阅读说明：本技术 一种光掩模板保护装置 (Photomask plate protection device ) 是由 顾峥 伍强 李艳丽 于 2020-06-15 设计创作，主要内容包括：本发明公开了一种光掩模板保护装置,包括：一对反射镜,所述反射镜相对平行设置；激光管,设于其中一个所述反射镜的一端,用于以一定的倾斜角度,向对面的另一个所述反射镜发射激光束；其中,利用所述激光束在两个所述反射镜之间来回反射,在光掩模板上形成激光阻挡网,使污染颗粒在受到激光束冲击后发生移动,并从所述光掩模板的关键区域上移除。本发明能有效防止颗粒污染光掩模板,减少有机物污染,避免缺陷印刷,并能提高成品率,提高光刻的工作效率。(The invention discloses a photomask plate protecting device, which comprises: a pair of mirrors, the mirrors being arranged in parallel relative to each other; the laser tube is arranged at one end of one of the reflectors and is used for emitting laser beams to the other reflector opposite to the reflector at a certain inclination angle; and the laser beam is reflected back and forth between the two reflectors to form a laser blocking net on the photomask plate, so that the pollution particles move after being impacted by the laser beam and are removed from a key area of the photomask plate. The invention can effectively prevent particles from polluting the photomask plate, reduce organic pollution, avoid defective printing, improve the yield and improve the working efficiency of photoetching.)

1. A photomask plate protection device, comprising:

a pair of mirrors, the mirrors being arranged in parallel relative to each other;

the laser tube is arranged at one end of one of the reflectors and is used for emitting laser beams to the other reflector opposite to the reflector at a certain inclination angle;

and the laser beam is reflected back and forth between the two reflectors to form a laser blocking net on the photomask plate, so that the pollution particles move after being impacted by the laser beam and are removed from a key area of the photomask plate.

2. The reticle protection device of claim 1, wherein the mirrors are disposed on opposite sides of a frame disposed on a photomask placement table, the reticle being placed on the photomask placement table within the frame.

3. The reticle protection device of claim 2, wherein at least one laser tube is disposed on the frame at an end of one of the mirrors.

4. A reticle protection device according to claim 1 or 3 wherein the mirrors are multilayer high reflection film planar mirrors.

5. The photomask plate protecting device of claim 4, wherein the reflectivity of the multilayer high-reflectivity film plane mirror is greater than or equal to 99.9%.

6. The reticle protection device of claim 1 wherein the tilt angle is an angle relative to a normal direction of the mirror surface, the size of the tilt angle is adjusted according to a required laser beam density, and the tangent of the tilt angle is not less than a radius of a laser beam spot divided by a distance between the two mirrors.

7. The reticle guard of claim 1, wherein the laser tube is a pulsed laser tube.

8. The reticle guard of claim 7, wherein the pulsed laser tube has a single pulse of energy driving contaminant particles in lateral motion at a speed of no less than 1 cm/s.

9. The reticle protection device of claim 1, wherein the critical area is an exposure area.

10. The photomask plate protecting device of claim 1, wherein the laser tubes are arranged in plurality and are used alternately.

Technical Field

The invention relates to the technical field of integrated circuit manufacturing and photoetching, in particular to a special photomask plate protecting device which does not use a protective film to prevent particle pollution.

Background

Protection of EUV reticles against defects during use of, for example, EUV (extreme ultraviolet) reticles remains a challenge for EUV lithography.

Referring to fig. 1, fig. 1 is a schematic diagram of a conventional mask structure. As shown in fig. 1, at present, a protective film is generally used on the surface of an EUV mask to prevent particles from contaminating the mask. The main metal pollution of the current model of extreme ultraviolet light 33X0 comes from chromium, iron, titanium, aluminum and the like. The mask plate is provided with a reflecting layer, the pattern area is positioned on the reflecting layer, and the protective film is positioned on the pattern area. The extreme ultraviolet light penetrates through the protective film to irradiate the mask plate, is reflected by the reflecting layer and then is reflected out of the mask plate through the protective film.

It is important to consider the protective film material and optimize it. The thickness of the protective film is generally in the order of nanometers, and thus the flexibility caused by gravity is large, and particularly, deformation is easily generated when being heated, as shown in fig. 2, which shows a flat initial state of the protective film and a sagging deformed state of the protective film. While the use of a frame or grid support reduces the flexibility of the protective film, it still causes severe non-uniform intensity distribution and variations in local Critical Dimension (CD) and overlay uniformity. Therefore, when a protective film is employed on the surface of an EUV reticle to prevent particle contamination, the protective film must be thin enough and transparent enough to transmit EUV light and to block any particles from being out of focus during exposure.

At 13.5nm extreme ultraviolet wavelength, most materials are highly absorbing and exposed to high intensity EUV light and are present in the constantly evacuated environment of the vacuum system. Various options have been explored to address the problems of light transmission and film durability of protective films. The basic challenge is that the protective film to be manufactured needs to be thin enough to limit the impact on the imaging, while being robust enough.

Polysilicon-based films are suitable for use at exposure powers below 200W, but tend to loose strength at higher powers. EUV films based on materials such as silicon nitride, graphite, ceramics, etc. have therefore been proposed as an alternative material to polysilicon. While each material can meet some specification requirements, none of the materials can meet all of the requirements.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a photomask plate protecting device.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a photomask blank protection device comprising:

a pair of mirrors, the mirrors being arranged in parallel relative to each other;

the laser tube is arranged at one end of one of the reflectors and is used for emitting laser beams to the other reflector opposite to the reflector at a certain inclination angle;

and the laser beam is reflected back and forth between the two reflectors to form a laser blocking net on the photomask plate, so that the pollution particles move after being impacted by the laser beam and are removed from a key area of the photomask plate.

Further, the reflecting mirrors are provided on opposite sides of a frame provided on a photomask placing table in which the photomask is placed.

Furthermore, the number of the laser tubes is at least one, and the laser tubes are arranged on the frame and positioned at one end of one of the reflectors.

Further, the reflecting mirror is a multilayer high-reflection film plane reflecting mirror.

Furthermore, the reflectivity of the multilayer high-reflection film plane reflector is more than or equal to 99.9 percent.

Further, the inclination angle is an angle relative to the normal direction of the surface of the reflecting mirror, the size of the inclination angle is adjusted according to the required laser beam density, and the tangent value of the inclination angle is not less than the radius of a laser beam spot divided by the distance between the two reflecting mirrors.

Further, the laser tube is a pulse laser tube.

Further, the pulsed laser tube has a single pulse of energy that drives contaminant particles in a lateral motion at a speed of no less than 1 cm/s.

Further, the key area is an exposure area.

Further, the laser tubes are arranged in a plurality and are used alternately.

The invention adopts a special protection mode of treating pollution particles without a protection film, can avoid the problem of efficiency loss caused by insufficient heat pressure and firmness and light transmittance when the protection film is adopted in the prior art, can effectively prevent particles from polluting a photomask plate, reduce organic matter pollution, avoid defective printing, improve the yield, reduce the problem diagnosis and photomask plate cleaning time caused by photomask plate pollution, improve the working efficiency of extreme ultraviolet lithography (EUVL), and save the cost and the period for developing a photomask plate protection film. The invention is especially suitable for the extreme ultraviolet lithography technology with the power of more than 250W.

Drawings

Fig. 1 is a schematic diagram of a conventional mask structure.

Fig. 2 is a schematic view of the state of the protective film deformed by gravity and heat.

Fig. 3 is a schematic structural diagram of a photomask protecting apparatus according to a preferred embodiment of the invention.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

In the following detailed description of the embodiments of the present invention, in order to clearly illustrate the structure of the present invention and to facilitate explanation, the structure shown in the drawings is not drawn to a general scale and is partially enlarged, deformed and simplified, so that the present invention should not be construed as limited thereto.

In the following detailed description of the present invention, please refer to fig. 3, fig. 3 is a schematic structural diagram of a photomask protecting apparatus according to a preferred embodiment of the present invention. As shown in fig. 3, a reticle protecting apparatus of the present invention includes: a mirror 12 and a laser tube (laser) 13.

Please refer to fig. 3. The mirrors 12 are provided in pairs on a photomask placing table (not shown), and are arranged in parallel with their mirror surfaces facing each other.

The mirrors 12 may be mounted on opposite sides of one frame 11. Then, the frame 11 is mounted on the photomask placing table, and a photomask plate is placed on the photomask placing table inside the frame 11.

Please refer to fig. 3. At least one laser tube 13 is provided. The laser tube 13 may be horizontally installed on the frame 11 and disposed on one end of one of the two mirrors 12 while facing the direction of the other mirror 12 opposite thereto at a certain inclination angle θ.

The mirror 12 may be provided in a stack of layers. The reflector 12 can be a high-reflectivity planar reflector 12 with a reflectivity of more than or equal to 99.9%. For example, a frame 11 having a size of about 110mm × 140mm may be used, and a multilayer high reflection film plane mirror 12 having two parallel surfaces is mounted on the frame 11. The reflectivity of the high reflection film plane reflector 12 to the used laser wavelength is more than or equal to 99.9 percent. The frame 11 and the high reflection film plane mirror 12 may be integrally bonded to the photomask placing stage with epoxy resin glue.

The laser tube 13 is used to emit a laser beam to the other mirror 12 on the opposite side. The laser tube 13 may be a gas pulse laser tube 13.

The inclination angle θ of the laser tube 13 when emitting the laser beam is a relative angle θ with respect to the direction of the normal 14 of the surface of the mirror 12. The size of the inclination angle theta can be adjusted according to the required laser beam density, and when the laser beam density needs to be large, the inclination angle theta can be reduced. But the tangent of the tilt angle theta should be no less than the radius of the laser beam spot divided by the distance between the two mirrors.

For example, when the diameter of the spot 16 is 2mm and the distance between the two mirrors 12 is 110mm, the tangent value of the inclination angle θ is not less than 0.0091 as large as 1mm/110 mm.

By using the principle that the laser beam can be reflected back and forth between the two reflecting mirrors 12, a dense laser blocking net 15 can be formed on the photomask plate. After laser emission, the laser beam can impact the pollution particles at a certain speed, so that the pollution particles can move rapidly after being impacted by the laser beam pulse, and can be effectively removed from a key area of the photomask plate under continuous pulse impact, and the pollution particles can be effectively blocked by the laser beam. The key area can be an exposure area of a photomask plate.

The basic calculation model of the working principle of the laser tube 13 of the present invention can be as follows:

the single photon momentum p satisfies:

when the laser power is 20w and the frequency is 6kHz, the single-pulse energy E satisfies the following conditions:

when the laser spot size is 2 × 2mm²When the temperature of the water is higher than the set temperature,

the single photon energy e satisfies:

assuming that the particle radius r is 50nm, the particle mass m satisfies:

the number of photons n of a single pulse (over a circular area with a diameter of 50 nm) satisfies:

the total momentum P satisfies:

P＝np＝8.5×10⁶×8.3×10^-28kgm/s＝6.8×10^-21kgm/s

the velocity v obtained by the contaminating particles then satisfies:

the laser tube 13 uses a pulsed laser whose power and repetition rate must meet the requirement that a single pulse of energy is sufficient to drive the contaminating particles in a lateral motion at a speed of not less than 1 cm/s. For example, when the organic matter is impacted by the pulse laser, the organic matter generates kinetic energy and speed, so that the organic matter can rapidly generate motion and be bombarded on an exposure area of the photomask, and the velocity obtained after single particle bombardment and collision is at least 1 cm/s.

Further, a plurality of laser tubes 13 may be provided. For example, one laser tube 13 may be provided at one end of one mirror 12 on each side and used to emit laser light to the other mirror 12 on the opposite side, respectively, but the two laser tubes 13 are used alternately. This reduces the attenuation associated with long-term use of a laser tube 13.

The above description is only a preferred embodiment of the present invention, and the embodiments are not intended to limit the scope of the present invention, so that all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be included in the scope of the present invention.