JP2002045806A - Cleaning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device with which an electronic material such as a silicon substrate and a glass substrate, for a semiconductor for a liquid crystal to be requested to have high cleanliness can be cleaned without damaging the surface of the electronic material. SOLUTION: This cleaning device, which has a holding part for holding the object to be cleaned and in which the object to be cleaned is cleaned by contacting it with a gas-dissolved water, has an ultraviolet irradiating unit arranged adjacently to the holding part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cleaning apparatus. More specifically, the present invention relates to a cleaning apparatus suitable for cleaning electronic materials that require high cleanliness, such as silicon substrates for semiconductors and glass substrates for liquid crystals.

[0002]

2. Description of the Related Art Conventionally, a cleaning technique using a high concentration chemical solution at a high temperature, which is called RCA cleaning, has been applied to the cleaning of electronic materials requiring a highly clean surface. Also,
It is also known that the cleaning effect can be enhanced by using ultraviolet irradiation in combination with cleaning using a high concentration chemical solution. For example, Japanese Patent Application Laid-Open No. 4-179225 discloses that sulfuric acid, hydrogen peroxide and water are used. Using a 1: 1 mixed solution, a 1: 1: 5 mixed solution of ammonium hydroxide, hydrogen peroxide and water,
There has been reported an example of cleaning an object to be cleaned coated with a resist while irradiating an ultraviolet ray with a low-pressure mercury lamp. In recent years, there has been a demand for a reduction in the cost of the cleaning process and a reduction in the environmental load, and the practical application of a room temperature cleaning technology using a dilute cleaning solution has been studied. Under such circumstances, the present inventors have developed an ultrasonic cleaning technique using ultrapure water in which a specific gas is dissolved. In particular, it has been found that so-called hydrogen water in which hydrogen gas has been dissolved at a high concentration exhibits an extremely high particulate removal effect when used in combination with ultrasonic waves, surpassing conventional high-concentration chemical solution cleaning. Furthermore, it has been found that hydrogen water is also effective in preventing natural oxidation of the substrate surface, and when the object to be cleaned is a bare silicon substrate, it also has an effect of promoting hydrogen termination on the outermost surface. The present inventors have discussed the mechanism of why only water obtained by dissolving only a few ppm of hydrogen gas in pure water or ultrapure water used for rinsing after cleaning exhibits such a cleaning effect, and the mechanism thereof. Conducted intensive research.
As a result, it was found that the main factor for removing fine particles and terminating hydrogen was hydrogen radicals generated in hydrogen water subjected to ultrasonic irradiation. On the other hand, it has been pointed out that the application of ultrasonic waves to cleaning may damage micropatterned patterns. For this,
In the electronics industry, in which processing miniaturization is further advanced in the future, it is necessary to determine whether ultrasonic cleaning using hydrogen water is appropriate or not depending on the surface to be cleaned. For this reason, there has been a demand for a cleaning apparatus capable of performing cleaning with hydrogen water without fear of damaging an object to be cleaned having a finely processed surface.

[0003]

SUMMARY OF THE INVENTION The present invention provides a cleaning apparatus for cleaning electronic materials requiring high cleanliness, such as silicon substrates for semiconductors and glass substrates for liquid crystals, without fear of damaging the surface. It was made for the purpose of providing.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that when cleaning an object to be cleaned by contacting the same with gas-dissolved water, ultraviolet light is applied to the gas-dissolved water. It has been found that by irradiation, a part of water molecules is decomposed to generate hydrogen radicals and hydroxyl radicals, and an extremely high cleaning effect is exhibited. Based on this finding, the present invention has been completed. That is, the present invention
(1) A cleaning apparatus having a holding unit for holding an object to be cleaned and cleaning the object to be cleaned by contacting the object with gas-dissolved water, comprising an ultraviolet irradiation device close to the holding unit. (2) The cleaning device according to (1), further including a vibration imparting device that imparts vibration to the gas-dissolved water in the vicinity of the holding unit.
(3) The cleaning device according to (1) or (2), wherein the gas-dissolved water is pure water in which hydrogen gas, oxygen gas, or a rare gas is dissolved.
(4) The cleaning device according to the above (1), (2) or (3), wherein the holding unit and the ultraviolet irradiation device are relatively movable. Further, as a preferred embodiment of the present invention, (5) the cleaning apparatus according to item 1, wherein the object to be cleaned is a plate-like object, and (6) the plate-like object is a silicon substrate for semiconductor, a glass substrate for liquid crystal, or a photomask. (7) The distance between the surface of the object to be cleaned held by the holding portion and the ultraviolet irradiation tube of the ultraviolet irradiation device is 10 mm.
The cleaning device according to item 1, wherein the (8) gas-dissolved water is pure water in which a gas having a saturation solubility of 30% or more is dissolved, and (9) the ultraviolet irradiation device emits. The cleaning device according to item 1, wherein the ultraviolet light has a wavelength of 100 to 280 nm, and (10) the cleaning device according to item 2, wherein the vibration imparting device is an ultrasonic irradiation device.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cleaning apparatus according to the present invention has a holding section for holding an object to be cleaned, and in a cleaning apparatus for cleaning the object to be cleaned by bringing the object into contact with gas-dissolved water. This is a cleaning device having an irradiation device. INDUSTRIAL APPLICABILITY The cleaning apparatus of the present invention can be suitably applied to cleaning of a plate-like object requiring high cleanliness, and is particularly suitable for cleaning a silicon substrate for a semiconductor, a glass substrate for a liquid crystal, a quartz substrate for a photomask, and the like. ing. There is no particular limitation on the holding unit that holds the object to be cleaned used in the apparatus of the present invention, and examples thereof include a chuck of a single-wafer spin cleaning apparatus and a fixture of a batch cleaning tank. The gas-dissolved water used in the apparatus of the present invention is not particularly limited, but pure water in which hydrogen gas, oxygen gas, or a rare gas such as helium, neon, argon, krypton, or xenon is dissolved can be suitably used. In the device of the present invention,
Gas-dissolved water in which one of these gases is dissolved can be used, or gas-dissolved water in which two or more of these gases are dissolved can be used. By cleaning using hydrogen gas, oxygen gas or gas-dissolved water in which a rare gas is dissolved, fine particles adhering to the surface of the object to be cleaned can be effectively removed. The concentration of the dissolved gas in the gas-dissolved water used in the apparatus of the present invention is not particularly limited, but is preferably 30% or more of the saturation solubility of each gas. For example, at 20 ° C., the saturated solubility in water is 1.63 mg / L of hydrogen gas, 44.0 mg / L of oxygen gas,
30% of saturated solubility because argon is 60.8mg / L
Is 0.49 mg / L of hydrogen gas, 13.2 mg / L of oxygen gas,
It becomes 18.2 mg / L of argon. If the dissolved gas concentration of the gas-dissolved water is less than 30% of the saturation solubility, the cleaning effect may be insufficient.

[0006] The gas-dissolved water used in the apparatus of the present invention has a greater cleaning effect as the concentration of the dissolved gas is increased. However, if the concentration exceeds the saturation concentration, bubbles may be generated and adhere to the surface of the object to be cleaned, causing uneven cleaning. There is. Therefore, it is preferable that the dissolved gas concentration of the gas-dissolved water does not exceed the saturated concentration. When a pressurized airtight container is used as the washing unit, gas-dissolved water having a saturation concentration or less at the pressure in the container can be used. The temperature of the gas-dissolved water used for cleaning is not particularly limited, but generally, the higher the temperature, the greater the cleaning effect. A small amount of an auxiliary substance for improving the cleaning effect can be added to the gas-dissolved water used in the apparatus of the present invention, if necessary. Examples of the auxiliary substance that enhances the cleaning effect include an alkaline reagent and a surfactant. By adding these auxiliary substances, a zeta potential control effect of preventing reattachment of foreign substances detached from the object to be cleaned is exhibited. In the apparatus of the present invention, there is no particular limitation on the method of bringing the object to be cleaned into contact with the gas-dissolved water. Alternatively, an object to be cleaned can be immersed in gas-dissolved water and brought into contact with the solution using a batch-type cleaning tank. The cleaning device of the present invention has an ultraviolet irradiation device near the holding unit that holds the object to be cleaned. The ultraviolet irradiation apparatus used in the apparatus of the present invention is not particularly limited, and examples thereof include an apparatus equipped with a hydrogen discharge tube, a xenon discharge tube, a mercury lamp, a laser, and the like. By providing an ultraviolet irradiation device near the holding unit and irradiating the gas-dissolved water under cleaning with ultraviolet light, the cleaning effect can be enhanced.

[0007] In the proposed hydrogen water cleaning, ultrasonic waves such as megasonics are applied. This is because the promotion of the desorption of the fine particles by the physical effect derived from the ultrasonic wave was originally expected. Certainly, physical force such as generation and growth of microbubbles due to microcavitation caused by ultrasonic waves and vibration with large acceleration exerts an effect on separation of foreign matter from the surface of the object to be cleaned. However, the decisive difference of hydrogen water from ordinary ultrapure water is that it effectively generates hydrogen radicals, which cause a chemical reaction with the surface of the object to be cleaned or foreign matter, thereby making it extremely expensive. A cleaning effect is exhibited. Hydrogen radicals are generated in water irradiated with ultrasonic waves even if they are not hydrogen water. Hydrogen water is particularly effective because hydrogen radicals generated by the decomposition of some water molecules by the action of ultrasonic waves (・It is considered that, among H) and the hydroxyl radical (.OH), a part of the hydroxyl radical reacts with the dissolved hydrogen gas to become water, so that the hydrogen radical becomes relatively excessive. However, when the cleaning water is irradiated with strong ultrasonic waves, cavitation occurs in the water, and the surface of the object to be cleaned may be damaged. When the object to be cleaned is a silicon substrate for a semiconductor whose surface has been subjected to fine pattern processing, damage due to cavitation is a particularly large problem.

According to the apparatus of the present invention, when the object to be cleaned is washed by bringing it into contact with the gas-dissolved water, water molecules are excited by ultraviolet energy by irradiating the gas-dissolved water with ultraviolet rays using an ultraviolet irradiation device. It is considered that they are decomposed into hydrogen radicals and hydroxyl radicals, and an excellent cleaning effect can be obtained as in the case of irradiating ultrasonic waves. In addition, in the case of ultraviolet irradiation, since no physical force such as an ultrasonic wave acts, cavitation does not occur and there is no possibility that the surface of the object to be cleaned is damaged. In the apparatus of the present invention, the distance between the surface of the object to be cleaned held by the holding portion and the ultraviolet irradiation tube of the ultraviolet irradiation device is preferably 10 mm or less, more preferably 2 mm or less. If the distance between the surface of the object to be cleaned and the ultraviolet irradiation tube exceeds 10 mm, the ultraviolet energy transmitted to the gas-dissolved water will be insufficient, and the cleaning effect may be insufficient. In the apparatus of the present invention, the wavelength of the ultraviolet light emitted from the ultraviolet irradiation device is not particularly limited, but is preferably 100 to 280 nm. Extreme ultraviolet light having a wavelength of less than 100 nm requires an ultraviolet irradiation device using a special material for a light source, a transmission window, a reflecting mirror, and the like, and may possibly reduce economic efficiency. When the wavelength of the ultraviolet ray exceeds 280 nm, the ultraviolet ray energy may be insufficient and the cleaning effect may be insufficient.

In the apparatus of the present invention, it is preferable to provide a vibration applying device for applying vibration to the gas-dissolved water near the holding section. The vibration imparting device to be installed is not particularly limited, and examples thereof include an ultrasonic irradiation device and a jet fluid nozzle. The ultrasonic irradiation apparatus can irradiate ultrasonic waves to gas-dissolved water using a megasonic irradiation nozzle, for example, as a nozzle of a single-wafer spin cleaning apparatus, or irradiate ultrasonic waves to a batch-type cleaning tank. You can also. There is no particular limitation on the frequency of the ultrasonic waves to be irradiated,
kHz or higher, preferably 400 kHz or higher, and more preferably 0.8 MHz or higher. However, it is desirable that the ultrasonic output be used at a lower level than in the case of ordinary ultrasonic cleaning so as not to damage the micromachined surface. As a jet fluid nozzle,
For example, as a nozzle of a single wafer spin cleaning apparatus, a nozzle for a bubble jet fluid in which gas-dissolved water sent at a high pressure and a gas sent at a high pressure are mixed in the nozzle, or a high-pressure gas-dissolved water with a small area at the center of the nozzle And a nozzle for cavitation jet fluid that jets low-pressure gas-dissolved water from a large-area opening around the nozzle. The output of ultrasonic waves and the strength of the jet fluid
It can be appropriately selected within a range that does not damage the surface of the object to be cleaned. In the cleaning device of the present invention, it is preferable that the holding unit and the ultraviolet irradiation device are relatively movable. There is no particular limitation on the method of making the holding unit and the ultraviolet irradiation device relatively movable. For example, the holder for holding the object to be cleaned can be made movable with respect to the fixed ultraviolet irradiation device, The holder for holding the object may be fixed and the ultraviolet irradiation device may be movable, or both the holder for holding the object to be cleaned and the ultraviolet irradiation device may be movable. By making the holding unit and the ultraviolet irradiation device relatively movable, the entire surface of the object to be cleaned can be almost uniformly irradiated with the ultraviolet light, or the ultraviolet light is focused particularly on a portion requiring cleaning. You can also.

FIG. 1A is a plan view of one embodiment of the cleaning apparatus of the present invention, and FIG. 1B is a side view thereof.
(c) is a plan view of another embodiment of the ultraviolet irradiation tube. In the apparatus of the present embodiment, the semiconductor silicon substrate 1 is held by three chucks 2. The ultraviolet irradiation tube 3 is fixed close to the semiconductor silicon substrate, the semiconductor silicon substrate is rotated, and gas-dissolved water 5 is jetted from the gas-dissolved water nozzle 4 onto the semiconductor silicon substrate.
After continuously cleaning the rotation of the semiconductor silicon substrate and the injection of the gas-dissolved water for a predetermined time, stop the injection of the gas-dissolved water, release the ultraviolet irradiation tube, increase the rotation speed of the silicon substrate for the semiconductor, and spin dry. can do. There is no particular limitation on the shape of the ultraviolet irradiation tube, and in addition to the rod shape shown in FIG. 1A, a bent shape shown in FIG. FIG. 2A is a plan view of another embodiment of the cleaning apparatus of the present invention, and FIG. 2B is a sectional view thereof. In the apparatus of this embodiment, the semiconductor silicon substrate 1 is held by a holding table 7 provided in a cleaning tank 6 and immersed in gas-dissolved water 5. The ultraviolet irradiation tube 3 swings between the position shown by the solid line and the position shown by the dotted line in FIG. 1A, and irradiates the gas-dissolved water on the surface of the silicon substrate for semiconductor with ultraviolet light. The silicon substrate for semiconductor which has been immersed in the gas-dissolved water for a predetermined time and cleaned has been taken out of the cleaning tank and dried. In the cleaning apparatus of the present invention, it is preferable that the gas-dissolved water has an appropriate flow so that foreign substances detached from the surface of the object to be cleaned do not adhere to the object to be cleaned again. In the embodiment shown in FIG. 1, gas-dissolved water injected from a nozzle comes into contact with the surface of an object to be cleaned and is then discharged out of the system in a transient manner. In the embodiment shown in FIG. 2, the gas-dissolved water flows into the cleaning tank from the inflow port 8 and flows out from the overflow port 9. By using the cleaning apparatus of the present invention, it is possible to obtain a high particulate removal effect comparable to conventional megasonic cleaning using ultrasonic waves, and to prevent damage to the surface of the object to be cleaned as in the case of cleaning without ultrasonic waves. be able to.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In Examples and Comparative Examples, a 6-inch silicon wafer forcibly contaminated with alumina abrasive particles having an average particle diameter of 0.3 μm and a 6-inch silicon wafer with a pattern having a minimum line width of 0.25 μm were used. It was used as an object to be cleaned. The initial contamination state of the contaminated wafer is as follows: fine particles having a particle size of 0.2 μm or more
00 / wafer. The number of fine particles was measured using a laser scattering foreign matter inspection apparatus [Topcon Corporation, WM-1500]. To wash the wafer, spin the wafer at 500 rpm using a spin washer, and spray hydrogen gas containing 1.2 mg / L of hydrogen gas from the nozzle at 1.5 L / min. Was washed for 30 seconds while swinging at a cycle of 10 seconds. When irradiating ultrasonic waves, ultrasonic waves having a frequency of 1.0 MHz were irradiated using a megasonic nozzle. After the completion of the cleaning process, the rotation speed of the wafer is set to 1,50.
Increased to 0 rpm and dried for 20 seconds. The fine particle removal rate was calculated from the number of fine particles on the wafer surface after cleaning and drying and the fine particles on the wafer surface before cleaning. In addition, the presence or absence of pattern damage was observed on the patterned wafer using a scanning electron microscope. Comparative Example 1 A simple spin cleaning using hydrogen water as it is through a normal nozzle was performed. The fine particle removal rate was 20%. No pattern damage was observed. Comparative Example 2 Using a megasonic nozzle, spin cleaning with megasonic was performed, in which hydrogen water was poured onto the wafer while irradiating ultrasonic waves with an output of 15 W / cm ² . The fine particle removal rate was 99%.
Also, the pattern collapsed slightly. Comparative Example 3 Megasonic spin cleaning was performed in the same manner as in Comparative Example 2 except that the output of the ultrasonic wave was reduced to 5 W / cm ² . The fine particle removal rate was 35%. No pattern damage was observed. Example 1 An ultraviolet irradiation tube (150 mm in length) having a center wavelength of 185 nm was fixed to the ordinary nozzle used in Comparative Example 1, and spin cleaning was performed while swinging on the wafer together with the nozzle. The distance between the ultraviolet irradiation tube and the wafer was adjusted to 2 mm.
The fine particle removal rate was 96%. Pattern damage
I was not able to admit. Example 2 The same ultraviolet irradiating tube as in Example 1 was fixed to the megasonic nozzle used in Comparative Example 2, and the megasonic combined spin cleaning in which hydrogen water was poured onto the wafer while irradiating ultrasonic waves with an output of 5 W / cm ² was used. Was done. The fine particle removal rate was 99%. No pattern damage was observed. Table 1 shows the results of Comparative Examples 1 to 3 and Examples 1 and 2.

[0012]

[Table 1]

As shown in Table 1, in Comparative Example 1 in which spin cleaning was performed using hydrogen water, the fine particle removal rate was low. Irradiation with strong ultrasonic waves improves the particle removal rate as in Comparative Example 2, but slightly collapses the pattern and damages the wafer surface. When the ultrasonic waves are weakened as in Comparative Example 3, the damage on the wafer surface is eliminated, but the particle removal rate decreases. On the other hand, in Example 1 in which spin cleaning was performed using hydrogen water while irradiating ultraviolet rays using the apparatus of the present invention, the fine particle removal rate was high, and the wafer surface was not damaged. Further, in Example 2, in which spin cleaning was performed using hydrogen water while irradiating ultraviolet rays while using weak ultrasonic irradiation, the wafer surface was not damaged, and the fine particle removal rate was further improved. From these results, it can be seen that cleaning with hydrogen water while irradiating with ultraviolet rays can obtain almost the same effect of removing fine particles as cleaning with hydrogen water while irradiating ultrasonic waves, and does not cause damage to the wafer surface.

[0014]

By using the cleaning device of the present invention,
It is possible to achieve both a high particulate removal effect comparable to conventional megasonic cleaning and the same protection of the surface of the object to be cleaned as in cleaning without using megasonic.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a cleaning device of the present invention;
It is a side view and a top view of other modes of an ultraviolet irradiation tube.

FIG. 2 is a plan view and a cross-sectional view of another embodiment of the cleaning device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate for semiconductors 2 Chuck 3 Ultraviolet irradiation tube 4 Gas dissolved water nozzle 5 Gas dissolved water 6 Cleaning tank 7 Holder 8 Inlet 9 Overflow port

Claims (4)

[Claims] 1. A cleaning apparatus having a holding section for holding an object to be cleaned and cleaning the object to be cleaned by contacting the object with gas-dissolved water, comprising an ultraviolet irradiation device close to the holding section. Cleaning equipment. 2. The cleaning apparatus according to claim 1, further comprising a vibration applying device for applying vibration to the gas-dissolved water near the holding section. 3. The cleaning apparatus according to claim 1, wherein the gas-dissolved water is pure water in which hydrogen gas, oxygen gas or rare gas is dissolved. 4. The cleaning device according to claim 1, wherein the holding portion and the ultraviolet irradiation device are relatively movable.