TW565885B - Method for growing gate dielectrics with a high dielectric constant by liquid phase anode oxidation technique - Google Patents

Abstract

A method for growing a gate dielectric material with a high dielectric constant by a liquid phase anode oxidation technique comprises growing a metal film on a clean surface of a silicon substrate; using a liquid phase anode oxidation method to oxidize the metal film into a metal oxide as a gate oxide layer; and performing an annealing process to increase the quality of the oxide layer. Such a technique can produce a gate dielectric layer having a high quality, a high dielectric constant, an ultra thin equivalent oxide thickness (EOT), and can be directly integrated into a CMOS process.

Description

565885 _ Case No. 91112489 _ Chromium is not five. Description of the invention (1) The present invention relates to a method for growing a high dielectric constant gate dielectric by a liquid phase anodizing technology, especially a method using a liquid phase anodizing The technology can grow high-quality, high-dielectric constant, ultra-thin Equivalent Oxide Thickness (E0T) gate dielectric layers, and can be directly integrated with complementary metal-oxide-semiconductor (CMOS) process θ Method 〇 The current complementary metal-oxide-semiconductor C M 0 S process technology has entered the era of deep sub-micron devices, and the more advanced nano-technology (< 100 nm) is also being rapidly developed and is approaching Mass production stage; with the continuous progress of process technology, the gate oxide layer of transistors is becoming thinner and thinner. Although traditional silicon dioxide has its irreplaceable advantages, the leakage current in the accumulation region As the thickness decreases, it tends to increase exponentially. Therefore, materials with high dielectric constant (high-k) need to be researched and developed as the gate oxide layer. Under the same equivalent oxide thickness, the gate with high dielectric constant has a high dielectric constant. The oxide layer can have a lower leakage current, and it is very likely to replace the dioxide and become the gate oxide layer in the next generation transistor. Conventional techniques for growing thin, high-k metal oxides include thermal oxidation, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and atoms. Atomic Layer Deposition (ALD). Among them, thermal growth must first deposit a layer of metal or a metal-containing compound on a substrate and then thermally oxidize the metal oxide layer. Although this method is traditional and simple and convenient, it must be performed in a high temperature environment; molecular beam epitaxial growth Chemical gas

Page 5 565885 (No. 91112489) _ V. Description of the invention (2) Phase deposition and atomic layer deposition methods can directly grow metal oxide layers on substrates, but require expensive equipment to achieve high levels in high temperature environments Vacuum. For the 0.13 micron (0.13 // m) process technology that has entered mass production today, the thickness of the gate oxide layer of the transistor is about 2 4 Λ, and when the thickness of the oxide layer is less than 30Α ' The direct tunneling effect began to seriously affect the insulation characteristics of the gate oxide, and a direct tunneling current appeared, causing the oxide leakage current (1 eakagecurrent) to increase, causing the transistor to be turned off. Static power dissipation (P 〇werdissipati ο η) at the time, and may cause erroneous switching of the circuit; while the component is miniaturized, the current driving ability of the transistor is also declining continuously. Current formula,

Id = 1/2 · // Cox · W / L (Vgs -Vt) 2 Where, Id: current; // · · mobility; cox: oxide layer capacitance; W: channel width; L: channel length;

Vgs: Gate-to-source voltage; Vt: Critical voltage It can be known that if the transistor current is to be increased, the oxide layer capacitance (c0x) must be increased to keep the current driving ability of the device even when the size is reduced. In order to solve the above problems, increasing the physical thickness (p h y s i c a 1 thickness) and the dielectric constant can simultaneously reduce the oxide layer leakage current and increase the oxide layer capacitance. Therefore, a high dielectric constant material is used instead of silicon dioxide as the

565885 _Case No. 9Π12489_ 年月 日 __ V. Description of the invention (3) Gate oxide layer is an inevitable trend, and this kind of high dielectric constant gate oxide layer is also called high-k gate dielectric. (High-k gate dielectrics) In view of this, the present inventor has relied on his many years of experience in related research, and through continuous experiments and attempts, the invention has finally emerged. Therefore, a method for growing a local dielectric constant dielectric using a liquid phase anodizing technique is to grow a metal thin film on a clean silicon substrate surface, and then oxidize the metal thin film by a liquid phase anodizing method. A metal oxide is used as the gate oxide layer, and then a thermal annealing process is performed to improve the quality of the oxide layer; using this technology, a high-quality, high dielectric constant, ultra-thin Equivalent Oxide Thickness (EOT) The gate dielectric layer can be directly integrated with a complementary metal-oxide-semiconductor (CMOS) process. The main purpose of the present invention is to provide a method for growing a high-dielectric-constant gate dielectric by a liquid-phase anodizing technique. A metal thin film is first grown on a clean silicon substrate surface, and then the liquid-phase anodizing method is used to The metal thin film is oxidized to a metal oxide as an interlayer oxide layer, and then undergoes a thermal annealing process to improve the quality of the oxide layer. Using this technology, the quality, the local dielectric constant, and the ultra-thin equivalent oxide thickness (Equivalent Oxide Thickness, EOT) gate dielectric layer, and can be directly integrated with complementary metal-oxide-semiconductor (CMOS) process. Another object of the present invention is to provide a method for fabricating a gold-oxygen half field-effect transistor with high dielectric constant gate dielectric. The fabrication of P wells and N wells on a silicon substrate and isolation oxides are completed first. Filling, and then growing a thin metal film on the surface of a clean silicon substrate,

565885 _Case No. 91112489_ Revised Year of the Month _ V. Description of the Invention (4) The thin film is oxidized to become a metal oxide to be used as the gate oxide layer. A thermal annealing process is performed to improve the quality of the oxide layer, and a gate layer is formed on the gate Electrode metal oxide layer, then define the gate area, and then use ion implantation to form the gate, drain and source of the transistor, deposit an oxide insulating layer on the gate layer, and etch the gate After the drain and source windows, a contact wire is deposited, and the interface trap concentration is reduced by thermal annealing, so that a gold-oxygen half field effect transistor with high dielectric constant gate dielectric can be fabricated. In order for your reviewing committee to understand the purpose, characteristics and effects of the present invention, the following specific embodiments are given in conjunction with the accompanying drawings to make a detailed description of the present invention, which will be described later: Example 1 Figures 1 (a) ~ (e) are manufacturing flowcharts of high-k gate dielectrics compatible with the CMOS process (taking A 1 2 03 as an example). As shown in the figure, metal Oxidation becomes a metal oxide, thereby growing a high-k gate dielectric. The process steps are as follows: the production of P well 2 and N well 3 is completed before a P-type silicon substrate 1 and the isolation is filled with oxide 4 (as shown in FIG. 1 (a)); An ultra-thin metal film 5 is deposited on the substrate 1 by evaporation or sputtering (as shown in FIG. 1 (b)), followed by a liquid phase anodizing technique (see FIG. 1). (C), the anode 6 is a P-type silicon substrate 1, the cathode 7 is a platinum sheet, and the electrolyte solution 8 is pure water or other organic or inorganic electrolyte solution), the metal is oxidized to a metal oxide layer, and then annealed In order to improve the quality of the oxide layer (not shown),

565885 _Case No. 91112489_ Modification of the month and year_ 5. Description of the invention (5) Form a gate alumina 9 and then grow a polycrystalline silicon gate 9 1 to complete the high-k gate dielectric (such as Figures 1 (c) ~ (e)). Embodiment 2 A gold-oxygen semi-diode (M 0 SD i ode) manufactured by pure water 81 constant voltage direct current anodizing is taken as an example. The operation steps are as described above. First, a 15 A pure aluminum ( 9 9 · 9 9 9 9) on a clean silicon substrate, and then subjected to constant voltage DC anodization with pure water 8 1 (DI wa ter). The electric field used is 7. 1 4 3 V / cm, and the oxidation time is 6.5 minutes, as shown in Figure 2. After that, the furnace is annealed in a nitrogen (N2) environment at a high temperature. The temperature is 650 ° C and the time is 60 seconds. Fabrication; metal aluminum (3 0 0 A) deposited on the gate electrode, the gate area (2. 25x10_4 cm2) was defined by photolithography, and finally metal aluminum was evaporated as the back contact of the wafer ( back contact) to complete the production of the entire component. The finished alumina film has an equivalent oxide layer thickness (EOT) of 23 A. When making a metal oxide half field effect transistor (M0SFET), the gate, source, and electrode (Gate-Source ^ Drain) of the transistor must be formed by ion implantation (i ο nimp 1 ant) after the gate definition is completed. ), And then depositing a contact wire on the gate, source and drain to form a gold-oxygen half field effect transistor. The results of the above examples are analyzed as follows: To study the importance of high temperature annealing on the characteristics of the device, we injected a constant current of -1 mA / cm2 at the gate end of the metal oxide semiconductor M0S element, and observed the gate voltage change. The results can be seen in Figure 3. Observed in the

Page 9 565885 __Case No. 91112489_ Revised Year of the Month _5. Description of the Invention (6) The oxide layer before the fire contains a large number of electron hole traps (electron and h ο 1 etraps). Being trapped during the oxidation process results in a large swing in the gate voltage. However, after high temperature annealing treatment, we can see that the swing of the gate voltage has significantly improved. From this we can see the importance of high temperature annealing to improve the quality of the dielectric layer after anodizing. The element current-voltage (I -V) characteristics are shown in Figure 4. In the accumulation region, a leakage current that is 100 to 100 times lower than that of the dioxide is obtained, and in the empty region ( Depletion region) and inverse region (inversi ο nregi ο η) can obtain a fully saturated current. This fully saturated current will not cause a serious decline in channel mobility. Figure 5 is a plot of the optical thickness measured by an elliptical thickness gauge and the electrical thickness measured by c — v from the following relationship: S 〇x / EOT = £ ai2〇 ^ / Ta] 2〇 ^ δεοτ / δτα ^^ ε〇 ^ / £ λ ^ where ε〇χ: the dielectric constant of the oxide layer; E〇τ: equivalent oxide layer thickness; book! The dielectric constant of aluminum oxide; the following: the optical thickness of alumina; the dielectric J seeks the high dielectric constant of the dielectric constant £ 9. 7 Figure 6 shows the thickness of various equivalent oxide layers and The Leak of the Dioxide Stone

565885 _Case No. 91112489_ Revised Year of the Month _5. Description of the invention (7) The current comparison shows that this process is a stable process that can be made repeatedly, and can be more oxidized under different equivalent oxide thicknesses. Silicon has a small leakage current characteristic, and the thinnest E 0 T can reach 14 A. Comparing the foregoing preferred embodiments, it can be seen that the present invention has a number of features; 1. The thin-film metal oxide layer grown by the liquid-phase anodizing technique can be used as the gate dielectric layer of a metal-oxide-semiconductor field-effect transistor (MOSFET). This liquid-phase anodic oxidation technology can perform good oxidation control of metal thin films at room temperature, so it can grow high-quality, high dielectric constant (k) metal oxide layers, and its equivalent oxide thickness (Equivalent Oxide Thickness (EOT) can be reduced to 1 4 A and still have better electrical characteristics. In the future advanced process technology of more than 1.3 microns, the equivalent oxide layer thickness must be reduced to less than 20 A. Therefore, this technology will be compatible with the most advanced process and play a role in the fabrication of gate oxide layers. An important role. 2. The present invention uses a low-cost and effective liquid-phase anodizing method. A layer of metal is first deposited on a substrate, and then liquid-phase anodizing (L i q u i d

Phase Anodic Oxidation (Anodization) technology allows the deposited metal to be effectively oxidized into a metal oxide layer under the appropriate oxidation voltage and time control. Compared with other known technologies, this process does not require expensive equipment and can be performed at room temperature, and does not need to grow in a high vacuum (< 10_7 torr) environment, so the thermal budget for the growing environment (thermal budget) and production costs can be effectively reduced and easily compatible with current design conditions and process equipment.

565885 _Case No. 91112489_ Revised Year of the Month _5. Description of the Invention (8) 3. The present invention uses room-temperature liquid-phase anodizing technology to oxidize metal layers to produce ultra-thin (EOT < 20 A) and The high-quality gate oxide layer can be directly integrated with the current CMOS process without modifying the process parameters and steps, so as to achieve the ultimate goal of minimizing components. 4. The liquid-phase anodizing method used in the present invention has high selectivity and applicability. For example, the growth method can be one of evaporation, sputtering, molecular beam epitaxial growth, or chemical vapor deposition; growing metal materials. It can be a metal whose oxide has a high dielectric constant, such as one of aluminum (A 1), tantalum (Ta), titanium (Ti), hafnium (Zr), and lanthanum (La); the anode is a wafer, and the cathode can be Platinum (Pt) or N-type semiconductor, the electrolyte can be pure water or other organic or inorganic electrolyte solution; the power supply used can be constant voltage direct current (DC), alternating current (AC) or direct current plus alternating current (DAC) anodizing And constant current anodization; and the thermal annealing machine can be one of the furnace tube or the rapid thermal annealing machine; the gas can be nitrogen, oxygen, ammonia (NH3), laughing gas (N20) Or one of the forming gases (90% N2 + 10% H2); when the furnace tube is used, the annealing temperature is about 50 ~ 9 0 ° C, and the annealing time is about 90 minutes When using a rapid thermal annealing machine, the annealing temperature is about Between 8 0 0~1 0 0 0 ° C, the annealing time is between about 0 seconds 0~6. In summary, the present invention has the following advantages: (1) Effectively reduce the thermal budget and production cost of the growing environment. (2) Can directly and today's complementary metal-oxide-semiconductor (CMOS) process

Page 12 565885 _Case No. 91Π2489_ Year Month Amendment _ V. Description of the invention (9) Integration without modifying process parameters and steps. (3) Grow a gate dielectric layer of high quality, high dielectric constant, and ultra-thin equivalent oxide thickness (EOT). Therefore, the present invention does have excellent industrial applicability and progress, and meets the requirements for invention patent applications. However, the invention patent application is submitted in accordance with the law. Although the present invention is disclosed as above with a preferred embodiment, 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. All equal changes and modifications made in accordance with the present invention shall be covered by the patent scope of the present invention, and the definition shall be based on the scope of the patent application, which shall be first declared.

Page 13 565885 _Case No. 91112489 _ Modified _ Brief Description of Drawings Figure 1 is a schematic diagram of the manufacturing process of high-k gate dielectrics (taking A1203 as an example) compatible with the CMOS process. Figure 2 is a schematic diagram of the structure of the liquid phase anodizing method. Figure 3 is a schematic diagram of the gate element injection of -111 ^ / (: 1112 constant current, gate voltage with time, and the gate voltage change over time. Figure 4 shows the oxidation with an equivalent oxide layer thickness of 2 3 A. Schematic diagram of the current-voltage (I-V) characteristics of aluminum. Figure 5 shows the optical thickness vs. electrical thickness. Figure 1 can be obtained _ A schematic diagram of a high-dielectric constant alumina dielectric layer with a dielectric constant of 9.7. Figure 6 is a schematic diagram of the leakage current with silicon dioxide at various equivalent oxide thicknesses. The drawing number is a brief description; 1 P-type silicon substrate 2 • P well 3 N well 4 • • • • Isolation oxide 5 metal Aluminum film 6 Anode 7 Cathode 8 Electrolyte solution 8 1 Pure water 9 Gate alumina 9 1 • • • • Polycrystalline silicon gate

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Claims (1)

565885 Case No. 91112489 Amended on June 6, Patent Application Scope 1. A method for growing a metal oxide layer using liquid phase anodizing technology, including the following steps: providing a broken substrate; growing a metal thin film on the surface of a clean silicon substrate; The phase anodization method oxidizes a metal thin film into a metal oxide to be used as a gate oxide layer; a thermal annealing process is performed to improve the quality of the oxide layer. 2. The method according to item 1 of the scope of patent application, wherein the anode is a silicon substrate, the cathode is one of a platinum sheet or an N-type semiconductor, and the electrolyte is one of pure water or other organic or inorganic electrolyte solutions. 3. The method according to item 1 of the scope of patent application, wherein the power supply used can be one of constant voltage DC, AC or DC plus AC anodizing, and constant current anodizing. 4 · The method described in item 1 of the scope of patent application, wherein the surface of the grown metal film on the silicon substrate must be insulated from the electrodes, and only the back of the silicon substrate is in contact with the electrodes to form a uniform oxidation field. 5. The method according to item 1 of the scope of patent application, wherein the thermal annealing processing machine can be one of a furnace tube or a rapid thermal annealing machine. 6. The method as described in item 5 of the scope of patent application, wherein the gas used in the thermal annealing treatment may be one of nitrogen, oxygen, ammonia, laughing gas or a combination of gas (90% N2 + 10% H2) . 7 · The method as described in item 5 of the scope of patent application, wherein if the furnace tube is annealed, the annealing temperature is between 500 and 900 ° C; if the rapid thermal annealing is used, the annealing is performed The temperature is between 8 0 ~ 100 ° C. Page 15 565885 _Case No. 91Π2489_ Year Month Amendment_ VI. Patent Application Range 8 · The method described in item 5 of the patent application range, wherein if the furnace tube is annealed, the annealing time is about 1 ~ 90 minutes; if using rapid thermal annealing, the annealing time is between 0 ~ 60 seconds. 9. The method according to item 1 of the scope of patent application, wherein the growth method can be one of evaporation, base ore, molecular beam house crystal growth, or chemical vapor deposition. 10 · The method according to item 1 of the scope of the patent application, wherein the growth metal material can be a metal whose oxide has a high dielectric constant, such as one of aluminum, group, titanium, titanium, or J-ring. 1 1 · A method for fabricating a metal-oxygen half field-effect transistor with high dielectric constant gate dielectric, the steps include the following steps: Provide a silicon substrate, complete the fabrication of P wells and N wells, and isolation oxidation Material filling; growing a metal thin film on the surface of a clean silicon substrate; oxidizing the metal thin film to a metal oxide as a gate oxide layer by a liquid phase anodic oxidation method; improving the quality of the oxide layer through a thermal annealing process; forming a gate electrode Layer on the gate metal oxide layer; define the gate region; use ion implantation to form the gate, drain and source of the transistor; deposit an oxide insulating layer on the gate layer; etch out the gate Electrode, drain, and source windows; deposit a contact wire, and use thermal annealing to reduce the interface trap concentration Page 16 565885 _ Case No. 91112489 _ year month and month amendment_ VI. Patent application scope 1 2 · The manufacturing method described in item 11 of the patent application scope, wherein the anode is a silicon substrate and the cathode is a platinum plate or N-type One of the semiconductors, the electrolyte is one of pure water or other organic and inorganic electrolyte solutions. 1 3 · The manufacturing method as described in item 11 of the scope of patent application, wherein the power supply used can be one of constant voltage DC, AC or DC plus AC anodizing, and constant current anodizing. 1 4 · The manufacturing method described in item 11 of the scope of patent application, wherein the surface of the growing metal film on the silicon substrate must be insulated from the electrode, and only the back of the silicon substrate is in contact with the electrode to form a uniform oxidation electric field. 15 · The manufacturing method according to item 11 of the scope of patent application, wherein the thermal annealing treatment machine can be one of a furnace tube or a rapid thermal annealing machine. 16 · The manufacturing method as described in item 15 of the scope of the patent application, wherein the gas used in the thermal annealing treatment may be nitrogen, oxygen, ammonia, laughing gas or a combination of gas (90% N2 + 10% H2) One. 1 7 · The manufacturing method described in item 15 of the scope of patent application, wherein if the furnace tube is annealed, the annealing temperature is between 500 and 900 ° C; if the thermal annealing is performed, , Its annealing temperature is between 8 0 ~ 100 ° C. 1 8 · The production method described in item 15 of the scope of patent application, wherein if the furnace is annealed, the annealing time is between 1 and 90 minutes: if the rapid annealing is used, the annealing time is about Between 0 ~ 60 seconds Page 17 565885 _Case No. 91112489 _ Amendment Month_ Sixth, the scope of patent application 19 · The production method described in item 11 of the scope of patent application, wherein the growth method can be evaporation, sputtering, molecular beam Epitaxial growth or chemical vapor deposition. 20 · The manufacturing method as described in item 11 of the scope of patent application, wherein the growth metal material can be a metal whose oxide has a high dielectric constant, such as I, Lu, Titanium, Tungsten, or one of them. 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