阅读说明：本技术 半导体材料的阴极荧光成像测试方法 (Cathode fluorescence imaging test method for semiconductor material ) 是由 许蕾蕾 黄增立 刘通 丁孙安 于 2019-01-12 设计创作，主要内容包括：本发明公开了一种半导体材料的阴极荧光成像测试方法,其包括：制备待测的半导体材料样品；应用聚焦离子束切割工艺对所述半导体材料样品进行切割,形成厚度为纳米尺寸量级的测试样品；在具有阴极荧光光谱仪的扫描电子显微镜中对所述测试样品进行阴极荧光成像测试。本发明将待测样品切割为厚度为纳米尺寸量级的测试样品(透射电子显微镜(TEM)超薄样品)在扫描电子显微镜(SEM)中进行阴极荧光成像测试,可以提升使用SEM设备进行阴极荧光成像的空间分辨率。(The invention discloses a cathode fluorescence imaging test method of a semiconductor material, which comprises the following steps: preparing a semiconductor material sample to be detected; cutting the semiconductor material sample by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size; the test sample was subjected to a cathodofluorescence imaging test in a scanning electron microscope with a cathodofluorescence spectrometer. According to the invention, the sample to be tested is cut into the test sample (transmission electron microscope (TEM) ultrathin sample) with the thickness of nanometer size magnitude, and the cathodofluorescence imaging test is carried out in the Scanning Electron Microscope (SEM), so that the spatial resolution of cathodofluorescence imaging carried out by using SEM equipment can be improved.)

1. A cathode fluorescence imaging test method of a semiconductor material is characterized by comprising the following steps:

preparing a semiconductor material sample to be detected;

cutting the semiconductor material sample by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size;

the test sample was subjected to a cathodofluorescence imaging test in a scanning electron microscope with a cathodofluorescence spectrometer.

2. The method for cathodic fluorescence imaging testing of semiconductor material as defined in claim 1, wherein said cutting said semiconductor material sample using a focused ion beam cutting process to form a test sample having a thickness on the order of nanometers specifically comprises:

providing a cutting device having a focused ion beam system;

welding the semiconductor material sample to the cutting device sample carrier web;

and cutting the semiconductor material sample in the cutting equipment by using a focused ion beam cutting process, and forming a test sample with the thickness of nanometer size on the sample carrying net.

3. The cathode fluorescence imaging test method of the semiconductor material according to claim 2, wherein the thickness of the test sample is 10 to 100 nm.

4. The method for cathodofluorescence imaging testing of semiconductor materials according to claim 2, wherein the cathodofluorescence imaging testing of the test sample in a scanning electron microscope with a cathodofluorescence spectrometer comprises in particular:

connecting the test sample to a sample stage of the scanning electron microscope through the sample carrying net and suspending the test sample at the edge of the sample stage;

emitting an electron beam from the scanning electron microscope toward the test sample to excite cathodofluorescence at a surface of the test sample;

and acquiring the cathode fluorescence by the cathode fluorescence spectrometer and imaging according to the cathode fluorescence.

5. The method for testing cathode fluorescence imaging of semiconductor material according to claim 4, wherein the accelerating voltage of the electron beam emitted from the scanning electron microscope to the test sample is 20 to 70kV, and the beam spot size of the electron beam is 0.5 to 10 nm.

6. The method for testing cathode fluorescence imaging of semiconductor material according to claim 4, wherein the temperature of the sample stage is 5-273K when the cathodofluorescence imaging test is performed on the test sample.

7. The method for cathodofluorescence imaging testing of semiconductor material according to claim 4, wherein the sample carrier is fixedly connected to the sample carrier of the scanning electron microscope by a conductive adhesive.

8. The method for cathodofluorescence imaging testing of semiconductor materials according to claim 4, wherein the scanning electron microscope emits an electron beam to the test sample in a line scan or a surface scan manner.

9. The cathode fluorescence imaging test method for semiconductor materials according to claim 4, wherein a CCD detector is arranged in the cathode fluorescence spectrometer, and the cathode fluorescence is collected and acquired by the CCD detector and subjected to spectral imaging.

10. The method for cathodofluorescence imaging testing of semiconductor material according to any of claims 1-9, wherein the sample of semiconductor material comprises a substrate and a semiconductor heterostructure formed on the substrate, the semiconductor heterostructure comprising a plurality of semiconductor layers arranged in sequence in a first direction; cutting the semiconductor material sample along the first direction by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size magnitude in the second direction; wherein the first direction and the second direction are perpendicular to each other.

Technical Field

The invention relates to the technical field of semiconductor material testing, in particular to a cathode fluorescence imaging testing method for a semiconductor material.

Background

When interacting with a sample of a material to be measured, a high-energy incident electron beam excites the sample to generate various signals, such as secondary electrons, backscattered electrons, X-rays, cathodoluminescent fluorescence (C L), and the like, the so-called cathodoluminescent fluorescence is light radiation generated by electron beam bombardment of the material to be measured, and the electron bombardment makes electrons in a valence band of the material jump to a conduction band to be an excited state, and the electrons return to the valence band to be recombined and are accompanied by photon radiation, namely called cathodoluminescent fluorescence.

The early C L imaging technology was combined with Scanning Electron Microscopy (SEM) to form an SEM-C L imaging system, see "Muir M D, Grant P R (1974) ch.9-cathodophyllinessence. in: Holt D B, et al (eds.)," Quantitative Scanning Electron microscopy, (Academic Press, new york) ". the spatial resolution of SEM-C L imaging system is mainly affected by three factors, the beam spot size, the Electron-hole generation area and the carrier diffusion area.

At present, in order to improve the spatial resolution of C L imaging and obtain high quality spectral images, it has been developed that the C L imaging technique is combined with a Transmission Electron Microscope (TEM) to form a TEM-C L imaging system, see Sekiguchi T (1999) Development of low energy emission spectroscopy and its application to the study of ZnO of mrs Proc.588:75, and the TEM-C L imaging system mainly uses an ultra-thin sample to reduce the generation range and diffusion length of carriers, and the higher the acceleration voltage of the Electron beam is advantageous to improve the spatial resolution of the sample due to the thinness of the sample, so that the TEM-C L imaging system improves the spatial resolution of C L imaging, and the TEM-C L imaging system has problems that on the one hand, the-C L system is more complex, the technical difficulty is large, and the equipment cost is increased, and the expensive TEM-C3580 is generally set as the acceleration voltage of the sample to be measured is generally not damaged (300 kV).

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a cathode fluorescence imaging test method for a semiconductor material, so that the spatial resolution of cathode fluorescence imaging performed by using an SEM-C L imaging system is improved, and the cost is reduced compared with that of a TEM-C L imaging system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for cathodofluorescence imaging testing of semiconductor materials, comprising:

preparing a semiconductor material sample to be detected;

cutting the semiconductor material sample by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size;

the test sample was subjected to a cathodofluorescence imaging test in a scanning electron microscope with a cathodofluorescence spectrometer.

Wherein the step of cutting the semiconductor material sample by using the focused ion beam cutting process to form a test sample with a thickness of nanometer dimension specifically comprises the steps of:

providing a cutting device having a focused ion beam system;

welding the semiconductor material sample to the cutting device sample carrier web;

and cutting the semiconductor material sample in the cutting equipment by using a focused ion beam cutting process, and forming a test sample with the thickness of nanometer size on the sample carrying net.

Wherein the thickness of the test sample is 10-100 nm.

Wherein the cathodofluorescence imaging test of the test sample in a scanning electron microscope with a cathodofluorescence spectrometer specifically comprises:

connecting the test sample to a sample stage of the scanning electron microscope through the sample carrying net and suspending the test sample at the edge of the sample stage;

emitting an electron beam from the scanning electron microscope toward the test sample to excite cathodofluorescence at a surface of the test sample;

and acquiring the cathode fluorescence by the cathode fluorescence spectrometer and imaging according to the cathode fluorescence.

The accelerating voltage of the electron beam emitted to the test sample by the scanning electron microscope is 20-70 kV, and the beam spot size of the electron beam is 0.5-10 nm.

When the cathodic fluorescence imaging test is carried out on the test sample, the temperature of the sample carrying platform is 5-273K.

The sample carrying net is fixedly connected to a sample carrying platform of the scanning electron microscope through conductive adhesive.

Wherein the scanning electron microscope emits an electron beam to the test sample in a line scanning or surface scanning manner.

And a CCD detector is arranged in the cathode fluorescence spectrometer, and the cathode fluorescence is collected and acquired by the CCD detector and is subjected to spectral imaging.

Wherein the semiconductor material sample comprises a substrate and a semiconductor heterostructure formed on the substrate, the semiconductor heterostructure comprising a plurality of semiconductor layers arranged in sequence in a first direction; cutting the semiconductor material sample along the first direction by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size magnitude in the second direction; wherein the first direction and the second direction are perpendicular to each other.

According to the cathode fluorescence imaging test method for the semiconductor material, provided by the embodiment of the invention, the sample to be tested is cut into the test sample (TEM ultrathin sample) with the thickness of nanometer size magnitude, and the cathode fluorescence imaging test is carried out in the Scanning Electron Microscope (SEM), so that the spatial resolution of cathode fluorescence imaging carried out by using the SEM-C L imaging system can be improved, and the cost is reduced compared with that of a TEM-C L imaging system.

Drawings

FIG. 1 is a process flow diagram of a cathodic fluorescence imaging test method in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a semiconductor material sample to be tested according to an embodiment of the present invention;

FIG. 3 is a flow chart of a process for dicing a semiconductor material sample to be tested according to an embodiment of the present invention;

FIG. 4 is a schematic structural view of a test specimen having a thickness on the order of nanometers in an embodiment of the present invention;

FIG. 5 is a process flow diagram of a cathodofluorescence imaging test performed on a test sample in accordance with an embodiment of the present invention;

FIG. 6 is an exemplary illustration of a cathodofluorescence imaging test performed on a test sample in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described in accordance with the drawings are exemplary only, and the invention is not limited to these embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.

The embodiment provides a cathode fluorescence imaging test method of a semiconductor material, and referring to fig. 1, the cathode fluorescence imaging test method includes the steps of:

and S10, preparing the semiconductor material sample to be tested.

Specifically, in the embodiment, as shown in fig. 2, the semiconductor material sample 1 includes a substrate 10 and a semiconductor heterostructure 20 formed on the substrate 10, the semiconductor heterostructure 20 includes a plurality of semiconductor layers a, b, c, d, e, f and g sequentially arranged in a first direction (e.g., X direction in fig. 2), and the thickness of each semiconductor layer a, b, c, d, e, f and g in the first direction can be set within a range of 1-10 nm. The dimension of the semiconductor heterostructure 20 in a second direction (e.g. the Y-direction in fig. 2) mutually perpendicular to the first direction is typically above the order of millimeter dimensions.

It should be noted that in other embodiments, the semiconductor heterostructure 20 may be provided with only one semiconductor layer, or with quantum wells or quantum dots. Further, the semiconductor material sample 1 may also be a bulk material.

And S20, cutting the semiconductor material sample by using a focused ion beam cutting process to form a test sample with the thickness of nanometer size.

Specifically, referring to fig. 3, the step S20 specifically includes:

s21, providing the cutting device with a focused ion beam system.

A Focused Ion Beam (FIB) technology is the most compatible technology with a semiconductor process, and thus, in the semiconductor integrated circuit manufacturing industry, the Focused Ion beam technology is widely applied to aspects of micro-nano-scale Ion beam etching, Ion beam deposition, Ion implantation, Ion beam material modification, and the like. One of the important uses of focused ion beam technology is the preparation of ultra-thin samples for Transmission Electron Microscope (TEM) observation by ion beam cutting.

And S22, welding the semiconductor material sample to the cutting device sample carrying net. The sample support mesh is typically a semi-circular copper mesh.

S23, cutting the semiconductor material sample in the cutting equipment by using a focused ion beam cutting process, and forming a test sample with the thickness of nanometer size on the sample carrying net. Specifically, referring to fig. 2 and 4, the semiconductor material sample 1 is cut along the first direction (X direction) using a focused ion beam cutting process to form a test sample 1a having a thickness in the second direction (Y direction) on the order of nanometers. Wherein, the thickness of the test sample 1a can be set within the range of 10 to 100 nm.

And S30, performing a cathode fluorescence imaging test on the test sample in a scanning electron microscope with a cathode fluorescence spectrometer, wherein the scanning electron microscope is provided with the cathode fluorescence spectrometer, so that an SEM-C L imaging system is formed.

Specifically, referring to fig. 5 and 6, the step S30 specifically includes:

s31, connecting the test sample 1a to the sample stage 4 of the scanning electron microscope 3 through the sample mesh 2 and suspending the test sample 1a at the edge of the sample stage 4. In a specific embodiment, the sample carrier 2 may be fixedly connected to the sample carrier 4 by using a conductive adhesive.

S32, emitting an electron beam 5 from the scanning electron microscope 3 toward the test sample 1a to excite cathodofluorescence 6 on the surface of the test sample 1 a. Wherein the scanning electron microscope 3 may emit an electron beam to the test sample 1a in a line scanning or surface scanning manner.

Preferably, the accelerating voltage of the electron beam emitted from the scanning electron microscope 4 to the test sample 1a is 20 to 70kV, and the beam spot size of the electron beam is 0.5 to 10 nm. Further, when the cathodofluorescence imaging test is performed on the test sample 1a, the temperature of the sample carrying platform 4 is 5-273K.

S33, acquiring the cathode fluorescence 6 by the cathode fluorescence spectrometer (not shown in fig. 6) and imaging according to the cathode fluorescence 6. The structural parameter information of the semiconductor material sample to be measured, such as dislocation, defect and the like of the semiconductor material sample, can be obtained through spectral imaging.

In a specific scheme, a CCD detector is arranged in the cathode fluorescence spectrometer, and the cathode fluorescence is collected and acquired by the CCD detector and is subjected to spectral imaging.

It should be noted that, as shown in fig. 6, a parabolic reflecting mirror 7 is further disposed between the test sample 1a and the scanning electron microscope 3, and the reflecting mirror 7 reflects the cathode fluorescence 6 toward the cathode fluorescence spectrometer so that the cathode fluorescence spectrometer can collect the cathode fluorescence. Wherein, the reflecting mirror 7 is provided therein with a through hole through which the electron beam 5 can be made incident on the test specimen 1 a.

According to the cathode fluorescence imaging test method for the semiconductor material, the sample to be tested is cut into the test sample (the TEM ultrathin sample) with the thickness of the nanometer size order, and the cathode fluorescence imaging test is carried out in the Scanning Electron Microscope (SEM), so that the generation range and the diffusion length of carriers can be reduced by the TEM ultrathin sample, the spatial resolution of cathode fluorescence imaging by using the SEM-C L imaging system is improved, and the cost is reduced compared with that of a TEM-C L imaging system.

In addition, because the TEM ultrathin sample is used, the acceleration voltage of an electron beam emitted by the SEM (between the acceleration voltage of the conventional SEM-C L system and the acceleration voltage of the TEM-C L system) can be increased during testing, on one hand, for the ultrathin sample, the increase of the acceleration voltage is beneficial to improving the spatial resolution and obtaining a higher-quality spectral image, and on the other hand, the acceleration voltage is smaller than the acceleration voltage of the TEM-C L system, so that the damage of the sample to be tested due to the overlarge acceleration voltage of the electron beam is avoided.

Further, in the cathode fluorescence imaging test method provided in the above embodiment, during testing, the TEM ultrathin sample is suspended at the edge of the sample stage, so that interference caused by cathode fluorescence generated by exciting the sample stage by electron beams transmitting the ultrathin sample can be avoided, and the accuracy of testing the material to be tested can be improved.

The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.