Disclosed is a method and system for inserting redundant paths (40,50) into an integrated circuit. Particularly, the invention provides a method for identifying a single via (30) in a first path (40) connecting two elements, determining if an alternate route is available for connecting the two elements (10,20) (other than a redundant via (54)), and for inserting a second path (50)into the available alternate route (70). The combination of the first (40) and second paths (50) provides greater redundancy than inserting a redundant via (54) alone. More importantly, such redundant paths (50) provide for redundancy when congestion prevents a redundant via (54) from being inserted adjacent to the single via (30). An embodiment of the method further comprises removing the single via (30) and any redundant wire segments (51), if all of the additional vias (52) used to form the second path can be made redundant.

The use of redundant routes to increase the yield and reliability of a vlsi layout

The invention details methods and apparatus for a routing system or router that includes a model. The model can be in many different forms including but not limited to: resolution enhancement technologies such as OPC; lithography model including but not limited to aerial image; pattern-dependent functions; functions for timing/signal integrity/power; manufacturing process variations; and measured silicon data. In one embodiment, the model can be described as input to the system and the model calculator can interact either with the data structure or the query engine of the detail router or both. The model calculator can accept input as a set of geometry description and produce output to guide the query functions. An example technique called set intersection is disclosed herein to combine multiple models in the system. A preferred embodiment of this invention includes a full chip grid-based router being aware of manufacturability.

Apparatus for a routing system

An initial graph of nodes is created within a routing space, and the number and locations of the nodes in the graph are adjusted. Links are created between nodes of the graph, and traces between specified nodes are created through the linked graph.

Process and apparatus for finding paths through a routing space

A system and method for routing wires using an automated circuit design tool includes a process for order negotiation to adjust the ordering of wires back and forth between conduits by considering both inter-region and intra-region constraints on the layout of the wires. Order negotiation is preferably carried out by looking both forward and backward during the processing of channels, and by flexibly accounting for intra-region, crosstalk, and grouping constraints, as well as conduit exit constraints. Pairs of nets within a conduit are classified in different categories, including (1) having internal constraints, and (2) not having internal constraints. Nets having internal constraints are generally used in order negotiation for limited purposes (e.g., breaking a loop), whereas nets having no internal constraints are generally used in order negotiation for a variety of other purposes as well, including improving the layout of other conduits.

Inter-region constraint-based router for use in electronic design automation

Some embodiments of the invention provide a router that can define a route that has different widths along different directions on the same layer. To facilitate the creation of such a route, some embodiments adaptively define the shape of interconnect-line ends (i.e., the shape of route-segment ends) on a particular layer based on the routing directions available on the particular layer. By so defining these shapes, these embodiments improve the alignment of route segments that have differing widths. In other words, dynamically defining the interconnect-line ends improves the shape of a route at bends along which the route transition from one width to another. Also, to facilitate the creation of a route with different widths and/or spacing in different directions on a particular layer, some embodiments define, for each available routing direction on the particular layer, an “unroutable” bloated region about a previously defined geometry (e.g., a previously defined obstacle, wire, or via pad) on the particular layer. An item's bloated region for a particular routing direction specifies the portion of the particular layer that is not available for route segments along the particular routing direction. As further described below, the item's bloated region for a particular direction is derived based on the minimum spacing required between the item and any route segment in the particular direction for the particular net.

Method and apparatus for routing

An efficient iterative, gridless, cost-based router for a computer controlled integrated circuit design. The fine routing process is used during the wire routing phase of an integrated circuit design and fabrication process. During the wire routing process, wires are routed between pins of nets. The routing process of the present invention is gridless and utilizes lanes that are defined based on the boundaries of objects. The cost-based router computes a cost for each wire path, and the cost is based on: (1) the manhattan wire distance: (2) the layers in which the wire runs; and (3) any overlap the wire has with soft obstacles (e.g., other wires, etc.); and (4) an estimated cost to the target. Cost computation is reduced by considering only obstacles within the layer in which a lane is run. The number of paths determined for a wire route is reduced by pruning possible paths based on the placement of obstacles within the integrated circuit. Further pruning is performed by picking the lowest cost child lane in cases when several lanes select the same lane. Paths are also pruned by stopping along any path whose work-in-progress cost estimation exceeds the final cost of a path already discovered. In multi-pin nets, the routing process selects that path (of equal cost paths) between a source pin and a target pin that also runs closer to another unconnected pin of the multi-pin net. When a source-target wire route is performed for a multi-pin net, the unconnected pin is treated as the target and the source is considered as the source-target wire route.

Efficient iterative, gridless, cost-based fine router for computer controlled integrated circuit design

An efficient, gridless, cost-based coarse router having layer assignment for a computer controlled integrated circuit design. The coarse routing process is used during the wire routing phase of an integrated circuit design and fabrication process. During the coarse wire routing process, a number of obstructions are defined. Next, the horizontal and vertical passages between adjacent obstructions, through which wires may be routed, are determined. The costs for possible wire paths connecting a pair of pins are computed based upon wire density histograms associated with the various passages through which the paths traverse. The lowest cost path is then selected. In order to increase the processing speed, a pruning method is employed to minimize the number of possible paths to be considered. In some instances, there may be areas which are overly congested. For overly congested areas, a pseudo obstruction is artificially created by the coarse router. Thereby, it may be more cost effective to route a portion of the wire through multiple different metal layers. The histogram is then updated and the next wire is iteratively routed.

Ashok Vittal

Papers

Efficient iterative, gridless, cost-based fine router for computer controlled integrated circuit design

Interative, gridless, cost-based layer assignment coarse router for computer controlled IC design