Ultraviolet Blocking Layer
Methods and apparatuses are disclosed relating to blocking ultraviolet electromagnetic radiation from a semiconductor. Ultraviolet electromagnetic radiation, such as ultraviolet electromagnetic radiation generated by a plasma process, which may otherwise damage a semiconductor can be blocked from one or more layers below an ultraviolet blocking layer.
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This application is a divisional of U.S. patent application Ser. No. 10/858,352, filed 01 Jun. 2004, by inventors Chien Hung Lu and Chin Ta Su, entitled Ultraviolet Blocking Layer.
BACKGROUND OF THE INVENTION1. Field of the Invention
Various embodiments relate in general to semiconductor devices and to processes for fabricating semiconductor devices. More particularly, various embodiments relate to semiconductors having an ultraviolet (UV) blocking layer and to processes for fabricating such semiconductors.
2. Description of Related Art
As device geometry has continued to shrink, dimensional requirements of devices become more exacting while the aspect ratios of etching or gap filling rise. Plasma process technology is indispensable for ULSI fabrication that meets these demands. Examples of plasma process applications include plasma implantation, plasma sputtering, physical vapor deposition (PVD), dry etching, and chemical vapor deposition (CVD), for example, plasma assisted CVD, plasma-enhancement CVD, and high-density plasma CVD.
However, plasma process-induced damage will cause severe damage on semiconductor devices and deteriorate the performance of semiconductor devices. Also, ultraviolet electromagnetic radiation (UV) induced from plasma process applications will alter device behavior and degrade gate oxide reliability. As described on page 356 of IEEE 99CH36296 37th Annual International Reliability Physics Symposium, San Diego, Calif., 1999, Shuto et al. used silicon nitride and silicon oxynitride to reduce plasma-induced damage. Unfortunately, neither the silicon nitride layer nor the silicon oxynitride layer used by Shuto et al. is sufficient to act as an ultraviolet blocking layer for plasma processes such as plasma-enhancement CVD or high-density plasma CVD. Thus there exists a need to provide an effective ultraviolet blocking layer for fabricating semiconductor devices.
SUMMARYOne aspect relates to providing a semiconductor device having a layer of silicon enriched oxide as a UV blocking layer to block process-induced ultraviolet electromagnetic radiation for improvement of device performance. The semiconductor device comprises a semiconductor substrate, and a layer of silicon enriched oxide having a ratio of a silicon concentration to an oxygen concentration sufficient for ultraviolet blocking. The layer of silicon enriched oxide can be formed from at least one of SiH4/N2O, SiH4/O2, TEOS/O2 and TEOS/O3 by conducting at least one of PECVD, SACVD and HDPCVD. The PECVD process can use SiH4/N2O and/or TEOS/O2. The HDPCVD process can use SiH4/O2. The SACVD process can use TEOS/O3. The layer of silicon enriched oxide may have a thickness of 100 Angstroms to 8000 Angstroms.
Another aspect relates to a method for fabricating semiconductor devices. The method comprises providing a semiconductor substrate, and forming a layer of silicon enriched oxide overlying the semiconductor substrate. The layer of silicon enriched oxide can be formed by selecting at least one of SiH4/O2, SiH4/N2O, TEOS/O2 and TEOS/O3, for example, by conducting plasma-enhancement chemical vapor deposition (PECVD), semi-atmosphere chemical vapor deposition (SACVD) and/or high-density plasma (HDPCVD).
Another aspect relates to a semiconductor processing method. An oxide enriched with silicon can be formed over a substrate. The substrate can include features. A process including UV radiation can be applied to define structure over the oxide. The oxide can have a ratio of a silicon concentration to an oxygen concentration sufficient to protect the features from the UV radiation.
Another aspect relates to another semiconductor processing method. A substrate is provided with a source of silicon and a source of oxygen. A ratio of a flow rate of the source of silicon to a flow rate of the source of oxygen is controlled, to form a silicon enriched layer on the substrate. The substrate can include features. The silicon enriched layer protects the features from UV radiation.
Other aspects and advantages of the present invention can be seen on review of the drawings, the detailed description and the claims which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
The Beer-Lambert Law describes the absorption of electromagnetic radiation by a layer as follows:
I=I0*e−ad
-
- where I0 represents the initial intensity of the electromagnetic radiation prior to absorption by the layer, I represents the intensity of the electromagnetic radiation as it has finished transiting the layer, d represents the layer thickness, and α represents the absorption coefficient. The ratio (I/I0) indicates the percentage of electromagnetic radiation that successfully transits the layer The absorption coefficient can also be expressed as follows:
α=(4πK)/λ - where K represents the extinction coefficient and λ represents the wavelength. The extinction coefficient is a dimensionless quantity. Many embodiments of the invention include an ultraviolet blocking layer with a sufficiently high extinction coefficient.
- where I0 represents the initial intensity of the electromagnetic radiation prior to absorption by the layer, I represents the intensity of the electromagnetic radiation as it has finished transiting the layer, d represents the layer thickness, and α represents the absorption coefficient. The ratio (I/I0) indicates the percentage of electromagnetic radiation that successfully transits the layer The absorption coefficient can also be expressed as follows:
Many types of standard silicon oxide are not appropriate for an ultraviolet blocking layer.
Many types of silicon rich oxide are not appropriate for an ultraviolet blocking layer. Silicon rich oxide contains more silicon than is expected from the chemical formula SiO2.
Some types of silicon rich oxide layers are appropriate for an ultraviolet blocking layer. Such silicon rich oxide layers can be called super silicon rich oxide (SSRO) layers, or silicon enriched oxide layers.
In embodiments of the present invention, the concentration of Si in the silicon oxide is increased until it is sufficient to act as an ultraviolet blocking layer. The amount of Si varies in various embodiments, and can be characterized by the extinction coefficient, by the ratio of silicon to oxygen in the material, and/or by the ratio of the flow rates of the sources.
In one embodiment, the layer of silicon rich oxide serving as the ultraviolet blocking layer is formed under the following conditions: the source gases of SiH4, O2, and Ar are introduced at respective flow rates of 100 sccm, 50 sccm, and 50 sccm at a low frequency RF power of 3000 W, and standard deposition time of 4 sec. Under such conditions, the silicon rich oxide can have a thickness of 600 Angstroms, an extinction coefficient of 1.7, and an index of refraction of 1.5 at 248 nm. In this case, the ratio of the silane flow rate to the oxygen flow rate is 2. Other embodiments can use different power levels, flow rates, flow rate ratios and/or source gases.
Secondary ion mass spectroscopy (SIMS) analysis was performed on a semiconductor sample with a silicon rich oxide layer serving as an ultraviolet blocking layer formed on a silicon substrate, and a standard silicon oxide layer formed on the silicon rich oxide layer serving as an ultraviolet blocking layer. The ratio of the silicon concentration to the oxygen concentration in the standard silicon oxide layer was about 0.7. The ratio of the silicon concentration to the oxygen concentration in the silicon rich oxide layer was about 13.6. For another silicon rich oxide layer serving as an ultraviolet blocking layer having an extinction ratio of about 1.3 at a wavelength of 248 nm, the ratio of the silicon concentration to the oxygen concentration in the silicon rich oxide layer is about 10. In other embodiments, different ratios of the silicon concentration to the oxygen concentration, such as a ratio of at least about 10, can be achieved in the silicon rich oxide layer by customizing process parameters, such as the ratio of the flow rates of the sources.
The process time is a factor in the thickness of the silicon rich oxide layer. Layers can be substantially planar, can have irregular features, and/or can have irregular thicknesses.
The ratio of SiH4 to O2 is a factor in controlling the extinction coefficient and the amount of extra silicon in the silicon rich oxide.
A layer need not have an (I/I0) ratio of 0% to serve as an ultraviolet electromagnetic radiation blocking layer. Various embodiments have an (I/I0) ratio sufficient to protect underlying features from UV damage in the particular manufacturing flow.
For comparison, the graph of
The graph of
A method of fabricating a semiconductor device is described below. Referring to
The layer of SSRO 26 has an extinction coefficient of about 1.3 to about 4. It can be deposited using SiH4/O2, SiH4/N2O, TEOS/O2, TEOS/O3 or a combination as process resource and argon or helium as carrier gas by conducting HDPCVD, PECVD or SACVD. The layer of SSRO 26 can be formed by SiH4/O2 at a flow rate of about 50˜200 sccm/20˜100 sccm. The layer of SSRO 26 can have a thickness of about 200 Angstroms to 1000 Angstroms and has a refractive index of about 2 to 5 at a range of wavelengths below 400 nm. Control of the thickness of the SSRO 26 can optimize the gap-filling performance of the dielectric 28. Thus, the appropriate thickness of the SSRO 26 can depend on the aspect ratio of the pattern. The extinction coefficient, refractive index and thickness of the layer of SSRO can vary with adjusting the process parameters such as flow rate of process resources, power or process time. The SSRO 26 serves as an ultraviolet blocking layer during the deposition of the dielectric 28.
Referring to
The features and processes discussed above for
By tuning process parameters such as the ratio of the flow rates of the sources, other embodiments can be made which have a refractive index greater than about 1.6 for a range of wavelengths less than 400 nanometers, an extinction coefficient at least about 1.3 for a range of wavelengths less than 400 nanometers.
While various embodiments have been described, it is to be understood that the invention is not limited to the disclosed embodiments. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. The invention is intended to cover all such substitutions and modifications included within the spirit and scope of the appended claims.
Claims
1. A semiconductor device having an ultraviolet blocking layer, said device comprising:
- a semiconductor substrate; and
- a layer of silicon enriched oxide overlying said semiconductor substrate, said layer of silicon enriched oxide having a ratio of a silicon concentration to an oxygen concentration sufficient for ultraviolet blocking, wherein said ratio is at least about 10.
2. The semiconductor device of claim 1, wherein the layer of silicon enriched oxide has an extinction coefficient of at least about 1.3 for a range of wavelengths less than 400 nanometers.
3. The semiconductor device of claim 1, wherein the layer of silicon enriched oxide has a refractive index greater than about 1.6 for a range of wavelengths less than 400 nanometers.
4. The semiconductor device of claim 1, wherein said layer of silicon enriched oxide has a thickness of about 100 Angstroms to 8000 Angstroms.
5. The semiconductor device of claim 1, wherein said layer of silicon enriched oxide is formed from at least one of the following reactants: SiH4/O2, SiH4N2O, TEOS/O2, and TEOS/O3.
6. The semiconductor device of claim 1, wherein said layer of silicon enriched oxide is formed by at least one of plasma-enhancement chemical vapor deposition (PECVD), semi-atmosphere chemical vapor deposition (SACVD) and high-density plasma chemical vapor deposition (HDPCVD).
7. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said semiconductor substrate beneath the layer of silicon enriched oxide; and
- a layer of dielectric overlying said layer of silicon enriched oxide.
8. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said semiconductor substrate beneath the layer of silicon enriched oxide; and
- a layer of dielectric overlying said layer of silicon enriched oxide
- wherein said layer of silicon enriched oxide has a thickness of about 200 Angstroms to 1000 Angstroms.
9. The semiconductor device of claim 1, wherein said layer of silicon enriched oxide is formed by at least SiH4 at a flow rate of about 50˜200 sccm and O2 at a flow rate of about 20˜100 sccm.
10. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said semiconductor substrate beneath the layer of silicon enriched oxide; and
- a layer of dielectric overlying said layer of silicon enriched oxide,
- wherein said conductors comprise at least one of polysilicon, polysilicon/silicide composite and metal.
11. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said semiconductor substrate beneath the layer of silicon enriched oxide; and
- a layer of dielectric overlying said layer of silicon enriched oxide,
- wherein said conductors comprise at least one of aluminum, aluminum alloy, and copper.
12. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said semiconductor substrate beneath the layer of silicon enriched oxide; and
- a layer of dielectric overlying said layer of silicon enriched oxide,
- wherein said dielectric is at least one of silicon oxide and silicon nitride and is deposited by at least one of PECVD, HDPCVD and SACVD.
13. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said layer of silicon enriched oxide.
14. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said layer of silicon enriched oxide,
- wherein said layer of silicon enriched oxide has a thickness of 1000 Angstroms to 3000 Angstroms.
15. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said layer of silicon enriched oxide,
- wherein said layer of silicon enriched oxide has a refractive index of at least about 1.6 for a range of wavelengths less than 400 nanometers.
16. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said layer of silicon enriched oxide,
- wherein said layer of silicon enriched oxide is formed by at least one of plasma-enhancement chemical vapor deposition (PECVD), semi-atmosphere chemical vapor deposition (SACVD) and high-density plasma chemical vapor deposition (HDPCVD).
17. The semiconductor device of claim 1, comprising:
- a plurality of patterned conductors overlying said layer of silicon enriched oxide,
- wherein said layer of silicon enriched oxide is formed by one or more reactants including at least one of SiH4/O2, SiH4/N2O, TEOS/O2, and TEOS/O3.
18. The semiconductor device of claim 17, wherein said conductors comprise at least one of polysilicon, polysilicon/silicide composite, aluminum, aluminum alloy and copper.
Type: Application
Filed: Dec 12, 2006
Publication Date: Apr 12, 2007
Applicant: Macronix International Co., Ltd. (Hsinchu)
Inventors: Chien Lu (Kaohsiung City), Chin Su (Yunlin County)
Application Number: 11/609,824
International Classification: H01L 31/112 (20060101); H01L 31/0232 (20060101); H01L 29/80 (20060101);