Method for evaluating epitaxial layers and test pattern for process evaluation

Claim 1

A method for determining the thickness of a crystalline semiconductor layer while epitaxially growing the crystalline semiconductor layer on a first surface of a crystalline semiconductor substrate comprising: forming a test pattern including a plurality of generally parallel stripe-shaped grooves in a first surface of a crystalline semiconductor substrate, the grooves being separated by respective parallel stripe-shaped ridges having surfaces coplanar with the first surface, the grooves and ridges extending along a predetermined crystalline direction of the substrate; epitaxially growing a crystalline semiconductor layer on the substrate including in the grooves and on the stripe-shaped ridges using a growth process that causes the crystalline semiconductor layer grown on the surfaces of the ridges to have triangular cross-sections in a plane transverse to the first surface that include sloping surfaces on which further epitaxial growth does not occur; and irradiating the stripe-shaped grooves and ridges with light while growing the crystalline semiconductor layer and monitoring the light diffracted from the stripe-shaped grooves, ridges, and the epitaxially growing crystalline semiconductor layer to determine the thickness of the epitaxially growing crystalline semiconductor layer.

Claim 2

A method for determining the thickness of a crystalline semiconductor layer while epitaxially growing the crystalline semiconductor layer on a first surface of a crystalline semiconductor substrate comprising: forming a test pattern including a plurality of generally parallel stripe-shaped grooves in a first surface of a crystalline semiconductor substrate, the grooves being separated by respective parallel stripe-shaped ridges having surfaces coplanar with the first surface, the grooves and ridges extending along a predetermined crystalline direction of the substrate; epitaxially growing a crystalline semiconductor layer on the substrate including in the grooves and on the stripe-shaped ridges using a growth process that causes the crystalline semiconductor layer grown on the surfaces of the ridges to have triangular cross-sections in a plane transverse to the first surface that include sloping surfaces on which further epitaxial growth does not occur; and irradiating the stripe-shaped grooves and ridges with light while growing the crystalline semiconductor layer and monitoring the light diffracted from the stripe-shaped grooves, ridges, and the epitaxially growing crystalline semiconductor layer to determine the thickness of the epitaxially growing crystalline semiconductor layer.

Claim 7

A method for determining the thickness of a second crystalline semiconductor layer epitaxially growing on a first crystalline semiconductor layer that is disposed on a first surface of a crystalline semiconductor substrate comprising: forming a test pattern including a plurality of generally parallel stripe-shaped grooves in a first surface of a first crystalline semiconductor layer disposed on a crystalline semiconductor substrate, the grooves being separated by respective parallel stripe-shaped ridges having surfaces coplanar with the first surface, the grooves and ridges extending along a predetermined crystalline direction of the substrate; epitaxially growing a second crystalline semiconductor layer on the first crystalline semiconductor layer including in the grooves and on the surfaces of the stripe-shaped ridges using a growth process that causes the second crystalline semiconductor layer grown on the surfaces of the ridges to have triangular cross-sections in a plane transverse to the first surface that include sloping surfaces on which further epitaxial growth does not occur; and irradiating the stripe-shaped grooves and ridges with light while growing the second crystalline semiconductor layer and monitoring the light diffracted from the stripe-shaped grooves, ridges, and the epitaxially growing second crystalline semiconductor layer to determine the thickness of the epitaxially growing second crystalline semiconductor layer.

Claim 8

A method for determining the thickness of a second crystalline semiconductor layer epitaxially growing on a first crystalline semiconductor layer that is disposed on a first surface of a crystalline semiconductor substrate comprising: forming a test pattern including a plurality of generally parallel stripe-shaped grooves in a first surface of a first crystalline semiconductor layer disposed on a crystalline semiconductor substrate, the grooves being separated by respective parallel stripe-shaped ridges having surfaces coplanar with the first surface, the grooves and ridges extending along a predetermined crystalline direction of the substrate; epitaxially growing a second crystalline semiconductor layer on the first crystalline semiconductor layer including in the grooves and on the surfaces of the stripe-shaped ridges using a growth process that causes the second crystalline semiconductor layer grown on the surfaces of the ridges to have triangular cross-sections in a plane transverse to the first surface that include sloping surfaces on which further epitaxial growth does not occur; and irradiating the stripe-shaped grooves and ridges with light while growing the second crystalline semiconductor layer and monitoring the light diffracted from the stripe-shaped grooves, ridges, and the epitaxially growing second crystalline semiconductor layer to determine the thickness of the epitaxially growing second crystalline semiconductor layer.

Claim 16

A method for evaluating an epitaxially grown AlGaAs multiple quantum well layer comprising: forming an insulating mask pattern having an opening on a part of a crystalline semiconductor substrate, the ratio of the width of the opening to the width of the insulating mask pattern varying; epitaxially growing a plurality of semiconductor layers including an AlGaAs multiple quantum well layer on the crystalline semiconductor substrate including the insulating mask pattern using a vapor phase growth method producing a thickness of the grown layer that depends upon and varies with the ratio of the width of the opening to the width of the insulating mask pattern; and measuring photoluminescence peak wavelengths of the AlGaAs multiple quantum well layer grown in the opening of the insulating mask pattern at different positions having different opening ratios of the insulating mask pattern and comparing the measured values with theoretical curves calculated for a standard quantum well structure to evaluate the thickness and the Al composition of the AlGaAs multiple quantum well layer.

Claim 17

A method for evaluating an epitaxially grown AlGaAs multiple quantum well layer comprising: forming an insulating mask pattern having an opening on a part of a crystalline semiconductor substrate, the ratio of the width of the opening to the width of the insulating mask pattern varying; epitaxially growing a plurality of semiconductor layers including an AlGaAs multiple quantum well layer on the crystalline semiconductor substrate including the insulating mask pattern using a vapor phase growth method producing a thickness of the grown layer that depends upon and varies with the ratio of the width of the opening to the width of the insulating mask pattern; and measuring photoluminescence peak wavelengths of the AlGaAs multiple quantum well layer grown in the opening of the insulating mask pattern at different positions having different opening ratios of the insulating mask pattern and comparing the measured values with theoretical curves calculated for a standard quantum well structure to evaluate the thickness and the Al composition of the AlGaAs multiple quantum well layer.

Claim 19

A method of producing a semiconductor laser including a diffraction grating comprising: preparing a crystalline semiconductor substrate of a first conductivity type having a (100) surface; successively growing a first conductivity type crystalline semiconductor lower cladding layer, a crystalline semiconductor active layer, a crystalline semiconductor barrier layer of a second conductivity type opposite the first conductivity type, and a second conductivity type crystalline grating semiconductor layer on the (100) surface of the crystalline substrate; forming the second conductivity type crystalline grating semiconductor layer into a periodic pattern of stripe-shaped grooves and ridges extending along a [011] direction of the crystalline semiconductor substrate parallel to each other and perpendicular to a resonator length direction of the semiconductor laser; epitaxially growing a crystalline second conductivity type upper cladding layer on the barrier layer in the grooves and on the ridges of the crystalline grating semiconductor layer using a growth process that causes the upper cladding layer grown on the ridges to have triangular cross-sections transverse to the (100) surface and including sloping surfaces on which further epitaxial growth does not occur; irradiating the grooves and ridges with light and monitoring the light diffracted from the grooves and ridges to determine the thickness of the upper cladding layer during epitaxial growth of the upper cladding layer; and forming first and second electrodes on the substrate and the upper cladding layer, respectively.

Claim 20

A method of producing a semiconductor laser including a diffraction grating comprising: preparing a crystalline semiconductor substrate of a first conductivity type having a (100) surface; successively growing a first conductivity type crystalline semiconductor lower cladding layer, a crystalline semiconductor active layer, a crystalline semiconductor barrier layer of a second conductivity type opposite the first conductivity type, and a second conductivity type crystalline grating semiconductor layer on the (100) surface of the crystalline substrate; forming the second conductivity type crystalline grating semiconductor layer into a periodic pattern of stripe-shaped grooves and ridges extending along a [011] direction of the crystalline semiconductor substrate parallel to each other and perpendicular to a resonator length direction of the semiconductor laser; epitaxially growing a crystalline second conductivity type upper cladding layer on the barrier layer in the grooves and on the ridges of the crystalline grating semiconductor layer using a growth process that causes the upper cladding layer grown on the ridges to have triangular cross-sections transverse to the (100) surface and including sloping surfaces on which further epitaxial growth does not occur; irradiating the grooves and ridges with light and monitoring the light diffracted from the grooves and ridges to determine the thickness of the upper cladding layer during epitaxial growth of the upper cladding layer; and forming first and second electrodes on the substrate and the upper cladding layer, respectively.