JPH05258693A - Scanning electron microscope - Google Patents

Abstract

PURPOSE:To automatically set the unsensitive time generated in an X-ray detector to a proper ratio (20%-30%), in a scanning electron microscope having an energy dispersing type X-ray analyzing device, and realize highly precise analyses extending from metals and ceramics to polymer materials. CONSTITUTION:The unsensitive time generated in an X-ray detector 8 is transferred from a pulse-height analyzer 14 to a CPU 16. In the CPU 16, the data for controlling a focusing lens power source 20 in conformation to the increase and decrease of the unsensitive time is transferred to a D/A converter 17, whereby the probe current is automatically set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope equipped with an energy dispersive X-ray analyzer, and more particularly, to an appropriate ratio of dead time generated by an X-ray detector (20% to 20% of the time required for analysis). 30%) can be automatically set,
It realizes highly accurate analysis from metals and ceramics to polymer materials.

[0002]

2. Description of the Related Art Conventionally, when X-ray analysis is performed by an energy dispersive X-ray analyzer, if the ratio of dead time to the analysis time becomes large, problems such as deterioration of energy resolution and generation of pseudo peaks occur. Occurs, and the analysis accuracy decreases. Therefore, conventionally, the probe current has been set by manually adjusting the convergent lens current while visually reading the dead time with a meter or the like.

[0003]

However, in the above-mentioned prior art, the dead time that changes when the sample is changed or the analysis position is changed is troublesome to manually set the convergent lens every time the analysis is performed. There was An object of the present invention is to provide means for controlling the convergent lens current to automatically set the probe current for an arbitrary dead time.

[0004]

The above object can be easily achieved by providing a mechanism for reading the dead time of the detector, digitizing it, and performing arithmetic processing by a computer to control the convergent lens current.

[0005]

The function of the present invention is to monitor the dead time,
The probe current is changed by controlling the converging lens current so that the dead time is in proportion to the predetermined analysis time.

[0006]

FIG. 1 shows an embodiment of the present invention. The X-ray 7 is excited when the sample 6 is irradiated with the electron beam 3 in a vacuum.
The excited X-rays 7 enter the X-ray detector 8 and are converted into electric charges corresponding to the energy of the X-rays 7 and are collected therein. The X-ray detector 8 and preamplifier 9 are mounted in a cryostat 10 and sealed in a vacuum to improve energy resolution. Here, when a large amount of X-rays 7 are incident, the dead time generated in the X-ray detector 8 becomes long,
Since this causes deterioration of resolution and a pseudo peak, the amount of X-rays 7 generated is changed to an appropriate value (usually
Depends on acceleration voltage and sample. ) Must be set. Therefore, in order to control the probe current arbitrarily with the length of the dead time, the dead time is measured from the wave height analyzer 15 to the CP.
U16 is read and digitized. Since the probe current is changed by increasing / decreasing the converging lens current, the length of the read dead time is set to an appropriate ratio (2 of the analysis time).
0% to 30%), the CPU 16 performs arithmetic processing, transfers the data to the D / A converter 17, and controls the converging lens power source 20. This makes it possible to automatically set the probe current corresponding to the dead time.
Conventionally, the dead time is visually read from the CRT 15 and the converging lens current is manually set by the variable resistor 19.

[0007]

According to the present invention, the dead time generated in the X-ray detector can be automatically set to an appropriate ratio (20% to 30%). This has the effect of simplifying line analysis and enabling highly accurate analysis of metals, ceramics, and polymeric materials.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

[Explanation of symbols]

1 ... Scanning electron microscope, 2 ... Electron gun, 3 ... Electron beam, 4
... Converging lens, 5 ... Objective lens, 6 ... Sample, 7 ... X-ray,
8 ... X-ray detector, 9 ... Preamplifier, 10 ... Cryostat, 11 ... Dewar, 12 ... Liquid nitrogen, 13 ... Linear amplifier, 14 ... Wave height analyzer, 15 ... CRT, 16 ... CP
U, 17 ... D / A converter, 18 ... Preamplifier, 19 ... Variable resistance, 20 ... Condenser lens power supply.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takeo Suzuki 832 Nagakubo, Horiguchi, Katsuta City, Ibaraki Prefecture

Claims (1)

[Claims] 1. A scanning electron microscope equipped with an energy dispersive X-ray analyzer, comprising means for automatically setting a probe current corresponding to an arbitrary dead time.