JPH0637009A - Ashing apparatus - Google Patents

Abstract

PURPOSE:To make it possible to control through precisely calculating an ashing rate, more particularly, concerning an ashing apparatus used in a manufacture of a semiconductor device. CONSTITUTION:An ashing apparatus comprises a reaction chamber 10 for ashing a resist formed on a substrate 16 using a plasma, a plasma generating chamber 12 for forming a reaction gas in the plasma and generating the plasma, an adjusting valve 15A for adjusting an introduction state of the reaction gas to the plasma generating chamber 12 and starting a gas introduction to the plasma generating chamber 12 according to a driving control signal SS, a substrate placing table 17 for placing the substrate 16 and heating the substrate 16, temperature detecting means 19 for detecting a temperature of the substrate 16, and control means 20 for outputting the driving control signal SS to the adjusting valve 15A at the time when a measuring temperature of the temperature detecting means 19 reaches a constant temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing device, that is, a device for ashing and removing a resist film used for manufacturing a semiconductor device.

In recent years, it has been attempted to reduce the time required for ashing, which is one of the steps of peeling a resist film, which is necessary for manufacturing a semiconductor device. However, until now, due to experience, etc., ashing was ended at a place where it seemed that ashing had ended sufficiently, so it often took longer than the time actually required, and it was easy to waste time. .

Therefore, in order to shorten the ashing time, an attempt has been made to obtain the ashing rate, which indicates the amount of ashing per unit time, with high accuracy and to accurately know the time required for ashing.

[0004]

2. Description of the Related Art Generally, a downflow asher according to a conventional example, as shown in FIG. 5, has a quartz window 1, a plasma generating chamber 2, a microwave waveguide 3, a shower head 4, a gas cylinder 5, an adjusting valve 5A, and a wafer mounting device. The pedestal 7 and the microwave generator 8 are provided to ash the resist film formed on the upper surface of the wafer 6.

When the resist film on the upper surface of the wafer 6 is ashed using the apparatus, first, the wafer 6 is placed on the wafer mounting table 7, and the wafer 6 is kept at a temperature of the resist ashing condition (hereinafter referred to as a set temperature). The wafer 6 is heated by the wafer mounting table 7 in order to raise the temperature.

Microwaves are generated by the microwave generator 8 almost at the same time as the heating of the wafer 6 is started. The microwave passes through the microwave waveguide 3 and is introduced into the plasma generation chamber 2 through the quartz window 1. Further, the regulating valve 5A is opened, and the reaction gas such as oxygen gas is introduced from the gas cylinder 5 into the plasma generation chamber 2, and the reaction gas is turned into plasma by the microwave.

The plasma of the reaction gas thus generated drops and reaches the resist film on the upper surface of the wafer 6, and the resist film is ashed. Further, unnecessary gas is exhausted from the exhaust port 9 at any time.

As described above, the resist film on the upper surface of the wafer 6 is ashed. In order to find the time required for ashing, it is necessary to ash the sample wafer in advance and find the ashing rate.

At this time, even if the ashing conditions are the same,
The ashing amount and ashing rate also differ depending on the state of the resist applied to the wafer. For example, in FIG.
As shown in the graph of, the same ashing condition, that is, the apparatus pressure of 1.0 Torr, the microwave output of 1.5 kw,
O ₂ gas flow rate 1350 SCCM, N ₂ flow rate 150 SCCM,
Consider a case in which ashing is performed only for resist coating, UV curing after resist coating, and resist coating followed by baking at 200 ° C. under ashing conditions of a stage temperature of 200 ° C.

At this time, the ashing amount is different for each time, and the ashing rate is 15552Å / min, 1 in order.
The difference is 4358Å / min and 14385Å / min. Therefore, when ashing, for example, the pressure in the reaction chamber,
Even if the ashing conditions such as the flow rate of the reaction gas are the same, it is necessary to successively obtain the ashing rate each time the state of the resist film changes.

Conventionally, when obtaining the ashing rate,
The sample wafer is ashed under predetermined ashing conditions, the sample wafer is taken out from the asher many times at regular intervals, the resist film thickness is measured each time, and the ashing amount is calculated. The ashing rate was calculated by the method of least squares or the like based on the part where the time change of was constant.

[0012]

By the way, at the time of ashing, the wafer 6 is mounted on the wafer mounting table 7 and oxygen gas or microwaves is introduced into the plasma generating chamber shortly after the heating is started to start the ashing. Was.

Then, as shown in FIG. 6, after about 20 seconds have passed from the start of ashing, the shape of the graph showing the relationship between the ashing time and the ashing amount is a straight line. That is, the ashing rate, which indicates the rate of change of the ashing amount with respect to time, is a constant value and has the slope of this straight line.

However, from about 20 seconds after the start of ashing, the shape of the graph is not a straight line but a curved line. This is because the wafer temperature has not reached the set temperature for about 20 seconds from the start of ashing, so the chemical reaction related to ashing during that time is not stable and the ashing amount is unstable. Seems to be.

Therefore, even if the sample wafer is ashed by using the above-mentioned apparatus to accurately obtain the ashing rate, the ashing rate varies depending on time, so that the sample wafer 6 is repeatedly taken out of the asher and the time is taken. Measure the ashing amount for each
It is necessary to precisely obtain the relationship between the ashing amount and the time, create a graph showing the relationship between the time and the ashing amount, and calculate the ashing rate based on the straight line portion of the graph. In addition, in the conventional example as shown in FIG.
The ashing amount is measured even once.

Therefore, in order to measure the ashing amount many times, the sample wafer has to be taken in and out from the asher many times, which complicates the measurement work and takes a long time. Such a problem occurs.

The present invention was created in view of the problems of the conventional example, and it is possible to realize a labor saving of the ashing amount measurement work required for calculating the ashing rate and a reduction of the time required therefor. The purpose is to provide a simple ashing device.

[0018]

As shown in FIG. 1, an ashing apparatus according to the present invention comprises a reaction chamber 10 for ashing a resist formed on a substrate 16 using plasma.
A plasma generation chamber 12 for generating the plasma by converting the reaction gas into a plasma, and adjusting the introduction state of the reaction gas into the plasma generation chamber 12, and controlling the drive control signal S.
A regulating valve 15A for starting gas introduction into the plasma generation chamber 12 based on S, a substrate mounting table 17 for mounting the substrate 16 and heating the substrate 16, and the substrate 16
And a control means 20 for outputting the drive control signal SS to the adjusting valve 15A when the temperature measured by the temperature detecting means 19 reaches a certain temperature. And achieve the above objective.

[0019]

[Operation] According to the ashing device of the present invention, as shown in FIG.
As shown in FIG. 3, it has a temperature detecting means 19 and a control means 20.

For example, the substrate 1 by the temperature detecting means 19
When the temperature of the substrate 16 is detected and the temperature of the substrate 16 reaches a certain temperature, the control means 20 outputs the drive control signal SS to the adjusting valve 15A, and the adjusting valve 15A outputs the reaction gas to the plasma generation chamber 12. Introduction is started.

Therefore, only when the substrate 16 reaches the set temperature, the reaction gas is introduced into the apparatus and the ashing of the resist film is started. Therefore, since the temperature of the substrate 16 is stable at the set temperature from the start of ashing, the relationship between the ashing time and the ashing amount is always proportional. Therefore, the ashing rate can be easily obtained by obtaining the ashing amount at any two arbitrary time points.

That is, to obtain the ashing rate, the ashing amount at any two arbitrary times is measured, the two points are plotted on a plane having the ashing time and the ashing amount as axes, and a straight line passing through the two points is drawn. The ashing rate can be easily obtained by subtracting the slope of the straight line.

As a result, the number of times the ashing amount needs to be measured at the time of calculating the ashing rate is only twice, and there is no need to take the wafer out of the asher many times and measure it as in the conventional example. It becomes possible to save the labor of the measurement work and to shorten the time required for it.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a downflow asher according to an embodiment of the present invention.

The downflow asher according to the embodiment of the present invention comprises a reaction chamber 10, a quartz window 11 and a plasma generation chamber 1.
2, microwave waveguide 13, shower head 14, gas cylinder 15, wafer mounting table 17, microwave generator 1
8, a sensor 19, a gas introduction control circuit 20, and an exhaust port 21.

The reaction chamber 10 is for ashing the photoresist film on the wafer 16 inside thereof, and the quartz window 11 is a plate made of quartz provided facing the plasma generation chamber 12 and is provided with microwaves. It is permeated into the plasma generation chamber 12.

The plasma generating chamber 12 is for introducing a reaction gas such as oxygen and a microwave into the inside thereof to turn the reaction gas into a plasma by the microwave, and the microwave waveguide 13 generates a microwave. The microwave generated from the device 18 is introduced into the plasma generation chamber 12.

The shower head 14 is made of a conductive material and adsorbs charged particles such as ions generated at the same time when the reaction gas is turned into plasma.
Reference numeral 5 is for introducing a reaction gas such as oxygen into the plasma generation chamber 12 in advance.

The adjustment valve 15A is a valve for adjusting the introduction of the reaction gas from the gas cylinder 15 into the plasma generation chamber 12, and when it is opened, the reaction gas is introduced into the plasma generation chamber 12 from the gas cylinder 15. Further, the adjusting valve 15A is opened based on the gas introduction start signal SS from the comparison circuit 20B to start introducing the reaction gas into the plasma generation chamber 12.

The wafer mounting table 17 mounts the wafer 16 thereon and heats it up to a set temperature, and the microwave generator 18 generates microwaves.

The sensor 19 is a thermocouple that detects the temperature of the wafer and outputs it to the gas introduction control circuit 20. The gas introduction control circuit 20 is composed of a memory circuit 20A and a comparison circuit 20B, and introduces the reaction gas in the gas cylinder 15 based on the temperature of the wafer.

Of these, the memory circuit 20A stores the preset temperature, and the comparison circuit 20B compares the preset temperature with the wafer temperature. The gas introduction start signal SS is output. Further, the exhaust port 21 exhausts unnecessary gas to the outside of the reaction chamber 10.

The wafer is ashed using the above apparatus. That is, first, the wafer 16 is mounted on the wafer mounting table 17, and the wafer 16 is heated to the set temperature by the wafer mounting table 17. At the same time, the temperature of the wafer 16 is detected by the sensor 19, and the detection signal is detected by the comparison circuit 20.
Output to B.

The comparison circuit 20B enables the storage circuit 20A.
When the set temperature stored in the temperature sensor is compared with the temperature of the wafer 16 output from the sensor 19, and the two are equal, the comparison circuit 20B outputs the gas introduction start signal SS to the adjusting valve 15A. Then, the gas introduction start signal SS
Based on the above, the regulating valve 15A is opened, and the reaction gas such as oxygen gas is introduced into the plasma generation chamber 12. That is, unlike the conventional method, after the wafer temperature reaches the set temperature,
For the first time, the reaction gas is introduced into the plasma generation chamber 12.

Almost at the same time, the microwave generator 1
The microwave is generated by 8 and the microwave waveguide 1
3 and is introduced into the plasma generation chamber 12 through the quartz window 11. The reactive gas such as oxygen gas introduced by the microwave is turned into plasma, and the ashing is started by this plasma.

Although charged particles such as ions are also generated during the plasma generation, the wafer 16 and the plasma generation chamber 12 are separated from each other, and the charged particles are adsorbed by the conductive shower head 14. Only neutral plasma drops and reaches the resist on the upper surface of the wafer 16 and reacts with the resist film to ash it. Further, unnecessary gas is exhausted from the exhaust port 21.

The photoresist film on the wafer 16 is ashed as described above. However, in order to obtain the time required for ashing, it is necessary to obtain the ashing rate by ashing the sample wafer in advance. The method of obtaining the ashing rate will be described below.

FIG. 2 shows the relationship between the ashing time and the ashing amount obtained by measuring the ashing amount at a certain time in order to obtain the ashing rate using the downflow asher according to the embodiment of the present invention. It is a graph.

FIG. 4 is a graph showing the relationship between the baking time and the resist film loss caused by the volatilization by heat when the wafer is baked at 200 ° C. As shown in this graph, the film loss caused by baking at 200 ° C. has a slight change with time,
The shape of the graph is a straight line.

The graph showing the relationship between the ashing amount and the ashing time in FIG. 2 is 200 ° C. as shown in FIG.
It also includes the amount of film loss caused by baking. Figure 2
According to the graph, the sample was baked at 200 ° C. after the resist was applied under the ashing conditions of the apparatus pressure of 1.0 Torr, microwave output of 1.5 kw, O ₂ gas flow rate of 1350 SCCM, N ₂ flow rate of 150 SCCM and stage temperature of 200 ° C. The graph showing the relationship between the ashing time and the ashing amount is precisely obtained by ashing the wafer with the downflow asher according to the present embodiment and measuring the ashing amount 10 times for 50 seconds every 5 seconds.

At this time, the graph is a straight line passing through the origin. That is, since the downflow asher according to the present embodiment is used for ashing, the temperature of the wafer 16 reaches the set temperature at the start of ashing, and the wafer 16 is in an equilibrium state. Therefore, the shape of the graph showing the relationship between the ashing time and the ashing amount is a straight line from beginning to end,
Unlike the conventional example, the curved portion immediately after the start of ashing does not appear in the graph.

Using the data of the ashing amount obtained every 5 seconds in this way, the slope of this graph is obtained by the method of least squares or the like, which is about 1.42 (μm / min).
This is the precisely determined ashing rate.

When the downflow asher according to the present embodiment is used, the graph showing the relationship between the ashing time and the ashing amount becomes a straight line passing through the origin, and thus the ashing obtained by measuring many times as described above. Even if the ashing rate is not obtained by using a complex method such as the least squares method by using the amount, an almost accurate ashing rate can be easily obtained only by measuring the ashing amount at any two different times. it can. The method will be described below with reference to FIG.

Here, a case is considered in which a sample wafer baked at 200 ° C. after coating a resist is ashed by the downflow asher according to the present embodiment under the same ashing conditions as when the ashing amount is measured every 5 seconds. .

At this time, unlike the case where the ashing amount is measured 10 times every 5 seconds, the ashing amount is measured only twice. Here, the ashing amount is measured only twice, 20 seconds and 40 seconds after the start of ashing.

At this time, the ashing amount of 20 seconds after the start of ashing is 4635Å, and the ashing amount of 40 seconds is 940.
It was 2Å. Therefore, on a plane in which the horizontal axis represents time (sec) and the vertical axis represents ashing amount (Å), these two data are A (20,4635), B as shown in FIG.
It is indicated by two points (40,9402).

When the slope of a straight line passing through these two points, that is, the ashing rate is calculated, (ashing rate) = (change amount of ashing amount) /
(Amount of change in time), so by substituting the numerical values of points A and B for each, (9402-4635) / (40-20) = 238.35 (Å / sec) = 14301 (Å / min) ≈1.43 (μm / min), which is 1.42 (μm
/ Min) and the ashing rate of almost the same value as the one accurately obtained can be obtained with only two measurement data.

Therefore, the wafer 16 is taken out from the asher 2 times for measuring the amount of ashing, and the wafer 16 is put in and taken out many times as in the conventional example and the case where the ashing rate is precisely obtained in this embodiment. No need.

Therefore, when measuring the ashing amount, it is not necessary to take out the wafer 16 from the asher many times to measure the ashing amount, which saves labor for the measurement work and shortens the time required for the measurement work. Can be realized.

Also, when calculating the ashing rate,
Since it is not necessary to obtain the ashing rate by a complicated method such as the least square method using a large number of data obtained by measuring many times, it is only necessary to obtain the slope of a straight line passing through two points. The calculation itself becomes simple.

As described above, the downflow asher according to the embodiment of the present invention has the sensor 19 and the gas introduction control circuit 20 as shown in FIG. Therefore, the reaction gas is introduced and ashing is performed only when the wafer 16 reaches the set temperature. Therefore, since the temperature of the wafer 16 is stable from the start of ashing,
The relationship between the ashing time and the ashing amount is completely proportional, and the graph is a straight line. Therefore, by obtaining the ashing amount at any two times, the ashing rate can be easily obtained.

Thus, unlike the conventional case, it is not necessary to take out the wafer 16 from the asher many times to measure the ashing amount when calculating the ashing rate, which saves labor for the measurement work and requires it. The time can be shortened.

The wafer 16 is an example of the substrate, and the wafer mounting table 17 is an example of the substrate mounting table. Further, the sensor 19 is an example of temperature detecting means, and the gas introduction control circuit 20 is an example of controlling means. Furthermore, the gas introduction start signal SS is an example of a drive control signal.

Although a photoresist is used as the resist film in this embodiment, an EB resist or the like also has the same effect.

[0055]

As described above, the ashing device according to the present invention has the temperature detecting means and the control means.

Therefore, the reaction gas is not introduced into the apparatus until the substrate reaches the set temperature, so that the resist film is not ashed. As a result, since the temperature of the substrate is stable at the set temperature from the start of ashing, the relationship between the ashing time and the ashing amount is always proportional. Therefore, the ashing rate can be easily obtained by obtaining the difference between the ashing amounts at any two points in time.

As a result, it is possible to save the labor of measuring the ashing amount and reduce the time required for the calculation of the ashing rate.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a downflow asher according to an embodiment of the present invention.

FIG. 2 is a graph showing a correlation between an ashing amount and an ashing time by a downflow asher according to an embodiment of the present invention.

FIG. 3 is a graph illustrating an ashing rate measurement method using a downflow asher according to an embodiment of the present invention.

FIG. 4 is a graph showing the correlation between the decrease in the resist film thickness and the baking time that occur during baking at 200 ° C. according to the example of the present invention.

FIG. 5 is a configuration diagram of a downflow asher according to a conventional example.

FIG. 6 is a graph showing a correlation between an ashing amount and an ashing time by a downflow asher according to a conventional example.

FIG. 7 is a graph showing the difference between the ashing time and the ashing amount depending on the resist coating state.

[Explanation of symbols]

 10 reaction chamber, 11 quartz window, 12 plasma generation chamber, 13 microwave waveguide, 14 shower head, 15 gas cylinder, 15A adjusting valve, 16 wafer (substrate), 17 wafer mounting table (substrate mounting table), 18 microwave generation Device, 19 sensor (temperature detection means), 20 gas introduction control circuit (control means), 20A storage circuit, 20B comparison circuit, 21 exhaust port, SS gas introduction start signal (drive control signal).

Claims (1)

[Claims] 1. A reaction chamber (10) for ashing a resist formed on a substrate (16) using plasma, and a plasma generation chamber (12) for converting the reaction gas into plasma to generate the plasma. An adjusting valve (15A) for adjusting the introduction state of the reaction gas into the plasma generation chamber (12) and for starting the introduction of gas into the plasma generation chamber (12) based on a drive control signal (SS); A substrate platform (17) on which the substrate (16) is placed and which heats the substrate (16), and a temperature detecting means (1) for detecting the temperature of the substrate (16).
9) and a control means (20) for outputting the drive control signal (SS) to the regulating valve (15A) when the temperature measured by the temperature detecting means (19) reaches a certain temperature. Characteristic ashing device.