Focusing and leveling system, focusing and leveling method and exposure device

Abstract

The invention provides a focusing and leveling system, a focusing and leveling method and an exposure device. According to the focusing and leveling system, a spectro-grating is arranged in front of a detector; light beams emitted by the light source unit are projected and imaged to a to-be-detected device after being transmitted by the projection grating, the light beams are reflected to the spectro-grating through the to-be-detected device, and the spectro-grating diffracts and separates signal light containing surface information of the to-be-detected device into two paths of signal light which are received by the detector. And the surface height of the device to be measured is represented by differential signals of the two paths of signal light separated through diffraction. The surface height of a to-be-measured device is represented by differential signals of two paths of signal light divided by the spectro-grating, and the whole focusing and leveling system is not provided with moving parts, so that the stability of the focusing and leveling system is improved, the reproducibility of the focusing and leveling system is improved, the maintenance time and frequency of the focusing and leveling system are reduced, the service life of the focusing and leveling system is prolonged, and the working efficiency of the focusing and leveling system is improved. And the yield of the whole machine is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography, and in particular to a focusing and leveling system, a focusing and leveling method, and an exposure device. Background Art

[0002] A projection exposure system projects the pattern on a mask onto a silicon wafer through an objective lens. During the exposure process, factors such as wafer thickness deviation, surface undulations, and the inaccuracy and non-repeatability of the focal plane of the projection objective (which produces a bright, clear, real image of the illuminated object on the screen) can cause the wafer to defocus or tilt relative to the focal plane of the projection objective. If this defocus or tilt causes certain areas of the exposure field to fall outside the effective depth of focus, it can severely impact the quality and yield of the integrated circuits. Therefore, a focus measurement system (FLS) is required to measure the height topography of the wafer surface before exposure. During the exposure process, the workpiece stage is controlled and continuously adjusted according to the wafer's surface topography, ensuring that the wafer surface is always positioned in the optimal focal plane of the projection objective, ensuring a clear image on the wafer.

[0003] For focusing measurement systems, there are a variety of different technical solutions for measuring the height topography of silicon wafer surfaces. To meet the requirements of accuracy, speed, non-destructiveness, and process adaptability, photoelectric sensors based on the triangulation principle are currently commonly used. The measured height is characterized by changes in the light intensity signal. To eliminate the effects of variations in the light source power and substrate reflectivity, a differential signal is required. To generate the differential signal, various spectroscopic methods are used, such as galvanometer modulation spectroscopic methods, Wollaston prism spectroscopic methods, fringe measurement methods, and triangular grating spectroscopic methods.

[0004] The following uses the galvanometer spectrometer solution as an example to explain the basic structure and working principle of the focusing measurement system. Figure 1 It is a schematic diagram of the principle of the focusing measurement system under the galvanometer spectrometer solution, which uses the reciprocating motion of the scanning reflector to modulate the light intensity, and characterizes the height of the object being measured by detecting the change in the differential signal. The light source module 101 of the focusing measurement system can provide a wide-band illumination beam. An optical object-image relationship is formed between the projection slit 102, the silicon wafer surface 103, the detection slit 104, and the detector 105. The focusing and leveling system also includes a projection light path optical imaging module 106, a detection light path optical imaging module 107, a relay light path optical imaging module 109, an illumination light path optical module 110 and a scanning galvanometer 108. As shown in FIG. Figure 1As shown, when the height of silicon wafer surface 103 changes, the corresponding light intensity reaching detector 105 through detection slit 104 changes. To eliminate the effects of light intensity variations and reflectivity differences at different locations on the silicon wafer surface on the measurement, a scanning galvanometer 108 is used to modulate the high-frequency modulation signal. The differential signal obtained through demodulation represents the change in the height of silicon wafer surface 103.

[0005] In this spectroscopic method, the scanning mirror is a moving component, typically vibrating at frequencies exceeding kHz. To ensure measurement accuracy, high requirements are placed on its amplitude and frequency stability. Under these conditions, prolonged operation poses a risk to the mirror's stability. To ensure the accuracy of the focusing measurement system, the scanning mirror requires regular calibration, maintenance, and replacement. This increases the maintenance time and frequency of the focusing measurement system, reduces its service life, and impacts overall machine productivity. Furthermore, time delays can introduce measurement errors.

[0006] Of course, there are other spectroscopic schemes that use fringe measurement methods to characterize the surface height of silicon wafers, which is essentially measuring phase changes. This scheme uses optical measurements under Scheimpflug conditions (SC conditions), but the structure is complex and feasibility is difficult. Summary of the Invention

[0007] The object of the present invention is to provide a focusing and leveling system, a focusing and leveling method and an exposure device to solve the above-mentioned problems in the prior art.

[0008] In order to solve the above technical problems, the present invention provides a focusing and leveling system, including a light source unit, a projection unit and a detection unit, the projection unit including a projection grating, and the detection unit including a spectroscopic grating and a detector; the light source unit is used to provide a light beam, and the light beam is projected and imaged onto the device under test after being transmitted through the projection grating, and the light beam is reflected by the device under test to the spectroscopic grating, and the spectroscopic grating diffracts and separates the signal light containing the surface information of the device under test into two signal lights, which are received by the detector, so as to characterize the surface height of the device under test through the differential signal of the two diffraction-separated signal lights.

[0009] Optionally, the spectroscopic grating includes a binary grating array.

[0010] Optionally, the binary grating array is a transmission grating or a reflection grating.

[0011] Optionally, the binary grating array includes periodically distributed black shadow areas and white shadow areas to spatially separate the signal light containing the surface information of the device under test into two signal lights: positive diffraction light and negative diffraction light.

[0012] Optionally, when the device under test is at zero position, half of all the sub-light spots passing through the projection grating are imaged in the black shadow area of the binary grating array, and the other half are imaged in the white shadow area of the binary grating array.

[0013] Optionally, the grating structures in the black shadow area and the white shadow area of the binary grating array are distributed in a mirror image.

[0014] Optionally, the number of periods of the binary grating array corresponds to the number of periods of the projection grating.

[0015] Optionally, the detector is a photodiode.

[0016] Optionally, the detector is a charge-coupled device, and the signal lights of different wavelengths in the positive diffraction light and the negative diffraction light have different diffraction angles in space and different imaging positions on the detector, so as to independently obtain the intensities of the signal lights of different wavelengths, and each signal light independently obtains a differential signal, and multiple differential signals are digitally processed by configuring different weights.

[0017] Optionally, the detection unit further includes a polarization splitting component, which is located in front of the detector and is used to split the signal light of different wavelengths into S-polarized light and P-polarized light. The S-polarized light and the P-polarized light are imaged on different detectors respectively to independently obtain the intensity of signal light of different polarization states and different wavelengths. A differential signal is independently obtained for each signal light, and multiple differential signals are digitally processed by configuring different weights.

[0018] Based on the same inventive concept, the present invention also provides a focusing and leveling method, in which the light beam emitted by the light source unit is projected and imaged onto the device under test after passing through the projection grating of the projection unit. The light beam is reflected by the device under test to the spectroscopic grating of the detection unit. The spectroscopic grating diffracts and separates the signal light containing the surface information of the device under test into two signal lights, which are received by the detector in the detection unit, so that the surface height of the device under test is represented by the differential signal of the two diffraction-separated signal lights.

[0019] Optionally, when the surface of the device under test is defocused, the intensities of the two signal lights increase and decrease, and the defocus amount of the surface of the device under test is represented by the differential signal of the two lights.

[0020] Optionally, the spectroscopic grating spatially separates the signal light containing the surface information of the device under test into two signal lights: positive diffraction light and negative diffraction light.

[0021] Optionally, the detector is a charge-coupled device, and the signal lights of different wavelengths in the positive diffraction light and the negative diffraction light have different diffraction angles in space. The imaging positions on the detector are different to independently obtain the intensities of the signal lights of different wavelengths, and each signal light independently obtains a differential signal. The multiple differential signals are digitally processed by configuring different weights.

[0022] Optionally, the defocus value of the device under test is:

[0023]

[0024] in, is the wavelength λ i The weight of The wavelength λ of the device under test i The reflectivity of the signal light, The light source unit has a wavelength λ i The proportion of signal light; is the defocus amount of the differential signal at different wavelengths.

[0025] Optionally, a polarization splitting component is arranged before the detector, and signal lights of different wavelengths pass through the polarization splitting component to form S-polarized light and P-polarized light. The S-polarized light and the P-polarized light are imaged on different detectors respectively to independently obtain the intensities of signal lights of different polarization states and different wavelengths. A differential signal is independently obtained for each signal light, and multiple differential signals are digitally processed by configuring different weights.

[0026] Optionally, the defocus value of the device under test is:

[0027]

[0028] in, is S polarized light, wavelength λ i The weight of P polarized light, wavelength λ i The weight of The wavelength λ of the device under test i , the reflectivity of S-polarized light, The wavelength λ of the device under test i , the reflectivity of P polarized light, The light source unit has a wavelength λ i , the proportion of S polarized light, The light source unit has a wavelength λ i , the proportion of P polarized light, Represents wavelength λ i , the defocus of S polarized light, Represents wavelength λ i , the defocus amount of P polarized light.

[0029] Based on the same inventive concept, the present invention also provides an exposure device, comprising any of the above-mentioned focusing and leveling systems.

[0030] In the focusing and leveling system provided by the present invention, a spectroscopic grating is provided in front of the detector; a light beam emitted by a light source unit is transmitted through a projection grating and then projected onto the device under test. The light beam is then reflected by the device under test to the spectroscopic grating, which spatially diffracts and separates the signal light containing surface information of the device under test into two signal lights, which are received by the detector. The differential signal of the two diffracted signal lights represents the surface height of the device under test. The present invention utilizes the differential signal of the two signal lights separated by the spectroscopic grating to represent the surface height of the device under test. The entire focusing and leveling system has no moving parts, which increases the stability of the focusing and leveling system, improves the reproducibility of the focusing and leveling system, reduces the maintenance time and frequency of the focusing and leveling system, increases the service life of the focusing and leveling system, and improves the overall machine productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0032] Figure 1 It is a schematic diagram of the principle of a focusing measurement system under a galvanometer spectrometer solution in the prior art.

[0033] Figure 2 Schematic diagram of a focusing and leveling system based on binary grating array spectroscopy according to an embodiment of the present invention.

[0034] Figure 3 Schematic diagram of the positional relationship between the projection grating and the binary grating array according to an embodiment of the present invention.

[0035] Figure 4 It is a schematic diagram of the light splitting effect of a single-period binary grating array structure according to an embodiment of the present invention.

[0036] Figure 5 4 is a curve diagram of the diffraction efficiency simulation results of the binary grating array according to an embodiment of the present invention.

[0037] Figure 6 Schematic diagram of the binary grating array spectroscopic imaging effect according to an embodiment of the present invention.

[0038] Figure 7 This is a simulation diagram of a curve showing a change in the differential signal of a measurement system with defocus according to an embodiment of the present invention.

[0039] Figure 8 FIG. 1 is a schematic diagram of the spectroscopic imaging effect of a binary grating array according to another embodiment of the present invention.

[0040] Figure 9 This is a schematic diagram of the spectroscopic imaging effect of a binary grating array according to another embodiment of the present invention.

[0041] Figure 10 It is a simulation curve diagram of the process error after digital weight processing under the typical process film layer structure of the embodiment of the present invention.

[0042] Figure 11 This is a simulation curve diagram of process error after digital weight processing under another typical process film layer structure of an embodiment of the present invention.

[0043] In the attached figure:

[0044] 101 - light source module; 102 - projection slit; 103 - silicon wafer surface; 104 - detection slit; 105 - detector; 106 - projection light path optical imaging module; 107 - detection light path optical imaging module; 108 - scanning galvanometer; 109 - relay light path optical imaging module; 110 - illumination light path optical module;

[0045] 201-light source unit; 202-projection grating; 203-device under test; 204-spectrometric grating; 204a-black shadow area; 204b-white shadow area; 205-detector; 206-projection light path imaging optical module; 207-detection light path imaging optical module; 208-illumination light path optical module; 209-relay imaging light path optical module; 701-detector; 801-polarization spectrometer assembly. DETAILED DESCRIPTION

[0046] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0047] As used in the present invention, the singular forms "a", "an", and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features specified as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features. In addition, as used in the present invention, an element is provided on another element, which generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements can be direct or indirect through an intermediate element, and should not be understood to indicate or imply the spatial position relationship between the two elements, that is, one element can be in any orientation such as inside, outside, above, below, or to the side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] Figure 2 FIG is a schematic diagram of a focusing and leveling system based on binary grating array spectroscopy according to an embodiment of the present invention. Figure 2 As shown, this embodiment provides a focusing and leveling system, comprising a light source unit 201, a projection unit, and a detection unit. The projection unit comprises an illumination optical path optical module 208, a projection grating 202, and a projection optical path imaging optical module 206. The detection unit comprises a detection optical path imaging optical module 207, a spectroscopic grating 204, a relay imaging optical path optical module 209, and a detector 205. The projection grating 202 and the spectroscopic grating 204 form an optical object-image relationship. The light source unit 201 is used to provide a light beam, and the illumination optical path optical module 208 collimates the light beam. The collimated light beam is transmitted through the projection grating 202 and then projected onto the device under test 203. The light beam is then reflected by the device under test 203 onto the spectroscopic grating 204. The spectroscopic grating 204 spatially diffracts and separates the signal light containing the surface information of the device under test into two signal lights, which are received by the detector 205. The surface height of the device under test 203 is characterized by the differential signal between the two diffracted signal lights.

[0049] It should be noted that in Figure 2The system includes two coordinate systems: one is the optical path coordinate system, where zp represents the direction of optical propagation or the optical axis, and xp and yp represent two directions in a plane perpendicular to the optical axis. The other is the physical coordinate system, which is the coordinate system where the device under test 203 resides. x represents the x-direction of horizontal position change of the device under test 203, y represents the y-direction of horizontal position change of the device under test 203, and z represents the direction of vertical position change of the device under test 203.

[0050] The light beam emitted by the light source unit 201 can be an ultraviolet beam, a visible beam, an infrared beam, or a mixture of the three bands, and can be a broadband beam. The illumination optical module 208 is used to collimate the light beam emitted by the light source unit 201 .

[0051] The projection light path imaging optical module 206 may include one or more refractive or reflective lenses for imaging the projection light beam onto the device under test 203. Of course, the projection light path imaging optical module 206 may also include optical lenses with special adjustment functions, such as wedges, parallel plates, aspherical mirrors, or free-form mirrors, for adjusting the imaging quality of the projection light path imaging optical module 206. Optionally, the projection light path imaging optical module 206 may also include an aperture for adjusting the field of view of the projection light beam.

[0052] DUT 203 can be a silicon wafer or any other surface requiring surface shape measurement in a precision machining process. Each projection beam forms an image on the surface of DUT 203 and is reflected by the surface to form a probe beam. The probe beams correspond one-to-one with the projection beams. The silicon wafer is tilted relative to the optical axis, resulting in diffused images on the wafer surface.

[0053] The detection light path imaging optical module 207 may include one or more refractive or reflective lenses for imaging the detection beam onto the beam splitter grating 204. Of course, the detection light path imaging optical module 207 may also include optical lenses with special adjustment functions, such as wedges, parallel plates, aspherical mirrors, or freeform mirrors, to adjust the imaging quality of the detection light path imaging optical module 207. Optionally, the detection light path imaging optical module 207 may also include an aperture to adjust the field of view of the detection beam. It should be understood that the detection light path imaging optical module 207 and the projection light path imaging optical module 206 may be symmetrically distributed on either side of the device under test 203.

[0054] In this embodiment, the spectroscopic grating 204 is, for example, a binary grating array. In other embodiments, the spectroscopic grating 204 may also be a triangular grating, which can also spatially split the light into two signal paths. The two signal paths are detected independently, and the differential signal is used to represent the height of the device under test.

[0055] Figure 3Schematic diagram of the positional relationship between the projection grating and the binary grating array in an embodiment of the present invention. The projection grating 202 is, for example, a transmission grating formed by coating an Al or Cr metal layer on a glass substrate. The grating period and angle of incidence of the projection grating 202 are determined by the range of the focusing and leveling system. The grating period of the projection grating 202 is, for example, 30 μm to 50 μm, and can be 40 μm. The binary grating array is a transmission grating or a reflection grating. In this embodiment, the binary grating array is, for example, a transmission grating, and includes periodically distributed black shaded regions 204a and white shaded regions 204b to spatially separate the transmitted diffracted light beam into two signal light paths: positive diffracted light and negative diffracted light. That is, the gratings in the black-shaded area 204a and the white-shaded area 204b are periodically distributed, and the corresponding transmitted diffracted light is spatially separated, labeled as +1-order diffracted light and -1-order diffracted light, or alternatively, as +3-order diffracted light and -3-order diffracted light. Therefore, the black-shaded area 204a is a transmission area for positive diffracted light, where positive diffracted light includes +n-order diffracted light, where n is an integer greater than 0; and the white-shaded area 204b is a transmission area for negative diffracted light, where negative diffracted light includes -n-order diffracted light, where n is an integer greater than 0. The binary grating array is periodically arranged, and the period number of the binary grating array corresponds to that of the projection grating, which can range from 15 μm to 40 μm. The projection grating 202 and the binary grating array are used in conjunction with each other, and they have a specific relative positional relationship. The specific positional relationship between the binary grating array and the projection grating 202 is such that when the device under test 203 is at zero position, half of all the sub-spots transmitted through the projection grating 202 are imaged within the black shaded area 204a of the binary grating array, and half are imaged within the white shaded area 204b of the binary grating array. In this embodiment, the device under test 203 is, for example, a silicon wafer. That is, when the silicon wafer surface is at zero position, half of all the sub-spots transmitted through the projection grating 202 are imaged within the +1st-order diffracted light transmission area, and half are imaged within the -1st-order diffracted light transmission area. When the silicon wafer surface is defocused, the positive and negative 1st-order diffracted light transmission areas increase and decrease, and the difference between the two signal light paths is used to represent the defocus of the silicon wafer surface.

[0056] Figure 4 This is a schematic diagram of the light splitting effect of a single-period binary grating array structure according to an embodiment of the present invention. The black shadow area 204a and the white shadow area 204b of the binary grating array have a mirror-image distribution. According to the grating formula, the specific period and order design of the grating are determined by the signal light wavelength and the light splitting angle requirements. The black shadow area 204a and the white shadow area 204b of the binary grating array have a mirror-image distribution, and can be plated with periodic steps of a specific size on a transparent substrate to achieve ±1 order diffraction light. Figure 4 As shown, the beam splitter grating 204 adopts a blazed grating structure, and the grating order is, for example, 4.

[0057] Figure 5 This figure shows the diffraction efficiency simulation results for a binary grating array according to an embodiment of the present invention. The material, period, and order of the binary grating array are selected based on the light source spectrum of the focusing and leveling system to achieve a good diffraction splitting ratio. The material for a reflective binary grating array can be metal, while the material for a transmissive binary grating array can be SiO2. For example, the period of the binary grating array is 1500nm-2000nm, and the height of the binary grating array is 500nm-600nm. Figure 5 This is the simulation result of the diffraction efficiency of a binary grating array. The horizontal axis is wavelength in nanometers (nm), and the vertical axis is diffraction efficiency. The input conditions for the binary grating array are as follows: wavelength is 200nm-400nm, the order of the binary grating array is 8, the period is 1700nm (each step width is 212nm), the height is 560nm (each step height is 70nm), and the refractive index is 1.5. The simulation results show that the diffraction efficiency of the binary grating array is approximately 70%, which meets the requirements.

[0058] The relay imaging optical path optical module 209 may include one or more refractive or reflective lenses for imaging the two signal lights onto the detector 205. Of course, the relay imaging optical path optical module 209 may also include optical lenses with special adjustment functions, such as wedges, parallel plates, aspherical mirrors, or free-form mirrors, for adjusting the imaging quality of the relay imaging optical path optical module 209. Optionally, the relay imaging optical path optical module 209 may also include an aperture for adjusting the field of view of the signal light.

[0059] Figure 6 This is a schematic diagram of the binary grating array spectroscopic imaging effect of an embodiment of the present invention. For example, there are two detectors 205, each of which is a photodiode. After the signal light is diffracted and separated by the spectroscopic grating 204, it is spatially divided into two signal light paths: +1-order diffracted light and -1-order diffracted light. These two spatially separated signal light paths are imaged by the relay imaging optical module 209 and then imaged on two independent detectors 205. When the silicon wafer surface is defocused, the intensities of the two signal light paths increase and decrease, and the difference between the two light paths is used to represent the amount of defocus on the silicon wafer surface.

[0060] Figure 7 This is a simulation diagram of a curve showing a change in the differential signal of a measurement system with defocus according to an embodiment of the present invention. Figure 7 The simulation conditions are as follows: wavelength of 200nm-400nm, NA of 0.02, incident angle of 80°, and grating period of the binary grating array of 30μm. Since both the projection grating 202 and the beam splitting grating 204 are periodically distributed, it can be expected that the response curve of the focusing and leveling system will also vary periodically. The linear range within a single period is the maximum range of the focusing and leveling system. Figure 7The maximum range of the mid-range focusing and leveling system is ±2.5um. Overall, high sensitivity is maintained throughout the entire range.

[0061] Therefore, a focusing and leveling system based on a binary grating array utilizes grating diffraction to achieve spectroscopic detection and position marking, thereby characterizing the surface height of the device under test. This focusing and leveling system, with no moving parts and excellent stability, is suitable for use in the UV range. Its modular design offers a simple structure, high integration, and strong implementability.

[0062] Figure 8 FIG. 1 is a schematic diagram of the spectroscopic imaging effect of a binary grating array according to another embodiment of the present invention. Figure 8 As shown, the detection unit sequentially includes a spectroscopic grating 204, a relay imaging optical path optical module 209, and a detector 701. In this embodiment, the detector 701 is, for example, a charge coupled device (CCD). Signal light reflected from the device under test 203 is spatially separated by the spectroscopic grating 204 into +1-order diffracted light and -1-order diffracted light. Signal light of different wavelengths within the ±1-order diffracted light has different spatial diffraction angles. The intensity of signal light of different wavelengths can be independently determined at different locations on the detector 701 by the relay imaging optical path optical module 209, similar to the working principle of a spectrometer. Each signal light independently generates a differential signal. Multiple differential signals are assigned different weights and digitally processed to improve process adaptability.

[0063] In this embodiment, the focusing and leveling system arrangement based on a binary grating array not only utilizes the grating diffraction of the binary grating array to achieve spectroscopic detection and position marking functions, thereby characterizing the surface height of the device under test, but also simultaneously achieves independent detection of signal light of different wavelengths. By adjusting different "weighting factors" and using "digital detection methods" for different process structures, process adaptability is improved.

[0064] Figure 9 FIG. 1 is a schematic diagram of the binary grating array spectroscopic imaging effect according to another embodiment of the present invention. Figure 9As shown, the detection unit includes, in sequence, a beam splitter grating 204, a relay imaging optical path optical module 209, a polarization beam splitter component 801, and a detector 701. The polarization beam splitter component 801 is located in front of the detector 701 and is used to split the signal light emitted by the relay imaging optical path optical module 209 into S-polarized light and P-polarized light. The signal light reflected from the device under test 203 is spatially divided into +1-order diffraction light and -1-order diffraction light by the spectroscopic grating 204. The light of different wavelengths in the ±1-order diffraction light has different spatial diffraction angles. It is spatially collimated by the relay imaging optical path optical module 209 and polarized into S-polarized light and P-polarized light by the polarization splitting component 801. The S-polarized light and the P-polarized light are imaged on different detectors 701 respectively. The intensities of signal lights of different polarization states and different wavelengths can be independently obtained. A differential signal is independently obtained for signal lights of each polarization and wavelength. Different weights are configured between the differential signals of signal lights of multiple polarizations and wavelengths for digital processing to improve process adaptability.

[0065] Based on the focusing and leveling system of the binary grating array, signal lights of different polarization states and wavelengths are measured independently. By adjusting different weight factors and processing them digitally, process errors are reduced and process adaptability is improved.

[0066] In this embodiment, the focusing and leveling system arrangement based on a binary grating array not only utilizes the grating diffraction of the binary grating array to achieve spectroscopic detection and position marking functions, thereby characterizing the surface height of the device under test, but also simultaneously achieves independent detection of signal light with different polarization states and wavelengths. By adjusting different "weighting factors" and using "digital detection methods" for different process structures, process adaptability is improved.

[0067] This embodiment also provides a focusing and leveling method, in which a light source unit 201 emits a light beam, which is projected onto a device under test 203 after being transmitted through a projection grating 202 in a projection unit. The light beam is then reflected by the device under test 203 to a spectroscopic grating 204 in a detection unit. The spectroscopic grating 204 and the projection grating 202 have a specific positional relationship so that the spectroscopic grating 204 spatially diffracts and separates signal light containing surface information of the device under test into two signal lights at a specific position, which are then received by a detector in the detection unit. The surface height of the device under test 203 is represented by a differential signal between the two diffraction-separated signal lights.

[0068] The specific positional relationship between the spectroscopic grating 204 and the projection grating 202 is such that when the device under test 203 is at zero position, half of all the sub-light spots passing through the projection grating 202 are imaged in the black shaded area 204a of the spectroscopic grating 204, and half are imaged in the white shaded area 204b of the spectroscopic grating 204. When the surface of the device under test 203 is defocused, the intensities of the two signal lights increase and decrease, and the difference between the two signal lights is used to represent the defocus amount of the device under test 203.

[0069] Specifically, the beam splitter grating 204 spatially diffracts the signal light containing the surface information of the device under test into two signal lights: positive diffracted light and negative diffracted light. Positive diffracted light includes +n-order diffracted light, and negative diffracted light includes -n-order diffracted light, where n is an integer greater than 0.

[0070] In one embodiment, the detector 205 is a photodiode. In another embodiment, the detector 701 is a charge-coupled device. The working principle of the charge-coupled device is similar to that of a spectrometer. Since the diffraction angles of light of different wavelengths in the positive diffracted light and the negative diffracted light are different in space, the imaging positions on the detector 701 are different, so that the intensity of the signal light of different wavelengths can be obtained independently. A differential signal is obtained independently for each wavelength of signal light, and the differential signals of the signal lights of multiple wavelengths are digitally processed by configuring different weights.

[0071] The specific signal processing ideas are as follows:

[0072] Differential signals of different wavelengths can be expressed as the defocus amount.

[0073] The defocus of the device under test is:

[0074]

[0075] in, is the wavelength λ i The weight of The wavelength λ of the device under test i Light reflectivity, The light source unit has a wavelength λ i The proportion of light; is the defocus amount of the differential signal at different wavelengths.

[0076] When measuring the device under test, the process error is the result of the interaction between light and the film. The process error is related to the light wavelength, polarization, incident angle and process film structure. Different wavelengths and different polarizations bring different process errors. Therefore, the wavelength weight factor can be adjusted for different processes. Digital processing method can reduce process errors and improve the process adaptability of the system.

[0077] In another embodiment, a polarization splitter component 801 is provided before the detector 701. Signal lights of different wavelengths pass through the polarization splitter component 801 to form S-polarized light and P-polarized light. The S-polarized light and P-polarized light are imaged on different detectors 701 respectively to independently obtain the intensities of signal lights of different polarization states and different wavelengths. A differential signal is independently obtained for each polarization and wavelength of light, and multiple polarization and wavelength differential signals are digitally processed by configuring different weights.

[0078] The specific signal processing ideas are as follows:

[0079] The defocus value obtained by the differential signal of different wavelengths and polarization lights can be expressed as and

[0080] Considering the differences in light source spectrum, reflectivity, and polarization of the device under test, the defocus of the device under test is:

[0081]

[0082] in, is S polarized light, wavelength λ i The weight of P polarized light, wavelength λ i The weight of The wavelength λ of the device under test i , the reflectivity of S-polarized light, The wavelength λ of the device under test i , the reflectivity of P polarized light, The wavelength λ of the light source unit i , the proportion of S polarized light, The wavelength λ of the light source unit i , the proportion of P polarized light, Represents wavelength λ i , the defocus of S polarized light, Represents wavelength λ i , the defocus amount of P polarized light.

[0083] When measuring the device under test, the process error is the result of the interaction between the signal light and the film. The process error is related to the signal light wavelength, polarization, incident angle and process film structure. Signal lights of different wavelengths and polarizations bring different process errors. Therefore, the weight factors of wavelength and polarization can be adjusted for different processes. and Digital processing method can reduce process errors and improve the process adaptability of the system.

[0084] Figure 10 It is a simulation curve diagram of the process error after digital weight processing under the typical process film layer structure of the embodiment of the present invention. Figure 10 The black solid line in the figure is the process error without digital weighting, and the dotted line is the process error after wavelength and / or polarization digital weighting. The vertical axis is the process error in nanometers (nm), and the horizontal axis is the photoresist thickness in nanometers (nm). Figure 10 As shown in the simulation results, the process error is about 15nm without digital weighting, and the process error is less than 0.3nm after polarization and wavelength digital weighting. The typical process film layer structure is photoresist, anti-reflection layer, silicon carbide, silicon dioxide, and silicon substrate.

[0085] Figure 11 This is a simulation curve diagram of process error after digital weight processing under another typical process film layer structure of an embodiment of the present invention. Figure 11 The black solid line in the figure is the process error without digital weighting, and the dotted line is the process error after wavelength and / or polarization digital weighting. The vertical axis is the process error in nanometers (nm), and the horizontal axis is the photoresist thickness in nanometers (nm). Figure 11 As shown in the simulation results, the process error is about 15nm without digital weighting, and the process error is less than 0.5nm after polarization and wavelength digital weighting. The typical process film layer structure is photoresist, anti-reflection layer, copper, silicon dioxide, and silicon substrate.

[0086] Therefore, based on the focusing and leveling system of the binary grating array, different polarization states and different wavelengths of light are measured independently. By adjusting different weight factors and processing them using digital methods, process errors are reduced and process adaptability is improved.

[0087] The present invention also provides an exposure device, comprising any one of the above-mentioned focusing and leveling systems, for executing any one of the above-mentioned focusing and leveling methods.

[0088] In summary, it can be seen that in a focusing and leveling system, focusing and leveling method, and exposure device provided in an embodiment of the present invention, a spectroscopic grating is provided in front of the detector; the light beam emitted by the light source unit is projected and imaged onto the device to be tested after being transmitted through the projection grating, and the light beam is reflected by the device to be tested to the spectroscopic grating, and the spectroscopic grating spatially diffracts and separates the signal light containing the surface information of the device to be tested into two signal lights, which are received by the detector, and the surface height of the device to be tested is represented by the differential signal of the two signal lights separated by diffraction. The present invention uses the differential signal of the two signal lights separated by the spectroscopic grating to represent the surface height of the device to be tested. There are no moving parts in the entire focusing and leveling system, which increases the stability of the focusing and leveling system, improves the reproducibility performance of the focusing and leveling system, reduces the maintenance time and frequency of the focusing and leveling system, increases the service life of the focusing and leveling system, and improves the overall machine yield. Furthermore, a binary grating array is used to simultaneously realize the functions of spectroscopic detection and position marking, and to spatially separate signal lights of different wavelengths, and synchronously realize independent detection of signal lights of different wavelengths. For different process structures, different "weight factors" are adjusted and "digital methods" are used for detection to improve process adaptability.

[0089] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In addition, the different parts between the various embodiments can also be used in combination with each other, and the present invention is not limited to this.

[0090] Furthermore, it should be recognized that although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent variations, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A focusing and leveling system, characterized in that: The system comprises a light source unit, a projection unit and a detection unit, wherein the projection unit comprises a projection grating, and the detection unit comprises a spectroscopic grating and a detector. The light source unit is used to provide a light beam, which is projected onto the device under test after being transmitted through the projection grating, and is reflected by the device under test to the spectroscopic grating. The spectroscopic grating diffracts and separates the signal light containing the surface information of the device under test into two signal lights, which are received by the detector, so that the surface height of the device under test is represented by the differential signal of the two diffraction-separated signal lights.

2. The focusing and leveling system according to claim 1, characterized in that: The beam splitting grating includes a binary grating array.

3. The focusing and leveling system according to claim 2, characterized in that: The binary grating array is a transmission grating or a reflection grating.

4. The focusing and leveling system according to claim 2, characterized in that: The binary grating array includes periodically distributed black shadow areas and white shadow areas, so as to spatially separate the signal light containing the surface information of the device under test into two signal lights: positive diffraction light and negative diffraction light.

5. The focusing and leveling system according to claim 4, characterized in that: When the device under test is at zero position, half of all the sub-light spots passing through the projection grating are imaged in the black shadow area of the binary grating array, and the other half are imaged in the white shadow area of the binary grating array.

6. The focusing and leveling system according to claim 4, characterized in that: The grating structures in the black shadow area and the white shadow area of the binary grating array are distributed in a mirror image.

7. The focusing and leveling system according to claim 2, characterized in that: The number of periods of the binary grating array corresponds to the number of periods of the projection grating.

8. The focusing and leveling system according to claim 1, characterized in that: The detector is a photodiode.

9. The focusing and leveling system according to claim 4, characterized in that: The detector is a charge-coupled device. The signal lights of different wavelengths in the positive diffraction light and the negative diffraction light have different diffraction angles in space and different imaging positions on the detector, so as to independently obtain the intensity of the signal lights of different wavelengths. Each signal light independently obtains a differential signal, and multiple differential signals are digitally processed by configuring different weights.

10. The focusing and leveling system according to claim 9, characterized in that: The detection unit also includes a polarization splitting component, which is located in front of the detector. The polarization splitting component is used to split the signal light of different wavelengths into S-polarized light and P-polarized light. The S-polarized light and the P-polarized light are imaged on different detectors respectively to independently obtain the intensity of signal light of different polarization states and different wavelengths. Each signal light independently obtains a differential signal, and multiple differential signals are digitally processed by configuring different weights.

11. A focusing and leveling method, characterized in that: The light beam emitted by the light source unit is transmitted through the projection grating of the projection unit and then projected onto the device under test. The light beam is reflected by the device under test to the spectroscopic grating of the detection unit. The spectroscopic grating diffracts and separates the signal light containing the surface information of the device under test into two signal lights, which are received by the detector in the detection unit. The surface height of the device under test is represented by the differential signal of the two signal lights separated by diffraction.

12. The focusing and leveling method according to claim 11, characterized in that: When the surface of the device under test is defocused, the intensities of the two signal lights increase and decrease, and the defocus amount of the surface of the device under test is represented by the differential signal of the two lights.

13. The focusing and leveling method according to claim 11, characterized in that: The spectroscopic grating spatially separates the signal light containing the surface information of the device under test into two signal lights: positive diffraction light and negative diffraction light.

14. The focusing and leveling method according to claim 13, characterized in that: The detector is a charge-coupled device. The signal lights of different wavelengths in the positive diffraction light and the negative diffraction light have different diffraction angles in space. The imaging positions on the detector are different to independently obtain the intensities of the signal lights of different wavelengths. Each signal light independently obtains a differential signal, and multiple differential signals are digitally processed by configuring different weights.

15. The focusing and leveling method according to claim 14, characterized in that: The defocus value of the device under test is: in, is the wavelength λ i The weight of The wavelength λ of the device under test i The reflectivity of the signal light, The light source unit has a wavelength λ i The proportion of signal light; is the defocus amount of the differential signal at different wavelengths.

16. The focusing and leveling method according to claim 14, characterized in that: A polarization splitter component is provided before the detector. Signal lights of different wavelengths pass through the polarization splitter component to form S-polarized light and P-polarized light. The S-polarized light and the P-polarized light are imaged on different detectors respectively to independently obtain the intensity of signal lights of different polarization states and different wavelengths. Each signal light independently obtains a differential signal, and multiple differential signals are digitally processed by configuring different weights.

17. The focusing and leveling method according to claim 16, characterized in that: The defocus value of the device under test is: in, is S polarized light, wavelength λ i The weight of P polarized light, wavelength λ i The weight of The wavelength λ of the device under test i , the reflectivity of S-polarized light, The wavelength λ of the device under test i , the reflectivity of P polarized light, The light source unit has a wavelength λ i , the proportion of S polarized light, The light source unit has a wavelength λ i , the proportion of P polarized light, Represents wavelength λ i , the defocus of S polarized light, Represents wavelength λ i , the defocus amount of P polarized light.

18. An exposure device, characterized in that: It comprises the focusing and leveling system according to any one of claims 1 to 10.

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