CN111323459A - Humidity sensor based on standard CMOS (complementary metal oxide semiconductor) process - Google Patents

Abstract

The invention relates to a humidity sensor based on a standard CMOS process. The metal-clad laminate comprises basic metal layers, n metal layers arranged above the basic metal layers and RDL layers arranged above the n metal layers, wherein the n metal layers are connected through metal through holes, the top metal layer in the n metal layers is connected with the RDL layers through the metal through holes, and n is an integer larger than 1; a POLYIMIDE layer is arranged above the RDL layer and is used as an insulating medium for sensing humidity; the device also comprises a signal processing circuit arranged below the basic metal layer. The humidity sensor provided by the invention has the advantages of high integration level, simple structure, low cost and strong anti-interference capability.

Description

A Humidity Sensor Based on Standard CMOS Process

technical field

The invention relates to the technical field of electronic equipment and electronic devices, in particular to a humidity sensor based on standard CMOS technology.

Background technique

With the rapid development of modern information technology, people have more and more accurate requirements for the measurement and control of humidity in different environments, so the requirements for the manufacturing process of humidity sensors are also higher and higher. Nowadays, the use of chip manufacturing technology to prepare humidity sensors has become the mainstream trend, mainly because the use of CMOS technology can realize large-scale mass production of products, saving production time and cost; it can also realize the integration of humidity sensing units and tiny signal detection circuits In the same chip, the external environment interference is reduced and the detection performance is improved. However, the specific production steps for the preparation of humidity sensing unit chips are different due to different processes. Most of them use a surface process compatible with CMOS technology, and the finished product cannot be obtained after one tape-out, and multiple subsequent processes are required for processing. , making the process complicated, reducing the yield and increasing the manufacturing cost.

Traditional humidity sensors such as hair hygrometer and wet and dry bulb hygrometer take the length of the hair and the temperature difference between the dry and wet bulbs as the characteristic quantities of humidity. They do not detect electrical signals and cannot be combined with industrial production control. However, although the electrolyte-type and ceramic-type humidity sensors invented later have realized the conversion of humidity into electrical signals, due to their large size, expensive materials, and complicated preparation process, they gradually cannot meet people's needs. The capacitive humidity sensor uses a variable capacitor as the sensor unit. The capacitor uses polyimide (POLYIMIDE, abbreviated as PI) as the dielectric. After absorbing moisture, the dielectric constant changes, which in turn causes the capacitance value of the capacitor to change. By detecting the capacitance The value of relative humidity can be known, and the polyimide is consistent with the standard CMOS process. The humidity sensor chip can be designed using the advantages of CMOS process manufacturing and the characteristics of polyimide on humidity. However, as mentioned above, using a surface process compatible with the CMOS process has certain limitations.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a humidity sensor based on a standard CMOS process, which has the characteristics of high integration, simple structure, low cost and strong anti-interference ability.

In order to achieve the above purpose, the technical solution of the present invention is: a humidity sensor based on a standard CMOS process, comprising a basic metal layer, an n-layer metal layer disposed above the basic metal layer, and an n-layer metal layer disposed above the n-layer metal layer In the RDL layer, the n-layer metal layers are connected through metal vias, and the top metal layer in the n-layer metal layers is connected with the RDL layer through metal vias, wherein n is an integer greater than 1.

In an embodiment of the present invention, a POLYIMIDE layer is further provided above the RDL layer to serve as an insulating medium for sensing humidity; when the chip is packaged, part of the POLYIMIDE layer is exposed to directly contact with the outside air to absorb moisture in the air , thereby causing the change of its own dielectric constant to accurately sense the ambient humidity.

In an embodiment of the present invention, the RDL layer is composed of an upper electrode plate and a lower electrode plate.

In an embodiment of the present invention, the upper pole plate and the lower pole plate adopt an elongated interdigitated structure or an annular interdigitated structure.

In an embodiment of the present invention, it further includes a signal processing circuit disposed under the basic metal layer, and the signal processing circuit is connected to the upper electrode plate and the lower electrode plate respectively.

Compared with the prior art, the present invention has the following beneficial effects: the humidity sensor of the present invention has high integration, simple structure, low cost and strong anti-interference ability.

Description of drawings

FIG. 1 is a structural diagram of a metal layer in a CMOS process.

Figure 2 shows a long strip-shaped interdigitated structure.

Figure 3 shows a ring-shaped interdigitated structure.

FIG. 4 is a humidity sensor of this example.

Detailed ways

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

The present invention provides a humidity sensor based on a standard CMOS process, comprising a basic metal layer, an n-layer metal layer disposed above the basic metal layer, and an RDL layer disposed above the n-layer metal layer, and the The n-layer metal layers are connected through metal through holes, and the top metal layer in the n-layer metal layers is connected with the RDL layer through metal through holes, wherein n is an integer greater than 1.

The following is a specific implementation process of the present invention.

The present invention provides a capacitive humidity sensor unit chip made by a standard CMOS process with an RDL layer (Redistribution Layer, rewiring layer). The humidity sensor can integrate a humidity sensing unit and a signal processing circuit on one chip, Therefore, the cost can be reduced and the stability of the sensor can be improved.

The process used in the present invention is a standard CMOS process, and the CMOS process should have a SUBSTRATE structure as shown in FIG. 1 . The back end of the process consists of n layers of metal layers and layers. The metal layers are connected through metal vias. For example, the metal M1 layer and the metal M2 layer are connected through VIA (via holes), which are represented by VIA1-2 in the figure. The metal M1 layer is always connected to the metal Mn layer (n is an integer greater than 1). ), the top metal Mn layer is connected to the RDL layer through metal vias VRDL.

On the premise of conforming to the standard CMOS process, the present invention adds a layer of POLYIMIDE which the process itself has on the RDL layer as an insulating medium for sensing humidity. When the chip is packaged, the PI part is exposed, directly in contact with the outside air, and absorbs the moisture in the air, thereby causing the change of its own dielectric constant and accurately sensing the ambient humidity.

In the present invention, the upper and lower pole plates of the humidity-sensing capacitor are fabricated on the RDL layer. The upper and lower pole plates are both located on the RDL layer, and the shape and composition can be any shape, such as a long interdigitated structure, a ring interdigitated structure, etc., as shown in Figure 2 , 3 shown. A signal processing circuit is placed under the humidity-sensing capacitor, and the upper and lower plates of the humidity-sensing capacitor are connected to the signal processing circuit, so that the capacitor is used as a part of the signal processing circuit; the result of the signal processing circuit can be output through the pad (PAD) of the chip, As shown in Figure 4.

The humidity sensor provided by the invention has high integration, simple structure, low cost and strong anti-interference ability.

The above are the preferred embodiments of the present invention, all changes made according to the technical solutions of the present invention, when the resulting functional effects do not exceed the scope of the technical solutions of the present invention, belong to the protection scope of the present invention.

Claims (5)

1. A humidity sensor based on a standard CMOS process, characterized in that it comprises a basic metal layer, an n-layer metal layer disposed above the basic metal layer, and an RDL layer disposed above the n-layer metal layer, and the The n-layer metal layers are connected through metal through holes, and the top metal layer in the n-layer metal layers is connected with the RDL layer through metal through holes, wherein n is an integer greater than 1. 2. The humidity sensor based on a standard CMOS process according to claim 1, wherein a POLYIMIDE layer is further provided above the RDL layer to serve as an insulating medium for sensing humidity; when the chip is packaged, part of the POLYIMIDE layer is When exposed, it is in direct contact with the outside air and absorbs moisture in the air, thereby causing the change of its own dielectric constant and accurately sensing the ambient humidity. 3 . The humidity sensor based on a standard CMOS process according to claim 1 , wherein the RDL layer is composed of an upper electrode plate and a lower electrode plate. 4 . 4 . The humidity sensor based on a standard CMOS process according to claim 3 , wherein the upper electrode plate and the lower electrode plate adopt a long interdigitated structure and a ring interdigitated structure. 5 . 5. The humidity sensor based on a standard CMOS process according to claim 3, further comprising a signal processing circuit arranged below the basic metal layer, the signal processing circuit being connected to the upper plate and the lower plate respectively .

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