Micromechanical pressure sensor

Abstract

A method for producing a pressure sensor comprises providing a substrate with a depression; attaching a micromechanical sensor element to the substrate in the depression; attaching an evaluation circuit to the substrate next to the depression; electrically connecting the evaluation circuit to the sensor element; covering the substrate around the depression by means of a potting die such that the depression is closed; potting the evaluation circuit between the substrate and the potting die; and removing the potting die.

Claims

1. A method for producing a pressure sensor, comprising: providing a substrate with a depression; attaching a micromechanical sensor element to the substrate in the depression; attaching to the substrate an evaluation circuit next to the depression; electrically connecting the evaluation circuit to the sensor element; covering the substrate around the depression using a potting die such that the depression is closed, the potting die having a sealing surface, the sealing surface directly contacting the substrate in a manner so as to completely encircle the depression; potting the evaluation circuit between the substrate and the potting die using a potting compound, the sealing surface of the potting die sealing the depression from the potting compound without use of any further sealing element between the potting die and the substrate; and removing the potting die.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described in more detail with reference to the figures.

(2) FIGS. 1-4 illustrate method steps during the production of a pressure sensor.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(3) FIG. 1 shows a first step 100 of a method for producing a pressure sensor. A substrate 105 comprises a depression 110 which may also be called a cavity. The substrate 105 customarily comprises a semiconductor material, for example silicon. On an upper surface of the substrate 105, a micromechanical sensor element 115 is attached in the depression 110 and an evaluation circuit 120 is attached next to the depression 110. The micromechanical sensor element 115 comprises a micromechanical structure (MEMS: Microelectromechanical System) which comprises a membrane 125 which is mounted movably in relation to the rest of the sensor element 115. The evaluation circuit 120 is customarily a semiconductor circuit which is generally designed as an application-specific integrated circuit (ASIC). The sensor element 115 and the evaluation circuit 120 are customarily fastened to the membrane 125 with an adhesive bonding technique.

(4) Electrical connections between the sensor element 115 and the evaluation circuit 120 are customarily produced via bonding wires 130 which preferably lead in each case to a conductive structure within or on the surface of the substrate 105. This operation is also referred to as contact connection, bonding or connecting electrically. An external terminal for the contact connection of the pressure sensor is not illustrated in FIG. 1.

(5) In a step 200, the substrate 105, the sensor element 115 and the evaluation circuit 120 are covered by means of a potting die 205. A region 210 around the evaluation circuit 120 and thereabove is left free here by the potting die 205. However, the potting die 205 provides as tight a seal as possible from the substrate 105 outside this region. In addition, the potting die 205 is formed in such a manner that it fits closely to the substrate 105 around the depression 110. A sealing surface between the substrate 105 and the potting die 205 can have a predetermined minimum width in a manner encircling the depression 110. It is not envisaged to provide a film or another temporary or permanent sealing element between the potting die 205 and the substrate 105. On the contrary, it is preferred for the potting die 205 to fit directly to the substrate 105 at the described points.

(6) In a third step 300, the region 210 between the potting die 205 and the substrate 105 is filled by means of a potting compound 305. Corresponding channels for guiding the potting compound 305 can be formed in the potting die 205. The potting compound 305 is customarily flowable under elevated temperature and optionally under elevated pressure in order to fill the region 210. The potting compound 305 customarily flows in the horizontal direction along the surface of the substrate 105, but cannot penetrate the region of the depression 110 since the potting die 205 forms an insurmountable barrier with the substrate 105.

(7) FIG. 4 shows a fourth step 400 in which the potting die 205 is removed again in the region 210 after the cooling, crosslinking or setting of the potting compound 305. As a result, a pressure sensor 405 is produced, the evaluation circuit 120 of which is covered by means of potting compound 305 and is therefore passivated, whereas its micromechanical sensor element 115 continues to be freely accessible. The pressure sensor 405 can be used in particular for determining a pressure or a difference in pressure between gases, for example on board a motor vehicle.