Method for manufacturing a handling device and method for reversible bonding using such a device

Abstract

A method for manufacturing a handling device includes depositing a single layer of an adhesive on a first surface of a first wafer; depositing an antiadhesive layer on a first surface of a second wafer different from the first wafer; bringing into contact the first wafer and the second wafer, the bringing into contact taking place at the level of the single adhesive layer of the first wafer and the antiadhesive layer of the second wafer; separating the first wafer and the second wafer; the first wafer including the single adhesive layer forming a handling device. The bringing into contact of the first wafer and the second wafer is carried out at a temperature T.sup.C such that T.sub.C>T.sub.g°100°C. where T.sub.g is the glass transition temperature of the material composing the single adhesive layer of the first wafer.

Claims

1. A method for manufacturing a handling device comprising: a step of deposition of a single layer of an adhesive on a first surface of a first wafer; a step of deposition of an antiadhesive layer on a first surface of a second wafer different from the first wafer; a step of bringing into contact the first wafer and the second wafer, the bringing into contact taking place at the level of the single adhesive layer of the first wafer and the antiadhesive layer of the second wafer; a step of separation of the first wafer and the second wafer; the first wafer comprising the single adhesive layer forming a handling device, wherein the step of bringing into contact the first wafer and the second wafer is carried out at a temperature T.sub.C such that T.sub.C>T.sub.g+100° C. where T.sub.c is the glass transition temperature of the material composing the single adhesive layer of the first wafer.

2. The method according to claim 1, wherein the temperature T.sub.c during the step of bringing into contact is greater than 160° C.

3. The method according to claim 1, wherein the antiadhesive composing the antiadhesive layer of the second wafer is chosen such that the adherence energy of said antiadhesive layer is less than 1 J.m.sup.−2 at the temperature at which the step of bringing into contact the first wafer and the second wafer is carried out.

4. A method for reversible bonding comprising a step of producing a handling device by a method according to claim 1 and a step of bringing into contact said handling device with a third wafer, the bringing into contact of said handling device with said third wafer taking place at the level of the surface comprising the single adhesive layer.

5. The method for bonding according to claim 4, wherein the step of bringing into contact the handling device with the third wafer is carried out at a temperature T.sub.CW such that T.sub.g<T.sub.CW<T.sub.g+50° C., where T.sub.g is the glass transition temperature of the material composing the single adhesive layer of the handling device.

6. The method according to claim 5, wherein the temperature T.sub.CW during the step of bringing into contact the handling device with the third wafer is less than 160° C.

7. The method for bonding according to claim 5, wherein the step of bringing into contact is preceded by a step of deposition of an antiadhesive layer on a first surface of the third wafer; the bringing into contact during the step of bringing into contact taking place at the level of the single adhesive layer of the handling device and the antiadhesive layer of the third wafer of interest.

8. The method according to claim 2, wherein the temperature T.sub.c during the step of bringing into contact is greater than 200° C.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0036] The figures are presented for indicative purposes and in no way limit the invention.

[0037] FIG. 1 shows a curve representing the total thickness variation (TTV) for different bonding temperatures in the case of a method according to the prior art.

[0038] FIG. 2 shows a flowchart of a method for manufacturing a handling device according to a first embodiment of the invention.

[0039] FIGS. 3A to 3E illustrate the different steps of a method for manufacturing a handling device according to a second embodiment of the invention.

[0040] FIG. 4 shows a curve representing the thickness of the single adhesive layer as a function of the distance from the edge of the first wafer in a third embodiment of the invention.

[0041] FIG. 5 shows a flowchart of a method for reversible bonding according to a first embodiment of the invention.

[0042] FIGS. 6A and 6B illustrated the different steps of a method for reversible bonding according to a second embodiment of the invention.

[0043] FIG. 7 shows a flowchart of a method for reversible bonding according to a third embodiment of the invention.

[0044] FIGS. 8A to 8C illustrate the different steps of a method for reversible bonding according to a fourth embodiment of the invention.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0045] Unless stated otherwise, a same element appearing in the different figures has a single reference.

[0046] As illustrated in FIG. 2 and FIGS. 3A to 3E, a first aspect of the invention relates to a method for manufacturing a handling device 10. In one embodiment, the method according to the invention comprises:

[0047] a step of deposition 101 (FIG. 2A) of a single adhesive layer 2 comprising a solvent on a first surface of a first wafer 1;

[0048] a step of annealing 102 of the first wafer 1 so as to eliminate solvent from the single adhesive layer 2;

[0049] a step of deposition 103 (FIG. 2B) of an antiadhesive layer 4 on a first surface of a second wafer 3 different from the first wafer 1;

[0050] a step of bringing into contact 104 (FIG. 2C) the first wafer 1 and the second wafer 3, the bringing into contact taking place by the single adhesive layer 2 of the first wafer 1 and the antiadhesive layer 4 of the second wafer 3;

[0051] a step of separation 105 (FIG. 2D) of the first wafer 1 and the second wafer 3.

[0052] In one embodiment, the step of separation 105 takes place immediately after the step 104 of bringing into contact, that is to say without any technological step (lithography, chemical mechanical polishing, etc.) taking place between the step 104 of bringing into contact and the step of separation 105.

[0053] In one embodiment, the step of deposition 101 of the single adhesive layer 2 is carried out by a spin coating technique and the thickness of the single adhesive layer 2 is comprised between 45 μm and 65 μm, for example equal to 55 μm. The material used to produce the single adhesive layer 2 may be a glue of BS15150 type sold by the Brewer company, which has a glass transition temperature comprised between 80 and 100° C. and makes it possible to obtain an adherence energy between said glue and the first wafer greater than 5 J.m.sup.−2. The step of annealing 102 is then carried out at a temperature of 220° C. This step of annealing 102 notably makes it possible to evaporate solvent from the single adhesive layer 2. As illustrated in FIG. 3A and in FIG. 4 (“after spreading” curve), the surface of the adhesive layer then has a high total thickness variation of the order of 35 μm.

[0054] In one embodiment, the step of deposition 103 of an antiadhesive layer 4 on a first surface of a second wafer 3 is carried out by spin coating and the thickness of the antiadhesive layer 4 is of the order of 50 nm, The material used to produce the antiadhesive layer 4 may be a fluorinated polymer of Novec 2702 type sold by the 3M Company.

[0055] In one embodiment, the step of bringing into contact 104 is carried out at a temperature of 210° C., At the end of this step of bringing into contact 104, the first wafer 1 is separated from the second wafer 3. As illustrated in FIG. 3E and in FIG. 4 (“after bonding/separation” curve), at the end of this step of separation 105, the first wafer 1 then has a single adhesive layer 2 of which the total thickness variation is low (7 μm) and much better than that obtained directly after its spreading (35 μm). The first wafer 1 comprising an adhesive layer 2 thereby obtained then forms a handling device 10.

[0056] The handling device 10 obtained by means of a method for manufacturing according to a first aspect of the invention may next be implemented in a method for reversible bonding,

[0057] As illustrated in FIG. 5 and FIGS. 6A and 6B, a second aspect of the invention relates to a method for reversible bonding implementing the handling device 10 obtained by a method according to a first aspect of the invention. Such a method for bonding is used when it is wished to carry out one or more manufacturing steps on a wafer of interest 5, for example a thinned wafer, and when this or these manufacturing steps necessitate a handling device 10 in order to prevent any damage at the level of the wafer of interest 5. As illustrated in FIG. 6A, in the method for reversible bonding according to the invention, a wafer of interest 5 is brought into contact with the handling device 10 at the level of the surface comprising the single adhesive layer 2.

[0058] In one embodiment, this step of bringing into contact 201 is carried out at a temperature of 150° C. In this configuration, the total thickness variation of the adhesive layer 2 is substantially equal to 7 μm for a thickness of the single adhesive layer 2 substantially equal to 55 μm. This TTV is much better than that that would have been obtained by means of a bringing into contact at 150° C. (without use of the handling device 10): 30 μm. Once the wafer of interest 5 is in place on the handling device 10, the latter may undergo new manufacturing steps 202.

[0059] In one embodiment, the manufacturing steps 202 following the reversible bonding step comprise a thinning step and a cutting out step. To do so, the wafer of interest 5 is thinned by means of a grinding technique until reaching a thickness of 80 μm then is cut out by means of a saw over a width of 1.5 mm. As illustrated in FIG. 6B, the wafer of interest 5 thereby obtained is next separated mechanically from the handling device 10 by traction in order to obtain a thin film of silicon without flaking or fissuring. The step of mechanical separation 203 is carried out at the level of the single adhesive layer/wafer of interest interface. In this embodiment, the adherence energy at the single adhesive layer/wafer of interest interface is substantially equal to 0.9 J.m.sup.−2. At the end of the step of separation 203, the wafer of interest 5 has a surface of which the total thickness variation is 7 μm and does not comprise any trace of polymer. The totality of the single layer adhesive 2 is thus still present on the handling device 10 and the latter may thus be reused directly. Moreover, the wafer of interest 5 does not necessitate a step of cleaning, no residue of adhesive being found on the surface thereof. The handling device 10 may thus be used immediately in a new method for reversible bonding.

[0060] In an alternative embodiment, the step of bringing into contact 201 is carried out at a temperature of 110° C. In this configuration also, the total thickness variation of the single adhesive layer 2 is substantially equal to 7 μm for a thickness substantially equal to 55 μm. However, the adherence energy at the single adhesive layer/wafer of interest interface becomes only 0.5 J.m.sup.−2. This embodiment makes it possible to facilitate separation between the handling device 10 and the wafer of interest 5 during the step of separation 203.

[0061] If the mechanical strains during the manufacturing steps 202 carried out on the wafer of interest 5 are high, it is preferable to choose a high adherence energy to the detriment of separation facility. It is however preferable to maintain the temperature of bringing into contact 201 the wafer of interest 5 with the handling device 10 below the temperature used during the method for manufacturing said handling device 10 during the step of bringing into contact 104 the single adhesive layer 2 with the antiadhesive layer 4.

[0062] In another embodiment illustrated in FIG. 7 and FIGS. 8A to 8C, the step of bringing into contact 201 is preceded by a step of deposition 200 (FIG. 8A) of an antiadhesive layer 6 on a first surface of the wafer of interest 5. In this embodiment, the bringing into contact 201 (FIG. 8B) thus takes place at the level of the single adhesive layer 2 of the handling device 10 and of the antiadhesive layer 6 of the wafer of interest 5.

[0063] By using an antiadhesive layer in the method for bonding according to one embodiment of the invention, the temperature during the step of bringing into contact 201 of the wafer of interest 5 with the handling device 10 may be less than the temperature used during the method for manufacturing said handling device 10 during the step of bringing into contact 104 the single adhesive layer 2 with the antiadhesive layer 4.

[0064] In one embodiment, the step of deposition 200 of the antiadhesive layer 6 on a first surface of the wafer of interest 5 is carried out by spin coating and the thickness of the antiadhesive layer 6 is 50 nm. The material used to produce the antiadhesive layer 6 may be a fluorinated polymer of Novec 2702 type sold by the 3M Company. The adherence energy between the single adhesive layer 2 of the handling device 10 and the antiadhesive layer 6 of the wafer of interest 5 is 0.4 J.m.sup.−2, which facilitates the separation of the wafer of interest 5 and the handling device 10.

[0065] The wafer of interest 5 may next undergo one or more manufacturing steps 202 as evoked previously. Once this or these manufacturing steps 202 have been carried out, the wafer of interest 5 and the handling device 10 are separated (FIG. 8C). In this embodiment also, the totality of the single adhesive layer 2 is still present on the handling device 10 at the end of the step of separation 203 and the latter may thus be reused directly. At the end of separation, the antiadhesive layer 6 is removed from the wafer of interest 5. This removal may for example be carried out by means of an oxygen plasma treatment at 80° C.