KR101272039B1 - Apparatus and method for Defect Detection of reflective mask for EUV Lithography - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting a reflective mask defect for an extreme ultraviolet exposure process, and more particularly, to a defect mask of a reflective mask through reflected light that is reflected by irradiating EUV light onto a reflective mask for an extreme ultraviolet exposure process. The present invention relates to a defect detection apparatus and method for a reflective mask for an extreme ultraviolet exposure process capable of detecting and imaging in-situ thereof . Detection and imaging can be processed in-situ to increase the productivity of the mask used in the extreme ultraviolet exposure process, the next-generation exposure technology.

Extreme ultraviolet, defect detection, resolution

Description

Apparatus and method for Defect Detection of reflective mask for EUV Lithography}

The present invention can detect defects with high reliability and can simultaneously process defect detection and imaging in a device that can be used for an extreme ultraviolet exposure process that can increase the productivity of a mask used in an extreme ultraviolet exposure process, which is a next-generation exposure technology. A reflective mask defect detection apparatus and method.

Lithography processes are currently the technology that has the most direct impact on miniaturization of semiconductor devices. The miniaturization of devices is not only the miniaturization of the product itself, but also the productivity of how many devices can be processed simultaneously on a single wafer, that is, directly related to the price competitiveness of each device.

The development of the semiconductor industry, therefore, can be said to reflect the history of lithography technology. As a result, device manufacturers and research institutes in each country have always made the development of this lithography technology the top priority and have made all their efforts in R & D to be ahead of the competition.

Lithography has evolved along Moore's law's device's growth prediction curve, and technology is being developed by developing light sources with shorter wavelengths to overcome resolution limitations. With the development of visible-ultraviolet-ultraviolet light in the past, it is possible to use KrF (248nm) and ArF (193nm) excimer lasers through g-line (436nm), h-line (405nm) and i-line (365nm). It became. As it is now difficult to further shrink wavelengths in the far-ultraviolet region, double patterning technology with various resolution enhancement techniques (RET) such as proximity effect correction, phase shift mask, and distortion lighting for further extension of resolution limits. It is studied until introduction. However, despite this technology, there is still another problem of the limitation of the light source to achieve 22 nm resolution.

Under these circumstances, the International Semiconductor Association (ISA) has proposed a candidate group for the next generation lithography process currently under study through a roadmap. These are several techniques such as proximity x-ray lithography (PXL), electron beam projection lithography (EPL), proximity electron lithography (PEL), extreme ultraviolet lithography (EUVL), maskless lithography (ML2), nanoimprint lithography (NIL), and more. .

Among the various technologies mentioned above, Extreme Ultraviolet Lithography (EUVL) has been discussed as the only alternative that has the capacity for large-scale production, as in current lithography. According to the 2007 ITRS announcement, the EUVL is applied to the actual device production as the next most applicable technology after 193nm immersion double patterning technology at 32nm based on DRAM half pitch, and at 22nm. It was rated as the highest technology.

EUV has the property of being scattered in a medium such as a material or air, so that it is not possible to use a transmissive mask in the exposure process and use a reflective mask for EUV of 13.5 nm.

When applied to reflective masks using metrology equipment that has been applied to transmissive masks, resolution and defect detection sensitivity are not satisfactory. In particular, defect inspection equipment is difficult to meet the specifications required when manufacturing a mask without using a device using a 13.5nm beam, it is urgent to develop a device using a 13.5nm beam.

Currently, the development of defect inspection equipment using a 13.5nm beam is being made, but the development of equipment applicable to the semiconductor production process has not been made.

In order to solve the above problems, an object of the present invention is to provide a defect detection apparatus and a defect detection method using the same for manufacturing a reflective mask used in the extreme ultraviolet exposure process, which is a next-generation exposure technology.

In order to achieve the above object, the present invention provides a

A stage having a support surface for receiving a reflective mask;

A light source unit for irradiating EUV light onto the reflective mask;

A defect detector for detecting the defect area by collecting light reflected from the reflective mask; And

A defect imaging unit for imaging evaluation of the region by collecting the reflected light by irradiating EUV light to the defect region,

Provided is a mask defect detection apparatus for an extreme ultraviolet exposure process capable of in-situ processing for detection of a defect area of a reflective mask and imaging of this portion.

In addition,

Load the reflective mask onto the stage's support,

EUV light is generated through plasma discharge of the light source unit,

EUV light is irradiated over the entire surface of the reflective mask,

Collecting defects reflected from the reflective mask to detect a defect area of the reflective mask by a defect detector;

Irradiating EUV light locally on a defect area of the reflective mask,

Collecting light reflected from the reflective mask to image a defect area in a defect imaging unit;

Provided is a method for detecting defects in a reflective mask for an extreme ultraviolet exposure process that can process in-situ detection and imaging of defect areas of a reflective mask.

The apparatus and method according to the present invention can detect with high sensitivity the defects of the reflective mask used in the extreme ultraviolet exposure process and have high reliability for the detection result. Such an apparatus and method are preferably applied to the mass production of masks used in the extreme ultraviolet exposure process.

The present invention provides an apparatus capable of detecting defects of a reflective mask used in an extreme ultraviolet exposure process and a defect detection method using the same.

1 and 2 are schematic diagrams showing a detection apparatus according to the present invention.

The detection apparatus includes a stage 10, a light source unit 20, a defect detection unit 30, and a defect imaging unit 40 in the chamber, and an interface 51 as necessary.

First, the stage has a support 11 for accommodating the reflective mask M, and an X-Y driver (not shown) is mounted at the bottom thereof to allow horizontal movement. Also, if necessary, a position sensor may be mounted to adjust the position of the reflective mask M or to control the measurement position.

The light source unit 20 is a device unit for generating EUV light and irradiating the reflective mask M. The light source unit 20 together with the light source 21, such as a shutter 23, a pinhole 25, a filter 27, and a mirror 29, may be used. An optical member is provided.

The light source 21 is for emitting EUV light, and in particular, an apparatus for generating extreme ultraviolet rays of 13.5 nm is used. For example, EUV light may be generated through plasma discharge, and the plasma discharge may be laser plasma, discharge plasma, or high temperature plasma.

EUV light emitted from the light source 21 is transmitted to the reflective mask M along a predetermined path. In this case, the EUV light is transmitted through reflection through a plurality of optical members, that is, the shutter 23, the pinhole 25 and the filter 27, the mirror 29, and, if necessary, a plurality of mirrors.

The shutter 23 is arranged to adjust the amount of irradiation light of the EUV light, and the pinhole 25 is arranged for interfering light among the EUV light.

The plasma emitted from the light source 21 includes both EUV light and vacuum ultraviolet (VUV), where a filter 27 is placed to selectively pass only EUV light and remove other light. The zirconium filter is used as the filter 27, and EUV light passing through the filter 27 is reflected by the mirror 29 and is incident on the reflective mask M on the support 11.

The mirror 29 may be a spherical mirror and a planar mirror according to its shape, and may be a condensing mirror or a reflective mirror depending on its role. One or more mirrors 29 may be used. In the case of using a plurality of mirrors, the mirrors 29 are arranged on the same axis so that the rotational center axes are substantially coincident with each other, and the EUV light can be satisfactorily incident on the reflective mask M at an incident angle of 0 to 25 °. To place. As an example, the incident angle with respect to the mask surface currently used in the extreme ultraviolet exposure process is generally 6 ㅀ, and the apparatus according to the present invention also allows EUV light to be incident at an angle of 6 ㅀ tilt from the normal of the reflective mask. It can be configured to be. At this time, the mirror 29 may be a multilayer thin film structure, preferably a Mo-Si-based multilayer thin film.

The arrangement order or the number of the optical member, that is, the shutter 23, the pinhole 25 and the filter 27, and the mirror 29 is not particularly limited in the present invention and can be changed by a person skilled in the art.

In addition, if necessary, additionally known optical members can be disposed. For example, a diffraction grating may be used to extract only EUV light having a wavelength of 13.5 nm among the light emitted from the light source 21, where the diffraction grating may be disposed before or after the filter 27.

The defect detection unit 30 is a device configuration for detecting a defect area of the reflective mask M. As shown in FIG.

EUV light incident on the reflective mask M on the support 11 is reflected again. At this time, the reflected light is collected and analyzed to detect a defective area of the reflective mask M. FIG. The defect detection unit 30 is composed of a reflectance meter 31 for collecting the reflected light, converts it into an electrical signal and outputs it, and a detector 33 for detecting a defect region through the electrical signal information.

The reflectivity meter 31 is a device for generating a voltage corresponding to the intensity of the reflected light to be collected, and may be a photomultiplier tube (PMT), a photodiode, a phototransistor, or a phototube, and preferably a photodiode. . The information of the reflected light collected by the reflectometer 31 may be identified through the detector 33 equipped with a module that performs a calculation process.

In addition, the defect detecting unit 30 performs a calibration for preventing a measurement error caused by the reflectance measuring device 31, for example, photodiode deterioration, and the correction is performed when the reflective mask M surface is placed. The reference mirror fabricated in the same structure as the reflective mask M may be disposed on the stage.

In addition, the defect detector 30 may further include a light source member, for example, a shutter (not shown) for protecting the reflectivity meter 31 before the reflected light arrives at the reflectivity meter 31.

The defect imaging unit 40 is an apparatus configuration for imaging evaluation of a defect area of the reflective mask M detected through the defect detection unit 30.

The defect imaging unit 40 is for imaging the defect region by analyzing a field spectrum of light reflected from the reflective mask M, and proceeds through an optical path of EUV light separate from the defect detection unit 30. Accordingly, a light source member for entering EUV light from the light source 21, for example, the mirrors 41 and 43, an imaging device 45 which collects and converts a field spectrum of reflected light into an electrical signal and outputs the electrical signal information. Computational device 47 for imaging the defect area through the.

As described above, the mirrors 41 and 43 may use one or more spherical mirrors and planar mirrors, which are arranged on the same axis so as to overlap the rotational center axes so that the focal positions are approximately coincident with EUV light from 0 to 25. It is arranged so as to be incident on the reflective mask M at an angle of incidence of °, preferably at an angle of 6 °.

In particular, the defect detection unit 30 inspection region and the defect imaging unit 40 inspection region are the same so that the defect region detection of the reflective mask M and the imaging of the defect region can proceed simultaneously with the movement of the mask stage without an additional alignment system. Position the mirror so that it is within the driving range of the stage.

The imaging device 45 may use a Charge Coupled Device (CCD), which is one of sensors for converting a field spectrum of reflected light into a charge to obtain an imaging. In addition, the computing device 47 uses an apparatus for reconstructing imaging through a program through the imaging information (phase and amplitude) half from the imaging device 45.

In addition to such arithmetic unit 47, the above-described detector 33 may be provided with an interface 51 such as a PC so that a large amount of data can be processed in a short time.

The above mentioned devices (except the interface) are each arranged in the chamber. The chamber is evacuated by a separate gas exhaust unit (ie, a vacuum pump) for controlling the generation and pressure of EUV light to maintain a vacuum state.

The device according to the invention may further comprise equipment such as an ellipsometer (not shown) for characterizing mask defects and a mass spectrophotometer (not shown) for gas analysis present in the chamber.

An ellipsometer is a device that detects the polarization state reflected from the sample. After the EUV light is irradiated onto the reflective mask M, the reflected light is detected by the polarizer (analyzer, analyzer) to obtain the polarization state of the reflected light. Information of the reflective mask M can be obtained at a resolution up to Angstroms. In addition, since the amplitude and phase of the polarized light are simultaneously measured, they are very sensitive to the thin film and the surface layer, and thus the atomic hole layer and the atomic partial layer can be analyzed. The ellipsometer includes a PM tube, a photodiode, etc. as a detector, and uses a polarizer to set or analyze polarization, and it is possible to configure a compensator or a phase modulator as necessary.

A method of detecting a defect of the reflective mask by using the apparatus as described above will be described with reference to FIG. 3.

First, the reflective mask M to be inspected is loaded onto the support 11 of the stage in the chamber (S1).

Next, EUV light is generated through plasma discharge (S2).

The plasma discharge may be a laser plasma, a discharge plasma, or a high temperature plasma, and the generated light passes through the shutter 23, the pinhole 25, and the zirconium filter 27 sequentially because the generated ultraviolet rays include ultraviolet rays and vacuum ultraviolet rays.

Next, EUV light is irradiated over the entire surface of the reflective mask M loaded on the support 11 (S3).

The position and angle of the plurality of optical members, that is, the mirror 29 or the like are adjusted as necessary so that the irradiated EUV light may be incident on the reflective mask M at an angle of 6 °.

Next, after collecting the reflected light reflected from the reflective mask (M) in the reflectivity meter (31) (S4), it is analyzed by the detector 33 to detect a defect (S5).

Various devices can be used as the reflectometer 31, and in the embodiment of the present invention, the photodiode and the detector are used to identify surface defects.

When the light is irradiated, the light is reflected at the same reflection angle as the incident angle, and the reflected light is reflected differently according to the surface state of the reflective mask M, that is, the defect present on the surface. The reflected light reflected from the reflective mask M is continuously collected through the photodiode to output a photocurrent, and the output photocurrent is proportional to the intensity of the reflected light. The remaining elements except the defect show the same or similar current change pattern because of the regularity, but the irregular current change pattern when the defect exists. Therefore, the intensity of the reflected light reflected from the reflective mask M through the photocurrent output from the photodiode can be known.

Subsequently, the correct defect region of the reflective mask M is identified through the coordinate information of the reflective mask M using a detector equipped with a module that detects a photocurrent change and performs a calculation process.

Next, for imaging the defect area of the reflective mask M, EUV light is irradiated locally to the defect area (S6).

The irradiated EUV light is incident on the reflective mask M through the mirrors 41 and 43, which are a plurality of optical members whose positions and angles are adjusted in advance so as to be incident at an angle of 6 degrees. .

Next, after collecting the field spectrum of the reflected light reflected from the reflective mask (M) in the imaging measuring unit 45 (S7), the field spectrum of the reflected light is analyzed by the computing device 47 to image the defect area (S8).

Various apparatuses can be used for imaging the defective region, and in the embodiment of the present invention, the CCD 45 and the computing unit 47 are implemented.

In other words, when the reflected light is collected on the photodiode of the CCD, electrons are generated according to the amount of photons, and the amount of electrons of the photodiode represents the brightness of light, thereby reconstructing the information to form image information. At this time, the field spectrum of the light reflected from the defect area of the reflective mask M has a predetermined amplitude and phase, which depends on the shape of the defect area. The amplitude can be measured experimentally by the operation unit 47, the phase can be calculated computationally using a Hybrid Input Output (HIO) algorithm. Electromagnetic waves with a field spectrum with a specific amplitude and phase reconstruct the image through inverse Fourier transform. As a result, it is possible to confirm the image of the local defect area of the reflective mask M. FIG.

As described above, not only the detection of defects of the reflective mask for the extreme ultraviolet exposure process using the apparatus according to the present invention, but also the in-situ detection of defects can be performed by locally imaging the area. In other words, not only the presence of defects but also the imaging of defect states not only increases reliability of defect detection of the reflective mask, but also enables immediate inspection to increase productivity of the reflective mask. .

As such, the apparatus and method according to the present invention can be suitably applied to the fabrication of defect-free reflective masks for mass production of extreme ultraviolet exposure processes.

As described above, preferred embodiments of the present invention are disclosed for purposes of illustration, and any person skilled in the art may make various modifications, changes, additions, etc. within the spirit and scope of the present invention. Changes, additions, and the like should be considered to be within the scope of the claims.

1 and 2 are schematic diagrams showing a detection apparatus according to the present invention.

3 is a flowchart showing a detection method according to the present invention.

Claims (13)

A stage having a support surface for receiving a reflective mask; An X-Y driver positioned at the bottom thereof to enable horizontal movement of the stage; A light source unit for irradiating EUV light onto the reflective mask; A defect detector for detecting the defect area by collecting light reflected from the reflective mask; And A defect imaging unit for imaging evaluation of the region by collecting the reflected light by irradiating EUV light to the defect region, The defect detection unit and the defect imaging unit are installed on the same stage drive shaft, and the reflective mask for the extreme ultraviolet exposure process that simultaneously detects the defect region of the reflective mask and processes the imaging of the portion through horizontal movement by the XY driver. Fault detection device. The method of claim 1, And the EUV light has a wavelength of 13.5 nm. The method of claim 1, The light source unit includes a light source for emitting EUV light; A shutter for adjusting an amount of light of the EUV light; A pinhole for adjusting the size of a beam and interference of EUV light passing through the shutter; A zirconium filter for selectively removing light other than EUV light passing through the pinhole; And a mirror for reflecting EUV light emitted from the light source along a predetermined path. The method of claim 3, And the mirror is a spherical mirror or a planar mirror. The method of claim 3, And the mirror has a Mo-Si multilayer thin film structure. The method of claim 1, The EUV light reflective mask defect detection apparatus for an extreme ultraviolet exposure process, characterized in that configured to be incident to the reflective mask at an angle of inclination 6 ° from the normal. The method of claim 1, The defect detecting unit includes a reflectance measuring instrument for collecting reflected light, converting the converted light into an electrical signal, and a detector for detecting a defective area through the electrical signal information. The method of claim 7, wherein The reflectivity measuring device is a reflective mask defect detection device for an extreme ultraviolet exposure process, characterized in that the photodiode. The method of claim 1, The defect imaging unit includes a light source member through which EUV light from the light source unit is incident, an imaging apparatus that collects and converts a field spectrum of reflected light into an electrical signal, and an arithmetic apparatus that images a defect region through the electrical signal information. Reflective mask defect detection apparatus for extreme ultraviolet exposure process characterized by the above-mentioned. 10. The method of claim 9, The imaging device is a reflective mask defect detection device for an extreme ultraviolet exposure process, characterized in that the CCD (Charge Coupled Device). delete delete Load the reflective mask to a support of the stage; EUV light is generated through plasma discharge of the light source unit, EUV light is irradiated over the entire surface of the reflective mask, Collecting defects reflected from the reflective mask to detect a defect area of the reflective mask by a defect detector; Irradiating EUV light locally on a defect area of the reflective mask, Collecting light reflected from the reflective mask to image a defect area in a defect imaging unit; And detecting a defect of a reflective mask for an extreme ultraviolet exposure process capable of simultaneously processing the detection and imaging of the defect area of the reflective mask by driving the defect area detection and imaging through horizontal motion in the same stage.

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