Membrane-based pressure sensor and method of manufacturing the same

Abstract

This disclosure presents a MEMS pressure sensor and its fabrication method. It includes: a first substrate, a buffer layer and a light-emitting diode (LED) sequentially disposed on its first surface, a passivation layer, a first lead, and a pad sequentially disposed on the second surface of the first substrate, and a first connection layer surrounding the LED; the first substrate has a pressure-transmitting window; a second substrate, a pressure-sensitive film and a second connection layer sequentially disposed on its first surface; the second substrate has a cavity penetrating its thickness, the cavity corresponding to the LED, and the area of ​​the pressure-sensitive film corresponding to the cavity is light-transmitting; a third substrate, a photoresistor layer disposed on its first surface and located within the cavity, a second lead and a pad disposed on the second surface of the third substrate and electrically connected to the photoresistor layer; the first surface of the third substrate is connected to the second surface of the second substrate. This effectively improves the sensor's accuracy, measurement range, and precision.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of pressure sensor technology, specifically relating to a MEMS pressure sensor and its fabrication method. Background Technology

[0002] In the field of pressure measurement, MEMS pressure sensors have replaced traditional pressure sensors due to their advantages such as small size, high sensitivity, and fast frequency response. Among them, MEMS piezoresistive pressure sensors are the most widely used. They rely on the bending of the pressure-sensitive film to generate stress in the piezoresistive strip area, thereby changing the resistance of the piezoresistive strip to achieve pressure measurement.

[0003] However, the pressure-sensitive film of a MEMS piezoresistive pressure sensor exhibits a deflection effect. This results in a very complex functional relationship between the pressure it experiences during bending (the sensor's input pressure) and the stress it generates. Furthermore, the output voltage of a MEMS piezoresistive pressure sensor is directly determined by the stress generated on the pressure-sensitive film. Therefore, the functional relationship between the output voltage and the input pressure of a MEMS piezoresistive pressure sensor is also very complex, as shown in the following formula:

[0004]

[0005]

[0006] Where P is the sensor input pressure, and V out C0 is the sensor output voltage, K1, K2, K3, and K4 are all constants.

[0007] Clearly, the aforementioned functional relationship cannot be used to fit test data from MEMS piezoresistive pressure sensors. Furthermore, when a linear function is used to replace the fitting of MEMS piezoresistive pressure sensor test data, it introduces errors into the sensor's calibration, leading to nonlinear errors in the measurement. These errors increase with the input pressure of the MEMS piezoresistive pressure sensor, severely reducing its accuracy and measurement range.

[0008] Furthermore, the formation of the pressure-sensitive thin film in a MEMS piezoresistive pressure sensor requires the fabrication of a sealed cavity beneath it. The fabrication of this sealed cavity requires bonding the silicon substrate and glass substrate of the MEMS piezoresistive pressure sensor together to form a bonding interface. This bonding interface generates bonding thermal stress at the operating temperature, which is transferred to the pressure-sensitive thin film, causing temperature drift in the MEMS piezoresistive pressure sensor and further reducing its accuracy. Summary of the Invention

[0009] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and disclose a MEMS pressure sensor and its fabrication method.

[0010] In a first aspect, embodiments of this disclosure provide a MEMS pressure sensor, the MEMS pressure sensor comprising:

[0011] A first substrate, a buffer layer disposed on a first surface of the first substrate, a light-emitting diode disposed on a surface of the buffer layer opposite to the first substrate, a passivation layer disposed on a second surface of the first substrate, a first lead and pad disposed on a surface of the passivation layer opposite to the first substrate and electrically connected to the light-emitting diode, and a first connection layer surrounding the light-emitting diode, wherein a pressure transmission window is provided at a corresponding position of the first substrate and the passivation layer.

[0012] The second substrate includes a pressure-sensitive film disposed on a first surface of the second substrate and a second connecting layer disposed on a surface of the pressure-sensitive film opposite to the second substrate and connected to the first connecting layer; the second substrate has a cavity extending through its thickness, the cavity corresponding to the light-emitting diode, and the area of ​​the pressure-sensitive film corresponding to the cavity is light-transmitting;

[0013] A third substrate, a photoresistor layer disposed on the first surface of the third substrate and located in the cavity, a second lead and a pad disposed on the second surface of the third substrate and electrically connected to the photoresistor layer; the first surface of the third substrate is connected to the second surface of the second substrate.

[0014] In some embodiments, the photoresistor layer includes an outer photoresistor and an inner photoresistor, wherein the outer photoresistor and the inner photoresistor are connected in series to form a detection circuit.

[0015] In some embodiments, both the outer photoresistor and the inner photoresistor are photoresistors with an open circular ring structure.

[0016] In some embodiments, the resistance and area of ​​the outer photoresistor and the inner photoresistor are equal.

[0017] In some embodiments, the inner photoresistor includes a first inner photoresistor and a second inner photoresistor located inside the first inner photoresistor.

[0018] The first inner photoresistor is connected in series with the second inner photoresistor.

[0019] In some embodiments, the first surface of the third substrate is bonded to the second surface of the second substrate, and the second bonding layer is bonded to the first bonding layer.

[0020] In some embodiments, the light-emitting diode includes an N-type light-emitting diode layer, a multiple quantum well layer, and a P-type light-emitting diode layer sequentially disposed on the buffer layer;

[0021] The N-type layer and the P-type layer of the light-emitting diode are electrically connected to the first lead and the pad, respectively.

[0022] In some embodiments, the input pressure and output voltage of the MEMS pressure sensor satisfy the following relationship:

[0023]

[0024] Where P is the input pressure of the MEMS pressure sensor, Vout is the output voltage of the MEMS pressure sensor, and K5, K6, and K7 are all constants.

[0025] In some embodiments, the thickness of the pressure-sensitive film ranges from 10 μm to 200 μm; and / or, the thickness of the photoresistor layer ranges from 1 μm to 50 μm.

[0026] Secondly, embodiments of this disclosure provide a method for fabricating a MEMS pressure sensor as described above, the method comprising:

[0027] Provide a first substrate;

[0028] A buffer material layer is deposited on the first surface of the first substrate, and the buffer material layer is etched to form a buffer layer;

[0029] A light-emitting diode N-type material layer is deposited on the first surface of the first substrate, and the N-type material layer is etched to form a light-emitting diode N-type layer;

[0030] An isolation layer is deposited and etched on the outside of the N-type layer of the light-emitting diode on the first surface of the first substrate, the isolation layer being used to isolate the N-type layer of the light-emitting diode and the P-type layer of the light-emitting diode;

[0031] A multi-quantum well material layer is deposited on the first surface of the first substrate, and the multi-quantum well material layer is etched to form a multi-quantum well layer;

[0032] A light-emitting diode P-type material layer is deposited on the first surface of the first substrate, and the P-type material layer is etched to form a light-emitting diode P-type layer;

[0033] A first bonding material layer is deposited on the first surface of the first substrate;

[0034] Deep vias are formed by etching the second surface of the first substrate.

[0035] A passivation material layer is deposited on the second surface of the first substrate and the inner wall of the deep through-hole to form a passivation layer;

[0036] A metal material layer is deposited on the second surface of the first substrate and in the deep via, and the metal material layer on the second surface of the first substrate is etched to form a first lead and a pad.

[0037] The first bonding material layer on the first surface of the first substrate is etched to form the first bonding layer, and the P-type layer of the light-emitting diode is exposed.

[0038] The passivation layer on the second surface of the first substrate is etched to form two square openings to expose the first substrate;

[0039] The exposed first substrate is wet-etched to form a pressure transmission window;

[0040] A second substrate is provided; wherein the second substrate is an SOI wafer;

[0041] The device layer of the SOI wafer is etched to form a second interconnect layer, and the substrate layer of the SOI wafer is then wet-etched to form a pressure-sensitive thin film and a cavity.

[0042] The first surface of the second substrate is anodicly bonded to the first surface of the first substrate;

[0043] Provide a third substrate;

[0044] The third substrate is etched to form a deep via, and then a metal layer is sputtered and etched on the second surface of the third substrate to form a second lead and a pad.

[0045] A photoresistor material layer is deposited on the first surface of the third substrate, and the photoresistor material layer is etched to form a photoresistor;

[0046] The first surface of the third substrate is anodicly bonded to the second surface of the second substrate to form a sealed cavity, thereby fabricating a MEMS pressure sensor.

[0047] The MEMS pressure sensor and its fabrication method disclosed herein have the following advantages compared with traditional MEMS piezoresistive pressure sensors:

[0048] 1. The MEMS pressure sensor of this embodiment has a relatively simple functional relationship between the output voltage and the input pressure. This functional relationship can be used to fit the sensor test data, so that the sensor does not have nonlinear error that increases with the increase of input pressure, effectively improving the accuracy and range of the sensor.

[0049] 2. In the MEMS pressure sensor of this embodiment, the upper and lower surfaces of the second substrate are anodicly bonded and fixed to form a bonding interface. The bonding thermal stress generated by these two bonding interfaces is equal in magnitude and opposite in direction for the second substrate and the pressure-sensitive film. Therefore, they can cancel each other out, thereby eliminating the temperature drift caused by the bonding thermal stress of the sensor and further improving the sensor accuracy.

[0050] 3. The MEMS pressure sensor of this disclosure can adjust the intensity of parallel light incident on the central circular region of the pressure-sensitive film by adjusting the current on the circular light-emitting diode, thereby adjusting the sensitivity and range of the sensor, which greatly improves the flexibility of the sensor. Attached Figure Description

[0051] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements are not necessarily drawn to scale.

[0052] Figure 1 This is a cross-sectional view of a MEMS pressure sensor according to an embodiment of this disclosure;

[0053] Figure 2 for Figure 1 A top view of the MEMS pressure sensor shown;

[0054] Figures 3 to 30 This is a process flow diagram of the fabrication method of the MEMS pressure sensor according to an embodiment of the present disclosure;

[0055] Figure 31 This is a detection circuit diagram showing the connection of photoresistors according to an embodiment of the present disclosure. Detailed Implementation

[0056] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0058] It should also be noted that, for ease of description, only the parts relevant to this disclosure are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0059] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0060] like Figure 1 and Figure 2 As shown, embodiments of this disclosure relate to a MEMS acceleration and pressure integrated sensor, including: a first lead and pad 1, a passivation layer 2, a first substrate 3, a buffer layer 4, a light-emitting diode N-type layer 5, a multiple quantum well layer 6, a light-emitting diode P-type layer 7, a first connection layer 8, a second connection layer 10, a pressure-sensitive film 11, a second substrate 12, a photoresistor layer 14, a third substrate 15, and a second lead and pad.

[0061] For example, such as Figure 1 and Figure 2 As shown, the first lead and pad 1 are located on the top layer of the MEMS pressure sensor, and the second lead and pad 16 are located on the bottom layer. In some embodiments, the materials of the first lead and pad 1 and the second lead and pad 16 are at least one of aluminum, copper, platinum, titanium, gold, etc., and the thickness of both the first lead and pad 1 and the second lead and pad 16 ranges from 50nm to 500nm. The first lead and pad 1 are connected to the N-type layer 5 of the light-emitting diode and the P-type layer 7 of the light-emitting diode through vias in the passivation layer 2, respectively. The second lead and pad 16 are electrically connected to the photoresistor layer 14 through vias in the third substrate 15.

[0062] Continue to refer to Figure 1 and Figure 2 The passivation layer 2 is located below the first lead and pad 1. In some embodiments, the material of the passivation layer 2 is at least one of silicon oxide or silicon nitride, and the thickness of the passivation layer 2 ranges from 100 nm to 5000 nm. The first substrate 3 is located below the passivation layer 2. In some embodiments, the material of the first substrate 3 is one of monocrystalline silicon or polycrystalline silicon, and the thickness of the first substrate 3 ranges from 400 μm to 1000 μm. The first substrate 3 has two cylindrical deep through holes, and the inner walls of the deep through holes are covered with the passivation layer 2.

[0063] Next, as Figure 1 and Figure 2 As shown, the buffer layer 4 is located below the first substrate 3. In some embodiments, the material of the buffer layer 4 is one of silicon carbide or aluminum nitride, and the thickness of the buffer layer 4 ranges from 100 nm to 2000 nm. The function of the buffer layer 4 is to isolate the first substrate 3 so as to grow a high-quality light-emitting diode N-type layer 5.

[0064] Continue to refer to Figure 1 and Figure 2 Below the buffer layer 4, the N-type layer 5, the multiple quantum well layer 6, and the P-type layer 7 of the light-emitting diode are arranged sequentially. These three layers together constitute a circular light-emitting diode. Of course, in addition to these, the light-emitting diode may also include other material layers, and this embodiment is not limited in this regard. In some embodiments, the material of the N-type layer 5 of the light-emitting diode is one of N-type doped gallium nitride, gallium arsenide, and zinc selenide, and the thickness of the N-type layer ranges from 50 nm to 1000 nm; the material of the multiple quantum well layer 6 is one of aluminum indium gallium nitride, and the thickness ranges from 0.5 μm to 10 μm, which can adjust the wavelength of the parallel light emitted downward by the circular light-emitting diode; the material of the P-type layer 7 of the light-emitting diode is one of P-type doped gallium nitride, gallium arsenide, and zinc selenide, and the thickness ranges from 50 nm to 1000 nm.

[0065] Immediately afterwards, such as Figure 1 and Figure 2 As shown, the structure protruding downwards around the perimeter of the aforementioned circular light-emitting diode is the first connecting layer 8. In some embodiments, the material of the first connecting layer 8 is silicon oxide, etc., and its thickness ranges from 10μm to 200μm. The two square areas above this layer, which are not covered by any material, form the pressure transmission window 9, as shown. Figure 20 As shown; below this layer is the second interconnecting layer 10. In some embodiments, the material of the second interconnecting layer 10 is either monocrystalline silicon or polycrystalline silicon, and its thickness ranges from 10 μm to 200 μm. The first interconnecting layer 8 and the second interconnecting layer 10 are connected together by an anodic bonding process.

[0066] Continue to refer to Figure 1 and Figure 2 The pressure-sensitive film 11 is located below the second connecting layer 10. In some embodiments, the pressure-sensitive film is made of a transparent material such as silicon oxide, and its thickness ranges from 10 μm to 200 μm. The parallel light emitted by the circular light-emitting diode passes only through the central circular region of the pressure-sensitive film 11, below which is a sealed cavity 13.

[0067] Next, as Figure 1 and Figure 2 As shown, the second substrate 12 is located below the pressure-sensitive film 11. In some embodiments, the material of the second substrate 12 is one of monocrystalline silicon or polycrystalline silicon, and the thickness ranges from 450μm to 2000μm. This layer is bonded together with the third substrate 15 below it to form a frustum-shaped closed cavity 13.

[0068] Continue to refer to Figure 1 and Figure 2The photoresistor layer 14 is located in the unbonded circular region in the middle of the upper surface of the third substrate 15. In some embodiments, the material of the photoresistor layer 14 is one of cadmium sulfide, aluminum sulfide, lead sulfide, or bismuth sulfide, and the thickness ranges from 1 μm to 50 μm. In some preferred embodiments, such as... Figure 28 As shown, the photoresistor layer 14 consists of three unclosed circular ring-shaped resistors: outer, middle, and inner. The resistor in the outer unclosed circular ring is called the outer photoresistor, and the resistors in the middle and inner unclosed circular rings connected in series form the inner photoresistor. The resistance and area of ​​the outer and inner photoresistors are equal, and they are connected in series to form a detection circuit, such as... Figure 31 As shown.

[0069] The working principle of the MEMS pressure sensor according to the embodiments of this disclosure will be explained below:

[0070] like Figure 1 and Figure 2 As shown, before the input pressure is applied to the MEMS pressure sensor, the circular light-emitting diode in the MEMS pressure sensor is supplied with a suitable voltage to emit parallel light downwards. This parallel light passes through the circular area in the middle of the pressure-sensitive film 11 and continues to illuminate the photoresistor layer 14 along the previous light path (the material constituting the pressure-sensitive film 11 is transparent, so the circular area in the middle of the pressure-sensitive film 11 is a circular plane lens). Because the area of ​​the inner and outer photoresistors is the same as the light intensity illuminating these two photoresistors, the resistance changes of the inner and outer photoresistors are equal, and the detection circuit does not generate an output voltage. However, when the input pressure is applied to the pressure-sensitive film 11 of the sensor through the pressure transmission window 9, the circular suspended area in the middle of the film bends downwards to form a curved lens. The curved lens, together with the medium above it (depending on the package type), forms a plano-convex lens, which refracts the parallel light from the circular light-emitting diode. This causes the light illuminating the circular area of ​​the photoresistor layer 14 to concentrate towards the center, increasing the light intensity received by the inner photoresistor and decreasing the light intensity received by the outer photoresistor. The resistance values ​​of the two photoresistors change in opposite directions, and the detection circuit generates an output voltage, thereby completing the detection of the input pressure.

[0071] Based on the above, it can be seen that the output voltage of the MEMS sensor is directly determined by the light intensity difference between the two photoresistors. This light intensity difference is related to the refraction of parallel light by the circular region in the middle of the pressure-sensitive film 11 after bending, while the bending of the pressure-sensitive film 11 is related to the input pressure of the sensor. These three relatively simple functional relationships make the functional relationship between the sensor's output voltage and input pressure relatively simple, as shown in the following formula:

[0072]

[0073] Where P is the input pressure of the MEMS pressure sensor, Vout is the output voltage of the MEMS pressure sensor, and K5, K6, and K7 are all constants.

[0074] It is easy to see from the above formula that the function of sensor output voltage and input pressure can be used to fit sensor test data, eliminating the nonlinear error that occurs in MEMS piezoresistive pressure sensors, and effectively improving the sensor's measurement accuracy and range.

[0075] In addition, the upper and lower surfaces of the second substrate 12 of the sensor are anodicly bonded and fixed to form a bonding interface. The bonding thermal stress generated by these two bonding interfaces is equal in magnitude and opposite in direction for the second substrate 12 and the pressure-sensitive film 11. Therefore, they can cancel each other out, thereby eliminating the temperature drift caused by the bonding thermal stress of the sensor and further improving the sensor accuracy.

[0076] In summary, the MEMS pressure sensor of the present disclosure has the following advantages compared with conventional MEMS piezoresistive pressure sensors:

[0077] 1. The MEMS pressure sensor of this embodiment has a relatively simple functional relationship between the output voltage and the input pressure. This functional relationship can be used to fit the sensor test data, so that the sensor does not have nonlinear error that increases with the increase of input pressure, effectively improving the accuracy and range of the sensor.

[0078] 2. In the MEMS pressure sensor of this embodiment, the upper and lower surfaces of the second substrate are anodicly bonded and fixed to form a bonding interface. The bonding thermal stress generated by these two bonding interfaces is equal in magnitude and opposite in direction for the second substrate and the pressure-sensitive film. Therefore, they can cancel each other out, thereby eliminating the temperature drift caused by the bonding thermal stress of the sensor and further improving the sensor accuracy.

[0079] 3. The MEMS pressure sensor of this disclosure can adjust the intensity of parallel light incident on the central circular region of the pressure-sensitive film by adjusting the current on the circular light-emitting diode, thereby adjusting the sensitivity and range of the sensor, which greatly improves the flexibility of the sensor.

[0080] Based on the same inventive concept, embodiments of this disclosure also provide a method for fabricating a MEMS pressure sensor as described above. The specific structure of this MEMS pressure sensor can be found in the preceding description and will not be repeated here. The method specifically includes the following steps:

[0081] Step 1: Provide the first substrate.

[0082] Specifically, in this step, such as Figure 3As shown, prepare a P-type silicon wafer, which is the first substrate 3.

[0083] Step 2: Deposit a buffer material layer on the first surface of the first substrate, and etch the buffer material layer to form a buffer layer.

[0084] Specifically, in this step, such as Figure 4 and Figure 5 As shown, an aluminum nitride layer is deposited on the upper surface of the first substrate 3, and the aluminum nitride layer is etched to form a buffer layer 4.

[0085] Step 3: Deposit an N-type material layer for light-emitting diodes on the first surface of the first substrate, and etch the N-type material layer to form an N-type layer for light-emitting diodes.

[0086] Specifically, in this step, such as Figure 6 As shown, an N-type gallium nitride layer is deposited on the upper surface of the first substrate 3, and the N-type gallium nitride layer is etched to form the N-type layer 5 of the light-emitting diode.

[0087] Step 4: Deposit and etch an isolation layer on the outside of the N-type layer of the light-emitting diode on the first surface of the first substrate. The isolation layer is used to isolate the N-type layer of the light-emitting diode and the P-type layer of the light-emitting diode.

[0088] Specifically, in this step, such as Figure 7 and Figure 8 As shown, an aluminum nitride layer is deposited and etched on the upper right surface of the first substrate 3 to isolate the N-type layer 5 of the light-emitting diode from the P-type layer 7 of the light-emitting diode.

[0089] Step 5: Deposit a multi-quantum well material layer on the first surface of the first substrate, and etch the multi-quantum well material layer to form a multi-quantum well layer.

[0090] Specifically, in this step, such as Figure 9 As shown, an aluminum indium gallium nitride layer is deposited on the upper surface of the first substrate 3, and the aluminum indium gallium nitride layer is etched to form the multi-quantum well layer 6.

[0091] Step 6: Deposit a P-type material layer for light-emitting diodes on the first surface of the first substrate, and etch the P-type material layer to form a P-type layer for light-emitting diodes.

[0092] Specifically, in this step, such as Figure 10 As shown, a layer of P-type gallium nitride is deposited on the upper surface of the first substrate 3, and the P-type gallium nitride layer is etched to form the P-type layer 7 of the light-emitting diode.

[0093] Step 7: Deposit a first bonding material layer on the first surface of the first substrate.

[0094] Specifically, in this step, such as Figure 11 As shown, a thick layer of silicon oxide is deposited on the upper surface of the first substrate 3, which is the subsequent first interconnect layer 8.

[0095] Step 8: Etch the second surface of the first substrate to form a deep via.

[0096] Specifically, in this step, such as Figure 12 and Figure 13 As shown, the lower surface of the first substrate 3 is etched to form a deep through-hole.

[0097] Step 9: Deposit a passivation material layer on the second surface of the first substrate and the inner wall of the deep via to form a passivation layer.

[0098] Specifically, in this step, such as Figure 14 As shown, a layer of silicon nitride is deposited on the lower surface of the first substrate 3 and the inner wall of the deep through-hole, which is the passivation layer 2.

[0099] Step 10: Deposit a metal material layer on the second surface of the first substrate and in the deep via, and etch the metal material layer on the second surface of the first substrate to form the first lead and pad.

[0100] Specifically, in this step, such as Figure 15 and Figure 16 As shown, a layer of metallic aluminum is sputtered onto the lower surface of the first substrate 3 and into the deep via, and then the aluminum on the lower surface of the first substrate 3 is etched. This forms the first lead and pad 1.

[0101] Step 11: Etch the first bonding material layer on the first surface of the first substrate to form the first bonding layer and expose the P-type layer of the light-emitting diode.

[0102] Specifically, in this step, such as Figure 17 and Figure 18 As shown, the silicon oxide layer on the upper surface of the first substrate 3 is etched to form the first interconnect layer 8, and the light-emitting diode P-type layer 7 is exposed.

[0103] Step 12: Etch the passivation layer on the second surface of the first substrate to form two square openings to expose the first substrate.

[0104] Specifically, in this step, such as Figure 19 As shown, the passivation layer 2 on the lower surface of the first substrate 3 is etched to form two square openings to expose the silicon in the first substrate 3.

[0105] Step 13: Perform wet etching on the exposed first substrate to form a pressure transmission window.

[0106] Specifically, in this step, such as Figure 20 As shown, the exposed silicon layer on the lower surface of the first substrate 3 is wet-etched to form the pressure transmission window 9.

[0107] Step 14: Provide a second substrate; wherein the second substrate is an SOI wafer.

[0108] Specifically, in this step, such as Figure 21 As shown, the second substrate is an SOI wafer, which includes a substrate layer (second substrate 12), a buried oxide layer (to be subsequently used to form a pressure-sensitive thin film 11) and a device layer (to be subsequently used to form a second interconnect layer 10) stacked sequentially.

[0109] Step 15: Etch the device layer of the SOI wafer to form a second interconnect layer, and then perform wet etching on the substrate layer of the SOI wafer to form a pressure-sensitive thin film and a cavity.

[0110] Specifically, in this step, such as Figure 22 and Figure 23 As shown, the device layer of the SOI wafer is etched to form the second interconnect layer 10, and then the substrate layer (the second substrate 12) of the SOI wafer is wet-etched to form the pressure-sensitive thin film 11 and the frustum-shaped cavity.

[0111] Step 16: Anodicly bond the first surface of the second substrate to the first surface of the first substrate.

[0112] Specifically, in this step, such as Figure 24 As shown, the upper surface of the second substrate 12 is anodicly bonded to the upper surface of the first substrate 3.

[0113] Step 17: Provide a third substrate.

[0114] Specifically, in this step, such as Figure 25 As shown, a piece of borosilicate glass is prepared as the third substrate 15.

[0115] Step 18: Etch the third substrate to form a deep via, and then sputter and etch a metal layer on the second surface of the third substrate to form a second lead and pad.

[0116] Specifically, in this step, such as Figure 26 As shown, the third substrate 15 is etched to form a deep via, and then aluminum is sputtered and etched on the lower surface of the third substrate 15 to form the second lead and pad 16.

[0117] Step 19: Deposit a photoresistor material layer on the first surface of the third substrate, and etch the photoresistor material layer to form a photoresistor.

[0118] Specifically, in this step, such as Figures 27 to 29 As shown, a layer of cadmium sulfide is deposited on the upper surface of the third substrate 15, and the cadmium sulfide layer is etched to form the photoresistor layer 14.

[0119] Step 20: Anodicly bond the first surface of the third substrate to the second surface of the second substrate to form a sealed cavity, thereby fabricating a MEMS pressure sensor.

[0120] Specifically, in this step, such as Figure 30 As shown, the upper surface of the third substrate 15 is anodicly bonded to the lower surface of the second substrate 12 to form the sealed cavity 13, thereby completing the preparation of the present invention.

[0121] Compared with conventional MEMS piezoresistive pressure sensors, the MEMS pressure sensor of the present disclosure has the following advantages:

[0122] 1. The MEMS pressure sensor of this embodiment has a relatively simple functional relationship between the output voltage and the input pressure. This functional relationship can be used to fit the sensor test data, so that the sensor does not have nonlinear error that increases with the increase of input pressure, effectively improving the accuracy and range of the sensor.

[0123] 2. In the MEMS pressure sensor of this embodiment, the upper and lower surfaces of the second substrate are anodicly bonded and fixed to form a bonding interface. The bonding thermal stress generated by these two bonding interfaces is equal in magnitude and opposite in direction for the second substrate and the pressure-sensitive film. Therefore, they can cancel each other out, thereby eliminating the temperature drift caused by the bonding thermal stress of the sensor and further improving the sensor accuracy.

[0124] 3. The MEMS pressure sensor of this disclosure can adjust the intensity of parallel light incident on the central circular region of the pressure-sensitive film by adjusting the current on the circular light-emitting diode, thereby adjusting the sensitivity and range of the sensor, which greatly improves the flexibility of the sensor.

[0125] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A MEMS pressure sensor, characterized by, The MEMS pressure sensor includes: A first substrate, a buffer layer disposed on a first surface of the first substrate, a light-emitting diode disposed on a surface of the buffer layer opposite to the first substrate, a passivation layer disposed on a second surface of the first substrate, a first lead and pad disposed on a surface of the passivation layer opposite to the first substrate and electrically connected to the light-emitting diode, and a first connection layer surrounding the light-emitting diode, wherein a pressure transmission window is provided at a corresponding position of the first substrate and the passivation layer. The second substrate includes a pressure-sensitive film disposed on a first surface of the second substrate and a second connecting layer disposed on a surface of the pressure-sensitive film opposite to the second substrate and connected to the first connecting layer; the second substrate has a cavity extending through its thickness, the cavity corresponding to the light-emitting diode, and the area of ​​the pressure-sensitive film corresponding to the cavity is light-transmitting; A third substrate, a photoresistor layer disposed on the first surface of the third substrate and located in the cavity, a second lead and a pad disposed on the second surface of the third substrate and electrically connected to the photoresistor layer; the first surface of the third substrate is connected to the second surface of the second substrate.

2. The MEMS pressure sensor of claim 1, wherein, The photoresistor layer includes an outer photoresistor and an inner photoresistor, and the outer photoresistor and the inner photoresistor are connected in series to form a detection circuit.

3. The MEMS pressure sensor of claim 2, wherein, Both the outer and inner photoresistors are photoresistors with an open circular ring structure.

4. The MEMS pressure sensor of claim 2, wherein, The resistance and area of ​​the outer photoresistor and the inner photoresistor are equal.

5. The MEMS pressure sensor according to claim 2, characterized in that, The inner photoresistor includes a first inner photoresistor and a second inner photoresistor located inside the first inner photoresistor. The first inner photoresistor is connected in series with the second inner photoresistor.

6. The MEMS pressure sensor according to any one of claims 1 to 5, characterized in that, The first surface of the third substrate is bonded to the second surface of the second substrate, and the second bonding layer is bonded to the first bonding layer.

7. The MEMS pressure sensor according to any one of claims 1 to 5, characterized in that, The light-emitting diode includes an N-type light-emitting diode layer, a multiple quantum well layer, and a P-type light-emitting diode layer sequentially disposed in the buffer layer; The N-type layer and the P-type layer of the light-emitting diode are electrically connected to the first lead and the pad, respectively.

8. The MEMS pressure sensor according to any one of claims 1 to 5, characterized in that, The input pressure and output voltage of the MEMS pressure sensor satisfy the following relationship: Where P is the input pressure of the MEMS pressure sensor, Vout is the output voltage of the MEMS pressure sensor, and K5, K6, and K7 are all constants.

9. The MEMS pressure sensor according to any one of claims 1 to 5, characterized in that, The thickness of the pressure-sensitive film ranges from 10 μm to 200 μm; and / or the thickness of the photoresistor layer ranges from 1 μm to 50 μm.

10. A method for fabricating a MEMS pressure sensor as described in any one of claims 1 to 9, characterized in that, The method includes: Provide a first substrate; A buffer material layer is deposited on the first surface of the first substrate, and the buffer material layer is etched to form a buffer layer; A light-emitting diode N-type material layer is deposited on the first surface of the first substrate, and the N-type material layer is etched to form a light-emitting diode N-type layer; An isolation layer is deposited and etched on the outside of the N-type layer of the light-emitting diode on the first surface of the first substrate, the isolation layer being used to isolate the N-type layer of the light-emitting diode and the P-type layer of the light-emitting diode; A multi-quantum well material layer is deposited on the first surface of the first substrate, and the multi-quantum well material layer is etched to form a multi-quantum well layer; A light-emitting diode P-type material layer is deposited on the first surface of the first substrate, and the P-type material layer is etched to form a light-emitting diode P-type layer; A first bonding material layer is deposited on the first surface of the first substrate; Deep vias are formed by etching the second surface of the first substrate. A passivation material layer is deposited on the second surface of the first substrate and the inner wall of the deep through-hole to form a passivation layer; A metal material layer is deposited on the second surface of the first substrate and in the deep via, and the metal material layer on the second surface of the first substrate is etched to form a first lead and a pad. The first bonding material layer on the first surface of the first substrate is etched to form the first bonding layer, and the P-type layer of the light-emitting diode is exposed. The passivation layer on the second surface of the first substrate is etched to form two square openings to expose the first substrate; The exposed first substrate is wet-etched to form a pressure transmission window; A second substrate is provided; wherein the second substrate is an SOI wafer; The device layer of the SOI wafer is etched to form a second interconnect layer, and the substrate layer of the SOI wafer is then wet-etched to form a pressure-sensitive thin film and a cavity. The first surface of the second substrate is anodicly bonded to the first surface of the first substrate; Provide a third substrate; The third substrate is etched to form a deep via, and then a metal layer is sputtered and etched on the second surface of the third substrate to form a second lead and a pad. A photoresistor material layer is deposited on the first surface of the third substrate, and the photoresistor material layer is etched to form a photoresistor; The first surface of the third substrate is anodicly bonded to the second surface of the second substrate to form a sealed cavity, thereby fabricating a MEMS pressure sensor.

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