EP1463684A2

EP1463684A2 - Method for producing a protective covering for a component

Info

Publication number: EP1463684A2
Application number: EP02806019A
Authority: EP
Inventors: Robert Aigner; Martin Franosch; Andreas Meckes; Klaus-Günter Oppermann; Marc Strasser
Original assignee: Infineon Technologies AG
Current assignee: Infineon Technologies AG
Priority date: 2002-01-11
Filing date: 2002-12-12
Publication date: 2004-10-06
Also published as: WO2003057618A2; US20050048757A1; US6955950B2; DE10200869A1; WO2003057618A3

Abstract

The invention relates to a method for producing a protective covering for a component provided on a substrate (102), according to which at least one sacrificial structure is produced on the substrate (102). The sacrificial structure covers at least one region of the substrate (102) that surrounds the component. Afterwards, a polymer layer (106) is deposited that surrounds the at least one sacrificial structure. An opening (108) is made inside the polymer layer (106) in order to expose a section of the sacrificial structure. The sacrificial structure is then removed, whereupon the opening (108) made in the polymer layer (106) is closed.

Description

description

Method for producing a protective cover for a component

The present invention relates to a method for producing a protective cover for a component, and in particular to the production of a protective cover for components which contain areas whose function would be impaired by injection molded housings, such as BAW filters (BAW = Bulk Acoustic Wave = acoustic bulk wave), resonators, sensors and / or actuators. In particular, the present invention relates to a method for producing such a protective cover for the components at the wafer level.

Components are conventionally produced on and / or in a substrate, with the substrate comprising the component being arranged in a protected manner in an injection-molded housing after the component has been finished. With this arrangement, the substrate and the component are completely embedded in the material of the injection-molded housing, at least in the region of the component. This procedure is disadvantageous for components whose function is impaired by this material, and which therefore require a free space for proper functionality, as is required, for example, with the above-mentioned BAW filters, resonators, sensors and actuators.

One approach which is known in the prior art to solve this problem with injection-molded housings is to provide a “counter substrate” into which a corresponding opening is made, so that when the component substrate and the housing substrate are joined together, the cavity in the Area of the component is arranged in the component substrate, so that the functionality of the component is no longer impaired here. Accordingly, a wafer with the corresponding structures for the components is produced (system wafer), which is connected to a second wafer (lid wafer), which has corresponding pits and holes, which were produced, for example, by etching the same, for example by a bonding process. In this way, the pits of the second wafer will form cavities over the sensitive structures of the first wafer, the connection points (contact pads) of the first wafer being accessible through the holes in the second wafer. This protects the sensitive structures.

As an alternative to the procedures just described, a ceramic housing can also be used.

The disadvantage of the known solutions described above for ensuring the functionality of the components is that a second substrate or a second wafer must always be structured here, which necessitates processing and processing separate from the first wafer. This leads to a very complex overall production and also increases the requirements with regard to the required process accuracy.

On the basis of this prior art, the object of the present invention is to create a simplified method for producing a protective cover for components, which allows the protective cover to be produced in a simple manner without the separate processing of further wafers and / or Substrates is required.

This object is achieved by a method according to claim 1.

The present invention provides a method of creating a protective cover for a device, a substrate is provided which comprises the component, the method comprising the following steps:

(a) creating at least one sacrificial structure on the substrate, the sacrificial structure covering at least a region of the substrate which comprises the component;

(b) depositing a polymer layer that encloses at least one sacrificial structure;

(c) forming at least one opening in the polymer layer to expose a portion of the sacrificial structure;

(d) removing the victim structure; and

(e) closing the opening formed in the polymer layer.

The present invention is based on the knowledge that the complex manner of producing protective covers for components, which is known in the prior art, can be dispensed with by including the production of the protective cover in the “ongoing” manufacturing process for the components A sensitive area of a component is produced using a sacrificial layer process and a sealing process with different polymer materials. The final strength of this “on-chip” lid is sufficiently large for further processing in standard packaging processes, ie processes in which the chips are introduced into housings are going to use.

According to a preferred exemplary embodiment of the present invention, the method according to the invention is applied at the wafer level, in order to enable the creation of a protective cover according to the method according to the invention in a simple manner for a large number of components formed in the wafer. Preferred developments of the present application are defined in the subclaims.

Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

1 shows the representation of a component with a protective cover, which was produced in accordance with a first exemplary embodiment of the present invention;

2A-2H show the individual manufacturing steps of the method according to the invention in accordance with a first exemplary embodiment; and

3A-3C show the manufacturing steps of the method according to the invention in accordance with a second exemplary embodiment.

In the following description of the preferred exemplary embodiments of the present invention, the same reference symbols are used for the similar elements shown in the various drawings.

1, an element 100 is shown which was produced in accordance with an exemplary embodiment of the present invention.

In the exemplary embodiment shown in FIG. 1, a substrate 102 is provided which comprises a component region 104. The component for which a protective cover is to be produced according to the method according to the invention is formed in the component region 104 of the substrate 102. The component can be a component completely arranged within the substrate 102, or a component that is partially exposed on a surface of the substrate 102. In connection with the present invention the term substrate is to be understood such that it already contains the finished processed components, and to simplify the illustration, only one component region is indicated schematically in the figures, without going into the more precise structure of the individual components. The components mentioned are, for example, BAW filters, resonators, sensors and / or actuators.

According to the present invention, a sacrificial structure, which can no longer be seen in FIG. 1, is first applied to the substrate 102 and has covered at least the sensitive region of the component region 104. According to the invention, a polymer layer 106 was then produced which at least surrounds the sacrificial structure. An opening 108 was formed in the polymer layer 106 to expose a portion of the sacrificial structure. The sacrificial structure was then removed, so that the cavity 110 shown in FIG. 1 resulted above the component region 104. Finally, the opening 108 was closed, in the exemplary embodiment shown in FIG. 1 by applying a further polymer layer 112 on the first polymer layer 106.

According to the invention, the problems occurring in the prior art are solved by dispensing with the use of a further substrate or a further wafer.

Instead, a sacrificial layer, for example a photo-structurable resist, is applied to the substrate / wafer 102 and then patterned, so that the sacrificial layer remains only in the areas that are later to be protected by the protective cover. The sacrificial layer is then coated with the polymer layer 106 so that the sacrificial layer is completely covered with it. It is important to ensure that a solvent that may be used for structuring the polymer layer does not dissolve or dissolve the sacrificial layer. Furthermore, the first polymer layer 106 is to be applied with a thickness which has a high final strength and hardness. As material for the Polymer layer can be used, for example, SU-8 from MicroChem, USA. The thickness of the applied first polymer layer 106 is preferably less than 20 μ. The polymer layer is then structured and provided with a few holes 108 over the sacrificial layer, so that the sacrificial layer can be dissolved through these holes. In connection with the dissolution of the sacrificial layer, however, it must be ensured that the solvent used here neither dissolves nor completely dissolves the material of the polymer layer.

According to a preferred exemplary embodiment of the present invention, the resulting structures, which have the thick protective lacquer (polymer layer), are then dried. If the resulting cavities 110 are sensitive and tend to stick during the drying process, a drying process in a supercritical point dryer can also be selected (SCPD = Super Critical Point Dryer).

As in the embodiment shown in FIG. 1, the resulting protective structure is then covered with the further polymer layer 112 and, if appropriate, completely enclosed by the same. The materials of the first polymer layer and the further polymer layer can be the same. The other polymer layer should also be as thick

Layer are applied, preferably with a thickness of less than 20 microns. This ensures that at the end of the process the layer sequence with sufficient hardness and final strength is available. Finally, according to a further exemplary embodiment, the further polymer layer (sealing layer) is structured in order to expose contact pads (connection surfaces) and, in the case of wafers, saw lines.

With regard to the sacrificial layer, it should be noted that in the simplest case this can be a photoresist. Alternatively, the sacrificial layer can also be made of metal, e.g. B. copper, titanium, A- aluminum, or be formed from an oxide, for example silicon dioxide (Si0 ₂ ).

As an alternative to the closure technique for the holes 108 described above (see FIG. 1), a laminated, photostructurable film can also be used instead of the further polymer layer 112.

According to a further embodiment, the openings can be closed by means of metal paste, e.g. B. by screen printing, which is particularly advantageous in combination with flip-chip bumps (bumps = bumps).

A first, preferred exemplary embodiment of the present invention is described in more detail below with reference to FIG. 2, in which a plurality of components on a wafer are provided with a protective cover. To simplify the illustration, only the relevant steps for producing the protective cover are shown in FIG. 2, but not the components formed in the wafer. For the following description, the term “wafer” is used inter alia with the meaning that all the necessary components have already been processed here.

2A, the wafer 114 is shown, which has a first surface 114a and a second surface 114b, which lies opposite the first surface 114a. A sacrificial layer 116 is formed on the first surface 114a of the wafer 114, for example made of a photoresist, a metal or an oxide layer. In a first method step, the sacrificial layer 116 is now exposed using a mask 118, as is indicated by the arrows shown in FIG. 2A. The mask 118 defines those areas which should subsequently remain above the sensitive areas of the wafer 114. Subsequent to the exposure, the sacrificial layer 116 is structured, for example by developing the sacrificial layer, so that the layer shown in FIG. 2B shows the structure consisting of the wafer 114 and consisting of two sacrificial structures 116a and 116b arranged above the sensitive regions of the components in the wafer. The sacrificial layer 116 structured in this way is then coated with a first polymer layer 106 by applying this to the first surface 114a and to the sacrificial structures 116a and 116b, as shown in FIG. 2C. The first polymer layer 106 is preferably deposited on the wafer 114 with a thickness of less than 20 μm.

In a subsequent step (see FIG. 2D), the polymer layer 106 is exposed using a further mask 120. The mask 120 defines areas in which openings are later formed in the first polymer layer 106 to the sacrificial structures 116a and 116b, and the mask 120 also defines additional pad areas and saw lines for a later separation of the wafer into individual elements. The exposed areas of the polymer layer 106 defined by the mask 120 are crosslinked by the exposure. The non-crosslinked areas of the polymer layer 106 are removed in a subsequent development step, so that the structure shown in FIG. 2E results. As can be seen, the first polymer layer 106 was structured so that the openings 108a are now formed which expose a part of the sacrificial structure 116a. Openings 108b were also created, which expose part of the sacrificial structure 116b. In addition, a saw line 122 as well as a connection area 124 were exposed on the wafer 114. Contact is subsequently made to the components generated in the wafer via the connection region 124.

Via the holes 108a and 108b created in the polymer layer 106, the sacrificial structure 116a and 116b underneath is detached, and thus the cavities 110a, 110b shown in FIG. 2F are generated. In order to close the openings 108a and 108b, a further polymer layer 112 is deposited on the structure shown in FIG. 2F in the exemplary embodiment shown, as shown in FIG. 2G. In the exemplary embodiment shown, the further polymer layer 112 is produced from the same material as the first polymer layer 106, but in other exemplary embodiments it can also be formed by a different material. As can be seen, the application of the further polymer layer 112 closes the openings 108a and 108b. In a subsequent step, the further polymer layer 112 is structured using a third mask 126, the third mask 126 defining the connection regions 124 and saw line 122 already described with reference to FIG. 2E. The exposed areas of the further polymer layer 112 are crosslinked, and the non-crosslinked areas are removed in a subsequent development step, so that the final structure of the wafer shown in FIG. 2H results.

In a further process step, not shown, the wafer 114 can then also be separated in order to generate the individual elements. These individual elements are then contacted and arranged in appropriate housings.

With regard to the structuring steps described above, it should be pointed out that when structuring the first polymer layer 106, the solvent used there should be selected such that the material of the sacrificial layer is not dissolved or dissolved. Likewise, when removing the sacrificial layer, it must be ensured that the solvent used there does not dissolve or dissolve the polymer material of the first polymer layer 106.

A second exemplary embodiment of the method according to the invention is described below with reference to the manufacture of a protective cover for a component on a sub-base. strat explained in more detail. FIG. 3A shows a structure which results after the first polymer layer has been opened. 3A shows a substrate 102, in which an active region 104 of a component arranged therein is shown schematically. The sacrificial layer 116 is here, for example, made of copper and arranged on a first surface 102a of the substrate, and covers the active region 104 of the component comprised in the substrate. Furthermore, a connection metallization 126 is formed on the first surface 102a of the substrate 102, which is preferably formed here from the same material, namely copper (Cu), as the sacrificial layer / sacrificial structure 116. This has the advantage that the sacrificial structure 116 and the metallization 126 are formed simultaneously by the deposition and structuring of a copper layer. There is a first one on the connection metallization 126

UBM 128a (UBM = under bump metallization = under metallization for the solder material), e.g. made of gold (Au). Furthermore, a second UBM 128b, e.g. made of gold (Au). The second UMB 128b extends from one to the other as shown in FIG. 3A

Surface 102 of the sacrificial layer 116 facing away from the substrate 102 onto the first surface 102a of the substrate 102. In order to enable the sacrificial layer 116 to be removed later, the second UBM 128b has an opening 130 which exposes the sacrificial layer 116. As can also be seen, the first polymer layer 106 comprises openings 108a and 108b in the area of the UBMs 128a and 128b.

In a subsequent method step, the sacrificial layer 116 is removed by applying a solvent to it, only the sacrificial layer 116 being removed due to the opening 130, but not the metallization 126, which is protected by the first UBM 128a. In the embodiment shown in FIG. 3, the openings 108a and 108b are closed by a solder paste 132a, 132b, as shown in FIG. 3B, in which the resultant Ending cavity 110 is shown above the active region 104 of the device of the substrate 102.

FIG. 3C shows a top view of the structure shown in FIG. 3B and again illustrates the areas exposed by the sacrificial layer 116. 3C, the area shown in broken lines is the area that is exposed by the sacrificial layer 116.

Corresponding contacting of the component in the substrate to the outside takes place via the connections 128a and 128b. The solder paste can be applied, for example, by the known reflow process after the sacrificial layer has been etched free.

Although preferred embodiments of the present invention have been explained above, the present invention is of course not limited to this.

Instead of the polymer materials described, other suitable materials such as, for example, deposited layers of silicon nitride, silicon oxide, metals, metal compounds can also be used.

The thickness of the applied polymer material layers is preferably between 1 μm and 100 μm. Furthermore, the thickness of the applied polymer material layers is preferably between 1 μm and 20 μm.

Reference character list

100 element

102 substrate

104 component area

106 polymer layer

108, 108a, 108b opening

110, 110a, 110b cavity

112 more polymer layers

114 wafers

114a first surface of the wafer

114b second surface of the wafer

116 sacrificial layer

116a, 116b victim structure

118, 120 mask

122 saw line

124 Connection area

126 connection metallization

128a, 128b UBM

130 opening

132a, 132b solder paste

Claims

claims

1. A method for producing a protective cover for a component, wherein a substrate (102; 114) is provided which comprises the component, the method comprising the following steps:

(a) creating at least one sacrificial structure (116a, 116b) on the substrate (102; 114), the sacrificial structure (116a, 116b) covering at least a region of the substrate (102; 114) which comprises the component;

(b) depositing a polymer layer (106) which encloses at least the at least one sacrificial structure (116a, 116b);

(c) forming at least one opening (108; 108a, 108b) in the polymer layer (106) to expose a portion of the sacrificial structure (116a, 116b);

(d) removing the sacrificial structure (116a, 116b); and

(e) closing the opening (108; 108a, 108b) formed in the polymer layer (106).

2. The method of claim 1, wherein step (c) comprises the following steps:

(c.l.) exposing the polymer layer (106) using a mask (120) to create cross-linked areas of the polymer layer (106), the mask (118) defining at least one opening (108a, 108b); and

(c.2.) Removing the non-crosslinked areas of the polymer layer (106).

3. The method of claim 1, wherein steps (b) and (c) comprise the following steps: (bl) depositing the polymer layer (106) on the substrate (102; 114) and on the sacrificial structure (116a, 116b);

(c1) exposing the polymer layer (106) using a mask (120) which covers the at least one opening (108; 108a, 108b) in the polymer layer (106) and an area of the polymer layer (106) surrounding the sacrificial structure (116a, 116b) ) defined, the exposure of the polymer layer (106) producing crosslinked areas in the polymer layer (106); and

(c.2) removing the non-crosslinked areas of the polymer layer (106).

4. The method of claim 3, wherein the mask (120) further defines an exposed connection area (124) for the component, which is exposed by removing the non-crosslinked areas of the polymer layer (106).

5. The method according to any one of claims 1 to 4, wherein step (a) comprises the following steps:

(a.l.) depositing a sacrificial layer (116) on the substrate (102; 114); and

(a.2.) Structuring the deposited sacrificial layer (116) in order to obtain the at least one sacrificial structure (116a, 116b).

6. The method according to any one of claims 1 to 5, wherein step (d) comprises the following steps:

Etching the victim structure (116a, 116b).

7. The method according to any one of claims 1 to 6, wherein step (e) comprises the following steps: (el) applying a further polymer layer (112) on the structure resulting after step (d); and

(e.2.) Structuring the further polymer layer (112) such that the further polymer layer (112) covers the polymer layer (106) deposited in step (e), whereby the at least one opening (108a, 108b) in the first polymer layer ( 106) by the material of the second polymer layer

(112) is closed.

8. The method according to claim 7, wherein the polymer layer (106) and the further polymer layer (112) consist of the same material.

9. The method according to any one of claims 1 to 6, wherein the

Step (e) comprises the lamination and photolithographic structuring of a film on the structure resulting after step (d) in order to close the at least one opening.

10. The method according to any one of claims 1 to 6, wherein step (e) comprises closing the opening (108a, 108b) by a metal paste (132a, 132b).

11. The method according to any one of claims 1 to 10, wherein the sacrificial structure (116a, 116b) is made of a material comprising a photoresist, a metal or an oxide.

12. The method according to any one of claims 1 to 10, wherein the polymer layer (106) consists of SU-8.

13. The method according to any one of claims 1 to 12, wherein the component is a BAW filter, a resonator, a sensor or an actuator.

14. The method according to any one of claims 1 to 13, wherein the substrate is a wafer (114) which comprises a plurality of identical or different components,

wherein in step (a) a sacrificial structure (116a, 116b) is generated for each of the components by applying and structuring a sacrificial layer (116) on the wafer (114),

wherein in step (b) and in step (c) the polymer layer (106) is applied to the wafer (114) and structured in order to create at least one opening (108a, 108b) for each component,

wherein in step (d) all victim structures (114a, 114b) are removed, and

the openings (108a, 108b) being closed in step (e).

15. The method according to claim 14, in which the wafer (114) is finally divided into individual elements.

16. The method according to claim 14 or 15, wherein the structuring of the polymer layer (106) comprises the definition of separating lines (126) on the wafer (114).

17. The method according to any one of claims 1 to 16, wherein the structure resulting after step (d) is dried before step (e).