KR100607729B1 - STI Formation Method of Semiconductor Device - Google Patents

Abstract

The present invention relates to a method for forming an STI of a semiconductor device. That is, in the formation of the STI of the semiconductor device, the present invention provides a chemical for removing an oxide film by depositing an oxide film several times in a thin thickness inside the trench of the STI structure to prevent excessive stress in the trench corners when the oxide film is polished by chemical mechanical polishing. By dispersing the stress in the mechanical polishing process, strong stress is not transmitted to both corner portions of the trench so that the gate can be stably formed, thereby preventing deterioration of semiconductor device characteristics.

Description

STI Formation Method of Semiconductor Device {METHOD FOR FORMING STI IN SEMICONDUCTOR DEVICE}

1A through 1B are flowcharts illustrating an STI forming process of a conventional semiconductor device;

2A through 2D are flowcharts illustrating an STI forming process of a semiconductor device according to an embodiment of the present invention.

<Brief description of the major symbols in the drawings>

100 silicon substrate 102 pad oxide film

104: silicon nitride film 108: primary oxide film

112: secondary oxide film 116: tertiary oxide film

120: STI

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming STIs in semiconductor devices, and more particularly, to a method for forming STIs in semiconductor devices that prevents deterioration of the characteristics of semiconductor devices due to excessive stress at trench edges during oxide film polishing by chemical mechanical polishing.

In recent years, as the integration of semiconductor devices continues to progress, shallow trench isolation (STI) structures have been used as device isolation structures to improve device isolation characteristics of semiconductor devices. The STI structure forms a trench having a predetermined depth in a semiconductor substrate, deposits an oxide film on the trench by chemical vapor deposition (CVD), and then forms an unnecessary oxide film by chemical mechanical polishing (CMP). A technique for forming an isolation layer by etching, which has better device isolation characteristics and a smaller overall oil area than a local oxide of silicon (LOCOS) structure in which a thick oxide layer is selectively grown on a semiconductor substrate to form an isolation layer. Currently, it is mostly used for high density semiconductor devices.

However, in the formation of the STI structure applied to the conventional method of isolation of semiconductor devices, an oxide film is embedded in a trench serving as a separation layer, and then, as described above, the oxide film is removed by chemical mechanical polishing to planarize the oxide film. In this chemical mechanical polishing process, the oxide film is changed while pressing the wafer under a considerable pressure, and particularly, excessive stress is applied at both corners of the trench, thereby preventing the uniform growth of the gate oxide film. there was.

1A to 1B illustrate a SIT forming process procedure of a conventional semiconductor device. Hereinafter, the conventional process will be described with reference to FIGS. 1A to 1B.

First, as shown in FIG. 1A, the pad oxide layer 102 and the silicon nitride layer 104 are deposited on the entire upper portion of the silicon substrate 100, and as a device isolation layer in a predetermined region of the silicon substrate through masking and etching. After the trench 106 is formed, an oxide film 108 is deposited to completely fill the trench 106 with the oxide film 108. Next, as shown in FIG. 1B, the oxide film is polished by chemical mechanical polishing (CMP) to remove the oxide film deposited outside the trench region on the silicon substrate, and the silicon nitride film 104 and the wet etching method are used. The pad oxide film 102 is sequentially removed to form the STI 109 filled with the oxide film.

However, in the conventional STI process, in the oxide etching for forming the separation layer, as the oxide film is etched through chemical mechanical polishing, a considerable amount of stress is applied during the polishing process, and particularly a strong stress is applied at both edge portions A of the STI 109. There was a problem in that the transfer to the deformation of the crystal structure near the corner, such as, which ultimately prevents the stable formation of the gate to deteriorate the characteristics of the semiconductor device.

Accordingly, it is an object of the present invention to form an STI of a semiconductor device, in which an oxide is polished by chemical mechanical polishing to prevent excessive stress at the corner of a trench, so that a gate can be stably formed. In providing.

According to an aspect of the present invention, there is provided a method of forming an STI of a semiconductor device, the method comprising: (a) depositing a pad oxide film and a silicon nitride film over an entire silicon substrate; (b) forming an STI mask pattern for forming an STI on the silicon nitride film; (c) forming a trench for the STI by etching the silicon substrate to a predetermined depth at the position where the STI is to be formed using the STI mask pattern; (d) removing the oxide film having a predetermined thickness over the entire silicon substrate through deposition and chemical mechanical polishing a plurality of times, and filling the inside of the trench with a multilayer oxide film having a predetermined thickness to form an STI.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation of the preferred embodiment according to the present invention.

2A to 2D illustrate a flowchart of an STI pattern forming process according to an exemplary embodiment of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 2A to 2D.

First, as shown in FIG. 2A, the pad oxide layer 102 and the silicon nitride layer 104 are sequentially deposited on the entire upper portion of the silicon substrate 100, and a predetermined region of the silicon substrate is formed by masking and etching (not shown). A trench 106 is formed in the trench. Subsequently, the first oxide film 108 is thinly deposited on the entire silicon substrate as shown in FIG. 2A, and then polished by chemical mechanical polishing to remove the primary oxide film 108 on the silicon substrate except for the inside of the trench region. Let's do it. As a result, a part of the primary oxide film 110 remains in the trench region.

Subsequently, as shown in FIG. 2B, the second oxide film 112 is thinly deposited on the entire upper portion of the silicon substrate 100, and then polished by chemical mechanical polishing to perform the secondary oxide film 112 on the silicon substrate except for the inside of the trench region. ) Will be removed. Accordingly, the primary oxide film 110 and the secondary oxide film 114 are stacked to a predetermined thickness in the trench region.

Subsequently, as shown in FIG. 2C, the third oxide film 116 is thinly deposited on the entire upper portion of the silicon substrate 100, and then polished by chemical mechanical polishing, thereby terminating the third oxide film 116 on the silicon substrate except for the inside of the trench region. ) Will be removed. Accordingly, the first, second, and third oxide layers 118 sequentially stacked in the trench region are deposited to have a predetermined thickness to fill the trench regions.

Thereafter, as shown in FIG. 2D, the silicon nitride layer 104 and the pad oxide layer 102 are sequentially removed by a wet etching method to fill the trench with first, second, and third oxide layers 110, 114, and 118 having a predetermined thickness. To form the STI 120. On the other hand, the thickness of the first, second and third oxide film is 1000Å to 5000Å to fill the inside of the trench with a target value of 3000Å, and the first, second, and third oxide film embedded in the trench are heat treated after chemical mechanical polishing. Allow water to be removed. At this time, the heat treatment temperature of each oxide film is 200 ℃ to 500 ℃ to perform a heat treatment for 5 to 6 minutes at the target value 350 ℃.

As described above, in the present invention, as the oxide film is deposited several times in the trench with a thin thickness, stress in the chemical mechanical polishing process for removing the oxide film is dispersed, thereby causing strong stress on both corner portions A of the trench. Is not transferred, so that the gate can be stably formed, thereby preventing deterioration of semiconductor device characteristics.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the invention should be determined by the claims rather than by the described embodiments.

As described above, in the STI formation of the semiconductor device, the oxide film is formed by depositing an oxide film several times in a thin thickness inside the STI structure trench to prevent excessive stress in the trench corners when the oxide film is polished by chemical mechanical polishing. By dissipating the stress in the chemical mechanical polishing process for removal, strong stress is not transmitted to both edges of the trench so that the gate can be stably formed, thereby preventing deterioration of semiconductor device characteristics. This has the advantage.

Claims (5)

In the STI formation method of a semiconductor element, (a) depositing a pad oxide film and a silicon nitride film over the entire silicon substrate; (b) forming an STI mask pattern for forming an STI on the silicon nitride film; (c) forming a trench for the STI by etching the silicon substrate to a predetermined depth at the position where the STI is to be formed using the STI mask pattern; (d) removing the first oxide film having a predetermined thickness through the deposition and chemical mechanical polishing on the entire silicon substrate to bury the first oxide film in the trench; (e) depositing and depositing a secondary oxide film on the upper portion of the first oxide film in the trench by removing the secondary oxide film having a predetermined thickness through deposition and chemical mechanical polishing on the entire silicon substrate; (f) depositing a third oxide film on the upper part of the silicon substrate by depositing and depositing a third oxide film having a predetermined thickness on the upper surface of the second oxide film in the trench by depositing and chemical mechanical polishing; STI forming method of a semiconductor device comprising a. delete The method of claim 1, The oxide film is formed to a thickness of 1000 kPa to 5000 kPa, and the target value is 3000 kPa, STI formation method of a semiconductor device. The method of claim 3, After performing the chemical mechanical polishing of the oxide film, the method of forming an STI of the semiconductor device, characterized in that further comprising the step of removing moisture through heat treatment. The method of claim 4, wherein The heat treatment is performed for 5 minutes to 6 minutes at a temperature of 200 ℃ to 500 ℃ STI forming method of a semiconductor device.

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