Method for permanently bonding wafers

Abstract

This invention relates to a method for bonding of a first contact surface of a first substrate to a second contact surface of a second substrate with the following steps, especially the following sequence: forming a first reservoir in a surface layer on the first contact surface and a second reservoir in a surface layer on the second contact surface, the surface layers of the first and second contact surfaces being comprised of respective native oxide materials of one or more second educts respectively contained in reaction layers of the first and second substrates, partially filling the first and second reservoirs with one or more first educts; and reacting the first educts filled in the first reservoir with the second educts contained in the reaction layer of the second substrate to at least partially strengthen a permanent bond formed between the first and second contact surfaces.

Having described the invention, the following is claimed: 
     
         1 . A method for bonding of a first contact surface of a first substrate to a second contact surface of a second substrate comprising the following steps:
 forming a first reservoir in a surface layer on the first contact surface and a second reservoir in a surface layer on the second contact surface, the surface layers of the first and second contact surfaces being comprised of respective native oxide materials of one or more second educts respectively contained in reaction layers of the first and second substrates, the second educts being selected from the group consisting of Ge, Al, GaP, GaAs, InP, InSb, InAs, GaSb, GaN, InN, Al x Ga 1−x As, In x Ga 1−x N, InAlP, CuInSe 2 , CuInGaSe 2 , CuInGaS 2 , and In 2−x Sn 2−x O 3−y ;   partially filling the first and second reservoirs with one or more first educts; and   reacting the first educts filled in the first reservoir with the second educts contained in the reaction layer of the second substrate to at least partially strengthen a permanent bond formed between the first and second contact surfaces.   
     
     
         2 . The method as claimed in  claim 1 , wherein the reacting takes place by diffusion of the first educts of the first reservoir into the reaction layer of the second substrate. 
     
     
         3 . The method as claimed in  claim 1 , wherein the reacting takes place at a temperature between room temperature and 200° C., during a maximum 12 day period. 
     
     
         4 . The method as claimed in  claim 1 , wherein the permanent bond has a bond strength of greater than 1.5 J/m 2 . 
     
     
         5 . The method as claimed in  claim 1 , wherein a reaction product is formed in the reaction layer of the second substrate during the reacting, said reaction product having a greater molar volume than a molar volume of the second educts contained in the reaction layer of the second substrate. 
     
     
         6 . The method as claimed in  claim 1 , wherein the reservoirs are formed by plasma activation. 
     
     
         7 . The method as claimed in  claim 1 , wherein the surface layer of said first contact surface is comprised of an amorphous material produced by thermal oxidation. 
     
     
         8 . The method as claimed in  claim 1 , wherein a growth layer is between the second contact surface and the reaction layer of the second substrate, said growth layer being comprised of the native oxide material of the second educts contained in the reaction layer of the second substrate. 
     
     
         9 . The method as claimed in  claim 8 , wherein before the reacting, the growth layer and/or the surface layer has an average thickness “A” between 1 angstrom and 10 nm. 
     
     
         10 . The method as claimed in  claim 1 , wherein one of said first reservoir and said second reservoir is formed in a vacuum. 
     
     
         11 . The method as claimed in  claim 1 , wherein the reservoirs are filled by one or more of the following steps:
 exposing the first contact surface to an atmosphere,   exposing the first contact surface to at least one fluid selected from the group consisting of deionized H 2 O and H 2 O 2 , and   exposing the first contact surface to at least one gas selected from the group consisting of N 2 , O 2 , and Ar with an ion energy in the range from 0 to 2000 eV.   
     
     
         12 . The method as claimed in  claim 1 , wherein the permanent bond is additionally strengthened by a reaction of the first educts filled in the second reservoir with the second educts contained in the reaction layer of the first substrate. 
     
     
         13 . The method as claimed in  claim 1 , wherein an average distance (B) between the first reservoir and the reaction layer of the second substrate immediately before the reacting is between 0.1 nm and 15 nm. 
     
     
         14 . The method as claimed in  claim 1 , wherein the first reservoir and the second reservoir are dimensioned to hold the first educts,
 wherein portions of the first educts held by the first and second reservoirs respectively react with the reaction layers of the second and first substrates, and   wherein remaining portions of the first educts held by the first and second reservoirs do not respectively react with the reaction layers of the second and first substrates and remain within the first and second reservoirs to hinder a formation of bubbles therein.   
     
     
         15 . The method as claimed in  claim 1 , wherein the second educts are selected from the group consisting of Ge and Al. 
     
     
         16 . A method of bonding a first contact surface of a first substrate to a second contact surface of a second substrate comprising the following steps:
 forming a first reservoir in a surface layer on the first contact surface and a second reservoir in a surface layer on the second contact surface, the surface layers of the first and second contact surfaces being comprised of respective native oxide materials of one or more second educts respectively contained in reaction layers of the first and second substrates, the second educts being selected from the group consisting of Ge, Al, GaP, GaAs, InP, InSb, InAs, GaSb, GaN, InN, Al x Ga 1−x As, In x Ga 1−x N, InAlP, CuInSe 2 , CuInGaSe 2 , CuInGaS 2 , and In 2−x Sn x O 3−y ;   partially filling the first and second reservoirs with one or more first educts;   forming a prebond connection between the first and second contact surfaces by bringing one or more portions of the first contact surface into contact with one or more portions of the second contact surface such that gaps are formed between the first and second contact surfaces at areas located between the respective contacted portions of the first and second contact surfaces; and   reacting the first educts filled in the first reservoir with the second educts contained in the reaction layer of the second substrate to form a reaction product to at least partially strengthen a permanent bond formed between the first and second contact surfaces, the reaction product being formed between the reaction layer of the second substrate and the surface layer of the second substrate, the reaction serving to bulge the surface layer of the second substrate toward the first contact surface to close the gaps and at least partially strengthen the permanent bond, the reaction serving to deform a portion of the reaction layer of the second substrate into the reaction product.   
     
     
         17 . The method as claimed in  claim 16 , wherein the permanent bond has a bond strength which is at least twice a strength of the prebond connection. 
     
     
         18 . The method as claimed in  claim 16 , wherein the areas in which the gaps are formed are filled with the bulged surface layer. 
     
     
         19 . The method as claimed in  claim 16 , wherein the permanent bond is additionally strengthened by a reaction of the first educts filled in the second reservoir with the second educts contained in the reaction layer of the first substrate. 
     
     
         20 . The method as claimed in  claim 16 , wherein the second educts are selected from the group consisting of Ge and Al. 
     
     
         21 . A method of bonding a first substrate to a second substrate, the first and second substrates being respectively comprised of first and second reaction layers, the method comprising the following steps:
 producing first and second surface layers respectively on the first and second reaction layers by reacting the first and second reaction layers with a first educt, the first and second surface layers having molar volumes that are respectively greater than molar volumes of the first and second reaction layers, the first and second surface layers respectively comprising first and second contact surfaces; the first and second reaction layers being comprised of one or more second educts;   forming first and second reservoirs respectively in the first and second surface layers;   filling the first and second reservoirs with the first educt; and   bringing a plurality of portions of the first contact surface into contact with a plurality of portions of the second contact surface to cause the first educt from the first and second reservoirs to respectively diffuse through the second and first surface layers and react with the second and first reaction layers, thereby bringing all of the portions of the first contact surface into contact with all of the portions of the second contact surface and permanently bonding the first substrate to the second substrate.   
     
     
         22 . The method as claimed in  claim 20 , wherein the second educts are selected from the group consisting of Ge, Al, GaP, GaAs, InP, InSb, InAs, GaSb, GaN, InN, Al x Ga 1−x As, In x Ga 1−x N, InAlP, CuInSe 2 , CuInGaSe 2 , CuInGaS 2 , and In 2−x Sn x O 3−y . 
     
     
         23 . The method as claimed in  claim 22 , wherein the second educts are selected from the group consisting of Ge and Al.