JPS59114834A - Method for measuring deep impurity level or crystal defect level contained in semiconductor device - Google Patents

Abstract

PURPOSE:To enable to accurately and simply perform the measurement of impurity level or crystal defect level in a micro region or the evaluation of the distribution thereof inside the surface by a method wherein a semiconductor sample is intermittently irradiated with energy beams, and the time response of the variation of capacitances or currents of the sample generated thereby is analyzed by an ICTS method. CONSTITUTION:To perform the measurement by the ICTS method, the time variation of the capacitances (or curres) of the sample S under the equal temperature after electron beam irradiation is measured by means of a capacity meter (ampere meter) 3, the analog output therefrom is digitized by an A/D converter 5a in a wave form analyzer 5, inputted and memorized in a computer 5c having wave form analyzing ability via an interface 5b, thus performing the analysis of the deep impurity level or crystal defect level. Besides, in order to display the distribution inside the surface of the impurity level or crystal defect level in bi-dimensional manner, while scanning an electron beam EB 1', the brightness modulation 10 for a CRT 9 incorporated in an electron beam irradiation device 1 can be performed by the output of the wave form analyzer 5. A DLTS method can be performed while the temperature of the sample is varied by the constitution of this device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring deep impurity levels or crystal defect levels contained in a semiconductor. This allows information on internal distribution to be obtained accurately and easily with high positional resolution.

Currently, in semiconductor devices, precise evaluation of deep impurity levels or crystal defect levels contained in semiconductor materials is an extremely important issue. That is, these are ICs.
, the performance, deterioration, and yield of LSIs, light emitting elements f, semiconductor lasers, etc. are greatly affected.

Once upon a time, progress was extremely difficult as there was no suitable method for measuring deep impurity levels or crystal defect levels, but DL
TS method (Deep Level Transient
Significant progress has been made in these measurements since spectroscopy was proposed.

The DLTS method is used to measure deep impurity levels or crystal defect levels by changing the temperature of the sample to liquid nitrogen temperature (
77K) Ka6450K! While changing slowly and continuously, the time change ΔC(t) in the capacitance based on the depletion layer in the pn junction or Schottky junction is taken out as the time change in voltage, and the difference in the signal between two specific times is expressed as II
The L degree is plotted on an X-Y recorder, and thereby information on deep impurity levels or crystal defect levels can be obtained spectroscopy.

, - method uses a method of systematically changing the sample temperature, so it has the advantage that it is easy to measure impurity or crystal defect levels over a wide range of energy. It also has significant drawbacks, which are discussed below.

Of course, with this method, it is impossible to measure deep impurity levels in minute regions or evaluate the in-plane distribution of crystal defect levels. This is because, although it is necessary to attach an electrode to the sample in this method, the positional resolution is determined by the size of this electrode, and the size of this electrode is usually a circular shape with a diameter of 0°5 to 11 IIm. Therefore, the required 07M fraction iv ability of 0, 1 to 1 OkI11 cannot be satisfied at all.

In an attempt to solve this problem, we applied the DLTS method to '2.
A scanning DLTS method that combines Vf beam irradiation has been proposed in the past. In this method, by fixing the irradiation position of the electron beam at the - point, measurements can be made in a specific minute area, while by scanning the sample surface, J2, with the beam, information about the in-plane distribution can also be obtained. . Even in this case, a fixed electrode is required to extract the measurement signal, but the information obtained is from an electron beam! @It is from the position where it is being shot. Namely, Kameko Bee L.

Since the diameter of the beam can be reduced to less than 200A, the positional resolution is significantly improved.

However, even the scanning DLTS method encounters the disadvantages that the DLTS method has. That is, as mentioned above, 'DLT
In the S method, in order to change the temperature, a sample stage with a heating and cooling device must be inserted into the high vacuum layer, which is not desirable in itself. When the temperature is changed, thermal expansion or contraction of the sample stage occurs continuously. Therefore, the irradiation position of the electron beam may actually move during measurement.
The more you narrow down the beam diameter in an attempt to increase the positional resolution, the more likely it is that this problem will increase. It can be said that the time constant of the time change of sample force No. 4a of the sample force 1 etc. is approximately every 1 second, and when the force becomes strong (the impurity level of the hammer) Hirokabe becomes quite deep), DLTS 1 husband (Koyoru 4) 1 fixed C
±Become incapacitated. Integrating and averaging the periodically occurring 7-Kurres 1 (No. 8 with all constants)
/) This is because the sample temperature changes during this period, and the relationship between the sample temperature and the signal becomes clear.

In order to overcome these drawbacks of the DLTS method, ICTS (Industrial Capacity
cs engineering ransient S pectoros
copy) It has been thoroughly considered and put into practical use. Using this method, it is possible to obtain spectroscopic information on deep impurity levels or crystal defect levels without changing the temperature and with a constant density of the sample.7. You can get it easily.

However, with only this conventional ICTS method, t±, Di LT
Similar to the S method, high positional resolution and information within 1 meter cannot be obtained.

The present invention was made based on the above findings, and includes an electron beam,
ICT using energy beams such as light beams
The S method is intended to provide an accurate and easy way to measure impurity levels or crystal defect levels in the ultra-fine I'\ region and their in-plane distribution 1). It is something to rub.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings of Xu H.

Figure 1 shows how the electron beam is transmitted from the river (X to γ
By emphasizing the device configuration for the first embodiment, it is possible to apply not only the CT S iJ: which is the object of the present invention, but also the DLTS method with the conventional configuration. It becomes a device that can also be used to record history17).

The electron beam irradiation device 1 is a well-known L electron scan electron microscope provided with a blanking function for intermittent electron beam EB. Sample stage 2 (±, DL that can be used in combination with the present invention) for the sample S placed in the electric beam irradiation device 1
For use in the TS method, the severity of the sample 7 can be changed.

from a sample with a pn junction or main junction,
＋ (or change when the voltage is υ is measured by a capacitance meter (nu is an ammeter) 3
waveform analyzer 5 and DL for ICTS method.
The signal is sent to an analog measuring device 6 for the TS method.

jfl fIH pulse generator 4 is a Plankinck electrician 44
This is for sending voltage pulses for blanking the electron beam to a.

To perform measurements using the ICTS method, the time change in the volume of the sample S (or Dij ) at the same height after electron beam irradiation is measured using a capacitance meter (?, 7. is current λ1). Fixed.

The analog output from now on will be sent to the A/D in the J molding analysis device 5.
The converter 5a converts the data into digital data, and the converter 5a has a waveform analysis capability via the surface 5b.
The information is input into the machine, stored, and analyzed for deep impurity levels or crystal defect levels.

In addition, in order to display the in-plane distribution of impurity levels or crystal defect levels in a -dimensional manner, while the electron beam EB is traveling, the output from the waveform analyzer 15 is used as the electron beam irradiation device l.
It is only necessary to perform brightness modulation of the CRT 9 incorporated in the CRT 9.

The DLTS method can be carried out using the apparatus configuration described above while changing the sample temperature. That is, in order to perform measurements using the normal analog DLTS method, the sample temperature must be varied.

Double box force output from capacitor 3.

The signal is input to an analog measuring device 6 such as a two-couple amplifier or a signal receiver, and the signal is measured at two specific points in time.

If the signal difference between t2 is determined and sent to the Y-axis of the X-Y recorder 8, and the cutting edge of a sample temperature sensor such as a thermocouple is introduced on the X-axis and the X-axis, measurement and analysis using the DLTS method can be performed. can be done. Also, the output from the analog measuring device 6
By performing brightness modulation in RT9, it is possible to obtain a one-dimensional image of the in-plane distribution. When the sample temperature needs to be controlled, the waveform analyzer 5 is used. In addition, analog DLTS
It is also possible to perform the ICTS method analogously with legal equipment.

FIG. 2 shows a configuration example of an apparatus for carrying out the present invention using a light beam instead of an electron beam. Components corresponding to those shown in the first diagram will be described with the same reference numerals, but the blanking pulse from the pulse voltage generator 4 directly acts on the light source 10 to interrupt the light beam LB. It is supposed to be done. The light beam is irradiated onto the sample S in vacuum or air through a transparent glass plate or the like.

The sample stage 2 is configured using a known technique so as to be movable three-dimensionally, so that the in-plane distribution can be measured with nf capability. A two-dimensional image of the in-plane distribution can be obtained on the CRT 9. Note that if scanning is possible by swinging the light beam LB, the movability of the sample stage is used for rough positioning of the sample.

Other analysis methods are the same as in the first embodiment. Of course, in the case of the second embodiment as well, the analysis using DLTSθma is
This can be done by adding an analog analyzer as in the first embodiment. Conversely, it is also possible to digitally perform analysis using the DLTS method using the apparatus shown in the second figure.

Furthermore, even if a known .r-on beam generator is used as the energy beam generator in the present invention, measurement with high positional resolution on the order of gm is possible.

In addition, in Figure 2, 7 is a display.

As detailed above, according to the present invention, defects in the conventional example,
In other words, the electron beam irradiation position may shift during measurement, or it may be impossible to measure very deep impurity levels or crystal defect levels near the small flame of the cap, which has a large time constant. It is possible to eliminate defects such as oscillations, etc., and because the measurement is performed under uniform vibration, extremely accurate measurements can be performed. Another great advantage is that svectoscopic information can be obtained accurately even at room temperature. In any case, the enhancement of the present invention is possible because it is possible to measure deep impurity levels or crystal defect levels in extremely small regions in semiconductors, and it is also possible to evaluate in-plane distribution. is clearly 6°

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of an apparatus for carrying out the method of the present invention. In the figure, ■ is an electron beam irradiation device, 2 is a sample h, 3 is a meter or ammeter, 5 is a waveform analyzer, 6 is an analog measuring device, and 10 is a light source, and is a designated representative.

Claims (1)

[Claims] A power method for measuring deep impurity levels or crystal defect positions contained in a semiconductor, which comprises: A method for measuring deep impurity levels or crystal defect levels contained in a semiconductor, characterized by analyzing the time response of the capacitance or current change of the sample that occurs using an ICTS method.