A method for increasing the etch rate of aluminum metal
By using a mixture of high-concentration N2 gas and appropriate pressure during the aluminum etching process, the problem of low aluminum etching rate was solved, the aluminum etching rate was improved, and production costs were reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2024-07-17
- Publication Date
- 2026-06-02
AI Technical Summary
The low etching rate of aluminum in existing technologies leads to high production costs, making it difficult to meet the high-efficiency manufacturing requirements of large-size integrated circuits.
A mixture of BCl3, Cl2, and N2 gas was used as the etching gas, with the N2 concentration increased to 40–100 sccm. Combined with a pressure of 8–10 mTorr, the etching rate of aluminum metal was improved.
By increasing the nitrogen concentration, the etching rate is significantly improved, production costs are reduced, and the manufacturing requirements of large-size integrated circuits are met.
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Figure CN119049968B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of logic integrated circuit manufacturing, and specifically relates to a method for improving the etching rate of aluminum metal. Background Technology
[0002] In the manufacturing process of logic integrated circuits, back-end interconnect technology plays a crucial role. It not only ensures unobstructed metal connections but also guarantees the normal operation of front-end transistors. With the rapid development of very large-scale integrated circuits (VLSI), most back-end metal interconnects now use copper, a material with lower resistivity, to improve chip performance. However, in the production of large-size integrated circuits, aluminum interconnects still have unique advantages over copper interconnects due to their cost-effectiveness and lower production costs.
[0003] The process flow for aluminum interconnects includes metal barrier layer deposition, aluminum deposition, aluminum line etching, and via etching, among which aluminum line etching is a crucial step. Aluminum line etching is a typical aluminum etching process, usually performed using a dry etching method.
[0004] In dry etching, etching rate is a key performance indicator. A faster etching rate can reduce production costs; therefore, increasing the etching rate without causing other negative effects is an important goal of process optimization. Currently, nitrogen (N2) is generally considered to be the most commonly used etching gas for aluminum etching; its addition to Al etching can form Al₂O₃. x N y (polymer) suppresses the lateral etching of chlorine (Cl2), so it is usually only used as a passivation gas. In conventional existing technology, the nitrogen concentration used for etching aluminum on wafers is usually around 10 to 20 sccm (standard cubic centimeter per minute) to meet the requirements for protecting the sidewalls. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for improving the etching rate of aluminum metal.
[0006] A method for increasing the etching rate of aluminum metal includes the following steps:
[0007] An aluminum layer is deposited on a substrate and a photoresist is coated on the surface. A mixed gas of BCl3, Cl2 and N2 is used as the etching gas to perform dry etching on the aluminum layer that is not covered by the photoresist, wherein the N2 concentration is 40-100 sccm.
[0008] Preferably, the concentration of BCl3 is 100–110 sccm.
[0009] Preferably, the concentration of Cl2 is 300–350 sccm.
[0010] Preferably, the concentration of N2 is 60 sccm.
[0011] Preferably, the pressure during dry etching is 8–10 mTorr.
[0012] The principle behind this invention, which uses a higher concentration of nitrogen gas for etching to increase the etching rate, is as follows:
[0013] The following reactions mainly occur during the etching process:
[0014] Al + 0.5N₂ → AlN (1)
[0015] AlN + 1.5Cl₂ → AlCl₃ (2)
[0016] BCl3→BCl3 + +BCl x (3)
[0017] BCl x +Cl - →BCl x+1 (4)
[0018] The Al-N bond energy is 297±96 kJ / mol, while the Al-Cl bond energy is 511.3±0.8 kJ / mol. Since the Al-N bond energy is much smaller than the Al-Cl bond energy, and under high vacuum conditions in the chamber, Al first combines with nitrogen to form the intermediate product AlN. AlN then reacts with Cl2 to form the etching product AlCl3. This means that nitrogen not only protects the sidewalls during etching but also acts as a catalyst, accelerating the etching rate. Therefore, the etching rate increases with increasing nitrogen concentration.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] This invention breaks with the conventional understanding of using low-concentration nitrogen as a passivation gas, and uses a high-concentration gas to etch the aluminum metal layer. The increase in nitrogen concentration helps to accelerate the etching rate. In practical applications, appropriately increasing the nitrogen concentration can greatly accelerate the etching rate, thereby reducing production costs. Attached Figure Description
[0021] Figure 1 This is the fitted curve of the results in Example 1.
[0022] Figure 2 This is the fitted curve of the results in Example 2. Detailed Implementation
[0023] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0024] As mentioned above, this invention provides a method for improving the etching rate of aluminum metal, specifically including the following steps:
[0025] A metallic aluminum layer is deposited on a substrate, and photoresist is coated on the surface. A mixed gas of BCl3 with a concentration of 100–110 sccm, Cl2 with a concentration of 300–350 sccm, and N2 with a concentration of 40–100 sccm is used as the etching gas to perform dry etching on the portion of the metallic aluminum layer not covered by the photoresist. The pressure during dry etching is 8–10 mTorr.
[0026] The technical solution of the present invention will be further explained and described below with reference to several preferred embodiments, but the experimental conditions and setting parameters therein should not be regarded as limitations on the basic technical solution of the present invention. Furthermore, the scope of protection of the present invention is not limited to the following embodiments.
[0027] Example 1
[0028] This embodiment uses the LAM METAL_L machine. The wafer structure used for etching is as follows: from bottom to top, it includes a wafer substrate, an aluminum layer, and a photoresist layer. The etching gases selected are BCl3 (concentration of 100 sccm), Cl2 (concentration of 300 sccm), and N2. The etching rate is characterized by reading the Endpoint Detection (EPD) time of the machine. The shorter the EPD time, the greater the etching rate.
[0029] In this embodiment, with the pressure controlled at 8 mTorr, experiments were conducted with nitrogen concentrations of 0, 5, 20, 40, and 60 (sccm). The experimental results are shown in Table 1 below.
[0030] Table 18 mTorr Etching EPD Results
[0031] Nitrogen concentration / sccm EPD time / second 0 296.4 5 287.78 20 266.24 40 244.68 60 232.13
[0032] The fitting curve obtained in this embodiment is as follows: Figure 1 As shown, its regression equation is
[0033] y = -1.0808x + 292.47, R 2 =0.9739.
[0034] Depend on Figure 1 It can be seen that as the nitrogen concentration increases, the EPD time decreases significantly, which indicates that the reaction rate increases significantly. Furthermore, when the nitrogen concentration increases to 60 sccm, the EPD still tends to decrease.
[0035] Example 2
[0036] Following the reaction conditions of Example 1, the pressure was adjusted to 10 mTorr, and experiments were conducted at nitrogen concentrations of 0, 20, 40, 60, 80, and 100 sccm. The experimental data are shown in the table below:
[0037] Table 2. EPD results under 10 mTorr pressure
[0038]
[0039]
[0040] The fitting curve obtained in this embodiment is as follows: Figure 2 As shown, its regression equation is
[0041] y = 0.0133x 2 -1.9855x + 274.67, R 2 =0.9899.
[0042] Depend on Figure 2 It can be seen that at a pressure of 10 mTorr, the EPD time still decreases significantly with increasing nitrogen concentration, but the rate of decrease becomes less pronounced after the nitrogen concentration reaches 60–100 sccm. Specifically, when the nitrogen concentration reaches 80 sccm, the etching rate decreases slightly. This is because the nitrogen concentration in the chamber is too high at this point, leading to a reduction in the proportion of etching gases Cl2 and BCl3 in the chamber, thus causing a slight decrease in the etching rate.
[0043] In summary, changes in nitrogen concentration affect the etching rate in aluminum etching, and the peak value stabilizes at a nitrogen concentration of around 60 sccm.
[0044] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto.
[0045] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and such modifications, changes or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention.
Claims
1. A method for increasing the etching rate of aluminum metal, comprising the following steps: A metallic aluminum layer is deposited on a substrate, and photoresist is coated on the surface; a mixed gas of BCl3, Cl2, and N2 is used as the etching gas to perform dry etching on the portion of the metallic aluminum layer not covered by the photoresist. The invention is characterized in that the N2 concentration is 40~100 sccm, the BCl3 concentration is 100~110 sccm, the Cl2 concentration is 300~350 sccm, and the pressure during dry etching is 8~10 mTorr.
2. The method for increasing the etching rate of aluminum metal according to claim 1, characterized in that, The concentration of N2 is 60 sccm.