DE102006048800B4 - Hard carrier multilayer system for supporting thin wafers in semiconductor fabrication - Google Patents

Abstract

Method for treating wafers with components during thinning of the wafer (1, 2, 3) and the subsequent separation of the components and the optionally intervening manufacturing steps, wherein the front side of the wafer (1, 2, 3) with the components and an already applied Separating layer (4) is coated before thinning with a layer system consisting of at least one elastomer (5) and a glass pane (6) or a, the glass in its mechanical strength similar material, wherein the elastomer layer (5) in more viscous Mold is applied to the wafer and between the wafer (1, 2, 3) and the glass sheet (6) or the glass similar in its mechanical strength material is pressed, wherein the elastomer layer already begins to harden and / or crosslink during pressing.

Description

field of use

The invention is intended to make it easier to produce thinner wafers and / or to process them more safely and / or to reduce the production costs involved in producing electrical components and / or circuits, and / or sensors, etc. to reduce and / or cost-effective and / or - but in particular - enable and / or facilitate the coating of the back of the thinned wafer.

State of the art

1. a) während des Abziehens der Schutzfolie bzw. Schutzschicht, die während des Abdünnens die Wafervorderseite schützt,
2. b) während des Auflegens des Wafers auf die Sägefolie, und
3. c) während des Transportes zwischen dem Abdünnen und dem Vereinzeln des Wafers und aller eventuell dazwischen geschalteten Fertigungsschritte, insbesondere aber bei der Beschichtung der Rückseite, wobei es unerheblich ist, ob dieser Beschichtungsprozess vor oder nach dem Vereinzeln des Wafers stattfindet.

The prior art technique may vary from user to user. Generally, however, the procedure is as follows. In the manufacture of electronic components and circuits (diodes, transistors, ICs, sensors, etc.) structures, layers, etc. are applied to wafers (slices of silicon, GaAs, etc.) by means of various technologies. At present, these wafers are provided with a protective film or other protective layer on completion of the necessary manufacturing steps on the front side (active side or side on which the applied structures are located). This film or layer has the task of the wafer top side and thus the applied electrical and mechanical structures during the subsequent subsequent thinning of the wafer to protect (by grind, lapping, grinding, etching, etc. of the back). After applying the film or layer, the wafer is thinned on the back side. This reduces the original thickness of the wafer. The remaining residual thickness is determined sustainably by the expected mechanical stresses and / or the subsequent process steps that have to be overcome without a significant increase in the risk of breakage. After thinning, a chemical treatment of the wafer back can be added to improve the fracture properties of the wafer. After any cleaning steps, the protective film is peeled off or removed from the wafer top side. It may now be followed by any further manufacturing steps and / or measures to improve properties and / or investigations. In many cases, the back of the thinned wafer is coated with a metallic layer. This coating process is usually done by sputtering or similar deposition in a vacuum and often requires thermal stress and / or thermal support. The wafer is then placed backside down (active side up) on a sawing foil (expansion foil or frame). Finally, the sawing of the wafer (singulation of the components) is carried out by means of rotary cutting discs or other mechanical sawing devices. Occasionally, laser separation processes are already being used. Occasionally, wafers are also broken, with occasional supporting methods of scratching being used. With the conventional methods, it is very difficult to handle thin wafers. These difficulties arise, inter alia, from the fact that the wafer must be subjected to mechanical stresses after thinning. These loads occur, inter alia:

1. a) during the removal of the protective film or protective layer, which protects the wafer front during thinning,
2. b) while placing the wafer on the sawing foil, and
3. c) during transport between the thinning and the dicing of the wafer and any production steps connected therebetween, but in particular in the coating of the back, it is irrelevant whether this coating process takes place before or after the separation of the wafer.

As an alternative to the methods shown, methods are already being used and / or developed in which the wafer on the surface (the structured side) is already pre-thinned by means of grinding scribing structures and / or scratches and / or chemical etching and plasma etching Trenches and / or structures is structured so that these structures are exposed during the subsequent thinning process by mechanical and or chemical methods and thus takes place a separation of the wafer.

In the WO 2004/051 708 A2 Now, a method will be described in which a release layer is used. In this case, this separating layer is preferably applied directly to the active side of the wafer and reinforced by means of suitable materials. In this case, this material assumes the function of a carrier which can be detached from the wafer again by means of the separating layer.

In the DE 10 2006 009 394 A1 In claim 2, a carrier layer is described, which consists of at least an elastomer and a hard layer.

Further documents from the described technology field are the US 2005/0 221 598 A1 and US 2004/0 038 469 A1 ,

Disadvantages of the prior art

In the listed as state of the art WO 2004/051 708 A2 becomes a carrier layer mentioned, which is described in terms of their technological design no further.

The in the DE 10 2006 009 394 A1 described hard layer is preferably made of a polyimide or polyamide. The disadvantage here proves that the solution described must be adjusted in terms of the coefficient of thermal expansion of this hard layer to the coefficient of thermal expansion of the wafer and in this case primarily to silicon. This is necessary because the wafer is subjected to different levels of thermal stress along with its carrier during the manufacturing steps to be passed through. As the thermal expansion coefficients of the hard layer and the wafer deviate from each other, resulting tensile and tensile stresses that lead to unwanted bending of the entire system (wafer and carrier).

Object of the invention

The invention is based on the object, in the DE 10 2006 009 394 A1 to improve the described method.

Solution of the task

This object is achieved by a method as defined in claim 1.

• - Glas, modifizierte Gläser oder den Eigenschaften von Glas ähnliche Materialien
• - Materialien, die dem Material des zu trägerndem Wafers gleich oder ähnlich sind.

The following materials are used for the hard coating:

• - Glass, modified glasses or the properties of glass-like materials
• - Materials that are the same or similar to the material of the wafer to be supported.

Starting from a wafer surface, which is coated by means of a release layer, a layer composite is now applied and connected to the wafer surface or pressed. The layer composite preferably consists of two layers, it being immaterial that extended layers may be included. The first layer of the composite layer consists of an elastomer such as silicone or a material of similar property. The second layer of the layer composite preferably consists of a glass or the material of the wafer to be supported.

The first layer, which consists of an elastomer, should be sufficiently soft during application to enclose the topography of the wafer surface, but preferably bumps or coat it over the entire surface. It is possible that this layer is liquid applied and pressed in the form of suitable spin or spray coating or other technologies for applying liquid materials. After application of this layer, the applied material is hardened and / or crosslinked. This can be done by supplying or removing energy in the form of light, heat or pressure, etc., or else by suitable chemical and / or mechanical reactions. However, it may be advantageous that this hardening and / or crosslinking of the first layer takes place only after the application of the second layer. This described first layer is applied directly to the wafer surface, preferably therefore on the active side of the wafer and its applied release layer.

After the application of the first layer, a second layer is now applied. This is preferably a layer of sufficient mechanical stability in order to be able to mechanically stabilize the wafer sufficiently later in the thinned state. Preferably, in this case, a disc of a glass application experienced. However, other wafers, such as wafers, may also be used if they have sufficient mechanical and chemical stability.

For applying the layer composite, consisting of the two described layers, two alternative methods are preferred.

The first method is based on the fact that the first layer, which preferably consists of an elastomer, is applied in liquid (viscous) form to the active side of the wafer and its separating layer. Now, the second layer, which preferably consists of a glass sheet, fixed over the active side of the wafer and now preferably compressed plane-parallel with the wafer under vacuum. In this case, the material of the first layer should preferably be distributed in such a way that an entire-area distribution on the wafer surface is achieved as far as possible without inclusions of air or bubbles. It is in this case according to the invention that the material of the first layer already begins to harden and / or crosslink. This hardening of the first layer can already take place under pressure. It may be advantageous to position the wafer together with the applied layer composite at another location at which the hardening and / or crosslinking of the first layer is then to take place and / or continue. This can be done by supplying or removing energy in the form of light, heat or pressure or else by suitable chemical and / or mechanical reactions such as vulcanization. Preferably, the wafer is now coated on its active side with a release layer, followed by a layer of an elastomer adjoins and in turn followed by a layer of glass. So beneficial, it may be desirable to use this second one Remove the glass layer again. Preferably, however, it is firmly connected to the first layer and remains on the wafer.

As an alternative to the described application of the elastomer of the first layer, it may be advantageous to apply this in the form of a glass pane with an elastomeric coating. This would be a disk application learn that would consist of an example of a glass on which another layer would be made of an elastomer. This layer system could be used in the form of a ready-made glass carrier application. The glass carrier would now be fixed over the active side of the wafer and its separating layer and preferably pressed plane-parallel with the wafer under vacuum. In this case, the contact pressure should be sufficient for the material of the first layer (elastomer) of the layer system to be sufficiently distributed so that an entire-area distribution on the wafer surface is achieved as far as possible without inclusions of air or bubbles. It is in this case according to the invention that the material of the first layer already begins to harden and / or crosslink. This hardening of the first layer can already take place under pressure. It may be advantageous to position the wafer together with the applied layer composite at another location at which the hardening and / or crosslinking of the first layer is then to take place and / or continue. This can be done by supplying or withdrawing energy in the form of light, heat or pressure or else by suitable chemical and / or mechanical reactions such as. Vulcanization done. Preferably, the wafer is now coated on its active side with a release layer, which is followed by a layer of an elastomer and to which in turn is followed by a glass pane. So advantageous, it may be desirable to remove this glass again. Preferably, however, it is firmly connected to the first layer and remains on the wafer.

It may be advantageous to supplement the two layers described by further layers and / or films. These may be layers which ensure or specifically reduce adhesion to the release layer and / or between the two layers (elastomer and glass). Furthermore, it may be desirable to supplement the second layer on its free side by means of suitable layers.

Both alternatives described offer the possibility of adaptation to potentially changing requirements on the wearer. By means of the thickness and the mechanical and / or chemical properties of the material of the first layer (preferably an elastomer), the requirements of different topographies and / or heights of the bumps can be met. Furthermore, the separation from the topography (but especially from the bumps) can be influenced by an optimized Shore hardness of the material. By means of the thickness and the mechanical properties of the second layer (preferably a glass pane), the requirements of different sized and / or differently thick wafers can be met in handling.

Advantages of the invention

The invention enables the realization of significant technological advantages in the manufacture and handling of wafers in the manufacture of electrical components, IC's, sensors, etc. The method makes manufacturing simpler and more cost effective. Furthermore, lower wafer thicknesses can be realized simpler, more economical and safer. In particular, however, a carrier is used which has a high mechanical stability as a layer system-at least from a polyamide separating layer and a glass pane or pane of similar mechanical self-consolidation. In particular, the described carrier is well adapted to the material of the wafer with respect to its thermal expansion coefficient.

About the benefits of WO 2004/051 708 A2 In addition, there are advantages in the economical and efficient coating of a support for thin wafers.

In particular, the procedure described, in which the carrier is applied by means of a layer system comprising a layer of elastomer and a glass pane, prevents the wafer and its support from being bent or otherwise deformed by mechanical forces, such as dead load or thermal influence, by different thermal expansion coefficients.

example Description

Assumed prerequisite is that the wafer has already undergone the manufacturing steps for applying the electrical components and / or mechanical structuring or layers significantly. It now has a diameter of 200mm, a thickness of 800μm and has on its active side bumps with a height of 80μm. Finally, the wafer should be thinned to a residual thickness of 50 μm.

The wafer has now been coated by means of a CVD process with a release layer on its active side. Thereafter, it may be advantageous that the surface is activated by means of an oxygen plasma.

About the wafer now a film system is fixed, which consists of a 200μm thick layer of a silicone elastomer (this is facing the wafer surface) and a 800μm thick glass (this is the wafer surface facing away) exists. In a bonder, as offered by companies such as the EV Group in Schärding, Austria, it is now pressed under vacuum with the wafer surface in such a way that the elastomer coats the entire wafer surface. It also undercuts the bumps without air bubbles or bubbles remaining. Even under the pressure of the bonder thermal energy is supplied to start the cross-linking of the elastomer. After a period of three minutes, the wafer can now be removed together with the carrier - which consists of an elestomer and the glass pane - the bonder. It may be advantageous to add further thermal energy to the support to complete the process of crosslinking the elastomer. Finally, the protruding edge of the carrier is cut off from the wafer by means of a trimmer.

In the following the invention will be explained in more detail with reference to the drawings.

It does not show to scale: 1
shows a carrier consisting of a glass pane 6 and a layer of elastomer 5 (eg silicone). The backing is for protection on the side of the elastomer with a film 9 coated, which is removed before applying the film on the wafer. First layer of the carrier (elastomer) referred to 5 Second layer of the support (preferably glass) designated with 6 Protective film marked with 9

2
Shows a carrier 1 after removing the protective film 9 , which with a wafer 1 on its structured side was pressed (bonded).

Wafer designates with 1
Structured (active) zone of the wafer designated with 2
Protective layer (passivation) of the structured (active) zone of the wafer designated with 3 Separating layer denoted by 4 First layer of the carrier (elastomer) referred to 5 Second layer of the support (preferably glass) designated with 6 Bumps designates with 7
Any scratches or etched trenches are marked with 8th

Claims (7)

Method for treating wafers with components during thinning of the wafer (1, 2, 3) and the subsequent separation of the components and the optionally intervening manufacturing steps, wherein the front side of the wafer (1, 2, 3) with the components and an already applied Separating layer (4) is coated before thinning with a layer system consisting of at least one elastomer (5) and a glass pane (6) or a material similar to the glass in its mechanical strength, wherein the elastomer layer (5) in more viscous Mold is applied to the wafer and between the wafer (1, 2, 3) and the glass sheet (6) or the material similar to the glass in its mechanical strength is pressed, wherein the elastomer layer already begins to harden and / or crosslink during compression. Method according to Claim 1 in which the elastomer (5) embeds and / or completely encloses the topography of the wafer (1, 2, 3) and allows it to be detached later in terms of its hardness. Method according to Claim 1 in which the glass pane (6) or the material similar to the glass in its mechanical strength ensures the mechanical stability of a carrier. Method according to Claim 1 , wherein the layer system is used as a ready-made system application. Method according to Claim 1 and 2 wherein the elastomer is a silicone. Method according to Claim 1 and 3 , wherein the disc (6) is used in the form of a glass wafer application. Method according to Claim 1 and 3 in which the wafer (6) is used in the form of a wafer.

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