CN-122028661-A - Etching method of metal layer

CN122028661ACN 122028661 ACN122028661 ACN 122028661ACN-122028661-A

Abstract

The application discloses an etching method of a metal layer, which comprises the steps of covering a photoresist on an aluminum metal layer, removing the photoresist of a target area through exposure and development in sequence, exposing the aluminum metal layer of the target area, forming the aluminum metal layer on a tungsten metal layer, forming the tungsten metal layer above a substrate, wherein the substrate is used for forming a semiconductor device, etching in a first stage until the predetermined depth of the aluminum metal layer in the target area is reached, and not exposing the tungsten metal layer, forming a first groove in the aluminum metal layer, etching in a second stage until the predetermined depth below the first groove is reached until the tungsten metal layer is exposed, forming a second groove, and the etching in the second stage comprises at least three etching steps, wherein the total flow of reaction gas introduced in the at least three etching steps gradually decreases, and the bias power gradually decreases. The application can improve the loading effect in the etching process, ends the problem of aluminum metal residue to a certain extent, and improves the yield of products.

Inventors

LU XIAOHAO
MA XIANFEI
XU JUN
LU CHENGBO
YU PENG
WANG RUIHUAN

Assignees

华虹半导体制造(无锡)有限公司

Dates

Publication Date: 20260512
Application Date: 20260116

Claims (6)

1. The etching method of the metal layer is characterized by comprising the following steps: Covering a photoresist on an aluminum metal layer, removing the photoresist of a target area through exposure and development in sequence, so that the aluminum metal layer of the target area is exposed, wherein the aluminum metal layer is formed on a tungsten metal layer, the tungsten metal layer is formed above a substrate, and the substrate is used for forming a semiconductor device; Etching in the first stage until the predetermined depth of the aluminum metal layer in the target area is reached, and the tungsten metal layer is not exposed, so that a first groove is formed in the aluminum metal layer; And etching in the second stage until the tungsten metal layer is exposed to a preset depth below the first groove, wherein the etching in the second stage comprises at least three etching steps, the total flow of the reaction gas introduced in the at least three etching steps is gradually decreased, and the bias power is gradually decreased.
2. The method of claim 1, wherein the reactive gases introduced during the second stage of etching include chlorine and boron trichloride.
3. The method of claim 2, wherein the ratio of chlorine gas and boron trichloride introduced remains unchanged during the at least three etching steps.
4. A method according to claim 3, characterized in that methane is also fed in during the at least three etching steps.
5. The method of any one of claims 1 to 4, wherein the depth of the first recess is 60% to 70% of the thickness of the aluminum metal layer.
6. The method of claim 5, wherein the gas introduced during the etching of the first stage comprises chlorine and boron trichloride.

Description

Etching method of metal layer Technical Field The application relates to the technical field of semiconductor devices and integrated circuits, in particular to a method for etching a metal layer. Background In a back end of line (BEOL) process of semiconductor integrated circuit fabrication, an aluminum (Al) thin film is generally used as a metal layer for extracting an electrode of a device, however, due to a problem of mutual dissolution of aluminum and silicon (Si), a tungsten (W) metal layer is formed between the aluminum metal layer and the silicon-containing thin film, and at the same time, the aluminum metal layer and the tungsten metal layer are integrally etched to form a desired pattern in consideration of an influence of stress. Referring to fig. 1, a schematic cross-sectional view of an aluminum tungsten metal layer etched by the etching method of the metal layer provided in the related art is shown. As shown in fig. 1, an aluminum metal layer 112 is formed on a tungsten metal layer 111, a photoresist 301 is covered on the aluminum metal layer 112, after exposure and development, the photoresist in a target area (an area to be etched) is removed, after etching, a groove 401 is formed in the aluminum metal layer 112, and the tungsten metal layer 111 at the bottom of the groove 401 is exposed. Since the aluminum metal layer 112 is thicker (typically greater than 3 micrometers (μm)), and the etched groove pattern has a larger line width (typically greater than 8 micrometers), a sub-groove (sub-groove) morphology (as shown by the area in the dashed line in fig. 1) is easily formed in the etched groove 401 due to a micro loading effect, which results in that it is difficult to control the etching to just stop at the tungsten metal layer 111, and aluminum metal residues caused by the inexhaustible etching may reduce the reliability of the device product. In view of this, the related art proposes to increase the thickness of the tungsten metal layer to overcome the problem of aluminum metal residue, but too thick tungsten metal layer may cause wafer warpage, thereby affecting the yield of the product. Disclosure of Invention The application provides a method for etching a metal layer, which can solve the problem that the method for etching an aluminum tungsten metal layer provided in the related art is easy to cause the residue of the aluminum metal layer due to a loading effect, and comprises the following steps: Covering a photoresist on an aluminum metal layer, removing the photoresist of a target area through exposure and development in sequence, so that the aluminum metal layer of the target area is exposed, wherein the aluminum metal layer is formed on a tungsten metal layer, the tungsten metal layer is formed above a substrate, and the substrate is used for forming a semiconductor device; Etching in the first stage until the predetermined depth of the aluminum metal layer in the target area is reached, and the tungsten metal layer is not exposed, so that a first groove is formed in the aluminum metal layer; And etching in the second stage until the tungsten metal layer is exposed to a preset depth below the first groove, wherein the etching in the second stage comprises at least three etching steps, the total flow of the reaction gas introduced in the at least three etching steps is gradually decreased, and the bias power is gradually decreased. In some embodiments, the reactive gases introduced during the second stage of etching include chlorine and boron trichloride. In some embodiments, the ratio of chlorine gas and boron trichloride introduced remains unchanged during the at least three etching steps. In some embodiments, methane is also introduced during the at least three etching steps. In some embodiments, the depth of the first recess is 60% to 70% of the thickness of the aluminum metal layer. In some embodiments, during the etching of the first stage, the gas introduced includes chlorine and boron trichloride. The technical scheme of the application at least comprises the following advantages: In the back-end process of the semiconductor device, when the etching process is carried out on the aluminum tungsten metal layer, a large amount of etching is carried out until the predetermined depth in the aluminum metal layer is reached, but the aluminum metal layer is not etched through, and then step etching is carried out until the tungsten metal layer is exposed. Drawings In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art. FIG. 1 is a schematic cross-sectional view of an aluminum tungs