CN103309177B - Workpiece platform system of photoetching machine - Google Patents

Abstract

A lithography machine workpiece platform system, including a frame, a base platform, two silicon wafer stages operating in an exposure station and a pretreatment station respectively, and a measuring grating, a dual-frequency laser, and a three-degree-of-freedom heterodyne grating interferometer And signal receiving and processing components. A three-free heterodyne grating interferometer is installed at the four corners of each silicon wafer stage, and the measuring grating is installed on the frame above the silicon wafer stage. The dual-frequency orthogonally polarized laser emitted by the dual-frequency laser is transmitted to the three-degree-of-freedom heterodyne grating interferometer through the optical fiber and then to the measurement grating. Measure optical signals to signal receiving and processing components. When the silicon wafer stage moves relative to the measuring grating, the six free displacements of the silicon wafer stage are obtained through calculation using the readings in the signal receiving and processing part. The lithography machine workpiece table system can improve the measurement accuracy, dynamic performance and other indicators of the silicon wafer table, thereby improving the overall performance of the lithography machine workpiece table system.

Description

A photolithography machine workpiece table system

technical field

The invention relates to a workpiece table system of a photolithography machine, in particular to a workpiece table system of a photolithography machine which uses a three-degree-of-freedom heterodyne grating interferometer to measure the displacement of a silicon wafer table.

Background technique

The lithography machine in semiconductor manufacturing equipment is the key equipment in the production of semiconductor chips. The ultra-precision workpiece table system is the core subsystem of the lithography machine, which is used to carry the mask plate and silicon wafer to complete the high-speed ultra-precision step-and-scan movement. The ultra-precision workpiece table system has become the most representative type of ultra-precision motion system due to its high-speed, high-acceleration, large-stroke, ultra-precision, and multi-degree-of-freedom motion characteristics. In order to realize the above-mentioned movement, the ultra-precision workpiece table usually uses a dual-frequency laser interferometer measurement system to measure the multi-degree-of-freedom displacement of the ultra-precision workpiece table. However, with the continuous improvement of motion indicators such as measurement accuracy, measurement distance, and measurement speed, dual-frequency laser interferometers have problems such as environmental sensitivity, difficulty in improving measurement speed, large space occupation, high price, and poor dynamic characteristics of the measurement target workpiece table. A series of problems make it difficult to meet higher measurement requirements.

Aiming at many problems in the application of dual-frequency laser interferometer in the position measurement of lithography machine workpiece table, in recent years, lithography machine manufacturers and research institutions in the world have carried out a series of research, the research mainly focuses on the use of grating measurement system to realize lithography The continuous improvement of the measurement requirements of the workpiece table, the research results have been disclosed in many patent papers.

U.S. patent document US7,102,729B2 (disclosure date: August 4, 2005) discloses a scheme for measuring the displacement of a workpiece table with multiple degrees of freedom using a grating measurement system, that is, multiple grating rulers are installed on the side and top surface of the workpiece table, The reading head corresponding to the grating scale is arranged around and on the top of the workpiece table; the defect of this scheme is that when the workpiece table moves in the x direction and the y direction in the horizontal plane, the side reading head cannot work, and there is no such thing in this patent document The corresponding solution is given, and there are other disadvantages in this scheme, such as the large laser optical path, which makes the measurement susceptible to environmental interference and affects the measurement accuracy, and the measurement scheme takes up a lot of space. U.S. patent document US7,940,392B2 (published on December 24, 2009) discloses another solution for measuring the multi-degree-of-freedom displacement of the workpiece table using a grating measurement system, that is, a planar grating is arranged above the workpiece table, and a plane grating is arranged on the top surface of the workpiece table. The corresponding grating reading head and the sensor used for vertical displacement measurement are arranged on the top. This solution does not have the problem of measuring back light and is not susceptible to environmental interference. However, the grating reading head in this solution can only measure horizontal displacement and vertical displacement. The measurement uses height sensors such as eddy currents or interferometers, and the use of multiple sensors in the measurement scheme not only affects the measurement accuracy of the workpiece table, but also increases the complexity of the scheme. U.S. patent document US7,483,120B2 (published on November 15, 2007) provides a specific implementation method of the above-mentioned measurement scheme, using 8 pieces of L-shaped plane gratings to be spliced as the workpiece table measurement grating, and four A grating reading head, but the patent scheme does not describe the degree of freedom of the reading head and the degree of freedom of the displacement measurement of the workpiece table. U.S. Patent Publication No. US2010/0321665A1 (published on December 23, 2010) discloses a grating reading head structure that can cooperate with planar grating measurement. Although the structure can measure vertical displacement, the reading head adopts the principle of homodyne measurement , there are disadvantages such as the measurement is susceptible to interference and the signal is difficult to process, and it is difficult to achieve high measurement accuracy. Chinese patent documents (Application No.: 201210449244.9, 201210448734.7) respectively disclose a heterodyne grating interferometer measurement system. The reading head structure of the two interferometer measurement systems uses a quarter-wave plate to change the polarization of the beam state, the optical structure is complex, and the non-ideality of the optical components will lead to measurement errors, which will increase the measurement error of using the grating interferometer to measure the displacement of the workpiece table; both interferometer measurement systems can only measure two degrees of freedom This will increase the number of interferometers arranged on the wafer stage, increase the difficulty of calculating the displacement of the workpiece stage, and reduce the measurement accuracy of the displacement of the workpiece stage.

Contents of the invention

Considering the limitations of the existing technical solutions, the object of the present invention is to provide a lithography machine workpiece table system, which uses a large-scale grating and a three-degree-of-freedom heterodyne grating interferometer to perform wafer table displacement Measurement. The three-degree-of-freedom heterodyne grating interferometer used in the system can achieve sub-nanometer measurement resolution and accuracy under high-speed, high-acceleration, and large-stroke conditions. At the same time, it has low environmental sensitivity, simple structure, small size, and light weight. , Easy to install and so on. The lithography machine workpiece table system adopts the measurement method of large-scale grating and three-degree-of-freedom heterodyne grating interferometer, which can realize the measurement of the six-degree-of-freedom displacement of the silicon wafer table with sub-nanometer accuracy, and can effectively reduce the volume and quality of the entire workpiece table system. , increase the dynamic performance of the silicon wafer stage and reduce the control difficulty of the silicon wafer stage, so that the overall performance of the photolithography machine workpiece stage system is improved.

Technical scheme of the present invention is as follows:

A photolithography machine workpiece platform system, including a frame, a base platform, and two silicon wafer stages respectively operating in an exposure station and a pretreatment station, characterized in that: the workpiece platform system also includes a measuring grating, a dual-frequency Laser, three-degree-of-freedom heterodyne grating interferometer and signal receiving and processing components;

The measuring grating adopts a planar reflective two-dimensional grating, which is composed of a measuring grating at the exposure station and a measuring grating at the pretreatment station. On the frame above the two wafer stages of the station, and the surface engraved with two-dimensional reflective grating grooves faces the upper surfaces of the two wafer stages;

Four three-degree-of-freedom heterodyne grating interferometers are respectively installed at the four corners of the two silicon wafer tables operating at the exposure station and the pretreatment station, and dual-frequency lasers are installed on the frame, which are respectively operated at the The four three-degree-of-freedom heterodyne grating interferometers on the silicon wafer stage of the exposure station and the four three-degree-of-freedom heterodyne grating interferometers running on the silicon wafer stage of the pre-processing station provide dual-frequency orthogonally polarized lasers, The dual-frequency laser provides reference electrical signals for the signal receiving and processing components at the same time;

The dual-frequency orthogonally polarized laser beams pass through each three-degree-of-freedom heterodyne grating interferometer and are vertically incident on the measurement grating to generate four beams of diffracted reflection light, which are retroreflected to the three-degree-of-freedom heterodyne grating for interference instrument, and then the three-degree-of-freedom heterodyne grating interferometer outputs four measurement optical signals, and the four measurement optical signals are sent to the signal receiving and processing components for processing;

When the two silicon wafer stages operating in the exposure station and the pretreatment station move relative to the measurement grating, the signal receiving and processing components output four sets of measurement displacements in the x, y and z directions respectively, and use eight sets of measurement displacements respectively. The six-degree-of-freedom displacement of the wafer stage operating in the exposure station and the pre-processing station is calculated from the value solution.

The three-degree-of-freedom heterodyne grating interferometer of the present invention includes a polarization beam splitter, a reference grating, a first refraction element and a second refraction element, and the surface of the reference grating is engraved with two-dimensional reflective grating groove lines; The orthogonally polarized laser is incident on the polarizing beam splitter and then split, the transmitted light is the reference light, and the reflected light is the measurement light;

After the reference light is incident on the reference grating, four beams of diffracted and reflected reference beams are generated, and the four beams of diffracted and reflected reference beams are deflected by the first refraction element to form four beams of parallel reference beams, and the four beams of parallel reference beams are reflected back to the polarizing beam splitter and then transmitted Four beams of transmitted reference light are formed; the measuring light is incident on the measuring grating to generate four beams of diffracted reflection measuring light, and the four beams of diffracted reflecting measuring light are deflected by the second refraction element to form four beams of parallel measuring light, and the four beams of parallel measuring light return to After being emitted to the polarization beam splitter, it is reflected to form four beams of reflected measurement light; the four beams of transmitted reference light and the four beams of reflected measurement light are respectively combined in pairs to form four-way measurement optical signals, and the four-way measurement optical signals are respectively transmitted to the signal receiving and processing through optical fibers. Parts are processed;

When the three-degree-of-freedom heterodyne grating interferometer moves linearly in the x-direction, y-direction and z-direction relative to the measuring grating, the signal receiving and processing components will output a three-degree-of-freedom linear displacement.

The preferred solution of the first refraction element and the second refraction element in the three-degree-of-freedom phase difference grating interferometer of the present invention is to use two right-angle prisms on the xoy plane and two right-angle prisms on the xoz plane to integrate the refraction prism.

Another preferred solution of the first refraction element and the second refraction element in the three-degree-of-freedom heterodyne grating interferometer of the present invention is to use lenses.

A heterodyne grating interferometer displacement measurement system provided by the present invention has the following advantages and outstanding effects:

Arranging this three-DOF grating interferometer in the lithography machine workpiece table system together with a large-scale grating can realize the measurement of the six-DOF displacement of the silicon wafer table with sub-nanometer precision, and can effectively reduce the volume and quality of the entire workpiece table system. The dynamic performance of the silicon wafer stage is increased and the control difficulty of the silicon wafer stage is reduced, so that the overall performance of the workpiece stage system of the lithography machine is improved. The three-degree-of-freedom heterodyne grating interferometer used in the lithography machine workpiece table system can achieve sub-nanometer measurement resolution and accuracy under high-speed, high-acceleration, and large-stroke conditions. At the same time, the measurement system has a simple structure, small size, Light weight, easy to install and so on.

Description of drawings

FIG. 1 is a schematic diagram of a workpiece table system of a lithography machine according to the present invention.

Fig. 2 is a schematic diagram of the relative positions of the measurement grating and the silicon wafer stage in the xoy plane of the present invention.

Fig. 3 is a schematic diagram of a structure embodiment of the first three-degree-of-freedom heterodyne grating interferometer of the present invention.

Fig. 4 is a schematic diagram of a second structure embodiment of a three-degree-of-freedom heterodyne grating interferometer according to the present invention.

In the figure, 1—frame; 2—vibration isolation foundation; 3—base platform; 4a—wafer stage at exposure station, 4b—wafer stage at pretreatment station; 5—measuring grating, 51 ——Measurement grating at exposure station, 52——Measurement grating at preprocessing station; 6——Double-frequency laser; 7——Three-degree-of-freedom heterodyne grating interferometer, 71——Polarization beam splitter, 72——Reference grating, 73—refractive prism, 74—lens; 8—signal receiving and processing components.

Detailed ways

The structure, principle and specific implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Please refer to Figures 1 and 2. Figure 1 is a schematic diagram of a lithography machine workpiece table system of the present invention, and Figure 2 is a schematic diagram of the relative positions of the measurement grating and the silicon wafer table in the xoy plane of the present invention, and the present invention is illustrated in conjunction with Figures 1 and 2 The lithography machine workpiece table system is described. As shown in Figure 1, the lithography machine workpiece table system includes a frame 1, a base table 3, a wafer table 4a running on the exposure station, and a wafer table 4b running on the pretreatment station; the workpiece table system also includes a measurement Grating 5, dual-frequency laser 6, three-degree-of-freedom heterodyne grating interferometer 7 and signal receiving and processing part 8, these parts are used to measure the silicon wafer stage 4a running in the exposure station and the silicon wafer stage 4a running in the pretreatment station Six degrees of freedom displacement of the film stage 4b.

The measurement frame 1 and the base 3 are placed on the vibration isolation foundation 2 through the vibration isolation device, and two wafer stages run on the base 3, that is, the wafer stage 4a running on the exposure station and the wafer stage 4a running on the pretreatment station. Wafer stage 4b, the two wafer stages are moved and exchanged according to the process arrangement, and the use of double wafer stages can effectively improve production efficiency.

Please refer to Fig. 1 and Fig. 2, the measurement grating 5 is made up of the exposure station measurement grating 51 and the pretreatment station measurement grating 52, the exposure station measurement grating 51 and the pretreatment station measurement grating 52 are respectively installed in the exposure station and the On the frame 1 above the two silicon wafer stages of the pretreatment station, the surface engraved with two-dimensional reflective grating groove lines faces the upper surfaces of the two silicon wafer stages. The measuring grating 5 adopts a plane reflective two-dimensional grating, and the surface appearance is a tiny grid array; the grating constant of the two-dimensional grating is usually on the order of microns, and the groove type of the two-dimensional grating adopts a specially designed square groove type to obtain The higher the ±1st order diffraction efficiency in the direction of the two grating vectors. The size requirements of the exposure station measurement grating 51 and the pretreatment station measurement grating 52 are very large (800mm×800mm), which is very difficult to manufacture. best way.

Four three-degree-of-freedom heterodyne grating interferometers 7 are respectively installed at the four corners of the silicon wafer stage 4a of the exposure station and the silicon wafer stage 4b of the pretreatment station, and a dual-frequency laser 6 is installed on the frame 1, and the optical fiber The transmission is respectively provided for the four three-degree-of-freedom heterodyne grating interferometers 7 running on the silicon wafer stage of the exposure station and the four three-degree-of-freedom heterodyne grating interferometers 7 running on the silicon wafer stage of the pre-processing station. Dual-frequency orthogonally polarized laser, the dual-frequency laser 6 provides reference electrical signals for the signal receiving and processing component 8 at the same time.

In fact, in order to meet the requirements of the laser power of the eight three-degree-of-freedom heterodyne grating interferometers and the layout of the silicon wafer stage, a dual-frequency laser is installed in the corresponding exposure station and pretreatment station on rack 1. 6. The four three-degree-of-freedom heterodyne grating interferometers 7 running on the wafer stage 4a of the exposure station and the four three-degree-of-freedom heterodyne grating interferometers running on the silicon wafer stage 4b of the pre-processing station respectively Instrument 7 provides dual-frequency orthogonally polarized laser light.

The dual-frequency orthogonally polarized laser beams pass through each three-degree-of-freedom heterodyne grating interferometer 7 and then are vertically incident on the measurement grating 5 to generate four beams of diffracted reflected light, which are retroreflected to the three-degree-of-freedom heterodyne grating interferometer 7. Then the three-DOF heterodyne grating interferometer 7 outputs four measurement optical signals, and the four measurement optical signals are sent to the signal receiving and processing unit 8 for processing.

In fact, in order to meet the layout requirements of the wafer stage cable, four three-degree-of-freedom heterodyne grating interferometers 7 operating on the wafer stage 4a of the exposure station and the wafer stage 4b operating on the preprocessing station are respectively Each of the four three-degree-of-freedom heterodyne grating interferometers 7 is provided with a set of signal receiving and processing components 8 .

When the two silicon wafer stages operating in the exposure station and the pretreatment station move relative to the measurement grating 5, the two sets of signal receiving and processing components 8 respectively output four sets of measurement displacements in x, y and z directions (z The direction is a small movement, and the movement range is about 1mm), and the six-degree-of-freedom displacement of the wafer stage running in the exposure station and the pre-processing station is calculated by using eight sets of measured values.

Please refer to FIG. 3 . FIG. 3 is a schematic diagram of a structure embodiment of a first three-degree-of-freedom heterodyne grating interferometer according to the present invention. As shown in FIG. 3 , the three-DOF heterodyne grating interferometer 7 includes a polarization beam splitter 71 , a reference grating 72 , a first refraction element and a second refraction element. The surface of the reference grating 72 is engraved with two-dimensional reflective grating groove lines for generating reference light, and has the same grating parameters as the measuring grating 5 . The first refraction element and the second refraction element are used for the propagating direction of the polarized light, and both adopt the refraction prism 73 integrated with two right-angle prisms located on the xoy plane and two right-angle prisms located on the xoz plane.

The dual-frequency laser 6 transmits the dual-frequency orthogonally polarized laser through an optical fiber and is incident on the polarizing beam splitter 71 to split the light. The transmitted light is the reference light, and the reflected light is the measurement light. light, the four beams of diffracted and reflected reference beams are deflected by the first refraction element to form four beams of parallel reference beams, and the four beams of parallel reference beams are retroreflected to the polarizing beam splitter 71 and then transmitted to form four beams of transmitted reference beams; the measurement beams are incident on the measurement After the grating 5, four beams of diffraction reflection measurement light are generated, and the four beams of diffraction reflection measurement light are deflected by the second refraction element to form four beams of parallel measurement light, and the four beams of parallel measurement light are reflected back to the polarizing beam splitter 71 to form four beams of reflection measurement light light; four beams of transmitted reference beams and four beams of reflected measurement beams are superimposed in pairs to form four measurement optical signals, which are respectively transmitted to the signal receiving and processing unit 8 via optical fibers for processing.

When the three-degree-of-freedom heterodyne grating interferometer 7 performs a linear motion of three degrees of freedom in the x direction, y direction and z direction relative to the measuring grating 5, the signal receiving and processing part 8 will output a three-degree-of-freedom linear displacement, and the three-degree-of-freedom The expression of motion displacement: x=k _x ×(α-β), y= _ky ×(γ-δ), z=k _z ×(α+β+γ+δ), k _x ＝Λ _x /4π , k _y =Λ _y /4π, k _z =λ/4(1+cosθ), where α, β, γ, and δ are the phase reading values of the signal receiving and processing part 8, and Λ _x and Λ _y are grating constants , λ is the laser wavelength, θ is the diffraction angle of the grating, Λ _x = Λ _y = 1 μm, λ = 632.8nm, the phase resolution of α, β, γ, δ is 2π/1024, the x, The measurement resolutions for y and z are 0.49nm, 0.49nm and 0.18nm, respectively.

Please refer to FIG. 4 , which is a schematic diagram of a second grating interferometer structure embodiment of the present invention. As shown in FIG. 4 , the first refraction element and the second refraction element of the grating interferometer 7 both use a lens 74 . Both the reference grating 72 and the measurement grating 5 are arranged at the focus of the two lenses 74, and the four beams of reference light diffracted and reflected from the reference grating 72 and the four beams of measurement light diffracted from the measurement grating 5 respectively enter the two lenses at a certain angle 74, after being deflected by two lenses 74, the output is parallel light. Compared with the use of refracting prisms, the structure of this scheme is simpler and easier to install and adjust. When changing the diffraction angle of the grating, there is no need to change the lens parameters and installation requirements, and the vertical The travel of the lens in the direction of the optical axis is relatively large.

Compared with the lithography machine workpiece table system using a laser interferometer to measure the displacement of the silicon wafer table, the work table system of the lithography machine that uses the grating to measure the displacement of the wafer table given in the above embodiment, on the basis of meeting the measurement requirements , can effectively reduce the volume and quality of the workpiece table, greatly improve the dynamic performance of the workpiece table, and comprehensively improve the overall performance of the workpiece table. The three-degree-of-freedom heterodyne grating interferometer used in the lithography machine workpiece table system can achieve sub-nanometer measurement resolution and accuracy under high-speed, high-acceleration, and large-stroke conditions. At the same time, the measurement system has a simple structure, small size, With the advantages of light weight and easy installation, in addition to the application in the lithography machine workpiece table system, the three-degree-of-freedom heterodyne grating interferometer can also be applied to precision machine tools, three-dimensional coordinate measuring machines, semiconductor testing equipment, etc. In precision measurement of degree of freedom displacement.

Claims (3)

1. a lithography machine stage system, comprise frame (1), base station (3), run on two silicon wafer stages exposing station and preprocessing station respectively, it is characterized in that: described workpiece table system also comprises measures grating (5), two-frequency laser (6), Three Degree Of Freedom heterodyne grating interferometer (7) and Signal reception and processing element (8);

Described measurement grating (5) adopts plane reflection type two-dimensional grating, measure grating (52) by exposure station measurement grating (51) and preprocessing station to form, exposure station measurement grating (51) and preprocessing station measurement grating (52) respectively correspondence are installed in the frame (1) above two silicon wafer stages exposing station and preprocessing station, and are carved with the upper surface of surface towards two silicon wafer stages of the two-dimentional reflection-type grating line of rabbet joint;

Four Three Degree Of Freedom heterodyne grating interferometers (7) are installed at the described corner place running on two silicon wafer stages of exposure station and preprocessing station respectively, frame (1) is installed two-frequency laser (6), by Optical Fiber Transmission be respectively run on exposure station silicon wafer stage on four Three Degree Of Freedom heterodyne grating interferometers (7) and four the Three Degree Of Freedom heterodyne grating interferometers (7) run on the silicon wafer stage of preprocessing station double frequency cross polarization laser is provided, two-frequency laser (6) provides reference electrical signal for Signal reception and processing element (8) simultaneously,

Described double frequency cross polarization laser respectively through each Three Degree Of Freedom heterodyne grating interferometer (7) afterwards vertical incidence to measuring grating (5), produce four bundle diffraction reflection light, four bundle diffraction reflection light retroeflection are to Three Degree Of Freedom heterodyne grating interferometer (7), then export four drive test amount light signals by Three Degree Of Freedom heterodyne grating interferometer (7), four drive test amount light signals are delivered in Signal reception and processing element (8) and process;

When described two silicon wafer stages running on exposure station and preprocessing station are respectively relative to measurement grating (5) motion, Signal reception and processing element (8) respectively export four groups of x, y and z to measuring displacement, utilize eight groups of measured values to calculate to run on the six-degree of freedom displacement of the silicon wafer stage of exposure station and preprocessing station respectively;

Described Three Degree Of Freedom heterodyne grating interferometer (7) comprises polarization spectroscope (71), with reference to grating (72), the first dioptric element and the second dioptric element, described reference grating (72) is carved with the two-dimentional reflection-type grating line of rabbet joint on the surface; Double frequency cross polarization laser is incident to polarization spectroscope (71) light splitting afterwards, and transmitted light is reference light, and reflected light is for measuring light;

Described reference light is incident to and produces four bundle diffraction reflection reference lighies afterwards with reference to grating (72), four bundle diffraction reflection reference lighies form four bundle parallel reference light through the first dioptric element post deflection, and four bundle parallel reference light retroeflection are to polarization spectroscope (71) transmission formation four bundle transmission reference light afterwards;

Described measurement light is incident to measurement grating (5) and produces four bundle diffraction reflections measurement light afterwards, four bundle diffraction reflections are measured light and are formed four bundle horizontal survey light through the second dioptric element post deflection, and four bundle horizontal survey light retroeflection to polarization spectroscope (71) back reflections form four bundle reflection measurement light;

Four described bundle transmission reference light and four bundle reflection measurement light coincidence formation between two four drive test amount light signal respectively, four drive test amount light signals process to Signal reception and processing element (8) through Optical Fiber Transmission respectively; When Three Degree Of Freedom heterodyne grating interferometer (7) relative to measure grating (5) carry out x direction, y direction and z direction three degree of freedom linear movement time, Signal reception and processing element (8) will export Three Degree Of Freedom linear displacement.

2. a kind of lithography machine stage system according to claim 1, is characterized in that: the first described dioptric element and the second dioptric element all adopt two right-angle prisms being positioned at xoy plane and be positioned at the integrated refractive prism (73) of two right-angle prisms of xoz plane.

3. a kind of lithography machine stage system according to claim 1, is characterized in that: the first described dioptric element and the second dioptric element all adopt lens (74).