TECHNICAL FIELD

The present invention relates to a charged particle beam device.

BACKGROUND ART

In recent years, a scanning electron microscope (SEM) has been used for observing a surface and a cross section of a target sample in a wide range of fields. In the SEM, secondary electrons (SE) having relatively low energy from 0 to 50 eV and backscattered electrons (BSE) having a wide distribution from 50 eV to energy of a primary electron beam, which are generated by interaction between the primary electron beam and the sample, are detected to form an image.

The SE and BSE include different sample information. For example, the SE includes unevenness information and electrical potential information of a surface of the sample. On the other hand, the BSE includes composition information and crystal information of the sample. In SEM observation, it is important to suitably discriminate and detect signal electrons according to sample information that is desired to acquire. For example, in PTL 1, both an analog detector that integrates and detects an intensity (total energy of SE) of SEs incident on a scintillator in pixel units and a pulse count detector that counts the number of the BSEs in the pixel units are provided, and acquired signals from both detectors are suitably used, so that a pattern edge of the sample is emphasized successfully.

The BSE, one kind of signal electrons emitted from the sample, is an electron that is scattered backward in a process of scattering an incident electron, which is the primary electron beam, in the sample, and is re-emitted from the surface of the sample. A scattering probability is sensitive to a composition of the sample, and as an atomic number of a substance constituting the sample becomes larger, more BSEs are released. Further, since the BSE has energy higher than that of the SE, the BSE is also emitted from a place deeper than the SE.

Statistically, the electrons scattered from a deep portion of the sample have lost much energy from the time of incidence. As an example of utilizing this, an observation method in which only a component having low energy loss (Low Loss-BSE) is subjected to high-pass detection to emphasize information on a surface of a sample is widely practiced.

On the other hand, when band-pass detection can be performed on any BSE energy band, it is expected that a structure and composition distribution in a depth direction of a sample can be observed. For example, PTL 2 describes a pulse-height detector that enables detection of BSE energy by band-pass. The pulse-height detector detects a pulse-height value proportional to energy of each BSE incident on the detector, and histograms the pulse-height values to acquire a BSE energy spectrum. An energy band is freely set for the acquired energy spectrum, and a sum of frequency values within the set energy band is associated with a brightness value to obtain a band-pass image.

CITATION LIST

Patent Literature

PTL 1: JP-A-2016-170896PTL 2: JP-A-2013-33671

SUMMARY OF INVENTION

Technical Problem

As long as a BSE band-pass image (a brightness value is proportional to the number of electrons in a specified energy band) and a BSE intensity image (a brightness value is proportional to a product of the number of electrons and electron's energy) can be acquired at the same time, it is effective for sample analysis. For example, a method of determining a region of interest (ROI) from a BSE intensity image and acquiring a band-pass image of the ROI can be considered.

The pulse-height detector capable of acquiring a BSE band-pass image detects the energy of each BSE. Since the pulse-height detector includes information on the number of detected BSEs and the energy of each BSE, the pulse-height detector can output an intensity image. However, it is difficult to obtain an intensity image with a high S (signal)/N (noise) ratio by using the pulse-height detector.

The reasons are a response speed limit of an amplifier circuit of the pulse-height detector and an upper limit on a pulse number (the number of BSEs) that can be detected per unit time in order to improve the energy resolution. A current value of the BSE that can be detected by a single pulse-height detector is approximately 10 pA or less. On the other hand, in order to obtain a high S/N ratio in the intensity image, a BSE current value of 100 pA or more is desirable.

Therefore, a charged particle beam device capable of acquiring an image with a high S/N ratio based on an intensity of a charged particle from a sample and an image with high energy resolution based on a pulse-height value is desired.

Solution to Problem

A charged particle beam device according to an aspect of the disclosure includes: a charged particle beam source configured to generate a charged particle beam with which a sample is irradiated; a charged particle detection unit configured to detect a charged particle generated when the sample is irradiated with the charged particle beam; an intensity data generation unit configured to generate intensity data of the charged particle detected by the charged particle detection unit; a pulse-height value data generation unit configured to generate pulse-height value data of the charged particle detected by the charged particle detection unit; and an output unit configured to output a first image of the sample based on the intensity data and a second image of the sample based on the pulse-height value data.

Advantageous Effect

According to one aspect of the disclosure, an image with a high S/N ratio based on an intensity of a charged particle from a sample and an image with high energy resolution based on a pulse-height value can be acquired.

