Subresolution auxiliary pattern correction mask and preparation method thereof

Abstract

The invention provides a sub-resolution auxiliary pattern correction mask and a preparation method, and relates to the technical field of photolithography, and the preparation method comprises the following steps: based on a light path structure of a super-resolution lithography system, constructing a calculation model suitable for super-resolution lithography principle optical simulation, patterns of the mask in the calculation model comprising discrete holes and dense hole arrays; based on the calculation model, super-resolution photoetching is simulated, and primary light field simulation is carried out on the discrete hole array and the dense hole array; based on respective primary light field distribution results, sub-resolution auxiliary graph addition of discrete holes is carried out, and secondary light field simulation is carried out; carrying out sub-resolution auxiliary graph optimization of the discrete holes based on respective secondary light field distribution results and carrying out tertiary light field simulation, and carrying out iterative optimization until the light field distribution of the discrete holes added with the sub-resolution auxiliary graphs is matched with the light field distribution of the dense hole array; determining a corrected pattern of the sub-resolution auxiliary pattern correction mask; and preparing a sub-resolution auxiliary pattern correction mask based on the corrected pattern.

Description

Technical Field

[0001] The present invention relates to the field of photolithography technology, in particular to a sub-resolution auxiliary pattern correction mask and a preparation method thereof. Background Art

[0002] As chip processing size continues to decrease and pattern complexity and arbitrariness continue to increase, dense patterns and sparse patterns often coexist on the same mask. Both theoretical and experimental results clearly show that there is a significant difference between the lithography process window of dense patterns and the lithography process window of sparse patterns, which leads to a smaller common process window when processing masks with both dense and sparse patterns. The lighting conditions suitable for dense pattern exposure are not suitable for sparse pattern exposure, which easily leads to low mask processing quality. Summary of the invention

[0003] In view of this, a first aspect of an embodiment of the present disclosure provides a method for preparing a sub-resolution auxiliary pattern correction mask, comprising: constructing a computational model suitable for optical simulation of super-resolution lithography principles based on an optical path structure of a super-resolution lithography system, the computational model comprising a light source, a mask and an object to be photolithographically processed, and the pattern on the mask comprising discrete holes and a dense hole array; simulating super-resolution lithography based on the computational model, and performing a light field simulation on the discrete holes and the dense hole array respectively to obtain respective primary light field distribution results; adding sub-resolution auxiliary patterns of the discrete holes and performing a secondary light field simulation based on the respective primary light field distribution results to obtain respective secondary light field distribution results; optimizing the sub-resolution auxiliary patterns of the discrete holes and performing a tertiary light field simulation based on the respective secondary light field distribution results, iteratively optimizing until the light field energy distribution of the discrete holes with the sub-resolution auxiliary patterns added matches the light field energy distribution of the dense hole array; determining a corrected pattern of the sub-resolution auxiliary pattern correction mask, the corrected pattern comprising discrete holes with the sub-resolution auxiliary patterns added and a dense hole array; preparing a sub-resolution auxiliary pattern correction mask based on the corrected pattern of the sub-resolution auxiliary pattern correction mask.

[0004] According to an embodiment of the present disclosure, the size of the sub-resolution auxiliary pattern is smaller than the resolution of the super-resolution lithography system; the aperture of the discrete holes and the aperture of the dense holes in the dense hole array are 70 nm to 500 nm.

[0005] According to an embodiment of the present disclosure, sub-resolution auxiliary graphics are added to the discrete holes based on the respective primary light field distribution results, including: comparing the primary light field distribution results of the discrete holes with the primary light field distribution results of the dense hole array to obtain light field distribution difference results; adding sub-resolution auxiliary graphics around the discrete holes based on the light field distribution difference results.

[0006] According to an embodiment of the present disclosure, sub-resolution auxiliary graphics of discrete holes are optimized based on their respective secondary light field distribution results, including: comparing the secondary light field distribution results corresponding to the discrete holes to which the sub-resolution auxiliary graphics are added with the secondary light field distribution results corresponding to the dense hole array, adjusting the size of the added sub-resolution auxiliary graphics and the gap between the sub-resolution auxiliary graphics and the corresponding discrete holes, and optimizing the sub-resolution auxiliary graphics of the discrete holes.

[0007] According to an embodiment of the present disclosure, a sub-resolution auxiliary graphic correction mask is prepared based on a corrected pattern of the sub-resolution auxiliary graphic correction mask, including: selecting a substrate, preparing a mask absorption layer on the substrate to obtain a mask; spin-coating an electron beam photoresist on the mask absorption layer; based on the corrected pattern of the sub-resolution auxiliary graphic correction mask, performing electron beam direct writing exposure and development on the mask spin-coated with the electron beam photoresist, and transferring the corrected pattern of the sub-resolution auxiliary graphic correction mask to the electron beam photoresist; transferring the pattern of the electron beam photoresist to the mask absorption layer to obtain a sub-resolution auxiliary graphic correction mask.

[0008] According to an embodiment of the present disclosure, transferring the pattern of the electron beam photoresist to the mask absorption layer includes: using ion beam etching to transfer the pattern of the electron beam photoresist to the mask absorption layer; wherein the control parameters of the ion beam etching include at least one of RF power, beam voltage, acceleration voltage, growth chamber pressure, and etching angle.

[0009] According to an embodiment of the present disclosure, the substrate includes a quartz substrate and a sapphire substrate; the material of the mask absorption layer includes a thin film material composed of one of Cr, Si, Cr / CrO, and Mo / Si, and the thickness of the mask absorption layer is 40 nm~120 nm; the electron beam photoresist includes one of AR-P 6200, ZEP520A, UV135, PMMA, AR-N7520 and hydrogen silsesquioxane polymer photoresist, and the thickness of the electron beam photoresist is 60 nm~120 nm.

[0010] According to the embodiment of the present disclosure, the RF power is 170 W to 220 W, the beam voltage is 300 V to 500 V, the acceleration voltage is 45 V to 75 V, and the growth chamber pressure is 1×10 -4 Torr~5×10 -4 Torr, the etching angle is 45°~75°.

[0011] According to an embodiment of the present disclosure, the object to be photolithographically processed includes a wafer; the super-resolution photolithography exposure structure formed by the mask and the wafer includes: a substrate, a metal reflective layer, a photoresist, a metal transmission layer, an air spacer layer, and a mask stacked in sequence; or, a substrate, a metal reflective layer, a photoresist layer, an air spacer layer, and a mask stacked in sequence; or, a substrate, a photoresist layer, a metal layer, an air spacer layer, and a mask stacked in sequence; or, a bottom metal layer, a dielectric layer, an intermediate metal layer, a photoresist layer, a surface metal layer, an air spacer layer, and a mask stacked in sequence; or, a metal reflective layer, a photoresist layer, an air spacer layer, a metal-dielectric multilayer film, and a mask stacked in sequence.

[0012] According to an embodiment of the present disclosure, any one of rigorous coupled wave analysis, finite difference time domain method and finite element method is used to perform light field simulation on discrete holes, discrete holes with added sub-resolution auxiliary patterns and dense hole arrays.

[0013] A second aspect of the disclosed embodiments provides a sub-resolution auxiliary pattern correction mask, which is prepared by the above-mentioned preparation method; the sub-resolution auxiliary pattern correction mask is provided with discrete holes for adding sub-resolution auxiliary patterns and a dense hole array, and in the process of super-resolution lithography based on the sub-resolution auxiliary pattern correction mask, the process window corresponding to the discrete holes for adding the sub-resolution auxiliary patterns is consistent with the process window corresponding to the dense hole array, and the focal depth corresponding to the discrete holes for adding the sub-resolution auxiliary patterns is consistent with the focal depth corresponding to the dense hole array.

[0014] The sub-resolution auxiliary pattern correction mask and preparation method provided by the embodiments of the present disclosure have at least the following technical effects:

[0015] By adding sub-resolution assist features (SRAF) around the relatively sparse patterns in the mask pattern, the discrete pattern is made similar to the dense pattern from an optical perspective. The exposure dose of the discrete pattern can be corrected by the SRAF pattern to obtain a process window consistent with the dense pattern, and the SRAF pattern will not appear in the exposure result, thereby improving the focal depth of the lithography and the uniformity of the process window.

[0016] Based on the mask layout of the contact hole structure with the SRAF pattern added, the exposure pattern of the super-resolution lithography can be precisely controlled by flexibly adjusting the relevant parameters such as the slit width and spacing of the SRAF pattern for contact hole patterns with different apertures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0018] Figure 1 A flow chart schematically shows a method for preparing a sub-resolution auxiliary pattern correction mask according to an embodiment of the present disclosure;

[0019] Figure 2 The mask layout of the contact hole structure with the SRAF pattern added according to the embodiment of the present disclosure is schematically shown;

[0020] Figure 3 A schematic diagram of a super-resolution lithography exposure structure according to an embodiment of the present disclosure is shown;

[0021] Figure 4 Schematically shows a mask layout of a discrete hole pattern according to an embodiment of the present disclosure;

[0022] Figure 5 Schematically shows a light field distribution diagram of a discrete hole pattern after super-resolution lithography simulation according to an embodiment of the present disclosure;

[0023] Figure 6 A discrete hole mask layout with an SRAF pattern added according to an embodiment of the present disclosure is schematically shown;

[0024] Figure 7 Schematically shows a light field distribution diagram of a discrete hole with an SRAF pattern added after super-resolution lithography simulation according to an embodiment of the present disclosure;

[0025] Figure 8 The mask layout of dense holes according to an embodiment of the present disclosure is schematically shown;

[0026] Fig. 9 Schematically shows a light field distribution diagram of dense holes after super-resolution lithography simulation according to an embodiment of the present disclosure;

[0027] Fig.10 The process flow chart of the SRAF correction mask according to the embodiment of the present disclosure is schematically shown;

[0028] Fig.11 Schematically shows an electron microscope image of a discrete hole mask according to an embodiment of the present disclosure;

[0029] Fig.12 Schematically shows an electron microscope image of a discrete hole mask with an SRAF pattern added according to an embodiment of the present disclosure;

[0030] Fig.13 The electron microscope image of a dense hole mask according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0032] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0033] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the claims, any reference symbol between brackets shall not be construed as a limitation to the claims.

[0034] like Figure 1 As shown, the preparation method of this embodiment may include operation S110 to operation S150.

[0035] In operation S110 , a computational model suitable for optical simulation of super-resolution lithography principles is constructed based on an optical path structure of a super-resolution lithography system.

[0036] In operation S120, super-resolution lithography is simulated based on the computational model, and light field simulations are performed on the discrete holes and the dense hole array respectively to obtain respective primary light field distribution results.

[0037] In operation S130, based on the respective primary light field distribution results, sub-resolution auxiliary graphics of discrete holes are added and secondary light field simulation is performed to obtain respective secondary light field distribution results; based on the respective secondary light field distribution results, sub-resolution auxiliary graphics of discrete holes are optimized and tertiary light field simulation is performed, and optimization is iterated until the light field energy distribution of the discrete holes with the sub-resolution auxiliary graphics added matches the light field energy distribution of the dense hole array.

[0038] In operation S140, a corrected pattern of the sub-resolution auxiliary pattern correction mask is determined, the corrected pattern including discrete holes and a dense hole array in which the sub-resolution auxiliary pattern is added.

[0039] In operation S150, a sub-resolution auxiliary pattern correction reticle is prepared based on the corrected pattern of the sub-resolution auxiliary pattern correction reticle.

[0040] In the embodiment of the present disclosure, the calculation model includes a light source, a mask and an object to be photolithographically processed, and the pattern on the mask includes discrete holes and a dense hole array. That is, the pattern on the mask initially does not have an SRAF pattern added, but only includes discrete holes and a dense hole array.

[0041] In the process of simulating super-resolution lithography, the lithography object can be simulated based on discrete holes and dense hole arrays to obtain the respective primary light field distribution results. The respective primary light field distribution results are then compared, and SRAF patterns are added to the discrete holes on the mask according to the comparison results. At this time, the pattern on the mask includes discrete holes and dense hole arrays with SRAF patterns added.

[0042] Then, based on the discrete holes and dense hole arrays with SRAF graphics added, secondary simulated lithography is performed on the lithography object to obtain their respective secondary light field distribution results. Based on their respective secondary light field distribution results, sub-resolution auxiliary graphics of discrete holes are optimized. Then, based on the discrete holes and dense hole arrays with optimized sub-resolution auxiliary graphics, tertiary simulated lithography is performed on the lithography object to obtain their respective tertiary light field distribution results. This is iterated until the light field energy distribution of the discrete holes with sub-resolution auxiliary graphics is consistent with the light field energy distribution of the dense hole array, that is, the energy received by the light field distribution of the discrete holes with SRAF graphics added is close to the energy received by the dense hole array. What is presented in the exposure result is that the process window of the discrete holes with SRAF graphics added is consistent with the dense hole array. The corrected pattern of the sub-resolution auxiliary graphics correction mask is determined. Then, through the optimization and iteration of the mask processing technology, a high-quality and stable sub-resolution auxiliary graphics correction mask is obtained to realize the preparation of the SRAF mask.

[0043] According to an embodiment of the present disclosure, by adding sub-SRAF patterns around relatively sparse patterns in the mask pattern, the discrete pattern is made similar to the dense pattern from an optical perspective, and the exposure dose of the discrete pattern can be corrected by the SRAF pattern to obtain a process window consistent with the dense pattern, and the SRAF pattern will not appear in the exposure result, thereby improving the focal depth of the lithography and the uniformity of the process window.

[0044] On the basis of the above embodiment, the size of the sub-resolution auxiliary pattern may be smaller than the resolution of the super-resolution lithography system.

[0045] As a possible implementation, the SRAF patterns added around the discrete holes can be rectangles of specific sizes, and the sizes of the rectangles are smaller than the resolution of the lithography system. Thus, no lithography patterns are formed during the exposure process, but the lithography imaging light intensity distribution of the mask pattern will be affected.

[0046] Based on the above embodiments, any one of the rigorous coupled wave analysis method, the finite difference time domain method, and the finite element method can be used to perform light field simulation on discrete holes, discrete holes with sub-resolution auxiliary patterns, and dense hole arrays. Different lithography scenarios select appropriate light field simulation technology for super-resolution lithography systems, which is not limited by the present disclosure.

[0047] On the basis of the above embodiment, in operation S130, adding a sub-resolution auxiliary pattern of discrete holes based on the respective primary light field distribution results may include:

[0048] The primary light field distribution result of the discrete holes is compared with the primary light field distribution result of the dense hole array to obtain the difference in light field distribution results.

[0049] Sub-resolution auxiliary patterns are added around the discrete holes based on the light field distribution difference results.

[0050] like Figure 2 As shown, the SRAF pattern can be distributed around the discrete hole, and the density of the pattern formed together with the discrete hole is comparable to that of the dense hole array, making the discrete pattern similar to the dense pattern from an optical perspective. Therefore, the SRAF pattern can be added to the discrete hole based on the difference between the light field distribution of the discrete hole and the light field distribution of the dense hole array.

[0051] On the basis of the above embodiments, performing sub-resolution auxiliary pattern optimization of discrete holes based on respective secondary light field distribution results may include:

[0052] The secondary light field distribution results corresponding to the discrete holes with added sub-resolution auxiliary patterns are compared with those corresponding to the dense hole arrays. The size of the added sub-resolution auxiliary patterns and the gap between the sub-resolution auxiliary patterns and the corresponding discrete holes are adjusted to optimize the sub-resolution auxiliary patterns of the discrete holes.

[0053] like Figure 2 As shown, for contact hole patterns with different apertures, the uniformity of the process windows of discrete patterns and dense patterns can be improved by adjusting the slit width (width) and spacing (space).

[0054] Contact holes with specific apertures can be selected as feature patterns, and the aperture of the contact holes can be 70 nm~500 nm. The light field simulation software is used to perform light field simulation on discrete holes and dense hole arrays, and SRAF patterns are added to the discrete holes. Then, light field simulation is performed on the discrete holes and dense hole arrays with SRAF patterns added. Iterative optimization is performed based on the simulation results. By adjusting the values ​​of different widths and spaces in the SRAF patterns, the light field distribution results under different parameters are obtained. The results are compared with discrete holes with the same aperture but without SRAF patterns, verifying the effectiveness of the SRAF structure. At the same time, light field simulation is performed on dense hole arrays with the same aperture and different periods, and compared with discrete holes with SRAF patterns added, and the pattern that matches the light field energy distribution is selected as the processing pattern of the mask.

[0055] After the processing pattern of the mask is obtained, a sub-resolution auxiliary pattern correction mask can be prepared based on the processing pattern of the mask.

[0056] On the basis of the above-mentioned embodiment, preparing a sub-resolution auxiliary pattern correction mask based on the corrected pattern of the sub-resolution auxiliary pattern correction mask may include:

[0057] A substrate is selected, and a mask absorption layer is prepared on the substrate to obtain a mask plate.

[0058] An electron beam resist is spin coated on the masked absorbing layer.

[0059] Based on the corrected pattern of the sub-resolution auxiliary pattern correction mask, the mask spin-coated with the electron beam photoresist is subjected to electron beam direct writing exposure and development to transfer the corrected pattern of the sub-resolution auxiliary pattern correction mask to the electron beam photoresist.

[0060] The pattern of the electron beam photoresist is transferred to the mask absorption layer to obtain a sub-resolution auxiliary pattern correction mask.

[0061] In the embodiment of the present disclosure, high transmittance (for example, 365 nm wavelength transmittance greater than 99.8%), high surface flatness (for example, 10×10 μm 2 The substrate material may include a quartz substrate and a sapphire substrate.

[0062] In the embodiment of the present disclosure, the mask absorption layer can be selected to have low transmittance (for example, the transmittance at 365 nm is less than 0.8%), high surface flatness and high stability (for example, the transmittance at 10×10 μm 2As a possible implementation, the material of the mask absorption layer may include a thin film material composed of one of Cr, Si, Cr / CrO, and Mo / Si. The thickness of the mask absorption layer may be 40 nm to 120 nm. The mask absorption layer may be grown on the substrate surface by a growth process of physical vapor deposition (PVD) or plasma enhanced chemical vapor deposition (PECVD).

[0063] In an embodiment of the present disclosure, after determining that the quality of the mask absorption layer meets the requirements, an electron beam photoresist can be spin-coated on the surface of the mask absorption layer. The electron beam photoresist can include one of AR-P 6200, ZEP 520A, UV135, PMMA, AR-N7520 and hydrogen silsesquioxane polymer photoresist, and the thickness of the electron beam photoresist can be 60 nm to 120 nm.

[0064] In an embodiment of the present disclosure, ion beam etching (IBE) may be used to transfer the pattern of the electron beam photoresist to the mask absorption layer.

[0065] The control of small-size graphics (graphics with feature sizes less than 20 nm) etching through IBE is very critical and difficult, and requires precise control of various control parameters of the IBE device. The control parameters of the IBE device may include at least one of RF power, beam voltage, acceleration voltage, growth chamber pressure, and etching angle.

[0066] RF power mainly regulates plasma density and the bombardment energy of ion beam on film. Beam voltage provides directional and collimated bombardment environment for ion beam, acceleration voltage can precisely regulate directionality and bombardment energy, and growth chamber pressure provides a good vacuum environment for process improvement and reduces collisions of ion beam during propagation. In addition, for different aspect ratios of photoresist, the etching angle between ion beam and substrate is also extremely critical, which can help to better discharge reaction byproducts while etching the film and obtain better graphic quality.

[0067] As some possible implementations, the RF power may be 170 W to 220 W, the beam voltage may be 300 V to 500 V, the acceleration voltage may be 45 V to 75 V, and the growth chamber pressure may be 1×10 -4 Torr~5×10 -4 Torr, the etching angle can be 45°~75°.

[0068] In an example of the present disclosure, the etching time is determined according to different absorption layer thicknesses and pattern sizes. In the present disclosure, for SRAF correction patterns with a feature size of ~20 nm, the thickness of the photoresist needs to be finely adjusted to meet the requirements of the IBE etching aspect ratio, and the IBE etching angle is adjusted according to the thickness of the photoresist. The photoresist thickness for the SRAF correction pattern is 75nm ~80 nm, and the corresponding etching angle is 28°~30°. For the 20 nm feature size pattern, the ideal etching result is obtained by precise control of the etching angle, and precise etching angle control is performed. Each parameter needs to work together and be precisely controlled to obtain an ideal etching result.

[0069] After etching is completed, the processing quality can also be confirmed. After confirmation, post-processing steps such as post-stripping cleaning, overlaying of focus inspection windows, focus inspection layer deposition, and final cleaning can be carried out. The mask can also be observed through a scanning electron microscope to check the mask processing quality.

[0070] On the basis of the above embodiments, the object to be photolithographically processed includes a wafer, and the mask and the super-resolution photolithography exposure structure formed by the wafer include but are not limited to at least one of the following:

[0071] A substrate, a metal reflective layer, a photoresist, a metal transmission layer, an air spacer layer, and a mask layer stacked in sequence;

[0072] A substrate, a metal reflective layer, a photoresist layer, an air spacer layer, and a mask layer stacked in sequence;

[0073] A substrate, a photoresist layer, a metal layer, an air spacer layer, and a mask layer stacked in sequence;

[0074] A bottom metal layer, a dielectric layer, an intermediate metal layer, a photoresist layer, a surface metal layer, an air spacer layer, and a mask are stacked in sequence;

[0075] A metal reflective layer, a photoresist layer, an air spacer layer, a metal-dielectric multilayer film, and a mask are stacked in sequence.

[0076] It should be noted that the specific type of the above-mentioned super-resolution lithography exposure structure can be selected according to actual application requirements, and the present disclosure does not limit it.

[0077] The embodiment of the present disclosure further provides a sub-resolution auxiliary pattern correction mask, which is prepared by the above-mentioned preparation method, and the specific details are not repeated here.

[0078] The sub-resolution auxiliary pattern correction mask is provided with discrete holes for adding sub-resolution auxiliary patterns and a dense hole array. In the process of super-resolution lithography based on the sub-resolution auxiliary pattern correction mask, the process window corresponding to the discrete holes for adding sub-resolution auxiliary patterns is consistent with the process window corresponding to the dense hole array, and the focal depth corresponding to the discrete holes for adding sub-resolution auxiliary patterns is consistent with the focal depth corresponding to the dense hole array.

[0079] According to the sub-resolution auxiliary pattern correction mask and preparation method of the embodiment of the present disclosure, adding SRAF patterns has a significant effect on improving the uniformity of the process window of the super-resolution lithography system; the exposure dose of the discrete pattern can be corrected by the SRAF pattern to obtain a process window consistent with the dense pattern. In addition, by flexibly adjusting the relevant parameters of the SRAF pattern, the exposure pattern of the super-resolution lithography can be precisely controlled, and the SRAF correction mask processing can be realized and good pattern conformality can be ensured, especially the pattern processing with a feature size of ~20 nm can be completed.

[0080] In order to further verify the feasibility of the sub-resolution auxiliary pattern correction mask and the preparation method provided by the embodiment of the present disclosure, a specific example is used below for illustration, and the specific process is as follows:

[0081] Step 1: Construct a computational model for the optical path structure of the super-resolution lithography system. Figure 3 As shown in the figure, it includes: a 365 nm light source system, a mask and a wafer. The structure of the wafer used for exposure is a metal transmission layer, a photoresist layer, a metal reflection layer and a quartz substrate from top to bottom. This example uses a characteristic hole with an aperture of 140 nm as the characteristic pattern. The discrete holes (such as Figure 4 and Figure 5 ), add discrete holes of SRAF graphics (such as Figure 6 and Figure 7 ) and dense hole arrays (e.g. Figure 8 and Fig. 9 ) is used to simulate the light field using the finite element method.

[0082] According to the results of super-resolution lithography simulation using the computational model, by adjusting the space and width values, it was found that when the space and width values ​​were 80 nm and 20 nm, the discrete holes with SRAF patterns added were adapted to the dense holes with a spacing of 80 nm in the process window.

[0083] The light intensity distribution results of the center position and edge position of the three types of patterns (the square hole selected by the dense hole array is the square hole in the center of the 3×3 array as the detection pattern) are statistically analyzed, as shown in Table 1.

[0084] Table 1 Light intensity distribution results

[0085] Discrete holes Adding Discrete Holes to SARF Graphics Dense holes center 6.91 15.3 14.7 edge 2.58 7.65 7.27

[0086] Based on Table 1, it can be seen that the light intensity received by discrete holes and dense holes is very different, while the light intensity distribution of the contact holes after adding the SRAF pattern is almost consistent with that of the dense pattern, indicating that adding the SRAF pattern can effectively improve the uniformity of the process window in super-resolution lithography.

[0087] Step 2: Based on the light field simulation results, the sub-resolution auxiliary pattern correction mask design layout is designed. The mask is optimized according to the optimized mask layout. The mask processing process is as follows: Fig.10 As shown, the substrate is selected from a substrate material with high transparency (365 nm wavelength transmittance greater than 99.8%), high surface flatness and high stability (10×10 μm 2 The RMS in the area is less than 0.6nm), and a quartz substrate is selected here.

[0088] Step 3: The material of the mask absorption layer is Cr. The mask absorption layer is grown on the substrate by vapor deposition. The growth method is a magnetron sputtering deposition process. The growth process is carried out at room temperature, and finally a 40nm Cr film is obtained. Based on the special requirements of super-resolution lithography for the mask, the mask absorption layer must have a transmittance of less than 0.8% at a wavelength of 365 nm, high surface flatness and high stability (at 10×10 μm 2 The requirements include RMS less than 1.0 nm in the range and low stress (film stress less than 200MPa).

[0089] Step 4: After confirming the quality of the mask absorption layer, spin-coat the surface of the mask absorption layer with electron beam photoresist, the electron beam photoresist is AR-P 6200 with a thickness of 70-90 nm, and then pre-bake the electron beam photoresist at a temperature of 80°C~150°C.

[0090] Step 5: Then move the mask to the electron beam lithography equipment, import the mask pattern corrected by SARF, and perform electron beam direct writing exposure. After the exposure, the sample is developed, fixed and hardened.

[0091] Step 6: After the hardening treatment is completed, the mask is moved to the etching equipment for dry etching, and the dry etching is selected ion beam etching (IBE). The etching process includes: the RF power can be 170 W to 220 W, the beam voltage can be 300 V to 500 V, the acceleration voltage can be 45 V to 75 V, and the etching chamber pressure can be 1×10 -4 Torr to 5×10 -4Torr, in this disclosure, a systematic optimization and regulation is carried out on the etching samples and etching conditions of the SRAF correction pattern with a feature size of ~20nm. The thickness of the photoresist can be 75nm to 80nm, and the corresponding etching angle is 28° to 30°. After the etching is completed and the residual glue is removed, the mask is cleaned to complete the preparation of the mask.

[0092] Step 7: Use SEM to observe the processing of the mask, such as Fig.11 , Fig.12 , Fig.13 As shown, it can be seen that the pattern quality and conformality are relatively excellent, indicating that the sub-resolution auxiliary pattern correction mask obtained based on the calculation simulation and layout design of the mask in the present disclosure can be realized through the mask processing technology.

[0093] It should be noted that the specific parameters, material types and processing methods involved in the above examples are all for the purpose of more clearly illustrating the sub-resolution auxiliary pattern correction mask and preparation method provided by the embodiments of the present disclosure, and are not intended to limit the present disclosure.

[0094] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above are only preferred embodiments of the present disclosure and the technical principles used. Those skilled in the art will understand that the present disclosure is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present disclosure. Therefore, although the present disclosure is described in more detail through the above embodiments, the present disclosure is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present disclosure, all of which belong to the protection scope of the present disclosure.

Claims

1. A method for preparing a sub-resolution auxiliary pattern correction mask, characterized in that: include: Based on the optical path structure of the super-resolution lithography system, a computational model suitable for optical simulation of super-resolution lithography principles is constructed, wherein the computational model includes a light source, a mask, and an object to be photolithographically processed, and the pattern on the mask includes discrete holes and a dense hole array; Based on the computational model, super-resolution lithography is simulated, and a light field simulation is performed on the discrete holes and the dense hole array respectively to obtain respective primary light field distribution results; Based on the respective primary light field distribution results, the sub-resolution auxiliary graphics of the discrete holes are added and the secondary light field simulation is performed to obtain the respective secondary light field distribution results; Based on the respective secondary light field distribution results, sub-resolution auxiliary patterns of the discrete holes are optimized and a third light field simulation is performed, and the optimization is iterated until the light field energy distribution of the discrete holes with the sub-resolution auxiliary patterns added matches the light field energy distribution of the dense hole array; Determining a corrected pattern of a sub-resolution auxiliary pattern correction mask, wherein the corrected pattern includes discrete holes and a dense hole array with added sub-resolution auxiliary patterns; The sub-resolution auxiliary pattern correction mask is prepared based on the corrected pattern of the sub-resolution auxiliary pattern correction mask.

2. The method according to claim 1, characterized in that The size of the sub-resolution auxiliary pattern is smaller than the resolution of the super-resolution lithography system; the aperture of the discrete holes and the aperture of the dense holes in the dense hole array are 70 nm to 500 nm.

3. The method according to claim 1, characterized in that The adding of sub-resolution auxiliary patterns of discrete holes based on the respective primary light field distribution results comprises: Comparing the primary light field distribution result of the discrete holes with the primary light field distribution result of the dense hole array to obtain a light field distribution difference result; Sub-resolution auxiliary patterns are added around the discrete holes based on the light field distribution difference results.

4. The method according to claim 1, characterized in that The sub-resolution auxiliary pattern optimization of the discrete holes based on the respective secondary light field distribution results comprises: The secondary light field distribution results corresponding to the discrete holes with added sub-resolution auxiliary patterns are compared with the secondary light field distribution results corresponding to the dense hole array, the size of the added sub-resolution auxiliary patterns and the gap between the sub-resolution auxiliary patterns and the corresponding discrete holes are adjusted, and the sub-resolution auxiliary patterns of the discrete holes are optimized.

5. The method according to claim 1 or 4, characterized in that: The method of preparing the sub-resolution auxiliary pattern correction mask based on the corrected pattern of the sub-resolution auxiliary pattern correction mask comprises: Selecting a substrate, preparing a mask absorption layer on the substrate, and obtaining a mask plate; Spin coating electron beam photoresist on the mask absorption layer; Based on the corrected pattern of the sub-resolution auxiliary pattern correction mask, electron beam direct writing exposure and development are performed on the mask spin-coated with the electron beam photoresist to transfer the corrected pattern of the sub-resolution auxiliary pattern correction mask to the electron beam photoresist; The pattern of the electron beam photoresist is transferred to the mask absorption layer to obtain the sub-resolution auxiliary pattern correction mask.

6. The method according to claim 5, characterized in that The transferring the pattern of the electron beam photoresist to the mask absorption layer comprises: Transferring the pattern of the electron beam photoresist to the mask absorption layer by ion beam etching; Wherein, the control parameters of the ion beam etching include at least one of radio frequency power, beam voltage, acceleration voltage, growth chamber pressure, and etching angle; The RF power is 170 W to 220 W, the beam voltage is 300 V to 500 V, the acceleration voltage is 45 V to 75 V, and the growth chamber pressure is 1×10 -4 Torr~5×10 -4 Torr, the etching angle is 45°~75°.

7. The method according to claim 5, characterized in that The substrate includes a quartz substrate and a sapphire substrate; The material of the mask absorption layer includes a thin film material composed of one of Cr, Si, Cr / CrO, and Mo / Si, and the thickness of the mask absorption layer is 40 nm to 120 nm; The electron beam photoresist comprises one of AR-P 6200, ZEP 520A, UV135, PMMA, AR-N7520 and hydrogen silsesquioxane polymer photoresist, and the thickness of the electron beam photoresist is 60 nm to 120 nm.

8. The method according to claim 6, characterized in that The object to be photolithographically processed includes a wafer; and the super-resolution photolithography exposure structure formed by the mask and the wafer includes: A substrate, a metal reflective layer, a photoresist, a metal transmission layer, an air spacer layer, and a mask layer stacked in sequence; Or, a substrate, a metal reflective layer, a photoresist layer, an air spacer layer, and a mask layer stacked in sequence; Or, a substrate, a photoresist layer, a metal layer, an air spacer layer, and a mask layer stacked in sequence; Or, a bottom metal layer, a dielectric layer, an intermediate metal layer, a photoresist layer, a surface metal layer, an air spacer layer, and a mask layer stacked in sequence; Alternatively, a metal reflective layer, a photoresist layer, an air spacer layer, a metal-dielectric multilayer film, and a mask are stacked in sequence.

9. The method according to claim 1, characterized in that: Any one of rigorous coupled wave analysis, time-domain finite difference method and finite element method is used to perform light field simulation on the discrete holes, the discrete holes with sub-resolution auxiliary patterns added and the dense hole array.

10. A sub-resolution auxiliary pattern correction mask, characterized in that: The sub-resolution auxiliary pattern correction mask is prepared by the preparation method according to any one of claims 1 to 9; the sub-resolution auxiliary pattern correction mask is provided with discrete holes for adding sub-resolution auxiliary patterns and a dense hole array, and in the process of super-resolution lithography based on the sub-resolution auxiliary pattern correction mask, the process window corresponding to the discrete holes for adding sub-resolution auxiliary patterns is consistent with the process window corresponding to the dense hole array, and the focal depth corresponding to the discrete holes for adding sub-resolution auxiliary patterns is consistent with the focal depth corresponding to the dense hole array.

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