CN103803484A - Silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching - Google Patents

Abstract

A silicon nitride film/silicon micro-nano-fabrication method based on friction-induced selective etching. The silicon oxide film/silicon is fixed on the sample stage, and the normal load not lower than the critical load is applied to the probe, and the probe is scored along the set track; after marking, it is etched in HF solution After a certain period of time, the silicon substrate in the scribed area is exposed, and then etched with a mixed solution of KOH solution and isopropanol to process the desired micro-nano structure. The method changes the etching characteristics of the material through friction-induced scribing, thereby forming a selective etching of a specific solution. The method has no damage to the silicon substrate, and the obtained micro-nano structure has more reliable service ability; it can process deeper/higher micro-nano structures, improve the aspect ratio/height-width ratio of the micro-nano structures, and have a wide application range; and The processing is simple and the processing cost is low.

Description

Silicon nitride film/silicon micro-nanofabrication method based on friction-induced selective etching

technical field

The invention relates to a micro-nano processing method for the surface of single crystal silicon.

Background technique

Nanotechnology has created a new era of human life in the 21st century, and nanomanufacturing is the basis for supporting the application of nanotechnology. my country is limited by the backwardness of nano-manufacturing technology, and the practical application of micro/nano electromechanical systems (MEMS/NEMS) is lagging behind. While improving the original processing technology, it is imminent to seek new nano-processing technology. Therefore, it is of great significance to carry out basic and applied research on nanofabrication, not only for the development of MEMS/NEMS, but also for my country to maintain a favorable position in the new round of technological competition.

Single crystal silicon is widely used in MEMS/NEMS because of its excellent mechanical and physical properties. According to different principles, the micro-nano processing methods currently applied to the surface of single crystal silicon mainly include photolithography technology, nanoimprint technology and so on. With the continuous improvement of processing precision, the cost of photolithography processing is getting higher and higher, and the limitations are getting bigger and bigger. For example, the minimum line width processed by deep ultraviolet lithography technology can reach 24nm, but deep ultraviolet light is easily absorbed by air, and this technology is not yet mature; in addition, nanoimprint technology is currently facing many technical bottlenecks and challenges, such as mold release The process has a serious impact on the embossing effect and the life of the mold. In addition, the embossing process is easy to cause damage to the base material.

In recent years, due to the advantages of high precision and multi-function, scanning probe technology is suitable for the field of micro-nano processing. Common scanning probe processing methods based on single crystal silicon generally rely on anodic oxidation or friction to perform local "masks". The control factors of anodic oxidation are complicated and the requirements for the environment are high, which greatly reduces the controllability of processing; However, the friction-induced "mask" strongly depends on the tribochemical reaction or structural deformation. The friction-induced "mask" is not dense enough, and its resistance to chemical etching is limited, which limits the height/depth of the processed micro-nano structure.

Contents of the invention

The object of the present invention is to provide a silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, which has no damage to the silicon substrate, and the obtained micro-nano structure has more reliable serviceability; The deeper/higher micro-nano structure improves the aspect ratio of the micro-nano structure and has a wide application range; and its processing is simple and the processing cost is low.

In order to realize the purpose of the invention, the technical solution adopted by the present invention is a silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, and its specific operation steps are as follows:

A. Install the probe with a spherical tip on a scanning probe microscope or multi-point contact micro-nano processing equipment, then fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe. The needle is scored on the surface of the silicon nitride film/single crystal silicon substrate according to the set normal load and predetermined trajectory;

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 1-5% for 30-50 minutes;

C. Add isopropanol to the KOH solution with a mass concentration of 10-25% to obtain a mixed solution. When adding, the volume ratio of isopropanol to KOH solution is 1:4-6; SiO thin film/single crystal silicon substrate is etched in the mixed solution for 2-60 minutes;

D. Place the silicon nitride film/single crystal silicon substrate etched in step C again in 1-5% HF solution and etch for 10-20 minutes.

The process and mechanism of the inventive method are:

The silicon nitride film deposited on the surface of single crystal silicon produced microcracks under the action of residual stress during the marking process of the probe, and in the subsequent HF solution etching, the microcracks in the silicon nitride film in the marking area promoted Diffusion of the etchant, which therefore etch at a rate greater than that of the unscribed areas, is preferentially selectively removed, thereby exposing the silicon substrate. The silicon in the scribed area is rapidly etched by the subsequent KOH solution, while the unscribed area still having a stable silicon nitride film layer is not etched. Under the excellent masking ability of the silicon nitride film, a deeper micro-nano structure can be processed, and finally the residual silicon nitride mask is removed by the HF solution.

Compared with prior art, the beneficial effect of the present invention is:

1. The probe is scratched on the silicon nitride film without damage to the silicon substrate, so the final micro-nano structure has no damage and has reliable service capability.

2. The processing can be carried out under normal temperature and normal pressure environment, no special environment such as vacuum and constant temperature is required, the processing is simple and the processing cost is low. The KOH solution and HF solution in the etching process are readily available.

3. The structure of the silicon nitride film is dense, and the corrosion resistance of the KOH solution is strong. It is difficult for the KOH solution to corrode the silicon nitride mask for a long time. Therefore, under the action of the mask, the KOH solution can remove the mask of the single crystal silicon area. A deeper micro-nano concave structure is etched.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is an atomic force microscope image of the groove structure on the surface of a single crystal silicon processed in Example 1.

Fig. 2 is an atomic force microscope image of the groove structure on the surface of the single crystal silicon processed in Example 2.

Fig. 3 is an atomic force microscope image of the groove structure on the surface of single crystal silicon obtained in the third embodiment.

Fig. 4 is an atomic force microscope image of the groove structure on the surface of the single crystal silicon obtained in the fourth embodiment.

Fig. 5a is an atomic force microscope image of the trench structure on the surface of single crystal silicon obtained in Example 5.

Fig. 5b is a cross-sectional profile diagram of the groove structure on the surface of the single crystal silicon processed in the fifth embodiment.

Fig. 6a is an atomic force microscope image of the groove structure on the surface of the single crystal silicon processed in Example 6.

Fig. 6b is a cross-sectional profile diagram of the groove structure on the surface of the single crystal silicon processed in the sixth embodiment.

Fig. 7a is an atomic force microscope image of the groove structure on the surface of the single crystal silicon processed in Example 7.

Fig. 7b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in the seventh embodiment.

Fig. 8a is an atomic force microscope image of the groove structure on the surface of single crystal silicon obtained in the eighth embodiment.

Fig. 8b is a cross-sectional profile diagram along the groove axis of the monocrystalline silicon processed in the eighth embodiment.

Fig. 9a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in Example 9.

Fig. 9b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in the ninth embodiment.

Fig. 10 is a scanning electron microscope image of a part of the large-area line array structure on the surface of single crystal silicon processed in Example 10.

Detailed ways

Embodiment one

A silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, the specific operation steps are as follows:

A. Install the probe with a spherical tip on the scanning probe microscope, fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe according to the set normal load and the predetermined trajectory are scored on the surface of the silicon nitride film/single crystal silicon substrate; the radius of curvature of the tip of the diamond ball probe in this example is 1.5 μm, the set normal load F is 3mN, and the predetermined trajectory is a straight line.

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 2% for 30 minutes;

C, isopropanol is joined in the KOH solution that mass concentration is 20% to obtain mixed solution, the volume ratio of isopropanol and KOH solution is 1:5 when adding; The single crystal silicon substrate is etched in the mixed solution for 30 minutes;

D. Place the silicon nitride film/monocrystalline silicon substrate etched in step C again in 2% HF solution and etch for 10 minutes.

Fig. 1 is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Figure 1 shows that in this example, a groove with a width of about 0.5 μm and a depth of about 200 nm has been processed on the surface of single crystal silicon.

Embodiment two

The operation of this example is basically the same as that of the first example, except that the normal load is changed to 4mN.

Fig. 2 is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Figure 2 shows that in this example, a groove with a width of about 0.6 μm and a depth of about 300 nm was processed on the surface of single crystal silicon.

Embodiment Three

The operation of this example is basically the same as that of the first example, except that the normal load is changed to 4.5mN.

Fig. 3 is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Figure 3 shows that in this example, a trench with a width of about 0.75 μm and a depth of about 360 nm was processed on the surface of single crystal silicon.

Embodiment four

The operation of this example is basically the same as that of the first example, except that the normal load is changed to 5mN.

Fig. 4 is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Figure 4 shows that in this example, a groove with a width of about 0.95 μm and a depth of about 400 nm was processed on the surface of single crystal silicon.

Examples 1 to 4 show that: the greater the load, the deeper the groove structure finally obtained.

Embodiment five

A silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, the specific operation steps are as follows:

A. Install the probe with a spherical tip on the scanning probe microscope, fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe according to the set normal load and the predetermined trajectory are scored on the surface of the silicon nitride film/single crystal silicon substrate; the radius of curvature of the tip of the diamond ball probe in this example is R=1.5μm, the set normal load F is 4mN, and the predetermined trajectory is a straight line.

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 1% for 40 minutes;

C, isopropanol is joined in the KOH solution that mass concentration is 10% to obtain mixed solution, the volume ratio of isopropanol and KOH solution is 1:4 when adding; The single crystal silicon substrate is etched in the mixed solution for 5 minutes;

D. Place the silicon nitride film/monocrystalline silicon substrate etched in step C again in 1% HF solution and etch for 15 minutes.

Fig. 5a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example, and Fig. 5b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in this example. Figure 5a and Figure 5b show that in this example, a groove with a width of about 0.6 μm and a depth of about 100 nm was processed on the surface of single crystal silicon.

Embodiment six

The operation of this example is basically the same as that of Example 5, except that the etching time in step C is changed to 15 minutes.

Fig. 5a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example, and Fig. 5b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in this example. Figure 5a and Figure 5b show that in this example, a groove with a width of about 0.6 μm and a depth of about 150 nm was processed on the surface of single crystal silicon.

Embodiment seven

The operation of this example is basically the same as that of Example 5, except that the etching time in step C is changed to 30 minutes.

Fig. 5a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example, and Fig. 5b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in this example. Figure 5a and Figure 5b show that in this example, a groove with a width of about 0.6 μm and a depth of about 240 nm was processed on the surface of single crystal silicon.

Examples five to seven show that: the longer the etching time of the mixed solution of KOH and isopropanol, the deeper the processed groove structure.

Embodiment Eight

A silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, the specific operation steps are as follows:

A. Install the probe with a spherical tip on the scanning probe microscope, fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe according to the set normal load and the predetermined trajectory are scored on the surface of the silicon nitride film/single crystal silicon substrate; the radius of curvature of the tip of the diamond ball probe in this example is R=1.5μm, and the set normal load F is linearly changed from 3mN to 6mN With variable load, the predetermined trajectory is a straight line.

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 5% for 30 minutes;

C, isopropanol is joined in the KOH solution that mass concentration is 25% to obtain mixed solution, the volume ratio of isopropanol and KOH solution is 1:6 when adding; The single crystal silicon substrate is etched in the mixed solution for 35 minutes;

D. Place the silicon nitride film/single crystal silicon substrate etched in step C again in 5% HF solution and etch for 20 minutes.

Fig. 8a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Fig. 8b is a profile diagram of the section along the groove axis of the single crystal silicon processed in this example. Fig. 8a and Fig. 8b show that in this example, grooves continuously changing in width from about 0.5 μm to 1 μm and depth from about 120 nm to 380 nm are processed on the surface of single crystal silicon along the direction of increasing load.

Embodiment nine

A silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, the specific operation steps are as follows:

A. Install the probe with a spherical tip on the scanning probe microscope, fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe according to the set normal load and the predetermined trajectory are scored on the surface of the silicon nitride film/single crystal silicon substrate; the normal load F set in this example is 3.5mN, and the predetermined trajectory is a line array composed of multiple parallel straight lines.

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 3% for 50 minutes;

C, isopropanol is joined in the KOH solution that mass concentration is 20% to obtain mixed solution, the volume ratio of isopropanol and KOH solution is 1:5 when adding; The single crystal silicon substrate is etched in the mixed solution for 30 minutes;

D. Place the silicon nitride film/single crystal silicon substrate etched in step C again in 4% HF solution and etch for 13 minutes.

Fig. 9a is an atomic force microscope image of the groove structure on the surface of single crystal silicon processed in this example. Fig. 9b is a cross-sectional profile diagram of the groove structure on the surface of single crystal silicon processed in this example. Figures 9a and 9b show that in this example, a line array structure consisting of multiple grooves with a width of about 0.55 μm and a depth of about 300 nm was processed on the surface of single crystal silicon.

Embodiment ten

A silicon nitride film/silicon micro-nano processing method based on friction-induced selective etching, the specific operation steps are as follows:

A. Install the probe with a spherical tip on the multi-point contact micro-nano processing equipment, then fix the cleaned silicon nitride film/single crystal silicon substrate on the sample stage, start the equipment, and control the probe according to the set The normal load and the predetermined trajectory are scored on the surface of the silicon nitride film/single crystal silicon substrate; the radius of curvature of the tip of the diamond ball probe in this example is R=5μm, and the set normal load F is 50mN. The predetermined trajectory is a line array in which multiple straight lines are drawn simultaneously within the range of 5mm×5mm; the multi-point contact micro-nano processing equipment used is "large-area friction-induced micron-scale processing device under multi-point contact mode" disclosed in ZL201220331439.9 patent .

B. Etching the scribed silicon nitride film/monocrystalline silicon substrate in an HF solution with a mass concentration of 2% for 30 minutes;

C, isopropanol is joined in the KOH solution that mass concentration is 20% to obtain mixed solution, the volume ratio of isopropanol and KOH solution is 1:5 when adding; The single crystal silicon substrate is etched in the mixed solution for 60 minutes;

D. Place the silicon nitride film/monocrystalline silicon substrate etched in step C again in 2% HF solution and etch for 10 minutes.

FIG. 10 is a scanning electron microscope image of a part of the large-area line array structure on the surface of single crystal silicon processed in this example. Figure 10 shows that in this example, a large-area linear array structure consisting of multiple grooves with a width of about 1.8 μm and a depth of about 0.7 μm was processed on the surface of single crystal silicon. The aspect ratio of the trenches in the array is close to 0.4.

The above examples show that by controlling parameters such as scribe trajectory, scribe range, scribe load, and etching time, various micro-nano structures can be processed on the surface of single crystal silicon, such as structures with constant depth, slope structures, and line arrays. structure, large-area textured structure, etc. Experiments have proved that the scribe load and etching time are positively correlated with the processing depth. In actual processing applications, the micro-nano groove structure with the required depth can be obtained by reasonably controlling the scribe load and etching time.

Claims (1)

1. silicon nitride film/silicon micro-nano the processing method based on friction induction selective etch, its concrete operation step is followed successively by:

A, be that spherical probe is arranged on scanning probe microscopy or the micro-nano process equipment of Multi-contact by tip, again silicon nitride film/the monocrystal silicon substrate of cleaning is fixed on sample stage, starting device, controls probe and delineates on silicon nitride film/monocrystal silicon substrate surface according to normal load and the desired trajectory set;

B, by delineation after silicon nitride film/monocrystal silicon substrate be placed in the HF solution etching 30-50 minute that mass concentration is 1-5%;

C, isopropyl alcohol is joined in the KOH solution that mass concentration is 10-25% to obtain to mixed solution, the volume ratio that adds fashionable isopropyl alcohol and KOH solution is 1:4-6; Silicon nitride film/the monocrystal silicon substrate again B being walked after etching is placed in mixed solution etching 2-60 minute;

D, C is walked to silicon nitride film/monocrystal silicon substrate after etching and is again placed in the HF solution etching 10-20 minute of 1-5%.

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