JPH0232567A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To form a lower layer wiring formed on a pressure sensitive diaphragm to a thickness to the minimum, satisfactorily keeping the thickness of a pad portion to be wire-bonded by superimposing the lower layer wiring and an upper layer wiring at an end of a semiconductor substrate where wire- bonding has been performed. CONSTITUTION:In manufacturing a semiconductor pressure sensor, gate resistors 4-7 and a thin pressure sensitive diaphragm 6a are formed at the center of a pressure sensor chip 9, and then a first A1 layer 20 is formed on the upper surface of the chip 9 by sputtering and the like. Further, first time A1 wiring processing is performed by photolithography, and unnecessary portions are removed by weight etching, and further a lower layer wiring 20a is formed by the same pattern as that of A1 wirings 10-15. Moreover, a resist layer 21 is uniformly formed on the upper surface of the chip 9 on which a wiring 20a is formed, and portions corresponding to pad portions 10b-15b to be wire-bonded in the layer 21 are removed, and further the lower wiring and an upper layer wiring 22a are formed on the chip 9.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention applies to semiconductor pressure sensors used in various control devices for automobiles and aircraft, and household appliances such as electronic blood pressure monitors and cleaners. The present invention relates to a manufacturing method, and in particular to a manufacturing method of a semiconductor pressure sensor that aims to improve temperature hysteresis characteristics and pressure hysteresis characteristics, as well as zero point temperature characteristics.

"Prior Art" FIGS. 2 and 3 are diagrams showing the configuration of a conventional semiconductor pressure sensor. As shown in these figures, the surface orientation (1
On the upper surface of the n-type silicon single crystal substrate (hereinafter referred to as Si substrate) 1 of 10), there is a silicon oxide (Sio) film 2 and a silicon nitride (SiI
A Na) film 3 is formed, and then four gauge resistors 4 to 7 made of P-type piezoresistors are formed by photolithography and diffusion techniques. On the other hand, S
A recess 8 reaching the vicinity of the gauge resistors 4 to 7 is formed in the center of the lower surface of the i-board 1, so that the gauge resistors ti'i1.4 to 7 and a thin pressure-sensitive diaphragm are formed in the center. 9
A semiconductor pressure sensor chip 9 is formed with a. On the upper surface of this pressure sensor chip 9, wiring portions 10a to 15a are connected to six ends of gauge resistors 4 to 7, respectively.
and pad part job-1 where wire bonding is performed.
Aluminum (A1) wiring 1O-15 consisting of 5b is formed. In such a configuration, each gauge resistor 4 to 7 is bridge-connected as shown in FIG. 4 via A1 wirings 10 to 15 and bonding wires, etc.
When connected to a constant current source, the resistance value of each gauge resistor 4 to 7 changes depending on the pressure acting on the pressure sensitive diaphragm 9a, thereby causing the output terminal T1. A detection voltage V corresponding to the pressure received by the pressure sensitive diaphragm 9a is output from Tt.

"Problems to be Solved by the Invention" By the way, in the conventional semiconductor pressure sensor described above, in order to bridge-connect the four gauge resistors 4 to 7 formed on the pressure sensitive diaphragm 9a, the At wirings 10 to
However, due to these At wirings 10 to 15, temperature hysteresis characteristics and pressure hysteresis characteristics became noticeable, and zero point temperature characteristics deteriorated. That is, as shown in FIG. 5, when the pressure sensitive diaphragm 9a bends under pressure, the wiring portions 10a=15a of the At wirings 10 to 15 also bend, thereby causing the sixth
A pressure hysteresis characteristic (constant temperature) occurs as shown in the figure. In addition, the pressure sensor chip 9 is made up of a Si substrate 1
, S + O with film 2 and S i,N 4 film 3, A
1 wiring 10 to 15 has a different coefficient of thermal expansion, and by joining materials with different coefficients of thermal expansion,
Temperature hysteresis characteristics (constant pressure) as shown in Figure 7
occurs. Such a hysteresis characteristic is caused by the At wiring 1
The larger the thickness of 0 to 15, the more pronounced the temperature characteristics as a pressure sensor deteriorate. Therefore, A1 wiring lO~
Although it is conceivable to form the pad portions 10b to +5b thinly (forming them thinly), it is necessary to ensure a thickness of about 1 to 2 μm in the case of the pad portions 10b to +5b because wire bonding is performed, and the thickness of the AI wiring lO It was not possible to reduce the overall thickness of ~15.

This invention was made in view of the above-mentioned circumstances, and aims to reduce the temperature hysteresis characteristics and pressure hysteresis characteristics caused by the Al1%li wire formed on the pressure-sensitive diaphragm to a low 3λ, and improve the zero point temperature characteristics. The purpose of the present invention is to provide a method for manufacturing a semiconductor pressure sensor that can be used.

``Means for Solving the Problems'' This invention provides a method for forming a gauge resistor and a pressure-sensitive diaphragm in the center of a semiconductor substrate, and then forming a predetermined distance from the end of the semiconductor substrate where wire bonding is performed to the gauge resistor. A first step of forming a lower layer wiring of a pattern, and after covering a portion of the lower layer wiring that overlaps with the pressure sensitive diaphragm with a resist layer, an upper layer wiring of the same pattern as the lower layer wiring is connected to the lower layer wiring and the resist layer. The resist layer is characterized by comprising a second step of forming one layer on top of the other, and a third step of removing the renost layer and a portion of the upper wiring formed on the resist layer.

"Function" - According to the manufacturing method described in F, the wiring from the edge of the semiconductor substrate to the gaming resistor is formed in two steps, the lower layer wiring and the upper layer wiring, and the final In this case, only the lower layer wiring is formed on the pressure-sensitive diaphragm,
Since the lower layer wiring and the lower layer wiring are formed overlappingly at the edge of the semiconductor substrate where wire bonding is performed, the thickness of the pad portion where wire bonding is performed can be maintained at a sufficient W. The lower layer wiring formed on the pressure diaphragm can be made thinner to the minimum necessary thickness.

"Embodiments" Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a process diagram showing a manufacturing process according to an embodiment of the present invention. The manufacturing process of a semiconductor pressure sensor according to an embodiment will be described below with reference to this figure.

■First, gauge resistors 4 to 7 and a thin pressure-sensitive tire flammable 9a are formed in the center, and the steps up to forming the semiconductor pressure sensor chip 9 shown in FIG. 1(A) are the same as in the conventional method. .

(2) Next, as shown in FIG. 1(b), a first AI layer 20 is formed on the upper surface of the pressure sensor chip 9 by sputtering, vacuum evaporation, or the like.

In this case, the thickness of the first AI layer 20 is set to the minimum necessary thickness so as to reduce temperature hysteresis characteristics and pressure hysteresis characteristics.

■Then, the first AI wiring process is performed by photolithography, and unnecessary parts of the A1 layer 20 are removed by wet etching using hot phosphoric acid solution, similar to the Al wirings 10 to 15 shown in Fig. 2. The lower layer wiring 20a is formed in the pattern (see FIG. 1(c)).

(2) Next, as shown in FIG. 1(d), a resist solution is uniformly applied to the upper surface of the pressure sensor chip 9 on which the lower wiring 20a is formed to form a resist layer 21.

■Then, by photolithography, the renost layer 2 is
1, the portions corresponding to the pad portions lOb to 15b on which the wire bonding shown in FIG. 2 is performed are removed (the first
(See figure (po)).

1) Next, as shown in FIG. 22 is formed.

In this case, the thickness of the second AI layer 22 is determined by the thickness of the portion overlapping with the lower layer wiring 20a, that is, the pad portion IOb to 15b.
The part corresponding to the thickness is suitable for wire bonding (1
˜2μ111) or more.

■Then, the resist layer 21 that is no longer needed is removed using a stripping solution (lift-off method), thereby removing the second Ai layer 21.
Of the layer 22, only the portion corresponding to the pad portions 10b-15b is left on the lower layer wiring 20a as the upper layer wiring 22a.

Through the following steps, the lower layer wiring 20a and the upper layer wiring 22a are formed on the upper surface of the pressure sensor chip 9, and the lower layer wiring 22a is formed on the upper surface of the pressure sensor chip 9.
A portion of 0a constitutes a portion corresponding to wiring portions 10a to 15a connected to the six ends of gauge resistors 4 to 7, respectively, and an upper layer wiring 22a and a portion of lower layer wiring 20a overlapping this upper layer wiring 22a constitute wires. A portion corresponding to the pad portion tab-tsb to which bonding is performed is configured. Thereby, by adjusting the thickness of the upper layer wiring 22a, the pad portion to which wire bonding is performed can be made sufficiently thick, and the lower layer wiring 20a formed on the pressure sensitive diaphragm 9a can be made as thick as necessary.
/IX thickness can be achieved.

"Effects of the Invention" As explained above, according to the present invention, after forming the gauge resistor and the pressure sensitive diaphragm in the center of the semiconductor substrate,
A first step of forming a lower wiring in a predetermined pattern from the end of the semiconductor substrate where wire bonding is to be performed to the gauge resistor, and forming a resist layer on the portion of the lower wiring shown in iq that overlaps with the pressure sensitive diaphragm. After covering, step 2 of forming upper layer wiring with the same pattern as the surface lower layer wiring on top of the surface layer lower layer wiring and surface layer Renost layer 2, and forming the +iff layer layer and the layer on the Renost layer. The third step is to remove a portion of the formed upper layer wiring, so that the lower layer wiring and the upper layer wiring are formed in an overlapping manner at the end portion of the semiconductor substrate where wire bonding is not performed, and the thickness of the upper layer wiring is reduced. By adjusting it, it is possible to secure P7 suitable for wire bonding, and
The part of the semiconductor w that overlaps with the pressure-sensitive diaphragm in the temporary center is at the bottom! Since the 6-gauge resistor is connected only by wiring, by making the lower layer wiring as thin as possible (<4゜), temperature hysteresis characteristics and pressure hysteresis characteristics can be reduced, and the zero point temperature can be reduced. The effect is that the characteristics can be improved.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the manufacturing process of an embodiment of this invention;
Fig. 2 is a plan view showing one component of a conventional semiconductor pressure sensor, and Fig. 3 is a cross-sectional view along line [+1-III] of Fig. 2.
The figure is a circuit diagram showing the electrical configuration of the pressure sensor in use, Figure 5 is a sectional view showing the operation of the pressure sensor, Figure 6 is a graph showing the pressure hysteresis characteristics of the pressure sensor, and Figure 7 is It is a graph showing the temperature hysteresis characteristics of the same pressure sensor. 4-7... Gauge resistance, 9... Pressure sensor chip, 9a... Pressure sensitive diaphragm, 20...
...First A1 layer, 20a... Lower wiring, 21... Resist layer, 22... Second A1 layer, 22a... Upper layer wiring.

Claims (1)

[Scope of Claims] (a) After forming a gauge resistor and a pressure-sensitive diaphragm in the center of a semiconductor substrate, a predetermined pattern of lower layer wiring from the end of the semiconductor substrate where wire bonding is performed to the gauge resistor. (b) After covering the portion of the lower layer wiring that overlaps with the pressure sensitive diaphragm with a resist layer, the upper layer wiring having the same pattern as the lower layer wiring is connected to the lower layer wiring and the resist layer. (c) a third step of removing the resist layer and a portion of the upper wiring formed on the resist layer; How to manufacture the sensor.