.

A light sensor (light detection means) 12 for detecting the intensity of light emitted from the phosphor 11 is installed on the upper wall surface of the chamber 2 at a position directly above the phosphor 11. Changes in light intensity are sequentially monitored by a monitor device (not shown) installed at the center.

Fluorescent material 11 used in resist removal apparatus 1 of this embodiment
has a characteristic that the light of a predetermined wavelength emitted by the phosphor 11 is absorbed by any of the decomposition gases generated by the decomposition reaction of the photoresist.
A phosphor (product name: NP803) manufactured by Nichia Chemical Industry Co., Ltd. that absorbs ultraviolet light of m and emits light with a wavelength of 306 nm.
etc. are used.

Next, a resist removing process using the resist removing apparatus 1 will be explained.

First, the wafer 4, which has undergone photoresist coating, exposure, development, and etching steps, is carried into the chamber 2 through an opening (not shown) and placed horizontally on the upper surface of the wafer mounting table 3.

Next, when the wafer mounting table 3 starts heating the wafer 4 while rotating at a predetermined speed, the low-pressure mercury lamp 8 is turned on, and the wavelength 2 of the ultraviolet light emitted by the low-pressure mercury lamp 8 is
A wavelength of 306 nm is emitted from the phosphor 11 that absorbed light of 54 nm.
m light is emitted.

The light with a wavelength of 306 nm emitted from the phosphor 11 is detected by the optical sensor 12 located directly above the phosphor 11 and converted into an electrical signal according to its intensity, as shown in FIG. In the stage before the photoresist decomposition reaction starts, its intensity is the maximum value βx (max
) is shown.

When the wafer 4 is heated to a predetermined temperature, oxygen/ozone mixed gas is sprayed from the gas introduction tube 6, and the low pressure mercury lamp 8
Excited oxygen molecules generated by the ultraviolet light are uniformly diffused over the surface of the wafer 4, and a decomposition reaction of the photoresist is started.

Then, decomposed gases such as water and carbon dioxide, which are decomposition products, are generated from the surface of the photoresist, and this water and excited oxygen molecules react to form OH, which absorbs light in the wavelength range of 306 to 347 nm. Radicals are generated.

The generated OH radicals are discharged from the exhaust pipe 10 to the chamber 2 along with other decomposed gases and excess oxygen/ozone mixed gas.
However, the wavelength of 306 nm emitted from the phosphor 11 when passing through the periphery of the wafer mounting table 3
absorbs light.

As a result, the intensity of the light detected by the optical sensor 12 rapidly decreases to a minimum value j! as the decomposition reaction reaches equilibrium. x(+n1n) (Figure 2).

As the decomposition reaction of the photoresist approaches the end point, the amount of decomposed gas generated decreases, and accordingly, the amount of OH radicals generated also decreases, so the intensity of the light from the phosphor 11 detected by the optical sensor 12 also decreases. gradually increases until the threshold j! x(th)
(Figure 2).

This darkness value Jx(th) is a value obtained experimentally in advance from the intensity of the light from the phosphor 11 detected by the optical sensor 12 when the generation of decomposed gas from the surface of the wafer 4 has stopped. This is a parameter that does not depend on the thickness of the photoresist film deposited on the surface of the wafer 4.

Therefore, when the intensity of the light monitored by the monitor device external to the resist removal device 1 reaches the darkness value,
The end point of the photoresist decomposition reaction can be accurately detected. - In this way, when the end point of the decomposition reaction is detected, the supply of oxygen/ozone mixed gas is immediately stopped, and the OH radicals and other decomposed gases remaining inside the chamber 2 are completely exhausted from the exhaust pipe 10. Then, the intensity of the light from the phosphor 11 detected by the optical sensor 12 returns to the maximum value βx (max), and the photoresist removal process is completed (FIG. 2).

As described above, according to this embodiment, the following effects can be obtained.

(1) Wavelength 30 at which OH radicals are emitted from the phosphor 11 when excited oxygen molecules react with water, which is a type of decomposed gas generated by the decomposition reaction of photoresist.
In order to absorb 6 nm light, the intensity of this light is measured by optical sensor 1.
2, it is possible to accurately detect the amount of decomposed gas generated and, by extension, the end point of the decomposition reaction of the photoresist without depending on the thickness of the photoresist film deposited on the surface of the wafer 4. be able to.

(2) According to the above (1), the throughput of the resist removal process is improved and the manufacturing cost of the semiconductor device is reduced.

(3) Due to 1) above, the yield of the resist removal process is increased.

Therefore, the reliability of the semiconductor device can be improved.

As above, the invention made by the present inventor has been specifically explained based on Examples, but the present invention is not limited to the above-mentioned Examples, and it is understood that various changes can be made without departing from the gist thereof. Needless to say.

For example, instead of forming the phosphor 11 on the periphery of the upper surface of the wafer mounting table 3, as shown in FIG. In addition to attaching the light-emitting plate 13 formed by adhesion, a light sensor 12 for detecting the intensity of light emitted from the fluorescent material 11 may be installed on the other side wall.

Further, in the example, the phosphor 11 that emits light with a wavelength of 306 nm that is absorbed by OH radicals was used as the light emitter, but the present invention is not limited to this, and the decomposition gas generated by the decomposition reaction of the photoresist is used as the light emitter. If it is a light emitter that emits light at a wavelength that is absorbed by either
It doesn't matter what type it is.

Furthermore, by selecting a light emitter according to the type of decomposition gas generated by the organic matter, it can be applied to removal of organic matter other than photoresist, such as dry cleaning of wafers.

In the above explanation, the invention made by the present inventor has been mainly applied to the field of application which is the background of the invention, which is the removal of resist from semiconductor wafers, but the invention is not limited to this. It can be widely applied to removal techniques that decompose and remove organic matter deposited on surfaces using a predetermined processing gas.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, light of a wavelength that is absorbed by the decomposed gas generated by the decomposition reaction of the organic matter is emitted into a part of the chamber of a removal device that decomposes the organic matter deposited on the surface of the object to be treated using a predetermined processing gas. By providing a light emitting body and a light detection means for detecting the amount of light absorbed by the decomposition gas,
To accurately detect the amount of decomposed gas generated based on changes in the amount of light absorbed by the decomposed gas, and ultimately the end point of the decomposition reaction, without depending on the amount of organic matter previously deposited on the surface of the object to be treated. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of a resist removing apparatus which is an embodiment of the present invention; FIG. 2 is a graph showing changes in the intensity of light reaching the light detecting means from the light emitter during the photoresist decomposition reaction; FIG. 3 is a cross-sectional view of a main part of a resist removing apparatus according to another embodiment of the present invention. ■...Resist removal device, 2...Chamber, 3...
・Wafer mounting table, 4... semiconductor wafer (workpiece),
5...Motor, 6...Gas introduction pipe, 7...Glass plate, 8...Low pressure mercury lamp (ultraviolet light source), 9...Reflector, 10...Exhaust pipe, 11... ... Fluorescent body (light-emitting body), 12... Optical sensor (light detection means), 13... Light-emitting plate. Figure 3 3

Claims (1)

[Scope of Claims] 1. When organic matter adhered to the surface of the object to be treated is decomposed and removed using a predetermined processing gas, the amount of light absorbed by the decomposed gas generated by the decomposition reaction of the organic matter is detected. A removal method characterized by detecting the end point of the decomposition reaction. 2. A removal device that introduces a processing gas into a chamber to decompose and remove organic matter adhering to the surface of an object to be treated, wherein a part of the chamber absorbs the decomposed gas generated by the decomposition reaction of the organic matter. What is claimed is: 1. A removal device comprising: a light emitting body that emits light of a wavelength that corresponds to the decomposed gas; and a light detection means that detects the amount of light absorbed by the decomposition gas. 3. A light emitting body is provided on the peripheral edge of the mounting table on which the object to be processed is placed, and a light detection means is provided in the vicinity of the light emitting body, so that the processing gas is supplied to the center of the surface of the object to be processed. A removing device according to claim 2. 4. A patent characterized in that a light emitter and a light detection means are disposed opposite to each other with a mounting table on which the object to be processed is placed, and a processing gas is supplied to the center of the surface of the object to be processed. A removing device according to claim 2. 5. The removal device according to claim 2, characterized in that a part of the chamber is provided with an ultraviolet light source and a phosphor. 6. The removal device according to claim 5, wherein the ultraviolet light source is a low-pressure mercury lamp.