JP6020626B2 - Device Ge substrate cleaning method, cleaning water supply device and cleaning device - Google Patents

Description

  The present invention relates to a technique for cleaning a germanium (Ge) substrate for electronic devices with a high degree of cleanness while suppressing surface roughness caused by dissolution and dissolution of Ge.

  Conventionally, high concentration chemicals and detergents typified by RCA cleaning have been used for cleaning an Si substrate as an electronic component. Further, as a cleaning method instead of such a high concentration chemical solution or detergent, a method using gas-dissolved water in which a gas such as hydrogen, oxygen, ozone or the like is dissolved in ultrapure water has been proposed (for example, Patent Document 1). ).

In recent years, miniaturization of devices has progressed, and Si-based materials have been adopted as gate and channel materials. For example, a Ge substrate is employed as a channel instead of a Si substrate in order to realize high mobility in CMOS (Chimos, Complementary Metal Oxide Semiconductor; complementary metal oxide semiconductor).
However, the Ge substrate has a problem of easy dissolution of Ge oxide. That is, the oxidation of Ge progresses due to the oxidizing substances (dissolved oxygen, hydrogen peroxide, etc.) in the liquid and becomes easy to dissolve, thereby causing troubles such as an increase in substrate surface roughness and film loss (hereinafter referred to as these). There is concern about this.

  Therefore, in the cleaning of the Ge substrate, there is a demand for a cleaning method that satisfies the purpose without oxidizing and dissolving the substrate surface as much as possible in the cleaning step and the rinsing step of rinsing the chemical. At present, no cleaning method has been established to obtain a sufficient cleaning effect while preventing oxidation and dissolution of the surface of the substrate.

JP 2012-186348 A

  The present invention has been made in view of the above-mentioned conventional situation, and in the Ge substrate cleaning process and the rinsing process, while effectively preventing surface roughness caused by oxidation, dissolution and dissolution of Ge, cleaning or rinsing can be effectively performed. It is an object of the present invention to provide a cleaning method, a cleaning water supply device, and a cleaning device that can perform cleaning.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors oxidize with dissolved oxygen or hydrogen peroxide in water and progress in dissolution. By washing or rinsing with water from which Ge has been removed, By being able to suppress the dissolution of Ge, by using reducing hydrogen gas-dissolved water in which hydrogen gas is dissolved, or by using water in which dissolution of oxygen in water is suppressed by dissolving nitrogen gas, Furthermore, it is possible to suppress the oxidation and dissolution of Ge, and the combination of removal of these dissolved oxygen and hydrogen peroxide with addition of hydrogen gas and nitrogen gas, physical cleaning such as ultrasonic waves, It has been found that the effect of removing impurities such as fine particles can be exhibited by using chemical cleaning with the addition of various chemicals.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A method for cleaning a Ge substrate for devices, wherein the Ge substrate for devices is ultrasonically cleaned using water from which dissolved oxygen and hydrogen peroxide have been removed, wherein the water used for the ultrasonic cleaning is hydrogen. A method for cleaning a Ge substrate for a device, which is gas-dissolved water in which a gas is dissolved.

[2] Oite to [1], wherein the dissolved oxygen concentration of water used for washing is 50 [mu] g / L or _less, the method of cleaning the Ge substrate for devices wherein the concentration of H 2 _{O 2} is equal to or less than 50 [mu] g / L.

[3], wherein Oite to [1] or [2], the water used for the cleaning, acid, alkali, to include one or more chemicals selected from chelating agents and the group consisting of surfactants A method for cleaning a Ge substrate for a device.

[ 4 ] In an apparatus for supplying cleaning water used for cleaning a Ge substrate for devices to an ultrasonic cleaning machine for a Ge substrate, degassing means for removing dissolved oxygen in water, and water from which dissolved oxygen has been removed by the degassing means ultra gas dissolving means for dissolving the hydrogen gas, and hydrogen peroxide removing means for removing the water of hydrogen peroxide, the treated water in the hydrogen peroxide removal means and dehydration gas means and said gas dissolving means flush water supply device of the Ge substrate device characterized by having a means for supplying a sonic cleaner.

[ 5 ] In [ 4 ], the chemical addition in which one or more chemicals selected from the group consisting of acids, alkalis, chelating agents and surfactants are added to the water from which dissolved oxygen has been removed by the degassing means A cleaning water supply device for a Ge substrate for devices, characterized in that the device has a means.

[ 6 ] In the apparatus for cleaning the device Ge substrate, the cleaning water supply device for the device Ge substrate according to [ 4 ] or [ 5 ] and the cleaning water from the cleaning water supply device for the device Ge substrate are supplied. cleaning apparatus of the Ge substrate device characterized by having an ultrasonic cleaner to be.

  ADVANTAGE OF THE INVENTION According to this invention, in the washing | cleaning process and rinse process of Ge board | substrate, it can wash | clean or rinse effectively, suppressing the surface roughness resulting from oxidation, melt | dissolution, and melt | dissolution of Ge. Furthermore, by adding a gas such as hydrogen gas or chemicals or using physical cleaning such as ultrasonic waves, an effect of removing impurities such as fine particles can be obtained, and a high cleaning effect can be obtained.

It is a systematic diagram which shows embodiment of the washing | cleaning apparatus of Ge board | substrate for devices of this invention.

  Embodiments of the present invention are described in detail below.

In the present invention, when cleaning the Ge substrate for devices, cleaning is performed using water from which dissolved oxygen (DO) in water and hydrogen peroxide (H ₂ O ₂ ) have been removed. Prevents surface roughness caused by oxidation, dissolution and dissolution.
In the present invention, the term “cleaning” includes both cleaning for removing contaminants such as fine particles and rinsing cleaning that is finishing cleaning after cleaning using chemicals.

In the present invention, water used for cleaning the Ge substrate may be gas-dissolved water in which a non-oxidizing gas such as hydrogen gas or nitrogen gas is dissolved, and includes chemicals such as acids, alkalis, chelating agents, and surfactants. By using such water, it is possible to suppress the oxidation, dissolution, and surface roughness of Ge and to sufficiently remove the contamination of fine particles and the like.
Further, a higher cleaning effect can be obtained by applying physical cleaning operations such as ultrasonic cleaning, high-pressure jet cleaning, and two-fluid cleaning to the Ge substrate.

<DO removal>
The DO removal device for feed water is not particularly limited as long as it does not deteriorate the water quality, and a vacuum deaeration tower, a membrane deaeration device, etc. are used, and a membrane deaeration device that is compact and easy to manage is suitable. The exhaust mechanism is not limited as long as it does not deteriorate the water quality. The oil-free scroll vacuum pump, the water-sealed vacuum pump, etc. are used for the vacuum pump using oil because there is a concern that the water quality deteriorates due to the reverse diffusion of the oil.

  In the present invention, the water used for cleaning the Ge substrate is preferably one in which the DO concentration is reduced to 50 μg / L or less, for example, about 1 to 10 μg / L by DO removal. If the DO concentration is higher than the above upper limit, the oxidation and dissolution of Ge may not be suppressed, and even if the DO concentration is excessively reduced, an effect commensurate with it cannot be obtained, and the cost required for deaeration. This is economically disadvantageous.

<H ₂ O ₂ removal>
It must contain the _H 2 _{O 2} in _water, but the removal of H 2 _{O 2} is not _required, in the case of water containing H 2 _{O 2,} to remove the H 2 _{O 2.} As a method for removing of H ₂ O ₂ is usually a catalyst and such as Pt and Pb, the method of the _H 2 _{O 2} to reduce and remove by using a sulfite type resin is used. If the H ₂ O ₂ removal mechanism is a reaction mechanism that decomposes H ₂ O ₂ into oxygen and water, the decomposition of H ₂ O ₂ prior to the removal of DO is the decomposition of H ₂ O ₂ . This is preferable in that the generated oxygen does not remain. In the case of a reaction mechanism in which H ₂ O ₂ is reduced to hydrogen by using a catalyst such as Pt, the reaction may be performed before or after DO removal.

In the present invention, the H ₂ O ₂ concentration of water used for cleaning the Ge substrate is preferably 1 μg / L or less, particularly preferably a detection limit value or less by the colorimetric method.

<Gas dissolution>
In the present invention, the non-oxidizing gas may be dissolved in the water that has been subjected to DO removal and H ₂ O ₂ removal as necessary as described above, and such gas-dissolved water is used. As a result, the effect of removing contamination such as fine particles can be enhanced.

  Any non-oxidizing gas may be used as long as it does not oxidize Ge. For example, one or more kinds of rare gases such as hydrogen gas, nitrogen gas, and argon gas can be used. Is preferred.

  For dissolving these non-oxidizing gases, it is preferable to use a gas-dissolving film that is compact and easy to manage. The amount of gas dissolved by the gas dissolution membrane is usually adjusted by a gas flow rate adjusting mechanism such as a mass flow controller according to the amount of water detected by a flow meter.

  The gas concentration of the gas dissolved water used for cleaning the Ge substrate is not particularly limited, and may be less than or equal to the saturation solubility at the water temperature of the cleaning water. The higher the dissolved gas concentration, the higher the cleaning effect. Therefore, it is preferable to increase the dissolved gas concentration in consideration of the cost required for gas dissolution. For example, it is preferable that the hydrogen gas is about 1.2 to 1.6 mg / L, and the nitrogen gas is about 14 to 18 mg / L.

<Chemical addition>
The washing water used in the present invention includes acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid and acetic acid, alkalis such as ammonia, TMAH (tetramethylammonium hydroxide) and choline, chelating agents, surfactants and the like. One kind or two or more kinds of chemicals may be added. By adding such chemicals, the effect of removing contaminants such as fine particles can be enhanced. In particular, the effect of removing fine particles and the like can be enhanced by adding an alkali such as ammonia and adjusting the pH of the washing water to 7 or more, preferably 9 to 14 alkaline. In addition, although alkaline chemicals may be used for this pH adjustment, an alkaline gas may be used, but it is preferable to use ammonia that is easy to handle and can easily control the concentration. In particular, it is possible to obtain a good cleaning effect by using washing water adjusted to pH 7 to 11 by adding ammonia at 1 mg / L or more, for example, about 1 to 200 mg / L. In addition, if the pH of the washing water is excessively high or the amount of ammonia added is excessively large, there is a possibility that damage to the object to be cleaned may occur, which is not preferable.
The chemical may be added after the gas is dissolved or before the gas is dissolved.

<Water supply piping>
There are no particular restrictions on the material of the water supply and the piping for supplying the cleaning water that has been subjected to the above-described treatment to the cleaning machine as long as it does not deteriorate the water quality, but CVP (vinyl chloride) having low gas permeability. ) And PVDF (polyvinylidene fluoride) are preferable.

<Water temperature>
Although the temperature of water supply and washing water depends on the heat resistance of each part of the water supply pipe and the water supply mechanism, it is usually in the range of 20 to 80 ° C., for example, preferably 20 to 30 ° C. or 60 to 80 ° C. .

<Washing method>
The cleaning method in the present invention is not particularly limited, and any conventionally known method such as a method of spraying cleaning water on the object to be cleaned and a method of immersing and cleaning the object to be cleaned is adopted. Ultrasonic cleaning performed while applying ultrasonic waves to the cleaning water, or high pressure that discharges cleaning water or a mixed fluid of cleaning water and gas from the discharge nozzle toward the object to be cleaned It is preferable to perform jet cleaning or two-fluid cleaning.

When performing ultrasonic cleaning, the object to be cleaned may be immersed in the cleaning water, and ultrasonic waves may be applied to the cleaning water in which the object to be cleaned is immersed, or by spraying the cleaning water to which the object is cleaned. Single wafer cleaning may be performed.
Although there is no restriction | limiting in the ultrasonic wave used in ultrasonic cleaning, The ultrasonic wave of 10 kHz-3 MHz generally used is used suitably.

When performing high-pressure jet cleaning, for example, the following conditions can be adopted as discharge conditions for the cleaning water discharged from the cleaning fluid discharge nozzle.
Washing water supply amount: 0.5-30 L / min
Nozzle hydraulic pressure: 5-20MPa

When performing two-fluid cleaning, as the gas (carrier gas), one or more of non-oxidizing gases such as nitrogen gas, hydrogen gas, and argon gas can be used. From the cleaning fluid discharge nozzle For example, the following conditions can be adopted as discharge conditions for the cleaning water and carrier gas to be discharged.
Washing water supply amount: 0.05 to 0.5 L / min
Nozzle hydraulic pressure: 0.05 to 0.5 MPa
Carrier gas pressure: 0.1-0.6 MPa

  The washing time varies depending on the quality of the washing water used, gas dissolution, the presence or absence of chemical addition, and other washing conditions, but in the case of single wafer washing, it is usually about 30 to 180 seconds.

<Washing device>
Hereinafter, the cleaning apparatus of the present invention will be described in detail with reference to FIG.
In FIG. 1, 1 is an H ₂ O ₂ removal device, 2 is a degassing membrane module, 3 is a gas dissolution membrane module, 4 is a cleaning machine, 5 is an ultrasonic nozzle, 6 is a Ge substrate that is an object to be cleaned, 7 is Indicates a turntable. P is an exhaust pump for evacuating the air chamber side of the degassing membrane module 2, F is a water flow meter, and G is a gas flow rate adjusting mechanism.

Water such as pure water after first H ₂ O ₂ was removed by H ₂ O ₂ removing device 1, is degassed with degassing membrane module 2, water DO is removed. The water from which DO has been removed by the degassing membrane module 2 is then dissolved in a non-oxidizing gas such as hydrogen gas by the gas dissolving membrane module 3. The gas flow rate to the gas dissolution membrane module 3 is controlled by the gas flow rate adjusting mechanism G based on the measured value of the water flow meter F, and the gas dissolved water having a predetermined dissolved gas concentration is prepared.

  After chemicals are added to the gas-dissolved water from the gas-dissolved membrane module 3 as necessary, ultrasonic waves are applied by the ultrasonic nozzle 5 of the cleaning machine 4 and sprayed onto the Ge substrate 6. The Ge substrate 6 is placed on a turntable 7, and spray cleaning is performed while the Ge substrate 6 is rotated.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Example 1]
With the cleaning apparatus shown in FIG. 1, a cleaning experiment was performed using a Ge substrate contaminated with Si particles (φ3 inches, number of fine particles before cleaning: about 2000 / substrate) as an object to be cleaned.
The number of fine particles on the surface of the Ge substrate before and after cleaning was determined by observing the surface of the Ge substrate with a laser microscope and measuring the number of fine particles of 0.5 μm or more. The removal rate was calculated from the number of fine particles before and after cleaning.

The specifications and conditions of each part are as follows.
Degassing membrane: “Liquicel G248” manufactured by Polypore
Gas-dissolved membrane: “Liquicel G248” manufactured by Polypore
H ₂ O ₂ removal device: “Nano Saver (registered trademark)” manufactured by Kurita Kogyo Co., Ltd.
Supply gas: Hydrogen gas Supply water: Pure water Water temperature: 25 ° C
Water volume 5L / min
Hydrogen gas flow rate: 78 mL / min

Pure water is used as feed water, H ₂ O ₂ is decomposed and removed by the H ₂ O ₂ removal device (Nano Saver) 1 to make the H ₂ O ₂ concentration <1 μg / L, and deaeration is carried out by the degassing membrane module 2. Water having a concentration of about 10 μg / L was supplied to the gas-dissolving membrane module 3 at 5 L / min. The total amount of hydrogen gas was dissolved at a supply hydrogen gas amount of 78 L / min so that the dissolved hydrogen gas concentration was 1.4 mg / L. Ammonia was added at 1 mg / L in the subsequent stage of the gas-dissolving membrane module 3, and the pH was adjusted to about 9.5 and supplied to the ultrasonic nozzle type single wafer cleaning machine 4. The ultrasonic wave had a megasonic (MS) frequency of 1 MHz and the cleaning time was 120 seconds.

  The number of fine particles on the Ge substrate after washing was examined to obtain the fine particle removal rate. Also, the surface roughness of the Ge substrate was analyzed by Ge analysis in water by ICP-MS (Ge elution concentration of Ge by oxidation and dissolution of Ge) and measurement of the surface roughness Rmax of the Ge substrate by AFM (Atomic Force Microscope). evaluated. The results are shown in Table 1.

[ Comparative Example 2]
In Example 1, H ₂ O ₂ removal of feed water, hydrogen gas dissolution, and ammonia addition were not performed, and ultrasonic cleaning with pure water (H ₂ O ₂ 1 μg / L) adjusted to about DO ₁₀ μg / L by degassing was performed. A cleaning experiment was conducted in the same manner except that the particle removal rate and the state of the surface of the Ge substrate were examined. The results are shown in Table 1.

[ Comparative Example 3]
In Example 1, the cleaning experiment was performed in the same manner except that the water was not dissolved in hydrogen gas and added with ammonia, and ultrasonic cleaning was performed with pure water removed to about H ₂ O ₂ <1 μg / L and DO 10 μg / L. Then, the particle removal rate and the state of the surface of the Ge substrate were examined, and the results are shown in Table 1.

[Example 4]
In Example 1, without ammonia addition of _{water, H 2 O 2 <1μg /} L, it is referred to as an ultrasonic cleaning with pure water and the dissolved hydrogen gas concentration 1.4 mg / L with removal of about DO10μg / L A cleaning experiment was conducted in the same manner except that the particle removal rate and the state of the surface of the Ge substrate were examined. The results are shown in Table 1.

[ Comparative Example 4 ]
A cleaning experiment was performed in the same manner as in Example 1 except that cleaning was performed without applying ultrasonic waves, and the fine particle removal rate and the state of the surface of the Ge substrate were examined. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, ultrasonic cleaning with pure water having H ₂ O ₂ concentration of 10 μg / L and DO concentration of several hundred μg / L without H ₂ O ₂ removal, degassing, hydrogen gas dissolution, and ammonia addition in the feed water A cleaning experiment was conducted in the same manner except for the above, and the particle removal rate and the state of the surface of the Ge substrate were examined. The results are shown in Table 1.

[Reference Example 1]
In place of the Ge substrate, a contaminated Si substrate contaminated to the same extent as the contaminated Ge substrate in Example 1 was used as an object to be cleaned. The state (Rmax) was examined, and the results are shown in Table 1.

Table 1 shows the following.
In Comparative Example 1 in which ultrasonic cleaning was performed without performing any treatment on pure water, the fine particle removal rate was not high, but there was a problem of surface roughness of the Ge substrate in particular. This result shows that even if pure water is used as the cleaning water, the surface roughness of the Ge substrate cannot be prevented.

In contrast, as washing water, H ₂ O ₂ is removed, DO removed by degassing, examples 1 was subjected to ultrasonic cleaning with those subjected to hydrogen gas dissolved and ammonia addition, the best results As a result, it is possible to obtain a high particle removal rate while suppressing surface roughness of the Ge substrate.

In contrast to Example 1, Example 4 in which only the addition of ammonia was not performed can suppress the surface roughness of the Ge substrate as in Example 1, and also obtains a high cleaning effect after Example 1. Is able to. From this result, it can be seen that the presence / absence of chemical addition is appropriately selected according to the cost efficiency and the required level of the cleaning result in consideration of the cleaning cost and the cleaning effect.
Also, except for not applying ultrasonic waves to Example 1 and Comparative Example 4 were carried out in the same manner, except that no made of H ₂ gas dissolved and ammonia added to Example 1 carried out in the same manner In Comparative Example 3, the fine particle removal rate is inferior, but the surface roughness of the Ge substrate is sufficiently suppressed.
Moreover, although the comparative example 2 which performed ultrasonic cleaning by performing only the DO removal by deaeration is inferior to the comparative example 1, the object of suppressing the surface roughness of the Ge substrate has been achieved.
The cleaning method of Comparative Example 4 can obtain a high rinsing effect while suppressing surface roughness of the Ge substrate in the final cleaning after the chemical cleaning that does not require removal of the fine particles.

  In Reference Example 1 in which the Si substrate was cleaned, it was found that there was no problem with the surface of the substrate, and that the surface was a problem specific to the Ge substrate.

1 H ₂ O ₂ removing device 2 degassing membrane module 3 gas dissolving membrane module 4 washer 5 ultrasonic nozzle 6 Ge substrate 7 turntable

Claims (6)

In the method for cleaning a Ge substrate for a device, the Ge substrate for a device is cleaned by ultrasonic cleaning using water from which dissolved oxygen and hydrogen peroxide have been removed,
A method for cleaning a Ge substrate for devices, wherein the water used for the ultrasonic cleaning is gas-dissolved water in which hydrogen gas is dissolved. _{2. The} method for cleaning a Ge substrate for a device according to claim 1, wherein the dissolved oxygen concentration of water used for the cleaning is 50 μg / L or less and the H ₂ O ₂ concentration is 50 μg / L or less.   3. The Ge substrate for a device according to claim 1, wherein the water used for the cleaning contains one or more chemicals selected from the group consisting of an acid, an alkali, a chelating agent, and a surfactant. Cleaning method. In an apparatus for supplying cleaning water used for cleaning a Ge substrate for a device to an ultrasonic cleaning machine for a Ge substrate, degassing means for removing dissolved oxygen in water, and hydrogen gas in water from which dissolved oxygen has been removed by the degassing means Gas dissolving means for dissolving water, hydrogen peroxide removing means for removing hydrogen peroxide in water, water treated by the hydrogen peroxide removing means, degassing means, and gas dissolving means for the ultrasonic cleaner And a cleaning water supply device for a Ge substrate for a device. 5. The chemical addition means according to claim 4 , wherein one or more chemicals selected from the group consisting of acids, alkalis, chelating agents and surfactants are added to the water from which dissolved oxygen has been removed by the deaeration means. A cleaning water supply device for a Ge substrate for a device. In the apparatus which wash | cleans the Ge substrate for devices, the ultrasonic cleaning by which the cleaning water supply apparatus of the Ge substrate for devices of Claim 4 or 5 and the washing water from the washing water supply apparatus of this Ge substrate for devices are supplied And a Ge substrate cleaning apparatus for devices.

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