Patent Application
20160041471
The present invention relates generally to semiconductor fabrication lithography and, more particularly, to a method and composition for reducing post-development defects and residues that may remain on a photoresist and semiconductor device after development of the photoresist.
Photoresists are commonly used in semiconductor fabrication processes where it is desired to transfer detailed patterns onto a surface. Typically, a layer of photoresist material may be deposited on the surface, followed by the selective exposure of the photoresist layer to an energy source, wherein portions of the photoresist layer are changed in character due to their exposure to the energy source. After such exposure, the photoresist layer is then developed by a wet development process employing liquid chemical solvents to selectively remove portions of the photoresist layer to provide the desired pattern. The surface may then be etched with this pattern.
According to an embodiment, a method is disclosed. The method may include: forming a mask layer on a base layer using lithographic development, the lithographic development may leave one or more post-development defects composed of basic salts; and removing the one or more post-development defects selective to the mask layer and the base layer using an ozonated acidified conductive water rinse. The ozonated acidified conductive rinse may be applied to the one or more post-development defects, the mask layer, and the base layer. The ozonated acidified conductive water rinse may leave substantially no residue.
According to another embodiment, a method is disclosed. The method may include: depositing a resist material on a base layer; removing a portion of the resist material using lithographic patterning and development to form an opening in the resist material. The lithographic patterning and development may generate post-development defects that may remain on the resist material and the base layer. The post-development defects may be composed of basic salt residues that may remain on a portion of the mask layer and a portion of the base layer. The post-development defects may be removed selective to the resist material and the base layer using an acidified conductive water rinse. The acidified conductive rinse may be applied to the post-development defects, the resist material, and the base layer. The acidified conductive water rinse may leave substantially no residue.
According to another embodiment, a rinse solution for use in removing post-development defects formed during lithographic patterning of a mask layer without substantially removing the mask layer comprising is disclosed. The rinse solution may be composed of ozonated acidified conductive water having a resistance ranging from 50,000 ohms to 500,000 ohms.
The following detailed description, given by way of example and not intended to limit the invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, in which not all structures may be shown.
The drawings are not necessarily to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention. In the drawings, like numbering represents like elements.
Detailed embodiments of the claimed structures and methods are disclosed herein; however, it can be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods that may be embodied in various forms. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this invention to those skilled in the art.
For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, and derivatives thereof shall relate to the disclosed structures and methods, as oriented in the drawing figures. It will be understood that when an element such as a layer, region, or substrate is referred to as being “on”, “over”, “beneath”, “below”, or “under” another element, it may be present on or below the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on”, “directly over”, “directly beneath”, “directly below”, or “directly contacting” another element, there may be no intervening elements present. Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
In the interest of not obscuring the presentation of embodiments of the present invention, in the following detailed description, some processing steps or operations that are known in the art may have been combined together for presentation and for illustration purposes and in some instances may have not been described in detail. In other instances, some processing steps or operations that are known in the art may not be described at all. It should be understood that the following description is rather focused on the distinctive features or elements of various embodiments of the present invention.
The present invention relates generally to semiconductor fabrication lithography and, more particularly, to a method and composition for reducing post-development defects and residues that may remain on a photoresist and semiconductor device after development of the photoresist. Conventional photoresist materials may exhibit a class of post-development defects in which fragments, pieces, or particles of the original components of the photoresist material, which should have been removed, remain in and around small openings in the photoresist after the photoresist has been exposed and developed. These defects may block or partially block such openings during a subsequent etching step. The post-development defects may be basic salts that form when the developer reacts with the photoresist material. Such post-development defects may interfere with the etching of the material under the photoresist, causing micro-masking defects, or interfere with ion implantation or deposition through these openings in the photoresist.
Typically, these post-development defects may be reduced using a rinsing process or a descum process after development. Typically, the rinsing process may be conducted using a puddle rinse with deionized water (DIW), which may not effectively remove most of the post-development defects. An acidified rinse solution containing a liquid acid may be used for greater effectiveness, but may leave a residue behind. The descum process is an oxygen-based plasma process that may remove a small amount, typically a few hundred angstroms, of the photoresist along with the post-development defects. The descum process, by its nature, may cause damage to the photoresist in order to remove the post-development defects, and may negatively impact subsequent etching or ion implantation steps.
One way to remove the post-development defects in a highly controlled manner, without leaving a residue behind and without the damaging effects of the descum process, may be to use acidified conductive water that leaves no residue behind. Embodiments by which to use acidified conductive water to remove post-development defects, without damaging the photoresist, are described in detail below with reference to
Referring now to
Referring now to
Referring now to
Typical developer solutions may be aqueous or semi-aqueous systems having a basic pH (i.e., having a pH greater than approximately 7), often having a pH of approximately 10 or greater. These developer solutions may contain a base such as tetramethylammonium hydroxide (TMAH), ammonium silicate, or other alkaline agents. The developer solutions may also include wetting agents or surfactants to improve surface wetting and retention of the dissolved photoresist material in the developer solution.
While the development step may remove substantially all of the patterned portion 212 (
Referring now to
In any of the above embodiments, the acid may be dissolved in the DIW such that the rinse solution 402 has a sufficient acidity to neutralize the basic post-development defects 304 without damaging the remaining portions of the resist layer 104. Therefore, the acid concentration may vary depending on the type of resist material used for the resist layer 104. The rinse solution 402 may have an acid concentration such that the electrical resistance of the rinse solution 402 may range from approximately 50,000 ohms approximately 500,000 ohms, which may be higher than the resistance of a typical rinse solution having a higher acid concentration that may damage the resist layer 104.
In another embodiment, the rinse solution 402 may be composed of the above acidified conductive water with the addition of dissolved ozone (i.e., ozonated acidified conductive water). Typically, ozone may be used in resist stripping solutions, at concentrations of approximately 15 ppm. The high concentration in the resist stripping solutions may react with the resist layer and may cause significant damage, allowing for the removal of at least a portion, and typically all, of a resist layer. In the present embodiment, the concentration of ozone in the ozonated acidified conductive water may be much lower. The concentration of ozone in the rinse solution 402 may be sufficient to neutralize the basic post-development defects 304, but not so high as to cause damage to the resist layer 104. In addition, the concentration of ozone may be sufficient to remove one or more layers of undeveloped resist material remaining in the openings. Therefore, the concentration of ozone may vary depending on the type of resist material used for the resist layer 104. In an embodiment, the concentration of ozone in the rinse solution 402 may range from approximately 0.01 ppm to approximately 8 ppm.
The rinse solution 402 may be applied to the structure using conventional rinsing techniques that incorporate rotating the structure 100 while applying the rinse solution. The rinse solution 402 may be applied at a temperature ranging from approximately 20° C. to approximately 60° C. and pressure ranging from approximately 1 atm to approximately 3 atm. In a preferred embodiment, the rinse solution 402 may be applied directly after the development step. In another embodiment, the rinse solution 402 may be applied after the development step and directly after a subsequent etching step, such as for example, reactive ion etching (RIE), used to pattern the base layer 102.
Typically, an acidified rinse may be used to reduce electrical charge in conventional resists that may be slightly basic rather than to remove defects and residues that may remain on a photoresist and semiconductor device after development of the resist as in present embodiments. In embodiments of the present invention, the rinse solution 402, whether it is acidified conductive water or ozonated acidified conductive water, may be used to neutralize and remove the post-development defects 304, which may be composed of basic salts. Because of the low concentration of ozone and the low acid concentration, the rinse solution 402 may remove the post-development defects 304 by neutralizing the basic salt residues without causing substantial damage to the remaining portions of the resist layer 104.
Referring now to
Referring now to
Referring now to
Referring now to
Typical developer solutions may be aqueous or semi-aqueous systems having a basic pH (i.e., having a pH greater than approximately 7), often having a pH of approximately 10 or greater. These developer solutions may contain a base such as tetramethylammonium hydroxide (TMAH), ammonium silicate, or other alkaline agents. The developer solutions may also include wetting agents or surfactants to improve surface wetting and retention of the dissolved photoresist material in the developer solution.
Typical negative resist developer solutions may be solvent or semi-aqueous systems having a basic pH that may dissolve lower molecular weight unexposed photoresist material while leaving behind higher molecular weight exposed resist material. The negative resist developer solutions may also include wetting agents or surfactants to improve surface wetting and retention of the dissolved unexposed negative resist material.
While the development step may remove substantially all of the resist layer 602 (
Referring now to
In any of the above embodiments, the acid may be dissolved in the DIW such that the rinse solution 402 has a sufficient acidity to neutralize the basic post-development defects 304 without damaging the remaining portions of the patterned portion 702. Therefore, the acid concentration may vary depending on the type of resist material used for the patterned portion 702. The rinse solution 402 may have an acid concentration such that the electrical resistance of the rinse solution 402 may range from approximately 50,000 ohms approximately 500,000 ohms, which may be higher than the resistance (i.e., less conductive) of a typical rinse solution having a higher acid concentration that may damage the patterned portion 702.
In another embodiment, the rinse solution 402 may be composed of the above acidified conductive water with the addition of dissolved ozone (i.e., ozonated acidified conductive water). Typically, ozone may be used in resist stripping solutions, at concentrations of approximately 15 ppm. The high concentration in the resist stripping solutions may react with the resist layer and may cause significant damage, allowing for the removal of at least a portion, and typically all, of a resist layer. In the present embodiment, the concentration of ozone in the ozonated acidified conductive water may be much lower. The concentration of ozone in the rinse solution 402 may be sufficient to neutralize the basic post-development defects 304, but not so high as to cause damage to the patterned portion 702. In addition, the concentration of ozone may be sufficient to remove one or more layers of undeveloped resist material remaining in the openings 302. Therefore, the concentration of ozone may vary depending on the type of resist material used for the patterned portion 702. In an embodiment, the concentration of ozone in the rinse solution 402 may range from approximately 0.01 ppm to approximately 8 ppm.
The rinse solution 402 may be applied to the structure using conventional rinsing techniques that incorporate rotating the structure 100 while applying the rinse solution. The rinse solution 402 may be applied at a temperature ranging from approximately 20° C. to approximately 60° C. and pressure ranging from approximately 1 atm to approximately 3 atm. In a preferred embodiment, the rinse solution 402 may be applied directly after the development step. In another embodiment, the rinse solution 402 may be applied after the development step and directly after a subsequent etching step, such as for example, reactive ion etching (RIE), used to pattern the base layer 102.
Typically, an acidified rinse may be used to reduce electrical charge in conventional resists that may be slightly basic rather than to remove defects and residues that may remain on a photoresist and semiconductor device after development of the resist as in present embodiments. In embodiments of the present invention, the rinse solution 402, whether it is acidified conductive water or ozonated acidified conductive water, may be used to neutralize and remove the post-development defects 304, which may be composed of basic salts. Because of the low concentration of ozone and the low acid concentration, the rinse solution 402 may remove the post-development defects 304 by neutralizing the basic salt residues without causing substantial damage to the remaining portions of the patterned portion 702.
Referring now to
Embodiments of the present invention may improve the fidelity of a photoresist image transfer process by removing post-development defects from a resist layer and a base layer using acidified conductive water that may leave no residue and may maintain the structure of the patterned resist layer. The post-development defects may be basic salt artifacts that remain on the resist layer and the base layer that form as a result of the developer reacting with light-exposed portions of the resist layer. The post-development defects may block the patterned openings in the resist layer, and may cause defects in subsequent etching steps of the base layer. Embodiments in which the rinse solution is composed of an acidified conductive water or an ozonated acidified conductive water may neutralize and remove the post-development defects without leaving a residue, unlike conventional rinsing techniques, and without damaging the resist layer, unlike conventional descumming techniques. Because the rinse solution may leave no reside, it may then easily be removed.
The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiment, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
