Method for manufacturing the shallow trench isolation structure

A method for manufacturing a shallow trench isolation (STI) structure is provided. In the method, a substrate is initially provided. Then, a patterned pad layer and a patterned mask layer are successively formed in order on the substrate. After that, a portion of the substrate is removed by using the patterned mask layer and the patterned pad layer as a mask to form trenches in the substrate. Next, a first insulation layer is formed in the trenches. Afterwards, a protection layer is conformally formed on the substrate. Then, a second insulation layer is formed on the protection layer above the first insulation layer. Next, the patterned mask layer and the patterned pad layer are removed. Finally, a portion of the protection layer and the second insulation layer are removed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 96116269, filed May 8, 2007. All disclosure of the Taiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a method for manufacturing an isolation structure and more particularly to a method for manufacturing a shallow trench isolation (STI) structure.

2. Description of Related Art

With the improvement of semiconductor technology, the size of the semiconductor component is continuously decreased even to the sub-micron. Meanwhile, components further shrink to more minute sizes. Accordingly, the isolation between components becomes a very important issue since the isolation can effectively prevent adjacent components from being short circuited.

In order to prevent adjacent components from being short-circuited, generally an isolation layer is added between components. The more widely-applied technique is a local oxidation of silicon (LOCOS) process. However, the LOCOS process has some disadvantages such as the problems resulted from the stress, or the bird's beak formed around the isolation structure. Nowadays, the most popular method used in the industry is a shallow trench isolation (STI) manufacturing process.

FIGS. 1A through 1Care cross-sectional views illustrating a conventional manufacturing process of an STI structure. Initially, as shown inFIG. 1A, a substrate100is provided. Then, a patterned pad layer102and a patterned mask layer104are successively formed in order on the substrate100. Thereafter, an etching process is implemented to form trenches106in the substrate100by using the patterned pad layer102and the patterned mask layer104as a mask.

Then, referring toFIG. 1B, an insulation material layer (not shown) is formed on the substrate100and fills up the trenches106. After that, a chemical mechanical polishing process is implemented by using the patterned mask layer104as a polishing stop layer to planarize the insulation material layer. As a result, an insulation layer108is formed in the trenches106. Then, a wet etching process is implemented to remove the residual insulation material layer on the patterned mask layer104. While the wet etching process is being implemented, a portion of the insulation layer108in the trenches106may also be simultaneously removed.

Continually, referring toFIG. 1C, the patterned mask layer104is initially removed, and then the patterned pad layer102is removed by the wet etching process so as to accomplish manufacturing the STI structure.

However, while the patterned pad layer102is being removed, the STI structure (the insulation layer108) underneath the surface of the substrate100may be etched by the etchant used in the wet etching process. As a result, divots are formed at the corner regions110of the insulation layer108, which affects the follow-up manufacturing process. For example, since a polysilicon layer is initially formed on the substrate and the etching process is then implemented during the process for manufacturing a gate, the polysilicon layer usually remains in the divots at the corner regions110of the insulation layer108when the divots exists thereat, which may cause a short circuit in the subsequently formed components.

In addition, the divots are formed not only while removing the patterned pad layer102, but usually formed while removing the patterned mask layer104.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the present invention is directed to a method for manufacturing a shallow trench isolation (STI) structure which can prevent the STI structure from forming divots at the corner regions of STI structure.

The present invention discloses a method for manufacturing the STI structure, which a substrate is initially provided. Then, a patterned pad layer and a patterned mask layer are successively formed in order on the substrate. After that, a portion of the substrate is removed to form trenches in the substrate by using the patterned mask layer and the patterned pad layer as a mask. Next, a first insulation layer is formed in the trenches. Thereafter, a protection layer is conformally formed on the substrate. Then, a second insulation layer is formed on the protection layer above the first insulation layer. Next, the patterned mask layer and the patterned pad layer are removed. Finally, a portion of the protection layer and the second insulation layer are removed.

According to a method for manufacturing a shallow trench isolation (STI) structure in an embodiment of the present invention, the material of the said protection layer is silicon oxynitride, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the method for removing the portion of the said protection layer and the second insulation layer includes a wet etching process, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, a wet etching process can be further implemented after the first insulation layer is formed and before the protection layer is formed.

According to the method for manufacturing the STI structure in an embodiment of the present invention, a wet etching process can be further implemented after the second insulation layer is formed and before the patterned mask layer and the patterned pad layer are removed.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the method for forming the said first insulation layer is initially forming an insulation material layer on the substrate, for example. Next, a chemical mechanical polishing process is implemented by using the patterned mask layer as a polishing stop layer.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the method for forming the said second insulation layer is initially forming an insulation material layer on the substrate, for example. Next, a chemical mechanical polishing process is implemented by using the patterned mask layer as a polishing stop layer.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the material of the said patterned pad layer is silicon oxide, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the method for forming the said patterned pad layer is thermal oxidation process, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the material of the said patterned mask layer is silicon nitride, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the material of the said first insulation layer is silicon oxide, for example.

According to the method for manufacturing the STI structure in an embodiment of the present invention, the material of the said second insulation layer is silicon oxide, for example.

Since a protection layer and another insulation layer are formed on the insulation layer in the trenches before the patterned mask layer and the patterned pad layer are removed in the present invention, when the patterned mask layer and the patterned pas layer are removed, the insulation layer in the trenches can be prevented from being damaged and from forming divots at the corner regions the insulation layer. In addition, the present invention also improves uniformity in the step height of the substrate surface by controlling the thickness of the protection layer.

In order to make the aforementioned features and advantages of the present invention more comprehensible, several embodiments accompanied with figures are described in detail below.

DESCRIPTION OF EMBODIMENTS

FIGS. 2A through 2Fare cross-sectional views showing a process for manufacturing a shallow trench isolation (STI) structure according to an embodiment of the present invention.

Initially, referring toFIG. 2A, a substrate200is provided. The substrate200is, for example, a silicon substrate. Then, a pad material layer (not shown) and a mask material layer (not shown) are successively formed in order on the substrate200. The material of the pad material layer is silicon oxide, and the method for forming the pad material layer is a thermal oxidation process, for example. The material of the mask material layer is silicon nitride, and the method for forming the mask material layer is a chemical vapor deposition (CVD) process, for example. Then, a photolithographic process and an etching process are implemented to pattern the mask material layer and the pad material layer so that a patterned pad layer202and a patterned mask layer204are formed.

Continually referring toFIG. 2A, a dry etching process is implemented to remove a portion of the substrate200by using the patterned mask layer204and the patterned pad layer202as a mask so that trenches206are formed in the substrate200. The said dry etching process may use CF4/O2/Ar as an etching gas.

Then, referring toFIG. 2B, an insulation material layer (not shown) is formed on the substrate200and fills up the trenches206. The material of the insulation material layer is silicon oxide and the method for forming the insulation material layer is a CVD process, for example. Next, for example, a chemical mechanical polishing process is implemented to remove the insulation material layer on the patterned mask layer204so as to form an insulation layer208in the trenches206by using the patterned mask layer204as a polishing stop layer. Thereafter, a wet etching process is implemented to remove the residual insulation material layer on the patterned mask layer204to avoid affecting the follow-up manufacturing process. Apparently, a portion of the insulation layer208is removed at the same time when the residual insulation material layer on the patterned mask layer204is removed by the wet etching process. Herein, hydrofluoric acid (DHF 200:1) is used as the etchant in the wet etching process.

Next, referring toFIG. 2C, a protection layer210is conformally formed on the substrate200. The material of the protection layer210may include SiON and the method for forming the protection layer210is a CVD process, for example. Forming the protection layer210is for preventing the insulation layer208from being damaged in the follow-up process so as to avoid affecting the performance of the components.

Following the foregoing, referring toFIG. 2D, another insulation material layer (not shown) is formed on the substrate200. The material of the insulation material layer is silicon oxide and the method for forming the insulation material layer is the CVD process, for example. Similarly, the chemical mechanical polishing process is implemented to remove the insulation material layer and the protection layer210on the patterned mask layer204so as to form an insulation layer212on the protection layer210above the insulation layer208by using the patterned mask layer204as the polishing stop layer. The etching rate of the protection layer210is approximate to that of the insulation material layer, and hence, after the chemical mechanical polishing process is implemented, the wet etching process may also be implemented to remove the residual insulation material layer or the protection layer210on the patterned mask layer204so as to avoid affecting the follow-up process. Apparently, a portion of the protection layer210and a portion of the insulation layer212on the insulation layer208are removed while the residual insulation material layer or the protection layer210on the patterned mask layer204is being removed by the wet etching process. Herein, in the wet etching process, phosphoric acid (H3PO4) is used as the etchant.

Afterwards, referring toFIG. 2E, the patterned mask layer204and the patterned pad layer202are removed. The method for removing the patterned mask layer204and the patterned pad layer202is, for example, a wet etching process using hydrofluoric acid (DHF 200:1) as the etchant. It should be noted that the residual insulation material layer or the protection layer210on the patterned mask layer204may have been removed in the previous step, and therefore, the patterned mask layer204and the patterned pad layer202can be completely removed in the current step.

It is important that the protection layer210has been formed above the insulation layer208, and therefore, the insulation layer208can be prevented from being etched at the same time when the patterned mask layer204and the patterned pad layer202are removed by the aforementioned wet etching process so as to prevent the insulation layer208from being etched and forming divots at the corner regions of the insulation layer208.

Continually, referring toFIG. 2F, for example, a wet etching process is implemented to remove a portion of the protection layer210and the insulation layer212so as to form the STI structure. Herein, in the wet etching process, hydrofluoric acid (DHF 500:1) is used as the etchant. In the present embodiment, for example, a portion of the protection layer210and the insulation layer212are removed by the wet etching process so that the height to the surface of the protection layer210on the insulation layer208is substantially equal to that to the surface of the substrate200. Apparently, in other embodiments, the thickness of the protection layer210can be controlled while the protection layer210is being formed depending on the actual needs of manufacturing processes so that the surface of the protection layer210on the insulation layer208is higher than the surface of the substrate200after the aforementioned wet etching process is implemented.

In more detail, in order to render the step height on the substrate surface with better uniformity, the height of the formed STI structure can be controlled by adjusting the thickness of the protection layer210so as to avoid excessive difference in the step height of the substrate surface.

According to the above description, a protection layer and another insulation layer are formed on the insulation layer previously formed in the trenches before the patterned mask layer and the patterned pad layer are removed in accordance with the present invention. Accordingly, in the follow-up manufacturing process, the insulation layer formed in the trenches is prevented from being damaged and forming divots at the corner regions of the insulation layer so as not to affect the follow-up manufacturing process and cause a short circuit in components.

Furthermore, in the process for manufacturing the STI structure in the present invention, the height of the formed STI structure can be further controlled by adjusting the thickness of the protection layer to improve uniformity in the step height on the substrate surface.