JP2014174100A - Humidity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high reliability humidity sensor including a monolithic IC for detecting a humidity change as a resistance change using a stress change due to moisture absorption of mold resin.SOLUTION: The humidity sensor of the present invention is formed by mounting a semiconductor element on a lead frame and encapsulating the semiconductor element with resin. An integrated circuit (monolithic IC) 2 is formed integrally on a silicon wafer, and a first resistance element 4 is formed on the integrated circuit 2. Mold resin 3 is formed so as to cover the integrated circuit 2 and the first resistance element 4. This configuration allows humidity detection on the basis of a resistance change rate of the first resistance element 4 to a predetermined moisture absorption rate of the mold resin 3.

Description

  The present invention relates to a humidity sensor. More specifically, the present invention relates to a mold-type semiconductor device in which a semiconductor element mounted on a lead frame is sealed with a resin. Humidity sensor with monolithic IC that detects changes in resistance

  An example of a humidity sensor control circuit is disclosed in Patent Document 1. The thing of this patent document 1 is related with the humidity detection circuit which detects the relative humidity of air continuously in the air-conditioning equipment for household appliances, a dehumidifier, a humidifier. Further, as elements of the humidity sensor, for example, those of Patent Documents 2 and 3 are known, but none of them is a device assuming a monolithic IC. If the humidity sensor can be realized as a monolithic IC, there are many advantages such as miniaturization of the IC and reduction of manufacturing costs.

  As a method of realizing the humidity sensor as a monolithic IC, for example, there is one described in Patent Document 4. According to Patent Document 4, the MOSFET has a structure in which a moisture sensitive member is placed on a gate insulating film and a gate electrode is placed thereon. This MOSFET functions as a humidity sensor for the humidity sensor by detecting the amount of fluctuation in the impedance of the MOSFET by utilizing the fact that the capacitance of the moisture sensitive member changes and the gate capacitance changes according to the humidity in the atmosphere. ing. When the element having such a configuration is used, it is considered that a process for allowing water vapor to permeate the interlayer film and the passivation film of the wiring layer in the sensing region is necessary.

JP 2010-249684 A JP-A-1-26139 JP 58-57701 A JP 58-2731 A

  However, in a normal monolithic IC using a silicon substrate, fluctuations in electrical characteristics are large in a Vth shift test, an NBTI (negative bias temperature instability) test, a hot carrier test, etc., when moisture is absorbed in an element constituting the IC, for example, a MOSFET. It is known to be. Therefore, in order to suppress the moisture absorption of the monolithic IC, it is common to apply a moisture absorption measure such as applying a nitride film to the passivation film of the wiring layer or providing a contact or VIA guard ring on the outer periphery of the chip. Is. Therefore, there is a problem that if high reliability is pursued, humidity sensitivity is lost, and if humidity sensitivity is pursued, reliability is lowered.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a monolithic IC having a monolithic IC that detects a change in humidity as a change in resistance by utilizing a change in stress due to moisture absorption of the mold resin. It is to provide a reliable humidity sensor.

  The present invention has been made to achieve such an object, and the invention according to claim 1 is a humidity sensor in which a semiconductor element is mounted on a lead frame and sealed with a resin. An integrated circuit (2) formed as an integral structure thereon, a first resistance element (4) formed on the integrated circuit (2), the integrated circuit (2), and the first resistance element ( 4) and a mold resin (3) formed so as to cover, and the humidity is determined based on a resistance change rate of the first resistance element (4) with respect to a predetermined moisture absorption rate of the mold resin (3). It is characterized by detecting. (Figure 1)

  According to a second aspect of the present invention, there is provided a humidity sensor comprising a semiconductor element mounted on a lead frame and sealed with a resin, the integrated circuit (2) formed as an integral structure on a silicon wafer, A first resistance element (4) formed on the integrated circuit (2) and a second resistance element formed on the integrated circuit (2) and having a polarity different from that of the first resistance element (4) (5) and a mold resin (3) formed so as to cover the integrated circuit (2) and the first and second resistance elements (4, 5). Humidity is detected based on a resistance ratio of the first resistance element (4) and the second resistance element (5) to the moisture absorption rate of 3). (Fig. 4)

The invention described in claim 3 is the invention described in claim 1 or 2, wherein the mold resin (3) is covered with a resin layer (3a) thicker than the mold resin (3). It is characterized by. (Fig. 5)
According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the first resistive element (4) is an N-type diffused resistor and is on the first resistive element (4). The resin layer is covered with a resin layer (6) having a higher moisture absorption rate than the mold resin (3) through the mold resin (3). (Fig. 7)
The invention according to claim 5 is the invention according to any one of claims 1 to 4, characterized in that the filler content of the mold resin (3) is 50% to 80%.

  ADVANTAGE OF THE INVENTION According to this invention, the highly reliable humidity sensor provided with the monolithic IC which detects a humidity change as a change of resistance using the stress change by moisture absorption of mold resin is realizable.

It is a block diagram for demonstrating Example 1 of the humidity sensor which concerns on this invention. It is a figure which shows the variation | change_quantity of drying-moisture absorption-drying of N type diffused resistance formed on silicon | silicone IC. It is a block circuit diagram of the humidity sensor of the present invention. It is a block diagram for demonstrating Example 2 of the humidity sensor which concerns on this invention. It is a block diagram for demonstrating Example 3 of the humidity sensor which concerns on this invention. It is a figure which shows the rate of change of resin moisture absorption and N type diffusion resistance. It is a block diagram for demonstrating Example 4 of the humidity sensor which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram for explaining a first embodiment of a humidity sensor according to the present invention, in which reference numeral 1 denotes a lead frame, 2 denotes a silicon IC (integrated circuit / monolithic IC), 3 denotes a mold resin, The 1st resistance element is shown.
The humidity sensor of the first embodiment is a humidity sensor in which a semiconductor element is mounted on a lead frame and sealed with resin. The integrated circuit (monolithic IC) 2 is formed as an integral structure on a silicon wafer. The first resistance element 4 is formed on the integrated circuit 2. The mold resin 3 is formed so as to cover the integrated circuit 2 and the first resistance element 4.

With such a configuration, it is possible to detect humidity based on a resistance change rate of the first resistance element 4 with respect to a predetermined moisture absorption rate of the mold resin 3.
FIG. 2 is a diagram illustrating the amount of variation of drying-absorption-drying of the N-type diffusion resistor formed on the silicon IC. The result shown in FIG. 2 is that the stress received from the mold resin 3 on the silicon IC 2 due to the moisture absorption of the mold resin 3 fluctuates, and the result appears as a variation in resistance value. By using such a phenomenon, it is possible to construct a humidity sensor.

  FIG. 3 is a block circuit diagram of the humidity sensor of the present invention, in which reference numeral 4 denotes an N-type diffusion resistor, 5 denotes a P-type diffusion resistor, and 10 denotes a sensing circuit. The silicon IC 2 receives stress due to moisture absorption of the mold resin 3. For example, an N-type diffused resistor 4 is used as a resistance that is highly sensitive to changes in stress. For example, a P-type diffused resistor 5 is used as a resistance that is low in sensitivity to stress changes. According to the block diagram shown in FIG. 3, the voltage input to the sensing circuit 10 is determined by the resistance ratio between the N-type diffusion resistor 4 and the P-type diffusion resistor 5, so that N depends on the degree of moisture absorption of the mold resin 3. The mold diffused resistor 4 changes and functions as a humidity sensor by sensing the voltage input to the sensing circuit 10.

  As described above, according to the present invention, the stress of the mold resin changes as the mold resin absorbs moisture, and the silicon IC senses the change in the stress of the mold resin without absorbing moisture. Therefore, it is possible to realize a highly reliable humidity sensor with a monolithic IC humidity sensor.

FIG. 4 is a block diagram for explaining Example 2 of the humidity sensor according to the present invention. Components having the same functions as those in FIGS. 1 and 3 are denoted by the same reference numerals. The N-type diffused resistor 4 shown in FIG. 3 is a first resistive element, and the P-type diffused resistor 5 is a second resistive element.
The humidity sensor according to the second embodiment is a humidity sensor in which a semiconductor element is mounted on a lead frame and sealed with resin. The integrated circuit (monolithic IC) 2 is formed as an integral structure on a silicon wafer. The first resistance element 4 is formed on the integrated circuit 2. The second resistance element 5 is a resistance element formed on the integrated circuit 2 and having a polarity different from that of the first resistance element 4. The mold resin 3 is formed so as to cover the integrated circuit 2 and the first and second resistance elements 4 and 5.

With such a configuration, the humidity can be detected based on the resistance ratio between the first resistance element 4 and the second resistance element 5 with respect to a predetermined moisture absorption rate of the mold resin 3.
The shape of the chip of the resistance element may be square or rectangular. In the case of the rectangle, as shown in FIG. 4, the N-type diffused resistor 4 is arranged by arranging the N-type diffused resistor 4 in parallel with the long axis. It is convenient to increase the stress sensitivity. Moreover, it is convenient to reduce the influence of the stress of the P-type diffusion resistance 5 by arranging the P-type diffusion resistance 5 in parallel with the minor axis direction. In order to increase the stress sensitivity of the N-type diffused resistor 4, it may be formed into an elongated rectangle.

  Further, the N-type diffusion resistor 4 whose resistance value changes according to the stress is convenient because the stress change of moisture absorption increases as the thickness of the mold resin 3 increases. The circuit 10 or the like is more convenient because the change in moisture absorption is smaller as the mold resin 3 is thinner.

  FIG. 5 is a configuration diagram for explaining a humidity sensor according to a third embodiment of the present invention, and is a configuration diagram of a humidity sensor having an N-type diffusion resistance region in which the thickness of the mold resin is increased. In the figure, reference numeral 3a denotes a protruding layer having a thick mold resin, 12 denotes an N-type diffusion resistance region, and 14 denotes an area other than the N-type diffusion resistance. In addition, the same code | symbol is attached | subjected to the component which has the same function as FIG.

In the humidity sensor of the third embodiment, the region 12 of the N-type diffused resistor 4 is covered with a protruding layer 3 a that is thicker than the mold resin 3.
As shown in FIG. 5, the mold resin 3 is thickened only in the region 12 of the N type diffused resistor 4 where the resistance value changes according to the stress to form the protruding layer 3a, and the mold resin in the region 14 other than the N type diffused resistor is formed. By thinning 3, it is possible to increase the sensitivity of moisture absorption only for the N-type diffusion resistor 4, and to reduce the characteristic fluctuation due to moisture absorption in the other regions 14.

  FIG. 6 is a graph showing the moisture absorption amount of resin and the change rate of N-type diffusion resistance, and shows the moisture absorption amount of resins A, B, and C and the change rate of N-type diffusion resistance when each resin is used. It can be said from FIG. 6 that the humidity sensitivity is better as the moisture absorption amount of the resin is larger. The moisture absorption amount of the resin has a correlation with the filler content. The smaller the filler content, the larger the moisture absorption amount. Therefore, it is possible to increase the moisture absorption sensitivity by using a resin having a low filler content, for example, 50% to 80%. However, the greater the amount of moisture absorption, the greater the expansion of the resin during moisture absorption, which increases the risk of peeling of the silicon and resin, peeling of the lead frame and resin, and disconnection of the bonding wire.

FIG. 7 is a configuration diagram for explaining a humidity sensor according to a fourth embodiment of the present invention, and is a configuration diagram of the humidity sensor in consideration of the hygroscopicity of the mold resin. In the figure, reference numeral 6 denotes a resin having a small moisture absorption amount and 7 denotes a resin layer having a large moisture absorption amount. In addition, the same code | symbol is attached | subjected to the component which has the same function as FIG.
In the humidity sensor of the fourth embodiment, the first resistance element 4 is an N-type diffused resistor, and a resin layer having a higher moisture absorption rate than the mold resin 3 is formed on the first resistance element 4 via the mold resin 3. 7 is covered.

  As shown in FIG. 7, the silicon IC 2, the lead frame 1, and the wire bonding are covered with a resin 6 having a small moisture absorption amount (for example, a filler content of 80% or more), and the resin 7 having a large moisture absorption amount is covered thereon. The risk as described above can be reduced. Further, as shown in FIG. 5, the resin 7 having a large amount of moisture absorption increases the thickness of the mold resin only in the region of the N-type diffusion resistance and thins the mold resin in the other region, so that only the N-type diffusion resistor 4 absorbs moisture. It is possible to increase the sensitivity and reduce the characteristic fluctuation due to moisture absorption in other areas.

  As described above, according to the present invention, the stress of the mold resin changes as the mold resin absorbs moisture, and the silicon IC senses the change in the stress of the mold resin without absorbing moisture. Therefore, it is possible to realize a highly reliable humidity sensor with a monolithic IC humidity sensor.

1 Lead frame 2 Silicon IC (integrated circuit / monolithic IC)
3 Mold Resin 3a Projection Layer 4 with Increased Mold Resin 4 First Resistance Element (N-type Diffusion Resistance)
5 Second resistance element (P-type diffused resistor)
6 Resin with a small amount of moisture absorption 7 Resin layer with a large amount of moisture absorption 10 Sensing circuit 12 Region of N-type diffusion resistance 14 Region other than N-type diffusion resistance

Claims (5)

In a humidity sensor that has a semiconductor element mounted on a lead frame and sealed with resin,
An integrated circuit formed as a monolithic structure on a silicon wafer;
A first resistance element formed on the integrated circuit;
A mold resin formed to cover the integrated circuit and the first resistance element;
A humidity sensor that detects humidity based on a resistance change rate of the first resistance element with respect to a predetermined moisture absorption rate of the mold resin. In a humidity sensor that has a semiconductor element mounted on a lead frame and sealed with resin,
An integrated circuit formed as a monolithic structure on a silicon wafer;
A first resistance element formed on the integrated circuit;
A second resistance element formed on the integrated circuit and having a polarity different from that of the first resistance element;
A mold resin formed to cover the integrated circuit and the first and second resistance elements;
A humidity sensor that detects humidity based on a resistance ratio between the first resistance element and the second resistance element with respect to a predetermined moisture absorption rate of the mold resin.   The humidity sensor according to claim 1, wherein the mold resin is covered with a resin layer thicker than the mold resin.   The first resistance element is an N-type diffused resistor, and the first resistance element is covered with a resin layer having a higher moisture absorption rate than the mold resin via the mold resin. The humidity sensor according to claim 1 or 2. The humidity sensor according to any one of claims 1 to 4, wherein a filler content of the mold resin is 50% to 80%.

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