JPH08313460A - Method and equipment for inspecting semiconductor - Google Patents

Abstract

PURPOSE: To obtain a method and equipment for analysis which enable specification of a source of generation of a particle (impurity particle) being present under the surface or a thin film of a semiconductor substrate by determining the composition and structure of the particle. CONSTITUTION: A particle 6 on a semiconductor sample 2 is found out by using an X-Y stage 3 whereon the semiconductor sample 2 is set, a continuous visible light laser beam 1 provided in the direction perpendicular to the semiconductor sample 2 and a detector 4 for detecting a laser scattered light, and the composition and structure of the particle are determined by using a focused ion beam 7, a high-luminance ultraviolet laser beam 9 and an electron beam 5 of which the optical axes are so regulated as to have the same origin as the continuous visible light laser beam 1 on the surface of the semiconductor sample 2 and an analyzer 8 having a time-of-flight mass spectrometer and a fluorescent X-ray analyzer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure analysis method for semiconductor devices and an evaluation method and device for impurity particles on a semiconductor substrate.

[0002]

2. Description of the Related Art With the recent high integration of semiconductor devices, the device structure has been three-dimensionally miniaturized and complicated. Therefore, detailed observation of the failure location and compositional analysis have been highlighted as very important elemental technologies for drastic improvement of the manufacturing process. One of the major causes of device malfunctions is the generation of particles during the manufacturing process and transportation.

The conventional particle evaluation methods include particle positioning performed by using a particle positioning device that is a combination of a visible light laser and an XY stage.
Scanning electron microscope and electron beam excitation X-ray fluorescence analyzer (S
EM-EDX) for determining the particle composition. With this method, it is possible to obtain information on which process the particles are generated from.

As a method for extracting information inside particles, some research examples have been reported on cutting of fine particles using a focused ion beam (FIB) and cross-section observation (for example, Tomiyasu et.al.in SIM.
S IX p565-568 (1994)). In addition, organic substances such as photoresist can be cited as one of the constituents of particles. Laser Ion that irradiates the sample surface with a laser to evaporate the sample and detects the fragment ions generated there
The effectiveness of ization mass spectrometry (LIMS) has been pointed out. (For example, L. Van Vaeck et. Al., Anal. Che
See m. 57 (1985) 2944. ) Such a technique is an effective elemental technique for determining the composition and structure of particles.

[0005]

However, according to the conventional particle evaluation method, when particles are positioned and then taken out of the apparatus and put into the vacuum chamber of another SEM-EDX apparatus, particles are generated, and organic particles For particles, the pollution source could not be specified only by information on elements such as carbon, and a technology capable of obtaining information on constituent components was required.

[0006] Particles are very troublesome to get into a semiconductor device produced from hundreds of single processes such as film formation, ion implantation and cleaning, and get in from anywhere. Moreover, their compositions and structures are different for the above reasons. Therefore, an object of the present invention is to provide a semiconductor inspection apparatus in which a semiconductor substrate or a mounted substrate is introduced into a single vacuum device, particle positions are specified in a room, and the composition and structure thereof are immediately analyzed. To do.

[0007]

The present invention drives an XY stage on which the semiconductor sample is fixed while irradiating the semiconductor sample with a visible light laser for particles existing on or inside the surface of the semiconductor sample. Then, the scattered light is detected to determine the position, the particles can be quickly confirmed by scanning secondary electron (SEM) images, and after elemental analysis, the composition and structure can be determined using FIB and high-intensity pulsed ultraviolet laser. Provided are various analytical methods and devices.

The present invention will be described in detail below. While irradiating the surface of the semiconductor sample with a visible light laser such as an argon laser or a He-Ne laser, the XY stage attached with the semiconductor sample is scanned, and the scattered light reaches the detector installed in the horizontal direction of the semiconductor sample. If it does, it is determined to be a particle. At this point, a scanning electron image in the vicinity of the particles is observed using an electron beam to determine whether the particles are particles, and the particles are analyzed by SEM-EDX to determine the composition.

When the particles are a dielectric substance or an organic substance (photoresist etc.) which easily charges up, a pulsed high-intensity ultraviolet laser (Q-switch Nd: YAG) is used.
The particles are irradiated with a laser fourth harmonic (266 nm) to evaporate a part or all of the particles, and fragment ions derived from the structure of the particles are detected by a time-of-flight mass spectrometer. It is possible to identify the organic matter that constitutes the particle from the detected fragment ions. By applying this method to particles, it is possible to estimate the composition of dielectric or organic particles.

When it is desired to obtain information only on the surface layer of particles, continuous ion beam consumes much sample and it is difficult to obtain information only on the semiconductor sample surface. FIB whose optical axis is adjusted so that it has the same origin on the electron beam and the surface of the semiconductor sample is pulsed to irradiate the particles, and the pulsed secondary ion signal is detected by the time-of-flight mass spectrometer. Sputtering on the sample surface can be minimized and only information on the particle surface can be detected. Here, the origin refers to the center point where the continuous visible light laser is projected on the surface of the semiconductor sample.

Further, when the particles are covered with a film, the factors causing the particles can be clarified by cutting the particles with a continuous beam and analyzing the cross section in the same manner.

[0012] Detecting particles on a mounted semiconductor substrate is much more difficult than when analyzing on the surface of a silicon wafer. Since the device pattern is finely processed and already contains irregularities of about μm, scattered light by the visible light laser is also generated at the pattern edge. For this reason, it is difficult to determine whether it is due to the shape of the sample or due to particles only by the development in which the laser light incident on the surface of the semiconductor sample is scattered. Therefore, two or more detectors are installed through the vacuum window in the horizontal direction of the XY stage on which the semiconductor sample is installed, and the scattered light generated by irradiating the irregularly shaped particles with laser light is three-dimensional. By utilizing the characteristics emitted to the laser, when the laser scattered light is simultaneously detected by these detectors, it is recognized as particles. This is because, in the case of the device pattern, it is flat in the plane direction at about μm, so the scattered light from the pattern is very likely to be simultaneously incident on a plurality of detectors installed in the horizontal direction of the sample. Low. Therefore, when the laser light collides with an irregular particle, the incident light is scattered in all directions, so that the particle can be distinguished.
After that, it is more preferable to confirm by SEM whether the particles are particles.

The configuration of the apparatus of the present invention will be described with reference to FIG. XY stage 3 on which semiconductor sample 2 is installed
And two or more detectors 4 for detecting the laser scattered light 11 installed in the horizontal direction of the semiconductor sample 2, and the continuous visible light laser beam 1 installed in the vertical direction of the semiconductor sample 2.
And the focused ion beam 7, the high-intensity visible laser beam 9, and the deflection magnetic field 10 whose optical axes are adjusted so that they have the same origin as the continuous visible laser beam 1 on the surface of the semiconductor sample 2.
It is equipped with an electron beam 5 whose optical axis is adjusted by and an analyzer 8 having a time-of-flight mass spectrometer and a fluorescent X-ray analyzer. The same origin means the center point where the continuous visible light laser beam 1 is projected on the surface of the semiconductor sample 2.

The mounted device is not only subjected to fine processing, but also has a structure in which thin multilayer films are laminated. Particles generated due to peeling of the thin film may be left under the thin film and cause a failure. It is possible to detect the presence of particles buried under the thin film detected by scattering of visible light laser by the visible light laser scattering, cut the surface thin film by FIB, and expose the particles to the surface. it can. Analyzing the exposed particles is the same as above.

[0015]

EXAMPLE An example of analyzing particles on a mounted 6-inch silicon wafer substrate by using the apparatus shown in FIG. About 1 μm at the position where scattered light is detected
EDX analysis was performed after SEM observation of the particles having a diameter. The measurement was performed at an acceleration voltage of 15 kV and 2 nA. The results of the EDX analysis obtained are shown in FIG. From the analysis of the spectrum, it was found that the particles contained Ti. It cannot be determined whether the Si peak is from the substrate or the information in the sample. FIG. 3 shows the result of TOF-SIMS analysis using FIB on the surface layer of the particles.
Then, after performing a sputter etching of a 20 μm square in the vicinity of the particles for 10 seconds with a continuous ion beam,
The result of the OF-SIMS analysis is shown in FIG. TOF-S
As the IMS measurement conditions, a Ga ⁺ ion beam of 30 kV was used as the primary ions, and the primary ion current was 5 nA. The ion beam pulse width was 5 nsec, and 600,000 pulses were integrated by repeating 10 kHz. Further, it was found from FIG. 3 that the surface layer was almost TiO ₂ . Also,
It was found from the mass spectrum results that the particles obtained by sputter-etching the surface layer were composed almost of TiN. From the above, it was possible to extract information such that the particles were derived from the TiN film used as a barrier metal and that the surface of the particles was oxidized in the subsequent process.

[0016]

According to the present invention, the position detection of particles on the surface of a semiconductor substrate and the analysis of the composition and structure thereof, which have been difficult until now, can be effectively performed by a single apparatus. This makes it possible to quickly determine the process of particle generation, which can be expected to contribute to stable yield of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a semiconductor inspection device that constitutes the present invention.

FIG. 2 is a SEM-EDX spectrum of detected particles.

FIG. 3 is a TOF-SIMS spectrum of the surface layer of particles.

FIG. 4 TOF of particles after sputter etching
-SIMS spectrum.

[Explanation of symbols]

 1 Particle Detection Visible Light Laser 2 Sample 3 XY Stage 4 Detector 5 Electron Beam 6 Particle 7 Focused Ion Beam 8 Analyzer 9 High Brightness Laser for Structural Analysis 10 Deflection Magnetic Field 11 Laser Scattered Light 12 Sample Chamber

Claims (6)

[Claims] 1. Particles are obtained by irradiating a semiconductor sample placed on an XY stage with a continuous visible light beam from a vertical direction of the semiconductor sample and detecting laser scattered light while driving the XY stage. Judge the position,
A semiconductor inspection method, wherein the composition of the particles is analyzed by irradiating the particles with an electron beam and detecting fluorescent X-rays excited. 2. A semiconductor sample placed on an XY stage is irradiated with a continuous visible light beam from a vertical direction of the semiconductor sample, and laser scattered light is detected while driving the XY stage to thereby generate particles. Judge the position,
A semiconductor inspection method, wherein molecular information is obtained by evaporating the particles on the surface of the semiconductor sample with a high-intensity ultraviolet pulse laser and detecting the generated sample-derived ions with a time-of-flight mass spectrometer. 3. Particles are obtained by irradiating a semiconductor sample placed on an XY stage with a continuous visible light beam from the vertical direction of the semiconductor sample and detecting laser scattered light while driving the XY stage. Judge the position,
Irradiating the particles by pulsing a focused ion beam, and detecting the secondary ions generated in a pulse form from the particle surface by a time-of-flight mass spectrometer only the surface layer of the particles present on the semiconductor sample surface A semiconductor inspection method characterized by obtaining elemental composition and structural information of. 4. The semiconductor inspection method according to claim 1, wherein the particle is irradiated with a focused ion beam to be cut, and the cut surface is analyzed. 5. The thin film deposited on the particles is removed by using a focused ion beam, the particles are exposed, and the particles are analyzed. Semiconductor inspection method. 6. An XY stage on which a semiconductor sample is installed, two or more detectors installed in the horizontal direction of the semiconductor sample, and a continuous visible light laser beam installed in the vertical direction of the semiconductor sample. A focused ion beam whose optical axis is adjusted to have the same origin as the continuous visible light laser beam on the semiconductor sample surface, a high-intensity visible light laser beam and an electron beam, and a time-of-flight mass spectrometer, A semiconductor inspection device comprising: a fluorescent X-ray analyzer.