Methods of characterizing semiconductor light-emitting devices based on product wafer characteristics
First Claim
1. A method of characterizing the emission wavelength of a semiconductor light-emitting device structure of a product wafer having a substrate, comprising:
- establishing a relationship between a device-layer stress S(x,y) and the emission wavelength λ
E(x,y) for the device structures formed on the product wafer by measuring the device-layer stress S(x,y) of a test product wafer, dicing the test product wafer to form dies, and measuring the emission wavelengths of the dies as a function of their device-layer stress and corresponding device structure locations (x,y);
measuring a change in curvature Δ
C(x,y) of the test product wafer based on curvature measurements of the substrate performed before and after substrate processing to form the device structures;
calculating the device-layer stress S(x,y) in the test product wafer based on the measured changed in curvature Δ
C; and
associating the actual emission wavelength λ
E with the device structures based on the relationship between the device-layer stress S(x,y) and the (x,y) positions on the test product wafer to establish a predicted emission wavelength for the device structures that corresponds to the emission wavelength λ
E.
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Abstract
Methods of characterizing semiconductor light-emitting devices (LEDs) based on product wafer characteristics are disclosed. The methods include measuring at least one product wafer characteristic, such curvature or device layer stress. The method also includes establishing a relationship between the at least one characteristic and the emission wavelengths of the LED dies formed from the product wafer. The relationship allows for predicting the emission wavelength of LED structures formed in the device layer of similarly formed product wafers. This in turn can be used to characterize the product wafers and in particular the LED structures formed thereon, and to perform process control in high-volume LED manufacturing.
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Citations
22 Claims
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1. A method of characterizing the emission wavelength of a semiconductor light-emitting device structure of a product wafer having a substrate, comprising:
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establishing a relationship between a device-layer stress S(x,y) and the emission wavelength λ
E(x,y) for the device structures formed on the product wafer by measuring the device-layer stress S(x,y) of a test product wafer, dicing the test product wafer to form dies, and measuring the emission wavelengths of the dies as a function of their device-layer stress and corresponding device structure locations (x,y);measuring a change in curvature Δ
C(x,y) of the test product wafer based on curvature measurements of the substrate performed before and after substrate processing to form the device structures;calculating the device-layer stress S(x,y) in the test product wafer based on the measured changed in curvature Δ
C; andassociating the actual emission wavelength λ
E with the device structures based on the relationship between the device-layer stress S(x,y) and the (x,y) positions on the test product wafer to establish a predicted emission wavelength for the device structures that corresponds to the emission wavelength λ
E. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of characterizing an emission wavelength of a semiconductor light-emitting device (LED) structure of a product wafer having a substrate and a device layer, comprising:
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a) measuring at least one characteristic of a test product wafer formed in substantially the same manner as the product wafer, wherein the at least one characteristic is selected from the group of characteristics comprising;
device layer stress and product wafer curvature;b) dicing the at least one test product wafer to form LED dies that have associated therewith a position on the test product wafer; c) measuring an LED emission wavelength for each the LED dies to establish a set of LED emission wavelengths that vary with position on the product wafer; d) determining a relationship between the at least one test product wafer characteristic, the set of LED emission wavelengths, and the positions of the LED dies; and e) using the relationship determined in act d) to predict the LED emission wavelength of the LED structures formed on the product wafer. - View Dependent Claims (8, 9, 10, 11)
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12. A method of forming semiconductor light-emitting devices (LEDs), comprising:
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forming a product wafer comprising LED structures formed on a substrate by a process having one or more process variables, with the substrate having a known initial curvature C0(x,y) prior to forming the LED structures thereon; measuring a curvature C(x,y) of the product wafer after forming the light-emitting device structures thereon, and determining a change in curvature Δ
C(x,y)=C(x,y)−
C0(x,y);calculating a stress S(x,y) in the product wafer based on the measured changed in curvature Δ
C(x,y);associating an emission wavelength λ
E of the LED structures with the calculated stress S(x,y) based on a relationship between the calculated stress S(x,y) and (x,y) positions of the light-emitting device structures on the product wafer; andcomparing the emission wavelength λ
E to an emission-wavelength variation tolerance and binning the LED structures into one or more bins based on the tolerance. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A method of forming semiconductor light-emitting devices (LEDs), comprising:
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forming a product wafer comprising LED structures formed on a semiconductor substrate by a process having one or more process variables; measuring a curvature uniformity of the product wafer after forming the LED structures thereon; and adjusting at least one of the one or more process variables to meet at least one of a curvature uniformity requirement and a stress uniformity requirement.
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19. A method of forming a semiconductor light-emitting device (LED), comprising:
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forming a product wafer comprising LED structures formed on a substrate by a process having one or more process variables, with the substrate having known initial curvature C0(x,y) prior to forming the light-emitting device structures thereon; measuring a curvature C(x,y) of the product wafer after forming the light-emitting device structures thereon, and determining a curvature uniformity based on C0(x,y) and C(x,y); determining a first number of die that fall within a first range of curvature uniformity; determining a second number of die that fall within a second range of curvature uniformity; and assigning a quality value for the product wafer based on the first and second numbers. - View Dependent Claims (20, 21)
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22. A method of forming semiconductor light-emitting devices, comprising:
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forming a product wafer comprising light-emitting device structures formed on a substrate by a process having one or more process variables, with the substrate having known initial curvature C0(x,y) prior to forming the light-emitting device structures thereon; measuring a curvature C(x,y) of the product wafer after forming the light-emitting device structures thereon, and determining a change in curvature Δ
C(x,y)=C(x,y)−
C0(x,y);associating an emission wavelength λ
E of the light-emitting device structures with the calculated wafer curvature C(x,y,) based on a relationship between the calculated curvature C(x,y) and (x,y) positions of the light-emitting device structures on the product wafer; andcomparing the emission wavelength λ
E to an emission-wavelength variation tolerance to determine which light-emitting structures can be used to form a light-emitting device.
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Specification