Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is
Reexamination Certificate
1998-12-17
2001-02-27
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
C257S030000, C257S301000, C257S305000, C438S243000
Reexamination Certificate
active
06194736
ABSTRACT:
BACKGROUND OF THE INVENTION
In construction of microelectronic devices, it is well known that there is a constant pressure for reduction of device size and/or increase of device capability at a given scale.
In the actual construction of reduced scale devices, attention must be paid to higher precision in configuring the materials from which the device components are formed. Attention must also be paid to the interaction of the various materials used in device construction during the device manufacture process, during device testing, and during device operation. In this regard, finer sized device components are more sensitive to adverse materials interactions since the amount of material forming the component is smaller. For example, an interaction that might have only affected the border area of a large component would affect an entire component of smaller scale (e.g., where the scale of the smaller component is the same size as the border area of the larger component). Thus, reduction in component scale forces consideration of materials interaction problems which could have been viewed as non-critical for larger scale components.
In the context of devices such as deep trench capacitors in semiconductor substrates, the various materials used to form the components of the capacitor such as the capacitor plates (electrodes), the dielectric barrier between electrodes, oxide collar structures to prevent or minimize parasitic effects, surface or buried straps to provide contact between the capacitor and the other circuitry of the device, etc. For example, the electrode in the trench is typically a highly doped polycrystalline silicon (polysilicon) material, the buried or surface strap is typically an amorphous silicon, and the semiconductor substrate is a monocrystalline silicon. The successful functioning of the capacitor depends in part on the ability of these diverse materials to maintain their original or desirably modified character during manufacture/useful life of the device.
Unfortunately, the nature of these materials is such that unwanted interactions may occur unless otherwise prevented.
For example, a problem may be caused by the difference in crystallinity (or grain size) between the monocrystalline silicon substrate and the amorphous or polycrystalline silicon trench electrode material, especially where there is an intervening amorphous silicon material. In such configurations, the amorphous or polysilicon layer may template on the monocrystalline surface and recrystallize. Often, defects are created at the interface with the monocrystalline silicon during recrystallization which may propagate into the monocrystalline silicon. The occurrence of such defects is believed to adversely affect memory cell performance (the memory cell containing the capacitor). Specifically, the defects are believed to cause a lack of predictability of the charge retention time for the capacitor (so-called variable retention time). Such lack of predictability may limit the usefulness of the resulting device and/or the ability to maximize design performance.
Thus, there is a desire for improved capacitor structures which allow better control of materials interactions to enable construction of reliable reduced scale devices. It is also desired to meet these needs in an economical manner that minimizes or avoids compromise of other device or component properties.
SUMMARY OF THE INVENTION
The invention provides technology which enables reduced scale capacitor structures of improved reliability. More specifically, the invention enables these benefits by the creation and use of quantum conductive barrier layers between regions of differing degrees of crystallinity (or differing grain size).
In one aspect, the invention encompasses a deep trench capacitor in a monocrystalline semiconductor substrate, the capacitor (i) comprising a buried plate in the substrate about an exterior portion of a trench in the substrate, (ii) a node dielectric about at least a lower interior portion of the trench, (iii) an electrode in the trench, and (iv) a conductive strap extending away from the trench electrode, at least a portion of the conductive strap being electrically connected to the trench electrode and the monocrystalline substrate, the capacitor further comprising (v) a quantum conductive barrier layer between the monocrystalline substrate and the trench electrode.
In another aspect, the invention encompasses structures having regions of similar composition (e.g., differing only by amount of dopant or by dopant composition, or having essentially no difference in composition), but differing degrees of crystallinity (or differing average grain size), separated by a quantum conductive dielectric barrier layer. Preferably, a region on one side of the layer is amorphous or monocrystalline whereas a region on the other side of the layer is polycrystalline.
In another aspect, the invention encompasses methods of making trench capacitors containing quantum conductive layers, the methods comprising reacting a silicon surface with a nitrogen compound to form a thin silicon nitride compound layer.
In another aspect, the invention encompasses methods of making trench capacitors containing quantum conductive layers, the methods comprising depositing by chemical vapor deposition, physical vapor deposition or sputtering, a material layer which is sufficiently thin to be quantum conductive, the material being a dielectric in bulk form.
Preferred quantum conductive layers are silicon nitride compounds such as silicon nitride or silicon oxynitride.
These and other aspects of the invention are described in further detail below.
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Chaloux Susan E.
Chen Tze-Chiang
Faltermeier Johnathan E.
Gruening Ulrike
Jammy Rajarao
Capella Steven
Crane Sara
International Business Machines - Corporation
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