JPS62291072A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To decrease internal strains in silicon developed as the temperature varies and reduce a voltage change of offset due to changes in temperature by causing a thermal expansion coefficient of material for an electrode interconnection layer to be within the specific limit. CONSTITUTION:In a case of semiconductor pressure sensor having a pressure sensitive semiconductor substrate 1 where a diffusion resistance layer 6 and electrode interconnection layer 11 connecting to the above layer 6 are formed on the one surface and a diaphragm is formed at an opposite face of the diffusion resistance layer 6, a thermal expansion coefficient of material for an electrode interconnection layer 11 is set so that it is 1.5-5 times that of silicon. For instance, the pattern interconnection layer 11 is formed through an oxide film 7 at the Si substrate 1 where the diffusion resistance 6 was formed. The interconnection layer 11 is formed according to a laminated layer structure of MoSi2/Mo/MoSi2 and an MoSi2 layer 11a is formed about 1000 Angstrom thick to improve an adhision to Si and an Mo layer 11b is formed on the MoSi2 layer 11a about 8000 Angstrom thick. Moreover, an MoSi2 layer 11c formed about 1000 Angstrom thick on the Mo layer 11b to prevent the oxidation of Mo layer and the oxide film 8 is laminated on the surface of the layer 11c.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention is characterized in that a diffusion resistance layer and an electrode wiring layer connected thereto are formed on one surface, and Regarding a semiconductor pressure sensor having a pressure-sensitive semiconductor substrate with a diaphragm formed on the opposite side of a diffusion resistance layer, it is particularly suitable as a semiconductor pressure sensor that is a component of a pressure transmitter used for pressure and flow measurement in industrial process instrumentation. It is used.

(Prior Art) A sectional view of a conventional example of this type of semiconductor pressure sensor is shown in FIG. 5, and a partially enlarged view f is shown in FIG. 6.

In the figure, 1 is a semiconductor pressure-sensitive board, 2 is a board stand, a 3V" envelope,
4 is a lead bin, 5 is a ending wire, 6 is a diffused resistor, 7.8 is an insulating film, and 9 is an At (aluminum) pattern wiring layer.

The above-mentioned semiconductor pressure sensor utilizes offset voltage changes by assembling diffused resistors with resistance changes that contradict each other in response to pressure into a circuit as shown in Figure 7. Causes changes (temperature characteristics). When providing a high-precision pressure sensor, it must have excellent temperature characteristics (offset against temperature changes) 14'i
(low pressure changes) is desired. Temperature characteristics 1・1
, it depends on not only the Si substrate but also the assembly method of the pressure-sensitive substrate to the envelope, the oxide film on the pressure-sensitive substrate, the At wiring, etc., and in order to improve the temperature characteristics, we focused on this point and developed technical techniques. Improvements were being made.

Figure 3 shows the temperature characteristics with respect to the 9-turn wiring thickness. As shown in the figure, as the wiring thickness becomes thinner, the temperature characteristics improve. However, reducing the wiring thickness has problems such as pattern breakage and bonding properties, and it has been difficult to reduce the wiring thickness to about 1 μm or less. When improvement in temperature characteristics is desired, even if At wiring is used and htyi is made as thin as possible, it has not been possible to provide a highly accurate semiconductor pressure sensor.

(Problems to be Solved by the Invention) By bringing the coefficient of thermal expansion of the material of the lean wiring closer to 81, it is possible to improve the temperature characteristics. Mo, W, etc. are cited as materials with a coefficient of thermal expansion close to St, but they have poor adhesion with Sl and poor densability.
It is impossible to use it as pattern wiring, and A
Even if an attempt was made to improve the mendability by creating a laminated structure with At, the thickness of At must be approximately 1 μm or more, and the temperature characteristics could not be improved.

In order to provide a highly accurate semiconductor pressure sensor, the present invention
The purpose is to improve temperature characteristics (that is, reduce offset voltage changes due to temperature changes).

(Means and effects for solving the problems) The present invention provides a pressure sensitive semiconductor having a diffused resistance layer and an electrode wiring layer connected thereto formed on one surface, and a diaphragm formed on the opposite surface of the diffused resistance layer. In a semiconductor pressure sensor having a substrate, the coefficient of thermal expansion of the material of the electrode wiring layer is 1.
It is characterized by being 5 to 5 times larger. That is, the coefficient of thermal expansion of the material of the electrode wiring layer is made close to that of silicon, thereby reducing the total internal strain in silicon that occurs due to temperature changes, and reducing offset voltage changes due to temperature changes.

(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of the same embodiment, but since this is an example corresponding to FIG. 6, corresponding parts are given the same reference numerals. That is, an oxide film 7 is formed on the 81 substrate 1 on which the diffused resistor 6 is formed.
1, a mother turn wiring layer is formed. Since this wiring layer has a problem of breakage of the elbow turn, a contact portion 4 with the substrate is formed by a technique such as plasma etching to prevent the problem of breakage. The wiring layer is formed of a laminated structure of Mo S l 2 /Mo /MoS i .

That is, as shown in FIG. 1, the %Mo512 layer 11h is about x
The thickness of oool should be determined to improve adhesion to 81. Mo)@llb is formed on the Mo S'r 2 layer 11 and has a thickness of about 80001. OdaMo
On the layer 11b, a Mo812 layer 11c is formed at a depth of about 1000× to prevent oxidation of the Mo layer. Therefore, this Mo
12 layers of S l 2 /Mo /Mo S have a total of 10000X.

The above-mentioned Mo S l □/Mo / Mo S 12 layer is formed by a method such as vapor deposition in a vacuum. Also, from Figure 2, the thermal expansion coefficient of Mo5t and Mo is A
Compared to t, the value is closer to St. Formed Mo
The S l 2 /Mo /Mo 8 l 2 layer is about 1
By annealing at 000° C. for about 30 minutes, the adhesion with Sl and the state of electrical contact are improved.

An oxide film 8 is laminated on the upper surface of the multi-turn wiring layer of MoS i /Mo / MoS i 2 to form electrical insulation from the outside.

Figure 2 shows the coefficient of thermal expansion. kt is MO8121MO
The coefficient of thermal expansion is quite large (about 9 times that of Sl, and Mo Si 2 e Mo is about 2 to 3 times that of Sl).

FIG. 3 shows the temperature characteristics with respect to the thickness of the 79 tan wiring layer.

The Mo S i 2 /Mo /Mo S i two layers are
Compared to the At layer, the offset voltage changes by about IA at the same layer thickness. Therefore, Mo5t /Mo/Mo5
By forming the patterned wiring layer with a material such as i2j- whose thermal expansion coefficient is close to Sl, temperature characteristics can be improved.

By making the pattern layer thickness as thin as possible using 12 layers of Mo S i 2 /Mo /Mo S, good temperature characteristics that could not be achieved conventionally can be obtained (see FIG. 3).

Also, in order to obtain the same temperature characteristics, MoSi2
The 12 layers of /Mo /Mo S can be made thicker, providing a margin against pattern breakage and the like.

Figure 4 shows the static pressure error characteristics. The static pressure error characteristic is a change in offset voltage when static pressure is applied, and it is desirable for this change to be small in order to improve the accuracy of the pressure sensor. Pattern wiring layer from At to Mo5I2
/Mo By setting /Mo512, the static pressure error is reduced. Therefore, the pattern wiring no. is changed from At to MoS.
By setting i 2 /Mo /MoS l□, not only the temperature characteristics but also the static pressure error characteristics were improved.

Note that the present invention is not limited to the above embodiments and can be applied in various ways. For example, if it is acceptable even if the electrical resistance of the patterned wiring layer is large, the patterned wiring layer may be formed only by Mosi□6. The object of the invention is to form the pattern wiring layer (electrode wiring layer) with a material whose thermal expansion coefficient is close to SL, and to form the pattern wiring layer (electrode wiring layer) with a material whose thermal expansion coefficient is 1.5 to 5 times that of SL. It is characterized by one thing. The reason why we set it to 1.5 times here is because there is no material that can be used for wiring if it is less than this, and the reason why we set it to 5 times is because
This is because if the temperature is higher than this, the temperature characteristics will become unusable.

[Effects of the Invention] As explained above, according to the present invention, the coefficient of thermal expansion of the material of the electrode wiring layer approaches SI, and S
Since the internal strain during t is reduced and the offset voltage change due to temperature change is reduced, a highly accurate semiconductor pressure sensor can be provided.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the present invention taken from 5 x 2, Fig. 2 is a chart showing the coefficient of thermal expansion of each material, Fig. 3,
Fig. 4 is a characteristic diagram explaining the present invention in detail, Fig. 5 is an overall internal 1111 view of the semiconductor pressure sensor, Fig. 6 is a sectional view of the main part of the sensor (conventional example), and Fig. 7 is the same. FIG. 2 is a sensor output measurement circuit diagram. 1... Semiconductor pressure sensitive substrate, 6... Diffused resistor, II&. 11 c ・”Mo812 layer, 1 l b ・-Mo
ll. Applicant's agent, patent attorney Takehiko Suzue! Figure 11 Figure 21 1 2 Thickness (〃) Figure 3j Difference in price 4. Toma

Claims (2)

[Claims] (1) In a semiconductor pressure sensor having a pressure sensitive semiconductor substrate in which a diffused resistance layer and an electrode wiring layer connected thereto are formed on one surface and a diaphragm is formed on the opposite surface of the diffused resistance layer, the electrode wiring layer is A semiconductor pressure sensor characterized in that the coefficient of thermal expansion of the material is 1.5 to 5 times that of silicon. (2) The electrode wiring layer is MoSi_2/Mo/MoS
The semiconductor pressure sensor according to claim 1, characterized in that it has a laminated structure of i_2 or a single layer structure of MoSi_2.