DE10256247A1 - Process for treating wafers comprises covering the front side of the wafer having components with a layer system consisting of a separating layer and a protective layer before the rear side of the wafer is coated - Google Patents

Abstract

Process for treating wafers comprises covering the front side of the wafer (1) having components (2) with a layer system consisting of a separating layer (3) and a protective layer (4). The wafer and the components are protected by the layer system during coating of the rear side of the wafer. An Independent claim is also included for a device for carrying out the process.

Description

field of use

The invention is intended to facilitate thinner wafers to manufacture and / or work more safely and / or the manufacturing effort in the manufacture of electrical components and / or circuits, and / or sensors etc. to reduce and / or cheaper to design and / or the use of laser beam cutting processes to enable and / or to facilitate and / or - but in particular - the coating the back of the thinned Enable wafers and / or facilitate.

State of technology

The procedure in the prior art can vary from user to user. In general, 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 (wafers made of silicon, GaAs etc.) using various technologies. These wafers are currently provided with a protective film or other protective layer on the front side (active side or side on which the applied structures are located) after completion of the manufacturing steps required for this. This film or layer has the task of protecting the top of the wafer and thus the applied electrical and mechanical structures during the subsequent thinning of the wafer (by grinding, lapping, grinding, etching, etc. on the back). After the film or layer has been applied, the wafer is thinned on the rear side. This reduces the original thickness of the wafer. The remaining residual thickness is determined sustainably by the mechanical loads to be expected and / or the subsequent process steps, which must be overcome without significantly increasing the risk of breakage. After thinning, chemical treatment of the back of the wafer can follow to improve the breaking properties of the wafer. After any cleaning steps, the protective film is removed or removed from the top of the wafer. Any further manufacturing steps and / or measures to improve properties and / or investigations can now follow. The back of the thinned wafer is often coated with a metallic layer. This coating process is usually carried out by means of sputtering or similar deposition processes in a vacuum and often requires thermal stress and / or thermal support. Then the wafer is placed with the back side facing down (active side up) on a sawing film (expansion film or frame). Finally, the wafer is sawn (separation of the components) using rotary cutting disks or other mechanical sawing devices. Laser separation processes are already used here in isolated cases. Occasionally, wafers are also broken, with occasional supporting methods of scribing being used. With the conventional methods, it is very difficult to treat or manufacture thin wafers. These difficulties arise, among other things, from the fact that the wafer has to be subjected to mechanical loads after thinning. These loads occur, among other things:
a) during the removal of the protective film or protective layer, which protects the front of the wafer during thinning,
b) during the placement of the wafer on the saw foil, and
c) during the transport between thinning and separating the wafer and any manufacturing steps that may be interposed. But especially when coating the back. It is irrelevant whether this coating process takes place before or after the wafer is separated.

As an alternative to the procedures outlined methods already applied and / or developed today, where the wafer is on the surface (the structured side) even before the thinning process by grinding incisions and / or scratches and / or chemical etching and or plasma etching of trenches and / or structures are structured so that these structures during the subsequent thinning process be exposed by mechanical and or chemical methods and thus the wafer is separated.

disadvantage the state of the art

With current procedures, it is very difficult and sometimes impossible the thinned Wafers or the already isolated components of the previously thinned wafer on the back of the wafer to coat. Here, the wafer and / or the components are treated very elaborately and / or very carefully. The difficulty lies in the extremely thin material thickness of the wafer and / or the individual components.

Task of invention

The invention has for its object to simplify the manufacturing process after thinning of wafers, to make it more economical and to facilitate the treatment of thin wafers, especially when coating the back. Furthermore, the invention is intended to make it possible for the wafer to be there during the process steps of thinning, the back coating and the singulation and all / or individual additional production steps to treat between safer and more economical.

Solution of the task

The wafer (this can also be is a wafer that is already on the wafer surface (the structured side) even before the thinning process by grinding Scoring structures and / or scoring and / or chemical etching and or plasma etching of trenches and / or structures are structured so that these structures during the subsequent thinning process be exposed by mechanical and or chemical methods and thus the wafer is separated) is before thinning (Material removal on the back) covered with a separating layer on the front. This interface will applied here preferably by means of CVD processes. in this connection are layer thicknesses of 100 - 200 nanometers possible. However, this layer thickness can also be smaller or larger. The adhesive properties of the layer can be determined by process engineering Set adjustment. The layer can also be made of plastic, Photoresist, ceramic, metal, glue and / or soluble organic or inorganic Substances and / or a layer composite and / or a mixture of the aforementioned materials exist. This separation layer is supposed to easier, a subsequent layer later easier from the wafer surface supersede to be able to. However, it should also have sufficient bonding strength by means of adhesion or other binding forces between the wafer surface (here now synonymous with the interface surface) and the subsequent Layer for which have and / or support subsequent processes and / or enable. This binding force can also be created as a whole or in part the adhesion property of the surface topography of the wafer surface result.

After applying the separation layer another layer is applied. This is preferably and a plastic mass (e.g. polymer) which is preferably by means of liquid Application (e.g. by spin coater) is applied. This layer can also be made of photoresist, ceramic, metal, glue and / or soluble organic or inorganic substances and / or a layer composite and / or a mixture of the aforementioned materials. The Layer replaces the application of an otherwise usual one Foil as it is before the subsequent thinning (grinding, grinding or similar Process for thinning of wafers) on the front (structured side) of the wafer is applied to protect it. So necessary and / or appropriate the applied layer by mechanical smoothing and / or rotation e.g. Spin coating and / or by using other appropriate and / or necessary procedures are leveled and / or smoothed. The layer can with and / or afterwards by thermal and / or by other suitable or necessary Procedure e.g. UV and / or IR radiation cured and / or fused become.

It can be advantageous that the Property of the coating for the purpose of later separation of the wafer using laser with regard to their properties on the application of laser beams with regard to their optical or other material properties is voted. An interaction of the layer and / or their change or damage while laser cutting can be prevented and / or mitigated.

The coating can be used for the purpose the later Fixing or holding recesses and / or devices and / or over the Area of Reach out wafers.

For further reinforcement and / or support and / or to facilitate the subsequent handling, the layer can by means of a carrier made of glass, metal and / or other suitable organic and / or inorganic materials and / or a mixture of the aforementioned materials and / or a layer network consisting of them are supported. Here you can also expressly Films such as grinding and / or grinding films for use come.

The layer applied should wafer surface while the subsequent Protect processes, handling and transports and thus the individual ones Fix components until they are accepted and / or detached. It is possible here by coordinating the layer and material properties and / or their layer thickness to match the layer so that it has other advantages or has better properties. So the flexibility, adhesion and / or the damping properties the layer can be influenced. It can be advantageous that the surface topography of the wafer is specifically leveled. This can in particular prove to be advantageous for already bumped wafers than here the protruding contacts are leveled and thus with yourself subsequent thin by means of grinding and / or grinding, this is usually not desired to be pushed through can be reduced or completely prevented. Furthermore, the Adjustments for the purpose of improving the processes during grinding, Grinding or other methods for thinning the wafer can be achieved.

The layer has several functions. It protects while of thinning the front of the wafer, reduces the mechanical stresses subsequent treatment and transport of the wafer arise, protects the front of the wafer from contamination, serves as a sawing film and especially the back coating simplify. It is irrelevant whether the back coating process before or after the separation, or omitted entirely.

So the wafers are thin enough it may be advantageous and / or necessary that the wafers are by means of Lasers and / or other suitable mechanical processes such as cut-offs and / or saws and / or etc. to be separated. Here, the wafer is made using a suitable optical method, preferably in the spectrum of infrared light and for the purpose of positioning (alignment - exact alignment of the wafer, so with the greatest possible Accuracy, the components can be separated) so that the for this provided structures and markings can be recognized. To aligning the wafer or the separating device becomes the separating process set in motion. Here drives preferably a laser and / or a different type of saw and / or Separating device, the structures, contours and / or intended for cutting Lines and intersects with its ray. This process will through suitable devices such as optical, electrical or mechanical Monitoring and control devices monitored and readjusted if necessary. While or after the wafer has been separated, it is provided and possible by suitable ones Facilities to discharge, blow off the resulting particles, gases and dusts, vacuum or wash off.

So the thinned wafer back of a metallization is subjected to, it may be advantageous to do this before the separation perform. Thus, the coatings on the otherwise exposed Avoid separating edges. For the purpose of stabilization and / or support it may be advantageous for the wafer with the described protective layer is held or fixed by a further layer and / or carrier. The Invention should further enable that the wafer for the purpose of back coating is processed in a vacuum. In particular, it should be possible that here metallic layers in vacuum by means of sputtering, vapor deposition and / or other suitable methods can be applied. in this connection is possible the coating temperatures of over 300 ° C.

After completion of all provided Processes, it may be necessary and / or desired, the applied To remove the layer. Preferably, another is placed on the back of the wafer Foil (e.g. blue tape) applied and then the front side applied Protective layer removed. When removing this layer, it can be advantageous that mechanical devices are used come, which make it easier to pull off. In particular, however, that between the wafer surface and Separating layer located in the protective layer is intended to detach the Lighten the film and / or the individual components. But it can also expedient and / or required be, the isolated components directly from the protective layer take off and / or replace. To reduce the binding forces or adhesive properties of the protective layer, it can be advantageous and / or desired be by means of suitable methods such as irradiation with UV or IR light, thermal treatment and / or other suitable Process for reducing binding forces and / or adhesive properties respectively.

On the front of the wafer and / or the separating layer of the isolated components remains. This can if necessary, be removed by appropriate methods. Advantageous however, it is to leave them. This can occur due to the small layer thickness pierce subsequent contacting processes or be breached.

Advantages of invention

The invention enables the realization of essential technological advantages in manufacturing and handling Wafers in the manufacture of electrical components, IC's, sensors, etc. The process simplifies production and makes it more cost-effective designed. Can continue thinner wafer slices easier, more economical and safer will be realized.

About the advantages of patent application DE 198 11 115 A1 from March 14th, 1998 there are advantages and improvements in the processes for the backside coating of thin wafers, especially if these coatings take place in a vacuum. In this case, the handling of the thin wafers or the already separated components is simplified because the protective layer applied fixes and / or mechanically supports the wafer and / or the separated components.

Another advantage is that Fact that the applied layer better the topography of the wafer surface than the films currently in use can level and thus the undesirable pressing of bumps on the wafer surface during the mechanical process for the purpose of thinning can be reduced and excluded.

Another advantage is that The fact that the applied layer by means of a vacuum process and / or varnishing processes (e.g. spin coating) is applied. So you can isolated process for the application of foils or the use of carriers omitted.

example Description

The assumed assumption is that the wafer already has the manufacturing steps to apply the electrical Components and / or the mechanical structuring or layers go through significantly Has.

The wafer surface is coated with a 150 nm thick nitride layer by means of a CVD process, which is subsequently to protect the active surface as a protective layer. At the same time she owns coordinated adhesion properties and serves as a separating layer.

Then it is spin coated a plastic mass of polyamide applied and then under Use of heat solidified.

The wafer is now grinded thinned and subsequently etched to remove surface damage. The The wafer is then sputtered in a vacuum system on the Back with Coated metal. Here heated the wafer reaches approx. 350 ° C. Finally the wafer is aligned in the spectrum of IR radiation using an optical method and isolated from the back using a laser beam. To At the end of the separation, the back is covered with a film (blue tape) and peeled off the protective layer on the front. The components are now removed from the film using Pic and Place contacted. Here, the applied separation layer is pierced.

The invention is described below the drawings closer explained.

The consequence of the process steps is only exemplary and can be of current or future processes differ. In particular, it may be advantageous to first remove the wafer after the 12th step (backside metallization) by means of the 9th step (laser cutting).

Show it:

Step 1: the schematic representation of the cross section of a wafer ( 1 ) with components arranged on it ( 2 ) and the original thickness.

Step 2: applying a release layer ( 3 ) eg using CVD coating processes.

Step 3: apply a protective layer ( 4 ), which later also serves as a carrier layer, by applying a plastic mass made of, for example, polymer. In this case, it can be advantageous to distribute and / or level the applied mass by means of suitable processes such as, for example, spin coating.

Step 4: hardening and / or solidifying the protective layer by heating or heating and / or by another suitable chemical and / or physical method ( 5 ) the plastic mass.

Step 5: inserting the wafer into a mechanical device for mechanical thinning (grinding and / or grinding etc.).

Step 6: the schematic representation of the cross section of a thinned wafer ( 1b ). On the back is a zone damaged by the thinning process ( 6 ).

Step 7: removing the damaged zone ( 6 ) using mechanical methods such as polishing etc. ( 7 ) and / or by chemical processes such as etching ( 8th ) the back.

Step 8: aligning the wafer using optical methods. In particular, it can be advantageous here to use suitable spectra (for example IR radiation) to 10 ) to be illuminated in order to thereby structure the structures and / or markings applied to the front (active or structured side) of the wafer for the purpose of positioning the wafer and / or positioning the cutting device (for example laser ( 11 )) using optical detection devices (e.g. IR camera) ( 9 ) to recognize.

Step 9: Separate the wafer using suitable cutting process. In particular, it can be advantageous a laser beam with / or without water jet support bring.

Step 10: For the purpose of cleaning, it can be advantageous to clean the wafer using a suitable method. In particular, liquid cleaning agents ( 12 ), but also spray and / or rinse off water and / or by means of a bath ( 13 ) apply. However, methods such as suction or blowing can also be used and / or used in addition.

Step 11: For the purpose of better fixing and holding the wafer, it may be advantageous and / or necessary to hold the wafer on a holder ( 14 ) to fix and / or fix. This can also be done by using a further holder and / or suitable processes such as gluing, static charging or similar processes. In principle, the possibility of fixing and / or holding is provided for all the manufacturing steps described in the example in such an advantageous and / or necessary manner.

Step 12: For the purpose of applying a coating to the back of the wafer, it may be advantageous and / or necessary to put it in a vacuum ( 15 ). The coating on the back ( 16 ) can consist of a metallic layer, which is carried out by means of suitable processes, for example vapor deposition and / or sputtering and / or other suitable chemical and / or physical processes.

Step 13: detaching or removing the individual elements of the wafer by means of suitable methods and or devices ( 17 ). It can be advantageous and / or necessary to support the detachment of the elements by suitable chemical and / or physical processes.

As an alternative to step 13, it may be advantageous and / or necessary to place the back of the wafer on another film and / or another carrier (for example carrier films such as blue tape) ( 18 ) to put down and / or stick on.

Subsequently, it may be necessary and / or advantageous to remove the protective layer. Suitable mechanical processes ( 19 ) to apply. It may be advantageous and / or necessary to prevent the protective layer from being removed by suitable chemical and / or physical methods support.

The invention also relates to a Execution device of the method according to the invention. Preferably is the device a system, a system or consists of interconnected systems in which facilities for coating the Separating layer, for coating the protective layer, the treatment the applied layers, thinning and separating Components are interconnected. The essential components the device according to the invention are a coating device for applying the separating layer and / or the protective layer or combinations of layer (s) and / or layer systems on the front of the wafer, a device to apply a back coating, a device for thinning of the wafer, a device for separating the components from a laser or a laser-assisted separating device and / or a mechanical separation device can exist, a device to reduce the adhesion of the protective layer on the front the wafer after dicing, and a device for detaching the components from the shift. The prerequisite is that the one to be thinned and separated Wafers within a manufacturing process for the manufacture of ICs, transistors, Diodes, sensors etc. already do the majority of the manufacturing steps to apply the electrical and mechanical structures and Has gone through layers. The wafer is now on top (the active side, i.e. the side on which the structures are located) covered with a separating layer and / or a protective layer or covered. The layer and / or the layer composite with the wafers arranged thereon are placed on a carrier e.g. fixed by a film and / or supported by a vacuum suction device. After that the wafer is fed into a system. Then the Machining process for thinning of the wafer instead. Here, using the known methods such as for example grinding, lapping and / or etching the Wafer thickness reduced. The wafer can be used during or after this process step can be cleaned. Furthermore, a chemical Treatment possible for the purpose of improving the breaking properties. To The wafer within the system system completes these process steps clocked further and e.g. fed to a separator. It It should be noted that one or more system components for thinning and combined one or more system components for separation can be. The wafer is fed to the separating device without the on the Front layer applied or the layer system applied has been removed. Here, on the edge and / or under the layer or the layer system a device for transport and for the purpose of later Expanding the layer or the layer system may be appropriate. The wafer is now made using a suitable optical and / or mechanical system aligned to the separator. It can preferably be a Process using infrared transmission or lighting for use reach. At this point the wafer is still with its Front side on the layer or the layer system. After alignment of the wafer is now the back of the wafer e.g. with help sawn up a laser beam or the corresponding electrical components are isolated. The laser is preferably emitted by a very thin water jet of approximately 25 μm diameter guided. The laser beam runs inside the water jet and is on the inner wall of the water jet totally reflected, so that wastage is avoided. It is provided that e.g. the layer or layer system for covering the front of the wafer is sufficiently porous so that the water jet penetrates it without damaging it. The layer remains and / or the layer system intact and the individual components keep their position on the slide. But it can also be a mechanical device for cutting such as cutting and / or sawing and / or Break apply. Subsequently, within the System or outside Connect cleaning process. The plant system can also be a plant or device for the purpose the mechanical and / or chemical coating of the back of the wafer include. In particular, there are vacuum technology processes and systems affected, by means of which in particular metallic layers by means of, for example, sputtering and / or vapor deposition and / or others Procedures are applied. It is provided that the back coating can be done before and / or after the separation process. Furthermore, that can Plant system around a component for removing the now isolated electrical components are expanded. It is also contemplated that the cut wafer with carrier and lacquer layer or film or without layer in a cassette system can be filed. When filing without a protective layer is one Device for separating from the protective layer in the system intended. The separating layer preferably consists of an agent CVD process applied nitride layer. But it can also expressly other skies and / or layer systems are used. Preferably the protective layer consists of a plastic with good adhesion properties. The protective layer is preferably connected to the wafer through adhesion, The connection of the protective layer to the wafer is essentially through adhesion causes detachment by heating by means of radiation with electromagnetic waves (e.g. IR or UV) or by introducing heat can be achieved.

Claims (24)

Process for treating wafers with components when thinning of the wafer and the later one Separating the components and any intermediate ones Manufacturing steps, the front of the wafer with the components before thinning covered with a layer system is that at least from a separation layer and a protective layer exists, with the wafer and / or the already isolated components the layer system applied on the front during the Coating the back of the wafer protected and / or be held by it. The method of claim 1, wherein for separating the Components a laser beam is used. The method of claim 1, wherein for separating the Components a mechanical process such as cutting, sawing and / or Breaking comes into play. The method of claim 1, 2 or 3, wherein the wafer through the layer system applied to the front of the wafer while of thinning protected becomes. Method according to one of claims 1 to 4, wherein the wafer through the layer system applied to the front of the wafer while the separation of the components is protected. Method according to one of claims 1 to 5, wherein the separation layer is a vacuum applied layer. Method according to one of claims 1 to 6, wherein the protective layer consists of a plastic mass. Method according to one of claims 1 to 7, wherein the protective layer is applied by means of a spin coater. Method according to one of claims 1 to 8, wherein the protective layer by means of heat is cured. Method according to one of claims 1 to 9, wherein the protective layer also takes on the function of a carrier. Method according to one of claims 1 to 10, wherein the protective layer is a multi-layer system. Method according to one of claims 1 to 11, wherein between thinning of the wafer and the separation of the components on the back of the Wafers a cleaning and / or chemical treatment for improvement the breaking properties of the wafer. Method according to one of claims 1 to 12, wherein for the purpose removal and / or detachment of the components, the adhesion of the protective layer is reduced. The method of claim 13, wherein the liability of the Protective layer by irradiation with electromagnetic waves, by heating, chemical action and / or reduced by mechanical action becomes. Method according to one of claims 1 to 11, with the steps: a) coating the front ( 2 ) of the wafer ( 1 ) in which the components ( 2 ) are arranged with a separating layer ( 3 ) b) coating a protective layer ( 4 ) on the front of the wafer c) hardening and / or solidifying ( 5 ) the protective layer d) thinning the wafer ( 1 ) from its back to a desired thickness ( 1b ) e) treatment of the back of the wafer ( 6 ) using chemical and / or mechanical processes ( 7 ) ( 8th ) for the purpose of improving the mechanical properties and the thinned wafer ( 1b ) f) coating the back of the wafer with a layer ( 16 ) f) separating the components, the protective layer ( 4 ) is not cut. g) reducing the adhesion of the protective layer ( 4 ) on the components and The method of claim 12, wherein steps e to g can be done in any order. The method of claim 12, wherein steps e up to g can be omitted individually A method according to any one of claims 1 to 14, wherein the wafer even before the release layer and / or the application the protective layer by means of grinding and / or scratching and or chemical and or physical etching processes is structured so that while of thinning and / or the subsequent one Backworking these structures open up and the wafer is thus isolated. The method of claim 15, wherein the separation process according to claim 2, 3 and 12 f. Method according to one of claims 1 to 16, the thinning being carried out by grinding, lapping, chemical wet etching and / or plasma etching. Method according to one of claims 1 to 17, wherein according to Applying the protective layer another layer in the form of a Foil is applied. Method according to one of claims 1 to 17, wherein according to Applying the protective layer another layer in the form of a inorganic and / or organic mass is applied. Device for carrying out the method according to a of claims 1 to 19. Device according to claim 20, comprising: a) one Coating device for applying the separating layer, b) a coating device for applying the protective layer, c) a device for thinning the wafer, d) a device for separating the components, e) a device for coating the back of the wafer g) a facility to reduce the adhesion of the protective layer to the separating layer f) a detachment facility of the components from the protective layer.