JP2002267684A - Semiconductor-type dynamic quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of preventing a reference value of a sensor from varying due to creep phenomena in a flexible thermosetting adhesive with the passage of days after assembly. SOLUTION: In a process for gluing a semiconductor sensor chip to a seating with a thermosetting adhesive 19a in which a plurality of resin beads 18a are arranged as shown in Fig. (b), the semiconductor sensor chip on the side supporting a weight 14 via a beam part 13 is not glued to the seating. By applying such a gluing method, a frame part 12 of the semiconductor sensor chip on the side connected to the beam part 13 is not deformed by the contraction of the thermosetting adhesive 19a in the process for gluing the semiconductor sensor chip to the seating. Therefore, it is possible to suppress the propagation of distortion to the beam 13 due to the creep phenomena of the thermosetting adhesive 19a, and reduce the amount of variation in the reference value with the passage of days after the gluing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor type dynamic quantity sensor and, more particularly, to a characteristic fluctuation reducing structure which can prevent the reference from fluctuating.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor type dynamic quantity sensor, as disclosed in Japanese Patent Application Laid-Open No. 10-123166,
There is a semiconductor acceleration sensor configured to be able to detect acceleration (mechanical quantity) by utilizing a piezoresistance effect of a resistance element provided on a beam portion.

Here, the semiconductor type acceleration sensor will be briefly described with reference to FIGS. 9 and 10. FIG. FIG.
0 is a view of the semiconductor sensor chip 1 in FIG.

First, as shown in FIG. 10, a semiconductor sensor chip 1 supports a weight 4 in a bilateral manner via four beams 3 symmetrically arranged inside a frame 2. Each beam 3 has two resistance elements (not shown) whose resistance changes according to the applied acceleration.
It is formed individually.

Since these beam portions 3 are portions where large distortion occurs when acceleration is applied to the semiconductor sensor chip 1, the applied acceleration can be detected by forming a resistance element in the beam portions 3. .

As shown in FIG. 9, the semiconductor sensor chip 1 is adhered to the pedestal 5 via the frame 2 with a flexible adhesive 9a. The integral body is adhered on the housing 6 by a flexible adhesive 9b.

Since the flexible adhesives 9a and 9b contain a plurality of resin beads 8a and 8b, the air gap between the weight 4 and the pedestal 5 is strictly controlled. It can be done easily.

The housing 6 is formed by laminating a plurality of ceramic substrates 6b, and a thin-film electrostatic shield 7 is formed between the ceramic substrates 6b over the entire area. .

[0009]

Here, the resin beads 8
The bonding step of bonding the semiconductor sensor chip 1 and the pedestal 5 with the flexible adhesive 9a containing a will be briefly described.

First, a liquid state flexible adhesive 9a containing resin beads 8a is applied between the semiconductor sensor chip 1 and the pedestal 5.

The flexible adhesive 9a is thermally cured by exposing it to an atmosphere at a predetermined temperature (about 150 ° C.) for a predetermined time (about 1 hour), and the semiconductor sensor chip 1 is bonded to the pedestal 5.

Thereafter, a reference value in a state where the applied acceleration is zero, which is a reference of the characteristics of the semiconductor acceleration sensor, is set.

However, it has been found that the set reference value gradually changes as the number of days after the bonding step elapses.

According to the inventors' earnest research, this problem is:
Warpage of semiconductor sensor chip 1 and flexible adhesive 9a
Was found to be due to the creep phenomenon.

That is, as shown in FIG. 11A, the semiconductor sensor chip 1 after dicing into individual chips.
Has a curved shape.

This is because when the semiconductor sensor chip 1 is formed,
In the wafer state, aluminum wiring and the like are formed on the wafer surface in a high temperature state, and after the formation, the wafer is returned to room temperature state.
This is because the wafer is deformed.

When the semiconductor sensor chip 1 warped in the curved shape is bonded to the pedestal 5 with the flexible adhesive 9a, as described above, the temperature is returned from a high temperature of about 150 ° C. to room temperature, as shown in FIG. As shown in b), the flexible adhesive 9a contracts.

At the same time, the center of the semiconductor sensor chip 1 is deformed toward the pedestal 5 with the resin beads 8a provided at both ends inside the flexible adhesive 9a as fulcrums.

After the bonding step, as time passes, as shown in FIG. 11C, the flexible adhesive 9a
Due to the creep phenomenon of the semiconductor sensor chip 1 shown in FIG.
The shape gradually returns to the shape before bonding as shown in FIG.

Therefore, even if the above-mentioned reference value is set in the state shown in FIG. 11B, that is, immediately after the bonding, the semiconductor sensor chip is creeped by the flexible adhesive 9a with the lapse of time thereafter. As a result, the resistance value of the resistance element formed on the beam portion 3 of the semiconductor sensor chip 1 changes, and as shown in the curve of FIG. The reference value fluctuates.

As the flexible adhesive 9a, a soft material is selected in order to suppress propagation of distortion from the pedestal 5 to the semiconductor sensor chip 1.

Here, if a hard material is selected as the flexible adhesive 9a, the harder the material, the slower the creep speed. Therefore, it is necessary to return the semiconductor sensor chip 1 to the shape shown in FIG. It takes a long time and will not be a problem in the market.

However, when a hard material is selected as the flexible adhesive 9a, if the pedestal 5 or the housing 6 supporting the semiconductor sensor chip 1 is deformed due to a change in temperature or the like,
The semiconductor sensor chip 1 is susceptible to the influence, and the reference value fluctuates even though no acceleration is applied.

Therefore, it is necessary to use a soft material for the flexible adhesive 9a to reduce the influence of the deformation of the pedestal 5 and the housing 6 on the semiconductor sensor chip 1.

In view of the above problems, an object of the present invention is to have a weight portion supported via a beam portion, and to detect a dynamic quantity by utilizing a piezoresistance effect of a resistance element formed on the beam portion. In a semiconductor type dynamic quantity sensor comprising a semiconductor sensor chip configured to be able to, and a pedestal bonded to the semiconductor sensor chip by a thermosetting adhesive containing beads,
It is an object of the present invention to provide a structure capable of preventing a reference value of a sensor from fluctuating due to a creep phenomenon of a flexible thermosetting adhesive due to a lapse of time after a bonding process.

[0026]

According to a first aspect of the present invention, there is provided a semiconductor dynamic quantity sensor having a displacement section which is displaced by application of a dynamic quantity, and comprising a semiconductor sensor chip for detecting displacement of the displacement section and beads. And a pedestal for fixing the semiconductor sensor chip with the thermosetting adhesive, the thermosetting adhesive is arranged at a position where the influence of distortion from the thermosetting adhesive is reduced. It is characterized by having.

By applying the bonding method as described above, even if the thermosetting adhesive shrinks in the bonding step between the semiconductor sensor chip and the pedestal, the influence of the distortion from the thermosetting adhesive increases. There is no thermosetting adhesive for the semiconductor sensor chip at such a position.

Thus, the semiconductor sensor chip at the position can be kept in a dicing cut state before and after the bonding step, and the semiconductor sensor chip does not deform due to the bonding step.

That is, in a position where the influence of the distortion from the thermosetting adhesive becomes large, the creep phenomenon of the thermosetting adhesive does not occur. Can be reduced.

According to a second aspect of the present invention, in the semiconductor dynamic quantity sensor, the semiconductor sensor chip has a weight portion suspended from the fixed portion via the beam portion, and the piezo-resistance of the resistance element formed on the beam portion. It is configured to be able to detect the mechanical quantity using the effect, and the arrangement position of the thermosetting adhesive is a region apart from the position where the beam portion and the fixed portion are connected, I have.

When the fixing portion of the semiconductor sensor chip at the position where the beam portion is connected is deformed, the resistance element is more susceptible to the distortion caused by the deformation, whereby the resistance value of the resistance element changes, and the resistance of the sensor is changed. The reference value fluctuates.

On the other hand, if the bonding method according to claim 2 is applied, even if the thermosetting adhesive shrinks in the bonding step between the semiconductor sensor chip and the pedestal, the semiconductor sensor chip at the position where the beam portion connects is formed. There is no thermosetting adhesive for the fixed part.

Thus, the fixing portion at the position can be kept in a state of being diced and cut on the semiconductor sensor chip before and after the bonding process, and the fixing portion does not deform due to the bonding process.

That is, since the creep phenomenon of the thermosetting adhesive does not occur at the position where the beam portion is connected, it is possible to reduce the amount of change of the reference value with the passage of time after the bonding step.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a semiconductor type acceleration sensor will be described below with reference to the drawings.
The semiconductor acceleration sensor according to the present embodiment is used in, for example, a VSC system for a vehicle.

FIG. 1 shows a cross-sectional structure of a main part of the semiconductor type acceleration sensor of the present embodiment, and FIG. 2 shows a plan structure of a semiconductor sensor chip 11 which is a core of the semiconductor type acceleration sensor. FIG. 2 is a view of the semiconductor sensor chip 11 in FIG.

FIG. 3 shows the semiconductor sensor chip 11.
FIG. 4 schematically shows the configuration of a full bridge circuit formed by a resistance element on the surface of FIG.

First, as shown in FIG. 2, the semiconductor sensor chip 11 is formed by electrochemically etching a material having a large piezoresistance coefficient, such as a silicon single crystal substrate, and has a size of 3 × 3 mm. The weight portion 14 is supported in a bilateral manner via four beam portions 13 symmetrically arranged inside a frame portion (fixed portion) 12 having a size of about 4 × 4 mm.

Each beam portion 13 is provided with two resistive elements (reference numerals R11 to R1 in FIGS. 3 and 4) by a diffusion method or the like.
4, indicated by R21 to R24), and the applied acceleration is detected by using a full bridge circuit formed by these resistance elements.

More specifically, as shown in FIG. 3, the resistance elements R11 and R11
R12, R13 / R14, R21 / R22, R23 / R
Each pair of 24 is provided in such a positional relationship that one of the pair contracts and deforms in accordance with the displacement of the weight portion 14, and the other expands and deforms.

Then, two resistive elements (R11 and R21, R13 and R23, R12 and R
22, R14 and R24) as one side, and a pair of input terminals T1 and T2 and a pair of output terminals T3 and T4 of this full bridge circuit Is connected via a thin-film wiring pattern.

As shown in FIG. 4, the full bridge circuit is configured such that the resistance elements deforming in the same direction are located on sides facing each other.

The input terminals T1 and T2 are connected to a power supply terminal + Vcc and a ground terminal GND, respectively.
The output terminals T3 and T4 are connected to a positive output terminal + V and a negative output terminal -V, respectively.

As shown in FIG. 1, the semiconductor sensor chip 11 is supported by a pedestal 15 via a frame 12, and the semiconductor sensor chip 11 and the pedestal 1 are supported.
The unitary member 5 is housed in a housing 16 described later.

The pedestal 15 is connected to the semiconductor sensor chip 11.
It is formed of a material having a thermal expansion coefficient equivalent to that of, specifically, silicon which is the same material.

In this case, the space between the frame 12 and the base 15 is
It is bonded by a flexible thermosetting adhesive 19a containing a plurality of resin beads 18a as spacers. In the bonded state, the space between the weight portion 14 of the semiconductor sensor chip 11 and the pedestal 15 is formed. Are arranged sufficiently close to each other to perform air damping of the weight portion 14.

More specifically, by selecting the diameter of the resin bead 18a, the weight 14 and the pedestal 15 are selected.
The size of the air gap therebetween is set in the range of 7 to 15 μm, preferably in the range of 8 to 15 μm.

Since the surface of the resin beads 18a is coated with gold plating, the thermosetting adhesive 1
By mixing a plurality of resin beads 18a with 9a, conduction between the semiconductor sensor chip 11 and the pedestal 15 can be obtained, so that charging of the semiconductor sensor chip 11 can be prevented.

Generally, resin beads have a low elastic modulus and are soft, but the resin beads 18a used in this embodiment preferably have an elastic modulus of 10 GPa or less.

In order to satisfy such requirements, for example, polydinivirbenzene resin, silicone resin, urethane resin, acrylic resin, polyimide resin, flexible epoxy resin, vinyl resin and the like can be used.

The thermosetting adhesive 19a is desirably a soft material having an elastic modulus of 500 MPa or less. For example, silicone resin, urethane resin, acrylic resin, polyamide resin, polyimide resin, flexible epoxy resin Etc. can be used.

The reason is that when the pedestal 15 and the housing 16 supporting the semiconductor sensor chip 11 are deformed due to a change in temperature or the like, if a hard material is used for the thermosetting adhesive 19a, the influence of the semiconductor sensor chip 11 is reduced. This is because the reference value fluctuates even when no acceleration is applied.

Therefore, it is necessary to use a soft material for the thermosetting adhesive 19a to reduce the influence on the semiconductor sensor chip 11 due to deformation of the pedestal 15 and the housing 16.

Further, as shown in FIGS. 5 and 6,
The pedestal 15 is fixed by adhesion onto a ceramic substrate 16b constituting the housing 16 while being accommodated in a recess 16a formed in the housing 16.

For such bonding, a thermosetting adhesive 19b containing a plurality of resin beads 18b is used (see FIG. 1). It is desirable to use one having an elastic modulus of 10 GPa or less, and desirably using one having an elastic modulus of 500 MPa or less as the thermosetting adhesive 19b.

As the adhesive, a thermosetting adhesive 19a,
The use environment of the semiconductor type acceleration sensor as in the present embodiment is raised as a reason for using 19b.

Since the semiconductor acceleration sensor according to the present embodiment is often used for a vehicle, if an adhesive that is bonded at room temperature is used, the bonding effect of the adhesive is high when the sensor mounting position is in a high temperature state. It may be gone.

Therefore, it is necessary to use thermosetting adhesives 19a and 19b which have an adhesive effect even at a high temperature.

The housing 16 is formed by laminating a plurality of ceramic substrates 16b, and is formed in a box shape having the above-mentioned concave portion 16a and a trapezoidal portion 16c adjacent thereto. .

An amplifying circuit 21 having a function of applying a power supply voltage to the semiconductor sensor chip 11 and amplifying the detection output of the semiconductor sensor chip 11 is provided on the trapezoidal portion 16 c. An adjustment circuit 22 for performing voltage level adjustment and the like is die-bonded.

The ceramic substrate 16b constituting the housing 16 includes a conductive paste (not shown) printed between the ceramic substrates 16b, a through hole (not shown) penetrating the ceramic substrate 16b, and the like. A plurality of wiring patterns for supplying power and extracting detection output are formed by utilizing the wiring patterns.

In this case, as shown in FIG. 6, external terminals 16d connected to these wiring patterns are provided on the upper edge of the housing 16, and the trapezoidal portion 16c has the same wiring pattern. And an internal terminal group 16e connected to the internal terminal 16e.

Incidentally, the semiconductor sensor chip 11, the amplifier circuit 2
1, between the adjustment circuit 22, the internal terminal group 16e,
They are connected by wire bonding.

Further, as shown in FIGS. 1 and 5,
For example, a thin film made of a conductive material such as an aluminum paste, a copper paste, or a tungsten paste is provided between a ceramic substrate 16b facing the concave portion 16a of the housing 16 and the ceramic substrate 16b located below the ceramic substrate 16b. Is formed over the entire area.

Although not specifically shown, the electrostatic shield 17 is connected to a ground line using a through hole formed in the ceramic substrate 16b.

A lid 20 (see FIG. 5) made of, for example, ceramic is provided on the housing 16 by bonding.
The inside of the semiconductor acceleration sensor is hermetically sealed.

In practice, at least the semiconductor sensor chip 11 and the pedestal 15 are subjected to a well-known burn-in process to stabilize the output characteristics.

More specifically, in the present embodiment, for example, a predetermined voltage (5 to 6) is applied to the semiconductor sensor chip 11.
(Approximately 120 V) while applying a voltage
The burn-in process of exposing to the atmosphere for a predetermined time (about 6 hours) or more is performed.

Next, the semiconductor sensor chip 11 and the pedestal 15
The step of bonding with will be described.

In the prior art, as shown in FIG. 7 (a), a semiconductor sensor chip 11 and a pedestal 15 are formed by a thermosetting adhesive 19a containing a plurality of resin beads 18a.
And the entire circumference is bonded.

In this case, when the frame portion 12 at the position supporting the weight portion 14 via the beam portion 13 is deformed, the resistance element is susceptible to the distortion generated by the deformation. The resistance value changes, and the reference value of the sensor changes.

Therefore, the semiconductor sensor chip 11 and the pedestal 1
If the entire circumference of the sensor 5 is adhered, the reference value of the sensor greatly fluctuates as shown by the curve (a) in FIG.

Therefore, in the present embodiment, as shown in FIG. 7B, a thermosetting adhesive 19a containing a plurality of resin beads 18a is used for bonding the semiconductor sensor chip 11 and the pedestal 15. In the above, it is arranged only on the side of the frame portion 12 at a position parallel to the beam portion 13 and is not set for the side of the frame portion 12 at the position where the beam portion 13 is connected,
At this position, the semiconductor sensor chip 11 and the pedestal 15 are not bonded.

By applying such a bonding method, the semiconductor sensor chip 11 is shrunk at the position where the beam portion 13 is connected due to the contraction of the thermosetting adhesive 19a in the step of bonding the semiconductor sensor chip 11 and the pedestal 15. There is no deformation.

Therefore, of the four sides of the frame 12, the beam 13
No creep phenomenon of the thermosetting adhesive 19a occurs on the side of the frame portion 12 on the side where is connected, and the strain generated in the frame portion 12 due to the creep phenomenon propagates to the beam portion 13. As shown in the curve (b) of FIG. 8, the amount of change in the reference value due to the passage of days after the bonding step can be reduced.

That is, to explain the features of the present invention, in the conventional sensor, the adhesive always appeared even when the cross section was viewed from all directions, but in the sensor to which the present invention was applied, the cross section was viewed from all directions. And that there is a cross section where the adhesive does not appear.

As shown in FIG. 7C, in the step of bonding the semiconductor sensor chip 11 and the pedestal 15, when only the frame 12 on the side to which the beam 13 is connected is bonded, FIG. As shown in the curve (c), the amount of change in the reference value can be slightly reduced as compared with the case where the semiconductor sensor chip 11 and the pedestal 15 are bonded all around.

However, compared to the embodiment shown in FIG. 7B, almost no effect can be obtained.

Note that the present invention is not limited to the above embodiment, but can be applied to various aspects.

For example, the present invention can be applied not only to a piezo-type acceleration sensor as in the present embodiment but also to a capacitance-type acceleration sensor, and furthermore, a semiconductor-type pressure sensor for detecting the pressure of a medium to be measured. It can be applied to other physical quantity sensors.

Further, in this embodiment, the semiconductor sensor chip 11 is formed of a silicon single crystal substrate, but may be formed of another material having a large piezoresistance coefficient.

The material of the housing 16 and the lid 20 is not limited to ceramic, but may be formed of an insulating material such as glass or a metal.

The electrostatic shield 17 is connected to the housing 1
6, the configuration is provided on the entire bottom surface portion. However, the configuration is also provided on the lid portion 20, the configuration is provided only on the portion corresponding to the bottom surface of the semiconductor sensor chip 11, or the configuration is provided on almost the entire position covering the semiconductor sensor chip 11. Various modes can be implemented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a main part of a semiconductor acceleration sensor according to an embodiment.

FIG. 2 is a diagram showing a planar structure of the semiconductor acceleration sensor according to the embodiment. FIG. 2 is a view taken in the direction of the arrow A in FIG.

FIG. 3 is a diagram schematically showing a configuration of a full bridge circuit formed on the semiconductor sensor chip of the embodiment.

FIG. 4 is a diagram showing a connection structure of the full bridge circuit shown in FIG. 3;

FIG. 5 is a view showing a cross-sectional structure of the entire semiconductor acceleration sensor according to the embodiment.

FIG. 6 is a diagram showing the entire planar structure of the present embodiment with the lid removed.

FIG. 7 is a diagram illustrating a bonding method according to a related art, the present embodiment, and a comparative example.

FIG. 8 is a graph showing the relationship between the number of days after the bonding step and the reference value variation amount in the semiconductor acceleration sensor.

FIG. 9 is a diagram showing a cross-sectional structure of a main part of a conventional semiconductor acceleration sensor.

FIG. 10 is a diagram showing a planar structure of a conventional semiconductor acceleration sensor. FIG. 10 is a view as viewed in the direction of the arrow B in FIG.

FIG. 11 is a view showing a step of bonding the semiconductor sensor chip and the base with a flexible thermosetting adhesive.

FIG. 12 is a graph showing a relationship between the number of days after a bonding process and a reference value variation amount in a conventional semiconductor acceleration sensor.

[Description of Signs] 1 ... Semiconductor sensor chip, 2 ... Frame part, 3 ... Beam part, 4 ... Weight part, 5 ... Pedestal, 6 ... Housing, 6b ... Ceramic substrate, 7 ... Electrostatic shield, 8a, 8b ... Resin beads, 9a, 9b: Flexible adhesive, 11: Semiconductor sensor chip, 12: Frame, 12a: Bonding pad, 13: Beam, 14: Weight, 15: Base, 16: Housing, 16a ... Recessed part, 16b: ceramic substrate, 16c: trapezoidal part, 16d: external terminal, 16e: internal terminal, 17: electrostatic shield, 18a, 18b: resin beads, 19a, 19b: thermosetting adhesive, 20: lid Reference numeral 20: amplifying circuit, 21: adjusting circuit, R11 to R14, R21 to R24: resistive element, T1, T2: input terminal, T3, T4: output terminal, + Vcc: power supply terminal, GND ... Ground terminal, + V: positive output terminal, -V: negative output terminal,

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[Procedure amendment]

[Submission date] April 23, 2001 (2001.4.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

[0027] By applying the adhesive how as described above, also the thermosetting adhesive is contracted in the bonding process between the semiconductor sensor chip and the pedestal, the influence of distortion from the thermosetting adhesive becomes larger There is no thermosetting adhesive for the semiconductor sensor chip at such a position.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

[0050] To meet such requirements, for example, a polydiene vinyl Rubenzen resins, silicone resins, urethane resins, acrylic resins, polyimide resins, flexible epoxy resins, and vinyl resins can be utilized.

Claims (2)

[Claims] 1. A semiconductor sensor chip having a displacement portion which is displaced by application of a mechanical quantity and detecting displacement of the displacement portion, and a pedestal for fixing the semiconductor sensor chip with a thermosetting adhesive containing beads. Wherein the thermosetting adhesive is disposed at a position such that the influence of distortion from the thermosetting adhesive is reduced. 2. The semiconductor sensor chip has a weight portion suspended from a fixed portion via a beam portion, and detects a dynamic quantity using a piezoresistance effect of a resistance element formed on the beam portion. The arrangement position of the thermosetting adhesive is a region apart from a position where the beam portion and the fixing portion are connected, wherein the thermosetting adhesive is disposed. Semiconductor type dynamic quantity sensor.