JPH03224275A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To prevent the formation of a wide area with a thick oxide film inside a diaphragm area by forming additional patterns having thin-thicknesses oxide films on parts of the diaphragm area other than those for gauge resistances. CONSTITUTION:Additional patterns 16 and 17 are formed on part of a dia phragm area 14 other those where gauge resistances 5-8 and connection resistances 9-13 or parts of them are provided. When the thicknesses of the oxide films of the patterns 16 and 17 are made thinner than those of the oxide films of the resistances 5-8, no wide area having a thick oxide film is formed in the diaphragm area and, accordingly, the internal stress of the diaphragm area is reduced. Therefore, a semiconductor pressure sensor which has a small absolute offset voltage value and makes large fluctuation is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to semiconductor pressure sensors used in various control units.Prior art Fig. 3 is a plan view of a conventional semiconductor pressure sensor. CL A rectangular diaphragm region 14 formed at the center of the (100) plane of the n-type silicon semiconductor chip, and a rectangular diaphragm region 14 formed at the center of each side of the diaphragm region 14 arranged on one surface within this diaphragm region 14. The four gauge resistors 5 to 8 are electrically connected between these gauge resistors 5 to 8 to form a bridge circuit together with the gauge resistors 5 to 8.Low resistance connecting resistors 9 to 8
13 and a bridging resistor 9 is electrically connected to the gauge resistors 5 and 6.
Although a bonding pad 1 for external bias is formed on a part of the connecting resistor 9, there are also gauge resistors 7 and 8.
Gi
Even if the external bias bonding pad 2 is connected, the connecting resistor 1 electrically connects the gauge resistor 6゜7.
A lead-out resistor 10a is connected to o, and this lead-out resistor 1
A bonding pad 3 for output is connected to 0a, and a lead resistor 13a is connected to a bridging resistor 13 that electrically connects the G gauge resistors 5 and 8, and a pump for output is connected to the lead resistor 13a. Even if the pad 4 is connected, FIG. 4 is a cross-sectional view showing the manufacturing process of this semiconductor pressure sensor along line A-A in FIG. 3. This semiconductor pressure sensor is manufactured as follows. First, as shown in FIG. 4(a), a silicon oxide film 21 is formed on the GQ n-type silicon semiconductor substrate 2o by thermal oxidation, and a resist (not shown) is deposited on this silicon oxide film 21. The oxide film 21 and the resist where the resistors 9 to 13 are to be formed are
Even if the resist is removed by photolithography and etching,
The fine resist into which boron ions have been implanted at a high concentration is removed, and a resist 22 is further formed over the entire area on this semiconductor substrate 20, as shown in FIG. Even if the resist 22 and oxide film 21 in the area where 8 is to be formed are removed by photolithography and etching, boron ions are implanted at a low concentration using the resist 22 as a 4-in-1 mask. By heating this semiconductor substrate, the boron ions are thermally diffused in the connecting resistors 9 to 13 and the gauge resistors 5 to 8. Board 2
Although the silicon oxide film 2a is deposited over the entire area on the surface of the silicon oxide film 2a by the CVD method, and the oxide film 23 where the bonding pads 1 and 2 are to be formed is removed by the photolithography method and etching method, the aluminum metal film 2a is then deposited on the entire surface of the silicon oxide film 2a. is formed over the entire area on the semiconductor substrate 20, and the bonding pads 1 and 2 are formed by photolithography and etching.Furthermore, this semiconductor substrate 2o is divided into chips to obtain the semiconductor pressure sensor shown in FIG. With the semiconductor pressure sensor shown in Figure 3! Top Pounding Pad 1. When a constant external bias voltage is applied to 2, current flows through gauge resistors 5-8 and tie resistors 9-13; however, when no pressure is applied to diaphragm region 14, current flows through gauge resistors 5-8 and tie resistors 9-13. The resistance values are equal to each other. When pressure is applied to the diaphragm region 14 from the outside, stress is generated in the diaphragm region 14. Due to the piezoresistance effect caused by this stress, the resistance values of the gauge resistors 5 to 8 forming the bridge circuit are no longer equal, and an output voltage corresponding to the pressure applied to the diaphragm region 14 is generated between the bonding pads 3 and 4.Problems to be Solved by the Invention In such a conventional semiconductor pressure sensor, as shown in FIG. (Migage resistance 5 to 8 and connecting resistance 9 to 13
The remaining region 15 where is not formed is the diaphragm region 1
4, this residual region 15 is located at the center of the diaphragm region 14 and has a relatively large area, as shown in FIG. 4(d).
Even though two thick silicon oxide films 21 and 23 are formed in 5, the coefficient of thermal expansion of the silicon semiconductor of the diaphragm region 14 is different from that of the silicon oxide film.The remaining region has a large area and a thick silicon oxide film. 15, internal stress (residual stress) is generated in the diaphragm region 14. This internal stress causes the voltage between the bonding pads 3 and 4 in the absence of external pressure to be measured, that is, the offset voltage to be zero. The present invention has the problem that the offset voltage is small in absolute value and has a large variation.The present invention solves these problems. The semiconductor pressure sensor of the present invention has a diaphragm region formed on a semiconductor chip, and a bridge circuit arranged on one side of the diaphragm region. An additional pattern is formed in a portion of the diaphragm area other than the gauge resistor, and the thickness of the oxide film in this additional pattern is determined by the gauge resistor.
The semiconductor pressure sensor of the present invention includes a diaphragm region formed on a semiconductor chip, a plurality of gauge resistors arranged on one surface of this diaphragm region, and a plurality of gauge resistors arranged on one side of the diaphragm region. It is equipped with a low-resistance bridging resistor that electrically connects the gauge resistors and forms a bridge circuit together with these gauge resistors.
An additional pattern is formed in a portion of the diaphragm area other than the gauge resistor and the tether resistor, and the thickness of the oxide film in this additional pattern is made thinner than the thickness of the oxide film formed in the area other than the gauge bottle width, the tether resistor, and the additional pattern. Further, the semiconductor pressure sensor of the present invention includes a rectangular diaphragm region formed in the center of a semiconductor chip, and a rectangular diaphragm region disposed on one surface within this diaphragm region, and formed in the center of each side of the diaphragm region. It is equipped with four gauge resistors and a low-resistance connecting resistor that electrically connects these gauge resistors and forms a bridge circuit together with these gauge resistors, and an additional pattern is provided in the portion of the diaphragm area other than the gauge resistors and the connecting resistors. is formed, and the thickness of the oxide film in this additional pattern is made thinner than the thickness of the oxide film formed in the area other than the gauge resistor and the additional pattern. Since there is no large area having an oxide film, the internal stress in the diaphragm region is reduced.Example An example of the present invention will be described below. FIG. 1 is a plan view of this example. Semiconductor pressure sensor CL of the embodiment includes a rectangular diaphragm region 14 formed in the center of the (lOO) plane of an n-type silicon semiconductor chip, and a rectangular diaphragm region 14 formed on one surface of the diaphragm region 14 on each side of the diaphragm region 14. Four gauge resistors 5 to 8 formed in the center, and low resistance connecting resistors 9 to 13 that electrically connect these gauge resistors 5 to 8 and constitute a bridge circuit together with them.
The thickness of the semiconductor chip other than the diaphragm region 14 is 290 μm. The length of one side of the semiconductor chip is 3.5 μm. The thickness of the diaphragm region 14 is 7 μm.
At 0 μm, the connecting resistor 9 is electrically connected to the gauge resistor 5.6.
Although a bonding pad 1 for external bias is formed on a part of the connecting resistor 9, there are also gauge resistors 7 and 8.
The connecting resistors 11 and 12 are connected to the connecting resistors 10 and 10, which electrically connect the gauge resistors 6°7 to the connecting resistors 11 and 12, respectively.
NiG! Even though the output resistor 10a is connected to the output bonding pad 3, the output resistor 13a is similarly connected to the connecting resistor 13 that electrically connects the gauge resistors 5 and 8. The resistor 13a has a bonding pad 4 for output.
Even if the gauge resistance 5 is connected, in the semiconductor pressure sensor of this example, the gauge resistance 5
Additional patterns 16 and 17 are formed in parts of the diaphragm region 14 other than the connecting resistors 9 to 13, and the thickness of the silicon oxide film in the additional patterns 16 and 17 is as follows.
It is thinner than the silicon oxide film formed in areas other than the gauge resistors 5 to 8, the connecting resistors 9 to 13, and the additional patterns 16 and 17. Figure 2 shows the actual implementation along the P-P line in Figure 1. The semiconductor pressure sensor of this example is a sectional view showing the manufacturing process.The semiconductor pressure sensor of this example is manufactured as follows. First, as shown in FIG. 2(a), an n-type silicon semiconductor substrate 20 is placed. Silicon oxide film 21 is formed by thermal oxidation method.
is formed to a thickness of 500 nm, and this silicon oxide film 2
Even if a resist (not shown) is deposited on top of the
Oxide film 21 in the area where connecting resistors 9 to 13 are to be formed
Even if the resist and the resist are removed by photolithography and etching, the resist is removed by H→
After boron ions are implanted at a high concentration as a layer mask, the resist is removed and the semiconductor substrate 20 is then removed as shown in FIG. 2(b).
A resist 22 is further formed over the entire area above, and the resist 22 and oxide film 21 in the areas where the gauge resistors 5 to 8 and the additional patterns 16 and 17 are to be formed are removed by photolithography and etching. 22; As a mask, borosilicate ions are implanted at a low concentration. Then, by heating this semiconductor substrate 20, After the boron ions are thermally diffused, as shown in FIG. 2(c), this semiconductor substrate 20
A silicon oxide film 23 is deposited over the entire upper area by the CVD method.
Even if the oxide film 23 is deposited to a thickness of 0 nm, the oxide film 23 is removed in the areas where the bonding pads 1 and 2 are to be formed by photolithography and etching.
An aluminum metal film is formed over the entire area on the semiconductor substrate 20 by photolithography and etching.

In the semiconductor pressure sensor of this embodiment, CL is applied to a portion corresponding to the remaining area 15 in the conventional example shown in FIG.
Even if the additional patterns 16.17 are formed, since only one layer of silicon oxide film 16.23 exists on the additional patterns 16.17, no internal stress is generated in the diaphragm region 14\ Therefore, the external stress to be measured is It is possible to reduce the absolute value of the offset voltage in a state where there is no pressure from
-5 mV, standard deviation σ = 3 mV, whereas in this example, x = -1 mV, σ = 1 mV. In this example, connecting resistors 9 to 13 are formed within the diaphragm region 14. Force＼Diaphragm area 1
It may be formed on the semiconductor chip outside of 4.
In that case, an additional pattern 16.1 shown in FIG.
In this embodiment, the C1 additional patterns 16 and 17 were formed by the same method as the method for forming the gauge resistors 5 to 8, but for example, the conventional pattern shown in FIG. 4(d) The semiconductor pressure sensor of the present invention can also be formed by etching the silicon oxide film 21 to 23 on the remaining region 15 of the sensor to make it thin. Since no internal stress is generated in the diaphragm region, the semiconductor pressure sensor of the present invention can reduce the offset voltage.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the semiconductor pressure sensor of the present invention. FIG. 2 is a cross-sectional view taken along the line P--P of FIG. 1. FIG. 3 is a plan view of a conventional semiconductor pressure sensor. A- in Figure 3
It is a cross-sectional view taken along line A, 2... bonding pad for external bias, 3.4... bonding pad for output, 5-8... gauge resistance 9-13... connection Resistance K 14...Diaphragm 16, 17...
・Additional patterns.

Claims (3)

[Claims] (1) A diaphragm region formed on a semiconductor chip, and a plurality of gauge resistors arranged on one surface of the diaphragm region to form a bridge circuit, and a portion of the diaphragm region other than the gauge resistors. An additional pattern is formed on the semiconductor pressure sensor, and the thickness of the oxide film in the additional pattern is smaller than the thickness of the oxide film in the gauge resistor. (2) A diaphragm region formed on a semiconductor chip, a plurality of gauge resistors arranged on one surface of the diaphragm region, and the gauge resistors are electrically connected to form a bridge circuit together with the gauge resistors. an additional pattern is formed in a portion of the diaphragm region other than the gauge resistor and the connector resistor, and the thickness of the oxide film in the additional pattern is equal to the gauge resistor, the connector resistor, and the A semiconductor pressure sensor whose thickness is smaller than the thickness of the oxide film formed in areas other than the additional pattern. (3) a rectangular diaphragm region formed in the center of the semiconductor chip; four gauge resistors disposed on one surface of the diaphragm region and formed in the center of each side of the diaphragm region; a low-resistance connecting resistor that electrically connects between the gauge resistors and forming a bridge circuit together with the gauge resistor; an additional pattern is formed in a portion of the diaphragm region other than the gauge resistor and the connecting resistor; A semiconductor pressure sensor in which the thickness of the oxide film in the pattern is smaller than the thickness of the oxide film formed in areas other than the gauge resistor, the connecting resistor, and the additional pattern.