Dielectric substrate with reflecting films
AssigneeOki Semiconductor Co., Ltd.
InventorsToshiyuki Nakamura, Satoshi Machida, Sachiko Yabe, Takashi Taguchi
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Abstract
A semiconductor device has a transparent dielectric substrate such as a sapphire substrate. To enable fabrication equipment to detect the presence of the substrate optically, the back surface of the substrate is coated with a triple-layer light-reflecting film, preferably a film in which a silicon oxide or silicon nitride layer is sandwiched between polycrystalline silicon layers. This structure provides high reflectance with a combined film thickness of less than half a micrometer.
Claims12
A semiconductor device having a dielectric substrate transparent to light, the dielectric substrate having a pair of major surfaces, one of the major surfaces being a front surface having a device formation film thereon, and another of the major surfaces being a back surface, the semiconductor device comprising:
- a first film of a first material that reflects sensing light illuminated thereon from an external source, the first film disposed on the back surface of the dielectric substrate;
- a second film of a second material that reflects the sensing light, disposed on the first film, the second material differing from the first material;
- and
- a third film of a third material that reflects the sensing light, disposed on the second film,
- wherein the second film has a lower refractive index than the first and third films,
- wherein the first film comprises polysilicon, the second film comprises silicon oxide, and the third film comprises polysilicon, and
- wherein the first film has a thickness of substantially 42 nm, the second film has a thickness of substantially 110 nm, and the third film has a thickness of substantially 42 nm.
The semiconductor device of 1, wherein the dielectric substrate includes sapphire, the semiconductor device further comprising:
- a fourth film disposed on the front surface of the dielectric substrate, the fourth film including silicon;
- and
- a fifth film disposed on the fourth film, the fifth film including silicon oxide.
The semiconductor device of 1, wherein the dielectric substrate comprises a sapphire substrate.
The semiconductor device of 4, wherein the fourth film comprises silicon.
The semiconductor device of 4, further comprising a fifth film disposed on the fourth film.
The semiconductor device of 6, wherein the fourth film comprises silicon and the fifth film comprises silicon oxide.
A semiconductor device having a dielectric substrate transparent to light, the dielectric substrate having a pair of major surfaces, one of the major surfaces being a front surface having a device formation film thereon, and another of the major surfaces being a back surface, the semiconductor device comprising:
- a first film of a first material that reflects sensing light illuminated thereon from an external source, the first film disposed on the back surface of the dielectric substrate;
- a second film of a second material that reflects the sensing light, disposed on the first film, the second material differing from the first material;
- and
- a third film of a third material that reflects the sensing light, disposed on the second film,
- wherein the second film has a lower refractive index than the first and third films,
- wherein the first film comprises polysilicon, the second film comprises silicon nitride, and the third film comprises polysilicon, and
- wherein the first film has a thickness of substantially 42 nm, the second film has a thickness of substantially 80 nm, and the third film has a thickness of substantially 42 nm.
Dependencies are inferred from the claim text.