Biosensor based on barrier gate structure tunneling field effect transistor

Abstract

The application relates to the technical field of semiconductor devices, in particular to a biosensor based on a barrier gate structure tunneling field effect transistor, which comprises a silicon substrate, an insulating layer, a channel, a gate dielectric layer, a source, a drain, a gate, a biological nanocavity and a biological medium layer; the silicon substrate, the insulating layer, the channel and the gate dielectric layer are stacked in sequence from bottom to top; the source and the drain are distributed on the two sides of the channel, both contact the channel and the gate dielectric layer, and are stacked on the upper surface of the insulating layer; the end of the channel close to the source is a P+ doped area, and the end close to the drain is graphene; the end of the graphene close to the P+ doped area is an N+ doped area, and the middle part is a P barrier area; the biological nanocavity and the gate are stacked in sequence on the upper surface of the gate dielectric layer opposite to the P barrier area; and the biological medium layer is stacked on the side surface of the biological nanocavity close to the source and contacts the gate. The application reduces the on-state current, reduces the power consumption, improves the on-off current ratio, and solves the problems of low sensitivity of the biosensor in the prior art.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor devices, and particularly relates to a biosensor based on a barrier gate structure tunneling field effect transistor. BACKGROUND

[0002] In recent years, with the emergence of various viruses, the development of biosensors has become increasingly important. However, the existing biosensors have the problem of low sensitivity. For example:

[0003] Baruah et al. (K. Baruah and S. Baishya, Numerical assessment of dielectrically-modulated short-double-gate PNPN TFET-based label-free biosensor. Microelectronics Journal, 2023, 133, 105717.) proposed a dielectrically-modulated Ge-source short-double-gate PNPN tunnel FET-based label-free biosensor, which uses Ge material for the source, but has low off-state current and sensitivity of only 10 5 , which is not good for biological detection.

[0004] Narang et al. (R. Narang, K. V. S. Reddy, M. Saxena, R. S. Gupta and M. Gupta, A Dielectric-Modulated Tunnel-FET-Based Biosensor for Label-Free Detection: Analytical Modeling Study and Sensitivity Analysis. IEEE Transactions on Electron Devices 2012, 59, 2809.) proposed a PNPN tunnel field effect transistor (TFET) sensor, which has a high on-off current ratio of 10 10 , but has high subthreshold swing, which is still not good for biological detection.

[0005] The patent document with the publication number CN118641608A discloses "a biosensor based on a charge plasma tunneling field effect transistor and a preparation method thereof", which sets a biological detection cavity above and below the source region, and uses the second gate electrode to control the hole concentration of the source region tunneling junction. When detecting biological samples, the sensor has a sensitivity of up to 11 orders of magnitude, but has low sensitivity to low dielectric constant biological samples.

[0006] Therefore, there is an urgent need to design a high-sensitivity biosensor to solve the above technical problems. SUMMARY

[0007] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a biosensor based on a barrier gate structure tunneling field effect transistor, which greatly reduces the off-state current, reduces power consumption, and improves the on-off current ratio, solving the problem of low sensitivity of the biosensor in the prior art.

[0008] To solve the above technical problems, the technical solution of the present application is: a biosensor based on a barrier gate structure tunneling field effect transistor, comprising a silicon substrate, an insulating layer, a channel, a gate dielectric layer, a source, a drain, a gate, a biological nanocavity and a biological medium layer; wherein,

[0009] The silicon substrate, the insulating layer, the channel and the gate dielectric layer are stacked in order from bottom to top;

[0010] The source and the drain are distributed on both sides of the channel and contact the channel and the gate dielectric layer, and are stacked on the upper surface of the insulating layer;

[0011] The end of the channel close to the source is a P+ doped region of silicon material, and the end close to the drain is graphene; the end of the graphene close to the P+ doped region is an N+ doped region, and the middle part is a P barrier region;

[0012] The biological nanocavity is stacked on the upper surface of the gate dielectric layer opposite to the P barrier region;

[0013] The gate is stacked on the upper surface of the biological nanocavity, and the biological medium layer is stacked on the side of the biological nanocavity close to the source and contacts the gate.

[0014] Further, the thickness of the channel is 5-10 nm;

[0015] And / or the length of the P+ doped region is shorter than the length of the graphene.

[0016] Further, the doping concentration of the P+ doped region is 1x10 20 cm -3 ;

[0017] And / or the doping concentration of the N+ doped region is 1x10 20 cm -3 ;

[0018] And / or the doping concentration of the P barrier region is 5x10 18 cm -3 -5x10 19 cm-3 .

[0019] Further, the material of the gate dielectric layer is silicon dioxide or hafnium dioxide or aluminum oxide.

[0020] Further, the metal material used by the source and the drain is the same.

[0021] The application also relates to a preparation method of a biosensor based on a barrier gate structure tunneling field effect transistor.

[0022] Depositing an insulating layer on a silicon substrate;

[0023] Growing a channel on the insulating layer; wherein the P+ doped region in the channel is generated by ion implantation, graphene is generated by chemical vapor deposition, the N+ doped region is generated by ion implantation, and the P barrier region is generated by ion implantation;

[0024] Depositing a gate dielectric layer above the channel by using an atomic layer deposition process;

[0025] Depositing an oxide on the gate dielectric layer,

[0026] Preparation of the metal gate, the source and the drain by using evaporation and sputtering technology of a metal electrode;

[0027] Etching the oxide below the gate to form a biological nanocavity.

[0028] After the above technical solution, the application has the following beneficial effects:

[0029] 1. The application uses silicon and graphene to form a heterojunction as a conductive channel, so that in the study of tunneling, the characteristics of high saturation current of graphene material can be retained while the low on-state current is retained, and the shortcomings of low saturation current of traditional tunneling are overcome.

[0030] 2. The application introduces an N+ doped region to graphene at the heterojunction, so that the conduction band of graphene is lower than the valence band of the silicon region, so that electrons can directly tunnel from the valence band of silicon to the conduction band of graphene. To ensure controllable tunneling, a P barrier region is introduced on the back side of the tunneling junction to block the tunneling electrons. In addition, the N+ doped region greatly reduces the space charge region at the tunneling junction, further reducing the tunneling distance of the electrons, thereby increasing the tunneling current, reducing the sub-threshold swing, and at the same time when the device is turned off, the tunneling does not occur, and the heavily doped reverse PN junction further reduces the on-state current. The lower the on-state current, the lower the power consumption, and thus the purpose of reducing power consumption is achieved.

[0031] 3、The application introduces a P barrier region behind the tunneling junction, which is controlled by the gate to form a barrier gate structure. The barrier gate controls the barrier height. Excessive barrier height hinders the passage of tunneling electrons, thereby realizing the switching of the device. In the process of biosensing, based on the dielectric modulation effect, the biological in the biological nanocavity is analogized as an insulating layer with different dielectric constants. The barrier region in the graphene material is controlled by the barrier gate. The biological nanocavity acts as a gate capacitor, thereby realizing higher detection sensitivity of the biological. At the same time, due to the high electron mobility of graphene, under the control of the barrier gate, better control is shown, and the sub-threshold swing of the sensor is further reduced. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structure diagram of the biosensor based on the barrier gate structure tunneling field effect transistor of the application;

[0033] Figure 2 It is a band diagram of the channel of the sensor under the opening and closing conditions of the application;

[0034] Figure 3 It is a transfer characteristic curve diagram of the sensor when detecting biological of the application;

[0035] Figure 4 It is a sensitivity diagram of the sensor when detecting biological of the application;

[0036] Figure 1 In the figure, 1, P+ doped region; 2, graphene; 3, N+ doped region; 4, P barrier region; 5, source; 6, drain; 7, insulating layer; 8, silicon substrate; 9, gate dielectric layer; 10, biological medium layer; 11, gate; 12, biological nanocavity;

[0037] Figure 4 In the figure, (a) is a tunneling voltage sensitivity diagram, and (b) is a current sensitivity diagram. DETAILED DESCRIPTION

[0038] In order to make the content of the application more easily and clearly understood, the application will be further described in detail below according to specific embodiments and in combination with the drawings.

[0039] As Figure 1 shown, a biosensor based on a barrier gate structure tunneling field effect transistor, comprising a silicon substrate 8, an insulating layer 7, a channel, a gate dielectric layer 9, a source 5, a drain 6, a gate 11, a biological nanocavity 12 and a biological medium layer 10; wherein,

[0040] The silicon substrate 8, the insulating layer 7, the channel and the gate dielectric layer 9 are stacked in order from bottom to top;

[0041] The source 5 and the drain 6 are distributed on both sides of the channel and contact the channel and the gate dielectric layer 9, and are laminated on the upper surface of the insulating layer 7;

[0042] The end of the channel close to the source 5 is a P+ doped region 1 of silicon material, and the end close to the drain 6 is graphene 2; the end of the graphene 2 close to the P+ doped region 1 is an N+ doped region 3, and the middle part is a P barrier region 4;

[0043] The biological nanocavity 12 is laminated on the upper surface of the gate dielectric layer 9 opposite to the P barrier region 4;

[0044] The gate 11 is laminated on the upper surface of the biological nanocavity 12, and the biological dielectric layer 10 is laminated on the side of the biological nanocavity 12 close to the source 5 and contacts the gate 11.

[0045] The above embodiment relates to a biosensor based on a barrier gate structure tunneling field effect transistor, which adopts an SOI (silicon on insulator) technology. The insulating layer 7 deposited on the intrinsic silicon substrate 8 is 200 nm thick, the channel is grown on the insulating layer 7, and is formed by a heterostructure composed of silicon and graphene 2, and the thickness is 5 nm-10 nm, wherein the silicon is 40 nm long, and the graphene is 60 nm long. The graphene is generated by chemical vapor deposition and transferred to the insulating layer 7 on the silicon substrate 8; the silicon in the channel is P+ doped by ion implantation to form the P+ doped region 1, and the concentration is set to 1×1019 cm-3; the N+ doped region 3 is located at one end of the graphene 2 close to the silicon, is 3 nm-5 nm long, is doped by ion implantation, and the concentration is 1×1019 cm-3, so that the conduction band of the N+ doped region 3 is lower than the valence band of the P+ doped region 1 (the energy band is divided into a conduction band and a valence band, the conduction band is located above the valence band, and the energy band height can be adjusted by doping. The overall energy band of the P+ doped region 1 rises due to P doping, and the energy band of the graphene is lowered by N+ doping, so that the conduction band of the N+ doped region 3 is lower than the valence band of the P+ doped region); the P barrier region 4 is located at the middle position of the graphene 2 and is 20 nm long, and the doping concentration is 5×1019 cm-3-5×1020 cm-3. 20 -3 20 -3 18 -3 19 -3 ​​​​​​​Between them, P potential barrier region 4 is doped by P, with a higher energy band to ensure that when the gate voltage is 0V, the device remains closed; Atomic layer deposition process is used to deposit gate dielectric layer 9 above the channel, which has a high dielectric constant (the higher the dielectric constant of the gate dielectric layer, the higher the effective capacitance of the gate, which means that the control of the gate on the channel is better, and the dielectric constant of the silicon dioxide used in this embodiment is 3.9, the dielectric constant of hafnium dioxide HfO2 and aluminum oxide Al2O3 is higher, and the effect is relatively better); Then continue to deposit 25nm long and 10nm high oxide above P potential barrier region 4, and then use metal electrode evaporation and sputtering technology to prepare metal gate 11, source 5 and drain 6, source 5 and drain 6 should use the same metal; Finally, etch the oxide below the gate 11 to form a biological nanocavity 12 with a length of 20nm and a height of 10nm, and the side of the oxide close to the source 3 forms a biological medium layer 10.

[0046] The detected biomolecules are confined in the biological nanocavity 12, and different biological species are distinguished by different dielectric constants k. For example, considering the case where a single biological completely fills the biological nanocavity 12, the dielectric constant k of urease is 1.5, the dielectric constant k of biotin is 2.6, the dielectric constant k of phage is 6, and the dielectric constant k of gelatin is 12; The sensitivity of detection is determined by the gate dielectric layer 9 and the biological nanocavity 12 together, the larger the dielectric constant k of the biological, the larger the effective gate capacitance, and the higher the sensitivity. The biosensor in this embodiment can detect the concentration of a single biological according to the dielectric constant of the single biological after being filled in the biological nanocavity 12, and can also distinguish each single biological according to the dielectric constant.

[0047] It should be noted that in this embodiment, the detection sensitivity is divided into current sensitivity and voltage sensitivity, which is embodied in:

[0048] Current sensitivity S I The current I of the sensor when there is a biological bio The current I in air air The ratio of:

[0049]

[0050] Voltage sensitivity The tunneling voltage V of the sensor when there is a biological bio The tunneling voltage V in air air The absolute difference between:

[0051]

[0052] The working principle of the biosensor based on the barrier gate structure tunneling field effect transistor involved in the above embodiment is as follows:

[0053] The biosensor based on barrier gate structure tunneling field effect transistor adopts silicon-graphene as conductive channel, and introduces N+ doped region 3 at the heterojunction, so that the silicon-graphene 2 heterojunction has a normally open tunneling condition. Figure 2 The energy band diagram of the sensor in the on and off conditions is shown in the figure, the energy band is divided into conduction band and valence band, the conduction band is above the valence band, and the forbidden band is in the middle. The source 5 side is silicon, which has a larger forbidden band width, and adopts P+ doped region 1, so the energy band is higher. The drain 6 side is graphene, which only has a forbidden band width of 0.26eV, and has N+ doped region 3 at the junction with silicon, so the energy band is lower, which has met the tunneling condition. The conduction band of graphene 2 is lower than the valence band of silicon, and the protrusion of the energy band can be seen in the middle of graphene 2, which is caused by P doping of the P barrier region 4. The P barrier region 4 is controlled by the gate to form a barrier gate structure, thereby controlling the on-off of the device. Figure 2 The two red solid lines in the middle represent the tunneling energy band. When the gate voltage is large, the energy band of the P barrier region 4 is low, at this time, the electrons tunnel from the valence band of the source region to the conduction band of graphene 2, and then have enough energy to pass through the low barrier to reach the drain 6. The two black dashed lines in the figure represent the non-tunneling energy band. When the gate voltage is small, the energy band of the P barrier region 4 is high, and the tunneling electrons cannot cross the barrier, thereby realizing the off of the device. In the off state, the tunneling current is provided by the reverse-biased heavily doped PN junction at the tunneling junction, so the current is small; in the on state, the height of the energy band of the P barrier region 4 decreases, and the electrons have enough energy to cross the barrier after tunneling, thereby realizing the on of the device.

[0054] The sensor is based on dielectric modulation effect, and the biological molecules are analogous to insulating layers with different dielectric constants and are limited in the biological nanocavity 12. When the biological nanocavity 12 is filled with the biological to be detected, the dielectric constant under the entire gate 11 will change, and the effective capacitance of the gate 11 will also change, so that the gate 11 has different degrees of control over the channel, and the electron hole concentration of the barrier region in the channel will also change, and the height of the barrier will not be the same. The sensor under different dielectric constants of the biological will exhibit different tunneling voltages. The greater the change of the dielectric constant of the biological, the greater the tunneling voltage exhibited by the sensor. By analyzing the tunneling voltage and tunneling current of the sensor under different biological conditions, the sensitivity of the sensor to different biological can be obtained, and different biological can be clearly distinguished.

[0055] The biosensor based on barrier gate structure tunneling field effect transistor involved in the above embodiment is simulated, and the specific process is as follows:

[0056] In the simulation process, the drain 6 voltage is always set to 0.1V, and the dielectric constant k is set to 1, 1.5, 2.6, 6 and 12 respectively according to different biological categories, and the transfer curve is as follows: Figure 3The tunneling voltage of the sensor is 1.18V and the sub-threshold swing is high under the condition of air, i.e. the condition of dielectric constant k=1. The minimum sub-threshold swing is 10.8mV / dec (the sub-threshold swing refers to the change of the gate voltage when the current increases by one order of magnitude from the off to the full on of the device. The change of the gate voltage is 10.8mV when the current increases by one order of magnitude at the voltage of 1.18V. Figure 3 As can be seen from the transfer curve, when k=1, the gate voltage changes about 0.01V after the current increases by one order of magnitude at the voltage of 1.18V, and the value is 10.8mV through calculation. The smaller the value is, the steeper the rising part of the transfer curve is, and the more beneficial to the improvement of the current sensitivity is. With the increase of the biological dielectric constant, the tunneling voltage is smaller. When the biological dielectric constant k reaches 12, the tunneling voltage of the sensor is reduced to 0.16V, the tunneling voltage sensitivity reaches 1.02V, and the minimum sub-threshold swing reaches 4.8mV / dec. Figure 4 The sensitivity graph of the sensor in detecting the biological is shown. As can be seen, when the gate voltage is 1.18V, the sensor has the maximum current sensitivity in detection, and has a sensitivity of 8.85×10 12 to the biological with k=12. Even when k=1.5, the sensor can reach 8 orders of magnitude, compared with the prior art mentioned in the background art. The sensor in the embodiment has higher sensitivity in the field of biological detection.

[0057] Based on the above ideal embodiments according to the present application, the relevant staff can make various changes and modifications without deviating from the technical idea of the present application according to the above description. The technical scope of the present application is not limited to the contents of the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1.A biosensor based on barrier gate structure tunneling field effect transistor, characterized in that, it comprises a silicon substrate (8), an insulating layer (7), a channel, a gate dielectric layer (9), a source (5), a drain (6), a gate (11), a biological nanocavity (12) and a biological medium layer (10); wherein, the silicon substrate (8), the insulating layer (7), the channel and the gate dielectric layer (9) are sequentially stacked from bottom to top; the source (5) and the drain (6) are distributed on both sides of the channel and both contact the channel and the gate dielectric layer (9) and are stacked on the upper surface of the insulating layer (7); the end of the channel close to the source (5) is a P+ doped region (1) of silicon material, and the end close to the drain (6) is graphene (2); the end of the graphene (2) close to the P+ doped region (1) is an N+ doped region (3), and the middle part is a P barrier region (4); the biological nanocavity (12) is stacked on the upper surface of the gate dielectric layer (9) opposite to the P barrier region (4); the gate (11) is stacked on the upper surface of the biological nanocavity (12), and the biological medium layer (10) is stacked on the side of the biological nanocavity (12) close to the source (5) and contacts the gate (11). 2.The biosensor based on barrier gate structure tunneling field effect transistor according to claim 1, characterized in that, the thickness of the channel is 5-10 nm; and / or the length of the P+ doped region (1) is shorter than the length of the graphene (2). 3.The biosensor based on barrier gate structure tunneling field effect transistor according to claim 1, characterized in that, The P+ doped region (1) has a doping concentration of 1 x 10 20 cm -3 -3 and / or the doping concentration of the N+ doped region (3) is 1 x 10 20 cm -3 ; and / or the doping concentration of the P barrier region (4) is 5x1018cm-3 18 cm -3 -5x1018cm-3 19 cm -3 . 4.The biosensor based on barrier gate structure tunneling field effect transistor according to claim 1, characterized in that, the material of the gate dielectric layer (9) is silicon dioxide or hafnium dioxide or aluminum oxide. 5.The biosensor based on barrier gate structure tunneling field effect transistor according to claim 1, characterized in that, the metal materials used by the source (5) and the drain (6) are the same. 6.A method for preparing the biosensor based on barrier gate structure tunneling field effect transistor according to any one of claims 1-5, characterized in that, the method comprises: depositing an insulating layer (7) on a silicon substrate (8); growing a channel on the insulating layer (7); wherein, the P+ doped region (1) in the channel is generated by ion implantation, the graphene (2) is generated by chemical vapor deposition, the N+ doped region (3) is generated by ion implantation, and the P barrier region (4) is generated by ion implantation; depositing a gate dielectric layer (9) above the channel using atomic layer deposition process; depositing an oxide on the gate dielectric layer (9), preparing a metal gate (11), a source (5) and a drain (6) using evaporation and sputtering techniques of metal electrodes; etching the oxide below the gate (11) to form a biological nanocavity (12).

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