Method For Processing A Substrate
Original Publication Date: 2001-Oct-17
Included in the Prior Art Database: 2001-Oct-17
Rama Hegde: AUTHOR [+3]
A semiconductor substrate having an exposed semiconductor surface is placed into a processing chamber at a first temperature and the processing chamber is evacuated to a pressure greater than approximately 0.10 Torr. The chamber temperature is then increased to a second temperature while flowing a non-reactive gaseous species into the processing chamber. The temperature of the processing chamber is then adjusted to a third temperature, wherein the third temperature is a processing temperature at which a layer is formed over the exposed semiconductor surface. A source gas is then flowed into a processing chamber and a layer is formed over the exposed semiconductor surface. In accordance with one embodiment, the layer includes a semiconductor layer, such as silicon or epitaxial silicon. In accordance with another embodiment the layer includes a high-k dielectric layer.
METHOD FOR PROCESSING A SUBSTRATE
The present invention relates generally to methods for preparing a substrate, and more particularly, to methods used in preparing semiconductor substrates having exposed semiconductor surfaces.
Surface preparation methods of semiconductor substrates is becoming increasingly critical as integrated circuit geometries become smaller. For example, exposed silicon surfaces of a semiconductor substrate should be free of contaminants, impurities, and native oxides before subsequent layers of silicon or other materials, particularly epitaxial silicon or high dielectric constant (high-k) materials are deposited on the silicon surface. For the purposes of this specification a high dielectric constant film is any film having a dielectric constant greater than approximately 4.5. The presence of unwanted oxide or other contaminants on the silicon surface may interfere with the film deposition quality or electrical properties of the semiconductor device and result in noise, degraded performance, or failure of the integrated circuit.
Methods of preparing exposed silicon surfaces often include first heating the substrate in a hydrogen ambient (hydrogen pre-bake) in a single-wafer processing chamber at a temperature greater than approximately 900°C immediately prior to film deposition. However, although the hydrogen pre-bake removes native oxide, it can also result in a high interface state density and produce threshold voltage shifts in the semiconductor device. Another concern with the hydrogen pre-bake includes a possibility of undesirably etching the exposed silicon surface, especially at high-stress regions of the substrate. In addition, while the hydrogen pre-bake may be acceptable for some film depositions, adverse effects, such as excessive dopant diffusion, silicon dioxide damage and surface roughening make this process undesirable for preparation of a silicon surface for epitaxial silicon deposition. Other prior art methods for preparing exposed silicon surfaces include using wet cleans, such as a dilute hydrofluoric acid dip to: (1) remove oxide from the silicon surface and (2) passivate the silicon surface with hydrogen. In conventional hot walled batch epitaxial reactors, however, slow ramp rates can result in the loss of passivated hydrogen and leave the surface at a highly reactive state before the deposition starts. The use of ultrahigh vacuum (approximately 10-9 Torr) chemical vapor deposition (CVD) processing has been proposed to eliminate this problem. However, ultrahigh vacuum processing increases processing costs and it is not readily extendable for use with conventional batch processing systems.
The present invention is illustrated by way of example and not limited in the accompanying figures, in which like references indicate similar elements, and in which:
FIG. 1 includes a block diagram illustrating a sequence of processing steps use...