WO2012118280A2

WO2012118280A2 - Apparatus for generating stabilized extreme ultraviolet light using plasma

Info

Publication number: WO2012118280A2
Application number: PCT/KR2012/000734
Authority: WO
Inventors: 장명식; 임재원
Original assignee: 주식회사 에프에스티
Priority date: 2011-02-28
Filing date: 2012-01-31
Publication date: 2012-09-07
Also published as: WO2012118280A3; KR101172622B1

Abstract

The present invention relates to an apparatus for generating stabilized extreme ultraviolet light using plasma, which comprises: a laser source which outputs a laser beam; a gas cell which receives the laser beam outputted from the laser source, receives gas supplied from a gas supply path, and generates extreme ultraviolet light by forming plasma by the laser beam and gas with respect to a plasma induction path corresponding to a section at which a focus is formed; a first vacuum chamber unit which accommodates the gas cell and maintains a constant vacuum; a second vacuum chamber unit which has a space to receive the extreme ultraviolet light generated by the gas cell and to emit the extreme ultraviolet light to the outside, and maintains a constant vacuum; a gas supply unit which supplies the gas supply path of the gas cell with gas for inducing the laser beam and plasma; and a first vacuum pump and a second vacuum pump for forming the vacuums of the first vacuum chamber unit and second vacuum chamber unit, respectively.

Description

Stabilized EUV Generator Using Plasma

The present invention relates to a stabilized extreme ultraviolet light generating apparatus using plasma, and more particularly, to a stabilized pole using plasma capable of generating effective and highly efficient Extreme Ultraviolet (EUV) light while simplifying a structure. An ultraviolet generator.

As the degree of integration of a semiconductor integrated circuit increases, the circuit pattern becomes finer, and the resolution of the exposure apparatus using visible light or ultraviolet rays, which have been conventionally used, is insufficient. In the semiconductor manufacturing process, the resolution of the exposure apparatus is proportional to the numerical aperture (NA) of the transfer optical system and inversely proportional to the wavelength of light used for exposure. For this reason, as an attempt to increase the resolution, an attempt has been made to use an Extreme Ultraviolet (EUV) light source having a short wavelength instead of visible or ultraviolet light for exposure transfer. As the EUV light generating device used in such an exposure transfer device, there are a laser plasma EUV light source and a discharge plasma EUV light source.

The wavelength used in the EUV exposure apparatus is an EUV light source having a wavelength of 13.5 nm, and the use of Ne plasma using Ne gas as a target material of a laser plasma light source has been widely researched and developed because of relatively high conversion efficiency (obtained with respect to input energy). EUV light intensity ratio). Since Ne is a gaseous material at room temperature, the problem of debris is difficult. However, in order to obtain a high output EUV light source, there is a limit to using Ne gas as a target, and it is also desired to use other materials.

When the laser plasma EUV light source is generated, excitation laser is absorbed, or EUV light, which is 13.5 nm generated from the plasma, is absorbed by the atmosphere or ordinary condensing mirror. There is a problem. In order to increase the efficiency of EUV light, a vacuum environment (<10 ^-3 torr) below a certain pressure is required, and a condenser mirror and a lens coated with a special material should be used.

Therefore, it is necessary to develop an EUV light generator using laser plasma more efficiently by applying such conditions.

The present invention for solving the above problems can be minimized by the vacuum induction and gas efficiency during the extreme ultraviolet ray generation by applying different vacuum degree of the plasma generation section and output section, and effectively reduce the EUV light source generated from the plasma It is an object of the present invention to provide a stabilized extreme ultraviolet generator using a plasma that can be collected.

It is also an object of the present invention to provide an automated extreme ultraviolet generator that can generate extreme ultraviolet rays accurately and effectively by automatically controlling alignment, beam monitoring, and beam uniformity of laser beams caused by extreme ultraviolet rays. .

The present invention for achieving the above object is a laser source for outputting a laser, the laser is supplied from the gas supply passage for the plasma induction furnace corresponding to the section in which the laser output from the laser source is in focus And a gas cell for generating extreme ultraviolet rays by forming a plasma by means of a gas and the gas cell, the first vacuum chamber part maintaining a constant vacuum degree, and receiving the extreme ultraviolet rays generated from the gas cells to receive the extreme ultraviolet rays. A second vacuum chamber part for maintaining a constant vacuum degree as a space for exiting to the outside, a gas supply part for supplying gas for guiding the laser and plasma into a gas supply path of the gas cell, and the first vacuum chamber part and a second vacuum chamber part; It comprises a first vacuum pump and a second vacuum pump for forming the vacuum degree of the vacuum chamber portion, respectively.

The second vacuum chamber portion may have a higher vacuum degree than the first vacuum chamber portion.

The first vacuum chamber part and the second vacuum chamber part may include a partition wall through which extreme ultraviolet rays are transmitted in one vacuum chamber, and the first vacuum chamber part and the second vacuum chamber part may be divided into a first vacuum chamber part and a second vacuum chamber part.

The apparatus may further include a driver including at least one focusing mirror and a reflecting mirror before the light emitted from the laser source is incident on the gas cell, and controlling a position and an angle of the focusing mirror and the reflecting mirror. It is done.

In addition, the second vacuum chamber unit, a dichroic mirror for reflecting only the extreme ultraviolet light incident from the first vacuum chamber to the outside, a beam splitter for dividing the remaining light transmitted through the dichroic mirror, the light split through the beam splitter An image sensor that detects focusing of a laser beam incident on the gas cell by receiving one of the light beams, and focusing provided at the tip of the image sensor or the image sensor to detect whether the laser beam is focused on each gas cell position And a light detector configured to detect a state of a laser beam by receiving the driving unit for driving the lens back and forth and the other light split by the beam splitter.

In addition, an ND filter or an analyzer may be further provided at the front end of the image sensor and the photo detector.

The first vacuum chamber unit may include a window for receiving a laser beam output from the laser source, and the window may be installed at a Brewster angle.

In addition, the gas cell is characterized in that formed of a transparent material.

In addition, the gas cell is characterized in that formed of quartz.

The gas cell may further include a gas cell pump and a gas drain part for maintaining the vacuum degree of the plasma induction furnace and draining the gas supplied through the gas supply path through the exhaust path.

The present invention constructed and operated as described above has an advantage of increasing plasma efficiency generated by using Ne gas for inducing plasma and effectively collecting optimal EUV light generated from plasma. In addition, by configuring the chamber portion having a different degree of vacuum, there is an advantage that can stably output the extreme ultraviolet rays generated in the gas cell.

In addition, the extreme ultraviolet ray generating apparatus using the plasma according to the present invention has the effect of having a small size and relatively high luminance than other EUV light sources.

In addition, by controlling the reflection angle and position through the drive unit and detecting the laser beam through the image sensor, the system automation of the extreme ultraviolet generator is realized, which improves precision, high-speed alignment, and safely controls the device. have.

1 is a schematic configuration diagram of a stabilized EUV apparatus using a plasma according to the present invention,

2 is a schematic configuration diagram of a gas cell for plasma induction of a stabilized extreme ultraviolet light generating apparatus using plasma according to the present invention;

3 is a configuration diagram of an extreme ultraviolet generator for automatic laser alignment according to another embodiment of the present invention;

4 shows an image sensor image for laser automatic alignment according to the embodiment of FIG. 3.

100: laser source

200: first vacuum chamber

201: second vacuum chamber

202: bulkhead

210: window

300: gas cell

310: gas supply passage

320: exhaust passage

330 plasma induction furnace

400: first reflection mirror

410: second reflecting mirror

420: Focusing Mirror

421: drive unit

430 dichroic mirror (dichroic mirror)

431 dichroic mirror drive unit

440: beam splitter

450: image sensor

451: Focusing Lens

452: image sensor driver

460: ND filter

470: photodetector

500 gas supply unit

600: first vacuum pump

610: second vacuum pump

620: Gas Cell Pump

630: gas drain portion

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the stabilized extreme ultraviolet light generating apparatus using a plasma according to the present invention.

The stabilized extreme ultraviolet ray generating apparatus using the plasma according to the present invention, the laser source 100 for outputting the laser, the laser output from the laser source in the plasma induction furnace 330 corresponding to the section in which the focus is received Gas chamber 300 receiving gas from the gas supply path 310 to form a plasma by laser and gas to generate extreme ultraviolet rays, and accommodating the gas cell to maintain a constant vacuum degree. A second vacuum chamber unit 201 which maintains a constant vacuum degree as a space for receiving the extreme ultraviolet rays generated from the gas cell and emitting the extreme ultraviolet rays to the outside, and the laser is supplied to the gas supply path of the gas cell. And a gas supply unit for supplying gas for inducing plasma and a first vacuum pump for forming vacuum degrees of the first vacuum chamber part and the second vacuum chamber part, respectively. And a second vacuum pump.

The stabilized extreme ultraviolet light generating apparatus according to the present invention has a light efficiency according to the degree of vacuum in the process in which EUV light is generated in the gas cell (first vacuum chamber part) and then EUV light is output outside the vacuum chamber using gas plasma. EUV stabilized by dividing the first vacuum chamber part 200 and the second vacuum chamber part 201 having different vacuum degrees, and performing EUV light generation and EUV light transmission functions in each chamber part to prevent degradation. It is a main technical point to provide an extreme ultraviolet generator capable of generating light.

1 is a schematic configuration diagram of a stabilized EUV apparatus using a plasma according to the present invention. As shown in the present invention, the laser source 100, the first vacuum chamber part 200, the gas cell 300, the second vacuum chamber part 201, the gas supply part 500, and the plurality of vacuum pumps 600 are large. 610, it is composed of a plurality of optical components for delivering a laser beam.

The laser source 100 is a source source for outputting a laser having an arbitrary wavelength. The laser source 100 generates extreme ultraviolet rays having a wavelength of 50 nm or less through plasma induction of the laser output from the laser source. In the present invention, for example, using a femto sencond-class laser source as a detailed specification as a medium titanium sapphire amplification laser system, Wavelength 800nm, Repetition rate 1kHz, Pulse duration <50fs, Energy per pulse> 3.5mJ at 1 kHz Laser sources with energy stability <0.5% and M ² <1.3 can be used.

The first vacuum chamber part 200 is an area in which extreme ultraviolet rays are generated, and the second vacuum chamber part 201 corresponds to an area for stably supplying extreme ultraviolet rays generated in the first vacuum chamber part. In the present invention, the plasma is induced by the laser beam and the gas supplied from the outside to generate the extreme ultraviolet rays, the extreme ultraviolet rays are generated through the gas cell to be described later. At this time, since a gas such as Ne, Xe, He, etc. is supplied into the gas cell from the outside, it is difficult to maintain a constant vacuum degree, and thus, in the chamber where the gas cell is located, EUV light efficiency generated in the gas cell may be reduced. Therefore, the gas cell is located in the first vacuum chamber portion which maintains a constant vacuum degree, and EUV light generated in the gas cell is transferred directly to the second vacuum chamber portion having a lower vacuum degree to prevent the efficiency from falling.

Here, the first vacuum chamber portion and the second vacuum chamber portion may be configured separately and have a structure to be delivered through the window, it is configured to maintain a different vacuum degree through a partition wall in a preferred embodiment of the present invention In addition, EUV light is transmitted through windows or microholes installed in the bulkhead.

The first vacuum chamber part and the second vacuum chamber part are configured with a first vacuum pump 600 and a second vacuum pump 610, respectively, to maintain different vacuum degrees, and to form a lower vacuum degree in the second vacuum chamber. A plurality of vacuum pumps suitable for this can be installed. For example, it consists of Medium Vacuum class vacuum pumps such as Cryo pump, Diffusion Pump, Turbo Pump and Ion pump. Vacuum chambers each portion is preferably first the 10 ^-3 torr or less, a second vacuum chamber maintained in a vacuum chamber to a vacuum degree of less than 10 ^-6 torr.

2 is a schematic configuration diagram of a gas cell for plasma induction of the extreme ultraviolet ray generating apparatus using the plasma according to the present invention. The gas cell is made of a transparent material, preferably made of quartz, a through path through which a laser can pass is formed, and in the center thereof, a plasma induction furnace 330 which is a focal region where a laser output from a laser source is focused. ), An exhaust path 320 is formed at both sides of the plasma induction furnace, and a gas supply path 310 for supplying gas to the plasma induction furnace is connected to the plasma induction furnace.

The plasma induction furnace corresponding to the center portion of the gas cell is focused by the laser output from the laser source, and the Ne gas is supplied through the gas induction furnace 310 passing through the plasma induction furnace from the external gas supply unit 500. Supply. In addition, exhaust paths 320 are formed at both sides of the plasma induction furnace to exhaust the supplied gas to the outside and maintain the degree of vacuum in the plasma induction furnace. If the gas supplied through the gas supply path is diffused outside the region where the laser focus is focused, smooth plasma induction may not be possible due to the scattering of gas particles. In addition, although a constant degree of vacuum is maintained in the plasma induction furnace, if the constant degree of vacuum cannot be maintained due to various problems of the vacuum system (vacuum chamber sealing, impurities, etc.), this exhaust gas may also be an obstacle to EUV light generation. Maintain gas evacuation and vacuum through the furnace. The exhaust path is exhausted through an external vacuum pump and exhausted through a gas drain 610 connected to the pump. In order to generate EUV light, it is important to make a plasma region by reacting a laser point light source with Ne gas. As mentioned above, the material of the gas cell is made of glass such as quartz, and it can be observed from the outside whether the plasma is generated normally by the reaction of the input laser light and the injection gas. The integrated gas cell is not only easy to replace, but also very advantageous for alignment after replacement, easy to drain the gas, and very effective in maintaining the vacuum of the vacuum chamber by reducing the amount of gas leaking from the gas cell into the vacuum chamber. .

In one embodiment according to the present invention, the diameter (A) of the plasma flow path, which is a plasma generation region closely related to the size of the point light source considering the inflow pressure of Ne gas and the laser power density, is 0.3 to 0.6 mm and the length ( B) consists of 5 to 10mm. The laser spot light source is first introduced into the gas cell, and the last emitted tube diameter (C) is manufactured with a diameter of 1 to 3 mm to avoid the interference caused by the size of the focused laser point light source and to minimize the inflow of Ne gas into the vacuum chamber. do.

Ne gas required for the reaction (D) is composed of 0.5 ~ 2mm, the supply pressure is limited to 30 ~ 100 torr, which is effective considering the power density of the laser point light source and the space region of the B section, the plasma generation region It is for plasma generation. In order to prevent the supplied Ne gas from flowing into the vacuum chamber through the point C, the diameter (E) is 5 to 10 mm larger than the diameter of the point C where the laser is introduced to facilitate the vacuum pumping. At this time, to make gas pumping more easily, give 30 to 60 degrees of inclination angle based on the entrance and exit direction.

Ultraviolet (EUV) light generated by plasma induction is generated through the gas cell configured as described above.

Referring back to FIG. 1, the gas cell 300 is positioned in the first vacuum chamber, and the laser output from an external laser source is incident to the gas cell to generate EUV light. In this case, a window 210 for transmitting a laser is provided at one side of the vacuum chamber. In the present invention, the window is positioned at Brewster's angle. Therefore, the reflection loss is minimized to minimize the femtosecond laser beam reflection loss.

The laser beam transmitted through the window is focused and transmitted through a plurality of mirrors to be focused on the plasma induction path of the gas cell. In an embodiment according to the present invention, a focusing mirror 420 is provided between the first reflecting mirror 400 and the second reflecting mirror 410 so as to effectively implement focusing and mechanical size (chamber size). It installs and delivers the beam to the gas cell. The first beam reflected and reflected by the first reflecting mirror is focused through the focusing mirror 420 and reflected by the second reflecting mirror. Light reflected back from the second reflection mirror is incident to the gas cell. As such, the configuration for light transmission can be easily changed, and if necessary, can be incident directly into the gas cell from the laser source.

In addition, the gas cell is configured to be located close to the partition wall, the extreme ultraviolet rays generated in the gas cell is transmitted to the second vacuum chamber portion is emitted to the outside in a more stable state by a low degree of vacuum. Here, the second vacuum chamber part is provided with a dichroic mirror (dichroic mirror; 430), and by adjusting the angle of the mirror, EUV light of wavelengths such as 13 nm and 6 nm of a desired size can be output. This can be implemented through a dichroic mirror driver 431 (picomotor) capable of controlling the angle of the dichroic mirror.

On the other hand, the present invention can provide an automated device for laser monitoring and automatic alignment implementation of the extreme ultraviolet generating device configured as described above. 3 is a diagram illustrating a configuration of an extreme ultraviolet generator for automatic laser alignment according to another embodiment of the present invention, and FIG. 4 is a view illustrating an image sensor image for automatic laser alignment according to the embodiment of FIG. 3.

First, referring to FIG. 3, an image sensor 450 installed outside the second vacuum chamber with respect to the beam axis emitted from the gas cell and an image sensor driver 452 for driving the image sensor in the beam axis direction are provided. In addition, the light detector 470 for detecting the state information such as optical power or output by reflecting the beam incident to the image sensor is provided, and the first and second reflecting mirrors, focusing mirror, dichroic mirror Each drive unit for controlling the angle is provided.

The driver 421 is mounted on the first reflecting mirror, the second reflecting mirror, and the focusing lens so that the light emitted from the laser source can be accurately focused in the plasma induction path of the gas cell, thereby implementing angle adjustment or position adjustment. At this time, a preferred example of the driving unit is a pico motor (Pico motor) is applied.

The image sensor 450 located on the gas cell beam axis is installed for beam alignment and beam monitoring. As shown in FIG. 4, beam spots for the first and second points of the gas cell can be detected. The image sensor is obtained by moving the image sensor in the optical axis direction by the separate image sensor driver 452, and the resultant value is fed back to the driver 421 to automatically control the beam alignment. The beam incident on the image sensor reflects extreme ultraviolet light through the dichroic mirror and enters the remaining transmitted light. In another embodiment, the focusing lens is installed at the tip of the image sensor to move the focusing lens to change the beam spot, thereby detecting whether the gas cell is focused.

Meanwhile, a beam splitter, such as a beam splitter 440, is installed in the middle of the beam axis incident to the image sensor and then reflects a part of the light incident to the image sensor to perform beam power monitoring, beam output check, beam status check, beam uniformity, and the like. In order to confirm, a photo detector such as a photo detector is installed outside the second vacuum chamber to detect an operating state of the extreme ultraviolet generator in real time. In addition, an ND filter or an analyzer 460 may be installed at the tip of the image sensor and the light detector to control an incident beam.

While the invention has been described and illustrated in connection with a preferred embodiment for illustrating the principles of the invention, the invention is not limited to the construction and operation as shown and described. Rather, those skilled in the art will appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims

A laser source for outputting a laser;

A gas cell configured to generate extreme ultraviolet rays by receiving a gas from a gas supply path to a plasma induction furnace corresponding to a section in which the laser output from the laser source is incident and focusing;

A first vacuum chamber part accommodating the gas cell and maintaining a constant vacuum degree;

A second vacuum chamber part configured to receive the extreme ultraviolet rays generated from the gas cell and maintain a constant vacuum degree as a space for emitting the extreme ultraviolet rays to the outside;

A gas supply unit supplying a gas for guiding the laser and the plasma into a gas supply path of the gas cell; And

And a first vacuum pump and a second vacuum pump for forming vacuum degrees of the first vacuum chamber part and the second vacuum chamber part, respectively.
The method of claim 1, wherein the second vacuum chamber portion,

Stabilized extreme ultraviolet light generating device using a plasma, characterized in that having a higher vacuum than the first vacuum chamber.
The method of claim 1 or 2, wherein the first vacuum chamber portion and the second vacuum chamber portion,

The stabilized extreme ultraviolet generator using the plasma, characterized in that the first vacuum chamber portion and the second vacuum chamber portion having a partition wall through which the extreme ultraviolet rays are transmitted in one vacuum chamber.
The method of claim 1,

And a driving unit having at least one focusing mirror and a reflecting mirror before the light emitted from the laser source is incident on the gas cell, and controlling the position and angle of the focusing mirror and the reflecting mirror. Stabilized extreme ultraviolet generator using plasma.
The method of claim 4, wherein the second vacuum chamber portion,

A dichroic mirror reflecting only the extreme ultraviolet light incident from the first vacuum chamber to the outside;

A beam splitter dividing the remaining light through the dichroic mirror;

An image sensor which receives one of the light split through the beam splitter and detects focusing of a laser beam incident on the gas cell;

A driving unit for driving the focusing lens provided at the front end of the image sensor or the front of the image sensor in order to detect whether the laser beam is focused for each position of the gas cell; And

And a light detector configured to detect the state of the laser beam by receiving the light split from the beam splitter and detecting the state of the laser beam.
The method of claim 5,

The front end of the image sensor and the photo detector is a stabilized extreme ultraviolet generator using a plasma characterized in that the ND filter or an analyzer is further provided.
The method of claim 1, wherein the first vacuum chamber portion,

And a window for receiving a laser beam output from the laser source, wherein the window is installed at a Brewster angle.
The method of claim 1, wherein the gas cell,

An apparatus for generating extreme ultraviolet rays using plasma, which is formed of a transparent material.
The method of claim 1, wherein the gas cell,

An extreme ultraviolet ray generating device using plasma, characterized in that formed of quartz.
The method of claim 1, wherein the gas cell,

And a gas cell pump and a gas drain part for maintaining the vacuum degree of the plasma induction furnace and draining the gas supplied through the gas supply path through the exhaust path.