Biosensor of tunneling field effect transistor based on barrier gate structure

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a biosensor of a tunneling field effect transistor based on a barrier gate structure, which comprises a silicon substrate, an insulating layer, a channel, a gate dielectric layer, a source electrode, a drain electrode, a gate electrode, a biological nano cavity and a biological dielectric layer, the silicon substrate, the insulating layer, the channel and the gate dielectric layer are sequentially stacked from bottom to top; the source electrode and the drain electrode are distributed on two sides of the channel, are in contact with the channel and the gate dielectric layer, and are laminated on the upper surface of the insulating layer; the end part, close to the source electrode, of the channel is a P + doped region, and the end part, close to the drain electrode, of the channel is graphene; the end part, close to the P + doped region, of the graphene is an N + doped region, and the middle part of the graphene is a P barrier region; the biological nanometer cavity and the grid electrode are sequentially stacked on the upper surface, right facing the P barrier region, of the grid dielectric layer. The biological medium layer is stacked on the side face, close to the source electrode, of the biological nanometer cavity and makes contact with the grid electrode. Off-state current is reduced, power consumption is reduced, the switching current ratio is increased, and the problem that a biosensor in the prior art is low in sensitivity is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a biosensor based on a barrier gate structure tunneling field effect transistor. Background Art

[0002] In recent years, with the emergence of various viruses, the development of biosensors has become increasingly important. However, 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 label-free biosensor based on dielectrically modulated Ge source short double-gate PNPN tunnel FET, whose source electrode uses Ge material, but the off-state current is low and the sensitivity is only 10 5 , but the effect on biological detection is poor.

[0004] Narang et al. (R.Narang, KVSReddy, M.Saxena, RSGupta and M.Gupta, ADielectric-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 with an on / off current ratio of up to 10 10 , but its subthreshold swing is relatively high, and its sensitivity for biological detection is still not high.

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

[0006] Therefore, there is an urgent need to design a highly sensitive biosensor to solve the above technical problems. Summary of the invention

[0007] The technical problem to be solved by the present invention 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 and power consumption, while improving the switching current ratio, solving the problems of low sensitivity of biosensors in the prior art.

[0008] In order to solve the above technical problems, the technical solution of the present invention 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 electrode, a drain electrode, a gate electrode, a bio-nano cavity and a bio-dielectric layer; wherein,

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

[0010] The source electrode and the drain electrode are distributed on both sides of the channel, and both contact the channel and the gate dielectric layer, and both 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 bio-nano cavity is stacked on the upper surface of the gate dielectric layer facing the P barrier region;

[0013] The gate is stacked on the upper surface of the bio-nano cavity, and the bio-medium layer is stacked on the side of the bio-nano cavity close to the source electrode and contacts the gate.

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

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

[0016] Furthermore, the doping concentration of the P+ doping region is 1×10 20 cm -3 ;

[0017] and / or the doping concentration of the N+ doping region is 1×10 20 cm -3 ;

[0018] and / or the doping concentration of the P barrier region is 5×10 18 cm -3 -5×10 19 cm-3 .

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

[0020] Furthermore, the source electrode and the drain electrode are made of the same metal material.

[0021] The present invention also relates to a method for preparing a biosensor based on a barrier gate structure tunneling field effect transistor, the method comprising:

[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, the 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 using an atomic layer deposition process;

[0025] Deposit oxide on the gate dielectric layer.

[0026] The metal gate, source and drain are prepared by using the evaporation and sputtering technology of metal electrodes;

[0027] The oxide under the gate is etched to form a bio-nanocavity.

[0028] After adopting the above technical solution, the present invention has the following beneficial effects:

[0029] 1. The present invention uses silicon and graphene to form a heterojunction as a conductive channel, so that when studying tunneling, it is still possible to retain the low off-state current while retaining the high saturation current characteristics of the graphene material, thus overcoming the disadvantage of low saturation current of traditional tunneling.

[0030] 2. The present invention introduces an N+ doped region into graphene at the heterojunction, thereby making the conduction band of graphene 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 that the tunneling is controllable, a P barrier region is also introduced on the back side of the tunnel junction to block the passage of tunneling electrons. In addition, the space charge region at the tunnel junction greatly reduced by the N+ doped region further reduces the tunneling distance of electrons, thereby increasing the tunneling current and reducing the subthreshold swing. At the same time, when the device is turned off, tunneling does not occur, and the heavily doped reverse PN junction further reduces the off-state current. The lower the off-state current, the lower the power consumption, thereby achieving the purpose of reducing power consumption.

[0031] 3. The present invention also introduces a P barrier region on the back side of the tunnel junction, which is controlled by the gate to form a barrier gate structure. The barrier gate controls the barrier height. Too high a 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 organisms in the bio-nano cavity are analogized to insulating layers with different dielectric constants. The barrier region in the graphene material is controlled by the barrier gate, and the bio-nano cavity acts as a gate capacitor, thereby achieving higher detection sensitivity for the organism. At the same time, due to the characteristics of high electron mobility of graphene, under the control of the barrier gate, it shows better control force, further reducing the subthreshold swing of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The structure diagram of the biosensor based on the barrier gate structure tunneling field effect transistor of the present invention;

[0033] Figure 2 is an energy band diagram of the channel of the sensor of the present invention under the on and off conditions;

[0034] Figure 3 is a transfer characteristic curve diagram of the sensor of the present invention when detecting organisms;

[0035] Figure 4 is a sensitivity diagram of the sensor of the present invention when detecting organisms;

[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. bio-dielectric layer; 11. gate; 12. bio-nanocavity;

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

[0038] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0039] like Figure 1 As shown, a biosensor based on a barrier gate structure tunneling field effect transistor includes 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 bio-nano cavity 12 and a bio-dielectric layer 10; wherein,

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

[0041] The source electrode 5 and the drain electrode 6 are distributed on both sides of the channel, and both contact the channel and the gate dielectric layer 9, and are both stacked 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 bio-nano cavity 12 is stacked on the upper surface of the gate dielectric layer 9 facing the P barrier region 4;

[0044] The gate 11 is stacked on the upper surface of the bio-nano cavity 12 , and the bio-medium layer 10 is stacked on the side of the bio-nano cavity 12 close to the source 5 and contacts the gate 11 .

[0045] The biosensor based on the barrier gate structure tunneling field effect transistor involved in the above embodiment adopts SOI (silicon on insulating substrate) technology. The insulating layer 7 deposited on the intrinsic silicon substrate 8 is 200nm thick. The channel is grown on the insulating layer 7 and is composed of a heterostructure composed of silicon and graphene 2 with a thickness of 5nm-10nm, wherein the silicon is 40nm long and the graphene is 60nm 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 a P+ doped region 1, and the concentration is set to 1×10 20 cm -3 The N+ doped region 3 is located at one end of the graphene 2 close to the silicon, with a length of 3nm-5nm. It uses ion implantation technology with a concentration of 1×10 20 cm -3 , so that its conduction band is lower than the valence band of the P+ doped region 1 (the energy band is divided into conduction band and valence band, the conduction band is located above the valence band, and the energy band height can be adjusted by doping. Since the P+ doped region 1 uses P doping, the overall energy band will rise. By N+ doping the graphene, its energy band will be lowered, so 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 in the middle of the graphene 2, is 20nm long, and has a doping concentration of 5×10 18 cm -3 -5×10 19 cm -3The P barrier region 4 has a higher energy band through P doping to ensure that the device remains in the off state when the gate voltage is 0V; an atomic layer deposition process is used to deposit a 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 gate has better control over the channel. This embodiment uses silicon dioxide with a dielectric constant of 3.9. The dielectric constants of hafnium dioxide HfO2 and aluminum oxide Al2O3 are higher, and the effect is relatively better), and the thickness is 1nm-3nm; then, an oxide with a length of 25nm and a height of 10nm is continued to be deposited above the P barrier region 4, and then the metal gate 11, the source 5 and the drain 6 are prepared by the evaporation and sputtering technology of the metal electrode. The source 5 and the drain 6 should use the same metal; finally, the oxide under the gate 11 is etched 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 dielectric layer 10.

[0046] The detected biological molecules are confined in the bio-nano cavity 12, and different biological species are distinguished by different dielectric constants k. For example, when a single organism completely fills the bio-nano cavity 12, uricase k = 1.5, biotin k = 2.6, bacteriophage k = 6, and gelatin k = 12; the detection sensitivity is determined by the gate dielectric layer 9 and the bio-nano cavity 12. The larger the dielectric constant k of the organism, the larger the effective gate capacitance and the higher the sensitivity. The biosensor in this embodiment can detect the concentration of a single organism based on the dielectric constant after the single organism is filled in the bio-nano cavity 12, and can also distinguish each single organism based on 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 specifically reflected in:

[0048] Current sensitivity S I I is the current of the sensor when there is a living thing bio With the current I in the air air Ratio:

[0049]

[0050] Voltage sensitivity is the tunneling voltage V of the sensor when there is a living organism bio The tunneling voltage V in air air The absolute value difference of

[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] A biosensor based on a barrier gate tunneling field effect transistor uses silicon-graphene as a conductive channel and introduces an N+ doped region 3 at the heterojunction, so that the heterojunction between silicon and graphene 2 has a normally open tunneling condition. Figure 2 : The energy band diagram of the channel of the sensor of this embodiment under the on and off conditions, the energy band is divided into a conduction band and a valence band, the conduction band is above the valence band, and the middle is a forbidden band. One side of the source 5 is silicon, which has a larger forbidden band width, and adopts a P+ doped region 1, and the energy band is higher. One side of the drain 6 is graphene, which has a forbidden band width of only 0.26eV, and there is an N+ doped region 3 at the junction with silicon, so the energy band is lower. At this time, the tunneling condition is met, and the conduction band of the graphene 2 is lower than the silicon valence band. A bulge of the energy band can be seen in the middle of the graphene 2, which is caused by the 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 switch of the device. Figure 2 The two red solid lines in the figure represent the tunneled 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 the graphene 2, and then have enough energy to reach the drain 6 through the low barrier. The two black dotted lines in the figure represent the non-tunneled 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 closure of the device. In the closed state, the tunneling current is provided by the reverse heavily doped PN junction at the tunneling junction, so the current is small; in the open state, the energy band height of the P barrier region 4 decreases, and the electrons have enough energy to cross the barrier after tunneling, thereby realizing the opening of the device.

[0054] The sensor is based on the dielectric modulation effect, and analogizes biological molecules to insulating layers with different dielectric constants, and confines them in the biological nanocavity 12. When the biological nanocavity 12 is filled with the organism to be detected, the dielectric constant under the entire gate 11 will change, and the effective capacitance of the gate 11 will also change accordingly. In this way, the gate 11 will have different degrees of control over the channel, and the electron hole concentration in the barrier region of the channel will also change accordingly. The height of the barrier will be different, and the sensor will show different tunneling voltages under these organisms with different dielectric constants. The greater the change in the biological dielectric constant, the greater the tunneling voltage shown 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 organisms can be obtained, and different organisms can be clearly distinguished.

[0055] A simulation experiment was conducted on the biosensor based on the barrier gate structure tunneling field effect transistor involved in the above embodiment, as follows:

[0056] During the simulation, the drain 6 voltage is always set to 0.1 V, and the dielectric constant k is set to 1, 1.5, 2.6, 6 and 12 respectively, referring to different biological categories. The transfer curves are shown in Figure 3As shown. Under air conditions, that is, when the dielectric constant k = 1, the tunneling voltage of the sensor is 1.18V, and the subthreshold swing is relatively high, with the minimum subthreshold swing being 10.8mV / dec (the subthreshold swing refers to the change in gate voltage when the current increases by one order of magnitude from the device being turned off to fully turned on). Figure 3 It can be seen from the transfer curve that when k=1, when the voltage is 1.18V, after the current rises by 1 order of magnitude, the gate voltage changes by about 0.01V, which is calculated to be 10.8mV. The smaller this value is, the steeper the rising part of the transfer curve is, and the more beneficial it is to improve its current sensitivity); as the biodielectric constant increases, the tunneling voltage becomes smaller. When the biodielectric constant k reaches 12, the sensor tunneling voltage is reduced to 0.16V, the tunneling voltage sensitivity reaches 1.02V, and the minimum subthreshold swing also reaches 4.8mV / dec. Figure 4 The sensitivity diagram of the sensor when detecting organisms is shown. It can be seen that when the gate voltage is 1.18V, the sensor has the maximum current sensitivity when detecting organisms with k=12, with a current sensitivity of up to 8.85×10 12 The sensitivity can reach 8 orders of magnitude even when k=1.5. Compared with the prior art mentioned in the background technology, the sensor in this embodiment shows higher sensitivity in the field of biological detection.

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

Claims

1. A biosensor based on a barrier gate 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 electrode (5), a drain electrode (6), a gate electrode (11), a bio-nano cavity (12) and a bio-dielectric layer (10); wherein: The silicon substrate (8), the insulating layer (7), the channel and the gate dielectric layer (9) are stacked in sequence from bottom to top; The source electrode (5) and the drain electrode (6) are distributed on both sides of the channel, and both contact the channel and the gate dielectric layer (9), and are both 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 bio-nano cavity (12) is stacked on the upper surface of the gate dielectric layer (9) facing the P barrier region (4); The gate (11) is stacked on the upper surface of the bio-nano cavity (12), and the bio-medium layer (10) is stacked on the side of the bio-nano cavity (12) close to the source electrode (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 channel thickness is 5nm-10nm; 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 doping concentration of the P+ doping region (1) is 1×10 20 cm -3 ; and / or the doping concentration of the N+ doping region (3) is 1×10 20 cm -3 ; and / or the doping concentration of the P barrier region (4) is 5×10 18 cm -3 -5×10 19 cm -3 .

4. The biosensor based on barrier gate structure tunneling field effect transistor according to claim 1, characterized in that: The gate dielectric layer (9) is made of silicon dioxide, 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 source electrode (5) and the drain electrode (6) are made of the same metal material.

6. A method for preparing a biosensor based on a barrier gate structure tunneling field effect transistor according to any one of claims 1 to 5, characterized in that: Methods include: Depositing an insulating layer (7) on a silicon substrate (8); A channel is grown 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 an atomic layer deposition process; depositing an oxide on the gate dielectric layer (9), The metal gate (11), the source electrode (5) and the drain electrode (6) are prepared by using the evaporation and sputtering technology of the metal electrode; The oxide below the gate (11) is etched to form a bio-nano cavity (12).

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