CN117105166A

CN117105166A - Micromachining method

Info

Publication number: CN117105166A
Application number: CN202210540376.6A
Authority: CN
Inventors: 许杨
Original assignee: Shanghai Industrial Utechnology Research Institute
Current assignee: Shanghai Industrial Utechnology Research Institute
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2023-11-24

Abstract

The application provides a micro-machining method, which comprises the following steps: providing a substrate, and forming a protective layer on the surface of the substrate; etching the protective layer based on a pattern mask to form a window exposing the surface of the substrate; forming heavy metal films on the surface of the protective layer, the inner wall and the bottom of the window; patterning the heavy metal film by adopting a physical bombardment mode to form a patterned heavy metal film; removing the protective layer through a wet etching process, and retaining the patterned heavy metal film on the substrate; and carrying out micro-machining on the surface of the substrate through a dry etching process. The application reduces the etching difficulty of heavy metal in the micro-device or structure, also avoids heavy metal residues from entering the surface to be micro-machined, and is beneficial to improving the dimensional accuracy of the micro/micro nano structure.

Description

Micromachining method

Technical Field

The application belongs to the field of semiconductor integrated circuit manufacturing, in particular to the field of MEMS manufacturing process.

Background

Gold, platinum and other heavy metals having high electrical and thermal conductivity, excellent corrosion resistance and solderability, are widely used in the industry of integrated circuits, photovoltaic elements, microelectromechanical systems and the like as important materials for the fabrication of many micro-nano devices or structures, particularly MEMS devices or structures, and have the further advantage that thin films such as gold are relatively easy to prepare and can be deposited in a variety of ways, including sputtering, evaporation, electroplating and electroless plating. Films grown in these ways generally have the advantages of good adhesion, low stress and high ductility and purity. In addition, gold, for example, has the advantage of high reflectivity and easy bonding with other metals, making it an ideal material in the fabrication of optoelectronic devices.

However, the difficulty of etching heavy metals such as gold and platinum is high, which brings trouble to practical application, wet etching or ion beam etching is commonly adopted in the industry at present, and the wet etching has the limitation that the shape and the size are difficult to control, so that the wet etching is not suitable for manufacturing micro-nano structures or devices and other application scenes.

Accordingly, a micromachining method using Ion Beam Etching (IBE) technology is provided herein to reduce the difficulty of etching heavy metals.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present application is to provide a micro-machining method, which is used to solve the problems of high difficulty in etching heavy metals, low morphology and/or dimensional accuracy in micro/micro nano structures or devices in the prior art.

To achieve the above and other related objects, the present application provides a micromachining method comprising the steps of:

providing a substrate, and forming a protective layer on the surface of the substrate;

etching the protective layer based on a pattern mask to form a window exposing the surface of the substrate;

forming heavy metal films on the surface of the protective layer, the inner wall and the bottom of the window;

patterning the heavy metal film by adopting a physical bombardment mode to form a patterned heavy metal film;

removing the protective layer through a wet etching process, and retaining the patterned heavy metal film on the substrate;

and carrying out micro-machining on the surface of the substrate through a dry etching process.

Optionally, the physical bombardment mode is an ion beam etching process.

Optionally, the heavy metal film comprises a metal simple substance film of gold, platinum, silver, copper, iron, lead, cadmium and nickel, or a lamination of simple substance films of any two or more metals, or an alloy film composed of the two or more metals.

Alternatively, the substrate includes a silicon substrate, a gallium arsenide substrate, a gallium nitride substrate, a SiC substrate, a glass substrate, or a quartz substrate.

Optionally, the protective layer comprises silicon nitride or polysilicon.

Optionally, in the step of removing the protective layer by a wet etching process, the etching rate of the protective layer is greater than the etching rate of the substrate. Optionally, the substrate is a silicon substrate and the protective layer is a silicon oxide layer.

Optionally, the thickness of the protective layer ranges from 0.1 μm to 5 μm.

Optionally, a bottom silicon material is disposed on the substrate, and a surface of the substrate is micro-processed by a dry etching process to form a silicon groove or a silicon through hole in the bottom silicon material.

Alternatively, the surface of the silicon substrate is micro-processed by a dry etching process to form a silicon trench or a through silicon via in the silicon substrate.

As described above, the micromachining method of the present application has the following advantageous effects:

according to the application, the protection layer is formed before the heavy metal film, and the heavy metal film etching is performed in a physical bombardment mode, so that the heavy metal etching in the micro/micro nano structure or device can be realized; and then, removing the protective layer by utilizing a wet etching process, so that heavy metal residues bombarded into the protective layer can be removed together, the heavy metal residues are prevented from entering the surface to be micro-machined, and the dimensional accuracy of the micro-structure is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. It is apparent that the drawings in the following description are only some embodiments of the application.

Fig. 1A to 1D are schematic structural views showing steps of a micromachining method according to a comparative example of the present application.

Fig. 2 shows a process flow diagram of a micromachining process in accordance with an embodiment of the present application.

Fig. 3A to 3G are schematic structural views showing steps of a micromachining method according to an embodiment of the present application.

Description of element reference numerals

100. Substrate board

101. 211 heavy metal residue

103. Silicon residue after etching

105. 205 through silicon via

110. 220 heavy metal film

115. 225 patterned metal film

120. 230 photoresist

200. Silicon substrate

210. Protective layer

215. Window

Detailed Description

Other advantages and effects of the present application will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present application with reference to specific examples. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application.

It should be emphasized that the term "comprises/comprising" when used herein is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments in combination with or instead of the features of the other embodiments.

As described in detail in the embodiments of the present application, the cross-sectional view of the device structure is not partially enlarged to a general scale for convenience of explanation, and the schematic drawings are only examples, which should not limit the scope of the present application. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.

For ease of description, spatially relative terms such as "under", "below", "beneath", "above", "upper" and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Furthermore, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers or one or more intervening layers may also be present.

In the context of the present application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, as well as embodiments where additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

The term "substrate" herein means the substrate itself or a substrate having thin film material formed thereon, including but not limited to semiconductor substrates such as silicon substrates, gallium arsenide substrates, gallium nitride substrates, siC substrates; or other insulating substrates such as glass substrates, quartz substrates.

It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present application by way of illustration, and only the components related to the present application are shown in the drawings rather than the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

In the manufacturing process of the micro-electro-mechanical system or the photoelectric device, after the heavy metal is etched, the substrate of the bottom layer or the thin film material formed on the substrate needs to be etched downwards along the etched position of the heavy metal. Due to the physical bombardment mode such as ion beam etching, heavy metal atoms are easily sputtered into the lower layer material in the process of etching heavy metal, so that a micro-mask effect is caused in the subsequent micro-machining process.

Referring to fig. 1A to 1D, there is shown a micromachining method of a comparative example of the present application, the micromachining method comprising: 1) As shown in fig. 1A, a substrate 100 is provided, and a heavy metal film 110 is grown on the substrate 100; 2) As shown in fig. 1B, the heavy metal film 110 is etched by a dry etching process based on a pattern mask, for example, the heavy metal film 110 is etched by an ion beam etching process (IBE) according to a pattern region defined in the photoresist 120 to form a patterned heavy metal film 115, and a heavy metal material is removed to expose a predetermined region of a substrate, wherein a thin heavy metal residue 101 is generated on the surface of the predetermined region of the substrate due to physical bombardment of a high-energy ion beam; 3) As shown in fig. 1C and 1D, after performing the photolithography process, the substrate is etched through these residual heavy metal particles. For example, the heavy metal underlayer to be etched is a silicon substrate, and at step 3), the surface of the substrate is etched through these residual heavy metal particles, and the etched area of the silicon substrate is formed as a through silicon via 105, and the through silicon via has a silicon residue 103 (often referred to as "silicon grass") after etching, which affects the device performance, forms in the through silicon via, and cannot be completely removed by optimizing the etching conditions.

In order to solve the problem that heavy metal remains on the surface of the lower layer of the heavy metal film after the step of etching the heavy metal and the micro-mask effect caused by the heavy metal, the application provides a micro-machining method, which comprises the following steps:

By forming a protective layer before forming the heavy metal film; preferably, the silicon dioxide layer is etched by using a physical bombardment method such as Ion Beam Etching (IBE), and some heavy metals are bombarded into the protective layer during ion beam etching to form a thin heavy metal residue on the surface of the protective layer, and then the protective layer is removed by wet etching, and meanwhile, the residual heavy metal particles are removed together, so that the micro-mask effect caused by the heavy metals remained on the surface of the substrate or the bottom layer material arranged on the substrate is avoided.

Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings, as shown in fig. 2 and 3A to 3G, and provide a micromachining method including the steps of:

as shown in fig. 3A, step 1) is first performed, a substrate 200 is provided, and a protection layer 210 is formed on the surface of the substrate. Specifically, a Physical Vapor Deposition (PVD), a Chemical Vapor Deposition (CVD), or a Plasma Enhanced Chemical Vapor Deposition (PECVD) process may be used to deposit a protective layer 210 on the substrate 200, wherein the protective layer 210 comprises silicon oxide, silicon nitride, or polysilicon. The substrate 200 includes a silicon substrate, a gallium arsenide substrate, a gallium nitride substrate, a SiC substrate glass substrate, or a quartz substrate. In some examples, the substrate may have an underlying material, such as silicon, disposed thereon. The thickness of the protective layer can be adjusted according to the thickness of the required heavy metal film; in general, the thickness of the protective layer may be slightly smaller than that of the heavy metal film, for example, in the range of 0.1 μm to 5 μm, and particularly, 0.1 μm to 2 μm. In this embodiment, the substrate 200 may be a silicon substrate, the protective layer 210 may be a silicon oxide layer, and the silicon oxide layer may be deposited on the silicon substrate by a CVD process.

As shown in fig. 3B, step 2) is then performed to etch the protective layer 210 based on the pattern mask to form a window 215 exposing the substrate surface. In an example, defining a patterned region corresponding to the window on the silicon oxide layer through a photolithography process, and etching the silicon oxide layer according to the patterned region to form a window 215, wherein the bottom of the window 215 exposes the substrate surface; and removing the residual photoresist on the surface of the silicon oxide. As an example, the position and/or size of the window 215 may be appropriately determined according to the morphology of the corresponding heavy metal film.

As shown in fig. 3C, step 3) is performed, and a heavy metal film 220 is formed on the surface of the protective layer 210, the inner wall and the bottom of the window 215. Specifically, a heavy metal film 220 is coated on the surface of the protective layer 210, the inner wall and the bottom of the window 215 by magnetron sputtering, wherein the heavy metal film includes a metal simple substance film of gold, platinum, silver, copper, iron, lead, cadmium, nickel, or a lamination of simple substance films of any two or more metals, or an alloy film composed of the two or more metals.

After step 3), step 4) is continued, and as shown in fig. 3D to 3E, the heavy metal film 220 is patterned by using a physical bombardment method, so as to form a patterned heavy metal film 225. Specifically, step 4) includes: spin-coating photoresist 230 on the surface of the heavy metal film 220, and then forming a required patterned region on the surface of the heavy metal film through exposure, development and etching processes; etching the heavy metal film 220 by an Ion Beam Etching (IBE) process according to the patterned region defined in the photoresist 230, and removing the heavy metal film in the region uncovered by the photoresist to expose the surface of the protective layer 210, thereby obtaining a patterned heavy metal film 225; and finally, removing the photoresist covered on the surface of the patterned heavy metal film. Since some heavy metal atoms bombarded by the ion beam enter the surface of the protective layer 210, a thin heavy metal residue 211 is formed, so that heavy metal particles are prevented from being bombarded into the substrate to be micro-machined or a bottom layer material arranged on the substrate.

As shown in fig. 3F, step 5) is performed, the protective layer 210 is removed by a wet etching process, and the patterned heavy metal film 225 remains, and the surface of the substrate is exposed. Specifically, the silicon oxide layer or the silicon nitride layer is selectively removed by performing a wet etching process using a Buffered Oxide Etchant (BOE), and since the BOE has an etching selectivity of silicon nitride or silicon oxide to silicon, i.e., a rate at which silicon nitride or silicon oxide is etched is greater than a rate at which silicon is etched when the wet etching process is performed using the BOE, a silicon substrate or a silicon material disposed on the substrate is hardly consumed.

Finally, step 6) is performed, referring to fig. 3G, the surface of the substrate is micro-machined by a dry etching process. In one example, an underlying silicon material is disposed on a substrate, and the surface of the substrate is micromachined by the dry etching process to form a microstructure, such as a trench or via, in the underlying silicon material. In another example, the substrate is a silicon substrate whose surface is micro-machined by a dry etching process to form a micro-structure in the silicon substrate, such as through silicon via 205 shown in fig. 3G. Specifically, the step of forming the through silicon via 205 includes: the silicon substrate is etched through a dry etching process based on the pattern mask. The wet etching process completely removes the protective layer, so that etching is not required to be performed through the surface with heavy metal residues, bulk silicon with clear boundaries is obtained, and the etched silicon residues are avoided.

The application provides a micro-machining method, which has the following beneficial effects:

Therefore, the application effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present application and its effectiveness, and are not intended to limit the application. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the application. Accordingly, it is intended that all equivalent modifications and variations of the application be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims

1. A micromachining method comprising the steps of:

2. The micromachining method according to claim 1, wherein: the physical bombardment mode is an ion beam etching process.

3. The micromachining method according to claim 1, wherein: the heavy metal film comprises a metal simple substance film of gold, platinum, silver, copper, iron, lead, cadmium and nickel, or a lamination of simple substance films of any two or more metals, or an alloy film composed of the two or more metals.

4. The micromachining method according to claim 1, wherein: the substrate includes a silicon substrate, a gallium arsenide substrate, a gallium nitride substrate, a SiC substrate, a glass substrate, or a quartz substrate.

5. The micromachining method according to claim 1, wherein: the protective layer comprises silicon nitride or polysilicon.

6. The micromachining method according to claim 1, wherein: in the step of removing the protective layer through a wet etching process, the etching rate of the protective layer is greater than that of the substrate.

7. The micromachining method according to claim 1, wherein: the substrate is a silicon substrate, and the protective layer is a silicon oxide layer.

8. The micromachining method according to claim 1, wherein: the thickness of the protective layer ranges from 0.1 μm to 5 μm.

9. The micromachining method according to claim 1, wherein: the substrate is provided with a bottom silicon material, and the surface of the substrate is subjected to micro-processing by a dry etching process to form a silicon groove or a silicon through hole in the bottom silicon material.

10. The micromachining method according to claim 7, wherein: and carrying out micro-machining on the surface of the silicon substrate through a dry etching process to form a silicon groove or a silicon through hole in the silicon substrate.