Sample holder, device and method for detaching of a first substrate

Abstract

A method and device for detaching a first substrate, which is connected to a second substrate by an interconnect layer, from the second substrate by embrittlement of the interconnect layer. A method for bonding of a first substrate to a second substrate with an interconnect layer which can be embrittled by cooling. A use of a material which can be embrittled for producing an interconnect layer between first and second substrates for forming a substrate stack. A substrate stack, formed from a first substrate, a second substrate and an interconnect layer located therebetween, the interconnect layer formed from a material which can be embrittled. A wafer chuck for holding a first substrate when the first substrate is being detached from a second substrate with fixing means which can be activated by lowering the temperature.

Claims

1. A method for detaching a pair of substrates from each other, said method comprising: providing a first substrate and a second substrate that is temporarily bonded to the first substrate by an interconnect layer to form a substrate stack, said interconnect layer having a first side connected to the first substrate and a second side connected to the second substrate, wherein the interconnect layer is comprised of a plurality of layers including at least one adhesive layer and at least one separation layer; holding the first substrate to a holding area of a first wafer chuck, said first wafer chuck including a cooling body having a cooling area and a fixing means to fix the first substrate to the holding area; activating the fixing means to fix the first substrate to the holding area of the first wafer chuck; cooling the interconnect layer to a temperature that is at or below a critical temperature for embrittlement of the at least one separation layer, thereby forming cracks in the at least one separation layer, said critical temperature being at or below 0 C., wherein the cooling of the interconnect layer includes flowing of a cooling fluid through the cooling area of the cooling body of the first wafer chuck and wherein the cooling of the interconnect layer forms cracks through only a portion of the at least one separation layer in a partial embrittlement; and detaching the first substrate from the second substrate.

2. The method as claimed in claim 1, wherein the critical temperature is below 100 C.

3. The method as claimed in claim 1, wherein the interconnect layer is comprised of: a silicone, and/or a plastic, and/or wax.

4. The method as claimed in claim 3, wherein the interconnect layer further comprises: organic components and/or inorganic components and/or metals and/or metal ions and/or metal alloys and/or ceramics.

5. The method as claimed in claim 4, wherein the inorganic components are inorganic molecules.

6. The method as claimed in claim 1, wherein the interconnect layer is comprised of a plastic selected from the group consisting of: a thermoplastic, a duroplastic, and an elastomer.

7. The method as claimed in claim 1, wherein at least one layer of the interconnect layer is comprised of organic molecules.

8. The method as claimed in claim 1, wherein said cooling body of the first wafer chuck has a thermal conductivity between 0.1 W/(m*K) and 5000 W/(m*K).

9. The method as claimed in claim 1, wherein the method further comprises: holding the second substrate to a holding area of a second wafer chuck, said second wafer chuck including a cooling body having a cooling area through which a cooling fluid flows to cool the interconnect layer to the temperature that is at or below the critical temperature for embrittlement of the at least one separation layer.

10. The method as claimed in claim 9, wherein the interconnect layer is cooled from both sides of the substrate stack to symmetrically cool the interconnect layer.

11. The method as claimed in claim 9, wherein a flow direction is the same for the cooling fluid flowing through the cooling area of the first wafer chuck and the cooling fluid flowing through the cooling area of the second wafer chuck.

12. The method as claimed in claim 9, wherein a flow direction is the opposite for the cooling fluid flowing through the cooling area of the first wafer chuck and the cooling fluid flowing through the cooling area of the second wafer chuck.

13. The method as claimed in claim 1, wherein the method further comprises: exposing the interconnect layer to ultrasound during and/or after cooling of the interconnect layer and/or embrittlement of the at least one separation layer of the interconnect layer.

14. The method as claimed in claim 1, wherein the interconnect layer is cooled from one side of the substrate stack.

15. The method as claimed in claim 1, wherein the critical temperature is in a range between 0 C. and 150 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows a schematic cross section of a first embodiment of a substrate stack according to the invention with an interconnect layer, not to scale,

(2) FIG. 1b shows a schematic cross section of a second embodiment of the substrate stack according to the invention located on a film, not to scale,

(3) FIG. 1c shows a schematic cross section of a third embodiment of the substrate stack according to the invention with an interconnect layer comprised of several layers, not to scale,

(4) FIG. 1d shows a schematic cross section of a fourth embodiment of the substrate stack according to the invention, not to scale,

(5) FIG. 1e shows a schematic cross section of a fifth embodiment of the substrate stack according to the invention with an interconnect layer which has a structured layer, not to scale,

(6) FIG. 1f shows a schematic cross section of a sixth embodiment of the substrate stack according to the invention with an interconnect layer comprised of a bond layer and a separating layer, not to scale,

(7) FIG. 2a shows a schematic cross section of a first embodiment of a device according to the invention in the counterflow principle, not to scale,

(8) FIG. 2b shows a schematic cross section of a second embodiment of a device according to the invention in the cocurrent flow principle, not to scale,

(9) FIG. 3 shows a schematic cross section of a third embodiment of the device according to the invention, not to scale,

(10) FIG. 4 shows a schematic cross section of a fourth embodiment of the device according to the invention, not to scale,

(11) FIG. 5 shows a schematic cross section of a fifth embodiment of the device according to the invention, not to scale,

(12) FIG. 6 shows a schematic cross section of a sixth embodiment of the device according to the invention, not to scale,

(13) FIG. 7 shows a schematic cross section of a seventh embodiment of the device according to the invention, not to scale,

(14) FIG. 8 shows a schematic cross section of an eighth embodiment of the device according to the invention, not to scale,

(15) FIG. 9 shows a schematic cross section of a ninth embodiment of the device according to the invention, not to scale,

(16) FIG. 10 shows a schematic cross section of a first embodiment of a debond process according to the invention, not to scale,

(17) FIG. 11 shows a schematic cross section of a second embodiment of a debond process according to the invention, not to scale,

(18) FIG. 12 shows a schematic cross section of a third embodiment of a debond process according to the invention, not to scale.

(19) In the figures the same components or components with the same function are identified with the same reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

(20) FIGS. 1a, 1b, 1c, 1d and 1e show substrate stacks 1, 1, 1, 1.sup.IV each comprised of a first substrate 2, 2 which is made as a product substrate, an interconnect layer 3, 3, 3, 3 which is made as cement, and a second substrate 4 which is made as a carrier substrate. The interconnect layer 3, 3, 3, 3 joins the first substrate 2, 2 to the second substrate 4. The substrates 2, 2, 4 have a diameter D.

(21) The interconnect layer 3 in the first embodiment according to FIG. 1a is comprised of a single layer which is made as a single-component system or multicomponent system.

(22) In the second embodiment according to FIG. 1b the substrate stack 1 has an in particular back-thinned product substrate 2 which has been fixed via its surface 2o which has not been back-thinned by the interconnect layer 3 on the carrier substrate 4. One back-thinned side 2r is fixed on a film, 5, in particular a dicing tape. The film 5 is clamped on a frame 6.

(23) The substrate stack 1 according to FIG. 1c is comprised of the product substrate 2 which is fixed to the carrier substrate 4 via the interconnect layer 3 which comprises in particular several layers 14. Each of the layers 14 can be comprised of a single component or of several components. In particular not all the layers 14 need be adhesive layers.

(24) In the embodiment according to FIG. 1d the substrate stack 1 is provided with an interconnect layer 3 which is made as a ZoneBOND system. The interconnect layer 3 has one adhesive layer 14 which extends over the entire contact area between the two substrates 2, 4. One adhesion-reduced layer 14 covers one of the surfaces of the interconnect layer 3 so that the joining force acts at least predominantly, preferably essentially exclusively on an outer ring section which surrounds the adhesion-reduced layer 14.

(25) In the embodiment according to FIG. 1e the substrate stack 1.sup.IV is comprised of the product substrate 2 which is fixed to the carrier substrate 4 via the interconnect layer 3. The interconnect layer 3 is formed from a structured layer 14. The embodiment of the invention calls for structuring the layer 14. The structuring forms cavities 20 in which a filler material 22 can be accommodated. The structuring takes place by a known process, in particular by imprint lithography or photolithography. The embodiment of the invention yields a patterned cement surface 3o which by one of the embrittlement processes causes a lowering of the adhesion force between the cement surface 3o and the carrier substrate surface 4o. In particular the filler material 22 which has been deposited in the cavities 20 reduces its volume by the temperature reduction such that the effective adhesive area between the cement 3, 3, 3, 3 and the carrier substrate 4 is reduced.

(26) The structured layer 14 according to one alternative embodiment can also be part of a multilayer system and therefore can be covered by another named layer 14.

(27) In the embodiment according to FIG. 1f the substrate stack 1.sup.V is comprised of the product substrate 2 with topographies, in particular bumps 23. The product substrate is fixed to the carrier substrate 4 via the interconnect layer 3.sup.IV. The interconnect layer 3.sup.IV is comprised of a layer 14 of cement and a separating layer 14.sup.IV. The layer 14 of cement is used in particular to embed the topographies 23 of the product substrate 2.

(28) FIG. 2a shows a schematic cross section of a simplified first embodiment of a cooling unit 7, not to scale, which is operated in the counterflow principle. The cooling unit 7 is comprised of at least one, preferably exactly two, cooling bodies 9 with a cooling area 9k. The cooling bodies 9 have channels 10 and/or chambers 11 which are supplied with a cooling fluid 18, in particular a cooling liquid, still more preferably a cooling gas, via in particular re-routable lines 8, 8 which are made as feed and drain line. In order to ensure more efficient removal of the heat which has been absorbed by the cooling area 9k, the embodiment of the invention is preferably operated in counterflow. The two cooling fluids which are flowing through the channels 10 and/or chambers 11 of the cooling bodies 9 have anti-parallel or multidirectional flow vectors.

(29) The substrates 2 and/or 4 can be fixed by the fixing elements 21, in particular vacuum tracks, on the cooling units 7, 7, 7 which are made preferably as wafer chucks. The fixing takes place before and/or during and/or after an embrittlement for debonding of the substrates 2, 4.

(30) In the embodiment according to FIG. 2b, the cooling units 7 operate in the cocurrent flow principle. The two cooling fluids 18 which are flowing through the channels 10 and/or chambers 11 of the cooling bodies 9 have parallel or unidirected flow vectors.

(31) FIG. 3 shows a cooling unit 7 comprised of a cooling body 9, two lines 8, 8 which are made as a feed and drain line and which are used for supply and drainage, as well as several discharge openings 12 which are distributed along the cooling area 9k and which allow a discharge of the cooling fluid 18 via a cooling body surface 9o which is facing the substrate stack 1, 1, 1, 1, 1.sup.IV.

(32) The cooling body 9 is cooled by the cooling fluid 18 which is flowing, in particular circulating in the channels 10 and/or the chambers 11. At the same time part of the cooling fluid 18 discharges from the openings 12 and leads to an additional, more intense cooling of the substrate stack 1, 1, 1, 1, 1.sup.IV. The discharged cooling fluid 18 which has been heated in particular by the substrate stack 1, 1, 1, 1, 1.sup.IV and which has passed into the gaseous phase is removed along the cooling body surface 9o.

(33) For monitoring of the cooling process, according to one development of this invention a measurement of the amount of heat which has been absorbed by the cooling fluid 18 is taken by a temperature comparison measurement.

(34) FIG. 4 shows a cooling unit 7 comprised of a cooling body 9, a line 8 which is made as a feed line and several discharge openings 12 which allow discharge of the cooling fluid 18 via the cooling body surface 9o.

(35) The cooling body 9 is cooled by the cooling fluid 18 which is flowing in the channels 10 and/or the chambers 11. At the same time part of the cooling fluid 18 discharges from the discharge openings 12 and leads to an additional, more intense cooling of the substrate stack 1, 1, 1, 1, 1.sup.IV. The discharged cooling fluid 18 which has been heated in particular by the substrate stack 1, 1, 1, 1, 1.sup.IV and which has passed into the gaseous phase is removed along the cooling body surface 9o.

(36) In particular, the discharge rate and the discharge pressure of the cooling fluid 18 on the discharge openings 12 can be regulated by a control (by means of a control apparatus which is not shown and which is responsible for the control of the described processes and components and equipment) of the cooling fluid pressure.

(37) The cooling body 9 is preferably made as a choke valve which is comprised of several discharge openings 12. Isenthalpic expansion of the cooling fluid 18 is preferred and thus further cooling of the gas can take place by a correspondingly precompressed cooling fluid 18 (if the cooling fluid 18 is in the correct temperature range and has a positive Joule-Thomson coefficient). The discharge openings 12 are used as choke valves, the cooling bodies 9 as insulation.

(38) In one especially preferred embodiment clean air as the cooling fluid 18 from the vicinity is compressed by compressors to more than 20 bar, in particular more than 50 bar, still more preferably more than 100 bar, most preferably more than 150 bar, most preferably of all more than 200 bar. Temperature drops of several degrees Celsius are possible by isenthalpic expansion of the air to a pressure of less than 100 bar, in particular less than 50 bar, still more preferably less than 25 bar, most preferably less than 10 bar, most preferably of all less than 5 bar. In particular, this isenthalpic expansion yields a temperature drop of more than 5 C., in particular more than 10 C., still more preferably more than 25 C., most preferably more than 35 C., most preferably of all more than 45 C. These temperature drops can induce the embrittlement effect if the material of the interconnect layer is designed for the corresponding temperature range.

(39) FIG. 5 shows a cooling unit 7 comprised of a fixing element 21 which is made as a porous body and which on the one hand is used for fixing of the substrate stack 1, 1, 1, 1, 1.sup.IV, 1.sup.V by means of negative pressure and on the other for exhausting the cooling fluid 18 which has been discharged from the discharge openings. Furthermore the cooling unit 7 has a tank 13 which is embedded in particular in the fixing element 21 and which comprises in particular of a nonporous and/or other type of material, with a feed line 8 and several discharge openings 12.

(40) The discharge openings 12 are outputs of the tank 13. One aspect of the invention includes the feed of a cooling fluid 18 via the feed line 8 into the tank 13 and discharge of the cooling fluid 18 from the discharge openings. Subsequently the exhaust of the cooling fluid 18 which has passed in particular into the gaseous aggregate state takes place via the porous cooling body 9. The cooling takes place in this preferred embodiment predominantly by the cooling fluid 18 which has been routed from the discharge openings 12 directly to the substrate stack.

(41) This embodiment of the invention is thus suited in particular as a cooling wafer chuck which at the same time has a fixing possibility for debonding by the application of a vacuum via the porosity of the cooling body 9.

(42) The porous body 21 according to one development of the invention is made laterally vacuum-tight by construction engineering measures. In particular the porous body 21 is inserted into a component (not shown) which surrounds the porous body so that there is no vacuum leak on the sides of the cooling body 9.

(43) FIG. 6 shows a cooling unit 7.sup.IV which is comprised of a cooling body 9.sup.IV, whose diameter D or the diameter d of its cooling area 9k is smaller than the diameter D of at least one of the substrates 2, 2, 4. This measure makes available a cooling body 9.sup.IV with which sequential embrittlement of the interconnect layer 3, 3, 3, 3 can take place by a relative movement to a substrate stack 1, 1, 1, 1, 1.sup.IV. This embodiment is advantageous for substrate stacks 1, 1, 1, 1, 1.sup.IV whose interconnect layer 3, 3, 3, 3 is bonded solely on parts of the contact surface between the substrates 2, 4, in particular on the outer periphery, while other sections are not connected or are connected only with low adhesion force.

(44) These cooling bodies 7.sup.IV can advantageously be used for embrittlement of a ZoneBOND substrate stack according to FIG. 1d without unduly thermally loading the central region of the substrate stack 1.

(45) FIG. 7 shows a cooling unit 7.sup.V which has an annular cooling body 9.sup.V. The annular cooling body 9.sup.V constitutes an improvement of the invention in document WO2012/139627A1. The annular embodiment of the cooling body 9.sup.V allows in particular fully peripheral cooling which is however limited to the outer periphery of a substrate stack 1, and preferably simultaneous lifting (detachment) of the carrier substrate 4 after the embrittlement.

(46) The cooling body 9.sup.V has at least one line 8 which is made as a feed line and at least one line 8 which is located in particular opposite, and which is made as a drain line. Via an annular channel 10 the cooling fluid 18 is routed from the feed line into at least one chamber 11 to a cooling surface 9k.

(47) FIG. 8 shows a cooling unit 7.sup.VI which has a receiving tank 15 in which the cooling fluid 18 is stored. Within the receiving tank 15 there is a wafer chuck 16 on which a substrate stack 1 can be deposited in order to be completely immersed in the cooling fluid 18. Preferably the wafer chuck 16 has loading units 17 for this purpose, with which loading and unloading of the substrate stack 1, 1, 1, 1, 1.sup.IV is enabled.

(48) The loading units 17 are sealed by means of seals (not shown) against the wafer chuck 16.

(49) Alternatively the wafer chuck 16 itself can be made as a movable loading unit.

(50) This embodiment of the invention allows automated loading and unloading of the substrate stack 1, 1, 1, 1, 1.sup.IV by a robot. The control takes place via the control apparatus.

(51) FIG. 9 shows a cooling unit 7.sup.VII which in addition to the receiving tank 15 and the wafer chuck 16 has frame holder 19 which is located in particular outside the receiving tank 15. The substrate stack 1 which is fixed on a film 5 is immersed into the cooling fluid 18 while the frame 6 is fixed by the frame holder 19 which can in particular be moved and controlled separately.

(52) The frame holder 19 can be located outside or inside the receiving tank 15. By taking the frame holder 19 into the receiving tank 15 the substrate stack 1 could be taken completely into the cooling fluid 18.

(53) FIG. 10 shows a first debond process of the invention (detachment method) in which the cooling unit 7, 7, 7, 7, 7.sup.IV is used in the counterflow principle to cool the substrate stack 1, 1, 1, 1, 1.sup.IV and at the same time as a debonding wafer chuck. The two substrates 2 and 4 are each separated from one another by a cooling body 9 which is at the same time a debonder wafer chuck by a shear stress .

(54) The embrittlement of the interconnect layer 3, 3, 3, 3 takes place briefly before (preferably) and/or during the debonding. The substrates 2 and 4 are fixed at least during detachment/debonding by the fixing elements 21, in particular vacuum tracks.

(55) FIG. 11 shows a second debond process of the invention in which a cooling unit 7 is used in the counterflow principle to cool the substrate stack 1, 1, 1, 1, 1.sup.IV and at the same time as a debonder wafer chuck. The two substrates 2 and 4 are each separated from one another by a tensile stress F by one cooling body 9 at a time which is at the same time a debonder wafer chuck. The embrittlement of the cement 3, 3, 3, 3 takes place briefly before (preferably) and/or during the debonding. The substrates 2 and 4 are fixed by the fixing elements 21, in particular vacuum tracks.

(56) By the embodiment of the invention it could be possible for the first time to separate a substrate stack 1, whose substrates 2 and 4 are blanket-bonded to one another by a cement 3, 3, 3, 3, from one another by a normal force on the entire contact surface of the substrates 2, 4 at the same time, in particular without deformation of the substrates 2, 4.

(57) FIG. 12 shows a third debond process of the invention in which the cooling unit 7.sup.V is used for cooling the periphery of the substrate stack 1 and at the same time as a clamping ring for the carrier substrate.

(58) The two substrates 2 and 4 are separated from one another by a tensile stress F which has been applied to the periphery, in particular over the entire periphery and which leads to bending of the carrier substrate 4. The embrittlement of the cement 3, 3, 3, 3 takes place shortly before and/or during the debonding. The product substrate is fixed via the film 5 on a lower wafer chuck 16 which preferably has fixing elements 21.

REFERENCE NUMBER LIST

(59) 1, 1, 1, 1, 1.sup.IV, 1.sup.V substrate stack 2, 2 product substrate 2o product substrate surface 2r back-thinned product substrate surface 3, 3, 3, 3, 3.sup.IV interconnect layer, in particular cement 3o, cement surface 4 carrier substrate 4o carrier substrate surface 5 film 6 frame 7, 7, 7, 7, 7.sup.IV, 7.sup.V, 7.sup.VI cooling unit 8, 8 lines 9, 9, 9, 9, 9.sup.IV, 9.sup.V cooling body, in particular cooling plate 9o, 9o cooling body surface 9, 9k, 9k, 9k cooling area 10 channel 11 chamber 12, 12 opening 13 tank 14, 14, 14, 14, 14.sup.IV layer 15 receiving tank 16 wafer chuck 17 loading units 18 cooling fluid 19 frame holder 20 cavity 21, 21 fixing elements, in particular vacuum tracks 22 filler material 23 topography D, D diameter d, d diameter effective cooling area F normal force shear force