A multi-channel GaN pressure sensor device and a method of manufacturing the same

Abstract

The application discloses a multi-channel GaN pressure sensor device and a preparation method thereof. The device comprises, from bottom to top, a substrate, a channel structure layer, a gate electrode arranged on the channel structure layer, and a source electrode and a drain electrode arranged on both sides of the channel structure layer. The channel structure layer is composed of a plurality of stacked GaN layers and AlGaN barrier layers, and the GaN layer is arranged below the AlGaN barrier layer. The multi-channel pressure sensor formed by stacking the AlGaN / GaN material multiple times can greatly improve the related performance parameters in the micro-nano scale, has high sensitivity, high reliability and low detection limit.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a multi-channel GaN pressure sensor and its fabrication method. Background Technology

[0002] Pressure sensors are transducers that convert pressure signals into readily observable electrical signals, and are widely used in all aspects of life. Currently, semiconductor pressure sensors are mainly based on Si materials, utilizing the piezoresistive effect of silicon diffusion resistors. However, the diffusion process suffers from poor temperature stability, and at high temperatures, the diffusion resistor and the isolation PN junction of the substrate degrade, even undergoing punch-through, leading to complete failure. As a typical representative of wide-bandgap semiconductors, GaN boasts a bandgap of 3.4 eV, three times that of Si, along with higher saturated electron drift velocity, a larger critical breakdown electric field strength, and better thermal conductivity. More importantly, GaN can form AlGaN / GaN heterojunctions with AlGaN.

[0003] Due to the piezoelectric and self-polarization effects, AlGaN / GaN heterostructures form a high-concentration, high-electron-mobility two-dimensional electron gas (2-EDG) on the surface of the GaN channel layer, making them highly sensitive to external pressure changes and suitable as high-sensitivity pressure sensors. Pressure sensors employing AlGaN / GaN heterostructures primarily utilize the piezoelectric effects of AlGaN and GaN to convert pressure changes into changes in the concentration and mobility of the two-dimensional electron gas. As external pressure increases, the AlGaN barrier layer is typically under tensile stress because its lattice constant is smaller than that of the GaN layer. When an external force is applied to the film, the AlGaN / GaN heterostructure experiences compressive stress, pushing atoms in the AlGaN barrier layer closer together than those in the GaN layer. Therefore, the tensile stress in the AlGaN barrier layer decreases, the piezoelectric polarization weakens, and the channel electron density decreases. Furthermore, strain changes in the AlGaN barrier layer induce polarized Coulomb field (PCF) scattering, leading to a further decrease in electron mobility. In summary, under the action of external stress, the electron density and electron mobility of the channel decrease, and the channel current decreases.

[0004] In the absence of external pressure, the electrical parameters (source and drain voltages) of a multi-channel GaN pressure sensor are set to operate in the variable current linear region. In this state, the channel current is controlled by the gate-source voltage, and the drain-source current is measured. Under external pressure, the sensitivity of the multi-channel GaN pressure sensor can be obtained from the change in channel current with pressure. Currently, there are no multi-channel GaN pressure sensors available. At the micro / nano scale, traditional single-channel GaN pressure sensors suffer from low sensitivity, poor reliability, and high detection limits. Multi-channel GaN pressure sensors offer superior performance parameters that overcome these shortcomings. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] One object of the present invention is to provide a multichannel GaN pressure sensor.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a multi-channel GaN pressure sensor device, comprising a substrate, a channel structure layer, a gate disposed on the channel structure layer, and a source and a drain located on both sides of the channel structure layer, arranged sequentially from bottom to top;

[0009] The channel structure layer consists of multiple stacked GaN layers and AlGaN barrier layers. The GaN layer is located below the AlGaN barrier layer. When the channel structure layers are stacked, the upper GaN layer is in contact with the lower AlGaN barrier layer.

[0010] In a preferred embodiment of the multi-channel GaN pressure sensor of the present invention, the substrate material is silicon; the lower surface of the substrate is further provided with a groove, which is a standard back hole process for pressure sensors. Its main purpose is to allow the pressure to be released at the channel rather than on the substrate, so as to prevent the two-dimensional electron gas concentration at the channel from changing insignificantly.

[0011] As a preferred embodiment of the multi-channel GaN pressure sensor device of the present invention, the source and the drain are both Ti / Al / Ni / Au stacked layers, and the source and the drain cover all the multilayer stacked GaN layers and AlGaN barrier layers.

[0012] In a preferred embodiment of the multi-channel GaN pressure sensor of the present invention, the number of stacked GaN layers and AlGaN barrier layers is 3 to 10.

[0013] In a preferred embodiment of the multi-channel GaN pressure sensor of the present invention, the thickness of the GaN layer is 20-200 nm, and the thickness of the AlGaN barrier layer is 5-50 nm.

[0014] The thickness of the GaN layer gradually decreases from bottom to top.

[0015] In a preferred embodiment of the multi-channel GaN pressure sensor of the present invention, the GaN layer of the lowest channel structure layer is in contact with the substrate, and the gate forms a Schottky contact with the AlGaN barrier layer of the highest channel structure layer.

[0016] In a preferred embodiment of the multi-channel GaN pressure sensor of the present invention, the gate is a Ni / Au stack.

[0017] Another object of the present invention is to provide a method for fabricating a multi-channel GaN pressure sensor device as described above, comprising,

[0018] Multilayer stacked channel structure layers are formed on the surface of a silicon substrate using metal-organic chemical vapor deposition or molecular beam epitaxy. Each channel structure layer consists of stacked GaN layers and AlGaN barrier layers.

[0019] The stacked multilayer GaN / AlGaN layers are isolated on both sides by mesa isolation to achieve active region isolation; wherein, the active region is the area between the source and drain electrodes;

[0020] Source and drain electrodes are formed in the active region through photolithography, metal evaporation, and annealing processes.

[0021] The gate electrode is formed in the gate electrode region by photolithography and metal evaporation processes;

[0022] The main purpose of fabricating grooves on the lower surface of a silicon substrate is to ensure that the pressure is released at the channel rather than on the substrate, so as to ensure that the concentration of two-dimensional electron gas at the channel changes.

[0023] In a preferred embodiment of the fabrication method of the multi-channel GaN pressure sensor of the present invention, a groove is prepared on the lower surface of a silicon substrate. A photoresist layer is coated on the upper surface of the silicon substrate corresponding to the non-groove area using a photolithography process. The photoresist layer corresponding to the groove area is removed by exposure, development, and hardening processes to expose the pattern to be etched. The groove area is partially etched away by an etching process until a support layer of 1-3 μm thickness is etched down to form a groove. The photoresist layer is then removed.

[0024] In a preferred embodiment of the fabrication method of the multi-channel GaN pressure sensor of the present invention, the annealing is performed in a nitrogen atmosphere at 700–1000°C for 10–1000 s. Compared with the prior art, the present invention has the following beneficial effects:

[0025] The AlGaN / GaN heterostructure provided by this invention forms a high-concentration, high-electron-mobility two-dimensional electron gas (2-EDG) on the surface of the GaN channel layer due to piezoelectric and self-polarization effects. This makes it highly sensitive to external pressure changes. The piezoelectric effect of AlGaN and GaN can be used to convert pressure changes into changes in the concentration and mobility of the two-dimensional electron gas, thereby causing changes in the channel current. The multi-channel GaN pressure sensor provided by this invention exhibits better performance parameters (higher sensitivity, higher reliability, and lower detection limit) compared to traditional single-channel GaN pressure sensors at the micro / nano scale. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0027] Figure 1 This is a schematic diagram of the structure of a multi-channel GaN pressure sensor device according to an embodiment of the present invention.

[0028] Figure 2 This refers to the change in channel current of the multi-channel GaN pressure sensor in this embodiment of the invention with external pressure when the number of channels n=5.

[0029] Figure 3 In this embodiment of the invention, the multi-channel GaN pressure sensor has AlGaN / GaN and InAlN / GaN layers as its multi-channel structure layers. Under an external force F = 5mN, the channel current of the GaN pressure sensor varies with the number of channels.

[0030] Figure 4 This invention relates to a multi-channel GaN pressure sensor, showing the reliability variation of the GaN pressure sensor with different numbers of channels.

[0031] Figure 5 This invention relates to a multi-channel GaN pressure sensor, and describes the pressure limit that the GaN pressure sensor can detect under different numbers of channels.

[0032] Figure 6This invention relates to a multi-channel GaN pressure sensor device. Under different numbers of channels and different annealing temperatures, the channel current of the multi-channel GaN pressure sensor device changes. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] Example 1

[0037] See Figure 1 This is a schematic diagram of the structure of a multi-channel GaN pressure sensor device according to an embodiment of the present invention. The multi-channel GaN pressure sensor device according to an embodiment of the present invention includes a substrate, five stacked channel structure layers 200, a gate 300 disposed on the uppermost channel structure layer 200, and a source 400 and a drain 500 located on both sides of the channel structure layer 200, arranged sequentially from bottom to top.

[0038] The channel structure layer 200 is composed of stacked GaN layers 201 and AlGaN barrier layers 202. The GaN layer 201 is located below the AlGaN barrier layer 202. When the channel structure layers 200 are stacked, the upper GaN layer 201 is in contact with the lower AlGaN barrier layer 202. The thickness of the bottom GaN layer 201 is 100nm, and the thickness of each GaN layer decreases by 3nm from bottom to top. The thickness of the AlGaN barrier layer 202 is 20nm.

[0039] In this structure, the GaN layer 201 of the bottommost channel structure layer 200 is in contact with the substrate, and the gate 300 forms a Schottky contact with the AlGaN barrier layer 202 of the topmost channel structure layer 200. The gate 300 is a Ni / Au (50 / 150nm) stack.

[0040] Both source 400 and drain 500 are Ti / Al / Ni / Au stacks, and source 400 and drain 500 cover all 5 stacked channel structure layers 200.

[0041] The substrate material is silicon; a groove 101 is also provided on the lower surface of the substrate.

[0042] The specific manufacturing process of the above-mentioned multi-channel GaN pressure sensor is as follows:

[0043] (1) Five stacked channel structure layers 200 are formed on the surface of a silicon substrate by metal-organic chemical vapor epitaxy. Each channel structure layer 200 consists of stacked GaN layers 201 and AlGaN barrier layers 202. The thickness of the bottom GaN layer 201 is 100nm, and the thickness of each GaN layer decreases by 3nm from bottom to top. The thickness of the AlGaN barrier layer 202 is 20nm.

[0044] (2) Using a mixed gas of Cl2 and BCl3, an active region isolation is achieved by etching 700 nm on both sides of the 5-layer stacked channel structure layer 200 through an inductively coupled plasma etching system; wherein, the active region is the source-drain region.

[0045] (3) Source and drain electrodes are formed in the active region by photolithography, metal evaporation and annealing. Ti / Al / Ni / Au (20 / 150 / 50 / 50nm) stack is selected as the source and drain electrode metal, and ohmic contact is formed by annealing in a nitrogen atmosphere at 850℃ for 1 min.

[0046] (4) A Ni / Au gate electrode is formed in the gate electrode region by photolithography and metal evaporation processes. The Ni / Au gate electrode forms a good Schottky contact with the AlGaN barrier layer 202.

[0047] (5) A groove 101 is prepared on the lower surface of the silicon substrate to ensure that the pressure is released at the channel rather than on the substrate. A photoresist layer is coated on the upper surface of the silicon substrate corresponding to the non-groove 101 area by photolithography. After exposure, development and hardening processes, the photoresist layer corresponding to the groove 101 area is removed to expose the pattern to be etched. The part corresponding to the groove 101 area will be partially etched away by etching process to form groove 101 and remove the photoresist layer.

[0048] The source 400 voltage of the multi-channel GaN pressure sensor is set to 0V, the drain 500 voltage to 5V, and the gate 300 voltage to -4V, allowing the pressure sensor to operate in the variable current linear region. External pressure will cause changes in the channel current. The sensitivity of the multi-channel GaN pressure sensor can then be obtained from the change in current with pressure.

[0049] like Figure 2 As shown, the channel current of the multi-channel GaN pressure sensor in this embodiment of the invention varies with external pressure when the number of channels n=5.

[0050] Example 2

[0051] Referring to the manufacturing process of Example 1, pressure sensors with n (1 to 8) channels were fabricated, and the corresponding source 400, drain 500 and gate 300 voltages were set.

[0052] like Figure 3 In this embodiment of the invention, when an external force F = 5 mN is applied, the change in the channel current of the multi-channel GaN pressure sensor is measured as the number of channels n changes, thereby characterizing the sensitivity of the device. It can be seen that the GaN pressure sensor with 5 channels is the most sensitive in pressure detection.

[0053] like Figure 4 In this embodiment of the invention, when an external force of 5mN is applied, the same electrical parameters that are easy to test are set to conduct a reliability test, and the reliability of the multi-channel GaN pressure sensor is reflected by the current change of the multi-channel GaN pressure sensor.

[0054] like Figure 5 In this embodiment of the invention, each is set with the same electrical parameters, and a small external force is applied to GaN pressure sensors with different numbers of channels. The minimum pressure that can detect changes in channel current is measured to reflect the detection limit of the multi-channel GaN pressure sensor.

[0055] comprehensive Figure 4 and Figure 5 It can be seen that the multi-channel GaN pressure sensor with 5 channels improves reliability and detection limit by at least an order of magnitude compared with the traditional single-channel GaN pressure sensor.

[0056] Example 3

[0057] This embodiment 3, based on embodiment 2, changes the material used for the barrier layer to InAlN and follows the testing method of embodiment 2. The results are as follows: Figure 3 Under the same external force conditions, the change in channel current of a multi-channel GaN pressure sensor was measured as the number of channels (n) varied. Figure 3 The results show that multi-channel GaN pressure sensors formed from both different materials exhibit high sensitivity, reaching a peak at a channel number n=5. This demonstrates that the channel structure layer of multi-channel GaN pressure sensors is not limited to AlGaN / GaN multi-channel, but can also be InAlN / GaN multi-channel, indicating that the multi-channel structure of multi-channel GaN pressure sensors is applicable to different materials.

[0058] Example 4

[0059] In Example 4, based on Example 1, the annealing temperature of the multi-channel GaN pressure sensor in the final process is changed to 700℃, 850℃, 950℃, and 1100℃, and the change in current of the multi-channel GaN pressure sensor is observed.

[0060] Test results are as follows Figure 6 The GaN pressure sensor exhibits the best performance at an annealing temperature of 850℃. Sensitivity decreases at annealing temperatures of 700℃ and 950℃. This is because a good ohmic contact cannot be formed at 700℃, while at 950℃, the two-dimensional electron gas is destroyed, leading to a reduction in channel current. At 1100℃, the channel is destroyed, and the GaN pressure sensor fails.

[0061] This invention provides a multi-channel GaN pressure sensor. Because the lattice constant of the uppermost AlGaN layer is smaller than that of the GaN layer, the AlGaN layer in the AlGaN / GaN heterostructure is typically under tensile stress. When an external force is applied to the film, the AlGaN / GaN heterostructure experiences compressive stress, pushing atoms in the AlGaN barrier closer together than those in the GaN layer. Therefore, the tensile stress in the AlGaN layer decreases, piezoelectric polarization weakens, leading to a decrease in channel electron density and electron mobility. As the external pressure acting on the pressure sensor gradually increases, the channel current decreases under the piezoelectric effect. Due to the piezoelectric and self-polarization effects of the AlGaN / GaN heterostructure, a high-concentration, high-electron-mobility two-dimensional electron gas (2-EDG) is formed on the surface of the GaN channel layer, which is highly sensitive to changes in external pressure. The piezoelectric effects of AlGaN and GaN can be used to convert pressure changes into changes in the concentration and mobility of the two-dimensional electron gas, thereby causing changes in the channel current. The embodiments of the present invention construct a multi-channel pressure sensor by stacking AlGaN / GaN materials, which can significantly improve the relevant performance parameters.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-channel GaN pressure sensor, characterized in that: It includes a substrate (100), a channel structure layer (200), a gate (300) disposed on the channel structure layer (200), and a source (400) and a drain (500) located on both sides of the channel structure layer (200) from bottom to top. The channel structure layer (200) is composed of stacked GaN layers (201) and AlGaN barrier layers (202). The GaN layer (201) is located below the AlGaN barrier layer (202). The GaN layer (201) and AlGaN barrier layer (202) are stacked to form a channel. When the channel structure layer (200) is stacked, a multi-channel structure is formed by the upper GaN layer (201) contacting the lower AlGaN barrier layer (202).

2. The multi-channel GaN pressure sensor device as described in claim 1, characterized in that: The substrate (100) is made of silicon; a groove (101) is also provided on the lower surface of the substrate (100).

3. The multi-channel GaN pressure sensor device as described in claim 1 or 2, characterized in that: The source (400) and the drain (500) are both Ti / Al / Ni / Au stacks, and the source (400) and the drain (500) cover all the multilayer stacked GaN layers (201) and AlGaN barrier layers (202).

4. The multi-channel GaN pressure sensor device as described in claim 3, characterized in that: The number of stacked GaN layers (201) and AlGaN barrier layers (202) is 3 to 10.

5. The multi-channel GaN pressure sensor device as described in claim 4, characterized in that: The thickness of the GaN layer (201) is 20~200nm, and the thickness of the AlGaN barrier layer (202) is 5~50nm; The thickness of the GaN layer (201) gradually decreases from bottom to top.

6. The multi-channel GaN pressure sensor device as described in claim 4 or 5, characterized in that: The GaN layer (201) of the bottommost channel structure layer (200) is in contact with the substrate, and the gate (300) forms a Schottky contact with the AlGaN barrier layer (202) of the topmost channel structure layer (200).

7. The multi-channel GaN pressure sensor device as described in claim 6, characterized in that: The gate (300) is a Ni / Au stack.

8. The method for fabricating a multi-channel GaN pressure sensor device as described in any one of claims 1 to 7, characterized in that: include, Multilayer stacked channel structure layers are formed on the surface of a silicon substrate using metal-organic chemical vapor deposition or molecular beam epitaxy. Each channel structure layer consists of stacked GaN layers and AlGaN barrier layers. The barrier layers are made of AlGaN and InAlN, both of which can form multi-channel GaN pressure sensor devices. The stacked multilayer GaN / AlGaN layers are isolated on both sides by mesa isolation to achieve active region isolation; wherein, the active region is the area between the source and drain electrodes; Source and drain electrodes are formed in the active region through photolithography, metal evaporation, and annealing processes. The gate electrode is formed in the gate electrode region using photolithography and metal evaporation processes; A groove is fabricated on the lower surface of a silicon substrate to release pressure at the channel.

9. The method for fabricating a multi-channel GaN pressure sensor as described in claim 8, characterized in that: The process involves preparing a groove on the lower surface of a silicon substrate, coating a photoresist layer on the upper surface of the silicon substrate corresponding to the non-groove area using a photolithography process, and then removing the photoresist layer corresponding to the groove area through exposure, development, and hardening processes to expose the pattern to be etched. The etching process is used to etch away the portion corresponding to the groove area until the support layer is only 1-3 μm thick, forming a groove, and then the photoresist layer is removed.

10. The method for fabricating a multi-channel GaN pressure sensor as described in claim 8, characterized in that: The annealing is performed in a nitrogen atmosphere at 700~1000℃ for 10~1000s.

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