Novel ion source structure for RGA

Abstract

The invention relates to the field of vacuum measurement and analysis, and discloses a novel ion source structure for RGA. An ion emission assembly is a tungsten filament, the two ends of the tungsten filament are fixed to the side wall of an ion source cavity through ceramic insulators, a focusing acceleration assembly comprises a lens electrode and an extraction electrode which are coaxially arranged in sequence, a gas introduction assembly is a quartz capillary tube, and one end of the gas introduction assembly extends to the position, close to the filament, in the ion source cavity. The other end of the gas introduction assembly is connected with an external gas circuit, the cooling assembly is a water-cooled jacket surrounding the outer side of the ion source cavity, the water-cooled jacket is provided with a water inlet and a water outlet, and through a tungsten filament emission and focusing acceleration cooperation assembly structure, it is ensured that gas molecules are efficiently ionized, and a quartz capillary tube accurately introduces gas to be analyzed; low ionization efficiency caused by gas diffusion is avoided, the problem that a traditional ion source is overheated after working for a long time is solved through the water-cooled jacket, a stable ion source foundation is provided for RGA accurate detection, and the requirement for gas component analysis in a high-vacuum environment is met.

Description

Technical Field

[0001] This invention belongs to the field of vacuum measurement and analysis technology, specifically a novel ion source structure for RGA. Background Technology

[0002] Residual gas analyzers (RGAs) are key equipment used in ultra-high vacuum and process engineering fields to detect and analyze the composition and partial pressure of gases in vacuum systems. RGAs typically employ electron impact (EI) ionization, and their ion source usually consists of a filament, an ionization chamber, and a transmission lens. When the filament is heated by an electric current, it emits electrons, which are accelerated under the influence of an electric field to bombard gas molecules, causing them to ionize.

[0003] Currently, most commercial RGA systems are equipped with a ring-shaped filament, typically a single or double filament in an arc shape, surrounding the ion cage. Its advantage is its simple structure, but its disadvantages are: 1. The electron bombardment region is quite limited, resulting in limited ionization efficiency; 2. Some ions may remain in the ion cage for too long, resulting in low transport and extraction efficiency and affecting sensitivity.

[0004] Therefore, improving the structure of electron bombardment ion sources to increase ionization efficiency and ion extraction rate, thereby enhancing the sensitivity of RGA detection, is a technical requirement in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a novel ion source structure for RGA in order to solve the problems mentioned above.

[0006] The technical solution adopted in this invention is as follows: A novel ion source structure for RGA includes an ion emission component, a focusing and acceleration component, a gas introduction component, and a cooling component. The ion emission component is a tungsten filament, and both ends of the tungsten filament are fixed to the side wall of the ion source cavity through ceramic insulators. The focusing and acceleration component includes a lens electrode and an extraction electrode arranged coaxially in sequence. The gas introduction component is a quartz capillary, with one end extending into the ion source cavity near the filament and the other end connected to an external gas path. The cooling component is a water-cooled jacket surrounding the outside of the ion source cavity, with an inlet and an outlet. Through the synergistic structure of the tungsten filament emission and focusing and acceleration components, efficient ionization of gas molecules is ensured. The quartz capillary accurately introduces the gas to be analyzed, avoiding low ionization efficiency caused by gas diffusion. The water-cooled jacket solves the overheating problem of traditional ion sources during long-term operation, providing a stable ion source foundation for accurate RGA detection and adapting to the gas composition analysis needs under high vacuum environments.

[0007] In a preferred embodiment, the surface of the tungsten filament is coated, an ion cage is provided on the inner side of the tungsten filament, and square wave strip-shaped grooves are opened on the surface of the ion cage corresponding to the tungsten filament. The iridium coating improves the high temperature resistance and sputtering resistance of the tungsten filament, extends the filament service life, and the heating current is adjustable to meet the ionization energy requirements of different gases. In a preferred embodiment, both the lens electrode and the lead-out electrode are made of oxygen-free copper. The oxygen-free copper material ensures excellent conductivity of the electrode, and the gold plating layer reduces electrode sputtering caused by ion bombardment and maintains electric field stability. Precise voltage setting and electric field strength adjustment can efficiently focus and accelerate the ion generated by ionization to the subsequent mass analyzer, solving the problem of low detection sensitivity caused by ion divergence in traditional ion sources.

[0008] In a preferred embodiment, a heating jacket is fitted around the quartz capillary of the gas introduction component, and the heating jacket is electrically connected to a temperature controller. A gas distributor is provided at the gas outlet of the capillary. The heating jacket can prevent high-boiling-point organic gases from condensing inside the capillary, ensuring stable gas introduction. The gas distributor evenly disperses the introduced gas around the filament, avoiding uneven ionization caused by excessively high local gas concentration, improving the stability of ion generation, and adapting to the analysis scenarios of complex mixed gases.

[0009] In a preferred embodiment, the ion source cavity is made of stainless steel, and the ion source cavity is provided with an ion extraction hole inside and a vacuum interface is provided on the outside of the ion source cavity. Stainless steel has strong corrosion resistance and is suitable for high vacuum and corrosive gas environments. The ion extraction hole and the focusing acceleration component are coaxially designed to ensure that the accelerated ions accurately enter the subsequent optical path. The vacuum interface and high vacuum requirements provide a low-interference environment for gas ionization and improve detection accuracy.

[0010] In a preferred embodiment, the water-cooling jacket of the cooling component is made of copper. The high thermal conductivity of copper ensures efficient heat transfer, and the circulating cooling water quickly removes the heat generated by filament heating and ion collisions. Precise temperature control avoids changes in gas adsorption characteristics caused by overheating of the cavity, while preventing damage to surrounding components from high temperatures and ensuring long-term stable operation of the ion source.

[0011] In a preferred embodiment, the surface of the ceramic insulator is coated with a boron nitride coating, and the connection end between the insulator and the filament is provided with a groove. After the end of the filament is embedded in the groove, it is pressed and fixed by a molybdenum sheet. The boron nitride coating improves the high-temperature insulation performance of the insulator, and the groove and molybdenum sheet fixing structure ensure that the filament is firmly installed and avoids poor contact caused by vibration.

[0012] In a preferred embodiment, the inner edges of both the lens electrode and the lead-out electrode are rounded, and an annular insulating pad is provided between the two electrodes. The rounded corners reduce electric field distortion, and the insulating pad ensures the insulation strength between the electrodes and maintains the stability of the electric field.

[0013] In a preferred embodiment, the outer wall of the ion source cavity is provided with a pressure sensor interface, and the interface is connected to a vacuum pressure sensor to monitor changes in vacuum in real time, thereby avoiding filament burnout or detection errors caused by high pressure.

[0014] In a preferred embodiment, a heat insulation pad is provided between the ion source cavity and the water cooling jacket. The pad is evenly distributed along the circumference of the cavity. The heat insulation pad balances the temperature distribution of the cavity, prevents the adsorption of gas molecules in local low-temperature areas, further reduces background interference, and improves detection stability.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. Traditional RGA ion sources suffer from problems such as uneven gas introduction, ion divergence, low ionization efficiency, and long ion residence time in the ionization region, resulting in low detection sensitivity. This structure improves ion transmission efficiency through the precise electric field design of the focusing acceleration component and the uniform gas distribution of the gas splitter, enabling accurate detection of trace residual gases in high vacuum environments.

[0016] 2. Traditional ion source filaments are prone to loss due to high-temperature sputtering and contamination, and high-boiling-point gases are prone to condensation, leading to ion source blockage. This structure, through iridium-plated filaments and capillary heating jackets, not only extends the life of core components but also avoids gas condensation, making it suitable for complex scenarios such as semiconductor manufacturing and spacecraft vacuum testing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the novel ion source structure of the RGA of the present invention; Figure 2 This is a schematic diagram of the novel ion source structure in this invention; Figure 3 This is a schematic diagram of the novel ion source circuit driving structure in this invention; Figure 4 This is a schematic diagram of the three-dimensional structure of the filament and ion cage in this invention.

[0018] The following are labeled in the diagram: 1. Ion emission assembly; 2. Focusing and acceleration assembly; 3. Gas introduction assembly; 4. Cooling assembly; 5. Tungsten filament; 6. Lens electrode; 7. Lead-out electrode; 8. Quartz capillary; 9. Inlet; 10. Outlet; 12. Ion cage. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0020] Example: Reference Figure 1-3 A novel ion source structure for RGA includes an ion emission component 1, a focusing and accelerating component 2, a gas introduction component 3, and a cooling component 4. The ion emission component 1 is a tungsten filament 5, with both ends of the tungsten filament 5 fixed to the sidewall of the ion source cavity via ceramic insulators. The focusing and accelerating component 2 includes a lens electrode 6 and an extraction electrode 7 arranged coaxially in sequence. The gas introduction component 3 is a quartz capillary tube 8, with one end extending into the ion source cavity near the filament and the other end connected to an external gas path. The cooling component 4 is a water-cooled jacket surrounding the outside of the ion source cavity, with an inlet 9 and an outlet 10. Through the synergistic effect of the tungsten filament 5 emission and the focusing and accelerating component structure, efficient ionization of gas molecules is ensured. The quartz capillary tube 8 accurately introduces the gas to be analyzed, avoiding low ionization efficiency caused by gas diffusion. The water-cooled jacket solves the overheating problem of traditional ion sources during long-term operation, providing a stable ion source foundation for accurate RGA detection and adapting to the gas composition analysis needs under high vacuum environments.

[0021] Reference Figure 1-2 The tungsten filament 5 has a coating treatment on its surface. An ion cage 12 is provided on the inner side of the tungsten filament 5, and the surface of the ion cage 12 is provided with square wave strip-shaped grooves corresponding to the tungsten filament 5. The iridium coating improves the high temperature resistance and sputtering resistance of the tungsten filament 5, extends the filament's service life, and the heating current is adjustable to meet the ionization energy requirements of different gases. According to the square wave strip distribution of the filament bend, square wave strip-shaped grooves are correspondingly opened around the ion cage 12, thereby maximizing the electron emission area.

[0022] Reference Figure 1-2 Both the lens electrode 6 and the lead electrode 7 are made of oxygen-free copper. The oxygen-free copper material ensures the excellent conductivity of the electrode, and the gold plating layer reduces electrode sputtering caused by ion bombardment and maintains the stability of the electric field. The precise voltage setting and electric field intensity adjustment can efficiently focus and accelerate the ion generated by ionization to the subsequent mass analyzer, solving the problem of low detection sensitivity caused by ion divergence in traditional ion sources.

[0023] Reference Figure 1-2The gas introduction component 3 has a heating sleeve on the outside of the quartz capillary 8, which is electrically connected to the temperature controller. The gas outlet end of the capillary is equipped with a gas splitter. The heating sleeve can prevent high-boiling-point organic gases from condensing in the capillary and ensure stable gas introduction. The gas splitter evenly disperses the introduced gas around the filament, avoiding uneven ionization caused by excessively high local gas concentration, improving the stability of ion generation, and adapting to the analysis scenario of complex mixed gases.

[0024] Reference Figure 1-4 The ion source cavity is made of stainless steel and has an ion extraction port inside. A vacuum interface is located on the outside of the ion source cavity. Stainless steel is highly corrosion resistant and suitable for high vacuum and corrosive gas environments. The ion extraction port and the focusing acceleration component 2 are coaxially designed to ensure that the accelerated ions accurately enter the subsequent optical path. The vacuum interface and high vacuum requirements provide a low-interference environment for gas ionization and improve detection accuracy.

[0025] Reference Figure 1-4 The water cooling jacket of the cooling component 4 is made of copper. The high thermal conductivity of copper ensures efficient heat transfer, and the circulating cooling water quickly removes the heat generated by the filament heating and ion collision. Precise temperature control avoids changes in gas adsorption characteristics caused by overheating of the cavity, while preventing damage to surrounding components from high temperature, ensuring long-term stable operation of the ion source.

[0026] Reference Figure 1-2 The surface of the ceramic insulator is coated with boron nitride, and the connection end between the insulator and the filament is provided with a groove. After the end of the filament is embedded in the groove, it is pressed and fixed by a molybdenum sheet. The boron nitride coating improves the high temperature resistance and insulation performance of the insulator. The groove and molybdenum sheet fixing structure ensures that the filament is installed firmly and avoids poor contact caused by vibration.

[0027] Reference Figure 1-2 The inner edges of both the lens electrode and the lead-out electrode are rounded, and an annular insulating pad is provided between the two electrodes. The rounded corners reduce electric field distortion, and the insulating pad ensures the insulation strength between the electrodes and maintains the stability of the electric field.

[0028] Reference Figure 1-4 The outer wall of the ion source cavity is equipped with a pressure sensor interface, which is connected to a vacuum pressure sensor to monitor changes in vacuum in real time, thus avoiding filament burnout or detection errors caused by high pressure.

[0029] Reference Figure 1-2 A heat insulation pad is provided between the ion source cavity and the water cooling jacket. The pad is evenly distributed along the circumference of the cavity. The heat insulation pad balances the temperature distribution of the cavity, prevents the adsorption of gas molecules in local low-temperature areas, further reduces background interference, and improves detection stability.

[0030] Example 1: Two sets of ionization chambers work simultaneously: Some gas molecules are ionized in the first ionization chamber. A specific DC voltage is applied to the lens electrode to form a focusing electric field. Ions are focused and transported to the second ionization chamber through the lens electrode. At the same time, gas molecules that are not ionized in the first ionization chamber are ionized in the second ionization chamber. Ions are focused and accelerated under the action of the lens electrode and the extraction electrode and extracted to the subsequent mass analyzer. Example 2: The first ionization chamber operates alone: ​​Gas molecules are ionized in the first ionization chamber. A specific DC voltage is applied to the lens electrode to form an accelerating electric field. After passing through the first ionization chamber, the ions are accelerated and transported under the action of the lens electrode, and then accelerated and extracted by the extraction electrode to the subsequent mass analyzer.

[0031] Example 3: The second ionization chamber operates independently: After passing through the first ionization chamber, gas molecules are ionized in the second ionization chamber to generate ions. A specific DC voltage is applied to the lens electrode to form an accelerating electric field. Under the action of the lens electrode, the ions are accelerated and transported, and then accelerated and extracted to the subsequent mass analyzer via the extraction electrode.

[0032] Example 4: Two sets of filaments are distributed around each ionization chamber. Each set of filaments can be made of different materials depending on the specific operating conditions and can be used independently, making the application scenarios diverse.

[0033] The implementation principle of a novel ion source structure embodiment for RGA of the present invention is as follows: The external gas to be analyzed enters the ion source through the quartz capillary 8 of the gas inlet component 3. If the gas is a high-boiling-point organic vapor, the temperature controller activates the heating jacket to prevent the gas from condensing in the capillary. After the gas reaches the outlet, it is evenly dispersed through multiple diversion holes of the quartz diverter and directed toward the tungsten filament 5 of the ion emission component 1 to ensure effective contact between the gas and the filament and avoid uneven ionization caused by excessively high or low local gas concentrations.

[0034] The tungsten filament 5 of the ion emission component 1 is heated by electricity, and the iridium-plated filament emits thermionic electrons at high temperature. The thermionic electrons are focused and accelerated in the electric field formed by the lens electrode 6 and the lead-out electrode 7, and collide with the introduced gas molecules, causing the gas molecules to ionize and generate ions. The focusing electric field gathers the dispersed ions into an ion beam, and the accelerating electric field further accelerates the ion beam to a preset energy. Finally, the ion beam enters the mass analyzer for subsequent detection through the lead-out hole of the ion source cavity.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel ion source structure for RGA, comprising an ion emission assembly (1), a focusing and acceleration assembly (2), a gas introduction assembly (3), and a cooling assembly (4), characterized in that: The ion emission component (1) is a tungsten filament (5), and the two ends of the tungsten filament (5) are fixed to the side wall of the ion source cavity by ceramic insulators. The focusing acceleration component (2) includes a lens electrode (6) and an extraction electrode (7) arranged coaxially in sequence. The gas introduction component (3) is a quartz capillary tube (8). One end of the gas introduction component (3) extends into the ion source cavity near the filament, and the other end of the gas introduction component (3) is connected to an external gas path. The cooling component (4) is a water-cooled jacket surrounding the outside of the ion source cavity. The water-cooled jacket is provided with an inlet (9) and an outlet (10).

2. The novel ion source structure for RGA as described in claim 1, characterized in that: The surface of the tungsten filament (5) is coated, and an ion cage (12) is provided on the inner side of the tungsten filament (5). The surface of the ion cage 12 is provided with square wave strip-shaped holes corresponding to the tungsten filament (5).

3. The novel ion source structure for RGA as described in claim 1, characterized in that: Both the lens electrode (6) and the lead-out electrode (7) are made of oxygen-free copper.

4. A novel ion source structure for RGA as described in claim 1, characterized in that: The gas inlet assembly (3) has a heating sleeve on the outside of the quartz capillary (8), and the heating sleeve is electrically connected to the temperature controller, and the gas outlet end of the capillary is provided with a gas splitter.

5. A novel ion source structure for RGA as described in claim 1, characterized in that: The ion source cavity is made of stainless steel, and the ion source cavity is provided with an ion extraction hole inside, and a vacuum interface is provided on the outside of the ion source cavity.

6. A novel ion source structure for RGA as described in claim 1, characterized in that: The water jacket of the cooling component (4) is made of copper.

7. A novel ion source structure for RGA as described in claim 1, characterized in that: The surface of the ceramic insulator is coated with boron nitride, and the connection end between the insulator and the filament is provided with a groove. After the end of the filament is embedded in the groove, it is pressed and fixed by a molybdenum sheet.

8. A novel ion source structure for RGA as described in claim 1, characterized in that: The inner edges of the lens electrode (6) and the lead-out electrode (7) are rounded, and an annular insulating pad is provided between the two electrodes.

9. A novel ion source structure for RGA as described in claim 1, characterized in that: The outer wall of the ion source cavity is provided with a pressure sensor interface, and the interface is connected to a vacuum pressure sensor.

10. A novel ion source structure for RGA as described in claim 1, characterized in that: A heat insulation pad is provided between the ion source cavity and the water cooling jacket, and the pad is evenly distributed along the circumference of the cavity.

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