Optical waveguides – Having particular optical characteristic modifying chemical... – Of waveguide core
Reexamination Certificate
1998-11-05
2001-05-15
Lee, John D. (Department: 2874)
Optical waveguides
Having particular optical characteristic modifying chemical...
Of waveguide core
C385S129000, C385S145000, C216S067000
Reexamination Certificate
active
06233388
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an applications for POLYMER OPTICAL WAVEGUIDE AND METHOD FOR FABRICATING THE SAME earlier filed in the Korean Industrial Property Office on Nov. 5, 1997 and there duly assigned Ser. No. 58238/1997 and for POLYMER OPTICAL WAVEGUIDE AND METHOD FOR FABRICATING THE SAME earlier filed in the Korean Industrial Property Office on Nov. 2, 1998 and there duly assigned Ser. No. 46821/1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the class of devices known as optical waveguides and in particular to polymer optical waveguides for use in optical communication with near infrared light.
2. Description of the Related Art
In optical waveguides formed of an optical polymer which has low light loss in the optical communication wavelength region containing the near infrared region, it is necessary to minimize light scattering loss at the boundary between core and cladding of the waveguide. In order to minimize light scattering loss, when etching an optical waveguide it is imperative to appropriately control parameters such as the uniformity of a side wall of an etched waveguide, the vertical profile of the side wall and the etch rate. Since such parameters are directly affected by the plasma density and ion energy during etching and are optimized under contrary conditions, the plasma density and the ion energy must be independently controlled. Particularly, in the case of etching an optical waveguide formed of polymer containing halogen atoms, it is important to reduce damage in an optical waveguide by increasing the etch rate to minimize the exposure to the plasma. Again, it is necessary to independently control the plasma density and ion energy.
A general method for fabricating an optical waveguide will now be described. First, a lower cladding layer is formed on a substrate and then a core layer is formed on the lower cladding layer. Subsequently, a photoresist layer is formed on the core layer, exposed and then developed the resultant, to form a photoresist pattern. The core layer is etched using a photoresist pattern and then patterned. Then, an upper cladding layer is formed on the patterned core layer, thereby completing the optical waveguide.
As an etching method of the core layer, a reactive ion etching (RIE) method is widely used, in view of processing stability, preciseness and productivity. However, with the RIE method, the etch rate is very low, i.e., not more than 500 nm/min, which causes the substrate to be exposed to plasma for a long time to be damaged. In addition to damage to the etched plane, the vertical profile of the etched plane is nonuniform. And, in the case of increasing the plasma density for the purpose of enhancing the etch rate, the ion energy increases, which causes to damage the etched plane. Conversely, in the case of decreasing the plasma density for the purpose of reducing damage to the etched plane, the etch rate is lowered, and the substrate is exposed to the plasma for a long time, bringing about film damage.
Based on our observation of the art, we have observed that what is needed is a polymer optical waveguide which does not suffer from plasma damage during the manufacturing process. Specifically, a composition and a manufacturing method are needed which will allow a high etch rate without damage to the optical waveguide.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved polymer optical waveguide.
It is also an object of the present invention to provide a polymer optical waveguide with minimal light scattering loss at the boundary between the core and the cladding.
It is a further object of the present invention to provide an improved method of making a polymer optical waveguide.
It is a still further object of the present invention to provide a method of making a polymer optical waveguide in which the etch rate of the core layer is high.
It is a yet further object of the present invention to provide a method of making a polymer optical waveguide in which the substrate is not damaged by the etching process.
It is a still yet further object of the present invention to provide a method of making a polymer optical waveguide in which the vertical profile of the etched plane is uniform.
It is another object of the present invention to provide a method of making a polymer optical waveguide in which the etched plane is not damaged by the etching process.
It is still another object of the present invention to provide a method of making a polymer optical waveguide in which the problems associated with too high or too low plasma density in the etching process are avoided.
To achieve the above objects, the present invention provides a polymer optical waveguide and a method for manufacturing this waveguide which minimizes damage to the optical waveguide during manufacture by improving the etch rate, uniformity, etching ratio and vertical profile of an etched plane of the optical waveguide. Specifically, in one aspect of the present invention, there is provided a polymer optical waveguide comprises a core formed of polymer containing fluorine (F) in amount of 12-37 wt % on the basis of total weight of the polymer, and having repeating units with at least two —C(═O)—N—C(═O) functional groups or at least four —N—C(═O)— functional groups, and a cladding in contact with the core and formed of polymer having a refractive index lower than the polymer for forming the core.
According to another of the present invention, there is provided a method for fabricating a polymer optical waveguide comprising the steps of:
forming a lower cladding layer on a substrate;
forming a core layer on the lower cladding layer;
patterning the core layer by etching the core layer in a predetermined pattern;
forming an upper cladding layer on the patterned core layer,
wherein etching of the core layer is performed by an inductively coupled plasma (ICP) process on condition that ICP power and RF (radio frequency) chuck power are 170-750 W and 20-340 W, respectively, and the core layer is formed of a polymer containing fluorine (F) in amount of 12-37 wt % on the basis of total weight of the polymer, and having repeating units with at least two —C(═O)—N—C(═O) functional groups or at least four —N—C(═O)— functional groups.
REFERENCES:
patent: 5649045 (1997-07-01), Fjare et al.
patent: 5733481 (1998-03-01), Hayashida et al.
Han Kwan-Soo
Jang Woo-hyuk
Kim Eun-ji
Kim Jung-hee
Rhee Tae-hyung
Bushnell , Esq. Robert E.
Lee John D.
Samsung Electronics Co,. Ltd.
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