CN101602479A - Capacitive sensing device and manufacturing method thereof - Google Patents

Abstract

A capacitive sensing device and a method for fabricating the same, the capacitive sensing device includes: a substrate, the upper surface of which is provided with a positioning layer and an opening part at a preset position; a polysilicon layer arranged on the substrate, a diaphragm formed at the opening part and a plurality of adjusting holes arranged on the diaphragm; a first insulating layer arranged on the polysilicon layer and forming a cavity part above the diaphragm; the first metal layer is arranged on the first insulating layer and is provided with a plurality of through holes connected with the cavity part; the polysilicon layer and the first metal layer form a sensing capacitor which is connected with a sensing circuit to sense through the vibration of the diaphragm. The method mainly uses polysilicon as a sacrificial layer, and can achieve the purpose of precise etching by matching with an oxide layer and a positioning layer. Polysilicon is used as a vibrating diaphragm to form a sensing capacitor by matching with a metal layer, and another metal layer can be additionally arranged to form a reference capacitor, so that the structural strength of the component can be greatly improved in addition to the functions required by the circuit.

Description

Capacitive sensing device and manufacturing method thereof

technical field

The present invention relates to a capacitive sensing device and a manufacturing method thereof, in particular to a capacitive sensing device and a manufacturing method thereof which can be mass-manufactured by using a CMOS (Complementary Metal Oxide Semiconductor) process and can reduce costs.

Background technique

Please refer to FIG. 1 , which is a structural cross-sectional view of a MEMS microphone in the prior art. As shown in the figure, its main structure includes a silicon substrate 12 , a diaphragm 14 and a back plate 16 . Wherein, the upper and lower surfaces of the silicon substrate 12 are respectively provided with a dielectric layer 121 , 123 , and a resonant chamber 125 is provided in the middle. The vibrating membrane 14 is formed by depositing polysilicon and doping with boron or phosphorus ions.

A phosphorosilicate glass is deposited on the vibrating membrane 14 as a sacrificial layer. An insulating layer 161 , a backplane 16 of polysilicon doped with boron or phosphorus ions, and a protection layer 163 are sequentially deposited on the sacrificial layer. Afterwards, two contact windows are etched on the protection layer, and metal pads 181 and 183 are formed on each contact window to connect the vibrating film 14 and the back plate 16 respectively. In addition, a plurality of sound holes 165 are etched on the back plate 16, and the sacrificial layer is etched away.

Although the micro-electromechanical microphone with this structure can achieve the effect of inductive sound collection, its back plate 16 is mainly composed of polysilicon, which is relatively fragile and easily damaged during processing.

In addition, the sacrificial layer is made of phosphosilicate glass, which is difficult to etch to remove the sacrificial layer, and it is easy to corrode other parts of the component, such as the polysilicon back plate 16 and the vibrating film 14, and the insulating layer 161, which is also an oxide. The precision of etching is difficult to master. It may cause uneven thickness of the vibrating membrane 14, or even perforation, and the strength of the back plate 16 will be more fragile.

Contents of the invention

The technical problem to be solved by the present invention is to provide a capacitive sensing device, which mainly uses polysilicon to make a diaphragm and forms a sensing capacitor with a metal layer, which can strengthen the structural strength of the device.

Another object of the present invention is to provide a capacitive sensing device, in which a plurality of adjustment holes are provided on the diaphragm, so that parameters such as the elastic coefficient of the diaphragm can be adjusted according to requirements.

Another object of the present invention is to provide a capacitive sensing device, in which another metal layer can be added to form a reference capacitance with the original metal layer, and the structural strength of the device can be further strengthened.

Another object of the present invention is to provide a method for manufacturing a capacitive sensing device, which mainly uses polysilicon to make a sacrificial layer, which can improve the etching accuracy when removing the sacrificial layer.

Another object of the present invention is to provide a method for manufacturing a capacitive sensing device, which can manufacture a sensing device with sufficient strength, which is beneficial for subsequent application and manufacturing.

Yet another object of the present invention is to provide a method for manufacturing a capacitive sensing device, which is manufactured using a CMOS process and can integrate the capacitive sensing device into an integrated circuit.

To achieve the above object, the present invention provides a capacitive sensing device, the main structure of which includes: a substrate with a positioning layer on its upper surface and an opening at a preset position; a polysilicon layer on the On the substrate, a vibrating film is formed at the opening, and a plurality of adjustment holes are arranged on the vibrating film; a first insulating layer is arranged on the polysilicon layer, and a cavity is formed above the vibrating film; and a first metal layer, disposed on the first insulating layer, provided with a plurality of through holes connected to the cavity; wherein, the polysilicon layer and the first metal layer form a sensing capacitor, which can be connected to a sensing circuit The vibration of the diaphragm is used for sensing.

The present invention also provides a method for manufacturing a capacitive sensing device, which mainly includes the following steps: providing a substrate, and forming a positioning layer on the upper surface of the substrate; depositing a polysilicon layer on the positioning layer, and Etching at preset positions forms a plurality of etching holes; forming an oxide layer including each etching hole on the predetermined surface of the polysilicon layer; depositing a polysilicon sacrificial layer on the oxide layer; depositing silicon dioxide to form a first insulating layer covering the a sacrificial layer and a polysilicon layer; depositing or sputtering a first metal layer on the first insulating layer; etching a plurality of via holes to the sacrificial layer from preset positions of the first metal layer; etching and removing the sacrificial layer to form a hollow a cavity; etching a preset position of the substrate to the positioning layer to form an opening; and etching away the positioning layer at the position of the opening.

The capacitive sensing device of the present invention is manufactured using a standard CMOS process, so the capacitive sensing device can be directly integrated into the integrated circuit during circuit planning, which not only improves the reliability of the product, but also reduces the production cost due to the simplification of the process. significantly reduce.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention.

Description of drawings

Fig. 1 is the structural sectional view of the MEMS microphone of prior art;

2A to 2K are schematic diagrams of each step of a preferred embodiment of the present invention;

3A and 3B are schematic diagrams of some steps of another embodiment of the present invention;

FIG. 4A and FIG. 4B are schematic diagrams of the packaging state of the embodiment shown in FIG. 3B respectively;

Fig. 5 is a structural sectional view of another embodiment of the present invention;

Fig. 6 is a structural sectional view of another embodiment of the present invention.

Among them, reference signs:

12: Silicon substrate 121: Dielectric layer

123: Dielectric layer 125: Resonance chamber

14: Diaphragm 16: Backplane

161: insulating layer 163: protective layer

165: Sound hole 181: Welding pad

183: welding pad

20: Capacitive sensing device 22: Substrate

221: Positioning layer 223: Opening

24: Polysilicon layer 241: Etched hole

243: oxide layer 245: adjustment hole

247: Diaphragm 25: Sacrificial layer

255: cavity part 26: first insulating layer

28: The first metal layer 281: Protective layer

283: Through hole

30: Capacitive sensing device 32: Second insulating layer

34: Second metal layer 341: Protective layer

343: Through hole

42: Encapsulation layer 44: Encapsulation layer

445: Groove

50: Capacitive sensing device 52: Flange

60: Capacitive sensing device

Detailed ways

First, please refer to FIG. 2A to FIG. 2K , which are schematic diagrams of various steps of a preferred embodiment of the present invention. As shown in the figure, the manufacturing flow of this example mainly provides a substrate 22 first, and deposits an alignment layer 221 on the upper surface of the substrate 22 . A polysilicon layer 24 is then deposited on the positioning layer 221, as shown in FIG. 2A.

Wherein, the substrate 22 can be a silicon substrate. The alignment layer 221 can be selected as one of a silicon nitride layer and a silicon dioxide layer.

After the deposition of the polysilicon layer 24 is completed, a plurality of etching holes 241 are formed by etching at the preset positions, as shown in FIG. 2B . Since the alignment layer 221 is made of silicon dioxide or silicon nitride, which has a large chemical property difference from polysilicon, the etching can precisely reach the alignment layer 221 and stop.

After the etching is completed, an oxide layer 243 is formed on the predetermined surface of the polysilicon layer 24 including the sides of the etching holes 241 , as shown in FIG. 2C .

Polysilicon is deposited on the oxide layer 243 to form a sacrificial layer 25, as shown in FIG. 2D.

Deposit silicon dioxide to cover the sacrificial layer 25 and the polysilicon layer 24 to form a first insulating layer 26, as shown in FIG. 2E. Wherein, the first insulating layer 26 can still be doped with one of boron, phosphorus and combinations thereof in the silicon dioxide.

A first metal layer 28 is formed on the first insulating layer 26 by depositing, evaporating or sputtering, as shown in FIG. 2F . A protection layer 281 can also be deposited and formed on the first metal layer 28 as required, as shown in FIG. 2G .

After the first metal layer 28 or the protective layer 281 is completed, etching is performed on the preset position of the first metal layer 28 or the protective layer 281 to form a plurality of via holes 283 connected to the sacrificial layer 25, as shown in FIG. 2H .

Then, the sacrificial layer 25 is etched away with an etchant through the through holes 283 to form a cavity portion 255, as shown in FIG. 2I. Since the present invention uses polysilicon to make the sacrificial layer 25, and the periphery of the sacrificial layer 25 is surrounded by silicon dioxide or silicon nitride materials such as the first insulating layer 26, the oxide layer 243, and the alignment layer 221, the sacrificial layer 25 is removed. During etching, the sacrificial layer 25 can be accurately removed without remaining or eroding other parts.

After the sacrificial layer 25 is removed, the substrate 22 is etched to remove the portion corresponding to the cavity portion 25 to form an opening portion 223 , as shown in FIG. 2J . Then the positioning layer 221 at the position of the opening 223 is etched away, so that the part of the polysilicon layer 24 located between the cavity 255 and the opening 223 forms a diaphragm 247, and the fabrication of the capacitive sensing device 20 of this embodiment can be completed. As shown in Figure 2K.

Wherein, the etching hole 241 of the original polysilicon layer 24 becomes the adjustment hole 245 . The position and quantity of the adjustment holes 245 can be adjusted according to the elastic coefficient of the diaphragm 247 or other parameter requirements. The polysilicon layer 24 and the first metal layer 28 form a sensing capacitor, which can be sensed by a sensing circuit according to the capacitance change generated by the vibration or deformation of the diaphragm 247 .

Please refer to FIG. 3A and FIG. 3B , which are schematic diagrams of some steps of another embodiment of the present invention.

The front stage manufacturing steps of the present embodiment are the same as those shown in Fig. 2A to Fig. 2F, and it is mainly shown in Fig. 2

After step F, silicon dioxide is deposited on the first metal layer 28 to form a second insulating layer 32 . And a second metal layer 34 is formed on the second insulating layer 32 by depositing, evaporating or sputtering. A protection layer 341 can also be deposited and formed on the second metal layer 34 as required, as shown in FIG. 3A .

Then, the second metal layer 34 or the passivation layer 341 are etched to form a plurality of via holes 343 connected to the sacrificial layer 25 . Then, the sacrificial layer 25 is etched away with an etching solution through each through hole 343 to form a cavity portion 255 .

After the sacrificial layer 25 is removed, the substrate 22 is etched to remove the portion corresponding to the cavity portion 25 to form an opening 223 , and the positioning layer 221 at the position of the opening 223 is etched away. Then the part of the polysilicon layer 24 located between the cavity 255 and the opening 223 can form a diaphragm 247 , and the fabrication of the capacitive sensing device 30 of this embodiment is also completed, as shown in FIG. 3B .

Wherein, the polysilicon layer 24 and the first metal layer 28 form a sensing capacitance, which can be sensed by a sensing circuit according to the capacitance change generated by the vibration or deformation of the diaphragm 247 . The second metal layer 34 can optionally form a reference capacitor with the first metal layer 28 , which can be used as a reference for the sensing circuit. The second metal layer 34 can also independently form a shielding layer according to requirements, or simply become a structure for strengthening the sensing device, and the like.

Please refer to FIG. 4A and FIG. 4B , which are schematic diagrams of the packaging of the embodiment shown in FIG. 3B . As shown in the figure, the capacitive sensing device 30 of the present invention can be packaged in different packaging styles.

If an encapsulation layer 42 is formed on the lower surface of the substrate 22 of the capacitive sensing device 30 during encapsulation, the opening 223 becomes a back cavity to provide a resonance effect. And each through hole 343 becomes a sound hole, for the change of sound wave or air pressure to enter, so that the diaphragm 247 vibrates or deforms, as shown in FIG. 4A .

If an encapsulation layer 44 is selected to be formed on the second metal layer 34 of the capacitive sensing device 30 during encapsulation, the cavity portion 255 becomes a back cavity at this time, providing a resonance effect. The opening 223 is a sound hole for transmission of sound waves or changes in air pressure, as shown in FIG. 4B . Considering the matching of the space size of the cavity portion 255 and the resonant frequency, a groove 445 of an appropriate size can also be formed at a corresponding position of the packaging layer 44 as required, and form a back cavity together with the cavity portion 255 .

The above packaging aspects can also be implemented in the embodiment shown in FIG. 2K .

Please refer to FIG. 5 , which is a cross-sectional view of another embodiment of the present invention. As shown in the figure, the embodiment of the present invention shown in FIG. 3B can be further etched to remove the oxide layer 243 to become the capacitive sensing device 50 of this embodiment. Since the oxide layer 243 and the first insulating layer 26 assimilate the oxide, the first insulating layer 26 will be corroded during etching, and the flanges 52 can be formed between the through holes 343 to prevent the diaphragm 247 from sticking.

Please refer to FIG. 6 , which is a cross-sectional view of another embodiment of the present invention. As shown in the figure, in the capacitive sensing device 60 of this embodiment, after the first insulating layer 26 is formed, the portion above the sacrificial layer 25 is etched and removed before subsequent steps are performed.

Since the capacitive sensing device of the present invention is produced using a standard CMOS process, the capacitive sensing device can be directly integrated into the integrated circuit during circuit planning, which not only improves the reliability of the product, but also simplifies the production cost due to the process And significantly reduced.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (12)

1. a capacitive sensing device is characterized in that, includes:

One substrate, its upper surface is provided with an alignment layers, and is provided with a peristome in predeterminated position;

One polysilicon layer is located on this substrate, forms a vibrating diaphragm in this peristome place, and is provided with most adjustment holes in this vibrating diaphragm;

One first insulating barrier is located on this polysilicon layer, and forms a cavity portion in this vibrating diaphragm top; And

One the first metal layer is located on this first insulating barrier, is provided with most through holes and connects this cavity portion;

Wherein, this polysilicon layer and the first metal layer form a sense capacitance, connect a sensing circuit and carry out sensing by the vibration of vibrating diaphragm.

2. capacitive sensing device according to claim 1 is characterized in that, this substrate is a silicon substrate, and this alignment layers then is silicon dioxide layer or silicon nitride layer.

3. capacitive sensing device according to claim 1 is characterized in that the upper surface of this vibrating diaphragm is provided with an oxide layer, and this first metal layer is provided with a protective layer.

4. capacitive sensing device according to claim 1 is characterized in that, this first insulating barrier is a silicon dioxide layer, and this silicon dioxide layer is doped with boron or phosphorus.

5. capacitive sensing device according to claim 1 is characterized in that, includes:

One second insulating barrier is located on this first metal layer; And

One second metal level is located on this second insulating barrier;

Each through hole runs through second insulating barrier and second metal level respectively.

6. capacitive sensing device according to claim 5 is characterized in that, this first metal layer and second metal level form a reference capacitance, and this second insulating barrier is a silicon dioxide layer, and this second metal level is provided with a protective layer.

7. the preparation method of a capacitive sensing device is characterized in that, includes the following step:

One substrate is provided, and forms an alignment layers in the upper surface of this substrate;

Deposit a polysilicon layer on this alignment layers, and form most etch-holes in the predeterminated position etching;

The side that comprises each etch-hole in the default surface of this polysilicon layer forms an oxide layer;

Deposit spathic silicon forms a sacrifice layer on this oxide layer;

Deposition of silica forms one first insulating barrier and covers this sacrifice layer and polysilicon layer;

Deposition, evaporation or sputter one the first metal layer are on this first insulating barrier;

By most through holes of the predeterminated position etching of the first metal layer to this sacrifice layer;

This sacrifice layer is removed in etching, forms a cavity portion;

The predeterminated position of substrate is etched to this alignment layers, forms a peristome; And

The alignment layers of peristome position is removed in etching.

8. preparation method according to claim 7 is characterized in that, remove the step of this sacrifice layer in this etching after, include the step that this oxide layer is removed in an etching.

9. preparation method according to claim 7 is characterized in that, this alignment layers selects to deposit a silicon dioxide layer on substrate or a silicon nitride layer forms, and the silica of this first insulating barrier then is doped with boron or phosphorus.

10. preparation method according to claim 7 is characterized in that, includes the step that forms a protective layer on this first metal layer.

11. preparation method according to claim 7 is characterized in that, this deposition, evaporation or sputter one the first metal layer include the following step after the step on this first insulating barrier:

Deposition of silica forms one second insulating barrier on this first metal layer; And

Deposition, evaporation or sputter one second metal level are on this second insulating barrier;

The most individual through holes of this predeterminated position etching by the first metal layer to the step of this sacrifice layer then is:

By most through holes of the predeterminated position etching of second metal level to this sacrifice layer.

12. preparation method according to claim 11 is characterized in that, includes a step that forms a protective layer on this second metal level.

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