Field effect transistor based pressure sensing device and method of manufacturing the same

Abstract

The application discloses a pressure sensor device based on a field effect transistor and a manufacturing method thereof. The pressure sensor device based on the field effect transistor comprises an SOI substrate, a silicon germanium epitaxial layer arranged above the SOI substrate, an SGOI substrate formed by oxidation concentration, a gate etched on the SGOI substrate, a metal source end and a metal drain end arranged on both sides of the gate respectively, a contact electrode arranged on the metal source end and the metal drain end respectively and connected with a lead wire, so as to be used as a source electrode and a drain electrode respectively, and a groove etched on the back surface of the SGOI substrate as a pressure sensing point. The pressure sensor device based on the field effect transistor and the manufacturing method thereof have the advantages that, under a pressure state, the silicon germanium back surface is subjected to a tensile stress, the carrier mobility changes, the size of the source-drain output current changes, the silicon germanium field effect transistor with reverse initial strain can delay stress release, the pressure value can be quantitatively calibrated, and the measurement range is increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sensors, and particularly relates to a pressure sensor device based on an (oxidized concentrated silicon germanium) field effect transistor and a manufacturing method of a pressure sensor device based on an (oxidized concentrated silicon germanium) field effect transistor. BACKGROUND

[0002] With the progress of science and technology, pressure sensors play an important role in the fields of automobiles, manufacturing, aerospace, etc., and the development of microelectronic devices also promotes the miniaturization of pressure sensors. In the 1960s, MEMS-based sensors were born, which are manufactured by means of microelectronics and micromechanical technology, but the size of MEMS-type pressure sensors is large, which is not conducive to improving system integration.

[0003] Nowadays, pressure sensors are mainly divided into piezoresistive sensors, capacitive sensors, inductive sensors, piezoelectric sensors, strain sensors, etc. according to the working mode.

[0004] The principle of capacitive sensors is that pressure causes displacement of electrode plates, thereby changing the capacitance. Although the size of capacitive sensors has been successfully reduced, their input and output are nonlinear, which leads to difficult signal processing and low sensitivity. Inductive sensors are based on the principle of electromagnetic induction, and are easily affected by electromagnetic fields in the environment during work, making it difficult to apply in complex environments. Field effect transistor pressure sensors utilize the characteristics of transistors, and adjust the conduction path by controlling the gate electric field, thereby realizing the measurement of pressure. This makes field effect transistor pressure sensors have higher sensitivity and faster response speed.

[0005] Field effect transistor pressure sensors belong to a kind of strain pressure sensors, which utilize the strain generated by pressure to change the carrier mobility, thereby changing the output current and threshold voltage. It has the advantages of small size, high sensitivity, and compatibility with integrated circuit manufacturing processes, but when the working pressure exceeds a certain range, excessive strain will cause stress release, and the pressure sensor device cannot work normally.

[0006] Therefore, in view of the above problems, further improvement is needed. SUMMARY

[0007] The main purpose of the present application is to provide a field effect transistor based pressure sensor device and its manufacturing method, which uses an oxidized and concentrated silicon germanium field effect transistor as a pressure sensor, changes the output voltage and current by changing the pressure, and senses the pressure value. It is a feasible solution to break through the performance bottleneck of traditional field effect pressure sensors. Under pressure, the silicon germanium back surface is subjected to tensile stress, and the change in carrier mobility causes the source-drain output current to change. The silicon germanium field effect transistor with reverse initial strain can delay stress release, realize quantitative calibration of pressure value, and increase the measurement range.

[0008] To achieve the above purpose, the present application provides a field effect transistor based pressure sensor device, which comprises an SOI substrate, a silicon germanium epitaxial layer arranged above the SOI substrate, an SGOI substrate formed by oxidizing and concentrating, a gate etched on the SGOI substrate, a metal source end and a metal drain end arranged on both sides of the gate, respectively, a contact electrode arranged on the metal source end and the metal drain end, respectively, and a lead wire connected thereto, so as to serve as a source and a drain, respectively, and a recess etched on the back surface of the SGOI substrate as a pressure sensing point.

[0009] As a further preferred technical solution of the above technical solution, the SOI substrate comprises a silicon substrate, a buried oxide layer and a top silicon layer, the buried oxide layer is located between the silicon substrate and the top silicon layer, the thickness of the buried oxide layer is 200-800 nm, and the top silicon layer is low-concentration p-type doped with a thickness of 10-30 nm.

[0010] As a further preferred technical solution of the above technical solution, the top silicon layer grows the low-germanium-concentration silicon germanium epitaxial layer away from one side of the buried oxide layer, the germanium fraction of the silicon germanium epitaxial layer is 0.1-0.25, and the thickness is 30-80 nm.

[0011] As a further preferred technical solution of the above technical solution, for the formation of the SGOI substrate, an oxidation concentration technique is used to oxidize at high temperature, the germanium in the silicon germanium epitaxial layer diffuses downward, the silicon is selectively oxidized, the top silicon layer and the low-germanium-concentration silicon germanium epitaxial layer thereon are converted into high-germanium-concentration silicon germanium, and the compression strain is retained, so as to form the SGOI substrate as a whole.

[0012] As a further preferred technical solution of the above technical solution, the gate comprises a gate oxide layer and a gate contact electrode, and the gate contact electrode is located away from one side of the SGOI substrate.

[0013] As a further preferred technical solution of the above technical solution, the recess on the back surface of the SGOI substrate corresponds to the gate on the front surface, and the range of the recess is greater than that of the gate.

[0014] To achieve the above object, the application further provides a manufacturing method of a pressure sensor device based on a field effect transistor, comprising the following steps:

[0015] Step S1: providing an SOI substrate, epitaxially growing a low-germanium-content silicon germanium epitaxial layer on the surface of the SOI substrate, and selectively oxidizing at high temperature to form an SGOI substrate with compressive strain;

[0016] Step S2: depositing a gate oxide layer on the surface of the SGOI substrate, and preparing a gate contact electrode on the gate oxide layer as a gate after photoetching an image;

[0017] Step S3: depositing metal nickel on one side of the SGOI substrate with the gate, annealing at high temperature to form a NiSiGe / p-SiGe Schottky junction as a metal source end and a metal drain end, removing the metal nickel, depositing metal to form an ohmic contact and make electrode leads for the metal source end and the metal drain end respectively, so as to serve as a source and a drain respectively;

[0018] Step S4: etching a groove on the back surface of the SGOI substrate to expose a buried oxide layer as a contact point for applying external pressure.

[0019] The application has the following beneficial effects:

[0020] 1) High sensitivity: the pressure directly acts on the surface of the silicon germanium sensor device, and the reaction speed is fast;

[0021] 2) Large measurement range: the silicon germanium field effect transistor prepared by oxidation concentration has initial compressive strain, can delay the energy accumulation and release of tensile strain, and increase the working range of the device;

[0022] 3) Small size: the CMOS size can be as small as tens of nanometers and is continuously shrinking, which is much smaller than the size of the MEMS type sensor;

[0023] 4) Compatible with integrated circuit manufacturing process technology, and has broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. (a) is a schematic diagram of a P-type SOI substrate structure, and Fig. (b) is a schematic diagram of a silicon germanium epitaxial layer grown on an SOI substrate;

[0025] Figure 2 Fig. is a schematic diagram of the structure of an SGOI substrate formed after oxidation concentration;

[0026] Figure 3 Fig. is a schematic diagram of the formation of a gate;

[0027] Figure 4 Fig. is a schematic diagram of a metal source / drain end region;

[0028] Figure 5A schematic diagram of etching a pressure groove region on the back of the SGOI substrate;

[0029] Figure 6 A schematic diagram of wiring for the pressure sensor device.

[0030] The reference signs include: a silicon substrate 10, a buried oxide layer 11, a top silicon layer 12, a silicon germanium epitaxial layer 13, a high germanium concentration silicon germanium 20, a gate oxide layer 30, a gate contact electrode 31, a metal source / drain 40, a groove 50. DETAILED DESCRIPTION

[0031] The following description is presented to enable any person skilled in the art to practice the present application as claimed. The preferred embodiments disclosed herein are only examples of the present application and alternative embodiments will be apparent to those skilled in the art upon reading the following description. The detailed description includes specific details for the purpose of providing a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without these specific details. In some instances, well-known structures and functions have not been described in detail in order to avoid obscuring the concept of the present application.

[0032] In the preferred embodiments of the present application, those skilled in the art should note that the grounding and the like involved in the present application can be regarded as prior art.

[0033] Preferred embodiments.

[0034] As Figures 1-6 shown, the present application discloses a field effect transistor-based pressure sensor device, which comprises an SOI substrate, a silicon germanium epitaxial layer 13 arranged above the SOI substrate, an SGOI substrate formed by oxide concentration, a gate photoetched on the SGOI substrate, a metal source end and a metal drain end (i.e. the metal source / drain 40 in Figures 4-5 ), respectively arranged on both sides of the gate, a contact electrode and a lead wire respectively arranged on the metal source end and the metal drain end, so as to serve as a source and a drain, respectively, and a groove 50 etched on the back of the SGOI substrate as a pressure sensing point (the groove is trapezoidal, and the back etching method is reactive ion etching or solution etching).

[0035] Specifically, the SOI substrate comprises a silicon substrate 10, a buried oxide layer 11 and a top silicon layer 12, the buried oxide layer 11 is located between the silicon substrate 10 and the top silicon layer 13, the thickness of the buried oxide layer 11 is 200-800 nanometers, and the top silicon layer 12 is a low concentration p-type doped layer with a thickness of 10-30 nanometers.

[0036] More specifically, the top silicon layer 12 grows the silicon germanium epitaxial layer 13 with a low germanium concentration on the side away from the buried oxide layer 11, the germanium fraction of the silicon germanium epitaxial layer 13 is 0.1-0.25, and the thickness of the silicon germanium epitaxial layer 13 is 30-80 nanometers.

[0037] Further, for the formation of the SGOI substrate, by using oxidation concentration technology, oxidation is carried out at high temperature (oxidation temperature is 900-1100 degrees Celsius), the germanium in the silicon germanium epitaxial layer 13 diffuses downward, so that the silicon is selectively oxidized, the top silicon layer 12 and the silicon germanium epitaxial layer 13 above it with low germanium concentration are converted into high germanium concentration silicon germanium 20, and the compressive strain is retained, thereby forming the SGOI substrate as a whole.

[0038] Further, the gate includes a gate oxide layer 30 and a gate contact electrode 31, and the gate contact electrode 31 is located on the side of the gate oxide layer 30 away from the SGOI substrate. The material of the gate oxide layer 30 is aluminum oxide or hafnium oxide, and the thickness is 2-10 nanometers; the gate contact electrode 31 is a metal such as tungsten, aluminum, nickel, etc., and the thickness is several tens to several hundred nanometers.

[0039] Preferably, the groove 50 on the back of the SGOI substrate corresponds to the gate on the front, and the range of the groove 50 is greater than that of the gate.

[0040] Preferably, the metal of the metal source / drain end is nickel, and the Schottky junction of the source / drain end is NiSiGe / p-SiGe.

[0041] The electrode lead material of the source and the drain is aluminum, nickel or copper.

[0042] The application also discloses a manufacturing method of a field effect transistor-based pressure sensor device, comprising the following steps:

[0043] Step S1: providing an SOI substrate, epitaxially forming a low-germanium-content silicon germanium epitaxial layer 13 on the surface of the SOI substrate, and selectively oxidizing at high temperature to form a SGOI substrate with compressive strain;

[0044] Step S2: depositing a gate oxide layer 30 on the surface of the SGOI substrate, and preparing a gate contact electrode 31 on the gate oxide layer 30 as a gate after photoetching;

[0045] Step S3: depositing metal nickel on one side of the SGOI substrate with the gate, annealing at high temperature to form a NiSiGe / p-SiGe Schottky junction as a metal source end and a metal drain end, and removing the metal nickel, and depositing metal to form ohmic contact and electrode lead as a source and a drain respectively;

[0046] Step S4: etching a groove 50 on the back of the SGOI substrate to expose the buried oxide layer 11 as a contact point for applying external pressure.

[0047] In step S1, the preparation method for epitaxial silicon germanium is molecular beam epitaxy or chemical vapor deposition;

[0048] In step S3, the thickness of the deposited metal nickel is 20-40 nm, and the annealing method for forming the source and drain (i.e., the metal source / drain 40) includes thermal annealing, microwave annealing or laser annealing, and different annealing temperatures form different Schottky barrier heights. An ohmic contact metal is deposited on the SGOI substrate of the metal source / drain 40, and the electrode lead material of the metal source / drain is aluminum, nickel or copper, and the deposition method can be magnetron sputtering or thermal oxidation.

[0049] In steps S2 and S3, the preparation method for the electrode metal is electron beam evaporation, magnetron sputtering or chemical vapor deposition.

[0050] As shown in Figure 6 , a pressure is applied to the back-etched groove, and the surface will be deformed by tensile stress. One end of the test electrode is connected to a negative voltage (i.e., an applied voltage), and the other end is connected to ground. By measuring the change in threshold voltage (i.e., test voltage) of the gate contact electrode, the strain is calculated to deduce the pressure value.

[0051] For the present application, when a pressure is applied to the silicon germanium channel (i.e., the groove), the crystal structure generates a strain opposite to the initial strain, the carrier mobility in the channel changes, the output current changes, and the pressure value is sensed. The sensor of the present application has the advantages of small size, high sensitivity, fast response speed, large measurement pressure range, compatibility with integrated circuit technology, etc., and has a wide application prospect.

[0052] It is worth mentioning that the ground and other technical features involved in the present patent application should be considered as prior art. The specific structure, working principle and possible control method and spatial arrangement method of these technical features can be selected conventionally in the art, and should not be considered as the invention point of the present patent. The present patent will not be further detailed.

[0053] For those skilled in the art, the technical solutions described in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A field effect transistor based pressure sensing device, characterized by, The SOI substrate includes a silicon substrate, a buried oxide layer and a top silicon layer, the buried oxide layer is located between the silicon substrate and the top silicon layer, the thickness of the buried oxide layer is 200-800 nm, and the top silicon layer is low-concentration p-type doped and has a thickness of 10-30 nm. The top silicon layer grows the low-germanium-concentration silicon germanium epitaxial layer away from the buried oxide layer, the germanium fraction of the silicon germanium epitaxial layer is 0.1-0.25, and the thickness of the silicon germanium epitaxial layer is 30-80 nm. For the formation of the SGOI substrate, the oxidation concentration technique is used to perform oxidation at high temperature, the germanium in the silicon germanium epitaxial layer diffuses downward, the silicon is selectively oxidized, the top silicon layer and the low-germanium-concentration silicon germanium epitaxial layer thereon are converted into high-germanium-concentration silicon germanium and retain the compressive strain, and thus the SGOI substrate is formed as a whole. The manufacturing method of the field effect transistor-based pressure sensor device comprises the following steps: Step S1: providing an SOI substrate, epitaxially growing a low-germanium-concentration silicon germanium epitaxial layer on the surface of the SOI substrate, and selectively oxidizing at high temperature to form a SGOI substrate with compressive strain; Step S2: depositing a gate oxide layer on the surface of the SGOI substrate, preparing a gate contact electrode on the gate oxide layer, and performing photoetching to form a gate; Step S3: depositing metal nickel on one side of the SGOI substrate with the gate, annealing at high temperature to form a NiSiGe / p-SiGe Schottky junction as a metal source end and a metal drain end, removing the metal nickel, depositing metal to form ohmic contact and electrode leads for the metal source end and the metal drain end respectively, so as to serve as a source and a drain respectively, the thickness of the deposited metal nickel is 20-40 nm, the annealing method for forming the source end and the drain end includes thermal annealing, microwave annealing or laser annealing, different annealing temperatures form Schottky junctions with different barrier heights, the ohmic contact metal is deposited on the SGOI substrate of the metal source / drain end, the electrode lead material of the metal source / drain end is aluminum, nickel or copper, and the deposition method includes magnetron sputtering or thermal oxidation; Step S4: etching a recess on the back surface of the SGOI substrate to expose the buried oxide layer as a contact point for applying external pressure. The gate includes a gate oxide layer and a gate contact electrode, and the gate contact electrode is located away from the SGOI substrate.

2. A field effect transistor based pressure sensing device according to claim 1, characterized in that The recess on the back surface of the SGOI substrate corresponds to the gate on the front surface, and the range of the recess is greater than that of the gate.

3. A field effect transistor based pressure sensing device according to claim 2, wherein, ​

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