Gap detection system and method, and focal plane correction method

1 . A gap inspection system, configured to inspect global gap data between a mask and a substrate, comprising:

a support frame;

a mask frame, comprising an autofocus module for real-time monitoring the gap data between the mask and the substrate;

a wafer stage module, comprising a wafer chuck for adjusting a position and an orientation of the substrate;

a front-side surface topography inspection module, mounted on an upper substrate of the support frame for inspecting the substrate, to acquire primary surface topography parameters;

a folding surface topography inspection module, switchable between an inspection position and a retract position for inspecting the mask, to acquire secondary surface topography parameters; and

a control system, configured to acquire position parameters of the mask and the substrate and calibration parameters of the front-side surface topography inspection module and the folding surface topography inspection module, and configured to calculate global gap data between the mask and the substrate in conjunction with the position parameters, the calibration parameters, the primary surface topography parameters, and the secondary surface topography parameters after measuring a tilt angle between the mask and the substrate.

2 . The gap inspection system according to claim 1 , wherein the mask frame further comprises:

a support plate, mounted on the upper substrate of the support frame, and

a mask holder, mounted on the support plate, wherein

the mask is vacuum-chucked on the mask holder and the autofocus module is mounted on the support plate.

3 . The gap inspection system according to claim 1 , wherein the wafer stage module further comprises:

a coarse stage, mounted on a lower substrate of the support frame, and

a fine stage, mounted on the coarse stage, wherein

the coarse stage and the fine stage are configured to adjust the position and the orientation of the substrate, and the wafer chuck is mounted on the fine stage.

4 . The gap inspection system according to claim 1 , wherein the front-side surface topography inspection module is one of a mechanical phase-shifting laser interferometer, a dynamic phase-shifting laser interferometer, a Twyman-Green-type dynamic phase-shifting interferometer, and a short-coherence Fizeau-type laser interferometer.

5 . The gap inspection system according to claim 1 , wherein the folding surface topography inspection module comprises:

a position adjustment mechanism, mounted on a side substrate of the support frame, and configured to drive the folding surface topography inspection module to switch between the inspection position and the retract position; and

a surface topography inspection lens group, a beam-steering mirror group, and a reference mirror group, for optical path deflection by 90° to enable surface topography inspection of the mask.

6 . The gap inspection system according to claim 5 , wherein the folding surface topography inspection module is an upright folding surface topography inspection module or an inverted folding surface topography inspection module, and

the folding surface topography inspection module moves linearly or rotationally by the position adjustment mechanism, so as to switch the positions between the inspection position and the retract position.

7 . The gap inspection system according to claim 1 , wherein the gap inspection system further comprises:

a vibration-isolated foundation and an active vibration isolation platform, constituting a system frame together with the support frame for providing a stable metrology reference base and structural mounting interface.

8 . A method for gap inspection based on the gap inspection system according to claim 1 , comprising:

S 1 , calibrating relative positional relationships of the mask, the substrate, the front-side surface topography inspection module, and the folding surface topography inspection module, to acquire position parameters of the mask and the substrate;

S 2 , calibrating the front-side surface topography inspection module and the folding surface topography inspection module by using an interferometric absolute flatness reference standard, to acquire the calibration parameters;

S 3 , inspecting the substrate by using the front-side surface topography inspection module to obtain the primary surface topography parameters;

S 4 , inspecting the mask by using the folding surface topography inspection module to obtain the secondary surface topography parameters;

S 5 , switching the folding surface topography inspection module to the retract position and moving the substrate to a global gap inspection position to obtain the gap data between the mask and the substrate by using the autofocus module, performing precise leveling on the mask and the substrate according to the gap data to make the mask and the substrate parallel to each other, and calculating a global gap data between the mask and the substrate according to the position parameters, the calibration parameters, the primary surface topography parameters, and the secondary surface topography parameters; or

switching the folding surface topography inspection module to the retract position and moving the substrate to the global gap inspection position to obtain the gap data between the mask and the substrate by using the autofocus module, calculating a tilt angle between the mask and the substrate, and then calculating the global gap data between the mask and the substrate according to the position parameters, the calibration parameters, the tilt angle, the primary surface topography parameters, and the secondary surface topography parameters.

9 . The method for the gap inspection according to claim 8 , wherein the front-side surface topography inspection module is a small-aperture surface topography inspection module, and the S 3 comprises:

performing a full-aperture stitching inspection on the substrate by using the small-aperture surface topography inspection module, to acquire surface topography parameters of each stitched sub-area;

using surface topography parameters of a non-overlapping region as primary stitching data at a non-overlapping region of the stitched sub-area, and selecting surface topography parameters of a stitched sub-area farther from an edge of stitched sub-areas as secondary stitching data at an overlapping region of the stitched sub-area; and

merging the primary stitching data and the secondary stitching data to obtain the primary surface topography parameters.

10 . A method for focal plane correction based on the gap inspection system according to claim 1 , comprising:

S 1 , calibrating relative positional relationships of the mask, the substrate, the front-side surface topography inspection module, and the folding surface topography inspection module, to acquire position parameters of the mask and the substrate;

S 2 , calibrating the front-side surface topography inspection module and the folding surface topography inspection module by using an interferometric absolute flatness reference standard, to acquire the calibration parameters;

S 3 , inspecting the substrate by using the front-side surface topography inspection module to obtain the primary surface topography parameters;

S 4 , inspecting the mask by using the folding surface topography inspection module to obtain the secondary surface topography parameters;

S 5 , switching the folding surface topography inspection module to the retract position and moving the substrate to a global gap inspection position to obtain the gap data between the mask and the substrate by using the autofocus module, performing precise leveling on the mask and the substrate according to the gap data to make the mask and the substrate parallel to each other, and calculating a global gap data between the mask and the substrate according to the position parameters, the calibration parameters, the primary surface topography parameters, and the secondary surface topography parameters; or

switching the folding surface topography inspection module to the retract position and moving the substrate to the global gap inspection position to obtain the gap data between the mask and the substrate by using the autofocus module, calculating the tilt angle between the mask and the substrate, and then calculating the global gap data between the mask and the substrate according to the position parameters, the calibration parameters, the tilt angle, the primary surface topography parameters, and the secondary surface topography parameters; and

S 6 , performing the focal plane correction according to the global gap data, so that an upper surface of the substrate is located on a target focal plane.