WO2008002045A1

WO2008002045A1 - Method for forming predetermined patterns on a wafer by direct etching with neutral particle beams

Info

Publication number: WO2008002045A1
Application number: PCT/KR2007/003068
Authority: WO
Inventors: Suk-Jae Yoo; Bong-Ju Lee
Original assignee: Korea Basic Science Institute
Priority date: 2006-06-29
Filing date: 2007-06-25
Publication date: 2008-01-03
Also published as: KR100754369B1

Abstract

There is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, comprising a) penetrating the neutral particle beam through a mask into which the pattern is formed, b) directly colliding the neutral particle beam passed through the mask with the wafer onto which no photo-resist is coated, and c) removing wafer-forming material of a region that comes in contact with the neutral particle beam to form negative pattern on the wafer. The method makes it possible to form the pattern on the wafer by direct etching, even without coating of the photo-resist, exposure, developing or removal of the photo-resist. And it avoids disadvantages caused by direct contact of shields with the wafer, such as difficulty in the organized arrangement of the shields onto the wafer and damage to the wafer by the shields.

Description

METHOD FOR FORMING PREDETERMINED PATTERNS ON A WAFER BY DIRECT ETCHING WITH NEUTRAL PARTICLE

BEAMS

Technical Field

[1] The present invention relates to a method for forming predetermined patterns on a wafer. More particularly, the present invention relates to a method for forming predetermined patterns on a wafer by direct etching with neutral particle beams. Background Art

[2] Conventional methods that have been widely used for lithography is optical lithography, which is shown in Fig. 1. Such an optical lithography comprises an exposure step of exposing to a light a resist 30 formed on a wafer 20 which are masked by a proximately positioned mask 10 having a patterned image thereon, and a developing step of etching the exposed region (or unexposed region) with a developing solution. The theoretical resolution of the optical lithography is determined by Formula 1:

[3] Formula 1

[4] λ

Resolution = k r NA

[5] wherein, k represents system coefficient, λ represents wavelength and NA represents numerical aperture.

[6] As shown in Formula 1, as the wavelength of the light is reduced, the resolution is upgraded and smaller feature size is obtained. Two representative light sources are KrF laser with 248 nm wavelength and ArF laser with 193 nm wavelength. The theoretic resolution for optical lithography using the ArF laser is 70 nm, while about 75 nm feature sizes have been currently achieved. Although optical lithography using F laser with a shorter wavelength (wavelength: 157 nm, resolution: 65 - 50 nm) is being attempted, it has yet not to be widely adopted due to high costs associated with equipment exchange.

[7] Examples of NGL (Next Generation Lithography) to form fine patterns having below 70 nm feature sizes include those that employ optical sources such as EUV (Extreme Ultraviolet, wavelength: 10 - 100 nm) or X-ray, and those that employ particle beam sources such as electron beam or ion beam. An exemplary technology of EUVL (Extreme Ultraviolet lithography) is to form an image on the wafer using light source with 13.5 nm wavelength and a mask with a magnification ratio of 4. Although EUVL is a potential NGL source that is currently being developed with much worldwide interest, it uses a reflective mirror instead of an optical lens system. As a result, markedly low reflecting efficiency of the reflective mirror will continue to make developing a new EUV source difficult. An example of using X-ray as an NGL light source is PXL (Proximity X-ray Lithography) in which X-ray with a wavelength of 1.3 nm is used for lithography through a mask located at a proximity of a wafer with a patterned image thereon. However, due to the limitation of its 1:1 imaging ratio, this method has the disadvantage of requiring a mask having a high resolution image thereon.

[8] Unlike a photon (a light particle), the wavelength of an electron beam or an ion beam is defined by Formula 2, suggested by de Broglie:

[9] Formula 2

[10]

mυ

[11] wherein, λ is wavelength, h is Planck's constant, m is particle mass and v is particle velocity.

[12] As shown in Formula 2, the wavelength of particle beams could be substantially reduced by controlling the particle mass and the particle velocity. For instance, the wavelength of an electron with 100 keV is just 0.004 nm. As thus, from purely the wavelength aspect, the electron is much more favorable than the photon. As an electron beam lithography, PEL (Proximity Electronic-beam Lithography) that irradiates an electron beam onto a mask having a finely patterned image thereon and placed in a proximity of the wafer, and EPL (Electronic-beam Projection Lithography) that uses an optical lens system can be mentioned. However, the methods are also suffered from the blurring of an image caused by space charges that changes the electrons trajectory, which are generated by gathering of the charged electrons at a focal point.

[13] In order to overcome the problems mentioned above, a neutral particle beam lithography has been suggested. U.S. Patent No. 5,894,058 discloses a method of forming a fine pattern on the wafer. The patented method comprises directly distributing multiple fine particles, each of which works as a shield, onto a wafer and irradiating the surface of the wafer with collimated neutral atomic beams to form fine patterns thereon. However, the method has disadvantages that patterned arrangement of the fine particles on the surface of the wafer are not readily attained, and that direct contact of the fine particles with the wafer may cause damage to the surface of the wafer. Moreover, the above method removes the region that is not covered with the shield, and provides positive pattern on the wafer. However, the positive pattern has a limit to provide fine pattern. Specifically, in order to form 70 nm fine pattern on the wafer, the shield should have below 70 nm size. However, it is not easy to manufacture the shield having below 70 nm size. Disclosure of Invention Technical Problem

[14] An object of the present invention is to provide a method for forming a predetermined pattern on a wafer in a simple and efficient manner.

[15] Another object of the present invention is to provide a method for forming a predetermined pattern on a wafer that avoids the disadvantages caused by direct contact of the shield with the wafer, mentioned in the above.

[16] Further another object of the present invention is to provide a method for forming a predetermined pattern on a wafer in which negative pattern is formed on the wafer to obtain a highly fine pattern. Technical Solution

[17] According to a preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, comprising: a) penetrating the neutral particle beam through a mask into which the pattern is formed; b) directly colliding the neutral particle beam passed through the mask with the wafer onto which no photo-resist is coated; and c) removing wafer- forming material of a region that comes in contact with the neutral particle beam to form negative pattern on the wafer.

[18] According to another preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, wherein the neutral particle beam of the step a) is obtained from the steps of: a-1) inside a plasma discharging space, producing plasma of a processing gas through a plasma discharge; a-2) colliding plasma ions of the plasma with a metal plate positioned at top of the plasma discharging space to produce neutral particles; and a-3) penetrating the neutral particles through a plasma limiter positioned below the plasma discharging space and configured to have holes or slits to pass the neutral particles through while interrupting the plasma ions and electrons from passing through.

[19] According to further another preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, further comprising, while performing the plasma discharge of the step a- 1), applying a magnetic field to the plasma discharging space across the metal plate in order to increase density of the plasma ions near the metal plate. [20] According to most preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, further comprising, while performing the plasma discharge of the step a-1), applying magnetic field to the plasma discharging space across the metal plate by a magnetron unit comprised of a central pole and a side pole having a race track arrangement into which the side pole surrounds the central pole.

[21] According to still another preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, further comprising penetrating the neutral particles that had passed through the plasma limiter of the step a-3) through a collimator positioned below the plasma limiter in order to collimate the neutral particles.

[22] According to still yet another preferred embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, wherein the metal plate has concaved mirror shape and an aperture plate having an aperture is additionally installed at between the mask and the wafer to focus the neutral particle beam upon the aperture formed on the aperture plate.

[23] According to the specific embodiment of the present invention, there is provided a method for forming a pattern on a wafer by direct etching with neutral particle beam, wherein the processing gas is a chlorinated gas or a fluorinated gas and the wafer is a silicon wafer. Herein, the magnification of the mask is preferably adjusted in a range of 1 to 20.

Advantageous Effects

[24] The method of the present invention provides the following advantages:

[25] (1) The method of the present invention makes it possible to form a required pattern on the water by direct etching, even without coating of the photo-resist, exposure to light, developing with a developing solution or removal of the photo-resist, which are required in a conventional optical lithography.

[26] (2) The method of the present invention avoids the disadvantages caused by direct contact of the shield with the wafer, such as difficulty in patterned arrangement of shields that come in contact with the wafer and the damage to the wafer by the shields.

[27] (3) When focusing system is adopted, the method of the present invention does not depend upon the feature size of the mask. Specifically, the method makes it possible to easily form fine patterns smaller than 70 nm using the mask having feature size of 50 nm 200 nm that could be easily manufactured, by suitably adjusting the magnification ratio M.

[28] (4) The method of the present invention makes it possible to control the pathway of the neutral particles. Specifically, the production of the plasma through the plasma discharge and the production of the neutral particles by collisions of the plasma ion with the metal plate provide well collimated neutral particles and high conversion efficiency to the neutral particles. Brief Description of the Drawings

[29] Fig. 1 is a schematic diagram showing how an image is formed through a conventional optical lithography.

[30] Fig. 2 is a schematic diagram illustrating a preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams, in accordance with a preferred embodiment of the present invention.

[31] Fig. 3 is a schematic diagram illustrating a preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams in which the pattern is formed through proximity etching, in accordance with the present invention.

[32] Fig. 4 is a schematic diagram illustrating another preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams, in accordance with the present invention.

[33] Fig. 5 is a schematic diagram illustrating a preferred embodiment of the arrangement of the magnetron unit used in the method of the present invention.

[34] Fig. 6 is a schematic diagram illustrating further another preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams in which the pattern is formed through projection etching, in accordance with the present invention. Mode for the Invention

[35] The present invention relates to a method for forming a pattern on a wafer by direct etching with neutral particle beam. According to the present invention, the method comprises: a) penetrating the neutral particle beam through a mask into which the pattern is formed; b) directly colliding the neutral particle beam passed through the mask with the wafer onto which no photo-resist is coated; and c) removing wafer- forming material of a region that comes in contact with the neutral particle beam to for m negative pattern on the wafer.

[36] As used herein, "direct etching" means a process to etch the region that comes in contact with the neutral particle beam to form the pattern that is formed on the mask onto the wafer, by direct collision of the neutral particle beam with the surface of the wafer onto which no photo-resist is coated. As thus, the direct etching forms the predetermined pattern formed on the mask onto the water by direct collision of the neutral particle beam with the surface of the wafer onto which no photo-resist is coated. Herein, the mask is positioned above the wafer and is not in contact with the wafer. As a mask, a stencil mask having the magnification of 1 may be used. The stencil mask is located at a proximity of the water. The etching using the stencil mask may be called as proximity etching. When focusing system is adopted, the magnification of the mask is suitable adjustable up to 20, and this etching may be called as projection etching.

[37] Fig. 2 is a schematic diagram illustrating a preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams, in accordance with a preferred embodiment of the present invention. As shown in Fig. 2, the method of the present invention uses the neutral particle beam 100 to form a pattern on the wafer 600. The neutral particle beam 100 is not a charged one, contrary to the electron beam or ion beam. As thus, blurring caused by the change in the trajectory caused by space electric charge can be avoided, which is compared with the electron beam or the ion beam.

[38] The method of the present invention uses the mask 500 to form a pattern on the wafer 600. Onto the mask 500, a predetermined pattern is formed. The mask is positioned above the wafer and is not in contact with the wafer 600. This is distinguishable from shields that come in contact with the wafer 600, disclosed in US 5,894,058.

[39] The neutral particle beam 100 collides with the wafer 600 and etches the region of the wafer 600 that collides with the neutral particle beam 100. In this circumstance, the wafer 600 is not coated with any photo-resist. The neutral particle beam 100 etches wafer- forming material. This simplifies the etching process, compared with the conventional consecutive processes comprised of photo-resist doping, exposure, developing, and photo-resist removal. Further, the method of the present invention forms the pattern by negative etching. In order words, the pattern on the wafer 600 is a reflected image to the pattern formed on the mask 500. This is one of the distinguishing points from the positive etching formed by the shield, disclosed in US 5,894,058.

[40] Fig. 3 is a schematic diagram illustrating a preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams in which the pattern is formed through proximity etching, in accordance with the present invention. As mentioned in the above, the method of the present invention uses neutral particle beam 100 to form a pattern on the wafer 600. The neutral particle beam 100 is preferably produced by collision of plasma ions 102b of a processing gas produced inside a plasma discharging space 101 from a plasma discharge, with a metal plate 200 positioned at top of the plasma discharging space 101. Even though the neutral particle beam 100 may be produced by collision of the plasma with neutral processing gas, this is not adequate for the difficulty in the control of the directionality of the neutral particle and low production efficiency of the neutral particle beam 100. Therefore, such a technique is not suitable for direct etching with the neutral particle beam 100. The metal plate 200 converts the plasma ions 102b to neutral particles by collisions with the plasma ions 102b. The metal plate 200 may be made of tantalum (Ta), molybdenum (Mo), tungsten (W), gold (Au), platinum (Pt), stainless steel or alloys thereof, but are not limited thereto. Contrary to that of WO 01/84611 and WO 2004/036611, the metal plate 200 does not require any holes for the pathway of neutral particles. The plasma ions 102b produced inside the plasma discharging space 101 are directed to the metal plate 200 positioned at top of the plasma discharging space 101. This can be easily carried out by applying a minus bias voltage to the metal plate 200. The power of the bias voltage can be suitably adjustable depending upon the energy of the neutral particle beam to be required. Typically, the minus bias voltage has the strength of 10 - 100 V, preferably 30 - 50 V. When a minus bias voltage is impressed to the metal plate 200, the plasma ions 102b are directed to the metal plate 200 substantially or perfectively perpendicularly and collide with the metal plate 200. The surface of the metal plate 200, where plasma ions 102b collide, may be polished to improve conversion efficiency to neutral particles and to prevent energy loss during the collisions.

[41] In order to increase the production efficiency of the plasma ions 102b, magnetic field is applied across the metal plate 200 to the plasma discharging space 101. To accomplish this, a magnetron unit 700 is installed at the rear of the metal plate 200. Preferred embodiment of the arrangement of the magnetron unit 700 is shown in Fig. 5. As shown in Fig. 5, the magnetron unit 700 is comprised of a central pole 701 and a side pole 702 having a race track arrangement into which the side pole 702 surrounds the central pole 701. Herein, the upper of the central pole 701 has N pole (or S pole) and the bottom of the central pole 701 has S pole (or N pole), and the side pole 702 has complementary arrangement to the central pole 701. If necessary, the central pole 701 may be a permanent magnet and the side pole 702 may be a magnetic absorbent body. The magnetic field applied across the metal plate 200 by the magnetron unit 700 having race track arrangement controls the movement of the electrons 102a. In other words, it forces the electrons 102a to circulate around mirror race track inside the plasma discharging space 101. The electrons 102a rotating around mirror race track collides with neutral particles of the processing gas 102c that are not converted into plasma to produce plasma ions 102b. The plasma ions 102b thus produced are directed to the metal plate 200 with aid of the minus bias voltage. As a result thereof, the magnetic field applied across the metal plate 200 captures the electrons 102a around the race track and increases the density of the plasma ions 102b near the metal plate 200. The strength of the magnetic field by the magnetron unit 700 can be suitably adjustable depending upon the kind and the amount of the processing gas. Typically, the magnetic field having the strength of 1000 - 5000 gauss is applied. At below 1000 gauss, the strength is not enough to capture the electrons. At above 5000 gauss, it is not cost effective. The magnetron unit 700 is generally made of the permanent magnet. In order to reinforce the magnetic field inside the plasma discharging space 101, the magnetron unit 700 is preferably covered with a cover 703. Preferably, the cover 703 has high magnetic susceptibility to focus the magnetic field into the plasma discharging space 101 and to reduce the loss thereof. Generally, soft iron is widely used as magnetic shielding agent.

[42] By the collision with the metal plate 200, the plasma ions 102b undergo neutraliza tion such as auger neutralization. The neutral particles thus produced are reflected to the plasma discharging place 101 and enter, via the plasma discharging place 101, into a plasma limiter 300 positioned below the plasma discharging place 101. The plasma limiter 300 is configured to have holes or slits 301, preferably slits. These holes or slits 301 allow the neutral particles to penetrate while interrupting the passage of the plasma ions 102b and the electrons 102a so that the neutral particles could pass through the plasma limiter 300 selectively. To effectively prevent the plasma ions 102b and the electrons 102a from passing through the plasma limiter 300, a means 302 for applying magnetic field or electric field to the plasma limiter 300 could be additionally installed at the plasma limiter 300. The means for applying magnetic or electric field 302 changes the moving direction of the plasma ions 102b and the electrons 102a, and further prevents them from reaching to the surface of the wafer 600. In combination of the holes or silts 301 for the pathway of the neutral particle beam 100 with the means for applying magnetic or electric field 302, the plasma limiter 300 could avoid the adverse effects caused by the plasma ions 102b and the electrons 102a. More preferably, as shown in an inset of the Fig. 3, the plasma limiter 300 comprises a magnet 302a at a center to apply the magnetic field into the holes or slits 301, conductive metal membranes 302b positioned at both surfaces of the magnet 302a to apply the electric field into the holes or slits 301, and dielectric membranes 303 positioned at both surfaces of the conductive metal membranes 302b to insulate the conductive metal membranes 302b. In order to reduce the loss of the magnetic field applied by the magnet 302a, a magnetic shielding film 304 may be formed at bottom of the magnet 302a. As a magnetic shielding agent, any one well known in the art may be used. Preferable is soft iron. The conductive metal membranes 302b is connected to a power supply (not shown). Each of the dielectric membranes 204 may be formed of an insulating material or by oxidizing the surface of the conductive metal membrane 302b . The conductive metal membrane 302b may be partially formed at surface of the magnet 302b. If necessary, the magnetic shielding film 304 may be used as conductive metal membrane 302b. [43] Fig. 4 is a schematic diagram illustrating another preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams in accordance with the present invention. According to the preferred embodiment of the present invention, in order to improve the directionality of the neutral particle beam that had passed through the plasma limiter 300, a collimator 400 is additionally installed. The collimator 400 is configured to have multi holes 401. The neutral particles, which had collided with the side wall of the holes 401 more than once, loose their energy during collision, and can no longer perform their role. Therefore, of the neutral particles which had penetrated the collimator 400, the ones perpendicular to the holes 401 can be solely used. As thus, the directionality of the neutral particles is improved by the collimator 400. In general, the collimator 400 is made of dielectric material such as ceramics. Ceramic material absorbs the energy of the neutral particles through collision. Herein, a ratio of the length (L) to the diameter (R) of the hole 401 (L/R) is suitably adjustable regarding the operation condition (for exmaple, the pressure of the processing gas, the operation temperature, etc) and the etching profile to be formed. Most preferably, the length of the hole 401 is determined from a mean free path (a mean distance that the neutral particle can move without collision), and the diameter (R) is determined from the length of the hole divided by a ratio of the depth of the etching profile to the width of the etching profile. If the ratio of the depth of the etching profile to the width of the etching profile to be required is set to 10: 1, the ratio of the length (L) to the diameter (R) of the hole 401 (L/R) is preferably 10:1. When the processing gas is supplied at a pressure of 1 mTorr, the length (L) of the holes 401 is set to the mean free path (calculated as 2 cm) and the diameter of the hole 401 is set to 2 mm.

[44] The neutral particle beam 100 collimated by the collimator 400 enters into the mask

500 positioned below the collimator 400. Onto the mask 500, a predetermined pattern is formed. The mask 500 is positioned at a proximity of the wafer 600. The neutral particle beam 100 that had passed though the mask 500 collides with the wafer 600 and forms the pattern by direct etching formed on the mask 500 onto the wafer 600. For example, when the wafer is a silicon wafer, a fluorinated gas such as SF or CF may

6 4 be used as a processing gas. The processing gas is converted to plasma through a plasma discharge. Then, the plasma ions of the plasma are converted to the hyper- thermal neutral particles by collisions with the metal plate 200. Herein, the neutral particles preferably have 1 - 100 eV, more preferably 10 - 30 eV. The neutral particles having below 1 eV do not exhibit sufficient etching capacity, and the neutral particles having above 100 eV may cause physical damage to the wafer 600.

[45] The unexplained reference number 601 is a target holder moving up and down by operation of an elevating device connected to a elevating axis (not shown) so that it can carry in the wafer 600 such as a wafer to be newly processed and carry out the processed the wafer 600.

[46] Fig. 6 is a schematic diagram illustrating further another preferred embodiment of the method for forming predetermined patterns on a wafer by direct etching with neutral particle beams in which the pattern is formed through projection etching, in accordance with the present invention. As shown in the Fig. 6, the projection etching requires focusing of the neutral particle beam 100. In order to focus the neutral particle beam 100, the metal plate 200 has a concaved mirror shape. In combination with the metal plate 200 having concaved mirror shape, an aperture plate 800 having an aperture 801 at a center is additionally installed at between the mask 500 and the wafer 600. Herein, the focal point of concaved the metal plate 200 is adjusted to the aperture 801. The pattern formed by the projection etching shown in Fig. 6 is also the reflected image as shown in Figures 3 and 4, but it is a reversed image to the pattern of the mask 500. The feature size formed on the wafer 600 can be easily controlled simply by adequately adjusting the feature size of the mask 500 and the ratio ofthe distance (L') between the mask 500 and the aperture plate 800 to the distance (L) between the wafer 600 and the aperture 800. For instance, in order to form 20 nm fine patterns on the wafer 600, the feature size of the mask 500 may be set to 100 nm while the magnification ratio M (M=LVL) is adjusted to 5. To form 20 nm fine patterns on the wafer 600 using a mask 500 having 200 nm feature size instead of the mask 500 with 100 nm feature size, simple adjustment of the magnification M to 10 would be satisfactory. Therefore, the method further makes it possible to form a fine pattern with feature sizes less than 70 nm on the wafer without reducing the feature size of the mask 500, as well as to eliminate the undesired effects of non-linear neutral particles. Desirably, the magnification ratio M is adjusted to less than 20, because exceeding the ratio could lead to undesired effects caused by particles that exist in the space between the mask 500 and the aperture plate 800. The reference numerals, which are not specifically explained, are same as those above mentioned.

Claims

[1] A method for forming a pattern on a wafer by direct etching with a neutral particle beam, comprising: a) penetrating the neutral particle beam through a mask into which the pattern is formed; b) directly colliding the neutral particle beam passed through the mask with the wafer onto which no photo-resist is coated; and c) removing wafer- forming material of a region that comes in contact with the neutral particle beam to form negative pattern on the wafer.

[2] The method as set forth in claim 1, wherein the neutral particle beam of the step a) is obtained from the steps of: a-1) inside a plasma discharging space, producing plasma of a processing gas through a plasma discharge; a-2) colliding plasma ions of the plasma with a metal plate positioned at top of the plasma discharging space to produce neutral particles; and a-3) penetrating the neutral particles through a plasma limiter positioned below the plasma discharging space and configured to have holes or slits to pass the neutral particles through while interrupting the plasma ions and electrons from passing through.

[3] The method as set forth in claim 2, further comprising, while performing the plasma discharge of the step a-1), applying a magnetic field to the plasma discharging space across the metal plate in order to increase density of the plasma ions near the metal plate.

[4] The method as set forth in claim 3, wherein the magnetic field is applied to the plasma discharging space across the metal plate by a magnetron unit comprised of a central pole and a side pole having a race track arrangement into which the side pole surrounds the central pole.

[5] The method as set forth in claim 2, further comprising penetrating the neutral particle beam that had passed through the plasma limiter of the step a-3) through a collimator positioned below the plasma limiter and configured to have holes in order to collimate the neutral particles.

[6] The method as set forth in claim 5, wherein a length of each of the holes of the collimator is adjusted to a mean free path of the processing gas, and a diameter of each of the holes of the collimator is adjusted to a value that obtained from the length of the holes divided by a ratio of a depth of etching profile of the pattern to a width of the etching profile of the pattern.

[7] The method as set forth in claim 2, wherein the metal plate has concaved mirror shape and an aperture plate having an aperture is additionally installed at between the mask and the wafer to focus the neutral particle beam upon the aperture formed on the aperture plate. [8] The method as set forth in claim 2, wherein the wafer is silicon wafr and the processing gas is a chlorinated gas or a fluorinated gas. [9] The method as set forth in claim 2, wherein the mask is not in contact with the wafer and configured to have magnification of 1 to 20. [10] The method as set forth in claim 9, wherein the mask is a stencil mask configured to have magnification of 1 that is not in contact with the wafer and positioned at a proximity of the wafer.