1. Field
The present invention relates generally to optoelectronic packages, and more particularly to optoelectronic packages having improved features and a process for manufacturing the same.
2. Related Art
Optoelectronic devices are electrical-to-optical or optical-to-electrical transducers that convert electrical signals into photon signals, and vice versa. Some optoelectronic devices are light emitters, such as lasers and light-emitting diodes (LEDs), while others are photodetectors or sensors of light. For example, a photodiode is a photodetector capable of converting light into either current or voltage, and a phototransistor is a bipolar transistor with its base-collector junction sensitive to light. A PIN photodiode is a photodetector with a wide, near intrinsic, light absorption semiconductor layer sandwiched between P and N contact regions. An avalanche photodiode (APD) is a photodetector that shows an internal current gain when a high reverse bias voltage is applied to it; the internal current gain is due to impact ionization or the avalanche effect. APDs working in the so-called Geiger or Photomultiplier mode, often referred to as SiPMs, also fall under this category. Typical applications for PINs and APDs are long range fiber optic telecommunications and laser rangefinders, i.e., devices that use a laser beam to determine the distance to a reflective object.
The integration and packaging of semiconductor optoelectronic devices share many common challenges with its counterparts in integrated circuits (ICs) and microelectromechanical systems (MEMs), such as electrical, thermal, and stress issues. Optoelectronic devices also have some unique characteristics and thus face some unique challenges.
With regard to integration and design characteristics, most optoelectronic devices have a large active area, with feature dimensions up to a few centimeters, and their functional layer depth may be as thick as the chip or the wafer: up to a few hundred microns. In most cases, the contacts are on both the front and back sides of the device. For PIN and APD devices, the supply voltage may be as high as a few hundred volts. In general, optoelectronic devices may need optical coupling and/or blocking capabilities, such as anti-reflection coating and filtering. In addition, the integration and packaging of optoelectronic devices generally require precise mechanical dimensions and alignment, an optical coating or encapsulation that is transparent at the wavelength(s) of interest, suitable optics (e.g., lenses), and a surface finish on the encapsulating material.
The challenges of integration and packaging of optoelectronic devices include low throughput assembly lines, small wafer sizes, and the need to integrate heterogeneous semiconductors onto a single device. The assembly lines for optoelectronic devices run at relatively low throughput; for example, ten thousand parts per year may be considered as volume production. In general, production orders may range from a few devices to a few thousand devices. The wafer size for optoelectronic devices are small compared to ICs. For example, wafer processing lines for optoelectronic devices run 2″ to 6″ wafers, which are small compared with the 6″ to 12″ wafers used in the IC industry. Another challenge is to integrate heterogeneous semiconductors, such as group IV (silicon) semiconductors and group III-V semiconductors, into a single device.
Optoelectronic devices are considered as specialty items compared to ICs in the semiconductor industry. However, optoelectronic devices also face cost reduction pressure from both commercial and military market segments.
In the present invention, improved features of optoelectronic devices are disclosed. In addition, a matrix assembly technology is disclosed to meet the market demand for low cost, high volume, miniaturized, and surface-mount technology (SMT) compatible optoelectronic products.