Tomohiro Okumura

Fine pattern etching of molybdenum thin film and silicon substrate by using atmospheric line-shaped microplasma source

An atmospheric line-shaped microplasma source was developed for fine pattern etching. Observation of plasma emission of the developed plasma source has revealed that the finest plasma line is formed when helium (He) gas is supplied to the inner gas feed and reaction gas to the outer gas feeds. When reaction gas is supplied to the outer gas feeds, fluorine radical (F*) emission intensity increases with the gas flow rate, eventually exceeding the maximum emission intensity obtained when a mixture of reaction gas and He gas is supplied to the inner gas feed. Fine pattern etching of molybdenum thin film and silicon substrate was experimentally carried out using microplasma sources in two different configurations: one with the copper electrode covered to protect it from plasma exposure (type 1), and the other with the aluminum electrode end knife-edged and exposed to a plasma (type 2). The experiment revealed that the type 2 source provides a higher etching rate than of the type 1 source. The type 2 source can produce a fine etched pattern with lines of several ten to several hundred µm width. The maximum etching rate of silicon substrate is 79.0 µm/min.

New inductively coupled plasma source using a multispiral coil

The authors have developed a new inductively coupled plasma source (ICPS), using a multispiral coil with 1/3 the inductance of the conventional ICPS coil. This source can produce plasma of 1011 cm−3 or higher density with ±5% fluctuation, at pressures below 10 mTorr.

Elongated Inductively Coupled Thermal Plasma Torch Operable at Atmospheric Pressure

An elongated inductively coupled plasma (ICP) torch that enables instantaneous thermal processing over a large area has been newly developed. Its circular chamber configuration enabled the generation of elongated thermal plasma. A racetrack chamber with a groove showed improvement of plasma stability. The surface temperature distribution over a substrate was measured using a simplified perpendicular-racetrack-type torch with a length of 130 mm; the surface of a glass substrate was heated to 798 K at a scanning speed of 50 mm/s and the peak temperature variation over a substrate along the longitudinal line was within ±5.5 K in the best case. A sputtered amorphous silicon thin film was successfully crystallized.

Fine pattern etching of silicon substrates by using atmospheric line shaped micro plasma source

In this paper, various micro plasma sources have been proposed. We have already proposed two types of line shaped micro plasma sources. This report presents a new type of line shaped micro plasma source for finer processing than the former two types and its application to fine pattern etching of a silicon substrate.

Production‐Worthy USJ Formation by Self‐Regulatory Plasma Doping Method

A new method of plasma doping that achieves tight control on dosimetry and uniformity has been developed. It uses a self‐regulatory behavior of plasma processes that brings high accuracy on dose control and uniformity within 1.5%. The largest advantage of this self‐regulatory plasma doping (SRPD) is that the accuracy of the process control is much less dependent on the uniformity of the plasma, which makes a revolutionary difference to the plasma process as it becomes free from the primary hardware constraint. A typical doping of boron using B2H6/He gas mixture at dose of 1×1015 ions/cm2 can achieve a uniformity of less than 1.5% across a 300mm silicon wafer when the plasma uniformity above the wafer plane is as poor as 10%. The SRPD process also forms very abrupt junctions such as less than 2nm/decade at the junction depth of 10nm due to an instantaneous amorphization of the wafer surface within the first 5 seconds of the process duration. Combined with the throughput advantage at low energy against the ...

Annealing performance improvement of elongated inductively coupled plasma torch and its application to recovery of plasma-induced Si substrate damage

The annealing performance of an elongated inductively coupled plasma (ICP) torch that enables instantaneous thermal processing over a large area has been improved by using a ceramic chamber that ensures better mechanical and thermal properties than a quartz chamber, realizing a substrate temperature higher than 1,600 K. Si wafers damaged by the bombardment of ions from Ar plasma were irradiated by the ICP torch for recovery. The thickness of the damaged layer was monitored by spectroscopic ellipsometry (SE), and the changes in Si crystal structure were examined by transmission electron microscopy (TEM). Significant decreases in damaged layer thickness and TEM contrast, which corresponds to the degree of damage, were observed after the ICP torch irradiation.

Fine pattern etching of molybdenum by using atmospheric line shaped micro plasma source

Various atmospheric micro plasma sources for maskless etching have been proposed. This report briefly summarizes the concept of our line shaped micro plasma source and presents fine pattern etching experiment of molybdenum thin film.

Study on chemical binding states of silicon in conjunction with ultra‐shallow plasma doping by using Hard X‐ray Photoelectron spectroscopy (HX‐PES)

We took HX‐PES measurement (Si 1s) on ultra shallow plasma doped silicon samples before and after spike RTA, flash lamp anneal (FLA) and all solid‐state laser anneal (ASLA) in SPring‐8 for the first time. After PD, the carrier density of n‐Si substrate decreased to intrinsic Si level due to defect induced carrier traps. After annealing by either spike RTA or FLA, the PD samples showed excellent chemical binding states with high impurity activation and recrystallization. After annealing by ASLA, PD samples showed ultimate high impurity activation at surface several nanometer layer.

Lead-free soldering process for coil terminals by using atmospheric pressure plasma technique

Recently, much attention is paid to the environmental problems caused by lead”, and practical use of lead-free solder i s especially accelerated in the field of printed writing boards. However, lead solder commonly used for terminals of coils hasn’t yet replaced by lead-free solder. From solder-plated terminals, lead flows into the lead-free solder bath during wave soldering process, so we are faced with a problem of lead concentration in a solder bath. Conventionally, it is possible to plate coil terminals with lead solder by dipping it into the solder bath, but such a procedure cannot be applied to iead-free solder. So the process of removing insulator film coated on a copper wire and plating the treated copper wire with lead-free solder is strongly required. Technologies such as mechanical grinding, laser irradiation and chemical wet etching have been conventionally used. For the purpose in this work we investigated lead-free soldering process using atmospheric pressure plasma applicable for wire of diameter less than 0.3mm. For your references, our previous works on micro plasma technology are listed in the next page2h3’. 2. Experimental setup Schematic of the plasma source is shown in Fig. 1. The plasma source comprises a tube containing a gas feed and pedestals, parallel plate electrodes and a grounded metal case. The tube with openings to both ends is instalted between the electrodes, and mixed gas is supplied from the gas inlet and flows out from the gas outlet through the tube. A coated copper wire is inserted from the gas outlet, and is placed between the pedestals. At this time, a coated copper wire is floating without contacting inner wall of the tube. The dimensions of the gap between the electrodes; G=lmm, length of the electrodes; L=Smm, width of the gas feed; W=Smm and height of the gas feed; H=O.7mm. Further, diameter of coated copper wires is 200pm and diameter of copper wires is 150p-1, therefore thickness of insulator film consisting of polyester-imide is 50pm. Mixed gas consists of He, 0 2 , and CF4 flows through the tube. By applying radio frequency (1 3.56MHz) voltage to the upper electrode, plasma is generated between the electrodes. After etching insulator film, we measured diameter of the treated copper wire by using a blade. type micrometer. Further, we dipped the wire into the Sn-Ag-Cu solder bath, not including any fluxes, for 3s at 250°C and measured plated length of solder along the line direction. (a) Configuration.