CN1527399A - Field-effect transistor - Google Patents

Abstract

The present invention discloses one kind of FET, and aims at providing one kind of FET device with improved short channel characteristic. The FET in the technological scheme of the present invention includes FET body comprising grid, source, drain, channel and substrate, the source and the drain of the FET is made of SiC material. The FET of the present invention can inhibit well the DIBL effect of device, lower the threshold voltage drift and off-state leakage current greatly and raise the current on/off ratio. The FET of the present invention exhibits superior characteristic compared with FET in conventional structure, has improved device channel performance and has huge application probability.

Description

A kind of field-effect transistor

Technical field

The present invention relates to semiconductor device, particularly a kind of field-effect transistor.

Background technology

Along with the continuous scaled down of device feature size, the short-channel effect of device, leakage causes potential barrier reduction (DIBL) effect and hot carrier's effect is on the rise, and makes device performance degeneration.The short-channel effect of device mainly be since along with channel length reduce electric charge occurs and share, be that the depletion region electric charge is subjected to grid-control system no longer fully under the grid, wherein some is subjected to the source, leaks control, and reducing along with channel length, the depletion region electric charge of the grid-control system of being subjected to reduces, more grid voltage is used for forming inversion layer, makes the grid voltage that reaches threshold value constantly reduce.Cause threshold voltage shift increase, the off-state leakage current of device to increase, the quiescent dissipation of device also increases thereupon, the performance degradation of device.

Summary of the invention

At above-mentioned deficiency, the purpose of this invention is to provide the improved field-effect transistor of a kind of short-channel properties.

For achieving the above object, technical scheme of the present invention is: a kind of field-effect transistor, comprise have grid, the field effect transistor tube body of source end, drain terminal, raceway groove and substrate, the source end of described field-effect transistor and drain terminal are the SiC material.

The doping content (Np) in described fieldistor channel district is 8e17cm ^-3

Described fieldistor channel length (L) is 100nm;

Described field-effect transistor gate oxide thickness (t _Ox) be 3nm;

The field-effect transistor of described SiC source, drain structure can be body silicon structure MOSFET, and the doping content in its source, drain region is 8e17cm ^-3-1e20cm ^-3Also can be SOI MOSFET structure, the doping content in its source, drain region is 1e20cm ^-3, the doping content in lightly doped drain (LDD) district is 8e17cm ^-3-1e19cm ^-3

The present invention creatively uses the SiC material at the source of field-effect transistor end and drain terminal, and (doping content of general field-effect transistor is 1e20cm to have reduced the doping content of field-effect transistor source and drain ^-3), make body silicon with structure of the present invention and the SOI MOSFET DIBL effect of suppression device well, reduce the threshold voltage shift and the off-state leakage current of device greatly, improved the current on/off ratio of device, shown the characteristic that is better than conventional structure MOSFET, improved the short-channel behavior of device, and in the source, when the doping content in drain region is low, this advantage performance very obvious.

Description of drawings

Fig. 1 is the structural representation of field-effect transistor of the present invention.

Fig. 2 is the variation with source, drain region doping content, the threshold voltage shift that is caused by the DIBL effect of the body silicon MOSFET of SiC source, drain structure and conventional structure MOSFET and the comparative result of sub-threshold slope.

Fig. 3 is when drain terminal voltage is respectively O.1V with 1.5V, the body silicon MOSFET of SiC source, drain structure and the source end of conventional structure MOSFET and the potential profile of channel region.

Fig. 4 is the variation with source, drain region doping content, the body silicon MOSFET of SiC source, drain structure and the current on/off ratio comparison diagram of conventional structure MOSFET.

Fig. 5 is the source, when the drain region is low-doped, the comparison diagram of the body silicon MOSFET of SiC source, drain structure and the transfer characteristic of conventional structure MOSFET.

Fig. 6 is the source, when the drain region is low-doped, the input-output characteristic of conventional structure MOSFET.

Fig. 7 is the source, when the drain region is low-doped, the body silicon MOSFET input-output characteristic of SiC source, drain structure.

Fig. 8 is the variation with LDD district doping content, the comparative result figure of the threshold voltage shift that is caused by the DIBL effect of SiC structure SOI MOSFET and conventional structure SOIMOSFET.

Fig. 9 is the variation with LDD district doping content, the ON state current of SiC structure SOI MOSFET and conventional structure SOIMOSFET and the comparative result of off-state current.

Figure 10 is the comparative result of SiC structure SOI MOSFET and conventional structure SOI MOSFET current on/off ratio.

Embodiment

The present invention will be described in detail below in conjunction with specific embodiment.

Shown in Fig. 1 a and Fig. 1 b, field-effect transistor of the present invention comprise have grid 1, the field effect transistor tube body of source end 2, drain terminal 3, raceway groove 4 and substrate 5, the source end 2 and the drain terminal 3 of described field-effect transistor are selected the SiC material for use, and channel length (L) is 100nm, gate oxide thickness (t _Ox) be 3nm, the doping content (N of channel region _p) be 8e17cm ^-3Wherein, Fig. 1 a is that source, drain region are the body silicon MOSFET of SiC material, and the doping content in source, drain region is 8e17cm ^-3-1e20cm ^-3Fig. 1 b is that source, drain region and lightly doped drain (LDD) district 7 all is the SOI MOSFET of SiC material, and the doping content in source, drain region is 1e20cm ^-3, the length (LDDdiff) in lightly doped drain (LDD) district is 100nm, doping content is 8e17cm ^-3-1e19cm ^-3, the degree of depth of burying oxide layer 6 is 400nm.

For investigating the present invention in the effect of improving aspect the device short-channel properties, following sunykatuib analysis the body silicon and the SOI MOSFET Devices Characteristics of SiC source, drain structure, and compare with conventional structure MOSFET.

The influence of aspects such as the threshold voltage shift that the variation of adopting two-dimensional device simulation softward-ISE to simulate the doping content (LDDdoping) in LDD district in the doping content (SDdoping) in source, drain region in the body silicon structure of the present invention and the soi structure is caused by the DIBL effect device, ON state current, off-state current.Wherein, the threshold voltage shift that is caused by the DIBL effect is $\mathrm{\Δ}{V}_{T\left(\mathrm{DIBL}\right)}=V_{T(V_{\mathrm{ds}}=0.1v)}-V_{T(V_{\mathrm{ds}}=1.5v)}$ (threshold voltage is meant when drain terminal voltage is 0.1V, the drain terminal electric current $I_{\mathrm{ds}}=\frac{W}{L}\×5\×{10}^{-7}A/\mathrm{\μm}$ The time gate voltage).ON state current (Ion) and off-state current (Ioff) are by calculating at V _DsDuring=1.5v, the I-V curve of gate voltage when 0v sweeps to 1.5v obtains.That is: Ion:V _g=V _DsDrain terminal electric current during=1.5V; Ioff:V _g=0V, V _DsDrain terminal electric current during=1.5v.

Embodiment 1: the variation of source, drain region doping content is to the influence of device performance in the body silicon device

Fig. 2 is the variation with source, drain region doping content, the threshold voltage shift that is caused by the DIBL effect of SiC source, drain structure MOSFET and conventional structure MOSFET and the comparative result of sub-threshold slope.As can be seen, the threshold voltage shift of SiC source, drain structure MOSFET in the source, the doping content in drain region is far smaller than conventional structure MOSFET when low.Doping content when source, drain region is 1e18m ^-3The time, the threshold voltage shift of conventional structure MOSFET device is 105mV, and the threshold voltage shift of SiC source, drain structure MOSFET device is 20mV, is SiC so work as the material of device source drain terminal, and the lower (1e18m of doping content ^-3) time, the drift of the threshold voltage of device will reduce 5 times.And the sub-threshold slope of SiC source, drain structure MOSFET is also less than the MOSFET of conventional structure.

In order to further specify the reason that SiC source, drain structure can suppression device DIBL effects, Fig. 3 has provided when drain terminal voltage is respectively 0.1V and 1.5V, the source end of SiC source, drain structure MOSFET and conventional structure MOSFET and the potential profile of channel region.As can be seen, drain terminal voltage changes to 1.5V from 0.1V, and the source end potential barrier of conventional structure MOSFET has reduced 0.15V, and the source end potential barrier of SiC source, drain structure MOSFET does not almost change, only reduced 0.02V, suppressed of the break-through of drain terminal power line effectively to the source end.By above analysis as can be seen, use SiC source, the drain structure DIBL effect of suppression device well.

It can also be seen that by Fig. 3, when drain terminal voltage is 0.1V, the source end potential barrier of SiC source, drain structure MOSFET is higher than conventional structure MOSFET, this another benefit that will bring to device is: device is when OFF state, because the source end potential barrier of device is higher, stoped charge carrier to flow to the source end by drain terminal, the off-state leakage current of device can reduce greatly.

Fig. 4 has provided the current on/off ratio comparison diagram with variation SiC source, drain structure MOSFET and the conventional structure MOSFET of source, drain region doping content.As can be seen, when the doping content in source, drain region is low (as 8e17m ^-3Or 1e18m ^-3), the current switch of SiC source, drain structure MOSFET device compares conventional structure MOSFET and wants a big 1-2 magnitude.Fig. 5,6,7 provided the source again respectively, when the drain region is low-doped, the transfer characteristic of SiC source, drain structure MOSFET and conventional structure MOSFET and the contrast of input-output characteristic.As can be seen, the characteristic of SiC source, drain structure MOSFET will be better than conventional structure MOSFET far away.

To sum up, when the doping content in source, drain region was hanged down, the body silicon MOSFET of SiC source, drain structure had all shown the characteristic that is better than conventional device at the aspects such as current on/off ratio of the DIBL of suppression device effect, the off-state leakage current that reduces device, raising device.As seen, the body silicon device of SiC source, drain structure has very big development potentiality.

The variation of LDD district doping content is to the influence of device performance in the embodiment 2:SOI device

Fig. 8 has provided the comparative result of the threshold voltage shift that is caused by the DIBL effect of variation SiC source, drain structure and conventional structure SOI MOSFET with LDD district doping content.As can be seen, when the doping content in LDD district by 8e17cm ^-3Change to 1e19cm ^-3The time, the threshold voltage shift of two kinds of structures all increases, this is because of the increase with LDD district doping content, the horizontal depletion region of raceway groove one side broadens, source, leakage increase with the electric charge of sharing of grid, the control ability of grid weakens, and the easier source end that is penetrated into of the power line of drain terminal increases the threshold voltage shift of device.And can reduce the DIBL effect of device greatly with SiC source, drain structure, make the SOI MOSFET of the threshold voltage shift of device less than conventional structure.Doping content when the LDD district is 5e18cm ^-3The time, the difference of the threshold voltage shift of two kinds of structure devices reaches 60mV.But the reduction of DIBL effect is to be cost with the part drive current of sacrificing device.

Fig. 9 has provided variation SiC source, drain structure and the ON state current of conventional structure SOI MOSFET and the comparative result of off-state current with LDD district doping content.As can be seen, the ON state current of SiC source, drain structure and off-state current are all less than the SOI MOSFET of conventional structure, but as can be seen by coordinate, the variation of ON state current is the minor variations on the same magnitude, and by the Roadmap of calendar year 2001 ITRS as can be known, when the channel length of device is 100nm, the ON state current of device is greater than 300 μ A/ μ m, as shown in phantom in Figure 9, for the SOI MOSFET of SiC source, drain structure, when the doping content in LDD district greater than 3.5e18cm ^-3The time, all satisfy the requirement of Roadmap.And we it can also be seen that by Fig. 9, and the doping content when the LDD district is 5e18cm ^-3The time, the off-state current of SiC source, drain structure device is 10 ^-11Magnitude, and conventional structure is 10 ^-8Magnitude is done source, drain region with the SiC material, and the off-state current of device can reduce widely.Thereby for the design of low consumption circuit has indicated a direction.

Figure 10 has further provided the comparative result of two kinds of structure devices current on/off ratios again, can make the switch attitude current ratio of device improve 2-4 the order of magnitude with SiC source, drain structure.

To sum up, the SOI MOSFET of SiC source, drain structure reduces the off-state leakage current of device in the DIBL of suppression device effect, and the aspects such as current on/off ratio that improve device have all shown great advantage, have improved the short-channel properties of device.

The present invention proposes the source that employing SiC material is made device in body silicon and SOI MOSFET, the drain region, can improve the short-channel properties of device, sunykatuib analysis shows, the SiC material is except there being the high heat conductance of reporting in the document, high critical electric field, broad-band gap, outside the advantages such as high carrier saturation drift velocity and high radiation preventing ability, the SiC source, the body silicon of drain structure and SOI MOSFET be the DIBL effect of suppression device well, reduce the threshold voltage shift and the off-state leakage current of device greatly, improve the current on/off ratio of device, shown the characteristic that is better than conventional structure MOSFET, improved the short-channel behavior of device, and in the source, when the doping content in drain region is low, it is very obvious that this advantage shows, so the SiC material has huge application potential aspect the preparation small size semiconductor device.

Claims (8)

1, a kind of field-effect transistor, comprise have grid, the field effect transistor tube body of source end, drain terminal, lightly doped drain (LDD), raceway groove and substrate, it is characterized in that: the source end of described field-effect transistor and drain terminal are the SiC material.

2, a kind of field-effect transistor according to claim 1 is characterized in that: the doping content in fieldistor channel district (Np) is 8e17cm ^-3

3, a kind of field-effect transistor according to claim 1 is characterized in that: described transistor channel length (L) is 100nm.

4, a kind of field-effect transistor according to claim 1 is characterized in that: described field-effect transistor gate oxide thickness (t _Ox) be 3nm.

5, according to claim 1 or 2 or 3 or 4 described a kind of field-effect transistors, it is characterized in that: described field-effect transistor is body silicon structure MOSFET, and the doping content in its source, drain region is 8e17cm ^-3-1e20cm ^-3

6, according to claim 1 or 2 or 3 or 4 described a kind of field-effect transistors, it is characterized in that: described field-effect transistor is a SOI MOSFET structure, and the doping content in its source, drain region is 1e20cm ^-3

7, a kind of field-effect transistor according to claim 6 is characterized in that: the doping content in described field-effect transistor lightly doped drain (LDD) district is 8e17cm ^-3-1e19cm ^-3

8, a kind of field-effect transistor according to claim 6 is characterized in that: the LDD district of described SOI MOSFET structure is the SiC material.

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