Preheat oven to 350°. Toss wafer crumbs with brown sugar and butter; press into an ungreased 13x9-in. pan. Bake until lightly browned, 8-10 minutes.
For topping, place butter and brown sugar in a small saucepan. Bring to a boil over medium heat; cook and stir 1 minute. Pour evenly over crust.
Bake 10 minutes. Remove from oven; let stand 2 minutes. Sprinkle with chocolate chips; let stand until chips have softened. Spread evenly over top; sprinkle with pecans. Cool completely before cutting.