Patent Application
20060159847
FIELD OF THE INVENTION
The present invention relates generally to semiconductor processing and manufacturing apparatus. More specifically, the invention relates to methods and apparatus for forming dielectric films or layers at low temperature.
BACKGROUND OF THE INVENTION
The deposition of silicon nitride and/or silicon oxide films on the surface of semiconductor substrates using low temperature processing, particularly for SiN films, has recently received a great deal of attention in the semiconductor industry. Silicon nitride films are used extensively in the semiconductor industry for device passivation, mechanical protection, capping layers, contaminant barriers, on-chip capacitor dielectrics, interlayer dielectrics, freestanding membranes, and the like.
While the past ten or more years of CMOS junction development have been addressed primarily through variations to conventional implant-and-anneal-in-Si techniques, the next advances in the industry will likely involve modifications to both the material systems and their manner of introduction. Complicating these changes is the expectation that the channel and the gate stack material systems will simultaneously be undergoing revolutionary change, with a likely need to avoid interdiffusion or recrystallization, and thus can be expected to put an upper limit on the thermal budget allowed in the CMOS front end processing.
Accordingly, further developments are needed.
In general, the present invention provides methods and apparatus for forming dielectric films.
In one aspect, the present invention provides a method and apparatus configured to form dielectric films or layers at low temperature. In one embodiment dielectric films such as silicon nitride (SixNy) and silicon dioxide (SiO2) are deposited at temperatures equal to or below 550° C.
In another aspect of the present invention dielectric films are deposited using monomolecular precursors having one or more Si—N linkages or bonds. In one embodiment, monomolecular precursors are provided of the formula:
N(SiR3)3
Where R=H, alkyl, aryl, or amido.
In one embodiment the monomolecular precursor is trisilylamine (N(SiH3)3). In an alternative embodiment, monomolecular precursors are comprised of cyclic Si—N compounds. Examples of cyclic Si—N compounds include, but are not limited to, cyclic polyamides or polyamines (C replaced by Si).
In yet another aspect of the present invention, a method and apparatus configured to provide cross flow injection of reactant gases is provided. In one embodiment, reactant gasses (such as a monomolecular precursor and NH3) flow into vertically positioned adjustable injectors that mix reactants prior to injection into the wafer region. Gases exit the injectors through multiple holes that are positioned throughout the injectors to promote flow uniformity and velocity axially in the chamber. This is found to promote deposition of good quality films, and of particular advantage allows for carrying out the process at low temperatures.
In a further aspect of the invention, an apparatus is provided, comprising: a processing chamber, a wafer carrier positioned in the chamber and supporting a plurality of substrates; and an adjustable injector tube comprising a plurality of vertically positioned injectors along the vertical length of the injector tube. The vertically positioned injectors are configured to convey gases across the surface of said plurality of substrates.
BRIEF DESCRIPTION OF THE DRAWINGS
Advantages and embodiments of the present invention will become apparent upon reading the following detailed description and upon reference to the following figures, in which:
In one aspect, the present invention provides a method and apparatus configured to form dielectric films or layers at low temperature. In one embodiment dielectric films such as silicon nitride (SixNy) and silicon dioxide (SiO2) are deposited at wafer temperatures equal to or below 550° C.
In another aspect of the present invention dielectric films are deposited using monomolecular precursors having one or more Si—N linkages or bonds. In one embodiment, monomolecular precursors are provided of the formula:
N(SiR3)3
Where R=H, alkyl, aryl, or amido.
In one embodiment the monomolecular precursor is trisilylamine (N(SiH3)3). In an alternative embodiment, monomolecular precursors are comprised of cyclic Si—N compounds. Examples of cyclic Si—N compounds include, but are not limited to, cyclic polyamides or polyamines (Carbon replaced by Silicon). The silicon precursors replace silane, dichlorosilane or other carbon and/or chlorine containing precursors, which typically are used as the source of silicon for these applications.
In a further aspect of the present invention, a method and apparatus configured to provide cross flow injection of reactant gases is provided. In one embodiment, reactant gasses (such as a monomolecular precursor and NH3) flow into vertically positioned adjustable injectors that mix reactants prior to injection into the wafer region. Gases exit the injectors through multiple holes that are positioned throughout the injectors to promote flow uniformity and velocity axially in the chamber. This is found to promote deposition of good quality films, and of particular advantage allows for carrying out the process at low temperatures.
Referring to
Additionally, this premixing of the gasses helps prevent deposition of high silicon concentration films within the injector surface that may have a significantly different thermal expansion coefficient than Si3N4 which would cause flaking of the film from the injector's inner walls contributing to particle generation and defects on the wafer surface. Mixing of the gasses inside the injector tube 10 in a zone of the chamber that is at a considerably lower temperature than the molecules activation energy promotes a conformal film composition deposition through the entire process chamber and injector surfaces. A conformal film composition is desired in many applications, for example when performing in-situ cleaning due to etch rate variations of varying films using NF3 or Fluorine compounds.
Gases exit the injectors through multiple holes or injectors 12 that are positioned throughout the adjustable injector tube 10 to promote flow uniformity and velocity axially in the chamber. In some embodiments, gasses exit the injector holes, deflect from the chamber walls to optimize gas flow uniformity flow horizontally and parallel to the surface of the wafers and exit the chamber opposite the injection side of the chamber. Exhaust slots are positioned opposite the injectors in the wall of the chamber. The exhaust slots are preferably positioned through the chamber to promote flow uniformity and velocity axially in the chamber. This cross flow direction of the reactant gasses enables uniform deposition of the film within the wafer (radial) and wafer to wafer (axial) direction. By creating a cross flow gas pattern, depletion effects are overcome that are experienced in reactors which have only one injection point localized in the chamber. Abundance of available reactants is created in all locations of the reaction chamber. Gas velocities and density are adequate to establish uniform distribution of reactants in the radial direction across the wafer's surfaces. A uniform axial gas distribution is established with the injector hole size and positions creating a uniform pressure inside the injector tube, which equates to a uniform flow rate and velocity exiting the injector holes across the entire hole pattern of the injector tube.
In one embodiment, the process chamber is configured in such a manner as to practice the inventive method on a plurality of substrates, typically numbering up to 200 substrates or wafers stacked in a wafer boat. In one example a batch process chamber contains between 50 and 150 wafers. A “mini-batch” reactor may also be employed wherein a batch of substrates numbering between 1 and 50 are housed in a process chamber. Alternatively the mini-batch process chamber is configured to process between 1 and 25 substrates. One example of a mini-batch system is described in PCT patent application Ser. No. PCT/US03/21575 entitled Thermal Processing System and Configurable Vertical Chamber, the entire disclosure of which is incorporated by reference herein. While a number of examples are described it should be understood that the present invention may be carried out in a variety of chambers.
Preferably, injection of the reactant gases is configured such that wafers at the top of the wafer boat are in the abundance reaction regime or in a reduced starvation regime. Injection preferably provides a means to transfer the precursors past the lower ½ of the wafer load and increase partial pressures of available reactants at the upper ½ of the wafer load.
Using a monomolecular precursor in conjunction with the above described cross flow apparatus enables higher deposition rates due to a higher rate of gas transport to the reaction surface. This technique overcomes gas transport issues placing enough reaction constituents at the wafer surface thereby moving reaction kinetics to a surface limited regime where film uniformities are optimized and deposition rates are maximized.
In another aspect, the present invention provides additional apparatus embodiments that provide for cross-flow delivery of the monomolecular precursors at low temperature to form a monomolecular film.
Of particular advantage, embodiments of the present invention provide for depositing dielectric films or layers at low temperature and by delivering the reactant gases to the wafers in a cross flow manner. Referring again to
In some embodiments the gas is initially directed away from the wafers 108 toward the liner 120 or chamber wall to promote further mixing of the reactant gas before it reaches the wafer. In other embodiments, gases are initially directed toward the wafers 108. The injector tube 116 and thus the injectors 118 are adjustable, so that any desired orientation may be achieved, i.e. the gases may exit the injectors throughout a rotation of 360 degrees.
In other embodiments, two or more injector tubes 116 may be employed. In this embodiment, separate gases are delivered through separate injector tubes, and the gases mix in the chamber once the gases exit the injectors 118. Alternatively, one or more of the injector tubes 116 may convey mixed gases as shown in
Specifically, referring to
As described above, the injector tubes are adjustable and may be rotated as desired.
Exemplary embodiments have been described with reference to specific configurations. The foregoing description of specific embodiments and examples of the invention have been presented for the purpose of illustration and description, and although the invention has been illustrated by certain of the preceding examples, it is not to be construed as being limited thereby.
| Number | Date | Country | |
|---|---|---|---|
| 60615135 | Sep 2004 | US |
