A method of focusing for electron beam lithography

Abstract

The application discloses a focusing method for electron beam lithography, which comprises the following steps: obtaining a lithography pattern of a sample to be lithographed which is formed with a photoresist layer; determining a device setting area and a non-device setting area of the sample to be lithographed according to the lithography pattern; forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed; controlling the electron beam to perform focusing parameter adjustment by using the conductive particles in the conductive pattern; and when the focusing parameter of the electron beam is adjusted to a preset parameter range, controlling the electron beam to perform exposure on the photoresist layer at a position to be exposed in the device setting area, so as to transfer the lithography pattern to the sample to be lithographed. The technical scheme of the application can ensure that the process of electron beam lithography has high resolution, thereby improving the yield of integrated circuits prepared by using the electron beam lithography process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuit manufacturing technology, and particularly relates to a focusing method for electron beam lithography. BACKGROUND

[0002] The most important process in semiconductor integrated circuit manufacturing is lithography, that is, a pre-designed circuit pattern is transferred to a photoresist layer coated on a semiconductor wafer, and then the photoresist layer pattern is transferred to the semiconductor wafer through an etching process.

[0003] Common lithography techniques include optical lithography and electron beam lithography. In the optical lithography technique using photons as a medium, the resolution improvement is technically complex and difficult, and cannot meet the preparation requirements of high-integration integrated circuits. In the electron beam lithography using electrons as a medium, because the wavelength of electrons is very short, it is easy to achieve a lithography precision of tens of nanometers or even nanometers, and therefore has a wide application prospect in research and development and production.

[0004] However, how to effectively focus and eliminate astigmatism of the electron beam of the scanning electron microscope on the flat surface of the photoresist layer, and ensure that the size of the electron beam spot is small enough, is a major challenge faced by the electron beam lithography technology of the scanning electron microscope. SUMMARY

[0005] The present application provides a focusing method for electron beam lithography to solve the technical problem that the electron beam cannot be effectively focused and astigmatism-eliminated on the surface of the photoresist layer in the prior art, so that the size of the electron beam spot cannot be ensured to be small enough.

[0006] The present application provides a focusing method for electron beam lithography, comprising:

[0007] obtaining a lithography pattern of a sample to be lithographed formed with a photoresist layer;

[0008] determining a device setting area and a non-device setting area of the sample to be lithographed according to the lithography pattern;

[0009] forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed;

[0010] controlling the electron beam to perform focusing parameter adjustment using the conductive particles in the conductive pattern;

[0011] when the focusing parameter adjustment of the electron beam is adjusted to a preset parameter range, controlling the electron beam to expose the photoresist layer at a position to be exposed in the device setting area, so as to transfer the lithography pattern to the sample to be lithographed.

[0012] Optionally, forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed comprises:

[0013] placing a mask including a hollow structure on a surface of the sample to be photolithographed on which the photoresist layer is formed; wherein the hollow structure of the mask exposes the non-device setting area of the sample to be photolithographed;

[0014] depositing a conductive material in the hollow structure to form a conductive pattern on the surface of the photoresist layer of the non-device setting area.

[0015] Optionally, the thickness of the conductive pattern is less than or equal to 50 nm.

[0016] Optionally, the conductive material of the conductive pattern is a metal material.

[0017] Optionally, the focusing parameter adjustment of the electron beam using the conductive particles of the conductive pattern includes:

[0018] determining a path function of relative movement between the sample to be photolithographed and the electron beam according to the relative positions of the device setting area and the non-device setting area;

[0019] determining the focusing position of the electron beam on the sample to be photolithographed and the step moving parameter according to the path function;

[0020] controlling the relative movement between the sample to be photolithographed and the electron beam to the electron beam aligning with the focusing position based on the step moving parameter.

[0021] controlling the focusing parameter adjustment of the electron beam using the conductive particles of the conductive pattern at the focusing position.

[0022] Optionally, the focusing parameter adjustment of the electron beam using the conductive particles of the conductive pattern at the focusing position includes:

[0023] sequentially increasing the magnification of the electron beam and focusing and de-astigmatizing using the conductive particles of the conductive pattern at the focusing position until the magnification of the electron beam is adjusted to a first preset magnification.

[0024] Optionally, before controlling the relative movement between the sample to be photolithographed and the electron beam to the electron beam aligning with the focusing position based on the step moving parameter, the method further includes:

[0025] controlling the movement of the sample to be photolithographed to the electron beam aligning with a region of interest of the sample to be photolithographed based on the step moving parameter; the region of interest is located in the conductive pattern; the distance between each position point in the region of interest and the focusing position is less than or equal to a first control value.

[0026] Optionally, the magnification of the electron beam in the region of interest is less than or equal to a second preset magnification.

[0027] The second preset magnification is less than the magnification of the electron beam at the focus position.

[0028] Optionally, a minimum distance between the focus position and a starting exposure position in the device setting region is less than or equal to a second control value.

[0029] Optionally, before forming the conductive pattern on the surface of the photoresist layer in the non-device setting region of the sample to be photolithographed, the method further comprises:

[0030] Spinning the photoresist material on the surface of the sample to be photolithographed to form the photoresist layer on the surface of the sample to be photolithographed.

[0031] The technical scheme of the present application, by obtaining the photolithography pattern of the sample to be photolithographed, determining the device setting region and the non-device setting region of the sample to be photolithographed according to the photolithography pattern, forming the conductive pattern on the surface of the photoresist layer in the non-device setting region, and using the conductive particles in the conductive pattern as reference particles to adjust the focus parameters, the focus parameter adjustment process does not affect the device setting region, and can prevent the influence of the charge on the reference position marked by the electron beam, thereby improving the accuracy of the reference position marked, and improving the accuracy of the exposure position when the device setting region is formally exposed at the reference position, thereby improving the accuracy of the transferred photolithography pattern. At the same time, since the conductive pattern is directly formed on the surface of the photoresist layer, there is no gap between the conductive pattern and the surface of the photoresist layer, and after adjusting the focus parameters using the conductive particles in the conductive pattern as reference particles, focusing and astigmatism, the defocus amount and astigmatism in the formal exposure process can be controlled within an effective range when the electron beam is formally exposed in the device setting region, thereby ensuring that the electron beam lithography process has high resolution, and thereby improving the yield of integrated circuits prepared by the electron beam lithography process.

[0032] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0034] Figure 1 is a flow chart of a focusing method of electron beam lithography provided by an embodiment of the present application;

[0035] Figure 2 is a top view structural schematic diagram of a sample to be lithographed provided by an embodiment of the present application;

[0036] Figure 3 is a film layer structural schematic diagram of a sample to be lithographed provided by an embodiment of the present application;

[0037] Figure 4 is a top view structural schematic diagram of another sample to be lithographed provided by an embodiment of the present application;

[0038] Figure 5 is a film layer structural schematic diagram of another sample to be lithographed provided by an embodiment of the present application;

[0039] Figure 6 is a flow chart of a focusing method of electron beam lithography provided by an embodiment of the present application;

[0040] Figure 7 is a flow chart of a focusing method of electron beam lithography provided by an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the personnel in the art without creative labor should belong to the protection scope of the present application.

[0042] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0043] Embodiment One

[0044] Figure 1is a flow chart of a focusing method of electron beam lithography provided by an embodiment of the present application, the embodiment can be applied to the case of using electron lithography technology for lithography, and the method can be executed by an electron beam lithography device which can be implemented in the form of hardware and / or software, for example, a scanning electron microscope. As shown in Figure 1 , the method comprises the following steps.

[0045] S110, obtaining a lithography pattern of a sample to be lithographed which has a photoresist layer.

[0046] The lithography pattern of the sample to be lithographed is the circuit pattern to be formed on the sample to be lithographed; the lithography pattern is transferred to the photoresist layer of the sample to be lithographed, and then the pattern on the photoresist layer is transferred to the sample to be lithographed through etching, deposition and other processes.

[0047] In an optional embodiment, a photoresist material can be spin-coated on the surface of the sample to be lithographed to form a photoresist layer on the surface of the sample to be lithographed. The sample to be lithographed includes but is not limited to a single crystal silicon wafer, and the photoresist layer can be a positive photoresist layer or a negative photoresist layer, which is not limited in the embodiment of the present application. When the photoresist layer is a positive photoresist layer, the material of the photoresist layer includes but is not limited to polymethyl methacrylate (PMMA) with a molecular weight of 950K, and the thickness of the spin-coated photoresist layer can reach 200 nanometers.

[0048] S120, determining a device setting area and a non-device setting area of the sample to be lithographed according to the lithography pattern.

[0049] Specifically, the sample to be lithographed can generally include a wafer with a large size, and after forming devices (such as resistors, capacitors, inductors, transistors, etc.) of integrated circuits on the wafer, the wafer can be cut to obtain a plurality of integrated circuits. At this time, the sample to be lithographed generally includes a plurality of device setting areas, each device setting area can be used as an integrated circuit setting area, and there will be a non-device setting area between the device setting areas, which can be used as a boundary line between two adjacent device setting areas. Therefore, according to the lithography pattern, the position of the circuit pattern of the integrated circuit to be set in the sample to be lithographed can be determined, that is, the setting position of the integrated circuit is determined, and thus the device setting area of the sample to be lithographed is determined. The area other than the device setting area is the non-device setting area.

[0050] Exemplarily, Figure 2 is a top view structural schematic diagram of a sample to be lithographed provided by an embodiment of the present application, Figure 3 is a film layer structural schematic diagram of a sample to be lithographed provided by an embodiment of the present application, which is combined with reference to Figure 2 and Figure 3The sample to be photolithographed formed with the photoresist layer 20 can include a substrate 10 (for example, a single crystal silicon wafer) and the photoresist layer 20 located on the surface of the substrate 10; according to the photolithographic pattern, it can be determined that the sample to be photolithographed includes a plurality of device setting areas 101 arranged in an array and non-device setting areas 102 surrounding each device setting area 101. Since the device setting area 101 of the sample to be photolithographed is the position where the circuit pattern of the integrated circuit is arranged, that is, according to the photolithographic pattern, the preset exposure position in the photoresist layer 20 of the device setting area 101 is exposed, so that the photolithographic pattern can be transferred to the photoresist layer 20 of the device setting area 101, and then through etching, deposition and other processes, the pattern on the photoresist layer 20 is transferred to the substrate 10 of the sample to be photolithographed, so that the device setting area 101 forms the pattern of the integrated circuit; and no specific circuit pattern needs to be formed in the non-device setting area 102.

[0051] S130, forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be photolithographed.

[0052] S140, controlling the electron beam to perform focus parameter adjustment using the conductive particles in the conductive pattern.

[0053] S150, when the focus parameter adjustment of the electron beam is adjusted to the preset parameter range, controlling the electron beam to expose the photoresist layer at the exposure position in the device setting area, so as to transfer the photolithographic pattern to the sample to be photolithographed.

[0054] The principle of the electron beam lithography process for photolithography of the sample to be photolithographed is that by hitting the electron beam spot on the surface of the sample to be photolithographed formed with the photoresist layer, the atoms at the position of the photoresist layer irradiated by the electron beam are emitted and shifted, so as to change the solubility of the photoresist layer in the developer and realize the transfer of the photolithographic pattern. Before the formal exposure of the photoresist layer in the sample to be photolithographed, that is, before the exposure of the preset exposure position in the device setting area, the focus parameter adjustment can be first determined in other areas, that is, in the non-device setting area, using the reference particles, for example, adjusting the working distance between the electron beam emitting source and the sample to be photolithographed, astigmatism, magnification, alignment position of the electron beam, etc., so that after the reference particles have clear and sharp imaging, the burn-in can be used as a reference mark to facilitate the alignment of the next step. However, if the particles in the photoresist layer are directly used as reference particles, the electron beam spot will directly hit the photoresist layer when burn-in is performed, which will cause the surface of the photoresist layer to accumulate electrons and generate static electricity. When the static electricity accumulates to a certain extent, the electron beam will not be able to perform burn-in, so that the reference mark cannot be formed on the photoresist layer, thereby affecting the alignment of the electron beam and the exposure dose during the subsequent formal exposure, so that the transferred photolithographic pattern is not accurate.

[0055] Specifically, Figure 4 is another top view structural schematic diagram of a sample to be photolithographed provided by the embodiment of the present application,Figure 5 is another schematic diagram of a film layer structure of a sample to be photolithographed provided by an embodiment of the present application, in combination with reference to Figure 4 and Figure 5 by forming a conductive pattern 30 on the surface of the photoresist layer 20 of the non-device setting area 101 of the sample to be photolithographed; at this time, before formal exposure of the device setting area 101 of the sample to be photolithographed, the focusing parameters of the electron beam, including but not limited to working distance, astigmatism, magnification, etc., can be adjusted by taking the conductive particles in the conductive pattern 30 of the non-device setting area 102 as reference particles; when the focusing parameters are adjusted to the preset focusing parameters, for example, the magnification is adjusted to the first preset magnification (for example, greater than or equal to 100,000 times), and the conductive particles have clear and sharp imaging, the position where the conductive particles are located can be burned as a subsequent reference mark; during the formal exposure, the position of the reference mark is the reference position (for example, point P in the figure), and the electron beam is controlled to expose each exposure position (for example, point F in the figure) of the device setting area to change the performance of the photoresist layer at the exposure position, so that the photolithography pattern is transferred to the photoresist layer 20, and finally the processes such as etching and deposition are performed to transfer the photolithography pattern on the photoresist layer 20 to the substrate 10 of the sample to be photolithographed.

[0056] Among them, since the conductive pattern 30 has the conductive property, even if the electric charge is generated on the surface of the conductive pattern 30, the electric charge can be led out by the conductive pattern 30, so as to prevent the electric charge from affecting the burning process of the electron beam; at the same time, since the conductive pattern 30 is directly formed on the surface of the photoresist layer 20, there is no gap between the conductive pattern 30 and the surface of the photoresist layer 20, so that after adjusting the focusing parameters by taking the conductive particles in the conductive pattern 30 as reference particles, focusing and astigmatism are performed, the electron beam can also maintain high imaging clarity when performing formal exposure in the device setting area, so that the electron beam will not affect the exposure dose in the device setting area due to insufficient focusing and / or astigmatism when performing formal exposure in the device setting area.

[0057] The embodiment can determine the device setting area and the non-device setting area of the sample to be photolithographed according to the photolithography pattern of the sample to be photolithographed, form the conductive pattern on the surface of the photoresist layer in the non-device setting area, and use the conductive particles in the conductive pattern as reference particles to adjust the focusing parameters, so that the device setting area is not affected by the focusing parameter adjustment process, and the reference position can be calibrated without affecting the electron beam due to the inability to discharge the charge, thereby improving the accuracy of the calibrated reference position. When the device setting area is exposed at the reference position, the accuracy of the exposure position can be improved, and the accuracy of the transferred photolithography pattern can be improved. At the same time, the conductive pattern is directly formed on the surface of the photoresist layer, so that there is no gap between the conductive pattern and the surface of the photoresist layer. After the focusing parameters are adjusted using the conductive particles in the conductive pattern as reference particles, the defocus amount and the astigmatism in the formal exposure process can be controlled in an effective range, so that the electron beam lithography process has high resolution, and the yield of the integrated circuit prepared by using the electron beam lithography process is improved.

[0058] Embodiment two

[0059] Based on the above embodiment, the embodiment of the application describes the specific process of forming the conductive pattern in detail. Figure 6 is a flowchart of a focusing method of an electron beam lithography provided by the second embodiment of the application, as shown in Figure 6 , the method comprises:

[0060] S210, obtaining a photolithography pattern of a sample to be photolithographed formed with a photoresist layer.

[0061] S220, determining a device setting area and a non-device setting area of the sample to be photolithographed according to the photolithography pattern.

[0062] S230, placing a mask including a hollow structure on the surface of the sample to be photolithographed formed with the photoresist layer.

[0063] S240, depositing a conductive material in the hollow structure to form a conductive pattern on the surface of the photoresist layer in the non-device setting area.

[0064] The mask can include a hollow structure and a shielding structure, the shielding structure can cover the device setting area of the sample to be photolithographed, and the hollow structure can expose the non-device setting area of the sample to be photolithographed. The hollow structure of the mask can be determined according to the photolithography pattern. The photolithography patterns of different samples to be photolithographed are different, and the masks applied are also different.

[0065] Specifically, the mask can be a hard mask such as a metal mask, which can be placed close to the surface of the photoresist layer in the sample to be photolithographed; by providing a conductive material deposition source on the side of the mask away from the photoresist layer, the conductive material is deposited on the surface of the photoresist layer in the non-device setting area through the hollow structure of the mask, while the surface of the photoresist layer in the device setting area is shielded by the shielding structure of the mask, so that the conductive material will not be deposited in the device setting area, so that only the device setting area retains the conductive material after the mask is removed. The structure formed by the retained conductive material is the conductive pattern. In this way, by setting the conductive pattern only in the non-device setting area, the photoresist layer in the device setting area is exposed, and when the focusing parameter adjustment is performed using the conductive particles in the conductive pattern, the electron beam will not affect the photoresist layer in the device setting area. At the same time, the device setting area is not provided with a conductive pattern, so that the electron beam can directly irradiate the surface of the photoresist layer during the formal exposure, ensuring that the exposure dose is within a controllable range.

[0066] In an exemplary embodiment, after the mask is placed on the surface of the photoresist layer, the sample to be photolithographed can be placed in a vacuum coating machine to deposit a conductive material of a certain thickness; after the mask including the hollow structure is removed, a conductive pattern can be formed on the surface of the photoresist layer in the non-device setting area of the sample to be photolithographed.

[0067] In an optional embodiment, the thickness of the deposited conductive pattern can be less than or equal to 50 nm, so that the thickness of the conductive pattern is small enough to ensure that the surface of the conductive pattern in the non-device setting area has a small height difference with the surface of the photoresist layer in the device setting area, so that when the electron beam is moved to the device setting area for formal exposure after focusing and astigmatism are performed using the conductive particles in the conductive pattern in the non-device setting area, the focusing and astigmatism of the electron beam can be kept within a controllable range, thereby improving the accuracy of the photolithographic pattern transfer.

[0068] The conductive material of the conductive pattern can be any material with good conductivity, and in an optional embodiment, the conductive material of the conductive pattern can be a metal material. Since the metal material has good conductivity, and the metal material has clear grain boundaries, it is beneficial to the focusing and astigmatism of the electron beam when the grains in the metal material are used as reference particles.

[0069] S250, controlling the electron beam to perform focusing parameter adjustment using the conductive particles in the conductive pattern.

[0070] S260, when the focusing parameter of the electron beam is adjusted to a preset parameter range, controlling the electron beam to expose the photoresist layer in the device setting area to be exposed to transfer the photolithographic pattern to the sample to be photolithographed.

[0071] The embodiment forms the conductive pattern on the surface of the photoresist layer in the non-device setting area by placing the mask including the hollow structure on the surface of the photoresist layer and forming the conductive material on the surface of the photoresist layer at the hollow structure by deposition, so that the subsequent focusing parameter adjustment process is separated from the formal exposure process, and after the focusing and astigmatism are performed by using the conductive particles in the conductive pattern, the focusing and astigmatism of the electron beam can still be within a controllable range in the formal exposure process, thereby improving the accuracy of the transferred photoresist pattern, ensuring that the electron beam lithography process has high resolution, and improving the yield of the integrated circuit prepared by using the electron beam lithography process.

[0072] Embodiment three

[0073] Based on the above embodiment, the embodiment specifically describes the method for controlling the electron beam to perform the focusing parameter adjustment by using the conductive particles in the conductive pattern. Figure 7 is a flowchart of the focusing method of the electron beam lithography provided by the embodiment three, as shown in the figure, the method comprises the following steps. Figure 7

[0074] S310, obtaining a photoresist pattern of a sample to be lithographed formed with a photoresist layer.

[0075] S320, determining a device setting area and a non-device setting area of the sample to be lithographed according to the photoresist pattern.

[0076] S330, forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed.

[0077] S340, determining a path function of the relative motion between the sample to be lithographed and the electron beam according to the relative position of the device setting area and the non-device setting area.

[0078] According to the relative position of the device setting area and the non-device setting area in the sample to be lithographed, the moving direction and range of the electron beam relative to the sample to be lithographed and the focusing point for the focusing parameter adjustment when the relative motion between the electron beam and the sample to be lithographed occurs before the formal exposure are determined, which are taken as the path function of the relative motion between the sample to be lithographed and the electron beam.

[0079] S350, determining the focusing position and the step moving parameter of the electron beam on the sample to be lithographed according to the path function.

[0080] The focusing position is the focusing point of the electron beam for the focusing parameter adjustment on the sample to be lithographed, and the focusing point is a position point on the conductive pattern in the non-device setting area; the step moving parameter is the moving amount and direction of the electron beam on the sample to be lithographed when the relative motion between the electron beam and the sample to be lithographed occurs. ​

[0081] Specifically, as shown in Figure 4 In an example embodiment, when the e-beam lithography process is performed on the photoresist layer of each device setting area 101, the photoresist layer of each device setting area 101 is exposed in sequence, and after the exposure of the photoresist layer in one device setting area 101 is completed, the e-beam is moved to the vicinity of the next device setting area 101. In order to prevent the e-beam from scanning the device setting area 101 and affecting the exposure dose of the device setting area 101, a corresponding step movement parameter is set to ensure that the e-beam does not scan the device setting area 101 when the sample to be exposed moves, i.e., the e-beam only scans the non-device setting area 102. In a preferred embodiment, the determined step movement parameter can make the e-beam only scan the position of the conductive pattern when the sample to be exposed moves. At this time, the movement amount of the sample to be exposed in the lateral X and / or longitudinal Y direction should be within the range of the conductive pattern area, until the alignment position of the e-beam on the sample to be exposed reaches the focus position P.

[0082] In an example embodiment, when each device setting area 101 is a square area of 5mm x 5mm, the width of the non-device setting area 102 between two adjacent device setting areas 101 is 5mm, and the width of the conductive pattern arranged in the non-device setting area 102 is 3mm, the movement amount of the sample to be exposed in the width direction of the conductive pattern should be no more than 1.5mm, and the magnification of the e-beam during the movement of the sample to be exposed should be no more than 100 times, to ensure that the scanning range of the e-beam is only the range of the conductive pattern area.

[0083] S360, based on the step movement parameter, controlling the sample to be exposed to move to the region of interest of the e-beam.

[0084] The region of interest is located in the conductive pattern, and the distance between each position point in the region of interest and the focus position is less than or equal to the first control value.

[0085] Specifically, continuing to refer to Figure 4In the movement of the sample to be lithographed, before the movement of the electron beam relative to the sample to be lithographed to the focusing position on the sample to be lithographed, the sample to be lithographed can be controlled to move to a region of interest M of the sample to be lithographed, which is a region within a certain range near the device setting area 101 to be exposed, i.e., before the formal exposure of the device setting area 101, the sample to be lithographed can be quickly moved according to the path function, so that the electron beam relative movement to the region of interest M near the device setting area 101 to be exposed, to coarsely adjust the alignment position of the electron beam on the sample to be lithographed, and the magnification in the region of interest M should be less than or equal to the second preset magnification, for example, the second preset magnification can be 100 times, which is not limited in the embodiment of the present application. At the same time, since the distance between each position point S in the region of interest M and the focusing position P is less than or equal to the first control value, the region of interest M is a region close to the focusing position P, so as to prepare for the fine adjustment of the alignment position of the electron beam in the next step.

[0086] Optionally, the region of interest can generally be the intersection position of the conductive pattern between the two adjacent rows of device setting areas 101 and the conductive pattern between the two adjacent columns of device setting areas 101, so as to ensure that the region of interest is close enough to the device setting area 101, and the region of interest has a large enough area to meet the coarse adjustment requirement of the alignment position of the electron beam.

[0087] Wherein, before the sample to be lithographed is controlled to move to the region of interest M of the sample to be lithographed, the movement path of the electron beam on the sample to be lithographed is within the region of the conductive pattern. Wherein, the first control value can be related to the thickness uniformity of the sample to be lithographed and the perpendicularity of the center axis of the electron beam optical path, for example, the first control value can be 1mm.

[0088] S370, based on the step movement parameter, controlling the sample to be lithographed and the electron beam relative movement to the focusing position.

[0089] S380, controlling the electron beam to adjust the focusing parameter by using the conductive particles of the conductive pattern at the focusing position.

[0090] Specifically, with reference to the foregoing Figure 4, the path function, after the sample to be lithographed is moved to the region of interest M of the sample to be lithographed, the alignment position of the electron beam is further fine-adjusted so that the electron beam is closer to the device setup region 101 of the formal exposure, at this time, the sample to be lithographed or the electron beam is controlled to move based on the step movement parameters so that the movement path of the electron beam in the sample to be lithographed is located in the region where the conductive pattern is located, until the electron beam is aligned with the focusing position P; the focusing position P is a position point closer to the starting exposure position F in the device setup region 101 of the formal exposure; the focusing parameter adjustment is realized by focusing, de-astigmatism, and increasing the magnification of the conductive particles of the conductive pattern at the focusing position P until the imaging of the conductive particles is clear and sharp, and the magnification reaches the first preset magnification, and then a burn-in point is formed to form a reference mark, and then the electron beam is controlled to move to the starting exposure position F of the device setup region 101 in the sample to be lithographed.

[0091] The minimum distance between the focusing position P and the starting exposure position F in the device setup region should be less than or equal to the second control value, so as to ensure that after moving from the focusing position P to the starting exposure position F in the device setup region, the defocus amount and the astigmatism degree are still within the required range, that is, the focusing and astigmatism at the focusing position P are consistent with or slightly different from the focusing and astigmatism at the starting exposure position F. Similarly, the second control value should be related to the thickness uniformity of the sample to be lithographed, the perpendicularity of the central axis of the electron beam optical path, etc. For example, the second control value can be 1 mm.

[0092] Optionally, the second preset magnification in the region of interest M is much smaller than the first preset magnification in the formal exposure, that is, the second preset magnification should be smaller than the magnification at the focusing position P.

[0093] Optionally, when at the focusing position, the focusing parameter adjustment using the conductive particles of the conductive pattern at the focusing position can be: increasing the magnification of the electron beam in sequence, and using the conductive particles of the conductive pattern at the focusing position for focusing and de-astigmatism, until the magnification of the electron beam is adjusted to the first preset magnification, that is, the magnification is increased in sequence while the focusing and de-astigmatism are adjusted, so as to prevent the magnification from suddenly changing and the parameter adjustment direction of the focusing and de-astigmatism from being determined, and to improve the adjustment efficiency of the focusing parameter. For example, the first preset magnification can be 100,000 times.

[0094] S390, when the focusing parameter of the electron beam is adjusted to the preset parameter range, the electron beam is controlled to expose the photoresist layer at the exposure position in the device setup region to transfer the lithography pattern to the sample to be lithographed.

[0095] The embodiment determines the path function of the relative movement of the electron beam and the sample to be photolithographed by the relative positions of the device setting area and the non-device setting area, so that the electron beam and the sample to be photolithographed move to the region of interest according to the path function, then move from the region of interest to the focus position for focus parameter adjustment, and after the focus parameter adjustment at the focus position, enter the device setting area for formal exposure, thereby preventing the electron beam from scanning the device setting area and affecting the exposure dose of the device setting area during the relative movement of the electron beam and the sample to be photolithographed, and ensuring that the defocus amount and the degree of astigmatism of the electron beam after moving to the device setting area for formal exposure can be within a controllable required range, thereby facilitating the improvement of the lithography accuracy and the lithography efficiency.

[0096] It should be understood that the various forms of flow shown above can be reordered, added to, or deleted from without departing from the scope of the present application. For example, the steps recited in the present application can be performed in parallel, in series, or in a different order, and the present application is not limited herein as long as the desired results of the technical solutions of the present application can be achieved.

[0097] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of focusing electron beam lithography, characterized by, The method comprises: obtaining a lithography pattern of a sample to be lithographed formed with a photoresist layer; determining a device setting area and a non-device setting area of the sample to be lithographed according to the lithography pattern; forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed; controlling the electron beam to perform focus parameter adjustment using conductive particles in the conductive pattern; when the focus parameter adjustment of the electron beam is adjusted to a preset parameter range, controlling the electron beam to expose the photoresist layer at a position to be exposed in the device setting area, so as to transfer the lithography pattern to the sample to be lithographed; forming a conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be lithographed comprises: placing a mask plate comprising a hollow structure on the surface of the sample to be lithographed formed with the photoresist layer; wherein the hollow structure of the mask plate exposes the non-device setting area of the sample to be lithographed; and depositing a conductive material in the hollow structure to form a conductive pattern on the surface of the photoresist layer in the non-device setting area. The conductive pattern comprises a focus position; the focus position comprises conductive particles used for focus parameter adjustment; and the minimum distance between the focus position and a starting exposure position in the device setting area is less than or equal to a second control value.

2. The method of focusing electron beam lithography according to claim 1, wherein, The thickness of the conductive pattern is less than or equal to 50 nm.

3. The method of claim 1, wherein, The conductive material of the conductive pattern is a metal material.

4. The method of claim 1, wherein, The method comprises: determining a path function of relative motion between the sample to be lithographed and the electron beam according to the relative positions of the device setting area and the non-device setting area; determining a focus position and a step movement parameter of the electron beam on the sample to be lithographed according to the path function; controlling the sample to be lithographed and the electron beam to move relative to each other based on the step movement parameter, so that the electron beam is aligned with the focus position; and controlling the electron beam to perform focus parameter adjustment using conductive particles of the conductive pattern at the focus position.

5. The method of focusing for e-beam lithography of claim 4, wherein, The method comprises: increasing the magnification of the electron beam in sequence, and performing focusing and stigmation using the conductive particles of the conductive pattern at the focus position, until the magnification of the electron beam is adjusted to a first preset magnification.

6. The method of focusing for e-beam lithography of claim 4, wherein, Before the step of controlling the sample to be lithographed and the electron beam to move relative to each other based on the step movement parameter, so that the electron beam is aligned with the focus position, the method further comprises: controlling the sample to be lithographed to move to a region of interest of the sample to be lithographed based on the step movement parameter, so that the electron beam is aligned with the region of interest; the region of interest is located in the conductive pattern; and the distance between each position point in the region of interest and the focus position is less than or equal to a first control value.

7. The method of focusing for e-beam lithography of claim 6, wherein, The magnification of the electron beam in the region of interest is less than or equal to a second preset magnification; The second preset magnification is less than the magnification of the electron beam at the focus position.

8. The method of claim 1, wherein the focusing of the electron beam is performed by a lens system. Before forming the conductive pattern on the surface of the photoresist layer in the non-device setting area of the sample to be photoetched, further comprising: Spinning photoresist material on the surface of the sample to be photoetched to form the photoresist layer on the surface of the sample to be photoetched.

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