Method of treating an anti-reflective coating on a substrate

Details Method of treating an anti-reflective coating on a substrate Method of treating an anti-reflective coating on a substrate

1994-10-12

2003-12-30

Jones, Dwayne C. (Department: 1614)

Coating processes

Direct application of electrical, magnetic, wave, or...

Pretreatment of substrate or post-treatment of coated substrate

C204S157150, 43

Reexamination Certificate

active

06669995

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a method of treating an anti-reflective coating on a substrate and also to a method of forming an electronic device. The method of forming an electronic device includes treating an anti-reflective coating on a substrate.
BACKGROUND OF THE INVENTION
Microelectronic devices used in the construction of integrated circuits are manufactured by means of photolithographic techniques. Fabricating various structures, particularly electronic device structures, typically involves depositing at least one layer of a photosensitive material, typically known as a photoresist material, on a substrate. The photoresist material may then be patterned by exposing it to radiation of a certain wavelength to alter characteristics of the photoresist material. Typically, the radiation is from the ultraviolet range of wavelengths. The radiation preferably causes desired photochemical reactions to occur within the photoresist. Preferably, the photochemical reactions alter the solubility characteristics of the photoresist, thereby allowing removal of certain portions of the photoresist. Selectively removing certain parts of the photoresist allows for the protection of certain areas of the substrate while exposing other areas. The remaining portions of the photoresist may be used as a mask or stencil for processing the underlying substrate.
An example of such a process is in the fabrication of semiconductor devices wherein, for example, layers are formed on a semiconductor substrate. Certain portions of the layers may be removed to form openings through the layers. The openings may allow diffusion of desired impurities through the openings into the semiconductor substrate. Other processes are known for forming devices on a substrate.
Devices such as those described above, may be formed by introduction of a suitable impurity into a wafer of a semiconductor to form suitably doped regions therein. In order to provide distinct P or N regions, which are necessary for the proper operation of the device, introduction of impurities should occur through only a limited portion of the substrate. Usually, this is accomplished by masking the substrate with a diffusion resistant material,which is formed into a protective mask to prevent diffusion through selected areas of the substrate.
The mask in such a procedure is typically provided by forming a layer of material over the semiconductor substrate and, afterward creating a series of openings through the layer to allow the introduction of the impurities directly into the underlying surface within a limited area. These openings in the mask are readily created by coating the mask with a material known as a photoresist. Photoresists can be negative photoresist or positive photoresist materials.
A negative photoresist material is one which is capable of polymerizing and being rendered insoluble upon exposure to radiation. Accordingly, when employing a negative photoresist material, the photoresist is selectively exposed to radiation, causing polymerization to occur above those regions of the substrate which are intended to be protected during a subsequent operation. The unexposed portions of the photoresist are removed by a solvent which is inert to the polymerized portion of the photoresist. Such a solvent may be an aqueous solvent solution.
Positive photoresist material is a material that, upon exposure to radiation, is capable of being rendered soluble in a solvent in which the unexposed resist is not soluble. Accordingly, when applying a positive photoresist material the photoresist is selectively exposed to radiation, causing the reaction to occur above those portions of the substrate which are not intended to be protected during the subsequent processing period. The exposed portions of the photoresist are removed by a solvent which is not capable of dissolving the exposed portion of the resist. Such a solvent may be an aqueous solvent solution.
Photoresist materials may be similarly be used to define other regions of electronic devices.
In an effort to increase the capability of electronic devices, the number of circuit features included on, for example, a semiconductor chip, has greatly increased. When using a process such as that described above for forming devices on, for instance, a semiconductor substrate, increasing the capability and, therefore, the number of devices on a substrate requires reducing the size of the devices or circuit features. One way in which the size of the circuit features created on the substrate has been reduced is to employ mask structures having smaller openings. Such smaller openings treat smaller portions of the substrate, thereby creating smaller structures in the photoresist. In order to produce smaller structures in the photoresist, shorter wavelength ultraviolet radiation is also used in conjunction with the mask to image the photoresist. Such shorter wavelengths of radiation have also been particularly effective at curing or hardening photoresist materials used in fabricating the devices.
Until recently, in forming electronic devices, photoresists have been used that are sensitive at g-line (436 nm) and i-line (365 mn) for most microelectronic applications. Examples photoresists sensitive to such wavelengths are novolak-type photoresists. As the desire to form smaller features, on the order of sub-micron and sub-half-micron, on substrates has increased, photoresists have been formulated that are sensitive to UV radiation in the range of about 248 nm. Such wavelengths are referred to as deep UV since they are deep within the UV range. Photoresists which are sensitive to such wavelengths are known as deep UV photoresists. Many deep UV photoresists differ significantly from commonly used photoresists used to make devices with larger sized features. In particular, deep UV photoresists differ from novolak-type formulations and also have different optical properties.
Typically, systems for creating electronic devices as described above include a UV radiation source for exposing the photoresist.
As methods for producing miniature electronic structures improve, the desire to produce even smaller structures has continued to increase. Problems encountered in further device miniaturization include obtaining desired resolution in the UV radiation source and improved focusing resolution and depth of focus of the UV radiation on the photoresist. Other problems encountered include radiation leakage through the mask. Radiation leakage has been addressed by ensuring that the UV radiation to which the mask and the photoresist are exposed is well within the deep UV range and, in particular, less than 245 nm in wavelength. Additionally, the problem of long exposure times to increase the penetration of the UV radiation through planarization layers. Further problems include the ability of the patterns formed in the resist to withstand high powered dry processes without the loss of the image integrity.
As stated above, progress in processes for forming structures in photoresists has led to the creation of sub-micron and even sub-half-micron structures. For example, structures as small as 0.3 microns have even been created. In addition to the above-described problems, another common problem encountered as structure size has decreased is that thinner layers of photoresist must be used to ensure, among other things, that depth of focus requirements of the exposure tool are met. The exposure tool referring to the radiation source, optics, mask and other components used to expose the photoresist. The photoresists used, especially at such lesser thicknesses are highly transmissive of ultraviolet wavelengths used. The transmissivity of the photoresist combined with the high reflectivity to the UV wavelengths of commonly used substrates results in the reflection of the UV radiation back into the photoresist resulting in further photochemical reactions taking place in the photoresist. The further photochemical reactions resulting from the UV radiation reflected off of the substrate typically result in uneven exp

Affiliated with

Also associated with

Rating

Method of treating an anti-reflective coating on a substrate does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of treating an anti-reflective coating on a substrate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of treating an anti-reflective coating on a substrate will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3178819