DE102006009353B4 - Multilayer system for supporting thin wafers in semiconductor manufacturing with the property of holding by means of electrostatic charging - Google Patents

Abstract

Method for treating wafers with components during thinning of the wafer (1) and the subsequent singulation of the components and the optionally intermediate manufacturing steps, wherein the front side of the wafer (1) is coated with a layer with separating properties (4) and a carrier layer (5, 6) with electrostatic properties, wherein the wafer (1) is fixed by the carrier layer (5, 6) due to its electrostatic properties.

Description

Area of application

The invention is intended to facilitate the production of thinner wafers and/or their safer processing, and/or to reduce and/or make more cost-effective the manufacturing effort for electrical components and/or circuits, and/or sensors, etc., and/or—but especially—to enable and/or facilitate the coating of the backside of the thinned wafer. This simplification lies in its suitability for electrostatic holding and support of wafers.

State of the art

1. a) während dem Abziehen 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 procedure in the prior art can vary from user to user. In general, however, the procedure is as follows. In the production of electronic components and circuits (diodes, transistors, ICs, sensors, etc.), structures, layers, etc. are applied to wafers (disks made of silicon, GaAs, etc.) using various technologies. Currently, after completion of the necessary production steps, these wafers are provided with a protective film or other protective layer on the front side (active side or side on which the applied structures are located). This film or layer has the task of protecting the top side of the wafer and thus the applied electrical and mechanical structures during the subsequent thinning of the wafer (by grinding, lapping, sanding, etching, etc. of the back side). After the film or layer has been applied, the back side of the wafer is thinned down. This reduces the original thickness of the wafer. The remaining thickness is determined by the expected mechanical stresses and/or the subsequent process steps, which must be withstood without significantly increasing the risk of breakage. After thinning, the back of the wafer can be chemically treated to improve its fracture properties. After any cleaning steps, the protective film is peeled off or removed from the top of the wafer. Further manufacturing steps and/or measures to improve properties and/or tests can then follow. The back of the thinned wafer is often coated with a metallic layer. This coating process is usually carried out using sputtering or similar deposition techniques in a vacuum and often requires thermal stress and/or thermal support. The wafer is then placed backside down (active side up) onto a sawing film (expansion film or frame). Finally, the wafer is sawn (separating the components) using rotary cutting wheels or other mechanical sawing devices. Laser cutting processes are also occasionally used for this purpose. Occasionally, wafers are also broken during this process, although scribing techniques are occasionally used to assist with this. Using conventional methods, it is very difficult to treat or produce thin wafers. These difficulties arise, among other things, from the fact that the wafer must be subjected to mechanical stress after thinning. These stresses occur, among other things, in the following ways:

1. a) during the removal of the protective film or layer that protects the front side of the wafer during thinning,
2. b) during the placement of the wafer on the sawing foil, and
3. c) during transport between wafer thinning and dicing, and any manufacturing steps that may occur in between. This is especially true during the coating of the backside. It is irrelevant whether this coating process takes place before or after wafer dicing.

As an alternative to the methods described, methods are already being used and/or developed today in which the wafer is structured on the surface (the structured side) before the thinning process by grinding scribe structures and/or scribing and/or chemical etching and/or plasma etching of trenches and/or structures in such a way that these structures are exposed during the subsequent thinning process by means of mechanical and/or chemical processes, thus resulting in the wafer being singulated.

1. The US 2004 / 0 038 469 A1 discloses a method for thinning the back side of a wafer.

In the inventor application with international patent application WO 2004 / 051 708 A2 (Publication) now describes a method in which a separating layer is used. This separating layer is preferably applied directly to the active side of the wafer and reinforced with suitable materials. This material acts as a carrier, which can be removed from the wafer again using the separating layer.

Disadvantages of the state of the art

In the international patent application listed as prior art WO 2004 / 051 708 A2 (Offensive document) mentions a carrier layer, which is not further described with regard to its technological design. In the application DE 10 2006 004 834 A1 A multilayer system is described in the German Patent and Trademark Office (Offenlegungsschrift) consisting of at least one hard layer, which is primarily intended to stabilize the carrier, and a soft layer, which is intended to adapt to the topography of the wafer surface – the active side of the wafer – and primarily protect it. The use of the method in both inventions simplifies the handling and support of a wafer. However, the methodology for applying methods for holding or fixing wafers and their carriers using electrostatic methods is not further described.

Object of the invention

The invention is based on the problem described in the international patent application WO 2004 / 051 708 A2 (publication document) - the carrier layer listed in the application DE 10 2006 004 834 A1 (Open Application) at the German Patent and Trademark Office – in such a way that it can be applied economically, efficiently, and technologically simply. In particular, the aim is to simplify the holding and/or fixing of the wafer and its carrier by also applying electrostatic charging methods.

Solution to the task

In the international patent application WO 2004 / 051 708 A2 (Offensive document) describes a wafer coated with a separating layer. With the application DE 10 2006 004 834 A1 In the German Patent and Trademark Office's (open-ended application) document, this is further described as a multilayer system. It consists of at least one elastomer layer and one hard layer.

The invention describes that the described layers and/or further layers are modified, manufactured, and/or enriched with suitable materials in such a way that they can be electrostatically charged themselves or fixed by other electrostatically charged surfaces and/or devices. It is possible for the carrier to be provided with a layer specifically to achieve suitable electrostatic properties, which facilitates or even enables this.

This property of electrostatic charging or the ability to be attached to other electrostatically charged surfaces and/or devices may result from the materials used to produce the layer and/or layers. However, it can be achieved by adding suitable materials to these materials, such as suitable metals, oxides, or other inorganic and/or organic materials.

Advantages of the invention

The invention enables the realization of significant technological advantages in the manufacturing and handling of wafers in the production of electrical components, ICs, sensors, etc. The process simplifies production and makes it more cost-effective. Furthermore, thinner wafers can be realized more easily, economically, and reliably.

About the advantages of international patent applications WO 2004 / 051 708 A2 (Publication document) there are advantages in the economical and efficient coating of a carrier for thin wafers.

In particular, the described procedure, in which the carrier is applied by means of a layer system (multilayer film) consisting of a layer of elastomer and a layer of polyimide in the form of a fabricatable film, simplifies economic use.

The wafer can now be fixed using the electrostatic properties of its carrier and/or the interaction of the carrier with electrostatically charged surfaces and devices. This is particularly true for applications where the wafer is processed in a vacuum.

Example description

The assumption is that the wafer has already undergone significant manufacturing steps for applying the electrical components and/or mechanical structuring or layers. It now has a diameter of 200 mm, a thickness of 800 µm, and bumps with a height of 80 µm on its active side. The wafer will then be thinned to a remaining thickness of 50 µm.

The wafer is then coated with a carrier layer, regardless of whether this consists of one or more layers. Due to the properties of the carrier and its layer or layers, it can be electrostatically charged by itself or by a other surface or device. These devices can be chucks, such as those used by UNAXIS, Lichtenstein, for vacuum processes, and/or those manufactured and offered as chucks or devices by ProTec®, Siegen, Germany.

The invention is explained in more detail below with reference to the drawings.

They do not show to scale:

Drawing 1

Shows a prefabricated film consisting of a polyimide layer (e.g., ^Kapton® ) and an elastomer layer (e.g., silicone). The film is coated with a protective film on the elastomer side, which is removed before the film is applied to the wafer.

First layer of the carrier (preferably elastomer) designated 5

Second layer of the carrier (preferably polyimide) (which is suitable here as an example for electrostatic charging) designated 6

Attention! Instead of the second layer (6) shown, any other layer or all layers may be suitable for electrostatic charging.

Protective film marked with 9

Drawing 2

• Wafer bezeichnet mit 1
• Strukturierte (aktive) Zone des Wafers bezeichnet mit 2
• Schutzschicht (Passivierung) der strukturierten (aktiven) Zone des Wafer bezeichnet mit 3 Trennschicht bezeichnet mit 4
• Erste Schicht des Trägers (vorzugsweise Elastomer) bezeichnet mit 5
• Zweite Schicht des Trägers (vorzugsweise Polyimid) bezeichnet mit 6
• Bumps bezeichnet mit 7
• Eventuelle Ritz- oder Ätzgräben bezeichnet mit 8

Shows a finished foil which has been bonded to a wafer on its structured side.

• Wafer marked with 1
• Structured (active) zone of the wafer designated 2
• Protective layer (passivation) of the structured (active) zone of the wafer designated by 3 Separating layer designated by 4
• First layer of the carrier (preferably elastomer) designated 5
• Second layer of the carrier (preferably polyimide) designated 6
• Bumps marked with 7
• Any scratch or etching trenches marked with 8

Claims (5)

Method for treating wafers with components during thinning of the wafer (1) and the subsequent singulation of the components and the optionally intermediate manufacturing steps, wherein the front side of the wafer (1) is coated with a layer with separating properties (4) and a carrier layer (5, 6) with electrostatic properties, wherein the wafer (1) is fixed by the carrier layer (5, 6) due to its electrostatic properties. Procedure according to Claim 1 , wherein the carrier layer consists of at least one elastomeric layer (5) which is suitable for electrostatic charging and/or can be fixed by electrostatic surfaces and/or devices. Procedure according to Claim 1 , wherein the carrier layer consists of at least one hard layer of polyimide (6) which is suitable for electrostatic charging and/or can be fixed by electrostatic surfaces and/or devices. Procedure according to Claim 1 , wherein the carrier layer (5) consists of at least one layer which is suitable for electrostatic charging and/or can be fixed by electrostatic surfaces and/or devices. Procedure according to Claim 1 , wherein the carrier layer (5) consists of at least several layers which are suitable for electrostatic charging and/or can be fixed by electrostatic surfaces and/or devices.

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