CN115863167A - Method for removing strip-shaped polymer in thick aluminum etching - Google Patents
Method for removing strip-shaped polymer in thick aluminum etching Download PDFInfo
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- CN115863167A CN115863167A CN202211445399.5A CN202211445399A CN115863167A CN 115863167 A CN115863167 A CN 115863167A CN 202211445399 A CN202211445399 A CN 202211445399A CN 115863167 A CN115863167 A CN 115863167A
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Abstract
The invention discloses a method for removing strip-shaped polymers in thick aluminum etching, which comprises the following steps: step one, forming an aluminum layer on the surface of the first oxide layer on the bottom layer structure to form a photoresist pattern. And step two, etching the aluminum layer by adopting a first dry etching process and over-etching the first oxide layer, wherein the over-etched etching gas adopts chlorine-containing gas to reduce polymer accumulation. And step three, performing ashing treatment to remove the photoresist pattern and the polymer, wherein the ashing treatment further comprises stripping the residual photoresist pattern and the polymer by adopting circular flushing. And step four, carrying out a wet stripping process in the acid tank, wherein the wet stripping process divides the wet etching time to form multiple wet segmented etches, washing for multiple times after each wet segmented etch is finished, and reducing the etching time of each time through the wet segmented etches, so that the acid liquor in the acid tank is kept fresh, and the stripping effect is improved. The invention can improve the effect of removing the polymer generated in the thickness etching.
Description
Technical Field
The invention relates to a semiconductor integrated circuit manufacturing method, in particular to a method for removing strip-shaped polymers in thick aluminum etching.
Background
In a semiconductor integrated circuit, an aluminum layer is often used as a metal wire in a metal interconnection structure, the metal wire needs to be formed by patterned etching after the deposition of the aluminum layer is completed, photoresist is needed to be used as a mask during the etching of aluminum, and polymer is often generated during the etching. In particular, thick aluminum of more than 3 microns is desirable in some applications, such as in the third metal layer (M3) of micro-electromechanical systems (MEMS) 3-axis (3D) Anisotropic Magneto Resistance (MR), MEMS 3D AMR. The etching of thick aluminum is more likely to generate thick polymer (polymer), and cleaning the polymer becomes the primary task after etching and is also the difficulty of etching the layer.
The existing thick aluminum etching process method comprises the following steps:
step one, metal ET and over-etching (OE) of a bottom oxide layer (oxide) are carried out, wherein fluorine-containing gas is adopted for over-etching, namely F + etching ox, and the fluorine-containing gas comprises CHF3. In step one, a polymer is produced.
And step two, performing ASHING (ASHING) treatment for removing the photoresist.
And step three, performing a WET stripping (WET Strip) process in an acid tank to remove residual photoresist and polymer. In practice, however, the polymer formed after the etching of the thick aluminum is usually a stripe (line) polymer, which is difficult to remove, and in order to improve the effect of removing the polymer, the existing improvement method is to increase the time of the wet stripping process, for example, to 1 minute.
However, as shown in fig. 1, the electron microscope photograph of the conventional thick aluminum etching process is taken; the aluminum line 101 after etching has polymer 102 remained, and the polymer 102 has a stripe structure, which is also referred to as a stripe polymer.
Disclosure of Invention
The invention aims to provide a method for removing strip-shaped polymers in thick aluminum etching, which can improve the effect of removing the polymers generated in the thick aluminum etching.
In order to solve the technical problem, the method for removing the strip-shaped polymer in the thick aluminum etching provided by the invention comprises the following steps:
providing a bottom layer structure with a first oxide layer formed on the surface, forming an aluminum layer on the surface of the first oxide layer, forming photoresist on the surface of the aluminum layer and patterning the photoresist to form a photoresist pattern, wherein the photoresist pattern opens an area to be etched.
And secondly, etching the aluminum layer by adopting a first dry etching process and over-etching the first oxide layer at the bottom of the aluminum layer, wherein the over-etched etching gas adopts chlorine-containing gas to reduce polymer accumulation.
And step three, performing ashing treatment to remove the photoresist pattern and the polymer, wherein the ashing treatment further comprises stripping the residual photoresist pattern and the polymer by adopting cyclic flushing, and the polymer removal capacity is increased by the cyclic flushing.
And fourthly, carrying out a wet stripping process in the acid tank, wherein the wet stripping process divides wet etching time to form multiple wet segmented etching, washing the acid tank for multiple times after each wet segmented etching is finished, and reducing the etching time of each time through the wet segmented etching, so that the acid liquor in the acid tank is kept fresh, and the stripping effect is improved.
In a further improvement, in the first step, the thickness of the aluminum layer is greater than 3 microns.
In a further improvement, in the second step, the etching gas for over-etching is a mixed gas of Cl2, BCl3 and N2.
In a further improvement, the etching gas used for etching the aluminum layer in the first dry etching process comprises a fluorine-containing gas.
In a further improvement, in step three, the sub-steps of the single cycle in the cycle flushing include:
DIW scouring was used.
Flushing with DIW, oxygen and nitrogen.
The cycle number of the cyclic flushing is more than or equal to 2.
The further improvement is that in the fourth step, the process time of the wet segmented etching is 10-15 s.
The further improvement is that in the fourth step, the washing is carried out for 2-3 times after the wet segmented etching is finished each time.
In a further improvement, the wet stripping process comprises more than 2 times of the wet segmented etching.
In a further improvement, the acid tank adopts acid liquid comprising SST-A2.
In a further improvement, the wet stripping process is performed in a single-chip operation manner in the fourth step.
In a further improvement, in the first step, an adhesion layer and a barrier layer are further formed between the first oxide layer and the aluminum layer;
in a further refinement, the adhesion layer comprises a Ti layer.
The barrier layer comprises a TiN layer.
In a further improvement, in the first step, the aluminum layer is used as an interconnection line.
The underlying structure includes a semiconductor substrate.
And completing a metal interconnection structure at the bottom of the first oxidation layer on the semiconductor substrate.
In a further improvement, the semiconductor substrate is provided with a MEMS triaxial AMR magnetic sensor.
In a further improvement, the aluminum layer is a third metal layer of the MEMS triaxial AMR magnetic sensor.
In order to overcome the problem that polymers are difficult to remove in thick aluminum etching, the invention improves each step of wet stripping from thick aluminum etching to an acid tank, wherein, the first dry etching process is specially set for the etching gas for subsequent over-etching of the first oxide layer after etching the aluminum layer, namely, chlorine-containing gas is adopted to replace fluorine-containing gas in the prior art, thus reducing polymer accumulation.
On the basis of reducing polymer accumulation, a cyclic washing step is added in the ashing treatment, and compared with the ashing treatment without the washing step in the prior art, the polymer removal capacity can be increased after the cyclic washing is added.
In the wet stripping process of the acid tank, the etching effect is not improved by simply prolonging the wet etching time, and the defects that the acid liquor in the acid tank is old and the polymer stripping effect is reduced are caused because the wet etching time is simply prolonged.
The invention integrates the improvement of the first dry etching process, the ashing treatment and the wet stripping process, and finally can improve the removal effect of the polymer generated in the thickness etching and can realize the complete removal of the polymer generated in the thickness etching.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1 is an electron microscope photograph of a thick aluminum layer after the conventional etching process;
FIG. 2 is a flowchart of a method for removing polymer stripes during thick aluminum etching according to an embodiment of the present invention;
FIGS. 3A-3D are schematic device structures of steps of a method for removing a strip-shaped polymer in thick aluminum etching according to an embodiment of the present invention;
FIG. 4 is an electron microscope photograph showing the completion of the method for removing polymer stripes during etching of thick aluminum according to the embodiment of the present invention.
Detailed Description
FIG. 2 is a flowchart of a method for removing a polymer strip during etching of thick aluminum according to an embodiment of the present invention; as shown in fig. 3A to fig. 3D, the schematic device structure diagram in each step of the method for removing the strip-shaped polymer in the thick aluminum etching according to the embodiment of the present invention is shown; the method for removing the strip-shaped polymer in the thick aluminum etching comprises the following steps:
step one, as shown in fig. 3A, a bottom layer structure with a first oxide layer 201 formed on a surface thereof is provided, and an aluminum layer 202 is formed on the surface of the first oxide layer 201. A photoresist 203 is formed on the surface of the aluminum layer 202.
As shown in fig. 3B, the photoresist 203 is patterned by exposure and development to form a photoresist 203 pattern, and the photoresist 203 pattern opens the area to be etched.
In an embodiment of the present invention, the thickness of the aluminum layer 202 is greater than 3 μm.
An adhesion layer and a barrier layer are further formed between the first oxide layer 201 and the aluminum layer 202;
the adhesion layer includes a Ti layer.
The barrier layer comprises a TiN layer.
The aluminum layer 202 serves as an interconnection line, that is, the aluminum layer 202 serves as an aluminum line after etching.
The underlying structure includes a semiconductor substrate.
And completing a metal interconnection structure at the bottom of the first oxidation layer 201 on the semiconductor substrate.
In some embodiments, a MEMS tri-axis AMR magnetic sensor is formed on the semiconductor substrate.
The aluminum layer 202 is a third metal layer of the MEMS triaxial AMR magnetic sensor.
Step two, as shown in fig. 3C, the aluminum layer 202 is etched by using a first dry etching process, and the first oxide layer 201 at the bottom of the aluminum layer 202 is over-etched, wherein the over-etched etching gas is a chlorine-containing gas, so as to reduce polymer accumulation.
In the embodiment of the invention, the etching gas for over-etching adopts the mixed gas of Cl2, BCl3 and N2.
The etching gas used in the first dry etching process for etching the aluminum layer 202 includes a fluorine-containing gas, and typically, the fluorine-containing gas includes CHF3.
And step three, as shown in fig. 3D, performing an ashing process to remove the photoresist 203 pattern and the polymer, wherein the ashing process further comprises stripping the residual photoresist 203 pattern and the polymer by using a cyclic flush, and the cyclic flush is used to increase the polymer removal capability.
That is, the ashing process according to the embodiment of the present invention is a cyclic flushing step added to the ashing process according to the prior art, which is implemented only by dry plasma processing.
In the embodiment of the present invention, the sub-steps of a single cycle in the cyclic flushing include:
DIW scouring is used.
The flushing is carried out by adding oxygen and nitrogen into DIW.
The cycle number of the cyclic flushing is more than or equal to 2.
And step four, as shown in fig. 3D, performing a wet stripping process in the acid tank, wherein the wet stripping process divides wet etching time to form multiple wet segmented etches, and the wet segmented etches are washed for multiple times, so that the etching time of each time is reduced through the wet segmented etches, the acid liquor in the acid tank is kept fresh, and the stripping effect is improved.
In the embodiment of the invention, the process time of the wet segmented etching is 10-15 s.
And carrying out the washing for 2-3 times after the wet segmented etching is finished each time.
The wet stripping process comprises more than 2 times of wet segmented etching.
The acid solution adopted by the acid tank comprises SST-A2, and the SST-A2 comprises the following components: (CH 3) 2SO/H2O2/NH4F1%.
The wet stripping process is performed using a single wafer run.
In order to overcome the problem that the polymer is difficult to remove in the thick aluminum etching, the embodiment of the invention improves each step of wet stripping from the thick aluminum etching to the acid tank, wherein the first dry etching process is specially configured for the etching gas for the subsequent over-etching of the first oxide layer 201 after the aluminum layer 202 is etched, namely, chlorine-containing gas is used for replacing fluorine-containing gas in the prior art, so that the accumulation of the polymer can be reduced.
On the basis of reducing polymer accumulation, a cyclic flushing step is added in the ashing treatment, and compared with the ashing treatment without the flushing step in the prior art, the polymer removal capacity can be increased after the cyclic flushing is added.
In the wet stripping process of the acid tank, the etching effect is not improved by simply prolonging the wet etching time, and the defects that the acid liquor in the acid tank is old and the polymer stripping effect is reduced are caused simultaneously due to the simply prolonged wet etching time.
The embodiment of the invention comprehensively improves the first dry etching process, the ashing treatment and the wet stripping process, and finally can improve the removal effect of the polymer generated in the thickness etching and can completely remove the polymer generated in the thickness etching.
As shown in fig. 4, it is an electron microscope photograph after the method for removing the stripe polymer in the thick aluminum etching according to the embodiment of the present invention is completed,
the present invention has been described in detail with reference to the specific embodiments, but these should not be construed as limitations of the present invention. Many variations and modifications may be made by one of ordinary skill in the art without departing from the principles of the present invention, which should also be considered as within the scope of the present invention.
Claims (15)
1. A method for removing strip-shaped polymers in thick aluminum etching is characterized by comprising the following steps:
providing a bottom layer structure with a first oxide layer formed on the surface, forming an aluminum layer on the surface of the first oxide layer, forming photoresist on the surface of the aluminum layer and patterning the photoresist to form a photoresist pattern, wherein the photoresist pattern opens a region to be etched;
etching the aluminum layer by adopting a first dry etching process and over-etching the first oxide layer at the bottom of the aluminum layer, wherein the over-etched etching gas adopts chlorine-containing gas to reduce polymer accumulation;
third, ashing treatment is carried out to remove the photoresist pattern and the polymer, the ashing treatment also comprises stripping the residual photoresist pattern and the polymer by adopting cyclic flushing, and the polymer removal capacity is increased by the cyclic flushing;
and step four, carrying out a wet stripping process in the acid tank, wherein the wet stripping process divides wet etching time to form multiple wet segmented etches, the wet segmented etches are washed for multiple times after each wet segmented etch is finished, and the wet segmented etches reduce the etching time for each time, so that the acid liquor in the acid tank is kept fresh, and the stripping effect is improved.
2. The method for removing the stripe polymer in the thick aluminum etch as claimed in claim 1, wherein: in the first step, the thickness of the aluminum layer is more than 3 microns.
3. The method of claim 2 for removing stripe polymer in thick aluminum etch, wherein: in the second step, the etching gas for over-etching adopts the mixed gas of Cl2, BCl3 and N2.
4. The method of claim 3 for removing polymer stripes in thick aluminum etch, wherein: and the etching gas used for etching the aluminum layer in the first dry etching process comprises fluorine-containing gas.
5. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: in step three, the sub-steps of a single cycle in the cycle flushing include:
adopting DIW scouring;
flushing with DIW, oxygen and nitrogen;
the cycle number of the cyclic flushing is more than or equal to 2.
6. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: in the fourth step, the process time of the wet segmented etching is 10-15 s.
7. The method of claim 6 for removing striped polymer in thick aluminum etch, wherein: in the fourth step, the washing is carried out for 2-3 times after the wet segmented etching is finished each time.
8. The method of claim 7 for removing polymer stripes in thick aluminum etch, wherein: the wet stripping process comprises more than 2 times of wet segmented etching.
9. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: the acid solution adopted by the acid tank comprises SST-A2.
10. The method of claim 9 for removing striped polymer in thick aluminum etch, wherein: in the fourth step, the wet stripping process is carried out in a single-chip operation mode.
11. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: in the first step, an adhesion layer and a barrier layer are further formed between the first oxide layer and the aluminum layer.
12. The method of claim 11, wherein the removing the polymer strip in the etching of thick aluminum is performed by: the adhesion layer comprises a Ti layer;
the barrier layer comprises a TiN layer.
13. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: in the first step, the aluminum layer is used as an interconnection line;
the underlying structure comprises a semiconductor substrate;
and completing a metal interconnection structure at the bottom of the first oxidation layer on the semiconductor substrate.
14. The method for removing the stripe-shaped polymer in the thick aluminum etching as claimed in claim 1, wherein: and an MEMS triaxial AMR magnetic sensor is formed on the semiconductor substrate.
15. The method of claim 14, wherein the removing the polymer strip in the thick aluminum etching comprises: the aluminum layer is a third metal layer of the MEMS triaxial AMR magnetic sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211445399.5A CN115863167A (en) | 2022-11-18 | 2022-11-18 | Method for removing strip-shaped polymer in thick aluminum etching |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211445399.5A CN115863167A (en) | 2022-11-18 | 2022-11-18 | Method for removing strip-shaped polymer in thick aluminum etching |
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| Publication Number | Publication Date |
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| CN115863167A true CN115863167A (en) | 2023-03-28 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211445399.5A Pending CN115863167A (en) | 2022-11-18 | 2022-11-18 | Method for removing strip-shaped polymer in thick aluminum etching |
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- 2022-11-18 CN CN202211445399.5A patent/CN115863167A/en active Pending
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