CN114859668B - Photoetching morphology calculation method of electron beam ice etching process - Google Patents

Abstract

The invention belongs to the technical field of electron beam lithography, and particularly relates to a lithography morphology calculation method of an electron beam ice lithography process. According to the invention, TRACER, BEAMER and LAB simulation software provided by GenISys are used as a platform to calculate the photoresist morphology of the electron beam ice etching process, and the photoetching morphology of the electron beam photoresist in the ice etching process is calculated based on experimental photoetching layout, initial electron beam energy and electron quantity, electron beam spot size, substrate material and thickness, photoresist material, thickness and contrast experimental data, wherein the photoetching morphology comprises water ice, anisole, alcohols, alkanes, other ice photoresists without solution development process and electron beam photoresists without development process in simulation. The invention can provide reference for photoetching morphology prediction of the electron beam ice etching process, and provides key and indispensable theoretical guidance for the ice etching process in the experimental preparation level, and has the advantages of strong pertinence, effectively shortening the experimental period and reducing the experimental cost.

Description

A method for calculating photolithography profiles in electron beam ice etching process

Technical Field

The invention belongs to the technical field of electron beam lithography, and in particular relates to a lithography morphology calculation method for an electron beam ice etching process.

Background Art

With the rapid development of information technology, electron beam lithography (EBL) plays an important role in the fields of electronic devices, optical devices and nanoscience due to its advantages such as high resolution, high alignment accuracy and high flexibility. However, this technology faces huge challenges for high-density dense nanostructures, ultra-large aspect ratio structures and nanostructures and devices with three-dimensional height changes. Therefore, a new type of electron beam lithography technology, ice lithography technology (IL) with ice as photoresist, came into being. It has attracted increasing attention in the field of advanced lithography due to its advantages such as no development, easy stripping, green environmental protection, high-precision in-situ overlay and flexible preparation of nanostructures on multiple types of substrates. Although the electron beam ice lithography process has been experimentally studied and a series of progress has been made, there is no report on the calculation method of the ice photoresist morphology of the electron beam ice lithography process. The lack of this calculation method will limit the further development and application of this emerging lithography technology.

Therefore, it is necessary to establish a calculation method that can predict the morphology of ice photoresist in electron beam ice etching process, and calculate the lithographic morphology of ice photoresist under different lithography conditions, so as to provide theoretical reference and guidance for the preparation of graphic structures in actual electron beam ice etching process experiments, and effectively shorten the experimental cycle and reduce experimental costs.

Summary of the invention

The purpose of the present invention is to propose a calculation method for predicting ice photoresist morphology in electron beam ice etching process, so as to solve the problem of lack of calculation method in the background technology of the above-mentioned electron beam ice etching process.

The present invention provides a method for calculating the lithography profile of the electron beam ice etching process, which is performed by TRACERv2.1.0, BEAMERv4.8.0 and LABv4.7.0 simulation software based on Monte Carlo algorithm and convolution operation provided by GenISys, and the specific steps are as follows:

(1) Import the ice photoresist material parameters in the TRACER software Material Archive; where:

The parameters of the ice photoresist material include mass density, chemical molecular formula and average excitation energy;

(2) Calculate the point/line spread function ( E ^a ) of each electron motion trajectory and all ice photoresist thickness layers in the TRACER software, that is, the ice engraving morphology of a single pixel line pattern:

By setting the substrate material type and thickness, ice photoresist material type and thickness, initial electron beam energy (keV) and the number of electrons, and running the simulation, the motion trajectory of electrons in the ice photoresist and the substrate and the point/line spread function ( E ^a ) of all ice photoresist thickness layers can be obtained. By plotting the E ^a data, the electron loss energy density distribution can be obtained, that is, the electron beam ice engraving morphology of a single pixel line pattern (ideal electron beam spot with a diameter of 0 nm);

(3) In the BEAMER software, the spatial distribution of the ability of ice photoresist molecules to absorb electron energy (AEA), i.e., the ice morphology, is calculated by combining the photolithography pattern and the point/line spread function ( E ^a ) file:

First, import the photolithography pattern to be simulated, then import the point/line spread function ( E ^a ) of different ice photoresist thickness layers in the E-Beam module of the BEAMER software and set the electron beam spot size, simulation area and grid accuracy. Run the simulation and plot the data file to obtain the spatial distribution of the electron energy absorbed by the ice photoresist molecules (AEA), that is, the ice morphology.

(4) Calculate the grayscale ice engraving morphology in LAB software based on experimental data:

(4.1) In the BEAMER software, convert the grayscale lithography layout to be simulated into the .ldb file format recognized by the LAB software;

(4.2) Import the ice photoresist contrast data and the corresponding point/line spread function ( E ^a ) in the Calibration module of the LAB software, and set the simulation environment, including the photoresist type, thickness, and grid accuracy, to obtain the ice photoresist simulation parameter file at a specific thickness. The parameters include: exposure rate coefficient (DillC), dissolution rate of fully exposed photoresist (Rmax), dissolution rate of unexposed photoresist (Rmin), slope (Slope), and threshold inhibitor concentration (Mth);

(4.3) Import the grayscale photolithography layout, ice photoresist simulation parameter file and point/line spread function ( E ^a ) file into the E-Beam module in the LAB software, set the photoresist thickness, exposure dose, electron beam spot size, grid accuracy and simulation area, run the simulation, and plot the data file to obtain the spatial distribution of the electron energy absorption ability (AEA) of the ice photoresist molecules, that is, the ice morphology.

In the present invention, the ice photoresist material type is water ice (ASW) at extremely low temperature (120 K-140 K), anisole, alcohols, alkanes, other ice photoresists that do not require a solution development process, or electron beam photoresists that do not require a development process in simulation.

In the present invention, the substrate type is all materials that can be subjected to electron beam lithography or ice lithography, such as Si, InP, Si ₃ N ₄ , Au, carbon nanotubes, and the like.

In the present invention, the photolithography pattern is any graphic structure that can be prepared by photolithography.

Compared with the prior art, the method of the present invention has the following beneficial effects:

First, the present invention broadens the simulation scope of the electron beam lithography process and proposes a simulation calculation method for the electron beam ice lithography process, which can be used to calculate the lithography morphology of the electron beam photoresist in the ice lithography process, including water ice (ASW) at extremely low temperatures (120 K-140 K), anisole, alcohols, alkanes, other ice photoresists that do not require a solution development process, and electron beam photoresists that do not require a development process in the simulation;

Second, the present invention can calculate the photoresist morphology under different photolithography conditions based on the actual experimental photolithography pattern, initial electron beam energy and electron quantity, electron beam spot size, substrate material and thickness, photoresist material, thickness and contrast experimental data;

Third, the calculation method proposed in the present invention provides a reference for the prediction of the lithography morphology of the electron beam ice etching process, and provides key and indispensable theoretical guidance for the ice etching process at the experimental preparation level. It has the advantages of strong pertinence, effective shortening of the experimental cycle, and reduction of experimental costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a simulation calculation of the present invention.

FIG. 2 shows the motion trajectory of 10 ⁶ electrons in the Si-based (500 μm thick) cryogel ASW with a thickness of about 480 nm at an initial electron beam energy of 100 keV in Example 1.

3 is the electron loss energy density distribution obtained from the point/line spread function .tpsf file ( E ^a ) of all ice photoresist ASW thickness layers at an initial electron beam energy of 100 keV in Example 1, that is, the electron beam ice engraving morphology of a single pixel line pattern (ideal electron beam spot with a diameter of 0 nm).

FIG. 4 is a schematic diagram of a 100 nm×100 μm single line lithography pattern used in Example 2 and the lithography process completed based on convolution operation in the software.

FIG5 shows the distribution of the electron energy absorption ability (AEA, i.e., ice lithography) of the ice photoresist molecules for a 100 nm×100 μm single line lithography pattern obtained in Example 2 under the conditions of 10 keV initial electron beam energy and a Si-based (500 μm thick) cryogel ASW with a thickness of about 380 nm.

FIG6 is a schematic diagram of (a) a zone plate focusing lens (Fresnel zone plates) after the metallization process in Example 3 and (b) a lithography layout of a zone plate with an outermost ring width of 100 nm and an anti-collapse reinforcement rib structure used in the simulation.

Figure 7 shows the distribution of the electron energy absorption ability of ice photoresist molecules for a zone plate lithography pattern with an outermost ring width of 100 nm having an anti-collapse reinforcement rib structure, obtained in Example 3 under the conditions of 100 keV initial electron beam energy and an ice gel ASW of about 4 μm thick on a Si substrate (500 μm thick). (AEA=0.38, i.e., ice-engraved morphology).

FIG8 is a schematic diagram of (a) a Kinoform lens after the metallization process in Example 4 and (b) a grayscale photolithography layout of the Kinoform lens used in the simulation.

FIG. 9 is the normalized contrast curve experimental data of cryogel ASW with an electron beam acceleration energy of 10 kV and a Si-based thickness of 190 nm in Example 4.

FIG. 10 is the normalized distribution of electron energy absorption ability AEA of ice photoresist molecules ASW in the outer ring region of the Kinoform lens calculated in Example 4 in combination with experimental data, that is, the ice engraving morphology.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the examples. Any simple changes to the simulation materials, conditions, photolithography patterns and calculation parameters in the embodiments are within the protection scope of the present invention.

Example 1: Calculate the motion trajectory of 10 ⁶ electrons in about 480 nm thick cryogel water ice (ASW) on Si substrate (500 μm thick) at an initial electron beam energy of 100 keV and the point/line spread function of all ice photoresist ASW thickness layers ( E ^a , i.e., the single-pixel line pattern ice engraving morphology corresponding to an ideal electron beam spot with a diameter of 0 nm), the specific steps are:

(1) Import the newly defined material parameters of ice photoresist water ice ASW in the TRACER software Material Archive, including the mass density of ASW 0.93 g/cm ³ , the chemical formula H ₂ O, and the average excitation energy 75 eV;

(2) Calculate the electron motion trajectory and the point/line spread function ( E ^a ) of all ice photoresist thickness layers in TRACER software. Set the substrate material to Si and the thickness to 500 μm, the ice photoresist material type to ASW and the thickness to 480 nm, the initial electron beam energy to 100 keV, and the number of electrons to 10 ⁶ . Run the simulation to obtain the electron motion trajectory inside the ice photoresist ASW and Si substrate shown in Figure 2 and the electron loss energy density distribution obtained from the point/line spread function .tpsf file ( E ^a ) of all ice photoresist ASW thickness layers shown in Figure 3. Since the ice etching process does not require the traditional solution-based development process and directly uses the interaction between the electron beam and ice to complete the lithography, the electron loss energy density distribution contour lines of different energies are defined as the ice etching morphology under different exposure intensities, that is, the electron beam ice etching morphology of a single pixel line pattern (ideal electron beam spot with a diameter of 0 nm).

Example 2: For a 100 nm×100 μm single line lithography pattern, the ice-engraved morphology of 10 ⁶ electrons on a Si substrate (500 μm thick) with a thickness of about 380 nm was calculated under an initial electron beam energy of 10 keV. The specific steps are as follows:

(1) Import the newly defined material parameters of ice photoresist water ice ASW in the TRACER software Material Archive, including the mass density of ASW 0.93 g/cm ³ , the chemical formula H ₂ O, and the average excitation energy 75 eV;

(2) Calculate the point/line spread function .lpsf file ( E ^a ) of all ice photoresist thickness layers in TRACER software. Set the substrate material to Si and thickness to 500 μm, the ice photoresist material type to ASW and thickness to 380 nm, the initial electron beam energy to 10 keV, and the number of electrons to 10 ⁶ , and run the simulation to obtain the point/line spread function .lpsf file ( E ^a ) of different ASW thickness layers;

(3) Combine the lithography layout and the point/line spread function .lpsf file ( E ^a ) in the BEAMER software to calculate the distribution of the electron energy absorption ability (AEA, i.e., ice morphology) of the ice photoresist molecules (ASW). First, import the 100 nm×100 μm single-line lithography layout to be simulated in Figure 4, then import the point/line spread function .lpsf files of different ASW thickness layers in step (2) in the E-Beam module and set the electron beam spot size to 10 nm, the simulation area (the central area of the single-line layout) and the grid accuracy (high-precision mode: 3 nm). Run the simulation and plot the data file to obtain the distribution of the electron energy absorption ability (AEA, i.e., ice morphology) of the ice photoresist molecules shown in Figure 5. AEA has the same meaning as the electron loss energy density distribution, that is, different AEA values are defined as ice morphology under different exposure intensities.

Example 3: For the Fresnelzone plates with an outermost ring width of 100 nm and an anti-collapse reinforcing rib structure, the ice-engraved morphology of 10 ⁶ electrons on Si-based (500 μm thick) about 4 μm thick cryogel water ice (ASW) at an initial electron beam energy of 100 keV is calculated. The specific steps are:

(1) Import the newly defined material parameters of ice photoresist water ice ASW in the TRACER software Material Archive, including the mass density of ASW 0.93 g/cm ³ , the chemical formula H ₂ O, and the average excitation energy 75 eV;

(2) Calculate the point/line spread function .lpsf file ( E ^a ) of all ice photoresist thickness layers in TRACER software. Set the substrate material to Si and thickness to 500 μm, the ice photoresist material type to ASW and thickness to 4 μm, the initial electron beam energy to 100 keV, and the number of electrons to 10 ⁶ , and run the simulation to obtain the point/line spread function .lpsf file ( E ^a ) of different ASW thickness layers;

(3) Combine the lithography layout and the point/line spread function .lpsf file ( E ^a ) in the BEAMER software to calculate the distribution of the electron energy absorption ability (AEA, i.e., ice-engraved morphology) of the ice photoresist molecules (ASW). First, import the zone plate lithography layout with an outermost ring width of 100 nm with an anti-collapse stiffener structure to be simulated in Figure 6 (b), then import the point/line spread function .lpsf file of different ASW thickness layers in step (2) in the E-Beam module and set the electron beam spot size to 10 nm, the simulation area (outer ring area, i.e., the black box area in Figure 6b), and the grid accuracy (high-precision mode: 3 nm). Run the simulation and plot the data file to obtain the distribution of the electron energy absorption ability (AEA, i.e., ice-engraved morphology) of the ice photoresist molecules shown in Figure 7. The results show that when the AEA is 0.38, the aspect ratio of the outermost ring of the ice-engraved morphology is about 18:1, and the aspect ratio of the inner ring is also close to 25:1.

Example 4: For the grayscale photolithography of Kinoform lens, the ice-engraved morphology of 10 ⁶ electrons on Si substrate (500 μm thick) with a thickness of about 190 nm was calculated in combination with the experimental data of contrast curve under the initial electron beam energy of 10 keV. The specific steps are as follows:

(1) Import the newly defined material parameters of ice photoresist water ice ASW in the TRACER software Material Archive, including the mass density of ASW 0.93 g/cm ³ , the chemical formula H ₂ O, and the average excitation energy 75 eV;

(2) Calculate the electron trajectory and the point/line spread function of all ice photoresist thickness layers in TRACER software. Set the substrate material to Si and the thickness to 500 μm, the ice photoresist material type to ASW and the thickness to 190 nm, the initial electron beam energy to 10 keV, and the number of electrons to 10 ⁶ , and run the simulation to obtain the point/line spread function .lpsf file ( E ^a ) of different ASW thickness layers;

(3) In the BEAMER software, convert the grayscale lithography layout of the Kinoform lens to be simulated in Figure 8 (b) into the .ldb file format recognized by the LAB software. In the grayscale lithography layout, each ring is divided into 9 parts, and the grayscale colors of different parts represent normalized exposure doses of different gradients;

(4) Calculate the grayscale ice engraving morphology in LAB software combined with the cryogel ASW experimental data:

(4.1) In the Calibration module of the LAB software, import the contrast experimental data (contrast γ is 1.9) of the cryogel ASW (thickness is 190 nm) shown in Figure 9 and the point/line spread function .lpsf file in step (2) and set the photoresist type to positive photoresist, thickness to 190 nm, and grid accuracy (x, y, and z directions are all 10 nm), thereby obtaining the simulation parameter file of the cryogel ASW with a thickness of 190 nm (DillC is 0.000196, Rmax is 0.005, Rmin is 0.000244, Slope is 3.726139, and Mth is 0.897078);

(4.2) In the E-Beam module of the LAB software, import the Kinoform lens grayscale lithography pattern in .ldb format in step (3), the ice photoresist simulation parameter file in step (4.1), and the point/line spread function .lpsf file in step (2), set the photoresist thickness (190 nm), exposure dose (0.8 C/ ^cm2 ), electron beam spot size to 10 nm, grid accuracy (10 nm in the x and y directions, 5 nm in the z direction), and simulation area (the outermost ring area, i.e., the black dashed area in Figure 8b), run the simulation and plot the data file to obtain the distribution of the electron energy absorption ability of the ice photoresist molecules (AEA, i.e., the ice etched morphology) shown in Figure 10.

Claims (3)

1. A method for calculating the lithography profile of an electron beam ice etching process, characterized in that the specific steps are as follows: (1) Import the ice photoresist material parameters in the TRACER software Material Archive; where: The parameters of the ice photoresist material include mass density, chemical molecular formula and average excitation energy; (2) Calculate the point/line spread function E ^a of each electron motion trajectory and all ice photoresist thickness layers in TRACER software, that is, the ice engraving morphology of a single pixel line pattern: Set the substrate material type and thickness, ice photoresist material type and thickness, initial electron beam energy and electron quantity, run simulation, obtain the electron motion trajectory inside the ice photoresist and substrate and the point/line spread function E ^a of all ice photoresist thickness layers, plot the E ^a data, and obtain the electron loss energy density distribution, that is, the electron beam ice engraving morphology of a single pixel line pattern; (3) In the BEAMER software, the spatial distribution of the ability of ice photoresist molecules to absorb electron energy, AEA, is calculated by combining the photolithography pattern and the point/line spread function E ^a file, i.e., the ice morphology: First, import the photolithography pattern to be simulated, then import the point/line spread function Ea of different ice photoresist thickness layers ⁱⁿ the E-Beam module of BEAMER software and set the electron beam spot size, simulation area and grid accuracy. Run the simulation and plot the data file to obtain the spatial distribution AEA of the electron energy absorbed by the ice photoresist molecules, that is, the ice morphology. (4) Calculate the grayscale ice engraving morphology in LAB software based on experimental data: (4.1) In the BEAMER software, convert the grayscale lithography layout to be simulated into the .ldb file format recognized by the LAB software; (4.2) Import the ice photoresist contrast data and the corresponding point/line spread function E ^a into the Calibration module in the LAB software, and set the simulation environment, including the photoresist type, thickness, and grid accuracy, to obtain the ice photoresist simulation parameter file at a specific thickness. The parameters include: exposure rate coefficient, dissolution rate of fully exposed photoresist, dissolution rate of unexposed photoresist, slope, and threshold inhibitor concentration; (4.3) Import the grayscale photolithography layout, ice photoresist simulation parameter file and point/line spread function E ^a file into the E-Beam module in the LAB software, set the photoresist thickness, exposure dose, electron beam spot size, grid accuracy and simulation area, run the simulation, and plot the data file to obtain the spatial distribution AEA of the ice photoresist molecule's ability to absorb electron energy, that is, the ice morphology. 2. The calculation method according to claim 1 is characterized in that the ice photoresist material type is water ice ASW, anisole, alcohols, alkanes or ice photoresist that does not require a solution development process at an extremely low temperature of 120 K-140 K, or electron beam photoresist that does not require a development process in simulation, and the substrate material type is all materials that can undergo electron beam lithography or ice etching processes. 3. The calculation method according to claim 1 is characterized in that the photolithography pattern is all graphic structures that can be prepared by photolithography.