KR20000008510A - Method of forming align key by trench etch - Google Patents

Abstract

PURPOSE: A method for forming a align key is provided to improve decreasing of align reliability and occurring of errors by forming a trench. CONSTITUTION: The method comprises the steps of: forming a silicon oxide film for buffer layer; forming a photoresist film on the silicon oxide film; forming a silicon oxide pattern by photolithography; implanting dopants in a substrate surface including the silicon oxide pattern; and forming a trench used for align key by etching a exposed portion of the substrate.

Description

How to Form Align Key by Etching Trench

The present invention relates to a method for forming an alignment key through trench etching, and more particularly, to a technique for forming an alignment key trench having a step in a semiconductor substrate through trench etching using a buffer oxide pattern as a mask.

In general, integrated circuits have a variety of electrical elements within a certain area, arranged for purpose, to handle a series of electrical operations, analysis and transmissions that process analog or digital signals and connect them to other external components. will be. In the recent micro fabrication, an impurity is implanted only in a predetermined region on a silicon substrate, or a thin film layer is formed to obtain an arbitrary structure of the element and connect them to other circuits or elements.

As such, the pattern of a predetermined region is formed by lithography. In particular, the alignment / exposure operation refers to a process of determining a pattern position of a thin film and applying a photosensitive film using ultraviolet rays. Here, in order to align the thin film to be laminated, the alignment is performed by using an alignment key formed in a previous process, and the formation of the key is used in each photo process. Each liner (aligner) is used to make a special shape, and their commonality is to perform the alignment by using the signal intensity of light generated by irradiating light on the step and the step generated in the pattern.

Therefore, an important point in aligning the key pattern using the step difference is that the step gradient is determined as the light intensity is determined by the step gradient of the pattern. The slope is gentle, which reduces the light intensity and decreases the accuracy at alignment.

That is, in the conventional alignment key formation, as the key is formed using a separate film, the reproducibility of the alignment is degraded when the thin film (oxide film, polysilicon film, metal wiring, etc.) is damaged, and an error occurs. Is generated. In addition, in the initial process, a disadvantage arises in that a separate film is formed to form a key to perform a photo / etch process.

An object of the present invention devised in view of the above problems is to use a separate thin film in the prior art in order to minimize the reproducibility degradation of the alignment and the occurrence of errors due to damage of the thin film due to the gentle step at the time of key formation After forming a buffer oxide layer pattern and performing a thermal oxidation process, an alignment key formation method using trench etching to form an alignment key trench by performing an impurity ion implantation process and a trench etching process through a buffer oxide layer pattern and a semiconductor substrate. The purpose is to provide.

1 is a longitudinal sectional view of an alignment key forming process through trench etching according to the present invention;

* Description of the symbols for the main parts of the drawings *

10: semiconductor substrate 12: buffer oxide film

14: alignment trench

In order to achieve the above object, an alignment key forming method through trench etching according to the present invention is

Sequentially forming a buffer oxide film and a photosensitive film on the semiconductor substrate;

Forming a photosensitive film pattern by an exposure and development process using an exposure mask;

Forming an oxide film pattern for a buffer by using an etching selectivity difference using the photosensitive film pattern as a mask;

Removing the photoresist pattern from the resultant and then performing a thermal oxidation process;

Performing an impurity ion implantation process on the entire surface of the resultant product; And

An etching process using an etching selectivity difference between the buffer oxide layer pattern and the semiconductor substrate is performed to form an alignment key trench having a stepped portion by exposing a predetermined portion in the semiconductor substrate.

The alignment key forming method using the trench etching to have the structure as described above is to form an alignment key trench having a step in the semiconductor substrate through the trench etching process, so that the alignment due to the damage of the thin film is formed by using a separate thin film. The reproducibility decreases and the error can be minimized.

Hereinafter, a method of forming an alignment key through trench etching according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a longitudinal cross-sectional view of an alignment key forming process through trench etching according to the present invention.

First, the buffer oxide film 12 and the photoresist film are sequentially formed on the semiconductor substrate 10, and then a photoresist pattern is formed through an exposure and development process on an exposed portion that is intended as a photoresist pattern using an exposure mask.

The buffer oxide film pattern 12 is formed by an etching process using an etching selectivity difference between the photosensitive film pattern and the buffer oxide film 12 using the photoresist pattern as a mask.

Here, the etching selectivity between the photoresist pattern and the buffer oxide film 12 pattern is about 450 mW / min in the range of 350 to 550 mW / min, and the buffer oxide film 12 is 80 mW in the range of 70 to 90 mW / min. / min or so.

At this time, the etching conditions for the formation of the buffer oxide film 12 pattern include "pressure 350 mTorr, gap between anode and cathode 1.5 cm, high frequency power 200 watt, He gas 150 sccm, SF ₆ gas. Is carried out under the condition of 150 sccm ".

After removing the photoresist pattern from the resultant product, a thermal oxidation process was performed on the entire surface to activate the buffer oxide film 12 pattern, and then an impurity ion implantation process was performed, and the buffer oxide film 12 pattern was used as a mask. An in-situ etching process using an etching selectivity difference with the semiconductor substrate 10 exposes a predetermined portion of the semiconductor substrate 10 to form an alignment key trench 14 having a step difference.

At this time, the boron (B) impurity ion having an energy of 5E15 80KeV is injected at 3900 kV / min in the range of 3700-4100 kV / min under the conditions of the impurity ion implantation process and is 2400-2800 kV / min in the semiconductor substrate 14. At 2600 차 / min.

The etching conditions of the trench 14 are "300 mTorr in the range of 200-400 mTorr pressure, 1.5 cm in the range of 0.5-2.5 cm between the anode and cathode, and 70 watt in the range of 60-80 watt of high frequency power. , 150 sccm in an O ₂ gas range of 50 to 250 sccm, and 150 sccm "in an SF ₆ gas range of 50 to 250 sccm.

Here, regardless of the impurity ion implantation process, the etch ratio / uniformity for each thin film was 2204 Å / min for the photoresist pattern, 1155 Å / min for the buffer oxide film 12, and the etch ratio distribution of each process / thin film was 6 It is stable to set it as% or less.

As described above, the photolithography process is stable even in miss-alignment by forming an alignment key through the trench etching technique by breaking the existing method of forming each alignment exposure key in layers and layers, and using a separate thin film. When forming, it is possible to minimize the decrease in the reproducibility of the alignment due to the damage of the thin film and the error.

As described above, according to the present invention, after forming a buffer oxide pattern using a photolithography process and performing a thermal oxidation process, an impurity ion implantation process and a trench etching process through a buffer oxide layer pattern and a semiconductor substrate are performed. By forming the inkey trench, it has the following advantages:

First, by forming an alignment key through the trench etching technique by breaking the conventional method of forming each alignment exposure key in layers and layers, the alignment is caused by damage of the thin film due to the smooth step in forming the key using a separate thin film in the prior art. It is possible to minimize the reproducibility decrease and the occurrence of errors.

Second, the photolithography process that proceeds by forming a separate thin film for key formation in the initial process can be omitted.

Third, even in processes such as oxidation / deposition / etching performed during pattern formation, the inclination of the step may be preserved as it is, thereby forming a useful alignment key.

Claims (4)

Sequentially forming a buffer oxide film and a photosensitive film on the semiconductor substrate; Forming a photosensitive film pattern by an exposure and development process using an exposure mask; Forming an oxide film pattern for a buffer by using an etching selectivity difference using the photosensitive film pattern as a mask; Removing the photoresist pattern from the resultant and then performing a thermal oxidation process; Performing an impurity ion implantation process on the entire surface of the resultant product; And Forming an align key through trench etching, wherein the etch process uses an etching selectivity difference between the buffer oxide layer pattern and the semiconductor substrate to form an alignment key trench having a step difference by exposing a predetermined portion in the semiconductor substrate. Way. The method of claim 1, wherein the etching selectivity between the photoresist pattern and the buffer oxide pattern is about 350 to 550 s / min and the buffer oxide is about 70 to 90 s / min. How to form an alignment key. The trench etching method according to claim 1, wherein boron impurity ions having an energy of 5E15 80KeV are implanted at 3700-4100 kW / min in the impurity ion implantation process to form a step of 2400-2800 kW / min in the semiconductor substrate. Formation method of alignment key through. According to claim 1, The etching conditions of the trench is "pressure 200 ~ 400 mTorr, the gap (gap) between the anode and the cathode 0.5 ~ 2.5 cm, high frequency power 60 ~ 80 watt, O ₂ gas 50 ~ 250 sccm And forming an alignment key through trench etching, wherein the SF ₆ gas is carried out under a condition of 50 to 250 sccm ".