CN114620669A

CN114620669A - Micro-cantilever probe and manufacturing method thereof

Info

Publication number: CN114620669A
Application number: CN202011454662.8A
Authority: CN
Inventors: 潘强
Original assignee: Shanghai Industrial Utechnology Research Institute
Current assignee: Shanghai Industrial Utechnology Research Institute
Priority date: 2020-12-10
Filing date: 2020-12-10
Publication date: 2022-06-14

Abstract

The invention provides a micro cantilever beam probe and a manufacturing method thereof, wherein the method comprises the following steps: providing an SOI substrate which sequentially comprises a back substrate, an insulating layer and top silicon from bottom to top, and forming a hard mask layer on the top silicon; patterning the hard mask layer, wherein the patterned hard mask layer covers the region where the probe tip is located; forming a cantilever arm groove in the top silicon, wherein the cantilever arm groove is opened from the top surface of the top silicon, extends towards the insulating layer and does not reach the insulating layer; and etching the top layer silicon by taking the patterned hard mask layer as a mask until the insulating layer is exposed at the bottom of the cantilever arm groove so as to synchronously obtain a cantilever arm and a probe positioned above the cantilever arm. The cantilever arm and the probe are synchronously formed, the bonding glue is utilized to protect the probe tip structure from being damaged in the process, the process is more stable and controllable, and the high-quality micro-cantilever arm probe can be stably manufactured in batches.

Description

Micro-cantilever probe and manufacturing method thereof

Technical Field

The invention belongs to the field of micro-electromechanical system (MEMS) sensor manufacturing, and relates to a micro-cantilever probe and a manufacturing method thereof.

Background

Atomic Force Microscopy (AFM) is an analytical instrument that can be used to study the surface structure of materials, including insulators. A typical AFM probe generally comprises two parts: a cantilever with one end fixed, and a sharp probe attached to the other free end. The working principle is that one end of a micro-cantilever beam arm which is extremely sensitive to weak force is fixed, and a micro needle point at the other end is lightly contacted with the surface of a sample. Due to the van der waals force action between atoms at the tip of the needle tip and atoms on the surface of the sample, the cantilever arm can slightly deflect, and then the movement track of the cantilever arm can be obtained by detecting the deflection change of the laser beam irradiated on the back of the cantilever arm, so that an image of the surface topography of the sample is obtained.

The AFM probe is used as a key component in an atomic force microscope system, and the structure and the performance of the AFM probe have great influence on the performance, the measurement precision and the image quality of the atomic force microscope. In the early days, AFM probes were made by manual operations, such as gold foil as cantilever arm, and manually attaching tiny diamond particles as probe to the free end of the cantilever arm. The manufacturing method has the advantages of high difficulty, poor manufacturing repeatability, no guarantee of probe quality and low yield. On the other hand, since the probe is frequently replaced due to damage or contamination, it is necessary to develop a stable and suitable method for mass production of AFM probes.

In 2004, Takayuki Shibata proposes that a diamond piezoelectric cantilever probe is manufactured by a reverse die stamping method, and the wear resistance is high. However, the shape of the probe tip manufactured by the method is influenced by the shape of the die, and the taper of the probe tip is poor and the quality is poor. Researchers also try to manufacture the micro cantilever beam arm probe by using an MEMS micro-electro-mechanical system (MEMS) machining process before, but the tip of the probe manufactured firstly is easy to damage in subsequent processes such as photoetching and the like, and the sharpness and the yield of the tip are influenced. In addition, when the probe tip and the back cavity structure are manufactured by the wet etching process, a proper mask material needs to be selected, the manufacturing process is complicated, the stability of the wet etching process is poor, and the quality of the probe tip cannot be guaranteed.

Therefore, how to provide a micro cantilever probe and a method for manufacturing the same to stably manufacture high quality micro cantilever probes in batch is an important technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a micro cantilever probe and a method for fabricating the same, which are used to solve the problems of the prior art that the tip of the micro cantilever probe is easy to damage and the process stability is poor.

In order to achieve the above and other related objects, the present invention provides a method for fabricating a micro cantilever probe, comprising the steps of:

providing an SOI substrate which sequentially comprises a back substrate, an insulating layer and top silicon from bottom to top, and forming a hard mask layer on the top silicon;

patterning the hard mask layer, wherein the patterned hard mask layer covers the region where the probe tip is located;

forming a cantilever arm groove in the top silicon, wherein the cantilever arm groove is opened from the top surface of the top silicon, extends towards the insulating layer and does not reach the insulating layer;

and etching the top layer silicon by taking the patterned hard mask layer as a mask until the insulating layer is exposed at the bottom of the cantilever arm groove so as to synchronously obtain a cantilever arm and a probe positioned above the cantilever arm.

Optionally, the method further comprises the following steps:

removing the patterned hard mask layer;

providing a temporary substrate, and bonding the temporary substrate and the SOI substrate through bonding glue, wherein the temporary substrate faces the top silicon, and the probe is embedded in the bonding glue;

forming a cavity structure penetrating the back substrate in a vertical direction, and removing a portion of the insulating layer exposed by the cavity structure to expose the cantilever arm;

and removing the temporary substrate and the bonding glue.

Optionally, the cavity structure is formed by dry etching.

Optionally, a dry etching is used to remove the exposed portion of the insulating layer by the cavity structure.

Optionally, the method further includes performing thermal oxidation treatment on the SOI substrate to form an oxide layer on the surfaces of the probe and the cantilever.

Optionally, a dry etching method is adopted to form the cantilever arm groove, and the top layer silicon is etched by the dry etching method to synchronously obtain the cantilever arm and the probe.

Optionally, the hard mask layer is made of at least one of aluminum and aluminum oxide.

Optionally, the side walls of the probe are sloped.

Optionally, the temporary substrate comprises one of a silicon wafer and a glass sheet.

The invention also provides a micro-cantilever probe which is manufactured by adopting the manufacturing method of the micro-cantilever probe.

As described above, the micro cantilever probe and the manufacturing method thereof of the present invention have the following beneficial effects:

(1) according to the invention, the graphical hard mask layer based on the probe tip graph and the cantilever arm groove with partial etching depth are respectively defined by two times of photoetching and etching, then the top layer silicon is etched by taking the graphical hard mask layer as a mask, the cantilever arm and the probe can be synchronously obtained, and the problems of poor photoresist coating effect and poor photoresist thickness uniformity caused by graph height difference in the process flows of step-by-step etching of the probe structure and the cantilever arm groove structure are avoided;

(2) a bonding adhesive temporary bonding process is adopted, when the cavity structure on the back of the probe is manufactured, the bonded temporary substrate is used as a bearing substrate, and the bonding adhesive can protect the probe tip structure from being damaged in the process;

(3) the probe, the cantilever beam arm and the back cavity structure are manufactured by adopting a dry etching process, and compared with a wet etching process, the steps of deposition and removal of a required special mask can be omitted, and the process is more stable and controllable.

Drawings

FIG. 1 is a process flow diagram of a method for fabricating a micro cantilever probe according to the present invention.

Fig. 2 shows a schematic diagram of forming a hard mask layer on top silicon of an SOI substrate sequentially including a back substrate, an insulating layer and top silicon from bottom to top in the method for fabricating a micro cantilever probe according to the present invention.

Fig. 3 is a schematic view showing that a first photoresist layer is formed on the hard mask layer and patterned according to the method for manufacturing the cantilever probe of the present invention.

Fig. 4 is a schematic diagram showing the method for manufacturing the cantilever probe according to the present invention, in which the patterned first photoresist layer is used as a mask to dry-etch the hard mask layer and stops on the top silicon surface.

Fig. 5 is a schematic diagram showing that a second photoresist layer is formed on the top silicon layer and the second photoresist layer is patterned to obtain a cantilever pattern according to the method for manufacturing a cantilever probe of the present invention.

Fig. 6 shows a schematic diagram of the method for manufacturing the cantilever probe according to the present invention, in which the patterned second photoresist layer is used as a mask to dry-etch the top silicon layer to obtain the cantilever groove.

Fig. 7 is a schematic diagram showing the method for manufacturing the cantilever probe according to the present invention, in which the patterned hard mask layer is used as a mask to etch the top silicon layer until the insulating layer is exposed at the bottom of the cantilever groove.

Fig. 8 is a schematic diagram illustrating the patterned hard mask layer removed by the method for fabricating a cantilever probe according to the present invention.

Fig. 9 is a schematic view showing a temporary base provided for the method of fabricating the cantilever probe of the present invention, the temporary base being bonded to the SOI substrate by a bonding paste.

Fig. 10 is a schematic view showing a method of fabricating a micro cantilever probe according to the present invention, in which a cavity structure penetrating through the back substrate in a vertical direction is formed, and a portion of the insulating layer exposed by the cavity structure is removed to expose the cantilever.

FIG. 11 is a front cross-sectional view of a microcantilever probe of the invention.

FIG. 12 is a side cross-sectional view of a microcantilever probe of the invention.

Description of the element reference numerals

S1-S4

1 SOI substrate

101 backing sole

102 insulating layer

103 top layer silicon

2 hard mask layer

3 first photoresist layer

4 cantilever arm groove

5 second photoresist layer

6 suspension beam arm

7 Probe

8 temporary substrate

9 bonding glue

10 cavity structure

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Please refer to fig. 1 to 12. It should be noted that the drawings provided in this embodiment are only for schematically illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings and not drawn according to the number, shape and size of the components in actual implementation, and the form, quantity and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may be more complicated.

In this embodiment, a method for fabricating a micro cantilever probe is provided, please refer to fig. 1, which is a process flow diagram of the method, including the following steps:

s1: providing an SOI substrate which sequentially comprises a back substrate, an insulating layer and top silicon from bottom to top, and forming a hard mask layer on the top silicon;

s2: patterning the hard mask layer, wherein the patterned hard mask layer covers the region where the probe tip is located;

s3: forming a cantilever arm groove in the top silicon, wherein the cantilever arm groove is opened from the top surface of the top silicon, extends towards the insulating layer and does not reach the insulating layer;

s4: and etching the top layer silicon by taking the patterned hard mask layer as a mask until the insulating layer is exposed at the bottom of the cantilever arm groove so as to synchronously obtain a cantilever arm and a probe positioned above the cantilever arm.

As an example, referring to fig. 2, step S1 is executed: an SOI substrate 1 comprising a back substrate 101, an insulating layer 102 and a top silicon 103 in sequence from bottom to top is provided, and a hard mask layer 2 is formed on the top silicon 103.

By way of example, the material of the back substrate 101 includes, but is not limited to, silicon, and the material of the insulating layer 102 includes, but is not limited to, silicon dioxide.

As an example, the SOI substrate 1 can be an SOI silicon wafer with the thickness of 400-800 microns, the thickness range of the insulating layer 102 is 0.5-2 microns, and the thickness range of the top silicon 103 is 15-20 microns. In this embodiment, an SOI silicon wafer with a thickness of 400 microns is taken as an example, the thickness of the insulating layer 102 is 2 microns, and the thickness of the top silicon 103 is 15 microns.

By way of example, the hard mask layer 2 may be formed using sputtering, electroplating, physical vapor deposition, chemical vapor deposition, or other suitable methods. The hard mask layer 2 may be made of a material having a high selectivity with respect to the top silicon 103, including but not limited to aluminum, aluminum oxide, and the like. In this embodiment, the hard mask layer 2 is an aluminum layer with a thickness of 0.5 μm.

Referring to fig. 3 and 4, step S2 is executed: and patterning the hard mask layer 2, wherein the patterned hard mask layer 2 covers the region where the probe tip is located.

Specifically, as shown in fig. 3, a first photoresist layer 3 is formed on the hard mask layer 2 through a photoresist coating process, and the first photoresist layer 3 is patterned through processes such as exposure, development, and the like.

As shown in fig. 4, the hard mask layer 2 is dry-etched by using the patterned first photoresist layer 3 as a mask, and stops on the surface of the top silicon 103 to obtain the patterned hard mask layer 2, and the patterned hard mask layer 2 covers the region where the probe tip is located.

By way of example, the probe tip has a diameter in the range of 0.35-0.8 microns. In this embodiment, the probe tip diameter is 0.5 μm, for example.

Referring to fig. 5 and fig. 6, step S3 is executed: forming a cantilever groove 4 in the top silicon 103, wherein the cantilever groove 4 is opened from the top surface of the top silicon 103 and extends toward the insulating layer 102 but does not reach the insulating layer 102.

Specifically, as shown in fig. 5, a second photoresist layer 5 is formed on the top silicon layer 103 through a glue coating process, and the second photoresist layer 5 is patterned through exposure, development and other processes, so as to obtain a cantilever arm pattern.

By way of example, the cantilever arms to be formed have a width in the range of 20-40 microns and a length in the range of 150-200 microns. In this embodiment, the width of the cantilever arm is 25 micrometers, and the length is 180 micrometers.

As shown in fig. 6, the top silicon 103 is dry etched by using the patterned second photoresist layer 5 as a mask, so as to obtain a cantilever groove 4, where the cantilever groove 4 is opened from the top surface of the top silicon 103, extends toward the insulating layer 103, and does not reach the insulating layer 102.

As an example, the depth of the cantilever arm groove 4 obtained in this step is in a range of 2 to 6 micrometers, and 4 micrometers is taken as an example in this embodiment.

Referring to fig. 7, step S4 is executed: and etching the top layer silicon 103 by taking the patterned hard mask layer 2 as a mask until the insulating layer 102 is exposed at the bottom of the cantilever arm groove 4, so as to synchronously obtain a cantilever arm 6 and a probe 7 positioned above the cantilever arm.

As an example, before the top silicon 103 is etched by using the patterned hard mask layer 2 as a mask, a photoresist stripping and cleaning step may be performed in advance.

As an example, the top silicon 103 is etched by dry etching until the cantilever arm groove 4 stops on the insulating layer 102 of the SOI substrate, so as to obtain the cantilever arm 6 and the probe 7 simultaneously.

In the invention, the insulating layer is used as a stop layer, so that the thickness of the cantilever beam arm can be ensured.

As an example, the height of the probe 7 is in a range of 8 to 12 micrometers, the thickness of the cantilever 6 is in a range of 2 to 6 micrometers, in this embodiment, the height of the probe 7 is 10 micrometers, and the thickness of the cantilever 6 is 4 micrometers.

As an example, the side wall of the probe 7 is inclined, for example, the longitudinal section of the probe is trapezoidal, the bottom angle of the trapezoid may be 81 to 89 degrees, and in this embodiment, the bottom angle of the trapezoid is 84 degrees as an example.

Referring to fig. 8, the patterned hard mask layer 2 is further removed by a wet etching process.

Referring to fig. 9, a temporary base 8 is provided, and the temporary base 8 is bonded to the SOI substrate 1 through a bonding glue 9, wherein the temporary base 8 faces the top silicon 103, and the probes 7 are embedded in the bonding glue 9.

Specifically, the temporary substrate 8 is used to provide a carrying platform for subsequent processes, and may be, but is not limited to, a silicon wafer, a glass sheet, and the like, and the thickness of the temporary substrate may be 400-500 μm, or other suitable thickness, in this embodiment, the temporary substrate 8 is a silicon wafer.

Specifically, the bonding glue 9 serves as an adhesion layer between the SOI substrate 1 and the temporary base 8 on one hand, and serves as a protection layer of the probe 7 on the other hand, so as to protect a tip structure of the probe 7 from being damaged in a subsequent processing process, and ensure the quality of a probe tip.

Referring to fig. 10, a cavity structure 10 penetrating the back substrate 101 in the vertical direction is formed, and a portion of the insulating layer 102 exposed by the cavity structure 10 is removed to expose the cantilever arm 6.

As an example, the back substrate 101 is etched by a deep silicon etching process (dry etching) until stopping on the insulating layer 102 to obtain the cavity structure 10 before the back side lithography of the SOI substrate 1, and then the portion of the insulating layer 102 exposed by the cavity structure 10 is removed by dry etching.

Referring to fig. 11 and 12, the temporary substrate 8 and the bonding paste 9 are removed, that is, the temporary substrate 8 and the SOI substrate 1 are debonded, so as to obtain a micro cantilever probe, wherein fig. 11 is a front cross-sectional view of the micro cantilever probe, and fig. 12 is a side cross-sectional view of the micro cantilever probe.

As an example, the SOI substrate 1 may be further subjected to a thermal oxidation process to form an oxide layer (not shown) on the surfaces of the probe 7 and the cantilever 6, so as to obtain a silicon-based micro-cantilever probe with a smooth surface.

As an example, the thickness of the oxide layer ranges from 0.1 to 0.2 micrometers, and in this embodiment, the thickness of the oxide layer is 0.1 micrometers as an example.

Thus, the micro cantilever arm probe is manufactured and has the advantages of smooth surface and high-quality needle point.

It should be noted that, in other embodiments, the manufacturing parameters of the above steps can be adjusted according to the performance requirements of the desired probe, and the protection scope of the present invention should not be limited excessively herein.

In conclusion, the micro cantilever arm probe and the manufacturing method thereof respectively define the graphical hard mask layer based on the probe point graph and the cantilever arm groove with partial etching depth through two times of photoetching and etching, and then etch the top layer silicon by taking the graphical hard mask layer as a mask, so that the cantilever arm and the probe can be synchronously obtained, and the problems of poor photoresist coating effect and poor photoresist thickness uniformity caused by graph height difference in the process flow of step-by-step etching probe structure and cantilever arm groove structure are avoided; the invention adopts a bonding adhesive temporary bonding process, when the cavity structure at the back of the probe is manufactured, the bonded temporary substrate is used as a bearing substrate, and the bonding adhesive can protect the probe tip structure from being damaged in the process; according to the invention, the probe, the cantilever beam arm and the back cavity structure are manufactured by adopting a dry etching process, and compared with a wet etching process, the steps of deposition and removal of a required special mask can be omitted, and the process is more stable and controllable. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A manufacturing method of a micro cantilever arm probe is characterized by comprising the following steps:

2. The method of making a microcantilever probe as claimed in claim 1, further comprising the steps of:

removing the patterned hard mask layer;

and removing the temporary substrate and the bonding glue.

3. The method of claim 2, wherein the method comprises: and forming the cavity structure by adopting dry etching.

4. The method of fabricating a cantilever probe according to claim 2, wherein: and removing the exposed part of the insulating layer by the cavity structure by adopting dry etching.

5. The method of fabricating a cantilever probe according to claim 2, wherein: the method further comprises the step of carrying out thermal oxidation treatment on the SOI substrate to form an oxide layer on the surfaces of the probe and the cantilever.

6. The method for manufacturing a microcantilever probe according to claim 1 or 2, wherein: and forming the cantilever arm groove by adopting dry etching, and etching the top layer silicon by adopting dry etching to synchronously obtain the cantilever arm and the probe.

7. The method for manufacturing a cantilever probe according to claim 1 or 2, wherein: the hard mask layer is made of at least one of aluminum and aluminum oxide.

8. The method for manufacturing a microcantilever probe according to claim 1 or 2, wherein: the side walls of the probe are inclined.

9. The method for manufacturing a microcantilever probe according to claim 1 or 2, wherein: the temporary substrate comprises one of a silicon wafer and a glass sheet.

10. A micro cantilever beam probe is characterized in that: the micro cantilever probe is manufactured by the manufacturing method of the micro cantilever probe according to any one of claims 1 to 9.