High performance LDMOS device having enhanced dielectric strain layer
View Patent ↗An LDMOS device includes a substrate having a surface and a gate electrode overlying the surface and defining a channel region in the substrate below the gate electrode. A drain region is spaced apart from the channel region by an isolation region. The isolation region includes a region of high tensile stress and is configured to induce localized stress in the substrate in close proximity to the drain region. The region of high tensile stress in the isolation region can be formed by high-stress silicon oxide or high-stress silicon nitride. In a preferred embodiment, the isolation region is a shallow trench isolation region formed in the substrate intermediate to the gate electrode and the drain region.
1. A method for fabricating an LDMOS device, the method comprising:
providing a substrate having a surface;
forming an isolation region, the isolation region comprising a region of tensile stress, relative to the substrate;
forming a gate electrode overlying the surface and defining a channel region in the substrate below the gate electrode; and
forming a drain region in the substrate spaced apart from the gate electrode at the surface by the isolation region,
wherein the isolation region creates a localized stress in a region of the substrate at least partially surrounding the drain region and the isolation region,
and wherein the isolation region is spaced apart from the channel region by a distance to substantially avoid inducing stress in the channel region.
2. The method of claim 1 , wherein forming an isolation region comprises forming a shallow trench isolation region.
3. The method of claim 2 , wherein forming a shallow trench isolation region comprises forming a silicon oxide liner in the shallow trench and forming a high-stress silicon nitride region on the silicon oxide liner.
4. The method of claim 2 , wherein forming a shallow trench isolation region comprises filling the trench with an insulating material using a high aspect ratio process (HARP).
5. The method of claim 4 , wherein filling the trench comprises depositing a stress-inducing silicon oxide by way of a sub-atmospheric chemical vapor deposition process using tetraethylorthosilane (TEOS) and ozone.
6. The method of claim 5 , wherein depositing a stress-inducing silicon oxide comprises using a ratio of ozone to TEOS comprising an excess amount of ozone, relative to an amount necessary for stoichiometric TEOS.
7. The method of claim 1 , wherein the isolation region is configured to apply localized tensile stress in the substrate.
8. The method of claim 1 , wherein forming a gate electrode overlying the surface and defining a channel region in the substrate comprises forming the gate electrode and underlying channel region a sufficient distance from the isolation region, such that the isolation region does not apply substantial stress to the channel region.