A method and device for forming a spherical cavity inside a silicon-based material

Abstract

The present invention relates to the field of micro-nano manufacturing technology, and in particular to a method and device for forming a spherical cavity inside a silicon-based material, the method comprising the following steps: (S.1) using laser processing to prepare a silicon-based material with a cavity; (S.2) placing the silicon-based material with a cavity prepared in (S.1) in a thermal field for a heat treatment process; (S.3) adding an electric field to the environment described in (S.2) to induce shaping of the silicon-based material, and completing a three-dimensional structure of a spherical cavity inside the silicon-based material. The present invention first heat treats the silicon-based material after laser processing. After the heat treatment, the atomic mobility of silicon atoms in the cavity of the silicon material is greatly improved, and then the electric field is added to further induce shaping of the silicon-based material to promote the formation of the three-dimensional structure inside the silicon-based material. The present invention has the advantages of being simple and controllable during the preparation process, and the performance of micro-nano devices can be effectively improved by this method.

Description

Technical Field

[0001] The invention relates to the field of micro-nano manufacturing technology, and in particular to a method and equipment for forming a spherical cavity inside a silicon-based material. Background Art

[0002] In the field of micro-nano processing, laser processing methods show excellent writing properties inside silicon-based materials. However, when laser processing inside silicon-based materials, the peak energy density of laser processing is high, resulting in artificial defects inside silicon-based materials. Due to the lack of human intervention in the internal structure of silicon-based materials, errors are prone to occur in the process of writing the formed structure, resulting in poor compatibility of the formed structure with the device, which in turn affects the performance of micro-nano devices.

[0003] The preparation method based on single-photon absorption in the prior art is more efficient than the preparation method based on multi-photon absorption, but it also has some defects. For example, the energy loss caused by the absorption of the front focal area is large, and the surface and the front focal area are damaged, resulting in limited embedding depth. These technical defects lead to the generation of unstable cavities around the silicon processing position during the laser processing of the silicon base. For the formation of the internal structure of the silicon base, there is currently a lack of research on the influence of the interaction between various physical fields on the structural formation, which makes it difficult to achieve the stable formation of the target structure. Summary of the invention

[0004] The present invention aims to overcome the problem that the laser processing method in the prior art will produce defects during the process of processing the cavity inside the silicon-based material, affecting the performance of the micro-nano device. The present invention provides a method for forming a spherical cavity inside the silicon-based material based on thermoelectric coupling.

[0005] To achieve the above-mentioned purpose, the present invention is implemented by the following technical solutions:

[0006] A method for forming a spherical cavity inside a silicon-based material comprises the following steps:

[0007] Step S.1: preparing a silicon-based material having a cavity by laser processing;

[0008] Step S.2: placing the silicon-based material with the cavity prepared in step S.1 in a thermal field and performing a heat treatment process;

[0009] Step S.3 adds an electric field to the environment described in step S.2 to induce shaping of the silicon-based material, thereby completing the three-dimensional structure of the spherical cavity inside the silicon-based material.

[0010] In the prior art, during the laser processing of silicon-based materials, a cavity can be formed inside the silicon-based material, but the cavity obtained by this method has many defects inside and usually cannot form a spherical cavity. Therefore, after the laser processing is completed, the present invention performs a thermoelectric coupling treatment on it, so that the cavity with defects can be formed into a spherical cavity.

[0011] The principle is as follows: the present invention first heat treats the silicon-based material after laser processing. After the heat treatment, the atomic mobility of silicon atoms in the cavity of the silicon material is greatly improved, thereby improving the isotropic mobility of silicon atoms, thereby promoting silicon atoms to make up for defects, so that the cavity inside the silicon-based material can reach the state of minimum surface energy, that is, forming a spherical cavity.

[0012] In addition, after the heat treatment, the present invention further induces the silicon-based material to form a three-dimensional structure inside the silicon-based material by adding an electric field. In the presence of an electric field, the charge moves in the direction of the electric field line. The direction of charge movement is determined by the amount of charge in the electric field.

[0013]

[0014] in is the current density A / μm, is the electrical conductivity of the conductor S / μm, is the electric field strength V / μm.

[0015] When the electron wind acts on the defect, the force generated by the electron wind is proportional to the drift velocity of the electron (assuming that the defect temporarily stays on an obstacle). In addition, the drift electron velocity is proportional to the current density, that is, the electron wind force is proportional to the current density.

[0016] The electronic wind force calculation formula is:

[0017]

[0018] in is the force per unit length acting on the defect, is the Taylor orientation coefficient; is the current density; is the magnitude of the electronic wind force; is the electronic force coefficient.

[0019] From the above relationship, it can be seen that the magnitude of the electron wind force is positively correlated with the current density, and the electron wind force is positively correlated with the force acting on the silicon substrate. Therefore, S3 can change the current density by adjusting the electric field intensity range, and then adjust the electron wind force on the silicon substrate, repair the irregular cavity inside the initial laser-processed silicon substrate, and achieve the expected spherical cavity state.

[0020] Preferably, the silicon-based material has a length and width of 100 μm×100 μm and a thickness of 50 μm.

[0021] Preferably, in step S.1, the diameter of the cavity is 10 μm.

[0022] Preferably, the spacing between the cavities in the vertical z-axis direction is 20 μm, the spacing in the horizontal x-axis direction is 20 μm, and the spacing in the y-axis direction is 20 μm.

[0023] Preferably, in the laser processing in step S.1, a Nd:YAG laser transmitter with a wavelength of 1.064 μm is used, and the laser transmitter emits lasers at a time interval of 1 to 10 ns.

[0024] Preferably, the laser writing depth during the laser processing in step S.1 is 45-85 μm.

[0025] When a laser is emitted by a laser emitter and a silicon substrate with a writing depth of 45 to 85 μm is engraved, the laser emitted by the laser emitter is considered weak but not negligible, but the upper and lower surfaces of the silicon substrate will not be damaged.

[0026] Preferably, in step S.2, the thermal field temperature is controlled between 1100 and 1150°C.

[0027] Silicon will reach its melting point at a high temperature of 1414°C. The purpose of this experiment is to increase the atomic mobility of silicon and improve the isotropic migration characteristics of silicon atoms, that is, to promote silicon atoms to make up for defects and make the cavity in the silicon base reach the state with the minimum surface energy - spherical cavity. The thermal field temperature of this spherical cavity preparation method is controlled at 1100~1150°C to ensure that the silicon base obtains the maximum isotropic mobility without melting.

[0028] Preferably, the heat treatment time in step S.2 is 20 to 60 minutes.

[0029] Preferably, in step S.3, the electric field is provided with zirconium dioxide plates as positive and negative electrodes, and the distance between the two zirconium dioxide plates is 50 mm.

[0030] Preferably, the electric field output in step S.3 has an electric field strength of 0.1 V / μm-0.5 V / μm.

[0031] Preferably, after the preparation and molding of the present invention, the spherical cavity forming condition is observed under an infrared transmission microscope.

[0032] Although other microscopic observation methods such as scanning electron microscopy, transmission electron microscopy, and atomic force microscopy can observe the information of micro-nano writing of materials, they will cause permanent damage to the silicon substrate. Phase measurement can provide a powerful non-destructive tool for the mechanism of laser-matter interaction, which can show the changing refractive index inside the dielectric material. This experiment uses infrared transmission to observe the shape of the silicon-based cavity to determine the degree of cavity formation and the state of the cavity.

[0033] An apparatus for forming a spherical cavity inside a silicon-based material, comprising a box-type resistance furnace;

[0034] The box-type resistance furnace is internally fixedly provided with a cathode zirconium dioxide plate and an anode zirconium dioxide plate;

[0035] The cathode zirconium dioxide plate and the anode zirconium dioxide plate are connected to the positive and negative electrodes of the power supply respectively.

[0036] Preferably, the cathode zirconium dioxide plate and the anode zirconium dioxide plate are 100 mm long and 100 mm wide;

[0037] The distance between the cathode zirconium dioxide plate and the anode zirconium dioxide plate is 50 mm.

[0038] Therefore, the present invention has the following beneficial effects:

[0039] (1) The present invention can effectively eliminate the defects of the cavity formed during laser processing by means of thermoelectric coupling to form a spherical cavity;

[0040] (2) The present invention has the advantages of being simple and controllable during the preparation process;

[0041] (3) This method can effectively improve the performance of micro-nano devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of the device for forming a spherical cavity inside a silicon-based material according to the present invention.

[0043] Among them: a box-type resistance furnace 1, a cathode zirconium dioxide plate 2, and an anode zirconium dioxide plate 3.

[0044] Figure 2 This is a schematic diagram of the irregular cavity after laser processing of the present invention.

[0045] Figure 3 Schematic diagram of the spherical cavity after thermoelectric coupling.

[0046] Figure 4 It is a schematic diagram of forming a spherical cavity according to the present invention.

[0047] Figure 5This is a diagram showing the change in the number of spherical cavities under the action of the electric field of the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments of the specification. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0049] Example 1

[0050] like Figure 1 As shown, a device for forming a spherical cavity inside a silicon-based material comprises a box-type resistance furnace 1;

[0051] The box-type resistance furnace 1 is internally fixedly provided with a cathode zirconium dioxide plate 2 and an anode zirconium dioxide plate 3;

[0052] The cathode zirconium dioxide plate 2 and the anode zirconium dioxide plate 3 are connected to the positive and negative electrodes of the power supply respectively.

[0053] The cathode zirconium dioxide plate 2 and the anode zirconium dioxide plate 3 are 100 mm long and 100 mm wide;

[0054] The distance between the cathode zirconium dioxide plate 2 and the anode zirconium dioxide plate 3 is 50 mm.

[0055] Example 1

[0056] like Figure 2 As shown, a method for forming a spherical cavity inside a silicon-based material comprises the following steps:

[0057] Step S.1: Use laser processing to prepare a preliminary silicon-based material with a cavity. The length and width of the silicon-based material are 100μm×100μm, and the thickness is 50μm. It is expected that the cavity diameter will be 10μm, the spacing on the vertical z-axis is 20μm, the spacing on the horizontal x-axis is 20μm, and the spacing on the y-axis is 20μm.

[0058] The laser processing preferably uses a Nd:YAG laser transmitter with a wavelength of 1.064μm. The laser transmitter clamping device is fixed on the test bench and fixed by bolts. The emission port of the laser transmitter is opposite to the predetermined position of the silicon base, and the laser transmitter emits the laser at a time interval of 5ns. During the writing process of step 1, the laser transmitter is fixed on the test bench, and then the silicon-based material to be prepared is fixed on the test bench and calibrated with the laser transmitter used for processing at the predetermined position. The laser transmitter is enabled and the laser is focused on the target area with a focusing time of 0.1s. After the laser transmitter operation is completed, the laser transmitter is paused and the laser transmitter focus position is transferred to the predetermined position of the next cavity. The above operation is repeated until all predetermined positions are processed into cavities by laser, such as Figure 3 shown.

[0059] Step S.2: Place the silicon-based material with a cavity obtained in step S.1 in the above-mentioned equipment, close the resistance furnace door, and before heat treatment, introduce argon gas into the box-type resistance furnace until the internal air is exhausted, seal the box-type resistance furnace, turn on the power of the box-type resistance furnace, and set the heat treatment temperature (1150°C) and heat treatment duration (about 30 minutes).

[0060] Step S.3: Add an electric field in the environment described in step S.2 and maintain it for 150 minutes. The electric field uses zirconium dioxide as the positive and negative plates of the electric field. The electric field output electric field strength is 0.3V / μm. The zirconium dioxide plate is 100mm long and 100mm wide, and the distance between the plates is 50mm. The conductive wire in the high-temperature heat treatment zone is made of high-temperature resistant metal copper wire. The cathode zirconium dioxide plate and the anode zirconium dioxide plate are placed in the box-type resistance furnace described in step 2 with the cathode zirconium dioxide plate on the left and the anode zirconium dioxide plate on the right, facing each other. The zirconium dioxide plate is fixed to the box-type resistance furnace, and one end of the conductive wire is connected to the positive and negative poles of the power supply, and the other end is connected to the positive and negative poles of the zirconium dioxide plate. Under the thermal field conditions of step 2, an electric field is introduced to induce shaping of the silicon substrate to promote the formation of the internal three-dimensional structure of the silicon substrate, and a silicon substrate with a spherical cavity is obtained. Figure 4 shown.

[0061] Step S.4: The silicon-based material with the spherical cavity after the treatment in step S.3 is allowed to stand, and after the silicon-based material is cooled, it is taken out and the formation of the spherical cavity is observed under an infrared transmission microscope.

[0062] The infrared transmission microscope device is an InGaAs camera. The infrared transmission microscope device selected in this preparation method can observe the wavelength range of 0.9-1.7μm, has low noise, and a rate of 200 frames per second. The square pixels are suitable for industrial OEM semiconductor detection, silicon wafer crack detection, and other applications to detect internal defects that are invisible in the visible light band. Rectangular pixels are suitable for spectral imaging, low light conditions, etc. The infrared transmission microscope device will obtain good image quality with low dark current and excellent signal-to-noise ratio. The preferred method is to obtain the amplitude image and phase image of the silicon-based sample after the cavity is formed through the device, and then compare the image with the preset target. If the preset spherical cavity state is reached, the silicon-based material with the cavity is preserved.

[0063] Figure 5 This is a graph showing the change in the number of formed cavities after the present invention is treated in an electric field. It can be seen from the graph that the number of formed spherical cavities increases successively during the electric field treatment process. After 150 minutes of electric field treatment, all the cavities can be transformed into spherical cavities.

[0064] Example 2

[0065] A method for forming a spherical cavity inside a silicon-based material comprises the following steps:

[0066] Step S.1: Use laser processing to prepare a preliminary silicon-based material with a cavity. The length and width of the silicon-based material are 100μm×100μm, and the thickness is 50μm. It is expected that the cavity diameter will be 10μm, the spacing on the vertical z-axis is 20μm, the spacing on the horizontal x-axis is 20μm, and the spacing on the y-axis is 20μm.

[0067] The laser processing preferably uses a Nd:YAG laser transmitter with a wavelength of 1.064μm. The laser transmitter clamping device is fixed on the test bench and fixed by bolts. The emission port of the laser transmitter is opposite to the predetermined position of the silicon base, and the laser transmitter emits the laser at a time interval of 1ns. During the writing process of step 1, the laser transmitter is fixed on the test bench, and then the silicon-based material to be prepared is fixed on the test bench and calibrated with the laser transmitter used for processing at the predetermined position. The laser transmitter is enabled and the laser is focused on the target area with a focusing time of 0.1s. After the laser transmitter operation is completed, the laser transmitter is paused and the laser transmitter focus position is transferred to the predetermined position of the next cavity. The above operation is repeated until all predetermined positions are processed into cavities by laser.

[0068] Step S.2: Place the silicon-based material with a cavity obtained in step S.1 in the above-mentioned equipment, close the resistance furnace door, and before heat treatment, introduce argon gas into the box-type resistance furnace until the internal air is exhausted, seal the box-type resistance furnace, turn on the power of the box-type resistance furnace, and set the heat treatment temperature (1100°C) and heat treatment duration (about 60 minutes).

[0069] Step S.3: Add an electric field in the environment described in step S.2. The electric field uses zirconium dioxide as the positive and negative plates of the electric field. The electric field output electric field strength is 0.1V / μm. The zirconium dioxide plate is 100mm long, 100mm wide, and the plate spacing is 50mm. The conductive wire in the high-temperature heat treatment area is made of high-temperature resistant metal copper wire. The cathode zirconium dioxide plate and the anode zirconium dioxide plate are placed in the box-type resistance furnace described in step S.2 in a manner that the cathode zirconium dioxide plate is on the left and the anode zirconium dioxide plate is on the right, and the left and right are directly opposite. The zirconium dioxide plate is fixed to the box-type resistance furnace, one end of the conductive wire is connected to the positive and negative poles of the power supply, and the other end is connected to the positive and negative poles of the zirconium dioxide plate. Introduce an electric field under the thermal field conditions of step S.2 to induce shaping of the silicon base to promote the formation of the three-dimensional structure inside the silicon base, and obtain a silicon-based material with a spherical cavity.

[0070] Example 3

[0071] A method for forming a spherical cavity inside a silicon-based material comprises the following steps:

[0072] Step S.1 uses laser processing to prepare a preliminary silicon-based material with a cavity. The length and width of the silicon-based material are 100μm×100μm and the thickness is 50μm. It is expected that the cavity diameter will be 10μm, the spacing on the vertical z-axis is 20μm, the spacing on the horizontal x-axis is 20μm, and the spacing on the y-axis is 20μm.

[0073] The laser processing preferably uses a Nd:YAG laser transmitter with a wavelength of 1.064μm. The laser transmitter clamping device is fixed on the test bench and fixed by bolts. The emission port of the laser transmitter is opposite to the predetermined position of the silicon base, and the laser transmitter emits the laser at a time interval of 10ns. During the writing process of step 1, the laser transmitter is fixed on the test bench, and then the silicon-based material to be prepared is fixed on the test bench and calibrated with the laser transmitter used for processing at the predetermined position. The laser transmitter is enabled and the laser is focused on the target area with a focusing time of 0.1s. After the laser transmitter operation is completed, the laser transmitter is paused and the laser transmitter focus position is transferred to the predetermined position of the next cavity. The above operation is repeated until all predetermined positions are processed into cavities by laser.

[0074] Step S.2: Place the silicon-based material with a cavity obtained in step S.1 in the above-mentioned equipment, close the resistance furnace door, and before heat treatment, introduce argon gas into the box-type resistance furnace until the internal air is exhausted, seal the box-type resistance furnace, turn on the power of the box-type resistance furnace, and set the heat treatment temperature (1150°C) and heat treatment duration (approximately 60 minutes).

[0075] Step S.3: Add an electric field in the environment described in S.2. The electric field uses zirconium dioxide as the positive and negative plates of the electric field. The electric field output electric field strength is 0.5V / μm. The zirconium dioxide plate is 100mm long, 100mm wide, and the plate spacing is 50mm. The conductive wire in the high-temperature heat treatment area is made of high-temperature resistant metal copper wire. The cathode zirconium dioxide plate and the anode zirconium dioxide plate are placed in the box-type resistance furnace described in step S.2 in a manner that the cathode zirconium dioxide plate is on the left and the anode zirconium dioxide plate is on the right, and the left and right are directly opposite. The zirconium dioxide plate is fixed to the box-type resistance furnace, one end of the conductive wire is connected to the positive and negative poles of the power supply, and the other end is connected to the positive and negative poles of the zirconium dioxide plate. Introduce an electric field under the thermal field conditions of step S.2 to induce shaping of the silicon base to promote the formation of the three-dimensional structure inside the silicon base, and obtain a silicon-based material with a spherical cavity.

[0076] Example 4

[0077] A method for forming a spherical cavity inside a silicon-based material comprises the following steps:

[0078] Step S.1: Use laser processing to prepare a preliminary silicon-based material with a cavity. The length and width of the silicon-based material are 100μm×100μm, and the thickness is 50μm. It is expected that the cavity diameter will be 10μm, the spacing on the vertical z-axis is 20μm, the spacing on the horizontal x-axis is 20μm, and the spacing on the y-axis is 20μm.

[0079] The laser processing preferably uses a Nd:YAG laser transmitter with a wavelength of 1.064μm. The laser transmitter clamping device is fixed on the test bench and fixed by bolts. The emission port of the laser transmitter is opposite to the predetermined position of the silicon base, and the laser transmitter emits the laser at an interval of 8ns. During the writing process of step 1, the laser transmitter is fixed on the test bench, and then the silicon-based material to be prepared is fixed on the test bench and calibrated with the laser transmitter used for processing at the predetermined position. The laser transmitter is enabled and the laser is focused on the target area with a focusing time of 0.1s. After the laser transmitter operation is completed, the laser transmitter is paused and the laser transmitter focus position is transferred to the predetermined position of the next cavity. The above operation is repeated until all predetermined positions are processed into cavities by laser.

[0080] Step S.2: Place the silicon-based material with a cavity obtained in step S.1 in the above-mentioned equipment, close the resistance furnace door, and before heat treatment, introduce argon gas into the box-type resistance furnace until the internal air is exhausted, seal the box-type resistance furnace, turn on the power of the box-type resistance furnace, and set the heat treatment temperature (1120°C) and heat treatment duration (about 40 minutes).

[0081] Step S.3: Add an electric field in the environment described in step S.2. The electric field uses zirconium dioxide as the positive and negative plates of the electric field. The electric field output electric field strength is 0.4V / μm. The zirconium dioxide plate is 100mm long, 100mm wide, and the plate spacing is 50mm. The conductive wire in the high-temperature heat treatment area is made of high-temperature resistant metal copper wire. The cathode zirconium dioxide plate and the anode zirconium dioxide plate are placed in the box-type resistance furnace described in step S.2 in a manner that the cathode zirconium dioxide plate is on the left and the anode zirconium dioxide plate is on the right, and the left and right are directly opposite. The zirconium dioxide plate is fixed to the box-type resistance furnace, one end of the conductive wire is connected to the positive and negative poles of the power supply, and the other end is connected to the positive and negative poles of the zirconium dioxide plate. Introduce an electric field under the thermal field conditions of step S.2 to induce shaping of the silicon base to promote the formation of the internal three-dimensional structure of the silicon base, and obtain a silicon-based material with a spherical cavity.

[0082] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, according to the ideas provided by the present invention, there will be changes in the specific implementation methods, and these changes should also be regarded as the scope of protection of the present invention.

Claims

1. A method for forming a spherical cavity inside a silicon-based material, characterized in that: The following steps are involved: Step S.1: using laser processing to prepare an irregular cavity inside the silicon-based material; In the laser processing process in step S.1, a Nd:YAG laser transmitter with a wavelength of 1.064 μm is used, the laser transmitter emits a laser time interval of 1 to 10 ns, and the laser writing depth is 45 to 85 μm; Step S.2: placing the silicon-based material with a cavity prepared in step S.1 in a heat field and performing a heat treatment process, wherein the temperature of the heat field is controlled between 1100 and 1150° C. and the heat treatment time is 20 to 60 minutes; Step S.3: Add an electric field in the environment of step S.2, with the electric field strength of 0.1V / μm-0.5V / μm, and adjust the electric field strength range to change the current density, thereby adjusting the electronic wind force on the silicon-based material, inducing the silicon-based material to be shaped, repairing the irregular cavity inside the initial laser-processed silicon-based material, and completing the three-dimensional structure of the spherical cavity inside the silicon-based material; The electric field strength calculation formula in step S.3 is: ,in is the current density A / μm, is the electrical conductivity of the conductor S / μm, is the electric field strength V / μm; The electronic wind force calculation formula in step S.3 is: ,in is the force per unit length acting on the defect, is the Taylor orientation coefficient; is the current density; is the magnitude of the electronic wind force; is the electronic force coefficient.

2. A method for forming a spherical cavity inside a silicon-based material according to claim 1, characterized in that: The heat treatment in step S.2 is performed under the protection of an inert gas.

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