Hydrogen plasma reduction of metal oxide films to metal

Abstract

Metal oxide films are reduced to metal by atmospheric pressure argon and hydrogen plasma at temperatures of 25-250°C. A 40nm thick copper oxide layer on a 300mm diameter copper-clad silicon wafer can be completely removed in less than 2 minutes by argon and hydrogen plasma at 150°C. The rapid reduction rate from metal oxide to metal indicates that this process is extremely suitable for front-end and back-end semiconductor manufacturing, such as flux-free flip-chip bonding of microbumps.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefit of the following U.S. provisional patent application pursuant to 35 U.S.SC § 119(e), which is incorporated herein by reference.

[0002] U.S. Provisional Patent Application No. 63 / 545,316, filed October 23, 2023, by Williams et al., titled "HYDROGEN PLASMA REDUCTION OF METAL OXIDE FILMS TO METAL" (Agent Reference Number SRFXP013.P1).

[0003] The present invention relates to a plasma apparatus and a method for using the plasma apparatus to remove a metal oxide film from a metal. In particular, the present invention relates to reducing a metal oxide film to a metal using atmospheric pressure argon and hydrogen plasma, wherein the metal is selected from the group including nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lead, bismuth, and alloys thereof. [Background technology]

[0004] Plasma is composed of an ionized gas containing free electrons, cations, and anions. Plasma is "quasi-neutral," meaning the sum of the charges relative to the number of free electrons, cations, and anions is zero. Plasmas used in material processing are generally weakly ionized, meaning only a small fraction of the species in the gas are charged. These free electrons in the gas discharge are accelerated to extremely high speeds, exhibiting an electron temperature in the range of 1.0–3.0 electron volts (eV). These high-energy electrons collide with molecules such as oxygen (O2) or hydrogen (H2), dissociating them into atoms such as O or H. These atoms react with other species in the gas or on the substrate, facilitating desired material processes such as surface cleaning and activation for adhesion, metal oxide removal for intermetallic bonding, thin film etching, and thin film deposition. For example, a copper oxide (CuO) film on a copper surface can be removed by the reaction CuO + 2H = Cu + H2O with H atoms. The physics and chemistry of weakly ionized plasmas are described in several textbooks. For example, see Lieberman and Lichtenberg, “Principles of Plasma Discharges and Materials Processing,” (John Wiley & Sons, Inc., New York, 2005); FFChen and JPChang, “Lecture Notes on Principles of Plasma Processing,” (Kluwer Academic / Plenum Publishers, New York, 2003); and Raizer, YP, “Gas Discharge Physics,” (Springer-Verlag, Berlin, 1991).

[0005] Over the past 25 years, atmospheric pressure plasma has been developed as an alternative to vacuum plasma. Atmospheric pressure plasma can generate much higher concentrations of reactive species than vacuum plasma, allowing for higher throughput substrate processing. This significantly reduces the manufacturing costs of expensive products such as semiconductor devices. The physics, chemistry, and applications of atmospheric pressure plasma are described in numerous publications (see, for example, Winter, et al., “Atmospheric pressure plasma jets: an overview of devices and new directions,” Plasma Sources Science and Technology, vol.24.6, p.064001 (2015); Tendero, et al., “Atmospheric pressure plasmas: A review,” Spectrochimica Acta Part B: Atomic Spectro., vol 61.1, p.2 (2006); and Schutze, et al., “The atmospheric-pressure plasma jet: A review and comparison to other plasma sources,” IEEE Trans.Plasma Sci.26, 1685-1694 (1998)). These gas discharges depend on how the ionization process is controlled. At atmospheric pressure, the gas density is very high, which can cause the ionization reaction to run out of control and generate high-temperature arcs, which are not useful for material processing.

[0006] In U.S. Patents 9,406,485, 10,032,609, 10,800,092, and 11,518,082, Cheng et al. describe a plasma apparatus and method operating with argon or helium at atmospheric pressure and low temperature to generate high concentrations of reactive species in the exhaust stream. Ions and electrons form a collision sheath at the boundary to uniformly fill the gas volume between electrodes and repel electrons to maintain the plasma. The atmospheric pressure argon (or helium) plasma is driven by a 27.12 MHz radio frequency (RF) power supply. A 13.56 MHz RF power supply is also likely to be usable for this application. Depending on the RF output level, the neutral gas temperature range is 323–573 K. Molecular gas is supplied with helium or argon at a concentration of 0.5–5.0 volume%.

[0007] Moravej et al., in "Physics of High-Pressure Helium and Argon Radio-Frequency Plasmas" J.Appl.Phys., vol.96, p.7011 (2004), showed that weakly ionized, homogeneous glow plasmas can be generated at atmospheric pressure. In these plasmas, the average electron density is 10 11 ~10 12 cm -3 However, the neutral gas density is 2.0 x 10⁻⁶ 19 cm -3 The average electron temperature is in the range of 1.0 to 2.0 eV. These authors found that argon plasma is far more difficult to stabilize than helium plasma for several reasons. Firstly, the cross-section of argon is large, comparable to that of nitrogen and oxygen molecules, resulting in a high ionization rate. Secondly, the mass of argon is 20 times that of helium, which reduces the electron mobility in the gas. To maintain a reasonable current through argon discharge, the electron density is 10 12 cm -3The pressure can be increased to a value exceeding [a certain threshold]. In this state, the plasma may transition from alpha mode to gamma mode ionization (see Yang, et al., “Comparison of an Atmospheric Pressure, Radio-Frequency Discharge Operating in the Alpha and Gamma Modes,” Plasma Sources Sci.Technol., vol.14, p.314 (2005); and Shi and Kong, “Mechanisms of the Alpha and Gamma Modes in Radio-Frequency Atmospheric Glow Discharges,” J.Appl.Phys., vol.97, p.023306 (2005)). When the transition from alpha mode to gamma mode occurs, the protective sheath of the electrode wall is destroyed, and ionization occurs. This process causes the plasma to contract into a small spot, resulting in a plasma that is no longer uniform and is no longer useful for material processing.

[0008] To maintain a uniform, weakly ionized argon plasma at atmospheric pressure, the RF output must be limited to a value well below the alpha-to-gamma mode transition. Cheng et al., in U.S. Patent No. 9,406,485, disclosed that a 25 mm linear beam plasma was operated at 150–180 W with 15.0 liters per minute (LPM) of argon and 0.5 LPM of oxygen. The oxygen plasma was used for cleaning and activating the surfaces of silicon, alumina ceramics, carbon fiber reinforced epoxy composites, polyimide, polyurethane, polyethylene, aluminum, and titanium. Atmospheric pressure argon plasma was found to have a faster activation rate than atmospheric pressure helium plasma.

[0009] Cheng et al., in U.S. Patents 9,406,485, 10,032,609, 10,800,092, and 11,518,082, disclose that copper oxide can be removed from copper by treatment with atmospheric pressure argon and hydrogen plasma. A 25 mm linear beam plasma source was operated at 160 W with 15.0 LPM of argon and 1.0 LPM of forming gas (95% nitrogen and 5% hydrogen). In other experiments, a 25 mm linear beam plasma was operated at 150 W with 10.0 LPM of argon and 0.2 LPM of pure hydrogen. In both cases, the plasma source scanned the copper substrate at a distance of 2–3 mm. The thick layer of copper oxide that caused the purple color on the metal surface was removed, revealing the characteristic copper color of the reduced metal. The etching rate of copper oxide is not described.

[0010] In "Atmospheric pressure plasma reduction of copper oxide to copper metal" (J.Vac.Sci.Technol.A., vol.39, p.023001 (2021)), Joyce et al. disclose the removal of copper oxide from copper using atmospheric pressure argon and hydrogen plasmas. These authors measured the etching rate of copper oxide (CuO) with a plasma beam at various substrate temperatures. The etching rate differed depending on whether the sample was a copper lead frame or a copper metal film deposited on a silicon wafer. Table 1 shows the effect of temperature on the recorded CuO removal rate for copper films on wafers. Increasing the substrate temperature from 25°C to 250°C increased the rate approximately tenfold. At 150°C, the oxide removal rate was 0.2 nanometers per second (nm / s). [Table 1]

[0011] In the study by Joyce et al., the Atomflo® 600 atmospheric pressure plasma system was used to remove copper oxide. This system features a 100 mm linear beam plasma operating with a 500 W high-frequency output (27.12 MHz), 33.0 LPM of argon, and 7.0 LPM of forming gas (95% nitrogen and 5% hydrogen), with a standoff distance of 2 mm from the sample. Table 1 shows the scanning speed required to remove a 40 nm thick copper oxide layer from a copper film on a silicon wafer. This value was calculated using the method described in the paper by Joyce et al. The 40 nm thick CuO layer on copper gives the metal a brownish, cloudy appearance.

[0012] Table 1 also lists the time required to complete the process of removing oxides on a 300 mm wafer. Since the plasma beam width is 100 mm, three scans are required across the wafer diameter, i.e., a total of 3 × 300 = 900 mm of scanning. The processing time (minutes) is equal to 900 / S / 60, where S is the scanning speed (mm / s). It is obvious to those skilled in the art that this process is too slow for commercial applications, as it takes 12–15 minutes to complete at substrate temperatures in the 150–200°C range. Therefore, a much faster copper oxide removal process is needed that can achieve a 300 mm wafer throughput within minutes at substrate temperatures below 200°C.

[0013] Besides copper, removal of metal oxides using atmospheric pressure argon and hydrogen plasma would also be beneficial for other metals used in semiconductor manufacturing. For example, this process can be used for deoxidation of two-dimensional arrays of metal microbumps on flip chips. The metal microbumps consist of a tin-silver alloy cap on a copper pillar. In microbump arrays where the pitch (i.e., spacing) between pillars is less than 50 microns, it is necessary to remove oxides from the tin-silver solder cap in a manner that leaves no organic residue. The use of organic flux is not an option. Atmospheric pressure argon and hydrogen plasma can remove oxides without generating organic residues, but for commercial applications, the removal rate must be substantially higher than that shown in Table 1. In view of the foregoing, there is a need for a plasma apparatus and method suitable for removing metal oxides from metals at a throughput suitable for semiconductor manufacturing. These and other needs are met by the embodiments of the present invention described hereinafter. SUMMARY OF THE INVENTION

[0014] One embodiment of the present invention includes an atmospheric pressure plasma apparatus. The apparatus is supplied with at least argon and hydrogen gas to remove metal oxides from a metal selected from the group comprising nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lead, bismuth, and alloys thereof. Plasma is generated within a housing through which a gas stream flows and which is in contact with two electrodes. The electrodes are driven by radio frequency power sufficient to break down the gas and convert it into an ionized gas discharge. Within this device, collisions between hydrogen molecules and high-energy free electrons generate a high density of hydrogen radicals. The hydrogen radicals flow out of the device and travel toward a substrate disposed downstream. The substrate having metal features on its surface is brought into contact with H atoms, and the metal oxides on the surfaces of the metal features are MO x(s) +2xH (g) =M (s) +xH2O (g) is rapidly removed by the reaction, where the subscripts s and g refer to solid and gas, respectively. In the case of copper, the reaction is CuO (s) +2H (g) =Cu(s) +H2O (g) In one embodiment of the present invention, the substrate includes one or more semiconductor devices in the form of dies, wafers, boards, panels, or other structures used in the manufacture and packaging of integrated circuits.

[0015] In another embodiment of the present invention, an atmospheric pressure plasma source supplied with at least argon and hydrogen gas generates a high density of hydrogen radicals across a linear beam ranging in length from 10 mm to 300 mm. The hydrogen radicals emanating from the plasma device are uniformly distributed across the entire beam. In one embodiment of the present invention, a self-contained plasma device scans a substrate having a width equal to or less than the width of the plasma beam, and metal oxides on the surface of metal features on the substrate are rapidly removed at a uniform rate across the entire substrate by contact with hydrogen radicals from the plasma beam. In another embodiment of the present invention, a self-contained plasma device scans a substrate having a width greater than the width of the plasma beam, and metal oxides on the surface of metal features on the substrate are removed at a uniform rate across the entire substrate by scanning and stepping the plasma beam across the substrate.

[0016] In another embodiment of the present invention, an atmospheric pressure plasma source is coupled to a chamber containing a substrate, and the chamber is filled with an inert gas selected from the group of argon and nitrogen. Within the chamber, the substrate comes into contact with a high density of hydrogen radicals in a substantially oxygen-free gas stream. The plasma apparatus and chamber are designed so that a linear plasma beam can scan the substrate, thereby ensuring uniform contact between the substrate and the high density of hydrogen radicals, and rapidly removing metal oxides from metal features distributed throughout the substrate. The inert gas in the chamber may be supplied directly from a self-contained plasma device, or it may be supplied separately to the chamber in addition to the gas stream supplied by the plasma device. In this embodiment of the present invention, a substantially oxygen-free gas stream means that the oxygen concentration is less than 1,000 parts per million (ppm).

[0017] In another embodiment of the present invention, an atmospheric pressure plasma source driven by an RF output and supplied with argon and hydrogen gas generates a high concentration of hydrogen radicals in a substantially particle-free argon stream. The atmospheric pressure plasma source is driven by an RF output and supplied with argon and hydrogen gas. Hydrogen radicals emanating from the self-contained plasma device are uniformly distributed across a linear beam having a width of 10 to 300 mm. The beam of reactive gas comes into contact with the substrate and removes metal oxides from metal features on the substrate without substantially depositing particles larger than 0.1 microns in diameter on the substrate surface. In one embodiment of the present invention, an atmospheric pressure plasma device driven by an RF output and supplied with argon and hydrogen gas scans over a substrate to remove metal oxides from metal features on the surface without substantially depositing particles. Here, the substrate includes one or more semiconductor devices in the form of dies, wafers, boards, panels, or other structures used in the manufacture and packaging of integrated circuits.

[0018] Another embodiment of the present invention is a method for rapidly removing metal oxides from a metal surface by contact with hydrogen radicals emanating from an atmospheric pressure plasma source. The plasma source is driven by a high-frequency output and supplied with gas streams of at least argon and hydrogen. In this embodiment of the present invention, the plasma is generated in a linear beam with a width of 10 to 300 mm, and the hydrogen radicals generated in the plasma beam emanate from the device and come into uniform contact with the substrate. The plasma device scans the substrate to remove metal oxides from metal features on the surface with a throughput of less than a few minutes. In this method of removing metal oxides from metal features on a surface, the process is completed without substantially depositing particles with a diameter of 0.1 microns or larger on the surface.

[0019] Other embodiments of the present invention include an apparatus and a method for depositing a thin film. A self-contained plasma device is combined with a gas injector for volatile precursor molecules and a chamber that accommodates a substrate and is supplied with an inert gas selected from the group of argon and nitrogen. Within the chamber, the substrate is brought into contact with high-density hydrogen radicals flowing out of the plasma device and the volatile precursor molecules flowing out of the injector. The hydrogen radicals and the precursor molecules react with each other, whereby a coating is deposited on the substrate. The chamber is designed such that the plasma device and the injector can scan over the substrate to deposit a uniform coating, and the gas environment is maintained substantially free of oxygen, that is, at an oxygen concentration of less than 1,000 ppm, throughout the entire deposition process. The volatile precursor molecules are selected such that reaction with the hydrogen radicals produces a coating having a desired composition and structure on the substrate.

[0020] Other exemplary embodiments include an apparatus for removing metal oxides from a metal. This apparatus includes a chamber filled with an inert gas such that the oxygen concentration within the chamber is maintained at less than 1,000 parts per million; an atmospheric pressure plasma source located within the chamber, supplied with argon and hydrogen to generate hydrogen radicals and operating at a linear power density greater than 10.0 W / mm; a temperature control plate located within the chamber supporting a substrate containing a metal feature having a metal oxide layer on its surface; and means for moving the substrate and the atmospheric pressure plasma source relative to each other, thereby causing hydrogen radicals emanate from the plasma source to come into contact with the metal oxide layer and convert it into metal and water vapor. The power supply can operate at a high frequency of 13.56 or 27.12 MHz. The inert gas can be selected from the group including argon and nitrogen. The concentration of hydrogen that can be added to the argon gas stream through the plasma can be 0.1 to 5.0 volume percent. The substrate can be heated to a temperature of 20 to 250°C. The substrate can be selected from a group of semiconductor materials including integrated circuits, chips, dies, wafers, panels, chip packages, and printed circuit boards. The metal can be selected from a group including nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lead, bismuth, and their alloys. The metal feature can be a two-dimensional array of microbumps with copper pillars and tin alloy solder caps having a diameter of less than 100 microns, and the metal oxide layer on the tin alloy solder caps is removed.

[0021] In further embodiments, the plasma source may include a linear aperture that generates a beam of reactive gas with a width of 1 to 300 mm. The width of the linear aperture may be at least the same as the width of the substrate containing the metal feature having the metal oxide layer to be removed.

[0022] An exemplary method for removing a metal oxide layer from a metal includes filling a chamber with an inert gas such that the oxygen concentration in the chamber is maintained below 1,000 parts per million, disposing an atmospheric pressure plasma source in the chamber, and operating the atmospheric pressure plasma source using a gas flow of argon and hydrogen and a high-frequency power supply having a power density exceeding 10.0 W / mm to generate hydrogen radicals, disposing a temperature control plate in the chamber, wherein the temperature control plate supports a substrate comprising a metal feature having a metal oxide layer on a surface of the metal feature, and moving the substrate and the atmospheric pressure plasma source relative to each other, such that hydrogen radicals flowing out from the plasma source come into contact with the metal oxide layer and convert it into metal and water vapor. Embodiments of this method of the present invention can be further modified according to any of the apparatus or method embodiments described herein.

[0023] Other exemplary embodiments include a device for forming metal interconnects. The device includes a chamber filled with an inert gas such that the oxygen concentration in the chamber is maintained below 1,000 parts per million, an atmospheric pressure plasma source disposed within the chamber, wherein the atmospheric pressure plasma source is supplied with argon and hydrogen and operates at a linear power density exceeding 10.0 W / mm, a bond head disposed within the chamber, wherein the bond head holds a flip chip with microbumps at a temperature of 20 to 250°C, a temperature control plate disposed within the chamber and heated to 20 to 250°C, wherein the temperature control plate supports a substrate comprising microbumps or metal pads having dimensions substantially similar to the microbumps on the flip chip, and means for scanning the bond head with the flip chip from above the plasma source down onto the substrate, such that the metal oxide on the microbumps is removed by the plasma, and the flip chip is bonded to the substrate to form metal interconnects. Embodiments of this apparatus of the present invention can be further modified according to any of the apparatus or method embodiments described herein.

[0024] Other exemplary embodiments include a method for forming a metal interconnect. This method includes filling a chamber with an inert gas such that the oxygen concentration in the chamber is maintained at less than 1,000 parts per million, arranging an atmospheric pressure plasma source in the chamber, wherein the source is supplied with argon and hydrogen and operates at a linear power density greater than 10.0 W / mm, mounting a bond head in the chamber, the bond head holding a flip-chip having microbumps at a temperature of 20 to 250°C, arranging and heating a temperature control plate in the chamber, the temperature control plate supporting a substrate including microbumps or metal pads having substantially the same dimensions as the microbumps on the flip-chip, and scanning the bond head having the flip-chip from above the plasma source down onto the substrate, thereby removing metal oxides on the microbumps by the plasma and bonding the flip-chip to the substrate to form a metal interconnect. Embodiments of this method of the present invention can be further modified in accordance with any of the embodiments of the apparatus or method described herein.

[0025] Further exemplary embodiments include an apparatus for plasma chemical vapor deposition of thin films. This apparatus includes a chamber filled with an inert gas such that the oxygen concentration in the chamber is maintained at less than 1,000 parts per million; an atmospheric pressure plasma source located in the chamber, which is supplied with argon and hydrogen and operates at a linear power density greater than 10.0 W / mm to generate hydrogen radicals; a gas injector located in the chamber, which is supplied with volatile precursor molecules containing one or more elements to be deposited in a thin film; a temperature control plate located in the chamber and heated to 20-500°C, the plate holding a substrate; and means for moving the substrate, the plasma source and the gas injector relative to each other so that hydrogen radicals emanating from the plasma source combine with precursor molecules emanating from the injector and react with each other to deposit a thin film on the substrate. Embodiments of this apparatus of the present invention can be further modified according to any embodiment of the apparatus or method described herein.

[0026] Further exemplary embodiments include a method for depositing a thin film on a substrate. This method includes filling a chamber with an inert gas such that the oxygen concentration in the chamber is maintained at less than 1,000 parts per million, arranging an atmospheric pressure plasma source in the chamber, the atmospheric pressure plasma source being supplied with argon and hydrogen and operating at a linear power density greater than 10.0 W / mm to generate hydrogen radicals, arranging a gas injector in the chamber, the gas injector being supplied with volatile precursor molecules containing one or more elements to be deposited in the thin film, arranging and heating a temperature control plate in the chamber and heating the temperature control plate to 20 to 500°C, the temperature control plate supporting the substrate, and arranging and heating the substrate, plasma source and gas injector relative to each other so that hydrogen radicals emanate from the plasma source combine with precursor molecules emanate from the injector and react with each other to deposit a thin film on the substrate. Embodiments of this method of the present invention can be further modified according to any of the embodiments of the apparatus or method described herein.

[0027] These embodiments and other embodiments of the present invention will become apparent to those skilled in the art from the following drawings and a detailed description of preferred embodiments.

[0028] Referring to the drawings here, similar reference numbers represent corresponding parts throughout the entire structure. [Brief explanation of the drawing]

[0029] [Figure 1] This is a schematic diagram of exemplary argon and hydrogen plasma apparatus for removing metal oxides from metal features on a substrate. [Figure 2] The images show two pieces of copper-coated silicon wafer after oxidation treatment at 150°C for 5 minutes and 30 seconds. The copper oxide film shows a brown appearance, suggesting that it is a 40 nanometer (nm) thick copper oxide layer. [Figure 3]The images show copper-clad silicon wafer samples scanned at speeds of 5, 10, and 15 mm / s using a 25 mm linear beam plasma source supplied with argon and hydrogen and operating at an RF output of 180 W. The wafers were maintained at 150°C during plasma processing. [Figure 4] The images show copper-clad silicon wafer samples scanned at speeds of 20, 25, 30, and 40 mm / s using a 25 mm linear beam plasma source supplied with argon and hydrogen and operating at an RF output of 550 W. The wafers were maintained at 150°C during plasma processing. [Figure 5] The images show copper-clad silicon wafer samples scanned at speeds of 10, 15, and 20 mm / s using a 50 mm linear beam plasma source supplied with argon and hydrogen and operating at an RF output of 270 W. The wafers were maintained at 150°C during plasma processing. [Figure 6] The images show copper-clad silicon wafer samples scanned at speeds of 15, 20, and 25 mm / s using a 50 mm linear beam plasma source supplied with argon and hydrogen and operating at an RF output of 580 W. The wafers were maintained at 150°C during plasma processing. [Figure 7] The image shows a copper-clad silicon wafer sample after scanning at a speed of 25 mm / s using a 50 mm linear beam plasma source supplied with argon and hydrogen and operating at an RF output of 580 W. During each plasma treatment, the wafer temperature was maintained at 130, 150, and 190 °C. [Figure 8] This is a schematic diagram of an exemplary plasma source in one embodiment of the present invention, showing how a metal oxide is removed from a substrate using a supply gas activated from the plasma in an environment purged with an inert gas. [Figure 9] An exemplary linear beam plasma source is shown in side view and isometric view. [Figure 10] An outlet diagram of an exemplary linear beam plasma source is shown. [Figure 11] This is a schematic diagram of an exemplary apparatus for removing metal oxides under atmospheric pressure and joining flip-chips with microbumps using argon and hydrogen plasma in an inert gas environment. [Figure 12] This is a schematic diagram of an exemplary apparatus for plasma-enhanced chemical vapor deposition of thin films under atmospheric pressure using argon and hydrogen plasma in an inert gas environment. [Modes for carrying out the invention]

[0030] Figure 1 is a schematic diagram of an atmospheric pressure plasma apparatus. A linear plasma source is mounted in a chamber. The chamber is supplied with argon or nitrogen to create an inert gas environment with an oxygen concentration of less than 1,000 ppm, preferably less than 100 ppm. A temperature-controlled sample stage is located inside the chamber and can be heated to 20-250°C. The sample, which contains metal features to be treated with atmospheric pressure plasma, is placed on the heated stage. The sample can be selected from a wide variety of different materials, which will be obvious to those skilled in the art. For example, the sample may be a silicon wafer with an embedded integrated circuit, or it may be a semiconductor die, lead frame strip, printed circuit board, or any other substrate used in the manufacture of microelectronic devices. A robot (not shown in the schematic diagram) is located below the heated stage and is used to scan the sample below the plasma beam at a constant speed in the range of 0-1,000 mm / s.

[0031] Figure 2 shows an example of a sample treated with atmospheric pressure argon and hydrogen plasma. This photograph shows two pieces cut from a 200 mm diameter copper-coated silicon wafer. The copper coating is 100 nanometers (nm) thick. On the right is a quarter of the Cu-coated silicon wafer. On the left is a 25 x 25 mm piece. 2 These are smaller pieces. These samples were heated in air at 150°C for 5 minutes and 30 seconds. During heating, the copper changed color to an orange-brown due to the formation of a copper oxide (CuO) layer approximately 40 nm thick. In the examples described later, the small pieces were placed in the apparatus shown in Figure 1 and plasma-treated to remove the 40 nm thick copper oxide layer.

[0032] The process used to remove copper oxide is as follows: The sample is placed on a temperature-controlled stage in a chamber, and the chamber is purged with a constant flow rate of argon to reduce the residual oxygen concentration in the gas to less than 1,000 ppm. The sample is heated to 20°C to 150°C. Then, atmospheric pressure argon and hydrogen plasma are operated and scanned over the sample at a constant speed. After the treatment, the sample is cooled to room temperature in an inert gas stream. Finally, the sample is removed from the chamber and inspected to confirm whether the brown copper oxide layer has been removed. [Examples]

[0033] Example 1 A method for removing copper oxide from copper using a 25mm linear beam plasma. As shown in Figure 3, these are samples of Cu-coated silicon wafers processed with 25 mm wide argon and hydrogen plasmas at scanning speeds of 5, 10, and 15 mm / s. The temperature-controlled stage was 150°C, and the standard plasma recipe used was 180 W RF power, a total gas flow rate of 9.9 LPM, and 1.1 vol% hydrogen. At a scanning speed of 5 mm / s, almost all copper oxide was removed. However, at scanning speeds of 10 mm / s and 15 mm / s, the processed area showed a brownish-orange color, indicating that not all copper oxide had been removed. These data demonstrate that a scanning speed of 5 mm / s or less is necessary to remove 40 nm of CuO from copper under conditions of 150°C and 180 W RF power.

[0034] Figure 4 shows copper-coated silicon wafer samples processed with 25 mm wide argon and hydrogen plasma at scanning speeds of 20, 25, 30, and 40 mm / s using a 550 W RF output. The total flow rate supplied to the plasma is 19.0 LPM, and the hydrogen concentration is 1.8 vol%. In this case, the samples are maintained at 150°C. Except for the sample scanned at 40 mm / s, the processed areas show a bright copper color, indicating that all oxides have been removed. Therefore, the high-power recipe for 25 mm linear beam plasma (550 W, 19.0 LPM gas flow rate, 1.8% hydrogen) is at least 6 times faster than the standard recipe for 25 mm linear beam plasma (180 W, 9.8 LPM gas flow rate, 1.1% hydrogen). In an example where a 40 nm thick copper oxide layer must be removed from a copper film on a 300 mm wafer, the 25 mm linear beam plasma source needs to be scanned 12 times in the diametrical direction of the wafer to cover the entire surface. At a scanning speed of 30 mm / s, this process is completed in 2 minutes. This is significantly faster than the 15.4 minutes reported by Joyce et al. (see Table 1 above). In short, the present invention offers a significant improvement in plasma processes for removing oxides from metal features on semiconductor substrates.

[0035] Example 2 A method for removing copper oxide from copper using a 50mm linear beam plasma. As shown in Figure 5, these are Cu-coated silicon wafer samples processed using 50 mm wide argon and hydrogen plasmas at scanning speeds of 10, 15, and 20 mm / s. A standard plasma recipe uses an RF output of 270 W, a gas flow rate of 19.6 LPM, and 1.1 vol% hydrogen. The temperature control stage is maintained at 150°C. The samples used in these experiments were approximately 25 x 25 mm in size. 2 The edges of the sample were secured to the hot plate with thin strips of Kapton tape. Referring to Figure 5, no significant etching of copper oxide was observed at scanning speeds of 15 and 20 mm / s, but some of the copper oxide was removed at 10 mm / s. In another experiment, it was confirmed that all oxide could be removed from the copper film at a scanning speed of 5 mm / s.

[0036] Figure 6 shows a sample of a Cu-coated silicon wafer treated with a 50 mm wide argon and hydrogen plasma at a 580 W RF output, with the sample held at 150°C. Plasma scanning speeds of 15, 20, and 25 mm / s were tested. The gas flow rate to the plasma was 55.0 LPM, and the hydrogen concentration was 1.4 vol%. All three samples exhibited a bright copper color, indicating complete removal of the oxide at all scanning speeds. The 580 W recipe for a 50 mm linear beam plasma source is at least 5 times faster than the standard 270 W recipe (i.e., Figure 5). In an example of removing a 40 nm thick copper oxide layer from a copper film on a 300 mm wafer, the 50 mm linear beam plasma needs to be scanned six times in the diametrical direction of the wafer to cover the entire surface. At a scanning speed of 25 mm / s, this process is completed in 1.2 minutes. This is approximately 13 times faster than the process time reported by Joyce et al. at the same sample temperature of 150°C (see Table 1). In summary, the present invention achieves a significant improvement over the prior art.

[0037] Figure 7 shows the results of copper oxide removal using a 580W RF output and 50mm wide argon and hydrogen plasma at substrate temperatures of 130, 150, and 190°C. In all cases, the scanning speed was 25mm / s, the total flow rate was 55.0 LPM, and the hydrogen concentration was 1.4 vol%. It can be seen that the copper oxide removal rate increases with increasing substrate temperature. At a scanning speed of 25mm / s, it is insufficient to remove a 40nm thick CuO layer at 130°C, just sufficient at 150°C, and more than sufficient at 190°C. Furthermore, in the image of the sample treated at 190°C, the edges of the plasma beam scanning the surface are sharper compared to the sample treated at 150°C. A similar dependence on substrate temperature has been previously reported by Joyce et al. (J.Vac.Sci.Technol.A.vol.39,p.023001(2021)). They observed a thermal activation energy of 3.7 kcal / mole during the etching of copper oxide with argon and hydrogen plasma under atmospheric pressure. [Table 2]

[0038] Table 2 shows a comparison of the results achieved with 25 mm wide and 50 mm wide plasma sources. The third column of the table shows the linear power density (W / mm), which is the input RF power divided by the plasma beam width. It is clear that when the power density exceeds 10 W / mm, the removal rate of the copper oxide layer by atmospheric pressure argon and hydrogen plasmas improves significantly. For the 25 mm wide plasma source, the etching rate of CuO is six times faster at a linear power density of 22.0 W / mm compared to 7.2 W / mm. A similar large increase in CuO etching rate is also observed with the 50 mm wide plasma source. The last column of Table 2 shows the time required to completely remove a 40 nm thick layer of copper oxide from a copper film on a 300 mm silicon wafer. At equivalent scanning speeds, the 50 mm wide plasma beam completes the process twice as fast as the 25 mm wide plasma beam. These results suggest that a 40 nm CuO layer can be removed from a 300 mm wafer in just 30 seconds using an atmospheric pressure plasma source with a 100 mm wide beam operating at 22.0 W / mm (2.2 kW). Such results are highly advantageous for the semiconductor manufacturing industry and highlight the importance of this invention.

[0039] Example 3 Comparison of Argon and Oxygen Systems vs. Argon and Hydrogen Systems at Atmospheric Pressure Plasma Figure 8 shows a schematic diagram of an exemplary plasma source (or head) 5 in an embodiment of the present invention. This removes metal oxides by combining an inert gas-purged environment with an activated supply gas from the plasma (either argon and hydrogen, or argon and oxygen). The plasma source includes an optional cover plate 4 that can be directly attached to the plasma head 5. The supply gas enters the plasma head 5 through an inlet 11 and is converted into a weakly ionized plasma, generating free electrons, ions, and an activated gas. The activated gas 8 flows out of the plasma head 5 through a linear outlet slit 12 and comes into contact with the metal substrate 6. The cover plate 4 and the plasma head 5 are coplanar with each other and mounted on the substrate 6, maintaining a small gap 7 between the plasma head 5 and the metal substrate 6. Air is rapidly removed from the gas volume in the small gap 7 by the activated gas flow. A suitable gap size is 0.1 to 5.0 mm, preferably 0.1 to 2.0 mm. Additional purge gas may be introduced through purge holes 9 and 10 in the cover plate 4. The purge gas is selected from the group of inert gases, argon, and nitrogen. The purge gas assists the active gas in removing air from the gas volume within the gap 7, thereby maintaining an inert gas environment while the active hydrogen removes metal oxides from the metal junctions. An inert gas environment is defined as an environment where the oxygen concentration is sufficiently low that it does not cause reoxidation of the metal substrate 6 after exposure to the active hydrogen generated by the plasma process. An example of an inert gas environment is when the oxygen concentration is less than 1,000 ppm, preferably less than 100 ppm. Exemplary purge holes 9 and 10 may include elongated slits or one or more holes through which the purge gas flows around the active gas 8.

[0040] A slight positive pressure is established within the gap 7 so that there is sufficient gas flow to expel all air from around the cover plate 4. This allows the plasma reduction process to be carried out in an inert gas environment with an oxygen concentration of less than 500 ppm. The low-oxygen environment promotes the removal of metal oxides and prevents re-oxidation of the metal, especially when the substrate 6 is heated. Figure 9 shows side and isometric views of an exemplary 25 mm linear beam plasma source, consistent with the schematic diagram in Figure 8. Figure 10 shows an outlet diagram of an exemplary linear beam plasma source, consistent with the schematic diagram in Figure 8 and the drawing in Figure 9. Figures 8 to 10 show exemplary plasma sources that can be implemented in any embodiment described herein, which can be used with a variable combination of argon and oxygen, or argon and hydrogen, feed gas mixtures, and feature an adjustable linear beam width (25 mm, 50 mm, or 100 mm width) and an adjustable RF output level for plasma generation. Note that while a 25 mm wide beam is used in the following examples, this exemplary plasma source is also capable of beams of 50 mm and 100 mm.

[0041] In one process, this exemplary plasma source can be supplied with a 25 mm wide linear beam and tuned to operate with argon and oxygen feed gases. The process recipe is defined as follows: RF output 150 W, argon flow rate 8.0 LPM, and oxygen flow rate 0.03 LPM. Looking into the outlet slit, a bright glow uniformly distributed across the entire width of the beam can be observed. No bright spots are visible. Viewed from the side, a thin sheet of glowing gas can be observed extending approximately 10 mm outward from the exit slit. This glow is due to metastable oxygen molecules emitting visible light during collisional de-excitation (Jeong, et al., “Reaction Chemistry in the Afterglow of an Oxygen-Helium, Atmospheric-Pressure Plasma,” J.Phys.Chem.A, vol.104, p.8027(2000)). When the device is operated at much higher input power, exceeding 200W, the gas discharge becomes unstable, exhibiting a non-uniform glow, and bright spots or streamers are observed downstream of the slit. At sufficiently high power, an arc can form in a small area between the power supply electrode and ground, potentially damaging the device. These observations, along with other facts known to those skilled in the art, indicate that a uniform glow discharge exists only within a limited range of power levels. For linear beam plasma sources operating with argon and oxygen, the high power limits have been found to be 180, 300, and 580 W for slit widths of 25, 50, and 100 mm, respectively. These power limits correspond to linear plasma densities of 5.8–7.2 W / mm.

[0042] In other processes, the exemplary plasma source can be retuned to supply a 25 mm wide linear beam operating with argon and hydrogen. This process recipe is defined as follows: RF output 180 W, argon flow 7.7 LPM, and mixed gas 2.1 LPM of argon with 5.0% hydrogen. The outlet diagram shows a uniform glow evenly distributed across the entire slit. The visible emission is due to transitions between excited states of argon atoms and hydrogen atoms (Golloch, et al., “Atomic Emission Spectrometry,” De Gruyter, Berlin (2020)). When observed from the side, no glow is observed because there are no excited states of excited argon or hydrogen atoms that are long enough to exist downstream of the plasma region between the power supply electrode and the ground electrode. The linear power density applied in this case is 7.2 W / mm.

[0043] Furthermore, in another process, a 25 mm linear beam plasma source can be operated at high power using argon and hydrogen. This process recipe is defined as follows: RF output 450 W, argon flow 7.7 LPM, and mixed gas 2.1 LPM of argon with 5.0% hydrogen. The outlet diagram shows a uniform glow evenly distributed throughout the slit. The glow observed with this recipe is significantly brighter than the glow observed at 180 W (i.e., Figure 9). No visible glow is observed when viewed from the side, and no streamers are emitted from the slit. Unlike atmospheric pressure argon and oxygen plasmas, this plasma remains unstable even at high RF output. In this case, the linear power density is 18.0 W / mm. The high RF power density recorded here, and the examples described in Table 2 above, are unexpected and demonstrate the unusually high stability of atmospheric pressure argon and hydrogen plasmas.

[0044] Example 4 Method for removing oxides from microbumps on a flip chip In “Semiconductor Advanced Packaging,” Springer Nature, Singapore (2021), John H. Lau presents numerous examples of using microbumps on flip chips to form interconnects between integrated circuits in two-dimensional and three-dimensional (2D and 3D) semiconductor packages. Microbumps consist of copper pillars and solder caps made of tin or a tin metal alloy, e.g., Sn-Ag, on top of them. The microbumps are distributed in a 2D array across the entire bottom of the chip. The dimensions of the bumps range from 8 to 50 micrometers (μm), and the distance between bump centers, i.e., the pitch, ranges from 10 to 150 μm. During packaging, the chip (or die) is flipped over, picked up, and bonded to a package or another die by thermocompression bonding (TCB). A flip chip with microbumps having a pitch of 10 μm can be placed at 1 cm². 2 It can have up to one million interconnect points, making it highly sought after for advanced computing applications such as artificial intelligence.

[0045] The tin solder caps on copper pillars contain a layer of metal oxide that needs to be removed before or during thermocompression bonding. Traditionally, organic fluxes have been used to remove the oxide by forming tin formate, which sublimes and is removed from the surface when the chip is heated. However, this process leaves organic residue, which is difficult, if not impossible, to remove for pitch sizes less than 50 μm. An attractive alternative to flux is the removal of metal oxide from the solder caps by treatment with atmospheric pressure argon and hydrogen plasma. In this case, the metal oxide removal process is performed immediately before bonding.

[0046] Figure 11 shows an exemplary apparatus for flux-free flip-chip bonding. Atmospheric pressure plasma, a bond head, and a heating stage are housed together in a chamber purged with an inert gas. The inert gas, either argon or nitrogen, flows into the chamber from one end, passes through the linear plasma source, the bond head, and the heating stage, and is then discharged from the opposite end. The chamber design and inert gas flow are configured to maintain an oxygen concentration of less than 1,000 ppm, preferably less than 100 ppm. A semiconductor package is mounted on a heating stage, for example, set to a temperature of 175°C. The semiconductor package is selected from, but is not limited to, integrated circuits, dies, wafers, panels, and printed circuit boards. The bond head has means for picking up the flip-chip so that the array of microbumps on the chip faces downwards. The bond head then rapidly heats the chip to 175°C, moving from left to right, first over the linear plasma source, and then descending over the semiconductor package and onto it. Atmospheric pressure argon and hydrogen plasma exposes the microbumps to a high flow rate of hydrogen radicals, removing the metal oxide layer from the solder. Next, a bond head moves across the package, aligns with the microbumps or pads on the package surface, descends, and bonds to the package by applying heat and pressure. Throughout the entire process of chip pickup, inversion, plasma treatment, and bonding, the chip is maintained in an inert gas environment. This ensures that metal oxide does not regrow on the solder surface before bonding is complete. In the process described above, the flip chip and package may be heated to other temperatures in the range of 125–250°C without departing from the scope of the invention.

[0047] The linear plasma source shown in Figure 11 is selected such that the plasma beam width is equal to or greater than the width of the flip-chip. For flip-chips with a width of 2 to 25 mm, a 25 mm linear beam plasma may be used. Conversely, for flip-chips with a width of 60 to 100 mm, a 100 mm linear beam plasma may be used. Adopting other plasma beam widths does not deviate from the scope of the present invention. The scanning speed required to remove the metal oxide from the solder cap of the microbump depends on the initial thickness of the oxide, the composition of the solder, and the processing temperature. The speed can vary in the range of 1 to 1,000 mm / s. A preferred speed is one that is just sufficient to remove the metal oxide from the microbump, no more and no less. Particularly useful scanning speeds are those that allow the flip-chip to be processed with argon and hydrogen plasma for 1 to 3 seconds. 25x25mm 2 An exemplary process for the die involves processing it with a 25 mm linear beam plasma at a speed of 25 mm / s, thereby obtaining an exposure time of 1 second.

[0048] In another embodiment of the present invention, the apparatus comprises two linear beam plasmas mounted on an inert gas chamber housing a bond head and a heating stage. One plasma head is positioned upward and is used to scan a flip chip to remove metal oxides from microbumps. A second plasma head is positioned downward and is used to scan a semiconductor package to remove metal oxides from microbumps or metal pads on its surface. In one embodiment of the present invention, the semiconductor package is a 300 mm wafer, and the apparatus is used for flux-free flip-chip bonding of chip-on-wafer (CoW).

[0049] Example 5 Methods for depositing thin films Another embodiment of the present invention is a method for depositing a thin film using atmospheric pressure argon and hydrogen plasma. An exemplary apparatus for this embodiment of the present invention is shown in Figure 12. Here, an inert gas stream sufficient to maintain an oxygen concentration of less than 1,000 ppm, preferably less than 100 ppm, is supplied to the chamber. A temperature-controlled stage is provided on which the sample is placed and heated to a temperature in the range of 20 to 500°C. An atmospheric pressure plasma source is mounted at the top of the chamber, operating at a high-frequency output, for example, 13.56 or 27.12 MHz, and is supplied with argon and hydrogen. Gas injectors are mounted on one or both sides of the plasma source to supply volatile precursors containing the elements to be deposited in the thin film. The heating stage is mounted on a robotic assembly that positions the sample at a constant z-distance from the plasma source and moves the sample at a constant speed in the x and y directions in the range of 2 to 200 mm / s. This allows the sample to be precisely moved below the plasma and precursor gas beams, resulting in the deposition of a uniform coating across the entire surface of the sample. The appropriate z-distance is 1.0–10.0 mm.

[0050] Materials that can be deposited using the apparatus shown in Figure 12 include, but are not limited to, organic polymers, metals, and semiconductors. Examples of polymer films that can be deposited by this embodiment of the present invention include, but are not limited to, polyethylene, polytetrafluoroethylene, polypropylene, and polyimide. In the case of polyethylene, a dilute concentration of ethylene is supplied to the precursor injector along with an argon stream and mixed with hydrogen radicals emanating from atmospheric pressure argon and hydrogen plasma. The ethylene and hydrogen radicals react to produce ethylene radicals:

number

[0051] In another embodiment of the present invention, a thin metal film can be deposited on a substrate using the apparatus shown in Figure 12. Examples of depositable metal films include, but are not limited to, titanium, vanadium, tungsten, nickel, palladium, platinum, copper, silver, gold, and aluminum. For this process, a volatile organometallic compound containing the desired metal atom is selected. The appropriate vapor pressure of the organometallic compound is in the range of 0.1 to 100.0 Torr at room temperature. These compounds are known to those skilled in the art of thin film deposition. For example, in the case of titanium, a diluted concentration of tetrakis(dimethylamino)titanium (TDMAT) is supplied to a precursor injector along with an argon stream and mixed with hydrogen radicals emanating from atmospheric pressure argon and hydrogen plasma. The TDMAT and hydrogen radicals react in the gas phase and on the surface to form a titanium film:

number

[0052] In another embodiment of the present invention, semiconductor thin films including (but not limited to) polycrystalline silicon, amorphous silicon hydrogenation, germanium, gallium arsenide, and gallium nitride are deposited using the apparatus shown in Figure 12. As an example of a method for depositing amorphous silicon hydrogenation, atmospheric pressure argon and hydrogen plasma are operated in conjunction with the injection of a stream of disilane diluted with argon. Hydrogen radicals generated by the plasma combine with disilane in the gas phase and on the substrate surface to form an amorphous silicon hydrogenation film:

number

[0053] This concludes the description, including preferred embodiments of the present invention. The above description, including preferred embodiments of the present invention, is provided for illustrative purposes only. It is not intended to be exhaustive or to limit the present invention to the exact form disclosed. Many modifications and variations are possible within the scope of the teachings above. Additional variations of the present invention may be devised without departing from the concept of the invention described in the following claims.

Claims

1. An apparatus for removing a metal oxide layer from a metal, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million, An atmospheric pressure plasma source disposed within the chamber, wherein the atmospheric pressure plasma source is supplied with argon and hydrogen, generates hydrogen radicals, and operates at a linear power density exceeding 10.0 W / mm, A temperature control plate disposed within the chamber, the temperature control plate supporting a substrate including the metal feature having a metal oxide layer on the surface of the metal feature, The apparatus includes means for moving the substrate and the atmospheric pressure plasma source relative to each other so that the hydrogen radicals flowing out from the plasma source come into contact with the metal oxide layer and convert it into metal and water vapor.

2. The apparatus according to claim 1, wherein the plasma source includes a linear aperture that generates a beam of reactive gas with a width of 1 to 300 mm.

3. The apparatus according to claim 2, wherein the width of the linear opening is at least the same as the width of the substrate including the metal feature having the metal oxide layer to be removed.

4. The apparatus according to claim 1, wherein the power supply operates at a high frequency of 13.56 or 27.12 MHz.

5. The apparatus according to claim 1, wherein the inert gas is selected from the group consisting of argon and nitrogen.

6. The apparatus according to claim 1, wherein the concentration of hydrogen added to the argon gas stream passing through the plasma is 0.1 to 5.0 volume percent.

7. The apparatus according to claim 1, wherein the substrate is heated to a temperature of 20 to 250°C.

8. The apparatus according to claim 1, wherein the substrate is selected from the group of semiconductor materials including integrated circuits, chips, dies, wafers, panels, chip packages, and printed circuit boards.

9. The apparatus according to claim 1, wherein the metal is selected from the group including nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lead, bismuth, and alloys thereof.

10. The apparatus according to claim 1, wherein the metal feature is a two-dimensional array of microbumps having copper pillars and tin alloy solder caps with a diameter of less than 100 microns, and the metal oxide layer on the tin alloy solder caps is removed.

11. A method for removing a metal oxide layer from a metal, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million. The atmospheric pressure plasma source is placed in the chamber, and the atmospheric pressure plasma source is operated using a gas flow of argon and hydrogen and a high-frequency power supply having a power density of more than 10.0 W / mm to generate hydrogen radicals. The arrangement involves placing a temperature control plate within the chamber, wherein the temperature control plate supports a substrate containing the metal feature having a metal oxide layer on the surface of the metal feature, The method comprising moving the substrate and the atmospheric pressure plasma source relative to each other so that the hydrogen radicals flowing out from the plasma source come into contact with the metal oxide layer and are converted into metal and water vapor.

12. The method according to claim 11, wherein the plasma source includes a linear aperture that generates a beam of reactive gas having a width of 1 to 300 mm.

13. The method according to claim 12, wherein the width of the linear opening is at least the same as the width of the substrate containing the metal feature having the metal oxide layer to be removed.

14. The method according to claim 11, wherein the high-frequency power supply operates at 13.56 or 27.12 MHz.

15. The method according to claim 11, wherein the inert gas is selected from the group consisting of argon and nitrogen.

16. The method according to claim 11, wherein the concentration of hydrogen in the gas stream passing through the plasma source is 0.1 to 5.0 volume percent.

17. The method according to claim 11, wherein the substrate is heated to a temperature of 20 to 250°C.

18. The method according to claim 11, wherein the substrate is selected from the group of semiconductor materials including integrated circuits, chips, dies, wafers, panels, chip packages, and printed circuit boards.

19. The method according to claim 11, wherein the metal is selected from the group including nickel, palladium, platinum, copper, silver, gold, gallium, indium, tin, lead, bismuth, and alloys thereof.

20. The method according to claim 11, wherein the metal feature is a two-dimensional array of microbumps having copper pillars and tin alloy solder caps with a diameter of less than 100 microns, and the oxide on the tin alloy solder caps is removed.

21. A device for forming metal interconnections, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million, An atmospheric pressure plasma source disposed within the chamber, wherein the atmospheric pressure plasma source is supplied with argon and hydrogen and operates at a linear power density exceeding 10.0 W / mm, A bond head disposed within the chamber, the bond head holds a flip tip having microbumps at a temperature of 20 to 250°C, A temperature control plate disposed within the chamber and heated to 20 to 250°C, wherein the temperature control plate supports a substrate including microbumps or metal pads having substantially the same dimensions as the microbumps on the flip chip, The apparatus includes means for scanning the bond head having the flip chip from above the plasma source down onto the substrate, thereby removing metal oxides on the microbumps with the plasma and bonding the flip chip to the substrate to form the metal interconnect.

22. A method for forming a metal interconnection, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million. The arrangement involves placing an atmospheric pressure plasma source within the chamber, wherein the source is supplied with argon and hydrogen and operates at a linear power density exceeding 10.0 W / mm, The bond head is installed in the chamber, the bond head holds the flip tip having microbumps at a temperature of 20 to 250°C, the installation is... The arrangement and heating involves placing a temperature control plate in the chamber and heating it to 20 to 250°C, wherein the temperature control plate supports a substrate including microbumps or metal pads having substantially the same dimensions as the microbumps on the flip chip. The method comprising scanning the bond head having the flip chip from above the plasma source down onto the substrate, thereby removing metal oxides on the microbumps with the plasma and bonding the flip chip to the substrate to form the metal interconnect.

23. Apparatus for plasma chemical vapor deposition of thin films, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million, An atmospheric pressure plasma source disposed within the chamber, wherein the atmospheric pressure plasma source is supplied with argon and hydrogen and operates at a linear power density exceeding 10.0 W / mm to generate hydrogen radicals, A gas injector is placed in the chamber, and the gas injector is supplied with volatile precursor molecules containing one or more elements to be deposited in a thin film. A temperature control plate is placed inside the chamber and heated to 20 to 500°C, wherein the plate holds the substrate, and The apparatus includes means for moving the substrate, the plasma source, and the gas injector relative to each other, thereby causing the hydrogen radicals flowing out from the plasma source to combine with the precursor molecules flowing out from the injector and react with each other to deposit the thin film on the substrate.

24. A method for depositing a thin film on a substrate, The chamber is filled with an inert gas so that the oxygen concentration inside the chamber is maintained at less than 1,000 parts per million. The arrangement involves placing an atmospheric pressure plasma source within the chamber, wherein the atmospheric pressure plasma source is supplied with argon and hydrogen, operates at a linear power density exceeding 10.0 W / mm, and generates hydrogen radicals. The arrangement involves placing a gas injector inside the chamber, wherein the gas injector is supplied with volatile precursor molecules containing one or more elements to be deposited in the thin film, The process involves placing a temperature control plate in the chamber and heating the temperature control plate to 20 to 500°C, wherein the temperature control plate supports the substrate, and the arrangement and heating are performed accordingly. The method, comprising moving the substrate, the plasma source, and the gas injector relative to each other so that the hydrogen radicals flowing out from the plasma source combine with the precursor molecules flowing out from the injector and react with each other, thereby depositing the thin film on the substrate.

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