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Wafer level testing of optical devices

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20140111793 patent thumbnailZoom

Wafer level testing of optical devices


A wafer includes multiple optical devices that each includes one or more optical components. The optical components include light-generating components that each generates a light signal in response to application of electrical energy to the light-generating component from electronics that are external to the wafer. The optical components also include receiver components that each outputs an electrical signal in response to receipt of light. The wafer also includes testing waveguides that each extends from within a boundary of one of the optical devices across the boundary of the optical device and also provides optical communication between a first portion of the optical components and a second portion of the optical components. The first portion of the optical components includes one or more of the light-generating components and the second portion of the optical components include one or more of the receiver components.
Related Terms: Optic Optical Waveguide Electrical Signal Optical Component Wafer

USPTO Applicaton #: #20140111793 - Class: 356 73 (USPTO) -


Inventors: Mehdi Asghari, Dazeng Feng

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The Patent Description & Claims data below is from USPTO Patent Application 20140111793, Wafer level testing of optical devices.

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FIELD

The present invention relates to optical devices and more particularly to optical devices positioned on a wafer.

BACKGROUND

Multiple optical devices are generally fabricated on the same wafer. However, only a certain percentage of the device on a wafer will have the required performance levels. Testing optical devices before they are removed from the wafer can save the cost of removing defective devices from the wafer and then performing additional testing on each device. However, testing optical devices while they are on a wafer requires that light be injected into the devices and then extracted after being processed by the devices. The extracted light can then be processed to determine the performance level of the devices. Due to challenges associated with alignment of the devices and the light source, this process of injecting light into the devices can be undesirably difficult, time-consuming, and/or inaccurate. As a result, an improved system for testing optical devices at the wafer level is needed.

SUMMARY

A wafer includes multiple optical devices that each includes one or more optical components. The optical components include light-generating components that each generates a light signal in response to application of electrical energy to the light-generating component from electronics that are external to the wafer. The optical components also include receiver components that each outputs an electrical signal in response to receipt of light. The wafer also includes testing waveguides that each extends from within a boundary of one of the optical devices across the boundary of the optical device and also provides optical communication between a first portion of the optical components and a second portion of the optical components. The first portion of the optical components includes one or more of the light-generating components and the second portion of the optical components include one or more of the receiver components.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic of a wafer that includes optical devices that each includes one or more optical components. A first portion of the optical components on the wafers includes transmitting functionality and a second portion of the optical components on the wafers includes receiving functionality. Testing waveguides each extends across the boundary of a device and provides optical communication between the first portion of the optical components on one of the devices and the second portion of the optical components on the device.

FIG. 1B is a schematic of a wafer where the optical devices each includes the first portion of optical components and the second portion of optical components. Testing waveguides each provides optical communication between a first portion of the optical components on one of the devices and a second portion of the optical components located on another one of the devices.

FIG. 1C is a schematic of a wafer. Testing waveguides each provides optical communication between a first portion of the optical components on one of the devices and a second portion of the optical components located on another one of the devices.

FIG. 2A is a schematic of a device that has transmitting functionality.

FIG. 2B is another schematic of a device that has transmitting functionality.

FIG. 3A is a schematic of a device that has receiving functionality.

FIG. 3B is another schematic of a device that has receiving functionality.

FIG. 4A is a schematic of a transceiver.

FIG. 4B is another schematic of a transceiver.

FIG. 5A illustrates a system that includes a transmitter according to FIG. 2A in optical communication with receiver according to FIG. 3A.

FIG. 5B illustrates a system that includes a transmitter according to FIG. 2B to a receiver according to FIG. 3B.

FIG. 5C illustrates a system that includes transceivers according to FIG. 4A in optical communication with one another.

FIG. 6A illustrates a portion of a wafer constructed according to FIG. 1A. The wafer includes multiple transceivers that are each constructed according to FIG. 4A.

FIG. 6B illustrates a portion of a wafer constructed according to FIG. 1A. The wafer includes multiple transceivers that are each constructed according to FIG. 4B.

FIG. 6C illustrates a portion of a wafer constructed according to FIG. 1C. The wafer includes transmitters constructed according to FIG. 2A.

FIG. 6D illustrates the wafer of FIG. 6A further divided into transmitters and receivers to provide a wafer according to FIG. 1C.

FIG. 6E illustrates a portion of a wafer constructed according to FIG. 1B. The wafer includes multiple transceivers that are each constructed according to FIG. 4A.

FIG. 6F illustrates a portion of a wafer constructed according to FIG. 1B. The wafer includes multiple transceivers that are each constructed according to FIG. 4B.

FIG. 7 is a topview of a portion of the wafer shown in FIG. 6F modified to include facet recesses.

FIG. 8A illustrates a wafer suitable for construction of optical devices that can be tested before being separated from the wafer.

FIG. 8B is a cross-section of a ridge waveguide suitable for formation on a wafer constructed according to FIG. 8A.

FIG. 9 is a cross section of a optical component that can be operated as a modulator and/or light sensor.

FIG. 10 is a cross section of a laser that can be included in a module component.

FIG. 11A through FIG. 11D illustrates a laser built on a chip that is separate from a wafer and is then integrated into the wafer before the devices on the wafer are separated from one another and from the wafer. FIG. 11A is a topview of a portion of a device on a wafer where the chip is integrated tin the device.

FIG. 11B is a cross section of the device shown in FIG. 11A taken along the line labeled B.

FIG. 11C is a cross section of the multi-channel device shown in FIG. 11A taken along a line extending between the brackets labeled C in FIG. 11A.

FIG. 11D is a cross section of the multi-channel device shown in FIG. 11A taken along a line extending between the brackets labeled D in FIG. 11A.

FIG. 12A through FIG. 12C illustrate a suitable facet recess formed at the interface of two devices on a wafer having a light-transmitting medium on a base. FIG. 12A is a topview of the portion of the wafer having a facet recess.

FIG. 12B is a cross section of the wafer shown in FIG. 12A taken along a line extending between the brackets labeled C in FIG. 12A.

FIG. 12C is a perspective view of one of the devices shown in FIG. 12A after the devices are separated along the line labeled S in FIG. 12A. The perspective view shows the resulting facet and the portion of the facet recess that remains intact on the device after the separation.

FIG. 12D is a topview of a portion of another embodiment of a wafer having a facet recess.

DESCRIPTION

A method of forming optical devices includes generating a wafer that includes several of the same device. The method also includes testing the performance of the devices followed by separating the devices from the wafer. Separating the devices from the wafer includes separating the devices from one another. As a result, the devices can be individually sold, processed further, tested, incorporated into other systems, etc.

Each of the devices includes one or more optical components. A first portion of the optical components include transmitting functionality in that one or more of the components can generate light in response to receiving electrical energy from electronics that are external to the wafer. For instance, the first portion of components can include a light-generating component such as a laser. A second portion of the optical components includes receiving functionality in that they can generates and/or outputs an electrical signal that is a function of the light received by the component. For instance, a second portion of components can include a light sensor such as a photodiode, PIN diode, PN diode, avalanche photodiodes, and light sensors that employ a depletion region.

The wafer also includes testing waveguides. Each testing waveguide provides optical communication between one of the first portions of components and one of the second portions of components. As a result, each testing waveguide provides optical communication between components with transmitting functionality and components with receiving functionality. Electronics that are external to the wafer can be connected to the components so as to operate the components. For instance, the external electronics can operate the light-generating components such that they generate light and the light sensors such that they output an electrical signal that is a function of the level of light received by the light sensor. As a result, the external electronics can use the output of the light sensor to test the performance of the light generating components and the light sensors. Additionally, the first portion of components and/or the second portion of components on a device can include active and/or passive components in addition to the light generating components and light sensors. Because the light generated by the one or more light-generating components on a device is also processed by these additional components, the output of the one or more light sensors on a device also indicates the performance of these additional components. As a result, the performance of these components can also be tested before the devices are separated from the wafer.

Each testing waveguides extends from the first portion of optical components on a device across the perimeter of the device. Accordingly, a portion of the testing waveguide that was connected to one or more components on a device is located on another device or on a portion of the wafer outside of the device. As a result, the testing waveguides are split when the devices are separated from the wafer. Accordingly, the communication that each testing waveguide originally provides between one or more light-generating components and one or more light sensors is severed upon separation of the devices from the wafer. The portion of the testing waveguide that remains on a device can serve as the input and/or output waveguides for that device. As a result, the testing waveguides originally provide the optical communication needed for testing the components, but portions of the same waveguides later serve as input and/or output waveguides.

FIG. 1A is a schematic of a wafer that includes optical devices 10. At least a portion of the devices on the wafer are the same device. In some instances, all of the devices on the wafer are the same in order to reduce the number of steps required during fabrication of the wafer. After formation of the devices on the wafer, the optical devices 10 are separated from the wafer so they are independent of each other. Separating the devices from the wafer includes separating them from one another. As a result, the lines 12 on FIG. 1A that illustrate the boundary or perimeter of adjacent devices can represent lines along which the devices are separated from one another and accordingly from the wafer.

The optical devices 10 each includes one or more optical components 14. Examples of suitable optical components include, but are not limited to, facets through which light signals can enter and/or exit a waveguide, a taper for changing the mode size of a light signal guide by the waveguide, entry/exit ports through which light signals can enter and/or exit a waveguide from above or below the device, multiplexers for combining multiple light signals onto a single waveguide, demultiplexers for separating multiple light signals such that different light signals are received on different waveguides, optical couplers, optical switches, lasers that act a source of a light signal, light sensors such as sensors that convert all or a portion of the light signal to an electrical signal, amplifiers for amplifying the intensity of a light signal, attenuators for attenuating the intensity of a light signal, modulators for modulating a signal onto a light signal, modulators that convert a light signal to an electrical signal, and vias that provide an optical pathway from the bottom side of a device to the top side of the device. Although not illustrated, the devices can optionally include electrical devices.

One or more of the optical components 14 can include electrical components. For instance, the optical components can include contact pads (not shown) for making electrical contact with electronics that are external to the device. As an example, a laser can include contact pads that are to be electrically connected to laser driving electronics that are external to the device. Other optical components that may include contact pads for operating the component include, but are not limited to, light sensors, modulators, amplifiers, attenuators, polarizers, polarization splitters, and heaters.

A first portion 16 of the optical components 14 on the devices have a transmitting functionality. For instance, the first portion 16 of the optical components 14 include one or more light-generating components that each generates light in response to application of electrical energy to the light-generating component. The electrical energy can be applied from electronics that are external to the wafer. An example of a light-generating components includes, but is not limited to, a distributed feedback (DFB) laser, a Fabrty-Perot (FP) laser, an RSOA (reflection semiconducting optical amplifier), and a Ge laser.

A second portion 18 of the optical components 14 included on the devices have a receiving functionality. For instance, the second portion 18 of the optical components 14 include one or more receiver components that are each configured to output an electrical signal that is a function of the light received by the receiver component. For instance, the receiver components can output an electrical signal that indicates the reception and/or intensity of light received by the receiver component. In some instances, the receiver components are operated by electronics that are external to the wafer. In some embodiments of the receiver component, the electronics apply a forward bias and/or reverse bias to the receiver component and the receipt of light by the receiver component changes the flow of electrical current through the receiver component. The electrical signal that exhibits the change in electrical current serves as the electrical signal output by the receiver component or generated by the optical component. Suitable examples of receiver components that are configured output an electrical signal that indicates receipt of light, but are not limited to, photodiodes, PIN diodes, PN diodes, avalanche photodiodes, and light sensors that employ a depletion region.

The wafer includes one or more testing waveguides 20. Each of the testing waveguides 20 provides optical communication between the first portion 16 of the optical components 14 on one of the devices and the second portion 18 of the optical components 14 on one of the devices. Although FIG. 1A shows the testing waveguides 20 providing optical communication between the first portion 16 of components 14 and the second portion 18 of components 14 on the same device, the one or more testing waveguides 20 can provide optical communication between the first portion 16 of components 14 on one of the devices and the second portion 18 of components 14 on another device as shown in FIG. 1B. Additionally, each device need not have both transmitting functionality and receiving functionality. For instance, the testing waveguides 20 can provide optical communication between devices having transmitting functionality and devices having receiving functionality as shown in FIG. 1C.

The testing waveguides 20 each extends from the first portion 16 of the components 14 on one of the devices to a location that is outside of the device. Additionally, the testing waveguides 20 each extends from outside of one of the devices to the second portion 18 of the components 14 on the device. Accordingly, each of the testing waveguides 20 extends across the boundary or perimeter of the device with which the testing waveguide 20 is in optical communication. As a result, separating the devices from the wafer causes the testing waveguides 20 to be split. For instance, a sacrificial portion 22 of each testing waveguide 20 is separated from the devices upon separation of the devices from the wafer. However, as is evident from FIG. 1A, the separation of the devices from the wafer leaves the sacrifical portion of the testing waveguides 20 on at least some of the devices. In some instances, it may be desirable to remove the sacrificial portion 22 of the testing waveguide 20 from all or a portion of the devices. For instance, it may be desirable to separate the sacrificial portion 22 of the testing waveguide 20 from all or a portion of the devices. As a result, separating the devices from the wafer can optionally include separating the devices along lines such as the line labeled S in FIG. 1A. This additional separation provides devices that exclude sacrificial portions 22 of the testing waveguides 20. This separation can be done using methods such as dicing, cleaving, and etching.

Because the testing waveguides 20 provide optical communication between components 14 that include one or more light-generating components and components that include one or more receiver components, the performance of the components can be tested before the devices are separated from the wafer. For instance, external electronics (not shown) can be connected to the contact pads on the wafer such that the external electronics can operate various components on the devices. In particular, the external electronics can be connected to the wafer so as to operate the light-generating components and the receiver components. The external electronics can use the one or more receiver components to test for the presence and/or intensity of light being produced by the one or more light-generating components. When the first portion 16 of components and the second portion 18 of components include components in addition to the one or more receiver components and the one or more light-generating components, the performance of these components can also be tested. For instance, when the first portion 16 of components and/or the second portion 18 of components on a device includes one or more modulators, the external electronics can also be configured to operate the one or more modulators. The output from the one or more receiver components on the device can be monitored while operating the one or more modulators and the one or more light-generating components. In this instance, the output of the one or more receiver components indicates the performance level of the one or more modulators.

Using the above testing methods, devices that fail the testing procedures can be identified. For instance, light-generating components that fail to generate light or fail to generate sufficiently intense light can be identified. When the number of devices on a wafer that have components failing the testing procedures exceeds a threshold, the entire wafer can be discarded without separating the devices from the wafer. Alternately, devices that are identified as failing the testing procedures need not be separated from the wafer while the device that pass the testing procedures can be separated from the wafer. As a result, the ability to test these devices while still on the wafer reduces the need for further processing of failed devices.



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stats Patent Info
Application #
US 20140111793 A1
Publish Date
04/24/2014
Document #
13694047
File Date
10/22/2012
USPTO Class
356 73
Other USPTO Classes
International Class
01J1/04
Drawings
18


Optic
Optical
Waveguide
Electrical Signal
Optical Component
Wafer


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