Alignment Method

Abstract

A mechanism for aligning a stamp and a substrate during a substrate conformal imprint lithography (SCIL) process is provided. A stamp marker including a first diffraction grating is disposed on the stamp, and a substrate marker is disposed on the substrate. The two markers are illuminated with two different lights. Each marker is configured to redirect a greater proportion of its respective form of light (received by that marker) toward a light sensor than the other markers.

Description

[Technical Field]

[0001] The present invention relates to the field of aligning a stamp and a substrate in an imprint lithography process. [Background technology]

[0002] In imprint lithography, a stamp with a relief surface is used to pattern a substrate layer. A substrate having a formable imprint composition layer on its surface is contacted with the relief surface of the stamp so that the formable layer conforms to the relief of the stamp. The formable layer solidifies (often referred to as "curing") during contact, and the stamp is then removed from the substrate, leaving a relief pattern of the formed material on the substrate that has a pattern complementary to that of the stamp.

[0003] One type of imprint lithography utilizes a flexible stamp made of an elastomeric material, such as a rubber polymer. Such stamps are sometimes called "soft stamps," and the lithography is sometimes referred to as "soft lithography." Substrate Conformal Imprint Lithography (SCIL™) is one such soft-stamp technique. Summary of the Invention [Problem to be solved by the invention]

[0004] The fabrication of multilayer devices, such as semiconductor devices, generally requires lateral alignment of the device layers. The application of imprint lithography, particularly soft stamp imprint lithography, to the fabrication of patterned multilayer devices requires improved lateral alignment between the stamp and the substrate. [Means for solving the problem]

[0005] The present invention aims to improve the alignment process for imprint processes using flexible stamps. In non-contact lithography processes, alignment can be achieved with lithographically generated optical markers, but this has drawbacks in imprint lithography. The inventors have discovered that for (soft stamp) imprint lithography, it is beneficial to have alignment markers within the stamp in the form of diffractive markers. However, it has also been found that such markers have reduced contrast compared to markers on the substrate, making alignment of both markers difficult. The signals from the substrate marker and the stamp marker are typically detected simultaneously, resulting in a mixture and being nearly indistinguishable.

[0006] The present invention, as defined by the claims, aims to achieve the above-mentioned goals.

[0007] The disclosed solution takes advantage of the fact that diffraction-based markers allow illumination under angles such that the first or higher order reflected diffracted light is captured by the alignment sensor and used for alignment, while at the same time, disturbing specular reflections from the substrate marker are much stronger than the reflected diffracted light from the stamp marker and are not captured by the sensor.

[0008] According to a first aspect, there is provided a method of determining alignment between a stamp and a substrate in an imprint process, the stamp having a stamp marker comprising a first diffraction grating having a first period on a surface of the stamp, and the substrate having a substrate marker on a surface of the substrate, said method comprising: using a light sensor to capture marker light at an angle relative to the stamp and substrate; illuminating at least the stamp marker with a first light, wherein the first light and the stamp marker are configured such that a first percentage or more of the first light is directed by the stamp marker to a light sensor, and the first light and the substrate marker are configured such that a second percentage or less of the first light incident on the substrate marker is directed to a light sensor, wherein the first percentage is greater than the second percentage; illuminating at least the substrate marker with a second light different from the first light, wherein the second light and the substrate marker are configured such that a third percentage or more of the second light is directed by the stamp marker to the light sensor, and wherein the second light and the stamp marker are configured such that a fourth percentage or less of the second light is directed to the light sensor, the third percentage being greater than the fourth percentage; and determining alignment between the stamp and the substrate using a response of the light sensor caused by the redirected first and second light.

[0009] The stamp has a stamp marker including a first diffraction grating having a first period on a surface of the stamp, and the substrate has a substrate marker on a surface of the substrate.

[0010] The combination of the first light and the stamp marker and the combination of the first light and the substrate marker have different angles for the maximum and minimum light intensity directed to the sensor. The combination of the stamp marker and the first light results in a maximum value at the light sensor. In contrast, the combination of the first light and the substrate marker results in a value less than the maximum at the light sensor. The combination of the first light and the substrate marker preferably results in a minimum value or close to the minimum value.

[0011] Similarly, the combination of the second light and the substrate marker and the combination of the second light and the stamp marker have different angles for the maximum and minimum light intensity directed at the sensor: the combination of the substrate marker and the second light results in a maximum at the light sensor, while the combination of the second light and the stamp marker results in a less than maximum at the light sensor.

[0012] In this way, the light used to detect the stamp marker is not (substantially) redirected by the substrate marker to the light sensor. Similarly, the light used to detect the substrate marker is not (substantially) redirected by the stamp marker to the light sensor.

[0013] In other words, the light sensor can distinguish between light redirected from only the stamp marker or the substrate marker, thereby improving detection of both markers.

[0014] In this way, the lateral position of the substrate can be determined without the signal being substantially affected by the stamp markers, and the lateral position of the stamp can be determined without the signal being substantially affected by the substrate markers.

[0015] The difference between the first and second ratios is preferably as large as possible, but is at least five times greater than the second ratio or at least two times greater than the second ratio. Similarly, the difference between the third and fourth ratios is preferably as large as possible, but is at least five times greater than the fourth ratio or at least two times greater than the second ratio.

[0016] The substrate marker can include a grating having a second period (i.e., a second grating). The first and second periods are preferably different, and the larger of the first and second periods is preferably at least 20% larger than the smaller of the first and second periods. Using different periods results in different maximum and minimum angles for each grating. The first period can be shorter than the second period.

[0017] Illuminating the substrate marker with the second light can include illuminating the substrate marker with light having a wavelength and an angle of incidence such that the first or higher diffraction order of light is incident on the optical sensor. Using higher diffraction orders provides a clearer indication of the marker location. Therefore, preferably, the third or higher diffraction order is incident on the optical sensor.

[0018] The step of illuminating the stamp marker with the first light can include illuminating the stamp marker with light having a wavelength and an angle of incidence such that light in a first or higher diffraction order is incident on the light sensor. In some examples, the step of illuminating the stamp marker with the first light can include illuminating the stamp marker with light having a wavelength and an angle of incidence such that light in a third or higher diffraction order is incident on the light sensor.

[0019] In some instances, the diffraction orders used for the stamp markers are different from the diffraction orders used for the substrate markers.

[0020] The first light has a peak intensity at a first wavelength and the second light has a peak intensity at a second, different wavelength, and in some examples, the greater of the first wavelength and the second wavelength is at least 20% greater than the lesser of the first wavelength and the second wavelength.

[0021] Preferably, the step of illuminating at least the stamp marker with the first light is performed at a different time than the step of illuminating at least the substrate marker with the second light. Different wavelengths of light and different diffraction orders may result in different intensities at their respective maxima. Thus, the step of illuminating at least the stamp marker with the first light is performed for a first period of time, and the step of illuminating at least the substrate marker with the second light is performed for a second period of time, and the lengths of the first and second periods can be different.

[0022] According to some embodiments of the present invention, the substrate marker is a contrast marker configured to reflect a portion of the second light to the light sensor. Thus, the present invention allows for the use of a combination of both diffractive and contrast markers as substrate markers.

[0023] The optical sensor can be an image sensor, and the step of determining alignment between the stamp and the substrate using the response of the optical sensor comprises determining the alignment by processing an image at the image sensor from the first light and an image at the image sensor from the second light.

[0024] Also proposed is a lithography process that includes any of the methods described herein for determining alignment. The lithography process includes the steps of aligning a stamp with a substrate, imprinting a pattern into the substrate or a material thereon, and etching the substrate. These processes can be repeated multiple times, with each repetition having a different pattern.

[0025] There is also provided an alignment system for determining alignment between a stamp and a substrate in an imprint process, the stamp having a stamp marker including a first diffraction grating on a surface of the stamp with a first period, and the substrate having a substrate marker including a second diffraction grating on a surface of the substrate with a second period different from the first period, the alignment system comprising: a light sensor for capturing the marker light at an angle relative to the stamp and the substrate; an illumination system illuminating at least the stamp marker with a first light, the first light and the stamp marker configured such that at least a first percentage of the first light is directed by the stamp marker to a light sensor, and the first light and the substrate marker configured such that not more than a second percentage of the first light is directed by the substrate marker to a light sensor, the first percentage being greater than the second percentage; the illumination system illuminating at least the substrate marker with a second light different from the first light, the second light and the substrate marker configured such that not less than a third percentage of the second light is directed by the substrate marker to a light sensor, and the second light and the stamp marker configured such that not more than a fourth percentage of the second light is directed by the stamp marker to a light sensor, the third percentage being greater than the fourth percentage; and a processing system communicatively coupled to the light sensor and configured to process a response of the light sensor caused by the redirected first and second lights to determine alignment between the stamp and the substrate.

[0026] The alignment system can include the stamp and / or the substrate.

[0027] There is provided an imprint system including an alignment system as defined herein. The imprint system may be configured to perform an imprint process as defined herein. The imprint system may preferably be configured to use a deformable stamp.

[0028] The stamp has a stamp marker including a first diffraction grating having a first period on a surface of the stamp, and the substrate has a substrate marker on a surface of the substrate.

[0029] There is a processing system communicatively coupled to the light sensor and configured to use or process a response of the light sensor caused by the redirected first light and the redirected second light to determine alignment between the stamp and the substrate.

[0030] 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 in performing defined functions.

[0031] According to a third aspect, there is provided a computer program comprising computer program code means which, when executed by an alignment system or system as described above, causes the alignment system or system to perform the method steps as described above. The system may have a processing system for executing instructions to cause the system to perform the method steps.

[0032] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0033] For a better understanding of the present invention and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1A] 1A and 1B are cross-sectional views of the imprint process. [Figure 1B] 1A and 1B are cross-sectional views of the imprint process. [Figure 2A] 1 shows a stamp according to the present invention; [Figure 2B] 1 shows a substrate according to the present invention; [Figure 3A] Illustrates alignment between stamp and substrate. [Figure 3B] Illustrates alignment between stamp and substrate. [Figure 4A] FIG. [Figure 4B] FIG. [Figure 4C] FIG. [Figure 5A] FIG. [Figure 5B] FIG. [Figure 5C] FIG. [Figure 6] FIG. 10 is a diagram showing the illumination of a reflective board marker. [Figure 7] 1 illustrates a method according to the invention. [Figure 8] 1 shows an apparatus according to the invention; [Figure 9] FIG. 1 is a simplified block diagram of a computer in which one or more portions of the embodiments may be employed. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will now be described with reference to the drawings.

[0035] The detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, the appended claims and the accompanying drawings. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0036] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0037] The figures are only schematic and are not drawn to scale. The same reference numbers are used throughout the figures to denote the same or similar parts.

[0038] Embodiments propose a mechanism for aligning a stamp and a substrate during an imprint process, such as a substrate conformal imprint lithography (SCIL) process or other imprint process utilizing a deformable stamp. A stamp marker including a first diffraction grating is disposed on the stamp, and a substrate marker is disposed on the substrate. The two markers are illuminated with two different lights. Each marker is configured to redirect one type of light (received by that marker) relatively more than the other marker toward a light sensor.

[0039] 1A and 1B illustrate a manufacturing process for improving contextual understanding.

[0040] Known processes for the fabrication of microdevices involve the successive application of device layers to a substrate. A typical process cycle for applying such device layers involves the deposition of a layer of a desired material, e.g., an insulator or a (semi-)conductor, followed by structuring, or so-called patterning, of the applied layer.

[0041] In the present disclosure, the structuring of a material layer is carried out using an imprinting or embossing method. This process involves applying (in a cycle of steps) a material layer 102 to the surface 101 of a substrate 100, for example, as droplets using inkjet printing or uniformly dispersing it on the substrate surface 101 using spin coating or doctor blade techniques. The applied material layer 102 is shapable. This material layer 102 is brought into contact with a stamp 104 having a relief surface 106 representing the pattern 106' that needs to be replicated or imaged in the material layer 102 (FIG. 1A), so that the stamp imprints the shape of the relief surface on the material layer 102.

[0042] While the stamp 104 is in contact with the material layer 102, the material layer first adopts the shape of the relief surface 106 of the pattern 106′ and is then hardened beyond (re)formability using some kind of curing process. Examples of curing processes use a chemical reaction to solidify the layer under the application of heat or radiation, or by solvent removal from the layer, as described in Publication Nos. EP 2,087,403 A2 and EP 2,091,666 A2 and the references cited therein. After removing the stamp 104 from the material layer 102, a formed relief material layer remains having a relief surface 108 that represents the complementary pattern 108 of the pattern 106′ ( FIG. 1B ). This formed material layer can serve as a base for patterning a substrate layer using some kind of etching process, or it can directly serve as a patterned device layer, with or without further modification or processing.

[0043] Generally, in devices with multiple stacked device layers, the pattern in one device layer must be laterally aligned with the pattern in one or more other such layers or the base substrate. Therefore, an alignment step is also performed during the application of a new device layer. In the exemplary process as described herein, this means that the alignment step must be performed before the stamp 104 contacts the material layer 102, because when they are in contact, lateral repositioning of the substrate 100 and stamp 104 is difficult or impossible or may result in drag or undesired deformation of the material layer 102.

[0044] The illustrated stamp 104 consists of two parts: a conformable relief portion 104A and a glass plate 104B. The relief portion is used to imprint the material layer 102 and can be made from a transparent polymer. The glass plate is rigid and contains at least one groove 105. Negative pressure is applied to the groove to hold the relief portion firmly to the glass plate.

[0045] Successive layers of the semiconductor substrate 100 must be properly aligned with one another for the resulting device to function. If the layers are not properly aligned, signals will not be transmitted between the layers and the device will not function properly. The substrate includes one or more markers, and the conformable relief portion of the stamp 104 also includes one or more markers. Proper alignment of the stamp with the substrate and the patterned layer underlying the stamp requires proper alignment of the markers on the stamp with the markers on the substrate.

[0046] The markers of the stamp are generally located in conformable relief where the imprinted pattern is to be formed, and the alignment between the relief 104A and the glass plate 104B may be imprecise.

[0047] In some printing processes, the stamp is a hard stamp that does not deform substantially. Such a stamp can be made of, for example, quartz.

[0048] In other printing processes, such as the SCIL process, the stamp is deformable. Such a stamp can be manipulated into contact with the substrate gradually during the imprinting process by temporarily deforming the stamp during the contact step of the process. In such cases, the illustrated stamp 104A would have a conformable relief portion comprising a rubber, elastomer, or other deformable polymer material. A particularly advantageous example of such a deformable polymer includes or consists of a polysiloxane-based polymer. Often, although not necessarily, the relief portion is carried (e.g., glued) by a relatively rigid but deformable support portion in the form of, for example, a (thin) glass plate (not separately shown in FIGS. 1A and 1B). This helps improve manipulation of the stamp 104A by the stamp holder (also called the stamp manipulator) 104B.

[0049] In some embodiments, the stamp holder can include a groove plate, for example, in the form of a glass plate with one or more grooves. The groove plate is rigid and includes at least one groove, but preferably includes multiple grooves 105, within which the pressure of gas can be controlled to manipulate the stamp. For example, a low pressure (compared to ambient pressure) can be applied, causing the stamp to be pulled into or firmly held by the groove plate (via support portions, if the stamp includes such support portions). Conversely, release of the stamp can be achieved by increasing the pressure to ambient pressure or above. For clarity, only a limited number of system components are shown, but detailed descriptions of how such systems are designed and used to carry out such imprint methods are provided in the following documents, each of which is incorporated herein by reference in its entirety: 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" (and references cited therein).

[0050] The present disclosure relates to an improved approach for aligning a stamp with a substrate. The following description provides a descriptive understanding of embodiments.

[0051] 2A, the stamp, e.g., the conformable relief portion of the stamp, has a stamp marker in the form of a diffraction grating 204. The stamp can include multiple diffraction gratings, i.e., markers, which can be disposed in the conformable relief portion.

[0052] 2B, the substrate 100 includes a substrate marker, for example, in the form of a diffraction grating 200. Multiple substrate markers (e.g., diffraction gratings) can be placed at different locations on the substrate so that the substrate and stamp can be aligned both laterally and rotationally.

[0053] Alternatively, the substrate markers may be in the form of reflective or contrast markers configured to reflect light, suitable embodiments being described in more detail below.

[0054] Figures 3A and 3B show alternative locations for markers 200 on a substrate. Markers 200 on substrate 100 may be located on the front side of the substrate, as depicted in Figure 3A, or on the back side of substrate 100, as shown in Figure 3B. Other suitable locations will be apparent to those skilled in the art.

[0055] Since the alignment between the substrate 100 and the stamp 104 uses an optical process, optical imperfections can disrupt the alignment process.

[0056] The glass plate of the stamp 104 may include grooves that are used to apply negative pressure to conformal relief portions to adhere them to the glass plate. The use of multiple markers on both the substrate 100 and the stamp 104 means that even if one or more of the markers are located close to the grooves, alignment can still be achieved using markers that are not affected by the grooves.

[0057] 4A shows a portion of the alignment process in which a substrate marker 200 is illuminated. This substrate marker 200 has a diffraction grating with period Λ and diffracts some light towards a light sensor 300. In an operational example, the third diffraction order is directed towards the light sensor 300. However, it may be the first, second or higher diffraction orders that are diffracted towards the light sensor 300.

[0058] The wavelength of the illumination light and the period of the diffraction grating both affect the angle of redirection, as shown and explained together in Figures 4B and 4C. In Figure 4B, a longer wavelength is used, and as shown, a shallower angle of incidence is used to ensure that the light is directed onto the light sensor. In Figure 4C, the period Λ of the diffraction grating is shortened, and as a result, an even shallower angle of incidence is used to ensure that the illumination light is directed onto the light sensor. Using a shorter period and shallower angle improves accuracy.

[0059] Detection of the intensity of the light redirected by the marker indicates the (lateral) position of the marker. If the light redirected by the substrate marker indicates a particular lateral position of the substrate marker and the light redirected by the stamp marker indicates a particular lateral position of the stamp marker, the degree of alignment between the stamp and the substrate can be determined.

[0060] The redirected light incident on the light sensor is preferably perpendicular or substantially perpendicular to the plane of the substrate 100 and stamp 204 .

[0061] As can be seen in Figures 4A, 4B, and 4C, light redirected from the substrate marker passes through the stamp marker. It is recognized that if the stamp marker also redirects illumination light toward the light sensor 300, it may be difficult to distinguish between light redirected from the stamp marker 204 and the substrate marker 200. The inability to distinguish between light redirected from the stamp marker and light redirected from the substrate marker may hinder detection of alignment, or lack thereof, between the substrate 100 and the stamp 200. Furthermore, if the stamp marker 204 is configured to redirect light that illuminates (and is redirected by) the substrate marker, the stamp marker may attenuate or otherwise alter the light redirected by the substrate marker, making identification of alignment more difficult.

[0062] Figure 5A shows a stamp marker 204 and Figure 5B shows a substrate marker 200 for use in an embodiment of the present invention. As can be seen, both markers 204, 200 include a grating, but the period of the grating in stamp marker 204 is shorter / smaller than the period of the grating in substrate marker 200.

[0063] Due to the different periodicities of the stamp marker and the substrate marker, the illumination light redirected by the substrate marker will have a maximum at a different angle than the same illumination light redirected by the stamp marker 204. Therefore, illumination light can be directed by the substrate 200 towards the light sensor. However, the same illumination light incident on the stamp marker 204 will have a minimum at the image sensor 300. In this way, the illumination light can be used to detect the substrate marker 200, but due to the different periodicities, no light, or significantly reduced light, will be redirected by the stamp marker 204 towards the light sensor 300.

[0064] This provides a mechanism by which the proportion of first light redirected by the stamp marker towards and received by the light sensor differs from the proportion of first light directed towards and received by the substrate marker. This same mechanism also results in the proportion of second light redirected by the stamp marker towards and received by the light sensor differing from the proportion of second light directed towards and received by the substrate marker. The first and second lights can be adjusted or selected such that the received first light is redirected to a greater extent by the stamp marker than by the substrate marker, and such that the received second light is redirected to a greater extent by the substrate marker than by the stamp marker.

[0065] In one example embodiment, the stamp is illuminated with a first light having a first wavelength λ1 and incident at an angle θ1 relative to the plane of the stamp, and the stamp marker 204, having a first period λ1, diffracts the light, and a diffraction order (e.g., the third diffraction order) is redirected towards the light sensor 300. The first light incident on the substrate marker 200 is also diffracted, but not incident on the light sensor 300 at a maximum. Thus, the combination of the first light and the stamp marker 204 redirects a first fraction of the first light incident on the stamp marker to the light sensor. The combination of the first light and the substrate marker 200 redirects a second fraction of the first light incident on the substrate marker to the light sensor 300. The first fraction is at least twice the second fraction, and preferably at least five times the second fraction. Preferably, the combination of the first light and the stamp marker 204 results in maximum incidence on the light sensor, while the combination of the first light and the substrate marker 200 results in minimum incidence on the light sensor 300. Thus, when the stamp is illuminated with the first light and the light sensor detects its lateral position, it is the position of the stamp marker (and therefore the stamp 104) that is detected, and not the substrate 100.

[0066] Just as the lateral position of the stamp marker 204 is detected using the first light, the lateral position of the substrate marker 200 is detected using a second light. The second light has a second wavelength λ2 and is incident on the substrate at an angle θ2. The second light is such that the substrate marker 200, having a second period Λ2, diffracts a certain diffraction order (e.g., the third diffraction order) toward the image sensor. Any second light incident on the stamp marker 200 is diffracted, but no maximum is incident on the light sensor 300. Thus, the combination of the second light and the substrate marker 200 redirects a third fraction of the second light incident on the substrate marker to the light sensor 300. The combination of the second light and the stamp marker 204 redirects a fourth fraction of the second light incident on the stamp marker to the light sensor 300. The third fraction is at least twice the fourth fraction, and preferably at least five times the fourth fraction. Preferably, the combination of the second light and the substrate marker 204 results in a maximum incidence on the light sensor, while the combination of the second light and the stamp marker 200 results in a minimum incidence on the light sensor 300. Thus, when the substrate is illuminated with the second light and the light sensor detects its lateral position, it is the position of the substrate marker (and therefore the substrate 100) that is detected, and not the stamp 104.

[0067] FIG. 5C shows both the first and second lights illuminating the stamp and substrate.

[0068] The lateral position of the stamp 104 can be determined using a first light, and the lateral position of the substrate 100 can be determined using a second light to determine the alignment between the stamp and the substrate. If the stamp and the substrate are not correctly aligned, or are within a predetermined alignment, the lateral positions of either or both of them can be adjusted accordingly. The alignment between the substrate and the stamp can then be determined again to confirm that the substrate and the stamp are aligned.

[0069] Although the above example first illuminates the arrangement with a first light to determine the location of the stamp marker 204, followed by illumination with a second light to determine the location of the substrate marker 200, those skilled in the art will appreciate that the order of the first and second lights is not important and the second light can equally be used before the first light. In summary, it is preferred that illumination with the first light be at a different time than illumination with the second light.

[0070] The first light has a peak intensity at a first wavelength λ1, and the second light has a peak intensity at a second wavelength λ2. The first wavelength λ1 and the second wavelength λ2 are preferably different. In some examples, the larger of the first wavelength and the second wavelength is at least 20% greater than the smaller of the first wavelength and the second wavelength.

[0071] Similarly, the first period Λ1 and the second period Λ2 are preferably different. The larger of the first and second periods is preferably at least 20% larger than the smaller of the first and second periods. Furthermore, the first period is preferably smaller than the second period.

[0072] Although the above example describes the third diffraction order as being incident on the light sensor 300, the apparatus could equally be configured so that the first, second or any higher order is incident on the light sensor 300. In fact, the combination of the first light with the stamp marker could result in an nth order incident on the light sensor, and the combination of the second light with the substrate marker 200 could result in an mth order incident on the light sensor, preferably where m≠n.

[0073] The stamp is illuminated with a first light for a first period of time, and the substrate is illuminated with a second light for a second period of time. The first and second periods can be different because the intensity of the diffracted light varies depending on the diffraction order and other factors. The intensity of the light at the light sensor during the first and second periods should be sufficient to determine the position of the stamp marker or substrate marker, respectively.

[0074] A different example of the invention is described in which the stamp marker 204 is a diffraction grating but the substrate marker 200 is a contrast marker. The contrast marker operates in reflection and can be, for example, a cross-shaped chrome mark. In this example, a first light illuminates the stamp, as described above. Just as in the example above, the combination of the first light and the substrate marker 200 does not result in a maximum at the light sensor 300, so the combination of the first light and the substrate marker in this example does not result in a maximum at the light sensor because there is no diffraction and no (direct) reflected light is incident on the light sensor.

[0075] 6 shows the illumination of the substrate marker 204 with a second light having a wavelength λ2 and an angle of incidence θ2 and its reflection towards the light sensor 300. The second light incident on the substrate 200 and stamp 104 is not reflective off the stamp marker, so little or no light is reflected from the stamp marker 204 towards the light sensor.

[0076] The optical sensor 300 can detect the intensity of the redirected light, but a further example of an optical sensor is an image sensor that detects the position of the peak of the redirected light. Determining the alignment between the stamp and the substrate includes processing the image at the image sensor from the first light and the image at the image sensor from the second light.

[0077] A lithography process can include the steps of aligning a stamp with a substrate, imprinting a pattern on or at the substrate, and etching the substrate. A lithography process can include several of these (or more) steps, each with a different pattern.

[0078] 7 illustrates a method 50 according to one embodiment. According to one example of the present invention, there is a method for determining alignment between a stamp 104 and a substrate 100 in a substrate conformal imprint lithography process. The stamp 104 includes a stamp marker 204 including a first diffraction grating having a first period, and the substrate includes a substrate marker 200 on a surface of the substrate. The method includes positioning a photosensor 51 substantially perpendicular to the stamp and substrate, and illuminating the stamp marker 204 with a first light 52. The substrate marker is then illuminated with a second, different light 53.

[0079] The first light and the stamp marker 204 are configured together such that at least a first percentage of any first light incident on the stamp marker 204 is redirected towards the light sensor 300. The first light and the substrate marker are configured together such that less than a second percentage of any first light incident on the substrate marker 200 is redirected towards the light sensor.

[0080] The second light and the substrate marker are configured together such that a third percentage or more of any second light incident on the substrate marker is redirected towards the light sensor 300. The second light and the stamp marker 204 are configured together such that less than a fourth percentage of any second light incident on the stamp marker 204 is redirected towards the light sensor.

[0081] The first rate is at least two times, preferably five times, greater than the second rate, and the third rate is at least two times, preferably five times, greater than the fourth rate.

[0082] The alignment between the stamp and the substrate is then determined in step 54 using the response of the light sensor to the redirected first light and the redirected second light.

[0083] FIG. 8 illustrates an alignment system 800 according to one embodiment.

[0084] The alignment system 800 is for aligning a substrate 100 and a stamp 104 in a substrate conformal imprint lithography process. The stamp includes a stamp marker formed by a diffraction grating having a first period on a surface of the stamp, and the substrate includes a substrate marker on a surface of the substrate. The alignment system includes an optical sensor 300 arranged substantially perpendicular to the stamp 104 and the substrate 100, an illumination system 400, and a processing system 500.

[0085] The illumination system 400 is configured to illuminate the stamp marker 204 with a first light and illuminate the substrate marker 200 with a second, different light.

[0086] The first light and stamp marker 204 are configured such that at least a first percentage of any first light incident on the stamp marker is redirected towards the light sensor 300. The first light and substrate marker 200 are configured such that a second percentage of any first light incident on the substrate marker 200 is redirected towards the light sensor 300, the first percentage being at least two times greater than the second percentage.

[0087] The second light and substrate marker 200 are configured such that a third percentage or more of any second light incident on the substrate marker 200 is redirected towards the light sensor 300. The second light and stamp marker 204 are configured such that less than a fourth percentage of any second light incident on the stamp marker is redirected towards the light sensor 300. The third percentage is at least twice the fourth percentage.

[0088] The processing system 500 is communicatively coupled to the optical sensor 300 and configured to process the optical sensor's response to the redirected first light and the redirected second light to determine alignment between the stamp and the substrate.

[0089] The processing system of the alignment system is configured to control the operation of the illumination system 400 and / or the light sensor 300 to control the alignment system in performing predetermined functions.

[0090] The present invention may also be embodied as a computer program comprising computer program code means adapted to implement the method as described above when executed by the alignment system described above.

[0091] 7 illustrates an example of a computer 70 in which one or more portions of the embodiments may be employed. The various operations described above may utilize the functionality of the computer 70. For example, one or more portions of the system for providing a subject-specific user interface may be incorporated into any of the elements, modules, applications, and / or components described herein. In this regard, it should be understood that the system functional blocks may be executed on a single computer or distributed across multiple computers and locations (e.g., connected via the Internet), such as in a cloud-based computing infrastructure.

[0092] The computer 70 may include, but is not limited to, a PC, a workstation, a laptop, a PDA, a palm device, a server, storage, etc. Generally, from a hardware architecture perspective, the computer 70 may include one or more processors 71, 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 include additional elements, such as controllers, buffers (caches), drivers, repeaters, receivers, etc., to enable communication. Additionally, the local interface may include address, control, and / or data connections to enable appropriate communication between the aforementioned components.

[0093] Processor 71 is a hardware device for executing software that may be stored in memory 72. Processor 71 may be virtually any custom or commercially available processor, central processing unit (CPU), digital signal processor (DSP), or coprocessor among several processors associated with computer 70, and processor 71 may be a semiconductor-based microprocessor (in the form of a microchip) or microprocessor.

[0094] The memory 72 can be any one or combination of volatile memory elements (e.g., random access memory (RAM), e.g., 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), electronically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), tape, compact disc read-only memory (CD-ROM), disk, diskette, cartridge, cassette, etc.). Furthermore, the memory 72 can incorporate electrical, magnetic, optical, and / or other types of storage media. The memory 72 can have a distributed architecture in which various components are located remotely from each other but are accessible by the processor 71.

[0095] The software in memory 72 may include one or more separate programs, each including an ordered list of executable instructions for implementing logical functions. According to an exemplary embodiment, the software in memory 72 includes a suitable operating system (O / S) 74, a compiler 76, source code 75, and one or more applications 77. As shown, application 77 comprises multiple functional components for implementing the features and operations of the exemplary embodiments. According to an exemplary embodiment, application 77 of computer 70 may represent various applications, computational units, logic, functional units, processes, operations, virtual entities, and / or modules, although application 77 is not intended to be limiting.

[0096] 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. It is contemplated by the inventors that application 77 for implementing the exemplary embodiment may be applicable to all commercially available operating systems.

[0097] The application 77 can be a source program, an executable program (object code), a script, or any other entity comprising a set of instructions to be executed. In the case of a source program, the program is typically converted via a compiler (such as compiler 76), assembler, interpreter, etc., which may or may not be contained in memory 72 and operate appropriately in conjunction with the O / S 74. Additionally, the application 77 can be written in an object-oriented programming language, which has classes of data and methods, or a procedural programming language, including, but not limited to, C, C++, C#, Pascal, BASIC, API calls, HTML, XHTML, XML, ASP script, JavaScript, FORTRAN, COBOL, Perl, Java, ADA, .NET, etc.

[0098] The I / O devices 73 may include input devices such as, but not limited to, a mouse, keyboard, scanner, microphone, camera, etc. Additionally, the I / O devices 73 may include output devices such as, but not limited to, a printer, display, etc. Finally, the I / O devices 73 may further include devices that communicate both input and output, such as, but not limited to, a network interface card or modulator / demodulator (for accessing remote devices, other files, devices, systems, or networks), radio frequency (RF) or other transceivers, telephone interfaces, bridges, routers, etc. The I / O devices 73 also include components for communicating over various networks, such as the Internet or an intranet.

[0099] If computer 70 is a PC, workstation, intelligent device, etc., the software in memory 72 may further include a basic input / output system (BIOS) (omitted for simplicity). The BIOS is a set of essential software routines that initializes and tests hardware at startup, starts O / S 74, and supports data transfers between hardware devices. The BIOS is stored in some type of read-only memory, such as ROM, PROM, EPROM, EEPROM, etc., so that the BIOS can be executed when computer 70 is started.

[0100] When computer 70 is operating, processor 71 is configured to execute software stored in memory 72, to communicate data to and from memory 72, and to generally control the operation of computer 70 in accordance with the software. Applications 77 and O / S 74 are read, in whole or in part, by processor 71, possibly buffered within processor 71, and then executed.

[0101] It should be noted that if application 77 is implemented in software, application 77 may be stored on virtually any computer-readable medium for use by or in connection with any computer-related system or method. In the context of this specification, a computer-readable medium may be an electrical, magnetic, optical, or other physical device or means that can contain or store a computer program for use by or in connection with a computer-related system or method.

[0102] The application 77 may be embodied in any computer-readable medium for use by or associated with an instruction execution system, apparatus, or device, such as a computer-based system, a processor-containing system, or other system that can fetch instructions from and execute instructions from the instruction execution system, apparatus, or device. In the context of this document, a "computer-readable medium" may be any means that can store, communicate, propagate, or transfer a program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable medium may be, for example, but is not limited to, an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium.

[0103] 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 entirely in software, the functional steps illustrated in the process flowcharts can be performed by appropriately programmed physical computing devices, such as one or more central processing units (CPUs) or graphics processing units (GPUs). Each process, and its individual component steps illustrated in the flowcharts, can be performed 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 perform an encoding or decoding method as described above when the program is executed on the one or more physical computing devices.

[0104] The storage medium includes volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM, optical disks (such as CDs, DVDs, and BDs), and magnetic storage media (such as hard disks and tapes). Various storage media may be installed in a mobile computing device or may be transportable such that one or more programs stored on the storage medium are read by a processor.

[0105] To the extent that embodiments are implemented partially or entirely in hardware, the blocks shown in the block diagrams of Figures 1 and 5 may be separate physical components, logical subdivisions of a single physical component, or all implemented in an integrated manner in one physical component. The functionality of a block shown in the figures may be split among multiple components in implementation, or the functionality of multiple blocks shown in the figures may be combined into a single component in implementation. Hardware components suitable for use in 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 may be implemented as a combination of dedicated hardware to perform some functions and one or more programmed microprocessors and associated circuitry to perform other functions.

[0106] Variations to the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. Where a computer program is described above, the computer program can be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. It is noted that where the term "suitable for" is used in the claims or the description, it is intended to be equivalent to the term "comprised of." Any reference signs in the claims should not be construed as limiting the scope.

[0107] The flowcharts and block diagrams in the figures 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 flowcharts or block diagrams may represent a module, segment, or portion of instructions, comprising one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, may be implemented by a special-purpose hardware-based system that performs the specified functions or operations or executes a combination of special-purpose hardware and computer instructions.

Claims

1. 1. A method for determining alignment between a stamp and a substrate in an imprint process, wherein the stamp includes a stamp marker including a first diffraction grating having a first period on a surface of the stamp, and the substrate includes a substrate marker on a surface of the substrate, the method comprising: using a light sensor to capture marker light at an angle relative to the stamp and the substrate; illuminating at least the stamp marker with a first light, the first light and the stamp marker are configured such that more than a first proportion of the first light is directed by the stamp marker toward the light sensor; the first light and the substrate marker are configured such that less than a second percentage of the first light incident on the substrate marker is directed to the light sensor, wherein the first percentage is greater than the second percentage; illuminating at least the substrate marker with a second light different from the first light, the second light and the substrate marker are configured such that more than a third proportion of the second light is directed by the substrate marker to the light sensor; the second light and the stamp marker are configured such that less than a fourth percentage of the second light is directed toward the light sensor, and the third percentage is greater than the fourth percentage; determining alignment between the stamp and the substrate using a response of the light sensor caused by the redirected first and second light; A method having the following.

2. 2. The method of claim 1, wherein the first ratio is at least two or at least five times greater than the second ratio, and / or the third ratio is at least two or at least five times greater than the fourth ratio.

3. The method of claim 1 or 2, wherein the substrate marker is a contrast marker configured to reflect a portion of the second light to the light sensor.

4. The method of claim 1 or 2, wherein the substrate marker comprises a grating having a second period.

5. The method of claim 4 , wherein the first period and the second period are different.

6. The method of claim 5 , wherein the larger of the first period and the second period is at least 20% larger than the smaller period.

7. 7. The method of claim 4, wherein the first period is smaller than the second period.

8. 8. The method of claim 4, wherein the step of illuminating at least the substrate marker with the second light comprises illuminating the substrate marker with light having a wavelength and an angle of incidence such that light in a first or higher diffraction order is incident on the light sensor.

9. 9. The method of claim 1, wherein the first light has a peak intensity at a first wavelength and the second light has a peak intensity at a second, different wavelength.

10. 10. The method of claim 1, wherein the step of illuminating the stamp marker with the first light comprises illuminating the stamp marker with light having a wavelength and an angle of incidence such that light of a first or higher diffraction order is incident on the light sensor.

11. 11. The method of claim 1, wherein the step of illuminating at least the stamp marker with the first light occurs at a different time than the step of illuminating at least the substrate marker with the second light.

12. 12. The method of claim 1, wherein the step of illuminating at least the stamp marker with the first light is performed for a first period of time and the step of illuminating at least the substrate marker with the second light is performed for a second period of time, and the first period and the second period have different lengths.

13. the optical sensor is an image sensor; 13. The method of claim 1, wherein determining alignment between the stamp and the substrate using the response of the optical sensor comprises determining the alignment by processing an image on the image sensor from the first light and an image on the image sensor from the second light.

14. 1. A system for determining alignment between a stamp and a substrate in an imprint process, the system comprising: an alignment system, a stamp, and a substrate; the stamp includes a stamp marker including a first diffraction grating having a first period on a surface of the stamp; the substrate includes a substrate marker including a second diffraction grating on a surface of the substrate, the second diffraction grating having a second period different from the first period; The alignment system includes: a light sensor for capturing marker light at an angle relative to the stamp and the substrate; 1. An illumination system for illuminating at least a stamp marker with a first light and for illuminating at least the substrate marker with a second light different from the first light, comprising: the first light and the stamp marker are configured such that at least a first percentage of the first light is directed by the stamp marker toward the light sensor; the first light and the substrate marker are configured such that less than a second percentage of the first light is directed by the substrate marker to the light sensor, the first percentage being greater than the second percentage; the second light and the substrate marker are configured such that at least a third percentage of the second light is directed by the substrate marker to the light sensor; an illumination system, wherein the second light and the stamp marker are configured such that less than a fourth percentage of the second light is directed by the stamp marker toward the light sensor, and the third percentage is greater than the fourth percentage; a processing system communicatively coupled to the light sensor for processing a response of the light sensor caused by the redirected first light and the second light to determine alignment between the stamp and the substrate; and A system having:

15. A computer program when executed by a system according to claim 14, causing the system to carry out a method according to any one of claims 1 to 13.

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