Semiconductor Laser Diode Pad Segmentation for High-Speed Modulation
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Solution Overview
Problem
The demand for semiconductor laser diodes capable of high-speed modulation (15 GHz to 30 GHz) poses challenges in designing pads for bonding wires, leading to reduced design margin and increased manufacturing time due to the need for shorter resonator lengths, which can degrade productivity and affect the connection of modulation and bias signals.
Innovation Solution
A semiconductor laser diode design featuring a primary surface with two short sides and two long sides, including an active layer, electrodes, and pads connected by interconnections along the long sides, allowing for narrower interconnection widths that maintain connectivity without inhibiting resonator length shortening and reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the resonator length is shortened to achieve high-speed modulation (15 GHz to 30 GHz), then the modulation speed is improved, but the pad size is reduced which degrades wire bonding productivity
Solution Approach 1:
The invention divides the electrical connection path into two separate pads (first pad and second pad) instead of using a single pad. The first pad is connected to the electrode through an inner interconnection, and the second pad is connected to the first pad through an outer interconnection. This segmentation allows each pad to be smaller while maintaining adequate bonding area, thus enabling high-speed modulation without degrading wire bonding productivity.
2Speed
If the resonator length is shortened to achieve high-speed modulation, then the modulation speed is improved, but the design margin for pad shape is lost
Solution Approach 1:
By segmenting the electrical connection into two separate pads with distinct interconnections, the invention provides flexibility in pad shape design. Each pad can be independently optimized for its specific function (electrode connection vs. signal input), maintaining design margin even with shortened resonator length.
Solution Approach 2:
The invention applies different interconnection configurations to different pads: the first pad uses an inner interconnection with specific width constraints, while the second pad uses an outer interconnection with narrower width. This local differentiation allows each pad to be optimized for its specific electrical and mechanical requirements, preserving design flexibility.
3Device complexity
If a single pad is used for both modulation signal and bias current, then the structure is simplified, but the bonding time increases and productivity decreases
Solution Approach 1:
The invention segments the single pad into two separate pads (first pad and second pad), each dedicated to specific electrical connections. This segmentation reduces the time required for wire bonding since the wires can be bonded to separate locations, thereby improving productivity despite the increased structural complexity.
Solution Approach 2:
The outer interconnection acts as an intermediary element that electrically connects the first pad to the second pad. This intermediary structure allows the modulation signal wire to be bonded to the second pad while the bias current wire is bonded to the first pad, enabling separate bonding operations that improve productivity.
Data Source
AI summary
A semiconductor laser diode is disclosed. The semiconductor laser diode including a primary surface constituted by two short sides and two long sides, comprises: an active layer; an electrode provided above the active layer; a first pad connected to the electrode; a second pad connected to the first pad; an inner interconnection configured to connect the electrode to the first pad electrically, the inner interconnection being provided along the long sides; and an outer interconnection configured to connect the first pad to the second pad electrically, the outer interconnection being provided along the long sides, the outer interconnection having a width along the short sides narrower than a width of the first pad along the short sides and a width of the second pad along the short sides. The active layer, the first pad, and the second pad are arranged along the long sides.