METHOD OF ROOM TEMPERATURE COVALENT BONDING
A method of bonding includes using a bonding layer having a fluorinated oxide. Fluorine may be introduced into the bonding layer by exposure to a fluorine-containing solution, vapor or gas or by implantation. The bonding layer may also be formed using a method where fluorine is introduced into the layer during its formation. The surface of the bonding layer is terminated with a desired species, preferably an NH 2 species. This may be accomplished by exposing the bonding layer to an NH 4 OH solution. High bonding strength is obtained at room temperature. The method may also include bonding two bonding layers together and creating a fluorine distribution having a peak in the vicinity of the interface between the bonding layers. One of the bonding layers may include two oxide layers formed on each other. The fluorine concentration may also have a second peak at the interface between the two oxide layers.
1 . (canceled)
2 . A bonding method comprising:
forming a first bonding layer on a first element, wherein forming the first bonding layer comprises:
depositing a first film on the first element,
introducing fluorine into the first film,
polishing the first film,
depositing a second film directly on the first film to define an interface between the first film and the second film,
introducing fluorine into the second film, and
polishing the second film;
forming a second bonding layer on a second element;
bringing into contact a surface of the second film with a surface of the second bonding layer at about room temperature; and
forming a direct bond between the second film and the second bonding layer without an intervening adhesive.
3 . The method of claim 2 , wherein forming the first bonding layer comprises depositing the first film and subsequently introducing fluorine into the first film; and depositing the second film and subsequently introducing fluorine into the second film.
4 . The method of claim 3 , wherein introducing fluorine into the first film comprises implanting fluorine ions in the first film.
5 . The method of claim 3 , wherein introducing fluorine into the first film comprises exposing the first film to hydrogen fluoride (HF).
6 . The method of claim 2 , wherein polishing the second film comprises polishing sufficiently for forming covalent bonds between the first bonding layer and the second bonding layer at about room temperature
7 . The method of claim 6 , wherein polishing the second film comprises polishing the second film to have a surface roughness of about 1 Å to 3 Å.
8 . The method of claim 2 , wherein forming the first bonding layer comprises exposing the first element to a fluorine-containing species.
9 . The method of claim 2 , further comprising annealing the first element after introducing fluorine into the first film.
10 . The method of claim 2 , wherein forming the second bonding layer comprises forming a third film on the second element, polishing the third film, forming a fourth film on the third film and polishing the fourth film.
11 . The method of claim 10 , further comprising introducing fluorine in the third film and the fourth film.
12 . The method of claim 2 , further comprising terminating a surface of the first bonding layer with a nitrogen-containing species.
13 . The method of claim 12 , wherein terminating the surface comprises terminating the surface of the first bonding layer by exposing the surface to an ammonium hydroxide dip, an ammonium hydroxide gas, or an ammonium hydroxide-containing plasma.
14 . The method of claim 12 , wherein terminating the surface of the first bonding layer with the nitrogen-containing species produces Si—N covalent bonds between the second film and the second bonding layer.
15 . The method of claim 2 , further comprising heating the second film at a temperature in a range of about 100° C. to 300° C.
16 . The method of claim 15 , wherein heating comprises chemical vapor depositing the second film layer.
17 . The method of claim 2 , wherein depositing the second film is conducted after introducing fluorine into the first film.
18 . The method of claim 2 , further comprising forming a fluorine concentration within the first bonding layer, the fluorine concentration having a first peak at an interface between the first and second films and a second peak remotely from the first interface.
19 . The method of claim 18 , wherein forming the second bonding layer comprises forming a third film on the second element and a fourth film on the third film, the second bonding layer having a second fluorine concentration, the second fluorine concentration comprising a third peak at a third interface between the third and the fourth films.
20 . The method of claim 2 , wherein forming the first bonding layer comprises depositing the first film using a gas containing fluorine.
21 . The method of claim 2 , further comprising exposing the first film to a plasma containing one of SF 6 and CF 4 .
22 . The method of claim 2 , wherein each of the first and second films comprise silicon oxide.
23 . The method of claim 2 , wherein the first bonding layer comprises a surface SiOF layer.
24 . A bonding method comprising:
forming a first bonding layer, wherein forming the first bonding layer comprises:
forming a first film including fluorine,
polishing the first film,
depositing a second film directly on the first film after polishing the first film, the second film including fluorine,
polishing the second film; and
directly bonding the first bonding layer to a second bonding layer after polishing the second film.
25 . The method of claim 24 , wherein the directly bonding comprises forming a bond between the second film and the second bonding layer at about room temperature.
26 . The method of claim 24 , further comprising forming a fluorine concentration within the first bonding layer, the fluorine concentration having a first peak at a first interface between the first and second films and a second peak at a second interface between the first and second bonding layers.
27 . The method of claim 24 , wherein the first and second films each comprise silicon oxide.
28 . The method of claim 24 , further comprising terminating the second film with nitrogen species prior to directly bonding.