A nitride semiconductor light-emitting device has an active layer of a single-quantum well structure or multi-quantum well made of a nitride semiconductor containing indium and gallium. A first p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided in contact with one surface of the active layer. A second p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided on the first p-type clad layer. The second p-type clad layer has a larger band gap than that of the first p-type clad layer. An n-type semiconductor layer is provided in contact with the other surface of the active layer.

Nitride semiconductor light emitting device

Claimed and disclosed is a treatment apparatus for treating a substrate under decompressed atmosphere, comprising: a chamber, an exhausting means for exhausting the chamber, a first electrode provided in the chamber on which the substrate is mounted or held, a second electrode provided in the chamber opposing the first electrode, a liquid supply source containing a liquid material from which a process gas is generated, a housing provided between the liquid supply source and the chamber to be communicated to the liquid supply source and the chamber, a porous heating unit arranged in the housing for generating the process gas by heating the liquid material supplied from the liquid supply source into the housing in order to vaporize the liquid material, a process gas introduction section provided between the housing and the chamber for guiding the process gas from the housing to the chamber and vibrators to vibrate the porous heating unit. The porous heating unit which is capable of generating heat for itself has an element for electrically heating the porous heating unit. This porous heating unit is arranged in the housing for generating the process gas by heating the liquid material supplied from the liquid supply source into the housing in order to vaporize the liquid material. The treatment apparatus further comprises a process gas introduction section disposed between the housing and the chamber for guiding the process gas from the housing to the chamber.

Plasma treatment method and apparatus

A method for performing design rule checking on OPC corrected or otherwise corrected designs is described. This method comprises accessing a corrected design and generating a simulated image. The simulated image corresponds to a simulation of an image which would be printed on a wafer if the wafer were exposed to an illumination source directed through the corrected design. The characteristics of the illumination source are determined by a set of lithography parameters. In creating the image, additional characteristics can be used to simulate portions of the fabrication process. However, what is important is that a resulting simulated image is created. The simulated image can then be used by the design rule checker. Importantly, the simulated image can be processed to reduce the number of vertices in the simulated image, relative to the number of vertices in the OPC corrected design layout. Also, the simulated image can be compared with an idea layout image, the results of which can then be used to reduce the amount of information that is needed to perform the design rule checking.

Design rule checking system and method

An integrated verification and manufacturability tool provides more efficient verification of integrated device designs than verification using several different verification tools. The integrated verification and manufacturability includes a hierarchical database to store shared design data accessed by multiple verification tool components (e.g., layout versus schematic, design rule check, optical process correction, phase shift mask assignment and machine language conversion). The hierarchical database includes representations of one or more additional, or intermediate layer structures that are created and used by the verification tool components for operations performed on the design being verified. Use of a single hierarchical database having shared data for access and use by multiple verification components streamlines the verification process, which provides an improved verification tool.

Integrated verification and manufacturability tool

Gallium nitride (GaN) is an extremely promising wide band gap semiconductor material for optoelectronics and high temperature, high power electronics. Actually, GaN is probably the most important semiconductor since silicon. However, achievement of its full potential has still been limited by a dramatic lack of suitable GaN bulk single crystals. GaN has a high melting temperature and a very high decomposition pressure; therefore it cannot be grown using conventional methods used for GaAs or Si like Czochraslski or Bridgman growths.Since there is no GaN bulk single crystal commercially available, all technological development of GaN-based devices relies on heteroepitaxy. Most of the current device structures are grown on sapphire or 6H-SiC. However, since their lattice parameters and thermal expansion coefficients are not well-matched to GaN, the epitaxial growth generates huge densities of defects, with threading dislocations (TDs) being the most prevalent (109–1011 cm−2). As a comparison, homoepitaxially grown GaAs exhibits ~102–104 dislocation cm−2, and homoepitaxial Si almost 0. Actually this large density of TDs in GaN drastically limits the performance and operating lifetime of nitride-based devices. Therefore, there is currently a tremendous technological effort to reduce these defects.Metal organic vapour phase epitaxy (MOVPE) is currently the most widely used technology. Actually, all optoelectronic commercial device structures are fabricated using MOVPE. In MOVPE, the most appropriate precursor for nitrogen is ammonia (NH3), whereas either trimethyl or triethylgallium may be used as a gallium source. MOVPE of GaN requires a high partial pressure of NH3, high growth temperatures (~1000–1100°C) and a growth chamber specially designed to avoid premature reactions between the ammonia and gallium alkyls. Since sapphire (or 6H-SiC) and GaN are highly mismatched, direct growth of GaN is impossible. Therefore, the growth of GaN on any substrate first requires the deposition of a buffer layer, which, to some extent, accommodates the mismatch. Using appropriate nucleation layers allows a reduction of the dislocation density to the low 108 cm−2 range.Though laser diodes (LDs) were demonstrated in the late 1990s with such defect layers, the real breakthrough in laser technology was the dramatic improvement of the LD lifetime at the end of 1997, with the lifetime reaching 10 000 h. This was made possible by implementation of epitaxial lateral overgrowth (ELO) technology, which significantly reduces the dislocation density to below 107 cm−2.In ELO technology, parts of the highly dislocated starting GaN are masked with a dielectric mask, after which growth is restarted. At the beginning of the second growth step, deposition only occurs within the openings, with no deposition observed on the mask. This is referred to as selective area epitaxy (SAE). The TDs are prevented from propagating into the overlayer by the dielectric mask, whereas GaN grown above the opening (coherent growth) keeps the same TD density as the template, at least during the early stages of growth.Currently, two main ELO technologies exist: the simpler one involves a single growth step on striped openings. In this one-step-ELO (1S-ELO), growth in the opening remains in registry with the GaN template underneath (coherent part), whereas the GaN over the mask extends laterally (wings). This leads to two grades, namely highly dislocated GaN, above the openings, and low dislocation density GaN, above the masks. With this technique, devices have to be fabricated on the wings. Conversely, in the two-step-ELO (2S-ELO) process, the growth conditions of the first step are monitored to obtain triangular stripes. Inside these stripes, the TDs arising from the templates are bent by 90° when they encounter the inclined lateral facet. In the second step, the growth conditions are modified to achieve full coalescence. In this 2S-ELO technology, only the coalescence boundaries are defective. ELO technology produces high quality GaN, with TD densities in the mid 106 cm−2, line widths of the low temperature photoluminescence near band gap recombination peaks below 1 meV, and deep electron trap concentration below 1014 cm−3 (compared with mid 1015 cm−3 in standard GaN). Numerous modifications of the ELO process have been proposed either to avoid technological steps (maskless ELO) or to improve it (pendeoepitaxy, PE). To further reduce the TD density, multiple-step-ELO and pendeo have also been implemented.However, even ELO quality GaN is not good enough for the next generation of LDs. ELO samples do not yet offer a full surface suitable for laser technology. What is needed for LDs with at least 30 mW output power is high quality freestanding GaN with TDs close to or even below 106 cm−2. To reach this crystalline perfection, elaborate technologies are currently being implemented. They, at some stage, involve TD reduction mechanisms occurring in the ELO process.Self-supported GaN with at least ELO quality at an affordable cost is believed to be the next breakthrough in GaN technology.

https://iopscience.iop.org/article/10.1088/0034-4885/67/5/R02/pdf

Metal organic vapour phase epitaxy of GaN and lateral overgrowth

A reactive gas supplied to a chamber 1 is put into plasma by supplying radio frequency power to the chamber 1 intermittently or while repeating high and low levels alternately and a specimen A in the chamber 1 is treated by the plasma. A positive pulse-like bias voltage synchronized with a period in which the radio frequency power is not supplied or a period in which low-level power is supplied is applied to the specimen A for preventing charging.

Plasma treatment method and plasma treatment system

A two-phase molecular dynamics simulation of coexisting solid and liquid has been carried out to investigate the melting point of wurtzite-type GaN crystals. The melting point is determined by examining the movement of the interface between the solid and liquid during the simulation. The potential is a two-body interatomic one composed of the long-range Coulomb interaction, the Gilbert-type short-range repulsion, the covalent bonding and covalent repulsion of the modified Morse type, and the van der Waals interaction. The melting point and the interface morphology depend on the crystallization direction. The melting point Tm(K) increases with pressure P(GPa), but there appears a discontinuity in the vicinity of 8–9GPa. This is due to the solid-electrolyte-like behavior of Ga atoms with a partial charge in the high-pressure region. The discontinuity has not yet been confirmed by experiment. The least-squares fitted result is Tm=2538+177P−4.62P2 at pressures lower than 8GPa and Tm=2825+210P−5P2 at pressures...

Molecular dynamics simulation for evaluating melting point of wurtzite-type GaN crystal

A method of correcting design patterns in cells, having hierarchial structure and corresponding to exposure patterns, for proximity effects when exposing resist coated on a substrate to a charged-particle beam or to light. A first frame zone is provided having a predetermined width inside the boundary of each cell, and a second frame zone is provided having a predetermined width inside the first frame zone. Proximity effect correction operations are performed such that a pattern in the second frame zone and a pattern inside the second frame zone are used as a pattern to be corrected and a pattern in the first frame zone is used as a reference pattern when correcting pattern data in each cell for proximity effects and a pattern in the first frame zone in each cell is added to the pattern to be corrected and a pattern in the second frame zone in each cell is used as a reference pattern when correcting pattern data in a cell directly overlying each cell for proximity effect.

Method and apparatus for writing a pattern on a semiconductor sample based on a resist pattern corrected for proximity effects resulting from direct exposure of the sample by a charged-particle beam or light

A scanning electron microscope is disclosed in which an objective lens includes a first pole piece (18) and a second pole piece (21). The first pole piece is provided with a hole through which an electron beam (12) passes, and is disposed between an electron gun (11) for emitting the electron beam and the second pole piece. The second pole piece (21) has a planar portion on which a specimen (22) is placed, and the second pole piece being mounted on a supporting block (23) movable in a plane sub­stantially perpendicular to the projecting direction of the electron beam.

A scanning electron microscope and a method of displaying cross sectional profiles using the same

The behavior of interstitial Mg atoms at an edge dislocation is studied in the wurtzite-type GaN crystal by molecular dynamics (MD) simulation. Parameters for a two-body interatomic potential are determined by the Hartree–Fock ab initio method. First, an edge dislocation extending to the [0001] direction is generated in an MD basic cell composed of about 11,000 atoms. Second, Mg atoms are placed at substitutional and interstitial positions in the MD basic cell, and the Mg atoms are traced. It is found that the diffusivity of Mg atoms at a dislocation is enhanced along the dislocation. At 1000 K, the diffusivity of interstitial Mg atoms inside the dislocation core is approximately three orders of magnitude larger than that of interstitial Mg atoms located outside the dislocation. The enhanced diffusion along the dislocation originates from unbalanced atomic forces between the Mg atom and surrounding atoms.

https://iopscience.iop.org/article/10.1143/JJAP.44.6495/pdf

Kenji Harafuji

Papers

Plasma treatment method and plasma treatment system

Molecular dynamics simulation for evaluating melting point of wurtzite-type GaN crystal

Method and apparatus for writing a pattern on a semiconductor sample based on a resist pattern corrected for proximity effects resulting from direct exposure of the sample by a charged-particle beam or light

A scanning electron microscope and a method of displaying cross sectional profiles using the same

Magnesium Diffusion at Dislocation in Wurtzite-Type GaN Crystal