Sensor component with reduced stray fields

Abstract

The invention is based on a sensor component comprising a first sensor (10) with a micromechanical functional part (100) and with an electronic evaluation circuit (200), which are electrically connected to each other, - wherein the micromechanical functional part (100) comprises at least one differential capacitor with a central electrode (CM), a first counter electrode (C1) and a second counter electrode (C2), - wherein the electrodes (CM, C1, C2) are electrically connected to the electronic evaluation circuit (110) via a central electrode conductor (130M), a first counter electrode conductor (130C1) and a second counter electrode conductor (130C2), - wherein the sensor component has at least a second sensor (20) which is electrically connected to the electronic evaluation circuit by means of at least one further electrical conductor (1302). The core of the invention consists in the fact that the two counter-electrode conductors (L1, L2) are arranged spatially asymmetrically to the central electrode conductor (130M) and that at least one further conductor (1302) of the second sensor (20) is arranged between the two counter-electrode conductors on the one hand and the central electrode conductor on the other.

Description

State of the art

[0001] Micromechanically constructed sensors are known in the prior art, for example, as inertial sensors. Capacitive sensors, such as accelerometers with electrode comb structures, are widely used. These comb structures generally form a differential capacitor with a movable center electrode positioned between two fixed counter electrodes. The three electrodes of the differential capacitor are connected to an electronic evaluation circuit to assess the changing capacitances. In the prior art, the signal line from the center electrode is positioned between the two signal lines from the counter electrodes. If the micromechanical functional part and the electronic evaluation circuit are located on two different substrates, these substrates are connected to each other via contact surfaces and bond wires.The contact surface for the center electrode is again located between the contact surfaces for the two counter electrodes.

[0002] The sensor's signal leads generate electric fields that influence the sensor's environment and the signals themselves. This, in turn, affects the sensor's measurement signal. Changes in the electric fields, such as those caused by altered environmental conditions, will also affect the sensor's measurement signal. Influencing environmental conditions include the sensor's packaging, temperature, humidity, and the position of the signal leads. For example, the aging of a plastic housing or gel surrounding the sensor can change its dielectric constant. Similarly, temperature and humidity also alter the dielectric constant. Furthermore, external mechanical forces can deform bond wires, leading to changes in the relative positions of the signal leads. Finally, external electromagnetic fields can also influence the sensor.

[0003] Document DE 10 2004 039 924 A1 discloses a micromechanical sensor with a differential capacitor in which each signal line is shielded by being separated from the next signal line by a ground connection.

[0004] Furthermore, sensor components in which several sensors are integrated are known in the prior art. Object of the invention

[0005] The object of the invention is to create a capacitive sensor component with reduced electrical stray fields and with as few bonding surfaces and bonding wires as possible. Advantages of the invention

[0006] The invention is based on a sensor component comprising a first sensor with a micromechanical functional part and an electronic evaluation circuit, which are electrically connected to each other. - wherein the micromechanical functional part comprises at least one differential capacitor with a central electrode, a first counter electrode and a second counter electrode, wherein the electrodes are electrically connected to the electronic evaluation circuit by means of a central electrode conductor, a first counter electrode conductor and a second counter electrode conductor, wherein the sensor element comprises at least one second sensor which is electrically connected to the electronic evaluation circuit by means of at least one further electrical conductor.

[0007] The core of the invention consists in the fact that the two counter-electrode conductors are arranged spatially asymmetrically to the central electrode conductor and that at least one further conductor of the second sensor is arranged between the two counter-electrode conductors on the one hand and the central electrode conductor on the other.

[0008] Advantageous embodiments of the invention can be found in the dependent claims. drawing The Fig. Figures 1 a and b show the schematic structure of a capacitive micromechanical sensor in the prior art. Fig. Figure 2 shows the schematic structure of a micromechanical capacitive sensor component according to the invention. Description

[0009] The Fig. Figures 1a, b, and c show the schematic structure of a capacitive micromechanical sensor in the prior art. Such a sensor is disclosed in publication DE 10 2004 039 924 A1.

[0010] Fig. Figure 1a shows the schematic structure of the capacitive sensor. A micromechanical functional part 100 and an electronic evaluation unit 110 are depicted, electrically connected by conductor connections 130. In the example shown here, the micromechanical functional part 100 and the electronic evaluation unit 110 are arranged on two different substrates 1, 2. Each substrate therefore has contact surfaces 120 to which the conductor connections 130 are made. In this case, the conductor connections 130 are designed as bond wires. Specifically, the substrate contact S and the signal contacts C1, CM, and C2 on the evaluation unit 110 are shown. Each of these contacts is electrically connected to a counterpart on the micromechanical functional part 100 by means of its own conductor connection 130. Specifically, these are the substrate line or ground line 130S and the three signal lines 130C1, 130CM, and 130C2.The signal lines are arranged directly next to each other, and the ground connection in the form of the substrate line 130S runs alongside them. Interference between the signal lines due to electric fields is therefore easily possible.

[0011] Fig. Figure 1b shows the schematic structure of the micromechanical functional part 100 of the capacitive sensor. It depicts a differential capacitor with a movable center electrode CM and two symmetrically arranged, fixed counter electrodes C1 and C2. The center electrode CM can be deflected in the X direction, for example, as a result of an applied acceleration, which changes the partial capacitances of the differential capacitor defined by electrodes C1 and CM and C2 and CM, respectively. The electronic evaluation circuit 110 is connected to the differential capacitor via the three signal lines described above and determines the partial capacitances. The first and second counter electrode conductors L1 and L2 from counter electrodes C1 and C2 are arranged symmetrically to the center electrode conductor LM from the center electrode CM. Crosstalk between the conductors due to parasitic electric fields leads to a change in the sensor measurement signal.

[0012] Fig. Figure 1c schematically shows the error capacitances of the micromechanical sensor. In a combined MEMS, two separate components, ASIC chip 2 and MEMS chip 1, are often electrically connected by bond wires 130. The bond wires can represent a source of error, especially in capacitive sensors with small measuring capacitances. For example, an accelerometer typically measures the differential capacitance between the drive node CM and the read nodes C1, C2. However, not only the measuring capacitance of the sensor itself is determined, but also the capacitance that exists between the bond wires. Assuming the accelerometer has an electrical sensitivity of 1 fF / g, then an asymmetry of 1 fF in the bond wire coupling means that a static error signal of 1 g is present. If, for example, the capacitance varies due to humidity, the measured value will also vary. If εR varies by 10%, this is equivalent to 100 mg of drift.

[0013] In the prior art, this effect is minimized by making the arrangement symmetrical, so that only the mismatch of the bond wires is taken into account; in addition, CM can be shielded with additional symmetrical electrical ground lines CS, thus reducing the absolute coupling capacitance.

[0014] Fig.Figure 2 shows the schematic structure of a micromechanical capacitive sensor element according to the invention in an exemplary embodiment. The invention utilizes the fact that modern micromechanical sensor elements often contain multiple sensors. The figure shows an exemplary sensor element according to the invention that combines two micromechanical sensors in a first chip 1. The sensor element includes on the first chip a first sensor 10, namely an accelerometer, with a micromechanical functional part 100 comprising a differential capacitor with a central electrode CM, a first counter electrode C1, and a second counter electrode C2. An electronic evaluation circuit 110 is integrated on a second chip 2, an ASIC.

[0015] The central electrode CM is electrically connected to the electronic evaluation circuit 110 via a central electrode conductor 130M, the first counter electrode C1 via a first counter electrode conductor 130C1, and the second counter electrode C2 via a second counter electrode conductor 130C2. The connecting conductors are formed by bond wires 130, which connect both chips via contact surfaces 120, the bond pads.

[0016] The sensor component has a second sensor 20 on the first chip 1, in this example a gyroscope, which is electrically connected to the electronic evaluation circuit by means of further electrical conductors 1302.

[0017] According to the invention, the two counter-electrode conductors 130C1, 130C2 are arranged spatially asymmetrically to the central electrode conductor 130M, and the further conductors 1302 of the second sensor 20 are arranged between the two counter-electrode conductors 130C1, 130C2 on the one hand and the central electrode conductor 130M on the other.

[0018] The drive signal CM is therefore no longer arranged symmetrically as was previously customary, but on the opposite side of the sensor.

[0019] According to the invention, in a combined sensor, the drive side and detection side of the first sensor are separated by an arrangement of the connections of the second sensor in between. Reference symbol list 1 first chip 2 second chip 10 first sensor 20 second sensor 100 micromechanical functional parts 110 electronic evaluation circuit 120 contact area 130 conductor connection CM center electrode C1 first counter electrode C2 second counter electrode 130M center electrode conductor 130C1 first counter electrode conductor 130C2 second counter electrode conductor 130S substrate line, ground line 1302 additional leaders QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2004 039 924 A1 [0003, 0009]

Claims

Sensor element comprising a first sensor (10) with a micromechanical functional part (100) and with an electronic evaluation circuit (110), which are electrically connected to each other, wherein the micromechanical functional part (100) comprises at least one differential capacitor with a central electrode (CM), a first counter electrode (C1) and a second counter electrode (C2), wherein the electrodes (CM, C1, C2) are electrically connected to the electronic evaluation circuit (110) by means of a central electrode conductor (130M), a first counter electrode conductor (130C1) and a second counter electrode conductor (130C2), wherein the sensor element comprises at least one second sensor (20) which is electrically connected to the electronic evaluation circuit by means of at least one further electrical conductor (1302), characterized in that the two counter electrode conductors (130C1,130C2) are arranged spatially asymmetrically to the central electrode conductor (130M) and at least one further conductor (1302) of the second sensor (20) is arranged between the two counter electrode conductors (130C1, 130C2) on the one hand and the central electrode conductor (130M) on the other hand. Sensor component according to claim 1, characterized in that the first sensor (10) with the micromechanical functional part (100) and the second sensor (20) are arranged on a first chip (1) and the electronic evaluation circuit (110) on a second chip (2). Sensor component according to claim 2, characterized in that the middle electrode conductor (130M), the first counter electrode conductor (130C1) and the second counter electrode conductor (130C2) are formed at least sectionally from a bond wire each. Sensor component according to one of the preceding claims, characterized in that the second sensor (20) is electrically connected to the electronic evaluation circuit (110) by a plurality of further conductors (1302) and the plurality of further conductors (1302) of the second sensor (20) is arranged between the two counter electrode conductors (130C1, 130C1) on the one hand and the middle electrode conductor (130M) on the other hand.

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