CN112366022B

CN112366022B - High-precision silver electrode with multilayer silver stacking structure and preparation method thereof

Info

Publication number: CN112366022B
Application number: CN202011246226.1A
Authority: CN
Inventors: 吕迅; 刘胜芳; 刘晓佳; 王志超
Original assignee: Semiconductor Integrated Display Technology Co Ltd
Current assignee: Semiconductor Integrated Display Technology Co Ltd
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2022-03-01
Anticipated expiration: 2040-11-10
Also published as: CN112366022A

Abstract

The invention provides a high-precision silver electrode with a multilayer silver stacked structure and a preparation method thereof, wherein the multilayer silver and metal oxide stacked structure difficult to etch are adopted, in the etching of the multilayer silver stacked structure, small intervals (spaces) can be formed because the etching rate of nitrated mixed acid to Ag is very high and the etching rate of metal oxide is relatively low, and liquid medicine is difficult to diffuse into the spaces due to the surface tension of liquid in the spaces, so that Ag can not be etched continuously in the over-etching process, CD loss can not be increased, the high-precision and high-reflectivity electrode is obtained, and the ultrahigh-resolution display requirement is met.

Description

High-precision silver electrode with multilayer silver stacking structure and preparation method thereof

Technical Field

The invention belongs to the technical field of novel display, particularly relates to an Ag electrode for display industries including organic light-emitting diodes, silicon-based micro-displays, digital micro-mirror chips and the like, and particularly relates to a high-precision silver electrode with a multilayer silver stacking structure and a preparation method thereof.

Background

The Ag reflectivity is as high as 98%, so that the Ag electrode structure is widely applied to top-emitting organic light-emitting diode devices, but the Ag electrode structure cannot be applied to ultra-high resolution displays such as silicon-based micro-displays and digital micro-mirror devices (DMDs) because the silver (Ag) can only use a wet etching process and the CD loss is larger (>1 mu m). At present, an aluminum (Al) electrode is mainly used for ultrahigh resolution display, but the aluminum reflectivity is low (-91%), and the Al is easy to cause hillock and pit due to stress concentration and release in an annealing process, and the surface flatness is poor; aluminum has poor conductivity and severe electromigration, and particularly, resistance becomes larger and larger as pixel size becomes smaller, electromigration becomes more and more severe, and electrical reliability becomes worse. Ag has good conductivity, so that the development of high-precision and high-reflectivity silver electrodes has great significance for ultrahigh resolution display.

At present, an ITO/Ag/ITO structure is mainly used for an Ag electrode, a nitration mixed acid (nitric acid, phosphoric acid and acetic acid) one-step etching process is adopted, the ITO etching rate of the nitration mixed acid is slow, the Ag etching rate is high, the etching time is long when the lower layer ITO is etched, a large amount of Ag is over-etched, and the Ag CD loss is large.

Disclosure of Invention

The invention aims to provide a high-precision silver electrode with a multilayer silver stacked structure, which comprises a multilayer silver and a difficult-to-etch metal oxide stacked structure.

The invention also aims to provide a preparation method of a high-precision silver electrode with a multilayer silver stacked structure, which adopts a multilayer silver and metal oxide stacked structure difficult to etch, wherein in the etching of the multilayer silver stacked structure, the etching rate of nitrated mixed acid to Ag is high, and the etching rate to metal oxide is low, so that a small interval (space) can be formed, and the liquid medicine is difficult to diffuse into the space due to the surface tension of the liquid in the small space, so that Ag can not be etched continuously in the over-etching process, CD loss can not be increased, a high-precision and high-reflectivity electrode can be obtained, and the requirement of ultrahigh-resolution display can be met.

The specific technical scheme of the invention is as follows:

the uppermost layer and the bottommost layer of the high-precision silver electrode with the multilayer silver stack structure are made of materials with high transmittance such as ITO, IGZO or IZO, the middle layer is made of multiple layers of Ag, and a metal oxide layer which is difficult to etch is arranged between every two layers of Ag. A multilayer stacked anode structure has not been reported at present, and the resistance increases by about 10% by interposing a metal oxide layer between silver, but the resistance can be reduced by increasing the number of stacked layers.

Furthermore, an Ag layer is arranged below the uppermost ITO, IGZO or IZO material layer with high transmittance; an Ag layer is arranged on the material layer with high transmittance such as ITO, IGZO or IZO at the bottommost layer;

furthermore, an Ag layer is arranged between every 2 layers of the difficult-to-etch metal oxide layers.

The difficult-to-etch metal oxide layer is made of a material with transmittance of more than 85%; a material having a high transmittance such as ITO, IGZO, or IZO is preferable.

The reason why a material having a high transmittance such as ITO, IGZO, or IZO is selected so as not to absorb light and not to affect the reflection of silver is that even if a small amount of light passes through the first 2 layers of silver, the light passes through the material such as ITO, IGZO, or IZO, reaches the surface of the lower layer of silver, and is reflected back.

The thickness of the Ag layer is 100-300A; the thickness of the metal oxide layer difficult to etch is less than or equal to 100A.

The smaller the interlayer distance is, the more difficult the solution is to diffuse into the gap due to the surface tension effect, so that the thickness of the Ag layer is 100-300A, and the thickness of the difficult-to-etch metal oxide layer is less than or equal to 100A.

The invention provides a preparation method of a high-precision silver electrode with a multilayer silver stacking structure, which comprises the following steps:

1) preparing a silver electrode with a multilayer silver stack structure: through PVD sputtering, the uppermost layer and the bottommost layer are made of ITO, IGZO or IZO, the materials of the uppermost layer and the bottommost layer are the same, multiple layers of Ag are arranged in the middle, and a metal oxide layer which is difficult to etch is arranged between every two layers of Ag;

2) photoetching;

3) etching by nitrifying mixed acid;

4) and stripping the photoresist.

The step 1) is specifically as follows:

1-1) sputtering a layer of ITO, IZO or IGZO on the bottommost layer by a PVD sputtering process, and controlling the thickness to be less than or equal to 100A;

1-2) sputtering a layer of Ag by a PVD sputtering process with the thickness of 100-300A;

1-3) sputtering PVD on the Ag layer to sputter a metal oxide layer which is difficult to etch, wherein the thickness is less than or equal to 100A;

1-4) repeating the steps 1-2) and 1-3) for 5-10 times in sequence;

1-5) sputtering a layer of Ag by a PVD sputtering process with the thickness of 100-300A;

1-6) finally, sputtering a layer of ITO, IZO or IGZO on the uppermost layer by a PVD sputtering process, and controlling the thickness to be less than or equal to 100A.

Preferably, the thickness of each layer of Ag is controlled to be the same, the thickness of the metal oxide difficult to etch is controlled to be the same, the thicknesses of the metal oxide at the bottommost layer and the metal oxide in the middle layer are consistent, the production cost is the lowest, and various thicknesses do not need to be adjusted.

In the step 2), photoetching is carried out, wherein the PR thickness is 1-5 mu m, and the exposure energy is 50-500 mj;

in the step 3), the nitrated mixed acid is a mixed solution of nitric acid, phosphoric acid and acetic acid, and is a commercially available product. Generally, the mixed acid is nitric acid/phosphoric acid/acetic acid, and the mass fraction ratio is 10-30%: 40-50%: 20 to 50 percent.

In the step 3), etching the part which is not protected by the photoresist by using the nitrated mixed acid, firstly etching the ITO at the uppermost layer, and wet etching for 5-20 s; etching the Ag and metal oxide stack layer for 20-200 s; finally, nitrating mixed acid to etch the ITO at the bottom layer for 5-20 s; the same nitrated mixed acid is used, the ITO at the uppermost layer, the ITO at the middle layer and the ITO at the bottommost layer can be processed and etched in one step, and the total time is controlled.

In the etching process of the step 3), etching the ITO at the uppermost layer for 5-20s, then finishing the etching of the ITO, and beginning to etch the Ag and the ITO below, wherein the etching rate of the nitrated mixed acid ITO is 3-8A/s, the etching rate of the Ag is 100 plus materials for 300A/s, capillary holes are formed, liquid medicine cannot diffuse into the silver layer with small space due to the action of surface tension, the lateral etching is small, and the CD loss is small; from the original >1 μm, it was reduced to < 0.2. mu.m.

In the step 4), the photoresist 120-600s is stripped by adopting NMP stripping liquid. The NMP stripping solution of the prior art can be realized.

The high-precision silver electrode with the multilayer silver stack structure prepared by the method achieves the purpose of reducing Ag etching CD loss by utilizing the principle that liquid medicine is difficult to diffuse into the electrode in a small space due to the surface tension of the liquid, thereby solving the problem that the Ag etching CD loss greatly does not meet the requirement of ultrahigh resolution display. The high-precision and high-reflectivity electrode is prepared, and the Ag high-reflectivity electrode is used in the display industry including organic light-emitting diodes, silicon-based micro-displays, digital micro-mirror chips and the like.

Drawings

FIG. 1 is a schematic flow diagram of a prior art one-step wet etching process;

FIG. 2 is a schematic process flow diagram of the preparation method of the present invention;

FIG. 3 is a comparison of the CD loss of Ag electrode prepared by the one-step wet etching process and the inventive preparation method;

FIG. 4 is a schematic diagram of a high-precision silver electrode structure of a multilayer silver stack structure according to the present invention;

in the figure, 1 is an uppermost ITO layer, 2 is a bottommost ITO layer, 3 is an Ag layer, 4 is a metal oxide layer difficult to etch, and 5 is photoresist;

FIG. 5 shows the appearance of ITO/Ag/ITO prepared by one-step wet etching process in the prior art.

Detailed Description

Example 1

A high-precision silver electrode with a multilayer silver stack structure is characterized in that the uppermost layer and the bottommost layer are made of ITO (indium tin oxide), the middle layer is made of multiple layers of Ag, a metal oxide layer difficult to etch is arranged between every two layers of Ag, and the structure is shown in figure 4.

Further, an Ag layer is arranged below the uppermost ITO layer; an Ag layer is arranged on the ITO layer at the bottommost layer;

The hard-to-etch metal oxide layer is preferably made of a material having a high transmittance such as ITO, IGZO, or IZO.

Example 2

A preparation method of a high-precision silver electrode with a multilayer silver stack structure comprises the following steps:

1) preparing a silver electrode with a multilayer silver stack structure:

1-1) sputtering a layer of ITO (indium tin oxide) on the bottommost layer by a PVD (physical vapor deposition) sputtering process to control the thickness to be 50A;

1-2) sputtering a layer of Ag with the thickness of 100A by a PVD sputtering process;

1-3) sputtering a layer of ITO on the Ag layer by means of PVD sputtering, wherein the thickness of the ITO layer is 50A;

1-4) repeating the steps 1-2) and 1-3) for 5 times in sequence;

1-5) sputtering a layer of Ag with the thickness of 100A by a PVD sputtering process;

1-6) finally, sputtering a layer of ITO on the uppermost layer by a PVD sputtering process, and controlling the thickness to be 50A.

2) Photoetching: PR thickness 1 μm, exposure energy 50 mj;

3) etching the part which is not protected by the photoresist by adopting mixed nitrating acid and mixed solution of nitric acid, phosphoric acid and acetic acid, wherein the mixed nitrating acid is a commercial product, and the mass ratios of the nitric acid, the phosphoric acid and the acetic acid are respectively 10%, 40% and 50%; etching the uppermost layer of ITO for 5 s; etching the Ag and metal oxide stack layer for 100 s; finally, etching the ITO at the bottom layer for 5s until the etching is finished;

4) and (4) stripping the photoresist, wherein the NMP stripping solution is used for stripping the photoresist for 120 s.

The Ag CD loss of the prepared high-precision silver electrode with the multilayer silver stacking structure is less than 0.2 mu m.

Example 3

1) preparing a silver electrode with a multilayer silver stack structure:

1-1) firstly sputtering a layer of IZO with the thickness controlled to be 100A on the bottommost layer by a PVD sputtering process;

1-2) sputtering a layer of Ag with the thickness of 300A by a PVD sputtering process;

1-3) sputtering and PVD sputtering a layer of IZO on the Ag layer with the thickness of 100A;

1-4) repeating the steps 1-2) and 1-3) for 10 times in sequence;

1-5) sputtering a layer of Ag with the thickness of 300A by a PVD sputtering process;

1-6) finally, sputtering a layer of IZO on the uppermost layer by a PVD sputtering process, and controlling the thickness to be 100A.

2) Photoetching, wherein the PR thickness is 5 mu m, and the exposure energy is 500 mj;

3) etching the part which is not protected by the photoresist by adopting nitrated mixed acid, wherein the mixed solution of nitric acid, phosphoric acid and acetic acid is a commercial product, and the mass ratio of the nitric acid to the phosphoric acid to the acetic acid is respectively 30%: 50%: 20 percent; etching the uppermost layer of IZO for 20 s; etching the Ag and metal oxide stack layer for 200 s; finally, etching the bottom IZO for 20 s; until the etching is finished;

4) stripping the photoresist: the NMP stripping solution strips the photoresist 600 s.

Example 4

1) preparing a silver electrode with a multilayer silver stack structure:

1-1) sputtering a layer of ITO (indium tin oxide) on the bottommost layer by a PVD (physical vapor deposition) sputtering process to control the thickness to be 60A;

1-2) sputtering a layer of Ag with the thickness of 110A by a PVD sputtering process;

1-3) sputtering a layer of ITO (indium tin oxide) on the Ag layer by means of PVD (physical vapor deposition) sputtering, wherein the thickness of the ITO is 60A;

1-4) repeating the steps 1-2) and 1-3) for 5 times in sequence;

1-5) sputtering a layer of Ag with the thickness of 110A by a PVD sputtering process;

1-6) finally, sputtering a layer of ITO on the uppermost layer by a PVD sputtering process, and controlling the thickness to be 60A.

2) Photoetching: PR thickness 1.1 μm, exposure energy 51 mj;

3) adopting mixed nitrating acid, mixed solution of nitric acid, phosphoric acid and acetic acid as a commercial product, wherein the mass ratios of the nitric acid, the phosphoric acid and the acetic acid are respectively 10%, 40% and 50%; etching the ITO on the uppermost layer for 6 s; etching the Ag and metal oxide stack layer for 110 s; finally etching the ITO at the bottom layer for 6s until the etching is finished;

4) and (4) stripping the photoresist, namely stripping the photoresist 130s by adopting NMP stripping liquid.

Example 5

1) preparing a silver electrode with a multilayer silver stack structure:

1-1) sputtering a layer of ITO (indium tin oxide) on the bottommost layer by a PVD (physical vapor deposition) sputtering process to control the thickness of 70A;

1-2) sputtering a layer of Ag with the thickness of 120A by a PVD sputtering process;

1-3) sputtering a layer of ITO on the Ag layer by means of PVD sputtering, wherein the thickness of the ITO layer is 70A;

1-4) repeating the steps 1-2) and 1-3) for 6 times in sequence;

1-5) sputtering a layer of Ag with the thickness of 120A by a PVD sputtering process;

1-6) finally, sputtering a layer of ITO on the uppermost layer by a PVD sputtering process, and controlling the thickness to be 70A.

2) Photoetching: PR thickness 1.2 μm, exposure energy 52 mj;

3) adopting mixed nitrating acid, mixed solution of nitric acid, phosphoric acid and acetic acid as a commercial product, wherein the mass ratios of the nitric acid, the phosphoric acid and the acetic acid are respectively 10%, 40% and 50%; etching the uppermost layer of ITO for 7 s; etching the Ag and metal oxide stack layer for 120 s; finally etching the ITO at the bottom layer for 7s until the etching is finished;

4) and (5) stripping the photoresist, and stripping the photoresist 140s by adopting an NMP stripping solution.

Comparative example 1

ITO/Ag/ITO prepared by one-step wet etching process in the prior art:

1) the ITO/Ag/ITO structure is a three-layer sandwich structure, and comprises an ITO layer, an Ag layer and an ITO layer from bottom to top, wherein the thicknesses of the ITO layer, the Ag layer and the ITO layer from bottom to top are 100A, 1000A and 100A; firstly, photoetching is carried out, the PR thickness is 1 mu m, and the curing energy is 50 mj;

2) according to the prior art, common nitrating mixed acid is used for etching, and the nitrating mixed acid adopts nitric acid/phosphoric acid/acetic acid mixed acid with the mass fraction ratio of 30%: 30%: after 40% etching, the CD loss is shown in FIG. 5, and the CD loss is more than 1 um.

The CD loss becomes small and the precision becomes high; the Ag reflectivity is as high as 98 percent, and the aluminum reflectivity is only 91 percent.

Further exploring the comparison of the ITO/Ag/ITO and ITO/Al/ITO reflectivity with different thicknesses, the results are as follows:

the experimental data of different thickness ITO/Ag/ITO high reflectivity are shown in the following table 1:

TABLE 1 ITO/Ag/ITO reflectivity at different thicknesses

Thickness A of upper ITO layer	50	50	50	50	50	50	60	70	80	90	100
												Thickness of Ag A	200	300	400	500	800	1000	1000	1000	1000	1000	1000
Thickness A of lower layer ITO	50	50	50	50	50	50	60	70	80	90	100
												Reflectance%	91.2	93.1	98.2	98.1	98.0	98.2	98.0	98.2	98.0	98.2	98.2

The reflectivity of the ITO/Ag/ITO structure is irrelevant to ITO and only relevant to the thickness of Ag, and after the thickness of Ag is more than 400A, the reflectivity does not increase along with the increase of the thickness.

The results of the ITO/Al/ITO reflectivity experiments with different thicknesses are shown in the following table 2:

TABLE 1 ITO/Al/ITO reflectivity at different thicknesses

Thickness A of upper ITO layer	50	50	50	50	50	50	60	70	80	90	100
												Thickness of Al A	200	300	400	500	800	1000	1000	1000	1000	1000	1000
Thickness A of lower layer ITO	50	50	50	50	50	50	60	70	80	90	100
												Reflectance%	85.2	87.1	89.2	90.1	91.0	91.2	91.0	91.3	91.1	91.2	91.2

The reflectivity of the ITO/Al/ITO structure is irrelevant to ITO and only relevant to Al thickness, and after the Al thickness is more than 800A, the reflectivity does not increase along with the increase of the thickness.

Moreover, the ITO/Ag/ITO reflectivity is higher than the ITO/Al/ITO reflectivity, and the CD loss of the silver electrode prepared by the method is less than 0.2 mu m, so that the requirement of ultrahigh resolution display can be met.

Claims

1. The high-precision silver electrode with the multilayer silver stacking structure is characterized in that the uppermost layer and the bottommost layer of the high-precision silver electrode with the multilayer silver stacking structure are ITO, IGZO or IZO, multiple layers of Ag are arranged in the middle, and a metal oxide layer difficult to etch is arranged between every two layers of Ag;

2. The multi-layer silver stack structure high-precision silver electrode according to claim 1, wherein an uppermost ITO, IGZO or IZO layer is followed by an Ag layer; and an Ag layer is arranged on the ITO, IGZO or IZO layer at the bottommost layer.

3. A high-precision silver electrode with a multilayer silver stack structure according to claim 1, wherein an Ag layer is formed between every 2 difficult-to-etch metal oxide layers.

4. The multi-layer silver stack structure high-precision silver electrode according to claim 1, wherein the hard-to-etch metal oxide layer is ITO, IGZO, or IZO.

5. A method for preparing a high-precision silver electrode having a multilayer silver stack structure according to any one of claims 1 to 4, comprising the steps of:

2) photoetching;

3) etching by nitrifying mixed acid;

4) and stripping the photoresist.

6. The preparation method according to claim 5, wherein the step 1) is specifically:

1-4) repeating the steps 1-2) and 1-3) for 5-10 times in sequence;

7. The preparation method according to claim 5, wherein in the step 3), the uppermost layer of ITO is etched for 5-20 s; etching the Ag and metal oxide stack layer for 20-200 s; and finally, nitrating the mixed acid to etch the ITO at the bottom layer for 5-20 s.

8. The method as claimed in claim 5, wherein in step 4), the photoresist is stripped for 120 seconds and 600 seconds by using NMP stripping solution.