JPH04107839A - Foreign material detector - Google Patents

Abstract

PURPOSE:To detect very fine contaminative organic substance and to make the rapid and accurate fixation of the substance by diffracting spectrally the fluorescence emitted by the organic substance which has been exited by an electron beam. CONSTITUTION:A sample 1 is stored in a vacuum chamber 2. An electron beam, being generated by an electron gun 3, is deflected by a scanning circuit 5, whereas light is allowed to enter a filter 10 to be incident on the surface of the sample 1 through the window glass 8 and an optical lens 9. Due to the filter 10, only the light of a specific wavelength enters a photomultiplier 11 where it is converted into electric signals. The filter 10 can be selected according to the wavelength of contaminative organic substance. Signals from a secondary electron detector 6 produce an secondary electron image of the surface of the sample on a display 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a foreign matter detection device, and more particularly to a foreign matter detection device that detects and fixes contaminant organic matter adhering to a sample.

[Conventional technology]

Conventionally, this type of contaminant organic matter detection device is an Auger electron spectrometer (Auger electron spectrometer) that irradiates a sample with an electron beam and detects Auger electrons from the contaminant organic matter.
tron 5pectro 5cope, hereafter flAEs
There are also fluorescent microspectrometers that can irradiate a sample with ultraviolet rays, observe the fluorescence from contaminated organic matter, and perform spectroscopy of the fluorescence.

In AES, a sample is placed in a vacuum chamber, and an electron beam accelerated to about 10 to 30 keV is irradiated onto the sample. When this electron beam is irradiated onto a contaminated organic substance, atoms such as carbon and hydrogen constituting the organic substance become excited, and when the excited electrons in these atoms return to the specified order, they emit Auger electrons. The energy of this Auger electron is uniquely determined by the type of the atom, so by obtaining the energy dispersion spectrum of this Auger electron, it is possible to obtain the abundance ratio of the elements that make up the contaminant organic matter. This is a device that can be fixed.

In addition, in a fluorescence microspectroscopy device, a sample is irradiated with ultraviolet light from a high-pressure mercury lamp or the like through an excitation filter with wavelengths selected. In an organic substance, when electrons excited by this incident light return to a normal state via an intermediate order, luminescent development occurs.

Since the spectrum of this light emission has a spectrum unique to the organic substance, it is possible to fix the contaminant organic substance by comparing it with the spectrum of a known substance. It is also possible to know the distribution of contaminant organic matter on a sample by observing the sample under ultraviolet light using a detection filter that passes only a specific fluorescence peak wavelength.

[Problem to be solved by the invention]

The conventional contaminant organic matter detection device described above has the following problems. First, in the former AES,
Although it is possible to determine the abundance ratio of the elements that make up the organic contaminants, that is, the composition of the organic matter, it is impossible to analyze the bonding state, indicating that there were two organic substances with almost the same composition ratio but completely different bonds. In this case, these two cannot be determined to be different.

On the other hand, in the latter type of fluorescence order differential spectrometer, the ultraviolet rays used as excitation light are narrowed down by an optical method, so the beam size can be narrowed down to only a few micrometers in diameter. If two different types of organic contamination exist at a location, the emission spectra from these two types of organic matter cannot be separated, and fixation of the organic matter becomes impossible. Further, when the thickness of the contaminant organic matter is thin, the excitation ultraviolet light is difficult to be absorbed into the organic matter, resulting in a problem that the fluorescence intensity is weak and sufficient intensity for detection cannot be obtained.

An object of the present invention is to provide a foreign object detection device that eliminates such drawbacks.

[Means to solve the problem]

The foreign matter detection device of the present invention is a foreign matter inspection device that detects foreign matter on a semiconductor substrate by injecting an electron beam onto a sample in a vacuum, and includes means for spectroscopy of fluorescence from contaminated organic matter excited by the electron beam. , and a detector that detects the spectroscopic fluorescence.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a contaminant organic substance detection apparatus according to an embodiment of the present invention. As shown in the figure, this foreign object detection device consists of a vacuum chamber 2 that houses a sample 1, and a vacuum chamber 2 that accommodates a sample 1.
An electron gun 3 that is built in and irradiates the sample 1 with an electron beam, a scanning circuit 5 that deflects and scans the electron beam on the sample surface, and a secondary electron detector 6 that captures secondary electrons generated from the sample 1. , a fluorescence detector 7 that detects fluorescence generated from contaminant organic matter in sample 1, and a CPU 4 that inputs and processes the secondary electron and fluorescence spectrum signals from sample 1;
It is comprised of a display 12 that inputs arithmetic processed signals and displays the presence of organic contaminants on the sample surface. The fluorescence detector 7 also includes a glass window 8 attached to the vacuum chamber 2, an optical lens 9 that converges fluorescence, a filter 10 that separates the fluorescence spectrum, and converts the fluorescence spectrum light that has passed through the filter 10 into an electronic signal. It is composed of a photomultiplier tube 11 for conversion.

FIGS. 2 and 3 are diagrams showing the state of the sample surface displayed on the monitor.

Next, the operation of this foreign object detection device will be explained. First, a sample 1 is stored in a vacuum chamber 2, an electron beam is generated from an electron gun 3, and the beam is deflected and scanned by a scanning circuit 5. Then, the zero-order light incident on the filter 10 is
As a result, only light of a specific wavelength enters the photomultiplier tube 11 and is converted into an electrical signal. Note that this filter 10 can be selected according to the wavelength of the contaminant organic matter to be observed. For example, if you want to observe contaminants caused by positive photoresist, you can select a filter that passes light at a wavelength of 600 nm. good.

Next, a secondary electron image of the sample surface is obtained on the display 12 by a signal from the secondary electron detector 6 sent to the CPU 4. In this secondary electron image, for example, as shown in FIG. 2, a plurality of contamination particles A are present.

B and C are projected adjacent to each other with a distance of about 1 μm. It is assumed that contamination particles A and C are organic contamination from positive photoresist, and contamination particle B is organic contamination from human skin. In this contaminated state, if a filter with a wavelength of 600 nm, which is the fluorescence peak wavelength of the positive photoresist, is selected, the fluorescence image will be as shown in Figure 3.
It can be visualized that among the contamination particles A, B, and C, only A and C are positive photoresist. Fourth
The figure is a block diagram of a foreign object detection device showing another embodiment of the present invention. As shown in the figure, in this foreign object detection device, wavelength selection of a fluorescence detector 7 for detecting fluorescence is performed by spectroscopy using a mirror 13 and a diffraction grating 14 instead of using the filter described above. This diffraction grating 14 is outstanding.
is controlled by a wavelength control circuit 15 connected to the CPU 4, and any wavelength can be selected.

By scanning the electron beam from the electron gun 1, this foreign matter detection device can detect the distribution of contaminant organic matter shown in FIG. 3, as in the previous embodiment. Furthermore, in this embodiment, the diffraction grating is irradiated with a fixed electron beam onto a certain organic contaminant, for example, contaminant particles A in FIG.
By rotating 4, it is possible to obtain a fluorescence spectrum from the contaminant organic matter, and more accurate fixation is possible than in the example.

〔Effect of the invention〕

As explained above, the present invention is equipped with a means for irradiating an electron beam onto a material and selectively detecting the fluorescence from the organic contamination when there is an organic contaminant. It is possible to detect organic contaminants, and by comparing this fluorescence spectrum with the fluorescence spectra of known organic substances, it is possible to obtain a foreign substance detection device that can reliably fix contaminant organic substances in a relatively short period of time. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a foreign object detection device showing one embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the state of a document surface displayed on a monitor, and FIG. 4 is a block diagram of a foreign object detection device showing an embodiment of the present invention. FIG. 2 is a block diagram of a foreign object detection device showing an example. 1... Material, 2... Vacuum chamber, 3... Electron gun, 4... CPU, 5... Scanning circuit, 6... Secondary electron detector, 7... Fluorescence detector , 8... glass window, 9
... Optical lens, 10... Filter, 11... Photomultiplier tube, 12... Display, 13... Mirror 14... Diffraction grating, 15... Wavelength control circuit.

Claims (1)

[Claims] In a foreign matter inspection device that detects foreign matter on a semiconductor substrate by injecting an electron beam onto a sample in a vacuum, there is provided a means for spectroscopy of fluorescence from contaminant organic matter excited by the electron beam, and a means for detecting the spectroscopic fluorescence. A foreign object detection device comprising: a detector.