KR20010003693A - Method of forming trench type isolation layer in semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming a trench type device isolation film is provided to relief a narrow width effect and to reduce a conjunction leakage current. CONSTITUTION: A pad oxide film(21) and a nitride film(22) are formed on a silicon substrate(20). The pad oxide film and the nitride film are sequentially etched by a photo etching process using an isolation mask to form a pattern of an oxide preventing film. Using the oxide preventing film consisting of the pad oxide film and the nitride film as an etching barrier, the silicon substrate is etched to form a trench. At that time, a surface of the silicon substrate is formed with a damaged layer due to the etching damage. The substrate is annealed under a hydrogen atmosphere. The annealing is carried out any one selected from a furnace, rapid thermal process, and a microwave, and an inert gas or a nitride gas is used as an atmosphere gas. An oxide film for burying a trench (23) is buried onto an upper portion of the substrate.

Description

Method of forming trench type isolation layer in semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor technology, and more particularly, to a process of forming an isolation layer for electrically separating devices, and more particularly, to a method of forming a trench type isolation layer.

The trench trench isolation (STI) process is a process instability factor such as deterioration of the field oxide film due to the reduction of design rules of the semiconductor device, and the reduction of the active area due to the bird's beak. It is emerging as a device isolation process that can fundamentally solve the same problem, and it is a promising technology to be applied to an ultra-high density semiconductor device manufacturing process of 1G DRAM or 4G DRAM level.

1A to 1F illustrate an STI process according to the prior art, and the prior art will be described with reference to the following.

In the STI process according to the related art, first, as shown in FIG. 1A, a pad oxide film 2 and a nitride film 3 are formed on a silicon substrate 1, and then selectively etched to form a trench mask and then patterned. The trench is formed by dry etching the silicon substrate 1 using the nitride film 3 as an etching mask. In this case, a defect layer A is formed on the surface of the trench-etched silicon substrate 1 by etching damage.

Next, as shown in FIG. 1B, a sacrificial oxide film 4 is grown by performing a trench sidewall sacrificial oxidation process to remove the defect layer 10 on the silicon surface by trench etching.

Subsequently, the sacrificial oxide film 4 is removed through wet cleaning using a hydrofluoric acid (HF) solution as shown in FIG. 1C.

A trench sidewall reoxidation process is then performed to remove dangling bonds in the trench sidewalls that degrade the junction leakage current characteristics as shown in FIG. 1D. At this time, the reference numeral '5' represents a thermal oxide film by the trench sidewall reoxidation process.

Next, an undercut is generated in the lower portion of the nitride film 3 by wet cleaning of the sacrificial oxide film 4 to prevent voids in the portion during the subsequent gap filling process. As illustrated in FIG. 1E, a chemical vapor deposition oxide film 6 having excellent step coverage is deposited along the entire structure surface.

Subsequently, as shown in Fig. 1F, an oxide film 7 for trench filling is deposited.

Subsequently, a chemical mechanical polishing (CMP) process is performed to planarize the oxide film 7 and to remove the nitride film 3 and the pad oxide film 2.

However, in the conventional STI process, as described above, the trench sidewall sacrificial oxidation process and the cleaning process are performed to remove the damage to the silicon substrate during the trench etching. In this case, the threshold voltage is reduced as the width of the active region decreases. There is a problem that causes the transistor to deteriorate by causing this narrow width effect.

In addition, when the trench sidewall sacrificial oxide is oxidized at the upper edge, the lower edge and the sidewall of the trench, the trench is etched at the corners of the trench upper and lower edges that have a rounded profile. do. If the angle is at the top corner of the trench, the electric field is concentrated at the edge of the active region, and the transistor characteristics are deteriorated. If the angle is at the top corner of the trench, the stress at the bottom corner of the trench increases, causing leakage. There is a problem that the current increases.

The present invention is a trench that can reduce the narrow effect, while reducing the physical damage of the silicon substrate during the trench etching, and reduce the electric field concentration phenomenon and junction leakage current caused by the angular profile in the upper and lower corners of the trench It is an object of the present invention to provide a method of forming a device isolation layer.

1A-1F are trench isolation scheme (STI) process diagrams according to the prior art.

2A-2C illustrate a trench isolation process (STI) process in accordance with one embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

20: silicon substrate

21: pad oxide film

22: nitride film

23: oxide film

B: defect layer due to etching damage

In order to achieve the above technical problem, a method of forming a trench type isolation layer may include: a first step of forming an oxide layer pattern on a silicon substrate; A second step of forming a trench by etching the exposed silicon substrate after performing the first step; A third step of performing heat treatment to remove the etching damage generated in the second step; And a fourth step of embedding an insulator in the trench.

According to the present invention, in order to remove the etching damage (defect) of the silicon substrate due to the trench etching, the trench sidewall sacrificial oxidation and cleaning process are not performed as in the prior art, and the heat treatment is performed after the trench etching. . When the heat treatment is performed, the warpage of the silicon crystal lattice caused by the physical damage on the trench sidewalls receives thermal energy and rearranges them to the most stable state, thereby recovering the physical damage caused during the trench etching. In particular, when hydrogen (H ₂ ) is used as the atmosphere gas during heat treatment, the junction leakage current may be reduced by hydrogen covalently bonding with the silicon dangling bond in the trench sidewall portion to improve interfacial properties. According to the present invention, since the trench sidewall sacrificial oxidation and cleaning process and the trench sidewall reoxidation process are not required, the trench isolation process is simplified, and the phenomenon of angles at the upper / lower corners of the trench by the oxidation process and the sacrificial oxide film are performed. It is possible to prevent undercuts caused by cleaning and to alleviate the narrow effect.

Hereinafter, preferred embodiments of the present invention will be described in order to enable those skilled in the art to more easily implement the present invention.

2A to 2C illustrate a semiconductor device manufacturing process according to an embodiment of the present invention. Hereinafter, the process will be described with reference to the accompanying drawings.

First, as shown in FIG. 2A, a thermal oxidation pad oxide film 21 and a nitride film 22 are sequentially formed on the silicon substrate 20 to have a thickness of 50 to 200 mW and 1000 to 3000 mW, respectively, and an element isolation mask ( (Not shown) to perform a photolithography process to selectively etch the nitride film 22 and the pad oxide film 21 to form an antioxidant pattern, and then to form an antioxidant pattern comprising the pad oxide film 21 and the nitride film 22. Is used as an etch barrier to form a trench by dry etching the silicon substrate 20 to a depth of 1500 to 4000 mm 3. In this case, a defect layer B is formed on the surface of the trench-etched silicon substrate 20 by etching damage.

Subsequently, heat treatment is performed in a hydrogen atmosphere as shown in Fig. 2B. Furnace (furnace) method, rapid thermal process (rapid thermal process, RTP) method, and microwave method can all be used for the heat treatment, and inert gas and nitrogen gas may be used as the atmosphere gas.

Next, as shown in FIG. 2C, an oxide film 23 for filling trenches is embedded in the entire structure.

Thereafter, the STI process is completed by performing a normal process such as a CMP process, a removal process of the nitride film 22 and the pad oxide film 21.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

According to the present invention described above, physical damage during trench etching can be healed without performing the trench sidewall sacrificial oxidation and cleaning process and the trench sidewall reoxidation process, thereby simplifying the trench isolation process. In addition, the present invention has the effect of preventing the undercut caused by the angular phenomenon in the trench upper / lower corners by the oxidation process and the cleaning of the sacrificial oxide film, and alleviate the narrow effect.

Claims (4)

Forming an anti-oxidation film pattern on the silicon substrate; A second step of forming a trench by etching the exposed silicon substrate after performing the first step; A third step of performing heat treatment to remove the etching damage generated in the second step; And A fourth step of embedding an insulator in the trench Trench type device isolation film forming method comprising a. The method of claim 1, The heat treatment, A method of forming a trench type isolation layer, which is performed by any one of a furnace method, a rapid heat treatment method, and an ultrahigh frequency method. The method according to claim 1 or 2, The heat treatment, A trench type isolation film formation method, characterized in that carried out in a hydrogen atmosphere. The method of claim 1, The heat treatment, A method of forming a trench type isolation film, which is carried out in an inert gas or nitrogen atmosphere.