As the cost of a complete mask set has dramatically increased and now represents a significant part of the overall project cost, it is critical for design teams, mask data preparation teams, and mask shops to implement a robust and repeatable Mask Data Preparation flow, which increases the productivity of the mask set creation and removes any risk of error.
Multi Project Wafers (MPWs, Shuttles, or Pizza masks) are becoming more prevalent in order to share mask costs between projects and are now used for manufacturing test chips, prototypes, and low production chips.
GOTcross is an advanced placement engine dedicated to MPWs and their specific requirements in terms of deliverability, chip packaging, and expected production outcome. GOTcross optimizes the placement solution in order to meet specific customer needs with respect to area minimization, cut set minimization, or customer delivery optimization.
Manufacturing and production requirements
Unlike general purpose placement engines, GOTcross is tailored for MPWs and takes into account packaging requirements: saw line width, guard rings, and margins, as well as production requirements, allowing the customer to define expected production outputs for some or all of his chips.
Customized optimization criteria
As MPWs are used for different purposes (test chips, low production chips…). GOTcross offers different optimization criteria: minimum area, minimum number of cut sets, optimized customer deliveries… Customers select pre-defined optimization modes or even create their own in order to best reflect their needs.
Optimized customer deliveries
Often MPWs regroup chips from different customers, different groups, different packaging requirements… that need to be retrieved independently after manufacturing. GOTcross optimizes the delivery of such chips by minimizing the number of cut sets necessary to saw them.
Extend capabilities with GOTmuch
Before placement GOTcross checks the integrity and mask manufacturability of all chips imported in the assembly and at the end it inserts dummy fill between chips in order to avoid Chemical Mechanical Polishing (CMP) issues. GOTcross can be used in standalone mode or within GOTmuch graphical multi-chip assembly editor for results visualization and manual tuning.
Automatic documentation and database merging
User documentation is generated by the click of a button. Format and available information are customized through a plug-in mechanism. Final layout data is generated as a single database or multiple databases that can be adjusted to offer the best trade-off between job deck complexity and file size.
Examples made with GOTcross
| Example 1 | Example 2 | |
|---|---|---|
| Optimization by Area |  |  |
| Lost area | 8.8 % | 10.3 % |
| Gross die | 104 | 77 |
| Number of cutsets | 12 | 12 |
| Optimization by Cutsets |  |  |
| Lost area | 20.8 % | 14.3 % |
| Gross die | 89 | 73 |
| Number of cutsets | 8 | 9 |
| Production gain in a Lot of wafers* | 16% | 5% |
* For example a lot of 24 wafers of 12”
Benefits
GOTcross has been developed to optimize silicon yield
- Drive placement by expected production output for each chip
- Take packaging, sawing requirements into account for placement
- Best placement solution fits customer needs
- Minimized number of wafers necessary to deliver chips to customer
- Create documentation for customers or manufacturing line in a fraction of a second
- Easier insertion in MDP flow and manual tune up if needed
- Export assembly in standard format GDSII and OASIS ®
- Fully automated
- 10-15% silicon savings in complex multi-criteria placements
Features
- Handles production requirements
- Handles manufacturing requirements
- Customized optimization criteria
- Customer deliveries
- Automatic documentation of the assembly
- Fully integrated in GOTmuch
- Output database merging ensures compatibility of all input chip layouts
- Fully scriptable
