Alignment method for imprint method

Abstract

A method of detecting a detection angle in a lithographic apparatus, the method comprising: using a calibration substrate having a refractive index n and having a first pair of marks, the pair of marks having a predetermined lateral displacement relative to each other, a first mark of the pair of marks being located at a first predetermined vertical position within the calibration substrate, and a second mark of the pair of marks being located at a second predetermined vertical position within the calibration substrate; the calibration substrate is supported on a first surface thereof, the pair of marks are irradiated by a light source, light redirected from the first mark and the second mark is detected by a detector having an optical axis, and the first mark of the pair of marks is located at a first predetermined vertical position, and the second mark of the pair of marks is located at a second predetermined vertical position. The detector is arranged to determine a first detected lateral displacement between the first mark and the second mark, where an optical axis of the detector is at a detection angle [alpha] 1 of less than 90 DEG with respect to a normal to the substrate, and a first detection angle is determined based on the first detected lateral displacement between the first mark and the second mark.

Description

Technical Field

[0001] The present invention relates to the field of alignment in imprint lithography, and more particularly to flexible stamp imprint lithography. Background Art

[0002] Imprint lithography, as disclosed in EP3126909A, is gaining increasing interest as a viable alternative to more traditional mask-based optical lithography techniques, as imprint lithography is expected to be able to provide smaller (smaller) feature sizes to be transferred onto a large area substrate (such as a substrate of a semiconductor device). In an imprint lithography technique such as substrate conformal imprint lithography ("SCIL"), a flexible stamp having a pattern of surface features is brought into contact with a material carrying a resist. The resist material is imprinted with the feature pattern and subsequently developed (e.g., cured) while being imprinted. Thereafter, the feature pattern is released from the resist material, leaving a patterned resist layer on the substrate.

[0003] In this process, a curable but flowable resist layer is applied to a substrate (e.g., a wafer) supported on a chuck. The flexible stamp is, for example, rubber, and the resist layer can be cured (solidified) during imprinting to leave a solidified relief in the resist layer that is complementary to the relief of the stamp relief layer after the stamp is removed from the resist. The imprinting process requires a thin flexible stamp to be arranged on a stamp manipulator, the thin flexible stamp being formed by a layer of polydimethylsiloxane ("PDMS") rubber adhered to a thin flexible plate (such as a metal plate or a glass plate), wherein the relief surface of the PDMS layer faces the glass plate side. This positions the glass plate against the stamp manipulator, and the relief surface of the stamp faces the resist layer. Summary of the Invention

[0004] During the imprinting process, the surfaces of the stamp and the resist layer of the substrate remain substantially parallel in the X-Y plane and have a still relatively small mutual distance in the Z-axis direction (sometimes also referred to as the vertical direction).

[0005] The stamp can be locally manipulated using a stamp manipulator. For example, the stamp can be locally and sequentially released from and adhered to the stamp manipulator by the stamp manipulator. In one example, the stamp manipulator has an opening that extends along the surface (X-Y plane) of the stamp manipulator and can be operated individually at a set pressure (such as overpressure or underpressure) to hold the stamp (underpressure) or release the stamp (overpressure). During the imprinting process, the stamp is released at an X-Y position (e.g., at the edge) so that the first contact occurs between the uneven trace surface and the resist at that position. Then, the stamp is gradually released from the stamp manipulator to make contact with the resist layer. Thus, the contact will grow from the first contact position along the X-axis and / or Y-axis directions according to the release scheme.

[0006] Alignment between the stamp and the substrate is achieved using marks on the stamp and the substrate. Each mark on the stamp and the substrate is irradiated, and the redirected light is detected to determine the positions of the marks (absolute position, relative position, and position relative to each other) h. Then, the position of the stamp can be compared with the position of the substrate to check if they are correctly aligned. If they are not correctly aligned, the stamp and / or the substrate should be moved accordingly.

[0007] The inventors have realized that since imprint lithography relies on the contact between the stamp and the substrate and it is difficult to correct misalignment after the first contact is established, alignment must be performed before the start of imprinting. However, this results in the need to perform alignment when there is a relatively large gap (i.e., the distance along the Z-axis direction) between the stamp and the substrate, which makes alignment complicated. For example, if the light used for illumination is not perpendicular, the large gap will cause parallax errors and the measured mark positions will be incorrect. Or if the camera is not perpendicular to the stamp / wafer surface, this will also result in parallax errors.

[0008] Another problem is to avoid problems caused by non-vertical illumination of the substrate.

[0009] Some implementations may use non-vertical illumination of the substrate, and in these cases, it is important to know the accurate detection angle. Another problem is the need to avoid problems caused by irradiating the substrate at an incorrect angle.

[0010] Therefore, there is a need to improve the alignment of the imprint process to reduce or eliminate such misalignment problems, even when there is a relatively large gap.

[0011] The present invention aims to solve one or more of these problems.

[0012] According to the present disclosure, there is provided a method for determining a detection angle (e.g., in a lithographic apparatus and / or an imprint system), the method comprising:

[0013] Use a calibration substrate having a refractive index n and having a first pair of marks, the pair of marks having a predetermined lateral displacement relative to each other, a first mark of the pair of marks being located at a first predetermined vertical position within the calibration substrate, and a second mark of the pair of marks being located at a second predetermined vertical position within the calibration substrate that is different from the first predetermined vertical position, the calibration substrate being supported on its first surface;

[0014] Irradiate the pair of marks with a light source;

[0015] Detect light redirected from the first mark and the second mark by a detector having an optical axis to determine a first detected lateral displacement between the first mark and the second mark, wherein the optical axis of the detector is at a detection angle α1 less than 90° (or greater than 0°, or less than 90° and greater than 0°) relative to the normal of the substrate; and

[0016] Determine a first detection angle based on the refractive index n of the substrate and the first detected lateral displacement between the first mark and the second mark.

[0017] By detecting the detection angle, it is possible to determine and thus take into account the parallax error caused by the detection angle as well as the gap between the stamp and the substrate. For example, using known parallax errors with a known gap, displacements in the x and y directions can be calculated. When viewed along the vertical axis, the first mark and the second mark may overlap.

[0018] The detection angle can be determined such that the parallax error is calculated and compensated in various ways during imprinting. Therefore, the detection angle does not need to be corrected to be perpendicular to the substrate, but by knowing the detection angle, the parallax error can be calculated and compensated in subsequent calculation and alignment steps. In addition, by determining the detection angle, the parallax error caused by substrates made of materials with different refractive indices can be calculated and compensated.

[0019] Therefore, the present invention does not attempt to reduce or eliminate parallax as in earlier systems and methods, but instead uses non-vertical detection to calculate parallax. In summary, the detection in the present invention is non-vertical and utilizes the corresponding parallax to determine the detection angle.

[0020] In some embodiments, a desired non-vertical detection angle may be required, and in these embodiments, the detection angle can be calculated and changed or corrected to the desired angle.

[0021] The methods and systems described herein can first be used to determine the camera tilt or detection angle, but can also ensure that the camera angle remains stable over time by repeating the measurement(s) at a later time.

[0022] The methods and systems presented herein can be used in an imprint lithography apparatus, or imprint system, such as in particular a substrate conformal imprint lithography apparatus using a deformable stamp, in all of which alignment between the substrate and the stamp must be done before imprinting, as described below.

[0023] The method may further comprise:

[0024] Rotating the calibration substrate so that it is supported on a different second surface thereof;

[0025] Illuminating the pair of markers by the light source;

[0026] Detecting the light redirected from the first marker and the second marker to determine a second detected lateral displacement between the first marker and the second marker;

[0027] Determining a second detected angle α2 based on the second detected lateral displacement between the first marker and the second marker.

[0028] By turning the calibration substrate onto its second surface, the same pair of markers can be detected and measured again. The average of the first detected angle and the second detected angle can be taken. When the calibration substrate is inverted, any error in the predetermined lateral displacement will be reversed.

[0029] The markers can be contrast markers configured to reflect light or diffraction markers configured to diffract light.

[0030] The lateral (i.e., in the X-Y plane) displacement between the first marker and the second marker can be zero. Alternatively, the lateral displacement can be a minimal amount such that the first marker and the second marker can be illuminated simultaneously without one marker obstructing the light from reaching the other marker.

[0031] The first detected angle α1 can be given by the following formula:

[0032]

[0033] where X1 is the measured displacement, LD is the lateral displacement, and Dw is the perpendicular distance between the first marker and the second marker.

[0034] The detected angle α2 can be given by the following formula:

[0035]

[0036] where X2 is the measured displacement, LD is the lateral displacement, and Dw is the perpendicular distance between the first marker and the second marker.

[0037] The method may further comprise:

[0038] Provide an impression mold including impression marks;

[0039] Irradiate the impression marks with a light source;

[0040] Detect light from the light source redirected by the impression marks;

[0041] Use at least the first detection angle to determine the lateral position of the impression marks.

[0042] Similar to detecting impression marks, substrate marks can be detected, and the method further includes:

[0043] Provide a second substrate including substrate marks;

[0044] Irradiate the substrate marks with the light source;

[0045] Detect light from the light source redirected by the substrate marks;

[0046] Use at least the first detection angle to determine the lateral position of the substrate marks.

[0047] Once the positions of the impression marks and the substrate marks are determined, the degree of alignment can be determined. Advantageously, the method can improve the accuracy of detecting alignment.

[0048] An alternative embodiment contemplates a detection angle where the light source remains fixed relative to the substrate or the substrate surface. With the present invention, the detection angle can be determined, and if the detection angle is not within a predetermined range, the light source is moved to a different detection angle.

[0049] According to the present invention, an alignment system is provided for determining the alignment between an impression mold and a substrate in a substrate conformal imprint lithography process. The system may include an alignment system and a substrate with a refractive index of n, and includes a first mark and a second mark, the first mark and the second mark having a predetermined lateral displacement relative to each other, the first mark of the pair of marks being located at a first predetermined vertical position within the substrate, and the second mark of the pair of marks being located at a second predetermined vertical position, the second predetermined vertical position being different from the first predetermined vertical position within the substrate. The alignment system includes:

[0050] A light source;

[0051] A light sensor having an optical axis and configured to detect light from the light source redirected by the substrate, wherein the optical axis of the light sensor is at a detection angle α1 less than 90° with respect to the normal of the substrate. Preferably, the angle is not 0°;

[0052] A processing system is communicatively coupled to the light source and the light sensor. The alignment system is configured to receive the calibration substrate. The processing system is configured to determine a first detected angular deviation α1 based on a first detected lateral displacement between the first marker and the second marker on the calibration substrate when the calibration substrate is received within the alignment system.

[0053] The processing system may also be configured to control the alignment system to perform the following steps:

[0054] Irradiate the pair of markers with the light source;

[0055] Detect the light redirected from the first marker and the second marker to determine a first detected lateral displacement between the first marker and the second marker;

[0056] An imprinting system for performing an imprinting process is also provided, the imprinting system including an alignment system as defined herein.

[0057] The imprinting system may include: a mold holder for holding and operating an imprinting mold, a substrate holder for holding a substrate to be imprinted, which is configured such that their lateral X-Y positions can be controlled and changed, and the imprinting system further includes a calibration substrate holder for holding a calibration substrate.

[0058] Any imprinting system as defined herein may be configured to perform any method as defined herein.

[0059] A computer program product including a computer program code unit, which when run by the alignment system or the imprinting system (e.g., its processing system) described herein, causes the alignment system to perform all steps of any method described herein.

[0060] The present disclosure relates to the alignment of markers in, for example, a SCIL process, particularly when the detector is arranged substantially perpendicular to the substrate. A disadvantage of this arrangement is that signals from the substrate markers and the mold markers may be mixed together and difficult to distinguish.

[0061] The processing system of the alignment system may be configured to control the operation of the illumination system and / or the light sensor to control the alignment system to perform defined functions.

[0062] A computer program product is provided, the computer program product including a computer program code unit, which when executed by the alignment system as described above, causes the system to perform all steps of the method as described above.

[0063] These and other aspects of the invention will become apparent and be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] For a better understanding of the disclosed methods and systems, and to more clearly show how they may be put into practice, reference will now be made, by way of example only, to the accompanying drawings, in which

[0065] Figure 1A , 1B and 1C show cross-sectional views of an imprinting process as performed by an imprinting system;

[0066] Figure 2A depicts a calibration substrate;

[0067] Figure 2B depicts an alternative calibration substrate;

[0068] Figure 3 depicts the method of the present invention;

[0069] Figure 4 depicts the illumination of a pair of markers;

[0070] Figure 5 is an enlarged depiction of the incident light on the first marker; and

[0071] Figure 6 is a simplified block diagram of a computer in which one or more parts of the embodiments may be employed. DETAILED DESCRIPTION

[0072] The present invention will be described with reference to the accompanying drawings.

[0073] The detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are intended for illustrative purposes only and are not intended to limit the scope of the invention. The devices, systems, and methods of the present invention, and these and other features, aspects, and advantages thereof, will be better understood from the following description, the appended claims, and the drawings. Although specific measures are recited in mutually different dependent claims, this does not indicate that the combination of these measures cannot be used advantageously.

[0074] Those skilled in the art will be able to understand and effect variations of the disclosed embodiments when practicing the claimed invention by studying the drawings, the disclosure, and the claims. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality.

[0075] The drawings are only schematic and are not drawn to scale. In all the drawings, the same reference numerals are used to indicate the same or similar parts.

[0076] The embodiments present an apparatus for aligning a stamper and a substrate during an imprinting process, such as a substrate conformal imprint lithography ("SCIL") process. Stamper marks are positioned on the stamper, and substrate marks are positioned on the substrate. The marks may include diffraction gratings, but may also include other types of marks. The two marks may be irradiated by the same or different light. Each mark is configured to redirect a form of light (received by the mark) to a light sensor in a proportion greater than the other mark.

[0077] Figure 1A , 1B and FIGS. 1C illustrate the manufacturing process for better understanding the context.

[0078] Known micro-device manufacturing processes include successively applying device layers to a substrate. A typical process cycle for applying such a device layer includes depositing a layer of a desired material, such as an insulator or a (semi)conductor, and then structuring or so-called patterning the applied layer.

[0079] In the present disclosure, structuring of the material layer is accomplished using an imprinting or embossing method. The process includes (in one step cycle) a process of applying the material layer 102 to the surface 101 of the substrate 100, for example, by using droplets of inkjet printing, or by uniformly dispersing on the substrate surface 101 using spin coating or doctor blade techniques. Any other application technique may also be used. The applied material layer 102 is formable.

[0080] As Figure 1A shown, the stamper 104 having a surface 106 with uneven traces represents a pattern 106' that needs to be replicated or imaged in the material layer 102. The stamper 104 is positioned above the substrate 104, and the distance between the substrate mark 103 and the stamper mark 105 is D. Once the stamper 104 and the substrate 100 are correctly aligned, the material layer 102 of the stamper is brought into contact with the stamper, such that the stamper imprints the shape of the uneven trace surface onto the material layer 102, as Figure 1B shown in.

[0081] During the contact of the stamper 104 with the material layer 102 (as Figure 1B shown), the material layer first takes (e.g., conforms to) the shape of the uneven trace surface 106 of the pattern 106', and then hardens using a certain curing process to a state where it cannot be (re)formed. Exemplary curing processes utilize chemical reactions to cure the layers upon application of heat or radiation, or cure the layers by removing solvents from the layers, as described in European patent applications EP2087403A2 and EP2091666A2 and the references cited therein.

[0082] After removing the stamp 104 from the material layer 102, a formed embossed material layer is left having an embossed surface 108 with a complementary pattern 108 representing the pattern 106'. Figure 1C ) The formed material layer can serve as a basis for patterning a substrate layer using certain etching processes, or it can be used directly as a patterned device layer, whether or not further modification or processing is carried out.

[0083] In some printing processes, the stamp is a rigid stamp that hardly deforms. Such a stamp can be made of, for example, quartz.

[0084] In other printing processes, such as the SCIL process, the stamp is deformable. Such a stamp can be manipulated so that during the imprinting process, it gradually contacts the substrate by temporarily deforming the stamp during the contact step of the process. In this case, the shown stamp 104A will have a conformable embossed portion that includes rubber or elastomer or other deformable polymer material. A particularly advantageous example of such a deformable polymer includes or comprises a polysiloxane-based polymer. Generally, but not necessarily, the embossed portion is carried (e.g., adhered to) by a relatively rigid but deformable support portion, such as a (thin) glass plate (not shown separately in Figure 1A 、 1B and 1C). This helps to improve the manipulation of the stamp 104A by the stamp holder (also called stamp manipulator) 104B.

[0085] In some embodiments, the stamp holder can include a grooved plate, for example in the form of a glass plate having one or more grooves. The grooved plate is rigid and includes at least one groove, but preferably includes a plurality of grooves 105, in which the pressure of a gas can be controlled to manipulate the stamp. For example, a negative pressure (compared to the ambient pressure) can be applied so that the stamp (through its support portion, if the stamp includes such a portion) can be pulled towards the grooved plate or firmly held by the grooved plate. Conversely, the stamp can be released by increasing the pressure to ambient pressure or even overpressure. Although only a limited number of system components are shown for clarity, a detailed description of how to design such a system and how to use such a system to perform such imprinting methods has been described in the following documents: WO03099463A2 METHOD AND DEVICE FOR TRANSFERRING APATTERN FROM A STAMP TO A SUBSTRATE; WO2008068701A2 METHOD AND APPARATUS FORAPPLYING A SHEET TO ASUBSTRATE; WO2008087573A2METHOD AND SYSTEM FORCONTACTING OF A FLEXIBLE SHEET AND A SUBSTRATE;WO2016045961A1 TRANSFER METHODAND APPARATUS AND COMPUTER PROGRAM PRODUCT(and the references cited in each publication), each of which is incorporated herein by reference in its entirety.

[0086] Generally, in a device having multiple stacked device layers, the pattern of one device layer needs to be laterally aligned (where laterally means in the X-Y plane) with the pattern of one or more other such layers or a substrate. For example, successive layers of a semiconductor substrate 100 must be properly aligned with each other for the device to function. After all, if the layers are not properly aligned, signals will not be transmitted between the layers and the device will not operate properly. Therefore, an alignment step is also performed during the application of a new device layer.

[0087] In the above exemplary method, this means that the alignment step must be performed before the stamper 104 contacts the material layer 102 (e.g., Figure 1A the situation shown), because when they are in contact, lateral repositioning of the substrate 100 and the stamper 104 is difficult or impossible, or may cause dragging or unnecessary deformation of the material layer 102, or damage to the stamper.

[0088] For alignment, the substrate includes one or more substrate markers 103, and the stamper 104A (e.g., as part of an adaptable portion) also includes one or more stamper markers 105. In order to properly align the stamper with the substrate and any pattern layer beneath the stamper, the markers on the stamper and the markers on the substrate should be properly aligned. The stamper and the substrate should be aligned within a predetermined margin in the X-Y plane.

[0089] This disclosure relates to an improved method for aligning a stamper with a substrate. The following description provides an illustrative understanding of embodiments in which the features may be interchangeable and / or combinable.

[0090] The method of the present invention uses a calibration substrate 100 as shown in Figure 2A . The calibration substrate 100 is formed of a material having a refractive index of n, which is substantially transparent to the light used to detect the markers. The calibration substrate has first markers 111, 112 on its first surface 110 and second markers 121, 122 on its second surface 120. Thus, in the Z direction, there is a known pre-positioning displacement D between the first markers and the second markers W。Each first marker 111 and 112 has a corresponding second marker in close proximity (in the X-Y plane) thereto, thereby forming a pair of markers. In Figure 2A the example of

[0091] However, in some examples, the first marker and the second marker may have a predetermined lateral displacement relative to each other in the X-Y plane. Figure 2B An alternative calibration substrate is depicted in N and the calibration substrate has a first marker 111 and a second marker 121 which have a small predetermined lateral (i.e., in the X-Y plane) displacement X relative to each other W therebetween.

[0092] The calibration substrate may form part of a lithographic apparatus or may be removable. It may have units removably attached to the apparatus. Such units may include clamps, clips and / or screws, etc.

[0093] Each of the first marker and the second marker may be a reflective marker (e.g., a chromium marker) or a diffractive marker (e.g., a grating structure).

[0094] Reference Figure 3 is made to

[0095] also, the method 200 disclosed herein includes using or providing 210 a calibration substrate 100 placed on its first surface 110 and irradiating 220 a pair of markers 111, 121 with light, e.g., from a light source. Figure 4 Reference is also made to

[0096] Detector 320 has an optical axis and detects light along the optical axis. Light rays are detected along the optical axis, and the optical axis forms a detection angle α with the normal of the substrate. Therefore, light propagating towards the detector at an angle α will be detected. Based on the redirected light from the first marker and the second marker, the relative lateral position (in the X-Y plane) of the first marker and the second marker can be detected, and the lateral displacement between the first marker and the second marker can be determined. The detection angle α can be determined 240 through the detected lateral displacement between the first marker and the second marker. The detection angle is the detection angle relative to the substrate normal.

[0097] Figure 5 is an enlarged view of the light redirected from the first marker 111 of the calibration substrate 100. For simplicity, Figure 5 the corresponding second marker and the light after redirection (reflection or diffraction) are not depicted. It can be seen that the light changes its path at the boundary between air and the calibration substrate 100 with a refractive index of n. The detection angle is α, and the reflection angle β is less than α because the refractive index of the calibration substrate is greater than that of air.

[0098] Due to the non-vertical illumination of the markers, the lateral offset (in the X-Y plane) between the vertical positions of the second marker 121 (the second surface 120 in this example) and the first marker 111 (the first surface 110 in this example) is given by X w and can be calculated as:

[0099]

[0100] where D w is the vertical distance between the first marker 111 and the second marker 121. For small angles, is close to 1 and can be neglected. Therefore, the detection angle α is:

[0101]

[0102] This assumes that the first marker 111 and the second marker 121 are located at the same lateral (i.e., X-Y) position. If there is a displacement between the first and second markers, the detection angle can be calculated as:

[0103]

[0104] where X N (as Figure 2B shown) is the predetermined lateral displacement between the second marker and the first marker.

[0105] To improve the accuracy of detection, the calibration substrate 100 can be rotated to be supported on its second surface 120, and the process can be repeated. That is, the pair of marks is irradiated by the light source 310 and detected by the detector 320. According to the detected and redirected light, the lateral displacement is detected and the second detection angle α2 is determined. The average of the first detection angle and the second detection angle can be taken.

[0106] There may be several pairs of marks on the calibration substrate 100, and the same process is repeated for each pair of marks. Each pair of marks can have the same lateral displacement X N and vertical displacement D W , or different pairs of marks can have different lateral displacements and / or different vertical displacements from each other. If there are eight pairs of marks on the calibration substrate and each pair of marks is detected when the substrate is supported on its first surface and on its second surface, a total of 16 detections will be made. The average detection angle can be determined.

[0107] Once the detection angle is determined, it can be used as part of the alignment process in the imprinting method. After all, the detection angle represents the orientation of the detector. For example, the same detector 320 (in an unchanged position or in other words a calibrated position) can be used to detect the imprint marks on the imprint. Using the determined detection angle and knowing the vertical position of the imprint marks, the lateral position of the imprint marks can be accurately determined relative to any other mark at any other given vertical position.

[0108] The determined detection angle can also be used in a similar way to determine the lateral position of the substrate marks on the second substrate. For example, the distance between the upper surface of the second substrate and the lower surface of the imprint may be 20 - 300 microns. The substrate marks may be irradiated and the redirected light may be detected. Using the determined detection angle and knowing the vertical position of the substrate marks, the lateral position of the substrate marks can be accurately determined.

[0109] The position of the imprint marks determined using the determined detection angle and the position of the substrate marks can be compared to detect the alignment of the imprint and the second substrate before imprinting the imprint on the second substrate. If the substrate and the imprint are aligned within a predetermined accuracy range, imprinting can continue. However, if they are not aligned with sufficient accuracy (e.g., within 5% of the feature size), the imprint and / or the substrate can be moved to correct any misalignment.

[0110] In some examples, the camera or detector 320 is designed to detect at a predetermined detection angle. In these examples, the determined detection angle can be compared with the predetermined detection. If necessary, the angle or position of the camera (or detector) can be changed. Then the new detection angle can be determined again and compared with the predetermined detection again.

[0111] Another application of the present invention is to check whether the detection angle is stable over a long period of time. For example, the detection angle can be checked after a predetermined time period. This can prevent the device from gradually becoming less accurate during use.

[0112] As described above, determining the detection angle can be done once before printing the substrate. Additionally or alternatively, it can also be done after n substrates are completed. For example, after every 100 substrates are printed, the detection angle can be determined or checked.

[0113] The calibration process for determining the detection angle can be automated or manual. Pattern recognition can be used to detect a mark at a first position on the z-axis. Since the relative lateral position of the corresponding second mark is known, the second mark can be detected.

[0114] For each pair of marks, the following formula can be written:

[0115] X n = Ax + Sx n ; Y n = Ay + Sy n

[0116] where X n and Y n are the measured offsets, n indicates multiple measurements (16 times in this example), Ax and Ay represent parallax errors, and Sx n and Sy n are the known correct offsets of the wafer. In total, we obtain 16 equations for X with the unknown variable Ax. And for Y we have 16 equations with the unknown variable Ay. This is a system of linear equations that can be solved using linear least squares fitting. In this way, we can calculate the parallax errors Ax and Ay.

[0117] The present invention may also include a processing system 350 that is communicatively coupled to the light source 310 and the light detector 320 and is configured to determine the detection angle based on the detected lateral displacement between the first mark 111 and the second mark 121 on the calibration substrate 100.

[0118] The processing system 350 may also be configured to control the alignment system to illuminate a pair of marks and detect the light redirected by the first mark and the second mark by the light detector 320.

[0119] The processing system 350 of the alignment system may be configured to control the operation of the illumination system 400 and / or the light sensor 300 to control the alignment system to perform defined functions.

[0120] The present invention can also be embodied in a computer program including computer program code units which, when run by the alignment system as described above, are adapted to implement the method as described above.

[0121] FIG. 7 shows an example of a computer 70 in which one or more portions of the embodiments may be employed. The various operations discussed above may utilize the functionality of computer 70. For example, one or more portions of a system for providing a user interface for a particular subject matter may be incorporated into any of the elements, modules, applications, and / or components discussed herein. In this regard, it should be understood that the system functional blocks may operate on a single computer or may be distributed across multiple computers and locations (e.g., via an Internet connection), such as a cloud-based computing infrastructure.

[0122] Computer 70 includes, but is not limited to, a PC, a workstation, a laptop computer, a PDA, a handheld device, a server, a memory, and so on. Generally, in terms of hardware architecture, computer 70 may include one or more processors 71, a memory 72, and one or more I / O devices 73 communicatively coupled via a local interface (not shown). The local interface may be, for example but not limited to, one or more buses or other wired or wireless connections as known in the art. The local interface may have additional elements such as controllers, buffers (caches), drivers, repeaters, and receivers to enable communication. In addition, the local interface may include addressing, control, and / or data connections to enable proper communication among the above-described components.

[0123] Processor 71 is a hardware device for running software that may be stored in memory 72. Processor 71 may actually be any custom or commercial processor, a central processing unit (CPU), a digital signal processor (DSP), or an auxiliary processor associated with computer 70, and processor 71 may be a semiconductor-based microprocessor (in the form of a microchip) or a microprocessor.

[0124] Memory 72 may include any one or combination of volatile memory elements (e.g., random access memory (RAM), such as dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and non-volatile memory elements (e.g., ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic tape, compact disc read-only memory (CD-ROM), disk, floppy disk, cartridge, cassette tape, etc.). In addition, memory 72 may comprise electronic, magnetic, optical, and / or other types of storage media. Note that memory 72 may have a distributed architecture where various components are located remotely from each other but may be accessed by processor 71.

[0125] The software in the memory 72 may include one or more separate programs, each program including an ordered list of executable instructions for implementing logical functions. According to an exemplary embodiment, the software in the memory 72 includes a suitable operating system (O / S) 74, a compiler 76, source code 75, and one or more application programs 77. As shown, the application program 77 includes a plurality of functional components for implementing the features and operations of the exemplary embodiment. The application program 77 of the computer 70 may represent various application programs, computing units, logics, functional units, processes, operations, virtual entities, and / or modules according to the exemplary embodiment, but the application program 77 is not meant to be limiting.

[0126] The operating system 74 controls the execution of other computer programs and provides scheduling, input-output control, file and data management, memory management, and communication control and related services. The inventors contemplate that the application program 77 for implementing the exemplary embodiment may be applicable to all commercially available operating systems.

[0127] The application program 77 may be a source program, an executable program (object code), a script, or any other entity including a set of instructions to be executed. When it is a source program, the program is typically translated by a compiler (such as the compiler 76), an assembler, an interpreter, etc., which may or may not be included in the memory 72, in order to operate properly with the O / S 74. In addition, the application program 77 may be written in an object-oriented programming language, which has classes of data and methods, or a procedural programming language, which has routines, subroutines, and / or functions, such as but not limited to C, C++, C#, Pascal, BASIC, API calls, HTML, XHTML, XML, ASP scripts, JavaScript, FORTRAN, COBOL, Perl, Java, ADA,.NET, etc.

[0128] The I / O device 73 may include input devices, such as but not limited to a mouse, a keyboard, a scanner, a microphone, a camera, etc. In addition, the I / O device 73 may also include output devices, such as but not limited to a printer, a display, etc. Finally, the I / O device 73 may also include devices that transfer both input and output, such as but not limited to a NIC or a modem / demodulator (for accessing remote devices, other files, devices, systems, or networks), a radio frequency (RF) or other transceiver, a telephone interface, a bridge, a router, etc. The I / O device 73 also includes components for communicating over various networks such as the Internet or an intranet.

[0129] If the computer 70 is a PC, workstation, smart device, etc., the software in the memory 72 may also include a Basic Input Output System (BIOS) (omitted for simplicity). The BIOS is a set of essential software routines for initializing and testing hardware at startup, starting the O / S 74, and supporting data transfer between hardware devices. The BIOS is stored in a type of read-only memory, such as ROM, PROM, EPROM, EEPROM, etc., so that the BIOS can be executed when the computer 70 starts up.

[0130] When the computer 70 is in operation, the processor 71 is configured to run the software stored in the memory 72 to transfer data to and from the memory 72 and generally control the operation of the computer 70 according to the software. The application program 77 and the O / S 74 are all or partially read by the processor 71, possibly buffered within the processor 71, and then run.

[0131] When the application program 77 is implemented in software, it should be noted that the application program 77 can be stored on almost any computer-readable medium for use by or in conjunction with any computer-related system or method. In the context of this document, a computer-readable medium can be an electronic, magnetic, optical, or other physical device or device that can contain or store a computer program for use by or in conjunction with a computer-related system or method.

[0132] The application program 77 can be implemented in any computer-readable medium for use by or in conjunction with an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other systems capable of retrieving and executing instructions from an instruction execution system, apparatus, or device. In the context of this document, a "computer-readable medium" can be any device that can store, transmit, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium.

[0133] The proposed image capture and / or processing method can be implemented in hardware or software or a combination of both (e.g., as firmware running on a hardware device). To the extent that an embodiment is implemented partially or fully in software, the functional steps shown in the process flow diagram can be executed by a suitably programmed physical computing device (such as one or more central processing units (CPUs) or graphics processing units (GPUs)). Each process (and each component step shown in the flow diagram) can be executed by the same or different computing devices. According to an embodiment, a computer-readable storage medium stores a computer program including computer program code configured to cause one or more physical computing devices to execute the encoding or decoding method as described above when the program runs on the one or more physical computing devices.

[0134] The storage medium may include volatile and non-volatile computer memories such as RAM, PROM, EPROM, and EEPROM, optical discs (such as CDs, DVDs, BDs), and magnetic storage media (such as hard disks and tapes). The various storage media may be fixed within the computing device or may be removable, such that one or more programs stored thereon can be loaded into the processor.

[0135] For embodiments implemented partially or fully in hardware, the blocks shown in the block diagrams of FIG. 1 and Figure 5 can be separate physical components, or logical subdivisions of a single physical component, or can all be implemented in an integrated manner in one physical component. The function of one block shown in the figure can be divided among multiple components in the implementation, or the functions of multiple blocks shown in the figure can be combined into a single component in the implementation. Hardware components suitable for the embodiments of the present invention include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs). One or more blocks can be implemented as a combination of dedicated hardware for performing some functions and one or more programmed microprocessors and associated circuitry for performing other functions.

[0136] Alignment methods, alignment systems, and calibration substrates can be used or implemented in corresponding imprinting methods and imprinting systems. The references cited herein disclose such systems in detail. Generally speaking, such systems have a stamp holder and a substrate holder, and they can be controlled and manipulated to adjust the lateral X-Y relative positions of the stamp and / or the substrate. Preferably, they are also configured to adjust the relative Z position. Such imprinting systems are usually also configured to implement any of the imprinting methods described herein. For example, an imprinting system includes hardware and software that can control the application of a stamp to a substrate and the release of the stamp from the substrate after the imprinted layer is cured. Preferably, the imprinting system is configured to be used with a deformable stamp (as described above) and as described in the references cited herein. Accordingly, specific components of the systems described in the references (such as chucks, stamp holders, and manipulator pressure, stamp release mechanisms) are considered to be part of the imprinting systems described herein and in the following documents: WO03099463A2 METHOD AND DEVICE FOR TRANSFERRING A PATTERN FROM A STAMP TO A SUBSTRATE; WO2008068701A2 METHOD AND APPARATUS FOR APPLYING A SHEET TO A SUBSTRATE; WO2008087573A2 METHOD AND SYSTEM FOR CONTACTING OF A FLEXIBLE SHEET AND A SUBSTRATE; WO2016045961A1 TRANSFER METHOD AND APPARATUS AND COMPUTER PROGRAM PRODUCT. For example, the currently disclosed alignment systems and methods can be applied to the imprinting system described in WO2016045961, where reference is made to FIGS. 2 to Figure 4 .

[0137] Those skilled in the art can understand and implement variations of the disclosed embodiments when studying the accompanying drawings, the disclosure, and the claims in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single processor or other unit may implement the functions of several items recited in the claims. Although specific measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used advantageously. If a computer program is described above, it can be stored / distributed on a suitable medium such as an optical storage medium or a solid-state medium provided together with other hardware or as part of other hardware, but can also be distributed in other forms such as via the Internet or other wired or wireless telecommunication systems. If the term "adapted to" is used in the claims or the specification, it should be noted that the term "adapted to" is intended to be equivalent to the term "configured to". Any reference signs in the claims should not be construed as limiting the scope.

[0138] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of an instruction that includes one or more executable instructions for implementing the specified (one or more) functions. In some alternative embodiments, the functions noted in the block may occur in the order shown in the figures. For example, depending on the functions involved, two blocks shown successively may actually be executed substantially simultaneously, or the blocks may sometimes be executed in the reverse order. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware system that performs the specified functions or actions or a combination of dedicated hardware and computer instructions.

Claims

1. A method for determining a detection angle, the method comprising: Using a calibration substrate having a refractive index n and having a first pair of marks, the pair of marks having a predetermined lateral displacement relative to each other, a first mark of the pair of marks being located at a first predetermined vertical position within the calibration substrate, and a second mark of the pair of marks being located at a second predetermined vertical position within the calibration substrate that is different from the first predetermined vertical position, the calibration substrate being supported on its first surface; Irradiating the pair of marks with a light source; Detecting, by a detector having an optical axis, light redirected from the first mark and the second mark to determine a first detected lateral displacement between the first mark and the second mark, wherein the optical axis of the detector has a detection angle α1 that is less than 90 degrees and greater than 0° relative to the normal of the substrate; and Determining the first detection angle based on the refractive index n of the substrate and the first detected lateral displacement between the first mark and the second mark.

2. The method according to claim 1, further comprising: Rotating the calibration substrate so that it is supported on its different second surface; Irradiating the pair of marks with the light source; Detecting the light redirected from the first mark and the second mark to determine a second detected lateral displacement between the first mark and the second mark; Determining a second detection angle α2 based on the second detected lateral displacement between the first mark and the second mark.

3. The method according to claim 2, further comprising determining the detection angle by determining an average of the first detection angle and the second detection angle.

4. The method according to any one of the preceding claims, wherein, The first mark is a contrast mark configured to reflect a portion of the light to the light sensor.

5. The method according to claim 1 or 2, wherein The second mark is a contrast mark configured to reflect a portion of the light to the light sensor.

6. The method according to any one of the preceding claims, wherein, The predetermined lateral displacement between the first mark and the second mark is zero.

7. The method according to any one of the preceding claims, wherein, The first mark is located on the first substrate surface, and the second mark is located on the second substrate surface.

8. The method according to any one of the preceding claims, wherein, The first detection angle α1 is given by: where X1 is the measured displacement, LD is the lateral displacement, and Dw is the vertical distance between the first mark and the second mark.

9. The method according to any one of claims 2 to 6, wherein The second detection angle α2 is given by: where X2 is the measured displacement, LD is the lateral displacement, and Dw is the vertical distance between the first mark and the second mark.

10. The method according to any of the preceding claims, further comprising: Using a stamp including stamp marks; Irradiating the stamp marks with the light source; Detecting the light redirected by the stamp marks from the light source; Using at least the first detected detection angle to determine the lateral position of the stamp marks.

11. The method according to any of the preceding claims, further comprising: Using a second substrate including substrate marks; Irradiating the substrate marks with the light source; Detect the light from the light source redirected by the substrate marker; Use at least the first detected detection angle to determine the lateral position of the substrate marker.

12. An alignment system for determining alignment between a stamper and a substrate in a conformal imprint lithography process, wherein, The alignment system includes: A light source; A light sensor having an optical axis and configured to detect light from the light source redirected by the substrate, wherein the optical axis of the light sensor is at a detection angle α1 greater than 0° with respect to the normal of the substrate; A processing system communicatively coupled to the light source and the light sensor; The alignment system is configured to receive a calibration substrate having a refractive index n and including a first marker and a second marker having a predetermined lateral displacement relative to each other, a first marker of the pair of markers being located at a first predetermined vertical position within the substrate, and a second marker of the pair of markers being located at a second predetermined vertical position within the calibration substrate different from the first predetermined vertical position; The processing system is configured to: When the calibration substrate is present within the alignment system, determine a first detection angle α1 based on a first detected lateral displacement between the first marker and the second marker on the calibration substrate; and Use the determined detection angle to determine the alignment between the stamp and the substrate.

13. The system according to claim 12, wherein, The processor is further configured to control the alignment system to perform the following steps: Irradiate the pair of markers with the light source; Detect the light redirected from the first marker and the second marker to determine a first detected lateral displacement between the first marker and the second marker.

14. The system according to claim 12 or claim 13, further comprising a calibration substrate having a refractive index n and a first pair of markers having a predetermined lateral displacement relative to each other, a first marker of the pair of markers being located at a first predetermined vertical position within the calibration substrate, and a second marker of the pair of markers being located at a second predetermined vertical position within the calibration substrate having the first marker.

15. An imprinting system for performing an imprinting process, the imprinting system including the alignment system according to any one of claims 12 to 14.

16. The imprinting system according to claim 15, comprising: An imprint holder for holding and manipulating an imprint stamp, a substrate holder for holding a substrate to be imprinted, the imprinting system being configured to enable control and change of the lateral X-Y positions of the imprint holder and the substrate holder, the imprinting system further including a calibration substrate holder for holding a calibration substrate.

17. The imprinting system according to any one of claims 15 to 16, configured to perform the method according to any one of claims 1 to 11.

18. A computer program product including a computer program code unit which, when run by the alignment system according to any one of claims 12 to 14, causes the imprinting system or the alignment system to perform all steps of the method according to any one of claims 1 to 11.

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