Abstract: For trench isolation technology or trench capacitor type memory cells, it is necessary to controllably dope the steep sidewalls of the trench. Implantation is ineffective and chemical doping sacrifices control.A thin transfer layer of polysilicon is deposited in the trench to conformally coat the sidewalls as well as the bottom of the trench and the top surface surrounding the trench. An impurity is implanted into the polysilicon at the bottom of the trench and around the top surface. Upon heating that impurity diffuses rapidly along the polysilicon layer inwardly and downwardly along the sidewalls. It then may be diffused into the substrate. The polysilicon layer may be etched away, or may be oxidized to SiO.sub.2 and etched away, or left in place.

Abstract: A transfer layer is utilized to laterally redistribute impurities from a more heavily doped region to a lighter doped region. The contact to the source-drain region in advanced memory arrays has a width of the order of the minimum feature size. The source-drain has similar minimum feature dimensions in width to keep the array optimally dense. Thus this contact is made "headless" and requires a "line on line" alignment. Some offset in forming the window is inevitable and that offset exposes the channel stop. The contact then shorts to the substrate.Using a polysilicon transfer layer with an appropriate post anneal the region immediately under the contact and along the window sidewall can be autodoped sufficiently to avoid shorts to the substrate, and provide a continuous electrical path for the deposited contact.

Abstract: A method of implanting ions into the sidewalls of isolation trenches is disclosed. The method utilizes a series of ion implants to produce concentrations of the ion, in most cases boron, along the depth of the trench. Since the ion concentration exhibits a Gaussian distribution function which tails off rapidly, the width of the trench is narrowed after the implantation to guarantee a sufficient boron concentration at the sidewalls of the trench. A layer of an insulating material is used to narrow the trench, where a conformal coating of the material will cover the sidewalls of the window and narrow the opening through the window. By increasing the boron doping in the sidewalls, the effects of boron segregation between the substrate and the isolation trench will be counteracted, thus eliminating the problem of creating an n-type inversion layer between the trench and the substrate.