Protection circuit for cancelling pulsed arc noise in a loop

Abstract

The application provides a protection circuit for offsetting pulse arc noise in a loop, comprising: a resistance voltage dividing circuit for voltage dividing an original noise voltage of the pulse arc noise in the loop to obtain an attenuated noise voltage; a high-pass filter circuit for filtering a direct current component of the attenuated noise voltage; a sampling circuit for sampling the attenuated noise voltage without the direct current component in real time and outputting a scaled noise current; an inverting amplification circuit for inverting and amplifying the scaled noise current according to a set amplification multiple to obtain an offset current which is equal in size and opposite in direction to an original noise current of the pulse arc noise; and a current injection circuit for injecting the offset current into the loop to offset the pulse arc noise.

Description

Technical Field

[0001] This invention relates to the field of circuit design technology, and in particular to a protection circuit for canceling pulse-type arc noise in a circuit. Background Technology

[0002] The critical dimension scanning electron microscope (CDSEM) is one of the mainstream measurement devices in chip manufacturing. CD-SEM equipment is used to measure the dimensions of two-dimensional patterns after photolithography or etching. These two-dimensional patterns are typically lines, holes, pillars, trenches, etc. During chip manufacturing, when wafer surfaces sometimes have abnormal defects such as photoresist bulges, peeling, and sharp corners, dimensional measurements can easily cause pulsed arcing between the CDSEM cap and the wafer. This pulsed arcing is essentially a voltage pulse, and it can easily damage the core, high-value spare component, the LCPS (Low Column Power Supply). Currently, LCPS spare parts employ two self-protection mechanisms against pulsed arcing: First, the internal power module of the LCPS has a thermistor. When the loop current increases, the resistance increases from a few tenths of ohms to several hundred ohms due to heat, stabilizing the loop current. Second, voltage feedback monitors the entire loop voltage. If voltage fluctuations occur and arguing occurs, the LCPS will detect the voltage fluctuations and feed the information back to the device's IP center, prompting the LCPS to immediately stop operating. However, in actual chip measurement, these two self-protection mechanisms are still insufficient to completely protect the LCPS spare parts. Although stopping the LCPS can protect it, by then, the pulsed arc has already flowed through the LCPS loop, significantly reducing the LCPS's lifespan after repeated occurrences. Therefore, it is necessary to design a more effective protection scheme. Summary of the Invention

[0003] In view of this, the present invention provides a protection circuit for canceling pulsed arc noise in a circuit, thereby eliminating the influence of pulsed arc noise on the circuit.

[0004] This invention provides a protection circuit for canceling pulsed arc noise in a circuit, the protection circuit comprising: A resistor voltage divider circuit is used to reduce the original noise voltage of pulse-type arc noise in the circuit to obtain an attenuated noise voltage. A high-pass filter circuit is used to filter out the DC component of the attenuated noise voltage to obtain an attenuated noise voltage without a DC component. The sampling circuit is used to sample the attenuated noise voltage without DC component in real time and output a scaled-down noise current. An inverting amplifier circuit is used to amplify the scaled-down noise current in reverse according to a set amplification factor, so as to obtain a canceling current that is equal in magnitude and opposite in direction to the original noise current of the pulsed arc noise. A current reinjection circuit is used to inject the offset current into the circuit in order to cancel the pulsed arc noise.

[0005] Optionally, the inverting amplifier circuit has an adjustable amplification factor in real time to cope with real-time changes in pulsed arc noise.

[0006] Optionally, the circuit further includes: A control circuit is used to adjust the amplification factor of the inverting amplifier circuit in real time based on the original noise current and the scaled-down noise current.

[0007] Optionally, the inverting amplifier circuit includes: Input resistor, the value of which can be adjusted in real time; Feedback resistor; An operational amplifier, wherein the non-inverting input terminal of the operational amplifier is grounded, the inverting input terminal is connected to the input resistor, and the output terminal of the operational amplifier is connected to the inverting input terminal through the feedback resistor; The control circuit is used to adjust the resistance value of the input resistor in real time according to the original noise current and the scaled-down noise current, so as to adjust the amplification factor.

[0008] Optionally, the input resistor is a digital potentiometer.

[0009] Optionally, the high-pass filter circuit is selected as a Butterworth filter, and the cutoff frequency is set to 20KHz.

[0010] Optionally, the sampling circuit is selected as a successive approximation register analog-to-digital converter (SAR-ADC).

[0011] Optionally, the current reinjection circuit employs a Class AB power amplifier.

[0012] The protection circuit for canceling pulsed arc noise in a circuit provided by this invention reduces the original noise voltage of the pulsed arc noise through a resistor voltage divider circuit. The resulting attenuated noise voltage is filtered by a high-pass filter circuit to remove the DC component, and then sampled in real time by a sampling circuit to output a scaled-down noise current. The sampled scaled-down noise current is sent to an inverting amplifier circuit, which generates a canceling current that is equal in magnitude and opposite in direction to the original noise current of the pulsed arc noise. Finally, a current reinjection circuit injects the canceling current into the original circuit to cancel the pulsed arc noise. Attached Figure Description

[0013] Figure 1 This is a structural block diagram of the protection circuit in one embodiment of the present invention; Figure 2 This is a structural block diagram of the protection circuit in another embodiment of the present invention; Figure 3 This is a schematic diagram of the specific structure of the protection circuit in one embodiment of the present invention; Figure 4 This is a schematic diagram of the specific structure of the current reinjection circuit in one embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0016] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0017] This invention provides a protection circuit for canceling pulsed arc noise in a circuit, such as... Figure 1 As shown, the protection circuit includes: The resistor voltage divider circuit 11 is used to reduce the original noise voltage of the pulse-type arc noise in the circuit to obtain an attenuated noise voltage. The high-pass filter circuit 12 is used to filter out the DC component of the attenuation noise voltage to obtain an attenuation noise voltage without DC component. The sampling circuit 13 is used to sample the attenuated noise voltage without DC component in real time and output a scaled-down noise current. The inverting amplifier circuit 14 is used to invert the scaled noise current according to the set amplification factor to obtain a canceling current that is equal in magnitude and opposite in direction to the original noise current of the pulsed arc noise. The current reinjection circuit 15 is used to inject a canceling current into the circuit in order to cancel the pulsed arc noise.

[0018] Furthermore, the pulsed arc noise changes in real time. Therefore, the amplification factor of the inverting amplifier circuit needs to be continuously adjusted to correctly cancel the pulsed arc noise. According to an embodiment of the present invention, the inverting amplifier circuit 14 has an adjustable amplification factor in real time to cope with the real-time changes in the pulsed arc noise. Let the amplification factor of the inverting amplifier circuit 14 be denoted as n. Regardless of how n changes, it always satisfies n = I0 / I0. in I0 represents the original noise current amplitude of the pulsed arc noise, I in This represents the scaled-down noise current amplitude obtained by the sampling circuit.

[0019] refer to Figure 2 In order to adjust the amplification factor of amplifier circuit 14 in real time, the protection circuit also includes: The control circuit 16 is used to adjust the amplification factor of the inverting amplifier circuit 14 in real time based on the original noise current and the scaled-down noise current.

[0020] In one implementation, the control circuit can be a control chip or an interactive computer.

[0021] Figure 3 A schematic diagram of the protection circuit of this invention applied to the LCPS circuit of a CDSEM device is shown. This is merely an illustrative example of the LCPS circuit and is not limited to it. L0, R0, and C0 are the equivalent parameters of the LCPS circuit, representing the equivalent inductance, equivalent resistance, and equivalent capacitance, respectively.

[0022] Figure 3 The specific structure of part of the protection circuit is also shown. (Reference) Figure 3 The circuit analysis for each part is as follows: (1) The original noise voltage V of the resistor voltage divider circuit for pulsed arc noise in The voltage is stepped down to obtain the attenuated noise voltage V. s The following relationship exists:

[0023] In the above formula, V in The input voltage is after passing through the cap of the CDSEM, and m is the attenuation ratio (also called the voltage division ratio of the resistor voltage divider circuit). Here, m is a constant value. The resistance values ​​of resistors R1 and R2 are designed as follows: 600≤R1 / R2≤1500.

[0024] Since the original noise voltage of arc noise is high and difficult to handle, it needs to be stepped down first. This protects the sampling circuit and the inverting amplifier circuit, significantly reduces the pulse noise voltage, and reduces the use of passive components.

[0025] It is understandable that arc noise is pulse-type, and therefore the voltage and current it generates are also pulse-type.

[0026] (2) The high-pass filter circuit filters out the attenuation noise voltage V s The DC component is used to obtain the attenuated noise voltage V without DC component. p According to one embodiment of the present invention, the high-pass filter circuit selects a Butterworth filter, which is characterized by a flat frequency response within the maximum band with no fluctuations in the passband and rapid attenuation to zero in the stopband, exhibiting excellent low-frequency filtering performance. A circuit diagram for its specific implementation can be found in [reference needed]. Figure 3 And the transfer function satisfies:

[0027] Where C1 and C2 represent the capacitance values, and R3 and R4 represent the resistance values.

[0028] To ensure that the waveform of the pulsed arc noise signal remains undistorted after passing through the high-pass filter circuit, a large-capacity capacitor, i.e., 10uF to 22uF, is selected for the high-pass filter circuit.

[0029] In order to obtain a pulsed arc noise signal without DC component and without distortion through the high-pass filter circuit, considering both filtering performance and practical feasibility, the cutoff frequency is set to 20KHz.

[0030] The high-pass filter circuit is designed based on the characteristics of pulsed arc noise. It is added to filter out and attenuate the noise voltage V. s The DC component, and the subsequent offset current, can cancel the pulsed arc noise without changing the DC component of the original output circuit of the CDSEM, thus preventing it from affecting the stability of the system.

[0031] (3) The attenuation noise voltage V without DC component p The signal is fed into the sampling circuit for real-time sampling. According to one embodiment of the present invention, in order to sample the pulsed arc noise signal in real time, the sampling circuit selects a successive approximation register (SAR) analog-to-digital converter (ADC). The SAR-ADC attenuates the noise voltage V without a DC component. p Sampling is performed to obtain the scaled-down noise current I.in Because the designed inverting amplifier circuit is current-mode, the attenuated noise voltage is converted into a scaled-down noise current I. in .

[0032] As one implementation method, the MAX11905 SAR ADC is selected, which mainly consists of a sample-and-hold circuit, a comparator, a clock timing controller, SAR logic control circuitry, and a DAC (analog-to-digital converter). The selected ADC can achieve a sampling rate of 1.6 Msps without delay or settling time limitations. Furthermore, it has a signal-to-noise ratio (SNR) of 98.3 dB and a total harmonic distortion (THD) of -123 dB, which can meet the sampling requirements of pulsed arc noise signals.

[0033] (4) Reference Figure 3 The inverting amplifier circuit includes: Input resistor R5, the value of which can be adjusted in real time; Feedback resistor R6; The operational amplifier has its non-inverting input grounded, its inverting input connected to the input resistor R5, and its output connected to the inverting input via the feedback resistor R6.

[0034] The input resistor R5 here is designed as a digital potentiometer, which facilitates digital adjustment of the resistance value. For example, the digital potentiometer R5 can be a MAX5432 8-pin TDFN, which has a wide operating temperature range (-50℃ to 150℃), low offset, and can achieve a data communication rate of up to 400Kbps. The adjustable resistance range is 50 to 100KΩ, which meets the design requirements.

[0035] To obtain a canceling current that is equal in magnitude and opposite in direction to the original arc noise current, the sampled scaled-down noise current I is used here. in An inverting amplifier circuit with an input gain of n and a bandwidth-gain product of at least n*f produces a canceling current I that is equal in magnitude and opposite in direction to the original arc noise current. out It is obvious that if R5 / R6 = m*n, then I out +I cap =0, which can cancel pulsed arc noise signals.

[0036] Figure 3 The control circuit is not shown, but it is understandable that the scaled-down noise current I... inSimultaneously, the signal is fed into both the control circuit and the inverting amplifier circuit. The control circuit compares the scaled-down noise current amplitude with the original noise current amplitude to obtain the real-time inverting amplification factor n. Based on the inverting amplification factor n, the input resistor R5 of the inverting amplifier circuit is adjusted in real time, thus achieving real-time adjustment of the amplification factor. The relationship between the resistance value R5 and the amplification factor n is R5 = n * m * R6, where m is the attenuation ratio of the resistor divider circuit. Here, R6 and m are constant values; therefore, by adjusting R5 in real time, the amplification factor n can be adjusted in real time.

[0037] (5) such as Figure 3 As shown, the current reinjection circuit will cancel the current I. out The current is reinjected into the LCPS circuit to cancel pulsed arc noise. This current reinjection circuit uses a Class AB power amplifier to achieve voltage following and to cancel the LCPS circuit output voltage V. cap The potential ensures that the current injected into the LCPS circuit can flow freely.

[0038] like Figure 4 As shown, an embodiment of the present invention employs a Class AB power amplifier composed of resistors R8 and R9, diodes D1 and D2, and two complementary transistors Q1 and Q2. (Reference) Figure 3 Satisfying V im =I out *R7, Injection Voltage V im After being boosted by diodes D1 and D2 and stepped down by transistors Q1 and Q2, the output V is... out If the boost voltage of the diode and the buck voltage of the transistor are equal, then if V out =V im This enables voltage following functionality. Furthermore, due to the characteristics of the two transistors, V can be prevented from... cap The reverse flow of current into the current feedback circuit effectively overcomes the output potential V in the LCPS circuit. cap .

[0039] The protection circuit for canceling pulsed arc noise in the circuit provided by this invention reduces the original noise voltage of the pulsed arc noise through a resistor voltage divider circuit. The resulting attenuated noise voltage is filtered by a high-pass filter circuit to remove the DC component, and then sampled in real time by a sampling circuit to output a scaled-down noise current. The sampled scaled-down noise current is sent to an inverting amplifier circuit, which generates a canceling current that is equal in magnitude and opposite in direction to the original noise current of the pulsed arc noise. Finally, a current reinjection circuit injects the canceling current into the original circuit to cancel the pulsed arc noise.

[0040] In practical applications, the protection circuit for canceling pulsed arc noise in the circuit provided in the embodiments of the present invention can be applied to the LCPS circuit of the CDSEM device. It can cancel the pulsed arc noise generated by the LCPS circuit inside the CDSEM device and prevent the pulsed arc noise signal from flowing through the LCPS component, so that the CDSEM device will not stop or crash due to pulsed arc.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protection circuit for canceling pulse-type arc noise in a circuit, characterized in that, The protection circuit includes: A resistor voltage divider circuit is used to reduce the original noise voltage of pulse-type arc noise in the circuit to obtain an attenuated noise voltage. A high-pass filter circuit is used to filter out the DC component of the attenuated noise voltage to obtain an attenuated noise voltage without a DC component. The sampling circuit is used to sample the attenuated noise voltage without DC component in real time and output a scaled-down noise current. An inverting amplifier circuit is used to amplify the scaled-down noise current in reverse according to a set amplification factor, so as to obtain a canceling current that is equal in magnitude and opposite in direction to the original noise current of the pulsed arc noise. A current reinjection circuit is used to inject the offset current into the circuit in order to cancel the pulsed arc noise.

2. The protection circuit according to claim 1, characterized in that, The inverting amplifier circuit has an adjustable amplification factor in real time to cope with real-time changes in pulsed arc noise.

3. The protection circuit according to claim 2, characterized in that, The circuit also includes: A control circuit is used to adjust the amplification factor of the inverting amplifier circuit in real time based on the original noise current and the scaled-down noise current.

4. The protection circuit according to claim 3, characterized in that, The inverting amplifier circuit includes: Input resistor, the value of which can be adjusted in real time; Feedback resistor; An operational amplifier, wherein the non-inverting input terminal of the operational amplifier is grounded, the inverting input terminal is connected to the input resistor, and the output terminal of the operational amplifier is connected to the inverting input terminal through the feedback resistor; The control circuit is used to adjust the resistance value of the input resistor in real time according to the original noise current and the scaled-down noise current, so as to adjust the amplification factor.

5. The protection circuit according to claim 4, characterized in that, The input resistor is a digital potentiometer.

6. The protection circuit according to claim 1, characterized in that, The high-pass filter circuit uses a Butterworth filter with a cutoff frequency of 20kHz.

7. The protection circuit according to claim 1, characterized in that, The sampling circuit uses a successive approximation register analog-to-digital converter (SAR-ADC).

8. The protection circuit according to claim 1, characterized in that, The current reinjection circuit uses a Class AB power amplifier.

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