JPH085570Y2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pressure sensor using a silicon diaphragm, and more particularly to a silicon diaphragm type pressure sensor suitable for eliminating the need for offset voltage adjustment.

[Conventional technology and its problems]

In the silicon diaphragm type pressure sensor, as shown in FIG. 3, diffusion gauges 3 serving as strain-to-electricity conversion elements are arranged in a line by diffusing impurities such as boron on the surface of the strain-generating portion 1 of the silicon diaphragm by a diffusion planar method. However, this diffusion gauge is formed in a bridge circuit.

When forming the bridge shown in FIG. 4, the accuracy of the individual resistance values becomes important, and if the resistance values vary, the offset voltage Voff under non-pressurized value will change from zero.

In particular, in the one-row arrangement shown in FIG. 3, the peripheral diffusion gauge is greatly affected by photolithography and diffusion, while the central diffusion gauge is hardly affected. As described above, when the degree of influence of photolithography or the like varies depending on each diffusion gauge, there is a problem in that the resistance value of the formed diffusion gauge varies, and the offset voltage under no pressure shifts from zero.

An object of the present invention is to provide a silicon diaphragm type pressure sensor in which the resistance values of diffusion gauges arranged in a line are uniform.

[Means for Solving the Problems] In order to achieve the above object, the pressure sensor according to the present invention of claim 1 is provided with a pair of central diffusion gauges provided in the vicinity of the central portion of the strain region of the silicon diaphragm. And an outer diffusion gauge provided at a peripheral portion of the strain-generating region at a target position centered on the central diffusion gauge, and a non-strain region outside the outer diffusion gauge, which are provided close to the outer diffusion gauge. Each of the diffusion gauges is arranged in a row, and the pair of central diffusion gauges and the pair of outer diffusion gauges and the pair of pseudo diffusion gauges are arranged in the same arrangement, and the outer diffusion gauges and the central diffusion gauges are arranged. The gauge is formed to have the same resistance value, and the outer diffusion gauge and the central diffusion gauge are bridge-connected.

A pressure sensor according to a second aspect of the present invention includes a pair of central diffusion gauges provided near a central portion of the strained area of a silicon diaphragm, and a peripheral edge of the strained area at a target position centered on the central diffusion gauge. The outer diffusion gauge provided in the section, and a pseudo diffusion layer provided around the respective diffusion gauges and having an area sufficiently larger than the gauge area, and each diffusion gauge is arranged in a row to form an outer diffusion gauge. The central diffusion gauge is formed to have the same resistance value, and the outer diffusion gauge and the central diffusion gauge are bridge-connected.

[Action]

Since the diffusion gauge having the same resistance value can be formed by providing the pseudo diffusion layer or the pseudo diffusion gauge, when the bridge circuit is configured, the offset voltage under no pressure can be made zero.

〔Example〕

 Embodiments of the present invention will be described below.

FIG. 1 is a plan view of a silicon diaphragm showing a first embodiment of the present invention. The silicon diaphragm has a rectangular strain-generating region 1 (inside the chain line) that is thinner than the thickness of the non-strain-generating region 2.
Is provided, and the diffusion gauge 3 is formed in this strain generation region. The diffusion gauge 3 is provided with a pair of central diffusion gauges 3A in the central portion and an outer diffusion gauge 3B in the peripheral portion at a target position around the central diffusion gauge. Non-strain area 2
Is provided with a pseudo diffusion gauge 4 in parallel with the outer diffusion gauge 3B so as to have the same arrangement as the central diffusion gauge 3A. Also, the pair of central and both outward diffusion gauges are arranged in a line.

In this way, by forming the pseudo diffusion gauge 4 in parallel with the outer diffusion gauge, in the photolithography process, the influence of the light transmitted through the adjacent diffusion gauge portion and reflected can be made the same as that of the central diffusion gauge portion. Therefore, the outer diffusion gauge portion is patterned under the same conditions as the central diffusion gauge portion, and each diffusion gauge portion can be processed into the same shape. Further, in the impurity (boron) diffusion process, even if the opening area of the mask corresponding to each diffusion gauge is different in the new diffusion source, the number of flying boron is large, so that the influence is small. However, when the emission of boron from the diffusion source decreases, the central diffusion gauge part with a large opening area tends to be large, while the outward diffusion gauge part with a small opening area tends to decrease, forming diffusion gauges with different resistance values. Will end up.

Therefore, by forming the pseudo diffusion gauge portion, the opening areas of the masks of the outer diffusion gauge portion and the central diffusion gauge portion can be made equal, so that it is not affected by the number of boron emitted from the diffusion source. Therefore, uniform diffusion can be performed.

In this embodiment, by providing the pseudo diffusion gauge,
The cause of the variation in the resistance value in the above two steps is eliminated.

Next, a second embodiment of the present invention will be described with reference to FIG.

Around the diffusion gauge 3, a pseudo diffusion layer 5 having an area sufficiently larger than the gauge area is formed. With this configuration, it is possible to reduce the effects of photolithography and diffusion described above, and it is possible to make the resistance values of the outer and central diffusion gauges uniform.

[Effect of device]

As described above, according to the present invention, since the resistance values of the diffusion gauges forming the bridge circuit can be the same, the offset voltage becomes zero, and the offset voltage adjustment can be omitted.

Further, since the pseudo diffusion gauge or the pseudo diffusion layer can be formed in the same process as the central and outer diffusion gauges, the manufacturing cost is not increased.

[Brief description of drawings]

FIG. 1 is a plan view of a silicon diaphragm constituting the pressure sensor of the present invention, FIG. 2 is a plan view showing another embodiment, FIG. 3 is a plan view of a conventional silicon diaphragm, and FIG. 4 is a bridge circuit diagram. is there. 1 ... Silicon diaphragm diaphragm strain region 2 ... Same non-strain region, 3 ... Diffusion gauge, 4 ... Pseudo diffusion gauge, 5 ... Pseudo diffusion layer

Claims (2)

[Scope of utility model registration request] 1. A pair of central diffusion gauges provided in the vicinity of a central portion of a strain generating area of a silicon diaphragm, and a peripheral portion of the strain generating area at a target position centered on the central diffusion gauge. An outer diffusion gauge, a non-strain area outside the outer diffusion gauge, and a pseudo diffusion gauge provided in proximity to the outer diffusion gauge, each diffusion gauge is arranged in a row, and a pair of The set of the central diffusion gauge, the outer diffusion gauge, and the set of the pseudo diffusion gauge are arranged in the same shape so that the outer diffusion gauge and the central diffusion gauge have the same resistance value, and the outer diffusion gauge and the central diffusion gauge are also formed. A pressure sensor characterized in that a bridge connection is made. 2. A pair of central diffusion gauges provided close to the central portion of the strain generating area of the silicon diaphragm, and a peripheral portion of the strain generating area at a target position centered on the central diffusion gauge. An outer diffusion gauge and a pseudo diffusion layer provided around the respective diffusion gauges and having an area sufficiently larger than the gauge area are provided, and the respective diffusion gauges are arranged in a row, and the outer diffusion gauge and the central diffusion layer are arranged. A pressure sensor characterized in that the gauge is formed to have the same resistance value, and the outer diffusion gauge and the central diffusion gauge are bridge-connected.