JP2001284306A - Apparatus and method for cleaning substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for cleaning a substrate that prevents damage to the substrate, and at the same time can carry out ultrasonic washing with a high particle elimination rate. SOLUTION: A substrate-cleaning apparatus 1 is equipped with a demineralized water containing gas concentration control part 11, a chemical liquid-mixing part 13, a substrate-cleaning both 27, an ultrasonic vibrator 21, an ultrasonic wave control part 15, a temperature sensor 31, and a temperature monitor 33. In this case, the temperature of cleaning fluid in the substrate- cleaning tank 27 is measured by the temperature sensor 31. Based on the measurement result, the temperature monitor 33 calculates changes in the temperature of the cleaning fluid in the cleaning both 27. According to the calculation result and the correlation between the change in the temperature of the cleaning fluid and the damage of a substrate S, a supply voltage to the ultrasonic vibrator 21 is reduced or is set to zero, or the concentration of the demineralized water containing gas is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate cleaning apparatus and a substrate cleaning method, and more particularly to cleaning a semiconductor substrate having a fine pattern formed thereon.

[0002]

2. Description of the Related Art Conventionally, in cleaning substrates such as semiconductor wafers, chemical cleaning using a chemical solution or running water, physical cleaning using an ultrasonic wave or a brush, or cleaning combining these chemical cleaning and physical cleaning has been conventionally used. Was.

Ultrasonic cleaning, which is physical cleaning, has been mainly used for removing fine particles adhering to the surface of a semiconductor substrate.

In recent years, wiring on the surface of a substrate has been further miniaturized due to miniaturization of semiconductor design rules. For this reason,
A problem has been that microscopic damage to a semiconductor substrate due to ultrasonic vibration is caused. In order to cope with this problem, the frequency of the ultrasonic wave to be irradiated has been increased, thereby preventing damage to the semiconductor substrate. Currently employed frequencies are from about 0.5 to about 2 MHz.

[0005] Ultrasonic cleaning, which has been used for cleaning semiconductor substrates, is roughly classified into a batch type and a single-wafer type. The batch type means, for example, as shown in FIG. 6, the ultrasonic vibrator 22 is attached to the bottom of the processing tank 27, two or more semiconductor substrates S are stored in the processing tank 27, and then filled with pure water or a chemical solution. Alternatively, the semiconductor substrate S is cleaned by oscillating ultrasonic waves from the ultrasonic vibrator 22 while flowing water.

[0006] Ultrasonic waves are highly effective in removing fine particles adhering to a semiconductor substrate. On the other hand, if an ultrafine pattern is formed on a semiconductor substrate, the ultrafine pattern may be damaged by ultrasonic vibration.

Therefore, when performing ultrasonic cleaning, an output power value that does not damage the semiconductor substrate is empirically determined, and the output power of the ultrasonic drive power supply is controlled in accordance with the empirical value. It has avoided damage to the substrate.

[0008]

However, from the study of the ultrasonic vibration intensity on the sound pressure monitor measured on the liquid surface of the chemical or pure water, it has been found that even if the output power from the ultrasonic vibrator drive power supply is the same. It has been found that when the concentration of the gas dissolved in the chemical solution or pure water is lower than a certain concentration, the intensity of the ultrasonic vibration transmitted through the cleaning solution increases. This indicates that avoiding damage to the substrate is not sufficient simply by considering the output power of the ultrasonic drive power supply. For this reason, it is conceivable to directly control the sound pressure in the cleaning tank and the concentration of the gas dissolved in the chemical solution or pure water, but measurement and adjustment require a great deal of time and cost. It is not suitable as a method for protecting a semiconductor substrate during processing or as a regular management method.

Although it has been known that the temperature rises when ultrasonic waves are irradiated into pure water or a chemical solution, there is a predetermined correlation between the temperature rise, the dissolved gas concentration and the damage to the semiconductor substrate. It was not known until some point. Therefore, the result of the temperature rise due to the ultrasonic irradiation was not used for avoiding damage to the semiconductor substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a substrate cleaning apparatus and a substrate cleaning method capable of performing ultrasonic cleaning without damaging a substrate and having a high particle removal rate. To provide.

[0011]

The present invention solves the above-mentioned problems by the following means.

That is, according to the present invention, there is provided a substrate cleaning tank for cleaning a charged substrate with a supplied cleaning liquid, ultrasonic irradiation means for irradiating the substrate cleaning tank with ultrasonic waves, A first temperature measuring means for measuring a first temperature, which is the temperature of the cleaning liquid, and receiving the measurement result of the first temperature measuring means, calculating a change amount or a change rate of the first temperature; Based on a calculation result, a correlation between the first temperature change amount and the substrate damage, or a correlation between the first temperature change rate and the substrate damage,
Temperature change control means for suppressing a change in the first temperature;
There is provided a substrate cleaning apparatus comprising:

The correlation includes the irradiation time of the ultrasonic wave as a parameter, and the temperature control means reduces the electric power supplied to the ultrasonic wave irradiation means or makes the electric power zero, thereby obtaining the first ultrasonic wave. It is desirable to suppress changes in temperature.

The correlation includes the concentration of the dissolved gas dissolved in the cleaning liquid as a parameter, and the temperature control means controls the change in the first temperature by changing the concentration of the dissolved gas. Is preferred.

It is desirable that the reduction of the power supplied to the ultrasonic irradiation means or the change of the dissolved gas concentration be performed during the cleaning of the substrate.

Preferably, the first temperature measuring means is arranged in the cleaning tank at a position other than a position affecting vibration of the substrate by the ultrasonic waves and a position affecting cleaning of the substrate. is there.

Further, the above-mentioned substrate cleaning apparatus further comprises a second temperature measuring means for measuring a second temperature which is a temperature of the cleaning water at a position where the irradiation of the ultrasonic waves is avoided. More preferably, the means calculates the amount of change of the first temperature or the rate of change of the first temperature based on the first temperature and the second temperature.

Further, according to the present invention, there is provided a substrate cleaning apparatus including a substrate cleaning tank for cleaning a supplied substrate with a supplied cleaning liquid, and an ultrasonic vibrator for irradiating the substrate cleaning tank with ultrasonic waves. A substrate cleaning method used, wherein a step of measuring a first temperature which is a temperature of a cleaning liquid in the cleaning tank during the irradiation of the ultrasonic wave, and a step of measuring a change in the first temperature and damage to the substrate. Suppressing the change in the first temperature based on the measurement result of the first temperature in accordance with the correlation.

The correlation includes the irradiation time of the ultrasonic wave as a parameter, and the step of controlling the first temperature change includes reducing the power supplied to the ultrasonic irradiation vibrator, or reducing the power to zero. It is desirable to include the step of performing.

The correlation may include a concentration of a gas dissolved in the cleaning liquid as a parameter, and the step of suppressing the first temperature change may include a step of changing the concentration of the dissolved gas. More preferred.

In the above-described substrate cleaning method, the first
The change in the temperature includes a change amount or a change rate.

Further, in the method for cleaning a substrate, the temperature of the cleaning liquid at a position where the irradiation of the ultrasonic wave is avoided may be a second temperature.
Further comprising the step of measuring the temperature of the first temperature, wherein the step of suppressing the change of the first temperature is performed based on the measurement result of the first temperature and the measurement result of the second temperature. It is preferable that this is a step of suppressing

It is desirable that the reduction of the power supplied to the ultrasonic vibrator or the change of the dissolved gas concentration is performed during the cleaning of the substrate.

The cleaning liquid supplied to the above-described substrate cleaning tank contains a chemical solution and pure water.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Cleaning Principle Applied to the Present Invention First, the cleaning principle that is the basis of the cleaning method according to the present invention will be described with reference to the drawings.

FIG. 1 is a graph showing the correlation between the temperature change rate of the cleaning liquid and the amount of pattern defects on the substrate surface. From the figure, it can be seen that when the ultrasonic cleaning is performed under a condition where the temperature changes drastically, damage to the substrate increases.

FIG. 2 is a graph showing the correlation between the ultrasonic irradiation time and the amount of temperature change in the cleaning tank. Of the four graphs 11 to 14 shown in FIG. 11, 11 and 12 show the temperature changes when degassed water is used as the cleaning liquid, and 13 and 14 show the temperature changes when gas-dissolved water is used.
Further, l1 and l3 indicate that the driving power of the ultrasonic vibrator is 50.
In the case of W, l2 and l4 indicate temperature changes when the driving power of the ultrasonic transducer is 200W, respectively.

From the figure, it can be seen that in the case of degassed water, the temperature of the cleaning liquid rises even when the driving power of the ultrasonic oscillator is as low as 50 W, but in the case of pure water in which gas is dissolved, the ultrasonic oscillator is used. It can be seen that even if the driving power of the cleaning liquid is as high as 200 W, the temperature of the cleaning liquid hardly changes.

From these two graphs, it can be seen that, first, the greater the rate of change in temperature, the greater the damage to the substrate, the higher the concentration of gas in pure water, the more the temperature rise can be suppressed, It can be seen that the lower the driving power of the vibrator, the more the temperature rise can be suppressed.

Therefore, the temperature change or the temperature change rate in the cleaning tank is monitored, and when the temperature change or the temperature change rate of the cleaning liquid exceeds the threshold value, for example, by comparing with a threshold value based on an empirical value or the like. By a) increasing the concentration of the dissolved gas, or b) reducing or reducing the driving power of the ultrasonic vibrator, it becomes possible to avoid damage to the substrate.

In addition to the above a) and b), a combination of a conventionally known method, c) a method of increasing the frequency of ultrasonic waves to be irradiated, is more effective in avoiding damage to the substrate. Coping is possible.

(2) First Embodiment Some embodiments of the present invention to which the above cleaning principle is applied will be described with reference to the drawings. In the following drawings, the same portions are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 3 is a block diagram showing a schematic configuration of the first embodiment of the substrate cleaning apparatus according to the present invention. The substrate cleaning apparatus 1 of the present embodiment implements the above-described cleaning principle with an indirect propagation type ultrasonic cleaning apparatus.

The cleaning apparatus 1 shown in FIG. 3 comprises a pure water-soluble gas concentration control section 11, a chemical mixing section 13, and an ultrasonic vibrator 2.
1, an ultrasonic control unit 15, a propagation tank 25, a cleaning tank 27, a temperature sensor 31, and a temperature monitor 33.

The pure aqueous gas concentration controller 11 receives pure water from a pure water plant (not shown), and receives gas from a gas generator (not shown) to convert the pure water into pure water. To dissolve. The pure water-dissolved gas concentration control unit 11 also has a gas concentration detector (not shown), controls the gas concentration dissolved in the pure water, and supplies degassed water or gas-dissolved water to the chemical liquid mixing unit 13. As the dissolved gas, for example, Ar, N
₂ , O ₂ , H ₂ , O _{3 and the} like are used.

The chemical mixing unit 13 receives the supply of degassed water or gas-dissolved water from the pure water-dissolved gas concentration control unit 11, and mixes the chemical with it. The chemical mixing unit 13 also has a chemical concentration detector (not shown), and controls the chemical concentration in degassed water or gas-dissolved water to supply a chemical or pure water to the cleaning tank 27. In addition, as a chemical solution, for example, HCl,
HF, H ₂ O ₂ , NH ₄ OH or the like is used.

The ultrasonic vibrator 21 is attached to the bottom of the propagation tank 25, receives driving power from the ultrasonic control unit 15 to generate ultrasonic waves, and
7 is irradiated with ultrasonic waves. The ultrasonic vibrator 21 also changes the frequency of the ultrasonic wave to be applied, based on a control signal given from the ultrasonic control unit 15.

The cleaning tank 27 receives the loading of the semiconductor substrate S, which is a cleaning target, from a charging device (not shown), and fills or flows a chemical solution or pure water supplied from the chemical solution mixing unit 13 into the tank. Thereby, the semiconductor substrate S
Wash.

The temperature sensor 31 is 2 in this embodiment.
It has a pair of thermocouples 31a and 31b. The thermocouple 31a is installed in the propagation tank 25 and measures the temperature in the propagation tank 25. Further, the thermocouple 31b is installed in the cleaning tank 27 at a position where the vibration of the ultrasonic wave is not shielded and does not affect the cleaning of the semiconductor substrate, and measures the temperature of the cleaning water in the cleaning tank 27. Note that both of the thermocouples 31a and 31b may be installed at the above-described positions in the cleaning tank 27. The temperature sensor 31 supplies the temperature in the propagation tank 31 and the temperature of the cleaning liquid in the cleaning tank 27 to the temperature monitor 33 in response to the detection results of the thermocouples 31a and 31b.

The temperature monitor 33 calculates the temperature change amount or the temperature change rate in the cleaning tank 27 based on the measurement result supplied from the temperature sensor 31 and compares it with a predetermined threshold value based on an empirical value or the like. The comparison result is fed back to the ultrasonic controller 15 and the pure aqueous gas concentration controller 11.

A substrate cleaning method using the substrate cleaning apparatus 1 shown in FIG. 3 is as follows.

The cleaning of the semiconductor substrate is generally performed by: 1) putting the semiconductor substrate into a cleaning tank 2) cleaning the semiconductor substrate with a chemical solution 3) cleaning the semiconductor substrate with pure water 4) drying the semiconductor substrate 5) semiconductor substrate It is carried out by sequentially performing each process of dispensing from the washing tank.

Here, the ultrasonic irradiation for the purpose of particle removal is performed in one of the above-mentioned steps of 1) chemical liquid cleaning and 2) pure water cleaning, or both steps. The operation of the substrate cleaning apparatus 1 in the above step will be described.

Cleaning tank 27 during cleaning with chemical solution or pure water
When the internal temperature rises, the temperature monitor 3 of the substrate cleaning apparatus 1
3 receives the measurement result of the temperature sensor 31, calculates the temperature change amount or the temperature change rate in the cleaning tank 27, and compares it with a predetermined threshold value as described above. When the temperature change amount or the temperature change rate exceeds the threshold value, the temperature monitor 33 issues an alarm and supplies a control signal to the ultrasonic control unit 15. Upon receiving the control signal, the ultrasonic control unit 15 reduces the drive power supplied to the ultrasonic transducer 21 or sets the drive power to zero. As a result, the rise of the temperature or the rate of temperature change is stopped, and the damage to the semiconductor substrate S is reduced.
The temperature monitor 33 also supplies a control signal to the pure water-soluble gas concentration control unit 11, and the pure water-soluble gas concentration control unit 11 increases the amount of gas to be dissolved in the pure water, whereby the semiconductor substrate S Avoid damage. In addition to the above two methods, the frequency of the driving power supplied to the ultrasonic vibrator may be changed to a high frequency region by a control signal to the ultrasonic control unit 15. 3) reduction of driving power, increase of dissolved gas amount or increase of driving power frequency
The three methods may be performed individually, may be performed by combining any two methods, or may be performed by combining the three methods. When performing a combination of a plurality of methods, they may be performed in any order,
Further, a plurality of methods may be performed simultaneously.

FIG. 4 is a block diagram showing a modification of this embodiment. In the substrate cleaning apparatus 2 shown in FIG. 1, the above-described cleaning principle is realized by a direct propagation type ultrasonic cleaning apparatus. That is, the difference between the substrate cleaning apparatus 2 shown in FIG. 4 and the substrate cleaning apparatus 1 shown in FIG. 3 is that the ultrasonic vibrator 22 is provided directly in contact with the bottom of the cleaning tank 27.
7 is that the cleaning liquid in 7 is directly irradiated with ultrasonic waves and that the thermocouple of the temperature sensor 32 is a pair of thermocouples 32a. Therefore, the other configuration and operation of the substrate cleaning apparatus 2 are substantially the same as those of the substrate cleaning apparatus 1 shown in FIG.
In the above-described embodiment or its modified example, the temperature was measured with two pairs and one pair of thermocouples, respectively, but the number of thermocouples may be one pair or two pairs in each case.
It may be more than a pair.

(3) Second Embodiment Next, a second embodiment of the substrate cleaning apparatus according to the present invention will be described with reference to FIG. The feature of the substrate cleaning apparatus 3 shown in FIG. 3 is that the substrate cleaning apparatus 3 further includes a cleaning liquid tank 28 disposed at a position not irradiated with ultrasonic waves, and the thermocouple 31 among the two pairs of thermocouples 31 a and 31 b of the temperature sensor 31.
a is located in the washing tank 28. Other configurations of the substrate cleaning apparatus 3 shown in FIG. 5 are substantially the same as those of the substrate cleaning apparatus 2 shown in FIG.

According to the present embodiment, the temperature of the cleaning liquid at the position where the ultrasonic wave is not irradiated is measured by the thermocouple 31a, and the temperature of the cleaning liquid in the cleaning tank 27 measured by the thermocouple 31b is determined based on this temperature. Since the change amount or the change rate is calculated, the temperature change amount or the temperature change rate can be calculated more accurately. As a result, more accurate temperature control becomes possible, and damage to the semiconductor substrate, which is the object to be cleaned, can be more precisely avoided. Other operations of the substrate cleaning apparatus 3, that is, the ultrasonic control unit 15 and the pure aqueous gas concentration control unit 1 by the temperature monitor 33
The control method 1 is substantially the same as that of the substrate cleaning apparatus 1 shown in FIG. In the present embodiment, the number of thermocouples is not limited to one, but may be two or three or more as described above.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments.
Various modifications can be made without departing from the spirit of the invention. In the above-described embodiment, a temperature sensor having a thermocouple has been described.However, the temperature sensor is not limited to this, and does not shield the vibration of the ultrasonic wave and does not affect the cleaning of the substrate. If so, the specific configuration does not matter. In the second embodiment, the cleaning liquid tank 28 is used as a specific example of the tank that is not irradiated with ultrasonic waves. However, the present invention is not limited to this. For example, pure water on the utility side outside the cleaning apparatus, for example, inside a pure water plant May be used as a reference value using pure water.

[0049]

As described in detail above, according to the present invention,
Ultrasonic cleaning with no damage to the substrate and a high particle removal rate becomes possible.

[Brief description of the drawings]

FIG. 1 is a graph illustrating a relationship between a temperature rise and a pattern defect for explaining the principle of the present invention.

FIG. 2 is a graph illustrating the relationship between ultrasonic irradiation time and temperature rise for explaining the principle of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a first embodiment of the substrate cleaning apparatus according to the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a substrate cleaning apparatus which is a modification of the embodiment shown in FIG. 3;

FIG. 5 is a block diagram showing a schematic configuration of a substrate cleaning apparatus according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a conventional batch type ultrasonic cleaning apparatus.

[Explanation of symbols]

 1-3 substrate cleaning device 11 pure aqueous gas concentration controller 13 chemical mixing unit 15 ultrasonic controller 21 and 22 ultrasonic transducer 25 propagation tank 27, 28 cleaning tank 31, 32 temperature sensor 31a, 31b, 32a thermocouple 33 Temperature monitor S Semiconductor substrate

Continued on the front page (72) Inventor Hiroshi Kawamoto 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd. Microelectronics Co., Ltd. (72) Inventor Kunihiro Miyazaki 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term in Toshiba Yokohama Office 3B201 AA03 AB01 BB04 BB85 BB92 BB93 BB96 BB98 CB01 CD42 CD43

Claims (10)

[Claims] A substrate cleaning tank that cleans the supplied substrate with the supplied cleaning liquid; an ultrasonic irradiation unit that irradiates the substrate cleaning tank with ultrasonic waves; and a temperature of the cleaning liquid in the substrate cleaning tank. A first temperature measuring means for measuring a first temperature, a change amount or a change rate of the first temperature is calculated in response to a measurement result of the first temperature measuring means,
A temperature that suppresses the change in the first temperature based on a correlation between the amount of change in the first temperature and damage to the substrate or a correlation between the rate of change in the first temperature and damage to the substrate. A substrate cleaning apparatus comprising: a change control unit. 2. The correlation includes an irradiation time of the ultrasonic wave as a parameter, and the temperature control means reduces the power supplied to the ultrasonic wave irradiation means or makes the electric power zero, thereby reducing 1
The substrate cleaning apparatus according to claim 1, wherein a change in temperature of the substrate is suppressed. 3. The correlation includes a concentration of a dissolved gas dissolved in the cleaning liquid as a parameter, and the temperature control means controls a change in the first temperature by changing a concentration of the dissolved gas. The substrate cleaning apparatus according to claim 1, wherein the cleaning is performed. 4. The apparatus according to claim 1, wherein the first temperature measuring means is disposed in the cleaning tank at a position other than a position affecting vibration of the substrate by the ultrasonic waves and a position affecting cleaning of the substrate. The substrate cleaning apparatus according to any one of claims 1 to 3, wherein: 5. The apparatus according to claim 1, further comprising: a second temperature measuring means for measuring a second temperature which is a temperature of the cleaning water at a position where the ultrasonic wave irradiation is avoided. And the first temperature change amount or the first temperature change amount based on the second temperature and the second temperature.
5. The substrate cleaning apparatus according to claim 1, wherein a rate of change of the temperature is calculated. 6. A substrate cleaning method using a substrate cleaning apparatus that includes a substrate cleaning tank for cleaning a charged substrate with a supplied cleaning liquid, and an ultrasonic oscillator that irradiates ultrasonic waves to the substrate cleaning tank. Measuring a first temperature which is a temperature of the cleaning liquid in the cleaning tank during the irradiation of the ultrasonic wave; and a step of measuring a first temperature according to a correlation between a change in the first temperature and damage to the substrate. Suppressing the change in the first temperature based on the measurement result of the first temperature. 7. The correlation includes an irradiation time of the ultrasonic wave as a parameter, and the step of controlling a change in the first temperature includes reducing power supplied to the ultrasonic irradiation vibrator, or The method for cleaning a substrate according to claim 6, further comprising a step of setting the number to zero. 8. The method according to claim 1, wherein the correlation includes a concentration of a gas dissolved in the cleaning liquid as a parameter, and the step of suppressing the change in the first temperature includes a step of changing the concentration of the dissolved gas. The method for cleaning a substrate according to claim 6 or 7, wherein: 9. The method according to claim 6, wherein the change in the first temperature includes a change amount or a change rate. 10. The method according to claim 1, further comprising the step of measuring a second temperature which is a temperature of the cleaning liquid at a position where the irradiation of the ultrasonic wave is avoided, wherein the step of suppressing a change in the first temperature is performed at the first temperature. The method for cleaning a substrate according to any one of claims 6 to 9, further comprising the step of suppressing a change in the first temperature based on the measurement result of the first temperature and the measurement result of the second temperature.