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A method for manufacturing an integrated pressure sensor

IP.com Disclosure Number: IPCOM000186688D
Publication Date: 2009-Aug-31
Document File: 5 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

A differential pressure sensor comprises a membrane (6) arranged over a cavity (7) on a semiconductor substrate (1). A lid layer (10) is arranged at the top side of the device and comprises an access opening (13a) for providing access to the top side of the membrane (6). A channel (9) extends laterally from the cavity (7) and intersects with a bore (15). The bore (15) is formed by laser drilling from the bottom side of the substrate (1) and provides access to the bottom side of the membrane (6). The bore (15) extends all through the substrate (1) and optionally into the lid layer (10).

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A method for manufacturing an integrated pressure sensor

Abstract

A differential pressure sensor comprises a membrane (6) arranged over a cavity (7) on a semiconductor substrate (1). A lid layer (10) is arranged at the top side of the device and comprises an access opening (13a) for providing access to the top side of the membrane (6). A channel (9) extends laterally from the cavity (7) and intersects with a bore
(15). The bore (15) is formed by laser drilling from the bottom side of the substrate (1) and provides access to the bottom side of the membrane (6). The bore (15) extends all through the substrate (1) and optionally into the lid layer
(10).

The invention relates to a method for manufacturing a pressure sensor having a flexible membrane integrated on a substrate.

This type of pressure sensor is e.g. described in US 6 584 854. It comprises a flexible membrane integrated on a first side of a substrate. An opening is formed through the substrate from a second side thereof by means of anisotropic etching in order to provide access to the bottom side of the membrane.

This type of design is advantageous for a pressure sensor because it allows to apply one pressure source to the bot- tom side of the substrate and the other to the top, which makes mounting the chip easier.

It is an object of the present invention to provide an economical method for manufacturing such a pressure sensor. This object is achieved by the method of claim 1. Accordingly, the opening is formed by drilling a bore through the substrate by means of a laser.

This procedure allows to create an accurately placed, well-defined opening, which uses little space on the substrate. In addition, laser drilling is a dry process, which avoids the risk of liquid remaining in the drilled opening or the cavi- ty below the membrane. Also, in contrast to an etching process, laser drilling is a locally confined process, and there is no risk of an undesired removal of material elsewhere - in contrast to this, using an etching process for forming an opening through the substrate may lead to undesired etching elsewhere, e.g. at the metal or silicon layers of the mem- brane or of the electrical leads.

Advantageously, the bore does not open into the cavity below the membrane directly, but rather it is laterally offset and connected thereto by means of a channel. This design allows to manufacture the membrane prior to drilling the bore without the membrane being in danger to be damaged in the drilling process.

In yet a further advantageous embodiment, a lid is formed on the first side of the substrate over the bore. Such a lid allows to close the opening and it can be optimized for that purpose, e.g. in view of its thickness or material.

Other advantageous embodiments are described in the dependent claims as well as in the following description, which makes refe...