CN114740695A

CN114740695A - Alignment method of wafer and mask and alignment method of nano structure

Info

Publication number: CN114740695A
Application number: CN202210534344.5A
Authority: CN
Inventors: 林岳明; 季明华
Original assignee: Shanghai Chuanxin Semiconductor Co ltd
Current assignee: Shanghai Chuanxin Semiconductor Co ltd
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2022-07-12

Abstract

The application relates to an alignment method of a wafer and a mask and an alignment method of a nano structure, wherein the alignment method comprises the following steps: s1, moving the mask plate to the wafer, wherein the mask plate and the wafer are positioned in a scanning area of an imaging device based on the near-field scanning optical microscope principle, and the reference mark used for aligning with the mask plate moved to the wafer in the step is exposed; s2, scanning the scanning area by using a scanning device to acquire first position data of the reference fiducial mark and second position data of the alignment mark; s3, determining a minimum relative distance between the first position data and the second position data for each first position data; and S4, moving the mask plate to enable the minimum relative distance to fall within a preset distance range. The alignment method of the wafer and the mask and the alignment method of the nano structure can realize optical imaging under the nano scale, thereby realizing high-precision alignment.

Description

Alignment method of wafer and mask and alignment method of nano structure

Technical Field

The invention relates to an alignment method of a wafer and a mask and an alignment method of a nanostructure, which are applied to an alignment technology and belong to the technical field of semiconductors.

Background

In a manufacturing process of a semiconductor device, when a stacked structure having a circuit pattern of the semiconductor device is formed, a photolithography process is performed for each layer. In the circuit pattern, a connection must also be formed between the upper layer and the lower layer. Therefore, overlay accuracy of the patterns of the respective layers is important. Currently, in the field of semiconductors such as microelectronics, the overlay achieved by a reticle generally includes three main categories: the projection method (realized by a projection lithography machine), the nanoimprint technology, and the contact lithography technology (i.e., the generalized contact lithography technology, which generally includes three types, namely, a contact type, a near-field type, and a vacuum type), wherein, in the latter two types of overlay technologies, the requirement for overlay alignment of a mask and a wafer is high, and particularly, as the integration level of a semiconductor chip is continuously improved, the feature size of the semiconductor chip is also continuously reduced along with the development of moore's law, the feature size is continuously reduced, and the requirement for the overlay accuracy and the feature size uniformity of the lithography/imprint process is also continuously improved.

For example, in order to improve the lithography accuracy, WO2015043450a1 discloses a super-resolution imaging lithography for non-contact lithography, in which a high-frequency evanescent wave portion of light field spatial frequency spectrum information transmitted through a mask pattern is moved to a low-frequency evanescent wave portion by an illumination light field generating device, thereby reducing the attenuation amplitude of sub-wavelength pattern evanescent wave information in the super-resolution imaging process and realizing long-working-distance gap imaging lithography. However, the method cannot be applied to an alignment process of the short-working-distance gap imaging lithography, and at present, the current short-working-distance gap imaging lithography realizes alignment based on the optical microscope principle, but the resolution of the conventional short-working-distance gap imaging lithography has 1/4 wavelength line width resolution limit. The wavelength of the used light source is reduced from an ultraviolet band (mercury lamp g line and i line) to a 193nm deep ultraviolet band, and if the light source enters a light source with shorter wavelength, such as Extreme Ultraviolet (EUV) and X ray, the high-power light source is difficult to obtain, the cost is high, and the compatibility and the inheritance of the matching technology are poor. Therefore, under the influence of the resolution limit of the conventional optical microscope technology, the exposure pattern is easily deviated from the actual position, the alignment precision of the photoetching machine is influenced, and the performance of the semiconductor device is further influenced.

Disclosure of Invention

The invention aims to provide an alignment method of a wafer and a mask plate so as to realize high-precision alignment.

In order to achieve the purpose, the invention provides the following technical scheme: a method for aligning a wafer and a mask, wherein at least two reference marks are formed on the wafer, the mask comprises at least two alignment marks and a detection hole which is arranged in a staggered mode with the alignment marks, and the method comprises the following steps:

s1, moving a mask plate onto a wafer, wherein the mask plate and the wafer are located in a scanning area of a scanning device, and the scanning device is based on a near-field scanning optical microscope principle, wherein the detection holes expose reference fiducial marks on the wafer, and each detection hole exposes only one reference fiducial mark;

s2, scanning the scanning area by using a scanning device to acquire first position data of a reference mark and second position data of the alignment mark;

s3, determining a minimum relative distance between the first position data and the second position data for each of the first position data;

and S4, under the condition that the minimum relative distance is larger than or smaller than a preset distance range, moving the mask plate to enable the minimum relative distance to fall within the preset distance range.

Further, the first position data includes X-direction data and Y-direction data; the second position data includes X-direction data and Y-direction data.

Further, the minimum relative distance is a straight-line distance between the reference fiducial mark and the alignment mark.

Further, in step S2, when the probe moves the probe hole, the probe moves in the Z direction to the near surface of the wafer for scanning to determine first position data of the reference fiducial mark located in the probe hole.

Further, in step S1, the reticle is moved onto the wafer by a moving system; and carrying out coarse alignment by using a low-resolution optical observation system and a displacement adjustment system, and moving the mask plate until each reference mark is exposed through one detection hole.

Further, the cross-sectional dimension of the detection hole is larger than the dimension of the reference fiducial mark.

Further, the cross section of the detection hole is in any one of a square shape, a rectangular shape, a circular shape and a trapezoidal shape; the alignment mark and the reference mark are in any one of a circle, a cross, a polygon, a Chinese character 'mi' -shaped L-shaped line and a T-shaped shape.

Further, the wafer is provided with at least one pattern layer, wherein a micro-nano structure with a marking function is formed on the at least one pattern layer, and the reference mark is an uneven part formed after the photoresist on the wafer covers the micro-nano structure with the marking function.

Further, the reference mark and the pattern on the pattern layer are manufactured and formed at the same time.

The invention also provides an alignment method of the nano structure, which comprises the following steps:

aligning the wafer and the mask plate by adopting the nanostructure alignment method;

photoetching/imprinting the wafer by using the mask plate to form a layer of pattern;

and repeating the steps to align the various masks with the wafer in sequence and form a plurality of layers of patterns on the wafer in sequence.

The invention has the beneficial effects that: the invention utilizes the scanning device based on the principle of the near-field scanning optical microscope to scan and image the reference mark positioned on the wafer and the alignment mark positioned on the mask, and because the scanning device is based on the principle of the near-field scanning optical microscope, the resolution of the image is only determined by the size of the aperture, thereby breaking through the diffraction limit of the imaging device based on the traditional optical microscope principle in the prior art, realizing the optical imaging under the nanometer scale, obtaining the coordinate data of the reference mark and the alignment mark on the nanometer scale, and further realizing the high-precision overlay alignment; the pattern to be photoetched/impressed is aligned with the actual position with high precision, the corresponding relation of each layer is ensured, the alignment precision is improved, and the performance of the semiconductor device is improved.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

Fig. 1 is a flowchart illustrating a method for aligning a wafer and a reticle according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a reticle and wafer structure according to the present invention for use in photolithography.

FIG. 3 is a cross-sectional view of a reticle of the present invention for use in photolithography.

FIG. 4 is a cross-sectional view of a reticle and wafer according to the present invention for use in photolithography.

Fig. 5 is a cross-sectional view of another reticle and wafer according to the present invention for use in lithography.

FIG. 6 is a cross-sectional view of another reticle of the present invention for use in photolithography.

Fig. 7 is a schematic structural diagram of a reticle and a wafer used in imprint technology according to an embodiment of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1 in combination with fig. 2 and 3, a method for aligning a wafer and a reticle according to an embodiment (embodiment) of the present invention is applied to the field of near-field lithography, and is used to align and position the reticle 1 and the wafer 2. The mask 1 comprises two alignment marks 11 and a detection hole 12 which is arranged in a staggered manner with the alignment marks 11, and at least two reference marks are formed on the wafer 2, wherein two of the reference marks are reference marks 21, and the reference marks 21 are used for the alignment of the mask 1 and the wafer 2. In this embodiment, the mask 1 and the wafer 2 are subjected to non-contact lithography, specifically, the wafer 2 is provided with the supporting pad 3, the mask 1 is placed on the supporting pad 3, and the wafer 2 and the mask 1 are not contacted through the supporting pad 3.

The alignment method of the wafer and the mask comprises the following steps:

s1, reticle 1 is moved onto wafer 2 and reticle 1 and wafer 2 are located within a scanning area of a scanning device (not shown). The scanning device is based on the near-field scanning optical microscope principle. Wherein, the reference mark 21 on the wafer 2 is exposed by the detection holes 12 on the mask 1, wherein each detection hole 12 exposes a required reference mark 21;

s2, scanning the scanning area by using the imaging function of the scanning device, and acquiring first position data of the reference mark 21 and second position data of the alignment mark 11 on the mask 1 in the step S1;

s3, determining a minimum relative distance between the first position data and the second position data for each first position data;

and S4, under the condition that the minimum relative distance is larger than or smaller than the preset distance range, moving the mask 1 to enable the minimum relative distance to fall within the preset distance range. Among them, Near-field Scanning Optical microscopy (NSOM) describes a sub-wavelength size light source, such as a nanoaperture light source, placed in the Near-field area of the sample (distance much smaller than wavelength), the illuminated area of the sample is determined only by the size of the light source or aperture and is independent of the wavelength of the light source. The light source and the sample are scanned mutually, and the optical image of the sample can be obtained by detecting the light intensity signal. The resolution of the image is determined only by the size of the aperture, which may be able to break through the diffraction limitations of prior art imaging devices based on conventional optical microscopy principles. Therefore, when the alignment method is applied to the nano-lithography technology, optical imaging under the nano scale can be realized, and alignment under the nano scale can be realized.

The steps S1 to S4 are to make a pattern layer on the wafer 2 having at least one pattern layer, and the steps are repeated a plurality of times to be called as overlay. Before step S1, the wafer 2 is usually formed with at least one pattern layer (not shown), in which at least one pattern layer is formed with micro-nano structures for marking. In this embodiment, the wafer 2 includes a base layer, a pattern layer formed on the base layer, and a dielectric layer located above the pattern layer, a layer to be etched 23 is formed on the dielectric layer, and a photoresist layer 22 is formed on the layer to be etched 23. The patterned layer on the base layer may be one or more layers. The layer to be patterned 23 is used for patterning, and is referred to as a patterning layer. The reference mark 21 is an uneven portion formed after the photoresist on the wafer 2 covers the micro-nano structure serving as the mark. Generally, the micro-nano structure for marking is formed on the pattern layer, and may be formed on only one pattern layer (only on the lowermost pattern layer), or formed on multiple pattern layers, or formed on the lowermost pattern layer. In practical applications, it is usually: the pattern layers are all formed with micro-nano structures for identification or the pattern layer at the bottommost layer is formed with a plurality of micro-nano structures, and at this time, the number of the reference marks 21 may be more than 2. In the present embodiment, for convenience of description, the number of the fiducial marks 21 and the number of the reference fiducial marks are both 2 (left and right areas of the wafer), and the 2 reference marks are used for the alignment of the current reticle 1 and the wafer 2 for forming the pattern on the layer to be lithographed 23.

When a plurality of reference marks (that is, the number of the reference marks is 2 greater than the number of the reference marks) are formed on the wafer 2, some of the reference marks are not used for alignment of the current reticle 1 and the wafer 2, for convenience of distinction, the reference marks used for alignment of the current reticle 1 and the wafer 2 are referred to as reference marks, and the reference marks not used for alignment of the current reticle 1 and the wafer 2 are referred to as non-reference marks. In practice, the non-reference fiducial marks and the reference fiducial marks may be relatively close, so that, in step S1, each detection hole may expose one or more non-reference fiducial marks in addition to only one reference fiducial mark, in which case the lithography system will identify the non-reference fiducial marks and the reference fiducial marks, so that steps S2-S4 can be performed (the first position data obtained from the reference fiducial marks in steps S2-S4).

In the above description, in the present embodiment, two reference fiducial marks are provided for aligning with the reticle 1 moved to the wafer 2 in step S1, but in other embodiments, the number of the reference fiducial marks for aligning with the reticle 1 moved to the wafer 2 in step S1 may be two or more, and correspondingly, the number of the reference fiducial marks 21 and the number of the detection holes 22 of the reticle 1 in step S1 may be two or more, and generally speaking, when one reticle 1 is used for one photolithography process, the number of the reference fiducial marks 21 and the number of the detection holes 22 on the reticle 1 correspond to the number of the reference fiducial marks 21 for aligning with the reticle 1 on the wafer 1.

Referring to fig. 4, the scanning device based on the near-field scanning optical microscope principle is digitally imaged by the probe 4 after point-by-point scanning and point-by-point recording on the surface of the sample (the sample in this embodiment is the mask 1 and the wafer 2). The probe 4 is movable in three-dimensional XYZ directions above the sample, which can adjust the distance between the probe 4 and the sample with an accuracy of several tens of nanometers.

The XY direction scanning and Z direction control movement can control the feedback follow-up of the Z direction scanning by the probe 4 with 1nm precision. The laser source and the polarization device emit incident laser, the incident laser is introduced into the probe 4 through the optical fiber, and the polarization state of the incident laser can be changed according to requirements so as to meet the requirements. When the incident laser irradiates the sample, the detector can collect the reflection signal modulated by the sample, and the reflection signal is amplified by the photomultiplier tube, and then the reflection signal is directly collected by the computer after analog-digital conversion, so as to obtain the surface appearance of the sample. The system control, data acquisition, image display and data processing are all completed by a computer.

In the imaging device based on the conventional optical microscope principle, there is a diffraction limit of resolution due to the diffraction effect of light, which is a principle obstacle to the improvement of optical resolution. The calculation formula of the optical resolution is as follows: and CD is K1 lambda/NA, wherein lambda is the wavelength of a light source, K1 is a process coefficient factor, and NA is the numerical aperture of the photoetching objective lens.

The optical resolution can be improved by shortening the wavelength lambda of the light source, reducing the process coefficient factor K1, improving the numerical aperture NA of the photoetching objective lens and the like. However, due to technical limitations, the increase of the numerical aperture of the current lithography objective lens is close to the limit, the wavelength of the used light source is reduced from the ultraviolet band (g line and i line of a mercury lamp) to the 193nm deep ultraviolet band, and even if various Resolution Enhancement Technologies (RET) are adopted, the theoretical limit of the Resolution of the 34nm line width cannot be broken through.

If the light enters a light source with shorter wavelength, such as Extreme Ultraviolet (EUV), X-ray and the like, not only is a high-power light source difficult to obtain, but also the compatibility and inheritance of the matching technology are poor, and the research and development cost is increased sharply.

The maximum optical resolution is typically 1/2-1/4 wavelengths, on the order of about 100-200 nm. The imaging device based on the conventional optical microscope principle in the prior art has the resolution limit, and is not influenced by the wavelength of incident laser, so that the incident laser based on the near-field scanning optical microscope principle does not need a super-short wavelength light source, and the cost is reduced. The precision of the semiconductor device can be 1nm, high-precision alignment can be realized, and the quality and the performance of the semiconductor device are improved.

Regarding the alignment method of the wafer and the mask, before the mask 1 is not moved onto the wafer 2, the mask 1 is located on a mask platform (not shown), the wafer 2 is located on a substrate platform (not shown), and the mask platform and the substrate platform can be moved relatively by using a mechanical adjusting system of a lithography machine to adjust the relative position between the two. The mechanical adjustment system, the reticle stage and the substrate stage are all prior art and are not described herein.

In step S1, the reticle 1 is moved onto the wafer 2 by the moving system; the low-resolution optical observation system and the displacement adjustment system are used for rough alignment, that is, the mask 1 is moved until each reference mark 21 is exposed through one detection hole 12. The movement system is generally a movement system such as a precision mechanical stage for realizing a wide range of movement, and is only intended to move the reticle 1 from the reticle stage to above the wafer 2. This displacement adjustment moves a low precision mechanical adjustment system. The low resolution optical viewing system may be a conventional microscope. Specifically, the reticle 1 and the wafer 2 are moved to the scanning area of a conventional microscope, and the reticle 1 is moved to perform scanning until the reference fiducial mark 21 on each wafer 2 is scanned. Regarding the identification of the reference fiducial marker 21 and the other fiducial markers, pattern identification (for example, the reference fiducial marker 21 and the other fiducial markers may be set to be different in shape) and/or coordinate identification (for example, the coordinate data of the reference fiducial marker 21 is different from the coordinate data of the other fiducial markers) may be implemented, and the identification manner thereof is implemented by using the prior art, and will not be described in detail herein.

The preset distance range is set according to the actual distance between the alignment mark 11 and the reference mark 21 located on the same side. The minimum relative distance falls within a predetermined distance range, and the reticle 1 and the wafer 2 are considered to be aligned.

The first position data includes X-direction data and Y-direction data; the second position data includes X-direction data and Y-direction data.

The minimum relative distance is the straight-line distance between the reference mark 21 and the alignment mark 11. Since the reference mark 21 and the alignment mark 1 are no longer on the same plane, the distance between the reference mark 21 and the alignment mark 1 can not be determined by using only the data in the X direction or the data in the Y direction, thereby achieving the purpose of aligning the mask 1 and the wafer 2. The minimum relative distance is obtained from the X-direction data and the Y-direction data. The linear distance is obtained according to a pattern algorithm to achieve optimal "overlay" of the overlay image.

In step S2, when the probe 4 moves to the position of the probe hole 12, the probe 4 moves downward in the Z direction to the near surface of the wafer 2, and scans within the probe hole 12 to determine first position data of the reference fiducial mark 21 located within the probe hole 12.

In step S3, for each reference mark 21, having the alignment mark 11 located on the same side as it, the distance between the reference mark 21 and the alignment mark 11 located on the same side is smallest compared to the distance between that reference mark 21 and the other alignment marks 11. The minimum relative distance is the distance between the reference fiducial mark 21 and the alignment mark 11 on the same side.

The recording of the first position data and the second position data, the determination of the minimum relative distance, and the size determination of the minimum relative distance and the preset distance range are realized by a control device, which is the prior art and is not described herein again.

By utilizing the principle of the near-field scanning optical microscope, the diffraction limit of an imaging device based on the traditional optical microscope principle in the prior art can be broken through, the imaging under the nanometer size is realized, the nanometer-scale coordinate data of the reference mark 21 and the alignment mark 11 are obtained, and the high-precision alignment is realized.

After a layer of pattern is formed on the wafer 2, a mask 1 with a new structure is provided when the next pattern preparation is carried out, a new material layer such as metal or medium and a photoresist layer is formed on the wafer 2, and the alignment method is repeated, so that the high-precision alignment again can be realized, and the quality of the semiconductor device is improved.

Referring to fig. 2 to 4, a wafer 2 according to an embodiment of the present invention may be aligned with a reticle by using the above-mentioned method for aligning the wafer with the reticle, and has at least two reference fiducial marks 21 thereon, for convenience of description, only one pattern layer (not shown) is currently formed on the wafer 2 in fig. 2 to 4, and a micro-nano structure for marking is formed on the pattern layer. As described above, the reference mark 21 is an uneven portion formed after the photoresist on the wafer 2 covers the micro-nano structure for marking.

The reference mark 21 has a shape of any one of a circle, a cross, a polygon, a m-shaped L-line, and a T-shape, but is not limited thereto and may have other shapes, which are not listed here. The specific shape of at least two alignment marks 11 may be the same or different. The number of reference fiducial markers 21 may be 2, 3, 4 or even more.

Preferably, the reference fiducial marks 21 are located close to the edge of the wafer 2 so as not to easily disrupt the integrity of the subsequently lithographically produced pattern. For a square wafer 2, the reference fiducial marks 21 may also be located at its top corners or at its sides.

In another embodiment, the micro-nano structure with the marking function can be simultaneously manufactured and formed with the pattern on the pattern layer (the first pattern layer) at the bottom layer on the wafer 2, so that the manufacturing steps are saved, the pattern of the micro-nano structure with the marking function for photoetching only needs to be manufactured on the pattern layer of the mask 1 for manufacturing the first pattern layer, and the operation is simple.

The mask 1 according to an embodiment of the present invention includes at least two alignment marks 11 and a detection hole 12 disposed to be offset from the alignment marks 11.

Specifically, the mask 1 may have a pattern to be photoetched (not shown) by the above-mentioned wafer-to-mask alignment method, and after the mask 1 and the wafer 2 are aligned, the pattern to be photoetched of the mask 1 is formed on the photoresist layer 22 by exposure. When the mask 1 is moved to the loading wafer 2, the reference mark 21 on the wafer 2 is covered and cannot be scanned subsequently. Therefore, the detection hole 12 of the mask 1 penetrates in the height direction thereof, and when the mask 1 is moved onto the wafer 2, the reference mark 21 can be exposed through the detection hole 12 and can be scanned.

The cross-sectional shape of the detection hole 12 is any one of a square, a rectangle, a circle, and a trapezoid, but the cross-sectional shape is not limited to a rectangle, a circle, and a trapezoid. In order to expose the reference fiducial marks 21 on the wafer 2, the size of the cross section of the probing hole 12 is larger than that of the reference fiducial marks 21.

The detection hole 12 is a through hole provided near the edge of the reticle 1, that is, the detection hole 12 is provided inside the surface of the light-transmitting mask substrate. This arrangement does not easily destroy the integrity of the patterned layer. The detection hole 12 may also be a groove having an opening that faces the substrate side.

The shape of the alignment mark 11 is any one of a circle, a cross, a polygon, a m-shaped L-row, and a T-shape, but the invention is not limited thereto, and other shapes are also possible, which are not listed here. The specific shape of at least two alignment marks 11 may be the same or different. The number of alignment marks 11 may be 2, 3, 4 or even more.

The specific shapes of the alignment mark 11 and the reference mark 21 may be the same or different, and may be specifically set according to the actual situation.

The alignment marks 11 may be formed separately by a layer of marks that is not the same layer as the patterned layer in the reticle (for the pattern to be lithographically patterned). By arranging the alignment mark 11 and the pattern layer as two different layers, the alignment mark is more convenient to detect, and the detection accuracy is higher.

Preferably, the alignment mark 11 is provided near the edge of the reticle 1 so that the integrity of the pattern layer is not easily damaged. For a square reticle 1, the alignment marks 11 may also be located at the top corners or at the sides thereof.

In the present embodiment, the reticle 1 further includes a antireflection layer 14, and the antireflection layer 14 is provided on the transparent mask blank 11, that is, the antireflection layer 14 side abuts against the transparent mask blank 11. Of course, in other embodiments, the antireflection layer 14 may not be provided.

The advantage of providing the antireflection layer 14 is that: when an incident light beam is irradiated onto the reticle 1, the antireflection layer 14 can reduce reflection of the incident light beam and increase transmission, thereby improving the utilization efficiency of the exposure power. The anti-reflection layer 14 is made of fluoride such as lanthanum fluoride, gadolinium fluoride, magnesium fluoride, aluminum fluoride, etc., erbium oxide (Er)₂O₃) Hafnium oxide (HfO)₂) Tantalum oxide (Ta)₂O₅) Aluminum oxide (Al)₂O₃) Oxide materials or one or more mixed materials, not listed here.

The antireflection layer 14 is made of a transparent material and is formed by the following steps: after the alignment mark 11 is formed, the antireflective layer 14 is formed on the transparent reticle substrate 11, and normally, the antireflective layer 14 covers the alignment mark 11, but since the antireflective layer 14 is made of a transparent material, it does not block the alignment mark 11. Of course, in other embodiments, the anti-reflection layer 14 may be disposed below the alignment mark 11, and in this case, the anti-reflection layer 14 is formed first, and then the alignment mark 11 is formed (as shown in fig. 6), so that it is more beneficial to ensure the accuracy of the probe 4 for acquiring the position data of the alignment mark 11.

In a preferred embodiment, the number of the reference mark 21, the alignment mark 11 and the detection hole 12 is the same. In the present embodiment, the number of the reference mark 21, the alignment mark 11, and the detection hole 12 is two.

The two alignment marks 11 are oppositely arranged on two sides of the mask 1, the two detection holes 12 are oppositely arranged on two sides of the mask 1, and the reference mark 21 is oppositely arranged on two sides of the wafer 2.

In this embodiment, the mask 1 and the wafer 2 are subjected to non-contact lithography, the wafer 2 is provided with a support pad 3, and the mask 1 is placed on the support pad 3. When the mask 1 is on the wafer 2, a gap 31 is formed between the two by the supporting pad 3. When the mask 1 and the wafer 2 are aligned, the linear distance between the alignment mark 11 and the reference mark 21 on the same side is a set value.

Therefore, when the position data of all the reference marks 21 and the alignment marks 11 are obtained by scanning, the actual distance between the alignment mark 11 and the reference mark 21 located on the same side is obtained according to the position data, and when the difference between the actual distance between the alignment marks 11 and the reference marks 21 on both sides and the set value is zero or within a certain range, the reticle 1 and the wafer 2 are determined to be aligned.

In order to further improve the quality of the semiconductor device, in another alternative embodiment, referring to fig. 5, a surface plasma layer 15 may be disposed on the mask 1 to receive the incident laser beam and generate an sp (surface plasma) wave having a wavelength lower than that of the incident beam, so as to reduce the reduction of the wavelength of the laser beam irradiating the pattern to be lithographed and improve the lithography resolution.

Specifically, the mask 1 includes a base body including a light-transmitting mask substrate 17, a surface plasmon layer 15 provided on the light-transmitting mask substrate 17, a pattern layer 18 provided on a side of the surface plasmon layer 15 remote from the light-transmitting mask substrate 17, and at least one imaging lens layer 19 provided on a side of the pattern layer 18 remote from the surface plasmon layer 15.

The surface plasmon layer 15 is configured to receive an incident beam and generate an SP wave having a wavelength lower than that of the incident beam, thereby improving resolution in the nanolithography. The SP wave irradiates the pattern layer 18, the imaging lens layer 19 is utilized to enable the spatial frequency of the diffraction light of the pattern layer 18 to move, the evanescent wave intensity carrying high-frequency spatial information is enhanced, and the information of the pattern layer 18 is transmitted to the photoresist layer 22 of the wafer 2 by means of the negative refraction imaging effect, so that super-resolution imaging lithography is realized.

The SP wave is a surface plasma wave which is a resonance wave generated by collective oscillation of free electrons on the surface of the metal along with incident light beams at the same frequency, the wave is locally transmitted on the surfaces of the metal and the medium, and the SP wave has a near-field enhancement effect and can enhance the intensity of an optical field in a near-field range. In addition, the wave vector of the SP wave is larger than that of the electromagnetic wave in vacuum under the same frequency.

The surface plasmon layer 15 includes an excitation layer 151, a coupling layer 152 formed on the excitation layer 151, and a reinforcing layer 153 formed on the coupling layer 152.

Wherein the excitation layer 151 is formed on the light transmissive mask substrate 17. The excitation layer 151 is configured to receive an incident light beam and generate SP waves having a wavelength lower than that of the incident light beam.

The excitation layer 151 may be a nanostructure prepared on the transparent mask substrate 17, and the nanostructure may be a one-dimensional nanostructure or a two-dimensional nanostructure. The specific structure can be set according to actual needs, and can be optimized according to the specific structure of the pattern layer 18.

The excitation layer 151 is a material capable of efficiently exciting SP waves with a specific transmission wavelength, such as metal Cr and dielectric TiO₂。

Coupling layer 152 is used to couple the SP wave to patterned layer 18.

The enhancement layer 153 is configured to enhance the SP wave intensity, reducing the interference of stray light fields. The enhancement layer 153 may be formed directly on the excitation layer 151, and also on the coupling layer 152, and is not particularly limited herein.

The reinforcing layer 153 includes a multi-layered structure in which metal layers and dielectric layers are alternately stacked, wherein the metal layersThe layer can be made of aluminum and the like, and the dielectric layer is MgF₂And the like.

The patterned layer 18 in this embodiment comprises a pattern of nanostructures, which is the pattern to be lithographically patterned. The pattern of nanostructures may be a one-dimensional or two-dimensional pattern. The nanostructure pattern may be filled in the polymer material PMMA.

In this embodiment, the imaging lens layer 19 may include a metal film layer prepared on the pattern layer 18 to realize near-field imaging of the pattern. The metal film layer may include materials that exhibit a negative dielectric constant over the incident wavelength range, including but not limited to Ag, Au, Al, and the like.

In this embodiment, the imaging lens layer 19 is provided with three layers, and in other embodiments, the imaging lens layer 19 may also be provided with other layers, such as two layers, four layers, five layers, and the like. Providing the imaging lens layer 19 in multiple layers can improve the quality of near field imaging of the pattern.

In other implementations, a protective layer may also be formed on imaging lens layer 19 to prevent physical damage and chemical corrosion of imaging lens layer 19 and patterned layer 18. The protective layer may be 5-10nm thick and the material may include, but is not limited to, SiO₂Diamond, etc.

The mask 1 utilizes the surface plasma wave to illuminate the pattern layer 18 and the imaging lens layer 19, enhances evanescent waves by exciting the surface plasma, compensates the loss of the evanescent waves outside the lens, and can reconstruct high-resolution imaging with super-diffraction limit on the other side of the imaging lens layer 19 to improve the resolution. The use of the reticle 1 may not change the conventional lithographic apparatus and therefore its cost is relatively low.

The mask 1 is matched with the alignment method of the wafer and the mask, so that high-precision alignment positioning can be realized, high-resolution imaging of super-diffraction limit can be realized, and the SP photoetching technology can be widely applied to ultra-fine photoetching in the semiconductor technology.

In this embodiment, the reticle 1 may also include the antireflection layer 14 provided on the light-transmitting mask substrate 17, as in the foregoing embodiments. The antireflection layer 14 is also located above the reference fiducial mark (not numbered) (i.e., the antireflection layer 14 covers the alignment mark), although the antireflection layer 14 may also be located below the reference fiducial mark.

The alignment method of the wafer and the reticle given in all the embodiments provided above is applied to the photolithography technology, that is, the pattern on the wafer 1 is formed by photolithography. However, in addition, the alignment method of the wafer and the mask can also be applied to the imprinting technology. The imprint technique differs from the above-described lithography technique only in the manner of formation of the patterned layer. As shown in fig. 7, in the imprint technology, it is also necessary to use a plurality of reticles 7, where the reticles 7 are formed with alignment marks 72 and grooves 71 for forming micro-nano structures of imprint patterns, the wafer 8 has reference marks 81, the wafer 8 is coated with an imprint resist 82, and a layer to be etched 83 is below the imprint resist 82. Of course, the wafer 8 also includes a base layer, at least one patterned layer, and a dielectric layer formed between two adjacent patterned layers. When a new pattern is required to be manufactured on the wafer 8 through the new mask 7, after the mask 7 and the wafer 8 are aligned through the alignment method, a new pattern layer is formed on the layer to be etched 83 through processes in the existing imprint technology, such as imprinting and curing. In fig. 7, in order to enable this alignment method, the reticle 7 also has probe holes 73 for the probes 4 to penetrate, the probe holes 12 exposing the reference fiducial marks 21 on the wafer 2. The reticle 7 may have another layer structure such as the antireflective layer 74. In the imprint technology, since the steps of the alignment method of the wafer and the reticle are the same as those in the first embodiment, they are not described herein.

aligning the wafer and the mask plate by adopting the alignment method of the wafer and the mask plate;

carrying out photoetching/imprinting on a wafer by using a mask plate to form a pattern;

and repeating the steps to align the various masks with the wafer in sequence and form a multi-layer pattern on the wafer in sequence. The pattern to be photoetched is aligned with the actual position in high precision, the corresponding relation of each layer is ensured, the alignment precision is improved, and the performance of the semiconductor device is improved.

In summary, the invention uses the near-field scanning optical microscope principle to scan and image the reference mark on the wafer and the alignment mark on the mask, the resolution of the image based on the near-field scanning optical microscope principle is only determined by the aperture, the diffraction limit of the imaging device based on the traditional optical microscope principle in the prior art is broken through, the optical imaging under the nanometer scale can be realized, the nanometer scale coordinate data of the reference mark and the alignment mark can be obtained, and the high-precision overlay alignment can be realized; the pattern to be photoetched/impressed is aligned with the actual position with high precision, the corresponding relation of each layer is ensured, the alignment precision is improved, and the performance of the semiconductor device is improved.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A method for aligning a wafer and a mask, wherein at least two reference marks are formed on the wafer, the mask comprises at least two alignment marks and a detection hole which is arranged in a staggered mode with the alignment marks, and the method comprises the following steps:

s1, moving the mask plate to the wafer, wherein the mask plate and the wafer are located in a scanning area of a scanning device, and the scanning device is based on a near-field scanning optical microscope principle, wherein the detection holes expose reference fiducial marks on the wafer, and each detection hole exposes only one reference fiducial mark;

and S4, moving the mask plate to enable the minimum relative distance to fall within the preset distance range under the condition that the minimum relative distance is larger than or smaller than the preset distance range.

2. The wafer and reticle alignment method of claim 1, wherein the first position data comprises X-direction data and Y-direction data; the second position data includes X-direction data and Y-direction data.

3. The wafer and reticle alignment method of claim 1, wherein the minimum relative distance is a straight line distance between the reference fiducial mark and the alignment mark.

4. The wafer and reticle alignment method of claim 1, wherein in step S2, when a probe moves the probe hole, the probe moves in a Z direction to a near surface of the wafer for scanning to determine first position data of a reference fiducial mark located in the probe hole.

5. The wafer and reticle alignment method of claim 1, wherein in step S1, the reticle is moved onto the wafer by a moving system; and carrying out coarse alignment by using a low-resolution optical observation system and a displacement adjustment system, and moving the mask plate until each reference mark is exposed through one detection hole.

6. The wafer and reticle alignment method of claim 1, wherein the cross-sectional dimension of the probe hole is larger than the dimension of the reference fiducial mark.

7. The wafer and reticle alignment method according to claim 6, wherein the cross-sectional shape of the probe hole is any one of square, rectangular, circular and trapezoidal; the alignment mark and the reference mark are in any one of a circle, a cross, a polygon, a Chinese character 'mi' -shaped L-shaped line and a T-shaped shape.

8. The method for aligning the wafer and the mask as claimed in any one of claims 1 to 7, wherein the wafer has at least one pattern layer, wherein at least one pattern layer is formed with a micro-nano structure for identification, and the reference mark is an uneven part formed after photoresist on the wafer covers the micro-nano structure for identification.

9. The wafer and mask alignment method according to claim 8, wherein the micro-nano structure for marking and the pattern on the pattern layer are manufactured and formed at the same time.

10. A method of alignment of nanostructures, comprising:

aligning a wafer with a reticle using the nanostructure alignment method of any one of claims 1-9;