Coating processes – Coating by vapor – gas – or smoke – Mixture of vapors or gases utilized
Reexamination Certificate
2003-02-27
2004-12-28
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Mixture of vapors or gases utilized
C427S255290, C427S255392, C427S255394, C427S314000, C427S372200
Reexamination Certificate
active
06835417
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and to a related process chamber for producing a layer made from a layer material on at least sections of a substrate surface of a substrate by sequential deposition of at least two chemical precursor compounds of the layer material from a vapor phase. In each case the system comprises at least
a holding device for holding in each case one substrate;
feed and discharge device for the vapor phases of the chemical precursor compounds;
substrate feed device for introducing at least one substrate;
heating source for heating the substrate and/or the substrate surface; and
a control device for the sequential introduction of at least two chemical precursor compounds.
The invention specifically relates to processes for depositing layers made from a layer material on at least sections of a substrate surface of a substrate arranged in a chamber interior of a process chamber.
A typical production step involved in the production of micromechanical or microelectronic components is that of producing layers on at least segments of a substrate from various layer materials, then treating and changing the chemical and/or physical properties of the layers which have been deposited, and structuring the layers which have been deposited and changed. The substrate is typically a wafer made from a semiconductor material. A high integration density, as is required in particular for electronic components, such as processors and semiconductor memory devices, requires very small layer thicknesses and small dimensions for structures in the layer. Nowadays, layer thicknesses of a few nanometers and structure dimensions of a few tens of nanometers are customary.
The ongoing miniaturization increases the demands imposed on layer quality. Such layer quality is determined by defect density, roughness, and homogeneity of a layer.
In this context, the term roughness describes a deviation of a surface of a layer from an ideally planar surface. The defect density is a measure of the number and size of impurities or structural defects in the layer. Impurities are in this context inclusions of a material other than the layer material. Examples of structural defects are voids or, in the case of layer materials which form crystals, lattice defects. The term homogeneity relates to a physical and chemical uniformity of the layer.
Standard processes for producing layers with a layer thickness of less than one micrometer on a substrate are epitaxial processes, physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes.
In CVD processes, a substrate that is placed in a CVD process chamber is exposed to a flow of one or more process gases. The process gases are, by way of example, gaseous chemical precursor compounds of the layer material or inert carrier gases which convey the precursor compounds in solid or liquid form. In the CVD process chamber and/or above the substrate surface, the layer material is produced photolytically, thermally and/or with plasma enhancement from the precursor compound(s) (also referred to below as precursors), and is deposited on the substrate surface and forms a layer. The deposition generally takes place either at atmospheric pressure or at subatmospheric pressure. A CVD process chamber in which deposition processes at subatmospheric pressure are possible is described in U.S. Pat. No. 5,935,338 (Lei et al., Applied Materials Inc.).
Since the deposition is closely linked to the supply of the precursors and therefore to the flow of the process gases, deposition of a homogeneous layer of uniform thickness requires complex and expensive CVD process chambers as well as precise process control.
A further drawback of CVD processes is poor edge coverage. On a structured substrate surface which has recesses with flanks which are vertical with respect to the substrate surface, the edge coverage represents a measure of the extent to which the layer material is deposited at the flanks at the upper end of the recess, facing the surface, and at the flanks at the lower end of the recess, facing the base of the recess.
The fact that both the precursors and the layer material as it were coexist in the immediate vicinity of the substrate surface furthermore results, during the deposition, in inclusions of the precursors in the layer which is being deposited and therefore in a defect density which is inherent to the process in the layer which has been deposited.
After a layer has been deposited, it may be necessary, prior to the structuring of the layer or prior to the application of a further layer, to carry out a temperature step. This temperature step may involve either heating or cooling, as a result of which, for example, layer materials are set, diffusion or implantation operations are stopped, thermomechanical stresses in the layer are reduced and the chemical composition is homogenized (annealing).
Processes which include a generally rapid, brief heating or cooling of a substrate are collectively known by the term RTP (rapid thermal processing) processes. RTP processes are also used to oxidize and nitride layers. There are usually dedicated RTP reactors available for RTP processes, as are known, for example, from U.S. Pat. No. 6,310,327 (Moore et al,). Such RTP reactors are equipped with radiation sources inside or outside a process chamber, by means of which rapid temperature changes on a substrate surface arranged in the process chamber are controlled. A drawback of combining CVD processes in CVD process chambers with RTP processors in RTP reactors is the difficulty of transferring the substrates between the CVD process chamber and RTP reactor. Each transfer increases the likelihood of the substrate surface being contaminated and in this context entails considerable set-up outlay and downtimes on installations in question.
Therefore, RTCVD installations (RTCVD: rapid thermal chemical vapor deposition) are also known, for example from U.S. Pat. No. 4,892,753 (Wang et al.) or U.S. Pat. No. 5,935,338 (Lei et al., Applied Materials), in which CVD process chambers are equipped with rapidly heating radiation sources which are known from RTP reactors. RTCVD installations of this type firstly in principle allow RTP and CVD processes to be carried out in a single process chamber. Furthermore, CVD processes can be improved in RTCVD installations. Rapid heating of the substrate surface acts as a reactive switch and allows very greatly improved process control and shorter deposition times.
However, RTCVD installations of this type have a number of drawbacks. For example, in standard CVD and RTCVD processes, the reaction products of the vapor phase deposition are deposited not on the substrate surface but rather also on the inner sides of a chamber wall, which surrounds a chamber interior of the process chamber. If, as a result, the temperature in the process chamber changes considerably, the materials of the chamber wall and the deposited layer material expand to different extents, with the result that the material which has been deposited on the inner wall flakes off and contaminates the process chamber with particles. Once they have been deposited on the substrate surface, these particles increase the defect density in the layer that has just been deposited.
A further drawback results in connection with the radiation sources. In RTCVD reactors, the radiation sources may, in principle be arranged inside or outside the process chamber. Arranging the radiation sources outside the RTCVD reactor requires the chamber wall to be transparent at least in sections. To prevent deposition of the reaction products on the inner side of transparent sections (windows) of the chamber wall, complex cooling of the windows is required. An example of a cooled window for RTCVD process chambers is described in U.S. Pat. No. 6,384,051 (Fidelmann). Furthermore, layers which have been deposited on the chamber walls in CVD process chambers are regularly removed by purging with etching gases. If the deposited layer materials are dielec
Gutsche Martin
Hecht Thomas
Saenger Annette
Seidl Harald
Sell Bernhard
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