Source: http://www.google.com/patents/US8173522?dq=5,581,513
Timestamp: 2017-08-21 18:39:06
Document Index: 694406835

Matched Legal Cases: ['art 1', 'art 2', 'art 3', 'art 4', 'art 5', 'art 6', 'art 7', 'art 8', 'art 9', 'art 10', 'art 11', 'art 12', 'art 13', 'art 1', 'art 2', 'art 3', 'art 4']

Patent US8173522 - Method and device for machining a wafer, in addition to a wafer comprising a ... - Google Patents
A process and an apparatus are described for the treatment of wafers, in particular for the thinning of wafers. A wafer with a carrier layer and an interlayer arranged between the carrier layer and the wafer is also described, in which the interlayer is a plasmapolymeric layer that adheres to the wafer...http://www.google.com/patents/US8173522?utm_source=gb-gplus-sharePatent US8173522 - Method and device for machining a wafer, in addition to a wafer comprising a separation layer and a support layer
Publication number US8173522 B2
Application number US 12/359,730
Also published as EP1568071A2, US7482249, US20060166464, US20090176349, WO2004051708A2, WO2004051708A3
Publication number 12359730, 359730, US 8173522 B2, US 8173522B2, US-B2-8173522, US8173522 B2, US8173522B2
Inventors Andreas Jakob, Klaus-D Vissing, Volkmar Stenzel
Original Assignee Thin Materials Ag
Patent Citations (70), Referenced by (1), Classifications (8), Legal Events (5)
Method and device for machining a wafer, in addition to a wafer comprising a separation layer and a support layer
US 8173522 B2
12. Process according to claim 11, in which a separation of the wafer (1, 2; 1 b, 2; 1 c, 2) into individual elements is effected by the thinning or by the removal of the interlayer (3) and carrier layer (4).
PRIOR ART First Aspect of the Invention
a) during the stripping or peeling (detachment) of the protective film or protective layer that protects the front side of the wafer during the thinning procedure,
b) during the placing of the wafer on the sawing film,
c) during the transportation between the thinning procedure and the division of the wafer (separation into parts of the wafer, i.e. into dies or chips) and all fabrication steps possibly occurring therebetween. In particular however these stresses occur during the coating of the rear side.
As an alternative to the aforedescribed processes nowadays processes are already employed and/or developed, in which the wafer is already structured on the front side (the structured side) before the thinning process by grinding scored structures and/or scoring and/or chemical etching and/or plasma etching of structures (this term also includes scraping) so that these structures are exposed during the subsequent thinning process by means of mechanical and/or chemical methods, thereby resulting in a division of the wafer. In this connection it is very often a disadvantage however that the now divided parts of the wafer (dies) can no longer be handled economically during the subsequent process steps. This is due to the fact in this case that the large number of already divided components have to be fixed so that they do not become detached and/or change their position during the fabrication steps that have to be carried out.
Disadvantages of the Prior Art First Aspect of the Invention
Object of the Invention First Aspect of the Invention
Achievement of the Object First Aspect of the Invention
application of a layer system to the front side of the wafer, wherein the layer system includes at least one interlayer in contact with the front side of the wafer, and a carrier layer,
thinning of the rear side of the wafer so that the layer system protects or carries (holds) the wafer or parts of the wafer during the thinning.
The wafer, which may also be a wafer that has been structured on the front side of the wafer (the structured side) already before the thinning process by means of grinding and/or scoring and/or chemical etching and/or plasma etching of grooves and/or other structures so that these structures are exposed during a subsequent thinning process by means of mechanical and/or chemical methods (e.g. etching), thus leading to a division of the wafer, is coated on the front side with an interlayer before the thinning (removal of material on the rear side). This interlayer is in this connection preferably applied by means of chemical vapour deposition (CVD) methods. This interlayer may for example be a plasmapolymeric coating, such as has been developed at the Fraunhofer Institut für Fertigungstechnik und Angewandte Materialforschung in Bremen. It is possible for the interlayer to be formed in its full thickness by the CVD process and/or by another vacuum technology process and/or to be assisted and/or achieved by (optionally prior) application of a suitable material. Preferably in this connection interlayer thicknesses of 1 to 1000 nm, more preferably 50 to 200 nm, are adjusted. The layer thickness may however also be smaller or larger. The adhesion properties of the interlayer can in the case of the plasmapolymeric coating applied by means of CVD processes be individually adjusted on both sides by process technology matching. The interlayer should on the one hand facilitate the subsequent peeling of an adjoining layer (carrier layer) from the wafer surface. The interlayer should however also exert a sufficient bonding force (by means of adhesion and/or other bonding forces) between the wafer surface and the adjoining carrier layer for the subsequent process steps and/or should assist and/or permit this. This bonding force may also result in part from the property of the surface topography of the wafer surface. The latter is in particular important if occurring shear forces have to be compensated, e.g. in the mechanical processes of thinning by means of grinding or other suitable methods. A constituent of the wafer can, as is understood by the term wafer within the scope of the present application, also be a passivating layer on the front side of the wafer, and more especially preferably if the wafer includes electronic components. Such a passivating layer (if present) is preferably located directly in contact with the layer of the wafer that carries the electronic components.
(pre-)structuring of the wafer by grinding and/or scoring and/or chemical etching and/or physical etching, so that the formed structures open during the thinning of the rear side or during a subsequent treatment of the rear side and divide the wafer.
Also preferred is an aforedescribed process according to the invention in which (a) a laser beam or (b) a mechanical method, preferably abrasive cutting, sawing or breaking, is used to divide the wafer. In this connection variant (b) in particular is preferably used for wafers that are not pre-structured for the separation.
Reduction of the adhesion (a) of the layer system to the wafer, or (b) of the carrier layer to the layer of the layer system adjacent to the wafer side, preferably the interlayer. The purpose of this procedure is in particular to permit the removal of the divided parts of the wafer by means of a vacuum device or another mechanical removal device, in which particularly preferably so-called Blue Tape does not have to be applied to the rear side of the wafer.
Preferably in this connection the reduction of the adhesion in the case (a) of the layer system or in the case (b) of the carrier system is achieved by (i) irradiation with electromagnetic radiation, (ii) thermal action, (iii) chemical action and/or (iv) mechanical action. The thermal action may in this connection consist of heating or cooling, or both.
The invention also enables the wafer or the composite of parts of the wafer already divided at this particular time to be processed in a vacuum for the purpose of coating the rear side. Thus, it is in particular possible in this connection to apply metallic layers in vacuo by means of sputtering, vapour deposition and/or other suitable methods. In this connection temperatures of over 300° C. are possible during the coating.
a) application of a layer system to the front side of the wafer, with an interlayer contacting the front side of the wafer, and a carrier layer,
b) hardening and/or consolidation of the carrier layer,
c) thinning of the rear side of the wafer,
d) smoothing of the rear side of the wafer so that the mechanical properties of the wafer are altered, preferably in such a way that the division of the wafer is effected or promoted and/or the coating of the thinned rear side of the wafer is promoted,
e) coating of the thinned rear side of the wafer, in which the layer system protects or carries the wafer and/or parts of the wafer during the coating,
f) division of the components of the wafer, in which the layer system protects or carries the wafer and/or parts of the wafer during the coating and the layer system is not separated during the division, and
g) preferably mechanical detachment of the interlayer from the carrier layer or from the wafer or from the (already divided) parts of the wafer.
Particularly preferred is a process according to the invention in which the layer system is applied so that the interlayer adheres to the front side of the wafer and adheres more strongly to the carrier layer than to the wafer.
means for the application of a layer system to the front side of a wafer, in which the layer system comprises at least an interlayer contacting the front side of the wafer, and a carrier layer, and
means for thinning the rear side of the wafer provided on the front side with the layer system, which means are designed so that the layer system protects or carries the wafer and/or parts of the wafer during the coating,
means for coating the thinned rear side of the wafer, which means are designed so that the layer system protects or carries the wafer and/or parts of the wafer during the coating, and/or
means for dividing the components of the wafer, which means are designed so that the layer system protects or carries the wafer and/or parts of the wafer during the division, in which the division is carried out as a separate step or is implemented by the thinning, and
the layer system is separated or not separated during the division, and/or
means for the structuring of the wafer by grinding and/or scoring and/or chemical etching and/or physical etching, which means co-operate with other constituents of the apparatus so that the structures that are formed open during the thinning of the rear side or during a subsequent treatment of the rear side and divide the wafer, and/or
means for reducing the adhesion (a) of the applied layer system to the wafer or (b) of the carrier layer to the adjacent layer of the layer system on the wafer side, preferably the interlayer, and/or
means for the detachment of the wafer or of parts of the wafer from the layer system.
Preferred constituents of the apparatus according to the invention are a coating device for the application of the interlayer and/or the carrier layer (protective or covering layer) or of combinations of layer(s) and/or layer systems to the front side of the wafer, a device for the application of a coating to the rear side, a device for thinning the wafer, a device for dividing the wafer parts (dies), which may consist of a laser or a laser-assisted separating implement and/or a mechanical separating implement, a device for reducing the adhesion of the carrier layer to the front side of the wafer (optionally together with the interlayer) after the division, and a device for stripping the components from the layer.
Advantages of the Invention First Aspect of the Invention
The rear side of the wafer is now thinned by means of grinding and then chemically etched to rectify surface damage. Following this the rear side of the wafer is coated with metal by means of sputtering in a vacuum plant. During this procedure the wafer heats up to ca. 350° C., without however the layer system being destroyed. Finally the wafer is straightened by means of an optical process using IR radiation and divided from the rear side by means of a laser beam. After completion of the division the rear side is coated with a film (Blue Tape) and the carrier layer together with the interlayer on the front side is stripped off. The divided wafer parts are now removed from the film by a pick and place procedure and contacted.
a) coating the front side of the wafer, in which the components are arranged, with an interlayer,
b) coating of a carrier layer on the front side of the wafer,
c) hardening and/or consolidation of the carrier layer,
d) thinning of the wafer from its rear side to a desired thickness,
e) treatment of the rear side of the wafer by means of chemical and/or mechanical processes for the purposes of improving the mechanical properties and improving the thinned wafer,
f) coating of the rear side of the wafer with a layer,
g) division of the wafer, in which the carrier layer is not separated,
h) reduction of the adhesion of the carrier layer to the parts of the wafer, and
a) a coating device for the application of the interlayer,
b) a coating device for the application of the carrier layer,
c) a device for thinning the wafer,
d) a device for dividing the components,
e) a device for coating the rear side of the wafer,
f) a device for reducing the adhesion of the carrier layer to the interlayer,
g) a device for stripping the components from the carrier layer.
The first aspect of the invention is illustrated in more detail hereinafter with the aid of FIGS. 1 to 15.
Prior Art/Starting Position Second Aspect of the Invention
Disadvantages of the Prior Art Second Aspect of the Invention
However, a small thickness provides not only advantages but also causes difficulties, especially in the further processing of the wafers: a greatly thinned wafer becomes increasingly fragile and bends due to stress in the function coating. In addition it still has only a very low thermal capacity, which leads to serious difficulties and challenges for the subsequent treatment steps. This affects in particular the rear side metallization, for which temperatures of about 370° to 380° C. have to be employed, and in addition a vacuum compatibility of the wafer to be coated has to be ensured. The greatly reduced mass and thus the likewise greatly reduced thermal capacity of the wafer means that the electrical circuits are significantly more highly loaded due to the high metallization temperatures.
Object of the Invention Second Aspect of the Invention
It should not evaporate into essential parts in vacuo.
It should be a separation-active substance (e.g. a silicone oil such as AK5 to AK50 from Wacker Chemie).
The person skilled in the art will preferably match the liquid precursor to the chemistry of the plasmapolymeric interlayer, and the precursor should preferably be applied so thinly (e.g. 0.1 to 50 nm) that the precursor becomes part of the plasmapolymeric coating due to the subsequent plasma process. It is particularly preferred in this connection if the initially liquid precursor becomes fully integrated into the interlayer. The liquid precursor is applied to the substrate (the wafer) preferably by immersion, spraying or spincoating, and a coating of the rear side of the wafer (that is the side of the wafer lying facing the front side) should be avoided.
An object according to the invention (wafer plus interlayer and carrier layer) is preferred in which the interlayer adheres largely unchanged to the wafer and to the carrier layer at temperatures of up to at least 350° C., preferably up to at least 380° C. and particularly preferably up to at least 400° C. A high temperature resistance is particularly important if steps that involve an increased temperature loading of the layer (e.g. rear side metallization) are planned within the framework of the further treatment of the wafer.
An object according to the invention is preferred in which the carrier layer consists of a polymeric material. Particular requirements are as a rule placed on this material: these include a sufficient temperature stability, preferably up to 400° C., for the subsequent processes. In addition the material should preferably be able to be applied by means of a spincoating process and should have as high a thermal conductivity and thermal capacity as possible. Moreover, the internal stresses should be very low or should match those of the thinned wafer in order to prevent bending, since only a flat wafer can be worked in a fault-free manner in the existing devices. The layer thickness of the carrier layer should preferably be able to be adjusted so that the thickness that has been removed by the thinning of the wafer is compensated. If a sufficient evenness of the carrier layer cannot be achieved by the application method, then in addition a grinding or polishing method should also be employed in order to satisfy these conditions.
a) supplying a wafer,
b) provision of the wafer with a plasmapolymeric interlayer so that this adheres to the wafer,
c) application of a carrier layer to the interlayer so that the interlayer adheres more firmly to the carrier layer than to the wafer,
production of a wafer with a carrier layer and an interlayer arranged between the carrier layer and the wafer, according to an aforedescribed process according to the invention (preferably according to a process described for the second aspect of the invention), wherein in step a) a wafer to be thinned is supplied, and
thinning of the rear side of the wafer,
production and optionally thinning of a wafer with a carrier layer and an interlayer arranged between the carrier layer and the wafer, according to an aforedescribed process of the invention (preferably according to a process described for the second aspect of the invention) and
application of a metal layer to the rear side of the wafer.
The above comments apply as appropriate with respect to the preferred modifications.
EXAMPLE 3 Application of an Interlayer as Gradient Layer Using a Liquid Precursor
[sccm] [sccm] [sccm]
Gas type Output Time Pressure
HMDSO O2 H2 [W] [sec] [mbar]
Part 1 70 24 700 300 0.03
Part 2 70 24 700 300 0.03
Part 3 70 32 700 180 0.03
Part 4 70 50 700 180 0.03
Part 5 60 50 700 180 0.03
Part 6 50 50 700 180 0.03
Part 7 35 75 700 180 0.03
Part 8 27 100 700 180 0.03
Part 9 27 100 1500 180 0.031
Part 10 27 100 2500 60 0.031
Part 11 200 200 2000 60 0.04
Part 12 200 900 2000 300 0.05
Part 13 10000 2500 300 0.22
Such a coating could be heat treated for 30 minutes at 400° C. without the dehesive properties of the coated wafer being lost.
EXAMPLE 4 Application of an Interlayer Thinner than the Gradient Layer Using a Liquid Precursor
Part 1 70 24 700 900 0.03
Part 2 70 24 700 1800 0.03
Part 3 200 900 1600 180 0.05
Part 4 10000 2500 120 0.22
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U.S. Classification 438/460, 438/461, 438/465
Cooperative Classification H01L2221/6834, H01L2221/68327, H01L21/6836, H01L2221/68395
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