Multi-wavelength light-induced photoelectron charge compensation device and method for SIMS analysis

Abstract

The invention discloses a multi-wavelength light-induced photoelectron charge compensation device and method for SIMS analysis, and the device comprises an adjustable wavelength light source which is used for generating light of which the wavelength is adjustable in a range from ultraviolet to visible light; the optical system is used for guiding the light generated by the adjustable wavelength light source to the surface of a sample bombarded by an SIMS primary ion beam, and ensuring that a photon beam spot is accurately overlapped with an ion beam bombarded area; and the control unit is used for dynamically adjusting the wavelength and the light intensity of the adjustable wavelength light source according to the stability of the SIMS secondary ion signal so as to optimize photoelectron emission and realize charge neutralization. The invention has the following beneficial effects: the technical scheme avoids physical damage of the electron gun to the sample and damage to the vacuum environment; the wavelength can be adjusted to cover ultraviolet light to visible light, and the device is suitable for various materials.

Description

Technical Field

[0001] This invention relates to the field of electronic optics, and in particular to a multi-wavelength light-induced photoelectron charge compensation device and method for SIMS analysis. Background Technology

[0002] Secondary ion mass spectrometry (SIMS) is a commonly used surface composition analysis technique in the chip industry. It achieves elemental analysis in the micrometer-scale region by bombarding the sample surface with a primary ion beam to excite secondary ions. However, when analyzing insulating samples, primary ion beam bombardment can lead to surface charge accumulation, causing problems such as distortion of the secondary ion signal and a decrease in mass resolution.

[0003] Existing charge compensation methods mostly employ electron guns to neutralize surface charges by emitting electrons, but they suffer from three major drawbacks: they disrupt the vacuum environment, affecting analytical stability; the charge neutralization is uneven, making it difficult to match the 200μm×200μm local analytical region of SIMS; and electron beam heating causes sample damage, limiting the application of fragile materials.

[0004] To address the aforementioned issues, this invention develops a tunable wavelength light-induced photoelectron charge compensation technique for SIMS analysis. This technique achieves charge neutralization through non-contact light excitation, adapts to the work function of different materials, and dynamically adjusts optical parameters to improve signal stability, thus avoiding the shortcomings of existing electron gun methods. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a multi-wavelength light-induced photoelectron charge compensation device and method for SIMS analysis, thereby solving one or more of the above-mentioned prior art problems.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: a multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis, the innovation of which is: comprising:

[0007] Tunable wavelength light source, used to generate light with tunable wavelength in the ultraviolet to visible range;

[0008] An optical system is used to guide the light generated by the tunable wavelength light source to the sample surface bombarded by the SIMS primary ion beam, ensuring that the photon beam spot precisely coincides with the ion beam bombardment area;

[0009] The control unit is used to dynamically adjust the wavelength and light intensity of the tunable wavelength light source based on the stability of the SIMS secondary ion signal, so as to optimize photoelectron emission and achieve charge neutralization.

[0010] In some implementations, the tunable wavelength light source is a xenon lamp, an LED, or a laser diode array.

[0011] In some embodiments, the optical system includes a lens, a filter, and a two-dimensional translation stage, the two-dimensional translation stage being used to adjust the position of the lens to calibrate the overlap between the light spot and the ion beam bombardment area.

[0012] In some implementations, the control unit includes a preset "material-recommended excitation wavelength" lookup table that can automatically recommend an initial excitation wavelength based on the work function or bandgap of the sample.

[0013] In some implementations, the control unit controls filter switching and incident angle adjustment via a motor, which includes a filter switching motor with limit positions and a stepper motor for adjusting the incident angle.

[0014] A method for achieving SIMS charge compensation using the aforementioned multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis includes the following steps:

[0015] a) After loading the insulating sample to be tested into the SIMS vacuum sample stage, select the initial excitation wavelength according to the work function or bandgap of the sample; b) Adjust the optical system to ensure that the photon beam spot precisely coincides with the primary ion beam bombardment area; c) Start the SIMS primary ion beam and tunable wavelength light source, and monitor the stability of the secondary ion signal; d) Based on the feedback of the secondary ion signal, dynamically adjust the wavelength and intensity of the light source to achieve charge neutralization.

[0016] In some implementations, the selection of the initial excitation wavelength in step a) satisfies To ensure that the photon energy is slightly greater than the sample work function, where The work function of the sample is expressed in units of . .

[0017] In some implementations, the optical path alignment in step b) includes:

[0018] Coarse alignment: A visible guide light, coaxial with an adjustable light source, is used to illuminate the sample surface to form a light spot;

[0019] Precise alignment: A sputtering pit is formed by pre-sputtering with a primary ion beam, and the position of the beam spot is adjusted to completely cover the sputtering pit.

[0020] In some implementations, the feedback parameter in step d) is the instantaneous fluctuation rate δ of the secondary ion signal, defined as the percentage of the difference between the signal peak and valley values ​​relative to the average value.

[0021] In some implementations, the dynamic adjustment in step d) includes:

[0022] Wavelength scan optimization: Perform small-step scans near the initial wavelength to select the optimal wavelength with the lowest signal fluctuation rate;

[0023] Light intensity adjustment: After locking the optimal wavelength, adjust the light intensity until the signal fluctuation rate drops below the preset threshold.

[0024] The beneficial effects of this invention are:

[0025] Non-destructive: Avoids physical damage to the sample and disruption of the vacuum environment caused by the electron gun.

[0026] Highly adaptable: The adjustable wavelength covers ultraviolet to visible light and is compatible with a variety of materials.

[0027] Localization neutralization: The light spot precisely overlaps with the ion beam region, improving signal uniformity.

[0028] Dynamic stability: Real-time feedback adjustment ensures signal volatility ≤5%.

[0029] Long-term reliability: Minimal light source drift, suitable for long-term analysis. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0031] Figure 1 This is a schematic diagram of the SIMS system integrating the photoelectric charge compensation device of the present invention.

[0032] Figure 2 This invention relates to an adjustable wavelength light source module.

[0033] Figure 3 This is a schematic diagram of the optical path system of the present invention.

[0034] Figure 4 This is a flowchart of the SIMS signal feedback control light source of the present invention. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figures 1 to 4 As shown, the embodiments of the present invention include: a multi-wavelength light-induced photoelectron charge compensation device and method for SIMS analysis, the specific implementation of which is as follows.

[0037] I. Specific Implementation Method of Multiwavelength Light-Induced Photoelectron Charge Compensation Device for SIMS Analysis

[0038] 1. Tunable wavelength light source

[0039] Used to generate tunable light in the ultraviolet to visible light range, adaptable to the photoelectric properties of different samples. Includes:

[0040] (1) Light source type: Xenon lamp, LED or laser diode array can be selected; among them, the xenon lamp with built-in deep ultraviolet deuterium lamp can provide a continuous spectrum output of 190nm~400nm, and the light output drift is less than 0.01% per hour, ensuring long-term stability.

[0041] (2) Wavelength coverage: Covers the ultraviolet to visible light range to meet the excitation requirements of materials such as SiO2 and SiN.

[0042] 2. Optical System

[0043] Used to guide the light source to the SIMS primary ion beam bombardment region, ensuring precise alignment of the photon beam spot with the ion beam analysis region. Includes:

[0044] (1) Core components: at least two lenses, filters, and a two-dimensional translation stage with XY displacement.

[0045] (2) Optical path calibration:

[0046] 1) Coarse alignment: Illuminate the sample surface with a visible guide light coaxial with the adjustable light source to form a visible light spot.

[0047] 2) Precise alignment: Start the primary ion beam pre-sputtering to form a micron-sized sputtering pit. Adjust the XY displacement stage to make the spot completely cover the pit area. The center alignment error is ≤20% of the spot diameter; if the spot diameter is 200μm, the error is ≤40μm.

[0048] (3) Ion beam compatibility: The design is adapted to the 60° incident angle of the Cs⁺ ion beam to ensure that there is no interference between the optical path and the ion beam path.

[0049] 3. Control Unit

[0050] Used for initial wavelength recommendation, optical path adjustment, signal feedback, and dynamic control. Includes:

[0051] (1) Hardware components: LED digital tube, keyboard, microcontroller, driver circuit.

[0052] (2) Software functions:

[0053] 1) Preset lookup table: based on the sample work function Automatic calculation of initial wavelength .

[0054] 2) Motor control:

[0055] a. Filter switching motor: equipped with limit function to achieve rapid switching of different wavelength filters.

[0056] b. Incident angle adjustment motor: A stepper motor is used to achieve fine wavelength adjustment through angle subdivision.

[0057] 3) Signal feedback: Real-time acquisition of SIMS secondary ion signals and calculation of instantaneous fluctuation rate. , It represents the percentage difference between the signal peak and trough values ​​relative to the average value.

[0058] II. Specific Implementation Methods of Multiwavelength Light-Induced Photoelectron Charge Compensation Method for SIMS Analysis

[0059] This method, based on the above-mentioned apparatus, comprises the following steps:

[0060] 1. System Initialization and Parameter Preset

[0061] (1) Sample property input: Input the sample material, and the system will retrieve its work function.

[0062] (2) Initial wavelength calculation: According to the formula Recommended initial wavelength .

[0063] (3) Optical path pre-alignment:

[0064] 1) Coarse alignment: Turn on the visible guide light and adjust the XY displacement stage to position the light spot in the target area on the sample surface.

[0065] 2) Precision alignment: Start the primary ion beam pre-sputtering to form a 200μm×200μm sputtering pit, and adjust the spot to cover the pit area.

[0066] 2. Synchronous Start-up and Signal Monitoring

[0067] (1) Synchronous operation: Maintain the initial wavelength and initial light intensity, and start the adjustable light source and primary ion beam.

[0068] (2) Signal baseline: Collect secondary ion signals within 10 seconds and calculate the average value and standard deviation.

[0069] (3) Real-time monitoring: δ value is continuously calculated as a feedback parameter.

[0070] 3. Dynamic control strategy

[0071] (1) Based on δ and the preset threshold:

[0072] 1) Steady state: If Maintain current parameters;

[0073] 2) Regulation mode: If ,implement:

[0074] a. Wavelength Scan: Switch filters within a range of ±20nm from the initial wavelength, selecting... The smallest wavelength;

[0075] a. Light intensity adjustment: Gradually adjust the light intensity (increasing the power by 5% each time) until δ≤5%.

[0076] 4. Process complete

[0077] After the SIMS analysis is completed, the light source is turned off after a 5-second delay, and the system is reset to its default state.

[0078] The advantages of this technical solution are:

[0079] Non-destructive: Avoids physical damage to the sample and disruption of the vacuum environment caused by the electron gun.

[0080] Highly adaptable: The adjustable wavelength covers ultraviolet to visible light and is compatible with a variety of materials.

[0081] Localization neutralization: The light spot precisely overlaps with the ion beam region, improving signal uniformity.

[0082] Dynamic stability: Real-time feedback adjustment ensures signal volatility ≤5%.

[0083] Long-term reliability: Minimal light source drift, suitable for long-term analysis.

[0084] Example

[0085] Taking SIMS analysis of SiO2 samples as an example:

[0086] 1. Sample preparation

[0087] When inputting SiO2 properties, the system recommends an initial wavelength of 300nm.

[0088] 2. Optical path calibration

[0089] Coarse alignment: The visible guide light spot is located at the center of the sample.

[0090] Precise alignment: Pre-sputtering forms a 200μm×200μm pit, with the spot covering the pit area, and the error is ≤30μm.

[0091] 3. Analysis Process

[0092] Initial state: δ=8%, exceeding the threshold of 5%.

[0093] Regulation:

[0094] Wavelength scan: δ=4.5% at 305nm.

[0095] Light intensity tuning: increased to 45%, δ decreased to 3.8%.

[0096] Stability analysis: Over a period of 30 minutes, the signal volatility remained stable at 3%~4%.

[0097] 4. Results

[0098] The stability of the secondary ion signal of SiO2 was improved by 60%, and there were no damage marks on the sample surface.

[0099] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis, characterized in that: include: Tunable wavelength light source, used to generate light with tunable wavelength in the ultraviolet to visible range; An optical system is used to guide the light generated by the tunable wavelength light source to the sample surface bombarded by the SIMS primary ion beam, ensuring that the photon beam spot precisely coincides with the ion beam bombardment area; The control unit is used to dynamically adjust the wavelength and light intensity of the tunable wavelength light source based on the stability of the SIMS secondary ion signal, so as to optimize photoelectron emission and achieve charge neutralization.

2. The multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis according to claim 1, characterized in that: The adjustable wavelength light source is a xenon lamp, an LED, or a laser diode array.

3. The multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis according to claim 1, characterized in that: The optical system includes a lens, a filter, and a two-dimensional translation stage. The two-dimensional translation stage is used to adjust the position of the lens to calibrate the overlap between the light spot and the ion beam bombardment area.

4. The multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis according to claim 1, characterized in that: The control unit includes a preset "material-recommended excitation wavelength" lookup table, which can automatically recommend the initial excitation wavelength based on the work function or bandgap of the sample.

5. The multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis according to claim 1, characterized in that: The control unit controls the filter switching and incident angle adjustment via a motor, which includes a filter switching motor with limit position and a stepper motor for adjusting the incident angle.

6. A method for achieving SIMS charge compensation using the multi-wavelength light-induced photoelectron charge compensation device for SIMS analysis as described in any one of claims 1-5, characterized in that: Includes the following steps: a) After loading the insulating sample to be tested into the SIMS vacuum sample stage, select the initial excitation wavelength according to the work function or bandgap of the sample; b) Adjust the optical system to ensure that the photon beam spot precisely coincides with the primary ion beam bombardment area; c) Start the SIMS primary ion beam and tunable wavelength light source, and monitor the stability of the secondary ion signal; d) Based on the feedback of the secondary ion signal, dynamically adjust the wavelength and intensity of the light source to achieve charge neutralization.

7. The multi-wavelength light-induced photoelectron charge compensation method for SIMS analysis according to claim 6, characterized in that: The selection of the initial excitation wavelength in step a) satisfies To ensure that the photon energy is slightly greater than the sample work function, where The work function of the sample is expressed in units of . .

8. The multi-wavelength light-induced photoelectron charge compensation method for SIMS analysis according to claim 6, characterized in that: The optical path alignment in step b) includes: Coarse alignment: A visible guide light, coaxial with an adjustable light source, is used to illuminate the sample surface to form a light spot; Precise alignment: A sputtering pit is formed by pre-sputtering with a primary ion beam, and the position of the beam spot is adjusted to completely cover the sputtering pit.

9. The multi-wavelength light-induced photoelectron charge compensation method for SIMS analysis according to claim 6, characterized in that: The feedback parameter in step d) is the instantaneous fluctuation rate δ of the secondary ion signal, which is defined as the percentage of the difference between the signal peak and valley values ​​relative to the average value.

10. The multi-wavelength light-induced photoelectron charge compensation method for SIMS analysis according to claim 6, characterized in that: The dynamic adjustment in step d) includes: Wavelength scan optimization: Perform small-step scans near the initial wavelength to select the optimal wavelength with the lowest signal fluctuation rate; Light intensity adjustment: After locking the optimal wavelength, adjust the light intensity until the signal fluctuation rate drops below the preset threshold.

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