JP2002100613A - Ashing method and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a resist mask having an affected layer on its surface by ashing processing with a simple method. SOLUTION: The ashing method is provided for removing the resist mask 12 having the affected layer 13 on its surface by using a plasma gas. The affected layer is removed under a condition where the affected layer does not burst at a first temperature, a variation of luminescence produced from the predetermined reaction gas in the plasma gas is detected, thereby, the temperature of semiconductor wafer is raised, and resists 14, 14a, residuals of resist mask, are removed by using the plasma gas under a condition at the second temperature raised. The luminescence is produced from an oxygen radical or reaction product, such as CO. In this case, the first temperature is set at 150 deg.C or below, and the second temperature is at 250 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ashing method and an ashing apparatus for ashing and removing a resist used as a mask in an ion implantation step or a dry etching step for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, a photolithography step is essential and is often used. In this photolithography step, a pattern is transferred to a resist film on a semiconductor wafer as is well known. Then, using the resist mask formed by the pattern transfer, effective impurities are selectively introduced into the semiconductor substrate by ion implantation,
The underlying material is selectively processed by dry etching.

The resist mask that is no longer required after the above process is generally removed by the ashing action of plasma containing oxygen radicals or ions.
The removal of the resist mask by the ashing function (hereinafter referred to as ashing processing) is accelerated as the temperature of the semiconductor substrate in the plasma processing increases. Then, in mass production of the semiconductor device, the removal time of the resist mask is shortened, and the manufacturing time of the semiconductor device is shortened. Therefore, the substrate temperature in the ashing process is increased, and the resist mask is removed under a high temperature environment.

[0004]

However, after the above-described ion implantation or dry etching, an altered layer is formed on the surface of the resist mask. In the above-described conventional technique, the deteriorated layer explosively ruptures in the ashing process, and resist dust generated at this time remains.

The above situation will be described below with reference to FIG. As shown in FIG. 3A, a resist mask 12 is formed on the substrate 1. The resist mask 12 has been subjected to the above-described ion implantation or dry etching process, and has a deteriorated layer 13 formed on the surface thereof and a resist therein. Here, the altered layer 13 is usually thermoset. Here, when the temperature of the substrate 11 is increased in the above-described ashing process, the altered layer 13 explosively explodes due to volume expansion due to thermal expansion of the resist 14 as shown in FIG. This explosive rupture (hereinafter referred to as popping phenomenon) causes a part of the altered layer 13 or the resist 1
3 is scattered, and as shown in FIG.
The resist dust 15 remains on the surface. Further, the resist dust scatters and adheres to the inner wall of the reaction chamber (chamber) of the ashing device and becomes a particle generation source.

For this reason, in the conventional technique, it is necessary to remove the resist dust, and as a result, the removal time of the resist mask increases. In addition, such resist dust becomes particles and reduces the yield of the semiconductor device. In addition, if the temperature in the ashing process is lowered to avoid the popping phenomenon, the time for removing the resist mask increases.

It is an object of the present invention to provide an ashing method and an ashing apparatus which can prevent the above-mentioned popping phenomenon and effectively remove a deteriorated layer of a resist mask by a simple method.

[0008]

According to the ashing method of the present invention, a first temperature is reduced by using a plasma gas to remove a resist mask formed on a semiconductor wafer and having a deteriorated layer on the surface using a plasma gas. Removing the altered layer in an environment, detecting a change in light emission from a predetermined reaction gas in the plasma gas, and raising the temperature of the semiconductor wafer under an environment of a second temperature. The remaining portion of the resist mask is removed using a gas. Here, the luminescence is from oxygen radicals or CO which is a reaction product. The emission wavelength from the oxygen radical is 777 nm, and the emission wavelength from the CO is 450 nm.

Further, the first temperature is set at 150 ° C. or lower, and the second temperature is set at 250 ° C. or higher.

According to another aspect of the present invention, there is provided an ashing apparatus for removing, using a plasma gas, a resist mask formed on a semiconductor wafer and having an altered layer on a surface thereof, a holding means for holding the semiconductor wafer in a reaction chamber. Heating means for heating the semiconductor wafer,
A control mechanism for controlling the heating temperature; and means for detecting light emission from the plasma gas, wherein the heating means is controlled through the control mechanism operated by a signal corresponding to a predetermined light emission from the light emission detection means. The heating temperature can be adjusted. Here, the heating temperature for removing the resist mask is initially set to a first temperature at which the altered layer on the surface of the resist mask does not burst, and the altered layer is removed. Removal is determined by the light emission detection means, and subsequently, the heating means through the control mechanism is set to a second temperature higher than the first temperature.

The luminescence is from oxygen radicals or CO which is a reaction product. Further, the heating means is a heating lamp attached to an upper surface or a lower surface of the semiconductor wafer.

As described above, according to the present invention, the altered layer on the surface of the resist mask formed after the above-described ion implantation or dry etching is effectively removed, and the altered layer generated by the conventional technique as described above explodes explosively. Is gone.
Further, the time for the ashing process of the resist mask is greatly reduced. Then, it is not necessary to remove the resist dust generated by the conventional technique, and the generation of particles composed of the resist dust is greatly reduced, and the production yield of the semiconductor device is improved.

[0013]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a schematic sectional view of a single wafer type ashing apparatus suitable for carrying out the ashing method of the present invention. FIG. 2 is a diagram for explaining the ashing method of the present invention. FIG. 1 shows a main part of an ashing apparatus for explaining the present invention.

As shown in FIG. 1, an upper electrode 2 and a lower electrode 3 are provided in an ashing chamber 1 so as to face each other. Then, on the lower electrode 3, a semiconductor wafer 4 which is subjected to the ashing process described above is placed. A heating source 5 is provided in the lower electrode 3 held on the semiconductor wafer 4. Here, as a heating source, a normal heater for applying a current to the resistor to heat the resistor is attached. Alternatively, an infrared lamp may be used instead of the heater.

Although not shown, an inlet for the reaction gas introduced into the chamber 1 and an outlet for the gas after the reaction are provided. Then, a high frequency power supply is attached between the above-described upper electrode 2 and lower electrode 3 having a parallel plate structure. Here, a cathode is connected to the upper electrode 2 and an anode is connected to the lower electrode 3.

Oxygen introduced as a reaction gas is plasma-excited to generate active species such as oxygen radicals or ions. Then, the active species react with the above-described resist mask, and ashing occurs. Therefore, a photosensor 6 for detecting and monitoring the plasma emission generated from these active species of oxygen or the emission from the reacted gas is provided on the side wall of the chamber 1.

A controller 7 for controlling the above-mentioned heating source 5 is attached. This controller 7
Is controlled by a signal from the photo sensor 6. That is, the controller 7 adjusts the heating source 5 in accordance with the detection intensity of a certain light emission received from the photo sensor 6, and raises or lowers the temperature of the semiconductor wafer 4.

Here, in order to enable high-speed temperature rise / fall, the above-mentioned lower electrode 3 is preferably formed so that its heat capacity becomes small.

The ashing device described above has a structure in which a high-frequency power source is connected to the parallel plate electrodes, and the reaction gas is plasma-excited by the high frequency. Here, as a method of plasma excitation, plasma excitation by microwaves and helicon waves, or an HPD such as an AC induction current method is used.
(High Plasma Density) may be used. In any case, the controller 7 adjusts the heating source 5 by the light emission received from the photo sensor 6. The temperature of the semiconductor wafer 4 can be freely controlled to increase or decrease.

Next, the ashing method of the present invention will be described with reference to FIG. FIG. 2A shows a temporal change in the above-described light emission intensity in the above-described ashing process for removing the resist mask. FIG. 2B is a schematic cross-sectional view of the resist mask for explaining a time change in removing the resist mask. Here, reference numerals for explaining the cross-sectional views of the resist mask are the same as those shown in FIG.

As described above, in manufacturing a semiconductor device, a semiconductor wafer having a resist mask used as a mask for ion implantation or dry etching is inserted into the ashing device described above. Then, an oxygen gas or a mixed gas of oxygen and a fluorine compound is introduced as a reaction gas into the chamber 1 of the ashing device, and the reaction gas is plasma-excited. The ashing process is performed in this manner.

In the ashing first step 8 shown in FIG. 2A in this ashing process, the semiconductor wafer 4
2, that is, the temperature of the substrate 11 and thus the resist mask 12 shown in FIG. 2B is maintained at a relatively low first temperature. Here, the first temperature is set to be 150 ° C. or less. At such a temperature,
The altered layer 13 on the surface layer of the resist mask 12 does not burst explosively. In the first ashing step 8, the altered layer 13 on the surface of the resist mask 12 shown in FIG. 2B is completely removed. Then, FIG.
As shown in the figure, in the first ashing stage 8, the emission intensity from oxygen radicals is high, and the reaction product (reaction gas)
Is relatively low. This is because the consumption of oxygen radicals is small and the amount of oxygen radicals in the plasma remains large because the ashing rate of the altered layer 13 is low, and conversely, the amount of reaction product CO generated at this stage decreases. is there.

Next, when the altered layer 13 is completely removed and the resist 14 is exposed, the ashing speed of the resist 14 increases. Then, the consumption of oxygen radicals increases, and the remaining amount of oxygen radicals in the plasma decreases. Conversely, at this stage, the amount of reaction product CO generated increases. Then, as shown in FIG.
In step 9, the emission intensity from oxygen radicals decreases,
The emission intensity from CO, which is a reaction product, increases.

Such a change in the light emission intensity is detected by the photo sensor 6 described in FIG. 1, and the controller 7 adjusts the heating source 5 so that the temperature of the semiconductor wafer 4, that is, FIG.
The temperature of the substrate 11 shown in (b) is set to a high temperature which is the second temperature. Here, the second temperature is preferably set to 250 ° C. or higher. Such a rise in the ashing temperature further increases the ashing speed.

The volume of the resist 14 is reduced by ashing, and is reduced to the size of the resist 14a as shown in FIG. Accordingly, as shown in FIG. 2A, the emission intensity from oxygen radicals increases, and the emission intensity from CO, which is a reaction product, decreases. Then, the resist 14 is completely removed by ashing, and the third step 10 of ashing is performed. In the third ashing step 10, the resist mask 12 on the substrate 11 is entirely removed by ashing.

The feature of the ashing method of the present invention resides in that the light emission intensity in the ashing process is monitored, the heating source of the semiconductor wafer is adjusted based on the light emission intensity, and the substrate temperature, that is, the ashing environment temperature is changed.

By doing so, the popping phenomenon of the deteriorated layer 13 described in the prior art can be completely prevented. At the same time, by increasing the ashing environment temperature with good timing, the ashing speed of the resist other than the affected layer can be further increased, and the overall ashing processing time can be greatly reduced. For example, when a resist mask is used as an ion implantation mask for a source / drain diffusion layer of a MOS transistor, the ashing processing time is reduced by about 30%.

In the above-described embodiment, the heating source is adjusted by changing the light emission intensity of the photosensor with time to control the environmental temperature of the ashing process. The present invention is not limited to the above emission intensity. The environmental temperature of the ashing process may be controlled by monitoring the change in the light emission intensity. Here, the heating source 5 may be provided not in the lower electrode 3 but in a position above the semiconductor wafer 4. In this case, an infrared lamp is attached as a heating lamp.

It should be noted that the present invention is not limited to the above-described embodiment, and it is obvious that the embodiment can be appropriately changed within the scope of the technical idea of the present invention.

[0030]

As described above, according to the ashing method of the present invention, in the ashing method of removing a resist mask having an altered layer on the surface by using a plasma gas, the ashing method is performed under an environment of a first temperature at which the altered layer does not burst. The altered layer is removed, a change in light emission from a predetermined reaction gas in the plasma gas is detected, the temperature of the semiconductor wafer is increased, and the remaining portion of the resist mask is removed using the plasma gas under a second temperature environment. Remove. Here, the light emission is from oxygen radicals or CO which is a reaction product. Further, the first temperature is set to 150 ° C. or lower, and the second temperature is set to 2 ° C.
Set to 50 ° C. or higher.

An ashing apparatus according to the present invention is an ashing apparatus for removing a resist mask using a plasma gas, comprising: holding means for holding a semiconductor wafer in a reaction chamber; heating means for heating the semiconductor wafer; A control mechanism for controlling the temperature, and a means for detecting light emission from the plasma gas, wherein the heating means is controlled through a control mechanism that operates with a signal corresponding to a predetermined light emission from the light emission detection means, The heating temperature can be adjusted. Here, the heating temperature for removing the resist mask is initially set to a first temperature at which the altered layer on the surface of the resist mask does not burst, and the altered layer is removed. The determination is made by the light emission detection means, and subsequently, the heating means through the control mechanism is set to a second temperature higher than the first temperature.

For this reason, the altered layer on the surface of the resist mask formed after the above-described ion implantation or dry etching is effectively removed, and there is no explosive rupture of the altered layer caused by the above-mentioned conventional technology. Become. Further, the time for the ashing process of the resist mask is greatly reduced.

For this reason, in the present invention, it becomes unnecessary to remove resist dust generated by the conventional technique. In addition, the generation of particles composed of such resist dust is greatly reduced, and the production yield of semiconductor devices is greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus for explaining an ashing apparatus of the present invention.

FIG. 2 is a diagram illustrating a temporal change in emission intensity and a cross-sectional shape change of a resist mask in an ashing process for explaining an ashing method according to the present invention.

FIG. 3 is a diagram showing a temporal change in a cross section of a resist mask in an ashing process for explaining a problem of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ashing chamber 2 Upper electrode 3 Lower electrode 4 Semiconductor wafer 5 Heating source 6 Photosensor 7 Controller 8 Ashing first stage 9 Ashing second stage 10 Ashing third stage 11 Substrate 12 Resist mask 13 Altered layer 14, 14a Resist 15 Resist waste

Claims (8)

[Claims] 1. An ashing method for removing, using a plasma gas, a resist mask formed on a semiconductor wafer and having an altered layer on its surface, wherein the altered layer is removed under a first temperature environment. A change in light emission from a predetermined reaction gas in the plasma gas is detected, the semiconductor wafer is heated, and under a second temperature environment, subsequently, the remaining portion of the resist mask is removed using the plasma gas. An ashing method, comprising: 2. The ashing method according to claim 1, wherein the light emission is generated from oxygen radicals or CO which is a reaction product. 3. An emission wavelength from the oxygen radical is 77.
The ashing method according to claim 2, wherein the emission wavelength from the CO is 7 nm and the emission wavelength from the CO is 450 nm. 4. The ashing according to claim 1, wherein the first temperature is set at 150 ° C. or lower, and the second temperature is set at 250 ° C. or higher. Method. 5. An ashing apparatus for removing, using a plasma gas, a resist mask formed on a semiconductor wafer and having an altered layer on the surface, comprising: holding means for holding the semiconductor wafer in a reaction chamber; Heating means for heating, a control mechanism for controlling the heating temperature, and a means for detecting light emission from the plasma gas, through the control mechanism operated by a signal corresponding to a predetermined light emission from the light emission detection means The ashing apparatus, wherein the heating means is controlled so that the heating temperature can be adjusted. 6. A heating temperature for removing the resist mask is first set to a first temperature at which the deteriorated layer on the surface of the resist mask does not burst, and the deteriorated layer is removed. 6. The method according to claim 5, wherein the removal of the layer is determined by the light emission detecting means, and subsequently, the second temperature is set higher than the first temperature by the heating means through the control mechanism. Ashing device. 7. The ashing apparatus according to claim 5, wherein said light emission is emitted from oxygen radicals or CO which is a reaction product. 8. The ashing apparatus according to claim 5, wherein said heating means is a heating lamp attached to an upper surface or a lower surface of said semiconductor wafer.