An electron beam heating treatment method and system for micro-nano structures

Abstract

This invention relates to the field of electron beam heating technology, specifically to an electron beam heating method and system for micro / nano structures. The method includes placing a sample on a vacuum sample stage and evacuating the vacuum chamber; activating an electron source to generate a focused electron beam; setting a target energy density distribution within a target area; and calculating a set of scanning speed data for the electron beam at various locations within the target area based on the target energy density distribution. The scanning speed data set includes the position coordinates of each scanning point and the corresponding desired scanning speed. This invention uses a variable-speed continuous scanning method instead of the traditional skip scanning method. The electron beam moves continuously along the scanning path without stopping or pausing, avoiding frequent and large-scale switching between high-speed movement and static dwell, significantly reducing the engineering implementation difficulty, and enabling the loading of a preset motion process for the scanning electron beam with higher precision.

Description

Technical Field

[0001] This invention belongs to the field of electron beam heating technology, specifically relating to an electron beam heating method and system for micro-nano structures. Background Technology

[0002] In fields such as micro / nano devices, micro / nano fluid channels, semiconductors, MEMS, two-dimensional materials, and nanoarrays, precise localized heating is often required for thermal processing or testing. Traditional heating methods (such as hot plates, infrared lamps, and laser heating) suffer from problems such as difficulty in precisely controlling the heat field distribution, severe heat diffusion between the heated area and its surroundings, and the inability to arbitrarily program the energy distribution. Electron beam heating, due to its small beam spot, high energy density, and good controllability, has become a potential tool for micro / nano-scale thermal processing.

[0003] Existing electron beam heating technologies mainly fall into three categories. The first category is focused small-spot scanning technology, represented by scanning electron microscopy (SEM). Its characteristics include high-speed, uniform electron beam scanning, low beam current (typically less than 5 microamps), low power (milliwatt level), and small impact scale (below millimeter level), primarily used for surface imaging rather than heating processes. The second category is electron beam welding and additive manufacturing technologies, characterized by very slow electron beam movement speed, high beam current (typically tens of milliamperes or more), high power (kilowatt level), and large impact scale (above centimeter level). These are mainly used for localized melting welding, resulting in intense thermal effects, making them unsuitable for fine heat treatment. The third category is scanning electron beam thermal testing technology applied in the aerospace field. This technology, by designing the residence time distribution, controls the electron beam to perform a skip-like, high-speed scan, achieving uniform or non-uniform heating, used to simulate the aerodynamic heating environment of aircraft reentry. However, the technology is difficult to achieve in terms of jumping motion, and it is hard to avoid motion fluctuations. It is also applied to extreme thermal environments with large beam current (hundreds of milliamperes), high power (tens of kilowatts), and large scale of action (tens of centimeters). If it is directly used to heat micro-nano structures at the millimeter scale, it is very easy to burn the sample. At the same time, it lacks in-situ observation capabilities.

[0004] Compared with the prior art, this invention employs a variable-speed continuous scanning method, where the electron beam speed changes continuously rather than jumping; the heating area targeted by this invention is on the millimeter scale (1mm×1mm~5mm×5mm), the beam current is in the microampere to milliampere range (10μA~10mA), and the power is moderate (a few watts to several hundred watts), suitable for the fine heat treatment of micro- and nano-structures; arbitrary programmable energy distribution (uniform, gradient, Gaussian, or custom) can be achieved by continuously changing the scanning speed, avoiding the implementation difficulties caused by jumping motion; at the same time, the device integrates an in-situ observation module, which can monitor the heating process in real time. Therefore, this invention is fundamentally different from the prior art in terms of scanning method, power scale, target scale, control method, and application scenarios.

[0005] To address the above problems, this invention proposes an electron beam heating method and system for micro / nano structures. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, the present invention aims to provide an electron beam heating method and system for micro-nano structures, which employs an electron beam to continuously scan within a target area and controls the amount of electron beam energy injected by changing the scanning speed in real time, thereby achieving a preset specific energy distribution.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: an electron beam heating treatment method for micro / nano structures, comprising the following steps:

[0008] S1. Place the sample on the vacuum sample stage and evacuate the vacuum chamber.

[0009] S2. Start the electron source to generate a focused electron beam;

[0010] S3. Set the target energy density distribution within the target area;

[0011] S4. Based on the target energy density distribution, calculate the scanning speed data set of the electron beam at each position in the target area. The scanning speed data set includes the position coordinates of each scanning point and the corresponding expected scanning speed.

[0012] S5. Within the target area, the electron beam is driven to move in a continuous scanning manner, and the scanning speed is continuously changed in real time to match the actual energy injection amount at each position with the target energy density distribution, so as to heat the sample.

[0013] Preferably, the target energy density distribution is a uniform distribution, a gradient distribution, a Gaussian distribution, or a custom distribution.

[0014] Preferably, the scanning speed data set is calculated as follows:

[0015] The target region is discretized into a uniform grid, and the center coordinates of each grid are the position coordinates of the scanning point.

[0016] Establish a set of energy balance equations between the time-averaged energy density of each grid and the scanning velocity of each scanning point;

[0017] Solve the system of equations to obtain the electron beam scanning velocity corresponding to each grid.

[0018] Preferably, the system of equations is solved using an iterative method, which includes:

[0019] Set the initial scan speed for each grid;

[0020] Calculate the current time-averaged energy density of each grid cell and compare it with the target energy density;

[0021] For grids with a time-averaged energy density higher than the target energy density, increase the scan rate corresponding to that grid; for grids with a time-averaged energy density lower than the target energy density, decrease the scan rate corresponding to that grid.

[0022] Repeat the iteration until the convergence condition is met.

[0023] Preferably, the continuous scanning method is a raster scanning method or a serpentine scanning method.

[0024] An electron beam heating system for micro / nano structures, comprising:

[0025] Electron beam generation module, used to generate and focus an electron beam;

[0026] The deflection scanning module is used to drive the electron beam to scan within the target area;

[0027] A signal generation module, connected to the deflection scanning module, is used to convert the scanning speed data group into a continuously changing electrical signal that drives the deflection scanning module;

[0028] A power control module, connected to the electron beam generating module, is used to adjust the accelerating voltage and beam current of the electron beam.

[0029] A vacuum sample module includes a vacuum chamber and a sample stage disposed within the vacuum chamber, the sample stage being used to hold a sample;

[0030] The central control module is connected to the signal generation module and the power control module respectively, and is used to set the target energy density distribution, calculate the scanning speed data set and send it to the signal generation module, and control the heating process.

[0031] Preferably, the signal generating module includes:

[0032] The storage unit is used to store a scan speed data set containing the position coordinates of each scan point and the desired scan speed;

[0033] The waveform synthesis unit is used to generate a deflection control signal that changes continuously with time based on the position coordinates of each scanning point and the desired scanning speed.

[0034] The power amplification unit is used to amplify the deflection control signal and output it to the deflection scanning module.

[0035] Preferably, the deflection control signal generated by the waveform synthesis unit is a position-time signal, wherein the slope of the position-time curve corresponds to the scanning speed of the electron beam, and the position signal between adjacent scanning points changes continuously, only changing in the slope.

[0036] Preferably, it also includes an in-situ observation module connected to the central control module, used to acquire morphological images or temperature field information of the sample surface.

[0037] Preferably, the central control module is also used to control the timing switching between the heating process and in-situ observation. During the heating process, it operates in an intermittent mode, pausing heating after each preset heating time, starting the in-situ observation module to acquire images, and resuming heating after the acquisition is completed.

[0038] Beneficial effects

[0039] 1. This invention uses a variable-speed continuous scanning method to replace the traditional skip scanning method. The electron beam moves continuously on the scanning path without stopping or pausing, avoiding frequent and large-scale switching between high-speed movement and static dwell, which significantly reduces the difficulty of engineering implementation and enables the loading of the preset motion process of the scanning electron beam with higher precision.

[0040] 2. This invention controls the energy injection amount at each position by continuously changing the scanning speed in real time, so that the actual energy density distribution matches the preset target energy density distribution. It can flexibly achieve uniform distribution, gradient distribution, Gaussian distribution or arbitrary custom distribution to meet the diverse heat treatment needs of micro and nano structures.

[0041] 3. This invention fills the application gap between existing electron beam technology in small-scale imaging (low power) and large-scale thermal processing (high power). It provides for the first time an electron beam heating process suitable for millimeter-scale micro-nano structures with medium beam current and high-speed scanning capability, providing an effective tool for applications such as annealing, crystallization, thermally induced reaction, thermal modification and heat transfer performance testing of micro-nano devices.

[0042] 4. This invention integrates an in-situ observation module, which can acquire morphological images and temperature field information of the sample surface before heating, during heating intervals, or after heating without disrupting the vacuum, thereby enabling real-time monitoring of the heating process and providing data support for process optimization. Attached Figure Description

[0043] Figure 1 Schematic diagram of the overall structure of the high-speed electron beam scanning injection processing equipment;

[0044] Figure 2 Electron beam injection experiment flowchart;

[0045] Figure 3 : A diagram illustrating the process of solving the scan velocity data set;

[0046] Figure 4 Flowchart of electron beam heating system. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the invention and are not intended to limit the scope of protection of the invention.

[0048] Example 1

[0049] Please see Figure 2-3 As shown, this embodiment provides an electron beam heating method for micro / nano structures, which includes the following steps:

[0050] S1: Sample preparation and loading.

[0051] The sample containing micro / nano structures is fixed onto the sample stage of the vacuum sample stage, ensuring good thermal conductivity between the sample and the stage. The micro / nano structures include, but are not limited to, nanowire arrays, micro / nano channels, two-dimensional material sheets, MEMS cantilever beams, semiconductor devices, or photolithographic patterns. After sample fixation, the vacuum chamber is evacuated to achieve a vacuum level equivalent to the working pressure, for example, better than 10. -3 Pa.

[0052] S2: Generates a focused electron beam.

[0053] An electron source is activated, and the electron beam is focused into a micrometer-scale beam spot through an electron optics tube. Specifically, a thermionic electron gun (such as lanthanum hexaboride LaB6 or tungsten filament) or a field emission electron gun can be used, and the accelerating voltage can be continuously adjusted within the range of 1kV to 100kV according to heating requirements. The electron optics tube focuses the electron beam into a micrometer-scale beam spot (typical beam spot diameter 1μm to 10μm) to meet the spatial resolution requirements for heating micro- and nanostructures.

[0054] S3: Set the target energy density distribution.

[0055] Users define the desired energy density distribution function E(x,y) within the target area through the software interface of the central control module. The typical size of the target area is 1mm×1mm to 5mm×5mm. Typical distribution types include uniform distribution (constant energy density throughout the target area), linear gradient distribution (energy density varies linearly along a certain direction), Gaussian distribution (energy density follows a Gaussian bell curve), and arbitrary custom distribution (defined by the user through input data points or function expressions).

[0056] S4: Calculate the scan speed data set.

[0057] Based on the target energy density distribution, calculate the scanning velocity data set of the electron beam at various locations within the target region. The specific calculation process is as follows:

[0058] Step 1: Discretize the target energy distribution. Use a uniform grid for spatial partitioning, with a grid side length of [value missing]. The X and Y directions are divided into m and n grids respectively, for a total of A grid is formed by sequentially connecting the various grids along a preset scanning path, such as a raster scanning path, and labeling each grid with a number 1, 2...N. The center coordinates of each grid are recorded as follows: The target energy density on this grid is denoted as .

[0059] Step 2: Calculate the electron beam power, and denote the region of the target energy density distribution as... Then the formula for calculating the electron beam power is:

[0060]

[0061] The electron beam acceleration voltage U is set according to the heating requirements, then the electron beam current... .

[0062] Step 3: Calculate the discrete energy. When the center of the electron beam spot moves at a constant speed... The speed is used to sweep across the grid along the X direction (whether along the X or Y direction depends on the scan path planning; here we take the X direction as an example). During the process, grid The received energy can be expressed as

[0063]

[0064] In the formula, Let be the beam spot radius of the electron beam.

[0065] Step 4: Within one scan cycle, the grid... The received average energy density is

[0066]

[0067] therefore Let be a function of the scanning speed corresponding to each grid, denoted as Mesh under ideal reconstruction conditions The received time-averaged energy density should be equal to the target energy density on that grid.

[0068]

[0069] Step 5: Solve the system of equations to obtain the scanning velocity array. Each grid can be established Solve the above equations simultaneously One equation yields a system of equations:

[0070]

[0071] This system of equations can be solved using an iterative method: Set the initial scanning velocity for each grid (e.g., based on the expected scanning field frequency f, set the electron beam scanning velocity for each grid to be...). An adjustment coefficient (e.g., 1.01) is set, and the time-averaged energy density of each grid is calculated and compared with the target energy density. For grids with a time-averaged energy density higher than the target energy density, the local electron beam scanning speed is increased by multiplying by the adjustment coefficient. For grids with a time-averaged energy density lower than the target energy density, the local electron beam scanning speed is decreased by dividing by the adjustment coefficient. This process is repeated iteratively until the set maximum number of iterations is reached or the expected target energy density field reconstruction accuracy is achieved (i.e., the maximum absolute value of the relative deviation between the time-averaged energy density of each grid and the target energy density meets the requirements), thereby obtaining the electron beam scanning speed corresponding to each grid. The scanning velocity data set is obtained by using the X-coordinate of each grid center as the first column of data, the Y-coordinate of each grid center as the second column of data, and the electron beam scanning velocity corresponding to each grid as the third column of data.

[0072] S5: Perform variable speed continuous scanning heating.

[0073] The heating program is initiated, and the electron gun outputs the set accelerating voltage and total beam current. The central control module sends the scan velocity data set calculated in step S4 to the signal generation module. Based on this, the signal generation module generates a continuously changing electrical signal to drive the deflection scanning module, causing the electron beam to move in a continuous scanning manner within the target area. By continuously changing the scan velocity in real time, the energy injection amount at each position is controlled, so that the actual energy injection amount at each position matches the target energy density distribution, thereby heating the sample.

[0074] During the scanning process, the scanning field frequency is ≥100Hz, enabling millisecond-level hot-loading response. The continuous scanning method can employ either raster scanning (i.e., fast mainline scanning in the X direction and slow step scanning in the Y direction) or serpentine scanning. It is worth noting that the scanning method of this invention differs fundamentally from the skip scanning method in existing technologies: throughout the entire scanning process, the electron beam moves continuously along the scanning path without pauses between scanning points. The deflection signal changes continuously without abrupt jumps, only undergoing the expected change in the slope of the scanning speed, thus fundamentally avoiding the mechanical oscillations and electromagnetic shocks caused by skip scanning.

[0075] Example 2

[0076] Please see Figure 1and Figure 4 As shown, this embodiment provides an electron beam heating system for micro / nano structures, including the following modules:

[0077] The electron beam generation module is used to generate and focus an electron beam. This module includes an electron source and an electron optics tube. The electron source can be a thermionic electron gun (LaB6 hexaboride or tungsten filament) or a field emission electron gun, with the accelerating voltage continuously adjustable from 1kV to 100kV. The electron optics tube focuses the electron beam into a micrometer-scale beam spot (typical beam spot diameter 1μm~10μm) to meet the spatial resolution requirements for heating micro / nano structures.

[0078] The deflection scanning module is used to drive the electron beam to scan within the target area. This module consists of a two-dimensional deflection coil (or electrostatic deflection plate), which generates a deflection magnetic field (or electric field) under the action of a driving current, causing the electron beam to deflect in the XY plane, thus achieving two-dimensional scanning.

[0079] A signal generation module, connected to the deflection scanning module, is used to convert the scanning speed data set into a continuously changing electrical signal that drives the deflection scanning module. This module is the core execution component connecting "mathematical programming" and "bead pattern motion," and specifically includes:

[0080] The storage unit stores scan speed data sets issued by the central control module, the data sets containing the position coordinates of each scan point. and the corresponding expected scan speed (where i = 1, 2, ..., N).

[0081] The waveform synthesis unit generates a deflection control signal that continuously varies with time based on the position coordinates of each scan point and the desired scan speed. The waveform synthesis unit uses direct digital synthesis (DDS) technology to generate the position command signal. Its specific working principle is as follows: First, based on the preset scan path (taking a standard raster scan path as an example), the side length of the spatial grid is... With speed Establish time correlation, the center of the electron beam spot passes through the first The time required for each grid (i.e., the dwell time) From the formula Real-time calculation. Because the target energy density differs across grid cells, the corresponding... Different, therefore The trigger pulse sequence changes in real time with the spatial position, forming a non-uniform time interval. Then, the displacement of each pixel is... With the calculated non-uniform time increment Combined, a continuous time-location lookup table is generated by accumulating these elements. ,in A digital signal processor (DSP) linearly interpolates the lookup table using a high-frequency clock (e.g., several MHz) to generate a continuous analog voltage ramp signal. The ramp signal has a slope at the boundaries of each pixel. Real-time switching, i.e., the speed at the end of the previous pixel. The speed of natural transition to the start of the next pixel The position signal itself remains absolutely continuous (without step jumps), changing only as expected in the slope. In the Y direction (slow stepping), after the waveform synthesis unit completes a full line scan in the X direction, it issues a step trigger signal based on the total accumulated time of that line, driving the Y-direction deflection coil to rise by one pixel spacing. This stepping occurs during a very short retrace period in the X-direction, and the continuity of the two-dimensional motion trajectory is ensured through timing synchronization.

[0082] The power amplification unit is used to amplify the deflection control signal output by the waveform synthesis unit and output it to the deflection scanning module to drive the deflection coil to generate a sufficient deflection magnetic field.

[0083] The power control module, connected to the electron beam generation module, is used to adjust the accelerating voltage and beam current of the electron beam. The accelerating voltage adjustment range is 1kV~100kV, the total beam current adjustment range is 10μA~10mA, and the beam current stability is better than ±0.5%.

[0084] A vacuum sample module includes a vacuum chamber and a sample stage disposed within the vacuum chamber. The vacuum chamber provides a vacuum environment with a vacuum level better than 10. -3 Pa. The sample stage is a three-axis motorized translation stage with a positioning accuracy of ±1μm, used to support samples and precisely position them in three dimensions. The sample stage can also be equipped with liquid nitrogen cooling or resistance heating modules to meet the heating treatment requirements under different temperature conditions.

[0085] The central control module, connected to both the signal generation module and the power control module, is used to set the target energy density distribution, calculate the scan speed data set and send it to the signal generation module, and control the heating process. The central control module consists of an industrial computer and real-time control software. It is responsible for loading the preset energy distribution map, automatically executing the scan speed data set calculation in step S4, sending the calculation results to the signal generation module, controlling the electron gun parameters, high voltage, and beam current, coordinating the heating and imaging timing, and recording all parameters and images.

[0086] The in-situ observation module, connected to the central control module, is used to acquire morphological images and / or temperature field information of the sample surface. The in-situ observation module includes an independent low-current scanning electron generator with an accelerating voltage of 1kV~30kV, a beam current ≤1nA, and a resolution better than 20nm. It can rapidly acquire high-resolution morphological images of the sample surface before heating, during heating intervals, or after heating without disrupting vacuum conditions. The in-situ observation module may also include an infrared camera for real-time acquisition of temperature field information of the sample surface.

[0087] The central control module is also used to control the timing switching between the heating process and in-situ observation. During heating, due to the large beam current during main beam heating, an intermittent observation mode is preferentially adopted: heating is paused after every 0.5 to 1 second (e.g., by quickly shutting off the main beam current through grid bias or deflecting it to a Faraday cup), and the in-situ observation module is activated to acquire images (time <0.1 seconds). After acquisition is completed, heating continues. This mode can acquire morphological evolution information during the heating process without removing the sample or disrupting the vacuum, achieving closed-loop optimization of the process.

[0088] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electron beam heating method for micro / nano structures, characterized in that, Includes the following steps: S1. Place the sample on the vacuum sample stage and evacuate the vacuum chamber. S2. Start the electron source to generate a focused electron beam; S3. Set the target energy density distribution within the target area; S4. Based on the target energy density distribution, calculate the scanning speed data set of the electron beam at each position in the target area. The scanning speed data set includes the position coordinates of each scanning point and the corresponding expected scanning speed. S5. Within the target area, the electron beam is driven to move in a continuous scanning manner, and the scanning speed is continuously changed in real time to match the actual energy injection amount at each position with the target energy density distribution, so as to heat the sample.

2. The electron beam heating method for micro / nano structures according to claim 1, characterized in that, The target energy density distribution can be a uniform distribution, a gradient distribution, a Gaussian distribution, or a custom distribution.

3. The electron beam heating method for micro / nano structures according to claim 1, characterized in that, The calculation method for the scan speed data set is as follows: The target region is discretized into a uniform grid, and the center coordinates of each grid are the position coordinates of the scanning point. Establish a set of energy balance equations between the time-averaged energy density of each grid and the scanning velocity of each scanning point; Solve the system of equations to obtain the electron beam scanning velocity corresponding to each grid.

4. The electron beam heating method for micro / nano structures according to claim 3, characterized in that, The system of equations is solved using an iterative method, which includes: Set the initial scan speed for each grid; Calculate the current time-averaged energy density of each grid cell and compare it with the target energy density; For grids with a time-averaged energy density higher than the target energy density, increase the scan rate corresponding to that grid; for grids with a time-averaged energy density lower than the target energy density, decrease the scan rate corresponding to that grid. Repeat the iteration until the convergence condition is met.

5. The electron beam heating method for micro / nano structures according to claim 1, characterized in that, The continuous scanning method is either raster scanning or serpentine scanning.

6. An electron beam heating system for micro / nano structures, characterized in that, include: Electron beam generation module, used to generate and focus an electron beam; The deflection scanning module is used to drive the electron beam to scan within the target area; A signal generation module, connected to the deflection scanning module, is used to convert the scanning speed data group into a continuously changing electrical signal that drives the deflection scanning module; A power control module, connected to the electron beam generating module, is used to adjust the accelerating voltage and beam current of the electron beam. A vacuum sample module includes a vacuum chamber and a sample stage disposed within the vacuum chamber, the sample stage being used to hold a sample; The central control module is connected to the signal generation module and the power control module respectively, and is used to set the target energy density distribution, calculate the scanning speed data set and send it to the signal generation module, and control the heating process.

7. The electron beam heating system for micro / nano structures according to claim 6, characterized in that, The signal generation module includes: The storage unit is used to store a scan speed data set containing the position coordinates of each scan point and the desired scan speed; The waveform synthesis unit is used to generate a deflection control signal that changes continuously with time based on the position coordinates of each scanning point and the desired scanning speed. The power amplification unit is used to amplify the deflection control signal and output it to the deflection scanning module.

8. The electron beam heating system for micro / nano structures according to claim 7, characterized in that, The deflection control signal generated by the waveform synthesis unit is a position-time signal, wherein the slope of the position-time curve corresponds to the scanning speed of the electron beam, and the position signal between adjacent scanning points changes continuously, only changing in the slope.

9. An electron beam heating system for micro / nano structures according to claim 6, characterized in that, It also includes an in-situ observation module, which is connected to the central control module, for acquiring morphological images or temperature field information of the sample surface.

10. An electron beam heating system for micro / nano structures according to claim 9, characterized in that, The central control module is also used to control the timing switching between the heating process and in-situ observation. During the heating process, it operates in intermittent mode, pausing heating after each preset heating time, starting the in-situ observation module to acquire images, and resuming heating after the acquisition is completed.

Images