A scanning electron microscope

Abstract

This invention relates to the field of semiconductor manufacturing and inspection, and particularly to a scanning electron microscope (SEM). The SEM includes: a high-voltage base for supporting and electrically connecting to a wafer under test; an objective lens including an upper electrode, a lower electrode, and an insulating element, wherein the lower electrode is electrically isolated from the upper electrode through the insulating element; and a high-voltage electrode for electrical connection to an external negative high-voltage power supply, configured to simultaneously apply a negative voltage to the high-voltage base and the lower electrode or to cut off the negative voltage, so that the potential of the lower electrode is the same as the potential of the wafer under test. This invention eliminates the potential difference between the lower electrode and the wafer under test by making the lower electrode of the objective lens equipotential with the wafer under test. This prevents contaminant particles on the surface of the wafer from being adsorbed onto the lower electrode but remains on the original surface of the wafer, avoiding cross-contamination of the wafer during inspection and transfer, thereby improving the yield of chip manufacturing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing and testing, and in particular to a scanning electron microscope. Background Technology

[0002] In the field of semiconductor manufacturing and inspection, such as chip fabrication, scanning electron microscopy (SEM) is widely used to observe and confirm the fine features or morphology of wafer surfaces after photolithography or etching. When the electron beam of an SEM reaches the wafer surface, it acts on the surface, generating secondary electrons (SE) or backscattered electrons (BSE). These signal electrons are randomly emitted from the wafer surface in various directions. A detector receives these signal electrons and converts them into corresponding detection signals, generating an image of the wafer surface's morphological features based on these signals. In this process, the number of signal electrons collected determines the image quality; if too few SE and BSE are recovered, the image will be unclear. Therefore, existing scanning electron microscopes typically apply a negative voltage to the wafer to increase the number of stray signal electrons collected, thereby improving image quality.

[0003] However, in existing scanning electron microscopes, the components above the wafer are still grounded, creating a potential difference between them. In some manufacturing processes, contaminant particles may be present on the wafer surface. This potential difference causes these particles to be attracted to the zero-potential components above the wafer. When one wafer is inspected and moved away, and the next wafer is introduced without a negative voltage applied, the contaminant particles previously attracted to the zero-potential components may fall onto the next wafer under external forces, such as gravity. This causes cross-contamination between different wafers, leading to decreased yield and inaccurate wafer measurements during chip manufacturing. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a scanning electron microscope that overcomes or at least partially solves the above problems.

[0005] One object of the present invention is to provide a scanning electron microscope to avoid cross-contamination of wafers under test during inspection and transfer processes, thereby improving the yield of chip manufacturing.

[0006] A further objective of this invention is to improve the reliability of maintaining equipotential between the lower electrode shoe and the wafer under test, thereby ensuring the effectiveness of wafer anti-contamination.

[0007] Another further objective of this invention is to improve the safety and reliability of scanning electron microscopes.

[0008] In particular, the present invention provides a scanning electron microscope, comprising: The high-voltage base is used to support the wafer under test and is electrically connected to the wafer under test. Objective lens, comprising an upper pole shoe, a lower pole shoe, and an insulating element, wherein the lower pole shoe is electrically insulated from the upper pole shoe by the insulating element; and The high-voltage electrode is used to connect to an external negative high-voltage power supply and is configured to simultaneously apply a negative voltage to the high-voltage base and the lower electrode shoe or to cut off the negative voltage so that the potential of the lower electrode shoe is the same as the potential of the wafer under test.

[0009] Alternatively, the scanning electron microscope also includes: An electrode adapter block, the input end of which is electrically connected to a high-voltage electrode, and the output end of which has a first high-voltage output branch and a second high-voltage output branch; The first high-voltage line is electrically connected between the first high-voltage output branch and the high-voltage base; and The second high-voltage line is electrically connected between the second high-voltage output branch and the lower pole shoe.

[0010] The scanning electron microscope has only a single high-voltage electrode. The electrode adapter simultaneously distributes the negative voltage of the single high-voltage electrode to the lower objective shoe and the high-voltage base. Alternatively, the scanning electron microscope also includes: A vacuum chamber is used to define a vacuum environment and house a high-pressure base and objective lens; in which The high-voltage electrode is inserted through the cavity wall of the vacuum chamber, including an outer end located outside the vacuum chamber and an inner end extending into the vacuum chamber. The outer end is used to connect to the negative high-voltage power supply, and the inner end is electrically connected to the input end of the electrode adapter block. The electrode adapter block, the first high-voltage line and the second high-voltage line are all arranged inside the vacuum chamber.

[0011] Optionally, the vacuum chamber is grounded, and an insulating sealing structure is provided between the high-voltage electrode and the cavity wall of the vacuum chamber to electrically insulate and isolate the high-voltage electrode from the vacuum chamber.

[0012] Alternatively, the scanning electron microscope also includes: An insulating base is fixedly installed at the bottom of the vacuum chamber to support the high-voltage base. The insulating base is a component made of insulating material to electrically insulate the high-voltage base from the vacuum chamber.

[0013] Optionally, the vacuum chamber includes: The housing has an upward-opening opening, and the housing is equipped with a vacuum pump interface for connecting to an external vacuum pump and a transfer window for the wafer to be tested to enter and exit. The top cover, which is sealed to the box body to cover the opening; and The upper pole shoe support is located above the upper cover and is sealed and fixedly connected to the upper cover by a sealing ring and connectors. The upper pole shoe is also fixedly connected to the upper pole shoe support.

[0014] Optionally, the insulating element includes: An insulating plate, in the shape of a ring, is arranged between the upper and lower pole shoes, and has assembly through holes; and An insulating fastener is inserted through the mounting hole and securely connects the lower pole shoe to the upper pole shoe.

[0015] Optionally, the lower electrode shoe is an annular plate arranged perpendicular to the main electron beam, with a lower electrode shoe through hole formed in its middle for the main electron beam and signal electrons generated on the surface of the wafer under test to pass through.

[0016] Alternatively, the scanning electron microscope also includes: The high-voltage component is fixedly mounted on an insulating plate. A high-voltage component through hole, coaxial with the lower pole shoe through hole, is opened in the middle of the plate. The high-voltage component is used to connect to an external positive high-voltage power supply to apply an electric field to the main electron beam and / or signal electrons passing through the high-voltage component through hole.

[0017] Alternatively, the scanning electron microscope also includes: An electron beam emission source, located above the objective lens, is used to emit a main electron beam onto the wafer under test, causing the wafer to generate signal electrons under the influence of the main electron beam; and The detector is located between the electron beam emission source and the objective lens. It has a detector through-hole for the main electron beam to pass through, and is used to receive signal electrons and generate corresponding detection signals.

[0018] The scanning electron microscope of this invention eliminates the potential difference between the lower objective shoe and the wafer under test by aligning the lower objective shoe with the wafer under test. This prevents contaminant particles on the wafer surface from being electrostatically attracted to the lower objective shoe, thus keeping them on the original wafer surface and allowing them to be removed along with it. Consequently, contaminant particles do not adhere to the lower objective shoe, fundamentally preventing cross-contamination caused by particles falling from the lower objective shoe onto the next wafer under test, thereby improving chip manufacturing yield. Furthermore, the scanning electron microscope of this invention directly reuses the lower objective shoe of the device itself as an equipotential component, achieving wafer anti-contamination without the need for additional components. This simplifies the structure and improves the integration and material utilization of the scanning electron microscope, thereby reducing its production and space costs.

[0019] Furthermore, the scanning electron microscope of the present invention, by setting an electrode adapter block and two high-voltage lines to form a one-to-two high-voltage power supply structure, realizes that negative voltage can be applied to the high-voltage base and the lower electrode shoe at the same time or the negative voltage can be cut off at the same time by relying solely on hardware circuitry. This avoids the timing deviation risk caused by software timing control, improves the reliability of maintaining equipotential between the lower electrode shoe and the wafer under test, and thus ensures the wafer anti-contamination effect.

[0020] Furthermore, the scanning electron microscope of the present invention achieves omnidirectional electrical insulation between the lower and upper pole shoes through a combination of an insulating plate and insulating fasteners, allowing the lower pole shoe to be independently energized. Additionally, by arranging the grounded upper pole shoe and the negative high-voltage lower pole shoe on different sides of the insulating plate, the present invention effectively separates the upper and lower pole shoes using the insulating plate, preventing high-voltage breakdown short circuits between them and improving the safety and reliability of the scanning electron microscope.

[0021] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0022] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a perspective view of a scanning electron microscope according to an embodiment of the present invention; Figure 2 yes Figure 1 A longitudinal cross-sectional view of a medium scanning electron microscope; Figure 3 yes Figure 2 A magnified schematic diagram of a portion of the structure of a medium-sized scanning electron microscope; Figure 4 It is a bar chart obtained by counting the number of contaminant particles on the wafer surface after detecting or measuring the wafer using a scanning electron microscope in existing technology; Figure 5 This is a bar chart obtained by counting the number of contaminant particles on the wafer surface after detecting or measuring the wafer using a scanning electron microscope according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the morphological features of the sample under test as observed by a scanning electron microscope in the prior art; Figure 7 This is a schematic diagram of the morphological features of a sample under test as observed by a scanning electron microscope according to an embodiment of the present invention. Detailed Implementation

[0023] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0024] To address the above problems, this invention provides a scanning electron microscope. Figure 1 This is a perspective view of a scanning electron microscope according to an embodiment of the present invention. Figure 2 yes Figure 1 A longitudinal cross-sectional view from a medium scanning electron microscope. Figure 3 yes Figure 2 A magnified schematic diagram of a portion of the structure in a medium-sized scanning electron microscope. (See diagram below.) Figures 1-3 As shown, the scanning electron microscope 10 of this embodiment generally includes: a vacuum chamber 100, an electron beam emission source 200, a detector 300, an objective lens 400, and a high-voltage base 510.

[0025] In this embodiment, the vacuum chamber 100 is used to define a vacuum environment and house the high-voltage base 510 and the objective lens 400. The high-voltage base 510 is used to support the wafer 20 under test. The objective lens 400 may include an upper pole piece 410, a lower pole piece 420, and an excitation coil. Specifically, an upper pole piece through hole 411 is formed in the middle of the upper pole piece 410, and a lower pole piece through hole 421 is formed in the middle of the lower pole piece 420. Both the upper pole piece through hole 411 and the lower pole piece through hole 421 are used to allow the main electron beam and signal electrons generated on the surface of the wafer 20 under test to pass through. An annular mounting cavity 412 is formed between the upper pole piece 410 and the lower pole piece 420, and the excitation coil is located in the annular mounting cavity 412. After the excitation coil is energized, it establishes a magnetic field to focus the electron beam.

[0026] Additionally, the electron beam emitter 200 is located above the objective lens 400 and is used to emit a main electron beam onto the wafer 20 under test. After being focused by the objective lens 400, the main electron beam bombards the upper surface 21 of the wafer 20 under test, causing the wafer 20 under test to generate signal electrons under the action of the main electron beam. The detector 300 is located between the electron beam emitter 200 and the objective lens 400, and has a detector through-hole 310 for the main electron beam to pass through, for receiving signal electrons and generating a corresponding detection signal.

[0027] Thus, the scanning electron microscope 10 of this embodiment of the invention, by configuring the vacuum chamber 100 to define a vacuum environment and accommodate the high-voltage base 510 and the objective lens 400, provides the necessary vacuum environment for scanning the main electron beam and generating signal electrons, so that the main electron beam can stably reach the surface of the wafer 20 under test and excite signal electrons.

[0028] Furthermore, the scanning electron microscope 10 of the present invention achieves unobstructed passage of the main electron beam and efficient reception of signal electrons by placing the detector 300 between the electron beam emission source 200 and the objective lens 400 and opening a detector through-hole 310 thereon for the main electron beam to pass through. This enables the detector 300 to simultaneously receive signal electrons returning from the wafer surface and generate corresponding detection signals while the main electron beam scans the wafer surface, thereby providing complete raw data for subsequent signal amplification, computer processing and morphological feature image generation.

[0029] In some embodiments, such as Figure 1 and Figure 2 As shown, the vacuum chamber 100 may include a housing 110, a top cover 120, and an upper pole shoe support 130. Specifically, the housing 110, the top cover 120, and the upper pole shoe support 130 are arranged sequentially from bottom to top.

[0030] like Figure 2 As shown, housing 110 refers to the main body of vacuum chamber 100, which forms a space to accommodate high-pressure base 510 and objective lens 400. Housing 110 has an upward-opening opening 111, and top cover 120 is sealed to housing 110 to cover opening 111. Top cover 120 has a top cover through hole 121 in the middle, and upper pole shoe support 130 is located above top cover 120 and is sealed and fixedly connected to top cover 120 by sealing ring and connector 132 to cover top cover through hole 121. Upper pole shoe 410 is fixedly connected to upper pole shoe support 130.

[0031] Specifically, a sealing ring is disposed between the upper electrode shoe support 130 and the upper cover 120, and is arranged around the outer periphery of the upper cover through hole 121. The upper electrode shoe support 130 has a support through hole 131 in its center, allowing the main electron beam and signal electrons generated on the surface of the wafer under test 20 to pass through. Multiple connectors 132 can be provided, and these connectors 132 are evenly distributed around the outer periphery of the support through hole 131. The connectors 132 can be screws. The connectors 132 pass through the upper electrode shoe support 130 from top to bottom and are fixedly connected to the upper cover 120 after the sealing ring is compressed, thereby fixing the upper electrode shoe support 130 onto the upper cover 120 and achieving a seal between the upper electrode shoe support 130 and the upper cover 120.

[0032] Additionally, the housing 110 is provided with a vacuum pump interface 112 for connecting to an external vacuum pump (not shown in the figure) and a transfer window 113 for the entry and exit of the wafer 20 under test. Specifically, a vacuum environment is formed inside the vacuum chamber 100 under the suction action of the external vacuum pump. Furthermore, the transfer window 113 is used for the entry and exit of the wafer 20 under test.

[0033] Thus, the scanning electron microscope 10 of this embodiment of the invention, by combining the housing 110, the top cover 120 and the upper pole shoe support 130 to form a vacuum chamber 100, achieves reliable sealing of the vacuum chamber 100 and stable support of the objective lens 400.

[0034] In some embodiments, such as Figure 1 and Figure 2 As shown, the scanning electron microscope 10 of the present invention may further include a high-voltage electrode 600 for electrical connection to an external negative high-voltage power supply (not shown). In this embodiment, the high-voltage base 510 is electrically connected to the wafer 20 under test. Specifically, the high-voltage base 510 may be a component made of conductive material and is electrically connected to the high-voltage electrode 600 so that a negative voltage is applied when powered by the negative high-voltage power supply. After the wafer 20 under test is placed on the high-voltage base 510, the potential of the high-voltage base 510 remains consistent with the potential of the wafer 20 under test.

[0035] like Figure 2 and Figure 3 As shown, the objective lens 400 may further include an insulator 430 located between the upper pole piece 410 and the lower pole piece 420, with the lower pole piece 420 electrically isolated from the upper pole piece 410 by the insulator 430. Specifically, the upper pole piece 410 is grounded and at zero potential. The lower pole piece 420 is electrically connected to the high-voltage electrode 600 so that a negative voltage can be applied when powered by a negative high-voltage power supply. The insulator 430 may be a component made of electrically insulating material, used to isolate the upper pole piece 410 and the lower pole piece 420 to prevent circuit continuity.

[0036] Furthermore, the high-voltage electrode 600 is configured to simultaneously apply a negative voltage to the high-voltage base 510 and the lower electrode shoe 420, or to cut off the negative voltage, so that the potential of the lower electrode shoe 420 is the same as the potential of the wafer 20 under test. Specifically, after the wafer 20 under test is placed on the high-voltage base 510 and the test begins, the high-voltage electrode 600 simultaneously applies a negative voltage to the high-voltage base 510 and the lower electrode shoe 420; after the test of the wafer 20 is completed, the high-voltage electrode 600 simultaneously cuts off the negative voltage to the high-voltage base 510 and the lower electrode shoe 420.

[0037] It should be noted that in existing technologies, the wafer under test 20 is subjected to a negative high voltage, while the lower electrode shoe 420 of the objective lens 400 is usually grounded, which is a high voltage state relative to the wafer under test 20. Therefore, there is a large potential difference between the two, forming a structure similar to a parallel plate capacitor, with electric field lines pointing from the lower electrode shoe 420 of the objective lens 400 to the wafer under test 20. However, this invention sets the lower electrode shoe 420 and the wafer under test to be at the same potential, eliminating the potential difference between them. That is, the electric field between the lower electrode shoe 420 and the wafer under test 20 essentially disappears, thereby eliminating the electrostatic adsorption force of the lower electrode shoe 420 of the objective lens 400 on the surface of the wafer under test 20 for contaminants. Regardless of whether the contaminants on the surface of the wafer under test 20 are negatively charged or uncharged, electrostatic adsorption can be avoided, providing a wider range of protection.

[0038] Based on this, the scanning electron microscope 10 of the present invention eliminates the potential difference between the lower pole piece 420 and the wafer 20 under test by making the lower pole piece 420 of the objective lens 400 at the same potential as the wafer 20 under test. This prevents contaminant particles on the surface of the wafer 20 from being electrostatically attracted to the lower pole piece 420, thus keeping them on the original surface of the wafer 20 and removing them from the vacuum chamber 100 along with the original wafer 20. There is no risk of contaminant particles accumulating inside the vacuum chamber 100 or falling back into the vacuum chamber. Therefore, contaminant particles will not adhere to the lower pole piece 420, fundamentally avoiding cross-contamination caused by particles falling from the lower pole piece 420 onto the next wafer 20 under test, thereby improving the yield of chip manufacturing.

[0039] In addition, the scanning electron microscope 10 of the present invention directly reuses the objective lens 400 and lower pole piece 420 of the device itself as an equipotential component, which can achieve wafer anti-contamination without adding additional components, thus simplifying the structure and improving the device integration and material utilization of the scanning electron microscope 10, thereby reducing the production cost and space cost of the scanning electron microscope 10.

[0040] In some embodiments, such as Figure 2 As shown, the scanning electron microscope 10 of the present invention may further include an electrode adapter block 700, a first high-voltage line 810, and a second high-voltage line 820.

[0041] Specifically, the input terminal 710 of the electrode adapter block 700 is electrically connected to the high-voltage electrode 600, and the output terminal 720 of the electrode adapter block 700 has a first high-voltage output branch 721 and a second high-voltage output branch 722. It should be noted that the electrode adapter block 700 has an internal conductive path, which can simultaneously distribute the voltage received at the input terminal 710 to the first high-voltage output branch 721 and the second high-voltage output branch 722. The first high-voltage line 810 is electrically connected between the first high-voltage output branch 721 and the high-voltage base 510, and the second high-voltage line 820 is electrically connected between the second high-voltage output branch 722 and the lower electrode shoe 420. When the negative high-voltage power supply supplies power to the high-voltage electrode 600, the negative voltage is simultaneously transmitted to the high-voltage base 510 and the lower electrode shoe 420, so that the high-voltage base 510 and the lower electrode shoe 420 are simultaneously subjected to a negative voltage. When the negative high-voltage power supply is de-energized, the negative voltage is simultaneously disconnected from the high-voltage base 510 and the lower electrode shoe 420, and they simultaneously return to zero potential.

[0042] In other words, the scanning electron microscope 10 of the present invention can be equipped with only a single negative high-voltage power supply and a single high-voltage electrode 600, and the negative voltage of the single high-voltage electrode 600 can be simultaneously distributed to the lower electrode shoe 420 and the high-voltage base 510 using the electrode adapter block 700. Since the two voltages of the lower electrode shoe 420 and the high-voltage base 510 come from the same negative high-voltage power supply, and their switching is controlled by the same high-voltage electrode 600, the voltages of the high-voltage base 510 and the lower electrode shoe 420 are always completely consistent, and their switching is completely synchronized, without any potential deviation caused by the asynchrony of the two independent power supplies.

[0043] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by setting the electrode adapter block 700 and two high-voltage lines to form a one-to-two high-voltage power supply structure, realizes that only the hardware circuit can simultaneously apply negative voltage to the high-voltage base 510 and the lower electrode shoe 420 or simultaneously cut off negative voltage, avoiding the timing deviation risk caused by software timing control, improving the reliability of maintaining the same potential between the lower electrode shoe 420 and the wafer under test 20, thereby ensuring the effect of wafer anti-contamination.

[0044] In some embodiments, the scanning electron microscope 10 of the present invention further includes two negative high-voltage power supplies, two high-voltage electrodes 600, and two high-voltage lines. The high-voltage base 510 is electrically connected to one negative high-voltage power supply via one high-voltage line and one high-voltage electrode 600, and the lower electrode shoe 420 is electrically connected to another negative high-voltage power supply via another high-voltage line and another high-voltage electrode 600. Furthermore, the two negative high-voltage power supplies, the two high-voltage electrodes 600, and the two high-voltage lines are configured to simultaneously apply negative voltage to the high-voltage base 510 and the lower electrode shoe 420 or to interrupt the negative voltage.

[0045] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by setting two high-voltage electrodes 600 electrically connected to the high-voltage base 510 and the lower pole piece 420 respectively, constitutes a dual-path independent power supply structure. This enables the simultaneous application or disconnection of negative voltage to the high-voltage base 510 and the lower pole piece 420 without relying on the electrode adapter block 700, thus improving the reliability of circuit transmission. In addition, the dual-path independent power supply structure can also be used for independent monitoring and adjustment of the voltages of the high-voltage base 510 and the lower pole piece 420, providing a hardware foundation for application scenarios requiring differentiated voltage settings in other detection modes, thereby improving the applicability and flexibility of the scanning electron microscope 10.

[0046] In some embodiments, such as Figure 1 and Figure 2 As shown, the high-voltage electrode 600 penetrates the cavity wall of the vacuum chamber 100 to serve as a vacuum feed-through conductive component, realizing electrical connection between the inside and outside of the vacuum chamber 100. Specifically, the high-voltage electrode 600 penetrates the upper electrode shoe support 130. Additionally, as... Figure 2 As shown, the high-voltage electrode 600 includes an outer end 620 located outside the vacuum chamber 100 and an inner end 610 extending into the vacuum chamber 100. The outer end 620 is used to connect to a negative high-voltage power supply, and the inner end 610 is electrically connected to the input end 710 of the electrode adapter block 700. The electrode adapter block 700, the first high-voltage line 810, and the second high-voltage line 820 are all arranged inside the vacuum chamber 100.

[0047] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by arranging the electrode adapter block 700, the first high voltage line 810 and the second high voltage line 820 inside the vacuum chamber 100, realizes that the entire power distribution process from one high voltage input to two high voltage outputs is completed in a vacuum environment, reducing high voltage loss and electromagnetic interference, and further improving the reliability of maintaining the same potential between the lower electrode shoe 420 and the wafer under test 20.

[0048] In some embodiments, the vacuum chamber 100 may be made of a metallic material, providing good sealing performance and structural strength. Specifically, the vacuum chamber 100 is grounded. Additionally, the upper pole shoe 410 of the objective lens 400 may be electrically connected to the upper pole shoe support 130 for grounding via the upper pole shoe support 130.

[0049] like Figure 2 As shown, an insulating sealing structure 630 is provided between the high-voltage electrode 600 and the cavity wall of the vacuum chamber 100 to electrically isolate the high-voltage electrode 600 from the vacuum chamber 100. Specifically, the insulating sealing structure 630 is provided at the position where the high-voltage electrode 600 passes through the vacuum chamber 100. The insulating sealing structure 630 isolates the conductive part of the high-voltage electrode 600 from the grounded vacuum chamber 100, and at the same time seals the opening in the cavity wall to maintain the vacuum level inside the vacuum chamber 100.

[0050] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by grounding the vacuum chamber 100 and setting an insulating and sealing structure 630 between the high-voltage electrode 600 and the cavity wall, not only achieves electrical insulation isolation between the conductive part of the high-voltage electrode 600 and the grounded vacuum chamber 100, preventing high voltage from discharging and short-circuiting the vacuum chamber 100, but also ensures the sealing performance of the vacuum chamber 100, thereby ensuring the vacuum working conditions of the scanning electron microscope 10.

[0051] In some embodiments, such as Figure 2 As shown, the scanning electron microscope 10 may also include an insulating base 520. The insulating base 520 is fixedly mounted to the inner bottom of the vacuum chamber 100 and is used to support the high-voltage base 510. The insulating base 520 is a component made of insulating material to electrically insulate the high-voltage base 510 from the vacuum chamber 100.

[0052] Specifically, the insulating base 520 is fixedly installed at the inner bottom of the vacuum chamber 100, and the high-voltage base 510 is fixedly installed on the insulating base 520 by means of a mounting member 530, so as to separate the high-voltage base 510 from the vacuum chamber 100 by means of the insulating base 520. The mounting member 530 can be a screw.

[0053] Specifically, the insulating material can include materials with good electrical insulation, vacuum performance, and mechanical properties, such as polyetheretherketone (PEEK) or alumina ceramic. In other words, the insulating base 520 can be a component made of PEEK or alumina ceramic to ensure that the insulating base 520 maintains stable insulation performance over a long period in a high vacuum environment.

[0054] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by setting an insulating base 520 to electrically isolate the high voltage base 510 from the vacuum chamber 100, ensures that the negative high voltage on the high voltage base 510 will not directly leak to the grounded vacuum chamber 100, ensures that the wafer under test 20 can be reliably applied with the required negative voltage, and avoids high voltage breakdown or leakage from damaging other components.

[0055] In some embodiments, such as Figure 3 As shown, the insulating component 430 may include an insulating plate 431 and an insulating fastener 432. The insulating plate 431 is annular and is arranged between the upper pole shoe 410 and the lower pole shoe 420. The insulating plate 431 has a mounting through hole 4311, and the insulating fastener 432 passes through the mounting through hole 4311 to fix the lower pole shoe 420 to the upper pole shoe 410.

[0056] Specifically, there can be multiple mounting through holes 4311 and insulating fasteners 432, each corresponding to the other. Additionally, the lower pole shoe 420 has multiple mounting holes 422 that correspond one-to-one with the multiple mounting through holes 4311. The insulating plate 431 is a plate-shaped component made of electrically insulating material, used to separate the upper pole shoe 410 and the lower pole shoe 420 in the vertical direction.

[0057] Additionally, the insulating fastener 432 can be a screw made of electrically insulating material, used to maintain electrical insulation while achieving mechanical fixation. Each insulating fastener 432 passes sequentially from bottom to top through its corresponding mounting hole 422 and assembly through hole 4311, and is then fixedly connected to the upper pole shoe 410 to securely mount the lower pole shoe 420 and the insulating plate 431 onto the upper pole shoe 410.

[0058] Therefore, the scanning electron microscope 10 of this embodiment of the invention achieves all-round electrical insulation between the lower pole piece 420 and the upper pole piece 410 through the combination of the insulating plate 431 and the insulating fastener 432, enabling the lower pole piece 420 to be independently energized. Furthermore, by arranging the grounded upper pole piece 410 and the negative high-voltage lower pole piece 420 on different sides of the insulating plate 431, the scanning electron microscope 10 of this embodiment of the invention achieves separation of the upper pole piece 410 and the lower pole piece 420 using the insulating plate 431, avoiding high-voltage breakdown short circuits between the upper pole piece 410 and the lower pole piece 420, and improving the safety and reliability of the scanning electron microscope 10.

[0059] In some embodiments, such as Figure 2 and Figure 3 As shown, the lower electrode shoe 420 is an annular plate arranged perpendicular to the main electron beam. Specifically, a lower electrode shoe through-hole 421 is formed in the middle of the lower electrode shoe 420. The main electron beam passes through the lower electrode shoe through-hole 421 from top to bottom and bombards the upper surface 21 of the wafer under test 20. The signal electrons generated on the upper surface 21 of the wafer under test 20 pass through the lower electrode shoe through-hole 421 from bottom to top and are received by the detector 300.

[0060] In addition, the lower surface of the lower electrode 420 is an annular plane facing the upper surface 21 of the wafer 20 under test. When a negative voltage is applied, the lower electrode 420 can act as a voltage equipotential plate, maintaining the same potential as the wafer 20 under test.

[0061] Therefore, the scanning electron microscope 10 of this embodiment of the invention, by setting the lower pole piece 420 as an annular plate perpendicular to the main electron beam, makes the lower pole piece 420 a voltage equipotential plate with the same potential as the wafer 20 under test. Under the equipotential state, the electrostatic adsorption force of the lower surface of the lower pole piece 420 on the surface of the wafer 20 under test is eliminated, while the through hole 421 of the lower pole piece ensures the normal passage of the main electron beam and signal electrons.

[0062] In some embodiments, such as Figure 2 and Figure 3 As shown, the scanning electron microscope 10 may also include a high-voltage component 900. The high-voltage component 900 is fixedly mounted on the insulating plate 431, and has a high-voltage component through hole 910 coaxial with the lower pole shoe through hole 421 in its middle. The high-voltage component 900 is used to electrically connect to an external positive high-voltage power supply (not shown in the figure) to apply an electric field to the main electron beam and / or signal electrons passing through the high-voltage component through hole 910.

[0063] Specifically, an annular stepped surface 4312 facing the upper electrode shoe 410 is formed on the insulating plate 431. The high-voltage component 900 can be a ring electrode structure. During installation, the top of the high-voltage component 900 is snapped onto the annular stepped surface 4312, and the bottom of the high-voltage component 900 is located between the upper electrode shoe 410 and the lower electrode shoe 420, with a lower electrode shoe through hole 421 adjacent to the lower electrode shoe 420. When a positive voltage is applied to the high-voltage component 900 by an external positive high-voltage power supply, the high-voltage component 900 can carry the positive voltage.

[0064] On the one hand, when the main electron beam passes through the high-voltage component 900, the positive high voltage of the high-voltage component 900 can apply an electric field to accelerate the main electron beam. On the other hand, an electric field is formed between the high-voltage component 900 carrying a positive voltage and the wafer under test 20 carrying a negative voltage, which can cause more stray SE and BSE to converge upwards and eventually be received by the detector 300, thereby improving image quality.

[0065] Therefore, the scanning electron microscope 10 of this embodiment of the invention provides positive high voltage acceleration when the main electron beam passes through by setting a high voltage component 900 that is electrically connected to an external positive high voltage power supply, and causes secondary electrons and backscattered electrons generated on the surface of the wafer 20 to converge toward the detector 300, thereby increasing the number of signal electrons generated and the collection efficiency, and improving the detection accuracy.

[0066] In addition, the scanning electron microscope 10 of this embodiment of the invention, by fixing the high voltage component 900 on the insulating plate 431, enables the insulating plate 431 to simultaneously achieve the dual functions of electrical insulation and mechanical load-bearing of components, reducing the number of internal parts of the objective lens 400, simplifying the assembly chain, reducing the space occupied inside the objective lens 400, and simplifying the objective lens structure.

[0067] In some embodiments, such as Figure 3As shown, the bottom of the high-voltage component 900 has a protrusion 920 extending from the lower electrode shoe through-hole 421 to approach the wafer 20 under test. The projected area of ​​the protrusion 920 in the main electron beam direction is much smaller than the area of ​​the upper surface 21 of the wafer 20 under test. Specifically, the ratio of the projected area of ​​the protrusion 920 in the main electron beam direction to the area of ​​the upper surface 21 of the wafer 20 under test is any value selected from 0.004 to 0.01. In one specific embodiment, the size of the wafer 20 under test can be 12 inches, and the projected area of ​​the protrusion 920 in the main electron beam direction can be 450 square millimeters. Correspondingly, the ratio of the projected area of ​​the protrusion 920 in the main electron beam direction to the area of ​​the upper surface 21 of the wafer 20 under test is 0.006.

[0068] Therefore, the scanning electron microscope 10 of this embodiment of the invention limits the ratio of the area of ​​the protruding portion 920 of the high-voltage component 900 to the wafer area to a range of 0.4% to 1%. The electrostatic adsorption effect of the high-voltage component 900 on the surface of the wafer 20 under test is negligible compared with the electrostatic adsorption effect of the lower electrode shoe 420. This achieves a balance between ensuring the signal electron focusing function of the high-voltage component 900 and minimizing the adsorption effect on particulate matter, thereby ensuring the effectiveness of the equipotential anti-contamination scheme.

[0069] Figure 4 It is a bar chart obtained by counting the number of contaminant particles on the wafer surface after detecting or measuring the wafer using a scanning electron microscope in existing technology. Figure 5 This is a bar chart obtained by counting the number of contaminant particles on the wafer surface after detecting or measuring the wafer using a scanning electron microscope according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the morphological features of the sample under test as observed by a scanning electron microscope in the prior art. Figure 7 This is a schematic diagram of the morphological features of a sample under test as observed by a scanning electron microscope according to an embodiment of the present invention.

[0070] like Figure 4 and Figure 5 As shown, the inventors of this application conducted a comparative experiment on the anti-contamination effect of wafers. Under existing technical conditions, using a 10-cycle test method, a total of 115 wafers were tested. The results showed that 14 wafers had more than 10 surface contamination particles, exceeding the standard by 12.2%. However, under the technical solution of this invention, using the same 10-cycle test method, a total of 106 wafers were tested, and 0 wafers had more than 10 surface contamination particles, exceeding the standard by 0%. This fully demonstrates that the equipotential anti-contamination scheme of this invention has a significant effect on preventing contamination of the tested wafer 20 by contamination particles.

[0071] In addition, the inventors of this application have verified the impact of equipotential design on image quality. Figure 6 and Figure 7 Images of morphological features generated by a scanning electron microscope (SEM) in the prior art and a scanning electron microscope 10 according to an embodiment of the present invention are shown for comparison. Figure 6 and Figure 7 It can be seen that there is no significant difference between the two images, and the image quality is within the acceptable range for semiconductor detection engineering. This indicates that the disappearance of the potential difference between the pole piece and the sample under test under the objective lens does not reduce the collection efficiency of signal electrons near the surface of the sample under test, and does not have a negative impact on image quality.

[0072] Therefore, the embodiments of the present invention verify the actual effect of the equipotential anti-contamination scheme of the scanning electron microscope 10 through experimental data, proving that the technical solution of the present invention can take into account both the anti-cross-contamination effect and the imaging detection performance, and overcome the technical bias in the field that the potential difference between the wafer and the objective lens pole piece must be maintained to ensure imaging.

[0073] Those skilled in the art should understand that, unless otherwise specified, the terms "upper," "lower," "inner," and "outer" used in the embodiments of the present invention to indicate orientation or positional relationship are merely for the purpose of facilitating the description and understanding of the technical solutions of the present invention, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0074] In the description of this embodiment, references to terms such as "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A scanning electron microscope, characterized by, The scanning electron microscope comprises: a high-voltage base for carrying a wafer to be measured and electrically connected to the wafer to be measured; an objective lens comprising an upper pole shoe, a lower pole shoe and an insulating member, the lower pole shoe being electrically insulated from the upper pole shoe by the insulating member; and a high-voltage electrode for being electrically connected to an external negative high-voltage power supply and configured to apply a negative voltage to the high-voltage base and the lower pole shoe simultaneously or cut off the negative voltage, so that the potential of the lower pole shoe is the same as that of the wafer to be measured. The scanning electron microscope further comprises:

2. The scanning electron microscope of claim 1, wherein, an electrode adapter block having an input end electrically connected to the high-voltage electrode and an output end having a first high-voltage output branch and a second high-voltage output branch; a first high-voltage line electrically connected between the first high-voltage output branch and the high-voltage base; and a second high-voltage line electrically connected between the second high-voltage output branch and the lower pole shoe. The scanning electron microscope further comprises:

3. The scanning electron microscope of claim 2, wherein, a vacuum chamber for defining a vacuum environment and accommodating the high-voltage base and the objective lens; wherein the high-voltage electrode penetrates a cavity wall of the vacuum chamber and comprises an outer end located outside the vacuum chamber for connecting the negative high-voltage power supply and an inner end extending into the interior of the vacuum chamber and electrically connected to the input end of the electrode adapter block, and the electrode adapter block, the first high-voltage line and the second high-voltage line are arranged inside the vacuum chamber.

4. The scanning electron microscope according to claim 3, wherein the vacuum chamber is grounded, and an insulating sealing structure is provided between the high-voltage electrode and the cavity wall of the vacuum chamber to electrically insulate the high-voltage electrode from the vacuum chamber. The scanning electron microscope further comprises:

5. The scanning electron microscope of claim 4, wherein, an insulating base fixedly installed on the inner bottom of the vacuum chamber for carrying the high-voltage base, and the insulating base is a member made of insulating material to electrically insulate the high-voltage base from the vacuum chamber. The vacuum chamber comprises:

6. The scanning electron microscope of claim 3, wherein, a box body having an upwardly open opening, and the box body is provided with a vacuum pump interface for connecting to an external vacuum pump and a transfer window for the wafer to be measured to enter and exit; an upper cover sealingly connected to the box body to cover the opening; and an upper pole shoe support seat located above the upper cover and sealingly and fixedly connected to the upper cover through a sealing ring and a connecting member, and the upper pole shoe is fixedly connected to the upper pole shoe support seat. The insulating member comprises:

7. The scanning electron microscope of claim 1, wherein, an insulating plate in the form of a ring-shaped plate arranged between the upper pole shoe and the lower pole shoe, and the insulating plate is provided with an assembly through hole; and an insulating fastener penetrating the assembly through hole and fixedly connecting the lower pole shoe to the upper pole shoe.

8. The scanning electron microscope according to claim 7, wherein the lower pole shoe is in the form of a ring-shaped plate arranged perpendicular to the main electron beam, and a lower pole shoe through hole is formed in the middle of the lower pole shoe for the main electron beam and signal electrons generated from the surface of the wafer to be measured to pass through. The scanning electron microscope further comprises:

9. The scanning electron microscope of claim 8, wherein, ​ A high-voltage part is fixedly installed on the insulating plate, and a high-voltage part through hole coaxial with the lower pole shoe through hole is formed in the high-voltage part, and the high-voltage part is electrically connected with an external positive high-voltage power supply to exert an electric field on the main electron beam and / or signal electrons passing through the high-voltage part through hole.

10. The scanning electron microscope of claim 1, wherein, The scanning electron microscope further comprises: An electron beam emission source above the objective lens for emitting a main electron beam to the wafer under test to generate signal electrons from the wafer under test under the action of the main electron beam; and A detector between the electron beam emission source and the objective lens, and a detector through hole for the main electron beam is formed in the detector for receiving the signal electrons and generating a corresponding detection signal.

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