Etching method of metal film layer

Abstract

The invention provides a method for etching metal film layers, which comprises the following steps of: sequentially etching each metal film layer from top to bottom through a first etching gas, and stopping etching until the lowest metal film layer is etched; performing dry etching on a part of the lowermost metal film layer by using a second etching gas, and then stopping etching; removing a photoresist and a polymer generated in the etching process by using a conventional dry photoresist removing method and a wet cleaning method; and taking the metal film layer which is penetrated by etching as a mask, and rapidly removing the residual part of the metal film layer by adopting wet etching. The method has the advantages that post corrosion of the metal side wall is prevented, the wet etching time is shortened, and the defects of metal residues of the TiW film layer, overlarge undercut of the TiW film layer and the like are overcome.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a method for etching a metal film layer. Background Art

[0002] Currently, the etching of TiN / AL / TiW sandwich metal film layers is mainly based on dry etching (TiN / AL) + wet etching (TiW). Chlorine-based gases BCL3 and CL2 are used to dry-etch TiN / AL, stopping on the TiW film layer, and then hydrogen peroxide is used to remove TiW. However, the TiW film layer is relatively thick, and the wet etching process time is relatively long.

[0003] This results in the following defects in the prior art:

[0004] 1. Corrosion (post-corrosion) is prone to occur on the sidewall of aluminum metal wire: Figure 1 Because chlorine-based gases (BCL3 and CL2) were used in the previous dry etching to etch TiN and Al, chlorine residue (ALCL3) would remain on the sidewalls of the metal lines. Dry stripping and wet cleaning could not completely remove the residual chlorine. When hydrogen peroxide was subsequently used to etch the TiW film for a long time, the hydrogen peroxide would react with the residual chlorine (ALCL3) on the sidewalls of the metal lines to produce HCL, which in turn corroded the Al metal lines and caused corrosion. To prevent TiW metal residue from remaining when wet etching the TiW film, a long and sufficient over-etching period was required, which aggravated the corrosion reaction and, in severe cases, hollowed out the metal lines, causing short circuits.

[0005] 2. The undercut of the TiW film sidewall is too large: Reference Figure 2 TiN / AL is dry-etched, and the stop layer is TiW. The TiW film is relatively thick and is completely removed by wet etching. To prevent TiW metal residue, sufficient over-etching time must be ensured. Because wet etching is isotropic, it will inevitably lead to severe undercutting of the TiW film sidewall. The undercut of TiW will be greater than 0.2um, causing the metal line resistance to increase.

[0006] Therefore, it is necessary to provide a new technical solution. Summary of the Invention

[0007] In order to solve the technical problems existing in the prior art, the present invention discloses a method for etching a metal film layer. The specific technical solution is as follows:

[0008] The present invention provides a method for etching a metal film layer, comprising the following steps:

[0009] S1, depositing a layer of SiO2 thin film on the thin film area of ​​the wafer, and sequentially depositing multiple metal film layers on the SiO2 thin film layer, placing a photoresist as a mask above the metal film layer, and etching each metal film layer sequentially from top to bottom using the first etching gas until the bottom metal film layer is etched and the etching is stopped;

[0010] S2, using the second etching gas to dry-etch a portion of the bottom metal film layer and then stop etching;

[0011] S3, using conventional dry stripping and wet cleaning to remove the photoresist and polymers generated during the etching process;

[0012] S4, using the metal film layer etched through above as a mask, wet etching is used to quickly remove the remaining metal film layer.

[0013] Furthermore, the second etching gas etches the bottom metal film layer, and the first etching gas etches the other metal film layers except the bottom metal film layer.

[0014] Furthermore, the multilayer metal film layer includes a TiN film layer, an Al film layer and a TiW film layer in order from top to bottom.

[0015] Furthermore, the first etching gas is a chlorine-based gas, and the chlorine-based gas includes BCL3 and CL2.

[0016] Furthermore, the second etching gas is a fluorine-based gas, and the fluorine-based gas includes CF4.

[0017] Furthermore, in step S2, the second etching gas etches 60%-70% of the thickness of the metal film layer.

[0018] Furthermore, the mask in step S4 is a TiN film layer and an Al film layer.

[0019] Furthermore, in step S4, 30% concentration of hydrogen peroxide is used for wet etching.

[0020] The present invention has the following beneficial effects:

[0021] 1. In the metal film etching method provided by the present invention, fluorine-based gas is used instead of chlorine-based gas to etch the TiW film layer in order to prevent the chlorine-based gas from undercutting the upper metal aluminum sidewall.

[0022] 2. The metal film etching method provided by the present invention first uses dry etching to etch the TiW film layer, and then uses wet etching to etch the remaining part of the TiW film layer, which greatly shortens the wet etching time and avoids defects such as metal residue and excessive undercut in the TiW film layer after wet etching of the wafer opening area.

[0023] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a schematic diagram of corrosion on the metal sidewall in the prior art.

[0026] Figure 2 This is a schematic diagram of the TiW film layer undercut being too large in the prior art.

[0027] Figure 3 This is a microscope photo of the metal sidewall of the embodiment of the present application.

[0028] Figure 4 This is a scanning electron microscope photograph of the TiW film layer in the embodiment of the present application. DETAILED DESCRIPTION

[0029] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0030] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

[0031] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0032] The present invention provides a method for etching a metal film layer, comprising the following steps:

[0033] S1, depositing a layer of SiO2 thin film on the thin film area of ​​the wafer, and sequentially depositing multiple metal film layers on the SiO2 thin film layer, placing a photoresist as a mask above the metal film layer, and etching each metal film layer sequentially from top to bottom using the first etching gas until the bottom metal film layer is etched and the etching is stopped;

[0034] S2, using the second etching gas to dry-etch a portion of the bottom metal film layer and then stop etching;

[0035] S3, using conventional dry stripping and wet cleaning to remove the photoresist and polymers generated during the etching process;

[0036] S4, using the metal film layer etched through above as a mask, wet etching is used to quickly remove the remaining metal film layer.

[0037] The second etching gas is directed to the bottom metal film layer, and the first etching gas is directed to other metal film layers except the bottom metal film layer.

[0038] In step S2, the second etching gas etches 60%-70% of the thickness of the metal film layer.

[0039] In one embodiment, the multi-layer metal film layer includes a TiN film layer, an Al film layer and a TiW film layer in order from top to bottom.

[0040] The first etching gas is a chlorine-based gas, and the chlorine-based gas includes BCL3 and CL2.

[0041] The second etching gas is a fluorine-based gas, and the fluorine-based gas includes CF4.

[0042] The mask in step S4 is a TiN film layer and an Al film layer.

[0043] In step S4, 30% concentration of hydrogen peroxide solution is used for wet etching.

[0044] refer to Figure 3A microscopic photograph of the metal sidewall shows that after the etching method of the present application is used, no corrosion or metal residue is observed in the microscopic photograph of the metal sidewall.

[0045] refer to Figure 4 A scanning electron microscope photograph of the TiW film shows that the thickness of the TiW film in the prior art is 0.1μm, while the thickness of the TiW film after dry etching with a fluorine-based gas in this application is only 0.03μm, allowing for rapid removal of the remaining TiW film in subsequent wet etching. Furthermore, compared to the undercut width of greater than 0.2μm in the prior art, the undercut width in this application is only 0.04μm, improving product quality.

[0046] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0047] Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention, and that those skilled in the art may make changes, modifications and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for etching a metal film layer, characterized in that: The following steps are included: S1, depositing a layer of SiO2 thin film on the thin film area of ​​the wafer, and sequentially depositing multiple metal film layers on the SiO2 thin film layer, placing a photoresist as a mask above the metal film layer, and etching each metal film layer sequentially from top to bottom using the first etching gas until the bottom metal film layer is etched and the etching is stopped; S2, using the second etching gas to dry-etch a portion of the bottom metal film layer and then stop etching; S3, using conventional dry stripping and wet cleaning to remove the photoresist and polymers generated during the etching process; S4, using the metal film layer etched through above as a mask, wet etching is used to quickly remove the remaining metal film layer.

2. The method for etching a metal film layer according to claim 1, wherein: The second etching gas is directed to the bottom metal film layer, and the first etching gas is directed to other metal film layers except the bottom metal film layer.

3. The method for etching a metal film layer according to claim 1, wherein: The multi-layer metal film layer includes a TiN film layer, an Al film layer and a TiW film layer in order from top to bottom.

4. The method for etching a metal film layer according to claim 3, wherein: The first etching gas is a chlorine-based gas, and the chlorine-based gas includes BCL3 and CL2.

5. The method for etching a metal film layer according to claim 3, wherein: The second etching gas is a fluorine-based gas, and the fluorine-based gas includes CF4.

6. The method for etching a metal film according to claim 1, wherein: In step S2, the second etching gas etches 60%-70% of the thickness of the metal film layer.

7. The method for etching a metal film layer according to claim 3, wherein: The mask in step S4 is a TiN film layer and an Al film layer.

8. The method for etching a metal film layer according to claim 3, wherein: In step S4, 30% concentration of hydrogen peroxide solution is used for wet etching.

Images