Overlay alignment device and overlay alignment method for transparent bicrystal substrate covered by thin film

Abstract

The invention belongs to the technical field of photoetching micromachining, and relates to an overlay alignment method and device for a transparent bicrystal substrate sample covered by a film. According to the invention, transmission light is utilized to realize bimorph crystal boundary imaging in the bimorph substrate; a reflection imaging system of the photoetching machine with a microscope realizes photoetching layout imaging on the surface of the sample; by accurately adjusting the position of the focal plane, under the condition of transmission / reflection dual-mode cooperative imaging, the photoetching layout and the bicrystal boundary line are clearly visible, so that the accurate alignment of the photoetching layout and the bicrystal boundary line is realized. The method does not depend on alignment of overlay marks, the overlay process is simplified, and the overlay freedom degree is improved. According to the overlay alignment device disclosed by the invention, a transmission light source is transferred out of a photoetching system through the reflective prism, so that the problem that the light source is not uniform due to a narrow space between the overlay mask and the objective table is solved, the problems of a strong light source and heat dissipation of the strong light source are thoroughly solved, and the penetrating power of transmission light is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photolithographic micromachining, and relates to a high-precision alignment-free marking overlay alignment device and method for a thin-film covered transparent bicrystal substrate sample. Background Art

[0002] Traditional lithography machines are mainly designed for opaque silicon-based or compound semiconductor substrates, and the alignment method mainly relies on a reflective optical imaging system and alignment marks. Currently, high-temperature superconducting quantum interference device (SQUID) sensors based on transparent bicrystal substrates such as strontium titanate (STO), magnesium oxide (MgO), and lanthanum aluminate (LAO) are developing rapidly in China. During the micromachining and manufacturing process of SQUID sensors, the most critical step is to align and overlay expose the Josephson junction pattern with the bicrystal grain boundary line. The reflective imaging system of traditional lithography machines cannot observe the bicrystal grain boundary line, and there is currently no lithography machine specifically for overlay of such transparent bicrystal substrates on the market. Most R & D personnel replace the stage with a transparent one and install a low-power red LED lamp below it to form a transmissive optical alignment system. This system can play a role in transmissive alignment to a certain extent, but it cannot completely solve the problem of overlay alignment of transparent bicrystal substrates.

[0003] The difficulties in overlay of transparent bicrystal substrates are as follows: (1) The overlay pattern template is located on the substrate surface, while the bicrystal grain boundary line is inside the substrate, and the two are not in the same focal plane, making it difficult to present clear images simultaneously. (2) It is difficult to identify the bicrystal grain boundary line of a high-quality bicrystal substrate through the reflective light imaging method equipped with a traditional lithography machine. However, when imaging with transmitted light, since the bicrystal grain boundary is an amorphous structure, it has a strong scattering effect on the incident light, resulting in a decrease in the transmittance at this location. Compared with the complete crystals on both sides of the bicrystal grain boundary line, a darker contrast will be formed at the bicrystal grain boundary line, and thus a dark bicrystal grain boundary line will appear in the image. Therefore, observation of the bicrystal grain boundary line requires the use of transmitted light imaging. (3) Before overlay, a high-temperature superconducting thin film of about a hundred nanometers of black yttrium barium copper oxide (YBCO), dysprosium barium copper oxide (DyBCO), etc. is generally deposited on the transparent bicrystal substrate, and a Au thin film of about a hundred nanometers may also be deposited on top as a protective layer or shunt layer. These relatively thick thin films will greatly attenuate the intensity of the transmitted light, and a high-power and intensity-adjustable light source is required to be competent. It is also difficult to solve the problems of installation and heat dissipation of a high-power light source in the narrow space between the mask plate and the stage of the lithography machine. (4) Before depositing the high-temperature superconducting thin film, the substrate is generally fixed on the heat sink with Ag glue. It is difficult to completely remove the Ag glue on the back of the substrate, and scratches will be generated during the removal process, which will interfere with the observation of the bicrystal grain boundary line and bring great difficulties to the judgment of the bicrystal grain boundary line in subsequent transmitted imaging. To achieve overlay micromachining of transparent bicrystal substrates, special methods must be studied and a device that can solve the above-mentioned many difficulties in one go must be developed.

[0004] Patent CN108008608 uses infrared light for back alignment and uses the transparent properties of silicon to infrared light to achieve penetrating imaging, but it relies on a specific wavelength light source (such as 1310nm) and has poor compatibility with non-silicon-based transparent substrates (such as glass and sapphire). CN118765156A discloses a method for preparing a high-temperature superconducting quantum interference device that accurately locates a twin crystal junction and a grain boundary, forming a micron-scale linear dot matrix positioning mark structure on a high-temperature superconducting material layer near the grain boundary; adjusting a transmission microscope to determine the relative position between the grain boundary and the positioning mark, so that the center of the Josephson microbridge junction pattern in the layout is aligned with the grain boundary to form a high-temperature superconducting quantum interference device. The method provided by this patent still requires the alignment of the positioning mark, which increases the complexity of the overlay and the length of the process.

[0005] It can be seen that when the current reflective imaging system cannot meet the micro-machining requirements of transparent twin-crystal substrates, it is crucial to explore the overlay method and device of transparent twin-crystal substrates covered with thin films. Summary of the invention

[0006] The present invention provides an overlay alignment device and method for transparent twin-crystal substrate samples covered with thin films. The present invention uses a reflective prism to change the optical path and move the light source of the transmitted light outside the stage, thus overcoming the limitations of the narrow space between the template frame and the stage and the difficulty in heat dissipation. The transmitted light source uses a high-power light source or a laser light source, which improves the penetration ability and film thickness application range of the thin film-covered twin-crystal substrate; at the same time, the reflective prism is used to extend the distance of the transmitted light source, improve the uniformity of the light source, and improve the imaging quality of the twin-crystal grain boundary line. The present invention uses transmitted light to realize the imaging of the twin-crystal grain boundary line located inside the twin-crystal substrate, and the reflective imaging system of the lithography machine with a microscope realizes the imaging of the lithography pattern located on the sample surface. Under the transmission / reflection dual-mode collaborative imaging conditions, it does not rely on the alignment of the overlay mark, thereby improving the overlay alignment accuracy.

[0007] The present invention provides an overlay alignment device applicable to a transparent double-crystal substrate covered with a thin film, comprising a sample, a transparent stage with a suction port, a vacuum chamber, a reflecting prism, a light-transmitting sealed window, an adjustable-intensity light source, a base, a vacuum pumping channel, and side walls; the base is matched with a leveling device of a lithography machine, the side walls are fixedly sealed above the base, and the transparent stage is horizontally fixed above the side walls; a suction port is provided at the center of the transparent stage, and the sample is placed directly above the suction port, completely covering the suction port; the interior of the base, the side walls, and the transparent stage form a vacuum chamber; a vacuum pumping channel is arranged inside the base and communicated with the vacuum chamber, and the sample is fixed by pumping air through the suction port; a light-transmitting sealed window is opened on the side wall to play a role in transmitting light; the reflecting prism is placed inside the vacuum chamber and fixedly connected to the base; the adjustable-intensity light source is placed outside the vacuum chamber, and the light of the adjustable-intensity light source is incident on the reflecting prism through the light-transmitting sealed window, changing the optical path to form transmitted light, passing through the sample from the transparent stage, and being incident on a microscope to present transmitted-light imaging; the light source of the microscope forms reflected light on the upper surface of the sample and is reflected into the microscope to present reflected-light imaging.

[0008] In the overlay alignment device of the present invention, the sample is a transparent double-crystal substrate sample covered with a thin film. The material of the transparent stage is quartz, glass, acrylic, or sapphire. Vacuum grease is applied at the joint of the side walls and the transparent stage to enhance the sealing effect of the vacuum chamber.

[0009] In the overlay alignment device of the present invention, the adjustable-intensity light source adopts a high-power LED light source or a laser light source, which improves the penetration ability of the double-crystal substrate covered with a thin film and the application range of the film thickness. The high-power LED light source refers to an LED light source with a power of more than 5 watts.

[0010] In the overlay alignment device of the present invention, the aperture of the light-transmitting sealed window is larger than the light-emitting port of the adjustable-intensity light source, and the reflection surface area of the reflecting prism is larger than the size of the sample; the distance between the adjustable-intensity light source and the light-transmitting sealed window is adjusted, and the optical path is changed by using the reflecting prism, so that the distance of the transmitted light source is extended, the light uniformity of the adjustable-intensity light source is improved, the imaging quality of the double-crystal boundary line is improved, and the overlay alignment accuracy is further improved. At the same time, since the adjustable-intensity light source is outside the exposure system of the lithography machine, problems such as size, power, and heat dissipation are solved. Preferably, the light of the adjustable-intensity light source is horizontally incident on the reflecting prism through the light-transmitting sealed window, changing the optical path by 90°, forming transmitted light, passing through the sample from the transparent stage and vertically upward, and being incident on the microscope.

[0011] In the overlay alignment device of the present invention, preferably, the base is an oblate cylinder, the transparent stage is a thin disc, the transparent stage is coaxially placed with the base, and the side wall is a cylindrical surface; the reflective prism is a triangular prism with an isosceles right angle on the side, and its inclined surface is placed just below the film suction port and faces the light-transmitting sealing window. Preferably, the reflective prism is glued and fixed to the base, and the height is less than the height of the vacuum chamber. Preferably, the film suction port and the light-transmitting sealing window are in the shape of circular holes for easy processing.

[0012] The present invention also proposes an overlay alignment method suitable for a transparent double-crystal substrate sample covered with a thin film, and the specific steps are as follows:

[0013] The first step is to load the sample. Spin-coat the photoresist on the transparent double crystal substrate sample covered with a thin film and pre-bake it, then place it above the film suction port of the transparent stage;

[0014] The second step is to find the twin crystal boundary line, turn on the adjustable intensity light source, emit transmitted light, and make the transmitted light pass through the transparent twin crystal substrate sample and the film on it; adjust the intensity of the lithography machine microscope and the adjustable intensity light source until a clear twin crystal boundary line is found in the sample;

[0015] The third step is to install the mask, and fix the photolithography mask to be aligned and exposed on the mask frame;

[0016] The fourth step is initial alignment, adjusting the position and angle of the twin crystal boundary so that it falls on the required Josephson junction on the SQUID mask;

[0017] The fifth step is rough alignment. Turn on the light source of the lithography machine microscope to form reflected light on the sample surface. Adjust the microscope to make the SQUID mask image clear and preliminarily align it with the twin grain boundary. At this time, the twin grain boundary will be blurred due to lack of focus. Carefully adjust the microscope to gradually move the clear position of the SQUID mask image from the SQUID mask down to the twin grain boundary, and make sure that the twin grain boundary and the SQUID mask can maintain coordinated imaging, and both are visible.

[0018] The sixth step is image optimization and precise alignment. The relative intensity of transmitted light and reflected light is finely adjusted to optimize the contrast between the photolithography mask and the twin crystal grain boundary, and to display the twin crystal grain boundary as thinly as possible. At the same time, the position and angle of the twin crystal grain boundary are carefully adjusted to achieve precise alignment of the position of the Josephson junction in the photolithography mask with the twin crystal grain boundary, thus completing the overlay alignment process of the transparent twin crystal substrate covered with a thin film.

[0019] In the first step of the overlay alignment method of the present invention, a thin film-covered transparent twin-crystal substrate sample is coated on one side with the coated side facing upward and placed just above the transparent stage suction port of the overlay device to completely cover the suction port.

[0020] In the second step of the overlay alignment method of the present invention, the specific method of finding the twin crystal boundary line is: adjusting the position of the lithography machine microscope so that the imaging position of the twin crystal substrate falls directly above the grain boundary; adjusting the intensity of the adjustable intensity light source so that the sample forms an image with obvious contrast of the twin crystal boundary line in the microscope; adjusting the magnification and focal plane position of the microscope, and adjusting the light intensity of the adjustable intensity light source again to find a clearer twin crystal boundary line in the sample. The adjustable intensity light source is placed outside the lithography system, and the transmitted light emitted is changed by a reflective prism, passes through the transparent twin crystal substrate and the thin film sample thereon, and presents a transmitted light image in the microscope.

[0021] In the third step of the overlay alignment method of the present invention, the photolithography mask is a superconducting quantum interference device (SQUID) mask.

[0022] In the fourth step of the overlay alignment method of the present invention, the position and angle of the twin crystal boundary line are adjusted so that the twin crystal boundary line falls on the required Josephson junction pattern position on the SQUID mask.

[0023] In the sixth step of the overlay alignment method described in the present invention, the transmitted light comes from an adjustable intensity light source, which is mainly used to penetrate the twin crystal sample with very low transparency due to the thin film covering and to image the twin crystal boundary so that it can be observed. The adjustable intensity light source has high power, high brightness and is adjustable, and has strong penetrating power. Preferably, the adjustable intensity light source is a high-power LED light or laser. The high-power LED light source refers to an LED light source with a power of more than 5 watts. The reflected light comes from the light source of the lithography machine microscope, which is mainly used for imaging the superconducting quantum interference device mask on the upper surface of the sample.

[0024] In the overlay alignment method of the present invention, the above-mentioned overlay alignment device is used.

[0025] The present invention also provides a high-temperature superconducting quantum interference device, which uses the above-mentioned overlay alignment device and / or the above-mentioned overlay alignment method to achieve precise alignment between the position of the Josephson junction in the SQUID mask and the twin crystal boundary, complete the overlay alignment process of the transparent twin crystal substrate covered with a thin film, and then perform exposure and ion beam etching processes to obtain a high-temperature superconducting quantum interference device.

[0026] The present invention also provides a photolithography machine, comprising the above-mentioned overlay alignment device.

[0027] The device and method of the present invention are applicable to any transparent twin-crystal substrate sample covered by a thin film. Optionally, the material of the transparent twin-crystal substrate includes strontium titanate (STO), magnesium oxide (MgO), lanthanum aluminate (LAO), strontium titanium doped lanthanum aluminate (LSAT) or yttrium stabilized zirconia (YSZ); the thin film is a high-temperature superconducting thin film, and optionally, its material includes yttrium barium copper oxide (YBCO) or dysprosium barium copper oxide (DyBCO). The transparent twin-crystal substrate covered by a thin film in the present invention is obtained by completing single-sided coating on a transparent twin-crystal substrate. The twin-crystal substrate is formed by two substrates with different orientations aligned and sintered together at a certain angle, and the bonding interface of the two substrates is a twin-crystal interface.

[0028] The working principle of the overlay alignment device and method described in the present invention is as follows: the transmitted light emitted by the adjustable intensity light source is reflected by the reflective prism, passes through the transparent twin crystal substrate and the high-temperature superconducting film on its upper surface, enters the microscope, and is imaged on the microscope display screen. This transmitted light imaging is mainly used to observe the twin crystal grain boundaries. The other light is the light source of the lithography machine microscope, which irradiates the upper surface of the sample, forms reflected light and enters the microscope, and is imaged on the microscope display screen. This is reflected light imaging, which is mainly used for imaging the SQUID layout. The two light beams of transmitted light and reflected light work together to form an image on the microscope. By adjusting the relative intensities of the two light sources, the twin crystal grain boundaries and the superconducting quantum interference device layout are clearly visible, and the precise alignment relationship between the SQUID layout and the twin crystal grain boundaries can be obtained, thereby realizing the micro-machining and manufacturing of SQUID sensor chips based on transparent twin crystal substrates.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] 1. The overlay alignment method and device described in the present invention utilizes transmitted light / reflected light dual-mode collaborative imaging to solve the technical problem of accurate alignment of the twin crystal boundary line of a transparent twin crystal substrate with the corresponding position of the Josephson junction in the SQUID layout.

[0031] 2. The overlay alignment method and device described in the present invention realize the simultaneous imaging of the layout and the twin grain boundary, so there is no need to make alignment marks on the sample, which completely solves the shortcomings of the prior art of relying on alignment marks, realizes markless alignment overlay, greatly simplifies the micromachining process, and improves the alignment freedom and accuracy.

[0032] 3. The overlay alignment method and device described in the present invention utilize a reflective prism to move the light source outside the stage, thereby solving the limitation of the narrow space between the mask and the stage on the high-power light source and the uniformity of the light source, and solving the problems of light source intensity, uniformity and heat dissipation, thereby improving the penetration ability of thin film-covered twin-crystal substrate samples, and thus improving the overlay capability and film thickness range. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 .Schematic diagrams of the structure and optical path of the transmission / reflection dual-mode lithography alignment device according to the present invention, (a) side view, (b) top view.

[0034] Figure 2 .Physical diagram of the transmission / reflection dual-mode lithography alignment device according to the present invention (a), front view of the core component (b), side sectional view (c), top view (d), 3D sectional view (e).

[0035] Figure 3 .On the strontium titanate STO double crystal substrate, SQUID version Figure 1 Comparison diagrams of the alignment relationship between the twin crystal grain boundary and the layout lithography in three imaging modes of reflection, transmission, and transmission / reflection cooperation.

[0036] Figure 4 .Comparison diagrams of the alignment relationship between the twin crystal grain boundary of SQUID pattern 2 prepared on the MgO double crystal substrate and the SQUID pattern in three imaging modes of reflection, transmission, and transmission / reflection cooperation.

[0037] Figure 1-2 In it, 101 microscope, 102 reflected light, 103 transmitted light, 104 sample, 105 transparent stage, 106 vacuum chamber, 107 suction port, 108 reflecting prism, 109 light-transmitting sealing window, 110 adjustable intensity light source, 111 base, 112 vacuum pumping channel, 113 side wall. Detailed implementation manners

[0038] The technical solutions of the present invention will be elaborated in detail below in conjunction with embodiments and drawings. Taking the preparation of a superconducting quantum interference device SQUID on a black high-temperature superconducting YBCO thin film epitaxially grown on transparent double crystal substrates such as strontium titanate STO and magnesium oxide MgO as an example, it does not mean that the present invention is only limited to the research and development scenario of high-temperature superconducting SQUID devices based on twin crystal grain boundary junctions. As long as it is a thin film device based on a transparent double crystal substrate and involves the alignment and lithography of the twin crystal grain boundary and the device layout using the methods and devices described in the present invention, it belongs to the protection scope of the present invention. Figure 1 It is a schematic diagram of the structure and optical path of the transmission / reflection dual-mode cooperative lithography alignment device applicable to a transparent double crystal substrate covered with a thin film according to the present invention.

[0039] Embodiment 1: A transmission / reflection dual-mode cooperative lithography alignment device applicable to a transparent double crystal substrate covered with a thin film. The lithography alignment device is matched with the URE-2000 / 34AL type lithography machine produced by the Institute of Optoelectronics, Chinese Academy of Sciences, and a microscope of the lithography machine is placed directly above. The specific structure of the lithography alignment device is as Figure 1-2Shown: including a sample 104, a transparent stage 105 with a wafer suction port 107, a vacuum chamber 106, a reflecting prism 108, a light-transmitting sealed window 109, an adjustable-intensity light source 110, a base 111, a vacuum pumping channel 112, and a side wall 113;

[0040] The base 111 is a flat cylinder, and its structure is matched with the leveling mechanism of the URE-2000 / 34AL type lithography machine; the side wall 113 is cylindrical and is fixedly sealed above the base 111. The transparent stage 105 is a thin quartz disc and is horizontally fixedly connected above the side wall 113, and vacuum grease is applied at the connection. A circular wafer suction port 107 with a diameter of 4 mm is provided at the center of the transparent stage 105. The size of the sample 104 is 10×10×0.5 mm 3 , and it is placed directly above the wafer suction port 107, completely covering the wafer suction port 107. The interior of the base 111, the side wall 113, and the transparent stage 105 form a sealed vacuum chamber 106. A vacuum pumping channel 112 is provided inside the base 111, which is communicated with the vacuum chamber 106. By pumping air through the vacuum pumping channel 112, a negative pressure is formed in the vacuum chamber 106, and then the sample 104 is sucked and fixed on the transparent stage 105 through the wafer suction port 107. A circular light-transmitting sealed window 109 with a diameter of 16 mm is opened on the side wall 113 to play a role in transmitting light. The reflecting prism 108 is a prism with an isosceles right triangle on the side, the right-angled side length is 15 mm, the width is 15 mm, one side of the right-angled side is fixedly pasted to the base 111, its inclined surface is placed directly below the wafer suction port 107, facing the light-transmitting sealed window 109, and its height is less than the height of the vacuum chamber 106. The adjustable-intensity light source 110 is a laser, and the light-emitting port diameter is 6 mm. It is placed outside the vacuum chamber 106. The distance between the adjustable-intensity light source 110 and the light-transmitting sealed window 109 is adjusted to 60 mm. The light of the adjustable-intensity light source 110 is horizontally incident on the inclined surface of the reflecting prism 108 through the light-transmitting sealed window 109, and the reflected light changes the optical path by 90° to form a transmitted light 103, which vertically shoots upward through the sample 104 from the transparent stage 105 and is incident into the microscope 101, and a transmitted image is presented inside the microscope.

[0041] Embodiment 2: A lithography alignment method for the transmission / reflection dual-mode collaboration suitable for a transparent double-crystal substrate sample covered with a thin film, specifically a lithography alignment method for a strontium titanate STO double-crystal sample coated with a yttrium barium copper oxide YBCO superconducting thin film and a SQUID mask plate, using the lithography alignment device described in Embodiment 1. The specific steps are as follows:

[0042] The first step is to load the sample. After the strontium titanate STO double-crystal sample covered with the YBCO thin film is spin-coated with photoresist and pre-baked, the coated side is facing up, and it is placed above the wafer suction port of the transparent stage, completely covering the wafer suction port;

[0043] The second step is to find the twin crystal grain boundary. The adjustable intensity light source of the overlay alignment device described in Example 1 is turned on to emit transmitted light through the transparent stage, the STO twin crystal substrate and the YBCO film thereon; the position of the lithography machine microscope is adjusted so that the imaging position of the STO twin crystal substrate falls just above the grain boundary; the intensity of the adjustable intensity light source is adjusted so that the STO twin crystal sample forms an image with obvious contrast of the twin crystal grain boundary in the microscope; the magnification and focal plane position of the microscope are adjusted, and the light intensity of the adjustable intensity light source is adjusted again to find a clear twin crystal grain boundary in the STO twin crystal sample;

[0044] The third step is to install the mask. Install the SQUID mask on the photolithography mask holder of the photolithography machine and press the mask suction key to fix it.

[0045] The fourth step is initial alignment, which is to adjust the position and angle of the twin crystal boundary so that the twin crystal boundary falls on the Josephson junction that needs to be aligned on the SQUID mask;

[0046] Step 5: Coarse alignment. Turn on the light source of the lithography machine microscope to form reflected light on the sample surface. Adjust the lens position to make the SQUID mask image on the microscope screen clear and preliminarily align it with the twin grain boundary. At this time, the twin grain boundary will be blurred due to lack of focus. Carefully adjust the microscope to gradually move the focal plane from the lithography mask to the twin grain boundary, and make sure that the twin grain boundary and the SQUID mask can maintain coordinated imaging and both are visible.

[0047] The sixth step is image optimization and precise alignment. The relative intensity of transmitted light and reflected light is finely adjusted to optimize the contrast between the photolithography mask and the twin crystal grain boundary, and to display the twin crystal grain boundary as thinly as possible. At the same time, the position and angle of the twin crystal grain boundary are carefully adjusted to achieve precise alignment of the position of the Josephson junction in the SQUID mask with the twin crystal grain boundary, thus completing the overlay alignment process of the transparent twin crystal substrate covered with a thin film.

[0048] Figure 3 The figure shows the grain boundary of the STO substrate twin crystal and the SQUID board. Figure 1 Image comparison under the three imaging modes of reflection, transmission, and transmission / reflection synergy described in Example 2. It can be seen that for reflective imaging ( Figure 3 a), only the SQUID pattern on the upper surface can be seen; while in transmission imaging ( Figure 3 b), the twin crystal boundary is clear, but the SQUID pattern is not visible; when the overlay alignment method described in Example 2 is used to achieve transmission / reflection collaborative imaging ( Figure 3c), it can take into account both the twin grain boundary and the layout, and the alignment relationship between the two is clear, realizing the aligned lithography microfabrication of the twin Josephson junction. More importantly, this method does not rely on lithography marks and can directly perform aligned lithography, increasing the lithography accuracy and freedom. At the same time, it also has strong penetration ability for twin samples with very low transparency covered by thin films, and can realize lithography microfabrication.

[0049] Embodiment 3: A lithography alignment method with transmission / reflection dual-mode collaboration suitable for thin-film covered transparent twin substrate samples, specifically a lithography alignment method for SQUID layout and twin grain boundary on an MgO twin substrate, using the lithography alignment device described in Embodiment 1. The specific operation steps are the same as those in Embodiment 2.

[0050] Figure 4 Shown is the SQUID layout lithographed on the MgO twin substrate Figure 2 Image comparison diagrams in the three imaging modes of reflection, transmission, and the transmission / reflection collaboration described in Embodiment 3. Similar to Embodiment 2, for reflection imaging ( Figure 4 a), only the pattern on the upper surface can be seen; during transmission imaging ( Figure 4 b), the twin grain boundary is clear, but the SQUID layout cannot be clearly seen; while when using the lithography alignment method described in Embodiment 3 to achieve transmission / reflection collaborative imaging ( Figure 4 c), it can take into account both the twin grain boundary and the SQUID layout. From Figure 4 it can be seen that under the transmission / reflection dual-mode imaging condition, both the twin grain boundary and the SQUID layout can be clearly seen, and the lithography between the two can be realized without relying on alignment marks, thus simplifying the lithography microfabrication process of the twin Josephson junction and increasing the success probability of the Josephson junction.

Claims

1. An overlay alignment device for a transparent double-crystal substrate for film covering, characterized in that, It includes a transparent bicrystal substrate sample covered with a thin film, a transparent stage with a wafer suction port, a vacuum chamber, a reflecting prism, a light-transmitting sealed window, an adjustable-intensity light source, a base, a vacuum pumping channel, and a side wall; the sample is placed directly above the wafer suction port, completely covering the wafer suction port; the inside of the base, the side wall, and the transparent stage form a vacuum chamber; a light-transmitting sealed window is opened on the side wall to play a role in transmitting light; the reflecting prism is placed inside the vacuum chamber and fixedly connected to the base; the adjustable-intensity light source is placed outside the vacuum chamber, and the light of the adjustable-intensity light source is incident on the reflecting prism through the light-transmitting sealed window, changing the optical path to form transmitted light, passing through the transparent stage and the sample thereon, and then incident on the microscope.

2. The overlay alignment device for a transparent double-crystal substrate for film covering according to claim 1, characterized in that, The sample is a transparent bicrystal substrate sample covered with a high-temperature superconducting thin film on one side; the aperture of the light-transmitting sealed window is larger than the light outlet of the adjustable-intensity light source, and the reflection surface area of the reflecting prism is larger than the sample size; the adjustable-intensity light source uses a high-power LED light source or a laser light source.

3. The overlay alignment device for a transparent twin substrate for film covering according to claim 2, characterized in that, The material of the transparent bicrystal substrate is selected from one of strontium titanate, magnesium oxide, lanthanum aluminate, lanthanum aluminate doped with strontium and titanium, or yttrium-stabilized zirconia; the material of the high-temperature superconducting thin film is selected from yttrium barium copper oxide or dysprosium barium copper oxide; the high-power LED light source refers to an LED light source with a power of more than 5 watts.

4. The overlay alignment device for a transparent twin substrate for film covering according to claim 1, characterized in that The base is matched with the leveling device of the lithography machine, the side wall is fixedly sealed above the base, and the transparent stage is horizontally fixed above the side wall; a wafer suction port is provided at the center of the transparent stage, and a vacuum pumping channel is arranged inside the base to communicate with the vacuum chamber, forming a negative pressure in the vacuum chamber to realize the function of fixing the sample.

5. The overlay alignment device for a transparent twin substrate for film covering according to claim 1, characterized in that, The material of the transparent stage is quartz, glass, acrylic, or sapphire; vacuum silicone grease is applied at the connection between the side wall and the transparent stage; the base is a flat cylinder, the transparent stage is a thin disc, the side wall is a cylindrical surface, and the wafer suction port and the light-transmitting sealed window are in the shape of round holes; the transparent stage and the base are coaxially placed, and the reflecting prism is fixedly pasted to the base, with a height less than the height of the vacuum chamber; The reflecting prism is a triangular prism with an isosceles right triangle on the side, and its reflecting inclined surface is placed directly below the wafer suction port, facing the light-transmitting sealed window; the light of the adjustable-intensity light source is horizontally incident on the reflecting prism through the light-transmitting sealed window, changing the optical path by 90°, forming transmitted light, and vertically upward shooting through the sample from the transparent stage, and then incident on the microscope.

6. A method for overlay alignment of a transparent double-crystal substrate suitable for film covering, characterized in that, The specific steps are as follows: The first step is to load the sample. After the transparent bicrystal substrate sample covered with a thin film is spin-coated with photoresist and pre-baked, with the coated side facing up, it is placed above the wafer suction port of the transparent stage, completely covering the wafer suction port; The second step is to find the bicrystal grain boundary. Turn on the adjustable-intensity light source to emit transmitted light, so that the transmitted light passes through the transparent bicrystal substrate and the thin film sample on it; adjust the intensity of the lithography machine microscope and the adjustable-intensity light source until a clear bicrystal grain boundary is found in the transmitted light imaging of the sample. The third step is to install the mask. Fix and install the photolithography mask to be aligned and exposed on the mask holder. The fourth step is the initial alignment. Adjust the position and angle of the bicrystal grain boundary so that it falls at the required Josephson junction on the high-temperature superconducting quantum interference device mask. The fifth step is rough alignment. Turn on the light source of the lithography machine microscope to form reflected light on the sample surface. Adjust the microscope to make the image of the high-temperature superconducting quantum interference device mask clear in the reflected light imaging and preliminarily align it with the twin crystal boundary. Carefully adjust the microscope to gradually move the focal plane from the high-temperature superconducting quantum interference device mask to the twin crystal boundary, and make sure that the twin crystal boundary and the high-temperature superconducting quantum interference device mask can maintain coordinated imaging, and both are visible. The sixth step is image optimization and precise alignment. The relative intensity of transmitted light and reflected light is finely adjusted to optimize the contrast between the photolithography mask and the twin crystal grain boundary, and to display the twin crystal grain boundary as thinly as possible. At the same time, the position and angle of the twin crystal grain boundary are carefully adjusted to achieve precise alignment of the position of the Josephson junction in the photolithography mask with the twin crystal grain boundary, thus completing the overlay alignment process of the transparent twin crystal substrate covered with a thin film.

7. The overlay alignment method for a transparent twin-crystal substrate covered with a thin film according to claim 6, characterized in that: In the first step, the film-covered transparent twin-crystal substrate sample is a transparent twin-crystal substrate covered on one side with a high-temperature superconducting film; the material of the transparent twin-crystal substrate is selected from one of strontium titanate, magnesium oxide, lanthanum aluminate, strontium titanium-doped lanthanum aluminate or yttrium-stabilized zirconia; the material of the high-temperature superconducting film is selected from yttrium barium copper oxide or dysprosium barium copper oxide; In the second step, the specific method of finding the grain boundary of the twin crystal is as follows: adjusting the position of the microscope of the photolithography machine so that the imaging position of the twin crystal substrate falls just above the grain boundary; Adjust the intensity of the adjustable intensity light source to make the sample form an image with a clear contrast of the twin grain boundary in the microscope; adjust the magnification and focal plane position of the microscope, and adjust the light intensity of the adjustable intensity light source again to find a clearer twin grain boundary in the sample; In the sixth step, the adjustable intensity light source is a high-power LED light or a laser; the high-power LED light source refers to an LED light source with a power of more than 5 watts.

8. The overlay alignment method for a transparent twin substrate applicable to film covering according to any one of claims 6-7, characterized in that, The adjustable intensity light source is placed outside the photolithography system. The emitted transmitted light changes its optical path through a reflective prism, passes through a transparent twin-crystal substrate and a thin film sample thereon, and presents a transmitted light image in a microscope.

9. The overlay alignment method for a transparent twin substrate applicable to film covering according to claim 8, wherein The overlay alignment method uses the overlay alignment device described in any one of claims 1-5.

10. A high-temperature superconducting quantum interference device, which uses the overlay alignment device described in any one of claims 1 to 5 and / or the overlay alignment method described in any one of claims 6 to 9 to achieve precise alignment between the position of the Josephson junction in the mask of the superconducting quantum interference device and the grain boundary of the twin crystal, completes the overlay alignment process of the transparent twin crystal substrate covered with a thin film, and then performs exposure and ion beam etching processes to obtain the high-temperature superconducting quantum interference device.

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