KR19990055183A - Alignment Key Formation Method of Semiconductor Device - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Semiconductor device manufacturing method.

2. Technical problem to be solved by the invention

An object of the present invention is to provide a method of forming an alignment key for accurate alignment in a process of forming an alignment key for overlapping accuracy of alignment in a photolithography process of a semiconductor device.

3. Summary of the Solution of the Invention

Forming a thin film on the semiconductor substrate having a large difference in atomic weight from that of the semiconductor substrate; And a second step of selectively etching the thin film to expose a portion of the semiconductor substrate.

4. Important uses of the invention

Semiconductor device manufacturing process.

Description

Alignment Key Formation Method of Semiconductor Device

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming an alignment key for a photolithography process.

In general, the photolithography process is performed through the HMDS coating, the spin coating of the photoresist film, the soft bake process, the exposure, the post-exposure bake process, and the developing step.

The HMDS (hexamethydisilazane) membrane _{(CH 3) Si 3 - NH} - Si , and has the structure of _{(CH 3) 3, (CH} 3) Si 3 - NH - Si (CH 3) 3 is the silicon substrate is Si and oxygen It causes a chemical reaction and (CH ₃ ) ₃ to cause a physical bond with the photoresist film to improve the adhesion between the substrate and the photoresist film.

In addition, the soft bake process is performed at 80 ° C to 100 ° C, and is a process for maintaining a solid photoresist state by evaporating 80% to 90% of the solvent present in the photoresist film by thermal energy.

The exposure step is a step of exposing a photoresist film to light energy of an electron beam and deep ultra violet (DUV), and is a step of selectively causing a photochemical reaction of the photoresist film.

The developing step is a step of finally reproducing a pattern shape by using a chemical reaction between an exposed area and a non-exposed area.

1A and 1B illustrate a mask for an alignment key formed by a conventional photolithography process, and FIG. 1C is a cross-sectional view of an alignment key formed by a conventional photolithography process, wherein reference numeral “11” denotes a frame; "12" represents a cell region, "13" represents an alignment key mask formed in the frame portion, and "14" represents a silicon substrate, respectively.

As shown in FIG. 1C, an alignment key is formed by partially etching the silicon substrate 11 by an etching process using the alignment key mask 13.

When only the silicon is used to form the alignment key by applying the electron beam photolithography process to the fabrication of a semiconductor device such as a DRAM, the back and secondary scattered electrons reflected when the alignment degree is measured by the electron beam are fine and are charged by the electron beam. The phenomenon occurs. In addition, the alignment key is calculated only by the step of the silicon substrate, so the alignment accuracy is poor, and the alignment itself is difficult and uneven.

The present invention devised to solve the above problems, in the alignment key formation process for measuring the alignment accuracy of the semiconductor device, the secondary scattered electrons can be large and can prevent the charging phenomenon by the electron beam, thereby aligning the alignment It is an object of the present invention to provide an alignment key forming method that can be easily and uniformly formed.

1A to 1C are cross-sectional views of an alignment key formation and a mask formed by a conventional photolithography process.

2A and 2B are cross-sectional views of an alignment key formed by a photolithography process according to an embodiment of the present invention.

3A and 3B are masks for a photolithography process according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

21: silicon substrate

22: tungsten silicide film

In order to achieve the above object, an alignment key forming method of a semiconductor device of the present invention includes: a first step of forming a thin film having a large difference in atomic weight from that of the semiconductor substrate on the semiconductor substrate; And a second step of selectively etching the thin film to expose a portion of the semiconductor substrate.

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

2A and 2B are cross-sectional views of an alignment key formed by a photolithography process according to an embodiment of the present invention, and FIGS. 3A and 3B are masks for a photolithography process according to an embodiment of the present invention. Reference numeral “31” denotes a frame, “32” denotes a cell area, and “33” denotes an alignment key mask. 3B also shows the alignment key located in the frame 31. As shown in FIG.

First, as shown in FIG. 2A, a tungsten silicide film 22 having a large difference in atomic amount from silicon is formed on a silicon substrate 21 having a lower layer where a predetermined process is completed.

Here, the alignment key may be formed using a metal such as aluminum or tungsten instead of the tungsten silicide film 22.

Next, as shown in FIG. 2B, the tungsten silicide layer 22 is etched using a mask for forming an alignment key to expose the silicon substrate 21.

The oxide film (not shown), the polysilicon film (not shown), and the tungsten silicide film 22 are sequentially formed on the silicon substrate 21 due to stress between the tungsten silicide film 22 and the silicon substrate 21. After the formation, the tungsten silicide film 22 may be etched in order, followed by etching of the polysilicon film (not shown) and the oxide film (not shown).

In another embodiment of the present invention, after the doped polysilicon film is formed on the silicon substrate, an alignment key for exposing the silicon substrate 21 is formed by etching the doped polysilicon film using a mask for forming the alignment key. .

In the above-described process, in addition to the step of measuring alignment, a material having a different atomic weight from that of the silicon substrate is located on the silicon substrate, so that the rear and secondary scattered electrons are large and the charging phenomenon by the electron beam can be prevented. It is easy to implement and the alignment is accurate and uniform.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope of the present invention without departing from the technical idea. It will be evident to those who have knowledge of.

According to the present invention, the alignment key is formed by depositing a material having a large atomic weight such as a tungsten silicide film, a doped polysilicon film, and a metal before forming the alignment key in the semiconductor device alignment key forming process. Improved yield increases the process stability by increasing the nesting accuracy.

Claims (3)

Forming a thin film on the semiconductor substrate having a large difference in atomic weight from that of the semiconductor substrate; And Selectively etching the thin film to expose a portion of the semiconductor substrate Alignment key forming method of a semiconductor device comprising a. The method of claim 1, A third step of forming an insulating film between the semiconductor substrate and the thin film The alignment key forming method of the semiconductor device further comprising. The method according to claim 1 or 2, And the thin film is a tungsten silicide layer or a doped polysilicon layer.