阅读说明：本技术 电子束或离子束在绝缘材料表面成像或微纳加工的方法 (Method for imaging or micro-nano processing of electron beam or ion beam on surface of insulating material ) 是由 王伟 庞陈雷 佘玄 杨青 吴兰 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种电子束或离子束在绝缘材料表面成像或微纳加工的方法,包括以下步骤：1)准备一片超薄导电盖板；2)制备超薄微窗导电盖板；3)对于待刻蚀区域的位置无定点要求的加工需求,将超薄微窗导电盖板覆盖于绝缘衬底表面并固定；对于待刻蚀区域的位置有定点要求的加工需求,使超薄微窗导电盖板的通孔精准覆盖待刻蚀区域,然后固定；4)放置于样品台表面,固定；5)接地处理；6)将样品台放置于真空腔中；7)将电子束或聚焦离子束穿过通孔聚焦于绝缘材料表面进行成像或者刻蚀。本发明流程简单,对样品不存在任何影响,目标覆盖区域位置可随意调整,并且超薄微窗导电盖板可循环使用,是一种高效、便捷、经济实用的方案。(The invention discloses a method for imaging or micro-nano processing an electron beam or an ion beam on the surface of an insulating material, which comprises the following steps: 1) preparing an ultrathin conductive cover plate; 2) preparing an ultrathin micro-window conductive cover plate; 3) covering the surface of an insulating substrate with an ultrathin micro-window conductive cover plate and fixing the ultrathin micro-window conductive cover plate for processing requirements without fixed point requirements on the position of a region to be etched; the processing requirement of fixed point requirement is met for the position of the area to be etched, so that the through hole of the ultrathin micro-window conductive cover plate accurately covers the area to be etched and is fixed; 4) placing on the surface of a sample table, and fixing; 5) grounding treatment; 6) placing the sample stage in a vacuum chamber; 7) and focusing the electron beam or the focused ion beam on the surface of the insulating material through the through hole for imaging or etching. The method has the advantages of simple flow, no influence on samples, random adjustment of the position of a target coverage area, and recycling of the ultrathin micro-window conductive cover plate, and is an efficient, convenient, economic and practical scheme.)

1. A method for applying electron beams or ion beams to the surface of an insulating substrate for imaging or micro-nano processing is characterized by comprising the following steps:

1) preparing an ultrathin conductive cover plate;

2) preparing an ultrathin micro-window conductive cover plate: preparing a micro through hole on the surface of the ultrathin conductive cover plate by using a laser drilling or chemical corrosion method;

3) covering the surface of an insulating substrate with an ultrathin micro-window conductive cover plate and fixing the ultrathin micro-window conductive cover plate by using a conductive adhesive tape for processing the position of the area to be etched without a fixed point requirement; aiming at the processing requirement that the position of the area to be etched has a fixed point requirement, carrying out an alignment operation flow under an optical microscope to ensure that the through hole of the ultrathin micro-window conductive cover plate accurately covers the area to be etched appointed by the surface of the insulating substrate, and then fixing the area to be etched on the surface of the insulating substrate by using a conductive adhesive tape;

4) placing the insulating substrate fixed with the ultrathin micro-window conductive cover plate on the surface of a sample table of equipment containing electron beams or ion beams, and fixing the insulating substrate with a conductive adhesive tape;

5) connecting the edge of the ultrathin micro-window conductive cover plate with a sample table, and carrying out grounding treatment;

6) placing the sample stage in a vacuum chamber of the apparatus;

7) and after parameters are set, an electron beam or a focused ion beam passes through the through hole of the ultrathin micro-window conductive cover plate and is focused on the surface of the insulating material for imaging or etching.

2. The method as claimed in claim 1, wherein the ultra-thin conductive cover plate of step 1) is a semiconductor plate or a metal plate which is not easy to deform and has conductive properties.

3. The method as claimed in claim 2, wherein the ultra-thin conductive cover plate is a silicon plate or a copper plate with a thickness of 100 and 500 μm.

4. The method as claimed in claim 1, wherein the through hole of the ultra-thin micro-window conductive cover plate in step 2) is cylindrical and has a diameter of 300-500 μm.

5. The method as claimed in claim 1, wherein the through hole of the ultra-thin micro-window conductive cover plate in step 2) is in a shape of a wide-mouthed horn as a whole, including a truncated cone shape and an inverted pyramid shape, the diameter of the bottom hole of the truncated cone through hole is 10-50 μm, and the diameter of the top hole is 300-500 μm.

6. The method according to claim 1, wherein the through holes of the conductive micro-through hole plate in the step 3) are aligned to cover the surface of the insulating substrate, and the method of preparing marks near the area to be etched of the insulating substrate and using a microscope is utilized.

Technical Field

The invention belongs to the field of micro-nano processing, and particularly relates to a method for imaging or micro-nano processing an electron beam or an ion beam on the surface of an insulating material.

Background

The focused ion beam processing (FIB) is an instrument which is widely used in the semiconductor industry field and the micro-nano research field. The principle is that ions are emitted by an ion source, the ions are focused into fine ion beams through an ion optical system (comprising an electrostatic lens, an electrostatic deflector, an aperture diaphragm and the like) and are incident on the surface of a solid target, atoms on the surface of the solid target can obtain the incident energy of the ion beams due to a transfer effect, and the surface atoms escape from the surface of the solid due to energy accumulation, so that the aim of sputtering and stripping is fulfilled. In the sputtering stripping etching process, charged particles such as secondary ions and secondary electrons are bombarded to leave the solid surface, including incident ions, a large number of charged particles exist on the surface of the sample, a small number of charged particles can be pumped out of the sample chamber by a multi-stage vacuum pump along with gas in the sample chamber, and are guided to leave an etching area based on the conductive characteristic of the block body. The machine is provided with a precise pattern generator, and the focused ion beam can carry out micro-nano pattern processing on the surface of the solid material through the control of the pattern generator. When the conductivity of the sample is poor or even the sample cannot conduct electricity, the incident charged particles stay in an etching area to cause local charge accumulation, a discharge phenomenon occurs when the charge is accumulated to a discharge threshold, and the accumulated charge and the discharge effect form an electromagnetic field which interferes the incident ion beam, so that negative effects are caused on precision etching, and a target micro-nano structure cannot be obtained. Therefore, the sample itself is required to have a certain conductive property. In practical application, the solution of applying FIB to the surface of an insulating material for micro-nano processing is to spray carbon, gold, platinum and other films on the surface of a sample through a scanning electron microscope (SEM coater), so as to solve the phenomenon of discharge of a non-conductive sample caused by surface charge accumulation in the characterization process of an electron microscope. However, the physical properties of the material determine the performance of the device based on the micro-nano structure, the performance of the device is affected by adding additional conductive films such as gold and carbon on the surface of the material, and the whole processing process is more complicated if the conductive film is removed by using methods such as chemical dissolution after etching. In addition, workers adopt a method of spraying electron flood while etching, and scan a processing area by using a large current of 200 nA to effectively neutralize the charge of the ion beam, so that a pattern consistent with a design scheme is obtained. The method of spraying the electronic flood flow puts higher requirements on the configuration of the machine, namely, the method puts more rigorous requirements on the research conditions of scientific researchers. At present, the micro-nano graph processing cannot be well realized by a focused ion beam technology on an insulating substrate without a conductive material, so that the application range of the focused ion beam technology is greatly limited, and great inconvenience is brought to the research and application of the related field of insulating materials.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a method for applying an electron beam or an ion beam to the surface of an insulating material for imaging or micro-nano processing in equipment containing the electron beam or the ion beam. According to the method, the ultrathin micro-window conductive cover plate covers the surface of the insulating material, so that charged particles generated when an electron beam or an ion beam bombards the surface of the insulating material can be effectively transferred, and the surface charge accumulation is reduced, thereby achieving the purposes of imaging, positioning and micro-nano processing the electron beam or the ion beam on the surface of the insulating material.

The equipment containing the electron beams or the ion beams can be equipment for imaging and micro-nano processing by utilizing the electron beams or the ion beams, such as a scanning electron microscope, a transmission electron microscope, an electron beam exposure machine, a focused ion beam micro-nano processing system and the like, and can also be other equipment containing the electron beams or the ion beams.

A method for applying electron beams or ion beams to the surface of an insulating substrate for imaging or micro-nano processing comprises the following steps:

1) preparing an ultrathin conductive cover plate;

2) preparing an ultrathin micro-window conductive cover plate: preparing a micro through hole on the surface of the ultrathin conductive cover plate by using a laser drilling or chemical corrosion method;

3) covering the surface of an insulating substrate with an ultrathin micro-window conductive cover plate and fixing the ultrathin micro-window conductive cover plate by using a conductive adhesive tape for processing the position of the area to be etched without a fixed point requirement; aiming at the processing requirement that the position of the area to be etched has a fixed point requirement, carrying out an alignment operation flow under an optical microscope to ensure that the through hole of the ultrathin micro-window conductive cover plate accurately covers the area to be etched appointed by the surface of the insulating substrate, and then fixing the area to be etched on the surface of the insulating substrate by using a conductive adhesive tape;

4) placing the insulating substrate fixed with the ultrathin micro-window conductive cover plate on the surface of a sample table of equipment containing electron beams or ion beams, and fixing the insulating substrate with a conductive adhesive tape;

5) connecting the edge of the ultrathin micro-window conductive cover plate with a sample table, and carrying out grounding treatment;

6) placing the sample stage in a vacuum chamber of the apparatus;

7) and after parameters are set, an electron beam or a focused ion beam passes through the through hole of the ultrathin micro-window conductive cover plate and is focused on the surface of the insulating material for imaging or etching.

The ultrathin conductive cover plate in the step 1) is a semiconductor plate or a metal plate which is not easy to deform and has a conductive characteristic.

The ultrathin conductive cover plate is a silicon plate or a copper plate, and the thickness of the ultrathin conductive cover plate is 100-500 mu m.

And 2) the through hole of the ultrathin micro-window conductive cover plate is cylindrical and has the diameter of 300-500 mu m.

And 2) the through hole of the ultrathin micro-window conductive cover plate is in a structure of a wide-mouth horn shape as a whole and comprises a circular truncated cone shape and an inverted pyramid shape, the diameter of the bottom hole of the circular truncated cone through hole is 10-50 microns, and the diameter of the top hole is 300 plus 500 microns.

The method comprises the steps of 3) aligning and covering the through holes of the conductive micro-through hole plate on the surface of the insulating substrate, preparing marks near the to-be-etched area of the insulating substrate and using a microscope.

The invention has the beneficial effects that: the method for imaging or micro-nano processing the surface of the insulating material by the electron beam or the ion beam has a simple flow, the ultrathin micro-window conductive cover plate used in the method for improving the local conductivity has no influence on a sample in the using process, the position of a target coverage area can be randomly adjusted, and the ultrathin micro-window conductive cover plate can be recycled, so that the method is a high-efficiency, convenient, economic and practical scheme.

Drawings

FIG. 1(a) is a cross-sectional view of an ultrathin micro-window conductive cover plate with a prepared through hole, covering the surface of an insulating substrate and being fixed on a sample platform;

FIG. 1(b) is a schematic view of FIG. 1 (a).

FIG. 2(a) is an SEM oblique view of a through hole prepared in a 100 μm thick silicon wafer by using a laser in an embodiment of the present invention, and the diameter of the through hole is 495 μm.

FIG. 2(b) is a SEM top view of inverted pyramid through holes etched by using a KOH solution in the embodiment of the invention, wherein the side length of a square opening at the bottom of the pyramid is 10 μm, and the side length of a square opening at the top end is 562 μm.

Fig. 3 is a flowchart of an alignment operation flow performed by a method of aligning the multilevel apposition marks on the surface of the insulating substrate and the surface of the silicon wafer so that the through hole of the ultra-thin micro-window conductive cover plate is aligned with the region to be etched in the embodiment of the present invention.

Fig. 4 is an SEM picture of an embodiment of the present invention in which an inverted pyramid-shaped via is used to etch a grating structure.

Detailed Description

The invention is further illustrated with reference to the following figures and examples, which are not intended to be limiting.

Example 1

S1.1, as shown in fig. 1(a), preparing a double-polished n-type monocrystalline silicon wafer as a substrate of the ultrathin micro-window conductive cover plate 104, wherein the thickness of the silicon wafer is preferably 0.1mm-0.2mm, so that the silicon wafer can be prevented from deforming and cracking, the repeated use is facilitated, and sufficient space is left between the upper surface of the silicon wafer and a scanning electron microscope to ensure that the electron gun is not in contact with the upper surface of the silicon wafer when the scanning electron microscope and a gallium ion beam are imaged on the axis.

The ultra-thin micro-window conductive cover plate 104 may be made of a flat semiconductor/conductor material, such as silicon, which has good conductivity and is not easily bent. The better the conductivity, the better the local conductivity is improved and the charge accumulation is prevented. The bending is not easy, so that the flat plate is in full contact with the insulating substrate, and the gap which is not beneficial to charge conduction is avoided, so that the charge mobility is reduced.

S1.2 preparation of the ultra-thin micro-window conductive cover plate 104, a laser can be used to prepare cylindrical through holes 102 with a diameter of 100 μm-500 μm on the surface of a monocrystalline silicon wafer, and as shown in FIG. 2(a), an SEM picture of through holes with a diameter of 500 μm prepared on the surface of a monocrystalline silicon wafer by laser is shown. Or performing anisotropic etching on the monocrystalline silicon wafer by using a wet etching process to form inverted pyramid-shaped etching pits 101 with a bottom opening diameter of 10-100 μm, as shown in fig. 2(b) which is an SEM picture of inverted pyramid through holes. The number and diameter of the through holes can be adjusted according to different requirements such as machining precision and machining area. The smaller the through hole is, the closer the distance between the inner wall of the through hole and the etching area is, the more favorable the transfer of charged particles sputtered in the etching process is, and therefore, the higher the processing precision is.

S1.3 mixing Quartz (SiO)₂) An insulating substrate 105 is placed on the surface of a sample stage 106, and an ultrathin micro-window conductive cover plate 104 with through holes is covered on SiO₂Insulating substrate 105 surface.

And (4) directly carrying out the next operation according to the testing processing requirement without fixed point requirement on the position of the area to be etched.

For the test processing requirement that the position of the area to be etched has a fixed point requirement, an alignment operation process can be carried out under an optical microscope, so that the through hole is aligned to the area to be etched.

S1.4, using a carbon conductive adhesive tape 103 to fix the edge area of the upper surface of the ultrathin micro-window conductive cover plate 104 and quartz (SiO)₂) The peripheral area and the side edge of the insulating substrate 105 which are not covered by the ultra-thin micro-window conductive cover plate 104 and the upper surface of the sample stage 106 are all covered, so that the ultra-thin micro-window conductive cover plate 104 and quartz (SiO)₂) The insulating substrate 105 is fixed on the upper surface of the sample stage 106 and is connected to the ground. The ultra-thin micro-window conductive cover plate 104 is communicated with the sample table 106 by using a carbon conductive adhesive tape 103, so that the conductive diffusion of charge particles is facilitated in the etching process, and the charge accumulation is prevented. The carbon conductive tape 103 here functions to fix the sampleAnd the purpose of communicating the three parts to ground can be replaced by conductive materials such as copper conductive adhesive tapes and the like. The prepared sample object is shown in FIG. 1(b)

S1.5 will carry the ultra-thin micro-window conductive cover plate 104, quartz (SiO)₂) The sample stage 106 of the insulating substrate 105 is placed in the high vacuum chamber, and the inclination angle and height of the sample stage are adjusted so that the sample stage 106 reaches a proper working distance. Using electron beam imaging to focus the electron beam on the surface of the ultrathin micro-window conductive cover plate 104, moving the sample stage to enable the through hole to reach the center of an imaging view field, selecting a proper ion beam current, enabling the focused ion beam to pass through the through hole 101 or 102 of the ultrathin micro-window conductive cover plate 104 and focus on the surface of an insulating material, drawing a target pattern by using pattern generator control software of a machine, and etching. The conductive characteristic of the ultrathin micro-window conductive cover plate 104 transfers charged particles sputtered by bombarding the surface of the sample with the focused ion beam, thereby being beneficial to the focused ion beam to carry out micro-nano structure processing on the surface of the insulating material. FIG. 4 (left part) and FIG. 4 (right part) show the focused ion beam on the insulating Substrate (SiO) using the through holes of FIG. 2(a) and FIG. 2(b), respectively₂) SEM pictures of surface etched channels.

Example 2

The monocrystalline silicon wet anisotropic etching process specifically comprises the following steps: oxidizing both sides of a double-side polished n-type silicon wafer with the thickness of 200 mu m, and depositing a silicon nitride film at high temperature to form a corrosion mask, namely SiO₂The film thickness is 60nm, the silicon nitride film thickness is 20nm, then a rectangular window of a region to be corroded is etched on one surface by using photoetching and plasma etching methods, the silicon wafer is immersed in KOH corrosive liquid with the concentration of 30% for anisotropic corrosion, and a square inverted pyramid-shaped pit with the bottom opening with the side length of 10 mu m is formed after 5.5 hours. Thereby being used as the ultrathin micro-window conductive cover plate which plays a role in conducting and diffusing electric charges in experiments. And then, in order to prevent the silicon nitride and the silicon oxide film from influencing the conductive property of the silicon wafer, removing the silicon nitride and the silicon oxide film by using hydrofluoric acid after the etching of the inverted pyramid-shaped through hole is finished.

The adopted monocrystalline silicon wet anisotropic etching process can etch inverted pyramid-shaped pits with any opening size by controlling the etching time.

Since the smaller the via hole, the more conductive dissipation of charged particles is facilitated, the processing accuracy is inversely proportional to the via hole diameter. For the case of high machining precision requirement, a through hole with a smaller hole diameter needs to be used. When the diameter of the through hole is too small, however, the SiO in the bottom hole region of the inverted pyramid is bombarded by the electron beam or the ion beam₂The secondary electrons or secondary ions generated during substrate process are blocked by the side wall of the through hole, so that the signal receiver can not capture the secondary electrons or secondary ions, the imaging brightness contrast is too dark, the whole inverted pyramid-shaped pit in the embodiment is in a wide-mouth horn-shaped structure, and the electron beams or ion beams can be favorably bombarded on SiO (silicon dioxide) in the pyramid bottom hole area₂Secondary electrons or secondary ions generated while the substrate is being processed are captured by the signal receiver for imaging. Example 2 is therefore proposed for cases requiring high machining precision.

Example 3

The alignment procedure is performed under an optical microscope, and an insulating substrate is firstly placed on an objective table and fixed by using a pressing sheet clamp. The three-dimensional adjusting frame is connected with the cantilever rod, and the ultrathin micro-window conductive cover plate is adhered to the bottom end of the cantilever rod. And manually adjusting the three-dimensional adjusting frame to enable the ultrathin micro-window conductive cover plate to be close to the upper surface of the insulating substrate. Under an optical microscope, the surface of the insulating substrate is observed through the through hole of the ultrathin micro-window conductive cover plate, and the microscope objective table is moved to enable the area to be etched to move into a view field. And adjusting the three-dimensional adjusting frame to attach the ultrathin micro-window conductive cover plate to the surface of the insulating substrate.

After alignment, the edge area of the upper surface of the silicon chip and SiO are coated by using a carbon conductive adhesive tape₂The upper surface area uncovered by the substrate and the upper surface of the sample table are completely covered, so that the silicon chip and the insulating SiO are enabled to be achieved₂The base is fixed on the upper surface of the sample table and is communicated with the sample table and the base.

Example 4

Since smaller through holes are more favorable for conductive dissipation of charged particles, the use of through holes with smaller apertures is an option for applications with high processing accuracy. However, when the diameter of the through hole is too small, light cannot penetrate through the small hole under a microscope for focusing and imaging, so that the multilevel homogeneous imaging method is prepared on the surface of the insulating substrate and the surface of the silicon waferAfter the position marks are marked, the alignment operation flow is carried out by the method of aligning the multistage apposition marks of the two parts so as to align the through hole of the ultrathin micro-window conductive cover plate to the area to be etched. As shown in FIG. 2(b), first, quartz (SiO)₂) The surface of the insulating substrate 105 is provided with cross positioning marks around the region 303 to be etched, a plurality of stages of positioning marks can be prepared according to actual requirements in an experiment, the transverse length of each stage of cross positioning mark is consistent with the longitudinal length of each stage of cross positioning mark, and two stages of positioning marks are prepared in the embodiment, namely a first stage positioning mark 3011 and a second stage positioning mark 3022. Meanwhile, circular via positioning marks 301 and 302 are prepared near the via 101 on the part of the ultra-thin micro-window conductive cover plate 104 of fig. 3(a) by using a laser, and the central points of these marks need to be the same as the central positions (3011, 3022) of the cross positioning marks on the surface of the insulating substrate 105. And the processing and positioning errors of the positioning marks at all levels are less than 30% of the side length of the square inverted pyramid.

After the positioning marks on the surface of the insulating substrate and the surface of the silicon wafer are prepared, the positioning marks at all levels are aligned under a microscope according to the steps of embodiment 3, and as shown in fig. 3(c), the aligned positioning marks are in the shape under the microscope.