CN116314002A - Implementation mode of PDSOI body contact structure - Google Patents

Abstract

An implementation mode of a PDSOI body contact structure belongs to the technical field of semiconductors. The invention also provides a novel device structure, the body region is connected with the P+ region through the P-type silicon region under the VSTI, and the metal silicide layer is arranged on the source electrode and the P+ body contact region to form ohmic contact, so that the potential of the body region is clamped, the threshold voltage is maintained stable, and the parasitic bipolar transistor is not easy to conduct. The invention not only effectively inhibits the floating body effect generated when the PD SOI device works, but also is compatible with the standard CMOS technology, so that the channel width is not changed, and the two ends of the body region are contacted.

Description

Implementation mode of PDSOI body contact structure

Technical Field

The invention provides a novel device structure, which effectively inhibits a floating body effect generated when a Partially depleted silicon-on-insulator (PDSOI) device works, in particular relates to a device structure for realizing a PDSOI device body contact technology, and belongs to the technical field of semiconductors.

Background

As device feature sizes decrease, moore's law is undergoing more and more serious challenges, and it is continued to develop, depending on the advent of innovative technologies, SOI technology has great potential for development in recent years.

Silicon-on-insulator (SOI) refers to a method of forming a single crystal silicon film on an insulating substrate, or a method of forming a single crystal silicon film by an insulating layer (typically SiO ₂ ) And separating the formed material structure from the supported silicon substrate. The differences between SOI devices and bulk silicon devices are mainly caused by the introduction of buried oxide layers (BOX), which can make three main changes in the structure of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices: the buried oxide layer isolates the active region of the device from the substrate, and the buried oxide layer replaces the substrate to make direct contact with the source and drain, and the active region is changed into a thin silicon film from the whole substrate. Therefore, compared with the bulk silicon technology, the SOICMOS technology has the advantages of no latch, high speed, low power consumption, miniaturization, radiation resistance and the like.

SOI devices are classified into fully depleted and partially depleted devices, the threshold voltage is very sensitive to the thickness of the silicon film because the silicon film is fully depleted during operation, and therefore the threshold voltage is not easily controlled, and the electrical characteristics of fully depleted SOI devices may be affected by the non-uniformity of the silicon film because the silicon film is very thin. Therefore, the current partially-depleted SOI device is more suitable for mass production application, but a floating body effect is generated when the partially-depleted SOI device works, a parasitic bipolar transistor is formed in the MOS tube, a source region and a drain region are regarded as an emitter and a collector of the bipolar tube, and a body region is regarded as a base of the bipolar tube. The "body" in a PDSOI device is floating and the parasitic bipolar transistor is easily triggered to turn on as shown in fig. 1. The floating body effect causes a king effect; the saturation region current suddenly increases; the drain breakdown voltage is reduced; parasitic bipolar transistor turn on forms positive feedback in the device, leading to early breakdown of the device; the problems of increased gate-induced drain leakage (GIDL, gateInducedDrainLeakage) current and the like seriously affect the performance of the device and even cause the device to fail.

Solutions to the floating body effect are mainly divided into two types, namely, a body contact mode is adopted to release accumulated holes. The body contact is to make the neutral area above the buried oxide layer and at the bottom of the silicon film in an electrically floating state contact with the outside, so that holes cannot accumulate in the neutral area, namely, the body is connected to a fixed potential (source end or ground); the other is to adopt source-drain engineering or substrate engineering to lighten floating body effect from the technical point of view.

The current common technical method for inhibiting the floating body effect by a body contact mode is to make a body region and P pass through a certain channel ⁺ The doped regions are connected. One of the methods is to use the non-fully oxidized area under the ultra shallow trench isolation (VSTI) adjacent to the source end along the gate width direction gate end as a channel connecting the body area and the p+ body contact area, as shown in fig. 2, the method can increase the device area compared with the floating body SOI device, the number of masks is increased during manufacturing, the source end cannot be doped to the bottom, and the process flow is complicated; another approach is to use a region under VSTI adjacent to the source terminal that is not fully oxidized, and the channel connecting the body region and the p+ body contact region is connected to the p+ doped region, as shown in fig. 3, which has the disadvantage that, except for the increased area and mask, the process flow is complicated, the body region of the structure is only in one direction to achieve body contact, if holes in the body region under the middle gate are released according to the proximity principle, the body potential cannot be clamped well, and the source terminal must not be injected to the bottom.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a novel device structure. As shown in fig. 4, the body region and the p+ region (adjacent to the n+ source region) are connected by the P-type silicon region under the VSTI, so that holes accumulated in the body region leak to the p+ region, and the source and the p+ body contact region can be electrically connected by forming ohmic contacts by arranging metal silicide layers on the source and the p+ body contact region, so that when the source is grounded, the body contact region is also grounded to release holes, the condition of providing grounding for the contact region is not required, and the electrode of the contact region is omitted. The structure can effectively leak holes accumulated in the body region and well inhibit the floating body effect of the device. And meanwhile, the structure is compatible with source-drain injection to bottom and non-bottom processes.

According to the invention, a VSTI structure is skillfully utilized, so that a P-type silicon region, a body region and a P+ region under the VSTI are connected, holes accumulated in the body region are leaked to the P+ region, body contact can be realized at two ends of the body region along the width direction of the gate, holes in the body region under the middle gate can be directly released to the P+ region according to a nearby principle through source-drain injection, the potential of the body region is better clamped, the threshold voltage is not greatly reduced, and a parasitic bipolar transistor is not easy to trigger and conduct, so that a floating body effect is well restrained. In addition, the source-drain width at two sides of the gate is unchanged, namely the channel width is constant from source to drain, so that current crowding can be avoided. In the structure, the heavily doped P+ injection can be replaced by a method of growing silicide to enable the silicide to be adjacent to the N+ diffusion region, so that Schottky contact is formed, and the junction capacitance is reduced.

Drawings

Fig. 1: parasitic bipolar transistor effects in the soi mos device;

fig. 2: a body contact mode for suppressing the floating body effect of a device is the first mode, wherein (a) a top view (b) is a cross section along the AA 'direction (c) is a cross section along the BB' direction

Fig. 3: a second prior body contact mode for inhibiting the floating body effect of the device, wherein (a) a top view (b) is a cross-sectional view along the AA' direction

Fig. 4: the invention provides a body contact structure capable of inhibiting a floating body effect of a device, wherein (a) a top view (b) is a cross-sectional view along the AA 'direction (c) is a cross-sectional view along the BB' direction.

Detailed Description

The device manufacturing method according to the present invention is as follows, taking the NMOS device of PDSOI as an example, as shown in the cross-sectional view of fig. 4:

(1) Firstly, preparing an SOI wafer, wherein the specific method can form a BOX layer on a silicon substrate, then form a top silicon film on the BOX layer as a body region, or implant oxygen ions on the silicon substrate to form the BOX layer inside the silicon substrate.

(2) An active region is defined, and a field oxide isolation region is formed around the active region, wherein the field oxide isolation is formed using a shallow trench isolation (STI, shallow Trench Isolation) process to form a field oxide isolation medium.

(3) The VSTI region is defined in the AA' direction as a body region extraction channel.

(4) And forming a P+ region in the active region by implanting boron ions.

(5) And forming a silicon dioxide gate dielectric layer in the active region, and forming polysilicon on the dielectric layer as a gate region.

(6) Source and drain regions (BB' direction) are formed on the active region by ion implantation, with the implanted ions being arsenic or phosphorous, and the implantation depth may or may not be as low as the top of the BOX layer. When the bottom is reached, the body region can be connected with VSTI in the AA' direction to carry out body extraction from the P+ region; when not reaching the bottom, the body extraction can be performed through P+ along the VSTI, and the body extraction can also be performed through P+ directly from the bottom body region of the source region.

Claims (3)

1. An implementation manner of a PDSOI body contact structure is characterized in that:

(1) Firstly, preparing an SOI wafer; firstly, forming a buried oxide layer, namely a BOX layer, on a silicon substrate, and then forming a top silicon film on the BOX layer to serve as a body region, or implanting oxygen ions on the silicon substrate to form the BOX layer in the silicon substrate;

(2) Defining an active region, and forming a field oxide isolation region around the active region;

(3) Defining a VSTI region in the direction parallel to the longitudinal symmetry axis of the grid electrode as a body region leading-out channel;

(4) Forming a P+ region in the active region by implanting boron ions;

(5) Forming a silicon dioxide gate dielectric layer in the active region, and forming polysilicon on the dielectric layer as a gate region;

(6) And forming a source region and a drain region on the active region by ion implantation, wherein the implanted ions are arsenic or phosphorus.

2. The implementation of a PDSOI body contact structure according to claim 1, wherein:

the ion implantation depth may or may not reach the bottom of the BOX layer; when the bottom is reached, the body region can be connected with VSTI in the AA' direction to carry out body extraction from the P+ region; when not reaching the bottom, the body extraction can be performed through P+ along the VSTI, and the body extraction can also be performed through P+ directly from the bottom body region of the source region.

3. A PDSOI body contact structure made in accordance with the implementation of claim 1 or 2.

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