A method for correcting the profile of blazed gratings manufactured based on electron beam grayscale lithography

Abstract

The present invention relates to a method for correcting the profile of a blazed grating manufactured using electron beam grayscale lithography. The present invention utilizes electron beam grayscale lithography for manufacturing. Based on atomic force microscopy test results, a functional relationship between the grating surface profile and the exposure dose distribution of the blazed grating is determined. The dose distribution is corrected based on this function, thereby achieving correction of the grating surface profile. Compared to the prior art, the present invention corrects the grating profile by correcting the dose distribution through a fitting function based on microscopic test results obtained in preliminary experiments. This method avoids the problem of decreased diffraction efficiency caused by grating surface curvature and effectively improves the performance of blazed gratings manufactured using electron beam grayscale lithography.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a blazed grating profile correction method based on electron beam grayscale lithography. Background Art

[0002] Spectral imaging helps us obtain rich spatial and spectral information of the target by acquiring continuous imaging data within a certain spectral band. It has become an important and indispensable technology in the fields of atmospheric measurement, agricultural control, geological identification, etc. In order to achieve continuous spectral imaging, blazed gratings with linear dispersion characteristics have been widely used. In order to manufacture blazed gratings, methods such as ion etching, electron beam grayscale lithography, and mechanical engraving have been proposed. Among them, the blazed gratings manufactured by electron beam grayscale lithography have the advantages of low roughness and small wave phase difference. However, since the development rate and exposure dose are not linearly related in actual processing, the conventional linear exposure dose change often causes the grating surface to bend, resulting in a decrease in diffraction efficiency. In order to achieve a linear grating surface profile to improve diffraction efficiency, commercial electron beam lithography calculation software such as BEAMER is often used for simulation calculations to correct the exposure dose to achieve a linear grating surface. However, this method is time-consuming and complex to operate, and there are discrepancies between simulation and experiment, which affects the practical application of blazed gratings manufactured using electron beam grayscale lithography technology. The commercial software correction method requires measuring the contrast curve to obtain development data, and then using software to simulate the dose distribution. However, the contrast measurement results deviate from the actual development process, and there are differences between the substrate material and the simulation. The dose distribution finally calculated cannot guarantee the expected grating profile. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a blazed grating profile correction method based on electron beam grayscale lithography.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The present invention provides a method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography, comprising the following steps:

[0006] The blazed grating is processed under a linear dose gradient using electron beam grayscale lithography. The profile of the blazed grating surface is measured using a microscope to obtain the position data of the blazed grating and the height data corresponding to its position.

[0007] Within one grating period, the measured data is fitted with the linear dose gradient data to obtain the profile-dose function of the blazed grating profile height and dose;

[0008] The dose distribution when the profile is a straight line is calculated according to the profile-dose function. The calculated dose distribution is used to process the blazed grating under the calculated dose distribution gradient using electron beam grayscale lithography technology.

[0009] Furthermore, the blazed grating is processed under a linear dose gradient using electron beam grayscale lithography technology, specifically including: spin coating a 1.5 μm thick PMMA photoresist on the substrate, the exposure pattern is evenly divided into 20 layers within a 9.1 μm period, the dose coefficient difference between each layer is 0.06, and exposure is performed using a 100 keV electron beam at 30 nA, followed by development in an IPA:H2O=2:1 solution for 4 minutes.

[0010] Furthermore, the microscope is an atomic force microscope.

[0011] Furthermore, the position data is the length data of the blazed grating profile in the horizontal direction, and the unit is μm.

[0012] Furthermore, the height data is the height data of the blazed grating profile in a vertical direction, and the unit is nm.

[0013] Furthermore, the linear dose gradient data includes position data and dose data corresponding to the position.

[0014] Furthermore, one grating period is 9.1 μm.

[0015] Furthermore, the data obtained from the measurement are fitted with the linear dose gradient data, specifically including: fitting the position data of the blazed grating and the height data corresponding to its position using a fitting function to obtain a spatial function of the position data of the blazed grating and the height data corresponding to its position, and replacing the position data of the spatial function with the dose data according to the linear dose gradient data to obtain a profile-dose function.

[0016] Furthermore, the fitting function is a nonlinear function, including: a polynomial function, an exponential function, and a logarithmic function.

[0017] Furthermore, the calculated dose distribution is a nonlinear dose distribution.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention adopts electron beam grayscale lithography technology to manufacture blazed gratings, and uses the functional relationship between the grating surface profile and the exposure dose distribution to correct the dose distribution, thereby realizing the correction of the grating surface profile and effectively correcting the grating surface shape of the blazed grating prepared by electron beam grayscale lithography.

[0020] (2) Compared with the prior art, the present invention can quickly and effectively realize linear blazed grating surface processing, avoid the performance degradation caused by grating profile bending, and achieve higher diffraction efficiency.

[0021] (3) The present invention uses experimental fitting correction, is simple to operate, and can better ensure the accuracy of the actual contour obtained. Compared with commercial software correction methods, this method uses experimental correction to avoid the discrepancy between simulation and reality, and can accurately correct the grating contour in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of processing a blazed grating by the electron beam grayscale lithography process of the present invention;

[0023] Figure 2 A three-dimensional profile image of the blazed grating processed with a linear dose coefficient using an atomic force microscope scan;

[0024] Figure 3 The atomic force microscope scanning height curve, fitting curve and ideal height curve of the blazed grating processed before and after dose coefficient correction within one cycle of the present invention;

[0025] Figure 4 This is the three-dimensional profile image of the blazed grating processed with the corrected dose coefficient using an atomic force microscope scan. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0027] This embodiment provides a blazed grating profile correction method based on electron beam grayscale lithography manufacturing technology, which is used for grating surface profile correction in electron beam lithography manufacturing technology, including the following steps:

[0028] Blazed grating processing: Blazed gratings are processed using electron beam grayscale lithography under linear dose gradient.

[0029] Blazed grating measurement: Atomic force microscopy is used to measure the blazed grating surface profile.

[0030] Blazed grating surface profile fitting: The measured blazed grating surface profile is fitted within one grating period to obtain the spatial function of the grating surface. The dose distribution during electron beam grayscale lithography exposure is used to convert this spatial function into a profile-dose function.

[0031] Blazed grating dose distribution correction: Use the contour-dose function to calculate the dose distribution corresponding to the target contour.

[0032] Corrected blazed grating processing: Using the corrected dose distribution, blazed gratings are processed using electron beam grayscale lithography under a corrected dose gradient.

[0033] Furthermore, the electron beam grayscale lithography technology utilizes the periodic and continuous change of the charge dose distribution in the exposure pattern to realize the blazed grating processing.

[0034] Furthermore, the photoresist used in the electron beam grayscale lithography manufacturing technology is a positive photoresist represented by PMMA.

[0035] Furthermore, the blazed grating surface profile fitting function is a nonlinear function such as a polynomial function, an exponential function, a logarithmic function, etc.

[0036] Furthermore, the profile-dose function is obtained by utilizing the spatial distribution of the dose through the spatial distribution of the grating surface.

[0037] Furthermore, the correction method is to use the profile-dose function to correct the dose distribution into a nonlinear distribution, thereby realizing the correction of the grating surface profile.

[0038] According to the electronic grayscale lithography process, this embodiment provides a blazed grating profile correction method based on the electron beam grayscale lithography manufacturing technology, wherein the processed structure is a blazed grating with a period of 9.1 μm and a 4° blaze angle. Figure 1 The figure shows a schematic diagram of a blazed grating profile correction method using electron beam grayscale lithography manufacturing technology. The electron beam grayscale lithography technology of the blazed grating forms a blazed grating by exposing different doses within the grating period to achieve different residual heights of the photoresist. The profile correction method is to achieve profile correction by adjusting the exposure dose coefficient corresponding to different grating areas during the exposure process through measurement feedback.

[0039] Next, a method embodiment of the present invention is provided, which is a method for correcting the profile of a blazed grating based on electron beam grayscale lithography manufacturing technology. The method comprises the following steps:

[0040] Blazed grating processing: Electron beam grayscale lithography is used to process blazed gratings under linear dose gradient. The specific processing process is as follows:

[0041] A 1.5 μm thick PMMA photoresist was spin-coated on the substrate. The exposure pattern was evenly divided into 20 layers within a 9.1 μm period, with a dose coefficient difference of 0.06 between each layer. Exposure was performed using a 100 keV electron beam at 30 nA, followed by development in an IPA:H2O=2:1 solution for 4 minutes.

[0042] Blazed grating measurement: Atomic force microscope is used to measure the profile of the blazed grating surface. The results are as follows: Figure 2 As shown, the grating surface exhibits obvious curvature.

[0043] Blazed grating surface profile fitting: The measured blazed grating surface profile is fitted within one grating period to obtain a function of the grating profile. The function used in this embodiment is a quadratic function (h = ax 2 +bx+c), the function obtained in this embodiment is: height = -4.52×position 2 -61.05×position+97.33, the unit of position is μm, the unit of height is nm. And according to the dose distribution during exposure, it is converted into a profile-dose function (h=dz 2 +ez+f). The function obtained in this embodiment is: height = -177.7×dose coefficient 2 +102.8×dose coefficient+288.2, height unit is nm.

[0044] Blazed grating dose distribution correction: Use the profile-dose function to calculate the dose distribution when the profile is a straight line, and correct the dose distribution to a nonlinear distribution to achieve a linear grating surface profile.

[0045] Corrected blazed grating processing: Using the corrected dose distribution, electron beam grayscale lithography is used to process the blazed grating under the corrected dose gradient. The specific processing process is as follows:

[0046] A 1.5 μm thick PMMA photoresist was spin-coated on the substrate. The exposure pattern was evenly divided into 20 layers within a 9.1 μm period. The dose coefficient of each layer was calculated in the previous step. Exposure was performed using a 100 keV electron beam at 30 nA, followed by development in an IPA:H2O=2:1 solution for 4 min.

[0047] The results are as follows Figure 4 As shown, the grating surface has been corrected and has good linearity.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography, characterized in that: The following steps are involved: The blazed grating is processed under a linear dose gradient using electron beam grayscale lithography. The profile of the blazed grating surface is measured using a microscope to obtain the position data of the blazed grating and the height data corresponding to its position. Within one grating period, the measured data is fitted with the linear dose gradient data to obtain the profile-dose function of the blazed grating profile height and dose; The dose distribution when the profile is a straight line is calculated according to the profile-dose function. The calculated dose distribution is used to process the blazed grating under the calculated dose distribution gradient using electron beam grayscale lithography technology.

2. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The blazed grating is processed under a linear dose gradient using electron beam grayscale lithography technology, specifically including: spin coating a 1.5 μm thick PMMA photoresist on a substrate, evenly dividing the exposure pattern into 20 layers within a 9.1 μm period, with a dose coefficient difference of 0.06 between each layer, using a 100 keV electron beam at 30 nA for exposure, and then developing in an IPA:H2O=2:1 solution for 4 minutes.

3. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The microscope is an atomic force microscope.

4. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The position data is the length data of the blazed grating profile in the horizontal direction, and the unit is μm.

5. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The height data is the height data of the blazed grating profile in the vertical direction, and the unit is nm.

6. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The linear dose gradient data includes position data and dose data corresponding to the position.

7. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The one grating period is 9.1 μm.

8. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The fitting of the measured data with the linear dose gradient data specifically includes: fitting the position data of the blazed grating and the height data corresponding to its position using a fitting function to obtain a spatial function of the blazed grating position data and the height data corresponding to its position; and replacing the position data of the spatial function with the dose data according to the linear dose gradient data to obtain a profile-dose function.

9. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 8, characterized in that: The fitting function is a nonlinear function, including: a polynomial function, an exponential function, and a logarithmic function.

10. The method for correcting the profile of a blazed grating manufactured based on electron beam grayscale lithography according to claim 1, characterized in that: The dose distribution obtained by calculation is a nonlinear dose distribution.

Images