KR20010064323A - Method for forming trench type isolation layer in semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming an isolation layer of a trench structure in a semiconductor device is provided to improve efficiency of an isolation process by enlarging an edge rounding effect of a trench. CONSTITUTION: A pad oxide layer and a nitride layer are formed on a semiconductor substrate(100). A photoresist pattern is formed on the nitride layer. The laminated nitride layer and the pad oxide layer are patterned according to the photoresist pattern. A shallow isotropic trench(108a) is formed by performing an isotropic dry etching process. An anisotropic trench(108b) is formed on within the substrate(100) in order to define an isolation region. The photoresist pattern is removed. A gap fill layer is formed within the trench. The nitride layer is removed and an isolation layer is formed thereon.

Description

Method for forming trench type isolation layer in semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a device isolation film of a semiconductor device, and more particularly, to a method of forming a device isolation film of a trench structure in a semiconductor device capable of increasing a trench corner rounding effect in a device isolation process of a trench structure to increase the yield of the device isolation process. It is about.

In general, by forming a device isolation film on a substrate to form a semiconductor device, for example, a transistor and a capacitor on the semiconductor substrate, it is possible to prevent the device from being electrically energized with an active region that can be electrically energized. Isolation regions are separated.

As described above, a device isolation process for separating devices includes a LOCOS process (Local Oxidation of Silicon), and a PBL process (Poly Buffered LOCOS) which improves the LOCOS process. In general, the LOCOS process masks a pad oxide film and a nitride film on a semiconductor substrate to etch the nitride film and performs an oxidation process on the etched portion to form an isolation layer, and the PBL process plays a role of a buffer between the pad oxide film and the nitride film. The device isolation film is formed through the silicon film.

However, the recent semiconductor technology requires a device separation technique of about 0.25 μm in order to achieve high integration and low power of the device, and thus there is a limit to the device separation method using the LOCOS process. For example, due to the stress of the pad oxide film and the nitride film, which are mask patterns, crystal defects occur in the semiconductor substrate during the oxidation process, and leakage current increases, and the device is formed by side diffusion and lateral oxidation of channel blocking ions due to prolonged high temperature oxidation. Bird's beak was generated to reduce the electrical properties of the.

Due to the limitation of the LOCOS method, a trench isolation device isolation process is used to form trenches in a semiconductor substrate with a narrow width and a deep depth so that the device can be easily separated even in a minute narrow area. STI process (Shallow Trench Isolation) is also widely used. This process involves forming trenches with a constant depth in the semiconductor substrate, depositing oxides in the trenches, and etching the unnecessary portions of the oxide film by chemical mechanical polishing (CMP). Forming an isolation layer.

1A through 1C are vertical cross-sectional views sequentially illustrating a trench fabrication process for a device isolation film of a semiconductor device according to the related art. Referring to this, a method of forming a device isolation film having a general trench structure is as follows.

First, as shown in FIG. 1A, a pad oxide film 12 and a nitride film 14 are sequentially stacked on a silicon substrate 10 as a semiconductor substrate, and a photo process using a device separation mask is performed to form the nitride film 14. The photoresist pattern 16 is formed on the top. The nitride film 14 and the pad oxide film 12 are patterned by using the photoresist pattern 16 and an anisotropic etching process.

A trench 18 of a predetermined depth is then formed in the substrate exposed by the patterned nitride film 14 and the pad oxide film 12 as shown in FIG. 1B. Here, the trench 18 of the substrate becomes a region where the device isolation film is to be formed later.

1C, the photoresist pattern 16 used for the trench etching process is removed.

Thereafter, after the oxide film is deposited as a gap fill film to sufficiently fill the inside of the trench 18, the surface of the oxide film is polished by a CMP (C \ hemical Mechanical Polishing) process, and the nitride film 14 is removed with a phosphate solution. In this manner, a device isolation film having a trench structure including an oxide film is completed in the substrate 10.

However, the trench of the device isolation film according to the manufacturing process as described above is sharp as the edge edge of the trench upper portion 20 as shown in Figure 1c, the stress is concentrated in the thermal process thereafter causing silicon defects around There was a disadvantage in that the field concentration phenomenon in which the electric field is concentrated during operation of the device. As such, when the electric field effect is concentrated in the trench edge portion of the device isolation layer, the leakage current of the semiconductor device increases.

An object of the present invention is to shallow the isotropic dry etching process during the trench etching process in order to solve the problems of the prior art as described above to gently etch the top corners of the trench to proceed to the general trench etching process to the electric field caught on the trench corners The present invention provides a method of forming a device isolation film having a trench structure of a semiconductor device capable of improving a concentration phenomenon.

1A to 1C are vertical cross-sectional views sequentially showing a trench fabrication process for a device isolation film of a semiconductor device according to the prior art;

2A to 2D are vertical cross-sectional views sequentially illustrating a trench manufacturing process for an isolation layer of a semiconductor device according to the present invention.

Explanation of symbols on the main parts of the drawings

100: silicon substrate

102: pad oxide film

104: nitride film

106: photoresist pattern

108a: shallow isotropic trench

108b: deep anisotropic trench

In order to achieve the above object, the present invention provides a method for forming a trench for a device isolation film on a semiconductor substrate, the method comprising sequentially depositing a pad oxide film and a nitride film on a substrate, and forming a photoresist pattern defining a device isolation region on the nitride film. Patterning the stacked nitride and pad oxide layers in accordance with the photoresist pattern; Forming deep, forming a deep anisotropic trench to define a region in which a device isolation film is to be formed in a substrate having a shallow isotropic trench, removing a photoresist pattern, and forming a gap fill film in the trench formed in the substrate. After planarization, the nitride film is Removing to form an isolation layer in the substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A through 2D are vertical cross-sectional views sequentially illustrating trench fabrication processes for device isolation layers of a semiconductor device according to the present invention, and a process of fabricating a device isolation layer having a trench structure according to the present invention will be described.

As shown in FIG. 2A, a pad oxide film 102 having a thickness of 30 to 200 Å and a nitride film 104 having a thickness of 800 to 1800 Å are sequentially stacked on the silicon substrate 100 as a semiconductor substrate. Then, the photolithography process using the device isolation mask is performed to form the photoresist pattern 106 defining the device isolation region on the nitride film 104. Subsequently, the laminated nitride film 106 and the pad oxide film 104 are patterned in accordance with the photoresist pattern 106.

As shown in FIG. 2B, a shallow isotropic trench 108a is formed by performing an isotropic dry etching process using plasma for edge rounding in the substrate exposed by the patterned nitride film 106 and the pad oxide film! 04. In this case, shallow isotropic trench formation is performed in-situ or ex-situ, and the etching target etches about 5% to 10% of the total trench depth, preferably 30 kPa to Etch to a depth of 100Å.

When the shallow isotropic trench formation is performed in situ, an F process gas or a mixed gas of F and Cl gas is used in a plasma apparatus, and the etching process is performed under a pressure and a high voltage condition than an anisotropic trench etching to be performed later. Conduct.

On the other hand, when the shallow isotropic trench formation is performed in an ex-situ, a microwave or ICP type plasma generator is used.

Next, as shown in FIG. 2C, a deep anisotropic trench 108b is formed in the substrate on which the shallow isotropic trench 108a is formed to define the region where the device isolation film is to be formed. In this case, the anisotropic trench etching process uses a conventional plasma anisotropic etching process.

As shown in FIG. 2D, when the photoresist pattern 106 is removed, the trench upper portion a has a smooth curved shape by an isotropic dry etching process using the plasma.

Although not shown in the drawings, a gap fill film is formed in the trench of the substrate having the gentle top portion a, and after the planarization thereof, the nitride film is removed to form the trench type isolation film according to the present invention in the substrate. .

As described above, when the device isolation film forming method of the trench structure of the semiconductor device according to the present invention is used, an isotropic dry etching process is performed during the trench etching process, and then a general anisotropic etching process is performed, thereby performing an isotropic dry etching process. Because the part is smooth, the trench edge rounding effect is increased.

Therefore, the device isolation film of the trench structure according to the present invention has the effect that the electric field is dispersed by the curved surface of the upper portion of the trench corners to reduce the leakage current of the semiconductor device.

Claims (5)

In the trench formation method for a device isolation film on a semiconductor substrate, Sequentially depositing a pad oxide film and a nitride film on the substrate; Forming a photoresist pattern defining an isolation region over the nitride film; Patterning the stacked nitride film and pad oxide film according to the photoresist pattern; Forming an isotropic dry etching process using plasma for edge rounding in the substrate exposed by the patterned nitride film and the pad oxide film to form a shallow isotropic trench; Forming a deep anisotropic trench in the substrate on which the shallow isotropic trench is formed to define a region where an isolation layer is to be formed; Removing the photoresist pattern; Forming a device isolation film in the substrate by removing the nitride film after forming a gap fill film in the trench formed in the substrate and planarizing the gap fill film. The device of claim 1, wherein the shallow isotropic trench is formed in-situ or x-situ, and the etching target etches about 5% to 10% of the total trench depth. Separator Formation Method. 3. The method of claim 2, wherein the shallow isotropic trench depth is from about 30 [mu] s to about 100 [mu] s. The method of claim 1 or 2, wherein the formation of the shallow isotropic trench is carried out in situ in the plasma equipment using a mixed gas of F-based gas or F and Cl-based gas at a pressure and high voltage conditions than the anisotropic trench etching A device isolation film forming method having a trench structure, characterized in that the etching process. The method of claim 1, wherein the formation of the shallow isotropic trench is performed using an microwave or ICP plasma generator when the shallow isotropic trench is formed in an ex-situ.