The present invention relates to a fabricating method of a shallow trench isolation structure, and more particularly to a fabricating method of a shallow trench isolation structure in the manufacture of a semiconductor device.
Nowadays, in the mainstream of integrated circuit production, a low voltage logic circuit and a high voltage semiconductor device are implemented on the same integrated circuit chip. For providing effective isolation between adjacent electronic components, in the low voltage logic circuit and a high voltage semiconductor device, an isolation structure is usually formed in the integrated circuit chip to separate adjacent electronic components from each other. As known, a shallow trench isolation (STI) structure is one of the most popular isolation structures. Moreover, the shallow trench isolation structures of the low voltage logic circuit and the high voltage semiconductor device are simultaneously produced in the same fabricating process.
As the device size of the low voltage logic circuit is gradually developed toward miniaturization because of the process progress, the width and the depth of the shallow trench isolation structure are reduced. If the dimension of the shallow trench isolation structure of the high voltage semiconductor device is identical to the dimension of the shallow trench isolation structure of the low voltage logic circuit, the isolation efficacy of the high voltage semiconductor device is unsatisfied. Therefore, there is a need of providing an improved fabricating method of a shallow trench isolation structure.
Therefore, the object of the present invention is to provide a fabricating method of a shallow trench isolation structure in order to achieve effective isolation.
In accordance with an aspect, the present invention provides a fabricating method of a shallow trench isolation structure. Firstly, a substrate is provided, wherein a high voltage device area is defined in the substrate. Then, a first etching process is performed to partially remove the substrate, thereby forming a preliminary shallow trench in the high voltage device area. Then, a second etching process is performed to further remove the substrate corresponding to the preliminary shallow trench, thereby forming a first shallow trench in the high voltage device area. Afterwards, a dielectric material is filled in the first shallow trench, thereby forming a first shallow trench isolation structure.
In an embodiment, a low voltage device area is further defined in the substrate, and a second shallow trench is further formed in the low voltage device area by the second etching process. The first shallow trench is deeper than the second shallow trench.
In an embodiment, an inclination angle of a sidewall of the preliminary shallow trench is from 105 to 135 degrees, so that the first shallow trench has a shoulder part with a gentle slope.
In an embodiment, after the first shallow trench isolation structure is formed, the fabricating method further includes the following steps. A pre-clean process is performed to treat the shallow trench isolation structure, so that a top surface of the shallow trench isolation structure is shrunk to a location below the shoulder part. Then, a high voltage gate dielectric layer is formed on the shallow trench isolation structure and a surface of the substrate.
In an embodiment, after the preliminary shallow trench is formed, the fabricating method further includes a step of forming a spacer on a sidewall of the preliminary shallow trench, wherein the spacer is made of the same material as the dielectric material.
In an embodiment, after the preliminary shallow trench is formed and before the second etching process is done, the fabricating method further includes a step of performing an ion implantation process to dope the high voltage device area of the substrate with a dopant, so that a high voltage well region is formed in the high voltage device area.
In an embodiment, the step of filling the dielectric material in the first shallow trench includes sub-steps of performing a high density plasma chemical vapor deposition process to deposit the dielectric material, and performing a chemical mechanical polishing process to flatten the dielectric material.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.
Firstly, as shown in
A pad oxide layer 10 is formed on a surface of the silicon substrate 1. In addition, the silicon substrate 1 is divided into two areas, i.e. a high voltage device area 11 and a low voltage device area 12.
Then, a zero-etch process is performed by using a photolithography and etching process to define an alignment mark (not shown) on the silicon substrate 1. Especially, for performing the zero-etch process, a pattern for defining a shallow trench isolation structure of the high voltage device area 11 should be previously created in the photo mask. After the zero-etch process is performed, a preliminary shallow trench 110 is formed in the high voltage device area 11 (see
Then, as shown in
Then, as shown in
Then, as shown in
Then, a shallow trench etching process is performed to simultaneously form a plurality of first shallow trenches 15 and a plurality of second shallow trenches 16 in the high voltage device area 11 and the low voltage device area 12, respectively. The depth of the first shallow trench 15 in the high voltage device area 11 is greater than the depth of the second shallow trench 16 in the low voltage device area 12 (see
However, a defect is possibly formed on the silicon substrate 1 after the shallow trench etching process is performed. For repairing the defect, the silicon substrate having the shallow trenches may be treated by a high temperature furnace process (at about 100° C.). Consequently, a silicon oxide repair linear layer (not shown) is formed on the sidewalls of the shallow trenches for repairing the defect and rounding the shape corners. Under this circumstance, the electrical isolation efficacy is enhanced.
Then, a high density plasma chemical vapor deposition (HDP-CVD) process is performed, and thus a silicon oxide layer 17 is filled within the first shallow trenches 15 and the second shallow trenches 16 and formed on the silicon nitride layer 14. Then, a chemical mechanical polishing process is performed to remove the silicon oxide layer 17 overlying the silicon nitride layer 14, the top surface of the silicon oxide layer 17 is substantially at the same level as the topside of the silicon nitride layer 14 (see
Then, as shown in
Then, as shown in
Then, as shown in
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
This is a divisional application of U.S. application Ser. No. 13/213211, filed on Aug. 19, 2011, which is currently pending. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | 13213211 | Aug 2011 | US |
Child | 14071664 | US |