Patent Application
20060244101
Recently, various kinds of sensors, such as a pressure sensor, an acceleration sensor and a flow rate sensor, have been used to monitor the various states of an automobile during the stoppage and the running thereof. Since these sensors are indispensable to conduct advanced system controls for improving the environment and the comfortableness, more sensors are being used. Recently, the electromagnetic waves caused from the outside of the automobiles and the electromagnetic noises caused inside the automobiles have been increasing. Therefore, it has been required to provide the sensors with excellent countermeasures against electromagnetic noises.
The electromagnetic noises that adversely affect the sensor as described above include noises from the power supply, noises from the output system, and radiation noises. The conventional countermeasures against electromagnetic noises include covering the outside portions of resin package 5, through which the power supply terminal 6, the grounding terminal 7 and the output terminal 8 extend, with feed-through capacitors 10 or connecting the outside portions of the resin package 5 to chip capacitors. Recently, a semiconductor chip that includes a noise filter circuit therein has been disclosed.
A semiconductor apparatus including a noise filter circuit disposed between a power supply pad or an output pad and a circuit, in which the wiring length between the power supply pad or the output pad and the noise filter circuit is shorter than the wiring length between a grounding pad and the noise filter circuit, is disclosed in JP P Hei. 9 (1997)-45855 A (hereafter Reference 2). In the low-pass filter disclosed in Reference 2, a capacitor is inserted between the power supply pad or the output pad and the grounding pad. And, considering the inductance components of the wiring connected, the wiring length between the power supply pad or the output pad and the capacitor is set shorter than the wiring length between the grounding pad and the capacitor.
The filter circuit disclosed in Reference 1 that employs the structure thereof and the filter constants thereof for the design parameters, however, is not sufficient for countermeasuring against electromagnetic noises since the influences of the electromagnetic noises change greatly depending on the parasitic capacitance of the wiring. Therefore, it is very important to control the parasitic capacitance on the chip.
In the filter circuit disclosed in the Reference 2, the wiring connecting a power supply pad or an output pad and a capacitor and the wiring connecting a grounding pad and the capacitor are connected in series at the capacitor. Therefore, to flow noise signals to the ground, it is necessary to reduce the impedance parasitic on the wiring connecting the power supply pad or the output pad to the capacitor and the impedance parasitic on the wiring connecting the grounding pad and the capacitor so as not to adversely affect the capacitor impedance. In other words, it is necessary to clarify the resistance components and the inductance components parasitic on the wiring, and it is important to control the resistance components and the inductance components parasitic on the wiring.
In view of the foregoing, there remains a need to clarify the parasitic resistance components and the wiring inductance components, which concern the influences of electromagnetic noises, and to provide a semiconductor apparatus and a physical quantity sensing apparatus provided with sufficient countermeasures against electromagnetic noises. The present invention addresses this need.
The present invention relates to a semiconductor apparatus and a physical quantity sensing apparatus that incorporate a filter circuit for countermeasuring against electromagnetic noises (hereinafter referred to sometimes as a “noise filter circuit” or simply as a “filter circuit”).
One aspect of the present invention is a semiconductor apparatus and a physical quantity sensing apparatus that include an internal circuit, a filter circuit for countermeasuring against electromagnetic noises, a power supply pad, a grounding pad, and a signal pad. The filter circuit can comprise resistance means and capacitance means. The power supply pad is for applying a power supply potential from the outside. The grounding pad is for applying a ground potential. The signal pad can be for inputting, outputting, or inputting and outputting signals. The length and the width of wiring between the signal or power supply pad and the internal circuit are set so that the resistance value Rf of the resistance means and the parasitic resistance component R1 of the wiring satisfy the following relational expression R1/Rf×100<25.
Another aspect of the present invention is a semiconductor apparatus and a physical quantity sensing apparatus that include the internal circuit, the power supply pad, the grounding pad, the signal pad, and a filter circuit comprising the capacitance means, which can be connected between the signal or power supply pad and the grounding pad. The length and the width of wiring between the signal or power supply pad and the capacitance means and the length and the width of wiring between the capacitance means and the grounding pad are set so that the impedance Za caused by the parasitic resistance component Ra and the inductance component La of the wiring between the signal or power supply pad and the capacitance means, the impedance Zk caused by the parasitic resistance component Rk and the inductance component Lk of the wiring between the capacitance means and the grounding pad, and the impedance Zc caused by the capacitance component of the capacitance means always satisfy the following relational expression Za+Zk<Zc in the frequency range of the electromagnetic noises to be cut.
The internal circuit, the filter circuit, the power supply pad, the grounding pad, and the signal pad can be formed in a single semiconductor chip. The capacitance means can be connected between the signal or power supply pad and the grounding pad by wiring. The signal pad can be an output pad for outputting signals to the outside. The internal circuit can comprise a physical quantity detecting element and an amplifier circuit for amplifying the signal output from the physical quantity detecting element. The capacitance means can be a capacitor.
The present invention is described in detail in reference with the accompanied drawing figures, which illustrate the preferred embodiments of the present invention. In the following, descriptions are made in connection with the embodiments of a semiconductor pressure sensor, to which the present invention is applied. Throughout the following descriptions and the accompanied drawing figures, the same reference numerals are used to designate the same or like constituent elements and their duplicated descriptions are omitted for the sake of simplicity.
Referring to
The pressure sensor 31 further includes a power supply pad 34 for applying a power supply potential from the outside, a grounding pad 35 for applying the ground potential from the outside, and an output or signal pad 36 for outputting signals to the outside. The signal pad 36 can also be an input pad for inputting signals or for inputting and outputting signals. A first resistor 42 and a second resistor 43 are connected in series to a wiring 41 connecting the power supply pad 34 to the internal power supply 40. A first capacitor 44 is connected between the grounding point and the connection node of the power supply pad 34 and the first resistor 42. A second capacitor 45 is connected between the grounding point and the connection node of the first resistor 42 and the second resistor 43. A third capacitor 46 is connected between the grounding point and the connection node of the second resistor 43 and the internal power supply 40. Two resistors 42 and 43 can constitute resistance means. Three capacitors 44, 45, and 46 can constitute capacitance means. The resistance means and the capacitance means can constitute a noise filter circuit. A similar noise filter circuit, comprising a third resistor 48, a fourth resistor 49, a fourth capacitor 50, a fifth capacitor 51, and a sixth capacitor 52, is connected to a wiring 47 connecting the output pad 36 and the amplifier circuit 33.
The configurations described above can be disposed in a semiconductor pressure sensor chip. The pressure sensor 31 includes a pressure detecting element including a glass pedestal and a semiconductor pressure sensor chip bonded to the glass pedestal, similarly as illustrated in
Typically, the frequencies of the electromagnetic noises applied to the automotive sensors fall within the range between several hundreds kHz and 1 GHz. Consequently, the parasitic resistance components and the inductance components of the wiring connecting the pads on a sensor chip and the filter circuits and the parasitic resistance component and the inductance component of the wiring connecting the filter circuit and the amplifier circuit cannot be ignored in determining the filter constants of the filter circuit formed in the sensor chip for cutting electromagnetic noises.
According to the first embodiment, attentions are paid, to the wiring 41 (
For adjusting or setting the parasitic resistance component R1a of the wiring between the power supply pad 34 and the first resistor 42, it is effective to appropriately adjust the length Da and the width of the wiring section between the power supply pad 34 and the connection node of the first capacitor 44 and the length Db and the width of the wiring section between the connection node of the first capacitor 44 and the first resistor 42. For adjusting the parasitic resistance component R1b of the wiring between the first resistor 42 and the second resistor 43, it is effective to appropriately adjust the length Dc and the width of the wiring section between the first resistor 42 and the connection node of the second capacitor 45 and the length Dd and the width of the wiring section between the connection node of the second capacitor 45 and the second resistor 43. For adjusting the parasitic resistance component R1c on the side of the internal power supply 40, it is effective to appropriately adjust the length De and the width of the wiring section between the second resistor 43 and the connection node of the third capacitor 46 and the length Df and the width of the wiring section between the connection node of the third capacitor 46 and the internal power supply 40 of the internal circuit 53.
The parasitic resistance component R1 with respect to the output pad 36 is adjusted in the same manner as described above. For adjusting the parasitic resistance component R1a of the wiring between the output pad 36 and the third resistor 48, it is effective to appropriately adjust the length Di and the width of the wiring section between the output pad 36 and the connection node of the fourth capacitor 50 and the length Dj and the width of the wiring section between the connection node of the fourth capacitor 50 and the third resistor 48. For adjusting the parasitic resistance component R1b of the wiring between the third resistor 48 and the fourth resistor 49, it is effective to appropriately adjust the length Dk and the width of the wiring section between the third resistor 48 and the connection node of the fifth capacitor 51 and the length Dl and the width of the wiring section between the connection node of the fifth capacitor 51 and the fourth resistor 49. For adjusting the parasitic resistance component R1c on the side of the amplifier circuit 33, it is effective to appropriately adjust the length Dm and the width of the wiring section between the fourth resistor 49 and the connection node of the sixth capacitor 52 and the length Dn and the width of the wiring section between the connection node of the sixth capacitor 52 and the amplifier circuit 33 (internal circuit 53).
For example, when the resistance values of the first resistor 42 and the second resistor 43 are the same 60Ω, the resistance value Rf in the noise filter circuit on the power supply side is 120Ω(=60Ω+60Ω). Similarly for the output side, when the resistance values of the third resistor 48 and the fourth resistor are the same 60Ω, the resistance value Rf in the noise filter circuit on the output side is 120Ω(=60Ω+60Ω). As illustrated in
The second capacitor 55 (capacitor means) is connected between the output pad 36 and the grounding point. In the same manner as in the noise filter circuit on the power supply side, the lengths and the widths of the wiring sections are adjusted or set so that the impedance Za caused by the parasitic resistance component Ra and the inductance component La of the wiring connecting the output pad 36 and the second capacitor 55 (wiring sections Di and Do in
The impedance Z of the wiring and the capacitance means to be considered is given by following Expression (1), where f, R, L and C stand for the electromagnetic noise frequency in Hz, the parasitic resistance in Ω, the inductance in H, and the capacitance, respectively, and where the induced reactor XL and the capacitive reactor XC of the wiring impedance are included:
Z=√{square root over (R2+(XL−XC)2)} (1),
XL=2πfL (2),
XC=1/(2πfC) (3).
The wiring inductance L is given by the following Expression (4), where D, w, and t are the wiring length in m, the wiring width in m, and the wiring thickness in m, and where μ0 is the magnetic permeability that is 4π×10−7:
L=(D×μ0/2π)(In{2×D/(w+t)}+0.5+0.2235×(w+t)/D) (4).
The dependence of the inductance on the wiring length and the wiring width obtained from Expression (4) is illustrated in
The induced reactor YL in the wiring impedance due to the inductance component is proportional to the electromagnetic noise frequency f as Expression (2) describes. The capacitance reactor XC is inversely proportional to the electromagnetic noise frequency f as Expression (3) describes. Therefore, as the electromagnetic noise frequency f becomes high, the induced reactor YL caused by the inductance component will not be ignorable and the impedance ZL caused by the inductance component parasitic on the wiring connecting the power supply pad 34 or the output pad 36 and the grounding point will be predominating over the impedance Zc caused by the capacitance component of the capacitor 54 or 55 in the noise filter circuit connecting the power supply pad 34 or the output pad 36 and the grounding point. Consequently, the filter effects will be impaired.
The impedance ZL caused by the inductance component is given by the sum Za+Zk of the impedance Za caused by the parasitic resistance component Ra and the inductance component La of the wiring connecting the power supply pad 34 or the output pad 36 and the capacitor 54 or 55 in the noise filter circuit (the wiring sections Da and Dg or the wiring sections Di and Do in
The inductance component La is given by Expression (4) using the wiring length Da+Dg or Di+Do between the power supply pad 34 or the output pad 36 and the capacitor 54 or 55 and the wiring width w thereof. In the same manner, the inductance component Lk is given by Expression (4) using the wiring length Dh or Dp between the capacitor 54 or 55 and the grounding point and the wiring width w thereof. In Expression (4), D stands for Da+Dg, Dh, Di+Do, or Dp. The wiring thickness is 1.0 μm. The inductance of the path between the power supply pad 34 or the output pad 36 and the capacitor 54 or 55 is given by La+Lk. The impedance Za+Zk is derived from the inductance component La+Lk.
The capacitor 60 is connected between the connection node of the two resistors 56, 57 and the grounding point. The capacitor 61 is connected between the connection node of the sensor internal circuit 53 and the resistor 57 and the grounding point. The two resistors 58 and 59 are connected in series with the wiring 47 connecting the sensor internal circuit 53 and the output pad 36, between the connection node of the second capacitor 55 and the sensor internal circuit 53. The capacitor 62 is connected between the connection node of the two resistors 58, 59 and the grounding point. The capacitor 63 is connected between the connection node of the sensor internal circuit 53 and the resistor 59 and the grounding point.
Countermeasures against electromagnetic noises required for the automotive sensors can be obtained by adjusting the length and the width of the wiring between the power supply pad or the output pad and the internal circuit so that the parasitic resistance component R1 of the wiring between the power supply pad or the output pad and the internal circuit and the resistance value Rf of the resistance means in the filter circuit can satisfy the relational expression R1/Rf×100<25, as disclosed in the first embodiment. Similarly, countermeasures against electromagnetic noises required for the automotive sensors also can be obtained by adjusting the length and the width of the wiring between the power supply pad or the output pad and the internal circuit so that the impedance Za of the wiring between the power supply pad or the output pad and the capacitance means in the filter circuit, the impedance Zk of the wiring between the capacitance means and the grounding pad, and the impedance Zc of the capacitance means always satisfy the relational expression Za+Zk<Zc in the frequency range of the electromagnetic noises to be cut.
A semiconductor apparatus and a physical quantity sensing apparatus that can withstand electromagnetic noise required for automotive devices are obtained. Since the chip that incorporates a noise filter circuit therein makes it unnecessary to connect a discrete filter device thereto, the manufacturing costs can be reduced and any fault due to the connection of the discrete filter device can be prevented. Thus, inexpensive and very reliable semiconductor apparatuses and various sensing apparatuses can be realized.
Although the invention has been described in connection with the illustrated embodiments, changes and modifications are obvious to those skilled in the art without departing from the true spirits of the invention. Therefore, the invention should be understood not by the specific descriptions made in connection with the embodiments thereof. For example, the dimensions and the electrical characteristics values described in connection with the embodiments are exemplary. The invention is applicable not only to pressure sensors but also to various kinds of sensors and semiconductor apparatuses other than sensors. Although the pressure sensor according to the invention have been described in connection with the output pad for outputting signals, the pressure sensor according to the invention can include an input pad for inputting signals or a signal pad for inputting signals and for outputting signals.
As described above, the semiconductor apparatus and the physical quantity sensing apparatus according to the invention are advantageous for the environments prone to electromagnetic noises. The semiconductor apparatus and the physical quantity sensing apparatus according to the invention are suited especially for automotive use, for measurement and for correction.
While the present invention has been particularly shown and described with reference to particular embodiments, it will be understood by those skilled in the art that the foregoing and other changes in form and details can be made therein without departing from the spirit and scope of the present invention. All modifications and equivalents attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention accordingly is to be defined as set forth in the appended claims.
This application is based on, and claims priority to, JP PA 2005-133557, filed on 28 Apr. 2005. The disclosure of the priority application, in its entirety, including the drawings, claims, and the specification thereof, is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-133557 | Apr 2005 | JP | national |
