DE102010034431B4 - Component with protected device structures and method of manufacture - Google Patents

Abstract

Component comprising a hermetically sealed housing (G), device structures (BS) with SAW, BAW or GBAW structures arranged in the hermetically sealed housing (G) and a self-assembling monolayer (SAM), wherein the self-assembling monolayer (SAM) covering all surfaces within the hermetically sealed housing including those of the device structures, the hermetically sealed housing being one of Chip Size Package (CSP), Wafer Level Package (WLP), Chip Sized Wafer Level Package (CS-WLP) or Thin Film Package systems is, the device further comprising a further layer, wherein the further layer SiO, SiN, SiON, polyimide or BCB and the further layer between the component structures (BS) and the self-organizing monolayer (SAM) is arranged.

Description

The invention relates to components with, for example, protected against moisture component structures and methods for producing corresponding components.

Components, eg. B. working with acoustic waves components may have component structures which are sensitive to moisture. For example, Surface Acoustic Wave (SAW) devices include electrode fingers for converting RF signals into surface acoustic waves, and vice versa. For example, changes in the electrode material caused by moisture lead to changes in the characteristics of the device. Thus, there is a risk of corrosion, which can affect the component functions up to total failure or damage the component structures at least partially.

To reduce the risk of damage sensitive component structures may be arranged in housings. Moisture that penetrates through a housing can affect the function of device structures. But even in hermetically sealed enclosures can be contained a lot of residual moisture, which may affect component functions. Such an amount of residual moisture may, for. B. may have been included by unavoidable process steps in the manufacture of a device.

From the EP 0 896 427 A2 are known surface acoustic wave devices, the device structures are covered with a protective layer comprising SiO ₂ or Si ₃ N ₄ .

From the US 2010/0181659 A1 are known electrical components with a frame structure (lead frame), wherein a self-organizing monolayer is arranged to reduce a stress load at an interface between a plastic material and a contact pad of the frame structure.

From the US 6,078,123 A SAW-working devices are known, wherein a photosensitive lacquer is applied to the penetration of water or dirt on a substrate around the edge of a SAW device.

In principle, such a protective layer has the following disadvantages: On the one hand, the mass occupation caused by the protective layer alters the component characteristics of the component. In particular, working with acoustic waves components are sensitive to a change in mass occupancy. On the other hand, the thickness of such a protective layer varies as a result of the production. Changes in the characteristics of the components are therefore fundamentally difficult to predict. Furthermore, such protective layers may be porous to some extent and permeable to water. Thus, there is a risk that the component structures on the one hand corrode and on the other hand are additionally covered by a respect to the acoustic properties disadvantageous protective layer. The protective effect of such a protective layer increases with increasing layer thickness. But the disturbing influence of the protective layer by an increasing mass occupancy also increases.

It is an object of the present invention to provide devices comprising sensitive device structures having SAW, BAW, or GBAW structures which provide enhanced protection, e.g. B. from moisture. It is a further object of the present invention to provide methods of making such devices.

These objects are achieved on the one hand by a component according to the independent claim 1 and by a method according to the independent method claim. Dependent claims indicate embodiments of the invention.

The invention specifies a component which comprises a housing, component structures arranged in the housing and a self-assembling monolayer. The self-assembling monolayer covers the component structures.

The package used is one of CSP (Chip Size Package), WLP (Wafer Level Package), CS WLP (Chip Sized Wafer Level Package) or Thin Film Package systems.

A self-organizing monolayer SAM = Self-assembled monolayer) comprises a monomolecular layer, wherein the molecules align themselves relative to each other and relative to a surface. Once the molecules have aligned, one can also speak of a self-assembled monolayer. The monolayer covers all surfaces within the housing, including the component structures. But it is also possible that the monolayer covers all surfaces outside the housing.

It has been recognized that such self-assembling monolayers can well protect component structures. The layer thickness of such a monolayer is precisely defined and subject to no fluctuation. The molecules can be optimally designed according to their specific application and comprise optimally adapted molecular groups. Such a monolayer is then sufficient temperature stable and may have the ability to repair broken sections.

The mass occupancy of the device structures caused by the monolayer is minimal, so any deterioration in the characteristics of the device is also minimal. However, the protective effect of such a monolayer from mechanical damage, for. As by dust particles or by mechanical abrasion, less pronounced than in thicker layers of, for example, SiO ₂ or Si ₃ N. ₄

The housing may comprise a substrate and a cover.

The device structures include Surface Acoustic Wave (SAW), Bulk Acoustic Wave (BAW) or Guided Bulk Acoustic Wave (GBAW) device structures. Such working with acoustic waves components are sensitive to a change in the mass occupancy of the electrodes.

The electrode surfaces of acoustic wave devices may include chemically inert metals such as gold or platinum. But it is also possible that electrodes comprise less noble metals such as aluminum or copper, which oxidize relative to it more easily. A self-organizing monolayer arranged on such component structures can protect the component structures well and easily from oxidation or corrosion.

In an embodiment, the device structures comprise surfaces of a metal or a metal oxide.

As indicated above, there is a risk of corrosion in a metal surface. Even if the surface comprises a metal oxide, underlying metal of the device structures may continue to corrode.

It has been found that molecules of a self-assembling monolayer adhere particularly well to a metal surface or a metal oxide surface. It is possible, for example, to expose a metal surface of the component structures for a defined time period to such a defined atmosphere that a thin metal oxide layer of a defined thickness is formed on the surface of the component structures. On such a metal oxide surface, the molecules of the self-assembling monolayer can then adhere very well.

In one embodiment, the self-assembling monolayer comprises an array of aligned and approximately parallel juxtaposed molecules. Such an arrangement of particularly low entropy allows a particularly dense arrangement of juxtaposed molecules and thus a particularly good protective effect with a small layer thickness.

In one embodiment, the monolayer comprises chain-shaped molecules having two ends. One of the two ends comprises a hydrophobic molecule group; the other of the two ends comprises a hydrophilic moiety. The hydrophilic molecule group is suitable for adhering to the component structures of the component.

In particular, the hydrophilic molecular group of the molecules of the monolayer can adhere particularly well to a metal surface or to a metal oxide surface of the component structures. Such adhesion may be based on a covalent bond, an ionic bond or a hydrogen bond. Such a bond can be sufficiently stable to heat.

In a variant of this embodiment, the hydrophobic molecular group comprises carbon and hydrogen atoms. In particular, the hydrophobic moiety may include longer chain hydrocarbons or perfluorinated hydrocarbons. The hydrophilic moiety may include an ÖH group, Si (OH) ₃ , a trichlorosilane group - SiCl ₃ -.

It is possible that the hydrophobic moiety at one end and the hydrophilic moiety at the other end are connected by a twelve to fourteen carbon chain chain. However, the chain of carbon atoms can itself represent the hydrophobic molecule group.

The device further comprises a further layer, the further layer comprising SiO ₂ , Si ₃ N ₄ , SiON _x (silicon oxynitride) or polymer layers such as polyimide or BCB (benzocyclobutene). The further layer is arranged between the component structures and the self-assembling monolayer.

Such a further layer constitutes a further protective layer in addition to the self-assembling monolayer. In particular, such a further layer constitutes a protective layer which offers protection against mechanical damage. Such a further protective layer can be made particularly thin and in combination, compared to conventional protective layers form a very good moisture barrier with the self-assembling monolayer.

• - Bereitstellen eines Bauelementstrukturen umfassenden Bauelements,
• - Bereitstellen einer Atmosphäre, die sich auf einer Oberfläche selbstorganisierende Moleküle umfasst,
• - Exponieren des Bauelements in der Atmosphäre solange, bis sich eine selbstorganisierte Monolage der Moleküle auf den Bauelementstrukturen ausgebildet hat.

A method for producing a device with good protection of device structures comprises the steps:

• Providing a component structure comprising components,
• Providing an atmosphere comprising self-assembling molecules on a surface,
• - Exposing the device in the atmosphere until a self-assembled monolayer of molecules has formed on the device structures.

In one embodiment of the method, the molecules are provided in the gas phase.

In this case, it is possible that the molecules of the gas phase condense on the surface of the component and in particular on the surface of the component structures and adhere to the corresponding surface with an end provided for particularly good adhesion.

The method includes the hermetic sealing of the housing

• - Kontaktieren einer Kontaktfläche der Bauelementstrukturen,
• - Aufbringen weiterer Bauelementstrukturen,
• - Aufbringen von Leiterbahnen oder Umverdrahtungen.

In an embodiment, the method comprises a further step selected from:

• Contacting a contact surface of the component structures,
• Application of further component structures,
• - Applying conductor tracks or rewiring.

The monolayer is applied before or after the further process step is carried out.

The application of conductor tracks or rewiring is an important step in the process, if miniaturized components are to be obtained, since via interconnects or rewirings electrical interconnections between external terminal contacts, for. B. solder contacts, and miniaturized internal connection contacts, z. B. chips or other device structures, can be produced.

The component may comprise connection pads for wire-bond connections or for bump connections. In particular, such pads may include under bump metallization of a noble metal such as gold or platinum.

• 1 eine selbstorganisierende Monolage auf SAW-Bauelementstrukturen, die nicht zur Erfindung gehört,
• 2 einen Querschnitt durch ein Bauelement, bei dem Bauelementstrukturen durch eine selbstorganisierende Monolage bedeckt sind, wobei 2 nicht zur Erfindung gehört,
• 3 einen Querschnitt durch ein Bauelement mit einem Gehäuse, wobei die gesamte Oberfläche innerhalb des Gehäuses durch eine selbstorganisierende Monolage bedeckt ist,
• 4 die Anordnung von Molekülen einer selbstorganisierenden Monolage auf einer Oberfläche.

In the following, the component is explained in more detail by means of exemplary embodiments and associated schematic figures. Show it:

• 1 a self-assembling monolayer on SAW device structures not belonging to the invention,
• 2 a cross-section through a device in which component structures are covered by a self-assembling monolayer, wherein 2 not part of the invention,
• 3 a cross section through a device with a housing, wherein the entire surface is covered within the housing by a self-organizing monolayer,
• 4 the arrangement of molecules of a self-assembling monolayer on a surface.

1 shows component structures BS in the form of electrode fingers of an interdigital transducer The component structures BS that is, the electrode fingers are through a self-assembling monolayer SAM covered. Such a self-organizing monolayer SAM This represents a particularly thin protective layer and protects the device structures, for example from moisture. In this case, the protective layer is particularly thin and already by definition or naturally by no thickness variation.

2 is not an embodiment of the invention.

2 shows a cross section through a device B in which component structures BS through a self-organizing monolayer SAM are covered. A cover A further covers those through the self-organizing monolayer SAM covered component structures BS , Such a cover may be the component and in particular the component structures BS Protect against mechanical influences. The cover A is hermetically sealed. Residual amounts of moisture or another for the component structures BS harmful atmosphere within the cover A have less harmful effect on the component structures BS because of the self-organizing monolayer SAM protects the component structures.

The housing comprises a substrate SU on which the component structures BS are arranged. The substrate SU and the cover together form the housing G ,

3 shows a cross section through a device according to the invention B in which the self-organizing monolayer SAM the entire surface of the cover A limited volume covers and protects.

4 shows an array of mutually aligned molecules M a self-organizing monolayer SAM , Each of the molecules has a hydrophilic end HPL and a hydrophobic end HPB , A chain of carbon atoms connects both ends. Intermolecular forces, eg. B. van der Waals forces, cause the molecules M Align each other and arranged relative to each other, in particular parallel to each other. The respective hydrophilic ends HPL of the molecules M adhere to an oxide layer OS , The oxide layer OS is on a metal layer MS arranged. A corresponding oxide layer OS can be obtained, for example, by exposing a metal surface to a defined, oxidizing atmosphere for a defined time. The molecules M the self-organizing monolayer SAM cover the oxide layer OS so dense that good protection from moisture is obtained. For good protection contributes in particular by the hydrophobic ends HPB caused hydrophobic side of the self-assembling monolayer SAM at.

LIST OF REFERENCE NUMBERS

A:

cover

B:

module

BS:

device structures

G:

casing

HPB:

hydrophobic end

HPL:

hydrophilic end

M:

Molecule of the self-assembling monolayer

MS:

metal layer

OS:

oxide

SAM:

self-organizing monolayer

Claims (8)

Component, comprising - a hermetically sealed housing (G), in the hermetically sealed housing (G) arranged component structures (BS) with SAW, BAW or GBAW structures and a self-organizing monolayer (SAM), wherein - the self-assembling monolayer (SAM) covering all surfaces within the hermetically sealed housing including those of the device structures, the hermetically sealed housing being one of Chip Size Package (CSP), Wafer Level Package (WLP), Chip Sized Wafer Level Package (CS-WLP) or Thin Film Package systems is, the device further comprising a further layer, wherein - the further layer SiO ₂ , Si ₃ N ₄ , SiON _x , polyimide or BCB has and - the further layer between the component structures (BS) and the self-assembling monolayer (SAM) is arranged , A device according to the preceding claim, wherein the device structures (BS) comprise surfaces of a metal (MS) or a metal oxide (OS). Component according to one of the preceding claims, wherein the self-assembling monolayer (SAM) has an array of aligned and juxtaposed molecules (M). Component according to one of the preceding claims, wherein the monolayer (SAM) has chain-like molecules (M) with two ends (HPL, HPB), the first end (HPB) has a hydrophobic molecular group and the second end (HPL) has a hydrophilic molecular group, - The hydrophilic molecule group adheres to the device structures (BS). Component according to the preceding claim, wherein - the hydrophobic molecule group comprises a hydrocarbon or a perfluorinated hydrocarbon and - the hydrophilic molecule group has an OH group, Si (OH) ₃ or SiCl ₃ . A method of fabricating a device, comprising the steps of: - providing device structures (BS) with SAW, BAW or GBAW structures, - applying a first layer on the device structure (BS), wherein the first layer SiO ₂ , Si ₃ N ₄ , SiON _x , polyimide or BCB, - providing an atmosphere which has self-organizing molecules (M) on one surface, - exposing the component structures (BS) in the atmosphere to a self-assembling monolayer (SAM) of the molecules (M) the component structures (BS) is arranged, wherein the self - assembling monolayer (SAM) is arranged on the first layer, hermetically sealing a housing (G) of the component, wherein the hermetically sealed housing of a Chip Size Package (CSP), Wafer Level Package (WLP), Chip Sized Wafer Level Package (CS-WLP) or Thin Film Package systems, wherein the self-assembling monolayer (SAM) on all surfaces within d it is applied hermetically sealed housing including those of the component structures. Method according to the preceding method claim, wherein the molecules (M) are provided in a gas phase. Method according to one of the preceding method claims, further comprising a further step selected from: Contacting a contact surface of the component structures (BS), Application of further component structures (BS), - Applying conductor tracks or rewiring, wherein the self-assembling monolayer (SAM) is applied before or after the further process step is carried out.

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