It was Wednesday morning when I approached my Manager for a discussion on my next assignment. We had delivered a project in the past week and after relaxing for a couple of days, we were preparing ourselves for next project. My Manager told me, he would discuss next project in the coming week, before that, there was a help required in other groups. There were three blocks need to be cleaned for DRC. “I have already discussed with Bharat and Arpita if you can also help on one of the blocks’ said my Manager. All the three blocks were the similar type with a similar number of DRC violations.
At Lunch, I met Bharat and Arpita. Bharat informed that his block had some 200 types of DRC and total count was about 2600. I and Arpita also had the same number in our blocks, when we got the blocks for DRC fixes. I told, “I was just looking at the block till now and was trying to understand how the block was designed and where the DRC violations are falling”. Bharat also had a similar comment. Arpita said “you are just looking at your blocks? I have fixed around 60-70 violations already”. Until tea-time, Bharat was able to fix some 60 violations and I was able to fix just 10. By the evening I and Bharat were discussing, ‘who designed these blocks? How someone can just make LVS clean Layouts without considering DRC.
Next day at Lunch, Bharat said, “I am fixing the DRC’s, but I have to move a lot of base layers and I am just able to correct bottom area DRC. My block is still showing 2400 DRC Violation count”. I told, I had corrected all the device placements and in fact, DRC Violation count in my block was increased to 2700. Arpita was looking at us with surprise and said “you guys are still nowhere near the target. I have only 600 remaining violations, Metals DRC’s are fixed and only some base layer violations are there. I hope I will be done by evening”. In the evening, I and Bharat were done with device placement related violations and both of us were having around 2000 pending violations. LVS was continuously clean for Bharat and I was also able to make my block LVS clean. We went to Arpita to see her progress, she was staring at the screen. “This dam DRC is eating my whole head. I am finding it difficult to disturb the floorplan at this point. But yeah my count is just 550. I will clean these tomorrow” she said in a typical girly tone. “And what about LVS” asked Bharat. Arpita “I will check that also tomorrow”.
3rd day was a cakewalk for me and Bharat, with every DRC run the count was going down by 200. By teatime, both of us were all set for weekend blue and was planning for TGIF. Arpita was looking worried, as she had to move some devices in her block, moreover she was clueless for 30 shorts she was getting.
The above-said assignment was a lifetime experience for me and Bharat. Both of us have a natural way of solving a problem. We always prefer to fix the issues in a systematic way, ‘analyze’ ‘understand’, ‘plan’ and ‘fix’. When we got the Blocks for fixes, we first Analysed the placement and causes of DRC violations. We never tried to jump on DRC fixes, but we put efforts to sort out the DRC violations in different segments for better understanding. Bharat planned to fix the violation by cleaning lower to an upper area of his Block, I preferred from lower hierarchy to upper. As we were knowing the reasons for the violations hence the fixes were coming with no extra violation, we were very confident in spite of a huge number of violations on the final day. We were verifying LVS time to time and making sure, no LVS violation should create any extra work for us.
Arpita took the task as if she is going to attack an enemy. Cut down DRC count as early as possible so that victory could be ensured. In reality, she was just cutting the ‘pawns’; ‘Bishops’, ‘rooks’ and ‘knights’ were far ways from her. I and Bharat were solving the problem of a friend by applying a systematic approach; looking carefully at each and every level of DRC issues and solved the problem without compromising quality parameters.

Author: Mr. Prafulla Galphade, 17+ years in VLSI Industry

5 COMMENTS

  1. It is good learning from this blog at critical time when design team has to deliver clean design in short time and facing many complicated DRC issues.

    In short time, as a team work with systematic and right approach to deliver clean design is very learning when whole team has done excellent job at their end.

  2. Very Good article.
    In latest technology, we have to go with this approach.
    DRC is bottleneck and needs to be taken care while doing floorplan itself.
    At least base Drc needs to be clean only then you are sure that there is no floor plan change at later stage.
    Meanwhile Floorplan needs to be EM complaint as we have fix patterning which needs a lot of movement if not taken care initially…

  3. The way you explained is really good .
    You have shared a good approach to solve the problem . It happens many a times …. That while working on drc clean layout people forget about floor plan . 🙂

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