CN114088981B - Side wall scanning probe and processing method thereof - Google Patents

Abstract

The invention discloses a side wall scanning probe and a processing method thereof. The front end of the cantilever is in a triangular arrow shape, the front end of the triangular arrow is connected with the cantilever supporting part through the thin wall part, and the upper part of the cantilever supporting part is provided with a metal reflecting layer. The conical needle point is positioned at the lower part of the arrow-shaped front end of the cantilever, and is connected with the prismatic table through the slender prism, and the prismatic table is connected with the arrow-shaped front end of the cantilever. The magnetic particle ball is positioned at the upper part of the arrow-shaped front end; the invention also provides a processing method of the conical needle tip and the silicon-based arrow type cantilever probe. The arrow type cantilever probe is manufactured by adopting the micro-nano processing technology, the arrow type cantilever is more accurate and convenient to observe and position, the middle thin-wall connecting part is matched with the deflection control of the coil magnetic field on the magnetic particle ball, the arrow type front end is allowed to deflect at a certain angle, and therefore the appearance imaging of the side wall of the sample is realized.

Description

A sidewall scanning probe and its processing method

technical field

The invention relates to the technical field of micro-nano operation, in particular to a sidewall scanning probe and a processing method thereof.

Background technique

Over the past few decades, atomic force microscopy (AFM) has become one of the most important measurement and characterization instruments in various disciplines such as life science, biology, material science, semiconductor industry, micro-nano technology, etc. Complex surface characterization is essential in modern semiconductor and MEMS devices, such as characterizing the sidewall roughness of nanostructures in photonic devices is a key challenge and plays an important role in optimizing the efficiency of nano-optical devices such as waveguides .

Traditional AFM scanning technology can only collect two-dimensional plane height maps, without the ability to measure vertically. At the same time, the design of the existing AFM cantilever probe cannot touch the surface with an inclination angle larger than the corner of the needle tip, and lacks the ability to scan the side wall. In response to the above-mentioned difficulties, Florian Krohs et al. used a focused ion beam (Focused ion beam, FIB) to process an AFM probe with a lateral tip combined with a specific sidewall scanning mode to complete scanning imaging of the sidewall morphology (FKrohs, Haenssler O C, Bartenwerfer M, et al. Atomic force microscopy for high resolution sidewall scans [C] International Conference on Manipulation. IEEE, 2015).

However, the existing sidewall scanning probes are mainly modified on traditional AFM probes by focused ion beams, and significant modifications to standard AFM equipment and scanning modes are required. On the one hand, the inherent seriality of the FIB process is not conducive to the mass production of probes, and on the other hand, a large number of modifications to the standard AFM equipment also make it difficult to promote the scanning scheme.

Contents of the invention

The present invention is aimed at the core component of the atomic force microscope (Atomic Force Microscopy, AFM) - the side wall scanning probe, adopts micro-nano processing technology to make the side wall scanning probe, and the arrow-shaped front end makes the tracking and positioning more accurate and convenient during scanning , the thin-walled connection part in the middle of the cantilever allows the arrow-type front end to achieve a certain angle of deflection, and the deflection control of the magnetic particle ball by the coil magnetic field is used to achieve high-precision sidewall scanning imaging. The suspended tapered needle tip can effectively protect the sample when the needle tip is deflected. , so as to realize high-resolution topographical imaging of the sidewall of the sample, and provide a powerful means with high resolution and high integration for the complex surface characterization of micro-nano structures.

The present invention is realized through at least one of the following technical solutions.

A side wall scanning probe comprises a cantilever and a front end connected to the cantilever; the upper surface of the cantilever is provided with a metal reflection layer; the upper surface of the front end is provided with magnetic particles, and the lower surface of the front end is provided with a needle point structure.

Preferably, the needle point structure is a tapered needle point structure, the tapered needle point structure includes a tapered needle point and a prism connected to the front end, and the tapered needle point is connected to the prism through a connecting piece.

Preferably, the shape of the tapered needle tip is a cone or a pyramid, the length of which is 1-3 μm, and the connecting piece connected to the prism is a prism, and the length of the prism is 5-10 μm.

Preferably, the side of the cantilever is connected to the side of the front end through a connecting piece.

Preferably, the connecting piece connected to the front end is a thin rectangular parallelepiped with a width of 0.5-1 μm and a length of 8-15 μm.

Preferably, the cantilever is in the shape of a flat cuboid, the cantilever has a length of 150-200 μm, a width of 30-60 μm, and a thickness of 1-3 μm.

Preferably, the front end is in the shape of an arrow, the length of the tip of the arrow is 10-20 μm, and the tip of the arrow is an equilateral triangle in plan view.

Preferably, the upper surface of the front end part is provided with grooves for positioning magnetic balls.

Preferably, the material of the cantilever is Si ₃ N ₄ material; the cantilever, the front end, and the tip structure are integrally formed;

The material of the metal reflective layer is one or more of Au, Cr, Ni, Ag, Al, Pt and Pd.

A method for processing a sidewall scanning probe comprises the following steps:

1) Cleaning the silicon substrate, making a cantilever and front end bottom surface mask on the silicon substrate, and transferring the cantilever and front end graphics by etching;

2) On the front-end pattern, use photolithography to make a needle-tip structure mask, and use a deep etching method to transfer the needle-tip structure pattern;

3) On the needle tip structure pattern in step 2), use photolithography to make the inner protective layer;

4) Using the inner protective layer as a mask, the tapered needle tip is made by corrosion;

5) Using partial wet oxidation to make polysilicon oxide layer as the bottom material of the cantilever;

6) Pattern the cantilever pattern by photolithography and etch to complete the pattern transfer, and use the plasma enhanced chemical vapor deposition method to form the Si ₃ N ₄ layer of the cantilever main body;

7) Patterning the metal reflective layer area by photolithography, and evaporating the Cr/Au reflective layer by electron beam evaporation to prepare the metal reflective layer;

8) Using photolithography to pattern the magnetic particle area, electron beam evaporation of magnetic material, and then performing rapid thermal annealing on the magnetic material to form magnetic particle balls;

9) Etching the silicon substrate to complete the release of the sidewall scanning probes to obtain the sidewall scanning probes.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The sidewall scanning probe of the present invention performs pattern transfer on ordinary silicon wafers, is compatible with existing processes, does not require other processes such as FIB, effectively reduces production costs and process complexity, and improves probe production efficiency and process reliability sex.

(2) The arrow-type front end of the scanning probe on the side wall of the present invention has a small shielding area, making the field of view tracking and positioning more accurate and convenient.

(3) The design of the cantilever thin-wall connection and the magnetic ball of the sidewall scanning probe of the present invention enables the arrow-shaped front end to realize sidewall scanning imaging, and the suspended tapered needle tip can effectively protect the sample to be tested when the needle tip is deflected.

Description of drawings

1 is a schematic structural view of a sidewall scanning probe according to an embodiment of the present invention;

FIG. 2A is a schematic diagram of etching a thin silicon substrate according to an embodiment of the present invention;

2B is a schematic diagram of a photolithography patterned overhang prism according to an embodiment of the present invention;

2C is a schematic diagram of the process of making a tapered needle tip according to an embodiment of the present invention;

Figure 2D is a schematic diagram of a tapered needle tip corroded by an embodiment of the present invention;

2E is a schematic diagram of a polysilicon oxide layer according to an embodiment of the present invention;

FIG. 2F is a schematic diagram of the transfer of the pattern of the sidewall scanning probe according to the embodiment of the present invention;

Fig. 2G is a schematic diagram of the structure of magnetic spheres prepared in the embodiment of the present invention;

FIG. 2H is a schematic structural diagram of a sidewall scanning probe prepared in an embodiment of the present invention;

FIG. 3 is a schematic diagram of a scanning mode of a sidewall scanning probe according to an embodiment of the present invention.

Detailed ways

For more concise and clear expression, in the following description, well-known functions and structures are not described in detail, so as to highlight the advantages and features of the present invention. In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

As shown in FIG. 1 , this embodiment provides a sidewall scanning probe, which includes a cantilever 1 , a magnetic particle 4 and a tapered tip 7 .

The front end 5 of the cantilever 1 is in the shape of a triangular arrow, and the arrow-shaped front end is connected to the cantilever 1 through a thin-walled part 3 (connector), and the upper surface of the cantilever 1 is provided with a metal reflective layer 2 . The magnetic particle ball 4 is spherical and is arranged on the upper part of the arrow-shaped front end 5 . The tapered needle point 7 is arranged at the lower part of the arrow-shaped front end 5 , and the tapered needle point is connected to the prism through the elongated prism 3 , and the prism is connected to the arrow-shaped front end 5 .

In this embodiment, the material of the cantilever 1 is Si ₃ N ₄ material.

In this embodiment, the cantilever is in the shape of a flat cuboid, the length of the cantilever is 200 μm, the width is 35 μm, and the thickness is 2 μm. The thin-walled portion of the probe is in the shape of a cuboid with a width of 0.5 μm and a length of 10 μm. The length of the arrow-shaped tip is 15 μm, and it is an equilateral triangle when viewed from above.

In this embodiment, the material of the magnetic balls is NdFeB, and the diameter of NdFeB particles is 4 μm.

In this embodiment, the shape of the tapered tip is a pyramid with a length of 2 μm, and the length of the connected prism is 7 μm.

In this embodiment, the material of the metal reflective layer 3 is one or more of Au, Cr, Ni, Ag, Al, Pt, and Pd.

Example 2

This embodiment provides a fine processing method for a sidewall scanning probe. As shown in Figure 2A-2H, the steps are as follows:

First, clean the thin silicon substrate 100 with a crystal orientation of <100>, dry it with nitrogen gas, pattern a 5 μm×5 μm square on the photoresist 101 by photolithography, and use the photoresist 101 as a mask to use inductively coupled plasma ( Inductivelycoupled plasma (ICP) equipment etches the thin silicon substrate 100 and transfers the tip pattern to the silicon substrate, as shown in Figure 2A;

The above samples were immersed in 80°C degumming solution for 20 minutes (minutes), cleaned with acetone for 10 minutes and isopropanol for 30 seconds (seconds), washed with a large amount of deionized water, blown dry with nitrogen to remove photoresist 101, and then spin-coated 8 by using thick glue technology. - 12 μm photoresist 101, and use photolithography to pattern the middle prism of the overhanging needle tip, use the photoresist 101 as a mask to transfer the prism pattern to the silicon substrate 100 by ICP, as shown in Figure 2B;

The above samples were immersed in 85°C degumming solution for 30 minutes (minutes), cleaned with acetone and ultrasonically for 15 minutes, and isopropanol for 1 minute. After cleaning with a large amount of deionized water, blow dry with nitrogen to remove the photoresist 101. Use photolithography to pattern the side wall protection. film, as shown in FIG. 2C ; then use the photoresist 101 as a mask, and use a KOH solution with a mass fraction of 30% to etch the silicon base 100 at 70° C. to complete the transfer of the tapered needle tip. Figure 2D;

The photoresist 101 was removed by a stripping process, and the sample was wet-oxidized in an environment of 950° C. for 15 minutes to perform partial oxidation. Generate a polysilicon oxide layer 102 of about 100 nm, as shown in Figure 2E;

Subsequently, the arrow-shaped sidewall scanning probe is patterned on the silicon substrate 100 by photolithography, and a 2 μm cantilever main body Si ₃ N ₄ layer 103 is deposited by plasma enhanced chemical vapor deposition (PECVD), Remove the photoresist and the Si ₃ N ₄ layer on the photoresist by using the stripping process, and complete the transfer of the sidewall scanning probe pattern, as shown in Figure 2F;

The area where the metal reflective layer 104 is located is patterned on the Si ₃ N ₄ layer 103 of the cantilever main body by photolithography, and the Cr/Au reflective layer is deposited by electron beam evaporation with a thickness of 5nm/50nm. The excess metal and photoresist are stripped off by using a deglue process to produce a metal reflective layer. Photolithographic patterning of the magnetic ball area, electron beam evaporation (Electron Beam Evaporation, EB) evaporation of Au/NdFeB Au layer, the thickness is 10nm/3μm/10nm, and the photoresist and residual metal layer are removed by the degumming process . Then the sample was subjected to rapid thermal annealing (Rapid Thermal Annealing, RTA) to complete the fabrication of magnetic particles, as shown in Figure 2G;

The sample was placed in a buffered oxide etch solution (Buffered Oxide Etch, BOE) solution to remove the polysilicon oxide layer 102 formed on the surface of the silicon base to facilitate the release operation below, and finally the sample was etched at 70° C. for 5 h with a mass fraction of 30% KOH solution. The release of the final probe sample is completed, that is, the sidewall scanning probe is produced, as shown in Figure 2H;

Example 3

It is basically the same as Embodiment 2, except that this embodiment also provides a scanning method of a sidewall scanning probe.

The interaction between the tip and the sample 16 is indirectly measured using a laser beam generator 11 , a mirror 12 and a four-quadrant photodiode 13 to detect the deflection of the sidewall scanning probe 14 . The deflection signal of the cantilever beam is used as the feedback of the closed-loop controller, and the applied force or amplitude of the cantilever beam is kept constant by adjusting the sampling height. Electromagnetic coil 15 is used to control the deflection angle of the probe. As shown in Figure 3;

After the installation of the sidewall scanning probe 14 is completed, laser and parameter calibration are performed on the probe and the device, and then the probe is moved to the area of the sample 16 to be tested, and the probe is generated at the resonance frequency of the sidewall scanning probe using a lock-in amplifier. Torsional resonance allows the oscillating probe tip to tap vertically and horizontally on the sample surface, while tap amplitude measurements are used to control X and Z scan motion.

When scanning begins, the sidewall scanning probe 14 approaches the vertical sidewall of the sample 16 while scanning parallel to the horizontal plane (along the X axis). At this time, the oscillation amplitude of the tip of the probe 14 is adjusted by the Z-axis scanning controller. When the distance between the position of the tip of the probe 14 and the side wall of the sample 16 is equal to the amplitude of the horizontal oscillation of the tip, the tip starts to strike the vertical wall of the sample 16 . As the distance between the needle tip and the side wall of the sample becomes smaller, the amplitude of the horizontal oscillation of the probe tip also begins to decrease. When it decreases to the set threshold, the Z-axis scanning controller moves the probe upward, and the electromagnetic coil 15 controls the probe at the same time. 14 deflection angle, restore the amplitude to the set point, and complete the scan of the side wall.

The preferred embodiments of the invention disclosed above are only to help illustrate the invention. The preferred embodiments are not exhaustive in all detail, nor are the inventions limited to specific embodiments described. Obviously, many modifications and variations can be made based on the contents of this specification. This description selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The invention is to be limited only by the claims, along with their full scope and equivalents.

Claims (3)

1. A sidewall scanning probe, characterized in that: comprising a cantilever (1) and a front end (5) connected to the cantilever (1); the upper surface of the cantilever (1) is provided with a metal reflective layer (2); The upper surface of the front end (5) is provided with a magnetic particle ball (4), and the lower surface of the front end (5) is provided with a needle point structure (7); The needle point structure (7) is a tapered needle point structure, the tapered needle point structure includes a tapered needle point and a prism connected to the front end (5), and the tapered needle point is connected to the prism through a connecting piece; The length of the tapered needle tip is 1-3µm, and the connecting piece connected to the prism is a prism; the length of the prism is 5-10µm; the front end (5) is in the shape of an arrowhead, and the length of the tip of the arrow is 10-20µm, and the tip of the arrow is viewed from above It is an equilateral triangle; the cantilever (1), the front end (5), and the needle point structure (7) are integrally formed; The side of the cantilever (1) is connected to the side of the front end (5) through a connecting piece; The connecting piece connected to the front end (5) is a thin-walled cuboid (3), with a width of 0.5-1 µm and a length of 8-15 µm; The cantilever (1) is in the shape of a flat cuboid, the cantilever has a length of 150-200 µm, a width of 30-60 µm, and a thickness of 1-3 µm; The upper surface of the front end (5) is provided with a groove for positioning the magnetic ball (4); The magnetic particle balls (4) are formed by performing rapid thermal annealing on magnetic materials. 2. A sidewall scanning probe according to claim 1, characterized in that: the material of the cantilever (1) is Si ₃ N ₄ material; The material of the metal reflective layer (2) is one or more of Au, Cr, Ni, Ag, Al, Pt and Pd. 3. The processing method of a sidewall scanning probe according to claim 1, characterized in that: comprising the following steps: 1) Cleaning the silicon substrate, making a bottom mask of the cantilever (1) and the front end (5) on the silicon substrate, and transferring the patterns of the cantilever (1) and the front end (5) by etching; 2) On the pattern of the front end (5), use photolithography to make a mask of the needle point structure (7), and use a deep etching method to transfer the pattern of the needle point structure (7); 3) On the pattern of the needle tip structure (7) in step 2), use photolithography to make the inner protective layer; 4) Using the inner protective layer as a mask, the tapered needle tip is made by corrosion; 5) Using local wet oxidation to make polysilicon oxide layer as the bottom material of the cantilever; 6) Pattern the cantilever pattern by photolithography and etch to complete the pattern transfer, and use the plasma enhanced chemical vapor deposition method to form the Si ₃ N ₄ layer of the cantilever main body; 7) Patterning the metal reflective layer area by photolithography, and evaporating the Cr/Au reflective layer by electron beam evaporation to obtain the metal reflective layer (2); 8) Using photolithography to pattern the magnetic particle area, electron beam evaporation of magnetic material, and then performing rapid thermal annealing on the magnetic material to form magnetic particle balls (4); 9) Etching the silicon substrate to complete the release of the sidewall scanning probes to obtain the sidewall scanning probes.

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