TWI222675B - Method for copper metallization on back of GaAs device - Google Patents

Abstract

A method for copper metallization on back of a GaAs device comprises replacing gold with copper on metallization of metal on back of a GaAs device. Since copper has a lower resistance, and better heat dissipation and mechanical strength, a device using copper as a metallization metal can improve the heat dissipation, mechanical strength and electrical conductivity of a device, and further improve the properties and the reliability of the device. The use of a film of W, WN, or TiWN as a diffusion barrier layer can effectively inhibit the problem associated with copper easily diffusing into a GaAs substrate and altering the properties of a device.

Description

1222675 --------- Case No. 92117929 __ ^ _ g_Amendment_ V. Description of the invention (1) [Technical field to which the invention belongs] The manufacturing method for the copper metallization of the back surface of the gallium arsenide element according to the present invention is the existing method The metallization part of the later process of the GaAs element is changed from the existing gold-based process to the copper process. Because copper has a lower resistance value and better heat dissipation than gold, it is also superior in mechanical degree. Moreover, the present invention uses a diffusion barrier layer to block the diffusion of copper, and also has good adhesion and blocking capabilities' and good adhesion and blocking capabilities, which can increase the mechanical strength of the wafer and prevent the chip from cracking in the subsequent process. . [Previous technology] According to 'Since the International Business Machines Corporation (IBM) successfully applied copper to the silicon integrated circuit (IC) process, the copper metallization process has been used in the silicon integrated circuit (IC) process. Become a very hot topic. Using copper as the metallized metal in the silicon integrated circuit (1C) process has the advantages of low resistivity and better resistance to electron migration effects. However, copper will diffuse into the stone, so copper was not used as a metal in the past. Metalized metal, after the group (Ta) and nitride button (T a N) as diffusion barriers to solve the problem of copper diffusion to silicon, copper will replace aluminum as a silicon integrated circuit (IC) process metallization metal. Although the use of copper as a metallized metal in silicon integrated circuit (IC) manufacturing processes is currently very popular, the use of copper as a metallized metal for GaAs field effect transistors (FETs) has not been used. Shi Shenhua Gallium Field Effect Transistors (Field-Effect Transistors,

1222675 Case No. 92Π7929 Amendment V. Invention Description (2) FETs) and Monolithic Microwave Integrated Circuits (MMICs) currently use gold (Au) as a metallized metal, such as for capacitors, Transmission lines and ground planes, etc., and the thickness of gold required for transmission lines and ground planes is greater than 2-3 // m, so the amount of gold used is extremely large and the cost is high. In addition, the gallium arsenide element has problems such as low thermal conductivity and fragile substrate, especially a gallium arsenide high frequency power element (Power FET s) that needs to emit a lot of heat, so the gallium arsenide high frequency power element chip The thickness needs to be as thin as 2 to 5 mi 1 s to increase the heat dissipation effect. However, this will make the substrate very easy to crack. If copper is used as the metallized metal on the back of the gallium arsenide element, it can improve the mechanical strength and also Improve heat dissipation. The traditional backside metallization process is mainly after the wafer is polished to a thickness of about 100 0 // m, and then a through hole (Via ho 1 e) process is performed, followed by plating with tungsten titanium (TiW), gold (Au) and other metals. It can increase the heat dissipation ability, as a ground metal, and increase the mechanical properties of the component, because the wafer is extremely thin at this time, a layer of metal on the back clock helps the mechanical strength of the wafer. Metallized materials need to have excellent thermal and electrical conductivity. Copper and gold have better mechanical strength 'so the chip can have better mechanical strength' and copper also has better thermal and electrical conductivity. If copper is used to replace gold, the component can have better heat dissipation characteristics and better grounding. Therefore, using copper instead of gold as the metallized metal has the advantages of low resistance, high thermal conductivity, and cheapness. However, due to the extremely rapid diffusion effect of copper on gallium aluminide, and copper will form a deep acceptor (Deep Aceptor) in gallium sulphide, which will reduce the electrical properties of gallium arsenide elements. In the industry, copper has not been used as a metallization material in the past. How to metalize copper as a deified gallium element?

Page 6 1222675 Case No. 92117929 V. The metal of invention description (3) becomes a patent for the Republic of China Patent Bulletin urgently requiring copper as a metallized metal "(2002/11/03) One (T a N), the front end of the titanium nitride (TiN body circuit) requires more layers of different aspect ratios, and the material used also blocks the diffusion effect of the copper metal against the Shixi material. Backside process

solved problem. In the following, another word 0. Do not use the patent No. 4 6 5 0 6 9 ", this patent is mainly for the use of materials such as 妲 (T a ^ of the previous paragraph) and other materials to form steel barriers on the base material of Shixi $ Ergang =) ] Nitriding process, so it can be used in backlogs, but the niche used in the present invention includes. Different, so the process is more simple and easy: Excellent. In addition, the patent No. 4 6 5 0 6 9 It is suitable for gallium halide elements, and can be applied to 〇

The "Republic of China Patent Announcement No. 4 3 6 95" patent "Copper process barrier layer manufacturing method" (2 0 0 1/0 5/0 3) is mainly a copper 2 barrier layer manufacturing method, The barrier layer used is titanium (T i), titanium nitride (T 1 N), and the method for forming the barrier layer is an ionized metal plasma sputtering process or an organic metal vapor phase epitaxial method (Metal Organic VaPor Epitax, MOCVD). Copper metal is recorded by ionized metal plasma. The radio wave frequency used is 13.56 MHz, the power is between 0 and 300W, or the copper ore is added by electricity, but the copper must be plated before A copper seed layer. However, the barrier layer of the present invention is obviously different from this patent. Since Patent No. 436995 is not used for the backside process, if the barrier layer manufacturing method of Patent No. 4 3 6 9 5 5 is used, It will not be possible to completely plate the metal on the side walls of the perforations (Via ho 1 e).

Page 7 1222675 _Case No. 92117929_ Revised Year of the Month _ V. Description of the Invention (4) In addition, the Republic of China Patent Announcement No. 2 8 0 "Paper metallized tantalum nitride diffusion shield manufacturing method" (19 9 6/0 7/0 1), mainly using tantalum nitride (TaN) as the barrier layer of copper metal, and the deposition method of nitride button (TaN) is the organic metal vapor phase stupid method (M eta 1 Organic Vapor Epitax (MOCVD) method, and the metal organic vapor phase stupid method (Metal Organic Vapor Epitax (MOCVD) method) needs to be taken out after plating, which is likely to cause oxidation or contamination of the wafer, which is inconvenient in the manufacturing process. However, the barrier layer of the present invention adopts a sputtering method. Using this method, the wafer can be directly plated with copper without breaking the vacuum, so it is more suitable for industrial processes.

Due to the high price of gold, and its relatively poor thermal conductivity and mechanical properties, it is not possible to effectively improve the mechanical properties and heat dissipation of the wafer ', and copper metallization can easily diffuse to the gallium substrate, and the copper metallization process cannot be applied to the back end. (backside) Various problems in the process and inconveniences need to be improved. Therefore, the present inventors exhausted their mental research to overcome, and then developed a method for the copper metallization of the back side of the gallium arsenide element, which mainly uses copper as the metallized metal in the back-end process of the gallium arsenide element, with proper diffusion barrier. The layer blocks copper and uses the traditional sputtering method, not only to obtain wafers with better characteristics, but also more convenient in manufacturing process and more suitable for industrial process.

[Summary of the Invention] Therefore, the main object of the present invention is to use copper as the metallized metal on the back of the gallium halide element by means of demineralization, evaporation or electroplating, and use tungsten (W), tungsten nitride (WN) And titanium tungsten nitride (TiWN)

Page 812222675 Case No. 92Π7929 Amendment 5. Invention Description (5) Dispersive barrier layer effectively prevents copper from diffusing into the gallium arsenide substrate. Using copper as the metallized metal can improve the heat dissipation, mechanical strength and conductivity of the component And component characteristics and reliability, and because of the convenient process, it can be used in industrial applications. In order to achieve the above object, the present invention is realized as follows: A method for manufacturing copper metallization on the back surface of a gallium arsenide element is plated with a layer of tungsten (W), tungsten nitride (WN), and titanium tungsten nitride on the back surface of the substrate. (Ti WN) and other films as a diffusion barrier layer, and then plated with a layer of copper as a metallized metal, the diffusion shield layer prevents copper from diffusing into the gallium halide substrate, and due to the metal characteristics of copper, the heat dissipation of the device can be improved, Mechanical strength, electrical conductivity and other characteristics.

[Embodiment] In order to make your reviewing committee understand the purpose, features and effects of the present invention, the following specific examples and the accompanying drawings are used to make a detailed description of the present invention, which will be described later:

Please refer to the first figure, which is a side sectional view of the present invention. As shown in the figure, first, the wafer is thinned to a thickness of 1 0 // // m, and then an inductively coupled plasma (ICP) dry type is used. The through hole (viah ο 1 e) is made by Qian Hai 丨 J. The hole needs to have an inclination so that the metal can be completely filled by subsequent sputtering or evaporation. Spread or vapor-deposit the diffusion barrier layer on the back of the wafer with a thickness of about 40 to 100 nm, and then coat a layer of copper with a thickness of about 2-10 // m, followed by sputtering or Plating copper to the desired thickness. In addition, the used sputtering machine needs to be equipped with a collimator (Col 1 imatoi ·), so that the sputtered metal can completely cover the inner wall of the hole, so as to obtain the structure of the first picture, which is quartz 1, wax

Page 9 1222675 _Case No. 92117929_ Month and year Amendment _ V. Description of the invention (6) 2. Wafer 3 and diffusion barrier layer / copper 4. Such as gallium arsenide metal semiconductor field effect transistor (Metal-Semiconductor Field Effect Transistor, MESFET), you need to clean before coating, first put the gallium arsenide substrate into boiling acetone and isoacetone for five minutes, then immerse in hydrofluoride A solution of acid (HF): hydrogen peroxide (Η202): water (Η20) is 1: 2: 20 for 20 seconds and a solution of hydrochloric acid (HC1): water (Η20) is 1 ·· 4 for 1 minute. A 40nm nitride button (TaN) film was sputtered on a 3-in (100) gallium arsenide substrate, and then the vacuum was not broken on the multitarget magnetron sputtering system. A 2-10nm copper (Cu) film and a 1 Onm nitride button (TaN) film on top of the nitride button (TaN) film. The top layer of tantalum nitride (T a N) film is used to prevent copper ( The Cu) layer oxidizes and prevents oxygen from penetrating into the film during high temperature annealing. Nitriding button (T a N) films are all sputter-sputtered by tantalum (Ta) and nitrogen / argon (N2 / Ar) mixed gas (20% N2 and 80% A r). In addition, the vacuum pressure before sputtering was 2. 6 X 1 0 ~ 5Pa, and the total air pressure during film sputtering was maintained at 0.8 Pa. Finally, put in an argon (Ar) atmosphere, and perform annealing for 30 minutes at a temperature of 400 ° C to 600 ° C. X-ray winding of the nitride button / copper / nitride button / gallium arsenide (TaN / Cu / TaN / GaAs) Shot analysis, please refer to the second figure, which is the χ-ray diffraction analysis chart after annealing at different temperatures, as shown in the figure. 'From bottom to top are just finished plating and 4 0 ° C, 50 0 t :, 5 5 0 ° C and 6 0 t: Annealing, as shown in the second figure, the diffraction peaks of the nitride button (TaN) and steel (Cu) are maintained to 5 5 0 T: still very clear, indicating copper / nitride button / Gallium Arsenide (Cu / TaN / GaAs) Structure Interface I

1222675 Case No. 92117929 Amendment V. Description of the invention (7) It is still very stable until 5 50 ° C. After annealing at 600 ° C, diffraction peaks of arsenic button (T a A s), copper gallium compound (C u3G a), and copper Kun (C u2 A s) appear, showing the group (Ta) and Kun GaAs reacts at 600 ° C. However, the diffraction peaks of tantalum nitride (TaN) and copper (Cu) still exist after annealing at 600 ° C, indicating that the reaction and diffusion are not comprehensive.

Tables 1 and 2 are the changes of 150 // m elements with and without copper metallization before and after annealing, and changes in source current (I dss), transconductance (Gm), and stop voltage (Vp) Value and percentage change, Idss is tested at a drain-source voltage (vds) of 2V, Gm is tested at a gate bias (Vgs) of 0V and Vds is 2 V, and VP is tested at an Ids of 1 50mA. The percentage change of saturation drain-source current (I dss), transconductance (Gra), and pin-off voltage (VP) of copper metallized components are 1.60%, 0.73% λ 1.3.5%, and The percentage changes of the metallized saturated drain-source current (I dss), transconductance (Gm), and pinch-off voltage (VP) are 3.9 3%, 3.03%, and 3.0%, respectively. It can be seen that copper has not diffused into the gallium arsenide to damage the device. Table I

Page 11 1222675 _Case No. 92117929_ Revised Year, Year, and Five. Description of the Invention (8) 150μm copper metallized element change 値 change percentage (¾) I dss (Ma) 0.51 Id ss / Id ss 1.60 △ Gm (Vgs = OV ) (mS / mm) 0.75 △ Gm / Gm 0.73 AVP (v) 0.04 AVP / VP 1.35

Table 2 Changes in 150 μm uncopper metallized components, percent change (¾) I dss (Ma) 0.91 I dss / I dss 3.93 △ Gm (vgs = ov) (mS / mm) 3.07 AGm / Gm 3.03 AVP (v ) 0.08 AVp / vP 3.00

Thermal stability test of RF characteristics of copper metallized and non-copper metallized components, as shown in Tables 3 and 4.

Page 12122675 _Case No. 92117929_Year Month and Date__ V. Description of the invention (9), tested with Vds at 7 V and Ids at 10 OmA, 1 // mx 1 0mm copper metal After annealing at 300 ° C for 2 hours, the maximum oscillation frequency (f max), the maximum power gain (Gmax), and the unidirectional power gain (UG) were 0.34 GHz, 0.38 dB, and 0.69, respectively. dB, and 1 // mx 1 0mm non-copper metallized components after 300 ° C, 2 hours annealing, the maximum oscillation frequency (f max), the maximum power gain (Gmax) and the unidirectional power gain (UG) The changes are -0.4 GHz, 0.1 dB, and 0.56 dB, respectively. The amount of change between the two before and after copper metallization is similar, so the electrical change is caused by the heating effect of the element itself. Copper metallization does not damage the performance of the element.

Table 3 Parameters of copper metallized components at 1 μmxl0mm before and after annealing. 値 / max (GHz) 10.37 10.03 A / max (GHz) 0.34 Gmax (dB) at 0.9GHz 17.24 16.86 △ Gmax (dB) at 0.9GHz UG (dB) at 0.38 0.9GHz 19.00 18.31 Δϋ〇 (dB) at 0_9GHz 0.69 Table 4

Page 13 1222675 V. Description of the invention (10) Case No. 92117929_Year Month Day Correction 1μmx10mm copper metallized element element parameters change after annealing before annealing 値 / max (GHz) 9.6 10 △ / max (GHz) -0.4 0.9 Gmax (dB) at GHz 17.36 17.26 △ Gmax (dB) at 0-9GHz 0.1 UG (dB) at 0-9GHz 19.86 19.30 Δϋ〇 (dB) at 0.9GHz 0.56 By the copper metallization on the back of the gallium arsenide element of the present invention, It has the following characteristics: 1. With copper as the back metallized component, it has excellent power properties, which can improve the heat dissipation, mechanical strength of the component, and improve the characteristics and reliability of the component. In addition to improving the component characteristics, copper can also reduce cost. Second, by using W (W), W N (N), and Titanium Nitride (J) films as diffusion barriers, it can effectively block the copper substrate and change the characteristics of the device. 3. The present invention only needs to use a single layer of barrier ribs, and has an excellent effect of blocking the diffusion of copper metal in the manufacturing process. 4. The present invention can adopt a sputtering method, and does not require copper plating on the wafer, which is more suitable for industrial use. According to the foregoing, the present invention is more innovative than conventional technology, and has the advantages of convenience and practical value. It is very novel and advanced. 5 Fish (> > Legality should be conductive and pass it by hand) > Guide heating and price (TiWN), etc. Diffusion into gallium arsenide is relatively simple, and it can break the vacuum, and can have the aforementioned advantages, which is consistent with the invention

Page 14 1222675 _Case No. 92117929_ Year Month Amendment _ V. Description of Invention (11) The statutory elements of a patent, an application for an invention patent is filed according to law. Although a preferred embodiment of the present invention has been disclosed as above, it is not intended to limit the scope of implementation of the present invention. Any person skilled in the art can make some changes and decorations without departing from the spirit and scope of the present invention. , And all equal changes and modifications made in accordance with the present invention shall be covered by the scope of patent application of the present invention, and its definition shall be subject to the scope of the patent application.

Page 15 1222675 _Case No. 92117929_ Year Month Date Amendment Brief Description of the Drawings The first picture is a side sectional view of the present invention. The second picture is an X-ray diffraction analysis chart after annealing at different temperatures.

Page 16

Claims (1)

1222675 _ Case No. 92117929_ Year Month__ VI. Application Patent Scope 1. A method for making copper metallization on the back of a gallium arsenide element, the method includes: making a through hole on the substrate (viah ο 1 e); a diffusion shielding layer is formed on the back of the substrate; and a copper metal layer is formed on the diffusion shielding layer. 2. The method of claim 1, wherein the substrate is made of gallium arsenide. 3. For the method of applying for the first item of the patent scope, a via hole can be made by using an inductively coupled plasma (ICP) dry money engraving method. 4. The method of claim 1, wherein the diffusion shielding layer can be formed on the back surface of the substrate by a sputtering method. 5. The method of claim 1, wherein the diffusion shielding layer can be formed on the back of the substrate by a vapor deposition method. 6. The method according to item 1 of the patent application range, wherein the thickness of the diffusion shielding layer may be 40 to 100 nm. 7. The method of claim 1, wherein the diffusion shielding layer may be a crane (W) film. 8. The method of claim 1, wherein the diffusion shielding layer may be a tungsten nitride (WN) film. 9. The method of claim 1, wherein the diffusion shielding layer may be a titanium tungsten nitride (TiWN) film. 10. The method of claim 1, wherein the copper metal layer can be sputtered. Page 17 1222675 _Case No. 92Π7929_ Year Month Amendment_ VI. Patent Application Scope A plating method is formed on the diffusion shielding layer. 1 1. The method of claim 1, wherein the copper metal layer can be formed on the diffusion shielding layer by an evaporation method. 1 2. The method according to item 1 of the scope of patent application, wherein the copper metal layer can be formed on the diffusion shielding layer by an electroplating method. 1 3. The method according to item 1 of the scope of patent application, wherein the thickness of the copper metal layer may be 2-10 // m 〇 Page 18