In-situ measurement method and system for electrical property defects of memory device

Abstract

The invention belongs to the field of electrical performance detection, and particularly discloses an in-situ measurement method and system for electrical performance defects of a memory device, and the method comprises the steps: radiating a modulated electron beam to a target position on the surface of a to-be-detected device, enabling the number of electrons radiated to the target position to be in a sine function relation with time, and obtaining a measured electrical performance defect of the to-be-detected device; acquiring an SEs signal # imgabs0 # of a target position, acquiring an actual potential signal # imgabs1 # of the target position, determining a proportionality coefficient # imgabs4 # between the SEs signal # imgabs2 # and the actual potential signal # imgabs3 #, enabling the target position of the device to be detected to be equivalent to a circuit in which a resistor and a capacitor are connected in parallel, and calculating to obtain a resistor R and a capacitor C of the target position according to the proportionality coefficient # imgabs5 #, the SEs signal # imgabs6 # and a modulated current signal # imgabs7 # of the electron beam; and determining the electrical property defect position of the device according to abnormal values in the resistors R and the capacitors C at the plurality of target positions. According to the invention, the defect contrast can be improved, the defect information can be better extracted, and the in-situ measurement of the electrical performance of the memory device is met.

Description

Technical Field

[0001] The present invention belongs to the field of electrical performance detection, and more specifically, relates to an in-situ measurement method and system for electrical performance defects of a storage device. Background Art

[0002] With the development of technology, semiconductor devices such as 3D NAND memory are smaller in size and more complex in structure. The performance of the device cannot be well evaluated by traditional size and shape measurement alone. It is necessary to measure the electrical properties of the device to detect defects such as impurities and thin films.

[0003] The scanning probe microscope is a widely used instrument for measuring electrical properties. It can directly measure the source-drain current of memory devices and realize defect detection. However, it can only be performed at the back end of the semiconductor manufacturing process and cannot determine the specific production node where the defect occurs, which reduces production efficiency.

[0004] Electron beams can also characterize the electrical properties of memory devices, while also supporting online non-destructive measurements at the front end of the production line. Defect detection of memory devices in the middle of the production line helps to quickly identify the source of defects, quickly make technical adjustments, and improve production efficiency. The electron beam radiates on the surface of the sample, and the detector detects secondary electrons (SEs) and forms an image, which can reflect the potential information on the surface of the sample. According to the electrical characteristics of the memory, it can be equivalent to a parallel circuit consisting of a resistor R and a capacitor C. When there are internal defects in the memory, its resistance R or capacitance C will change relative to the normal area, and its surface potential will be different from the normal area. However, traditional electron beam measurement uses a continuous electron beam, which stimulates the gate voltage, resulting in a decrease in the voltage contrast of the defective area measured.

[0005] Therefore, there is an urgent need for a new measurement system and method to achieve in-situ measurement of the electrical properties of storage devices and to identify internal defects efficiently and accurately. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides an in-situ measurement method and system for electrical performance defects of a memory device, the purpose of which is to achieve in-situ measurement of electrical performance during the memory production process and improve defect detection sensitivity.

[0007] To achieve the above object, according to one aspect of the present invention, an in-situ measurement method for electrical performance defects of a memory device is provided, comprising the following steps:

[0008] Collect the actual potential signal at the target position on the surface of the device under test

[0009] The modulated electron beam is radiated to the target position on the surface of the device under test, so that the number of electrons radiated to the target position is in a sinusoidal relationship with time, and the SEs signal at the target position is collected.

[0010] Calculate the SEs signal at the target position and the actual potential signal The ratio coefficient between

[0011] The target position of the device under test is equivalent to a circuit with resistance and capacitance in parallel. SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C of the target position are calculated;

[0012] The abnormal values ​​in the (R, C) values ​​of multiple target positions are determined, and the corresponding positions are the locations where the electrical performance defects of the device are located.

[0013] As a further preferred embodiment, according to the proportionality coefficient SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C at the target position are calculated as follows:

[0014]

[0015] Where K is the proportionality coefficient The effective value of I is the current signal of the modulated electron beam. The effective value, U se SEs signal The effective value of is the initial phase angle of SEs, To modulate the electron beam current signal The initial phase angle, is the proportionality factor The initial phase angle; ω is the signal frequency.

[0016] As a further preferred embodiment, K, U se , I is calculated as:

[0017]

[0018]

[0019] Where j is the imaginary unit and t is the time.

[0020] As a further preferred embodiment, the SEs signal at the target position on the surface of the device to be tested is collected by a scanning electron microscope.

[0021] As a further preferred embodiment, the actual potential signal of the target position on the surface of the device to be tested is collected by a scanning probe microscope.

[0022] As a further preferred method, obtaining the resistance R and the capacitance C of multiple target positions includes:

[0023] Uniformly select some of the target positions on the surface of the device under test as measurement points and determine the proportional coefficient of each measurement point And find the average value as the proportional coefficient shared by all target positions;

[0024] Then, at any target position on the surface of the device to be tested, the shared proportional coefficient and SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C corresponding to the target position are calculated.

[0025] As a further preferred method, irradiating the modulated electron beam to a target position on the surface of the device under test so that the number of electrons irradiated to the target position and time are in a sinusoidal function relationship, including:

[0026] A continuous electron beam is generated by an electron gun, and the extraction electrode extracts and accelerates the electrons. The electron beam is then converged by an electromagnetic lens. The continuous electron beam passes through an electron beam gate, which modulates the continuous electron beam so that the number of electrons passing through the electron beam gate is in a sinusoidal function relationship with time. The modulated electron beam is then converged by an electromagnetic lens and finally radiated to the target position on the surface of the device under test.

[0027] According to another aspect of the present invention, there is provided an in-situ measurement system for electrical performance defects of a memory device, comprising a processor, wherein the processor is used to execute the in-situ measurement method for electrical performance defects of a memory device.

[0028] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0029] The present invention modulates a continuous electron beam into a sinusoidal signal, that is, the number of electrons passing through a certain cross section presents a sinusoidal function change relationship over time. The modulated electron beam radiates on the sample surface, causing the potential on the sample surface to present a sinusoidal function change over time. This change will eventually be reflected in the measured SEs signal. According to the measured SEs signal, the actual potential signal and the input modulated electron beam current signal, the resistance R and capacitance C of the device equivalent circuit can be calculated, and the R and C values ​​of the measurement area are analyzed. The abnormal value area indicates that there may be defects in the corresponding position of the sample. Compared with the traditional scanning electron microscope detection method, the present invention uses a modulated electron beam to improve the defect contrast, thereby better extracting defect information, improving defect detection sensitivity, and supporting in-situ measurement of electrical properties during the memory production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the structure of an in-situ measurement device for electrical performance defects of a memory device according to an embodiment of the present invention;

[0031] Figure 2 FIG. 4 is an equivalent circuit diagram of a memory device according to an embodiment of the present invention.

[0032] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 - electron gun, 2 - extraction electrode, 3 - electromagnetic lens, 4 - electron beam gate, 5 - electromagnetic lens, 6 - sample to be measured, 7 - sample stage, 8 - SEs detector. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] An embodiment of the present invention provides an in-situ measurement method for electrical performance defects of a memory device, comprising the following steps:

[0035] The continuous electron beam is modulated so that it becomes a sinusoidal waveform on a time scale, and the modulated electron beam is radiated to the target position on the surface of the device under test. The number of electrons radiated to the target position is in a sinusoidal function relationship with time, which will cause the potential on the surface of the device to show periodic changes. The SEs signal at the target position on the surface of the device under test is obtained through the SEs detector inside the scanning electron microscope. SEs signals can reflect the potential information of the sample surface;

[0036] Using scanning probe microscopy to measure the actual potential signal at the target position on the surface of the device under test

[0037] According to SEs signal and the actual potential signal Determine the proportionality factor between the two

[0038] The device under test is equivalent to a circuit with resistors and capacitors in parallel, and the proportional coefficient The resistance R and capacitance C of the target position are calculated;

[0039] The resistance R and capacitance C of multiple target positions on the surface of the device under test are obtained, and the location of the device electrical performance defects is determined based on the abnormal values.

[0040] Specifically, the electron beam itself presents a current signal, and the current signal of the modulated electron beam The expression is:

[0041]

[0042] The surface potential of the sample will affect the emission of secondary electrons. When the surface potential of the sample is positive, the emitted secondary electrons will be attracted back into the sample, which will eventually affect the secondary electrons measured by the detector. Therefore, the image measured by the scanning electron microscope can reflect the voltage contrast of the sample surface. Under the radiation of, the secondary electron SEs signal measured by scanning electron microscope is:

[0043]

[0044] The actual potential signal on the sample surface is and There is a correlation between them, and the relationship is:

[0045]

[0046] The actual potential signal U on the sample surface can be measured using instruments such as a scanning probe microscope. se The proportionality coefficient can be calculated by

[0047] like Figure 2 As shown, considering the electrical characteristics of the memory device itself, it is equivalent to a circuit with a resistor R and a capacitor C in parallel. The complex impedances of the resistor and capacitor are:

[0048]

[0049] The complex impedance of a resistor and capacitor in parallel is expressed as:

[0050]

[0051] according to Figure 2 The equivalent circuit model shown is solved using Ohm's law:

[0052]

[0053] The real and imaginary parts of the above equation are equal to each other, and the values ​​of resistance R and capacitance C are obtained by solving:

[0054]

[0055] Where j is the imaginary unit, K is the effective value of the proportional coefficient, I is the effective value of the modulated current signal, and U se is the effective value of the SEs signal, is the initial phase angle of SEs, is the initial phase angle of the modulated current signal; is the initial phase angle of the proportional coefficient, ω is the signal frequency, and t is the time.

[0056] It can be seen from the above two formulas that the resistance R and capacitance C of the sample can be directly calculated by knowing the modulated electron beam current signal, proportional coefficient and SEs signal.

[0057] Measure multiple target positions on the sample surface to obtain the resistance R and capacitance C corresponding to each target position; compare the resistance R of each target position, and compare the capacitance C of each target position to obtain abnormal values, so as to determine the defect position. For resistance / capacitance data, when the data of a certain position shows obvious deviation compared with the data of other positions, the data is considered abnormal; in general, if one of the values ​​of resistance R and capacitance C is abnormal, it is considered that the corresponding target position has a defect. Defects refer to electrical performance defects such as impurities and thin films inside the device.

[0058] Furthermore, the proportional coefficient calibration can be performed first: some measurement points are selected on the sample surface to obtain the corresponding proportional coefficient mean; then each target position can directly use the proportional coefficient mean for subsequent calculations, which can reduce the amount of calculation and improve detection efficiency; to ensure the accuracy of the calibration results, measurement points must be evenly selected on the sample and the number must be sufficient.

[0059] Furthermore, the above-mentioned in-situ measurement method of the electrical performance defects of the memory device is implemented based on an in-situ measurement device, such as Figure 1 As shown, the device includes an electron gun 1, an extraction electrode 2, an electromagnetic lens 3, an electron beam gate 4, an electromagnetic lens 5, a sample stage 7 and a SEs detector 8, wherein:

[0060] The electron gun 1 generates a continuous electron beam as an electron source, the extraction electrode 2 extracts electrons from the needle tip and accelerates them, the electromagnetic lens 3 converges the electron beam, and the continuous electron beam then passes through the electron beam gate 4, which can control the passage of the electron beam. Under the action of the control system, the electron beam gate 4 modulates the continuous electron beam so that the number of electrons passing through the beam gate changes with time in a sinusoidal function relationship. The modulated electron beam passes through the convergence of the electromagnetic lens 5 again, and finally radiates to the surface of the sample to be tested 6. The sample to be tested 6 is mounted on the sample stage 7. The surface of the sample to be tested 6 is excited by the electron beam to produce secondary electrons. The SEs detector 8 is a built-in detector of the scanning electron microscope, which can detect the secondary electrons SEs. After the electron beam scans the target area, an SEs image is formed, which can reflect the voltage contrast information of the sample surface.

[0061] The control system controls the electron beam gate to obtain a modulated electron beam with a specific amplitude and frequency, and transmits the current signal to the signal analysis and processing unit. The modulated electron beam radiates on the sample surface to excite SEs. The detector measures the SEs signal in real time and transmits the signal to the signal analysis and processing unit. The proportional coefficient determined during the calibration process It will also be transmitted to the signal analysis and processing unit. The signal analysis and processing unit processes the obtained information, calculates the measurement results of the equivalent resistance R and capacitance C, and outputs images containing resistance R and capacitance C, similar to the SEs signal. At the same time, the analysis and processing unit will perform an overall analysis of the R and C values ​​in the measurement range, use the built-in algorithm to extract abnormal values ​​and mark the positions, and output an image with defects marked. Finally, the in-situ detection of the electrical performance of 3D NAND memory samples is realized.

[0062] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An in-situ measurement method for electrical performance defects of a memory device, characterized in that: The steps include: Collect the actual potential signal at the target position on the surface of the device under test The modulated electron beam is radiated to the target position on the surface of the device under test, so that the number of electrons radiated to the target position is in a sinusoidal relationship with time, and the SEs signal at the target position is collected. Calculate the SEs signal at the target position and the actual potential signal The ratio coefficient between The target position of the device under test is equivalent to a circuit with resistance and capacitance in parallel. SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C of the target position are calculated; The abnormal values ​​in the (R, C) values ​​of multiple target positions are determined, and the corresponding positions are the locations where the electrical performance defects of the device are located.

2. The in-situ measurement method of electrical performance defects of a memory device according to claim 1, characterized in that: According to the proportionality factor SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C at the target position are calculated as follows: Where K is the proportionality coefficient The effective value of I is the current signal of the modulated electron beam. The effective value, U se SEs signal The effective value of is the initial phase angle of SEs, To modulate the electron beam current signal The initial phase angle, is the proportionality factor The initial phase angle; ω is the signal frequency.

3. The in-situ measurement method of electrical performance defects of a memory device according to claim 2, characterized in that: K.U se 、The calculation formula of I is: Where j is the imaginary unit and t is the time.

4. The in-situ measurement method of electrical performance defects of a memory device according to claim 1, characterized in that: The SEs signal at the target position on the surface of the device under test is collected by scanning electron microscope 5. The in-situ measurement method of electrical performance defects of a memory device according to claim 1, characterized in that: The actual potential signal of the target position on the surface of the device under test is collected by scanning probe microscope 6. The in-situ measurement method of electrical performance defects of a memory device according to claim 1, characterized in that: Get the resistance R and capacitance C of multiple target locations, including: Uniformly select some of the target positions on the surface of the device under test as measurement points and determine the proportional coefficient of each measurement point And find the average value as the proportional coefficient shared by all target positions; Then, at any target position on the surface of the device to be tested, the shared proportional coefficient and SEs signal And the current signal of the modulated electron beam The resistance R and capacitance C corresponding to the target position are calculated.

7. The in-situ measurement method for electrical performance defects of a memory device according to any one of claims 1 to 6, characterized in that: The modulated electron beam is radiated to the target position on the surface of the device under test, so that the number of electrons radiated to the target position and time are in a sinusoidal function relationship, including: A continuous electron beam is generated by an electron gun, and the extraction electrode extracts and accelerates the electrons. The electron beam is then converged by an electromagnetic lens. The continuous electron beam passes through an electron beam gate, which modulates the continuous electron beam so that the number of electrons passing through the electron beam gate is in a sinusoidal function relationship with time. The modulated electron beam is then converged by an electromagnetic lens and finally radiated to the target position on the surface of the device under test.

8. An in-situ measurement system for electrical performance defects of a memory device, characterized in that: The method comprises a processor, wherein the processor is used to execute the in-situ measurement method of electrical performance defects of a memory device according to any one of claims 1 to 7.

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