JP2011504299A - Bevel plasma treatment to enhance wet edge cleaning - Google Patents

Abstract

【Task】
Various embodiments described herein provide an improved mechanism for removing unwanted deposits on a bevel edge to improve process yield. Embodiments provide an apparatus and method for treating a beveled edge of a copper-plated substrate to convert the beveled edge copper into a copper compound that can be wet etched by a fluid with a higher etch selectivity than copper. In one embodiment, wet etching of a copper compound with a high selectivity to copper can remove non-volatile copper at the substrate bevel edge in a wet etch processing chamber. Plasma treatment at the bevel edge removes copper at the bevel edge to a range of about 2 mm or less (eg, about 1 mm, about 0.5 mm, or about 0.25 mm) from the edge surface of the substrate with precise spatial control. Enable. Furthermore, the above-described apparatus and method for removing copper at the bevel edge does not have the problem of copper etching fluid splashing into the device region causing defects and thinning of the copper thin film. Therefore, the device yield can be greatly improved.
[Selection] Figure 2A

Description

  The present invention relates generally to substrate manufacturing techniques, and more particularly to an apparatus and method for converting a beveled edge thin film (such as copper) into a liquid soluble material using plasma exposure. The film converted at the bevel edge is then removed by a wet etchant having a high etch selectivity.

  In the processing of substrates such as semiconductor substrates (or wafers) or glass panels such as those used in the manufacture of flat panel displays, plasma is often utilized. During substrate processing, a substrate (or wafer) is divided into a plurality of dies or rectangular areas. Each of the plurality of dies becomes an integrated circuit. The substrate is then processed in a series of steps in which material is selectively removed (ie, etched) and deposited.

  Copper has a lower resistivity and better electromigration and stress void resistance than aluminum, making it an optimal conductor for device interconnection for many integrated circuit manufacturers. One method of forming a copper interconnect structure uses an electroplating process. In a typical copper electroplating process, a tantalum (Ta) and / or tantalum nitride (TaN) barrier layer is first deposited on the substrate. Next, a copper seed layer is formed on the barrier layer. The copper seed layer can be deposited by various techniques including chemical vapor deposition (CVD) and physical vapor deposition (PVD). The substrate is then placed in a bath of electrolyte plating solution to deposit a copper layer (also referred to as a gap fill layer) on the copper seed layer.

  After plating is complete, the substrate is typically transferred to a rinse station where a solution containing deionized water is supplied to remove and neutralize any excess or residual plating solution on the substrate. During the plating process, undesirable copper plating may occur on the bevel edge and / or backside of the substrate, which is a source of particulates. Removal of unwanted copper plating on the backside of the substrate is relatively easy. However, removal of unwanted copper plating on the bevel edge is more difficult.

  In view of the above, there is a need for an apparatus and method that provides an improved mechanism for removing undesirable deposits on the bevel edge for improved process yield.

  In general, embodiments meet the above requirements by providing an improved mechanism for removing unwanted deposits on the bevel edge to improve process yield. The above-described embodiments provide an apparatus and method for treating a bevel edge of a copper plated substrate to convert the bevel edge copper into a copper compound that can be wet etched by a fluid with a higher etch selectivity than copper. Alternatively, the copper compound can be etched in a dedicated bevel edge plasma etch chamber. Either wet etching or dry etching of the copper compound makes it possible to remove non-volatile copper in a wet etching process chamber or a dedicated dry etching plasma chamber. Plasma processing at the bevel edge is performed with precise spatial control to a range of about 2 mm or less (eg, about 1 mm, about 0.5 mm, or about 0.25 mm) from the edge surface of the substrate (edge itself). Allows removal of bevel edge copper. Furthermore, the above-described apparatus and method for removing copper at the bevel edge does not have the problem of copper etching fluid splashing into the device region causing defects and thinning of the copper thin film. Therefore, the device yield can be greatly improved.

  It should be understood that the present invention can be implemented in various forms, such as a process, apparatus, or system. In the following, several embodiments of the present invention will be described.

  In one embodiment, a method is provided for treating a copper film on a bevel edge of a substrate to convert the copper film into a copper compound that is removed by wet etching. The method comprises disposing a substrate on a substrate support in a plasma processing chamber. The method further comprises flowing a process gas through a gas supply incorporated in a gas distribution plate that is spaced apart from the substrate support. The method further comprises generating a processing plasma near the bevel edge of the substrate to convert the copper thin film on the bevel edge of the substrate into a copper compound. The generated processing plasma converts a copper thin film in a range of less than about 2 mm from the edge surface of the substrate into a copper compound. The method further comprises the step of placing the substrate in a wet etching apparatus that includes a wet etching fluid to remove the copper compound on the bevel edge.

  In another embodiment, a method is provided for treating a copper film on a bevel edge of a substrate to convert the copper film into a copper compound that is removed by wet etching. The method comprises the steps of removing the copper thin film on the back surface of the substrate and placing the substrate on a substrate support in the plasma processing chamber after removing the copper thin film on the back surface of the substrate. The method further comprises flowing a process gas through a gas supply incorporated in a gas distribution plate that is spaced apart from the substrate support. The method further comprises generating a processing plasma near the bevel edge of the substrate to convert the copper thin film on the bevel edge of the substrate into a copper compound. The generated processing plasma converts a copper thin film in a range of less than about 2 mm from the edge surface of the substrate into a copper compound. The method further comprises the step of placing the substrate in a wet etching apparatus that includes a wet etching fluid to remove the copper compound on the bevel edge. The wet etch selectivity for the copper film when the copper compound on the bevel edge is etched from the bevel edge by the wet etch fluid is greater than about 20: 1.

  Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

  The present invention can be readily understood from the following detailed description with reference to the accompanying drawings. In addition, the same code | symbol has shown the same structural element.

1 is a cross-sectional view illustrating a copper plated substrate in accordance with one embodiment of the present invention.

FIG. 2 illustrates an apparatus for removing unwanted copper from a substrate backside and bevel edge, in accordance with one embodiment of the present invention.

1 is a cross-sectional view of a portion of a copper-plated substrate after copper etching fluid has diffused from the back surface of the substrate to cover the bevel edge and a portion of the front surface of the substrate, in accordance with one embodiment of the present invention.

FIG. 3 illustrates a copper plated substrate after a processing step that removes unwanted copper on the back and bevel edges, in accordance with one embodiment of the present invention.

1 is a cross-sectional view illustrating a copper-plated substrate in which the vicinity of the bevel edge is exposed to plasma according to one embodiment of the present invention.

FIG. 4 shows a copper plated substrate after undergoing wet etching to remove bevel edge copper compounds in accordance with one embodiment of the present invention.

1 is a cross-sectional view illustrating a plasma system configured to generate bevel edge plasma in accordance with one embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view illustrating a region B including the bevel edge of FIG. 3 according to an embodiment of the present invention.

6 is a flowchart illustrating a process for removing copper at a bevel edge, in accordance with one embodiment of the present invention.

6 is a flowchart illustrating a process for removing copper at a bevel edge, in accordance with another embodiment of the present invention.

  Several exemplary embodiments of an improved mechanism for removing unwanted deposits on the bevel edge of a wafer are provided for increased process yield. It will be apparent to those skilled in the art that the present invention may be practiced without some or all of the specific details set forth herein.

  FIG. 1A illustrates a cross-sectional view of a copper plated substrate 105 having a substrate body 100 having a front surface 110, a back surface 120, and a very edge 130 between the front and back surfaces, in accordance with one embodiment of the present invention. Show. The substrate body 100 may be a wafer without other thin films and features. The substrate body 100 may have various thin films and features formed by pretreatment. The substrate 105 in FIG. 1A is upside down with the front side 110 of the substrate facing down. In FIG. 1A, there is a barrier layer 101 such as tantalum (Ta) and / or tantalum nitride (TaN) that covers the substrate front surface 110 and the edge surface 130. In one embodiment, the Ta, TaN, or Ta / TaN barrier layer thickness is less than 150 mm. The barrier layer 101 covers the front surface of the substrate, the bevel edge, and sometimes a part of the back surface of the substrate.

  On the barrier layer 101 is a copper seed layer necessary to initiate nucleation sites during copper plating. The copper seed layer 102 can be deposited by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The copper seed layer 102 shown in the embodiment of FIG. 1A is deposited by PVD and covers the front surface of the substrate, the bevel edge, and sometimes the back surface of the substrate. In one embodiment, the thickness of the copper seed layer may be less than 2000 mm, preferably less than 1000 mm. On the copper seed layer 102, there is a copper layer 103 deposited by a plating process such as electrolytic plating (ECP). The thickness of the copper layer is between about 500 mm and about 8000 mm.

  The copper layer 103 is formed on the seed layer 102 during the plating process. The copper layer 103 is mainly formed on the portion of the substrate covered by the copper seed layer 102. After the copper layer 103 is formed, there is a copper surface 131 that covers the edge surface 130 of the substrate and a copper surface 111 that covers the front surface of the substrate 100.

  During the plating process, undesirable copper plating may occur at the edge and / or back of the substrate. The extent of such undesirable plating depends in part on the formation of the seed layer. In addition, some copper plating processes use a shadow mask or similar technique during seed layer deposition to eliminate deposition on the outermost periphery (eg, the outer 2 mm) around the substrate. In the example shown in FIG. 1A, no shadow mask is used during the deposition of the seed layer.

  In one embodiment, an excessive formation of copper plating (in the figure, edge bead 150) is formed at the edge of layer 103. The edge bead 150 may be caused by a locally high current density at the edge of the seed layer 102, and is typically formed within 2 to 5 mm from the edge surface 130. Increasing the thickness by the edge bead 150 is not desirable because the surface of the substrate 105 is not flat by the edge bead. In addition, the edge beads 150 may fall off during subsequent processing, causing particulate problems. Layers 101, 102, and 103 form a composite layer 104.

  Copper deposited on the bevel edge and the backside of the substrate is undesirable. Devices cannot be formed at the bevel edge and the edge of the backside of the substrate. Copper films deposited in these areas can cause particulate problems during subsequent processing. Furthermore, copper deposited in these areas can contaminate the processing chamber used to process the substrate. Copper in a processing chamber contaminated with copper may be deposited or dropped onto other substrates that are processed in the processing chamber contaminated with copper and can diffuse into the device area and render the device inoperable.

  Furthermore, copper is a non-volatile metal and cannot be removed by a dry etching process. If undesired copper on the bevel edge and the backside of the substrate is etched during the plasma processing, the copper will remain in the processing chamber. To remove copper deposits, it is necessary to stop the chamber for wet cleaning, for example manually. Interrupting continuous processing for wet cleaning can have a significant impact on manufacturing throughput. Therefore, it is important to remove unwanted copper on the bevel edge and the backside of the substrate before the next plasma treatment.

  After plating the substrate 105 with the copper layer 103, the substrate 105 is subjected to a processing step of neutralizing and removing the copper electrolyte solution remaining in the plating step in one or more processing chambers. After the copper electrolyte solution is removed from the substrate 105, a back surface cleaning process is performed to remove the copper thin film deposited on the back surface 120 and the edge surface 130 of the substrate 105.

FIG. 1B is a diagram illustrating an apparatus 115 for removing unwanted copper from a substrate backside and bevel edge in accordance with one embodiment of the present invention. The substrate 105 is horizontally held in a downward state by a substrate holder (not shown). An inert gas flow such as nitrogen molecules (N ₂ ), helium (He), or argon (Ar) is introduced into the front surface of the substrate 105 through the fluid channel 160 while the substrate is rotated. The fluid flow path 160 is connected to a gas tank 165 that stores an inert gas supplied to the front surface of the substrate 105. A copper etch fluid is introduced from the dispenser 170 to the back surface 120 of the substrate 105. The dispenser 170 is coupled to a liquid flow path 171 connected to a tank 172 that contains a copper etching fluid. In one embodiment, the copper etch fluid is sulfuric acid. In another embodiment, the copper etch fluid is a mixture of sulfuric acid and hydrogen peroxide. In other embodiments, nitric acid, citric acid, or similar cleaning fluids may be used.

  The copper etch fluid diffuses across the back surface 120 of the substrate 105 and covers the copper surface 131 over the bevel edge and a portion of the front surface 111 of the substrate 105. As shown in FIG. 1B, the diffused cleaning fluid forms a thin film 180 on the substrate back surface 120, the copper surface 131 on the bevel edge, and the copper surface 111 on a portion of the substrate front surface. FIG. 1C is a cross-sectional view illustrating a portion of copper-plated substrate 105 after copper etching fluid has diffused from substrate back surface 120 to cover the bevel edge and a portion of the substrate front surface, in accordance with one embodiment of the present invention. The front edge of the copper etching fluid whose distance from the front edge of the copper etching fluid to the edge surface of the substrate body 100 is a distance “A” is moved to a position “E” on the front surface 111 of the substrate by the inert gas flow 161. Stay.

  The process described above uses an inert gas flow to prevent the copper cleaning fluid at a certain distance (such as distance A) from the bevel edge. For advanced technology, it is desirable to extend the available area on the substrate surface to the edge surface of the wafer. Typically, the goal is to extend the available area from the bevel edge to a position about 2 mm (e.g., “A” to 2 mm), preferably to a position about 1 mm from the bevel edge. In future technologies, the available area may be extended from the bevel edge to about 0.5 mm or less than 0.5 mm.

  However, the spatial control of the method and apparatus for removing unwanted copper from the substrate back and bevel edges described above is not very consistent and accurate. It is difficult to maintain the distance “A” consistently at about 2 mm. Also, the copper etch fluid may not completely remove the bevel edge copper. In addition, the copper etch fluid often splatters to other parts of the front surface 111, causing defects, spots, and copper thickness variations in the main device area.

  FIG. 1D illustrates the substrate 105 after a processing step that removes unwanted copper on the back and bevel edges, in accordance with one embodiment of the present invention. As shown in FIG. 1D, several copper islands 110 protrude on the bevel edge. The distance “A” is different for each substrate. Further, the copper etching fluid is scattered and the copper thickness is reduced in some regions (regions a and b, etc.).

  For advanced technologies that extend the available area to a position less than 1 mm from the substrate edge, the above process can be used to move the available area from the substrate edge to less than 1 mm with a precise control of about ± 0.1 mm or less. It does not have enough precision to expand.

FIG. 2A shows a cross-sectional view of a substrate 105 ′ where the vicinity of the bevel edge is exposed to plasma 190, in accordance with one embodiment of the present invention. Substrate 105 'has been wet etched to remove the copper on the back, for example using the process described above in FIG. 1B. However, wet etching to remove copper mainly removes copper on the backside of the substrate. Copper on the bevel edge is not subject to removal. Thus, copper is present only on the side surfaces of the bevel edge and the top surface of the substrate, as shown in FIG. 2A. The substrate 105 ′ is disposed on the substrate support 210 in the plasma chamber 200 with the front side facing up. A central portion of the upper surface 111 of the substrate 105 ′ is covered with a plasma shield 220. The exposed bevel edge is a portion from the edge surface 130 to the distance “B”. The copper surface 131 ′ is exposed to the plasma 190 at the edge surface 130, and is converted into a copper compound such as CuO _E , CuO _X F _Y , or CuO _C Cl _D by the plasma 190. E, X, Y, C, and D are numbers. The copper compound can be wet-etched with an etchant (such as a liquid containing ammonium citrate) having a high etching selectivity of the copper compound to Cu. Other examples of the etchant include HF, HCl, and citric acid.

  The distance “B” is an edge exclusion to be realized by the integration process. For example, if the integration process has an edge exclusion condition of 1 mm, the distance “B” is about 1 mm. The distance “B” is controlled by mechanical hardware, so it can be repeated and can be constant.

FIG. 2B illustrates the substrate 105 ′ after undergoing a wet etch to remove copper compounds such as CuO _E , CuO _X F _Y , or CuO _C Cl _D , according to one embodiment of the present invention. Only the thin copper film on the front surface of the substrate that has not been converted to a copper compound such as CuO _E , CuO _X F _Y , or CuO _C Cl _D remains on the substrate. The converted CuO _E , CuO _X F _Y , or CuO _C Cl _D thin film on the bevel edge is etched with a wet etchant. Etching fluids such as ammonium citrate have a high copper compound to copper selectivity ratio, so that the substrate surface is made into an etching fluid for a period of time sufficient to remove all copper compounds without leaving unetched islands. Can be contacted. In one embodiment, the wet etch selectivity is greater than about 20, which means that the ratio of the wet etch rate of the material to the wet etch rate of copper is about 20. In another embodiment, the wet etch selectivity is between about 50 and about 100.

Spatial control is greatly improved by converting the bevel edge copper thin film into a copper compound (such as CuO _E , CuO _X F _Y , or CuO _C Cl _D ) using plasma. Spatial control up to about 1 mm (or less than 1 mm) is possible. Also, the problem of unetched islands is eliminated. Furthermore, since the removal of copper in the previous step is primarily performed on the backside of the substrate, the copper etch fluid is much less likely to scatter to the frontside of the substrate, causing copper defects and thinning in the device area.

  As shown in FIG. 2B, the barrier layer 101 is left on the substrate 105. The barrier layer 101 can be wet etched or etched in a plasma chamber. Since the barrier layer 101 is typically formed of a volatile material (such as Ta and / or TaN), it can be dry etched in the plasma chamber.

  FIG. 3 illustrates one embodiment of a plasma processing chamber 300 for performing plasma processing near the bevel edge of the substrate. The chamber 300 has a substrate support 340 on which a substrate 350 is placed. In one embodiment, the substrate support 340 is an electrostatic chuck that is powered by an RF (radio frequency) power supply (not shown). In another embodiment, the substrate support 340 is a regular electrode. The substrate support 340 may be DC (direct current) or RF biased. A gas distribution plate 360 provided with a central gas supply unit 361 is provided opposite to the substrate support 340. The gas distribution plate 360 includes an edge gas supply unit 363 that supplies gas to the bevel edge of the substrate 350. The substrate support may further be RF powered, biased, or grounded. During the etching of the substrate 350, the chamber 300 may be supplied with RF power to generate a capacitively coupled etch plasma or an inductively coupled etch plasma. The substrate 350 has a bevel edge 317 that includes the upper and lower surfaces of the edge of the substrate, as shown in region B of FIG. 3 and enlarged region B of FIG. 3A. In FIG. 3A, the bevel edge 317 is highlighted with thick straight lines and curves.

  A lower edge electrode 320 made of a conductive material such as aluminum (Al) is provided so as to surround the edge of the substrate support 340. A lower dielectric ring 321 that electrically separates the substrate support 340 and the lower edge electrode 320 is provided between the substrate support 340 and the lower edge electrode 320. In one embodiment, the substrate 350 is not in contact with the lower edge electrode 320. Another lower insulating ring 325 is provided outside the lower edge electrode 320 to extend the surface of the lower edge electrode 320 on the substrate 350 side.

  Surrounding the gas distribution plate 360, an upper edge electrode 310 made of a conductive material such as aluminum (Al) is provided. Upper edge electrode 310 is electrically isolated from gas distribution plate 360 by upper dielectric ring 311. An upper insulating ring 315 is provided outside the upper edge electrode 310 to extend the surface of the upper edge electrode 310 on the substrate 350 side.

  In one embodiment, the lower edge electrode 320 is connected to the RF power source 323 and the upper edge electrode 310 is grounded. During processing of the bevel edge of the substrate, the RF power supply 323 provides RF power at a frequency between about 2 MHz and about 60 MHz and at a power between about 100 watts and about 2000 watts to generate a processing plasma. To do. During the bevel edge process, the substrate support 340 and the gas distribution plate 360 are kept electrically floating. In another embodiment, the lower electrode 340 is connected to the RF power source 324. During processing of the bevel edge of the substrate, the RF power source 324 supplies RF power at a frequency between about 2 MHz and about 60 MHz and at a power between about 100 watts and about 2000 watts to generate a processing plasma. To do. During the bevel edge process, the gas distribution plate 360 is maintained to be electrically floating, and the lower edge electrode 320 and the upper edge electrode 310 are both grounded.

  The two embodiments of the hardware configuration described above are exemplary only, and other configurations of bevel edge reactors may be used. For details of other types of bevel edge reactors, see US patent application Ser. No. 11 / 758,576 filed Jun. 5, 2007 (Attorney Docket LAM2P589) “Edge Electrodes with Variable Power”, June 5, 2007. US Patent Application No. 11 / 758,584 (Attorney Docket No. LAM2P592) “Edge Electrodes with Dielectric Covers”, US Patent Application No. 11 / 440,561, filed May 24, 2006 (Attorney Summary) No. LAM2P560) "Apparatus and Methods to Remove Films on Bevel Edge and Backside of Wafer", filed February 15, 2006 Application No. 11 / 355,458 (Attorney Docket Number LAM2P537) “Plasma Processing Reactor with Multiple Capacitive and Inductive Power Sources”, US Patent Application No. 11 / 363,703 filed Feb. 27, 2006. No. LAM2P538) See “Integrated Capacitive and Inductive Power Sources for a Plasma Etching Chamber”. The disclosure of each of the related patent applications cited herein is hereby incorporated by reference.

The processing plasma is configured to be confined by the upper dielectric ring 311, the upper edge electrode 310, the upper insulating ring 315, the lower dielectric ring 312, the lower edge electrode 320, and the lower insulating ring. One or more processing gases are supplied through the gas supply unit 361. In one embodiment, the gas supply is located near the center of the gas distribution plate 360. Alternatively, one or more process gases may be supplied through a gas supply located in other portions of the process chamber 300, for example, through the edge gas supply 363 located near the bevel edge of the substrate 350. It may be supplied at the edge.

In one embodiment, the spacing D _EE between the upper edge electrode 310 and the lower edge electrode 320 is less than 1.5 cm, thereby ensuring plasma confinement. With a D _EE of less than 1.5 cm, the ratio between the width (D _W ) and the opening gap near the substrate edge (D _EE ) can be less than 4: 1, thereby Plasma confinement is guaranteed. D _W is the width of the opening near the substrate edge. In one embodiment, D _W is the width of the lower insulating ring 325 or the width of the upper insulating ring 315. The chamber pressure is maintained between about 20 mTorr and about 100 Torr, more preferably between about 100 mTorr and about 2 Torr during bevel edge processing. The spacing D _S between the gas distribution plate 360 and the substrate 350 is less than 0.6 mm so that no plasma is formed between the gas distribution plate 360 and the substrate 350 during bevel edge processing.

  The embodiment of the plasma chamber 300 shown in FIG. 3 is merely exemplary. Other embodiments of the plasma chamber for bevel edge processing are possible. In another embodiment, an RF power source may be connected to the upper edge electrode 310 and the lower edge electrode 320 may be grounded to generate a capacitively coupled plasma. Alternatively, either the upper edge electrode 310 or the lower edge electrode 320 may be replaced with an induction coil embedded in a dielectric material. In this embodiment, the induction coil is connected to the RF power source and the opposite edge electrode is grounded. The RF power supply supplies power to generate an inductively coupled etch plasma for processing the bevel edge 317. For a further description of the plasma chamber, see US patent application Ser. No. 11 / 3440,561, “Apparatus and Methods to Remove Films on the Edge and Backside of Wafer,” filed May 24, 2006. The disclosures of the related patent applications cited herein are hereby incorporated by reference.

The plasma generated near the substrate edge and between the upper edge electrode 310 and the lower edge electrode 320 treats the copper exposed at the bevel edge, and the copper film at the bevel edge is removed from CuO _E , CuO _X F _Y , or CuO _C Cl. Convert to _D etc. In one embodiment, the processing plasma gas source includes an oxygen-containing gas, such as O ₂ , CO ₂ , and N ₂ O. The oxygen-containing gas assists in converting the copper thin film into an oxygen-containing compound such as CuO _E , CuO _X F _Y , or CuO _C Cl _D. The processing gas source may include a fluorine-containing gas (such as NF ₃ , SF ₆ , C ₂ F ₆ , or CF ₄ ) or a chlorine-containing gas (such as Cl ₂ or HCl). Fluorine-containing gas helps to convert a copper thin film with a fluorine-containing compound such as CuO _X F _Y. The chlorine-containing gas helps to convert the copper film into a chlorine-containing compound such as CuO _C Cl _D. In one embodiment, the process gas is diluted with an inert gas such as helium (He), argon (Ar), krypton (Kr), xenon (Xe), and radon (Ra).

  For process plasmas containing only oxygen-containing gas, the process temperature is above 200 ° C. The chamber pressure is maintained between about 20 mTorr and about 100 Torr, more preferably between about 100 mTorr and about 2 Torr during bevel edge processing. For a process plasma that includes an oxygen-containing gas and either a fluorine-containing gas or a chlorine-containing gas, the process temperature is between about 10 ° C. and about 50 ° C. and between about 15 ° C. and about 35 ° C. Is preferred. One or more plasma gases may be supplied through the central gas supply 361 or the edge gas supply 363, or through both gas supplies.

  As described above with respect to FIG. 2A, the substrate needs to undergo an initial backside wet etch to remove the backside copper before being sent to the plasma chamber 300 for plasma processing. Thereafter, the substrate is subjected to a plasma treatment for converting the copper thin film near the bevel edge into a Y material. Following the plasma treatment, the substrate is wet etched with one or more chemicals that have a high etch selectivity between the copper compound and copper. FIG. 4A shows a flowchart 400 of a process that uses plasma processing to assist in removing the copper thin film at the bevel edge. In step 401, a copper plated substrate is placed in a backside copper removal apparatus (such as the apparatus shown in FIG. 1B) to remove copper residue on the backside of the substrate. At step 403, the backside copper is removed. In one embodiment, a copper wet etchant is provided on the backside of the substrate. In order to prevent the copper wet etchant from reaching the front side of the substrate, an inert gas is blown onto the front side of the substrate. After the backside copper is removed, the substrate is rinsed and cleaned to remove residual copper wet etchant from the substrate surface.

After the backside copper is removed, the substrate is placed in a bevel edge plasma processing chamber at step 405. In step 407, a processing plasma is generated near the bevel edge to convert the copper film on the bevel edge into a copper compound. Note that the copper compound has a higher wet etching selectivity than copper for the wet etchant for the copper compound. The generated plasma exists only at the bevel edge. The bevel edge plasma processing chamber is configured to limit the plasma to a region near the bevel edge. The distance from the bevel edge of the substrate surface exposed to the processing plasma can be controlled by the reactor design such that it is less than about 5 mm, preferably less than about 2 mm, and most preferably less than 1 mm. Since the processing process is a dry process using appropriate hardware, the bevel edge processing can be spatially controlled so that the variation is about ± 0.1 mm and 1 mm or less. In step 409, the substrate is placed in a wet etcher (such as a tank) and etches converted copper compounds (CuO _E , CuO _X F _Y , CuO _C Cl _D, etc.) that have a higher etch selectivity than copper. Immerse in a wet etch fluid containing chemicals. In one embodiment, the wet etch selectivity is greater than about 20, which means that the ratio of the wet etch rate of the material to the wet etch rate of copper is about 20. In another embodiment, the wet etch selectivity is between about 50 and about 100. The copper compound plasma-treated at the bevel edge is etched, and the copper thin film on the front surface of the substrate remains without being etched. In one embodiment, the wet etching fluid comprises ammonium citrate. In another embodiment, the wet etch fluid includes hydrogen fluoride (HF). In yet another embodiment, the wet etching fluid comprises nitric acid or citric acid.

In the process illustrated in FIG. 4A, the copper-plated substrate is first plasma treated after the backside copper is removed and immediately after the backside copper is removed. However, the bevel edge copper plasma treatment and removal of the bevel edge copper compound with a wet etch fluid can be performed immediately after the backside copper is removed, but may not be performed immediately. A bevel edge plasma treatment that converts copper to a copper compound such as CuO _E , CuO _X F _Y , or CuO _C Cl _D , and removal of the copper compound may be performed after other dielectric deposition and etching processes. Good.

Alternatively, copper compounds such as CuO _E , CuO _X F _Y , or CuO _C Cl _D may be removed by plasma in a dedicated bevel edge plasma chamber similar to that shown in FIG. Copper compounds such as CuO _E , CuO _X F _Y , or CuO _C Cl _D can be obtained by BCl ₃ combined with a carrier gas such as argon (Ar), helium (He), or other types of inert gases. May be removed. The processing temperature is between about 100 ° C and about 300 ° C. The operating pressure is between about 20 mTorr and about 10 Torr.

FIG. 4B shows a process flow 450 using a dedicated bevel edge plasma etch chamber. Processing steps 401, 403, 405, and 407 are the same as the processing steps of FIG. 4A. In step 407, after the bevel edge copper thin film is converted to a copper compound such as CuO _E , CuO _X F _Y , or CuO _C Cl _D , the substrate is subjected to bevel edge plasma, such as treatment with the carrier gas and BCl ₃ described above. Is etched in a bevel edge plasma chamber in step 411 to remove copper compounds such as CuO _E , CuO _X F _Y , or CuO _C Cl _D. The bevel edge plasma chamber may be the same as that used to convert copper to copper compound in steps 405 and 407. Alternatively, the substrate with the copper compound may be transferred to another bevel edge plasma chamber for etching the copper compound. The bevel edge plasma chamber used to etch the copper compound needs to be dedicated due to the non-volatile nature of copper.

  The concept of the present invention can be applied to any substrate having copper at the bevel edge. The substrate need not be plated with copper. For example, in a substrate with a PVD or CVD copper seed layer, the bevel edge copper can be removed by the apparatus and method described above.

  The above-described embodiments provide an apparatus and method for treating a bevel edge of a copper plated substrate to convert the bevel edge copper into a copper compound that can be wet etched using a fluid with a higher etch selectivity than copper. Alternatively, the copper compound can be etched in a dedicated bevel edge plasma etch chamber. Etching of either a wet or dry copper compound allows for the removal of non-volatile copper in a wet etch process chamber or a dedicated dry etch plasma chamber. The plasma treatment at the bevel edge allows bevel edge copper to be removed to a range of 1 mm or less (eg, 0.5 mm or 0.25 mm) with precise spatial control. Furthermore, the above-described apparatus and method for removing copper at the bevel edge does not have the problem of copper etching fluid splashing into the device region causing defects and thinning of the copper thin film.

  For better understanding, the above invention has been described in some detail, but it will be apparent that some changes and modifications may be made within the scope of the appended claims. Accordingly, the embodiments are to be regarded as illustrative and not restrictive, and the invention is not limited to the details shown herein, but the appended claims and equivalents. It may be modified within the range.

Claims (20)

A method of treating a copper thin film on a bevel edge of a substrate to convert the copper thin film into a copper compound that is removed by wet etching,
Placing the substrate on a substrate support in a plasma processing chamber;
Flowing a processing gas through a gas supply unit incorporated in a gas distribution plate disposed away from the substrate support;
Generating a processing plasma in the vicinity of the bevel edge of the substrate to convert the copper thin film on the bevel edge of the substrate into a copper compound, the generated processing plasma being about from the edge surface of the substrate; Converting a copper thin film in a range of less than 2 mm into the copper compound;
Disposing the substrate in a wet etching apparatus including a wet etching fluid to remove the copper compound on the bevel edge.   The method of claim 1, wherein the wet etch selectivity for the copper film when the copper compound on the bevel edge is etched from the bevel edge by the wet etch fluid is greater than about 20: 1. . 3. The method of claim 2, wherein the copper compound is selected from the group consisting of CuO _E , CuO _X F _Y , and CuO _C Cl _D , where E, X, Y, C, and D are numbers. Is that way.   The method according to claim 1, wherein the processing gas includes an oxygen-containing gas and either a fluorine-containing gas or a chlorine-containing gas.   The method of claim 1, wherein the wet etch fluid comprises an etchant selected from the group consisting of ammonium citrate, hydrogen fluoride, nitric acid, and citric acid.   The method of claim 1, wherein the generated processing plasma is applied to a copper thin film in a range of about 1 mm or less from the edge surface of the substrate with a spatial control of about 1 / 0.1 mm. How to convert to.   2. The method of claim 1, wherein the substrate comprises a barrier layer, a copper seed layer on the barrier layer, and a plated copper layer on the copper seed layer, the copper thin film comprising: A method comprising both the copper seed layer and the plated copper layer. The method of claim 1, further comprising:
Removing the copper thin film on a back surface of the substrate prior to placing the substrate in the plasma processing chamber.   2. The method of claim 1, wherein the processing plasma near the bevel edge includes a lower edge electrode surrounding the substrate support in the plasma processing chamber, and the gas distribution plate facing the substrate support. The method is produced capacitively or inductively by an upper edge electrode surrounding the substrate.   10. The method of claim 9, wherein a distance between the upper edge electrode and the lower edge electrode is less than about 1.5 cm and confines the processing plasma.   2. The method according to claim 1, wherein the processing gas is a gas disposed by a gas supply unit disposed near a center of the substrate or near the bevel edge of the substrate, or a gas disposed near the center of the substrate. A method wherein the plasma processing chamber is supplied by a supply and an additional gas supply located near the bevel edge of the substrate.   10. The method of claim 9, wherein the distance between the gas distribution plate and the surface of the substrate opposite the distribution plate is such that a plasma is between the gas distribution plate and the surface of the substrate. A method that is less than about 0.6 mm to prevent it from being generated.   3. The method of claim 2, wherein the wet etch selectivity for the copper thin film when the copper compound on the bevel edge is etched from the bevel edge by the wet etch fluid is greater than about 100: 1. . A method of treating a copper thin film on a bevel edge of a substrate to convert the copper thin film into a copper compound that is removed by wet etching,
Removing the copper thin film on the back surface of the substrate;
Placing the substrate on a substrate support in a plasma processing chamber after removing the copper thin film on the back surface of the substrate;
Flowing a processing gas through a gas supply unit incorporated in a gas distribution plate disposed away from the substrate support;
Generating a processing plasma in the vicinity of the bevel edge of the substrate to convert the copper thin film on the bevel edge of the substrate into a copper compound, the generated processing plasma being about from the edge surface of the substrate; Converting a copper thin film in a range of less than 2 mm into the copper compound;
Disposing the substrate in a wet etching apparatus containing a wet etching fluid to remove the copper compound on the bevel edge;
With
The method, wherein the wet etch selectivity for the copper thin film when the copper compound on the bevel edge is etched from the bevel edge by the wet etch fluid is greater than about 20: 1. 15. The method of claim 14, wherein the copper compound is selected from the group consisting of CuO _E , CuO _X F _Y , and CuO _C Cl _D , where E, X, Y, C, and D are numbers. Is that way.   15. The method of claim 14, wherein the process gas includes an oxygen-containing gas and either a fluorine-containing gas or a chlorine-containing gas.   15. The method of claim 14, wherein the wet etch fluid comprises an etchant selected from the group consisting of ammonium citrate, hydrogen fluoride, nitric acid, and citric acid.   15. The method of claim 14, wherein the generated processing plasma converts a copper thin film in a range of about 1 mm or less from the edge surface of the substrate into the copper compound with a spatial control of about 0.1 mm. ,Method.   15. The method of claim 14, wherein the processing plasma near the bevel edge is a lower edge electrode surrounding the substrate support in the plasma processing chamber, and the gas distribution plate facing the substrate support. The method is produced capacitively or inductively by an upper edge electrode surrounding the substrate.   15. The method of claim 14, wherein the wet etch selectivity for the copper thin film when the copper compound on the bevel edge is etched from the bevel edge by the wet etch fluid is greater than about 100: 1. .

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