JP2003234320A - Method, chemical liquid, and device for cleaning substrate, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method, a cleaning chemical, and a cleaning device that exhibits high performance for removing particles on a substrate, and to provide a semiconductor device. <P>SOLUTION: The cleaning method of a substrate includes a first process for adjusting the concentration of dissolved nitrogen in demineralized water to the equilibrium concentration of dissolved nitrogen with air (approximately 16 ppm) or lower on a demineralized water supply line for supplying the demineralized water, and a second process for supplying a cleaning chemical that is prepared by mixing the demineralized water adjusted by the first process with at least hydrogen peroxide water to a cleaning tank, and for applying an ultrasonic wave to the cleaning chemical in which the substrate is dipped for cleaning. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate cleaning method for cleaning a substrate by applying ultrasonic waves, a cleaning liquid chemical, a cleaning device, and a semiconductor device. The present invention relates to a cleaning method, a cleaning chemical solution, a cleaning device, and a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, the removal of particles and the like adhering to substrates such as semiconductor substrates, liquid crystal glass substrates, and magnetic disks is performed by immersing the substrate in a cleaning chemical solution contained in a cleaning tank.
Ultrasonic waves are applied to this.

A conventional semiconductor substrate cleaning method (ultrasonic cleaning method) will be described with reference to the drawings. Referring to FIG. 6, NH ₄ OH (ammonia water), H ₂ O ₂ (hydrogen peroxide water) and pure water (ultra pure water) are individually supplied to the mixing valve from each factory line. NH ₄ OH, H ₂ O ₂ and pure water supplied in the mixing valve are mixed and supplied to the cleaning tank as an APM chemical solution. The semiconductor substrate is immersed in the APM chemical solution stored in the cleaning tank, and the megasonic (several hundred kHz) is applied to the APM chemical solution.
Ultrasonic waves) are applied. The semiconductor substrate is subjected to the chemical action of the APM chemical solution to form a thin film on the substrate surface, and particles (particulate impurities) are slightly lifted as compared to before the thin film is formed (hereinafter, this is referred to as “lift-up”). The lifted-up particles (particulate impurities) are physically separated (peeled) together with the thin film formed on the substrate surface by the etching action by NH ₄ OH and the APM chemical liquid molecule oscillation (medium action force) by megasonics. , Together with the waste chemical liquid, is discharged out of the tank. In this way, the particles attached to the substrate surface are removed.

It has been generally accepted that the pure water used here is ultrapure water obtained by vacuum degassing of dissolved gases such as dissolved oxygen, dissolved nitrogen and dissolved carbon dioxide. The reason is that when ultrapure water is used, the bubbling of dissolved gas (bubble cavitation) due to megasonics is suppressed, and as a result, the energy of megasonics can be directed more to APM chemical liquid molecule fluctuations. is there. Further, other advantages of using ultrapure water are that the generation of a natural oxide film can be suppressed, the generation of bacteria in the pipe can be prevented, and the ion exchange resin of the pure water device can be prevented from deteriorating.

Recently, however, it has been found that bubbling effectively acts to remove particles in ultrasonic cleaning. The reason is as follows. When megasonic is applied to ultrapure water, the transmittance of megasonic increases, so if there is an interface in the traveling direction of megasonic, the megasonic is reflected at the interface, and a standing wave due to the traveling wave and the reflected wave is generated. To do. When such a standing wave is present, a high sound pressure portion and a low sound pressure portion are formed in the cleaning chemical liquid, particles drifting in the cleaning chemical liquid are collected in the low sound pressure portion, and the collected particles are reattached to the substrate. However, there is a problem that uneven cleaning occurs. On the other hand, if bubbled gas is present in the cleaning chemical, the reflected wave is absorbed by the bubbled gas near the interface in the traveling direction of the megasonic, so standing waves can be prevented and uneven cleaning can occur. Can be prevented.

Therefore, ultrasonic cleaning is performed using pure water in which an inert gas such as nitrogen, which does not affect the generation of natural oxide film, the generation of bacteria, and the deterioration of the ion-exchange resin even when air bubbles (cavitation) are dissolved. Are beginning to do. The following are conventional technologies that exhibit such a tendency.

[0007] For example, the technique disclosed in Japanese Unexamined Patent Publication No. 10-335294 avoids the dissolution of oxygen and carbon dioxide in pure water and further supersaturates the dissolved nitrogen gas concentration, thereby causing a large amount of cavitation and spontaneous oxidation. This is to achieve both suppression of film growth and improvement of particle removal rate.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 10-109072, by controlling the dissolved gas concentration (for example, a predetermined concentration of nitrogen, argon, helium, etc. of 5 to 10 ppm), the ultrasonic wave becomes only a traveling wave, Since no standing wave is generated, cleaning unevenness is eliminated, reverse contamination is prevented, and particle removability is improved.

[0009]

When cleaning a substrate, the APM is used.
A chemical solution such as pure water in which hydrogen peroxide is dissolved is used. Due to the miniaturization of design rules in recent years, the pattern width and pattern interval formed on the substrate have become finer. As a result, even finer particles to be removed by cleaning the substrate are targeted, and the number of particles remaining on the substrate after cleaning is required to be closer to zero. However, even if the concentration of dissolved nitrogen gas in pure water used for APM chemicals is controlled by the conventional method,
It was difficult to realize the cleaning ability required for the substrate cleaning liquid with these chemicals.

An object of the present invention is to provide a substrate cleaning method, a cleaning chemical, a cleaning apparatus, and a semiconductor device which have a high performance of removing particles on the substrate.

[0011]

Means for Solving the Problems
After investigating the cause of the
APM chemical solution (NH_FourOH / H_TwoO_Two/ Pure water mixture
Liquid) or HPM chemical liquid (HCl / H_TwoO_Two/ Pure water mixture
H that is important for cleaning among the chemical liquids that make up_TwoO _TwoBut
Turned out not to work. That is, H_TwoO_Twoof
It was found that the aerated cavitation was not sufficient.
The cause is the dissolution in pure water that constitutes the majority of APM chemicals.
Since nitrogen is supplied directly to the cleaning tank without reducing the amount of nitrogen,
Most of the megasonic energy applied to the cleaning solution
Bubbling of dissolved nitrogen that does not directly contribute to cleaning
Because it is consumed for (cavitation)
is there. As a result, the fluctuation of the liquid molecules becomes inactive and H_TwoO
_TwoEffective because the number of evaporative bubbles generated from molecules does not increase
The particle removal function does not work.

Here, the reason why the inert gas such as nitrogen is dissolved in the pure water to be supplied in advance is to prevent the dissolution of oxygen in the pure water during the distribution process until it is supplied to the cleaning tank. is there.

In addition, H_TwoO_TwoIs a weak bond with water
(Hydrogen bond) is working, but H is present between nitrogen and water._Two
O_TwoIs only weaker than the bond between water and water
Yes. Therefore, the dissolved nitrogen is ultrasonically (megasonic)
Is bubbled preferentially. Dissolved H _TwoO_TwoIs dissolved nitrogen
It is more difficult to form bubbles, but it does not mean that bubbles do not form.
The substance bursts after foaming and dissolves in water. This H_TwoO
_TwoCreates a shock wave due to the bursting of the generated bubbles,
The shock wave of contributes greatly to cleaning. In other words, this shock wave
Is a thin film that is even thinner than when only the liquid crystal molecules fluctuate.
Contributes to pulling particles apart.

If the power (sound pressure) is considerably increased,
Bubble formation (cavitation) of H ₂ O ₂ can be performed to some extent, but in that case, substrate damage or the like (for example, pattern collapse) may occur.

Means for solving the above-mentioned problems based on the viewpoints of the inventor are as follows.

According to a first aspect of the present invention, in a method for cleaning a substrate, the concentration of dissolved nitrogen in pure water is equal to or less than the equilibrium dissolved nitrogen concentration (about 16 ppm) with the atmosphere on the pure water supply line for supplying pure water. The first step of adjusting (degassing) to the cleaning step, and supplying the cleaning solution prepared by mixing the pure water prepared in the first step and at least hydrogen peroxide to the cleaning tank to immerse the substrate. A second step of applying ultrasonic waves to the existing cleaning chemical liquid to perform cleaning. This is because by adjusting the dissolved nitrogen concentration to be equal to or lower than the dissolved nitrogen concentration in the equilibrium state with the atmosphere, H ₂ O ₂ important for cleaning comes to function. Here, the equilibrium dissolved nitrogen concentration means the dissolved nitrogen concentration of pure water in an equilibrium state with the atmosphere.

In a second aspect of the present invention, a first step of adjusting the concentration of dissolved nitrogen in pure water to the equilibrium dissolved nitrogen concentration with the atmosphere or less on a pure water supply line for supplying pure water,
A cleaning solution prepared by mixing pure water prepared in the first step, hydrogen peroxide, and ammonia is supplied to the cleaning tank, and ultrasonic waves are applied to the cleaning solution in which the substrate is immersed. The second step of performing cleaning is included. This is because H ₂ O ₂ important for cleaning functions even when an APM chemical solution (mixed chemical solution of NH ₄ OH / H ₂ O ₂ / pure water) is used. Since ammonia has a strong hydrogen bond with water, almost no bubbles are formed by ultrasonic waves (megasonic).

In the method for cleaning a substrate, the cleaning of the substrate in the second step is performed by ultrasonically bubbling at least hydrogen peroxide dissolved in the cleaning chemical solution,
In addition, it is preferable to rupture the hydrogen peroxide bubbles. This is because more efficient cleaning can be performed by the shock wave caused by the burst of hydrogen peroxide bubbles.

In the method for cleaning a substrate, the concentration of dissolved nitrogen in pure water is such that the standing wave is prevented from being generated (the reflected wave is blocked near the interface) by the bubbling of nitrogen and hydrogen peroxide. It suffices if the amount is 10 ppm or more and 16 ppm or less. This is because not only nitrogen bubbles but also hydrogen peroxide bubbles contribute to the prevention of standing wave generation.
When it is less than 10 ppm, the action of preventing standing waves from being generated by bubbles of nitrogen and hydrogen peroxide is lowered, and the cleaning efficiency is lowered. Further, when it exceeds 16 ppm, most of the energy of megasonic is spent for generation of N ₂ bubbles, and H ₂
The energy required for bubbling O ₂ is insufficient.

In the method for cleaning a substrate, the concentration of dissolved nitrogen in pure water before adjustment in the first step is
The equilibrium dissolved nitrogen concentration with the atmosphere (about 16 ppm) is preferable. This is to prevent the harmful oxygen from being dissolved in the distribution process before adjustment.

In the method for cleaning a substrate, the dissolved nitrogen concentration in the first step is adjusted by measuring the dissolved nitrogen concentration in pure water flowing on a pure water supply line for supplying pure water. It is preferable to adjust the degassing amount based on the obtained information on the dissolved nitrogen concentration. This is so that pure water having an appropriate dissolved nitrogen concentration can be automatically supplied.

A third aspect of the present invention is characterized in that the cleaning chemical liquid contains pure water whose dissolved nitrogen concentration is adjusted to be equal to or less than the equilibrium dissolved nitrogen concentration with the atmosphere, and hydrogen peroxide. This is because H ₂ O ₂ important for cleaning functions in combination with such pure water. Further, the dissolved nitrogen concentration of the pure water after the adjustment is 10 ppm or more and 16 p
It is preferably pm or less. H without standing waves
_{This is because 2} O ₂ is sufficiently bubbled to allow uniform and efficient cleaning.

In a fourth aspect of the present invention, a cleaning tank for containing a cleaning chemical solution for cleaning a substrate, an ultrasonic wave applying means for applying an ultrasonic wave to the cleaning chemical solution, pure water and at least peroxide. A mixing machine that mixes hydrogen to prepare a cleaning solution, and supplies the prepared cleaning solution directly or after adjusting the temperature to the cleaning tank, and hydrogen peroxide that supplies hydrogen peroxide to the mixing machine. A cleaning device comprising a supply line and a pure water supply line for supplying pure water to the mixer, a measuring device for measuring the dissolved nitrogen concentration of pure water flowing on the pure water supply line, and the pure water. A degassing device that adjustably degasses the dissolved nitrogen in the pure water flowing on the supply line, and the dissolved nitrogen in the pure water using the degassing device based on the information related to the dissolved nitrogen concentration measured by the measuring device. Control the concentration Characterized in that it comprises control apparatus and, a.

In a fifth aspect of the present invention, a cleaning tank for containing a cleaning chemical liquid for cleaning a substrate, an ultrasonic wave applying means for applying ultrasonic waves to the cleaning chemical liquid, pure water and hydrogen peroxide. And a mixture of ammonia and ammonia to prepare a cleaning chemical solution, and a mixer for supplying the cleaning chemical solution thus prepared directly or after temperature adjustment to the cleaning tank, and a peroxide for supplying hydrogen peroxide to the mixer. Hydrogen supply line,
An ammonia supply line for supplying ammonia to the mixer, and a pure water supply line for supplying pure water to the mixer,
In a cleaning device including: a measuring device for measuring the dissolved nitrogen concentration of pure water flowing on the pure water supply line, and a degassing device for degassing the dissolved nitrogen of pure water flowing on the pure water supply line in an adjustable manner. And a control device for controlling the dissolved nitrogen concentration of pure water using the degassing device based on the information related to the dissolved nitrogen concentration measured by the measurement device.

Further, in the cleaning device, it is preferable that the measuring device and the degassing device are arranged near the mixer on the pure water supply line. This is because the harmful oxygen is prevented from being dissolved in the distribution process after the adjustment.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In a substrate cleaning method, the concentration of dissolved nitrogen in pure water is adjusted to be equal to or less than the equilibrium dissolved nitrogen concentration (about 16 ppm) with the atmosphere on the pure water supply line for supplying pure water (degassing). And a cleaning chemical solution prepared by mixing pure water prepared in the first step with at least hydrogen peroxide is supplied to a cleaning tank, and the cleaning chemical solution in which the substrate is immersed is superfluous. A second step of applying a sound wave to perform cleaning,
Since the energy of megasonic (ultrasonic wave) consumed for bubbling of nitrogen is reduced by including, the sound pressure can be efficiently transmitted to the semiconductor substrate.

That is, the semiconductor substrate is subjected to the chemical action of the chemical solution to form a thin film on the substrate surface, and particles attached to the surface are slightly lifted up as compared with before the thin film is formed. The lifted particles are physically separated (peeled) together with the thin film formed on the substrate surface by the shock wave due to the fluctuation of the chemical liquid molecules by megasonics and the burst of the generated H ₂ O ₂ bubbles, and together with the chemical liquid waste tank Can be discharged outside. In particular, the shock wave caused by the burst of H ₂ O ₂ bubbles contributes to the separation of the particles in the state of a thinner thin film than when only the liquid crystal molecules oscillate. At the same time, it is possible to suppress the generation of standing waves by the bubbles of nitrogen and hydrogen peroxide generated by megasonics. As a result, the cleaning effect is dramatically improved.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cleaning device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of the cleaning device according to the first embodiment of the present invention. This cleaning device is an ultrasonic cleaning device for APM chemical liquid (mixed chemical liquid of NH ₄ OH / H ₂ O ₂ / pure water) adopting a chemical liquid disposable system, and includes a cleaning tank, an ultrasonic wave applying means, and a mixer. And an H ₂ O ₂ supply line and an NH ₄ OH supply line,
A pure water supply line, a measuring device, a degassing device, and a control device are provided.

The cleaning tank is a tank for containing a cleaning chemical solution (APM cleaning solution) for cleaning the semiconductor substrate, is connected to the mixer through a pipe, and has an inflow section for inflowing the cleaning chemical solution and the cleaning. And an outflow portion for outflowing the cleaning chemical liquid to the outside. There is a case where only one cleaning tank is used, or a cleaning tank and a rinse tank which are separated from each other are used.

The ultrasonic wave applying means is means for applying ultrasonic waves to the cleaning chemical liquid contained in the cleaning tank, and oscillates upward from the bottom side of the cleaning tank. The ultrasonic waves used in the examples have a frequency of 750 kHz and an output of 760 W.

The mixer mixes with the pure water supplied at a predetermined ratio.
Preparation of cleaning chemicals by mixing hydrogen peroxide and ammonia
It is a device to operate, pure water supply line, H_TwoO_TwoSupply line
And NH_FourEach line is connected to the OH supply line as a flow path.
The flow rate from the inlet is adjusted with a flow meter, and a constant temperature is maintained in a constant temperature bath.
Adjust (or mix directly using mixing valve)
)), A cleaning agent made by connecting to the cleaning tank via piping
The liquid is supplied to the cleaning tank. APM chemical (NH_FourOH / H_Two
O_Two/ Pure water (mixed chemical solution of pure water)_FourOH: H
_TwoO_Two: The composition of pure water is typically 1: 4: 20.

The H ₂ O ₂ supply line is a pipe for supplying circulating hydrogen peroxide solution to the mixer, and is connected to the mixer as a flow path. The concentration of hydrogen peroxide supplied from the H ₂ O ₂ supply line in the example is about 31 wt%.

The NH ₄ OH supply line is a pipe for supplying circulating ammonia water to the mixer, and is connected to the mixer as a flow path. The concentration of ammonia supplied from the NH ₄ OH supply line in the example is about 29 wt%.

The pure water supply line is a pipe for supplying circulating pure water to the mixer, is connected to the mixer as a flow path, and has a deaerator and a secondary side (downstream side) measuring device on the line. And. Pure water supplied from the primary side (upstream of the deaerator) has an equilibrium dissolved nitrogen concentration (15 to 16 ppm) with the atmosphere in order to prevent oxygen from dissolving.

In the embodiment, the degassing device is a device for vacuum degassing from the pure water flowing on the pure water supply line so that the concentration of dissolved nitrogen can be adjusted, and is equipped with a decompression pump, which is controlled by the control device. The valve is opened and closed to adjust the degree of vacuum. The dissolved nitrogen concentration here is the dissolved nitrogen concentration of the atmosphere and pure water in the equilibrium state (equilibrium dissolved nitrogen concentration: 15 to 16).
ppm) or less (for example, 12 to 13 ppm). Vacuum degassing here is based on Henry's law,
It is quantitatively performed under a reduced pressure of about 0.6 to 0.05 atm.

The measuring device is a device for measuring the dissolved nitrogen concentration of pure water flowing on the secondary side of the pure water supply line (downstream of the deaerator), and controls the information relating to the measured dissolved nitrogen concentration. Send to device.

The control device receives the information on the dissolved nitrogen concentration measured by the measuring device, and controls the dissolved nitrogen concentration of the pure water by adjusting the degree of vacuum in the degassing device based on this information.

Next, the operation of the cleaning apparatus according to the first embodiment will be described.

First, the dissolved nitrogen concentration of pure water flowing in from the primary side of the pure water supply line is not more than 15 to 16 ppm (equilibrium dissolved nitrogen concentration) of pure water in a state of equilibrium with the atmosphere by a degassing device ( For example, about 12 to 13 ppm). At this time, the dissolved nitrogen concentration of the pure water (after degassing) flowing through the secondary side of the pure water supply line is measured using a measuring device, and the control device is based on the information related to the measured dissolved nitrogen concentration. The vacuum valve opening of the deaerator is controlled by the control of.

Next, pure water with a reduced dissolved nitrogen concentration was flowed to the secondary side, and NH ₄ OH: H ₂ O ₂ : purified water with a reduced dissolved nitrogen concentration was mixed at a ratio of 1: 4: 20 in a mixer. After mixing (mixing), the APM chemical solution prepared by mixing is supplied to the cleaning tank. Megasonic of several 100 kHz is applied to the APM chemical solution which is housed in the cleaning tank and in which the semiconductor substrate is immersed. As a result, particles are removed from the semiconductor substrate immersed in the APM chemical solution.

Finally, an optional but pure water rinse is performed. After APM cleaning, the dissolved nitrogen concentration of pure water flowing in from the primary side of the pure water supply line was measured by using a degassing device.
(Equilibrium dissolved nitrogen concentration) or less (for example, about 12 to 13 ppm). Pure water with a reduced dissolved nitrogen concentration is caused to flow to the secondary side, and pure water with a reduced dissolved nitrogen concentration is directly supplied to the cleaning tank without being mixed with other chemicals by a mixer. Megasonic of several hundreds of kHz is applied to the pure water in which the dissolved nitrogen concentration is reduced, in which the semiconductor substrate is immersed in the cleaning tank. At this stage, the mixer is
NH ₄ from ₄ OH and H ₂ O ₂ supply lines
The supply of OH and H ₂ O ₂ is stopped.

Considering the cleaning according to Example 1, the APM
Most of the chemical liquid is composed of pure water. At this time, if the dissolved nitrogen concentration in the pure water is reduced to a concentration equal to or less than the equilibrium concentration with the atmosphere, the chemical liquid molecule fluctuations are activated. At the same time, the number of evaporative bubbles of dissolved H ₂ O ₂ molecules increases, and a large number of impacts due to the burst of the bubbles occur. Particles on the semiconductor substrate are peeled off from the substrate due to the impact of the fluctuations of the chemical liquid molecules and the bursting phenomenon of the bubbles. Therefore, as shown in FIG. Is significantly improved, and the device yield is greatly improved.

Considering the reason for this, the number of evaporative bubbles of dissolved H ₂ O ₂ molecules and the ratio of molecular fluctuation increase when the concentration of dissolved nitrogen in pure water is reduced. This is because the energy transmission (sound pressure) is suppressed from being consumed toward the bubbling of dissolved nitrogen that does not contribute to the cleaning effect at all.

Further, referring to FIG. 3, when the dissolved nitrogen concentration is lowered to the equilibrium concentration or less, the sound pressure is improved. This is because it becomes difficult for the nitrogen bubbles to absorb (consume) the sound pressure. is there. In addition, as a result of the megasonic energy being directed to bubble formation of hydrogen peroxide, the same amount of energy was used to prevent the standing wave from being generated by the hydrogen peroxide bubbles, but without adding new energy. This is because the shock wave generated by the burst of hydrogen peroxide bubbles (without raising energy) is used.

Next, a second embodiment will be described with reference to the drawings. FIG. 4 is a block diagram showing the configuration of the cleaning apparatus according to the second embodiment of the present invention. This cleaning device is an ultrasonic cleaning device for a HPM (mixed chemical liquid of HCl / H ₂ O ₂ / pure water) chemical liquid that adopts a chemical liquid disposable system, and supplies NH ₄ OH supply line of the cleaning device of FIG. 1 with HCl. The configuration is in line, and other configurations are similar to those of the first embodiment.
Here, the HPM chemical solution is used when performing metal cleaning of a semiconductor substrate that needs to remove metal contaminants on the surface.

Next, the operation of the cleaning apparatus according to the second embodiment will be described.

First, HPM cleaning (metal cleaning) is performed. HC from the HCl supply line and the H ₂ O ₂ supply line
l and H ₂ O ₂ are supplied to the mixer, pure water that has not been deaerated is supplied to the mixer from the pure water supply line, and HCl: H ₂ O ₂ : pure water is mixed in the mixer 1: 1. :
Mixing (mixing) at a ratio of 5 and supplying the HPM chemical solution prepared by mixing to a cleaning tank, and the HPM chemical solution is housed in the cleaning tank, and a semiconductor substrate (which needs to remove metal contaminants on the surface)
Is immersed and HPM cleaning is performed. This cleans the metal on the semiconductor substrate. The deaeration device on the pure water supply line at this stage is not deaerated. Further, no megasonic is applied to the HPM chemical solution.

Next, a primary rinse is performed. After HPM cleaning, the dissolved nitrogen concentration of pure water that flows in from the primary side of the pure water supply line is 15 to 16 ppm (equilibrium dissolved nitrogen concentration) of dissolved pure water in equilibrium with the atmosphere using a degasser. (For example, about 12 to 13 ppm). Flowing pure water with a reduced concentration of dissolved nitrogen in the secondary side, the mixer in H _{2 O 2:} pure water with a reduced concentration of dissolved nitrogen were mixed 1: (mixing) at a ratio of 50 to 100,
A PM chemical solution (H ₂ O ₂ / pure water mixed chemical solution) prepared by mixing is supplied to the cleaning tank. Mega sonic of several 100 kHz is applied to the PM chemical solution which is housed in the cleaning tank and in which the semiconductor substrate (which needs to remove metal contaminants on the surface) is immersed. As a result, particles are removed from the semiconductor substrate immersed in the PM chemical solution. The mixer at this stage has stopped the supply of HCl from the HCl supply line. In addition, the concentration of the hydrogen peroxide solution supplied from the H ₂ O ₂ supply line in the example is 31 wt%.

Finally, a secondary rinse is performed. PM cleaning
Then, the dissolved nitrogen of pure water flowing in from the primary side of the pure water supply line is dissolved.
Elementary concentration was measured using a degasser to determine the net
Dissolved nitrogen concentration of water 15-16ppm (equilibrium dissolved nitrogen concentration
Degree) or less (for example, about 12 to 13 ppm)
Reduce. Flow pure water with reduced dissolved nitrogen concentration to the secondary side
However, dissolved nitrogen as it is without mixing with other chemicals in the mixer
Pure water with a reduced concentration is supplied to the cleaning tank. Stored in cleaning tank
Semiconductor substrate (requires removal of surface metal contaminants
Some are pure) with a reduced dissolved nitrogen concentration
Megasonic of several 100 kHz is applied to water. This
At the stage of the mixer, the HCl supply line and H _TwoO_TwoCompanion
HCl and H from the supply line_TwoO_TwoHas stopped supplying
It

Through the above steps, it is possible to suppress particle removal or redeposition after metal cleaning due to activation of molecular fluctuation due to nitrogen deaeration and shock wave due to burst of hydrogen peroxide bubbles.

FIG. 5 shows the relationship between the concentration of dissolved nitrogen in pure water and the increased number of particles before and after metal cleaning when the cleaning method according to the second embodiment is used. From this figure, by reducing the dissolved nitrogen concentration, the total number of particles of 0.13 μm or more is 1 per wafer (3 mm outer circumference cut).
It can be seen that the number of increases can be set to 0 or less.
That is, it can be seen that a wafer substrate with few particles can be finally obtained by reducing the dissolved nitrogen concentration.

The primary rinse and the secondary rinse in the second embodiment are S used for metal cleaning (cleaning of natural oxide film).
It can also be used after PM cleaning (cleaning with a mixed chemical solution of H ₂ SO ₄ / H ₂ O ₂ ) and HF cleaning (cleaning with a mixed chemical solution of HF / pure water). In this case as well, the concentration of dissolved nitrogen can be reduced. It is possible to obtain a wafer substrate with less particles.

[0053]

According to the present invention, generation of bubbles (having no cleaning effect) due to dissolved nitrogen can be suppressed, and the efficiency of generating hydrogen peroxide bubbles (having a cleaning effect) can be relatively improved. You can That is, the sound pressure used to bubble the dissolved nitrogen can be used to bubble the hydrogen peroxide. As a result, the bursting of hydrogen peroxide bubbles can be promoted, and the particle removal rate can be greatly improved.

Further, since the sound pressure of the cleaning liquid can be efficiently transmitted to the semiconductor substrate, it is possible to remove particles by direct molecular vibration.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a configuration of a cleaning device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the concentration of dissolved nitrogen in pure water and the removal rate when the cleaning method according to Example 1 of the present invention is used.

FIG. 3 is a graph showing the relationship between the dissolved nitrogen concentration in pure water and the sound pressure when the cleaning method according to Example 1 of the present invention is used.

FIG. 4 is a block diagram schematically showing a configuration of a cleaning device according to a second embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the concentration of dissolved nitrogen in pure water and the increased number of particles when the cleaning method according to the second embodiment of the present invention is used.

FIG. 6 is a block diagram schematically showing a configuration of a conventional cleaning device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI theme code (reference) C11D 7/18 C11D 7/18 17/00 17/00 // C03C 23/00 C03C 23/00 AF term (Reference) 3B201 AA01 BB02 BB83 BB95 CC01 CC21 4G059 AA08 AB01 AB09 AB11 AC24 AC30 4H003 BA12 DA15 DC04 EA23 ED02 EE04 FA21

Claims (11)

[Claims] 1. A first step of adjusting the dissolved nitrogen concentration in pure water to a value equal to or lower than the equilibrium dissolved nitrogen concentration in the pure water on a pure water supply line for supplying pure water, and the first step was adjusted. A second step of supplying a cleaning chemical solution prepared by mixing pure water and at least hydrogen peroxide to a cleaning tank and applying ultrasonic waves to the cleaning chemical solution in which the substrate is immersed to perform cleaning. A method for cleaning a substrate, comprising: 2. A first step of adjusting the dissolved nitrogen concentration in pure water to a value equal to or less than the equilibrium dissolved nitrogen concentration in the pure water on a pure water supply line for supplying pure water, and the adjustment in the first step. A second step of supplying a cleaning chemical solution prepared by mixing pure water, hydrogen peroxide and ammonia to a cleaning tank, and applying ultrasonic waves to the cleaning chemical solution in which the substrate is immersed to perform cleaning. A method for cleaning a substrate, comprising: 3. The cleaning of the substrate in the second step is performed by ultrasonicating at least hydrogen peroxide dissolved in the cleaning chemical liquid into bubbles and bursting the hydrogen peroxide bubbles. The method for cleaning a substrate according to claim 1 or 2. 4. The method for cleaning a substrate according to claim 1, wherein the concentration of dissolved nitrogen in the pure water after the adjustment in the first step is 10 ppm or more and 16 ppm or less. . 5. The adjustment of the dissolved nitrogen concentration in the first step relates to the measured dissolved nitrogen concentration by measuring the dissolved nitrogen concentration in pure water flowing on a pure water supply line for supplying pure water. The substrate cleaning method according to claim 1, wherein the degassing amount is adjusted based on the information. 6. A cleaning chemical liquid comprising pure water whose dissolved nitrogen concentration is adjusted to be equal to or less than the equilibrium dissolved nitrogen concentration with the atmosphere, and hydrogen peroxide. 7. The cleaning chemical liquid according to claim 6, wherein the dissolved nitrogen concentration of the pure water is 10 ppm or more and 16 ppm or less. 8. A cleaning tank containing a cleaning chemical solution for cleaning a substrate, an ultrasonic wave applying means for applying ultrasonic waves to the cleaning chemical solution, and pure water and at least hydrogen peroxide are mixed to form a cleaning chemical solution. A mixer for producing the cleaning solution directly or after adjusting the temperature and supplying it to the cleaning tank, a hydrogen peroxide supply line for supplying hydrogen peroxide to the mixer, and pure water for the mixer. In a cleaning device including a pure water supply line for supplying, a measuring device for measuring a dissolved nitrogen concentration of pure water flowing on the pure water supply line, and a dissolved nitrogen of pure water flowing on the pure water supply line A degassing device that adjustably degasses, and a control device that controls the dissolved nitrogen concentration of pure water using the degassing device based on information related to the dissolved nitrogen concentration measured by the measuring device. Wash characterized by Apparatus. 9. A cleaning tank containing a cleaning chemical solution for cleaning a substrate, an ultrasonic wave applying means for applying ultrasonic waves to the cleaning chemical solution, and a cleaning chemical solution by mixing pure water, hydrogen peroxide and ammonia. And a mixer for supplying the cleaning chemical solution thus prepared directly or after adjusting the temperature to the cleaning tank, a hydrogen peroxide supply line for supplying hydrogen peroxide to the mixer, and the mixer. In a cleaning device including an ammonia supply line for supplying ammonia to the mixer and a pure water supply line for supplying pure water to the mixer, measurement for measuring the dissolved nitrogen concentration of pure water flowing on the pure water supply line An apparatus, a degassing apparatus for degassing the dissolved nitrogen of the pure water flowing on the pure water supply line in an adjustable manner, and using the degassing apparatus based on information related to the dissolved nitrogen concentration measured by the measuring apparatus. Cleaning device comprising Te and a control unit for controlling the concentration of dissolved nitrogen of the pure water, in that it comprises. 10. The cleaning device according to claim 8, wherein the measuring device and the degassing device are arranged in the vicinity of the mixer on the pure water supply line. 11. A semiconductor substrate cleaned by the method for cleaning a substrate according to any one of claims 1 to 5.