1. Field of the Invention
Embodiments of the present invention generally relate to semiconductor processing systems and methods. More specifically, embodiments of the invention relate to semiconductor processing methods utilized to remove polymers from a backside or frontside of a substrate without film damage during semiconductor fabrication.
2. Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors and resistors) on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for greater circuit density necessitate a reduction in the dimensions of the integrated circuit components.
As the dimensions of the integrated circuit components are reduced (e.g. to sub-micron dimensions), the importance of reducing presence of contaminant has increased since such contaminant may lead to the formation of defects during the semiconductor fabrication process. For example, in an etching process, by-products, e.g., polymers that may be generated during the etching process, may become a source of particulate, contaminating integrated circuits and structures formed on the substrate.
In order to maintain high manufacturing yield and low costs, the removal of contaminant and/or residual polymer from the substrate becomes increasingly important. Residual polymer present on the substrate bevel may be dislodged and adhered to the frontside of the substrate, potentially damaging integrated circuits formed on the frontside of the substrate. When residual polymer present on the substrate bevel is dislodged and adhered to a backside of a substrate, non-planarity of the substrate during a lithographic exposure process may occur and result in lithographic depth of focus errors. Additionally, residual polymer may also result in voids or open circuits if particles fall in vias or trenches during etch. Furthermore, residual polymer present on the backside of the substrate may also be dislodged and flaked off during robot transfer processes, substrate transport processes, subsequent manufacturing processes, and so on, thereby resulting in contamination in transfer chambers, substrate cassettes, process chambers, and other processing equipment that may be subsequently utilized in the circuit component manufacturing process. Contamination of processing equipment results in increased tool down time, thereby adversely increasing the overall manufacturing cost.
In conventional polymer removal processes, a scrubber clean is often utilized to remove polymers from a substrate bevel and backside. However, during the cleaning process, structures formed on the frontside of the substrate may also be damaged, resulting in product yield loss and device failure.
During etching, a photoresist layer is typically utilized as an etch mask layer that assists transferring features to the substrate. However, incomplete removal of the photoresist layer on the frontside of the substrate may also contaminant the structures formed on the substrate, resulting in product yield loss and device failure.
Therefore, there is a need for an apparatus and method to remove polymer from substrate backside or substrate frontside while maintaining integrity of structures formed on substrate frontside.
Embodiments of the present invention generally provide a method of cleaning a substrate such as by removing polymer from a substrate edge. In one embodiment, the method includes providing a cleaning gas comprising H2 and N2 or H2 and H2O, initiating a plasma from the cleaning gas, and removing polymer that formed on at least one of a frontside, a bevel edge, and a backside of the substrate with the plasma.
In another embodiment, the method includes providing an oxygen free cleaning gas comprising H2 and N2, initiating a plasma from the cleaning gas, and removing polymer that formed on at least one of a frontside, a bevel edge, and a backside of the substrate with the plasma, the substrate having at least one contact hole formed thereon.
In yet another embodiment, the method includes providing a cleaning gas comprising at least one of H2 and H2O, initiating a plasma from the cleaning gas, and removing polymer that formed on at least one of a frontside, a bevel edge, and a backside of the substrate with the plasma, the substrate having a structure with low-k dielectric film.
So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Embodiments of the present invention include methods of cleaning a substrate by removing polymers from a substrate bevel edge, frontside region, or backside of the substrate. The substrate bevel, backside and frontside region may be efficiently cleaned. In one embodiment where a photoresist layer is present on the frontside of the substrate, the photoresist layer may be removed as well. The embodiments are generally used to remove polymers from a substrate generated during a semiconductor substrate process, such as an etching or deposition process, among others. One exemplary polymer removal apparatus which may use the methods of the present invention described herein, with reference to
The processing chamber 100 includes a chamber lid 102, a bottom 170 and side walls 130 that enclose an interior volume 174. The chamber lid 102 has a bottom surface defining a ceiling 178 of the processing chamber 100. In the depicted embodiment, the chamber lid 102 is a substantially flat member. Other embodiments of the processing chamber 100 may have other types of lids, e.g., a dome-shaped ceiling and/or metallic construction.
A substrate support assembly 126 is disposed in the processing chamber 100 dividing the interior volume 174 into an upper zone 124 and a lower zone 122. The substrate support assembly 126 has an upper surface 176 utilized to receive a substrate 110 disposed thereon. In one embodiment, the substrate support assembly 126 has a step 136 formed in an upper periphery region of the substrate support assembly 126. The step 136 has a width selected to reduce a diameter of the upper surface 176 of the substrate support assembly 126. The diameter of the upper surface 176 of the substrate support assembly 126 is selected so that an edge 132 of the substrate 110 is exposed when the substrate is disposed on the substrate support assembly 126. Substrate edge 132 is shown in greater detail in
In
A purge gas source 104 is coupled to the chamber lid 102 through a gas supply conduit 118. The purge gas source 104 supplies purge gas to the processing chamber 100. A gas distribution plate 106 is coupled to the chamber ceiling 178 and has a plurality of apertures 108 formed therein. An internal plenum 148 is defined between the gas distribution plate 106 and the chamber ceiling 178 that facilitates communication of purge gases supplied from the purge gas source 104 to the plurality of apertures 108. The purge gases exit the apertures 108 and travel through the upper zone 124 of the processing chamber 100 so as to blanket a frontside 172 of the substrate 110. In one embodiment, the purge gas is selected to be non-reactive to the materials disposed on the frontside 172 of the substrate. In other embodiments, a purge gas source may be unnecessary.
A remote plasma source 154 is coupled to a gas outlet port 150 formed through a sidewall 130 of the processing chamber. In the embodiment depicted in
The remote plasma source 154 includes a remote plasma chamber 198 having an internal volume 196 coupling a gas panel 162 to the gas outlet port 150. One or more inductive coil elements 156 disposed adjacent to the remote plasma chamber 198 are coupled, through a matching network 158, to a radio frequency (RF) plasma power source 160 to generate and/or maintain plasma in the volume 196 formed from gases provided by the gas panel 162. The gas panel 162 provides reactive gases to the remote plasma source 154. In one embodiment, the gas panel 162 provides H2 and N2. In another embodiment, the gas panel 162 provides H2 and H2O. In still another embodiment, the gas panel 162 provides at least one of O2, NH3, or CO2 in combination with any of H2, N2 and H2O, though O2 may not be preferred in some embodiments because exposure to oxygen may damage features formed in layers on the frontside 172 of the substrate 110. The gases supplied to the remote plasma chamber 198 are dissociated as neutrals and radicals by plasma generated in the internal volume 196. The dissociated neutrals and radicals are further directed through the gas outlet port 150 to the processing chamber 100.
The elevation of substrate support assembly 126 may be selected to position the gas outlet port 150 above, below or aligned with the substrate edge 132 to selectively clean the top frontside 172, bevel edge 175, and/or backside 177 of the substrate 110. Outflow of the dissociated neutral and radicals from the gas outlet port 150 may be directed toward the step 136, as the substrate is rotated, thereby filling a cavity defined between the substrate backside 177 and the substrate support assembly 126. The cavity assists retaining gases so that the substrate frontside 172, substrate bevel 175, and the substrate backside 177 are exposed to the reactive gases for a longer period of time, thereby improving the polymer removal efficiency. Optionally, the substrate support assembly 126 may be positioned in a lower position (shown in phantom) so that the gas outflow from the gas outlet port 150 may be directed to an exposed edge on frontside 172 of the substrate 110, thereby assisting polymer removal, or remaining photoresist layer, if any, from the frontside 172 of the substrate 110.
In operation, the purge gas from the purge gas source 104 as well as the reacting gas from the plasma source 154 may be simultaneously supplied to both the frontside 172, periphery region of the substrate 110 to remove polymer 180, and/or remaining photoresist layer, if any, from the substrate 110. Alternatively, the gases from the purge source 104 and/or plasma source 154 may be pulsed into the processing chamber 100. During processing, the substrate support assembly 126 may be moved in a vertical direction, rotated, or orientated to position the substrate 110 between the upper zone 124 and lower zone 122 so that gases are delivered from the gas outlet port 150 to a desired region of the substrate 110. The rotation of the substrate 110 assists gases from the plasma source 154 to be applied uniformly to the substrate edge 132 or other desired region of the substrate 110.
Various material layers may be present on the substrate 110 during semiconductor processing, including a low-k layer, a barrier layer, a silicon containing layer, a metal layer, and a dielectric layer. Examples of material layers to be etched includes silicon carbide oxide (SiOC), such as BLACK DIAMOND® film commercially available from Applied Materials, Inc., silicon carbide (SiC) or silicon carbide nitride (SiCN), such as BLOk® film commercially available from Applied Materials, Inc., CVD oxide, SiO2, polysilicon, TEOS, amorphous silicon, USG, silicon nitride (SiN), boron doped or phosphorous doped silicon film, and the like.
During processing of the various material layers on the frontside 172 of substrate 110, polymer 180 may form on the edge 132 of the substrate 110. For exemplary purposes, an etching process that may cause polymer 180 to form on the edge 132 of the substrate 110 will be described. Although the process described here is an etching process, it is contemplated that the substrate 110 may be processed under different applications, such as deposition, thermal anneal, implant and the like.
During an etching process, the etched materials may combine with the components of the etchant chemistry, as well as with the components of the mask layers, if any, and by-products of the etch process, thereby forming polymer residues. The etch by-products and polymer residues 180 may deposit on the edge 132 of substrate 110, including frontside 172, bevel 175, and backside 177 of the substrate 110. Furthermore, portions of the photoresist layer utilized during the etching process may not be entirely consumed or removed from the substrate frontside 172 after the etching process. The photoresist layer remaining on the substrate frontside 172 may result in organic or polymer contamination on the substrate frontside 172 if not removed by the subsequent strip or ash process, thereby adversely affecting the performance of devices formed on the substrate 110.
The method 200 may begin at box 202, where a substrate may be transferred to a polymer removal chamber, such as a peripheral polymer removal chamber, the dashed box outline indicating that box 204 is optional in the cleaning process, as other suitable chambers for cleaning the substrate may be used. A dashed box outline in any of
At box 204, a cleaning gas comprising H2 and N2 or H2 and H2O is provided to the processing chamber, and at box 206, a plasma is initiated from the cleaning gas previously provided. In one embodiment, the plasma is a remote plasma, such as that shown in
The cleaning gas of method 200 may also further include at least one of O2, NH3, or CO2. Alternatively, the cleaning gas may include only H2 and N2 or, in another embodiment, H2 and H2O. The cleaning gas may be at most 5% H2O. In another embodiment, the cleaning gas may be at most 30% of H2. A carrier gas may also be used as part of the cleaning gas such as N2.
Referring now to
At box 304, an oxygen free cleaning gas comprising H2 and N2 is provided. Once the oxygen free cleaning gas has been provided, a plasma is initiated from the cleaning gas at box 306. The plasma is than used to remove polymer that formed on at least one of a frontside, bevel edge, and a backside of the substrate with the plasma at box 308. In this embodiment, the substrate has at least one contact hole formed thereon. A nickel silicide layer on the bottom of the contact hole may be exposed to the oxygen free cleaning gases during polymer removal. However, by using the oxygen free cleaning gas comprising H2 and N2, it is believed that the nickel silicide layer on the bottom of the contact hole remains undamaged during the cleaning process while removing any extraneous substrate polymer or other residue.
Method 300 may be used to clean a substrate after forming a structural layer 500 as depicted in
Referring now to
Once the cleaning gas has been provided, a plasma is initiated from the cleaning gas at box 406. In one embodiment, the plasma is a remote plasma. The plasma is than used to remove polymer that formed on at least one of a frontside, bevel edge, and backside of the substrate with the plasma at box 408. The intermetal low-k dielectric layer may be exposed to the cleaning gases during polymer removal. However, by using the cleaning gas chemistries described above in method 400, it is believed that the intermetal low-k dielectric layer on the substrate remains undamaged during the cleaning process.
Method 400 may be used to clean a substrate after forming an intermetal dielectric structure 600 as depicted in
Often during formation of intermetal dielectric structure 600, extraneous polymer or other etching residue may form on the edge of a substrate necessitating a cleaning process to remove the undesired and potentially contaminating polymer and residue from the substrate frontside, bevel edge, and backside. It is believed that processing the substrate having structure 600 according to boxes 404, 406, and 408 of method 400 depicted in
In any of the embodiments of the invention, the processed (e.g., etched) substrate may be transferred to a polymer removal processing chamber 100 to remove the polymer residuals, photoresist layer, if any, and etch by-products from the substrate 110 generated during previous processing techniques such as etching. The remote plasma source of the processing chamber 100 supplied active reactant, such as hydrogen nitrogen containing gases or hydrogen and water vapor containing gases, to the processing chamber 100 to assist removal of polymer residuals, photoresist layer and etch by-products from the substrate 110. As the plasma produced radicals are highly reactive radicals to polymers, upon supplying reactive species of the cleaning gas into the processing chamber 100, the species react with the polymers, forming volatile compounds, which are readily pumped and gassed out of the processing chamber 100.
In one embodiment, the reactive species supplied to the processing chamber 100 is generated from the remote plasma source from a gas mixture including H2 and water vapor (H2O). Alternatively, various gas mixture combinations of hydrogen (H2), oxygen (O2), nitrogen (N2), carbon dioxide (CO2), and ammonia (NH3) may be supplied to the remote plasma source to generate the reactive species. For example, in the embodiment where the intermetal dielectric layer on the substrate is etched, such as a silicon oxycarbide layer (SiOC), the reactive species supplied from the remote plasma source to the processing chamber includes H2O and H2. Alternatively, if a higher polymer removal rate is desired and dielectric layer damage is acceptable, an O2 and N2 based cleaning gas may be supplied to the remote plasma source. If the process requires a high polymer removal rate with an acceptable minimal ultra low-k dielectric damage and metal oxidation, the reactive species supplied from the remote source to the processing chamber may include H2 and CO2. In another embodiment where a contact hole or via is etched in a layer below the polymer, such as in a silicon oxide film layer (SiO2), and a layer of silicide in the contact hole or via, such as nickel silicide, is exposed, the reactive species supplied from the remote plasma source to the processing chamber includes H2 and N2.
As discussed above, as the substrate support assembly 126 may be moved and rotated, in the embodiments wherein a photoresist material is present on the substrate frontside 172, the photoresist material may be removed along with polymer residues, e.g., the photoresist material is stripped during the polymer removal process.
In the embodiment where the material etched on the substrate is a silicon oxycarbide film (SiOC), the gas mixture supplied through the remote plasma source to remove substrate frontside, bevel, and backside polymer includes H2 and H2O. H2 gas is supplied at a flow rate between about 1000 sccm and about 4000 sccm, such as about 2000 sccm. H2O is supplied at a flow rate between about 10 sccm and about 100 sccm, such as about 30 sccm. The remote plasma source may provide a plasma power at about 4500 Watts. An inert gas, such as Argon may be used to strike the plasma. The pressure controlled for processing is between about 1 Torr and about 5 Torr, such as about 2 Torr. A purge gas may be used such as N2, Ar, H2, and He.
After substrate frontside, bevel, and backside polymer have been removed, the substrate support assembly 126 may be dropped to the lower position readily to receive the reactive species from the remote plasma source to substrate frontside 172 to remove photoresist layer. During photoresist or frontside polymer removal process, the gas mixture supplied through the remote plasma source includes H2 and H2O. H2 gas is supplied at a flow rate between about 1000 sccm and about 4000 sccm, such as about 2000 sccm. H2O is supplied at a flow rate between about 10 sccm and about 100 sccm, such as about 30 sccm. The remote plasma source may provide a plasma power at about 4500 Watts. An inert gas, such as Argon may be used to strike the plasma. The pressure controlled for processing is between about 1 Torr and about 5 Torr, such as about 2 Torr. A purge gas may be used such as H2, and He. During frontside polymer removal, the pedestal height would be lower relative to the nozzle position.
In the embodiment where a contact hole or via is etched in a layer below the photoresist, such as in a silicon oxide film layer (SiO2), and a silicide layer in the hole or via is exposed, the gas mixture supplied through the remote plasma source to remove substrate frontside, bevel, and backside polymer includes H2 and N2. H2 gas is supplied at a flow rate between about 5 sccm and about 500 sccm, such as between about 50 sccm. N2 is supplied at a flow rate between about 100 sccm and about 4000 sccm, such as between about 1500 sccm. The pressure controlled for processing is between about 1 Torr and about 5 Torr, such as about 1.5 Torr.
Thus, the present invention provides methods for cleaning substrates by removing polymer residues formed on the frontside, bevel edge, or backside of a substrate. Efficient removal of polymer residuals not only eliminates contamination on a substrate but also prevents transfer of contamination into other processing chambers during subsequent processing, thereby improving product yield and enhancing productivity and process throughput. Moreover, the methods provide a process for removing the polymer residuals without damaging various layers and formations on the frontside of the substrate.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims priority to commonly assigned U.S. provisional patent application Ser. No. 61/056,786 filed on May 28, 2008, entitled “METHOD OF SUBSTRATE BACKSIDE POLYMER REMOVAL”.
Number | Date | Country | |
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61056786 | May 2008 | US |