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

Abstract

The application belongs to the field of electrical performance detection, and particularly discloses a kind of in-situ measurement method and system for electrical performance defects of memory device, which comprises: modulated electron beam radiation is radiated on the target position of the surface of the device to be measured, the number of electrons radiated to the target position is in sinusoidal function relationship with time, the SEs signal of the target position is collected, the actual potential signal of the target position is collected, the proportional coefficient between the SEs signal and the actual potential signal is determined, the target position of the device to be measured is equivalent to a circuit in which resistance and capacitance are connected in parallel, and the resistance R and capacitance C of the target position are calculated according to the proportional coefficient SEs signal and the current signal of the modulated electron beam; according to the abnormal values in the resistance R and capacitance C of multiple target positions, the position of the electrical performance defects of the device is determined. The application can improve the defect contrast, better extract defect information, and meet the in-situ measurement of electrical performance of memory device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrical performance detection, and more particularly relates to an in-situ measurement method and system for electrical performance defects of a memory device. BACKGROUND

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

[0003] A scanning probe microscope is a widely used electrical performance measuring instrument that can directly measure the source-drain current of a memory device to achieve defect detection. However, it can only be performed at the backend of the semiconductor manufacturing process, and cannot determine the specific production and manufacturing node where the defect is generated, which reduces production efficiency.

[0004] An electron beam can also characterize the electrical performance of a memory device, and also supports online non-destructive measurement at the front end of the production line. Defect detection of a memory device in the middle of the production line helps to quickly identify the source of the defect and quickly adjust the technology to improve production efficiency. The electron beam irradiates the surface of the sample, and the detector detects secondary electrons (SEs) and forms an image, which can reflect the potential information of the sample surface. According to the electrical characteristics of the memory, it can be equivalent to a parallel circuit composed of a resistor R and a capacitor C. When the memory has internal defects, its resistance R or capacitance C will change relative to the normal region, and its surface potential will be different from that of the normal region. However, the traditional electron beam measurement uses a continuous electron beam, which stimulates the gate voltage, resulting in a decrease in the voltage contrast of the defect region measured.

[0005] Therefore, there is an urgent need for a new measurement system and method to realize in-situ measurement of the electrical properties of a memory device and efficiently and accurately identify internal defects. SUMMARY

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

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

[0008] Collecting an actual potential signal of a target position on the surface of the device to be measured

[0009] The modulated electron beam is irradiated onto the target location on the surface of the device under test, such that the number of electrons irradiated to the target location has a sinusoidal relationship with time, and the SEs signal at the target location is acquired.

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

[0011] The target location of the device under test is equivalent to a circuit with a resistor and a capacitor in parallel. Based on the scaling factor... SEs signal and the current signal of the modulated electron beam The resistance R and capacitance C at the target location are calculated.

[0012] The location of the abnormal value among the (R, C) values ​​of multiple target locations is the location of the electrical performance defect of the device.

[0013] As a further preferred option, based on the proportionality coefficient SEs signal and the current signal of the modulated electron beam The resistance R and capacitance C at the target location are calculated using the following formulas:

[0014]

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

[0016] As a further preferred option, K and U se The formula for calculating I is:

[0017]

[0018]

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

[0020] As a further preferred method, the SEs signals at the target location on the surface of the device under test are acquired using a scanning electron microscope.

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

[0022] As a further preferred, the resistance R and the capacitance C of the plurality of target positions are obtained, comprising:

[0023] Uniformly select part of the plurality of target positions on the surface of the device to be measured as measurement points, and determine the proportional coefficient of each measurement point And take the average as the proportional coefficient shared by all target positions.

[0024] Further, for any target position on the surface of the device to be measured, the resistance R and the capacitance C corresponding to the target position are calculated through the shared proportional coefficient, the SEs signal And the current signal of the modulated electron beam

[0025] As a further preferred, the modulated electron beam is radiated on the target position on the surface of the device to be measured, and the number of electrons radiated to the target position and time are in a sinusoidal function relationship, comprising:

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

[0027] According to another aspect of the present application, a system for in-situ measurement of electrical performance defects of a memory device is provided, comprising a processor configured to execute the above-mentioned method for in-situ measurement of electrical performance defects of a memory device.

[0028] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0029] ​The continuous electron beam is modulated into a sinusoidal signal, that is, the number of electrons passing through a certain section changes with time in a sinusoidal function, and the modulated electron beam radiation causes the potential of the sample surface to change with time in a sinusoidal function, which is ultimately 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 the capacitance C of the equivalent circuit of the device can be calculated, and the R and C values of the measurement region are analyzed, and the abnormal value region indicates that the corresponding position of the sample may have defects. Compared with the detection method using the traditional scanning electron microscope, the defect contrast can be improved by using the modulated electron beam, so that the defect information can be better extracted, the defect detection sensitivity is improved, and the in-situ measurement of the electrical performance in the memory production process is supported. BRIEF DESCRIPTION OF DRAWINGS

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

[0031] Figure 2 An equivalent circuit diagram of a memory device according to an embodiment of the present application.

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

[0033] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0034] The in-situ measurement method for electrical performance defects of a memory device provided by the embodiment of the present application comprises the following steps:

[0035] The continuous electron beam is modulated so that the electron beam becomes a sinusoidal waveform in the time scale, and the modulated electron beam radiation at the target position on the surface of the device to be measured, and the number of electrons radiated to the target position and time are sinusoidal functions, which causes the potential of the device surface to change periodically, and the SEs signal of the target position on the surface of the device to be measured is obtained by the SEs detector inside the scanning electron microscope The SEs signal can reflect the potential information of the sample surface;

[0036] Measuring actual potential signal of target position on surface of device under test by using scanning probe microscope

[0037] According to SEs signal and actual potential signal Determine the proportional coefficient between the two

[0038] Equivalent the device under test as a circuit with parallel resistance and capacitance, and calculate the resistance R and capacitance C of the target position according to the proportional coefficient

[0039] Obtain the resistance R and capacitance C of multiple target positions on the surface of the device under test, and determine the location of the electrical performance defect of the device according to the abnormal value.

[0040] Specifically, the electron beam itself exhibits 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 to the sample again, ultimately affecting the secondary electrons measured by the detector. Therefore, the picture measured by the scanning electron microscope can reflect the voltage contrast of the sample surface. Select a memory sample for measurement and calibration. Under the radiation of modulated current , the secondary electron SEs signal measured by the scanning electron microscope is:

[0043]

[0044] The actual potential signal of the sample surface is and has a correlation, and the relationship is:

[0045]

[0046] The actual potential signal U of the sample surface can be measured by a scanning probe microscope or other instruments. According to the measured U se and U, the proportional coefficient

[0047] As Figure 2 shown, considering the electrical characteristics of the memory device itself, it is equivalent to a circuit with parallel resistance R and capacitance C. The complex impedance of the resistance and capacitance is respectively:

[0048]

[0049] ​The complex impedance of the resistance and the capacitance in parallel is expressed as:

[0050]

[0051] According to Figure 2 The equivalent circuit model is shown in the figure, and the Ohm's law is used to solve:

[0052]

[0053] The real part and the imaginary part of the above formula are equal to solve the values of the resistance R and the capacitance C:

[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, U se is the effective value of the SEs signal, is the initial phase angle of the 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 time.

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

[0057] The surface of the sample is measured at multiple target positions to obtain the resistance R and the capacitance C corresponding to each target position. By comparing the resistance R of each target position and the capacitance C of each target position, an abnormal value is obtained, and the defect position is determined. For the resistance / capacitance data, if the data of a certain position deviates significantly compared with other position data, it is considered to be abnormal; generally, if one of the resistance R and the capacitance C is abnormal, it is considered that the corresponding target position has a defect. The defect refers to impurities, thin films, and other electrical performance defects inside the device.

[0058] Further, the proportional coefficient can be calibrated first: select some measurement points on the surface of the sample to obtain the average value of the corresponding proportional coefficient; then each target position can directly use the average value of the proportional coefficient for subsequent calculation, which can reduce the calculation amount and improve the detection efficiency; in order to ensure the accuracy of the calibration result, the measurement points should be uniformly selected on the sample, and the number should be sufficient.

[0059] Further, the above in-situ measurement method of electrical performance defects of the storage device is realized based on an in-situ measurement device, as shown in Figure 1 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 an SEs detector 8, wherein:

[0060] The electron gun 1 generates a continuous electron beam as an electron source, the extraction electrode 2 extracts and accelerates electrons from the needle tip, the electromagnetic lens 3 converges the electron beam, the continuous electron beam then passes through the electron beam shutter 4, the electron beam shutter 4 can control the passing of the electron beam, and under the action of the control system, the electron beam shutter 4 modulates the continuous electron beam, so that the number of electrons passing through the beam shutter changes with time in a sinusoidal function. The modulated electron beam is again converged by the electromagnetic lens 5, and finally irradiates the surface of the sample to be tested 6, the sample to be tested 6 is installed on the sample stage 7, and the surface of the sample to be tested 6 is excited by the electron beam to generate secondary electrons SEs, and 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, the SEs image is formed, which can reflect the voltage contrast information of the sample surface.

[0061] The control system controls the electron beam shutter to obtain a modulated electron beam with a specific amplitude and frequency, and transmits the current signal to the signal analysis processing unit. The modulated electron beam irradiated on the sample surface will excite SEs, the probe detects the SEs signal in real time and transmits the signal to the signal analysis processing unit. The proportional coefficient determined in the calibration process will also be transmitted to the signal analysis processing unit. The signal analysis processing unit processes the obtained information, calculates the measurement results of the equivalent resistance R and the capacitance C, and outputs images containing the resistance R and the capacitance C, respectively, similar to the SEs signal. At the same time, the analysis processing unit will analyze the R and C values in the measurement range as a whole, extract abnormal values using built-in algorithms and mark the positions, and output images marked with defects. Finally, the in-situ detection of the electrical performance of the 3D NAND memory sample is realized.

[0062] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An in-situ measurement method for electrical performance defects of storage devices, characterized in that, Includes the following steps: Acquire the actual potential signal at the target location on the surface of the device under test. ; The modulated electron beam is irradiated onto the target location on the surface of the device under test, such that the number of electrons irradiated to the target location has a sinusoidal relationship with time. The secondary electron (SEs) signal at the target location is then acquired. ; Calculate the secondary electron SEs signal at the target location and actual potential signal The ratio coefficient between ; The target location of the device under test is equivalent to a circuit with a resistor and a capacitor in parallel. Based on the scaling factor... Secondary electronic SEs signal and the current signal of the modulated electron beam The resistance R and capacitance C at the target location are calculated using the following formula: in, proportionality coefficient The effective value, The current signal of the modulated electron beam The effective value, For secondary electron SEs signal The effective value; The initial phase angle of the secondary electrons SEs. To modulate the electron beam current signal The initial phase angle, proportionality coefficient The initial phase angle; The signal frequency; The abnormal values ​​in the resistor R and capacitor C at multiple target locations are identified, and their corresponding locations are the locations of electrical performance defects in the device.

2. The in-situ measurement method for electrical performance defects of storage devices as described in claim 1, characterized in that, , , The formula for calculation is: in, The imaginary unit, For time.

3. The in-situ measurement method for electrical performance defects of storage devices as described in claim 1, characterized in that, Secondary electron (SEs) signals at target locations on the surface of the device under test were acquired using a scanning electron microscope. .

4. The in-situ measurement method for electrical performance defects of storage devices as described in claim 1, characterized in that, The actual potential signal at the target location on the surface of the device under test is acquired by scanning probe microscopy. .

5. The in-situ measurement method for electrical performance defects of storage devices as described in claim 1, characterized in that, Obtain the resistance R and capacitance C at multiple target locations, including: A portion of the surface of the device under test is uniformly selected from multiple target locations as measurement points, and the scaling factor for each measurement point is determined. And calculate the average value, which will be used as a proportional coefficient shared by all target locations; Furthermore, at any target location on the surface of the device under test, the shared scaling factor and secondary electronic SEs signal are used to... and the current signal of the modulated electron beam The resistance R and capacitance C corresponding to the target position are calculated.

6. The in-situ measurement method for electrical performance defects of storage devices as described in any one of claims 1-5, characterized in that, The modulated electron beam is irradiated onto the target location on the surface of the device under test, such that the number of electrons irradiated to the target location has a sinusoidal relationship with time, including: A continuous electron beam is generated by an electron gun, electrons are extracted and accelerated by an extraction electrode, and then the electron beam is focused 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 has a sinusoidal relationship with time. The modulated electron beam is then focused by an electromagnetic lens and finally radiates to the target position on the surface of the device under test.

7. An in-situ measurement system for electrical performance defects of storage devices, characterized in that, Includes a processor for performing an in-situ measurement method for electrical performance defects of a storage device as described in any one of claims 1-6.

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