Shin-etsu Chemical Co., Ltd.

Furukawa Co., Ltd.

Masaaki Iguchi

Susumu Sakaguchi

Masahiro Ogihara

Yoshihiro Kubota

Shinji Makikawa

Akira Yamamoto

Toyohisa Sakurada

Kenichi Taguchi

Norifumi Yoshida

Shigeaki Saito

Kunihiro Ito

Kazuyoshi Watanabe

Etsuo Hatano

Toshihiko Ryuoh

Toshiharu Matsueda

A pellicle for lithography based on the exposure method especially adapted for lithographic lights having wave lengths of 500 nm or smaller, characterized in that the pellicle film is made of a high polymer organic silicon compound, preferably of a general molecular formula: ##STR1## where R.sup.1, R.sup.2, and R.sup.3 are the same or different alkyl groups having one to eight carbon atoms, and n is an integer between 100 and 40,000.

Pellicle for lithography

The dopant body of arsenic for doping of a semiconductor substrate, e.g., silicon wafer, is a sintered body of a powder mixture comprising silicon arsenide, silica and, optionally, arsenic oxide in a specified proportion. The dopant body can be easily prepared and has various advantages over conventional elementary arsenic powder or a shaped body of silicon arsenide alone in respect of the high mechanical strength of the dopant body and absence of the problem of environmental contamination.

Dopant of arsenic, method for the preparation thereof and method for

The single crystal wafer of lithium tantalate provided by the invention is characterized by the limited range of variation of the value of double refraction which should not exceed .+-.6.times.10.sup.-4 so that the value of the double refraction is given by 4.5.times.10.sup.-3 .+-.6.times.10.sup.-4. When single crystal wafers of lithium tantalate each satisfying the above requirements are used for the manufacture of SAW devices, the devices may have a very small deviation of the SAW sound velocity from the standard value and the range of variation of the SAW sound velocity within a wafer is also very small so that the SAW devices can be manufactured with greatly improved productivity and excellent quality.

Single crystal wafer of lithium tantalate

The x-cut single crystal wafer of lithium tantalate according to the invention is characterized by the orientation flat formed in a specific crystallographic orientation. The plane of the orientation flat should be (A) in parallel with the (018) plane or a plane which is in parallel with the x-axis and makes an angle of 15.degree. or smaller with the (018) plane or (B) in parallel with a plane which is in parallel with the x-axis and perpendicular to the (018) plane or a plane which is in parallel with the x-axis and makes an angle of 15.degree. or smaller with the plane which is in parallel with the x-axis and perpendicular to the (018) plane. In contrast to conventional lithium tantalate single crystal wafers provided with an orientation flat in a direction parallel to the 112.degree. Y direction, the location of the crystallographic orientation of the orientation flat is very easy and consequently great advantages are obtained in the working efficiency of locating the direction of the orientation flat and improved quality as well as increased yield of acceptable devices, e.g. SAW filters, prepared from the wafers.

In the crystal growing of GGG (gadolinium gallium garnet) by the Czochralski technique from a melt of the oxide mixture of gadolinium and gallium, zinc is added to the oxide melt as a dopant element in a limited amount so that the danger of crack formation in the grown single crystals can be greatly decreased contributing to the improvement of the productivity. Moreover, the GGG single crystal grown with zinc doping has remarkably reduced light absorption in the wavelength region of around 300 nm responsible to the yellowish tint of the crystals.

Method for the preparation of single crystals of gadolinium gallium

The invention provides a method for surface-finishing of a single crystal wafer of a ferroelectric material into a substrate plate suitable for use, for example, as a SAW filter element which is mirror-polished only on one of the surfaces, the other surface having an adequate roughness. Different from conventional methods, the inventive method comprises the successive steps of (a) slicing a single crystal boule into wafers, (b) lapping of the wafer on both surfaces to impart adequate roughness to the surfaces, (c) chemically etching the thus lapped surfaces to remove the strain produced in the preceding mechanical working, and (d) mirror-polishing one of the thus etched surfaces so that high uniformity of the thickness and greatly decreased warping of the wafer can be ensured.

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Tokyo, Japan

Masaaki Iguchi