CN215726504U

CN215726504U - Thin film sensor

Info

Publication number: CN215726504U
Application number: CN202121479386.0U
Authority: CN
Inventors: 万蔡辛; 俞江彬
Original assignee: Will Semiconductor Ltd
Current assignee: Will Semiconductor Ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2022-02-01
Anticipated expiration: 2031-07-01

Abstract

The utility model discloses a thin film sensor, which comprises a substrate; a case located above a substrate, a cavity being formed between the case and the substrate, the case including a communication hole communicating the cavity with an outside; a chip located on the substrate and in the cavity; the hydrophobic membrane is coated on the outer surfaces of the substrate and the chip; and the gel is filled in the cavity, and the upper surface of the gel is higher than that of the chip. The film sensor provided by the utility model has better moisture-proof and dust-proof capabilities.

Description

Thin film sensor

Technical Field

The utility model relates to the technical field of sensor manufacturing, in particular to a thin film sensor.

Background

The sensor is a device or apparatus which can sense a predetermined measured quantity and convert the measured quantity into a usable signal according to a certain rule (mathematical function rule), and in a film sensor for sensing external pressure, sound, optical signals and the like, a housing of a packaging structure of the film sensor is generally provided with a communication hole, as shown in fig. 1, the sensor 100 comprises a substrate 110, a housing 120 and a chip 130. The substrate 110 is selected from a PCB substrate, for example; the case 120 is positioned on the substrate 110, a cavity is formed between the case 120 and the substrate 110, and meanwhile, the case 120 includes a communication hole 121; the chip 130 is disposed on the substrate 110 and disposed in the cavity, and the chip 130 includes, for example, an ASIC (Application Specific Integrated Circuit) 131 and a MEMS (Micro-Electro-Mechanical System) 132. Further, an ASIC131 is disposed on the substrate 110, and a MEMS132 is disposed on the ASIC131, wherein the MEMS132 includes a movable structure, such as a membrane, for sensing an external signal. The housing 120 isolates the inside of the sensor from the external environment, and the presence of the communication hole 121 enables the movable structure of the chip 130 to come into contact with the external environment, thereby converting various physical quantities into electrical signals. However, the film is very sensitive to various impurities in the external environment, especially, liquid such as water and various impurities are easily adsorbed on the film, which results in sensitivity reduction and even failure of the sensor, and when water and various liquids are adsorbed on the surface of the substrate 110 or the chip 130, the water and various liquids can permeate into the film to corrode and cause malfunction or damage of the sensor circuit.

Therefore, a thin film sensor having good moisture-proof and dust-proof capabilities is desired.

SUMMERY OF THE UTILITY MODEL

In view of the above problems, an object of the present invention is to provide a thin film sensor that effectively improves the moisture and dust resistance of the thin film sensor.

According to an aspect of the present invention, there is provided a thin film sensor, comprising: a substrate; a case located above a substrate, a cavity being formed between the case and the substrate, the case including a communication hole communicating the cavity with an outside; a chip located on the substrate and in the cavity; the hydrophobic membrane is coated on the outer surfaces of the substrate and the chip; and the gel is filled in the cavity, and the upper surface of the gel is higher than that of the chip.

Optionally, the hydrophobic membrane is selected from self-assembled monomolecular membranes.

Optionally, the material forming the self-assembled monolayer is selected from 1H,1H,2H, 2H-perfluorodecyl trichlorosilane.

Optionally, the substrate is selected from a PCB substrate.

Optionally, the chip comprises: the MEMS device comprises an application specific integrated circuit, a micro electro mechanical system and a membrane, wherein the application specific integrated circuit is positioned on the substrate, and the micro electro mechanical system is positioned on the application specific integrated circuit and comprises the membrane which is used for sensing signals of an external environment.

Optionally, the gel is selected from polydimethylsiloxane silicone gel.

Optionally, the thin film sensor is selected from any one of a gas sensitive thin film sensor, a light sensitive thin film sensor, and a thin film acoustic sensor.

Optionally, the thin film sensor is packaged in a grid array.

The thin film sensor provided by the utility model can solve the moisture-proof problem of the thin film sensor from a wafer level by coating the self-assembled monomolecular film on the surface of the sensor structure, and meanwhile, the self-assembled monomolecular film has small thickness, has low influence on the sensitivity of the MEMS thin film and has small sensitivity of the thin film sensor due to the loss of the self-assembled monomolecular film.

Optionally, the self-assembled monomolecular film composed of FDTS has lower surface energy, so that the moisture-proof problem of the thin film sensor can be solved, the quantity of dust and other impurities adsorbed by the thin film and other parts can be reduced, the sensitivity of the thin film sensor is prevented from being reduced due to the fact that the thin film adsorbs the dust and other impurities, and the long-time stable work of the thin film sensor is facilitated. In addition, the thin film sensor provided by the embodiment of the utility model is compatible with a reflow soldering process, so that the thin film sensor is suitable for application scenes of mass production.

Optionally, after the housing is welded to the substrate, PDMS (polydimethylsiloxane) silicone gel is injected into the cavity through the communication hole on the housing to cover the leads and the pads exposed in the air, so that the thin film sensor can obtain a better moisture-proof effect, and the loss sensitivity is within an acceptable range, thereby enabling the thin film sensor to be applied in a scene with high humidity and low precision requirement in a working environment. Meanwhile, the silicon gel is injected into the cavity through the communicating hole and is compatible with a reflow soldering process, so that the method is suitable for application scenes of mass production and can be applied to damp-proof scenes with lower cost and lower precision requirement.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows a cross-sectional view and a top view of a prior art thin-film sensor;

FIGS. 2 a-2 d are cross-sectional views of a thin film sensor at various stages of its manufacture in accordance with an embodiment of the present invention;

FIG. 3 illustrates another thin film sensor according to an embodiment of the present invention.

Detailed Description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, the same elements or modules are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.

It should be understood that in the following description, "circuitry" may comprise singly or in combination hardware circuitry, programmable circuitry, state machine circuitry, and/or elements capable of storing instructions executed by programmable circuitry. When an element or circuit is referred to as being "connected to" another element or circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.

Also, certain terms are used throughout the description and claims to refer to particular components. As one of ordinary skill in the art will appreciate, manufacturers may refer to a component by different names. This patent specification and claims do not intend to distinguish between components that differ in name but not function.

In the present application, the term "sensor structure" refers to the collective designation of the entire sensor structure formed in the various steps of manufacturing the sensor, including all layers or regions that have been formed. In the following description, numerous specific details of the utility model, such as structure, materials, dimensions, processing techniques and techniques of the devices are described in order to provide a more thorough understanding of the utility model. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

Moreover, it is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Fig. 2a to 2d show cross-sectional views of different stages in the manufacturing process of a thin film sensor according to an embodiment of the utility model.

As shown in fig. 2a, the sensor structure has formed a substrate 210 and a chip 230.

The substrate 210 is, for example, a PCB substrate, and one or more pads 240 have been formed on the substrate 210.

Chip 230 includes an ASIC231 and a MEMS232, on which one or more pads 240 have been formed. The ASIC231 is located on the substrate 210, the MEMS232 is located on the ASIC231, and the MEMS232 includes a movable structure, such as a membrane, for sensing an external signal.

A hydrophobic film, such as a self-assembled monolayer 250, is formed on the sensor structure resulting in the sensor structure depicted in fig. 2 b. The thickness of the self-assembled monolayer 250 is usually within 10 nm.

The material for forming the self-assembled monolayer 250 is selected from FTDS (1H,1H,2H, 2H-perfluorodecyl trichlorosilane), for example, by vapor deposition or the like.

Optionally, the sensor structure is subjected to surface plasma treatment before deposition, so that the outer surface of the semiconductor structure has higher reactivity with the material forming the self-assembled monolayer 250, which is beneficial to improving the deposition effect and thus improving the yield of products.

However, the self-assembled monolayer 250 covers the bonding pad 240, which results in poor contact or failure to form electrical connection when the bonding pad 240 is connected to a lead in a subsequent process, and therefore, after the self-assembled monolayer 250 is formed, the self-assembled monolayer 250 on the surface of the bonding pad 240 is removed by polishing, and the top view thereof is shown in FIG. 2 c.

Optionally, the grinding process is selected from grinding processes used for removing metal oxide on the surface of the bonding pad in the prior art and parameters are adjusted appropriately.

Then, wires are connected to the pads 240 to electrically connect the substrate 210, the ASIC231 and the MEMS232 to each other, solder is applied to selected positions of the substrate 210, and the housing 220 is mounted and reflowed to obtain the thin film sensor 200 shown in fig. 2 d. The thin film sensor 200 is, for example, a Land Grid Array (LGA) package.

The thin film sensor of the embodiment of the utility model can solve the moisture-proof problem of the thin film sensor from the wafer level, the thickness of the self-assembled monomolecular film 250 is thinner, the influence on the sensitivity of the MEMS232 thin film is very low, and the sensitivity of the sensor 200 lost by the self-assembled monomolecular film 250 is very small.

The self-assembled monomolecular film 250 composed of FDTS has lower surface energy, not only can solve the moisture-proof problem of the film sensor 200, but also can reduce the quantity of dust and other impurities adsorbed by the film and other parts, avoid the sensitivity reduction of the sensor caused by the adsorption of dust and other impurities by the film, and is beneficial to the long-time stable work of the film sensor 200.

In addition, the thin film sensor provided by the embodiment of the utility model is compatible with reflow soldering, so that the thin film sensor is suitable for application scenes of mass production.

Alternatively, the thin film sensor 200 is selected from any one of a gas sensitive thin film sensor, a light sensitive thin film sensor, and a thin film acoustic sensor.

However, the lead and the pad 240 of the thin film sensor 200 are still exposed to the air, and if the humidity of the working environment of the thin film sensor 200 is too high and even dew condensation occurs, the lead may have a risk of breakdown due to too high humidity or short circuit due to dew condensation.

In order to overcome the above problems, an embodiment of the present invention provides a thin film sensor 201, as shown in fig. 3, on the basis of the thin film sensor 200, the following steps are added:

PDMS (polydimethylsiloxane) silicone gel 260 is injected into the cavity through the communication hole 221 on the case 220. The silicone gel 260 has good thixotropy and fluidity, and has good tensile property and shear resistance after being cured, and also has good light transmittance. The silicone gel 260 completely covers the leads and the bonding pads 240 exposed in the air, so that the film sensor 201 obtains a better moisture-proof effect under the condition of slight loss of sensitivity, and is suitable for application scenarios with high working environment humidity and low precision requirement on the film sensor 201.

The gel has strong fluidity, can be injected into the cavity through the communication hole 221 after the shell 220 is welded to the substrate 210 through reflow soldering, is not easy to splash and block in the injection process, has small strength after the gel is cured, has low requirement on the strength of the film, does not need the film to have larger rigidity, has smaller sensitivity loss of the film sensor 201, is suitable for application scenes of mass production, can be applied to moistureproof scenes with lower cost and lower requirement on precision

In summary, the thin film sensor according to the embodiment of the present invention can solve the moisture-proof problem of the thin film sensor from the wafer level by coating the self-assembled monolayer, and meanwhile, the self-assembled monolayer has a small thickness, has a low influence on the sensitivity of the MEMS thin film, and has a small sensitivity of the thin film sensor due to the loss of the self-assembled monolayer.

Optionally, after the housing is welded to the substrate, PDMS silicone gel is injected into the cavity through the communication hole on the housing to cover the lead and the pad exposed in the air, on the premise that the sensitivity of the loss is within an acceptable range, the thin film sensor can obtain a better moisture-proof effect to be applied in a scene where the humidity of a working environment is high and the precision requirement on the thin film sensor is not high, and meanwhile, the silicone gel is injected into the cavity through the communication hole to be compatible with a reflow soldering process, so that the moisture-proof film sensor is suitable for an application scene of mass production and can be applied to a moisture-proof scene with lower cost and lower precision requirement.

It should be noted that as used herein, the words "during", "when" and "when … …" in relation to the operation of a circuit are not strict terms indicating an action that occurs immediately upon the start of a startup action, but rather there may be some small but reasonable delay or delays, such as various transmission delays, between it and the reaction action (action) initiated by the startup action. The words "about" or "substantially" are used herein to mean that the value of an element (element) has a parameter that is expected to be close to the stated value or position. However, as is well known in the art, there is always a slight deviation that makes it difficult for the value or position to be exactly the stated value. It has been well established in the art that a deviation of at least ten percent (10%) for a semiconductor doping concentration of at least twenty percent (20%) is a reasonable deviation from the exact ideal target described. When used in conjunction with a signal state, the actual voltage value or logic state (e.g., "1" or "0") of the signal depends on whether positive or negative logic is used.

In accordance with the present invention, as described above, these embodiments do not set forth all of the details or limit the utility model to only the specific embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the utility model and the practical application, to thereby enable others skilled in the art to best utilize the utility model and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the utility model should be determined with reference to the appended claims and their equivalents.

Claims

1. A thin film sensor, comprising:

a substrate;

a case located above a substrate, a cavity being formed between the case and the substrate, the case including a communication hole communicating the cavity with an outside;

a chip located on the substrate and in the cavity;

the hydrophobic membrane is coated on the outer surfaces of the substrate and the chip; and

the gel is filled in the cavity, and the upper surface of the gel is higher than that of the chip.

2. The thin film sensor of claim 1, the hydrophobic membrane is selected from self-assembled monomolecular membranes.

3. The thin film sensor of claim 2, wherein the self-assembled monolayer is formed from a material selected from the group consisting of 1H,1H,2H, 2H-perfluorodecyltrichlorosilane.

4. The thin film sensor of claim 1, the substrate being selected from a PCB substrate.

5. The thin film sensor of claim 1, the chip comprising:

an application specific integrated circuit located over the substrate,

a micro-electro-mechanical system (MEMS) on the ASIC, the MEMS including a thin film for sensing a signal of an external environment.

6. The thin film sensor of claim 1, said gel being selected from polydimethylsiloxane silicone gel.

7. The thin film sensor of claim 1, which is selected from any one of a gas sensitive thin film sensor, a light sensitive thin film sensor, and a thin film acoustic sensor.

8. The thin film sensor of claim 7, in a grid array package.