Electron microscope diaphragm and preparation method thereof

Abstract

The invention discloses an electron microscope diaphragm and a preparation method thereof, the electron microscope diaphragm comprises a top layer metal, a top layer silicon, a buried oxide layer, a bottom layer silicon and a bottom layer metal which are distributed from top to bottom, the top layer silicon is connected with the bottom layer silicon through the buried oxide layer, the top layer metal is in adhesion connection with the top layer silicon, and the bottom layer metal is in adhesion connection with the bottom layer silicon; the outer boundary of the diaphragm is rectangular, and the length of the rectangle is 1-50mm; the diaphragm hole penetrates through the top layer metal, the top layer silicon, the buried oxide layer, the bottom layer silicon and the bottom layer metal, the characteristic size of the diaphragm hole is 2-1000 microns, and the diaphragm hole can be any geometric figure. The method has the advantages of being simple in principle, convenient to prepare, wide in application range and the like, and solves the problems that the diaphragm processing technology is high in requirement, and the non-circular diaphragm hole preparation requirement is difficult to meet.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology, and in particular relates to an electron microscope diaphragm and a preparation method thereof. Background Art

[0002] In the optical path design, the designer controls the on / off, position, beam aperture angle and other characteristics of the light by adding small holes. Such small holes are also needed in electron optics to control the electron beam, namely the electron microscope aperture.

[0003] In electron beam equipment, such as scanning electron microscopes and electron beam exposure machines, the electron beam position, size, beam aperture and other characteristics are constrained by the electron microscope aperture to control the beam and spot characteristics of the equipment.

[0004] Common electron microscope apertures are made of platinum, molybdenum, iridium, tantalum and other metals through etching and other processes. Such products have extremely high conductivity, high dimensional accuracy, roundness and coaxiality. The dimensional accuracy of the inner hole diameter of high-quality metal apertures can be within ±5 microns, the roundness does not exceed 1 micron, and the coaxiality does not exceed 20 microns. However, the processing technology of such apertures is demanding, and the verticality of the corners is insufficient when preparing non-circular aperture holes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to solve the problems that the existing aperture processing technology has high requirements and is difficult to meet the needs of preparing non-circular aperture holes, and to provide an electron microscope aperture and a preparation method thereof with simple principle, convenient preparation and wide application range.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] An electron microscope aperture comprises a top metal layer, a top silicon layer, a buried oxide layer, a bottom silicon layer and a bottom metal layer distributed from top to bottom, wherein the top silicon layer is connected to the bottom silicon layer via the buried oxide layer, the top metal layer is adhesively connected to the top silicon layer, and the bottom metal layer is adhesively connected to the bottom silicon layer; the outer boundary of the aperture is a rectangle, and the length of the rectangle is 1 mm to 50 mm; the aperture hole penetrates the top metal layer, the top silicon layer, the buried oxide layer, the bottom silicon layer and the bottom metal layer, and the characteristic size of the aperture hole is 2 μm to 1000 μm.

[0008] As a further improvement of the present invention, the top metal and the bottom metal have the same structural setting, the top metal includes a surface metal and a metal adhesion layer, the surface metal has a thickness of 20 nanometers to 140 nanometers, the metal adhesion layer has a thickness of 5 nanometers to 30 nanometers, and the metal adhesion layer is adhered and connected to the top silicon. In order to ensure that the supporting structure is not damaged during the preparation of the bottom structure, the bottom metal is particularly considered to have a compactness, and the thickness of the bottom metal can be appropriately increased. If necessary, an additional layer of silicon nitride can be added for mask protection.

[0009] As a further improvement of the present invention, the material of the surface metal is any one of molybdenum, tungsten, iridium, platinum, gold and titanium, and the material of the metal adhesion layer is chromium or titanium.

[0010] As a further improvement of the present invention, the thickness of the top silicon layer ranges from 0.2 micrometers to 70 micrometers, matching an acceleration voltage of 3 kV to 100 kV.

[0011] As a further improvement of the present invention, the resistivity of the top silicon layer is less than 1Ω.cm, and there is no requirement for the crystal orientation. As a further improvement of the present invention, the thickness of the buried oxide layer is 200 nanometers to 3 micrometers.

[0012] As a further improvement of the present invention, the thickness of the bottom silicon is 300 microns to 800 microns, the resistivity is less than 10Ω.cm, and the crystal orientation is required to be 100 crystal orientation.

[0013] As a further improvement of the present invention, the preparation process of the aperture hole includes: preparing a top through hole of arbitrary pattern on the top metal and the top silicon by one photolithography and two dry etchings, and then preparing a bottom through hole on the bottom metal, bottom silicon and buried oxide layer by one photolithography, one dry etching and two wet etchings.

[0014] As a further improvement of the present invention, the bottom through hole of the aperture hole covers the top through hole of the aperture hole, and the aperture of the aperture hole is determined by the top through hole.

[0015] As a general technical concept, the present invention also provides a method for preparing the above-mentioned electron microscope aperture, comprising the following steps:

[0016] The first step is to design the aperture hole graphic characteristics of the electron microscope according to the functional requirements of the equipment; determine the slicing method and the aperture boundary size in combination with the mechanical design of the equipment;

[0017] The second step is to select the matching top silicon thickness according to the device electron beam acceleration voltage;

[0018] The third step is to determine the coating material and thickness of the top metal and bottom metal in combination with the process equipment. The selected process equipment should ensure that the bottom metal film has good density and will not leak during the wet etching process;

[0019] The fourth step is to design the aperture hole layout on the front side and the opening layout on the back side;

[0020] The fifth step is to coat the front and back surfaces;

[0021] Step 6: Perform photolithography according to the front aperture hole photolithography pattern to transfer the designed aperture hole pattern to the SOI wafer;

[0022] Step 7: Use ion beam etching or deep reactive ion etching to perform metal and deep silicon etching;

[0023] Step 8: According to the photolithography pattern of the opening on the back side, a photolithography process is performed on the bottom silicon surface of the SOI wafer, and the opening on the back side is performed by ion etching;

[0024] The ninth step is to use potassium hydroxide solution to wet etch the opening on the back side while protecting the front side until the buried oxygen layer is reached.

[0025] Step 10, using a hydrofluoric acid dilution solution to remove the buried oxide layer;

[0026] Step 11: Slicing.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] The electron microscope aperture and the preparation method thereof of the present invention form the main structure of the electron microscope aperture through the top metal, top silicon, buried oxide layer, bottom silicon and bottom metal distributed from top to bottom. The top metal is bonded and connected to the top silicon, and the bottom metal is bonded and connected to the bottom silicon. The electron microscope aperture hole pattern characteristics and aperture boundary size can be flexibly set according to the functional requirements of the equipment. The present invention provides the top silicon thickness conditions required under the acceleration voltage of 3 to 100 kV to ensure that the electron beam in the unopened area can be completely blocked. The resistivity conditions of the top and bottom silicon are determined to ensure that the aperture can conduct electricity efficiently. The thickness range of the main structure is reasonably planned, so that the coating, photolithography and other processes involved in the preparation process of the electron microscope aperture can adopt conventional process methods, which has the advantages of mature process, stability and reliability. Furthermore, the outer boundary of the aperture is a rectangle, the length of the rectangle is 1 mm to 50 mm, and the characteristic size of the aperture hole is 2 microns to 1000 microns, which can be any geometric figure, and can be applied in the fields of scanning electron microscope, transmission electron microscope, electron beam exposure machine, precision measurement, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the maximum depth that electron beams with different energies can reach after penetrating 30 nanometers of molybdenum and top silicon.

[0030] Figure 2 Schematic diagram of the preparation process of the electron microscope aperture in a specific embodiment of the present invention; wherein, Figure (a) is a schematic diagram of the structure of the top silicon, the buried oxide layer and the bottom silicon; Figure (b) is a schematic diagram of the structure of the top metal plated on the top silicon and the bottom metal plated on the bottom of the bottom silicon; Figure (c) is a schematic diagram of the structure of the front opening; Figure (d) is a schematic diagram of the structure of the back opening; Figure (e) is a schematic diagram of the structure after the back wet etching; Figure (f) is a schematic diagram of the structure after the buried oxide layer is removed;

[0031] Figure 3 Schematic diagram of a photolithography layout in a specific embodiment of the present invention; wherein, Figure (a) is a schematic diagram of a front photolithography layout unit, and Figure (b) is a schematic diagram of a back photolithography layout unit;

[0032] Legend: 1. Top metal; 2. Top silicon; 3. Buried oxide layer; 4. Bottom silicon; 5. Bottom metal; 6. Aperture. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0034] In the description of the present invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0036] Example

[0037] like Figure 2 As shown, the electron microscope aperture of the present invention includes a top metal 1, a top silicon 2, a buried oxide layer 3, a bottom silicon 4 and a bottom metal 5 distributed from top to bottom, the top silicon 2 is connected to the bottom silicon 4 through the buried oxide layer 3, the top metal 1 is adhered to the top silicon 2, and the bottom metal 5 is adhered to the bottom silicon 4. The outer boundary of the aperture is a rectangle, and the length of the rectangle is 1 mm to 50 mm; the aperture hole 6 runs through the top metal 1, the top silicon 2, the buried oxide layer 3, the bottom silicon 4 and the bottom metal 5, and the aperture hole 6 is a square, and its side length is 2 microns to 1000 microns. For other geometric figures, the characteristic size can be adjusted accordingly.

[0038] In this embodiment, the top metal 1 and the bottom metal 5 have the same structural setting, and the top metal 1 includes a surface metal and a metal adhesion layer. The thickness of the surface metal is 20 nanometers to 140 nanometers, which can quickly conduct electrons while blocking the electron beam to prevent the accumulation of charges from interfering with the electron beam. The thickness of the metal adhesion layer is 5 nanometers to 30 nanometers, and the metal adhesion layer is adhered and connected to the top silicon 2, and the metal adhesion layer is used to strengthen the connection between the surface metal and the top silicon. In order to ensure that the supporting structure is not damaged during the preparation of the bottom structure, the bottom metal especially considers its compactness, and the thickness of the bottom metal can be appropriately increased. If necessary, an additional layer of silicon nitride can be added for mask protection.

[0039] Furthermore, the material of the surface metal is any low-resistivity non-magnetic metal selected from molybdenum, tungsten, iridium, platinum, gold and titanium, and the material of the metal adhesion layer is a low-resistivity non-magnetic metal material such as chromium or titanium that has good adhesion to silicon.

[0040] Figure 1 The maximum depth that electron beams with different energies can reach after penetrating 30 nanometers of molybdenum and the top silicon 2 is shown in FIG. 1 . As can be seen from the figure, the greater the electron beam energy, the greater the penetration depth.

[0041] In this embodiment, the thickness of the top silicon 2 ranges from 0.2 microns to 70 microns, matching the acceleration voltage of 3kV to 100kV. The specific thickness of the top silicon 2 depends on the acceleration voltage of the electron gun. The higher the acceleration voltage, the thicker the required thickness. Furthermore, the resistivity of the top silicon 2 is less than 1Ω.cm, and there is no crystal orientation requirement. The top silicon 2 plays a major role in blocking, shaping, and conducting the electron beam, and the aperture characteristics of the aperture are determined by the graphic hole characteristics on the top silicon 2.

[0042] In this embodiment, the buried oxide layer 3 is made of silicon dioxide, and the thickness of the buried oxide layer 3 is 200 nanometers to 3 micrometers.

[0043] In this embodiment, the thickness of the bottom silicon 4 is 300 micrometers to 800 micrometers, the resistivity is less than 10Ω.cm, and the crystal orientation is required to be 100. The bottom silicon 4 plays a supporting role for the overall pattern.

[0044] In this embodiment, the preparation process of the aperture hole 6 includes: preparing a top through hole of any pattern on the top metal layer 1 and the top silicon layer 2 by one photolithography and two dry etchings, and then preparing a bottom through hole on the bottom metal layer 5, the bottom silicon layer 4 and the buried oxide layer 3 by one photolithography, one dry etching and two wet etchings. Furthermore, the bottom through hole of the aperture hole 6 covers the top through hole of the aperture hole 6, and the aperture of the aperture hole 6 is determined by the through hole in the top silicon layer 2.

[0045] In this embodiment, a preparation method applicable to the above-mentioned electron microscope aperture is also provided, comprising the following steps:

[0046] The first step is to design the aperture hole graphic features of the electron microscope according to the functional requirements of the equipment, which can be any geometric shape; determine the slicing method and the aperture boundary size in combination with the mechanical design of the equipment;

[0047] The second step is to select a matching top silicon 2 thickness according to the device electron beam acceleration voltage;

[0048] The third step is to determine the coating material and thickness of the top metal 1 and the bottom metal 5 in combination with the process equipment, wherein the coating of the bottom metal 5 needs to ensure its density to prevent liquid seepage;

[0049] Step 4: Design the aperture layout on the front and the opening layout on the back. Figure 3 shown.

[0050] The fifth step is to coat the front and back surfaces; Figure 2 As shown in (b) in .

[0051] Step 6: Perform photolithography according to the front aperture hole photolithography pattern to transfer the designed aperture hole pattern to the SOI wafer; Figure 2 As shown in (c) in .

[0052] The seventh step is to perform metal and deep silicon etching using ion beam etching or deep reactive ion etching.

[0053] Step 8: According to the back hole opening lithography pattern, a photolithography process is performed on the bottom silicon surface of the SOI wafer, and ion etching is used to open holes on the back side; Figure 2 As shown in (d) in .

[0054] The ninth step is to use potassium hydroxide solution to wet etch the opening on the back side while protecting the front side until the buried oxide layer is reached. Figure 2 As shown in (e) in .

[0055] Step 10: Use hydrofluoric acid dilution to remove the buried oxide layer 3; Figure 2 As shown in (f) in .

[0056] Step 11: Slicing. Slice the patterned wafer with a dicing machine to obtain a certain number of electron microscope apertures.

[0057] In this embodiment, the main structure of the electron microscope aperture is formed by the top metal 1, the top silicon 2, the buried oxide layer 3, the bottom silicon 4 and the bottom metal 5 distributed from top to bottom. The top metal 1 is adhered to the top silicon 2, and the bottom metal 5 is adhered to the bottom silicon 4, which has the advantages of compact structure and reliable connection. The graphic characteristics of the electron microscope aperture and the size of the aperture boundary can be flexibly set according to the functional requirements of the equipment. The coating, photolithography and other processes involved in the preparation of the electron microscope aperture can adopt conventional process methods, which has the advantages of mature technology, stability and reliability. Furthermore, the outer boundary of the aperture is a rectangle, the length of the rectangle is 1 mm to 50 mm, and the characteristic size of the aperture hole is 2 microns to 1000 microns, which can be applied in scanning electron microscopes, transmission electron microscopes, electron beam exposure machines, precision measurement and other fields.

[0058] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the spirit and technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still fall within the scope of protection of the technical solutions of the present invention.

Claims

1. An electron microscope aperture, characterized in that: The invention comprises a top metal (1), a top silicon (2), a buried oxide layer (3), a bottom silicon (4) and a bottom metal (5) which are distributed from top to bottom. The top silicon (2) is connected to the bottom silicon (4) through the buried oxide layer (3). The top metal (1) is adhesively connected to the top silicon (2). The bottom metal (5) is adhesively connected to the bottom silicon (4). The outer boundary of the aperture is a rectangle, and the length of the rectangle is 1 mm to 50 mm. The aperture hole (6) runs through the top metal (1), the top silicon (2), the buried oxide layer (3), the bottom silicon (4) and the bottom metal (5). The characteristic size of the aperture hole (6) is 2 microns to 1000 microns.

2. The electron microscope aperture according to claim 1, characterized in that: The top metal (1) and the bottom metal (5) have the same structural setting. The top metal (1) includes a surface metal and a metal adhesion layer. The thickness of the surface metal is 20 nanometers to 140 nanometers. The thickness of the metal adhesion layer is 5 nanometers to 30 nanometers. The metal adhesion layer is adhered and connected to the top silicon (2).

3. The electron microscope aperture according to claim 2, characterized in that: The material of the surface metal is any one of molybdenum, tungsten, iridium, platinum, gold and titanium, and the material of the metal adhesion layer is chromium or titanium.

4. The electron microscope aperture according to claim 2, characterized in that: The thickness of the top silicon (2) ranges from 0.2 micrometers to 70 micrometers, matches an acceleration voltage of 3kV to 100kV, and has no requirements on crystal orientation.

5. The electron microscope aperture according to claim 4, characterized in that: The resistivity of the top silicon layer (2) is less than 1Ω.cm.

6. The electron microscope aperture according to claim 4, characterized in that: The thickness of the buried oxide layer (3) is 200 nanometers to 3 micrometers.

7. The electron microscope aperture according to claim 6, characterized in that: The thickness of the bottom silicon (4) is 300 micrometers to 800 micrometers, the resistivity is less than 10Ω.cm, and the crystal orientation is required to be 100 crystal orientation.

8. The electron microscope aperture according to any one of claims 1 to 7, characterized in that: The preparation process of the aperture hole (6) comprises: preparing a top through hole of any pattern on a top metal layer (1) and a top silicon layer (2) by one photolithography and two dry etchings, and then preparing a bottom through hole on a bottom metal layer (5), a bottom silicon layer (4) and a buried oxide layer (3) by one photolithography, one dry etching and two wet etchings.

9. The electron microscope aperture according to claim 8, characterized in that: The bottom through hole of the aperture hole (6) covers the top through hole of the aperture hole (6), and the aperture of the aperture hole (6) is determined by the top through hole.

10. A method for preparing an electron microscope aperture according to any one of claims 1 to 9, characterized in that: The following steps are involved: The first step is to design the aperture graphic features of the electron microscope according to the functional requirements of the equipment; Determine the dicing method and aperture boundary size based on the mechanical design of the equipment; The second step is to select a matching top silicon (2) thickness according to the device electron beam acceleration voltage; The third step is to determine the coating material and thickness of the top metal (1) and the bottom metal (5) in combination with the process equipment; The fourth step is to design the aperture hole layout on the front side and the opening layout on the back side; The fifth step is to coat the front and back surfaces; Step 6: Perform photolithography according to the front aperture hole photolithography pattern to transfer the designed aperture hole pattern to the SOI wafer; Step 7: Use ion beam etching or deep reactive ion etching to perform metal and deep silicon etching; Step 8: According to the back hole opening photolithography pattern, a photolithography process is performed on the bottom silicon (4) surface of the SOI wafer, and ion etching is used to open holes on the back side; Step 9: While protecting the front side, wet etching is performed on the back opening using potassium hydroxide solution until the buried oxide layer (3) is reached; Step 10, using a hydrofluoric acid dilution solution to remove the buried oxide layer (3); Step 11: Slicing.

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