WO2008053518A1

WO2008053518A1 - Semiconductor inspection equipment and semiconductor inspection method

Info

Publication number: WO2008053518A1
Application number: PCT/JP2006/321666
Authority: WO
Inventors: Keizo Yamada
Original assignee: Topcon Corporation
Priority date: 2006-10-30
Filing date: 2006-10-30
Publication date: 2008-05-08

Abstract

Semiconductor inspection equipment which can check the electrical characteristics of a device during a process, and can detect even a relatively small variation in characteristics. The semiconductor inspection equipment is constituted such that a semiconductor substrate is abutted against an electrode and irradiated with an electron beam, a substrate current induced in the semiconductor substrate by the electron beam is measured through the electrode, and the evaluation value of a microstructure formed in the semiconductor substrate is obtained from the measurements. The semiconductor inspection equipment is characterized in that the electrode is constituted of a plurality of substrate current detection electrodes electrically insulated from each other.

Description

Specification

Semiconductor inspection apparatus and semiconductor inspection method

Technical field

The present invention relates to a semiconductor inspection apparatus using an electron beam, and more particularly to a semiconductor inspection apparatus and a semiconductor inspection method suitable for evaluating a semiconductor device manufacturing process. Background art

[0002] In order to investigate the performance of semiconductor devices, a technique using a substrate current generated when an electron beam is irradiated onto a sample has been widely used. If this technology is used, it is difficult to discriminate with a conventional electron microscope using secondary electrons, and it is possible to detect non-destructive process problems that are difficult (see Patent Document 1).

This apparatus includes an electron gun for generating an electron beam, a tray for holding a measurement target wafer, an XY stage for determining an irradiation position of the electron beam, and a substrate current detection electrode for measuring a substrate current And so on. FIG. 20 is a diagram showing the main part. In this figure, 1 is a circular electrode, 2 is a support substrate for supporting the electrode 1, and 3 is a semiconductor wafer to be measured placed on the electrode 1 . Then, an electron beam is irradiated onto the electrode 1, thereby measuring a substrate current induced in the wafer 3 through the electrode 1 and the support substrate 2, and detecting a process defect based on the measurement result.

Patent Document 1: Japanese Patent Laid-Open No. 2005-026449

Disclosure of the invention

Problems to be solved by the invention

[0004] Meanwhile, there are semiconductor device defects that can be easily determined structurally and those that can be determined only by measuring electrical properties. Conventional technology mainly detects structural changes due to process fluctuations (for example, differences in size and differences in residual film), and changes in electrical characteristics that interfere with the detection can be ignored. Measurement methods have been used.

[0005] On the other hand, there is a need to directly measure electrical characteristics in-line. For example, wiring and vias that make up semiconductor devices, minute changes in electrical resistance at contact hole electrical conduction parts, and changes in transistor characteristics. These changes are per process step Since it appears as a result of structural changes, it is desirable that there is a strong correlation between the measured structure and the electrical properties and that it can be detected simultaneously. However, at present, the only way to know the electrical characteristics is to complete the device through all the process steps and conduct an electrical test, and it is very important to directly connect the process failure at each step to the electrical characteristics. It was difficult.

[0006] Although there is a need to detect a change in resistance value of several ohms in-line using an electron beam, the conventional method can detect only a high resistance on the order of mega-ohms. I got it. There was a problem that the channel characteristics of the transistor were completely unknown until the electrical test was conducted, and there was a request to know the electrical characteristics immediately after the transistor was formed.

The present invention is capable of checking the electrical characteristics of a device in the course of a process, and a semiconductor inspection apparatus capable of detecting a force and even a relatively small characteristic change (for example, a small change in resistance value) and To provide a semiconductor inspection method! Means for solving the problem

[0008] In order to solve the above-described problem, a semiconductor inspection apparatus according to the present invention causes a semiconductor substrate to abut an electrode, irradiates the semiconductor substrate with an electron beam, and is induced on the semiconductor substrate by the electron beam. In the semiconductor inspection apparatus configured to measure the measured substrate current through the electrode and obtain the evaluation value of the microstructure formed on the semiconductor substrate from the measurement result, the electrodes are electrically connected to each other. A plurality of substrate current detection electrodes insulated from each other.

[0009] According to the above configuration, a minute change in electrical characteristics such as a change in electrical resistance value of several ohms, not just a large resistance change such as mega ohms, can be measured immediately after each process in the wafer state. In addition, since the electrical characteristics can be known without having to complete the semiconductor device manufacturing process, the correlation between the process result and the electrical characteristics can be known immediately.

[0010] In the above invention, a plurality of current measuring means are provided which measure currents detected by the plurality of substrate current detection electrodes, respectively, and are independent from each other.

In the above invention, the plurality of substrate current detection electrodes are formed on the same plane. In the above invention, each of the plurality of substrate current detection electrodes is formed by electrodes having the same shape. To do.

In the above invention, the plurality of substrate current detection electrodes are constituted by a circular electrode at the center and a concentric annular electrode force surrounding the circular electrode.

In the above invention, the plurality of substrate current detection electrodes are formed of a plurality of strip-shaped electrodes.

[0011] In the above invention, the plurality of substrate current detection electrodes are constituted by a plurality of dot-like electrodes.

In the above invention, some or all of the plurality of substrate current detection electrodes are brought into contact with the upper surface of the semiconductor substrate.

In the above invention, some or all of the plurality of substrate current detection electrodes are brought into contact with the side surface of the semiconductor substrate.

In the above invention, the plurality of substrate current detection electrodes are constituted by mesh electrodes.

In the above invention, the electrode for the electrostatic chuck is provided on the same support substrate as the plurality of substrate current detection electrodes.

In the above invention, an insulating film is provided to cover the plurality of substrate current detection electrodes.

[0012] In order to solve the above-described problem, a semiconductor inspection method according to the present invention is configured such that a semiconductor substrate is brought into contact with a plurality of substrate current detection electrodes, and the semiconductor substrate is irradiated with an electron beam. A semiconductor configured to measure a substrate current induced in the semiconductor substrate by the plurality of substrate current detection electrodes and obtain an evaluation value of a microstructure formed on the semiconductor substrate as a result of the measurement In the inspection apparatus, in the first step of irradiating the semiconductor substrate with the electron beam, the second step of simultaneously measuring the current values generated in the plurality of substrate current detection electrodes, and the second step, And a third step of obtaining an evaluation value of the semiconductor substrate using each of the measured current values.

According to the above method, it is possible to measure a minute change in electrical characteristics such as a change in electrical resistance value of several ohms, not just a large resistance change such as mega ohms, immediately after each process in the wafer state. Also, do not complete the semiconductor device manufacturing process However, since the electrical characteristics can be known, the correlation between the process results and the electrical characteristics can be known immediately.

[0013] In the above invention, an evaluation value of the semiconductor substrate is obtained by using the plurality of substrate current detection electrodes having different impedances.

In the above invention, the electron beam is modulated into an AC signal having a desired frequency. In the above invention, the electrical characteristics of the semiconductor substrate are defined as unknowns, the simultaneous equations are solved using the equivalent circuit of the entire measurement circuit and the current values measured by the plurality of substrate current detection electrodes, and the electrical characteristics of the semiconductor substrate are determined. Ask for.

The invention's effect

[0014] According to the present invention, it is possible to measure a minute change in electrical characteristics such as a change in electrical resistance value of several ohms, not just a large change in resistance such as mega ohms, immediately after each process in a wafer state. In addition, inline evaluations such as the capacitance characteristics, resistance characteristics, channel characteristics, and transient frequency characteristics of active elements such as transistor characteristics based only on resistance values are possible. By combining with a conventional process evaluation device, it is possible to correlate the amount of process fluctuation measured for each process, the process result evaluation value, and the electrical characteristics.

Furthermore, according to the present invention, the electrical characteristics can be known without performing the semiconductor device manufacturing process to the end, so that the correlation between the process result and the electrical characteristics can be known immediately. Since the electrical characteristics can be known on the spot each time a process is performed, the effects of individual processes on the electrical characteristics can be directly measured, and the development of the process can be accelerated.

In addition, it is possible to know the electrical characteristics during device manufacturing, so if an electrical failure occurs, it is possible to immediately stop the process or change the process recipe to return it to the correct state. . As a result, the yield can be improved and the manufacturing cost of the device can be reduced. In addition, subtle changes in electrical characteristics can be measured, enabling better process management, and using the same process generation technology, it is possible to create faster and lower power consumption devices.

Brief Description of Drawings FIG. 1 is a configuration diagram of a semiconductor inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation flow of the semiconductor inspection apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a configuration of a main part of the semiconductor inspection apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an equivalent circuit and a measurement target part of a measurement example in the same embodiment.

FIG. 5 is a flowchart showing a measurement operation in the embodiment.

FIG. 6 is a diagram showing an equivalent circuit and a measurement target part of another measurement example in the embodiment.

FIG. 7 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a fifth embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a sixth embodiment of the present invention.

FIG. 12 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a seventh embodiment of the present invention.

FIG. 13 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to an eighth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a ninth embodiment of the present invention.

FIG. 15 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a tenth embodiment of the present invention.

FIG. 16 is a view showing a modification of the same embodiment. 17] FIG. 17 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to an eleventh embodiment of the present invention.

18] A diagram showing an equivalent circuit and a measurement target portion of a measurement example in the same embodiment. [19] FIG. 19 is a schematic configuration diagram showing a configuration of a main part of a semiconductor inspection apparatus according to a twelfth embodiment of the present invention.

FIG. 20 is a schematic configuration diagram showing a configuration of a main part of a conventional semiconductor inspection apparatus.

Explanation of symbols

1, la, lb, 6a-6d, 7a-7h, 8a-8d, 9a-91, 16, 26a-26d, 28, 36a, 36b

2 Support substrate

5a, 5b ammeter

10 electron gun

11 Electron beam source

12 condenser lens

13 Apachiya

14 Deflection lens

15 Objective lens

17a, 17b Upper electrode

18a ゝ 18b pad

19a ゝ 19b Support member

20 Wafer identification device

21 XY stage

22 trays

23 wafers

24 Secondary electron backscattered electron detector

25 Mesh electrode

27 Electrostatic chuck electrode 30 Current measuring device

35 Electron recovery electrode

50 Electrostatic chuck power supply

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the best mode for carrying out the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration of a semiconductor inspection apparatus according to an embodiment of the present invention. This semiconductor inspection apparatus irradiates an object to be measured (hereinafter referred to as a wafer) with an electron beam, measures a substrate current induced in the wafer by the electron beam, and forms the substrate current force on the wafer. The basic principle is to obtain an evaluation value of the fine structure.

As shown in FIG. 1, an electron gun 10 that generates an electron beam EB is attached to a chamber 20 that accommodates a wafer 23, and the electron gun 10 includes an electron beam source 11. A high voltage power source 40 is connected to the source 11. Inside the electron gun 10, a condenser lens 12, an aperture 13, a deflection lens 14, and an objective lens 15 are arranged in this order along the emission direction of the electron flow from the electron beam source 11. Among them, the deflection electrode 100 is connected to the deflection electrode 14 so that the electron beam EB can be deflected with high accuracy. Further, the energy, current amount, and focus state of the electron beam EB of the electron gun 10 can be arbitrarily controlled.

An XY stage 21 and a tray 22 for supporting the wafer 23 are accommodated in the chamber 20, and the wafer 23 is placed on the tray 22. The electron beam EB emitted from the electron gun 10 is directed to the surface of the wafer 23 placed on the tray 22, and the electron beam to the wafer 23 is moved by moving the position of the tray 22 by the XY stage 21. The irradiation position of EB can be adjusted. Further, a secondary electron reflected electron detector 24 for detecting secondary electrons and reflected electrons reflected on the wafer 23 is provided inside the chamber 20.

[0021] Here, in order to irradiate the wafer 23 with the electron beam EB irradiated from the electron gun 10 with a position accuracy of the order of nm, the XY stage 21 applies a fixed electron beam EB to the irradiation axis. The position of the wafer 23 is relatively moved. XY stage 21 As the drive device, a pulse motor, an ultrasonic motor, a linear motor, or a piezoelectric element is used. By using high-precision measurement technology such as a laser length meter and laser scale, the positional accuracy of the wafer 23 placed on the XY stage 21 is controlled to about several nm.

In addition, a current measuring device 30 is connected to the tray 22 on which the wafer 23 is placed, and the substrate current induced in the wafer 23 is measured by the current measuring device 30 via the tray 22. It has become like that. The current measuring device 30 is built in or near the tray 22 and can cut electromagnetic noise caused by external force. As the current measuring device 30, various types such as a resistance, a voltage conversion type device, an AC amplifier, and a charge amplifier can be used. The current measuring device 30 includes an AZD converter that converts the measured substrate current value into a digital signal, and outputs the measured value as digital data.

The electrostatic chuck power source 50 is a power source that applies a high voltage (about 500 V) to the electrostatic chuck that corrects the warp of the wafer 23.

In addition, the semiconductor inspection apparatus includes a two-dimensional scanning control apparatus (including a pattern matching engine) 110, a current waveform storage apparatus 120, a waveform shaping apparatus 130, a waveform processing apparatus 140, a display apparatus 150, and a database apparatus 160. These are constructed on an information processing apparatus such as a computer. Among them, the two-dimensional scanning control device 110 controls the deflecting device 100 so that the electron beam EB scans the surface of the wafer 23 two-dimensionally and adjusts the irradiation position of the electron beam EB with high accuracy. It is responsible for control of pattern matching. In the present embodiment, the two-dimensional scanning means that the line-shaped scanning is repeated a plurality of times at a constant interval. For example, it is a concept similar to horizontal scanning and vertical scanning on a television screen.

Here, supplementing pattern matching, the position of a pattern such as a hole formed on the wafer 23 is slightly different for each wafer even in the same lot. For this reason, in combination with alignment using the XY stage 21, pattern matching is performed for each wafer to compare the actual pattern with the reference pattern. This enables the irradiation position of the electron beam with a precision of several nanometers for each wafer. Adjust accurately. With this pattern matching In order to accurately shift the electron beam irradiation position, the semiconductor inspection apparatus includes the above-described deflection apparatus 100 with high resolution for accurately scanning the electron beam EB in a straight line. Further, the two-dimensional scanning control device 110 includes an image recognition device and software for performing pattern matching.

The current waveform storage device 120 stores the waveform of the substrate current value measured by the current measurement device 30 in association with the irradiation coordinates or time of the electron beam EB at that time. The waveform shaping device 130 shapes the waveform of the substrate current value and removes unnecessary noise components. The waveform processing device 140 calculates an evaluation value related to the shape of the fine structure formed on the wafer 23 by performing waveform processing on the waveform-shaped substrate current waveform. The display device 150 displays the evaluation value. The database device 160 stores the evaluation value.

Further, the tray 22 is provided with an electron beam irradiation position measuring device 180 for measuring the electron beam irradiation position, and the electron beam irradiation position measured by the measuring device 180 is output to the electron beam irradiation position storage device 170. The stored irradiation position data is output to the two-dimensional scanning control device 110 and the current waveform storage device 120.

Next, the outline of the operation of the semiconductor inspection apparatus will be described along the flow shown in FIG. In this example, the measurement target is a hole.

During measurement, first specify the position coordinates of the hole to be measured with respect to the control system of the XY stage 21 holding the wafer 23, move the XY stage 21, and center the holes formed on the wafer 23. Perform (alignment) (step S1).

[0027] Specifically, the center of the hall is roughly aligned with the position where the electron beam EB can be irradiated by the XY stage 21. Subsequently, the distance between the wafer 23 and the objective lens 15 is measured using the wafer objective lens distance measuring device 16 provided at the lower end of the electron gun 10 (Step S2), and the initial position of the electron beam focus is determined. To do. Next, the electron beam EB is irradiated while scanning two-dimensionally within a predetermined region including the hole, and secondary electrons generated at that time are collected to form a secondary electron image. Autofocus (step S3) is performed using the formed secondary electron image, and the strength of the objective lens is automatically adjusted so as to focus on the sample. Next, the secondary electron image obtained by scanning the focused electron beam. The image is compared with the template image stored in advance in the two-dimensional scanning control device 110 to perform pattern matching (step S4), and the amount of deviation between the center of the template image and the center of the hole is calculated. This calculated amount of deviation is input to the deflecting device 100, and the irradiation position of the electron beam EB is shifted, so that the irradiation position of the electron beam EB is accurately aligned with the center of the hole to be measured.

Subsequently, under the control of the two-dimensional scanning control device 110, the predetermined region on the surface of the wafer 23 is two-dimensionally scanned by the electron beam EB with reference to the hole center (step S5). That is, by controlling the objective lens 15 of the electron gun 10 so that the electron beam EB has a desired tip size and by controlling the control voltage in the deflecting device 100, the electron beam scanning is performed in a line at a constant pitch. repeat. As a result, secondary electrons and reflected electrons are generated from a minute region on the surface of the wafer 23 irradiated with the electron beam EB, and a substrate current is induced in the wafer 23.

[0029] Secondary electrons, reflected electrons, or substrate currents induced on the wafer 23 are measured by the secondary electron reflected electron detector 24 and the current measuring device 30, and the measured values are digital signals having the necessary resolution. Will be converted immediately. For example, the resolution of this digital signal is 16 bits and its sampling frequency is 400 MHz. This speed can be changed if necessary.

The secondary and reflected electrons obtained by two-dimensional scanning of the electron beam EB include hole surface shape information, and the substrate current measurement value includes information about the two-dimensional shape of the bottom surface of the hole. Position) or measurement time (electron beam EB irradiation time) is obtained as waveform information with respect to the time axis and is digitally recorded in the current waveform recorder 120 (eg, memory, flash memory, hard disk, magneto-optical disk, etc.) Be done

[0030] The signal waveform information acquired as described above is waveform-shaped by the waveform shaping device 130 in order to remove unnecessary noise and high-frequency components contained in the waveform. Examples of the waveform processing include moving average filter processing, waveform processing for removing a specific frequency, filter processing for extracting only a signal of a specific frequency, and Fourier filter processing. These waveform shaping processes can be performed in hardware or software. May be.

[0031] Next, only useful waveforms are extracted from the waveform-shaped waveforms, and hole bottom area measurement is performed (step S6). In this case, there are cases where the electron beam irradiation area does not contain a hole or the waveform is dirty due to the edge of the hole. As a result, the accuracy of the edge coordinate value obtained by the processing decreases. For this reason, a good current waveform useful for hole edge extraction is extracted only for a signal whose absolute value is larger than a certain value using a threshold method or the like. In addition to scanning the electron beam in a line, the current waveform is acquired by irradiating the measurement point with the electron beam for a certain period of time. In these cases, waveform processing similar to the above is performed, and necessary information is extracted.

[0032] The wafer 23 to be measured is recorded with an identification number provided on the wafer 23 or information so that it can be identified by a computer. More generally, there is an equipment operation management system called MES (Manufacturing Execution System) in a semiconductor factory, and it records all of what time each wafer has undergone what processing. By correlating with such information, it is useful for estimating failure classification and its cause.

Next, the electrodes placed on the tray 22 will be described in detail with reference to FIG.

The tray 22 is a table on which the wafer 23 to be measured is placed. For example, the tray 22 has a support substrate 2 made of A1 (aluminum) and two semicircular planar electrodes la and lb in close contact with the support substrate 2. ing. This embodiment is characterized in that it uses two (la, lb) electrodes for substrate current detection that are electrically independent from each other. Electrically insulated electrodes la and lb are provided on the left and right sides of the wafer 23, respectively, and wiring is performed so that current can be taken out to the outside. In Fig. 3, electrodes with exactly the same shape are used to have the same capacitance and resistance.

[0034] A wafer 23 to be measured is placed on these electrodes. When the electron beam is irradiated onto the wafer 23, an electric charge is generated in the electron beam irradiation portion, and the electric charge moves through the wafer 23 to generate currents in the electrode la and the electrode lb, respectively. These currents are measured independently by each ammeter connected to the electrode. The ammeter used here measures a very small current (about 1 picoampere or less), so it may be a resistance shunt type, but for more precise measurement, the measurement point is a virtual ground using a current-voltage converter. It is desirable to use an ammeter that In this case, since each electrode is virtually grounded, it is possible to eliminate the influence on each other even if a plurality of ammeters are used.

[0035] The total current generated in the substrate by electron beam irradiation is the sum of the current values measured through electrode la and electrode lb. Various materials can be used for the electrodes la and lb for detecting the substrate current as long as they are conductive materials. For example, aluminum, copper, nickel, plating film, organic material, conductive rubber, organic material, ceramic, semiconductor, etc. can be used. In addition, if necessary, an insulating film or a conductive film can be coated on the electrode so as not to damage the measurement target substrate.

For example, as the insulating film, a silicon oxide film, a silicon ticker film, a polyimide organic film, or the like can be used. As the conductive film, various materials such as conductive polyimide and ITO film can be used. Diamond or glass may be coated. Surface treatment such as ion plating of Ti, etc. Conversely, soft materials such as silicone can be used as cushions.

Depending on the purpose, each electrode la, lb should be flattened so that it is in good contact with the silicon wafer 23, kept at the same height, and designed to have the same electrical characteristics. You can use a 3D electrode to place many small electrodes. At this time, the height of each part may be different.

[0037] For the support substrate 2, a metal material, a ceramic, or an organic material can be used. Since tray 22 and wafer 23 or the entire device form one electrical circuit, it is very important to know the electrical circuit constants. For example, a capacitance is formed between the tray 22 and the wafer 23, through which the substrate current is measured. In the case of a normal silicon wafer 23 having no deposit on the back surface, the capacity formed is a capacity formed by a natural oxide film and reaches 10000 F. On the other hand, when an insulating film such as an oxide film is thickly deposited on the back surface of the silicon substrate, a capacitance of about several tens of z / zF is formed. The structure closest to the silicon wafer 23 is the objective lens, facing each other with a gap of about 3 mm. this Their capacity is a few pF. The current generated by the electron beam irradiation is distributed through the circuit that constitutes the entire device including the measurement target, and only the current flowing between the tray 22 and the wafer 23 contributes to the measurement current, so it has an appropriate capacity and resistance. It is desirable to design as follows.

FIG. 4 shows an example of an electrical equivalent circuit of a device formed on the wafer 23.

When the electron beam 4 is irradiated onto the electronic device 4 formed on the wafer 23, when the current is measured simultaneously with two electrodes, the substrate current is applied to the ammeters 5a and 5b through the equivalent resistances Rl and R2 existing in the two electrical paths. Flows. The current value measured by the ammeter 5a and the ammeter 5b is determined by the ratio of the equivalent resistance formed by the measurement object related to the absolute value of the measured resistance value. Such circuits are found in via chains and the like.

[0039] When the current is measured with a single current path without using two electrodes as in the conventional case (Fig. 20), the absolute value of the current value is the same even if a small resistance change occurs in the current path. It is difficult to detect a small change in resistance value with little change. However, when there are two current measurement paths, if the resistance value of either path changes even slightly, the total current value is distributed according to the ratio of the resistance values, so even if the absolute value of the resistance change is small. The ratio of the current measured at the two electrodes varies greatly to the extent that it can be measured. Therefore, if the circuit is configured so that the current ratio can be measured as in the present embodiment, a change in electrical resistance of several ohms generated in the measurement object can be measured.

FIG. 5 shows a measurement method when two substrate current detection electrodes are used.

For example, wiring that reaches the ground in advance is performed so that the size of the resistor R1 is about several ohms. Resistor R2 is the resistor to be measured. Assume that resistance R2 has changed several ohms due to some process failure. Irradiate the measurement target with an electron beam (Step Sl). The currents generated in the two electrodes la and lb are simultaneously measured by the ammeters 5a and 5b (step S2). The current value measured by each ammeter 5a, 5b changes by the ratio of each resistor. If the initial resistance value is several ohms and the resistance value changes several ohms due to a failure, a difference of more than twice the current value is measured in the two current paths (step S3).

[0041] For example, the resistance R1 was 1ρΑ and the resistance R2 was flowing ΙρΑ. The resistance R1 was 2pA and the resistance R If lpA flows to 2, the resistance value changes more than twice. Next, using this ratio, the electric resistance value of the part that caused the failure is calculated from the equivalent circuit (step S4). The calculation is performed automatically using a computer, and the result is stored in a computer recording device (step S5) and displayed on the screen (step S6).

FIG. 6 describes another method for measuring electrical characteristics of an electronic device using the electrode of this embodiment. As shown in the figure, the contact hole made on the silicon wafer 23 can be cited as an object to be measured. In this case, the contact hole is filled with W or polysilicon. In that case, you may want to measure the resistance in the lower part of the buried area. For example, when an electron beam accelerated at a certain accelerating voltage is irradiated onto the plug portion of the contact hole, electrons are injected into the irradiated portion or secondary electrons are emitted. For example, if electrons are injected into the plug, the electrons flow toward the electrodes la and lb (Fig. 3) placed in the plug force virtual ground state. Measure and record the amount of current generated by the electrons collected at the respective electrodes la and lb with the respective ammeters 5a and 5b. For example, 1ρΑ is recorded for the first electrode la and 2pA is recorded for the second electrode lb. The difference or ratio of this current value is regarded as the value. For example, if it is known in advance that the equivalent resistance of one of the current circuits to the two ammeters 5a and 5b is R1, the resistance value R2 to be measured is the ratio of the measured current value. It can be obtained by multiplying the reference resistance value R1. The resistance value estimated in this way is stored in a computer and displayed on a display.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 shows the electrode for measuring the substrate current used in this embodiment. This embodiment is characterized in that the electrode is divided into four parts. Electrodes 6a to 6d that are electrically isolated from each other on the front, rear, left, and right sides of the wafer are provided, and wiring is provided so that current can be taken out to the outside. A wafer is placed on these electrodes 6a-6d. Electron beam force A force that generates a substrate current when the S wafer is irradiated. The current passes through all of the electrodes 6a to 6d and the current value is measured independently. The total current generated in the substrate is the sum of the current values measured through electrodes 6a-6d. The electrodes 6a to 6d can be any conductive material. For example, aluminum, copper, nickel, conductive rubber, etc. can be used. If necessary, an insulating film can be coated on the electrode. For example An oxide film, a ticker film, a polyimide organic film, or the like can be used.

[0044] The gaps between the individual electrodes 6a to 6d may be left as they are, or an insulator may be disposed in the groove portion. It is desirable to leave a gap between them without strong capacitive coupling. The distance between the wafer and the electrode may be controlled by changing the height of the insulator. In the wafer characteristic measurement, the substrate current is measured using the two electrodes corresponding to the measurement points as in the case described in FIGS. Obtain the electrical characteristics of

FIG. 8 shows the configuration of the electrodes used in the third embodiment of the present invention.

The third embodiment is characterized in that eight independent substrate current detection electrodes 7 a to 7 h are arranged on the support substrate 2. Electrodes 7a to 7h that are electrically insulated from each other are provided on the front, back, left, and right of the wafer, and wiring is performed on each of the electrodes 7a to 7h so that a current can be taken out to the outside. The wafer is placed on these electrodes 7a-7h. When the electron beam is irradiated onto the wafer, a substrate current is generated, and the current passes through all of the electrodes 7a to 7h, and the current value is measured independently. The total current generated in the substrate is the sum of the current values measured through electrodes 7a-7h.

[0046] The electrodes 7a to 7h can be any inorganic or organic conductive material, and any semiconductor material can be used. It is not necessary to use the divided electrodes 7a to 7h at the same time. Select two electrodes that are necessary according to the location to be measured. Unused electrodes can be floating, grounded, or virtually grounded with respect to ground. They can be realized by turning on or off the switch of the current detection device. For the electrodes 7a to 7h, for example, aluminum, copper, nickel, conductive rubber, conductive polymer, or the like can be used. If necessary, an insulating film can be coated on the electrode. For example, a silicon oxide film, a silicon ticker film, a polyimide organic film, a fluorine resin, or the like can be used.

FIG. 9 shows the configuration of the electrodes used in the fourth embodiment of the present invention.

In the fourth embodiment, an electrode is constituted by a circular electrode 8a at the center and concentric annular electrodes 8b to 8d surrounding the circular electrode 8a. There are provided electrodes 8a to 8d that are concentrically separated from the center of the wafer and are electrically insulated from each other, Wiring is performed from each of the electrodes 8a to 8d so that a current can be taken out to the outside. The wafer is placed on these electrodes 8a-8d. The force that generates the substrate current when the wafer is irradiated with the electron beam. The current passes through all of the electrodes 8a to 8d, and the current value is measured independently. The total current generated in the substrate is the sum of the current values measured through electrodes 8a-8d. The electrodes 8a to 8d can be any conductive material. For example, aluminum, copper, nickel, conductive rubber, etc. can be used. If necessary, an insulating film can be coated on the electrode. For example, an oxide film, a ticker film, a polyimide organic film, or the like can be used. It is not necessary to use the divided electrodes 8a to 8h at the same time. Select the two electrodes that are necessary according to the location to be measured. Unused electrodes can be floating with respect to ground, grounded, or virtually grounded.

FIG. 10 shows the configuration of the electrodes used in the fifth embodiment of the present invention.

The fifth embodiment is characterized in that a plurality of electrodes 9a to 91 are provided in a strip shape. Wafer central force Electromagnetically insulated electrodes 9a to 91, which are arranged symmetrically on the left and right, are provided, and wiring is provided so that current can be taken out to the outside. A wafer is placed on these electrodes 9a-91. The force that generates the substrate current when the wafer is irradiated with the electron beam. The current passes through all of the electrodes 9a to 91 and the current value is measured independently. The total current generated in the substrate is the sum of the current values measured through electrodes 9a-91. The electrodes 9a to 91 can be any conductive material. For example, aluminum, copper, nickel, conductive rubber or the like can be used. If necessary, an insulating film can be coated on the electrode. For example, an oxide film, a ticker film, a polyimide organic film, or the like can be used.

[0049] The divided electrodes 9a to 9h do not need to be used at the same time, and two necessary electrodes are selected and used according to the measurement target location. Unused electrodes can be floating with respect to ground, grounded, or virtually grounded.

[0050] FIG. 11 shows the configuration of an electrode used in the sixth embodiment of the present invention! / Speak.

In the sixth embodiment, the rectangular dot electrodes 16, 16... Are arranged in a matrix on the support substrate 2. Wafer center force is also symmetrically arranged in the front, rear, left and right The electrodes 16, 16..., Which are electrically insulated from each other, are provided, and wiring is provided so that a current can be taken out to the outside. A wafer is placed on these electrodes 16, 16. When the electron beam is applied to the wafer, a substrate current is generated, and the current passes through all the electrodes and is measured independently. The total current generated in the substrate is the sum of the current values measured through all electrodes 16, 16. The electrodes 16, 16,... Can be any conductive material. The electrodes 16, 16,... May be made using etching, or may be made using plating. For example, aluminum, copper, nickel, conductive rubber, or other conductive materials can be used. If necessary, an insulating film can be coated on the electrodes 16, 16. For example, a silicon oxide film, a silicon ticker film, a polyimide organic film, or the like can be used. The divided electrodes 16a to 16h do not need to be used at the same time. Select and use the two electrodes that are necessary according to the location to be measured. Unused electrodes can be floating, grounded, or virtually grounded with respect to ground.

FIG. 12 shows the configuration of the electrodes used in the seventh embodiment of the present invention.

In the seventh embodiment, the substrate current detection electrode is provided so as to contact the upper and lower surfaces of the wafer. The electrical resistance or electronic element to be measured may only be on the wafer surface. For example, an element made on an SOI substrate. In that case, in general, it is possible to reduce the path resistance by directly measuring the substrate current through the substrate surface rather than performing the current measurement through the back surface of the substrate having a high resistance value. That is, it becomes easier to measure changes in low resistance.

In the figure, reference numerals 17a and 17b denote upper electrodes, which are supported by conductive rubber pads 18a and 18b that are in contact with the peripheral edge of the upper surface of the wafer 23, and a conductor that supports the pads 18a and 18b. The support members 18a and 18b are each attached to the support substrate 2 via an insulator, and are connected to the current measuring device 30 by lead wires. In addition, on the upper surface of the support substrate 2, dot-like electrodes similar to those in FIG. 11 are arranged in a matrix form via an insulator, and each electrode is connected to the current measuring device 30, and the back surface of the wafer 23 is these It is in contact with the electrode.

[0053] The upper electrodes 17a and 17b are integrally formed on a tray that supports the wafer 23, and the above-described 2 A plurality of electrodes can be provided without being limited to individual pieces. Measurement may be performed using only the upper electrodes 17a and 17b, or measurement may be performed in combination with the electrodes on the back surface. The upper electrode may be brought into contact with a place such as a pad provided in advance at the end of the wiring to measure the current, or the electrode may be brought into contact with the side surface of the wafer 23 to take out the current. Of course, you may combine them. When taking out the current from the electrode, it can be taken out in a direct current, or it can be taken out in an alternating current by forming a capacitor with an insulating film or the like.

FIG. 13 shows the configuration of the electrodes used in the eighth embodiment of the present invention.

In this eighth embodiment, a mesh electrode 25 is used as a surface electrode. For example, if the meshes are made at intervals such that they are arranged on the scribe line, it is possible to extract the near force current of each device without damaging the device. Each mesh may be electrically connected, or may be arranged so that they are insulated from each other and can be addressed with multiple wiring forces. The electrodes on the lower surface of the wafer are the same as those in FIG.

FIG. 14 shows the configuration of the electrodes used in the ninth embodiment of the present invention.

The ninth embodiment is characterized in that the substrate current detection electrodes 26 a to 26 d are arranged on the side surface of the wafer 23. Depending on the device, it may be difficult to measure current from the back or front surface of the wafer 23. In such a case, an electrode is provided on the side surface of the wafer 23 and current measurement is performed.

FIG. 15 shows the configuration of electrodes and their peripheral parts used in the tenth embodiment of the present invention.

Wafers that are used in semiconductor inspection equipment may be warped because films are deposited by various processes. In such a case, it is better to use an electrostatic chuck. An electrostatic chuck is a device that uses a voltage of about 500V between a wafer and a dielectric to electrically attract each other. Since a high voltage is applied to the electrode 27 for the electrostatic chuck, it is electrically insulated from the electrode 28 for current measurement. In FIG. 15, an electrode 27 is arranged on the periphery of the wafer so as to be effective in correcting the warpage of the wafer. The electrode 28 for current measurement is provided inside the wafer. In the case of FIG. 15, the electrostatic chuck uses a bipolar type, and the potential of the entire wafer varies as the electrostatic chuck is driven. I am trying not to. Since the electrostatic chuck becomes a noise source during measurement, turn off the power as much as possible so as not to affect it.

FIG. 16 shows an example in which an insulating film 29 is provided on the electrode. In this way, the electrostatic chuck can be stably applied even to a wafer having no insulating film on the back surface. In addition, since the measurement electrode 28 is not in direct contact with the silicon wafer, measurement instability due to contact Z non-contact can be avoided, and stable measurement is realized.

FIG. 17 shows an eleventh embodiment of the present invention.

In the present embodiment, as the substrate current detection electrode, the electron recovery electrode 35 is provided in a space near the measurement object without directly contacting the substrate. When the measurement object is irradiated with an electron beam, secondary electrons and reflected electrons pop out at the same time. The ejected secondary electrons or reflected electrons are converted into current using the electrode 35 provided in the vicinity of the measurement target. For example, as shown in FIG. 17, when the electrodes 36a and 36b are provided on the back surface of the wafer 23 and the electron recovery electrode 35 is provided on the front surface, the current measured by the wafer back electrodes 36a and 36b By comparing the current measured with the electrode 35 on the wafer surface, the electrical characteristics of the object to be measured can be measured. For example, if the equivalent resistance value of secondary electrons recovered from the surface of the wafer 23 is R3 and the resistance values measured through the back of the substrate are Rl and R2, respectively, the ratio of the measured current values or By evaluating the difference, the resistance value RX of the element to be measured formed on the substrate surface can be known.

[0059] The current used for measurement is not limited to direct current, but may be modulated to various frequencies.

For example, when the electrodes 36a and 36b are capacitively coupled to the wafer 23 to be measured, it is possible to change the constant of the measurement circuit by changing the frequency used for the measurement. The electric resistance and capacitance of the measurement target part can be obtained by calculation. For example, by preparing multiple electrodes for current detection with intentionally changed electrode capacities and comparing the amount of current detected for the same measurement object, the resistance value or capacitor of the measurement object part is compared. Capacitance or impedance can be obtained. In particular, when it is difficult to create a reference capacitance inside the device, it is possible to calculate the resistance or capacitance value of the measurement target by intentionally adding a known capacitance or resistance value to the electrode. Do this. FIG. 17 shows the case where a plurality of substrate current detection electrodes 36a and 36b are arranged on the back surface, but one may be used depending on the application. The electron recovery electrode 35 on the substrate surface side is not necessarily provided separately. For example, the electron recovery electrode can be provided on the surface or inside of the objective lens located closest to the wafer. An electron detector such as a scintillator can also be used as an electron recovery electrode.

FIG. 18 shows an equivalent circuit of the above embodiment. For example, you may want to know the resistance value Rx of the plug that fills the contact hole. In that case, it can be executed by creating a current path different from the current path formed by the plug and measuring the ratio of the current flowing through the path to the current value flowing through the plug. In the present embodiment, in order to create another path, the electrode 35 is arranged in the vicinity of the measurement target. When irradiated with an electron beam, secondary electrons or reflected electrons are generated. When we collected the electrons and measured the current, we created another path. The path for collecting the electrons by placing the electrode 35 has the same effect as connecting a circuit having a certain resistance and capacitance to the object to be measured. These electrical constants are considered to be the same unless the measurement configuration changes, so if the resistance value of the plug being measured changes, the ratio of the substrate current values will change. By measuring this ratio, it is possible to detect a very small resistance difference in the plug portion.

FIG. 19 shows a twelfth embodiment of the present invention.

This embodiment facilitates the resistance estimation of the above embodiment. For example, prepare four substrate current measurement electrodes to be used for measurement, each with the same known equivalent impedance. The ammeters 1 to 4 connected to the respective electrodes allow the input terminal to be switched to a virtual ground state or an insulation state by an external signal. In addition, an ammeter 5 is connected to the electron recovery electrode 35. For the first measurement, make sure that only ammeters 1 and 5 are in virtual ground. In this state, the measurement target is irradiated with an electron beam, the resulting current value is measured with ammeter 1 and ammeter 5, and the measured value is recorded. Next, with only ammeter 1 and ammeters 2 and 5 in a virtual ground state, irradiate the measurement object with an electron beam and measure the current value with each of ammeters 1, 2, and 5. Record. Similarly, with only the ammeters 1, 2, 3 and 5 in the virtual ground state, irradiate the target electron beam and measure the current values with the respective ammeters 1, 2, 3, and 5. Record. Finally everything Set the current meter to a virtual ground state, irradiate the object to be measured with an electron beam, and measure and record the current value with each ammeter.

As described above, the current value was measured in a state where the impedance on the substrate side was changed to 1, 1/4 of 1/4, 1/3, and 1/4 of the measurement target force. By analyzing the current values measured in these conditions by solving simultaneous equations, the resistance value of the contact plug can be estimated. In particular, the equivalent circuit constant created by the object to be measured and the electron recovery electrode 35 is unknown, but it can be eliminated by solving the simultaneous equations, and it is not necessary to know in advance the constant of the circuit created by the electron recovery electrode 35. ,.

[0064] In the above embodiment, it is possible to measure the impedance such as the capacitor capacity and reactance as well as the direct current resistance that can measure the force mainly focusing on the estimation of the resistance value. Capacitor capacity can be measured by irradiating the measurement target electronic element with a frequency-modulated electron beam.

[0065] The actual method is based on various AC impedance measurement methods as described in textbooks. The electron beam used for the measurement can be realized by irradiating a pulsed electron beam that does not need to be continuous. Transient response characteristics can be obtained by measuring the current waveform measured at each electrode that is generated when a pulsed electron beam is irradiated onto the measurement target. By analyzing the transient response waveform, for example, the impedance of the measurement object can be measured by determining the ratio of the time constants.

[0066] Appropriate numbers and combinations of the electrodes of the embodiment described above are used as necessary. When a plurality of electrodes are arranged, they can be used sequentially in time, and each combination may be variable with respect to the time axis.

[0067] It is desirable that the spacing and size of the electrodes used in the above embodiments be designed so as to match the electrodes of the wafer to be measured. Alternatively, it may be adjustable. The wafer used for the measurement in the above embodiment may be a wafer on which a device as a product is actually made, or a special circuit is provided on the wafer so that the present invention is easy to implement. In addition, a wiring that enables a special wiring between the electrode and the electrode may be separately provided on the back surface of the wafer. A TEG wafer devised so that the present invention can be easily implemented may be used. [0068] In particular, recent product wafers have a laminated structure in which the back surface is thinned, electrodes are provided on the back surface, and electrical connection is made with a semiconductor device manufactured on a semiconductor substrate that also has another wafer force. There are many things. (Flash memory stack) As in that case, when the present invention is carried out, the back surface of the wafer is thinned or thinned, or a wiring or a diffusion layer connecting the back surface of the wafer and the front surface is provided. Even if it is devised so that it can be easily connected to the electrode, there is no problem.

Industrial applicability

[0069] The present invention is useful for a semiconductor device or an apparatus used for analysis, manufacturing, measurement, or evaluation in a manufacturing process thereof. For example, the present invention can be used in the fields of analysis techniques, measurement techniques, evaluation techniques, inspection techniques, and semiconductor device manufacturing apparatuses and methods that use a method of irradiating a semiconductor substrate such as a wafer with an electron beam or ion beam. I'll do it.

Claims

The scope of the claims

[I] A semiconductor substrate is brought into contact with an electrode, the semiconductor substrate is irradiated with an electron beam, a substrate current induced in the semiconductor substrate by the electron beam is measured through the electrode, and a result of the measurement In a semiconductor inspection apparatus configured to obtain an evaluation value of a microstructure formed on the semiconductor substrate,

The electrode is composed of a plurality of substrate current detection electrodes electrically insulated from each other! / Semiconductor inspection equipment characterized by squeezing.

[2] The semiconductor detection device according to [1], further comprising a plurality of independent current measuring means for measuring currents detected at the plurality of substrate current detection electrodes.

[3] The semiconductor inspection apparatus according to claim 1 or 2, wherein the plurality of substrate current detection electrodes are formed on the same plane.

[4] The semiconductor inspection apparatus according to any one of [1] to [3], wherein each of the plurality of substrate current detection electrodes is formed of an electrode having the same shape.

[5] The plurality of substrate current detection electrodes are configured by a circular electrode in a central portion and a concentric annular electrode force surrounding the circular electrode. The semiconductor inspection apparatus described in 1.

[6] The semiconductor inspection apparatus according to any one of [1] to [3], wherein the plurality of substrate current detection electrodes include a plurality of strip-shaped electrodes.

[7] The semiconductor inspection apparatus according to any one of [1] to [3], wherein each of the plurality of substrate current detection electrodes includes a plurality of dot-shaped electrodes.

[8] The semiconductor inspection apparatus according to [1] or [2], wherein some or all of the plurality of substrate current detection electrodes are in contact with an upper surface of the semiconductor substrate.

[9] The semiconductor inspection apparatus according to [1] or [2], wherein some or all of the plurality of substrate current detection electrodes are in contact with a side surface of the semiconductor substrate.

10. The plurality of substrate current detection electrodes are mesh electrodes.

The semiconductor inspection apparatus according to any one of claims 1 to 3.

[II] An electrode for an electrostatic chuck is provided on the same support substrate as the plurality of substrate current detection electrodes. The semiconductor inspection device according to claim 1, wherein the semiconductor inspection device is a semiconductor device.

12. The semiconductor inspection apparatus according to any one of claims 1 to 11, wherein an insulating film is provided to cover the plurality of substrate current detection electrodes.

[13] The semiconductor substrate is brought into contact with the plurality of substrate current detection electrodes, the semiconductor substrate is irradiated with an electron beam, and the substrate current induced in the semiconductor substrate by the electron beam is passed through the plurality of substrate current detection electrodes. Measured and applied to a semiconductor inspection apparatus configured to obtain an evaluation value of a microstructure formed on the semiconductor substrate from the result of the measurement,

A first step of irradiating the semiconductor substrate with the electron beam;

A second step of simultaneously measuring current values generated in the plurality of substrate current detection electrodes; and a third step of obtaining an evaluation value of the semiconductor substrate using the respective current values measured in the second step. Steps,

A semiconductor inspection method characterized by comprising:

14. The semiconductor inspection method according to claim 13, wherein an evaluation value of the semiconductor substrate is obtained by using the plurality of substrate current detection electrodes having different impedances.

15. The semiconductor inspection method according to claim 13, wherein the electron beam is modulated into an AC signal having a desired frequency.

[16] The electrical characteristics of the semiconductor substrate are obtained by solving the simultaneous equations using the equivalent circuit of the entire measurement circuit and the current values measured by the plurality of substrate current detection electrodes, with the electrical characteristics of the semiconductor substrate being unknown. The semiconductor inspection method according to claim 13.