Ion microscopes and focused ion beam systems with a single optical instrument

Abstract

An ion microscope and focused ion beam system with a single optical device includes a vacuum chamber, an emitter, a gas pressure control device, an optical device, a voltage control module, and a signal control module. The emitter, optical device, and sample are housed within the vacuum chamber. The gas pressure control device stores gas and is connected to the chamber wall. The voltage control module is electrically connected to the emitter and optical device, generating a draw voltage to the emitter and a bias voltage to the optical device. The signal control module connects to the gas pressure control device and the voltage control module, generating a gas introduction control signal to allow the gas pressure control device to introduce gas into the internal space. The signal control module also adjusts the output bias voltage and draw voltage to generate heavy and light ion beams at the emitter.

Description

[Technical Field]

[0001] This invention relates to an ion beam system with optical devices, and more particularly to an ion microscope and a focused ion beam system with a single optical device. [Previous Technology]

[0002] Please refer to Figure 2, which is a schematic diagram of a conventional dual-beam focused ion beam system. Currently, focused ion beam systems (FIB) play an indispensable role in semiconductor fault analysis and circuit repair. The commonly used dual-beam focused ion beam system (Dual-Beam FIB; DB-FIB)2 mainly consists of two sets of optical components (columns) 21 and 22. One set is used to generate a heavy ion beam (e.g., gallium or xenon ions) to process the sample S, and the other set is used to generate an electron beam or light ion beam to obtain a microscopic image of the sample S. However, for dual-beam focused ion beam systems 2, and even for focused ion beam systems using three sets of optical structures, the need to use two or more separately and independently configured optical components for sample processing and microscopic imaging results in problems such as high equipment cost, complex equipment structure, and cumbersome operation.

[0003] To address the aforementioned problems, while single optical devices that integrate the generation of heavy ion beams for processing and electron beams for imaging exist, the designs of such devices are often unsuccessful due to the complexity of mechanical switching tools or the instability of the electron emitter. Furthermore, since the emitting material used in the focused ion beam and electron beam system of such single optical devices is liquid metal, the liquid metal flows to the emitter tip to emit the ion beam, and after cooling, forms a metal tip substrate for emitting the electron beam. The liquid metal diminishes after being heated and emitted. Although this system continuously replenishes liquid metal to the emitter tip, the inherent instability of the liquid's shape means that the position and size of the liquid metal at the emitter tip cannot be fixed after each heating and cooling cycle.

[0004] Accordingly, how to provide an ion microscope and a focused ion beam system with a single optical device to solve the above problems has become an urgent research topic. [Summary of the Invention]

[0005] In view of the above problems, the present invention discloses an ion microscope and a focused ion beam system with a single optical device, comprising a vacuum chamber, an emitter, a gas pressure control device, an optical device, a voltage control module, and a signal control module. The vacuum chamber has an internal space. The emitter, the optical device, and the sample are disposed within the internal space of the vacuum chamber. The gas pressure control device stores at least one gas and is connected to the cavity wall of the vacuum chamber. The voltage control module is electrically connected to the emitter and the optical device, generating a draw voltage to the emitter and a bias voltage to the optical device. The signal control module connects to the gas pressure control device and the voltage control module, generating a gas-introducing control signal to the gas pressure control device, causing the gas pressure control device to introduce at least one gas into the internal space of the vacuum chamber. The signal control module adjusts the bias voltage output from the voltage control module to the optical device and adjusts the absorption voltage output from the voltage control module to the emitter, so that the emitter generates a heavy ion beam for processing the sample and a light ion beam for imaging the sample through the at least one gas. The heavy ion beam for processing the sample is generated through a first gas in the at least one gas, and the light ion beam for imaging the sample is generated through a second gas in the at least one gas. The molecules of the first gas are larger than the molecules of the second gas, and the signal control module adjusts the absorption voltage according to the molecular types of the first gas and the second gas.

[0006] As described above, when the signal control module generates a gas introduction control signal to the gas pressure control device, the gas pressure control device introduces the first gas into the internal space of the vacuum chamber, and the signal control module generates the gas absorption voltage to the voltage control module, causing the emitter to emit one ion beam of the gas. The signal control module adjusts the bias voltage output from the voltage control module to the optical device, so that the focusing lens module can adjust the size of the spot formed by the ion beam on the sample surface. The scanning deflection module controls the movement of the ion beam on the sample surface to process and scan the sample. The signal detector detects the signal generated by the interaction between the ion beam and the sample and transmits it back to the signal control module to image the sample. Next, the signal control module generates a gas introduction control signal to the gas pressure control device, the gas pressure control device introduces the second gas into the internal space of the vacuum chamber, and the signal control module generates the gas absorption voltage to the voltage control module, causing the emitter to emit one ion beam of the gas. The signal control module adjusts the bias voltage output of the optical device from the voltage control module. The focusing lens module adjusts the size of the spot formed by the ion beam on the sample surface. The scanning deflection module controls the ion beam to scan the sample surface. The signal detector detects the signal generated by the interaction between the ion beam and the sample and sends it back to the signal control module for sample imaging. When the signal control module closes the gas regulating valve, preventing gas from entering the vacuum chamber, and waits for the pressure in the vacuum chamber to return to an ultra-high vacuum state, the signal control module generates an electron-drawing negative bias voltage to the voltage control module, causing the emitter to emit an electron beam. The signal control module adjusts the bias voltage output of the optical device from the voltage control module. The focusing lens module adjusts the size of the spot formed by the electron beam on the sample surface. The scanning deflection module controls the electron beam to scan the sample surface. The signal detector detects the signal generated by the interaction between the electron beam and the sample and sends it back to the signal control module for sample imaging.

[0007] As described above, when the signal control module generates a gas control signal to the gas pressure control device, multiple gases can be introduced simultaneously. Based on the different ionization energies of different molecules, the desired ion beam can be selected. Alternatively, a mass separator can be added to the optical device to select the desired ion beam. Or, after completing a specified task with a single gas, the gas regulating valve can be closed, preventing further gas introduction into the vacuum chamber. Once the pressure around the emitter returns to an ultra-high vacuum state, another gas can be introduced for the corresponding task. As described above, the ion microscope and focused ion beam system of this invention, through the design of a single optical device, adjustment of the gas type within the vacuum chamber, and application of different ionization voltages, can generate multiple charged particle beams for various applications such as multifunctional processing, high-precision processing, high-resolution imaging, and sample composition analysis, further realizing the flexible generation and application of different charged particle beams. Furthermore, the design of a single optical device not only significantly reduces equipment costs and system complexity but also further enhances operational convenience.

Implementation Method

[0008] Please refer to Figures 1A to 1C. Figure 1A is a block diagram of the ion microscope and focused ion beam system with a single optical device according to the present invention. Figure 1B is a schematic diagram of the emitter, optical device, and sample disposed in a vacuum chamber. Figure 1C is a magnified schematic diagram of the emitter tip. The ion microscope and focused ion beam system 1 with a single optical device includes a vacuum chamber 11, an emitter 12, a gas pressure control device 13, an optical device 14, a voltage control module 15, and a signal control module 16, wherein the voltage control module 15 and the signal control module 16 can be integrated into a voltage signal control device. The vacuum chamber 11 has an internal space, and the emitter 12, the optical device 14, and the sample S are disposed within the internal space of the vacuum chamber 11. The gas pressure control device 13 stores at least one gas and is connected to the chamber wall 111 of the vacuum chamber 11. The voltage control module 15 is electrically connected to the emitter 12 and the optical device 14, generating a draw voltage to the emitter 12 and a bias voltage to the optical device 14. The signal control module 16 is connected to the gas pressure control device 13 and the voltage control module 15, generating a gas introduction control signal to the gas pressure control device 13, causing the gas pressure control device 13 to introduce at least one gas into the internal space of the vacuum chamber 11. The signal control module 16 adjusts the bias voltage output from the voltage control module 15 to the optical device 14 and adjusts the draw voltage output from the voltage control module 15 to the emitter 12, causing the emitter 12 to generate a heavy ion beam for processing the sample S and a light ion beam for imaging the sample S through the at least one gas. The heavy ion beam for processing the sample S is generated by a first gas among the at least one gas, and the signal control module 16 adjusts the draw voltage according to the molecular type of the first gas. The light ion beam used for imaging sample S is generated by a second gas from at least one gas, and the signal control module 16 adjusts the absorption voltage according to the molecular type of the second gas, wherein the molecular weight of the first gas is greater than that of the second gas.

[0009] In this embodiment of the invention, the first gas system is a gas with a molecular weight greater than 21, including xenon, krypton, oxygen, nitrogen and argon, and the second gas system is a gas with a molecular weight less than 21, including hydrogen, neon and helium.

[0010] The ion microscope and focused ion beam system 1 with a single optical device further includes a signal detector 17 connected to the signal control module 16, which detects the signal generated by the interaction between the electron beam, the ion beam and the sample, so as to generate an imaging signal and transmit the imaging signal back to the signal control module 16 to image the sample.

[0011] The optical device 14 includes a focusing lens module 141, a scanning deflection module 142, and a mass separator module 143, which are disposed on the ion beam and electron beam emission path between the emitter 12 and the sample S, and are used to control the generated ion beam and electron beam. The focusing lens module 141 adjusts the size of the spot formed by the ion beam and electron beam on the sample. When the system generates a heavy ion beam for sample processing, the scanning deflection module 142 controls the movement and scanning of the ion beam on the sample surface. When the system generates a light ion beam and electron beam for sample imaging, the scanning deflection module 142 controls the movement and scanning of the ion beam and electron beam on the sample surface. When the signal control module generates a gas introduction control signal to the gas pressure control device 13, multiple gases, including a first gas and a second gas, can be introduced simultaneously. According to the different ion ion energies, an appropriate absorption voltage is applied to select the desired ion beam; or according to the different ion charge-to-mass ratios, the desired ion beam is selected through the mass separator module (also called a mass filter) 143. Alternatively, after completing a designated task with a single gas, the gas regulating valve 132 can be closed to prevent further gas introduction into the vacuum chamber 11. The vacuum pump 133 can then extract the gas from the vacuum chamber 11 before introducing another gas to perform the corresponding task. The mass screening module 143 allows ions with a specific charge-to-mass ratio to pass through without being deflected, while ions with different charge-to-mass ratios are deflected and blocked, thus allowing for further screening of the desired ions.

[0012] The gas pressure control device 13 includes a gas container 131, a gas regulating valve 132, and a vacuum pump 133. The vacuum pump 133 and the gas regulating valve 132 are respectively connected to the cavity wall 111 of the vacuum chamber 11 and the signal control module 16. The device regulates the introduction of gas into the vacuum chamber 11 according to the gas introduction control signal generated by the signal control module 16, and stops the introduction of gas into the vacuum chamber 11 according to the gas extraction control signal generated by the signal control module 16. The gas extraction control signal generated by the signal control module 16 is transmitted to the vacuum pump 133 to extract gas from the vacuum chamber 11 through the vacuum pump 133 connected to the vacuum chamber 11. It should be noted that in the embodiments of the present invention, the order in which the heavy ion beam, light ion beam, and electron beam are generated is not limited, but can be generated according to the user's needs. For example, when a user wants to process and image sample S, the first gas and the second gas can be introduced sequentially or simultaneously, and heavy ion beams and light ion beams can be generated according to the different ionization energies of different molecules. Alternatively, a mass filter (i.e., a mass filter module 143) can be added to the optical device 14 to select the desired ion beam by filtering ions with different charge-to-mass ratios. Or, after introducing the processing gas, all the gas in the vacuum chamber 11 can be extracted by the vacuum pump 133 before generating the electron beam for imaging.

[0013] In embodiments of the present invention, the vacuum chamber 11 can generate an ion beam by introducing a single gas, or by introducing a mixture of multiple gases into the vacuum chamber 11 to generate different ion beams, and generate an electron beam after all the gases in the vacuum chamber 11 are removed. Further, the signal control module 16 generates a first gas introduction control signal, causing the gas pressure control device 13 to introduce the first gas into the internal space of the vacuum chamber 11, and causing the voltage control module 15 to apply a corresponding absorption voltage to the emitter 12 according to the ionization energy of the introduced first gas, further generating an ionizing electric field that can ionize gas ions, ionizing the gas adsorbed on the tip surface of the emitter 12 to generate a first gas ion beam. This ionizing electric field further attracts the gas adsorbed on the needle handle of the emitter 12 to the tip surface. Taking xenon as an example, when xenon is introduced into the internal space of the vacuum chamber 11, a positive absorption voltage (i.e., ionization voltage) is applied to the emitter 12 through the voltage control module 15. When the applied electric field reaches the ionization energy that can cause the xenon adsorbed on the tip surface of the emitter 12 to detach, a xenon ion beam is generated. This ionization electric field will further attract the xenon adsorbed on the emitter 12 to the tip surface of the emitter 12 to continuously generate a xenon ion beam.

[0014] When the signal control module 16 generates a gas extraction control signal, the signal control module closes the gas regulating valve 132, so that the first gas is no longer introduced into the vacuum chamber 11. After the vacuum pump 133 extracts the first gas from the vacuum chamber 11, the signal control module 16 further generates a second gas introduction control signal to the voltage control module 15 and the gas pressure control device 13, so that the gas pressure control device 13 introduces the second gas into the internal space of the vacuum chamber 11, and the voltage control module 15 applies a corresponding ionization voltage to the emitter 12 according to the ionization energy of the second gas, so as to generate a second gas ion beam.

[0015] When the signal control module 16 generates a gas extraction control signal, the signal control module closes the gas regulating valve 132 so that the gas is no longer introduced into the vacuum chamber 11. After the vacuum pump 133 extracts the gas from the vacuum chamber 11 and the pressure around the emitter 12 returns to the ultra-high vacuum state, the signal control module 16 generates an electron absorption negative bias voltage to the voltage control module 15, so that the emitter 12 emits an electron beam.

[0016] The ion beam systems generated in the above embodiments of the present invention can provide different functions according to the weight of their corresponding gases, and the weight of the gases is distinguished by their molecular weight. Taking xenon and helium as examples, xenon is a heavy ion gas, while helium is a light ion gas relative to xenon. Therefore, a xenon ion beam formed using xenon can be used for sample S processing, while a helium ion beam formed using helium causes less damage to the structure of sample S, and is therefore suitable for high-resolution scanning imaging of sample S.

[0017] Furthermore, when two or more mixed gases are introduced into the vacuum chamber 11 simultaneously, the applied ionization voltage can be adjusted according to the different molecular ionization energies to select the desired ion beam. To avoid interference caused by the ionization energies of different molecules being too similar, a mass filter can be added to the optical device to select the desired ion beam, so as to flexibly apply the ion beams generated by various gases to different operating environments.

[0018] Furthermore, the introduced gases can be categorized according to their ionization energy, molecular size, and activity into gas types suitable for sample S processing, sample imaging, and mass spectrometry analysis. That is, by mixing different gases within the vacuum chamber 11 of a single optical structure and adjusting the applied ionization voltage accordingly, a wide range of ion beams can be used for generating processing ion beams, focusing imaging light ion beams and electron beams, and mass spectrometry analysis ion beams. For example, when the voltage applied by the voltage control module 15 causes the emitter 12 tip to reach the ionization voltage of the first gas, the first gas will detach from the surface of the emitter 12 tip to generate a first gas ion beam. When the voltage applied by the voltage control module 15 causes the emitter 12 tip to reach the ionization voltage of the second gas, the second gas will detach from the surface of the emitter 12 tip to generate a second gas ion beam. In addition, the signal control module 16 further adjusts the absorption voltage output from the voltage control module 15 to the emitter 12, causing the emitter 12 to generate a third gas ion beam for mass spectrometry analysis of sample S. The third gas ion beam comprises either an active gas ion beam or an ion beam formed by a molecular cluster.

[0019] In this embodiment of the invention, the tip of the emitter 12 has a wrinkled structure. The material of the emitter includes metals such as tungsten, iridium, molybdenum, palladium, platinum, rhodium, and gold.

[0020] Referring to Figures 1D and 1E together, in one embodiment of the present invention, the vacuum cavity 11 includes an optical device vacuum cavity 11A for carrying the emitter 12 and the optical device 14, and a sample vacuum cavity 11B for carrying the sample S. The optical device vacuum cavity 11A has a first cavity wall 111A and a first internal space, and the sample vacuum cavity 11B has a second cavity wall 111B and a second internal space. The first cavity wall 111A and the second cavity wall 111B together constitute the cavity wall 111 of the entire vacuum cavity 11. Furthermore, the first internal space of the optical device vacuum cavity 11A and the second internal space of the sample vacuum cavity 11B together constitute the internal space of the entire vacuum cavity 11.

[0021] The optical device vacuum chamber 11A and the sample vacuum chamber 11B are interconnected. The optical device vacuum chamber 11A contains a gas valve 11C. When the gas valve 11C is closed, the optical device vacuum chamber 11A and the sample vacuum chamber 11B can be separated. Furthermore, the first cavity wall 111A of the optical device vacuum chamber 11A and the second cavity wall 111B of the sample vacuum chamber 11B are also connected to a vacuum pump 133, so that the optical device vacuum chamber 11A and the sample vacuum chamber 11B can be simultaneously pumped to maintain a vacuum pressure. The gas container 131 is connected to the first cavity wall 111A of the optical device vacuum chamber 11A through a gas regulating valve 132, thereby supplying gas to the emitter 12 to facilitate the generation of a gas ion beam.

[0022] When the gas valve 11C is closed, the sample vacuum chamber 11B can block the gas supplied by the gas container 131 and continuously receive air from the vacuum pump 133 to improve the vacuum quality. Alternatively, when the gas valve 11C is closed, the sample vacuum chamber 11B can be aerated to allow the user to replace the sample S placed in the sample vacuum chamber 11B, while at the same time, the vacuum pump 133 continues to evacuate the optical device vacuum chamber 11A to maintain the vacuum quality within the optical device vacuum chamber 11A. The gas valve 11C can be a manual gas valve or an electrically controlled gas valve controlled by the signal control module 16.

[0023] In summary, the electron beam and ion beam system of the present invention, with its single optical structure, uses a robust and stable emitter structure to fix the emitter position, generating a stable charged particle beam. This ensures the stability and lifespan of the ion and electron sources. Furthermore, through the design of a single optical structure, adjustment of the gas type within the vacuum chamber, and application of different ionization voltages, it is possible to generate various charged particle beams for ion and electron beams, applicable to different needs such as multifunctional processing, high-precision processing, high-resolution imaging, and sample composition analysis. This further enables the flexible generation and application of different charged particle beams. Moreover, the single optical structure design not only significantly reduces equipment costs and system complexity but also further enhances operational convenience. [Simplified Explanation of the Diagram]

[0024] Figure 1A is a block diagram of the ion microscope and focused ion beam system with a single optical device of the present invention; Figure 1B is a schematic diagram of the emitter, optical device and sample set in a vacuum chamber; Figure 1C is a magnified schematic diagram of the emitter tip; Figure 1D is a schematic diagram of the vacuum chamber being divided into an optical device vacuum chamber and a sample vacuum chamber; Figure 1E is a schematic diagram of the gas passage between the gas pressure control device and the vacuum chamber; and Figure 2 is a schematic diagram of a conventional dual-beam focused ion beam system.

Claims

1. An ion microscope and focused ion beam system having a single optical device, comprising: a vacuum chamber having an internal space; an emitter disposed within the internal space of the vacuum chamber; and a gas pressure control device storing at least one gas and connected to a cavity wall of the vacuum chamber; and an optical device disposed between the emitter and a sample; A voltage control module, electrically connected to the emitter and the optical device, generates a draw voltage to the emitter and a bias voltage to the optical device; and a signal control module, connected to the gas pressure control device and the voltage control module, generates a gas introduction control signal to the gas pressure control device, causing the gas pressure control device to introduce at least one gas into the internal space of the vacuum chamber, and the signal control module adjusts the bias voltage output by the voltage control module to the optical device and adjusts the draw voltage output by the voltage control module to the emitter, so that the emitter generates a heavy ion beam for processing or analyzing the sample and a light ion beam for imaging the sample through the at least one gas; wherein the heavy ion beam for processing or analyzing the sample is generated through a first gas among the at least one gas, and the light ion beam for imaging the sample is generated through a second gas among the at least one gas, wherein the molecular weight of the first gas is greater than the molecular weight of the second gas, and the signal control module adjusts the draw voltage accordingly based on the type of molecule.

2. The ion microscope and focused ion beam system with a single optical device as described in claim 1, wherein the first gas comprises xenon, krypton, oxygen, nitrogen and argon, and the second gas comprises hydrogen, neon and helium.

3. The ion microscope and focused ion beam system with a single optical device as described in claim 1, wherein the first gas system is a gas with a molecular weight greater than 21 and the second gas system is a gas with a molecular weight less than 21.

4. The ion microscope and focused ion beam system with a single optical device as described in claim 1, wherein the at least one gas comprises a mixture of the first gas and the second gas, and the signal control module adjusts the absorption voltage output by the voltage control module to the emitter according to the molecular types of the first gas and the second gas.

5. The ion microscope and focused ion beam system with a single optical device as described in claim 1, wherein the signal control module generates the gas introduction control signal to the gas pressure control device, causing the gas pressure control device to introduce the first gas into the internal space of the vacuum chamber, and the signal control module further generates a gas extraction control signal to the gas pressure control device, causing the first gas to be extracted, and then the signal control module generates the gas introduction control signal to the gas pressure control device, causing the gas pressure control device to introduce the second gas into the internal space of the vacuum chamber.

6. The ion microscope and focused ion beam system having a single optical device as described in claim 1, wherein the optical device includes a quality filter for filtering a gas ion beam comprising the heavy ion beam and the light ion beam.

7. The ion microscope and focused ion beam system with a single optical device as described in claim 1, wherein the signal control module further generates a gas extraction control signal to the gas pressure control device, so that at least one gas is extracted, and the signal control module adjusts the absorption voltage output by the voltage control module to the emitter to a negative bias voltage, so that the emitter generates an electron beam for imaging the sample.

8. An ion microscope and focused ion beam system having a single optical device as described in claim 1, wherein one tip of the emitter is a wrinkled structure.

9. An ion microscope and focused ion beam system having a single optical device as described in claim 1, wherein the material of the emitter is a metal such as tungsten, iridium, molybdenum, palladium, platinum, rhodium, or gold.

10. An ion microscope and focused ion beam system having a single optical device as claimed in claim 1, wherein the optical device comprises: a focusing lens module for adjusting the size of a spot formed by the ion beam on the sample; and a scanning deflection module for controlling the movement and scanning of the ion beam on the sample surface.

11. The ion microscope and focused ion beam system with a single optical device as described in claim 1, further comprising a signal detector connected to the signal control module to detect the signal generated by the interaction between the ion beam and the sample, so as to generate an imaging signal to the signal control module.

Images