CN117976522A - Method for manufacturing nano line width metal pattern - Google Patents

Abstract

The invention provides a method for manufacturing a metal pattern with a nanometer line width, which comprises the following steps: providing a substrate, and forming an electron beam resist layer on the substrate; patterning the electron beam resist layer to form an opening penetrating through the electron beam resist layer, wherein the opening is funnel-shaped and comprises a bottom vertical part and a top inclined part positioned above the bottom vertical part; forming a metal layer on the electron beam resist layer, wherein the metal layer is formed in the opening, and the thickness of the metal layer is smaller than the height of the bottom vertical part; and removing the electron beam resist layer and the metal layer positioned above the electron beam resist layer by adopting a stripping method. In the method for manufacturing the nano line width metal pattern, the funnel-shaped pattern opening is formed by adopting electron beam gray scale exposure, so that on one hand, the pattern opening is prevented from being sealed prematurely in the metal deposition process, the thickness deviation of the metal pattern is reduced, and on the other hand, burrs remained on two sides of the metal pattern after the electron beam resist layer is stripped are avoided, and the high-quality metal pattern is formed.

Description

A method for making nanowire-width metal patterns

Technical Field

The invention belongs to the technical field of electron beam lithography and relates to a method for manufacturing a nanometer line width metal pattern.

Background technique

For metal patterns with nanometer-scale feature sizes, high-resolution electron beam exposure is usually used to form a mask pattern, and then dry etching or stripping processes are used to transfer the mask pattern to form the desired metal pattern. The main difficulty faced when using dry etching to transfer nano-sized metal patterns is that when the metal film has a certain thickness, the dry etching time is long. For example, for precious metals such as Au, Pd, and Pt, ion beam etching is generally used, and the etching rate is slow, so the etching time becomes longer. Long-term ion beam bombardment will cause deformation and denaturation of the resist mask layer, which not only causes the accuracy of pattern transfer to decrease, but also increases the difficulty of removing the residual resist mask layer; if a hard mask layer is used to reduce the impact of ion beam bombardment on the electron beam resist, the process complexity will increase. Compared with dry etching pattern transfer, the stripping process quickly dissolves the unexposed electron beam resist layer by chemical means, and the time, equipment and process costs can be greatly reduced. Therefore, the stripping process is one of the hot spots in the current research of micro-nano processing technology, and is often used in the preparation of various device structures such as electrodes and gratings.

The specific process of using the stripping process to transfer nano-scale metal patterns is to form a mask pattern through electron beam exposure, deposit a metal film, and then strip the unexposed electron beam resist together with the metal film (upper metal) thereon in a solution, and finally form a target pattern on the substrate. In order to completely disconnect the upper metal and the metal film deposited on the substrate when the electron beam resist is dissolved in the stripping solution, and to achieve complete stripping of the upper metal, the thickness of the electron beam resist is generally required to be more than three times the thickness of the upper metal to be stripped. However, the increase in the thickness of the electron beam resist layer will affect the resolution of the electron beam exposure. Although the use of stripping technology to achieve electron beam exposure pattern transfer has become an important means of preparing micro-nano structures, as the device size advances to the nanometer level, whether high-quality stripping can be successfully achieved is closely related to the control of the side wall profile morphology of the electron beam resist. Generally speaking, for patterns with a feature width of the nanometer level, the side wall profile morphology of the electron beam resist after exposure and development is vertical (or approximately vertical), undercut (the cross section of the mask pattern is an inverted trapezoid) and top cut (the cross section of the mask pattern is a regular trapezoid). When the side wall profile of the mask pattern is vertical and undercut, it is easy to adhere and accumulate at the edge of the step of the mask pattern during metal deposition, gradually closing the pattern opening, and it is impossible to continue to deposit metal in the target area, and ultimately it is impossible to obtain a metal pattern structure of the target thickness; when the side wall profile of the mask pattern is a top cut, part of the metal will also be deposited on the side wall slope during metal deposition, resulting in burrs on the side of the target pattern after stripping.

Therefore, how to solve problems such as large thickness deviation and edge burrs of metal patterns after peeling is a technical difficulty that needs to be urgently solved in the current nano-scale metal pattern production process.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for manufacturing a nanowire-width metal pattern, which is used to solve the problems of large thickness deviation and edge burrs of the metal pattern after peeling in the prior art.

To achieve the above-mentioned and other related purposes, the present invention provides a method for manufacturing a nanowire-width metal pattern, comprising the following steps:

providing a substrate, and forming an electron beam resist layer on the substrate;

Patterning the electron beam resist layer to form an opening, wherein the opening penetrates the electron beam resist layer, the opening is funnel-shaped, and the opening includes a bottom vertical portion and a top inclined portion located above the bottom vertical portion;

forming a metal layer on the electron beam resist layer, wherein the metal layer is formed in the opening, wherein the thickness of the metal layer is less than the height of the bottom vertical portion;

The electron beam resist layer and the metal layer located above the electron beam resist layer are removed by a lift-off method.

Optionally, the step of patterning the electron beam resist layer to form an opening comprises:

Using a layout design tool to draw a layout graphic, the layout graphic including a target graphic and a grayscale graphic located outside the target graphic;

Converting the layout pattern into a layout format corresponding to an electron beam exposure device, and then exposing the electron beam resist layer in the electron beam exposure device, wherein the exposure dose of the target pattern area is greater than the exposure dose of the grayscale pattern area;

The electron beam resist layer is developed in a developer to form the opening.

Optionally, the electron beam resist layer is a positive electron beam resist, the thickness of the electron beam resist layer is in the range of 100-500 nm, the exposure dose of the target pattern is in the range of 300-1200 μC/cm ² , and the exposure dose of the grayscale pattern is in the range of 100-600 μC/cm ² .

Optionally, after developing the electron beam resist layer in a developer, the method further includes fixing the electron beam resist layer in a fixer.

Optionally, the developer includes amyl acetate solution and methyl isobutyl ketone-isopropyl alcohol mixed solution, and the fixer includes isopropyl alcohol solution.

Optionally, the layout design tool includes L-edit or GDSⅡ, and the layout format corresponding to the electron beam exposure equipment includes V30 file, SCON file or GPF file.

Optionally, the width of the bottom vertical portion ranges from 20 to 100 nm.

Optionally, the material of the metal layer includes one or more of Au, Pt, Pd, Ti, Cr, Cu and Al.

Optionally, the metal layer is formed by magnetron sputtering, electron beam evaporation or thermal evaporation.

Optionally, the step of removing the electron beam resist layer and the metal layer located above the electron beam resist layer by a stripping method comprises:

The sample after the metal layer is formed is placed in an N-methylpyrrolidone solution at a preset temperature for heating, and then the sample is placed in deionized water, acetone, and isopropanol in sequence for ultrasonic cleaning.

As described above, in the method for making nanowire-width metal patterns of the present invention, electron beam grayscale exposure is used to form a funnel-shaped pattern opening. On the one hand, this prevents the pattern opening from being closed prematurely during the metal deposition process, thereby reducing the thickness deviation of the metal pattern. On the other hand, it avoids residual burrs on both sides of the metal pattern after the electron beam resist layer is stripped, thereby forming a high-quality metal pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow chart showing a method for fabricating a nanowire-width metal pattern according to the present invention.

FIG. 2 is a schematic diagram showing the formation of an electron beam resist layer on a substrate in the method for fabricating a nanowire-width metal pattern of the present invention.

FIG. 3 is a schematic diagram showing the formation of openings in an electron beam resist layer in the method for fabricating a nanowire-width metal pattern of the present invention.

FIG. 4 is an electron microscope image showing an opening formed in an electron beam resist layer in the method for fabricating a nanowire-width metal pattern of the present invention.

FIG. 5 is a schematic diagram showing the formation of a metal layer on an electron beam resist layer in the method for fabricating a nanowire-width metal pattern of the present invention.

FIG. 6 is a schematic diagram showing the stripping and removal of the electron beam resist layer and the metal layer located above the electron beam resist layer in the method for manufacturing nanowire-width metal patterns of the present invention.

FIG. 7 shows an electron microscope image of a nanowire-width metal pattern formed in the method for manufacturing a nanowire-width metal pattern of the present invention.

Component number description

1 Substrate

2 Electron beam resist layer

3 Opening

4 Metal Layer

Steps S1 to S4

Detailed ways

The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to Figures 1 to 7. It should be noted that the illustrations provided in this embodiment are only schematic illustrations of the basic concept of the present invention, and the drawings only show components related to the present invention rather than the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

This embodiment provides a method for manufacturing a nanowire-width metal pattern. Please refer to FIG. 1 , which shows a process flow chart of the manufacturing method, including the following steps:

S1: providing a substrate, and forming an electron beam resist layer on the substrate;

S2: patterning the electron beam resist layer to form an opening, wherein the opening penetrates the electron beam resist layer, the opening is funnel-shaped, and the opening includes a bottom vertical portion and a top inclined portion located above the bottom vertical portion;

S3: forming a metal layer on the electron beam resist layer, wherein the metal layer is formed in the opening, wherein a thickness of the metal layer is less than a height of the bottom vertical portion;

S4: removing the electron beam resist layer and the metal layer above the electron beam resist layer by using a stripping method.

First, referring to FIG. 2 , step S1 is performed: providing a substrate 1 , and forming an electron beam resist layer 2 on the substrate 1 .

As an example, the substrate 1 includes but is not limited to a silicon substrate, a silicon nitride substrate, a magnesium oxide substrate or a sapphire substrate. Specifically, in this embodiment, the substrate 1 is a silicon substrate.

As an example, the electron beam resist layer 2 uses a positive electron resist, including but not limited to ZEP520A, ARP6200 or PMMA950A4, etc. Specifically, ZEP520A is used in this embodiment.

As an example, the electron beam resist layer 2 is coated on the substrate 1 by a spinning process, the spinning speed is 3500 rpm, the spinning time is 45 seconds, and the thickness of the formed electron beam resist layer 2 is in the range of 100 to 500 nm. Specifically, in this embodiment, a 200 nm thick electron beam resist layer 2 is formed.

As an example, after coating the electron beam resist layer 2, the sample is placed in a baking oven for drying at a temperature of 180°C for 5 minutes.

It should be noted that, in other examples, if the substrate 1 is an insulating substrate, after forming the electron beam resist layer 2 , the method further includes forming a conductive adhesive layer on the electron beam resist layer 2 .

Next, please refer to FIG. 3 , and perform step S2 : patterning the electron beam resist layer 2 to form an opening 3 , wherein the opening 3 penetrates the electron beam resist layer 2 , and is funnel-shaped, and includes a bottom vertical portion and a top inclined portion located above the bottom vertical portion.

As an example, the bottom vertical portion is rectangular, the top inclined portion is in an inverted trapezoidal shape, the top end of the bottom vertical portion is connected to the bottom end of the top inclined portion, wherein the width of the bottom vertical portion is in the nanometer range, for example, 20 to 100 nm, and the width of the bottom vertical portion determines the line width of the subsequently formed metal pattern; specifically, in this embodiment, the width of the bottom vertical portion is 50 nm.

As an example, the steps of forming the opening 3 include:

(i) using a layout design tool to draw a layout pattern, wherein the layout pattern includes a target pattern and a grayscale pattern located outside the target pattern, wherein the width of the target pattern is set to 50 nm;

(ii) converting the layout pattern into a layout format corresponding to an electron beam exposure device, and then exposing the electron beam resist layer 2 in the electron beam exposure device, wherein the exposure dose of the target pattern is greater than the exposure dose of the grayscale pattern;

(iii) developing the electron beam resist layer 2 in a developer to form the opening 3.

As an example, layout design tools include L-edit software or GDSⅡ software. The layout design is usually a GDS file. Different electron beam exposure equipment will have corresponding dedicated graphic file formats. For example, during exposure, the layout needs to be converted into a V30 file in JEOL's exposure equipment, into a SCON file in Elionix's exposure equipment, and into a GPF file in Raith's exposure equipment. The conversion is performed according to demand. Specifically, in this embodiment, a JEOL JBX-6300FS electron beam exposure machine is used.

As an example, the exposure dose gradient is set based on the type and thickness of the electron resist and the contrast curve of the electron beam resist under the selected exposure and development conditions. In the present application, the electron beam acceleration voltage used during exposure is 100 kV, the beam current is 100 pA, the exposure dose of the target pattern is 300-1200 μC/cm ² , and the exposure dose of the grayscale pattern is 100-600 μC/cm ² . Since the exposure dose of the target pattern is greater than the exposure dose of the grayscale pattern, the electron beam resist layer 2 in the target pattern area is exposed through, and the electron beam resist layer 2 in the grayscale pattern area is not exposed through, and the funnel-shaped opening 3 is formed after development. Specifically, in the present embodiment, the exposure dose of the target pattern area is 400 μC/cm ² , and the exposure dose of the grayscale pattern area is 120 μC/cm ² .

As an example, the sample after electron beam exposure is placed in amyl acetate solution, methyl isobutyl ketone-isopropyl alcohol mixed solution or AR600-546 solution for development for 60 seconds, fixed in isopropyl alcohol for 60 seconds, and blown dry with a nitrogen gun.

As an example, please refer to FIG. 4 , which shows an electron microscope image of an opening formed in an electron beam resist layer. The opening is funnel-shaped, which is consistent with the designed opening shape.

Next, referring to FIG. 5 , step S3 is performed: a metal layer 4 is formed on the electron beam resist layer 2 , and the metal layer 4 is formed in the opening 3 , wherein the thickness of the metal layer 4 is smaller than the height of the bottom vertical portion.

As an example, a metal layer 4 is formed on the electron beam resist layer 2 by magnetron sputtering, electron beam evaporation or thermal evaporation, and the material of the metal layer 4 includes one or more of Au, Pt, Pd, Ti, Cr, Cu and Al; specifically, in this embodiment, an electron beam evaporation method is used to form a Ti metal layer, the evaporation rate is 0.1nm/s, and the deposition thickness is 70nm.

As an example, during the deposition of the metal layer 4, the rate at which the metal layer 4 is deposited into the opening 3 is lower than the rate at which the metal layer 4 is deposited onto the electron beam resist layer 2. The metal layer 4 with a thickness of 70 nm is deposited on the electron beam resist layer 2, and the thickness deposited onto the substrate 1 exposed in the opening 3 is approximately 30 nm.

As an example, the thickness of the metal layer deposited into the opening 3 is less than the height of the bottom vertical portion, so that the metal layer 4 located on the substrate 1 and the metal layer 4 located on the electron beam resist layer 2 are disconnected, which facilitates the subsequent stripping process to remove the electron beam resist layer 2 and the metal layer 4 located above the electron beam resist layer 2.

Next, referring to FIG. 6 , step S4 is performed: the electron beam resist layer 2 and the metal layer 4 located above the electron beam resist layer 2 are removed by a lift-off method.

As an example, the step of removing the electron beam resist layer 2 and the metal layer 4 located above the electron beam resist layer 2 by using a lift-off method includes:

(i) placing the sample after the metal layer 4 is deposited in an N-methylpyrrolidone solution at a temperature of 90° C., heating it for 30 minutes, and then ultrasonically cleaning it for 5 minutes, wherein the N-methylpyrrolidone solution is used as a debonding agent for the electron beam resist layer 2;

(ii) placing the sample in deionized water, acetone, and isopropanol in turn and ultrasonically cleaning them for 5 minutes respectively, removing the electron beam resist layer 2 together with the metal layer 4 thereon, and the metal layer 4 retained on the substrate 1 constitutes a nanowire width metal pattern.

As an example, the top inclined portion of the opening 3 is in an inverted trapezoidal shape, which effectively suppresses the accumulation effect of the deposited metal at the step, prevents the pattern opening from being closed prematurely during the metal deposition process, and reduces the thickness deviation of the metal pattern. In addition, the bottom vertical portion of the opening 3 is rectangular, which avoids residual burrs on both sides of the metal pattern after the electron beam resist layer 2 is peeled off, forming a high-quality metal pattern, laying the foundation for the application of electron beam exposure technology in the processing of devices such as nanogratings, wave zone plates, superconducting nanowires, and superconducting Josephson junctions.

As an example, after the electron beam resist layer 2 is stripped, the quality of the metal pattern is observed under a scanning electron microscope, as shown in FIG7 , which shows an electron microscope image of a nanowire width metal pattern, and ultimately a metal nanowire array with a line width of about 50 nm and a thickness of about 30 nm is formed on the Si substrate.

In summary, in the method for making nanowire-width metal patterns of the present invention, electron beam grayscale exposure is used to form a funnel-shaped pattern opening, which, on the one hand, prevents the pattern opening from being closed prematurely during the metal deposition process, reduces the thickness deviation of the metal pattern, and on the other hand, avoids residual burrs on both sides of the metal pattern after the electron beam resist layer is stripped, thereby forming a high-quality metal pattern. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims (10)

1. The manufacturing method of the nano line width metal pattern is characterized by comprising the following steps of:

Providing a substrate, and forming an electron beam resist layer on the substrate;

Patterning the electron beam resist layer to form an opening, wherein the opening penetrates through the electron beam resist layer, the opening is funnel-shaped, and comprises a bottom vertical part and a top inclined part positioned above the bottom vertical part;

Forming a metal layer on the electron beam resist layer, wherein the metal layer is formed in the opening, and the thickness of the metal layer is smaller than the height of the bottom vertical part;

and removing the electron beam resist layer and the metal layer above the electron beam resist layer by adopting a stripping method.

2. The method of fabricating a nano-linewidth metal pattern as recited in claim 1 wherein patterning the e-beam resist layer to form openings comprises:

Drawing a layout graph by adopting a layout design tool, wherein the layout graph comprises a target graph and a gray scale graph positioned at the periphery of the target graph;

Converting the layout pattern into a layout format corresponding to an electron beam exposure device, and then exposing the electron beam resist layer in the electron beam exposure device, wherein the exposure dose of the target pattern area is larger than that of the gray pattern area;

and developing the electron beam resist layer in a developing solution to form the opening.

3. The method for manufacturing the nano line width metal pattern according to claim 2, wherein: the electron beam resist layer adopts positive electron beam resist, the thickness range of the electron beam resist layer is 100-500 nm, the exposure dose range of the target pattern is 300-1200 mu C/cm ², and the exposure dose range of the gray pattern is 100-600 mu C/cm ².

4. The method for manufacturing the nano line width metal pattern according to claim 2, wherein: after developing the electron beam resist layer in the developing solution, the method further comprises the step of fixing the electron beam resist layer in a fixing solution.

5. The method for manufacturing the nano-wire width metal pattern according to claim 4, wherein the method comprises the following steps: the developing solution comprises amyl acetate solution and methyl isobutyl ketone-isopropanol mixed solution, and the fixing solution comprises isopropanol solution.

6. The method for manufacturing the nano line width metal pattern according to claim 2, wherein: the layout design tool comprises an L-wait or GDSII, and the layout format corresponding to the electron beam exposure equipment comprises a V30 file, an SCON file or a GPF file.

7. The method for manufacturing the nano line width metal pattern according to claim 1, wherein the method comprises the following steps: the width of the bottom vertical part ranges from 20 nm to 100nm.

8. The method for manufacturing the nano line width metal pattern according to claim 1, wherein the method comprises the following steps: the material of the metal layer comprises one or more of Au, pt, pd, ti, cr, cu and Al.

9. The method for manufacturing the nano line width metal pattern according to claim 1, wherein the method comprises the following steps: the metal layer is formed by a magnetron sputtering method, an electron beam evaporation method or a thermal evaporation method.

10. The method for manufacturing the nano line width metal pattern according to claim 1, wherein the method comprises the following steps: the step of removing the electron beam resist layer and the metal layer located above the electron beam resist layer by a lift-off method comprises:

And heating the sample after the metal layer is formed in an N-methylpyrrolidone solution with a preset temperature, and then sequentially putting the sample into deionized water, acetone and isopropanol for ultrasonic cleaning.