Patent Application
20120273010
1. Technical Field
The embodiments herein generally relate to semiconductor processing, and, more particularly, to the removal of excess noble metal material during contact electrode processing.
2. Description of the Related Art
In conventional semiconductor processing systems, many dangerous chemicals are used simply because an alternative has not been found. For example, during contact electrode processing in a front end of line (FEOL) application, aqua regia is commonly used to remove unreacted platinum and platinum metal alloys (e.g., NiPt/Pt). Aqua regia is a mixture of nitric acid and hydrochloric acid, usually in a molar ratio of 1:3.
Moreover, when used as a solvent, aqua regia typically forms shallow craters devoid of silicide in the Ni(Pt)Si film. Moreover, aqua regia is very corrosive and highly flammable.
These factors contribute to making aqua regia an undesirable compound for use in industrial processes. Aqua regia, however, is used in conventional systems because it is known to dissolve Pt and thereby resulting in soluble hexachloroplatinic acid. Ideally, aqua regia dissolves Pt because it is a mixture of nitric acid (HNO3) and hydrochloric acid (HCl). Since nitric acid is a powerful oxidizer, it will dissolves Pt to form platinum ions (Pt4+). Thereafter, the oxidized platinum ions react with chloride ions from the hydrochloric acid resulting in the chloroplatinate ion. Industrial use of aqua regia to dissolve Pt and form hexachloroplatinic acid, however, is far from ideal and leaves undesirable amounts of Pt and Pt residues during, for example, contact electrode processing in a FEOL application.
Therefore, what is needed is a composition and method that allows for the safe removal of advanced materials (e.g., platinum) during semiconductor processing and manufacturing.
The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The embodiments herein provide a novel composition and method to safely and effectively render platinum and other residuals (e.g., NiPt/Pt) soluble. Referring now to the drawings, and more particularly to
According to one embodiment herein, the measurements taken in steps 54 and 58 are performed using a scanning electron microscopy (SEM) instrument. For example, a Magellan 400L SEM instrument available from FEI Company, Hillsboro, Oreg., USA is used to measure the removal of Pt in step 54 with the following scanning parameters: low voltage high contrast detector (vCD) mode collecting backscattering electrons (BSE), where high voltage (HV)=−5 kV, specimen bias voltage (SB)=−3 kV and current=−100 pA. According to one embodiment of step 54, for example, SEM images of a prepared blanket coupon (such as a SiN substrate in step 50) are taken at different locations that are exposed to different chemistries (as described in further detail below). The images are then processed through image analysis software (e.g., ImageJ, available from the National Institutes of Health, USA) to determine the presence of Pt residues after reducing the background noise due to a change in roughness after chemical treatment.
According to one embodiment herein, an atomic force microscopy (AFM) instrument is used to measure the roughness change after a chemical exposure to the SiN substrate (as described in further detail below) instead of SEM instrumentation. For example, a DIM5000 AFM instrument available from Veeco Instruments, Inc., Plainview, N.Y., USA is used in step 54 to measure the roughness change after chemical exposure with the following parameters:scan rate: 0.996 Hz, tip velocity: 9.96 um/s. Data scale: 20 nm. According to one embodiment herein, roughness for pre and post conditions are then calculated and the roughness of the thin film deposition indicates the degree of Pt removal (e.g., 25-35 nm). For example, the greater the removal of Pt, the smoother the surface. To measure the oxide and nitrides etch rate in step 58 according to one embodiment herein, a film's thickness is measured on an ellipsometer (e.g., ellipsometers available from Gaertner Scientific Corp., Skokie, Ill., USA) at pre and post chemical exposure. The delta thickness (i.e., the difference in thickness between pre and post chemical exposure) obtained from pre and post exposures indicates the etch rate of oxide or nitride (e.g., 25-35 nm).
According to one embodiment herein, a metal chelator is used to bind to Pt (e.g., Pt 40) thereby making the Pt soluble in a solution.
According to one embodiment herein, the metal chelator illustrated in
Furthermore, according to one embodiment herein, the metal chelator mixture described above is a solution employed in the method shown in
According to one embodiment herein, a method to improve the fabrication process of device 1, as described above, includes several parameters. For example, to improve the FEOL application of Pt and the removal of NiPt with an underlying Ni silicide (e.g., NiPtSi 40), different processing techniques may be used to identify chemistries and processes that have the following parameters: the process temperature must be as low as possible (e.g., ≦40° C., but less than 200° C. to preserve the integrity of materials such as high-k dielectrics and the metal gate materials); process time must not exceed approximately 5 minutes for a batch and approximately 1 ms for a single wafer (e.g., a single chemistry solution to remove NiPt preferred to dual chemistry solution to remove NiPt then Pt—which yields undesirable times of approximately 10 minutes for the batch and approximately 2 minutes for a single wafer); process must not exceed an etch threshold for silicides (e.g., where an etch threshold is defined as <5 Å loss of material); process must not exceed an etch threshold for oxides and nitrides (e.g., where a etch threshold is defined as <5 Å loss of material); a list of chemicals that are not allowed (e.g., n-methylpyrrolidone, dimethylacetamide, diglycolamine, hydroxylamine); and the chemistry must be compatible with industrial sink, drain, and waste treatment (e.g., no flocculation or precipitation, aqueous-based solutions preferred).
As described above, one of the aspects of the embodiments herein is that the previously insoluble residues (e.g., Pt/NiPt residues) can be completely removed without the use of highly corrosive compounds (e.g., aqua regia) that causes unintentional side effects (e.g., forming shallow craters devoid of silicide in the Ni(Pt)Si film). In addition, the embodiments herein provide chemistries requiring short process times. Accordingly, due to the short process times, embodiments herein permit single wafer wet processing tools to be used in manufacturing environments. Furthermore, the embodiments herein provide a method permitting testing of many different formulations and chemistries in a very short time. Therefore, for example, by using a metal chelator and HF concentration in an organic solvent and water, previously insoluble compounds used during contact electrode processing—such as NiPt or other Pt residuals—can become soluble in accordance with the embodiments herein. With a soluble platinum residual, for example, and after a given process time, the embodiments herein undercut the SiN and lift off the Pt residue during the final rinse step.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of illustrated embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
