Humidity sensor and preparation method thereof

Abstract

The present invention relates to a humidity sensor and a method for preparing the same. A humidity sensor comprises: a semiconductor substrate; a dielectric layer formed on the surface of the semiconductor substrate; a metal capacitor structure provided on the upper surface of the dielectric layer; a stacked multi-layer humidity sensitive layer covering the metal capacitor structure, wherein at least one humidity sensitive layer is a metal oxide and at least one humidity sensitive layer is a polyimide; and electrodes are led out of the metal capacitor structure. The humidity sensitivity is improved by providing a plurality of humidity sensitive layers with different materials, thereby solving the problem of low sensitivity of existing sensors. At the same time, the humidity sensitive layer materials used are all commonly used materials for CMOS devices, so the preparation process can be well compatible with the CMOS process.

Description

Technical Field

[0001] The invention relates to the field of semiconductor device production, and in particular to a humidity sensor and a preparation method thereof. Background Art

[0002] Humidity measurement is not only used in daily life, but also widely used in industrial production, medical treatment, agriculture, meteorological analysis, aerospace and other fields. With the development of science and technology, humidity sensors are improving from simple humidity-sensitive elements to intelligent, integrated, and multi-parameter detection. In the process preparation of humidity sensors, making their manufacturing process compatible with integrated circuit technology (CMOS) is the main way to improve integration, accuracy and stability, and reduce process production costs.

[0003] Among the many types of humidity sensors, capacitive humidity sensors are more practical, have stable performance, mature technology, and are suitable for mass production. Capacitive humidity sensors use the fact that after the capacitor medium absorbs water vapor molecules in the air, its dielectric constant changes, thereby causing a change in capacitance. How to enhance the change in dielectric constant after moisture absorption and thus improve sensitivity is the key to making high-quality humidity sensors.

[0004] To this end, the present invention is proposed. Summary of the invention

[0005] The main purpose of the present invention is to provide a humidity sensor and a preparation method thereof, which improves the humidity sensitivity by setting a multi-layer humidity-sensitive layer with different materials, thereby solving the problem of low sensitivity of existing sensors. At the same time, the humidity-sensitive layer materials used are all commonly used materials for CMOS devices. Therefore, the preparation process can be well compatible with the CMOS process.

[0006] In order to achieve the above objectives, the present invention provides the following technical solutions.

[0007] A humidity sensor, comprising:

[0008] Semiconductor substrate;

[0009] A dielectric layer is formed on the surface of the semiconductor substrate;

[0010] A metal capacitor structure is provided on the upper surface of the dielectric layer;

[0011] The metal capacitor structure is covered with a plurality of stacked humidity-sensitive layers, wherein at least one humidity-sensitive layer is a metal oxide and at least one humidity-sensitive layer is a polyimide;

[0012] The metal capacitor structure is provided with electrodes.

[0013] A method for preparing a humidity sensor, comprising:

[0014] providing a semiconductor substrate;

[0015] A dielectric layer is formed on the semiconductor substrate;

[0016] forming a metal layer on the dielectric layer;

[0017] performing patterning on the metal layer to form a capacitor structure;

[0018] A plurality of stacked moisture-sensitive layers are covered on the capacitor structure, wherein at least one moisture-sensitive layer is made of a metal oxide material and at least one moisture-sensitive layer is made of a polyimide material;

[0019] The multi-layer moisture sensitive layer is etched, and electrodes are led out from the capacitor structure.

[0020] Compared with the prior art, the present invention achieves the following technical effects:

[0021] On the one hand, a multilayer humidity-sensitive layer made of different materials (metal oxides such as Al2O3, ZrO2 or HfO2, or organic materials such as polyimide) is arranged above the capacitor structure. This composite laminated humidity-sensitive structure can enhance the change in dielectric constant after moisture absorption, thereby improving humidity sensitivity.

[0022] On the other hand, metal oxides such as Al2O3, ZrO2, HfO2 or organic materials such as polyimide used in the humidity sensitive layer are commonly used materials for CMOS devices, which makes the preparation process of the humidity sensor compatible with the CMOS process and reduces the production cost.

[0023] On the other hand, metal oxides such as Al2O3, ZrO2, HfO2 or organic materials such as polyimide used in the humidity sensitive layer have good dielectric properties and can ensure the performance reliability of the sensor.

[0024] On the other hand, the preparation process of the sensor of the present invention is simple, and each process is a common process in semiconductor production, which is conducive to product promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0026] Figure 1 A schematic diagram of the structure of the humidity sensor provided by the present invention from a top view

[0027] Figure 2 for Figure 1 A cross-sectional view of the structure shown in the XX' direction;

[0028] Figures 3 to 6The morphology diagrams obtained in each step of the preparation method of the humidity sensor provided by the present invention. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0030] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0031] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element or an intervening layer / element may exist therebetween. In addition, if a layer / element is "on" another layer / element in one orientation, the layer / element may be "below" the other layer / element when the orientation is reversed.

[0032] In order to improve the sensitivity of the capacitive humidity sensor, the structural design and material selection of the humidity-sensitive material are critical. To this end, the present invention provides a humidity sensor with the following structure.

[0033] like Figure 1 and 2 The humidity sensor shown comprises:

[0034] A semiconductor substrate 1;

[0035] A dielectric layer 2 is formed on the surface of the semiconductor substrate 1;

[0036] A metal capacitor structure 3 is provided on the upper surface of the dielectric layer 2;

[0037] The metal capacitor structure 3 is covered with a stack of multiple humidity-sensitive layers, wherein at least one humidity-sensitive layer is a metal oxide and at least one humidity-sensitive layer is a polyimide. The figure shows a metal oxide layer 4 and a polyimide layer 5;

[0038] The metal capacitor structure 3 has electrodes 6 extending therefrom.

[0039] Among them, the semiconductor substrate 1 can be any base material known to those skilled in the art for carrying semiconductor integrated circuit components, such as silicon-on-insulator (SOI), bulk silicon, germanium, silicon germanium, gallium arsenide or germanium on insulator (such as GOI or SOG), etc.

[0040] The dielectric layer 2 can be made of dielectric materials with good insulation properties, such as silicon oxide, silicon oxynitride, and silicon nitride.

[0041] The metal capacitor structure 3 can be made of common metal materials such as gold, aluminum, titanium, tungsten, or metal compounds. The metal capacitor structure 3 can be of any structure, preferably Figure 1 and 2 The interdigital structure shown in the figure can increase the number of capacitors per unit area, improve integration and sensitivity, Figure 1 The structure shown contains 7 capacitors, but the present invention is not limited to this, and the number can be any number and can be adjusted as needed.

[0042] The multi-layer humidity-sensitive layer contains at least two different materials, one is a metal oxide, such as Al2O3, ZrO2 or HfO2, and the other is an organic material such as polyimide. The complementary nature of the two enhances the change in dielectric constant after moisture absorption, thereby improving humidity sensitivity. At the same time, the sensor also has the advantages of reliable performance.

[0043] The number of layers of the humidity-sensitive layer is not limited in the present invention, and it can be formed by cross-stacking two different materials. Two layers are preferred based on comprehensive considerations.

[0044] The present invention also provides a method for preparing the above humidity sensor, taking two humidity-sensitive layers as an example, comprising the following steps:

[0045] In the first step, a dielectric layer 2 is formed on a semiconductor substrate 1 to obtain Figure 3 The morphology shown. Usually, a suitable formation method is selected according to the material of the dielectric layer 2. Taking silicon oxide as an example, the deposition method used includes but is not limited to LPCVD, RTCVD or PECVD, and the silicon source can be monosilane, dichlorosilane, disilane, diisopropylaminosilane, bis(tert-butylamino)silane, bis(diethylamino)silane, hexachlorodisilane, tris(dimethylamino)silane, butylaminosilane, diethylaminosilane, dipropylaminosilane, hexaethylaminodisilane and other typical silicon sources.

[0046] In the second step, a metal layer is formed on the dielectric layer 2, preferably by using a PVD method, especially aluminum.

[0047] In the third step, the metal layer is patterned by combining photolithography and etching to form a metal capacitor structure 3 with interdigitated fingers, as shown in FIG. Figure 3 The morphology shown usually includes processes such as exposure and development.

[0048] In the fourth step, a metal oxide layer 4 is deposited as the first dielectric layer and the wet-sensitive layer to obtain Figure 3 As shown in the morphology, the first dielectric layer is made of a material with a relatively high dielectric constant, such as Al2O3, ZrO2 or HfO2, and the deposition method can be PVD or ALD.

[0049] In the fifth step, a polyimide layer 5 is spin-coated as the second dielectric layer and the humidity sensitive layer to obtain Figure 3 The morphology shown in the figure is that after the polyimide PI is spin-coated, it is cured at a temperature of 250 to 350°C for 30 minutes to 1 hour.

[0050] Step 6: dry-etch the polyimide layer 5 and the metal oxide layer 4 to expose the aluminum electrode PAD, and obtain Figure 1 and 2 The structure shown.

[0051] The above steps are all conventional steps involved in the CMOS process. Therefore, the preparation process of the present invention has good compatibility with the CMOS process.

[0052] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, a person skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A humidity sensor, characterized in that: include: Semiconductor substrate; A dielectric layer is formed on the surface of the semiconductor substrate; A metal capacitor structure is provided on the upper surface of the dielectric layer, and the metal capacitor structure is an interdigitated structure; The metal capacitor structure is covered with a stack of multiple wet-sensitive layers, wherein at least one wet-sensitive layer is a metal oxide and at least one wet-sensitive layer is a polyimide; the wet-sensitive layer close to the metal capacitor structure is a metal oxide material; the metal oxide is ZrO2 or HfO2; the metal oxide material covers the dielectric layer and the metal capacitor structure and forms a groove between adjacent electrodes of the metal capacitor structure, and the polyimide material fills the groove and covers the metal oxide material; The metal capacitor structure is provided with electrodes.

2. The humidity sensor according to claim 1, characterized in that: The dielectric layer is silicon oxide.

3. The humidity sensor according to claim 1, characterized in that: The metal capacitor structure adopts metal aluminum.

4. A method for preparing a humidity sensor according to any one of claims 1 to 3, characterized in that: include: providing a semiconductor substrate; A dielectric layer is formed on the semiconductor substrate; forming a metal layer on the dielectric layer; performing patterning on the metal layer to form a metal capacitor structure; A plurality of stacked moisture-sensitive layers are covered on the metal capacitor structure, wherein at least one moisture-sensitive layer is a metal oxide material and at least one moisture-sensitive layer is a polyimide material; the moisture-sensitive layer close to the metal capacitor structure is a metal oxide material; the metal oxide is ZrO2 or HfO2; The multi-layer moisture sensitive layer is etched, and electrodes are led out from the capacitor structure.

5. The preparation method according to claim 4, characterized in that: The moisture sensitive layer of the metal oxide is formed by a PVD method or an ALD method.

6. The preparation method according to claim 4, characterized in that: The moisture sensitive layer of polyimide is formed by spin coating and curing.

7. The preparation method according to claim 6, characterized in that: The curing method is: maintaining at 250-350° C. for 30 min-1 h.

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