1. A method for depositing a silicon oxide layer on a substrate comprising a silicon region and a silicon-germanium region, comprising the steps of:
forming a very thin silicon layer having a thickness ranging from 0.1 to 1 nm above the silicon-germanium;
depositing a silicon oxide layer on the substrate; and
wherein the silicon-germanium region is formed of a thin layer having its upper surface substantially at the same level as the upper silicon surface.
2. The method of claim 1, wherein the deposition of the silicon oxide layer is performed by chemical vapor deposition.
3. The method of claim 1, wherein the deposition of the silicon oxide layer comprises a previous chemical cleaning step.
4. The method of claim 1, wherein the very thin silicon layer is formed in an epitaxy chamber previously used to form the silicon-germanium region.
5. The method of claim 4, comprising the steps of:
a) forming the silicon-germanium in the presence of a germanium precursor and of a silicon precursor; and
b) stopping the introduction of the germanium precursor to form the very thin silicon layer.
6. The method of claim 5, wherein, at step b), the temperature is decreased.
7. The method of claim 5, wherein at step b), the introduction of the silicon precursor used at step a) is stopped and a silicon precursor containing more chlorinated species than the silicon precursor used as step a) is introduced.
8. The method of claim 5, wherein, at step b), HCl gas is added.
9. The method of claim 6, wherein the temperature ranges between 550 and 650\xb0 C. during the step of forming of the silicon-germanium region, then ranges between 450 and 550\xb0 C. during the step of forming of the very thin silicon layer.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for heating a fluid, the apparatus comprising:
a housing defining an interior, the housing having a fluid inlet into the interior and a fluid outlet out of the interior;
a fluid heating assembly positioned in the housing to heat fluid entering the interior, the heating assembly being rotatable with respect to the housing about an axis of rotation, the fluid heating assembly comprising a support shaft and a plurality of disks mounted on the support shaft and being oriented substantially perpendicular to the axis of rotation of the impeller assembly, the plurality of disks being positioned along the support shaft and being spaced from each other in an axial direction to form gaps therebetween, the disks including a conductive material;
a magnetic assembly configured to apply a magnetic field of adjustable intensity to the disks, the magnetic assembly being positioned in the interior of the housing, the magnetic assembly comprising:
a plurality of magnetic elements positioned adjacent to the disks; and
a support structure supporting the plurality of magnetic elements proximate to the gaps between the disks, the support structure moving the magnetic elements between a maximum exposure position with respect to the conductive material of the disks in which a relatively greater degree of heating is produced and a minimum exposure position with respect to the conductive material of the disks in which a relatively lesser degree of heating is produced.
2. The apparatus of claim 1, wherein the support structure comprises:
a pivot shaft pivotable with respect to the housing; and
a plurality of mounting plates having the magnetic elements mounted thereon, the mounting plates being mounted on the pivot shaft and being pivotable with the pivot shaft such that the mounting plates and magnetic elements are movable toward and away from the axis of rotation.
3. The apparatus of claim 2 wherein the support structure further comprises an actuator assembly for pivoting the pivot shaft, the actuator assembly including a pivot arm mounted on the pivot shaft to pivot with the pivot shaft, and an actuator acting on the pivot arm to pivot the pivot shaft.
4. The apparatus of claim 3 wherein the actuator comprises a linear actuator and is located outside of the interior of the housing.
5. The apparatus of claim 1 wherein the fluid inlet comprises a plurality of fluid inlets.
6. The apparatus of claim 5 wherein the plurality of fluid inlets are arranged in a linear array.
7. The apparatus of claim 1 wherein the fluid outlet comprises a plurality of fluid outlets.
8. The apparatus of claim 7 wherein the fluid outlets are arranged in a linear array.
9. The apparatus of claim 8 wherein the fluid inlet comprises a plurality of fluid inlets arranged in a linear array, and the linear array of inlets is oriented substantially parallel to the linear array of outlets.
10. The apparatus of claim 1 wherein the fluid inlet comprises a plurality of fluid inlets and an inlet manifold in fluid communication with the fluid inlets; and
wherein the fluid outlet comprises a plurality of fluid outlets and an outlet manifold in fluid communication with the fluid outlets.