TW388938B - Method for increasing etch selectivity of metal wire - Google Patents

Abstract

In an ordinary etching procedure in a production process of an IC metal wire, the photoresist layer used as the mask will be damaged and reduced in thickness during the etching process because the etch selectivity between the metal layer and the photoresist layer is not high. In the past, the size of the device is higher, therefore the properties of the IC will not be affected significantly. However, with the miniaturization of the devices, the thickness of the photoresist layer decreases as well. Gradually, the photoresist layer is no longer capable of providing sufficient anti-etching power. Therefore, the present invention provides an improved method of producing an IC metal wire, which comprises applying a nitrogen plasma treatment procedure on the photoresist layer prior to the etching procedure in order to increase the etch selectivity between the metal layer and the photoresist layer. As a result, the photoresist layer, regardless of a decrease in the thickness thereof along with the miniaturization of the device, can still provide a sufficient etch mask function without affecting the etching effect of the metal wire.

Description

V. Description of the invention (1) --- The present invention relates to the manufacture of semiconductor integrated circuits, and in particular to an improved process for metal wires of integrated circuits. A nitrogen treatment process is used to enhance the anti-etching ability of the photoresist layer. It can improve the etching selectivity of the metal guiding process, and is suitable for the process of reducing the size of the component. As everyone knows, as long as the electronic components are inevitable, they must be metal wires that carry current, and so are semiconductor integrated circuits. Many components must be properly connected by connecting the wires to achieve their proper functions. In the process of semiconductor integrated circuits, aluminum metal has a low resistivity and good adhesion to the silicon oxide layer. Therefore, it is generally used as the main conductive material of the component 'to reduce the RC time delay' and improve the component. Switching frequency. However, due to the aluminum deposited by sputtering, after annealing, it usually exists in the form of polycrystalline crystal (polily_crystalUne). When the current passes through the aluminum metal, the aluminum atoms will Moving to the grain boundary causes the so-called electromigration phenomenon. In severe cases, the aluminum metal wire is often broken. Therefore, the current process usually adds a small amount of copper to aluminum in order to prevent the content of about 0.5 to 4%, and it becomes an aluminum-copper alloy (AlCu). Then, using a photoresist layer pattern as a mask, an etching process is performed on the above-mentioned aluminum-copper alloy layer to define its pattern, that is, a required interconnecting wire is formed. However, the above conventional money engraving method has a potential problem that the etching selectivity between the metal layer and the photoresist layer is not large, which is not conducive to the process of reducing the size of the device. In order to further understand the problem, the following is a detailed description of the general process of forming metal wires with reference to Figures 丨 and ⑺. First, as shown in Figure 9

C: \ PrograraFiles \ Patent \ 0503-3692-e. Ptd page 4 V. Invention description (2) Provide a semiconductor substrate 10, such as a silicon wafer, on which necessary semiconductor elements can be formed For the sake of simplicity, only a flat substrate 10 is used here. Next, a physical vapor deposition (PVD) technique is used, such as an electron beam evaporation (eiectr0I1 beam evaporation) process or a SpUtterjng process, to form a copper alloy layer 11 overlying the substrate 10. Then, a photoresist layer 12 is formed on the surface of the aluminum-copper alloy layer 11 by a spin coating method, and a pattern for covering the wire portion is defined by a lithography imaging program. Next, please refer to FIG. 1B, using the pattern of the photoresist layer 12 as a mask, to perform an etching process on the aluminum-copper alloy layer 11 such as a reactive ion etching (RIE) process using a gas containing gas to form The required metal wire 11a. Among them, since the etching selectivity between the aluminum-copper metal layer and the photoresist layer 12 is not so great ', the photoresist layer used as a mask will also be consumed during the etching process' to become the structure 12a shown in the figure. In the past, due to the large size of the element, and the partially etched photoresist layer will react to form a polymer film 13 to protect the side wall of the metal wire 11a, so it can still make up for the lack of resistance of the photoresist layer 12 to the etch, without affecting the Element properties. However, the thickness of the photoresist layer 12 has been reduced as the size of the device has been reduced, and it has gradually failed to provide sufficient etching resistance. Figures 2A and 2B are schematic cross-sectional views to illustrate this problem. 6 First, as described in Figure 1A, an aluminum-copper metal layer 21 is formed by a physical vapor deposition technique to cover a semiconductor. On the substrate 21 "Next, a photoresist layer 22 is coated on the surface of the aluminum-copper metal layer 21, and a pattern covering the wire portion is defined by a lithography imaging program" Here, in order to define a smaller size

0: \? 1 * 〇 £ 3 * 3111 卩 1168 \? 816111 \ 0503-3692-6. 卩 VII (1 page 5 5. Description of the invention (3) Metal wire case, the thickness of the photoresist layer 22 is also matched Reduce a lot, as shown in FIG. 2A. Next, referring to FIG. 2B, using the pattern of the photoresist layer 22 as a mask, an etching process is performed on the aluminum-copper alloy layer 21, for example, using chlorine A reactive ion etching (RIE) process of the gas in order to form the required metal wires. However, the reduced thickness of the photoresist layer 22 does not provide sufficient resistance to etching. Therefore, when the etching process proceeds to the next stage, all the photoresist layers 22 has been depleted, so that the remaining aluminum-copper alloy layer 21a cannot form the required metal wire structure. In order to improve the above problem, an improved etching method has been proposed 'as shown in circle 2C, which is in an etching gas The so-called "passivation gas" is added, such as HC1, HBr, or CHF3, etc., to reduce the loss of the photoresist layer 22, and a polymer film can be formed to protect the sidewall of the metal wire 2la, thereby achieving improvement Efficacy of etch selectivity. However 'The polymers formed by these passivation gases are different from those formed by the photoresist layer etched in the past, which often changes the conditions of the reaction tank'. Not only may it affect the properties of the product components, but it also increases the complexity of the process. This leads to a decrease in production efficiency. Therefore, in order to further process the finer size of the fine body circuit, it is necessary to seek other solutions. In view of this, one object of the present invention is to provide a metal circuit for a integrated circuit The improved process can enhance the anti-etching ability of the photoresist layer, and enhance the etching selectivity between the metal layer and the photoresist layer, so as to meet the process requirements of the downsizing device. Another object of the present invention is to provide a integrated circuit metal Improved process of wires' which can use in_situ processing method to improve gold

C: \ Program Files \ Patent \ 0503-3692-e.ptd page 6

: Etch selectivity between the layer and the photoresist layer, # to simplify the process and affect the conditions of the reaction tank, thereby ensuring the properties of the product it. " The purpose of the description is "The present invention proposes-a kind of integrated circuit metal guide-nitrogen electricity into the tiger's skin sequence to increase the implementation of a photoresist layer before the sequence" to enhance the anti-shoe engraving ability of the photoresist Etching selection between the resist layers, even when the photoresist layer is thicker and the size of the element is reduced, "reducing the shaw can still provide sufficient military functions" without affecting the etching effect of the metal wire. According to an embodiment of the present invention, a A method of metal fabrication of a foundry circuit capable of improving the etching selectivity between a metal layer and a photoresist layer is suitable for the process of reducing the size of a component. The method includes the following steps: (a) forming a metal layer on a semiconductor substrate; (B) Applying a photoresist layer to cover the surface of the metal layer, and defining a pattern covering the wire portion by a lithography imaging program, wherein the thickness of the photoresist layer is smaller than that of the metal layer; (c) A nitrogen plasma treatment process is applied to the pattern to enhance its resistance to etching; and (d) a photoresist layer pattern treated with a nitrogen plasma is used as a mask, and a passivation-free gas is applied to the metal layer. gas) The dry etching process is used to form a metal wire pattern. According to another embodiment of the present invention, a method for manufacturing a metal circuit of a integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer is suitable for a process of reducing the size of a component, The method includes the following steps: (a) forming a stack including a diffusion barrier layer, a metal layer, and an anti-reflection layer on a semiconductor substrate; (b) ) Coating a photoresist layer on the surface of the anti-reflection layer

C: \ PrograraFiles \ Patent \ 0503-3692-e.ptd Page 7 V. Description of the invention (5) 1 'and define the pattern covering the part of the wire with the lithography imaging program, where the thickness of the photoresist layer is less than the above-mentioned stack (C) implement a nitrogen plasma treatment process on the pattern of the photoresist layer to enhance its resistance to etching; and (d) use the pattern of the photoresist layer treated with nitrogen plasma as a mask to counteract The stack of the reflective layer, the metal layer, and the diffusion barrier layer performs a dry-engraving process without passivation gas to form a metal wire scheme. Among them, the above-mentioned nitrogen plasma treatment process is performed under the conditions of nitrogen flow of about 100 seem, pressure of about 12 mTorr, system power (source power) of about 450W, and bias power (bias powerL @ 15〇w). 10 seconds "In addition, the above-mentioned nitrogen plasma treatment process and the dry name engraving process without passivation gas are performed in the same reaction tank. In order to make the above and other objects, features, and advantages of the present invention more obvious, 'Hereinafter, several preferred embodiments are given, and the drawings are described in detail.' The detailed description is as follows: Brief description of the drawings The cross-sectional views of Figures 1A and 1B show the traditional metal wire manufacturing process of larger components; Section 2A The cross section of Figure 2B 'shows that when the thickness of the photoresist layer decreases as the size of the device decreases, it cannot provide sufficient resistance to etching; the cross section of Figure 2C' shows a conventional metal wire improvement process' By adding a passivation gas to the etching gas, the etching selectivity between the metal layer and the photoresist layer is improved; and the cross-sections in FIGS. 3A and 3B are continued and shown in accordance with an implementation of the manufacturing method of the present invention. Manufacturing process; and

C: \ ProgramFiles \ Patent \ 0503-3692-e. Ptd page 8 V. Description of the invention (6) The cross-section circles in Figures 4A and 4B show the manufacturing process according to another embodiment of the manufacturing method of the present invention. Embodiment 1 Hereinafter, a first embodiment of the improved method of the present invention will be described in detail with reference to Figs. 3A and 3B. First, as shown in FIG. 3A, a semiconductor substrate 30 is provided, for example, a silicon wafer, on which a necessary semiconductor element can be formed. 'For simplicity, here is represented by a flat substrate 30 only. . Next, a physical vapor deposition (PVD) technique, such as an electron beam evaporation process or a sputtering process, is used to form an aluminum-copper alloy layer 31 and cover the substrate 30. Then, a photoresist layer 32 is formed on the surface of the aluminum-copper alloy layer 31 by a spin coating method, and a lithography process is used to define a scheme for covering the lead portion. Next, the substrate 30 is moved into a reaction tank, and a manufacturing process of a metal wire structure is performed. Different from those skilled in the art, here a nitrogen plasma treatment program is first performed on the pattern of the photoresist layer 32, for example, at a nitrogen flow rate of about 100 seem, a power of about 12 mTorr, a system power of about 45 0W, and a bias power Plasma treatment is performed at about 150 W for about 10 seconds, thereby enhancing the etching resistance of the photoresist layer 32. It should be noted that this step can be achieved without changing existing equipment. In fact, when the metal wire pattern is completed in the existing process, a nitrogen plasma processing program is used to neutralize the charged charge on the substrate, thereby The sucked broken wafer is removed (de_chuck), so the present invention just makes full use of this step to achieve additional effects' and does not increase the complexity of the process.

C: \ Program Files \ Patent \ 0503-3692-e.ptd Page 9 V. Description of the invention (7) Please refer to Figure 3B 'In the same reaction tank, use the above-mentioned photoresist layer treated with nitrogen plasma 32杳 索 杳 妆 * κ, ^ »1 is used as a mask, and a #carving procedure is performed on the aluminum-copper alloy layer 31. For example, if you use etch field and & Λτη, Α A reactive ion etching (RIE) process of gas' to form the required metal wire 3U. Among them, although the photoresist layer 32 is lost during the process, but because its anti-etching ability is greatly enhanced by the gas-gas plasma treatment, the thickness of the remaining photoresist layer 32a is still greater than that of a skilled person, which can fully provide The function of etching mask. In this way, by using a nitrogen electropolymerization processing program, the etching selectivity between the aluminum-copper metal layer 31 and the photoresist layer 32 can be improved without adding a passivation gas such as HC1, HBr, or CHF3, thereby defining a fine size. Of metal wires 31a. In addition, 'the above-mentioned passivation gas is not used, and other types of polymer films will not be formed during the etching process', thereby preventing the conditions of the reaction tank from being changed to affect the properties of the product components. Furthermore, since the nitrogen plasma treatment process and the reactive ion etching process containing a gas are sequentially executed in the same reaction tank, the process complexity is not increased. Embodiment 2 With the development of the reduction in the size of components, the implementation conditions of the lithography imaging program are also becoming more severe. Especially when defining a wire pattern over a metal layer with high reflection properties, an anti-reflection layer is used. ) Improved processes to eliminate interference caused by optical reflections and thus improve the accuracy of lithography imaging have become common. The following description with reference to Figs. 4A and 4B 'is another embodiment in which the above-mentioned improved method is applied to the structure of a wire including an anti-reflection layer. First, a diffusion is sequentially formed on a semiconductor substrate 30

C: \ ProgramFiles \ Patent \ 0503-3692-e.ptd page 10 V. Description of the invention (8) Diffusion barrier layer 37, a metal layer 31, and an anti-reflection layer 38 ' A titanium nitride (TiN) layer 37, an aluminum-copper alloy layer 31, and another titanium nitride layer 38 are formed to form a laminated structure as shown in FIG. 4A. Next, a photoresist layer 32 is formed on the antireflection layer over the surface of the antireflection layer by spin coating, and a pattern for covering the lead portion is defined by a lithography process. Next, the substrate 30 is moved into a reaction tank, and a manufacturing process of a metal wire structure is performed. Similarly, a nitrogen plasma treatment program is first performed on the pattern of the photoresist layer 32, for example, under the conditions of a nitrogen flow of about 100 seem, a pressure of about 12 mTorr, a system power of about 450 W, and a bias power of about 150 W. The plasma treatment is performed for about a second, whereby the etching resistance of the photoresist layer 32 can be enhanced. Please refer to FIG. 4B. In the same reaction tank, the above-mentioned pattern of the photoresist layer 32 treated with nitrogen gas is used as a mask, and the anti-reflection layer 38, the metal layer 31, and the diffusion barrier layer 37 are laminated. An etching process is, for example, a reactive ion etching (RIE) process using a gas-containing vessel to form a desired metal wire structure (38a, 31a, and 37a). Among them, although the photoresist layer μ is lost during the engraving process, but its anti-etching ability is greatly enhanced by the nitrogen plasma treatment, so it can fully provide the function of the etching mask and define a fine-sized metal wire. Once again, the etching selectivity between the aluminum-copper metal layer 31 and the photoresist layer 32 is improved by a nitrogen plasma treatment process, which is suitable for manufacturing fine-sized metal wires 31a. In addition, since the above-mentioned passivation gas is not used, other kinds of polymer films will not be formed during the etching process, so the reaction tank can be prevented

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5. Description of the invention (9) The conditions are changed to affect the properties of product components. In addition, the μa a shower, the upper gas and gas processing procedures and the gas-containing active ion etching procedures are sequentially performed in the same reaction tank, so the process complexity is not increased. · 'Although the present invention has been disclosed as above by the description of the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes and decorations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the appended patent application.

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Claims (1)

6. Application for Patent Fan Yuan 1. A method for manufacturing integrated circuit metal wires capable of improving the etching selectivity between the metal layer and the photoresist layer, which is suitable for the process of reducing the size of the component. The method includes the following steps: (a ) Forming a metal layer on a semiconductor substrate; (b) coating a photoresist layer on the surface of the metal layer, and defining a pattern covering the wire portion by a lithography imaging program, wherein the photoresist layer Those with a thickness smaller than that of the metal layer; (c) performing a nitrogen plasma treatment process on the pattern of the photoresist layer to enhance its resistance to etching; and (d) using the pattern of the photoresist layer treated with nitrogen plasma to As a mask, a dry etching process is performed on the metal layer without a passvation gas to form a metal wire scheme. 2. A method for manufacturing a metal circuit of an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer as described in item 1 of the scope of the patent application, wherein the step is (a) the metal layer is an AlCu layer ). 3. The method for manufacturing integrated circuit metal wires capable of improving the etching selectivity between the metal layer and the photoresist layer as described in item 1 of the scope of the patent application, wherein the step (c) of the nitrogen plasma treatment process is performed at a nitrogen flow rate of about 1 〇〇seem, the pressure of about 12 mTorr, the system power (source power) of about 450W, bias power (bias power) of about 150W plasma treatment for about 10 seconds. 4. A method for manufacturing a metal circuit of an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer as described in item 1 of the scope of patent application, wherein step (d) the dry etching process without passivation gas is a Engraving procedure for the active ion surname of the gas. C: \ ProgramFiles \ Patent \ 0503-3692-e.ptd page 13 6. Patent application scope 5. As described in item 1 of the scope of patent application, a integrated circuit can improve the selectivity between the metal layer and the photoresist layer A method for manufacturing a metal wire, wherein step (d) the passivation gas system HC1, HBr, or CHf3. , '6. As described in item 1 of the scope of the patent application, a method for manufacturing a metal circuit of an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer, wherein step (c) and step (d) are in the same reaction tank Proceeder. 7. —A method for manufacturing a metal wire for a foundry circuit which can improve the etching selectivity between a metal layer and a photoresist layer, and is suitable for the process of reducing the size of the component. The method includes the following steps: (a) forming a diffusion barrier layer (diffusion) A barrier Uyer, a metal layer, and an anti-reflection layer are stacked on a semiconductor substrate; (b) a photoresist layer is coated on the surface of the anti-reflection layer, and The shadow imaging program defines a pattern covering the wire portion, wherein the thickness of the photoresist layer is smaller than that of the laminate; '(c) A nitrogen plasma treatment process is performed on the pattern of the photoresist layer to enhance its resistance to etching ; And (d) using the photoresist layer pattern treated with nitrogen plasma as a mask, and performing a dry etching process without passivation gas on the anti-reflection layer, the metal layer, and the diffusion barrier layer, Used to form metal wire cases. 8. As described in item 7 of the scope of the patent application, a method for manufacturing a metal circuit for an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer, wherein the step (a) the diffusion barrier layer is a titanium nitride (TiN )Floor. 9. A metal layer and light can be improved as described in item 7 of the scope of patent application 6. Scope of patent application Method for manufacturing integrated circuit metal wires with selective etching between resist layers, wherein step (a) the metal layer is an aluminum-copper alloy layer (A1Cu iayer). 10. The manufacturing method of integrated circuit metal wire capable of improving the etching selectivity between the metal layer and the photoresistive layer as described in item 7 of the scope of patent application, wherein in step (a), the anti-reflection layer is a titanium nitride (TiN) layer . 11. As described in item 7 of the scope of the patent application, a method for manufacturing integrated circuit metal wires capable of improving the etching selectivity between a metal layer and a photoresist layer, wherein the step (c) of the nitrogen plasma treatment process is performed at a nitrogen flow rate of about 1 The plasma treatment was performed at a pressure of about 12 mTorr ', a system power of about 450 W, and a bias power of about 150 W for about 10 seconds. 12. As described in item 7 of the scope of patent application, a method for manufacturing a metal circuit of integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer, wherein step (d) the dry etching process without passivation gas is a Reactive ion etching procedure using chlorine gas. 13. A method for manufacturing a metal circuit of an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer as described in item 7 of the scope of the patent application, wherein step (d) the passivation gas system HC1, HBr, or CHF3. 14. A method for manufacturing a metal circuit of an integrated circuit capable of improving the etching selectivity between a metal layer and a photoresist layer as described in item 7 of the scope of patent application, wherein steps (c) and (d) are performed in the same reaction tank . C: \ Program Files \ Patent \ 0503-3692-e.ptd page 15