Method for bonding semiconductor wafers using a molecular bonding apparatus

Abstract

The present invention relates to an apparatus for the manufacture of semiconductor devices wherein the apparatus includes a bonding module that has a vacuum chamber to provide bonding of wafers under pressure below atmospheric pressure; and a loadlock module connected to the bonding module and configured for wafer transfer to the bonding module. The loadlock module is also connected to a first vacuum pumping device configured to reduce the pressure in the loadlock module to below atmospheric pressure. The bonding and loadlock modules remain at a pressure below atmospheric pressure while the wafer is transferred from the loadlock module into the bonding module.

1 . A method for bonding semiconductor wafers, the method comprising:
 evacuating a vacuum chamber of a bonding module to below atmospheric pressure;   transferring at least a first wafer and a second wafer from an external environment to a loadlock module that is connected to the bonding module;   evacuating the loadlock module to below atmospheric pressure after transferring at least the first wafer and the second wafer to the loadlock module;   transferring at least the first wafer and the second wafer from the evacuated loadlock module to the evacuated vacuum chamber of the bonding module while retaining the bonding and loadlock modules at a pressure below atmospheric pressure;   positioning the first wafer on a first bonding chuck and a positioning the second wafer on a second bonding chuck, respectively; and   moving the first wafer and the second wafer toward each other by movement of the first and/or second bonding chuck such that a main surface of the first wafer and a main surface of the second wafer locally come sufficiently close to each other to allow bonding to be initiated.   
     
     
         2 . The method according to  claim 1 , further comprising positioning the first wafer and the second wafer vertically or within 10° of a vertical position on the first and the second bonding chuck, respectively. 
     
     
         3 . The method according to  claim 1 , further comprising adjusting a vacuum pressure of the vacuum chamber after transferring at least the first wafer and the second wafer from the evacuated loadlock module to the evacuated vacuum chamber of the bonding module. 
     
     
         4 . A method for bonding semiconductor wafers, the method comprising:
 evacuating a vacuum chamber of a bonding module;   transferring at least a first wafer and a second wafer from an external environment to a loadlock module;   evacuating the loadlock module to below atmospheric pressure after transferring at least the first wafer and the second wafer to the loadlock module; and   transferring at least the first wafer and the second wafer from the evacuated loadlock module to the evacuated vacuum chamber of the bonding module by a robot device while retaining the bonding and loadlock modules at a pressure or pressures below atmospheric pressure.   
     
     
         5 . The method according to  claim 4 , further comprising:
 positioning the first wafer on a first bonding chuck and positioning the second wafer on a second bonding chuck; and   moving the first wafer and the second wafer toward each other by movement of the first bonding chuck and/or the second bonding chuck such that a main surface of the first wafer and a main surface of the second wafer come sufficiently close to each other to allow bonding of the first wafer and the second wafer to be initiated.   
     
     
         6 . The method according to  claim 5 , further comprising orienting the first wafer and the second wafer in a vertical orientation or within 10° of the vertical orientation on the first bonding chuck and the second bonding chuck, respectively, and allowing the bonding of the first wafer and the second wafer to be initiated while the first wafer and the second wafer are oriented in the vertical orientation or within 10° of the vertical orientation. 
     
     
         7 . The method of  claim 2 , wherein the first wafer and the second wafer are maintained in a vertical position or within 10° of the vertical position while moving the first wafer and the second wafer toward each other by movement of the first and/or second bonding chuck such that the main surface of the first wafer and the main surface of the second wafer come sufficiently close to each other to allow bonding to be initiated. 
     
     
         8 . The method of  claim 1 , wherein the loadlock module comprises a multi wafer storage system, and wherein the method further comprises storing a plurality of wafers in the multi wafer storage system at a pressure below atmospheric pressure, prior to transferring the plurality of wafers into the bonding module for bonding. 
     
     
         9 . The method of  claim 1 , further comprising transferring the bonded first and second wafers from the bonding module to another loadlock module, and subsequently removing the bonded first and second wafers from the another loadlock module, and wherein the bonded first and second wafers are not exposed to atmospheric pressure from the time the first wafer and the second wafers are transferred from the external environment to the loadlock module until the time the bonded first and second wafers are removed from the another loadlock module. 
     
     
         10 . The method of  claim 1 , wherein moving the first wafer and the second wafer toward each other by movement of the first and/or second bonding chuck such that a main surface of the first wafer and a main surface of the second wafer locally come sufficiently close to each other to allow bonding to be initiated comprises locating the first wafer and the second wafer at a predetermined distance to each other, and releasing the first wafer from the first bonding chuck and/or releasing the second wafer from the second bonding chuck at the predetermined distance. 
     
     
         11 . The method of  claim 10 , further comprising locally applying a force to at least one of the first wafer and the second wafer such that they locally become sufficiently close to each other at the location at which the force is applied to initiate bonding. 
     
     
         12 . The method of  claim 1 , wherein moving the first wafer and the second wafer toward each other by movement of the first and/or second bonding chuck such that a main surface of the first wafer and a main surface of the second wafer locally come sufficiently close to each other to allow bonding to be initiated comprises locating the first wafer and the second wafer at a predetermined distance to each other, and subsequently locally decreasing a clamping force applied by at least one of the first and second bonding chucks such that the first wafer and the second wafer locally become sufficiently close to each other to initiate bonding. 
     
     
         13 . The method of  claim 1 , further comprising gradually releasing the first wafer from the first bonding chuck and/or gradually releasing the second wafer from the second bonding chuck. 
     
     
         14 . The method of  claim 1 , wherein the bonding of the first and second wafers comprises molecular bonding of the first and second wafers. 
     
     
         15 . The method of  claim 1 , wherein evacuating the vacuum chamber of the bonding module to below atmospheric pressure comprises reducing the pressure within the vacuum chamber to a pressure in a range extending from 0.01 mbars and 10 mbars. 
     
     
         16 . The method of  claim 15 , wherein evacuating the loadlock module to below atmospheric pressure comprises reducing the pressure within the loadlock module to a pressure in a range extending from 1 mbars to 10 mbars. 
     
     
         17 . The method of  claim 16 , further comprising maintaining the first and second wafers at room temperature while allowing the bonding to be initiated. 
     
     
         18 . The method of  claim 1 , wherein transferring at least the first wafer and the second wafer from the evacuated loadlock module to the evacuated vacuum chamber of the bonding module comprises transferring at least the first wafer and the second wafer from the evacuated loadlock module directly to the evacuated vacuum chamber through a closable gate. 
     
     
         19 . The method of  claim 1 , further comprising controlling a propagation speed of a bonding wave between the first wafer and the second wafer upon allowing initiation of the bonding. 
     
     
         20 . The method of  claim 4 , further comprising positioning the first wafer and the second wafer in a vertical position, moving the first wafer and the second wafer toward each other in the vertical position, and initiating molecular bonding between the first wafer and the second wafer.