Method for dry etching copper thin film

Abstract

The present invention relates to a method for dry etching a copper thin film by using plasma processing, and the technical subject matter is a method for dry etching a copper thin film by using plasma etching, the method having an XHy type second etching gas supplied in order to increase the reactivity between hydrogen atoms and copper chloride (CuClx), which is generated during copper thin film etching using an AClb type first etching gas.

Description

Dry etching method for copper films

[0001] The present invention relates to a dry etching method for a copper thin film using a plasma process, and more particularly, to a dry etching method for a copper thin film for removing copper chloride by increasing the reactivity between copper chloride and hydrogen atoms generated during a plasma etching process.

[0002] The national research and development projects that supported this invention are as follows:

[0003] Assignment ID 1415184827

[0004] Assignment number 20016358

[0005] Ministry of Trade, Industry and Energy

[0006] Project Management (Professional) Institution Name: Korea Industrial Technology Evaluation and Planning Institute

[0007] Research Project Name: Electronic Components Industry Technology Development - Display Innovation Process Platform Construction

[0008] Research Project Name: Development of Copper Thin Film Dry Etching Process Equipment for Low-Resistance Micro-Metal Wires for High-Resolution AMOLEDs

[0009] Project execution organization name: AP Research Co., Ltd.

[0010] Research period: April 1, 2021 - December 31, 2024

[0011] The display industry, currently one of Korea's representative industries, has continued to grow centered on TFT-LCDs based on amorphous silicon and small AMOLEDs based on low-temperature polysilicon. In addition to the TFT-LCD and AMOLED panel businesses, which boast the world's best product production capabilities, Korea maintains its position as the world's best in the upstream businesses such as the materials, components, and equipment industries required for manufacturing TFT-LCD and AMOLED panels, as well as in the downstream markets such as smart devices and digital TVs that use LCD and OLED panels.

[0012] However, in the current situation where the TFT-LCD market leadership is shifting to China due to national investment competition and the profitability of the display industry is weakening, in order to maintain the status of the display industry as a strategic industry that feeds Korea and secure absolute competitiveness, research and investment in next-generation displays following AMOLED, which currently has a competitive edge, must be strengthened.

[0013] The next generation of displays following silicon-based TFT-LCD / AMOLED will be centered around ultra-high-resolution displays, including Plastic AMOLED. As a wearable display, which is a new market that goes beyond the limitations of the current small-sized Plastic AMOLED, ultra-high-resolution (at least 1,000 ppi) Flexible AMOLED technology for AR / MR is expected to become one of the main display products within the next 10 years.

[0014] Recently, the need for ultra-high-resolution AMOLED panels in mobile / IT displays, including displays for AR / MR, has been rapidly increasing, and micropatterning technology for low-resistance wiring is an essential core technology for implementing ultra-high-resolution panels.

[0015] In order to manufacture large displays with high resolution, especially ultra-high-resolution AMOLED panels that require multiple wiring, the width of electrode wiring is narrowing, and copper (Cu) electrode wiring that can secure high conductivity is required accordingly. However, for wiring patterning at the level of 1 to 2 ㎛, the existing wet etching process has great limitations, so dry etching technology is required.

[0016] However, the copper chloride (CuClx) etching compound generated after the reaction between chlorine (Cl) gas, a representative halogen gas used as a dry etching gas for copper thin films, and Cu has a high vaporization temperature characteristic of over 1300℃ at normal pressure. Therefore, in order to vaporize it, heating of over 400℃ is required at ~50 mTorr, which is a typical process pressure of the RIE Mode dry etching process, and the substrate must be heated to a temperature of over 200℃ even at a low pressure of 1.5 mTorr or less, which is difficult to use in the Capacitively Coupled Plasma (CCP) process equipment including the RIE Mode.

[0017] Technologies proposed and developed so far to overcome these problems include:

[0018] 1) Porous CuCl is formed by irradiating Cl plasma on a copper film. x A method of creating an etching compound and then removing it with an HCl solution.

[0019] 2) A method of heating the substrate to 400°C or higher as additional heating energy to vaporize the CuClx etching compound by reacting the copper thin film with Cl plasma, or forcibly vaporizing it by irradiating it with Ultraviolet (UV) or Infrared (IR) Light.

[0020] 3) Generated CuCl x A method of using a High Density Plasma (HDP) Source operating at a very low pressure of 5 mTorr or less to secure plasma conditions in which the etching compound is easily vaporized.

[0021] 4) There is a method of using CH3COOH / Ar or CH3OH / Ar gas as an etching gas, which can form an etching compound based on CuH that is easily vaporized above a certain temperature.

[0022] Method 1) requires a wet process using an additional HCl solution after forming solid copper chloride (CuClx) through a dry process, so it cannot fundamentally avoid the limitations of the wet etching process in applicability to micro-processes and has the problem of complicating the process.

[0023] 2) It is difficult to avoid deformation of the glass substrate and change in the properties of the TFT thin film when the temperature of the substrate exceeds 400℃ in the method, it is very difficult to secure process uniformity when applied to a large-area substrate, and it is fundamentally impossible to avoid the problem of forcibly vaporized etching byproducts being redeposited on a process vessel or vacuum pump at a relatively low temperature.

[0024] 3) There is no HDP source yet that can uniformly generate high temperature, high density plasma that can secure an etch rate of 100 nm / min or more at a very low pressure of 5 mTorr or less on a large-area substrate of the 8th generation or higher.

[0025] 4) Although the method has been reported to have successfully dry-etched copper electrode wiring for semiconductors, its application to large-area displays is difficult due to the slow etching speed and difficulty in handling process gases.

[0026] Therefore, the copper thin film dry technology studied to date cannot be applied to the mass production process of large-area panels of the 6th generation for high-resolution AMOLED, and a new alternative is needed.

[0027] The present invention was derived from the above-mentioned necessity, and its purpose is to provide a dry etching method for a copper thin film to remove copper chloride by increasing the reactivity between copper chloride and hydrogen atoms generated during a plasma etching process.

[0028] The present invention for achieving the above purpose is a dry etching method of a copper thin film using a plasma etching process, ACl bCopper chloride (CuCl) generated during the etching process of a copper thin film using a first etching gas of the type x ) to increase the reactivity between hydrogen atoms and XH y The technical gist of the present invention is a dry etching method for a copper thin film, characterized by supplying a second etching gas of a type.

[0029] In addition, the above ACl b It is preferable that the first etching gas of the type be one or a mixture of two or more of HCl, Cl2, BCl3, and CCl4.

[0030] Also, the above XH y The second etching gas of the type is NH3, CH4, C2H4, C3H8, C4H 10 , C m H n It is preferred that it be one of these or a mixture thereof.

[0031] In addition, the above ACl b The first etching gas of the type and the above XH y It is preferable that the plasma generated by the supply of the second etching gas of the type satisfies 0.5N(Cl+)≤N(H+) (N(H+) is the flux of H+ ions, N(Cl+) is the flux of Cl+ ions).

[0032] In addition, the above copper chloride (CuCl) x ) and the reaction between hydrogen atoms is Cu + Cl -> CuCl x (solid), 3CuCl x It is composed of the reaction formula (solid) + 3H(gas) -> Cu3Cl3(gas) + 3HCl(gas).

[0033] In addition, the lower the process temperature of the plasma etching process, the faster the production rate of Cu3Cl3 is than the production rate of copper chloride.

[0034] In addition, in order to increase the reactivity between the copper chloride and hydrogen atoms, it is desirable to further increase the electron temperature (Te).

[0035] The present invention is a method for dry etching a copper thin film by a plasma etching process, and is intended to remove copper chloride by increasing the reactivity between copper chloride and hydrogen atoms generated during the plasma etching process.

[0036] In particular, the present invention is ACl b Type 1 etching gas and XH y By additionally or simultaneously supplying a second etching gas of the type, the plasma flux (ratio of radicals) is controlled to induce a reaction between hydrogen atoms faster than the production rate of copper chloride, thereby efficiently removing copper chloride.

[0037] In addition, the present invention rapidly removes copper chloride by controlling ion flux, so that cumbersome processes such as wet etching or supplying heat or additional energy for removing copper chloride are not required at all, and the problem of chamber contamination due to recondensation during forced vaporization of copper chloride can also be minimized.

[0038] Figure 1 - Table showing the degree of change in etch rate according to HCl + H2 gas flow rate under the same power state.

[0039] Figure 2 - A table showing the degree of change in etching rate when the etching gas is HCl under the same power state and when the etching gas is HCl+NH3 and NH3 is added.

[0040] Figure 3 - Comparison of changes in the etch rate of a copper film according to an increase in total flow rate or addition of NH3 gas.

[0041] The present invention is a method for dry etching a copper thin film by a plasma etching process, and is intended to remove copper chloride by increasing the reactivity between copper chloride and hydrogen atoms generated during the plasma etching process.

[0042] In particular, the present invention is a plasma etching process using ACl b Type 1 etching gas and XH y By additionally or simultaneously supplying a second etching gas of the type, the plasma flux (ratio of radicals) is controlled to induce a reaction between the generated copper chloride and hydrogen atoms faster than the rate of generation of copper chloride, thereby efficiently removing copper chloride.

[0043] The present invention relates to a dry etching method of a copper thin film using a plasma etching process, wherein ACl b Copper chloride (CuCl) generated during the etching process of a copper thin film using a first etching gas of the type x ) to increase the reactivity between hydrogen atoms and XH y It is characterized by supplying a second etching gas of the type.

[0044] In this way, the present invention dry-etches a copper thin film by a traditional plasma etching process, and in particular, ACl b Type 1 etching gas and XH y By additionally or simultaneously supplying a second etching gas of the type, the plasma flux (ratio of radicals) is controlled to induce a reaction between the generated copper chloride and hydrogen atoms faster than the rate of generation of copper chloride, thereby efficiently removing copper chloride.

[0045] According to one embodiment of the present invention, the ACl b The first etching gas of the type supplies Cl+ ions during the plasma process, and uses one or a mixture of two or more of HCl, Cl2, BCl3, and CCl4.

[0046] In addition, according to one embodiment of the present invention, the XH y The second etching gas of the type that supplies H+ ions during the plasma process is NH3, CH4, C2H4, C3H8, C4H 10 , Cm H n Use one or a mixture of these.

[0047] It is not limited to the above materials, and any material that supplies Cl+ ions as the first etching gas and any material that supplies H+ ions as the second etching gas may be used.

[0048] In addition, according to one embodiment of the present invention, the ACl b The first etching gas of the type and the above XH y The plasma generated by the supply of the second etching gas of the type satisfies 0.5N(Cl+)≤N(H+) (N(H+) is the flux of H+ ions, N(Cl+) is the flux of Cl+ ions).

[0049] Here, the copper chloride (CuCl) x ) and the reaction between hydrogen atoms is Cu + Cl -> CuCl x (solid), 3CuCl x It is composed of the reaction formula of (solid) + 3H(gas) -> Cu3Cl3(gas) + 3HCl(gas), and copper chloride (CuCl x ) is removed, and volatile Cu3Cl3(gas) and 3HCl(gas) are generated, so that the etching process of the copper film is carried out smoothly.

[0050] According to the above reaction formula, the flux of ions involved in the reaction must satisfy at least 0.5N(Cl+)≤N(H+). If it is less than this, the production rate of copper chloride is faster than the removal rate, so the copper film is not properly etched and the etching rate drops significantly.

[0051] In the present invention, when hydrogen molecules are supplied to induce a reaction equation for the removal of copper chloride, a reaction equation of 3CuCl2(solid)+3 / 2H2(g)=Cu3Cl3(g)+3HCl(g) is induced, but this induces an endothermic reaction (△Ho[kJ / mol]) and the process does not proceed any further.

[0052] Therefore, in the present invention, hydrogen in an atomic state rather than a hydrogen molecule is supplied to facilitate the removal reaction of copper chloride, and for this purpose, XH is additionally added. y It supplies a second etching gas of the type.

[0053] XH y The second etching gas of the type is plasmaized to form X+ and H+ ions, which induce a reaction between copper chloride and hydrogen atoms.

[0054] Meanwhile, according to one embodiment of the present invention, the lower the process temperature of the plasma etching process, the faster the production rate of Cu3Cl3 is than the production rate of copper chloride. That is, even at temperatures below 200°C, the production rate of Cu3Cl3 was observed to be faster than the production rate of copper chloride, thereby enabling low-temperature processes (including room-temperature processes).

[0055] Therefore, the problem of chamber contamination due to recondensation caused by forcibly vaporizing copper chloride by applying existing high-temperature thermal energy is minimized.

[0056] In addition, according to one embodiment of the present invention, in order to increase the reactivity between the copper chloride and hydrogen atoms, a plasma source capable of further increasing the electron temperature (Te) may be used. By increasing the electron temperature, a high-density plasma can be supplied, thereby further increasing the flux of Cl+ ions and H+ ions. Here, XH is used as the second etching gas. y Supplying the etching gas of this type can further increase the flux of H+ ions, thereby making the reaction process for removing copper chloride more active.

[0057] The present invention can increase the copper chloride removal reactivity by controlling the plasma flux, so that a plasma source with a relatively low electron temperature (e.g., Inductively Coupled Plasma, ICP) can be used instead of a plasma source with a high electron temperature (e.g., Electronic Cyclotron Resonance, ECR). This increases the freedom of selection of plasma sources.

[0058] In addition, according to one embodiment of the present invention, in order to increase the reactivity between the copper chloride and hydrogen atoms, the flux of H+ ions is smaller than that of Cl+ ions due to the first etching gas, and in order to compensate for this, the second etching gas is supplied more than the flow rate of the first etching gas so that hydrogen ions are sufficiently supplied.

[0059] If more of the first etching gas is supplied, for example, if the flow rate of HCl gas is increased, the electron temperature due to the increase in pressure decreases, which reduces H+ ions and Cl+ ions, resulting in a drop in the etching rate. Therefore, by supplying an appropriate amount of the first etching gas and supplying more H+ ions with a smaller crosssection to increase the reactivity, the pressure increase factor is minimized.

[0060] Figure 1 is a table showing the degree of change in etching rate according to the HCl + H2 gas flow rate under the same power (ECR Power 5kW, RF Power 2kW).

[0061] According to one embodiment of the present invention, as the total flow rate of HCl + H2 gases increases, the etch rate increases. As the total flow rate of HCl + H2 gases, which are etching gases, increases, the flux of Cl+ ions and H+ ions increases, which ultimately induces a reaction between hydrogen atoms that is faster than the production rate of copper chloride, indicating that copper chloride is removed more efficiently.

[0062] Figure 2 is a table showing the degree of change in etch rate when the total flow is different under the same power (ECR Power 3kW, RF Power 2kW) condition, but when HCl 150sccm is used as etching gas and when NH3 is added to HCl+NH3 80sccm as etching gas.

[0063] According to one embodiment of the present invention, when NH3 gas, which is a second etching gas, is added to HCl, which is a first etching gas, the total flow rate is smaller than when HCl, which is a first etching gas, is used alone, but the etching rate increases. This is because the present invention supplies hydrogen in an atomic state rather than a hydrogen molecule to facilitate the removal reaction of copper chloride, and for this purpose, XH is additionally added. y This supports the effectiveness of supplying a second etching gas of this type. NH3, the second etching gas, is plasmaized to form N+ and H+ ions, which means that it induces a reaction between copper chloride and hydrogen atoms.

[0064] Figure 3 is a diagram comparing the experimental results of the tables in Figure 1 and Figure 2.

[0065] As explained above, according to FIG. 3, when the types of etching gases are the same, the more the total flow rate of the etching gas is, the more the etching rate increases when the first etching gas, HCl, and the second etching gas, NH3, are used simultaneously compared to when the first etching gas, HCl, is used alone, even if the total flow rate is small.

[0066] In this way, the present invention is to dry-etch a copper thin film by a plasma etching process, and to remove copper chloride by increasing the reactivity between copper chloride and hydrogen atoms generated during the plasma etching process.

[0067] In particular, the present invention is ACl b Type 1 etching gas and XH yBy additionally or simultaneously supplying a second etching gas of the type, the plasma flux (ratio of radicals) is controlled to induce a reaction between hydrogen atoms faster than the production rate of copper chloride, thereby efficiently removing copper chloride.

[0068] In addition, the present invention rapidly removes copper chloride by controlling ion flux, so that cumbersome processes such as wet etching or supplying heat or additional energy for removing copper chloride are not required at all, and the problem of chamber contamination due to recondensation during forced vaporization of copper chloride can also be minimized.

Claims

1. In a dry etching method of a copper thin film using a plasma etching process, ACl b Copper chloride (CuCl) generated during the etching process of a copper thin film using a first etching gas of the type x ) to increase the reactivity between hydrogen atoms and XH y A dry etching method for a copper thin film, characterized by supplying a second etching gas of a type.

2. In the first paragraph, the ACl b The first etching gas of the type is A dry etching method for a copper thin film, characterized in that it is a mixture of one or more of HCl, Cl2, BCl3, and CCl4.

3. In the first paragraph, the XH y The second etching gas of the type is NH3, CH4, C2H4, C3H8, C4H 10 , C m H n A dry etching method for a copper thin film, characterized in that it is one or a mixture thereof.

4. In the first paragraph, the ACl b The first etching gas of the type and the above XH y The plasma generated by the supply of the second etching gas of the type A dry etching method for a copper thin film, characterized in that 0.5N(Cl+)≤N(H+) is satisfied (N(H+) is the flux of H+ ions, N(Cl+) is the flux of Cl+ ions).

5. In the first paragraph, the reaction between the copper chloride (CuClx) and hydrogen atoms is Cu + Cl -> CuCl x (solid), 3CuCl x A dry etching method for a copper thin film, characterized in that it comprises a reaction formula of (solid) + 3H(gas) -> Cu3Cl3(gas) + 3HCl(gas).

6. A dry etching method for a copper thin film, characterized in that, in the fifth paragraph, the lower the process temperature of the plasma etching process, the faster the production rate of Cu3Cl3 is than the production rate of copper chloride.

7. In order to increase the reactivity between the copper chloride and hydrogen atoms in paragraph 1, A dry etching method for a copper thin film characterized by further increasing the electron temperature (Te).

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