I have to admit, I’ve always had difficulty trying to wrap my head around software, especially design tools. So I’ve come to have a deep respect for those individuals charged with the task of designing the design tools themselves. Not only do they need to be able to visualize the end result, they have to work backwards to anticipate the steps required to get there, and then figure out a way to archive that knowledge for later use. In essence, before a design tool can be designed, the methodology of the steps to achieve this must be established. Then, EDA tool designers create a tool based on these established methodologies to be able to automate the design processes for manufacturing.
Current 2D tools have no notion of a 3D hierarchy and thus no way to build IP libraries for 3D. To design 3D ICs, designers had to resort to tricking 2D tools by renaming design layers or creating multiple copies of standard cell libraries. This “design-by-hand” works fine for 2.5D structures like CMOS image sensors and homogenous 3D DRAM memory stacks, but as Lisa McIlrath, of R3Logic, pointed out during the panel discussion at DATE 2009, logic/memory stacks and true heterogeneous integration will need fully functioning 3D design tools.
Understanding the ramifications of this is what makes R3Logic’s latest achievement of that much more noteworthy. The company was recently awarded a patent for “methods and systems for computer aided design of 3D integrated circuits”. According to a company statement, the patented invention comprises both the method of defining a 3D technology file that can incorporate one or more 2D wafer technologies corresponding to different tiers in a 3D stack, and that of defining a 3D hierarchical structure for functional blocks within a 3D system. Managing multiple design libraries while properly handling IP blocks that reside on more than one tier is crucial to 3D system design, notes R3Logic, whether at the circuit layout or at the system architecture level.
Achieving this milestone brings th 3D design pioneer another step closer to proving the industry with the tools they’re seeking. I offer my congratulations and look forward to hearing more about it. – F.v.T
