JPH0660906B2 - Semiconductor acceleration sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor acceleration sensor having a semiconductor cantilever and measuring acceleration by utilizing a piezo effect.

[Prior Art] An example of a conventional semiconductor acceleration sensor is shown in FIG. This is the reference El. M. Laurence and Jay. Bee. Angel's "batch type silicon acceleration sensor" IEEE standard, electron device. ED 26, 1979, No. 12, 1911
1917 "LM Loylance. And JB Ang.
ell, “A Batch-Fabricated Silicon Accel
erometer, "IE ³ Electron Devices. vol.
ED-26, No. 12, PP. 1911-1917,
1979 ”, the outline will be described here with reference to FIG.

2 (a) is a plan view of the semiconductor acceleration sensor, and FIG. 2 (b) is a side view thereof. As shown in FIG. 2, a void 3 is formed on a semiconductor chip (hereinafter referred to as a silicon chip) 1. As a result, a semiconductor cantilever beam (hereinafter referred to as a silicon cantilever beam) 7 having a semiconductor weight (hereinafter referred to as a silicon weight) 5 is formed on the silicon chip 1 at the end.
A piezoresistor 9 is formed on the surface of the silicon cantilever 7 by impurity diffusion, and a high-concentration diffusion region 11 is formed on the silicon chip 1 adjacent to the piezoresistor 9.

In order to prevent the silicon cantilever beam 7 from being excessively deformed when an excessive acceleration is applied, an upper stopper 13 and a lower stopper 15 are provided above and below the silicon chip 1, respectively. The upper stopper 13 and the lower stopper 15 are each provided with a recess 13 so that the silicon cantilever 7 can be deformed.
a and 15a are formed.

An aluminum bonding pad 19 is formed on the lower surface of the upper stopper 13 adjacent to the high concentration diffusion region 11,
The lead wire 2 is attached to the aluminum bonding pad 19.
1 is connected.

The acceleration is measured using such a semiconductor acceleration sensor as follows. That is, when receiving acceleration, the silicon cantilever beam 7 bends, and thereby the resistance value of the piezoresistor 9 formed on the surface of the silicon cantilever beam 7 changes. The piezoresistor 9 is electrically connected to the outside by a lead-out wire 21 via a high-concentration diffusion region 11 and an aluminum bonding pad 19, and the resistance value of the piezoresistor 9 changes to change the output voltage, thereby increasing the acceleration. To be measured.

[Problems to be Solved by the Invention] However, a semiconductor acceleration sensor using such a piezoresistive effect generally has low sensitivity and its sensitivity is highly dependent on temperature resistance. Requires a circuit. In order to improve reliability and reduce cost, it is necessary to integrally form such an external circuit. However, since a resistor for adjustment and the like are also required, it is usually mounted on the HIC substrate 23 capable of forming a thick film resistor for this purpose.

Therefore, when the semiconductor acceleration sensor is mounted on the HIC substrate 23, there are the following problems.

It is necessary to bond one surface of the lower stopper 15 to the silicon chip 1 and then further bond the other surface of the lower stopper to the HIC substrate 23, which requires many working steps.

When the semiconductor acceleration sensor is wired on the HIC board 23, the number of terminals for power supply / output adjustment resistors increases, and
It is difficult to use the bonding wire in the configuration shown in the figure.

The high-concentration diffusion region 11 is formed, and when the piezoresistor 9 is used as a bridge, an error easily occurs due to temperature change and strain.

Due to thermal strain with the upper stopper 13, the resistance change of the piezoresistor 9 is easily caused.

[Means for Solving Problems] The present invention has been made in view of such conventional problems. A semiconductor cantilever beam supported at one end of a semiconductor chip is provided with a piezoresistor, and a semiconductor due to acceleration is used. A semiconductor acceleration sensor for detecting acceleration based on a change in resistance value of a piezoresistor caused by vibration of a cantilever, comprising an amplifier circuit and a temperature compensation circuit formed on the semiconductor chip and electrically connected to the piezoresistor. Integrated circuit and a substrate on which the semiconductor chip is mounted and which is disposed at a predetermined position below the semiconductor cantilever to serve as a lower stopper, and a thick film resistor for output adjustment is formed, and the semiconductor chip. A bonding pad formed and electrically connected to the integrated circuit, and the bonding pad and the semiconductor cantilever on the semiconductor chip. The above problem is solved by having an upper stopper of the semiconductor cantilever beam which is supported at a position away from the semiconductor.

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

FIG. 1 is a diagram showing an embodiment of the present invention.
(a), (b) is the top view and side view of a semiconductor acceleration sensor, respectively. In the figure, elements having the same functions as those of the conventional semiconductor acceleration sensor shown in FIG. 2 are designated by the same reference numerals.

In this embodiment, the lower stopper 15 of the conventional semiconductor acceleration sensor shown in FIG. 2 is not provided, but instead of this, a recess 15b is formed on the HIC substrate 23, and the recess 15b is formed on the silicon cantilever beam 7 and the silicon weight 5. In addition to being a lower stopper, the upper stopper 13b is formed in a U shape on the outer peripheral portion of the void 3 formed on the silicon chip 1 without being supported by the aluminum bonding pad 19 side on the silicon chip 1.

As a method of attaching the silicon chip 1 to the HIC substrate 23, there are methods such as die bonding of gold (Au), soldering, and adhesion by epoxy or the like.

In this embodiment, the piezoresistor 9 is connected to the integrated circuit 25 portion formed on the silicon chip 1, and the aluminum bonding pad 19 is freely provided around the integrated circuit 25 and provided on the HIC substrate 23. HIC
The substrate bonding pad 27 and the aluminum bonding pad 19 are connected by a bonding wire 29. The integrated circuit 25 has functions such as amplification and temperature compensation, and is formed on the silicon chip 1. .

With the above configuration, since the concave portion of the HIC substrate is used as the lower stopper of the silicon weight, it is not necessary to form the lower stopper as a single unit, and it is possible to reduce the number of parts and the number of attachments.

Further, in the silicon chip 1, the recess 15b may not be provided in the HIC substrate 23 by making the thickness of the silicon weight 5 thinner than the thickness of the attachment portion to the HIC substrate 23.

Further, since the upper stopper is not formed on the aluminum bonding pad, the aluminum bonding pad can be easily connected by the bonding wire, which facilitates the wiring and the wiring process.

Further, since it is not necessary to electrically connect the piezoresistor to the outside by using the high concentration diffusion region, it is possible to reduce the output error and the temperature change when the piezoresistor is used as the bridge.

Furthermore, since the support part for the upper stopper is formed on the outer periphery of the void of the silicon chip, even if strain is applied to the upper stopper due to heat, etc., the effect of strain on the silicon cantilever can be mitigated, and the piezo resistance Resistance change can be prevented.

[Effects of the Invention] According to the invention described above, the manufacturing process is simplified, the bonding wire can be used freely, the temperature change and strain due to the piezoresistance are small, and the resistance change of the piezoresistance is caused. It is possible to provide a semiconductor acceleration sensor that does not have the above.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and a side view of a semiconductor acceleration sensor according to this embodiment, and FIGS. 2 (a) and 2 (b) are a front view and a side view of a conventional semiconductor acceleration sensor. . 1 ... semiconductor chip, 7 ... semiconductor cantilever 9 ... piezoresistor, 13a ... upper stopper 15b ... lower stopper (recess) 19 ... aluminum bonding pad 23 ... HIC substrate, 25 ... integrated circuit

Claims (1)

[Claims] 1. A semiconductor acceleration sensor in which a semiconductor cantilever beam supported at one end of a semiconductor chip is provided with a piezoresistor, and the acceleration is detected based on a change in resistance value of the piezoresistive force caused by vibration of the semiconductor cantilever beam due to acceleration. An integrated circuit that is formed on the semiconductor chip and that includes an amplifier circuit and a temperature compensation circuit that are electrically connected to the piezoresistor; and the semiconductor chip is mounted at a predetermined position below the semiconductor cantilever. A substrate that is disposed and serves as a lower stopper, and a thick film resistor for output adjustment is further formed; a bonding pad that is formed on the semiconductor chip and is electrically connected to an integrated circuit; and the bonding on the semiconductor chip. A pad and an upper stopper of the semiconductor cantilever supported at a position remote from the semiconductor cantilever. A semiconductor acceleration sensor characterized by the above.