WO2007063987A1

WO2007063987A1 - Method for processing/washing with ultra-pure water plasma foams and apparatus for the method

Info

Publication number: WO2007063987A1
Application number: PCT/JP2006/324099
Authority: WO
Inventors: Katsuyoshi Endo; Hidekazu Goto; Hiromichi Toyota; Shinfuku Nomura
Original assignee: Osaka University; Ehime University
Priority date: 2005-12-02
Filing date: 2006-12-01
Publication date: 2007-06-07
Also published as: JPWO2007063987A1

Abstract

[PROBLEMS] To provide: a quite novel method for processing/washing a material with ultra-pure water plasma foams, which enables the processing or washing of the surface of the material under ultra-clean environments by utilizing plasma generated in ultra-pure water; and an apparatus for the method. [MEANS FOR SOLVING PROBLEMS] A material (6) to be treated is placed in ultra-pure water. The ultra-pure water is irradiated with ultrasonic wave to generate fine air bubbles and, at the same time, is also irradiated with an electromagnetic wave having a high frequency continuously with focusing on the air bubbles to thereby generate plasma in the air bubbles. The surface (7) of the material (6) can be processed or washed by supplying the air bubbles (5) having the plasma generated therein, air bubbles generated after disruption of the plasma, or active radicals generated after disruption of the air bubbles onto the surface.

Description

Processing with ultrapure water plasma foam · Cleaning method and equipment

Technical field

[0001] The present invention relates to a processing / cleaning method and apparatus using ultrapure water plasma bubbles, and more specifically, the surface of a substrate such as metal or semiconductor can be processed or cleaned in an ultraclean environment. The present invention relates to a processing and cleaning method and apparatus using ultra pure water plasma bubbles. Background art

[0002] Conventional metal and semiconductor substrate surface processing methods include mechanical polishing using machine tools, chemical polishing using chemical reactions, electrolytic polishing using electrochemical reactions, and air plasma. The plasma etching used is mentioned. However, in any of these methods, surface cleaning with ultrapure water is necessary in the final processing steps of ICs and LSIs, and the cleaning process is regarded as important. In the cleaning of substrates used for highly integrated devices of sub-micron size, it is extremely difficult to remove residual impurities.

[0003] On the other hand, as a technique for generating plasma in a liquid, Patent Documents 1 and 2 irradiate ultrasonic waves in the liquid, or generate fine bubbles by using heating or decompression. There has been proposed a method of generating plasma in bubbles by continuously irradiating electromagnetic waves inside. Also, a method of forming a silicon carbide film on the substrate surface by generating plasma in a liquid containing hydrocarbons to form a diamond film on the surface of the substrate or generating plasma in a liquid containing silicon. Is also proposed!

[0004] Further, in Patent Document 3, as a processing method using only ultrapure water, only ultrapure water is used except for a small amount of inevitable impurities, and this is subjected to a hydroxyl group increasing treatment for increasing the ion product. An ultrapure material that is processed to remove or form an oxide film by chemical elution reaction or acid reaction with hydroxyl groups or hydroxyl ions, when the workpiece is immersed in ultrapure water with increased hydroxyl ion concentration. A processing method using hydroxyl groups in water has been proposed.

[0005] Further, Patent Document 4 discloses that a workpiece and a high-pressure nozzle are disposed at a predetermined interval in a machining tank that also has the power of ultrapure water, and a machining surface of the workpiece. An ion exchange material or a catalyst material for increasing hydroxide ions is provided around the tip of the high pressure nozzle facing the A voltage is applied with the high pressure nozzle as the cathode and the work piece as the anode to generate a high-speed shear flow of ultra pure water sprayed from the high pressure nozzle near the surface of the work piece. Ultrapure water that supplies the processed hydroxide ions to the surface of the workpiece and removes the workpiece or forms an oxide film by chemical dissolution reaction or oxidation reaction with hydroxide ions. A method of adding hydroxide ions in the interior has been proposed.

Patent Document 1: Japanese Patent No. 3624238

Patent Document 2: Japanese Patent No. 3624239

Patent Document 3: Japanese Patent Laid-Open No. 10-58236

Patent Document 4: Japanese Patent No. 3316461

Disclosure of the invention

Problems to be solved by the invention

[0006] However, since the technology itself for generating plasma in a liquid is a technology that has been recently developed by the present inventors, the substrate has been processed using plasma generated in a liquid, When I washed my ideas were everywhere.

[0007] In view of the above situation, the present invention intends to solve the problem by generating plasma in ultrapure water and using the plasma to treat the surface of the object to be processed in an ultraclean environment. Processed

The object is to provide a completely new processing / cleaning method and apparatus using ultra-pure water plasma bubbles that can be cleaned.

Means for solving the problem

[0008] The present invention provides ultra-pure water without impurities as micron or nano-sized plasma bubbles using liquid plasma as a means for processing metal or semiconductor objects to be processed with high precision. Ultra precision machining is performed by contacting the workpiece using the flow of water. In this process, the processing accuracy (surface roughness of the workpiece after processing) depends on the size of the ultrapure water plasma bubbles. Therefore, if nano-sized ultrapure water plasma bubbles are used, nano-sized ultra-precision processing is possible.

[0009] In order to solve the above-mentioned problems, the present invention generates plasma bubbles by continuously and intensively irradiating ultrapure water with at least high-frequency electromagnetic waves, and the plasma bubbles or after the plasma is extinguished. Table of objects to be treated with bubbles or active radicals after bubbles disappeared in ultrapure water A processing / cleaning method using ultrapure water plasma bubbles, characterized in that it is supplied to the surface for processing or cleaning (claim 1).

[0010] Further, the present invention generates fine bubbles by irradiating ultrasonic waves in ultrapure water, and continuously and intensively irradiates high-frequency electromagnetic waves toward the bubbles to generate plasma in the bubbles. Processing with ultrapure water plasma bubbles that supply or process the plasma bubbles, or bubbles after plasma extinguishing or active radicals after bubble extinction are supplied to the surface of the object to be processed placed in ultrapure water A cleaning method is provided (claim 2).

Here, the flow of ultrapure water is used as means for supplying the plasma bubbles, or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles to the surface of the object to be processed (Claim 3). Specifically, the means for supplying the plasma bubbles, or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles to the surface of the object to be processed is an injection nozzle of ultra pure water, which is disposed in the ultra pure water. Ultrapure water is jetted from the jet nozzle toward the plasma bubbles to generate a flow of ultrapure water, and plasma bubbles or bubbles after the extinction of plasma or active radicals after the extinction of the bubbles are generated on the surface of the object to be processed.供給する (Claim 4)

[0012] Further, the present invention holds an object to be processed and an electromagnetic wave probe that generates plasma bubbles by continuously and intensively irradiating high-frequency electromagnetic waves in ultrapure water disposed in a processing chamber. An ultrapure water provided with a plasma bubble supply means for supplying the plasma bubbles or bubbles after the extinction of the plasma or active radicals after the extinction of the bubbles to the surface of the object to be processed held by the holder. A processing / cleaning device using plasma bubbles was constructed (claim 5).

[0013] Furthermore, the present invention provides an ultrasonic generation horn that generates fine bubbles by irradiating ultrasonic waves in ultrapure water disposed in a processing chamber, and continuously and intensively irradiates high-frequency electromagnetic waves. An electromagnetic wave probe for generating plasma bubbles by irradiation and a holder for holding an object to be processed are arranged, and the plasma bubbles, bubbles after extinction of plasma or active radicals after extinction of bubbles are held in the holder. A processing / cleaning apparatus using ultrapure water plasma bubbles provided with plasma bubble supply means for supplying to the surface of the processed material was constructed (claim 6).

[0014] Here, a pressure adjusting means for adjusting the pressure in the processing chamber is provided. (Claim 7) It is preferable that a gas supply means for supplying gas into the processing chamber (Claim 8) is further supplied to the surface of the object to be processed and used for processing the surface. It is also preferable to provide plasma bubble discharging means for removing plasma bubbles, bubbles after plasma extinction or active radicals after bubble extinction (claim 9).

The invention's effect

[0015] The processing / cleaning method and apparatus using the ultrapure water plasma foam according to the present invention as described above are processed since clean ultrapure water used for cleaning in the final process is used in all conventional methods. There is no surface contamination. Therefore, the cleaning process using ultrapure water at the final stage, which was necessary in the conventional method, is not necessary. In addition, no harmful substances as etching agents are required, which is necessary in the conventional method, and it is not necessary to discard the solution or gas after processing. It can be said that the present invention is an environmentally friendly and efficient method.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. In the present embodiment, force washing, which mainly describes processing, is exactly the same. In other words, even if there is no cleaning without processing, a gentle force is equivalent to cleaning.

FIG. 1 shows a conceptual diagram of a processing / cleaning method using ultrapure water plasma bubbles according to the present invention. First, in order to generate ultra pure water plasma bubbles, fine bubbles are locally generated in ultra pure water, and high frequency electromagnetic waves are continuously and intensively irradiated to the bubbles. Here, as a means for generating fine bubbles, irradiation with ultrasonic waves is the simplest and most efficient, but other means by local heating or reduced pressure can also be used. It has also been confirmed that bubbles are generated only by concentrated irradiation of high-frequency electromagnetic waves. Then, the plasma bubbles generated in this way are supplied to the surface of the object to be processed disposed in ultrapure water, and the surface is covered by the interaction with the plasma.

Reference numeral 1 in FIG. 1 is an electromagnetic wave generator that generates high-frequency electromagnetic waves, and 2 is an electromagnetic wave probe that is electromagnetically connected to the electromagnetic wave generator 1 to irradiate high-frequency electromagnetic waves into ultrapure water. is there. In FIG. 1, reference numeral 3 is an ultrasonic generator that generates ultrasonic waves, and 4 is an ultrasonic generator that is acoustically connected to the ultrasonic generator 3 to irradiate ultrasonic waves into ultrapure water. It is. Then, the ultrasonic generation horn 4 force ultrasonic wave is irradiated locally to make fine Bubbles are generated, and high-frequency electromagnetic waves are continuously emitted from the electromagnetic probe 2 toward the bubbles to generate plasma in the bubbles. In the bubbles generated by the ultrasonic generation horn 4, gas such as water corresponding to the saturated vapor pressure of ultrapure water or oxygen dissolved in the ultrapure water is confined, and high-frequency electromagnetic wave irradiation is performed. It turns into plasma. It is confirmed that OH radicals, H atoms, and O atoms are generated in the plasma bubbles 5 generated here. Even if the plasma in the bubbles disappears, the active radicals are present in the bubbles or in the liquid depending on the lifetime, so that the force proceeds. It is assumed that a large number of active radicals exist at the interface between the bubble and liquid having a high surface energy, and plasma bubbles, bubbles after extinction of plasma, or active radicals after extinction of bubbles are supplied to the surface of the object to be treated. Therefore, the processing method of the present invention can be said to be an extremely efficient and rational processing method.

[0019] The frequency of the electromagnetic wave generated by the electromagnetic wave generating device 1 is most easily absorbed by water molecules. 2. It is necessary to avoid 45 GHz, and in this embodiment, the range of 3 MHz to 1 GHz is used. In addition, the higher the frequency of the ultrasonic wave generated by the ultrasonic generator 3, the smaller the bubble size, but it is practically in the range of 10 kHz to 30 MHz. By the way, 20 kHz ultrasonic waves generate / z m size bubbles, and tens of MHz ultrasonic waves generate nm size bubbles. The smaller the bubbles, the higher the processing accuracy and the higher the processing speed.

[0020] The plasma bubbles 5 generated in this way, or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles are supplied to the surface 7 of the object 6 to be processed. In order to supply the plasma bubbles 5 or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles to the surface 7 of the workpiece 6, the flow of ultrapure water is used. Specifically, an injection nozzle 8 of ultrapure water is disposed in ultrapure water toward the region where the plasma bubbles 5 are generated, and the superposition of the plasma bubbles 5 from the injection nozzle 8 toward the plasma bubbles 5 is performed. The pure water is jetted to generate the flow of ultra pure water, and the plasma bubbles 5 or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles are supplied to the surface 7 of the workpiece 6 together with the ultra pure water. . The plasma bubbles 5 that have reached the surface 7 of the workpiece 6 are supplied by supplying OH radicals, H atoms, and O atoms to the surface 7 and changing the surface atoms into volatile or water-soluble substances to be removed. . For processing Since the plasma bubbles 5, or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles are no longer necessary, an appropriate plasma bubble discharging means that collects them by the bubble collecting means and discharges them outside the process area may be provided. I like it.

Example 1

FIG. 2 shows a conceptual diagram of the processing apparatus of the first embodiment of the present invention. In this processing apparatus A, a processing chamber 10 that can be sealed is filled with ultrapure water 11, and a flat plate-like object is formed at the lower end of a holder 12 that extends into the ultrapure water 11 from the upper surface side of the cache chamber 10. The surface 13 of the workpiece 13 is held to be horizontal, and the tip of the electromagnetic wave probe 15 raised from the lower surface side of the cabinet 10 is disposed immediately below the surface 14 of the workpiece 13; The In addition, a port 17 communicating with the gas phase portion 16 in the processing chamber 10 is provided in the upper portion of the processing chamber 10. The inside of the processing chamber 10 can be depressurized by exhausting from the port 17, and conversely, the inside of the cache chamber 10 can be pressurized by pumping gas from the port 17. . In FIG. 2, reference numeral 18 indicates a plasma generation region, and 19 indicates a plasma bubble.

[0022] The processed sample that was subjected to processing with this Karoe device A was

(1) Si wafer

p-type Si (OOl)

(2) Au evaporated wafer

Cr is deposited on p-type Si wafer by lOOnm, and Au is deposited on it by about 500nm.

There are two types.

[0023] The processing conditions are:

Liquid: pure water,

Pressure in the Karoe chamber: 200hPa,

Input power: 200W

Reflected power: 100W,

Electromagnetic frequency: 27. 12MHz,

Processing time: 3 minutes

It is. [0024] The surface obtained by processing the Si wafer and the Au vapor-deposited wafer under the above processing conditions was examined using a stylus roughness meter and a phase shift interference microscope. The measurement with a phase shift interference microscope was performed after depositing about 500 nm of A1 on the sample surface.

[0025] Fig. 3 shows the result of measuring the processed surface of the Si wafer with a phase shift interference microscope. It can be seen that the Si wafer has an area of about 4 mm in diameter that is covered to a maximum depth of about 400 nm! . The processing speed of Si Wha is about 130nmZ. This processing speed is sufficiently high compared with plasma etching!

[0026] On the other hand, Fig. 4 shows the result of measuring the processed surface of the Au vapor-deposited wafer with a stylus roughness meter. The Au vapor-deposited wafer is covered with a region with a diameter of about 2 mm up to a maximum depth of about 250 nm. You can see that The processing speed of Au evaporated wafer is about 80nmZ. Here, Au is a very stable material, and it is a remarkable point that it is processed. Since Au has a very high redox potential and is known to ionize when reacted with a substance, it is thought that a strong acid-acidic substance is produced during the Karoe process.

Example 2

FIG. 5 shows a conceptual diagram of a machining apparatus according to the second embodiment of the present invention. In this processing apparatus B, the inside of the processing chamber 20 is filled with ultrapure water 21, a supply port 22 of ultrapure water is provided on one side wall of the cache chamber 20, and a discharge port 23 is provided on the opposite side wall. The ultrapure water is caused to flow by being discharged from the discharge port 23 while continuously supplying ultrapure water from the supply port 22. Then, the electromagnetic probe 24 is raised from the lower surface side of the casing chamber 20 and the tip thereof is directed to the flowing portion of the ultrapure water, and the ultrasonic horn 25 is directed from the upper surface side to the flowing portion of the ultrapure water. Distribute. The plasma bubbles 27 generated in the plasma generation region 26 are supplied to the surface 30 of the workpiece 29 held by the holder 28 installed on the downstream side as the ultrapure water flows. Here, the surface 30 of the workpiece 29 is inclined with respect to the flow direction of the ultrapure water so as not to hinder the flow. Further, the discharge port 23 serves as a plasma bubble discharge means for discharging unnecessary plasma bubbles 27 and substances removed from the surface 30 by the cache.

[0028] The processed sample that was subjected to processing by the processing apparatus B was

(l) Au evaporated wafer This is one type of depositing 0: 10011111 on p-type 3 001) wafer and depositing Au on it about lOOnm.

[0029] The processing conditions are:

Liquid: ultrapure water,

Liquid flow rate in the processing chamber: 9.3LZ,

Pressure: atmospheric pressure,

Incident high frequency electromagnetic wave: Frequency 27.12MHz, input power: 350W, reflected power: 15W, incident ultrasonic wave: 21.7kHz, input power 15W,

Processing time: 2, 3, 4, 5, 10, 30 minutes

It is.

[0030] In processing using this processing apparatus B, when processing by irradiating both electromagnetic waves and ultrasonic waves, processing by irradiating only electromagnetic waves, processing by irradiating only ultrasonic waves, This is a photograph of the processed surface of a processed sample observed, showing the results for each processing time. Blanks in this table are unconfirmed.

[0031] From the results shown in Fig. 7, when processing was performed by irradiating electromagnetic waves and ultrasonic waves to generate plasma in the liquid (left column), the Au plating layer was removed over time, and the Cr surface was removed. It can be seen that the exposed area has increased. On the other hand, when plasma is generated by irradiating only electromagnetic waves (middle row), there is almost no change even after processing for 5 minutes. Furthermore, when only ultrasonic waves are irradiated, no change is seen even after 30 minutes.

[0032] Figs. 7 (a), (b), and (c) show the results of measuring the processed surface with a stylus roughness meter when the processing time is 2 minutes, 4 minutes, and 10 minutes, respectively. . A schematic diagram of the processed sample is shown on the left side of each measurement result, and the measurement position on the stylus roughness meter is indicated by an arrow. Figure 7 (a) is processed to a depth of several tens of nm, Figure 7 (b) is processed to a depth of about 50 nm, and Figure 7 (c) is a depth of about lOOnm (complete removal of the Au plating layer). Shown that it has been catered to.

FIG. 8 shows an emission spectrum (pressure 2 OOhPa) of plasma in liquid generated using the above-mentioned cache apparatus A, and FIG. 9 shows that generated in the atmosphere using the processing apparatus B. The light emission spectrum is shown. As a result, it can be seen from the emission spectrum when the pressure is 200 hPa that many OH radicals and H atoms are generated. In computer simulation, OH It is predicted that back bonds will break when dical and H atoms act on Si. In contrast, in the emission spectrum when exposed to the atmosphere, many O atoms are observed and few H atoms. Since O atoms are connected to acids, there is a possibility that Si processing does not proceed. In the future, it is expected that the activated species generated by controlling the atmosphere can be selected to change the processing characteristics.

Brief Description of Drawings

[0034] FIG. 1 is a conceptual diagram for explaining the processing principle of the present invention.

FIG. 2 is a conceptual cross-sectional view of the processing apparatus of the first embodiment.

FIG. 3 is a graph showing a result of measuring a processed surface of a Si wafer covered with the processing apparatus of FIG. 2 using a phase shift interference microscope.

FIG. 4 is a graph showing the results of measuring the processed surface of an Au-deposited wafer processed by the processing apparatus of FIG. 2 using a stylus roughness meter.

FIG. 5 is a conceptual cross-sectional view of a processing apparatus according to a second embodiment.

FIG. 6 is an observation result of a processed surface of an Au vapor-deposited wafer that is covered using the processing apparatus of FIG.

FIG. 7 is a graph showing the results of measuring the machined surface with a stylus roughness meter when machining time is 2 minutes, 4 minutes, and 10 minutes.

FIG. 8 is a graph showing an emission spectrum (pressure 200 h Pa) of in-liquid plasma generated using the processing apparatus of FIG. 2.

FIG. 9 is a graph showing an emission spectrum generated in the open atmosphere using the processing apparatus of FIG.

Explanation of symbols

[0035] A, B processing equipment

1 Electromagnetic wave generator

2 Electromagnetic probe

3 Ultrasonic generator

4 Ultrasonic generator horn

5 Plasma bubbles

6 Workpiece surface

Injection nozzle Processing chamber 1 Ultra pure water Holder Surface of workpiece

Electromagnetic probe Gas phase Port Plasma generation region Plasma bubble Processing chamber 1 Ultrapure water Supply port Discharge port Electromagnetic probe Ultrasonic horn Plasma generation region Plasma bubble holder Surface of workpiece

Claims

The scope of the claims

[1] Continuously and intensively irradiating at least high-frequency electromagnetic waves into ultrapure water to generate plasma bubbles, and the plasma bubbles, bubbles after extinction of plasma, or active radicals after extinction of bubbles are removed from ultrapure water. A processing / cleaning method using ultrapure water plasma bubbles, characterized in that it is supplied to the surface of an object to be processed disposed on the surface and processed or cleaned.

[2] Ultrafine water is irradiated with ultrasonic waves to generate fine bubbles, and high-frequency electromagnetic waves are continuously and intensively irradiated toward the bubbles to generate plasma in the bubbles. 2. Processing with ultrapure water plasma bubbles according to claim 1, wherein the bubbles, or the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles are supplied to the surface of the object disposed in the ultrapure water to be processed or washed. Cleaning method.

[3] The ultrapure water according to claim 1 or 2, wherein the flow of ultrapure water is used as means for supplying the plasma bubbles, bubbles after the extinction of the plasma, or active radicals after the extinction of the bubbles to the surface of the object to be processed. Processing with plasma bubbles · Cleaning method.

[4] The means for supplying the plasma bubbles, the bubbles after the extinction of the plasma or the active radicals after the extinction of the bubbles to the surface of the object to be processed is an ultra pure water jet nozzle, and the jet nozzle arranged in the ultra pure water Then, ultrapure water is jetted toward the plasma bubbles to generate a flow of ultrapure water, and plasma bubbles, bubbles after the extinction of plasma, or active radicals after the extinction of bubbles are supplied to the surface of the object to be processed. The processing using the ultrapure water plasma foam according to claim 3 'cleaning method.

[5] An ultra-pure water placed in the processing chamber is provided with an electromagnetic wave probe for generating plasma bubbles by continuously and intensively irradiating high-frequency electromagnetic waves, and a holder for holding an object to be processed. An ultrapure water plasma comprising a plasma bubble supply means for supplying the plasma bubbles, or bubbles after the extinction of the plasma or active radicals after the extinction of the bubbles to the surface of the object to be processed held by the holder. Processing with foam 'cleaning device.

[6] An ultrasonic generation horn that generates fine bubbles by irradiating ultrasonic waves in ultrapure water placed in the processing chamber, and plasma bubbles by continuously and intensively irradiating high-frequency electromagnetic waves. An electromagnetic wave probe for generating a gas and a holder for holding an object to be processed are provided, and the plasma bubbles, bubbles after extinction of plasma, or active radicals after extinction of bubbles are transferred to the holder. A processing / cleaning device using ultrapure water plasma bubbles, characterized in that it is provided with plasma bubble supply means for supplying to the surface of the object to be treated.

7. The processing / cleaning apparatus using ultra pure water plasma foam according to claim 5 or 6, further comprising pressure adjusting means for adjusting the pressure in the processing chamber.

8. A gas supply means for supplying a gas into the processing chamber is provided.

7. Processing / cleaning device using ultrapure water plasma foam according to any one of 7 above.

[9] The apparatus according to claim 5, further comprising plasma bubble discharging means for removing plasma bubbles supplied to the surface of the object to be processed and used for processing the surface, bubbles after disappearance of plasma, or active radicals after bubble disappearance. 8. Processing / cleaning equipment using ultrapure water plasma bubbles as described in any one of 8 above.