Fabrication methods and devices for high aspect ratio metallic gratings

Abstract

This invention relates to a method and device for fabricating high aspect ratio metal gratings. It includes: providing a support substrate and an intermediate substrate; fabricating an intermediate substrate mask layer on the intermediate substrate and patterning the prepared intermediate substrate mask layer; etching the intermediate substrate using the intermediate substrate mask layer and the patterned window of the intermediate substrate mask layer to obtain a metal deposition window after etching; removing the intermediate substrate mask layer and performing metal deposition on the intermediate substrate to obtain grating metal pillars filling the metal deposition window, wherein the lower end of the grating metal pillars is in contact with a metal seed layer; removing the intermediate substrate, adhesive layer, and support substrate to obtain a metal seed layer and a plurality of grating metal pillars supported on the metal seed layer. This invention can effectively fabricate high aspect ratio metal gratings, is compatible with existing processes, and improves the fabrication efficiency and process stability of metal gratings.

Description

Technical Field

[0001] This invention relates to a fabrication method and a device, and more particularly to a fabrication method and device for a high aspect ratio metal grating. Background Technology

[0002] With the widespread application of MEMS (Micro-Electro-Mechanical System) devices in military equipment, communication network information systems, and the automotive industry, microfabrication technology is booming. In practical applications, many MEMS devices, especially metal grating structures, require high aspect ratios and steep sidewalls.

[0003] In the early stages of fabricating high aspect ratio metal gratings, researchers proposed the following two processes: 1) Synchrotron radiation deep X-ray LIGA process. Although it yields microdevices with a large aspect ratio and fine structure, it requires expensive synchrotron radiation X-ray sources and X-ray masks, and has a long processing cycle, thus limiting its widespread application. 2) Dry etching technology ICP-RIE, which combines deep RIE (Reaction Ion Etching) and ICP (Inductive Coupled Plasma) technologies, but it can only be performed on silicon materials, which also limits its application.

[0004] To address the shortcomings of the two aforementioned processes, researchers have developed several alternative processes. Currently, the most practically valuable is ultraviolet lithography (UV-LIGA) technology, which mainly consists of three steps: SU-8 lithography, micro-electroforming, and plastic injection molding. Among these, SU-8 lithography and micro-electroforming are the key steps in the UV-LIGA process.

[0005] Because ultraviolet lithography requires the use of SU-8 photoresist, the process has the following drawbacks: 1) The applicability of this process is not as good as that of positive photoresist; 2) During the lithography process, SU-8 photoresist will generate large internal stress, which will cause cracks in the SU-8 photoresist layer or cause it to fall off from the substrate, destroying the quality and stability of its pattern structure and making it difficult to fabricate high aspect ratio metal grating structures; 3) Another problem with the SU-8 thick photoresist process is that the highly cross-linked photoresist is difficult to remove completely, especially after the electroforming process, and the special SU-8 photoresist remover is ineffective. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and device for fabricating high aspect ratio metal gratings, which can effectively fabricate high aspect ratio metal gratings, is compatible with existing processes, and improves the fabrication efficiency and process stability of metal gratings.

[0007] According to the technical solution provided by this invention, a method for fabricating a high aspect ratio metal grating includes:

[0008] A support substrate and an intermediate substrate are provided, wherein a metal seed layer is prepared on the support substrate, and the intermediate substrate is bonded and fixed to the metal seed layer by an adhesive layer on the metal seed layer;

[0009] An intermediate substrate mask layer is prepared on an intermediate substrate, and the prepared intermediate substrate mask layer is patterned to obtain several intermediate substrate mask layer patterning windows that penetrate the intermediate substrate mask layer.

[0010] The intermediate substrate is etched using an intermediate substrate mask layer and a patterned window of the intermediate substrate mask layer, so as to obtain several metal deposition windows that correspond to the patterned windows of the intermediate substrate mask layer after etching. The corresponding surface of the metal seed layer is exposed through the metal deposition windows.

[0011] Remove the intermediate substrate mask layer and perform metal deposition on the intermediate substrate to obtain grating metal pillars filling the metal deposition window, wherein the lower end of the grating metal pillars is in contact with the metal seed layer.

[0012] Remove the aforementioned intermediate substrate, adhesive layer, and support substrate to obtain a metal seed layer and a plurality of grating metal pillars supported on the metal seed layer.

[0013] The metal seed layer is first prepared on the supporting substrate, and then the adhesive layer is prepared on the metal seed layer.

[0014] After the adhesive layer is prepared, the intermediate substrate is bonded and fixed to the metal seed layer using the adhesive layer;

[0015] The process for preparing a metal seed layer on a support substrate includes sputtering.

[0016] The adhesive layer is a positive photoresist layer, wherein,

[0017] The adhesive layer is prepared on the metal seed layer by spin coating or spray coating, and after spin coating or spray coating, the adhesive layer is fixed on the metal seed layer by heat baking.

[0018] The intermediate substrate comprises a double-sided polished silicon wafer;

[0019] After the intermediate substrate is bonded and fixed to the metal seed layer by the adhesive layer, the surface of the intermediate substrate away from the supporting substrate is thinned.

[0020] After thinning the intermediate substrate, a mask layer is fabricated on the intermediate substrate.

[0021] The intermediate substrate mask layer includes a photoresist layer;

[0022] When etching the intermediate substrate using the intermediate substrate mask layer and the intermediate substrate mask layer patterning window, the etching depth reaches the metal seed layer.

[0023] The deposition process for grating metal pillars includes electron beam evaporation, sputtering, metal CVD, or electroplating.

[0024] Removing the aforementioned intermediate substrate, adhesive layer, and support substrate includes:

[0025] First, remove the adhesive layer to separate the intermediate substrate from the metal seed layer;

[0026] After separating the intermediate substrate from the metal seed layer, the metal seed layer is separated from the support substrate to remove the support substrate.

[0027] To remove the adhesive layer, the adhesive layer is soaked in acetone solution and then removed under ultrasonic vibration.

[0028] When separating the metal seed layer from the supporting substrate, a wet separation method is used, wherein...

[0029] During wet separation, KOH solution is used to separate the metal seed layer from the supporting substrate.

[0030] A high aspect ratio metal grating device is provided, wherein the metal grating device is prepared by the preparation method described above.

[0031] The advantages of this invention are: in the fabrication of metal gratings, commonly used equipment can be used, which is compatible with existing processes, reduces processing costs and improves processing efficiency; in the process, an intermediate substrate is used to replace the function of SU-8 photoresist, thereby enhancing the quality and stability of the pattern structure and enabling the fabrication of metal grating devices with higher aspect ratios. Attached Figure Description

[0032] Figures 1 to 11 A cross-sectional view of the process steps for fabricating a high aspect ratio metal grating according to an embodiment of the present invention, wherein...

[0033] Figure 1 This is a cross-sectional view of the metal seed layer obtained in this invention.

[0034] Figure 2 This is a cross-sectional view of the adhesive layer obtained in this invention.

[0035] Figure 3 This is a cross-sectional view of the intermediate substrate after it has been bonded and fixed to the metal seed layer by an adhesive layer according to the present invention.

[0036] Figure 4 This is a cross-sectional view of the intermediate substrate after thinning according to the present invention.

[0037] Figure 5This is a cross-sectional view of the intermediate substrate mask layer prepared according to the present invention.

[0038] Figure 6 This is a cross-sectional view of the intermediate substrate mask layer after patterning according to the present invention.

[0039] Figure 7 This is a cross-sectional view of the metal deposition window obtained by etching according to the present invention.

[0040] Figure 8 This is a cross-sectional view after the intermediate substrate mask layer has been removed according to the present invention.

[0041] Figure 9 This is a cross-sectional view of the grating metal pillars deposited according to the present invention.

[0042] Figure 10 This is a cross-sectional view after the adhesive layer and intermediate substrate have been removed.

[0043] Figure 11 This is a cross-sectional view of the metal seed layer after it has been separated from the supporting substrate according to the present invention.

[0044] The reference numerals in the attached figures are as follows: 1-Supporting substrate, 2-Metal seed layer, 3-Adhesive layer, 4-Intermediate substrate, 5-Intermediate substrate mask layer, 6-Raster metal pillar, 7-Intermediate substrate mask layer patterned window, 8-Intermediate substrate hole, 9-Adhesive layer hole. Detailed Implementation

[0045] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0046] To effectively fabricate high aspect ratio metal gratings, in one embodiment of the present invention, the fabrication method of the metal grating includes:

[0047] A support substrate 1 and an intermediate substrate 4 are provided, wherein a metal seed layer 2 is prepared on the support substrate 1, and the intermediate substrate 4 is bonded and fixed to the metal seed layer 2 by an adhesive layer 3 on the metal seed layer 2;

[0048] An intermediate substrate mask layer 5 is prepared on the intermediate substrate 4, and the prepared intermediate substrate mask layer 5 is patterned to obtain several intermediate substrate mask layer patterning windows 7 that penetrate the intermediate substrate mask layer 5.

[0049] The intermediate substrate 4 is etched using the intermediate substrate mask layer 5 and the intermediate substrate mask layer patterned window 7, so that after etching, a number of metal deposition windows corresponding to the intermediate substrate mask layer patterned window 7 are obtained, wherein the corresponding surface of the metal seed layer 2 is exposed through the metal deposition window.

[0050] Remove the intermediate substrate mask layer 5 and perform metal deposition on the intermediate substrate 4 to obtain a grating metal pillar 6 filling the metal deposition window, wherein the lower end of the grating metal pillar 6 is in contact with the metal seed layer 2.

[0051] Remove the intermediate substrate 4, adhesive layer 3 and support substrate 1 to obtain metal seed layer 2 and a plurality of grating metal pillars 6 supported on the metal seed layer 2.

[0052] Figures 1-3 An embodiment of the process steps for bonding and fixing the intermediate substrate 4 to the metal seed layer 2 through the adhesive layer 3 is shown. Specifically, the metal seed layer 2 is first prepared on the support substrate 1, and then the adhesive layer 3 is prepared on the metal seed layer 2.

[0053] After the adhesive layer 3 is prepared, the intermediate substrate 4 is bonded and fixed to the metal seed layer 2 using the adhesive layer 3;

[0054] The process for preparing the metal seed layer 2 on the support substrate 1 includes sputtering.

[0055] Figure 1 The diagram shows a schematic of the metal seed layer 2 after it has been fabricated on a support substrate 1. The support substrate 1 can be a commonly used silicon substrate. The fabrication process of the metal seed layer 2 includes sputtering. The metal material used in the metal seed layer 2 can be selected according to actual needs.

[0056] Figure 2 The image shows a schematic diagram of the bonding layer 3 after it has been prepared on the metal seed layer 2. Specifically, the bonding layer 3 is a positive photoresist layer.

[0057] The adhesive layer 3 is prepared on the metal seed layer 2 by spin coating or spraying, and after spin coating or spraying, the adhesive layer 3 is fixed on the metal seed layer 2 by heat baking.

[0058] Specifically, the adhesive layer 3 can be a commonly used positive photoresist layer. When the adhesive layer 3 is a positive photoresist, it can be prepared on the metal seed layer 2 by spin coating or spraying. The specific spin coating or spraying process conditions can be selected according to actual needs, based on the ability to prepare the desired adhesive layer 3. Furthermore, after spin coating or spraying, the adhesive layer 3 is heat-baked to fix it onto the metal seed layer 2. The heat-baking temperature of the adhesive layer 3 can be 100℃~120℃. The metal seed layer 2 can generally be a chromium / copper seed layer, a gold seed layer, a nickel seed layer, or a titanium seed layer; the type of metal seed layer 2 can be selected according to actual needs.

[0059] Furthermore, the intermediate substrate 4 comprises a double-sided polished silicon wafer;

[0060] After the intermediate substrate 4 is bonded and fixed to the metal seed layer 2 by the adhesive layer 3, the surface of the intermediate substrate 4 away from the supporting substrate 1 is thinned.

[0061] After thinning the intermediate substrate 4, the intermediate substrate mask layer 5 is fabricated on the intermediate substrate 4.

[0062] Specifically, the intermediate substrate 4 can also be made of other materials, depending on whether it can meet the requirements for etching to form a metal deposition window. When the intermediate substrate 4 is bonded to the metal seed layer 2 via the adhesive layer 3, a bonding machine is generally required. The bonding machine can be any commonly used existing equipment, specifically designed to meet the requirements for bonding the intermediate substrate 4 to the metal seed layer 2 via the adhesive layer 3. The bonding and fixing of the intermediate substrate 4 to the metal seed layer 2 also achieves the bonding and fixing between the intermediate substrate 4 and the supporting substrate 1, such as... Figure 3 As shown.

[0063] Because the intermediate substrate 4 is relatively thick, it needs to be thinned. Specifically, thinning refers to thinning the surface of the intermediate substrate 4 furthest from the supporting substrate 1. Specific thinning methods include mechanical and chemical polishing. The specific method of thinning can be selected according to actual needs, aiming to meet the requirements for thinning the intermediate substrate 4. Figure 4 As shown.

[0064] After thinning the intermediate substrate 4 to the required thickness, an intermediate substrate mask layer 5 is fabricated on the intermediate substrate 4, such as... Figure 5 As shown. In a specific implementation, the intermediate substrate mask layer 5 includes a photoresist layer;

[0065] When etching the intermediate substrate 4 using the intermediate substrate mask layer 5 and the intermediate substrate mask layer patterning window 7, the etching depth reaches the metal seed layer 2.

[0066] When the intermediate substrate mask layer 5 is a photoresist layer, the intermediate substrate mask layer 5 can be prepared on the intermediate substrate 4 using existing commonly used techniques. The photoresist used in the intermediate substrate mask layer 5 is a non-SU-8 type negative photoresist.

[0067] After the intermediate substrate mask layer 5 is fabricated on the intermediate substrate 4, the intermediate substrate mask layer 5 is patterned to obtain a patterned window 7. Generally, the patterned window 7 penetrates the intermediate substrate mask layer 5, so that a corresponding area of ​​the intermediate substrate 4 is exposed using the patterned window 7. Figure 6 As shown.

[0068] When the intermediate substrate 4 is a double-sided polished silicon substrate, a deep silicon etching process can be performed on the intermediate substrate 4. That is, the intermediate substrate 4 is etched using the patterned intermediate substrate mask layer 5. The depth of the deep silicon etching can be selected as the thickness of the intermediate substrate 4 and the thickness of the bonding layer 3, that is, etching down to the metal seed layer 2. Figure 7 As shown.

[0069] Figure 7 In the process of deep silicon etching, several intermediate substrate holes 8 penetrating the intermediate substrate 4 and several adhesive layer holes 9 penetrating the adhesive layer 3 are obtained. The intermediate substrate holes 8 and adhesive layer holes 9 are in one-to-one correspondence and correspond to the patterned window 7 of the intermediate substrate mask layer. The intermediate substrate holes 8 and adhesive layer holes 9 are interconnected, and the bottom of the adhesive layer hole 9 is the metal seed layer 2, which allows the corresponding surface and interior of the metal seed layer 2 to be exposed. At this time, a metal deposition window is formed by using an intermediate substrate hole 8 and the adhesive layer hole 9 corresponding to the intermediate substrate hole 8.

[0070] After etching to form the metal deposition window, the intermediate substrate mask layer 5 is removed using methods commonly used in this technical field. The implementation after the intermediate substrate mask layer 5 is removed from the intermediate substrate 4 is as follows. Figure 8 As shown. The intermediate substrate mask layer 5 can be removed using a dry etching process. Of course, other removal processes can also be used, depending on whether the intermediate substrate mask layer 5 can be effectively removed.

[0071] After removing the intermediate substrate mask layer 5, a metal deposition process is performed to prepare several grating metal pillars 6 filling the metal deposition windows, such as... Figure 9 As shown. In specific implementation, the deposition process of the grating metal pillar 6 includes electron beam evaporation, sputtering, metal CVD, or electroplating. The specific deposition process of the grating metal pillar 6 can be selected according to actual needs, based on the ability to prepare the grating metal pillar 6 that fills the metal deposition window.

[0072] Figure 9 In the middle, the lower end of the grating metal pillar 6 is supported on the metal seed layer 2, and the grating metal pillar 6 is in contact with the metal seed layer 2. Multiple grating metal pillars 6 are parallel to each other and perpendicular to the metal seed layer 2.

[0073] In order to form the required metal grating, the intermediate substrate 4, the adhesive layer 3 and the support substrate 1 need to be removed, that is, only the metal seed layer 2 and the grating metal pillar 6 perpendicular to the metal seed layer 2 are retained. Figure 10 and Figure 11 The diagram illustrates a process step for removing the intermediate substrate 4, the adhesive layer 3, and the support substrate 1.

[0074] Figure 10 and Figure 11In the process of removing the aforementioned intermediate substrate 4, adhesive layer 3, and support substrate 1, the following steps are included:

[0075] First, remove the adhesive layer 3 to separate the intermediate substrate 4 from the metal seed layer 2;

[0076] After the intermediate substrate 4 is separated from the metal seed layer 2, the metal seed layer 2 is separated from the support substrate 1 to remove the support substrate 1.

[0077] Specifically, when removing the adhesive layer 3, the adhesive layer 3 is soaked in an acetone solution and then removed under ultrasonic waves. When the adhesive layer 3 is removed, the intermediate substrate 4 can no longer connect to the metal seed layer 2 and the supporting substrate 1, thus allowing for the removal of the intermediate substrate 4. At this point, the metal seed layer 2 covers the supporting substrate 1, and the grating metal pillars 6 are vertically distributed on the metal seed layer 2, as shown below. Figure 10 As shown.

[0078] In practice, 99% acetone solution can be used. When removing the adhesive layer 3 using ultrasound, the ultrasonic cleaner should have a power of 300W to 600W, a frequency of 40kHz, and a temperature of 40℃ to 50℃. The ultrasonic working state for removing the adhesive layer 3 can be selected as needed, based on the ability to effectively remove the adhesive layer 3.

[0079] In one embodiment of the present invention, when separating the metal seed layer 2 from the supporting substrate 1, a wet separation method is used, wherein...

[0080] During wet separation, the metal seed layer 2 is separated from the supporting substrate 1 using KOH solution.

[0081] Specifically, when separating the metal seed layer 2 from the supporting substrate 1, the supporting substrate 1 needs to be placed in a KOH solution. The KOH solution can be used to separate the metal seed layer 2 from the supporting substrate 1. After the metal seed layer 2 is separated from the supporting substrate 1, the grating metal pillar 6 remains connected to the metal seed layer 2. Figure 11 As shown, at this point, the desired metal grating has been prepared.

[0082] In wet separation, a KOH solution with a concentration of 30% to 40% can be used. During separation, a water bath heating method is used to heat the solution to 70℃ to 85℃.

[0083] right Figure 11 The metal grating prepared in the process can have an aspect ratio of 50:1 to 100:1. The specific aspect ratio of the metal grating can be selected as needed, based on the actual application requirements.

[0084] In summary, the high aspect ratio metal grating device is prepared by the above-described preparation method.

[0085] Specifically, the metal grating device can be fabricated using the above-described process steps, and the fabricated metal grating device is as follows: Figure 11 As shown above, the specific process can be referred to the above description, and will not be repeated here.

[0086] In summary, this invention allows for the use of commonly used equipment and is compatible with existing processes in the fabrication of metal gratings, thereby reducing processing costs and improving processing efficiency. During the process, the intermediate substrate 4 replaces the function of SU-8 photoresist, which enhances the quality and stability of the pattern structure and enables the fabrication of metal grating devices with higher aspect ratios.

Claims

1. A method for fabricating a high aspect ratio metal grating, characterized in that, The aspect ratio of the metal grating is 50:1 to 100:1, and the fabrication method of the metal grating includes: A support substrate (1) and an intermediate substrate (4) are provided, wherein a metal seed layer (2) is prepared on the support substrate (1), and the intermediate substrate (4) is bonded and fixed to the metal seed layer (2) by an adhesive layer (3) on the metal seed layer (2); An intermediate substrate mask layer (5) is prepared on an intermediate substrate (4), and the prepared intermediate substrate mask layer (5) is patterned to obtain several intermediate substrate mask layer patterning windows (7) that penetrate the intermediate substrate mask layer (5). The intermediate substrate (4) is etched using the intermediate substrate mask layer (5) and the intermediate substrate mask layer patterned window (7) to obtain several metal deposition windows that correspond to the intermediate substrate mask layer patterned window (7) respectively after etching. The corresponding surface of the metal seed layer (2) is exposed through the metal deposition window. Remove the above intermediate substrate mask layer (5) and perform metal deposition on the intermediate substrate (4) to obtain a grating metal pillar (6) filled in the metal deposition window, wherein the lower end of the grating metal pillar (6) is in contact with the metal seed layer (2); Remove the intermediate substrate (4), adhesive layer (3) and support substrate (1) to obtain a metal seed layer (2) and a plurality of grating metal pillars (6) supported on the metal seed layer (2). Removing the aforementioned intermediate substrate (4), adhesive layer (3), and support substrate (1) includes: First, remove the adhesive layer (3) so that the intermediate substrate (4) can be separated from the metal seed layer (2); After the intermediate substrate (4) is separated from the metal seed layer (2), the metal seed layer (2) is separated from the support substrate (1) to remove the support substrate (1).

2. The method for fabricating a high aspect ratio metal grating according to claim 1, characterized in that: After the metal seed layer (2) is first prepared on the support substrate (1), the adhesive layer (3) is then prepared on the metal seed layer (2); After the adhesive layer (3) is prepared, the intermediate substrate (4) is bonded and fixed to the metal seed layer (2) using the adhesive layer (3); The process for preparing a metal seed layer (2) on a support substrate (1) includes sputtering.

3. The method for fabricating a high aspect ratio metal grating according to claim 1, characterized in that: The adhesive layer (3) is a positive photoresist layer, wherein, The adhesive layer (3) is prepared on the metal seed layer (2) by spin coating or spray coating, and after spin coating or spray coating, the adhesive layer (3) is fixed on the metal seed layer (2) by hot baking.

4. The method for fabricating a high aspect ratio metal grating according to claim 1, characterized in that: The intermediate substrate (4) comprises a double-sided polished silicon wafer; After the intermediate substrate (4) is bonded and fixed to the metal seed layer (2) through the adhesive layer (3), the surface of the intermediate substrate (4) away from the supporting substrate (1) is thinned; After thinning the intermediate substrate (4), the intermediate substrate mask layer (5) is prepared on the intermediate substrate (4).

5. The method for fabricating a high aspect ratio metal grating according to any one of claims 1 to 4, characterized in that: The intermediate substrate mask layer (5) includes a photoresist layer; When etching the intermediate substrate (4) using the intermediate substrate mask layer (5) and the intermediate substrate mask layer patterning window (7), the etching depth extends to the metal seed layer (2).

6. The method for fabricating a high aspect ratio metal grating according to any one of claims 1 to 4, characterized in that: The deposition process of the grating metal pillar (6) includes electron beam evaporation, sputtering, metal CVD or electroplating.

7. The method for fabricating a high aspect ratio metal grating according to claim 1, characterized in that, When removing the adhesive layer (3), the adhesive layer (3) is soaked in acetone solution and removed under ultrasonic vibration.

8. The method for fabricating a high aspect ratio metal grating according to claim 1, characterized in that, When separating the metal seed layer (2) from the supporting substrate (1), a wet separation method is used, wherein, During wet separation, the metal seed layer (2) is separated from the supporting substrate (1) using KOH solution.

9. A high aspect ratio metal grating device, characterized in that: The metal grating device is prepared by the preparation method of any one of claims 1 to 8.

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