Preheat oven to 375°. Combine cracker crumbs and butter; press onto the bottom of a greased 9-in. springform pan. Bake until lightly browned, 8-10 minutes. Cool in pan on a wire rack., For filling, in a small saucepan, sprinkle gelatin over cold water; let stand for 1 minute. Heat over low heat, stirring until gelatin is completely dissolved. Add the semisweet chocolate; stir until melted. , In a large bowl, beat the cream cheese, sugar substitute and sugar until smooth. Gradually add chocolate mixture and the cocoa. Beat in vanilla. Pour onto crust; refrigerate until firm, 2-3 hours., Arrange raspberries on top of cheesecake. Carefully run a knife around edge of pan to loosen.