Dry etching method for copper thin film

Abstract

The present invention relates to a method for dry etching of a copper thin film using a plasma process, characterized in that: in the method for dry etching of a copper thin film using a plasma etching process, a copper thin film is etched by a plasma etching process; an XHy-type second etching gas is supplied in order to improve the degree of reactivity between hydrogen atoms and copper chloride (CuClx) generated during etching of a copper thin film using an AClb-type first etching gas.

Description

Technical Field

[0001] This invention relates to a dry etching method for copper thin films using plasma technology, and to a dry etching method for removing copper chloride from copper thin films by increasing the reactivity between copper chloride and hydrogen atoms generated in the plasma etching process.

[0002] The following national research and development projects support this invention: Project ID: 1415184827 Project No. 20016358 Department Name: Ministry of Trade, Industry and Energy Project Management (Professional) Agency Name: Korea Institute of Industrial Technology Evaluation and Management Research Project Title: Electronic Components Industry Technology Development - Display Innovative Process Platform Construction Research Project Title: Development of Dry Etching Process Equipment Technology for Low-Resistance Micro-Metal Wiring for High-Resolution AMOLEDs Project implementing organization: APS Research Co., Ltd. The research period was from April 1, 2021 to December 31, 2024. Background Technology

[0003] Currently, the display industry, one of South Korea's representative industries, continues to grow, centered on amorphous silicon TFT-LCD and small AMOLED based on low-temperature polycrystalline silicon. South Korea maintains its leading position in the world not only in the TFT-LCD and AMOLED panel industry, which has the world's highest production capacity, but also in upstream industries such as materials, components, and equipment required for TFT-LCD and AMOLED panel manufacturing, as well as in downstream markets such as smart devices and digital TVs that use LCD and OLED panels.

[0004] However, given the current situation where investment competition at the national level lags behind, the market dominance of TFT-LCD has shifted to China, and the profitability of the display industry continues to weaken, in order to maintain the status of the display industry as a pillar strategic industry of South Korea and ensure absolute competitiveness, it is necessary to strengthen research and investment in the next generation of displays after AMOLED, which currently has a competitive advantage.

[0005] The core of the next generation of display technology after silicon-based TFT-LCD / AMOLED will be ultra-high resolution displays, including plastic AMOLED. As a new market that breaks through the current limitations of plastic AMOLED, which is centered on small products, ultra-high resolution (at least 1000ppi) flexible AMOLED technology for AR / MR wearable displays is expected to become one of the main display products in the next 10 years.

[0006] In recent years, with the rapid growth in demand for ultra-high resolution AMOLED panels in mobile / IT displays, including AR / MR displays, micro-patterning technology with low-resistance wiring has become a core technology necessary for realizing ultra-high resolution panels.

[0007] To manufacture large, high-resolution displays, especially ultra-high-resolution AMOLED panels that require multiple wirings, the width of the electrode wirings becomes narrower. Therefore, copper (Cu) electrode wirings that can ensure high conductivity are needed. However, existing wet etching processes have significant limitations in order to pattern the wirings at the 1-2μm level, so dry etching technology is required.

[0008] However, the copper chloride (CuCl) formed by the reaction of chlorine (Chlorine(Cl) gas), a representative halogen gas used in dry etching of copper thin films, with Cu is a typical example. x Etching compounds have a high vaporization temperature of over 1300°C under normal pressure. To vaporize them, heating to over 400°C is required at the conventional process pressure of ~50 mTorr in RIE mode dry etching. Even at low pressures below 1.5 mTorr, which are difficult to use in Capacitively Coupled Plasma (CCP) process equipment that includes RIE mode, the substrate needs to be heated to a temperature of over 200°C.

[0009] To overcome the problems mentioned above, the technologies proposed and developed to date include: 1) Irradiating a copper thin film with Cl plasma generates porous CuCl. x A method for removing etched compounds using HCl solution; 2) React the copper thin film with Cl plasma to generate CuCl. xEtching compounds, while simultaneously heating the substrate to above 400°C as additional heating energy to vaporize it, or irradiating it with ultraviolet (UV) or infrared (IR) light to force vaporization; 3) To ensure that the generated CuCl x The method employs a high-density plasma (HDP) source operating at extremely low pressures below 5 mTorr to achieve plasma conditions where etching compounds readily vaporize. 4) Methods such as using CH3COOH / Ar or CH3OH / Ar gases, which can form easily vaporized CuH-based etching compounds at temperatures above a certain level, as etching gases.

[0010] Method 1) involves the formation of solid copper chloride (CuCl) via a dry process. x After that, an additional wet process using HCl solution is required, so it cannot fundamentally avoid the limitations of wet etching in its applicability to micro-processes, and it also complicates the process.

[0011] 2) As the substrate temperature reaches above 400°C, it is difficult to avoid deformation of the glass substrate and changes in the physical properties of the TFT film. When applied to large-area substrates, it is very difficult to ensure process uniformity and cannot fundamentally avoid the problem of forced vaporization of etching byproducts being redeposited in process containers or vacuum pumps at relatively low temperatures.

[0012] 3) Currently, there is no HDP source that can uniformly generate high-temperature, high-density plasma on large-area substrates of generation 8 and above, ensuring an etching rate of over 100 nm / min under extremely low pressure below 5 mTorr.

[0013] Method 4) has been reported to successfully dry-etch copper electrode wiring for semiconductors, but the etching rate is slow and the process gas is difficult to handle, so it is difficult to apply to the field of large-area displays.

[0014] Therefore, the dry etching technology for copper thin films studied to date cannot be applied to the mass production process of 6th generation large-area panels for high-resolution AMOLED, and new alternatives are needed. Summary of the Invention

[0015] (a) Technical problems to be solved Based on the aforementioned necessity, the present invention aims to provide a dry etching method for removing copper chloride from copper films by increasing the reactivity between copper chloride and hydrogen atoms generated in the plasma etching process.

[0016] (II) Technical Solution The key technical point of the present invention for achieving the above objectives is a dry etching method for copper thin films, characterized in that, in the dry etching method for copper thin films utilizing plasma etching technology, in order to improve the utilization of AC1... b Copper chloride (CuCl) is generated during the etching process of copper thin films using the first etching gas. x The degree of reactivity between the XH atom and the hydrogen atom supplies XH y Type II etching gas.

[0017] In addition, the AC1 b The preferred etching gas is any one or a mixture of two or more of HCl, Cl2, BCl3, and CCl4.

[0018] In addition, the XH y The preferred second etching gas is NH3, CH4, C2H4, C3H8, or C4H. 10 C m H n Any one of them or a mixture thereof.

[0019] Furthermore, by supplying the AC1 b Type 1 etching gas and the XH y The plasma generated by the second type of etching gas preferably satisfies 0.5N(Cl) + )≤N(H + )(N(H + ) is H + Ion flux, N(Cl) + ) for Cl + (Ion flux).

[0020] In addition, the copper chloride (CuCl) x The reactions between Cu and hydrogen atoms include the following reaction: Cu + Cl → CuCl x (Solid) 3CuCl x (Solid) + 3H (gas) -> Cu3Cl3 (gas) + 3HCl (gas).

[0021] Furthermore, the lower the process temperature of the plasma etching process, the faster the formation rate of Cu3Cl3 compared to the formation rate of copper chloride.

[0022] Furthermore, in order to improve the reactivity between the copper chloride and hydrogen atoms, it is preferable to further increase the electron temperature (Te).

[0023] (III) Beneficial Effects This invention relates to a method for dry etching of copper thin films using plasma etching technology, which removes copper chloride by increasing the reactivity between copper chloride generated in the plasma etching process and hydrogen atoms.

[0024] In particular, the present invention provides AC1 by additionally or simultaneously supplying it. b Type 1 etching gas and XH y The second type of etching gas, by adjusting the plasma flux (adjusting the ratio of free radicals), induces hydrogen atom reactions that occur at a faster rate than the formation rate of copper chloride, thereby efficiently removing copper chloride.

[0025] Furthermore, this invention rapidly removes copper chloride by adjusting the ion flux, eliminating the need for cumbersome processes such as wet etching or supplying heat or additional energy for copper chloride removal. It also minimizes the chamber contamination problem caused by recondensation during the forced vaporization of copper chloride. Attached Figure Description

[0026] Figure 1 This table illustrates the degree of variation in etching rate based on the HCl+H2 gas flow rate under the same power conditions.

[0027] Figure 2 A table showing the degree of change in etching rate when the etching gas is HCl and when the etching gas is HCl+NH3 with the addition of NH3, under the same power conditions.

[0028] Figure 3 A graph comparing the changes in etching rate of copper films based on increasing the total flow rate or adding NH3 gas. Detailed Implementation

[0029] This invention relates to a method for dry etching of copper thin films using plasma etching technology, which removes copper chloride by increasing the reactivity between copper chloride generated in the plasma etching process and hydrogen atoms.

[0030] In particular, the present invention utilizes the addition or simultaneous supply of AC1 in the plasma etching process. b Type 1 etching gas and XH y The second etching gas is used to adjust the plasma flux (the ratio of free radicals), and the reaction between the induced copper chloride and hydrogen atoms is faster than the formation rate of copper chloride, thereby efficiently removing copper chloride.

[0031] The present invention is characterized in that, in the dry etching method for copper thin films utilizing plasma etching technology, in order to improve the utilization of Al... b Copper chloride (CuCl) is generated during the etching process of copper thin films using the first etching gas. x The degree of reactivity between the XH atom and the hydrogen atom supplies XH y Type II etching gas.

[0032] As described above, the present invention relates to dry etching of copper thin films using conventional plasma etching processes, particularly by additionally or simultaneously supplying AC1. b Type 1 etching gas and XH y The second etching gas is used to adjust the plasma flux (the ratio of free radicals), and the reaction between the induced copper chloride and hydrogen atoms is faster than the formation rate of copper chloride, thereby achieving efficient removal of copper chloride.

[0033] According to one embodiment of the present invention, the AC1 b The first etching gas is Cl supplied in the plasma process. + Ions, using any one or a mixture of two or more of HCl, Cl2, BCl3, and CCl4.

[0034] Furthermore, according to one embodiment of the present invention, the XH y The second type of etching gas is H2 supplied in the plasma process. + Ions, using NH3, CH4, C2H4, C3H8, C4H 10 C m H n Any one of them or a mixture thereof.

[0035] As the first etching gas, Cl can be supplied. + Any substance containing ions, as a second etching gas, can supply H... + Ions are any substances, not limited to the substances mentioned above.

[0036] Furthermore, according to one embodiment of the present invention, by supplying the AC1 b Type 1 etching gas and the XH y The plasma generated by the second type of etching gas satisfies 0.5N(Cl) + )≤N(H + )(N(H + ) is H + Ion flux, N(Cl) + ) for Cl + (Ion flux).

[0037] Among them, the copper chloride (CuCl) xThe reactions between Cu and hydrogen atoms include the following reaction: Cu + Cl → CuCl x (Solid), 3CuCl x (Solid) + 3H (gas) -> Cu3Cl3 (gas) + 3HCl (gas), thus removing copper chloride (CuCl) x This generates volatile Cu3Cl3 (gas) and 3HCl (gas), thus enabling the etching process of the copper thin film to proceed smoothly.

[0038] According to the above reaction equation, the ion flux participating in the reaction must be at least 0.5N(Cl). + )≤N(H + When the ion flux is below this range, the formation rate of copper chloride is faster than its removal rate, resulting in the inability to properly etch the copper film and a significant reduction in the etching rate.

[0039] In this invention, if hydrogen molecules are supplied in order to induce the removal reaction of copper chloride, the reaction 3CuCl2 (solid) + 3 / 2H2 (gas) = ​​Cu3Cl3 (gas) + 3HCl (gas) will be induced. However, this reaction will induce an endothermic reaction (ΔHo [kJ / mol]), which will cause the process to be unable to continue.

[0040] Therefore, in this invention, the removal reaction of copper chloride is facilitated by supplying atomic hydrogen rather than hydrogen molecules; for this purpose, XH is further supplied. y Type II etching gas.

[0041] XH y The second type of etching gas, after plasma treatment, forms X+ and H+. + Ions that induce a reaction between copper chloride and hydrogen atoms.

[0042] Furthermore, according to one embodiment of the present invention, the lower the process temperature of the plasma etching process, the faster the formation rate of Cu3Cl3 compared to the formation rate of copper chloride. That is, it has been observed that even below 200°C, the formation rate of Cu3Cl3 is faster than that of copper chloride, thereby enabling low-temperature processes (including room-temperature processes).

[0043] Therefore, it minimizes the chamber contamination problem caused by recondensation resulting from the existing method of forcibly vaporizing copper chloride by applying high-temperature thermal energy.

[0044] Furthermore, according to one embodiment of the invention, in order to improve the reactivity between the copper chloride and hydrogen atoms, a plasma source that can further increase the electron temperature (Te) can be used. By increasing the electron temperature, a high-density plasma can be supplied, thereby further increasing the Cl... + Ions and H +Ion flux. Where XH is supplied... y Using a type-2 etching gas as the second etching gas can further increase the H2O content. + The flux of ions makes the reaction process for removing copper chloride more active.

[0045] This invention can improve the reactivity of copper chloride removal by adjusting the plasma flux, thus allowing the use of plasma sources with relatively low electron temperatures (e.g., inductively coupled plasma (ICP)) without the need for plasma sources with high electron temperatures (e.g., electronic cyclotron resonance (ECR)). Therefore, the freedom of choice in plasma source selection can be increased.

[0046] Furthermore, according to one embodiment of the present invention, in order to improve the reactivity between the copper chloride and hydrogen atoms, the H+ in the first etching gas is used... + The flux of ions is less than that of Cl. + To compensate for the ion flux, a second etching gas needs to be supplied, and the supply volume needs to be greater than that of the first etching gas to adequately supply hydrogen ions.

[0047] When the first etching gas is supplied in excess, such as by increasing the flow rate of HCl gas, the increased pressure causes a decrease in electron temperature, thereby reducing the H... + Ions and Cl + The presence of ions leads to a decrease in the etching rate. Therefore, while supplying an appropriate amount of the first etching gas, a further supply of H₂ with a smaller cross-section is provided to improve the reactivity. + Ions, thereby minimizing factors that increase pressure.

[0048] Figure 1 This table illustrates the variation in etching rate based on HCl+H2 gas flow rate under the same power conditions (ECR power is 5kW, RF power is 2kW).

[0049] According to one embodiment of the present invention, the etching rate increases with the increase of the total flow rate of HCl+H2 gas. This indicates that as the total flow rate of HCl+H2 gas, the etching gas, increases, the etching rate increases. + Ions and H + The increased flux of ions can eventually induce hydrogen atom reactions that occur at a faster rate than the formation rate of copper chloride, thus removing copper chloride more efficiently.

[0050] Figure 2This table illustrates the variation in etching rate under the same power conditions (ECR power of 3kW, RF power of 2kW), but with different total flow rates, when the etching gas is 150 standard milliliters per minute (sccm) of HCl versus 80 standard milliliters per minute of HCl + NH3 with the addition of NH3.

[0051] According to one embodiment of the invention, compared to using the first etching gas HCl alone as the etching gas, the etching rate shows an increase when a second etching gas NH3 is added to the first etching gas HCl, despite a lower total flow rate. This indicates that the present invention facilitates the removal reaction of copper chloride by supplying atomic hydrogen rather than hydrogen molecules, and for this purpose, further supplying XH... y The second etching gas is effective. NH3, as the second etching gas, is plasma-treated to form N+ and H+. + Ions, which means they can induce a reaction between copper chloride and hydrogen atoms.

[0052] Figure 3 To be Figure 1 The table and Figure 2 The experimental results in the table are shown together with the comparative graph.

[0053] As mentioned above, according to Figure 3 When the types of etching gases are the same, the greater the total flow rate of the etching gases, the greater the etching rate. Moreover, compared with the case of using the first etching gas HCl alone, even if the total flow rate is low, the etching rate will increase when using the first etching gas HCl and the second etching gas NH3 simultaneously.

[0054] As described above, the present invention is a dry etching process for copper thin films using plasma etching, which removes copper chloride by increasing the reactivity between copper chloride generated in the plasma etching process and hydrogen atoms.

[0055] In particular, the present invention provides AC1 by additionally or simultaneously supplying it. b Type 1 etching gas with XH y The second type of etching gas, by adjusting the plasma flux (adjusting the ratio of free radicals), induces hydrogen atom reactions that occur at a faster rate than the formation rate of copper chloride, thereby efficiently removing copper chloride.

[0056] Furthermore, this invention rapidly removes copper chloride by adjusting the ion flux, eliminating the need for cumbersome processes such as wet etching or supplying heat or additional energy for copper chloride removal. It also minimizes the chamber contamination problem caused by recondensation during the forced vaporization of copper chloride.

Claims

1. A dry etching method for copper thin films, characterized in that, In the dry etching method for copper thin films using plasma etching technology, To improve the utilization of ACl b Copper chloride (CuCl) is generated during the etching process of copper thin films using the first etching gas. x The degree of reactivity between the XH atom and the hydrogen atom supplies XH y Type II etching gas.

2. The dry etching method for copper thin films according to claim 1, characterized in that, The ACl b The first etching gas is any one or a mixture of two or more of HCl, Cl2, BCl3, and CCl4.

3. The dry etching method for copper thin films according to claim 1, characterized in that, The XH y The second type of etching gas is NH3, CH4, C2H4, C3H8, C4H 10 C m H n Any one of them or a mixture thereof.

4. The dry etching method for copper thin films according to claim 1, characterized in that, By supplying the ACl b Type 1 etching gas and the XH y The plasma generated by the second type of etching gas satisfies 0.5N(Cl) + )≤N(H + ), where N(H + ) is H + Ion flux, N(Cl) + ) for Cl + Ion flux.

5. The dry etching method for copper thin films according to claim 1, characterized in that, The copper chloride (CuCl) x The reactions between ) and hydrogen atoms include the following reaction equations: Cu + Cl → CuCl x (solid), 3CuCl x (Solid) + 3H (gas) -> Cu3Cl3 (gas) + 3HCl (gas).

6. The dry etching method for copper thin films according to claim 5, characterized in that, The lower the process temperature of the plasma etching process, the faster the formation rate of Cu3Cl3 compared to the formation rate of copper chloride.

7. The dry etching method for copper thin films according to claim 1, characterized in that, To further increase the reactivity between the copper chloride and hydrogen atoms, the electron temperature (Te) is further increased.

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