Large-size plane grating pitch measuring device and measuring method thereof

Abstract

The invention provides a large-size plane grating pitch measuring device. The large-size plane grating pitch measuring device comprises an interferometer, a three-dimensional adjusting frame, a V-shaped support arranged on the three-dimensional adjusting frame and a clamping tool arranged on the V-shaped support. Wherein a to-be-measured large-size special-shaped grating is fixed on the clamping tool, the to-be-measured large-size special-shaped grating corresponds to the interferometer in the front-back position, and the to-be-measured large-size special-shaped grating is matched with the V-shaped support through the three-dimensional adjusting frame to adjust the grating posture. According to the large-size plane grating pitch measuring device and the measuring method thereof provided by the invention, the pitch measuring precision of the large-size special-shaped plane grating can be effectively improved, and the safety of the plane grating can be effectively ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of grating performance detection, and more specifically, to a large-size plane grating pitch measurement device and a measurement method thereof. Background Art

[0002] In high-end lithography machines, the ultra-precision motion stage is the core subsystem. Only a displacement measurement system that can meet the requirements of hundreds of millimeters, sub-nanometer resolution, and nanometer accuracy can support ultra-precision motion. At present, the displacement measurement system that can meet the requirements is the grating ruler measurement system. Its measurement optical path is short, only a few millimeters, so its measurement accuracy is not sensitive to the measurement environment, and it has the advantages of high measurement stability and simple structure.

[0003] The disadvantage of grating measurement is poor linearity, which is due to the manufacturing process error of the grating, and the measurement accuracy has an error accumulation effect. Therefore, if you want to use a grating ruler and obtain nanometer-level measurement accuracy and measurement repeatability, you need to consider the impact of the grating pitch error on the measurement.

[0004] The grating pitch is the spacing between each grating line in a certain grating line direction. It is one of the important technical indicators of the grating. The grating pitch is usually measured using a scanning electron microscope. The scanning electron microscope irradiates the surface of the analyzed sample in a grating scanning manner through an electron beam to obtain the surface structure and morphology information of the sample. Although it can obtain the grating pitch intuitively, the working mode of electron beam scanning determines that its working field is small. At present, the largest loading platform size of scanning electron microscope products produced by various manufacturers at home and abroad does not exceed 200mm. In some actual application scenarios, the size of the large-size plane grating involved is much larger than 200mm. The scanning electron microscope can only measure the local grating pitch of the grating, and cannot obtain the grating pitch error distribution of the entire surface.

[0005] In summary, in order to solve the above problems, there is an urgent need for a method that can perform high-precision grating pitch measurement on the entire surface of a large-sized plane grating. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a large-size plane grating pitch measuring device and a measuring method thereof, which can effectively improve the pitch measurement accuracy of large-size special-shaped plane gratings and effectively ensure the safety of the plane gratings.

[0007] The large-size plane grating pitch measuring device provided by the present invention comprises an interferometer, a three-dimensional adjustment frame, a V-shaped bracket arranged on the three-dimensional adjustment frame, and a clamping tool arranged on the V-shaped bracket; wherein the large-size special-shaped grating to be measured is fixed on the clamping tool, the grating to be measured corresponds to the front and rear positions of the interferometer, and the grating posture of the large-size special-shaped grating to be measured is adjusted by the three-dimensional adjustment frame and the V-shaped bracket.

[0008] In addition, a preferred solution is that the clamping tool includes a grating surface outer frame and a bonding surface outer frame that are interlocked, and the large-sized special-shaped grating to be measured is arranged between the grating surface outer frame and the bonding surface outer frame.

[0009] In addition, a preferred solution is that both the grating surface outer frame and the bonding surface outer frame are made of polyetheretherketone material.

[0010] In addition, a preferred solution is that a chamfering block corresponding to the chamfer of the large-sized special-shaped grating to be measured is provided on the grating surface outer frame, and the chamfering block is made of Teflon material; and,

[0011] A detachable handle is arranged on the outer frame of the grating surface.

[0012] In addition, a preferred solution is that a clamping knob is provided on the V-shaped bracket, and the clamping tool is fixed to the V-shaped bracket via the clamping knob.

[0013] In addition, a preferred solution is that the three-dimensional adjustment frame includes a two-dimensional adjustment frame and an electric turntable; wherein,

[0014] The two-dimensional adjustment frame is used to adjust the pitch angle and the roll angle of the V-shaped bracket, and the electric turntable is used to adjust the rotation angle of the two-dimensional adjustment frame.

[0015] In addition, a preferred solution is that the two-dimensional adjustment frame includes three layers of adjustment plates, and fastening bolts are arranged between each layer of adjustment plates.

[0016] In addition, a preferred solution is that the interferometer is a horizontal interferometer.

[0017] On the other hand, the present invention also provides a method for measuring the pitch of a large-sized special-shaped plane grating, which is measured using the aforementioned large-sized plane grating pitch measuring device, and the method comprises:

[0018] Fix the large-sized special-shaped grating to be tested on the clamping fixture;

[0019] The clamping tool is adjusted to a preset angle and then fixed to the V-shaped bracket;

[0020] Based on the three-dimensional adjustment frame, the phase information of two pre-selected grating lines of the large-sized special-shaped grating to be measured is measured by the interferometer;

[0021] The pitch error of the two preselected grid lines is determined based on the phase information of the two preselected grid lines.

[0022] In addition, a preferred solution is that, for any pre-selected grid line, the process of measuring the phase information of the pre-selected grid line by the interferometer based on the three-dimensional adjustment frame includes:

[0023] The grating posture of the preselected grating line is adjusted by a three-dimensional adjustment frame so that the 0th order diffraction light returns to the field of view of the interferometer; and the return light fringes of the large-sized special-shaped grating to be measured are adjusted to the minimum, and the 0th order phase at this time is measured and recorded;

[0024] The preselected grating lines are rotated to the grating Littrow angle by the three-dimensional adjustment frame so that the ±1-order diffraction light returns to the field of view of the interferometer; and the return light fringes of the large-sized special-shaped grating to be measured are adjusted to the minimum, and the ±1-order phase at this time is measured and recorded.

[0025] Compared with the prior art, the large-size plane grating pitch measurement device and the measurement method provided by the present invention have the following beneficial effects:

[0026] The large-size plane grating pitch measurement device and the measurement method thereof provided by the present invention can measure the pitch error of the large-size plane grating on the entire surface, and the measurement speed is fast. The pitch error can be obtained by only using the phase information of the 0th order and ±1st order diffracted light. In addition, the data can be obtained more directly, and there is no need to splice the grating line information obtained by scanning a small field of view to obtain the pitch error, which can avoid the system error caused by the splicing algorithm. In addition, the grating error measurement of two grating lines of the two-dimensional grating can be completed by changing the position of the detachable handle and cooperating with the V-shaped bracket; in addition, the outer frames of the grating surface and the bonding surface are both higher than the grating, which can well protect the grating during the test. Moreover, after the test, an acrylic cover plate is added to the two outer frames of the tooling, so that the grating can be completely wrapped, which can also play a good protective effect during the transfer and storage of the grating.

[0027] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] By referring to the following description and claims in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the accompanying drawings:

[0029] Figure 1 An axonometric view of a clamping tool provided according to an embodiment of the present invention;

[0030] Figure 2 A front axonometric view of a V-shaped bracket provided according to an embodiment of the present invention;

[0031] Figure 3 A rear axonometric view of a V-shaped bracket provided according to an embodiment of the present invention;

[0032] Figure 4 An axonometric diagram of a three-dimensional adjustment frame provided according to an embodiment of the present invention;

[0033] Figure 5 An assembly diagram of a large-size planar grating pitch measuring device provided according to an embodiment of the present invention;

[0034] Figure 6 A schematic diagram of the phase of the positive first-order diffraction light of a large-sized special-shaped grating to be tested according to an embodiment of the present invention.

[0035] Figure numerals: interferometer 1, large-sized special-shaped grating to be measured 2, grating surface frame 3, bonding surface frame 4, chamfered pressure block 5, detachable handle 6, clamping tool 7, V-shaped bracket 8, clamping knob 9, two-dimensional adjustment frame 10, electric turntable 11, fastening bolt 12.

[0036] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0037] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] The structure of the large-size plane grating pitch measuring device provided by the present invention is described in detail below. Figure 1 The isometric structure of the clamping tool provided according to an embodiment of the present invention is shown. Figure 2 The front axonometric structure of the V-shaped bracket provided according to an embodiment of the present invention is shown. Figure 3 The back axonometric structure of the V-shaped bracket provided according to an embodiment of the present invention is shown. Figure 4 The isometric structure of the three-dimensional adjustment frame provided according to the embodiment of the present invention is shown. Figure 5 It is an assembly diagram of a large-size planar grating pitch measurement device provided according to an embodiment of the present invention.

[0040] Combined with the figure Figures 1 to 5 It can be seen that the large-size plane grating pitch measuring device provided by the present invention comprises an interferometer 1 for optical analysis (usually a horizontal interferometer 1 is selected), a three-dimensional adjustment frame for adjusting the grating posture of the large-size special-shaped grating 2 to be measured, a V-shaped bracket 8 arranged on the three-dimensional adjustment frame, and a clamping fixture 7 arranged on the V-shaped bracket 8. In the actual assembly process, the large-size special-shaped grating 2 to be measured is first fixed on the clamping fixture 7, and then the clamping fixture 7 is arranged on the V-shaped bracket 8. At this time, it is necessary to ensure that the front and rear positions of the grating to be measured and the interferometer 1 correspond; in the actual measurement process, the grating posture of the large-size special-shaped grating 2 to be measured can be adjusted by the three-dimensional adjustment frame in conjunction with the V-shaped bracket 8.

[0041] It should be noted that the grating surface of the large-sized plane grating cannot be touched at all, and other surfaces cannot have scratches. It is very important to protect the grating during the test. The grating is made of microcrystalline glass as the substrate. The hardness of the parts in direct contact with it should be lower than that of the microcrystalline glass, and the grating surface is fully coated and cannot be touched. Therefore, in order to achieve stable clamping of the large-sized special-shaped grating 2 to be tested by the clamping fixture 7, the clamping fixture 7 can include a grating surface frame 3 and a bonding surface frame 4 that are interlocked with each other, and the large-sized special-shaped grating 2 to be tested is arranged between the grating surface frame 3 and the bonding surface frame 4.

[0042] Specifically, both the grating surface outer frame 3 and the bonding surface outer frame 4 need to be made of polyetheretherketone material. The hardness of polyetheretherketone material is lower than that of microcrystalline glass, and will not cause scratches on the grating surface, bonding surface and side surfaces.

[0043] In addition, a chamfering block 5 corresponding to the chamfer of the large-sized special-shaped grating 2 to be measured can be set on the grating surface outer frame 3, and the chamfering block 5 is made of Teflon material; and a metal detachable handle 6 is set on the grating surface outer frame 3. In actual use, the chamfering block 5 is used to fix the large-sized special-shaped grating 2 to be measured on the bonding surface outer frame 4 by pressing the chamfer of the side of the large-sized special-shaped grating 2 to be measured, so the material is selected from Teflon with lower hardness. In addition, the four metal detachable handles 6 can cooperate with the measurement of different grating lines.

[0044] It should be noted that when a large-sized plane grating is used for phase measurement, the grating line direction needs to be parallel to the gravity direction. However, the grating line direction of the two-dimensional plane grating involved in the present invention is at an angle (acute angle) of 45° with the grating edge. Therefore, a V-shaped bracket 8 is designed to hold the clamping fixture 7 of the large-sized special-shaped grating 2 to be measured. The grating can be installed at different angles on the V-shaped bracket 8. Figure 2 As shown, the clamped large-size special-shaped grating 2 to be measured is installed in the V-shaped bracket 8, and the detachable handle 6 is adjusted to complete the phase measurement of the two grating lines of 45° and 135° of the grating.

[0045] In addition, in order to ensure the fixing stability of the clamping tool 7 on the V-shaped bracket 8 , a clamping knob 9 is provided on the V-shaped bracket 8 , and the clamping tool 7 is fixed to the V-shaped bracket 8 via the clamping knob 9 .

[0046] Specifically, in order to realize the adjustment of the grating posture of the large-sized special-shaped grating 2 to be measured by the three-dimensional adjustment frame, the three-dimensional adjustment frame includes a two-dimensional adjustment frame 10 and an electric turntable 11; wherein the two-dimensional adjustment frame 10 is used to adjust the pitch angle and roll angle of the V-shaped bracket 8, and the electric turntable 11 is used to adjust the rotation angle of the two-dimensional adjustment frame 10 using a motor, and the motor can be controlled by a controller or a computer. The V-shaped bracket 8 is fixed to the table of the two-dimensional adjustment frame 10 by bolts. The two-dimensional adjustment frame 10 includes three layers of adjustment plates, and two two-dimensional adjustment frames 10 are arranged between each layer of the two-dimensional adjustment frame 10, in order to maintain the current grating posture and reduce the vibration of the table.

[0047] In order to explain in detail the working principle of the large-size plane grating pitch measuring device provided by the present invention, the present invention also provides a large-size special-shaped plane grating pitch measuring method, which uses the aforementioned large-size plane grating pitch measuring device for measurement, and the method comprises:

[0048] Fix the large-sized special-shaped grating 2 to be tested on the clamping fixture 7;

[0049] Adjust the clamping tool 7 to a preset angle and then fix it to the V-shaped bracket 8;

[0050] The phase information of two pre-selected grating lines of the large-sized special-shaped grating 2 to be measured is measured by an interferometer 1 based on a three-dimensional adjustment frame;

[0051] The pitch error of the two pre-selected grid lines is determined based on the phase information of the two pre-selected grid lines.

[0052] In addition, a preferred solution is that, for any pre-selected grid line, the process of measuring the phase information of the pre-selected grid line by the interferometer 1 based on the three-dimensional adjustment frame includes:

[0053] The grating posture of the preselected grating line is adjusted by a three-dimensional adjustment frame so that the 0th order diffraction light returns to the field of view of the interferometer 1; and the return light fringes of the large-sized special-shaped grating 2 to be measured are adjusted to the minimum, and the 0th order phase at this time is measured and recorded;

[0054] The preselected grating lines are rotated to the grating Littrow angle through a three-dimensional adjustment frame so that the ±1-order diffraction light returns to the field of view of the interferometer 1; and the return light fringes of the large-sized special-shaped grating 2 to be measured are adjusted to the minimum, and the ±1-order phase at this time is measured and recorded.

[0055] Before introducing in detail the specific process of the method for measuring the pitch of a large-sized special-shaped plane grating provided by the present invention, it is necessary to explain the principle of measuring the pitch error of the full-width grating adopted by the present invention.

[0056] The principle of measuring the pitch error of the grating full-width is as follows:

[0057] The light from interferometer 1 is incident on the optical element to be measured, and the 0th order diffracted light returns to interferometer 1. At this time, the phase of the 0th order diffracted light can be obtained, which is recorded as I0(x, y). According to the phase and the laser wavelength λ of interferometer 1, the surface error of the plane grating in the Z direction (i.e., XY plane) can be calculated.

[0058] The laser interferometer 1 emits a laser beam, and when the position of the grating relative to normal incidence is rotated by the Littrow angle α, the laser beam can return along the original path.

[0059] α=sin -1 (λ / 2d)

[0060] When d=833.3 nm, α=22.314803°. Therefore, the rotation angle range around the Y-axis covers ±22.314803°.

[0061] like Figure 1 The plane grating to be measured is rotated clockwise by the Littrow angle α along the Y direction, and the laser from interferometer 1 is incident on the large-size special-shaped grating 2 to be measured, and the light returning along the original path is the +1st order diffraction light in the X direction.

[0062] At this time, the phase of the +1st order diffraction light in the X direction can be obtained

[0063]

[0064] In the above formula, g is the theoretical value of the grating pitch. The phase of the +1st order diffracted light in the X direction (I x+1 (x, y)) is affected by two errors: the X-axis grating intercept error e X (x, y), and Z-direction surface error e Z (x, y).

[0065] Similarly, by rotating the grating counterclockwise by the Littrow angle in the Y direction, the phase of the -1 order diffracted light in the X direction can be obtained.

[0066]

[0067] In the above formula, g is the theoretical value of the grating pitch. The phase of the -1st order diffracted light in the X direction (I X-1 (x, y)) is affected by two errors: the X-axis grating intercept error e X (x, y), and Z-direction surface error e Z (x, y).

[0068] Based on the above two sets of phase values, the x-direction pitch error can be obtained:

[0069]

[0070] The specific process of the method for measuring the pitch of a large-sized special-shaped plane grating provided by the present invention is further described below in combination with the principle of measuring the pitch error of the full-width grating.

[0071] 1. Preparation: Open the vibration isolation foundation in advance (the entire large-size plane grating pitch measurement device is placed on the vibration isolation foundation to isolate external vibration signals), and install the large-size special-shaped grating to be measured into the clamping fixture;

[0072] 2. Select a suitable angle, remove the two corresponding detachable handles based on the measured angle, put the clamping tool into the V-shaped bracket, and fix the tool with the clamping knob 9;

[0073] 3. Adjust the grating posture so that the 0th order diffraction light corresponding to a pre-selected grating line returns to the interferometer field of view, tighten the fastening bolts 12 on the two-dimensional adjustment frame 10, adjust the grating return light fringes to the minimum, and measure and record the phase at this time;

[0074] 4. Control the electric turntable 11 to rotate to the grating Littrow angle, so that the ±1st order diffraction light of the pre-selected grating line returns to the interferometer field of view, adjust the fringes to the minimum, measure and record;

[0075] 5. Remove the clamping tool from the V-shaped bracket, adjust the position of the detachable handle, rotate the clamping tool 90° and install it back into the V-shaped bracket; during this process, an acrylic cover needs to be installed to protect the grating.

[0076] 6. Repeat steps 3 and 4 to record the phase information of another pre-selected grid line.

[0077] 7. Based on the above principle of measuring the pitch error of the full-frame grating, the measured phase information is processed to obtain the pitch error of the full-frame grating of the two grating lines.

[0078] As above Figures 1 to 6 The large-size plane grating pitch measuring device and the measuring method thereof according to the present invention are described by way of example. However, those skilled in the art should understand that various improvements can be made to the large-size plane grating pitch measuring device and the measuring method thereof proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A large-size plane grating pitch measurement device, characterized in that: It includes an interferometer, a three-dimensional adjustment frame, a V-shaped bracket arranged on the three-dimensional adjustment frame, and a clamping tool arranged on the V-shaped bracket; wherein, The large-sized special-shaped grating to be measured is fixed on the clamping fixture, the large-sized special-shaped grating to be measured corresponds to the front and rear positions of the interferometer, and the grating posture of the large-sized special-shaped grating to be measured is adjusted by the three-dimensional adjustment frame in cooperation with the V-shaped bracket.

2. The large-size plane grating pitch measuring device according to claim 1, characterized in that: The clamping fixture comprises a grating surface outer frame and a bonding surface outer frame which are buckled with each other, and the large-sized special-shaped grating to be measured is arranged between the grating surface outer frame and the bonding surface outer frame.

3. The large-size plane grating pitch measuring device according to claim 2, characterized in that: The grating surface outer frame and the bonding surface outer frame are both made of polyetheretherketone.

4. The large-size plane grating pitch measuring device according to claim 3, characterized in that: A chamfering block corresponding to the chamfer of the large-sized special-shaped grating to be measured is arranged on the grating surface outer frame, and the chamfering block is made of Teflon material; and A detachable handle is arranged on the outer frame of the grating surface.

5. The large-size plane grating pitch measuring device according to claim 1, characterized in that: A clamping knob is arranged on the V-shaped bracket, and the clamping tool is fixed on the V-shaped bracket through the clamping knob.

6. The large-size plane grating pitch measuring device according to claim 1, characterized in that: The three-dimensional adjustment frame includes a two-dimensional adjustment frame and an electric turntable; wherein, The two-dimensional adjustment frame is used to adjust the pitch angle and the roll angle of the V-shaped bracket, and the electric turntable is used to adjust the rotation angle of the two-dimensional adjustment frame.

7. The large-size plane grating pitch measuring device as claimed in claim 6, characterized in that: The two-dimensional adjustment frame comprises three layers of adjustment plates, and fastening bolts are arranged between each layer of adjustment plates.

8. The large-size plane grating pitch measuring device according to claim 1, characterized in that: The interferometer is a horizontal interferometer.

9. A method for measuring the pitch of a large-sized, irregular-shaped plane grating, characterized in that: The large-size plane grating pitch measuring device according to any one of claims 1 to 8 is used for measurement, and the method comprises: Fix the large-sized special-shaped grating to be tested on the clamping fixture; The clamping tool is adjusted to a preset angle and then fixed to the V-shaped bracket; Based on the three-dimensional adjustment frame, the phase information of two pre-selected grating lines of the large-sized special-shaped grating to be measured is measured by the interferometer; The pitch error of the two preselected grid lines is determined based on the phase information of the two preselected grid lines.

10. The large-size special-shaped plane grating surface measurement method according to claim 9, characterized in that: For any pre-selected grid line, the process of measuring the phase information of the pre-selected grid line by the interferometer based on the three-dimensional adjustment frame includes: The grating posture of the preselected grating line is adjusted by a three-dimensional adjustment frame so that the 0th order diffraction light returns to the field of view of the interferometer; and the return light fringes of the large-sized special-shaped grating to be measured are adjusted to the minimum, and the 0th order phase at this time is measured and recorded; The preselected grating lines are rotated to the grating Littrow angle by the three-dimensional adjustment frame so that the ±1-order diffraction light returns to the field of view of the interferometer; and the return light fringes of the large-sized special-shaped grating to be measured are adjusted to the minimum, and the ±1-order phase at this time is measured and recorded.

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