A high-precision measurement method for nanoimprint master
By preparing the test area and the graphics area on the nanoimprint master, and combining lossless and lossy measurement technology, the accuracy problem of the depth measurement of the high-deep aspect ratio nanoimprint master is solved, achieving high-precision depth measurement, and improving Chip production yield.
Patent Information
- Application Number
- CN202411282403.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-13
- Publication Date
- 2025-02-14
- Estimated Expiration
- 2044-09-13
AI Technical Summary
The prior art cannot achieve lossless high-precision measurement of the depth of high-deep and aspect ratio nanoimprint master, resulting in the impact of chip manufacturing accuracy and yield.
By preparing the imprinted master formal film and accompanying film, the graphics and testing areas were made on the formal film and accompanying film respectively, the depth of the test area was measured without loss by atomic force microscope, and the lossy measurement of the lobe cross-section scanning electron microscope or the focused ion beam was obtained by lossy measurement of the lobe cross-section scanning electron microscope or the focused ion beam The depth of the graphics area is calculated by combining the two.
The accuracy of the depth of the high-deep and aspect ratio nanoimprint master is achieved, with an error of no more than 5nm, ensuring the accuracy and yield of chip production and avoiding damage to the imprint master.
Smart Images
Figure CN118859647B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of nanoimprinting, and in particular relates to a high-precision measurement method for a nanoimprinting master. Background Art
[0002] Nanoimprint technology is a high-precision nanomanufacturing technology used to create nanoscale patterns on the surface of a substrate; it works by imprinting a hard template engraved with nanostructures onto a flexible or photosensitive substrate, and then transferring the pattern to the substrate by heating or UV curing. At present, nanoimprint technology is one of the most promising key technologies in the field of micro-nano processing. In the International Semiconductor Blueprint ITRS, this technology is listed as one of the important representatives of the next generation of semiconductor processing technology. Nanoimprint technology has technical advantages such as high precision, high efficiency, and low cost. It is suitable for large-scale mass production and industrialization needs of optoelectronic chips, so it is expected to become a basic technology in the future optoelectronic field. This technology adopts the principle of micro-replication of traditional mechanical molds, and can manufacture chips like stamping. Therefore, the imprint master is the source process, and its key dimensional accuracy directly affects the production yield of all subsequent chips.
[0003] The requirements for the depth dimension of the imprint master of optoelectronic chips are extremely stringent, usually requiring nanometer-level precision, such as tens of nanometers or even smaller. At the same time, in order to achieve higher integration, the structure on the imprint master often has a large aspect ratio (ratio of depth to width), which may be as high as 10:1 or higher; this high aspect ratio nanoscale structure poses a great challenge to the depth measurement of the imprint master. Currently commonly used non-destructive measurement technologies, such as atomic force microscopy (AFM), white light interferometry, etc., cannot accurately measure depth information because the scanning probe or light beam cannot reach the bottom of the structure. Although lossy measurements, such as split cross-section scanning electron microscopy (SEM) and focused ion beam (FIB), can measure depth, they will damage the expensive imprint master and affect the yield; therefore, the existing technology cannot achieve non-destructive and high-precision measurement of the depth of high aspect ratio nanoimprint masters. Once the depth measurement of the imprint master is inaccurate, it will seriously affect the manufacturing accuracy and yield of subsequent chips, causing significant economic losses.
[0004] In this regard, the present invention proposes a high-precision measurement method for a nanoimprint master, which ensures the accuracy of the nanoimprint master and is of great significance for improving the yield of optoelectronic chips and reducing manufacturing costs. Summary of the invention
[0005] The purpose of the present invention is to provide a high-precision measurement method for a nanoimprint master, so as to solve the technical problem that the prior art mentioned in the above background technology cannot accurately measure the depth of the nanoimprint master.
[0006] In order to achieve the above object, the present invention provides the following technical solutions:
[0007] A high-precision measurement method for a nanoimprint master comprises the following steps:
[0008] S1, preparing an imprint master sheet and an imprint master companion sheet in sequence by the same process, and making a pattern area and a test area on the imprint master sheet and the imprint master companion sheet respectively, wherein the test area is located outside the pattern area, and the aspect ratio of the test area is less than 1, so that a scanning probe of an atomic force microscope can contact the bottom of the structure and accurately measure the depth of the test area;
[0009] The imprint master companion sheet has the same critical dimensions and graphic area as the imprint master official sheet; to avoid the influence of etching load effect; the same process means: the etching rate ratio of the graphic area and the test area on the imprint master official sheet is fixed; the etching rate ratio of the graphic area and the test area on the imprint master companion sheet is fixed; the etching rate ratio of the imprint master official sheet is the same as the etching rate ratio of the imprint master companion sheet;
[0010] S2, depth measurement, including:
[0011] The depth of the graphic area on the imprint master companion sheet is measured by using a split cross-section scanning electron microscope or a focused ion beam method. The depth of the graphic area on the imprint master companion sheet is Z1. The split cross-section scanning electron microscope and the focused ion beam method can provide a nanometer-level or even higher longitudinal resolution, and can accurately measure the depth dimension of the nanoimprint master graphic area.
[0012] The depth of the test area on the imprint master sheet and the imprint master companion sheet is measured non-destructively by using an atomic force microscope; the depth of the test area on the imprint master companion sheet is H1; the depth of the test area on the imprint master sheet is H; there is only a very small interaction force between the scanning probe of the atomic force microscope and the surface of the object to be measured, and it is considered to be a non-destructive measurement technology, which will not damage the surface of the object to be measured;
[0013] S3, calculate the depth Z of the graphic area on the formal chip of the imprint master:
[0014] Z=(Z1 / H1)* H;
[0015] The etching rate ratio of the graphic area and the test area of the same imprint master is fixed. Since the etching time of the graphic area and the test area of the same imprint master is the same, it can be known that the depth ratio of the graphic area and the test area is fixed.
[0016] Preferably, in S1, a graphic area and a test area are prepared on the imprint master sheet and the imprint master companion sheet by electron beam lithography and etching processes; a photoresist pattern formed by electron beam lithography is used as an etching mask, and after etching, the desired nanoscale structure is transferred to the imprint master sheet and the imprint master companion sheet. After etching is completed, the residual photoresist mask is removed to obtain the final nanostructure.
[0017] Preferably, the etching time of the graphic area and the test area on the imprint master formal wafer is the same; the etching time of the graphic area and the test area on the imprint master companion wafer is the same.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] The present invention provides a high-precision measurement method for a nanoimprint master, which solves the technical problem that the existing non-destructive measurement technology cannot accurately measure the depth information of the imprint master, resulting in the inability to ensure the accuracy of the imprint master, thereby affecting the subsequent chip production yield, and realizes the accurate measurement of the depth information of the high aspect ratio nanoimprint master, with an error of no more than 5nm. The present invention introduces the concept of an imprint master companion sheet and a test area, and can perform lossy depth measurement on the graphic area on the imprint master companion sheet, and then combine the non-destructive measurement results of the test area of the imprint master formal sheet and the imprint master companion sheet to accurately calculate the depth of the graphic area of the imprint master formal sheet, thereby realizing high-precision measurement of the imprint master. This method ensures the accuracy of the imprint master from the source, thereby improving the yield of chip production. In addition, the present invention is not only applicable to imprint masters of specific sizes and materials, but also to other wafers or chips with high aspect ratio structures, and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 A schematic diagram of an imprinting master plate in a preferred embodiment of the present invention;
[0021] Figure 2 It is a schematic diagram of the imprinting master accompanying sheet in the preferred embodiment of the present invention. DETAILED DESCRIPTION
[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. All other embodiments obtained by ordinary technicians in the field without making creative work based on the embodiments of the present invention shall fall within the scope of protection of the present invention.
[0023] like Figure 1-Figure 2 As shown:
[0024] A high-precision measurement method for a nanoimprint master comprises the following steps:
[0025] S1, prepare the imprint master official sheet and the imprint master companion sheet in sequence by the same process, and make the pattern area and the test area on the imprint master official sheet and the imprint master companion sheet respectively, the test area is located outside the pattern area, and the depth-to-width ratio of the test area is less than 1; so that the scanning probe of the atomic force microscope can contact the bottom of the structure, and the depth of the imprint master companion sheet test area can be accurately measured. The imprint master companion sheet has the same critical dimensions and pattern area as the imprint master official sheet, so as to avoid the influence of the etching load effect.
[0026] The etching time of the graphic area and the test area on the imprint master regular wafer is the same; the etching time of the graphic area and the test area on the imprint master companion wafer is the same.
[0027] The same process means that: the etching rate ratio of the graphic area and the test area on the imprint master formal sheet is fixed; the etching rate ratio of the graphic area and the test area on the imprint master companion sheet is fixed; the etching rate ratio of the imprint master formal sheet is the same as the etching rate ratio of the imprint master companion sheet.
[0028] Specifically, in S1, a graphic area and a test area are prepared on the imprint master sheet and the imprint master companion sheet by electron beam lithography and etching processes; the photoresist pattern formed by electron beam lithography is used as an etching mask. After etching, the nanoscale structure required by the imprint master is transferred to the imprint master sheet and the imprint master companion sheet. After etching is completed, it is usually necessary to remove the residual photoresist mask to obtain the final nanostructure.
[0029] Electron beam lithography is a method of using a high-energy electron beam to expose photoresist to cause chemical changes, thereby forming the desired pattern on the photoresist layer. The main steps of electron beam lithography include: coating photoresist on a substrate, exposing the photoresist using an electron beam exposure system, chemical changes in the exposed part of the photoresist, and developing and removing the exposed or unexposed part of the photoresist to form the desired photoresist pattern; electron beam lithography can achieve nanometer-level resolution and is one of the key technologies for making nanoscale imprint masters.
[0030] Etching is the process of transferring the photoresist pattern to the imprint master; commonly used etching methods include wet etching and dry etching. The dry etching uses the physical and chemical effects of plasma active particles to selectively etch the imprint master. Dry etching methods include reactive ion etching (RIE), ion beam etching (IBE), etc.; the wet etching uses chemical solutions to selectively corrode the imprint master.
[0031] The etching load effect refers to the phenomenon that the size of the area to be etched on the substrate will affect the etching rate during the etching process; keeping the key dimensions and graphic areas of the imprint master and the imprint master companion consistent can avoid the different effects of the etching load effect on the two, thereby avoiding the accuracy of the final depth measurement of the graphic area of the imprint master; it can effectively avoid the interference of the etching load effect. The critical dimension refers to the main dimensional parameter in the imprint master that affects its performance and function. The critical dimension includes the width, depth and spacing of the graphics in the graphic area; the critical dimension is directly related to the accuracy and effect of the imprint process.
[0032] In the dry etching process, when the area on the material surface that is not covered by the mask or protective layer (open area) is large, the probability of being bombarded by etching ions per unit open area is small, resulting in a lower etching rate; conversely, when the open area is small, the probability of being bombarded by etching ions per unit open area is large, resulting in a higher etching rate. In the wet etching process, the consumption rate of the etchant is proportional to the size of the open area; the larger the open area, the faster the etchant is consumed, resulting in a decrease in the concentration of the etchant in the area, which in turn makes the etching rate lower; conversely, the smaller the open area, the slower the etchant consumption, the higher the concentration, and the faster the etching rate.
[0033] Atomic force microscopy (AFM) is a high-resolution scanning probe microscope. By accurately measuring the interaction force between the scanning probe of the atomic force microscope and the atoms of the object being measured, the three-dimensional surface morphology can be reconstructed, thereby achieving non-destructive and accurate measurement of depth and avoiding damage to the object being measured.
[0034] The working principle of atomic force microscopy is as follows: a very small scanning probe is installed at the end of a flexible cantilever beam. When the tip of the scanning probe scans close to the surface of the object being measured, an attractive or repulsive force will be generated between the tip and the atoms on the surface of the object being measured, causing the cantilever beam to bend. By accurately measuring the degree of bending of the cantilever beam, the three-dimensional morphology of the surface of the object being measured can be reconstructed; since there is only a very small interaction force between the scanning probe and the object being measured, it is considered a non-destructive measurement technology that will not damage the surface of the object being measured.
[0035] In the depth measurement of the nanoimprint master, the scanning probe of the atomic force microscope can vertically contact and scan the groove or protrusion structure on the surface of the imprint master to accurately measure the depth value. However, for structures with a high aspect ratio (aspect ratio greater than 1), the scanning probe may not be able to fully contact the bottom, thereby affecting the measurement accuracy. Therefore, the present invention designs a test area with an aspect ratio less than 1 on the imprint master formal sheet, so that the scanning probe of the atomic force microscope can fully contact the bottom of the structure.
[0036] S2, using the split cross-section scanning electron microscope (SEM) or focused ion beam (FIB) method to measure the depth Z1 of the graphic area on the imprint master companion wafer; using the atomic force microscope (AFM) to measure the depth H1 of the test area on the imprint master companion wafer; using the atomic force microscope to measure the depth H of the test area on the imprint master formal wafer.
[0037] Specifically, the imprint master companion film is cross-sectioned using a split cross-section scanning electron microscope or a focused ion beam method to expose the cross section of the graphic area. Then, through imaging using a split cross-section scanning electron microscope or ion beam scanning using a focused ion beam, the depth dimension of the graphic area can be directly measured, which serves as a reference value for subsequent calculation of the depth of the imprint master formal film.
[0038] The split cross-section scanning electron microscope and focused ion beam method can provide nanometer-level or even higher longitudinal resolution, and can accurately measure the depth dimension of the nanoimprint master pattern area; and the depth of the nanoimprint master is usually in the range of tens to hundreds of nanometers, which requires such high-resolution measurement methods.
[0039] Atomic force microscopy uses a scanning probe to scan the surface of the object being measured, and uses the interaction force between the scanning probe and the object to reconstruct the surface morphology of the object being measured. When the depth and width of the structure are relatively large, it is difficult for the scanning probe to fully contact the bottom of the structure, which will affect the measurement accuracy. The split cross-section scanning electron microscope and focused ion beam method directly image the cross section of the object being measured through an electron beam or ion beam, and can directly measure the depth of the structure without being affected by the shape of the structure.
[0040] Compared with atomic force microscopy, the resolution of split-section scanning electron microscopy and focused ion beam method can reach nanometer level when measuring the depth of high aspect ratio structures, while the resolution of atomic force microscopy is usually around tens of nanometers. For nanoscale structures, split-section scanning electron microscopy and focused ion beam method have higher resolution.
[0041] S3, the etching rate ratio of the graphic area and the test area of the same imprint master is fixed. Since the etching time of the graphic area and the test area of the same imprint master is the same, it can be known that the depth ratio of the graphic area and the test area of the same imprint master is fixed, and this ratio is consistent for the imprint master formal film and the imprint master companion film, so the depth Z of the graphic area of the imprint master formal film is (Z1 / H1)*H.
[0042] Specifically, in the process of making the nanoimprint master, the imprint master main sheet and the imprint master companion sheet undergo the same electron beam lithography and etching process; it can be seen that for the same nanoimprint master, whether it is the imprint master main sheet or the imprint master companion sheet, the etching time experienced by their graphic area and test area is exactly the same.
[0043] During the etching process, due to the different structures of the graphic area and the test area, there will be differences in etching rates, but this rate difference is the same for the imprint master formal film and the imprint master companion film of the same nanoimprint master; that is, the depth ratio of the graphic area and the test area of the imprint master formal film (Z / H) is equal to the depth ratio of the graphic area and the test area of the imprint master companion film (Z1 / H1); this ratio is fixed, because the etching time and process conditions experienced by the graphic area and the test area of the imprint master formal film are exactly the same, and the etching time and process conditions experienced by the graphic area and the test area of the imprint master companion film are exactly the same.
[0044] By directly measuring the depth Z1 of the graphic area and the depth H1 of the test area on the imprint master companion film, the fixed ratio Z1 / H1 can be obtained; then substituting the measured depth H of the test area of the imprint master formal film into the depth Z of the graphic area of the imprint master formal film, the depth Z of the graphic area of the imprint master formal film can be calculated:
[0045] Z = (Z1 / H1) * H;
[0046] In this way, through the lossy measurement of the imprint master companion film and the non-destructive measurement of the imprint master formal film, the precise depth of the graphic area of the imprint master formal film can be indirectly obtained, with an error of no more than 5nm, and the imprint master formal film will not be damaged.
[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A high-precision measurement method for a nanoimprint master, characterized in that: The following steps are involved: S1, preparing an imprint master plate and an imprint master companion plate in sequence by the same process, and making a pattern area and a test area on the imprint master plate and the imprint master companion plate respectively, wherein the test area is located outside the pattern area, and the aspect ratio of the test area is less than 1; The same process means that the etching rate ratio between the pattern area and the test area on the imprint master is fixed; The etching rate ratio between the pattern area and the test area on the imprint master companion sheet is fixed; The etching rate ratio of the imprint master main sheet is the same as the etching rate ratio of the imprint master companion sheet; S2, depth measurement, including: The depth of the graphic area on the imprint master companion sheet is measured by using a split cross-section scanning electron microscope or a focused ion beam method, wherein the depth of the graphic area on the imprint master companion sheet is Z1; The depth of the test area on the imprint master formal sheet and the imprint master companion sheet is measured non-destructively by using an atomic force microscope, wherein the depth of the test area on the imprint master companion sheet is H1, and the depth of the test area on the imprint master formal sheet is H; S3, calculate the depth Z of the graphic area on the formal chip of the imprint master: Z=(Z1 / H1)*H.
2. The high-precision measurement method of a nanoimprint master according to claim 1, characterized in that: In S1, a pattern area and a test area are prepared on an imprint master sheet and an imprint master companion sheet by electron beam lithography and etching processes.
3. The high-precision measurement method of a nanoimprint master according to claim 1, characterized in that: The etching time of the graphic area and the test area on the imprint master regular wafer is the same; the etching time of the graphic area and the test area on the imprint master companion wafer is the same.
Citation Information
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