The present invention relates to the fabrication of integrated circuits. More particularly, the present invention relates to anti-reflective layers used in defining openings in such fabrication.
One important process in fabrication of integrated circuits (ICs) is photolithography. Generally, photolithography involves reproducing an image from a mask in a layer of photoresist that is supported by underlying layers of a semiconductor substrate assembly. Photolithography is a very complicated and critical process in the fabrication of ICs. The ability to reproduce precise images in a photoresist layer is crucial to meeting demands for increasing device density.
In the photolithographic process, first an optical mask is positioned between the radiation source and the photoresist layer on the underlying layers of a semiconductor substrate assembly. A radiation source can be, for example, visible light or ultraviolet radiation. Then, the image is reproduced by exposing the photoresist to radiation through the optical mask. Portions of the mask contain an opaque layer, such as, for example, chromium, that prevents exposure of the underlying photoresist. The remaining portions of the mask are transparent, allowing exposure of the underlying photoresist.
The layers underlying the photoresist layer generally include one or more individual layers that are to be patterned. That is, when a layer is patterned, material from the layer is selectively removed. The ability to pattern layers and material enables ICs to be fabricated. In other words, the patterned layers are used as building blocks in individual devices of the ICs. Depending on the type of photoresist used (e.g., positive type or negative type photoresist), exposed photoresist is either removed when the substrate is contacted with a developer solution, or the exposed photoresist becomes more resistant to dissolution in the developer solution. Thus, a patterned photoresist layer is able to be formed on the underlying layers.
One of the problems experienced with conventional optical photolithography is the difficulty of obtaining uniform exposure of the photoresist underlying transparent portions of the mask. It is desired that the light intensity exposing the photoresist be uniform to obtain optimum results.
When sufficiently thick layers of photoresist are used, the photoresist must be or become partially transparent so that photoresist at the surface of underlying layers is exposed to a substantially similar extent as the photoresist at the outer surface. Often, however, light that penetrates the photoresist is reflected back toward the radiation source from the surface of the underlying layers of the substrate assembly. The angle at which the light is reflected is at least in part dependent upon the topography of the surface of the underlying layers and the type of material of the underlying layers. The reflective light density can vary in the photoresist throughout its depth or partially through its depth, leading to non-uniform exposure and undesirable exposure of the photoresist. Such exposure of the photoresist can lead to poorly controlled features (e.g., gates, metal lines, etc.) of the ICs.
In an attempt to suppress reflectivity, or in other words to minimize the variable reflection of light in a photoresist layer, anti-reflective coatings, i.e., anti-reflective layers, have been used between the underlying layers of a substrate assembly and the photoresist layer or between the photoresist layer and the radiation source. Such anti-reflective coatings suppress reflectivity from the underlying substrate assembly allowing exposure across a photoresist layer to be controlled more easily from the radiation incident on the photoresist from the radiation source.
Typically, anti-reflective coatings are organic materials. Organic layers can, however, lead to particle contamination in the integrated circuit (IC) due to the incomplete removal of organic material from the underlying layers after the photolithography step is performed. Such particle contamination can potentially be detrimental to the electrical performance of the IC. Further, the underlying layers upon which the organic materials are formed may be uneven, resulting in different thicknesses of the organic material used as the anti-reflective coating, e.g., thicker regions of organic material may be present at various locations of the underlying layers. As such, when attempting to remove such organic material, if the etch is stopped when the underlying layers are reached, then some organic material may be left. If the etch is allowed to progress to etch the additional thickness in such regions or locations, the underlying layers may be undesirably etched (e.g., punch through of an underlying layer may occur).
Further, inorganic anti-reflective layers have also been introduced for suppressing reflectivity in the photolithography process. For example, silicon-rich silicon dioxide, silicon-rich nitride, and silicon-rich oxynitride have been used as inorganic anti-reflective layers, for example, in the patterning of metal lines and gates.
After a patterned photoresist layer is formed on a substrate assembly, many other processes are typically performed in the fabrication of ICs. For example, the photoresist can act as an implantation barrier during an implant step, the photoresist can be used to define the outer perimeter of an area (e.g., a contact hole) that is etched in one or more underlying layers of the substrate assembly, or the photoresist may be used in any other typically used fabrication process. In many of such cases, the photoresist acts as a barrier during the etching process, such that only selective material of the one or more underlying substrate assembly layers is removed.
After the processes involving photolithographic techniques are carried out (e.g., implantation, etching, etc.), in many circumstances not only must the photoresist material used in the photolithographic process be removed, but the anti-reflective coating must also be removed. For example, in the formation of a container capacitor, such as the container capacitor storage cell described in U.S. Pat. No. 5,270,241 to Denison et al., entitled xe2x80x9cOptimized Container Stacks Capacitor DRAM Cell Utilizing Sacrificial Oxide Deposition and Chemical Mechanical Polishing,xe2x80x9d issued Dec. 14, 1993, a contact opening is defined using photolithographic processes in conjunction with the use of an anti-reflective layer prior to depositing a bottom electrode structure therein. In many cases, the photoresist and the anti-reflective coating used to define the contact opening needs to be removed prior to subsequent processing of the structure.
However, various issues arise during formation of such structures and other integrated circuit structures because of the need to remove the anti-reflective coating. For example, it is important to carry out the formation of integrated circuit structure in the least amount of steps. When anti-reflective coatings need to be removed prior to subsequent processing, an additional step, i.e., the step of removing the anti-reflective coating, is required. For example, the inorganic anti-reflective coatings may be removed in an additional step using suitable etching techniques such as dry etching or reactive ion etching with the use of a fluorine chemistry, e.g., CHF3 or CF4. However, wet etchants are generally more efficient at etching inorganic anti-reflective coating layers than dry etchants. The problem with wet etchants is that such etchants generally etch isotropically and critical dimensions of layers patterned using the anti-reflective coating cannot generally be adequately controlled.
There is a need for methods of forming and using inorganic anti-reflective material layers. For example, it is desirable to suppress reflectivity with the use of anti-reflective material layers in patterning steps for the formation of integrated circuit structures. The present invention provides various methods for forming inorganic anti-reflective coating material layers and methods for using such inorganic anti-reflective coating material layers in the formation of integrated circuit structures. For example, the present invention provides an anti-reflective coating material layer having a relatively high etch rate such that it can be removed simultaneously with the cleaning of a defined opening in a relatively short period of time without affecting the critical dimensions of the opening.
A method of forming an anti-reflective coating material layer according to the present invention includes providing a substrate assembly having a surface in a reaction chamber. A gas mixture of at least a silicon containing precursor, a nitrogen containing precursor, and an oxygen containing precursor is provided in the reaction chamber. An inorganic anti-reflective coating material layer is deposited on the substrate assembly surface using the gas mixture at a temperature in the range of about 50xc2x0 C. to about 400xc2x0 C. The deposition of the inorganic anti-reflective coating material layer includes subjecting the gas mixture to a glow discharge created by applying an electromagnetic field across the gas mixture. Further, the inorganic anti-reflective coating material layer deposited is SixOyNz:H, where x is in the range of about 0.39 to about 0.65, y is in the range of about 0.02 to about 0.56, z is in the range of about 0.05 to about 0.33, and where the atomic percentage of hydrogen in the inorganic anti-reflective coating material layer is in the range of about 10 atomic percent to about 40 atomic percent.
In one embodiment of the method, the silicon containing precursor is SiH4. Further, the nitrogen containing precursor and oxygen containing precursor is N2O.
In another embodiment, the provision of the gas mixture includes providing a total flow of SiH4 in a range of about 80 sccm to about 400 sccm; preferably a total flow of SiH4 is in the range of about 150 sccm to about 400 sccm. Further, provision of the gas mixture includes providing a flow of N2O in a range such that the ratio of the total flows of SiH4:N2O is in a range of about 0.25 to about 0.60.
In yet another embodiment of the method, the silicon containing precursor is disilane.
Another method of forming an anti-reflective coating material layer according to the present invention includes providing a substrate assembly having a surface in a reaction chamber. A gas mixture of at least SiH4 and N2O is provided in the reaction chamber. The provision of the gas mixture includes providing a total flow of SiH4 in a range of about 150 sccm to about 400 sccm. The inorganic anti-reflective coating material layer is deposited on the substrate assembly surface in the reaction chamber. The deposition includes subjecting the gas mixture to a glow discharge created by applying an electromagnetic field across the gas mixture.
In one embodiment of the method, the total flow of SiH4 is in a range of about 200 sccm to about 400 sccm. In another embodiment of the method, the temperature of the surface is maintained in the range of about 50xc2x0 C. to about 600xc2x0 C. In yet another embodiment of the method, the provision of the gas mixture further includes providing a flow of N2O in a range such that the ratio of the total flows of SiH4:N2O is in a range of about 0.60 to about 0.25.
An anti-reflective coating material layer according to the present invention consists essentially of SixOyNz:H, where x is in the range of about 0.39 to about 0.65, y is in the range of about 0.02 to about 0.56, z is in the range of about 0.05 to about 0.33, and where the atomic percentage of hydrogen in the inorganic anti-reflective coating material layer is in a range of about 10 atomic percent to about 40 atomic percent.
A method for use in fabrication of integrated circuits according to the present invention includes providing a substrate assembly having a surface and providing an oxide layer on the surface of the substrate assembly. Further, an inorganic anti-reflective coating material layer is formed on the oxide layer and a mask layer is provided on the inorganic anti-reflective coating material layer. The mask layer is patterned to define an opening to be formed in the oxide layer. The oxide layer is etched to define the opening in the oxide layer to a region of the surface of the substrate assembly. The opening is defined by at least one wall and the surface region. The mask layer is then removed and the at least one wall and the surface region defining the opening is cleaned with a wet etchant while simultaneously completely removing the inorganic anti-reflective coating material layer.
In one embodiment of the method, the oxide layer is BPSG. Yet further, cleaning the at least one wall and the surface region includes completely removing the anti-reflective coating material layer with less than about 100 angstroms of BPSG being removed.
In another embodiment of the method, the wet etchant cleans the at least one wall and the surface region defining the opening in a time period of less than about 60 seconds while simultaneously completely removing the inorganic anti-reflective coating material layer.
Yet further, in another embodiment, the inorganic anti-reflective coating material layer has a thickness in the range of about 100 xc3x85 to about 1000 xc3x85.
A method for use in fabrication of a capacitor structure according to the present invention is also provided. The method includes providing a substrate assembly with the substrate assembly including a conductive contact surface region. An oxide layer is provided on the substrate assembly. Further, an opening is defined through the oxide layer to the conductive contact surface region. The definition of the opening includes forming an inorganic anti-reflective material layer on the oxide layer, forming a mask layer on the inorganic anti-reflective material layer, patterning the mask layer to define the opening in the oxide layer, and etching the oxide layer to define the opening in the oxide layer to the conductive contact surface region of the substrate assembly with the opening defined by at least one wall and the conductive surface region. The mask layer is then removed and the at least one wall and the surface region defining the opening cleaned with a wet etchant while simultaneously completely removing the inorganic anti-reflective material layer. Thereafter, a capacitor electrode is formed in the opening after the opening is cleaned and the inorganic anti-reflective coating material layer is completely removed.
Another method for use in fabrication of integrated circuits according to the present invention includes providing a substrate assembly having an opening defined therein by at least one surface of BPSG. The opening is defined using an inorganic anti-reflective coating material layer with at least a portion of the anti-reflective coating material layer remaining on the substrate after the opening is defined. Thereafter, the inorganic anti-reflective coating material layer is completely removed with less than about 100 angstroms of the at least one surface of BPSG being removed.
In one embodiment of the method, the inorganic anti-reflective coating material layer has a thickness in the range of about 100 xc3x85 to about 1000 xc3x85. Further, completely removing the inorganic anti-reflective coating material layer includes cleaning the opening with a wet etchant in a time period of less than about 60 seconds while simultaneously removing the inorganic anti-reflective coating material layer.
Lastly, a method of forming a contact opening according to the present invention includes defining a contact opening in an oxide layer using an inorganic anti-reflective coating material layer. The contact opening extends to a conductive contact surface area. A portion of the inorganic anti-reflective coating layer remains after the contact opening is defined. Thereafter, the portion of the inorganic anti-reflective coating material layer is completely removed while cleaning the opening with less than about 100 angstroms of the oxide layer being removed.
In one embodiment of the method, the oxide layer is BPSG or rich BPSG. Further, the inorganic anti-reflective coating material layer may have a thickness in the range of about 100 xc3x85 to about 1000 xc3x85 and a wet etchant is used to clean the opening in a time period of less than about 60 seconds while simultaneously removing the inorganic anti-reflective coating material layer.