Hiroyasu Shichi

Developments of new concept analytical instruments for failure analyses of sub-100 nm devices

Abstract We have developed analytical instruments based on new concepts for failure analyses of devices of 100 nm dimensions or less. They are a sputtered neutral mass spectrometer with focused ion beam for highly sensitive element analysis in microarea (10 18 atoms/cm 3 in 30 nm area), transmission electron microscope (TEM) with electron energy loss spectrometer for chemical bond analysis in less than 2 nm area, Nanoprober for electrical characteristics inspection in actual circuits, computed tomography-TEM for three-dimensional observation of crystalline defect with 1 nm spatial resolution, atmospheric pressure ionization mass spectrometer for trace impurities ppq (parts per quadrillion) analysis in gases, and glow discharge optical emission spectrometer for rapid and precise composition analysis. Using these instruments, it was found that the formation of SiO 2 or TiO x film by water from titanic acid (TiO x ·H 2 O) is the cause of the high resistivity in a contact (CVD-W/CVD-TiN/Ti/Si) and vaporization of silicon dioxide by phosphorus trifluoride (PF 3 ) is the cause of voids in interlayer dielectric film borophosphosilicate glass.

Secondary Ion Yield Changes in Si due to Topography Changes during Cs^+ Ion Bombardment

Depth profiles of 30Si negative secondary ions were measured at Cs+ ion impact energies of 10.5 keV, 14.5 keV and 17.5 keV and a 45° impact angle by means of secondary ion mass spectrometry (SIMS). Yield changes due to surface topography changes occurred at 14.5 keV and 17.5 keV impact energy, although no surface topography change has ever been reported during Cs+ ion bombardment. No yield change was detected at 10.5 keV impact energy. The topography changes and ion yield changes are obviously affected by the Cs+ ion impact energy.

Novel Scanning Ion Microscope with H3+ Gas Field Ionization Source

A scanning ion microscope (SIM) equipped with the GFIS with a very high brightness and a small sized (~0.3 nm) source has been commercialized [2]. Variety of practical usages and valuable studies using the microscope has been reported so far [3]. The GFIS can emit different ion species by replacing its ionizing gas. The commercialized GFIS-SIM can select the helium ion for visualization of surface of specimen with a sub-nm resolution. It can also select the neon ion for higher precision nano-machining than Ga-FIB, which takes advantage of higher sputtering yield due to larger mass of ions. Similarly, we have developed a home-made SIM machine with a hydrogen GFIS for the purpose of suppressing a damage during observation comparing with the helium ion.

Cesium liquid metal ion source for secondary ion mass spectrometry

A Cs liquid metal ion source (LMIS) and focused ion beam system for microarea secondary ion mass spectrometry (SIMS) have been developed. Because of the chemical activity, low surface tension, and high vapor pressure of Cs, few successful Cs LMISs have heretofore been reported, as opposed to the many successful applications of Ga in LMIS. A new Cs‐LMIS design had to be developed to supply Cs to the emitter/reservoir under UHV to prevent oxidation, to prevent liquid Cs from dripping off the emitter substrate, and to minimize the surface area exposed so as to minimize thermal evaporation. The last consideration is very important since the evaporation rate of Cs is many orders of magnitude higher than, e.g., Ga at the melting point. A focused Cs beam was obtained with a newly designed SIMS system, which is about 0.1 μm beam size and a beam current density on the specimen of 0.8 A/cm2. An operating time of more than 600 h has been achieved at a total emission current of 1 μA without resupplying the source mat...

High Contrast of Scanning Ion Microscopy Images Shows Element Segregation

Scanning ion microscopy (SIM) provides image contrast clearly higher than that of scanning electron microscopy (SEM). SEM and SIM images of the same sample have been taken in the same instrument under the same field of view conditions, and then compared. SIM reveals element segregation, but SEM does not. It is shown that the elemental contrast of SIM, when using positive secondary ions as the imaging signal, is made by variation of the secondary ion yield of the implanted primary beam element. The variation is caused by differences of sample elements. The high contrast provided by SIM gives valuable information about elements and microcrystallites in material science.

Secondary ion mass spectrometry round-robin study of relative sensitivity factors in gallium arsenide

Round-robin studies on relative sensitivity factors (RSFs) in secondary ion mass spectrometry (SIMS) were conducted using bulk GaAs samples uniformly doped with various impurity elements. A total of 31 laboratories participated in two round-robins. More than 30 sets of relative ion intensities were obtained for B, Si, Cr, Mn, Fe, Cu, Zn, In and Te in GaAs. The RSFs for both positive and negative ions were derived for several types of SIMS instruments. The effect of primary ion incident angle was examined using quadrupole-based instruments and found to be the determining factor of the instrumental dependence of RSF.

Characteristics of krypton ion emission from a gas field ionization source with a single atom tip

A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. The characteristics of krypton ion emission from a single atom tip (SAT) have not been reported yet. In this study, the characteristics of krypton ion emission were investigated by field ion microscopy. At 65 K, the krypton ion emission current reached approximately 40 pA, which is 1 order of magnitude higher than that at 130 K. As the krypton gas pressure was increased, the krypton ion current increased. At a pressure of 0.3 Pa, the emission current was anticipated to reach 200 pA, which may be high enough for nanofabrication. The variation of the krypton ion current was as low as 5% in one hour. We concluded that a krypton ion beam instrument equipped with a GFIS will be a powerful tool for nanofabrication.

Comparison of Characteristics of Neon, Argon, and Krypton Ion Emissions from Gas Field Ionization Source with Single Atom Tip

A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been developed and commercialized using helium and neon ions [1]. Helium ions have been used mainly for observation, while neon ions have been mainly used for fabrication. The GFIS can emit different ion species by changing its ionization gas, but other noble gas ion species have not been used commercially yet. Heavier noble gases than neon are expected to be suitable for faster fabrication because the sputtering yields of heavier noble gas ions are higher than that of neon ions. On the other hand, the ion currents from a GFIS become larger at lower ion emitter temperatures. Although xenon gas is the heaviest, its boiling point of about 165 K is so high that large ion currents are not expected. In this study, the characteristics of neon, argon, and krypton ion emissions from a GFIS were investigated and compared from the viewpoint of practical fabrication.

Development a projection ion beam instrument that uses a gas ion source for metal-contamination-free microsampling

The authors have developed a metal-contamination-free ion beam instrument with a duoplasmatron that serves as a gas ion source and a projection ion beam optical system that generates a shaped gas ion beam. The luminance of the duoplasmatron ion source is low. However, a projection ion beam optical system can increase the ion current with sharp beam edge profiles enough for microsampling fabrication. A metal-contamination-free shaped gas beam can be used to achieve clean inline sampling and wafer return strategy. The irradiation system of the instrument has three electrostatic lenses, an E × B mass separator, and a mechanism for bending the ion beam to prevent neutral particles from irradiating the samples. The instrument also has a gas flow system for ion beam assisted deposition and a needle transport system for microsampling. Experiments using a prototype implementation demonstrated that microsampling can be achieved by using shaped gas ion beams.