JPS6074251A - Secondary electron detecting apparatus - Google Patents

Abstract

PURPOSE:To simplify an additional average circuit by irradiating a sample under the operating condition with pulse wise electron beam, analogously adding the secondary electrons through a secondary electron multiplying means and obtaining a digitized detected output. CONSTITUTION:A sample 3 such as an integrated circuit under the operating condition is irradiated with ultra-shortwave electron beam pulse 2a and the secondary electron 4a emitted from the sample 3 is applied to an analog adding means 14 having a small charging time constant and a large discharging time constant through a secondary electron multiplying means consisting of a scintillator 5, a light pipe 6 and a photomultiplier 7. Moreover, an output of the adding means 14 is applied to a load resistance 8 through an analog switch 15 to be controlled by a control circuit 17 and a digital detected signal can be obtained through an A/D converting circuit 16. Therefore, the circuit can be simplified by analogous additional average of the outputs of secondary electron multiplying means and the A/D converting circuit 16 can bae operated at a low speed.

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a secondary electron detection device, and particularly to a device for detecting secondary electrons generated by using an electron beam while a sample such as an integrated circuit is in an operating state. The present invention also relates to a preferred primary electron detection device, such as an inspection device for inspecting the operational state of the trial ('-1.1υ).

(2) Background of the technology In high-speed integrated circuits, ultra-large scale integrated circuits, etc., it is necessary to inspect the internal circuits integrated in these integrated circuits in a detailed state in addition to the static state. In many cases, it is necessary. In such cases, conventionally the above-mentioned L
The package lid of the sample, which operates at high speed such as SI, is removed and an extremely short electron beam pulse is irradiated from the electron beam device.

The extremely short electron beam pulse irradiated from the electron beam device described in 2 is synchronized with the pulse cycle that operates inside the sample, for example, pulses are sent at predetermined intervals, and a method called strobe method is generally used. Since secondary electrons proportional to the pulse are emitted, the secondary electrons are given to a secondary electron multiplier consisting of a scintillator, a light pipe, a flame λI-multi, etc., and the secondary electrons are multiplied. After applying it to a load resistance, a digitized output was obtained through an analog-to-digital conversion circuit.

However, - the above-mentioned ultrashort electron beam pulse has been sped up and must be irradiated with a pulse width on the order of tens of nanometers in order to perform Sonkl:I in the saw operation test II, so that it is emitted from the sample. The amount of secondary electrons is reduced to f+it,l, and the S/N ratio of the secondary electrons obtained is extremely poor.

(3) Problems of the Prior Art - 1 - In the diagram illustrating the circuit of FIG. 1, which is an example of a conventional secondary electron detection device for solving the above-mentioned problems, 1 is an electron gun of an electron beam device. Yes.

A sample 3 is irradiated with an ultrashort electron beam pulse 2 .

The sample is irradiated with an extremely short electron beam pulse synchronized with the operating pulse while the required circuit is operating at high speed, and secondary electrons 4 proportional to the irradiated beam are incident on the scintillator 5 and passed through the light pipe. The secondary electrons converted to light are multiplied by the claw (・maru 7) and the secondary electrons are lentilake 5.rai I-vibro.

] The electrons are taken out as the output of the lower stage of the tertiary electron multiplier composed of Al/multilayer 7. The output from the secondary electron stage A1 is applied to a resistor 8 constituting a load circuit.

-+'+l:l of the cough resistor 8 is grounded, and a tertiary electron multiplication output current flows through the arrow panono Nil, and a voltage drop proportional to this current includes the preamplifier -j': I
The digitally converted output is sent to the digital converter circuit 9 and sent to the digital adder jT7 equalizer circuit 10. I was given a gift.

It is taken out to the output terminal 11. In order to ensure that only a very small number of secondary electrons are emitted, an average circuit 10 is used to digitally add and average the digitally converted Ll and I forces.
In addition to this, the averaged value is taken out to the output terminal [1], but this does not complicate the above-mentioned averaging circuit and causes disadvantages such as an increase in the number of H/I in the analog-to-digital conversion circuit. The whole becomes i1'ii value, resulting in an unrealistic problem.

(4) Purpose of the Invention The present invention solves the above-mentioned drawbacks of the conventional technology by using a two-blow electric T-increase (p
After averaging the outputs of the seven means in an analog way, Ana I:
It is an object of the present invention to provide a secondary electron detection device in which the ana-I-co-digital conversion circuit also operates at low speed by outputting to the 2-digit digital conversion circuit.

(5) Structure of the Invention According to the present invention, the second object is to provide a detection means for detecting electrons emitted from a sample, and to convert the output of the detection means into an arc having a small charging time constant ε and a large discharging time constant. J-+:+
In addition to the analog adding means, the output added by the analog adding means is applied to one stage of load resistance via an analog input,
The present invention is characterized in that the output of the load resistor means is applied by an analog-to-digital conversion means and an digital output is taken out.

(6) Examples of the invention The following six secondary electron detection devices of the present invention are shown in Figures 2 to 4 and 1.
I will write about it.

FIG. 2 shows a system diagram of the secondary electron detection device of the present invention.

In the same I, the same as Figure 1, the same parts are the same. 74: +
>H name- to omit duplicate explanation.

The electron beam emitted from the electron gun 1 passes through the electrode 12 of the electron beam device for electrode 15j fl
A circuit trying to detect the dynamic state of test $13 is irradiated for 1 minute and I-
Electron distribution pulses are applied or actuated between internuclear regions 1 to 3 - (
b) An extremely weak electronic pulse proportional to the pulse period (
Yes, there are 111 examples of ultrashort deuteron pulses from 13 onwards, and 2
Human secondary electrons 4 and 1 are also pulsed on the scintillator 5
The multiplied secondary electrons are taken out from the A electron beam (which constitutes the secondary electron multiplier).

Incidentally, the pulse gate 1 electrode 12 is supplied with data 1 to pulses from the pulse gate 1 drive circuit 13, and the electronic beano is turned into pulses. The output of the secondary electron multiplier 5.6°7 is applied to an analog/average circuit 14. The arithmetic averaging circuit connects the cathode of the diode I to the output side of the secondary electron multiplier means 1-+, and connects the anode side to the charging capacitor 4J-C and the analog means +5 +7
) Connected to JP point a side, condenser C (7) K
i'4i(,1 grounded.

Output side rzi of Arp 1 cog switch means 15! One end of the negative IJ resistor 8 is connected to the output terminal, and it is also connected to the analog-to-digital conversion circuit. The conversion circuit 16 controls 3) 1 circuit 1
7 is controlled by 11:I-.

Above configuration δ 4. The operation will be explained with reference to the waveform diagrams of FIGS. 3 and 4.

Figure 3 ia) shows the operation clock of sample 3, and the electron gun 1
The ultrashort electron beam pulse 2a irradiated by
) is driven by the pulse drive circuit 13 with J knee so that it is irradiated with a phase difference of 1'' and tn,
-] The pulse 2a caused the sample 3 to emit the third electron signal 4a (not shown in cl), and the scintillator 5 caused a human body to be emitted. At this time, the secondary electron signal emitted from sample 3 is averaged according to the conditions at that time. .

The above-mentioned secondary electron signal is multiplied by the secondary electrons in the second stage, and the secondary electrons are multiplied by the capacitor C of the analog 1 cog addition and averaging circuit 14.
Analog addition is performed as shown in the 31st pl fdl by charging the capacitor C by flowing a current of the capacity shown by the arrow. ”2 analog addition′! A: '51 uniform rotation 1/
& is the charging time constant &', l:11 for the current D.
'-'+'; and the discharge l14 constant is very large.

In order to read the signal added to the antenna 1-I charged in the capacitor C in this way, it is necessary to set the signal ff11 to I+:"I as shown in FIG. 4. In other words, as shown in FIG. At this point when the rich addition output 19 reaches the predetermined period 'rΔ, Analyzer 1: ] If the output means 15 is set to the 'PON' state 20, the period TB becomes a read period, and as shown by the curve 21, the charge of the capacitor C is changed to the iθ load. jJ (discharge through resistor 8.

41D (b+l) When the charged voltage of the capacitor C is applied to the analog-to-digital conversion circuit 16 as shown in FIG. Before the start of the process, the digital data 22 is manually output.

(7) Effects of the invention Since the present invention is constructed and operates as shown in Section 2,
13 can be done very easily compared to the digital type, and there is no need to operate the analog/IJ/digital converter circuit (the analog/IJ/digital conversion circuit does not have to be operated at the moment when the analog/cog switch means is turned on). It is extremely easy to design.

[Brief explanation of drawings]

Fig. 1 is a system diagram of the secondary electron beam detection device of IIL, and Fig. 2 is a system diagram of the secondary electron beam detection device of the present invention. FIG. 2 is a waveform diagram illustrating the operation of the secondary electron detection device. 1...electron gun, 2.1)...hyperelectron heembulus, 3...Akira Ujiki 1. 4.4a...Secondary electron, 5. Shin-f-rake,
6...Light pipe. 7...Claws 1 to 1, 5.6.7 - -order electron multiplier, 8. - Load resistance. 9.16...Analog-denkle change 1 exemption IF'jl
I flame.

Claims (2)

[Claims] (1) A detection means for detecting secondary electrons emitted from the sample, and an output obtained by adding the output of the detection means to an analog addition means having a small charging time constant and a large discharging time constant, and the analog addition means. What is claimed is: 1. A secondary electron detection device characterized in that the output of the load resistance means is applied to the load resistance means via an analog switch, and the output of the load resistance means is added by an analog-to-digital conversion means to take out a digital output. (2) An electron beam device that irradiates a sample in an operating state with a pulsed electron beam to emit secondary electrons according to the operating state of the sample, and multiplies the secondary electrons emitted from the sample. A secondary electron multiplier, a diode with a small charging time constant and a large discharging time constant, and a voltage that corresponds to the secondary electrons in an analog manner in addition to a ':1 ndenzer and a secondary electron multiplier. and an analog addition means for adding the output of the analog addition means to a load resistance.
Claim 1, characterized in that it has an analog stage for supplying the L-Zζ-analytic signal to the co-transformer conversion circuit to obtain the digitized detection output.
+Secondary electron detection device described in lri.