Die-Skipping Wire Bonds for High Bandwidth Stacked Semiconductors
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Solution Overview
Problem
Conventional wire bonded semiconductor packages have limited signal bandwidth due to low inductance relative to parasitic capacitance, restricting the number of dies that can be wire bonded to each other and the substrate.
Innovation Solution
The semiconductor device employs a wire bonding technique where bond wires skip dies in the stack, increasing their length and thereby the inductance, to balance the inductance relative to parasitic capacitance, allowing for higher signal bandwidth by forming a stepped offset in the die stack along orthogonal axes and connecting alternating dies with longer bond wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional wire bonding is used to connect each die to the substrate, then the package structure is simple and easy to manufacture, but the signal bandwidth is limited to hundreds of megahertz due to low inductance relative to parasitic capacitance
Solution Approach 1:
The wire bonding process is segmented into two distinct groups: die-skipping wire bonds that connect alternating dies (skipping one die at a time) and conventional wire bonds that connect adjacent dies. This segmentation allows the die-skipping bonds to provide higher inductance for bandwidth-critical signal paths while conventional bonds handle power, ground, and less bandwidth-sensitive signals, thus resolving the bandwidth limitation without compromising manufacturing simplicity
Solution Approach 2:
Different wire bonding approaches are applied to different functional requirements: die-skipping wire bonds with higher inductance are used for signal paths requiring high bandwidth, while conventional wire bonds are used for power, ground, and lower bandwidth signals. This local differentiation of bonding quality optimizes signal bandwidth where needed while maintaining overall manufacturing ease
2Quantity of substance
If the number of dies in the stack is increased to meet high-capacity storage demands, then storage capacity increases, but the signal bandwidth limitation restricts the number of dies that can be wire bonded
Solution Approach 1:
The wire bonding connections are segmented into die-skipping bonds for signal paths requiring high bandwidth and conventional bonds for other connections. This allows a higher number of dies to be stacked while maintaining signal bandwidth performance for critical signal paths, thus enabling increased storage capacity without being constrained by the conventional bandwidth limitation
3Reliability
If die-skipping wire bonds are used to increase inductance and signal bandwidth, then signal path bandwidth increases to approximately 5 GHz, but the wire bond length increases and manufacturing complexity increases
Solution Approach 1:
The wire bonding system is segmented into two groups with different functions: die-skipping wire bonds (longer, higher inductance) for signal paths requiring high bandwidth, and conventional wire bonds (shorter, lower inductance) for power, ground, and less bandwidth-sensitive signals. This segmentation achieves high signal bandwidth where needed while limiting the increase in overall manufacturing complexity by using simpler conventional bonds for non-critical connections
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases signal path bandwidth from hundreds of megahertz to approximately 5 GHz, enabling more dies to be directly bonded in a single stack without adding structure or circuitry, thus enhancing frequency range and transmission rate.
Implementation Method 1
the bond wires used in today's stacked packages have low inductance as compared to the parasitic capacitance of the semiconductor dies. This large capacitance relative to inductance results in low signal bandwidth
Implementation Method 2
the bond wires used in today's stacked packages have low inductance as compared to the parasitic capacitance of the semiconductor dies
Data Source
AI summary
A semiconductor device is disclosed including a wire bonded die stack where the bond wires skip dies in the die stack to provide bond wires having a long length. In one example, the semiconductor dies are stacked on top of each other with offsets along two orthogonal axes so that the dies include odd numbered dies interspersed and staggered with respect to even numbered dies only one of the axes. Wire bonds may be formed between the odd numbered dies, skipping the even numbered dies, and wire bonds may be formed between the even numbered dies, skipping the odd numbered dies. The long length of the bond wires increases an inductance of the wire bonds relative to parasitic capacitance of the semiconductor dies, thereby increasing signal path bandwidth of the semiconductor device.