1. Field of the Invention
The present invention relates to a method of manufacturing the isolation structure of integrated circuit devices. More particularly, the present invention relates to a method of manufacturing a shallow trench isolation (STI) structure.
2. Description of the Related Art
With the rapid development in integrated circuits technology, device miniaturization and integration is the ultimate goal for many integrated circuit manufacturers. As the device dimensions continue to shrink and the level of integration increases, device isolation structures for separating the devices must be minimized correspondingly. As a result, the technique of isolating the devices becomes more complicated. In the past, one method of isolating a device structure was to perform a local oxidation of silicon (LOCOS) process to form a field oxide layer on a substrate. However, limited by the “Bird's Beak” shape, the field oxide layer cannot be further minimized. Thus, other types of device isolation techniques, such as the shallow trench isolation (STI) process, have been developed and widely adopted, especially in the sub-half micron process for forming integrated circuits.
Accordingly, at least one objective of the present invention is to provide a method for manufacturing a shallow trench isolation structure capable of forming a shallow trench isolation structure having a sidewall perpendicular to the substrate surface. Hence, the acute-angle corner between the sidewall of a conventional shallow trench isolation structure and the substrate surface is removed so that the issues of polysilicon stringers and abnormal electrical performance are resolved.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention s provides a method of manufacturing a shallow trench isolation (STI) structure on a substrate. First, a substrate is provided and then a dielectric film is formed on the substrate. Then, a buffer layer having a first thickness is formed on the dielectric film, and a hard mask layer having a second thickness is formed on the buffer layer. The hard mask layer, the buffer layer, the dielectric film and the substrate are patterned to form an opening in the hard mask layer, the buffer layer and the dielectric film, and a trench in the substrate. An insulating layer is formed to fill the opening and the trench. Thereafter, the hard mask layer, a portion of the insulating layer and the buffer layer are removed to form a shallow trench isolation structure protruding above the substrate surface.
According to the method of manufacturing shallow trench isolation structure in the embodiment of the present invention, the first thickness is between about 750 Ř950 Å, and the second thickness is between about 750 Ř950 Å. The method of removing the hard mask layer, a portion of the insulating layer and the buffer layer includes removing the hard mask layer to expose the buffer layer, removing a portion of the insulating layer using the buffer layer as a stop layer, and removing the buffer layer. Furthermore, the method of removing a portion of the insulating layer includes performing a dry etching process. The hard mask layer can be a silicon nitride layer, and the buffer layer can be a polysilicon layer. The method of patterning the hard mask layer, the buffer layer, the dielectric film and the substrate to form a trench in the substrate includes patterning the hard mask layer, the buffer layer and the dielectric film to form an opening in the hard mask layer, the buffer layer and the dielectric film and then removing a portion of the substrate to form a trench using the hard mask layer, the buffer layer and the dielectric film as a mask. The method of patterning the hard mask layer, the buffer layer and the dielectric film includes performing an anisotropic etching process.
The present invention also provides an alternative method of manufacturing a shallow trench isolation structure. First, a dielectric film, a polysilicon layer and a hard mask layer are sequentially formed over a substrate. The polysilicon layer has a thickness between about 750 Ř950 Å. The hard mask layer, the polysilicon layer, and the dielectric film are patterned to form an opening in the hard mask layer, the polysilicon layer and the dielectric film. The polysilicon layer exposed by the opening has a sidewall perpendicular to the substrate. Using the hard mask layer, the polysilicon layer and the dielectric film as a mask, a portion of the substrate is removed to form a trench in the substrate. An insulating material is deposited over the substrate to form an insulating material layer. The insulating layer outside the opening is removed to form an insulating layer that completely fills the opening and the trench. The hard mask layer, a portion of the insulating layer and the buffer layer are removed to form a shallow trench isolation structure that protrudes above the surface of the substrate. The portion of the shallow trench isolation structure protruding above the surface of the substrate has a sidewall perpendicular to the substrate.
According to the method of manufacturing shallow trench isolation structure in the embodiment of the present invention, the hard mask layer has a thickness between about 750 Ř950 Å. The method of removing a portion of the insulating material layer includes performing a chemical-mechanical polishing process. The hard mask layer can be a silicon nitride layer. The method of patterning the hard mask layer, the polysilicon layer and the dielectric film includes performing an anisotropic etching process.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference is now made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
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On the other hand, after removing a portion of the material layer using the hard mask layer 206a as a stop layer, the hard mask layer 206a and a portion of the insulating layer 212 can be sequentially removed to form a shallow trench isolation structure 212b as shown in
Thereafter, as shown in
Because a portion of the shallow trench isolation structure 212 is removed using the buffer layer 204a as a stop layer, the tapering portion of the shallow trench isolation structure in the opening surrounded by the patterned hard mask layer 206a can be removed. After the buffer layer 204a is removed, the portion of the shallow trench isolation structure 212b protruding above the surface of the substrate 200 has a sidewall perpendicular to the substrate.
With respect to the height of about 200 Šabove the surface of the substrate for a conventionally fabricated shallow trench isolation structure, the shallow trench isolation structure fabricated according to the present invention has a protruding height of about 750 Ř950 Šabove the substrate surface. Furthermore, the height of the shallow trench isolation structure protruding above the surface of the substrate can be determined by the thickness of the buffer layer or the mask layer. Using the etching properties of the buffer layer, a buffer layer having a sidewall perpendicular to the substrate surface can be formed. Hence, by using a buffer layer having a thickness equal to the thickness of the hard mask layer, the perpendicularity of the sidewall of the subsequently formed shallow trench isolation structure to the substrate surface can be increased. In other words, the buffer layer has the capacity to straighten the shallow trench isolation structure. Therefore, the issues of polysilicon stringers and abnormal electrical performance are resolved by forming the tapering shallow trench isolation structure for increasing the height of the shallow trench isolation structure above the substrate surface in the conventional method. Furthermore, the method for forming the shallow trench isolation structure according to the present invention is also suitable for the manufacturing process of trench type semiconductor devices (for example, trench type flash memory) for forming the device isolation structure in the in a subsequent process.
It is apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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94106402 | Mar 2005 | TW | national |