Four Main IC Manufacturing Stages
                      (Harrison 1989; Chen 1987)

The following chart lists 4 main manufacturing stages through which a 
wafer lot passes, where each stage is usually performed, and typical 
cycle time and yields for each stage.

STAGE                   LOCATION        CYCLE TIME    YIELD     
-----                   --------        ----------    --------------

1. Wafer Fabrication    Fabrication     20-40 days    92% 
                        Plant                         (good wafers)
        |               
        V

2. Wafer Probe          Fabrication     3-5 days      25-75% 
                        Plant                         (higher  
        |                                             for mature       
        V                                             products)

   (die bank inventory)

        |
        V

3. Chip Assembly        Assembly        3-10 days     92-98% 
                        Plant                         (units out
        |                                             per unit   
        V                                             started)

4. Chip test            Assembly        4-15 days     10-92% 
                        Plant                         (low for 
        |                                             new products)
        V

   (final goods inventory)               ---------    --------        
                                        30-70 days    30-40% 
                                         (overall)    (overall)