Add redundant implant for s8

compiler/pgates/single_level_column_mux.py

@@ -11,7 +11,7 @@ from tech import drc, layer
 from vector import vector
 from sram_factory import factory
 import logical_effort
-from utils import round_to_grid
+from globals import OPTS
 
 
 class single_level_column_mux(pgate.pgate):
@@ -119,6 +119,9 @@ class single_level_column_mux(pgate.pgate):
                                         offset=nmos_upper_position)
         self.connect_inst(["br", "sel", "br_out", "gnd"])
 
+        if OPTS.tech_name == "sky130":
+            self.add_implants()
+        
     def connect_poly(self):
         """ Connect the poly gate of the two pass transistors """
 
@@ -190,6 +193,19 @@ class single_level_column_mux(pgate.pgate):
         self.add_path(self.col_mux_stack[2],
                       [br_pin.bc(), mid1, mid2, nmos_lower_d_pin.center()])
  
+    def add_implants(self):
+        """
+        Add top-to-bottom implants for adjacency issues in s8.
+        """
+        # Route to the bottom
+        ll = (self.nmos_lower.ll() - vector(2 * [self.implant_enclose_active])).scale(1, 0)
+        # Don't route to the top
+        ur = self.nmos_upper.ur() + vector(self.implant_enclose_active, 0)
+        self.add_rect("nimplant",
+                      ll,
+                      ur.x - ll.x,
+                      ur.y - ll.y)
+       
     def add_pn_wells(self):
         """
         Add a well and implant over the whole cell. Also, add the