Amplification factor adjusting circuit and method for scanning electron microscope and scanning electron microscope

Abstract

The invention relates to the technical field of electronic circuits, and discloses an amplification factor adjusting circuit and method for a scanning electron microscope and the scanning electron microscop.The amplification factor adjusting circuit comprises a control circuit, an X scanning gear switching circuit, an X scanning feedback circuit, a Y scanning gear switching circuit and a Y scanning feedback circuit, the control circuit is respectively connected with the upper computer, the X scanning feedback circuit, the Y scanning feedback circuit, the X scanning gear switching circuit and the Y scanning gear switching circuit, the X scanning gear switching circuit is further connected with the X scanning feedback circuit, and the Y scanning gear switching circuit is further connected with the Y scanning feedback circuit. The circuit can realize the adjustment of 12 amplification gears in total, and the distance between the two gears is 4 times, so that the amplification factor calibration precision of the scanning electron microscope is greatly improved. And the circuit performs feedback regulation in the whole regulation range, so that the control precision is high, and the circuit is not influenced by load change.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a magnification adjustment circuit and method for a scanning electron microscope and a scanning electron microscope. Background Art

[0002] A scanning electron microscope is an electronic optical instrument used to observe microstructures. A focused electron beam is used to scan the sample surface line by line. The electron beam bombards the sample surface to generate secondary electrons or backscattered electrons. The efficiency of the electron beam bombardment is related to the sample surface morphology or material. The secondary electrons or backscattered electrons generated on the sample surface are collected, and the position of the electron beam scanning on the sample surface and the number of secondary electrons or backscattered electrons generated are expressed in the form of a two-dimensional image, that is, the secondary electron image or backscattered electron image of the scanning electron microscope is obtained. The resolution of the scanning electron microscope image can reach the nanometer level or even better than 1.0 nanometer, and it plays an irreplaceable role in the fields of new materials, new energy, national defense, scientific research, etc.

[0003] During the operation of the scanning electron microscope, the magnification will be changed according to the different samples observed or the different needs. The magnification of the scanning electron microscope is determined by the deflection range of the electron beam and the image display size. When the image display size is determined, the deflection range of the electron beam directly determines the magnification of the scanning electron microscope. The deflection range of the electron beam is determined by the size of the deflection magnetic field, and the deflection magnetic field is determined by the scanning coil structure, number of turns and power supply current. In the actual working process, the magnification of the scanning electron microscope is controlled by changing the power supply current of the deflection coil. The magnification of the scanning electron microscope is generally several times to hundreds of thousands of times, with a large span and high precision requirements.

[0004] Generally, the magnification of a commonly used scanning electron microscope is set at 4-6 levels, with a minimum of 10 times between two levels. Affected by the thermal drift or poor linearity of electronic components, the magnification accuracy is not high and the linearity is poor. Summary of the invention

[0005] In view of this, the present invention provides a magnification adjustment circuit and method for a scanning electron microscope and a scanning electron microscope to solve the problem of low magnification accuracy and poor linearity of the scanning electron microscope.

[0006] In a first aspect, the present invention provides a magnification adjustment circuit for a scanning electron microscope, the magnification adjustment circuit comprising: a control circuit, an X-scan switching circuit, an X-scan feedback circuit, a Y-scan switching circuit and a Y-scan feedback circuit, wherein:

[0007] The control circuit is connected to the host computer, the X-scan feedback circuit, the Y-scan feedback circuit, the X-scan switching circuit and the Y-scan switching circuit respectively, the X-scan switching circuit is also connected to the X-scan feedback circuit, and the Y-scan switching circuit is also connected to the Y-scan feedback circuit;

[0008] The control circuit switches the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and adjusts the gear current of the X-scan switching circuit according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears;

[0009] The control circuit switches the amplification mode and amplification gear of the Y scan switching circuit according to the Y scan control signal sent by the host computer, and adjusts the gear current of the Y scan switching circuit according to the deviation between the voltage signal fed back by the Y scan feedback circuit and the Y scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears.

[0010] The present invention provides a magnification adjustment circuit for a scanning electron microscope, which is divided into three magnification modes, each of which is further divided into four magnification gears. Therefore, the circuit can realize a total of 12 magnification gears, and the interval between two gears is 4 times, so that the calibration accuracy of the magnification of the scanning electron microscope is greatly improved. In addition, the circuit is feedback-adjusted within the entire adjustment range, with high control accuracy and is not affected by load changes.

[0011] In an optional implementation, the X-scan switching circuit and the Y-scan switching circuit both include: a mode switching circuit and a gear switching circuit, wherein:

[0012] The mode switching circuit is connected to the gear switching circuit, and both the mode switching circuit and the gear switching circuit are connected to the output end of the control circuit;

[0013] The mode switching circuit is used to switch the amplification modes of the X-scanning switching circuit and the Y-scanning switching circuit, and the gear switching circuit is used to perform gear switching in each amplification mode.

[0014] In an optional implementation, the gear switching circuit includes: a first switch, a second switch, a third switch, a fourth switch, a first resistor, a second resistor, a third resistor and a fourth resistor, wherein:

[0015] One end of the first switch is respectively connected to one end of the second switch, one end of the third switch, one end of the fourth switch and the mode switching circuit, the other end of the first switch is respectively connected to one end of the first resistor and one end of the second resistor, and the other end of the first resistor is grounded;

[0016] The other end of the second switch is respectively connected to the other end of the second resistor and one end of the third resistor, the other end of the third switch is respectively connected to the other end of the third resistor and one end of the fourth resistor, and the other end of the fourth switch is respectively connected to the other end of the fourth resistor, the output end of the X scan feedback circuit, and the input end of the Y scan feedback circuit.

[0017] In an optional implementation, the gear switching circuit further includes: a fifth switch, a sixth switch, a seventh switch, an eighth switch, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, and an eighteenth resistor, wherein:

[0018] One end of the fifth switch is respectively connected to one end of the sixth switch, one end of the seventh switch, one end of the eighth switch and the mode switching circuit, the other end of the fifth switch is respectively connected to one end of the fifth resistor, one end of the sixth resistor and one end of the scanning coil resistor, the other end of the fifth resistor is respectively connected to one end of the seventh resistor and one end of the eighth resistor;

[0019] The other end of the sixth switch is respectively connected to the other end of the seventh resistor, one end of the ninth resistor and one end of the tenth resistor, and the other end of the ninth resistor is respectively connected to one end of the eleventh resistor and one end of the twelfth resistor;

[0020] The other end of the seventh switch is respectively connected to the other end of the eleventh resistor, one end of the thirteenth resistor and one end of the fourteenth resistor, and the other end of the thirteenth resistor is respectively connected to one end of the fifteenth resistor and one end of the sixteenth resistor;

[0021] The other end of the eighth switch is respectively connected to the other end of the fifteenth resistor, one end of the seventeenth resistor and one end of the eighteenth resistor, and the other end of the seventeenth resistor is respectively connected to the other end of the eighteenth resistor, the other end of the sixteenth resistor, the other end of the fourteenth resistor, the other end of the twelfth resistor, the other end of the tenth resistor, the other end of the eighth resistor, the other end of the sixth resistor, the other end of the scanning coil resistor and the mode switching circuit.

[0022] In an optional implementation, the mode switching circuit includes: a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a thirteenth switch and a fourteenth switch, wherein:

[0023] One end of the ninth switch is respectively connected to one end of the tenth switch, one end of the eleventh switch, the output end of the X scan feedback circuit, and the output end of the Y scan feedback circuit; the other end of the ninth switch is respectively connected to the other end of the fifth switch, one end of the fifth resistor, one end of the sixth resistor, and one end of the scan coil resistor; the other end of the tenth switch is respectively connected to one end of the fifth switch, one end of the sixth switch, one end of the seventh switch, and one end of the eighth switch; the other end of the eleventh switch is connected to the output end of the X scan feedback circuit and the input end of the Y scan feedback circuit;

[0024] One end of the twelfth switch is respectively connected to one end of the thirteenth switch, one end of the fourteenth switch and the other end of the scanning coil resistor, the other end of the twelfth switch is respectively connected to one end of the first switch, one end of the second switch, one end of the third switch and one end of the fourth switch, the other end of the thirteenth switch is respectively connected to the other end of the fourth switch, the other end of the fourth resistor, the output end of the X scanning feedback circuit and the input end of the Y scanning feedback circuit, and the other end of the fourteenth switch is grounded.

[0025] In an optional implementation, the X-scan switching circuit and the Y-scan switching circuit further include: a first compensation circuit and a second compensation circuit, wherein:

[0026] One end of the first compensation circuit is respectively connected to the other end of the fifth switch, one end of the fifth resistor and one end of the sixth resistor, and the other end of the first compensation circuit is respectively connected to one end of the ninth switch and one end of the scanning coil resistor;

[0027] One end of the second compensation circuit is connected to the other end of the sixth resistor and one end of the thirteenth switch respectively, and the other end of the second compensation circuit is connected to the other end of the scanning coil resistor and one end of the twelfth switch respectively.

[0028] In an optional implementation, the control circuit includes: an MCU, an X control unit, an X power amplifier unit, a Y control unit and a Y power amplifier unit, wherein:

[0029] The input end of the MCU is connected to the host computer, and the output end of the MCU is respectively connected to the input end of the X control unit, the input end of the Y control unit, the X scanning switching circuit and the Y scanning switching circuit;

[0030] The input end of the X control unit is also connected to the X scan feedback circuit, the output end of the X control unit is connected to the input end of the X power amplification unit, the output end of the X power amplification unit is connected to the X scan switching circuit, the input end of the Y control unit is also connected to the Y scan feedback circuit, the output end of the Y control unit is connected to the input end of the Y power amplification unit, and the output end of the Y power amplification unit is connected to the Y scan switching circuit.

[0031] In a second aspect, the present invention provides a method for adjusting the magnification of a scanning electron microscope, based on the magnification adjustment circuit for a scanning electron microscope according to the first aspect or any corresponding embodiment thereof, the method comprising:

[0032] Switching the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and switching the amplification mode and amplification gear of the Y-scan switching circuit according to the Y-scan control signal sent by the host computer, wherein the amplification modes include 3 types, and each amplification mode includes 4 types of amplification gears;

[0033] The gear current of the X-scan switching circuit is adjusted according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal, and the gear current of the Y-scan switching circuit is adjusted according to the deviation between the voltage signal fed back by the Y-scan feedback circuit and the Y-scan control signal.

[0034] The present invention provides a magnification adjustment method for a scanning electron microscope, which divides the magnification adjustment circuit into three magnification modes, each of which is further divided into four magnification gears, and can achieve a total of 12 magnification gears, with a spacing of four times between two gears, so that the calibration accuracy of the magnification of the scanning electron microscope is greatly improved. In addition, the circuit is feedback-adjusted within the entire adjustment range, has high control accuracy, and is not affected by load changes.

[0035] In a third aspect, the present invention provides a scanning electron microscope, comprising the amplification adjustment circuit for a scanning electron microscope according to the first aspect or any corresponding embodiment thereof.

[0036] The scanning electron microscope provided by the present invention greatly improves the calibration accuracy of the magnification of the scanning electron microscope by adopting the magnification adjustment circuit for the scanning electron microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 is a principle block diagram of a magnification adjustment circuit for a scanning electron microscope according to an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of a magnification adjustment circuit for a scanning electron microscope according to an embodiment of the present invention;

[0040] Figure 3 is an equivalent circuit diagram of a magnification adjustment circuit for a scanning electron microscope according to an embodiment of the present invention;

[0041] Figure 4 is another equivalent circuit diagram of a magnification adjustment circuit for a scanning electron microscope according to an embodiment of the present invention;

[0042] Figure 5 is another equivalent circuit diagram of a magnification adjustment circuit for a scanning electron microscope according to an embodiment of the present invention;

[0043] Figure 6 is a principle block diagram of a control circuit according to an embodiment of the present invention;

[0044] Figure 7 is a partial circuit diagram of a control circuit according to an embodiment of the present invention;

[0045] Figure 8 It is a flow chart of a method for adjusting magnification of a scanning electron microscope according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0048] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] The present invention provides a magnification adjustment circuit for a scanning electron microscope, such as Figure 1 As shown, it includes: a control circuit, an X-scan switching circuit, an X-scan feedback circuit, a Y-scan switching circuit and a Y-scan feedback circuit. The control circuit is connected to the host computer, the X-scan feedback circuit, the Y-scan feedback circuit, the X-scan switching circuit and the Y-scan switching circuit respectively, the X-scan switching circuit is also connected to the X-scan feedback circuit, and the Y-scan switching circuit is also connected to the Y-scan feedback circuit.

[0051] Specifically, the control circuit switches the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and adjusts the gear current of the X-scan switching circuit according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears. The control circuit switches the amplification mode and amplification gear of the Y-scan switching circuit according to the Y-scan control signal sent by the host computer, and adjusts the gear current of the Y-scan switching circuit according to the deviation between the voltage signal fed back by the Y-scan feedback circuit and the Y-scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears.

[0052] In an embodiment of the present invention, the actual parameter for controlling the magnification of the scanning electron microscope is the scanning coil current, which is generally within ±3A. In order to control the heat generated by the scanning coil, the resistance of the scanning coil is generally relatively small, only a few tenths to a few ohms. The smaller the scanning current, the higher the magnification. In order to improve the magnification control accuracy, several gears are generally set, such as ampere level, milliampere level, and microampere level. If there are too few gears, relying solely on data fitting will reduce the control accuracy, and if there are too many gears, the circuit structure and the magnification calibration workload will be greatly increased. Therefore, this embodiment designs a magnification adjustment circuit with a total of 12 gears and a spacing of 4 times between two gears.

[0053] The present invention provides a magnification adjustment circuit for a scanning electron microscope, which is divided into three magnification modes, each of which is further divided into four magnification gears. Therefore, the circuit can realize a total of 12 magnification gears, and the adjustment of the interval between two gears is 4 times, so that the calibration accuracy of the magnification of the scanning electron microscope is greatly improved. In addition, the circuit is feedback-adjusted within the entire adjustment range, with high control accuracy, and is not affected by the heat generated by the scanning deflection coil during operation, which causes the change of its own load.

[0054] In an optional implementation, the X-scan switching circuit and the Y-scan switching circuit both include: a mode switching circuit and a gear switching circuit, wherein the mode switching circuit is connected to the gear switching circuit, and the mode switching circuit and the gear switching circuit are both connected to the output end of the control circuit.

[0055] Specifically, the X-scanning switching circuit includes: an X-scanning mode switching circuit and an X-scanning gear switching circuit. The X-scanning mode switching circuit is used to switch the amplification mode of the X-scanning switching circuit, and the Y-scanning mode switching circuit is used to switch the amplification mode of the Y-scanning switching circuit. The X-scanning gear switching circuit is used to switch the gear in each amplification mode of the X-scanning switching circuit, and the Y-scanning gear switching circuit is used to switch the gear in each amplification mode of the Y-scanning switching circuit.

[0056] Furthermore, the amplification modes of the X-scan switching circuit are divided into three modes: Mode1, Mode2, and Mode3. The scanning multiples use Mode1, Mode2, and Mode3 from low to high. Each amplification mode corresponds to four amplification gears: Stage1, Stage2, Stage3, and Stage4. Similarly, the amplification modes of the Y-scan switching circuit are divided into three modes: Mode1, Mode2, and Mode3. The scanning multiples use Mode1, Mode2, and Mode3 from low to high. Each amplification mode corresponds to four amplification gears: Stage1, Stage2, Stage3, and Stage4. The scanning multiples use four amplification gears: Stage1, Stage2, Stage3, and Stage4 from low to high.

[0057] In an optional implementation, an X-scan gear switching circuit is used as an example for description. Figure 2 As shown, the X-scanning gear switching circuit includes: a first switch K14, a second switch K12, a third switch K11, a fourth switch K13, a first resistor R50, a second resistor R49, a third resistor R48 and a fourth resistor R47. Among them, one end of the first switch K14 is respectively connected to one end of the second switch K12, one end of the third switch K11, one end of the fourth switch K13 and the X-scanning mode switching circuit, the other end of the first switch K14 is respectively connected to one end of the first resistor R50 and one end of the second resistor R49, and the other end of the first resistor R50 is grounded. The other end of the second switch K12 is respectively connected to the other end of the second resistor R49 and one end of the third resistor R48, the other end of the third switch K11 is respectively connected to the other end of the third resistor R48 and one end of the fourth resistor R47, and the other end of the fourth switch K13 is respectively connected to the other end of the fourth resistor R47 and the output end of the X-scanning feedback circuit.

[0058] Specifically, the first switch K14, the second switch K12, the third switch K11, and the fourth switch K13 are the amplification gear switching switches in Mode 1. When the first switch K14 is closed, the Stage 1 gear current is I_1; when the second switch K12 is closed, the Stage 2 gear current is I_2; when the third switch K11 is closed, the Stage 3 gear current is I_3; when the fourth switch K13 is closed, the Stage 4 gear current is I_4. In this circuit mode, the resistance of R47 is 1 / 150R, the resistance of R48 is 1 / 50R, the resistance of R49 is 2 / 25R, and the resistance of R48 is 8 / 25R.

[0059] In an optional embodiment, if Figure 2 As shown, the X-scan gear switching circuit also includes: a fifth switch K4, a sixth switch K3, a seventh switch K5, an eighth switch K6, a fifth resistor R24, a sixth resistor R32, a seventh resistor R23, an eighth resistor R31, a ninth resistor R22, a tenth resistor R35, an eleventh resistor R21, a twelfth resistor R30, a thirteenth resistor R20, a fourteenth resistor R34, a fifteenth resistor R19, a sixteenth resistor R33, a seventeenth resistor R28, and an eighteenth resistor R29.

[0060] Among them, one end of the fifth switch K4 is respectively connected to one end of the sixth switch K3, one end of the seventh switch K5, one end of the eighth switch K6 and the mode switching circuit, the other end of the fifth switch K4 is respectively connected to one end of the fifth resistor R24, one end of the sixth resistor R32 and one end of the scanning coil resistor CoilX, and the other end of the fifth resistor R24 ​​is respectively connected to one end of the seventh resistor R23 and one end of the eighth resistor R31. The other end of the sixth switch K3 is respectively connected to the other end of the seventh resistor R23, one end of the ninth resistor R22 and one end of the tenth resistor R35, and the other end of the ninth resistor R22 is respectively connected to one end of the eleventh resistor R21 and one end of the twelfth resistor R30. The other end of the seventh switch K5 is respectively connected to the other end of the eleventh resistor R21, one end of the thirteenth resistor R20 and one end of the fourteenth resistor R34, and the other end of the thirteenth resistor R20 is respectively connected to one end of the fifteenth resistor R19 and one end of the sixteenth resistor R33. The other end of the eighth switch K6 is respectively connected to the other end of the fifteenth resistor R19, one end of the seventeenth resistor R28, and one end of the eighteenth resistor R29. The other end of the seventeenth resistor R28 is respectively connected to the other end of the eighteenth resistor R29, the other end of the sixteenth resistor R33, the other end of the fourteenth resistor R34, the other end of the twelfth resistor R30, the other end of the tenth resistor R35, the other end of the eighth resistor R31, the other end of the sixth resistor R32, the other end of the scanning coil resistor CoilX, and the mode switching circuit.

[0061] Specifically, the fifth switch K4, the sixth switch K3, the seventh switch K5, and the eighth switch K6 are the amplification gear switching switches in Mode2 and Mode3. In Mode2, when the fifth switch K4 is closed, the Stage1 gear current is I_5; when the sixth switch K3 is closed, the Stage2 gear current is I_6; when the seventh switch K5 is closed, the Stage3 gear current is I_7; when the eighth switch K6 is closed, the Stage4 gear current is I_4. In Mode3, when the fifth switch K4 is closed, the Stage1 gear current is I_9; when the sixth switch K3 is closed, the Stage2 gear current is I_10; when the seventh switch K5 is closed, the Stage3 gear current is I_11; when the eighth switch K6 is closed, the Stage4 gear current is I_12.

[0062] In an optional embodiment, if Figure 2 As shown, the X-scan mode switching circuit includes: a ninth switch K1, a tenth switch K2, an eleventh switch K7, a twelfth switch K8, a thirteenth switch K9 and a fourteenth switch K10.

[0063] Among them, one end of the ninth switch K1 is respectively connected to one end of the tenth switch K2, one end of the eleventh switch K7, and the output end of the X scan feedback circuit and the output end of the Y scan feedback circuit; the other end of the ninth switch K1 is respectively connected to the other end of the fifth switch K4, one end of the fifth resistor R24, one end of the sixth resistor R32, and one end of the scan coil resistor CoilX; the other end of the tenth switch K2 is respectively connected to one end of the fifth switch K4, one end of the sixth switch K3, one end of the seventh switch K5, and one end of the eighth switch K6; the other end of the eleventh switch K7 is connected to the output end of the X scan feedback circuit and the input end of the Y scan feedback circuit. One end of the twelfth switch K8 is respectively connected to one end of the thirteenth switch K9, one end of the fourteenth switch K10 and the other end of the scanning coil resistor CoilX, the other end of the twelfth switch K8 is respectively connected to one end of the first switch K14, one end of the second switch K12, one end of the third switch K11 and one end of the fourth switch K13, the other end of the thirteenth switch K9 is respectively connected to the other end of the fourth switch K13, the other end of the fourth resistor R47, the output end of the X scanning feedback circuit and the input end of the Y scanning feedback circuit, and the other end of the fourteenth switch K10 is grounded.

[0064] Specifically, the ninth switch K1 and the twelfth switch K8 are switches for controlling the Mode 1 mode; the tenth switch K2 and the thirteenth switch K9 are switches for controlling the Mode 2 mode; the eleventh switch K7 and the fourteenth switch K10 are switches for controlling the Mode 3 mode.

[0065] When the ninth switch K1 and the twelfth switch K8 are closed, the X-scan switching circuit enters Mode 1. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 3 As shown. Figure 3 It can be seen from the equivalent circuit diagram shown that I_1 is the maximum current, I_2 is 1 / 4 of I_1, I_3 is 1 / 4 of I_2, and I_4 is 1 / 4 of I_3. Since the smaller the scan current, the higher the magnification. Therefore, when the fourth switch K13 corresponding to I_4 is closed, the Stage4 gear scanning multiple is the highest, and when the first switch K14 corresponding to I_1 is closed, the Stage1 gear scanning multiple is the lowest. The maximum voltage used by this circuit is I_1*(R100+CoilX), so the power supply is selected based on this standard, and the maximum feedback voltage is I_1*R50.

[0066] like Figure 2As shown, when the tenth switch K2 and the thirteenth switch K9 are closed, the X-scan switching circuit enters Mode 2 mode, and by switching the gear switches K4, K3, K5, and K6, and cooperating with the T-shaped resistance network, the maximum current flowing through the scanning coil resistor CoilX is reduced at a ratio of 1 / 4. In this mode, I_5 is the maximum current, I_6 is 1 / 4 of I_5, I_7 is 1 / 4 of I_6, and I_8 is 1 / 4 of I_7. Since the smaller the scanning current, the higher the amplification factor. Therefore, when the eighth switch K6 corresponding to I_8 is closed, the Stage 4 gear scanning factor is the highest, and when the fifth switch K4 corresponding to I_5 is closed, the Stage 1 gear scanning factor is the lowest. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 4 As shown. Figure 4 From the equivalent circuit diagram shown, it can be seen that the current flowing through the feedback resistor is 3*I_5. By adjusting the parallel value of R45 and R46, I_5 can be made 1 / 4 of I_4. Because the maximum value of the feedback voltage is certain (I_1*R50), the parallel resistance value of R45 and R46 can be calculated based on this, and the actual value of R45 and R46 can be adjusted accordingly. Figure 4 Where R* is the equivalent resistance of R45-R50.

[0067] like Figure 2 As shown, when the eleventh switch K7 and the fourteenth switch K10 are closed, the X-scan switching circuit enters Mode 3 mode, and by switching the gear switches K4, K3, K5, and K6, and cooperating with the T-shaped resistance network, the maximum current flowing through the scanning coil resistor CoilX is reduced at a ratio of 1 / 4. In this mode, I_9 is the maximum current, I_10 is 1 / 4 of I_9, I_11 is 1 / 4 of I_10, and I_12 is 1 / 4 of I_11. Since the smaller the scanning current, the higher the amplification factor. Therefore, when the eighth switch K6 corresponding to I_12 is closed, the Stage 4 gear scanning factor is the highest, and when the fifth switch K4 corresponding to I_9 is closed, the Stage 1 gear scanning factor is the lowest. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 5 As shown. Figure 5 As shown in the equivalent circuit diagram, in this mode, the resistance of R15 is fixed and selected as 2 / 3R, so the driving voltage is constant in this mode. The sum of the current flowing through R5 and R8 is 3 times that flowing through I_9, where I_9 is 1 / 4 of I_8. Therefore, according to Ohm's law, the parallel resistance value of R5 and R8 can be calculated, and the resistance distribution can be performed accordingly.

[0068] By adding a T-type resistor network in Mode 2 and Mode 3, the control accuracy of the magnification adjustment circuit used for the scanning electron microscope is improved.

[0069] In an optional embodiment, if Figure 2 As shown, the X-scan switching circuit also includes: a first compensation circuit and a second compensation circuit. One end of the first compensation circuit is respectively connected to the other end of the fifth switch K4, one end of the fifth resistor R24 ​​and one end of the sixth resistor R32, and the other end of the first compensation circuit is respectively connected to one end of the ninth switch K1 and one end of the scanning coil resistor CoilX. One end of the second compensation circuit is respectively connected to the other end of the sixth resistor R32 and one end of the thirteenth switch K9, and the other end of the second compensation circuit is respectively connected to the other end of the scanning coil resistor CoilX and one end of the twelfth switch K8.

[0070] Specifically, in actual use, due to the existence of processing errors, the scanning coil resistance CoilX will have a certain error. By adjusting R17, R25, R38 and R41, the sum of these four resistors and the scanning coil resistance can be equal to R.

[0071] In an optional embodiment, if Figure 6 As shown, the control circuit includes: MCU, X control unit, X power amplifier unit, Y control unit and Y power amplifier unit. Among them, the input end of MCU is connected to the host computer, the output end of MCU is respectively connected to the input end of X control unit, the input end of Y control unit, X scanning switching circuit and Y scanning switching circuit, the input end of X control unit is also connected to X scanning feedback circuit, the input end of Y control unit is also connected to Y scanning feedback circuit, the output end of X control unit is connected to the input end of X power amplifier unit, the output end of X power amplifier unit is connected to X scanning switching circuit, the output end of Y control unit is connected to the input end of Y power amplifier unit, and the output end of Y power amplifier unit is connected to Y scanning switching circuit.

[0072] Specifically, the MCU receives the control command sent by the host computer, and switches the amplification mode and amplification gear of the X / Y scanning switching circuit according to the control signal, and sends the control signal to the X / Y control unit. The X scanning feedback circuit also sends the collected feedback voltage to the X control unit, and in the X control unit, the gear current of the X scanning switching circuit is adjusted according to the deviation between the feedback voltage signal and the control signal. The X power amplifier unit transmits the adjusted gear current to the X scanning switching circuit. The Y scanning feedback circuit also sends the collected feedback voltage to the Y control unit, and in the Y control unit, the gear current of the Y scanning switching circuit is adjusted according to the deviation between the feedback voltage signal and the control signal. The Y power amplifier unit transmits the adjusted gear current to the Y scanning switching circuit. Among them, refer to some circuit structures in the control circuit. Figure 7 , where U2A is the X control unit and U1 is the X power amplifier unit. The Y control unit and the Y power amplifier unit are the same Figure 7 , it is no longer displayed here.

[0073] The present invention provides a magnification adjustment method for a scanning electron microscope, based on the magnification adjustment circuit for a scanning electron microscope of the above embodiment, such as Figure 8 As shown, the magnification adjustment method for a scanning electron microscope includes the following steps:

[0074] Step S11, switching the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and switching the amplification mode and amplification gear of the Y-scan switching circuit according to the Y-scan control signal sent by the host computer. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears.

[0075] Specifically, the ninth switch K1 and the twelfth switch K8 are switches for controlling the Mode 1 mode; the tenth switch K2 and the thirteenth switch K9 are switches for controlling the Mode 2 mode; the eleventh switch K7 and the fourteenth switch K10 are switches for controlling the Mode 3 mode.

[0076] When the ninth switch K1 and the twelfth switch K8 are closed according to the control signal, the X-scan switching circuit enters Mode 1. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 3 As shown. Figure 3 It can be seen from the equivalent circuit diagram shown that I_1 is the maximum current, I_2 is 1 / 4 of I_1, I_3 is 1 / 4 of I_2, and I_4 is 1 / 4 of I_3. Since the smaller the scan current, the higher the magnification. Therefore, when the fourth switch K13 corresponding to I_4 is closed, the Stage4 gear scanning multiple is the highest, and when the first switch K14 corresponding to I_1 is closed, the Stage1 gear scanning multiple is the lowest. The maximum voltage used by this circuit is I_1*(R100+CoilX), so the power supply is selected based on this standard, and the maximum feedback voltage is I_1*R50.

[0077] like Figure 2 As shown, when the tenth switch K2 and the thirteenth switch K9 are closed according to the control signal, the X-scan switching circuit enters Mode2 mode, and by switching the gear switches K4, K3, K5, and K6, and cooperating with the T-shaped resistance network, the maximum current flowing through the scanning coil resistor CoilX is reduced at a ratio of 1 / 4. In this mode, I_5 is the maximum current, I_6 is 1 / 4 of I_5, I_7 is 1 / 4 of I_6, and I_8 is 1 / 4 of I_7. Since the smaller the scanning current, the higher the amplification factor. Therefore, when the eighth switch K6 corresponding to I_8 is closed, the Stage4 gear scanning factor is the highest, and when the fifth switch K4 corresponding to I_5 is closed, the Stage1 gear scanning factor is the lowest. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 4 As shown. Figure 4From the equivalent circuit diagram shown, it can be seen that the current flowing through the feedback resistor is 3*I_5. By adjusting the parallel value of R45 and R46, I_5 can be made 1 / 4 of I_4. Because the maximum value of the feedback voltage is certain (I_1*R50), the parallel resistance value of R45 and R46 can be calculated based on this, and the actual value of R45 and R46 can be adjusted accordingly. Figure 4 Where R* is the equivalent resistance of R45-R50.

[0078] like Figure 2 As shown, when the eleventh switch K7 and the fourteenth switch K10 are closed according to the control signal, the X-scan switching circuit enters the Mode 3 mode, and by switching the gear switches K4, K3, K5, and K6, and cooperating with the T-shaped resistance network, the maximum current flowing through the scanning coil resistor CoilX is reduced at a ratio of 1 / 4. In this mode, I_9 is the maximum current, I_10 is 1 / 4 of I_9, I_11 is 1 / 4 of I_10, and I_12 is 1 / 4 of I_11. Since the smaller the scanning current, the higher the amplification factor. Therefore, when the eighth switch K6 corresponding to I_12 is closed, the Stage 4 gear scanning factor is the highest, and when the fifth switch K4 corresponding to I_9 is closed, the Stage 1 gear scanning factor is the lowest. At this time, the equivalent circuit diagram of the X-scan switching circuit is as follows: Figure 5 As shown. Figure 5 As shown in the equivalent circuit diagram, in this mode, the resistance of R15 is fixed and selected as 2 / 3R, so the driving voltage is constant in this mode. The sum of the current flowing through R5 and R8 is 3 times that flowing through I_9, where I_9 is 1 / 4 of I_8. Therefore, according to Ohm's law, the parallel resistance value of R5 and R8 can be calculated, and the resistance distribution can be performed accordingly.

[0079] Step S12, adjusting the gear current of the X-scan switching circuit according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal, and adjusting the gear current of the Y-scan switching circuit according to the deviation between the voltage signal fed back by the Y-scan feedback circuit and the Y-scan control signal.

[0080] Specifically, the X / Y control unit receives the voltage signal fed back by the X / Y scanning feedback circuit and the control signal of the MCU. In the X / Y control unit, the gear current of the X / Y scanning switching circuit is adjusted according to the deviation between the feedback voltage signal and the control signal. The X / Y power amplifier unit transmits the adjusted gear current to the X / Y scanning switching circuit for feedback adjustment within the full range.

[0081] The further functional description of the above method is the same as that of the above corresponding embodiment and will not be repeated here.

[0082] The present invention provides a magnification adjustment method for a scanning electron microscope, which divides the magnification adjustment circuit into three magnification modes, each of which is further divided into four magnification gears, and can achieve a total of 12 magnification gears, with a spacing of four times between two gears, so that the calibration accuracy of the magnification of the scanning electron microscope is greatly improved. In addition, the circuit is feedback-adjusted within the entire adjustment range, has high control accuracy, and is not affected by load changes.

[0083] The present invention provides a scanning electron microscope, comprising the amplification adjustment circuit for the scanning electron microscope according to the first aspect or any corresponding embodiment thereof.

[0084] The scanning electron microscope provided by the present invention greatly improves the calibration accuracy of the magnification of the scanning electron microscope by adopting the magnification adjustment circuit for the scanning electron microscope.

[0085] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A magnification adjustment circuit for a scanning electron microscope, characterized in that: The magnification adjustment circuit includes: a control circuit, an X-scan switching circuit, an X-scan feedback circuit, a Y-scan switching circuit and a Y-scan feedback circuit, wherein: The control circuit is connected to the host computer, the X-scan feedback circuit, the Y-scan feedback circuit, the X-scan switching circuit and the Y-scan switching circuit respectively, the X-scan switching circuit is also connected to the X-scan feedback circuit, and the Y-scan switching circuit is also connected to the Y-scan feedback circuit; The control circuit switches the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and adjusts the gear current of the X-scan switching circuit according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears; The control circuit switches the amplification mode and amplification gear of the Y scan switching circuit according to the Y scan control signal sent by the host computer, and adjusts the gear current of the Y scan switching circuit according to the deviation between the voltage signal fed back by the Y scan feedback circuit and the Y scan control signal. The amplification modes include 3 types, and each amplification mode includes 4 amplification gears.

2. The magnification adjustment circuit for a scanning electron microscope according to claim 1, characterized in that: The X-scan switching circuit and the Y-scan switching circuit both include: a mode switching circuit and a gear switching circuit, wherein: The mode switching circuit is connected to the gear switching circuit, and both the mode switching circuit and the gear switching circuit are connected to the output end of the control circuit; The mode switching circuit is used to switch the amplification modes of the X-scanning switching circuit and the Y-scanning switching circuit, and the gear switching circuit is used to perform gear switching in each amplification mode.

3. The magnification adjustment circuit for a scanning electron microscope according to claim 2, characterized in that: The gear switching circuit includes: a first switch, a second switch, a third switch, a fourth switch, a first resistor, a second resistor, a third resistor and a fourth resistor, wherein: One end of the first switch is respectively connected to one end of the second switch, one end of the third switch, one end of the fourth switch and the mode switching circuit, the other end of the first switch is respectively connected to one end of the first resistor and one end of the second resistor, and the other end of the first resistor is grounded; The other end of the second switch is respectively connected to the other end of the second resistor and one end of the third resistor, the other end of the third switch is respectively connected to the other end of the third resistor and one end of the fourth resistor, and the other end of the fourth switch is respectively connected to the other end of the fourth resistor, the output end of the X scan feedback circuit, and the input end of the Y scan feedback circuit.

4. The magnification adjustment circuit for a scanning electron microscope according to claim 3, characterized in that: The gear switching circuit further includes: a fifth switch, a sixth switch, a seventh switch, an eighth switch, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, and an eighteenth resistor, wherein: One end of the fifth switch is respectively connected to one end of the sixth switch, one end of the seventh switch, one end of the eighth switch and the mode switching circuit, the other end of the fifth switch is respectively connected to one end of the fifth resistor, one end of the sixth resistor and one end of the scanning coil resistor, the other end of the fifth resistor is respectively connected to one end of the seventh resistor and one end of the eighth resistor; The other end of the sixth switch is respectively connected to the other end of the seventh resistor, one end of the ninth resistor and one end of the tenth resistor, and the other end of the ninth resistor is respectively connected to one end of the eleventh resistor and one end of the twelfth resistor; The other end of the seventh switch is respectively connected to the other end of the eleventh resistor, one end of the thirteenth resistor and one end of the fourteenth resistor, and the other end of the thirteenth resistor is respectively connected to one end of the fifteenth resistor and one end of the sixteenth resistor; The other end of the eighth switch is respectively connected to the other end of the fifteenth resistor, one end of the seventeenth resistor and one end of the eighteenth resistor, and the other end of the seventeenth resistor is respectively connected to the other end of the eighteenth resistor, the other end of the sixteenth resistor, the other end of the fourteenth resistor, the other end of the twelfth resistor, the other end of the tenth resistor, the other end of the eighth resistor, the other end of the sixth resistor, the other end of the scanning coil resistor and the mode switching circuit.

5. The magnification adjustment circuit for a scanning electron microscope according to claim 4, characterized in that: The mode switching circuit includes: a ninth switch, a tenth switch, an eleventh switch, a twelfth switch, a thirteenth switch and a fourteenth switch, wherein: One end of the ninth switch is respectively connected to one end of the tenth switch, one end of the eleventh switch, the output end of the X scan feedback circuit, and the output end of the Y scan feedback circuit; the other end of the ninth switch is respectively connected to the other end of the fifth switch, one end of the fifth resistor, one end of the sixth resistor, and one end of the scan coil resistor; the other end of the tenth switch is respectively connected to one end of the fifth switch, one end of the sixth switch, one end of the seventh switch, and one end of the eighth switch; the other end of the eleventh switch is connected to the output end of the X scan feedback circuit and the input end of the Y scan feedback circuit; One end of the twelfth switch is respectively connected to one end of the thirteenth switch, one end of the fourteenth switch and the other end of the scanning coil resistor, the other end of the twelfth switch is respectively connected to one end of the first switch, one end of the second switch, one end of the third switch and one end of the fourth switch, the other end of the thirteenth switch is respectively connected to the other end of the fourth switch, the other end of the fourth resistor, the output end of the X scanning feedback circuit and the input end of the Y scanning feedback circuit, and the other end of the fourteenth switch is grounded.

6. The magnification adjustment circuit for a scanning electron microscope according to claim 5, characterized in that: The X-scan switching circuit and the Y-scan switching circuit further include: a first compensation circuit and a second compensation circuit, wherein: One end of the first compensation circuit is respectively connected to the other end of the fifth switch, one end of the fifth resistor and one end of the sixth resistor, and the other end of the first compensation circuit is respectively connected to one end of the ninth switch and one end of the scanning coil resistor; One end of the second compensation circuit is connected to the other end of the sixth resistor and one end of the thirteenth switch respectively, and the other end of the second compensation circuit is connected to the other end of the scanning coil resistor and one end of the twelfth switch respectively.

7. The magnification adjustment circuit for a scanning electron microscope according to claim 1, characterized in that: The control circuit includes: MCU, X control unit, X power amplifier unit, Y control unit and Y power amplifier unit, wherein: The input end of the MCU is connected to the host computer, and the output end of the MCU is respectively connected to the input end of the X control unit, the input end of the Y control unit, the X scanning switching circuit and the Y scanning switching circuit; The input end of the X control unit is also connected to the X scan feedback circuit, the output end of the X control unit is connected to the input end of the X power amplification unit, the output end of the X power amplification unit is connected to the X scan switching circuit, the input end of the Y control unit is also connected to the Y scan feedback circuit, the output end of the Y control unit is connected to the input end of the Y power amplification unit, and the output end of the Y power amplification unit is connected to the Y scan switching circuit.

8. A method for adjusting the magnification of a scanning electron microscope, characterized in that: Based on the magnification adjustment circuit for a scanning electron microscope according to any one of claims 1 to 7, the method comprises: Switching the amplification mode and amplification gear of the X-scan switching circuit according to the X-scan control signal sent by the host computer, and switching the amplification mode and amplification gear of the Y-scan switching circuit according to the Y-scan control signal sent by the host computer, wherein the amplification modes include 3 types, and each amplification mode includes 4 types of amplification gears; The gear current of the X-scan switching circuit is adjusted according to the deviation between the voltage signal fed back by the X-scan feedback circuit and the X-scan control signal, and the gear current of the Y-scan switching circuit is adjusted according to the deviation between the voltage signal fed back by the Y-scan feedback circuit and the Y-scan control signal.

9. A scanning electron microscope, characterized in that: The invention comprises a magnification adjustment circuit for a scanning electron microscope as described in any one of claims 1 to 7.

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