The present invention relates to a treatment apparatus for treating objects by cracking a gas in the presence of a catalyst. More specifically, optical energy is used in the treatment process of treating the objects by cracking the gas with the catalyst.
In order to remove organic substances during a process of manufacturing semiconductors or cleaning liquid crystal substrates, some methods have recently been developed, in which high-melting-point catalysts to ash or remove resists is used. For example, Japanese Laid Open Patent No. 2002-289586 has disclosed one of the methods. In this method, a high-melting-point metal, such as tungsten, is heated to be used as the high-melting-point catalyst, and a gas containing hydrogen atoms is allowed to react to produce atomic hydrogen by catalytic cracking in the presence of the catalyst. By bringing the atomic hydrogen into contact with a resist, the resist is removed.
The extended abstracts No. 2 of the 50th Workshop of Japan Society of Applied Physics and Related Societies, p. 844 (March, 2003) discloses another method using heated tungsten as the high-melting-point catalyst. In this method, ammonia is brought into contact with the tungsten to produce cracked ammonia, and the cracked ammonia is allowed to act on a resist to remove.
Japanese Journal of Applied Physics, Vol. 41 (2002), pp. 4639-4641 discloses another method in which H2 is brought into contact with heated tungsten to produce H, and the H is allowed to act on Si to carry out etching.
As described above, it is proposed that metal such as tungsten is used as the high-temperature-catalyst. It is considered that such an activated species is produced through the following mechanism. If a reactive gas, such as that of hydrogen molecules, comes into collision with the surface of a metal, the hydrogen molecules adsorb on the surface of the metal. At this point, the metal, such as tungsten, serves as a catalyst to produce a combined species of hydrogen atoms with the metal, for example, tungsten on the metal surface. Then, the tungsten is heated to, for example, 1,700° C. or more (a surface temperature) so that the hydrogen atoms separate from the surface of the tungsten by the heat energy. Thus, highly reactive hydrogen atoms are produced. By the thermal separation of hydrogen atoms, the surface of the tungsten is returned to a clean metal state in which dissociation and adsorption can be repeated by collision of hydrogen molecules with the metal. Thus, the catalytic reaction is continued.
Unfortunately, the metal serving as the high-melting-point catalyst is inevitably vaporized in the above-described methods because those methods involve thermal separation by heating the metal. The vaporized metal undesirably contaminates the object to be treated.
In view of the above-described disadvantages, the inventors of the present invention have conducted intensive research, and found that a highly reactive species of, for example, hydrogen can be separated from a catalyst by irradiating with light an element dissociated through adsorption by the catalyst.
The present invention is based on this finding, and the object of the present invention is to provide a treatment apparatus which produces a highly efficient activated species of a substance without contaminating objects to be treated and which, thus, treats the object at a high speed.
In a treatment apparatus according to the present invention, catalyst is used in order to dissolve molecular gas containing hydrogen atoms or oxygen atoms, and an object is treated by gas produced by the catalyst, comprises a catalyst irradiation unit, wherein the catalyst is irradiated, by the catalyst irradiation unit, with light having a wave number larger than work function of the catalyst expressed in wave number.
The work function refers to energy required to increase the potential of electrons confined in a substance to a potential over the bandgap, and is generally expressed as a potential difference in electron volt (eV). While light emitted from a substance is generally expressed as a wavelength (nm), it may be expressed as the reciprocal of the wavelength, namely, wave number in kayser (cm−1), to represent the electromagnetic energy of the light. The relationship is expressed by: Energy (E)=Planck Constant (h)×Light Velocity (c)/Wavelength (λ). An energy expressed in electron volt (eV) can be converted to be expressed in kayser (cm−1), that is, 1 eV=0.8066×104 cm−1. In the description herein, the emission of light having energy of more than a work function energy is described in a unified manner using a unit of energy, kayser (cm−1).
The treatment apparatus of the present invention may further include an object irradiation unit for irradiating an object with light having a wave number of more than the work function expressed in wave number of the catalyst.
Preferably, the wave number of the light is more than 5.08×104 cm−1.
The light may be Ar2 excimer light with a peak at a wave number of 7.934×104 cm−1.
The treatment apparatus may further include light emitting unit in which the Ar2 excimer light is emitted by dielectric barrier discharge using Ar as a discharge gas, and the discharge gas contains hydrogen atoms or oxygen atoms.
Alternatively, the light emitting unit may be a Xe2 excimer lamp with a peak at wave number of 5.81×104 cm−1 or a Kr2 excimer lamp with a peak at a wave number of 6.85×104 cm−1.
The catalyst may be selected from the group consisting of Pt, Rh, Pd, Ir, Ru, Re, and Au.
The cracked gas may be jetted onto the object.
In another form of the treatment apparatus according to the present invention, a molecular gas containing hydrogen atoms is dissociated in the presence of a catalyst, and the cracked gas treat an object.
The treatment apparatus may include irradiation means for irradiating the catalyst and the object with light having a wave number of more than the work function of the catalyst expressed in wave number. The light has a wave number of 6.67×104 cm−1 or more, and SiO2 is etched.
The treatment apparatus may further include a dielectric barrier discharge lamp emitting Kr2 excimer light with a peak at a wave number of 6.85×104 cm−1 or Ar2 excimer light with a peak at a wave number of 7.934×104 cm−1, and etches SiO2.
The treatment apparatus of the present invention irradiates a catalyst for cracking a gas containing hydrogen atoms or oxygen atoms with light having a wave number of more than work function of the catalyst expressed in wave number, thus facilitating the separation of the cracked product adsorbed and dissociated on the catalyst by the contact of the gas with the catalyst. For example, if ammonia (NH3) is used as the gas containing hydrogen atoms, the NH3 gas comes into collision with the catalyst, for example, tungsten (W), to adsorb on the catalyst. Then, the NH3 reacts with the W so that the NH3 is cracked and W—H is formed, in a manner known as adsorption and dissociation. As for the N atoms, some of the N atoms may combine with the tungsten, but many of the N atoms combine with each other to form nitrogen gas (N2) and are thus suspended in the air. The W—H produced by the adsorption and dissociation of NH3 is irradiated with light having energy of more than the work function of the catalyst tungsten, so that the bond of the W—H is broken, and thus activated H separates from the tungsten. By heating the tungsten by, for example, energization during irradiation, the separation can be further promoted. Consequently, an activated product can be produced without heating the catalyst tungsten, or simply by supplemental heating. Thus, the vaporization of the catalyst can be reduced and the object can be prevented from being contaminated with the vaporized catalyst.
The object may be irradiated with the light having a wave number of more than the work function of the catalyst expressed in wave number. Thus, the bonds of the organic substances and resist on the object, such as C—C and C—H, can be broken, in addition to producing high-concentration activated species in the presence of the catalyst. Consequently, for example, an ion-implanted resist, which is hard to decompose, can be removed, and the speed in removing the organic substances and resist can be increased.
The wave number of the light may be 5.08×104 cm−1. By applying the light onto the object, not only single bonds of the organic substances and resist on the object, such as C—C and C—H, but also double bonds, such as C═C and O═O, can be broken. Consequently, the speed in removing difficult-to-decompose resists, such as ion-implanted resists, can be increased, and the organic substances and resists can be removed at a higher rate.
The light may be Ar2 excimer light with a peak at a wave number of 7.934×104 cm−1. Since such light can break the C═O bond, triple bonds of C, N, and C and N, the speed in removing difficult-to-decompose resists, such as ion-implanted resists, can be increased, and the organic substances and resists can be removed at a higher rate.
The Ar2 excimer light may be emitted by dielectric barrier discharge using Ar as the discharge gas. The discharge gas may contain the molecular gas containing hydrogen atoms or oxygen atoms. Thus, the excimer light having a wave number of 7.934×104 cm−1 generated by Ar gas dielectric barrier discharge can be efficiently applied to the molecular gas containing hydrogen atoms or oxygen atoms to produce activated O or H. In this instance, the dielectric barrier discharge itself changes part of the molecular gas into activated H or O. Thus, the activated species H or O can be produced in a high concentration, and the speed in removing organic substances can be increased, accordingly.
The light having a wave number of larger than the work function of the catalyst may be emitted from a Xe2 excimer lamp with a peak at a wave number of 5.81×104 cm−1 or a Kr2 excimer lamp with a peak at a wave number of 6.85×104 cm−1. Since these excimer lamps can efficiently emit monochromatic light with a peak at those wave numbers, the organic substances can be removed without irradiating the object with excessive light or overheating the object with the excimer light. Also, since the dielectric barrier discharge lamp does not consume metal electrodes, the object is advantageously prevented from being contaminated.
The catalyst may be Pt, Rh, Pd, Ir, Ru, Re, or Au. In general, the catalyst is contaminated to wear away with a gas containing oxygen atoms generated from the object in some cases. By using a catalyst unreactive to oxygen, such as Pt, Rh, Pd, Ir, Ru, Re, or Au, the catalyst can be prevented from wearing away and the object can also be prevented from being contaminated.
The cracked product gas, such as activated O or H, may be delivered to the object effectively by jetting. Thus, the efficiency in using activated O or H can be increased, and consequently the organic substances can be removed at a high speed. In particular, if the object is placed in a normal atmosphere (in normal air) so as to be easily moved, continuous treatment can be performed by jetting.
The treatment apparatus may have irradiation unit for irradiating both the catalyst and the object with the light having a wave number of more than 6.67×104 cm−1 as light of more than work function expressed in wave number of the catalyst, wherein a molecular gas contains hydrogen atoms. Since the wave number of the light to be irradiate o the object is 6.67×104 cm−1, which accords with the absorption edge in the short wavelength region of SiO2, the light is absorbed into SiO2 and decompose the SiO2 into Si+SiO. The Si+ SiO are attacked by activated H produced by the catalytic reaction. Thus, the SiO2, which is difficult to etch by H alone, can be advantageously etched.
The light having a wave number of more than the work function expressed by wave number of the catalyst may be Kr2 excimer light with a peak at a wave number of 6.85×104 cm−1 or Ar2 excimer light with a peak at a wave number of 7.934×104 cm−1. In order to generate light having these wave numbers, a dielectric barrier discharge lamp can be used. Since the absorption edge in the short wavelength region of SiO2 lies at 6.67×104 cm−1, the Kr2 excimer light with a peak at a wave number of 6.85×104 cm−1 or the Ar2 excimer light with a peak at a wave number of 7.934×104 cm−1 is absorbed into SiO2 to decompose it into Si+ SiO. The Si+SiO are attacked by activated H produced by the catalytic reaction. Thus, the SiO2, which is difficult to etch by H alone, can be advantageously etched.
In the treatment apparatus of the present invention, when a reactive gas containing oxygen atoms or hydrogen atoms adsorbs and dissociates on a high-melting-point metal catalyst and, thus, separates from the catalyst, light is emitted onto the catalyst to enable activated species to separate from the catalyst without heating the catalyst, or simply by supplemental heating. Also, by irradiating the reaction gas with the light, in addition to the catalyst, high-concentration activated species can be produced. Furthermore, if the object to be treated is irradiated with the light to activate its surface and to break the chemical bonds at the surface, the treatment speed can be increased. The embodiments of the present invention will now be described in detail.
A treatment apparatus according to a first embodiment of the present invention is shown in
In the first embodiment, the light is generated under the conditions set forth below. The dielectric barrier discharge electrodes 3a and 3b, which are illustrated by circles in the figure, are of cylinders, each of which includes a quartz glass tube having an outer diameter of 20 mm, a thickness of 1 mm, and a length of 250 mm, and aluminium is inserted inside the quartz glass tube. A distance between electrodes is 6 mm. Discharge gas is Ar and a pressure thereof is 6.65 MPa, and a power thereof is 200 W. Thus, discharge plasma 4 emits Ar2 excimer light having a wave number of 7.934×104 cm−1 and the light is emitted to the catalyst 100 disposed in the activated species generation space 2a through the light extraction window 7.
In the present embodiment, a reaction is shown, wherein ammonia (NH3) gas is introduced. The NH3 introduced through the inlet 10a comes into collision with a tungsten wire, which is the catalyst 100, and adsorbs and dissociate on the surface of the tungsten (W), so that the introduced NH3 is dissociated, thereby forming W—H on the surface of the tungsten. As for the N atoms of the NH3, some of the N atoms react with the surface of the tungsten, so as to produce reacting substance but, probably, many of the N atoms are formed into nitrogen gas (N2) by collision with each other and are thus suspended in the air. The W—H formed on the surface of tungsten 100 which is the catalyst is irradiated to the catalyst with the light having a wave number of 7.934×104 cm−1, so that the bond of W—H is broken to separate H from the surface of the tungsten. In the present embodiment, the catalyst is irradiated, and further supplementally heated by, for example, energization so that the separation of H from the catalyst is promoted. After separation of hydrogen atoms, on the surface of the tungsten, clean face is formed. The clean tungsten surface is subjected to collision of hydrogen molecules to repeat the same reaction. Thus, high-concentration activated H is produced in the activated species generation space 2a. The activated H is delivered into the treatment space 2b along with the stream of the NH3 introduced through the inlet 10a or the stream of exhaust gas etc. forced to let out from the outlet 10b. The treatment space 2b contains an object to be treated, and the object is brought into contact with the high-concentration activated H produced in the activated species generation space 2a. The object has been contaminated with, for example, organic substances. The activated H reacts with the carbon and the oxygen in the organic substances, for example, CH4 and H2O, thus removing the organic substances from the object. In an example of the present embodiment, the catalyst 100 is made from tungsten wires, each of which has a 0.6 mm diameter, and the wires are arranged in a pitch of 15 mm. The object 9 was a glass substrate for a liquid crystal display, and the activated species produced from the NH3 in the treatment space 2b has a pressure of 1 Pa. In this structure, the catalyst tungsten was irradiated with the light and simultaneously heated to 1,550° C. supplementally by energization. As a result, the glass substrate would be cleaned by about 25 second treatment.
Description of other embodiments in which the treatment apparatus shown in
In a second embodiment, H2 is used as the molecular gas, and Mo is used as the catalyst 100. By bringing H2 into collision with Mo, the H2 is adsorbed and dissociated so that Mo—H is formed on the surface of the Mo. The Mo—H is irradiated with light so that the Mo—H bond is easily broken to separate H from the surface of the Mo. In this instance, the light has a wave number of more than 5.08×104 cm−1 so as to easily separate the H from the surface of the catalyst 100. This is because such light has sufficiently higher energy than the work function of the Mo (3.35×104 cm−1). In addition, the Mo may be supplementally heated by energization to efficiently separate H from the surface of the catalyst 100.
In a third embodiment, the treatment apparatus shown in
In a fourth embodiment, Pt, which has a relatively high work function (4.29×104 cm−1) among the above-mentioned oxidation-resistant metals, is used as the catalyst 100. If CO2 is used as the molecular gas for producing the activated species, the CO2 comes into collision with the Pt so that absorption and dissociation are take place, and products, such as Pt—O and Pt—C, are produced on the surface of the Pt. The products are irradiated with the light having a wave number of more than 5.08×104 cm−1 to separate activated O and C from the Pt surface. At this point, the Pt may be heated to efficiently separate the activated O and C from the Pt surface. The separated O and C can recombine with each other to be suspended in the air. Other activated O is delivered into the treatment space 2b and brought into contact with the object, for example, a liquid crystal substrate, placed in the treatment space 2b, thus removing organic substances from the object by oxidation. The light may be applied to the introduced molecular gas CO2 and the separated activated O in addition to the catalyst 100, thereby producing ozone or activated O atoms having higher energy levels. Also, by irradiating the CO2, part of the CO2 can be directly dissociated by the light but not by the catalyst 100. Consequently, a high-concentration activated species is produced and brought into contact with the object in the treatment space 2b, and thus high-speed treatment can be achieved.
In the fifth embodiment, the light is generated under conditions set forth below. The dielectric barrier discharge electrodes 23a, 23b, and 23c, which are illustrated by circles, are of cylinders, each of which includes a quartz glass tube having an outer diameter of 20 mm, a thickness of 1 mm, and a length of 250 mm, and aluminium is inserted inside the quartz glass tube. The electrodes are disposed at intervals of 6 mm. Discharge is performed with Ar having a pressure of 6.65 MPa, at a power of 200 W. Thus, discharge plasma 24a and 24b emits Ar2 excimer light having a wave number of 7.934×104 cm−1 and the light is applied to the treatment space 22, the catalyst 100, and the object 9 through the light extraction window 7. In an example of the present embodiment, the catalyst 100 is made from tungsten wires having a 0.6 mm in diameter wherein a pitch thereof is 15 mm. The object 9 was a glass substrate for a liquid crystal display. The distance between the object 9 and the light extraction window 7 was set at 150 mm, the distance between the catalyst 100 and the object 9 is set to 100 mm. The pressure of the treatment space 22 containing NH3 gas is 1 Pa. The tungsten was irradiated with the light and further heated supplementally to 1,550° C. The glass substrate for the liquid crystal display was cleaned by the treatment for about 25 seconds.
In the following sixth to eleventh embodiments, the object, as well as the catalyst 100 and the molecular gas, is irradiated with light.
A seventh embodiment of the present invention is shown in
In the present embodiment, high-frequency power is applied between the first electrode 41 and the second electrode 43 from the discharge power source 5 to generate discharge plasma 48, thereby generating Ar2 excimer light. By applying the Ar2 excimer light onto the catalyst 100 through the light extraction window 7, activated species cracked on the catalyst 100 can be easily separated from the catalyst 100. For example, NH, H, and the like are produced from the NH3 as the separated activated species. The activated species, such as NH and H, are jetted onto the object 9 from the activated species jet 47 of 1 mm by 1,000 mm. In the present embodiment, by shifting the object 9 or the treatment apparatus 40, the entire surface of the object 9 can be easily treated even if the object 9 has a large area.
An eighth embodiment is shown in
In the present embodiment, high-frequency power is applied between the first electrode 51 and the second electrode 53 from the discharge power source 5 to generate discharge plasma 58, thereby generating Ar2 excimer light. In addition, the discharge plasma 58 and the Ar2 excimer light directly act on the hydrogen contained in the discharge gas to partially change the hydrogen molecules into activated H. Furthermore, the hydrogen molecules are adsorbed and dissociated on the catalyst to crack into H. By applying the Ar2 excimer light onto the catalyst 100, the separation of the activated H is promoted to produce high-concentration activated H. The resulting activated H is jetted onto the object 9 from the activated species jet 57 of 1 mm by 1,000 mm. In the present embodiment, by shifting the object 9 or the treatment apparatus 50, the entire surface of the object 9 can be easily treated even if the object 9 has a large area and high-speed treatment can be achieved.
In the present embodiment, the light applied onto the catalyst 100 and the object 9 has a wave number of 5.43×104 cm−1 corresponding to the emission line spectrum of mercury. Other conditions, such as the distances form the object 9 and the temperature of tungsten serving as the catalyst 100, are the same as in the fifth embodiment. In an example of the present embodiment, a glass substrate for liquid crystal display was used as the object 9 and treated as in the fifth embodiment. As a result, the glass substrate was cleaned by treating it for about 45 seconds.
In an eleventh embodiment according to the present invention, SiO2 is etched. The treatment apparatus of the eleventh embodiment has the same structure as in
Thus the present invention possesses a number of advantages or purposes, and there is no requirement that every claim directed to that invention be limited to encompass all of them.
The disclosure of Japanese Patent Application No. 2004-043391 filed on Feb. 19, 2004 including specification, drawings and claims is incorporated herein by reference in its entirety.
Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
Number | Date | Country | Kind |
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2004-043391 | Feb 2004 | JP | national |