TW472378B - Electroplating of copper seed layer in a metal process - Google Patents

Abstract

The electroplating of copper seed layer in a metal process of the present invention first diffuses a diffusion barrier layer on a silicon layer, and applies a polysilicon film with a relative thickness thereon. Next, the silicon of the polysilicon film is replaced with copper by the chemical replacement method, thereby forming a copper seed layer with a good conformality. Finally, a thicker copper film is formed on the copper seed layer by electroplating method. In the present invention, the employed chemical replacement reacting solution further includes one or more than one etching solutions to effectively reduce the reacting by-product, thereby obtaining an excellent performance.

Description

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 472378 V. Description of the invention (/) [Application of the invention] The present invention relates to a method for plating a copper seed layer in a metal process, and particularly to a ULSI metal process. A method for forming a steel sublayer by replacing polycrystalline stone, amorphous stone or TaSix material. [Background of the Invention] In order to reduce the RC delay time, copper process is being developed on ULSI process technology. The process of electroplating copper is favored by the industry due to its low cost. In order to obtain good electrode conductivity, when conducting copper power ore, a low-resistance "seedlayer" must be applied to the surface of the desired power ore to obtain the required quality of copper for power ore. The seed layer is a thin copper layer applied on the surface of the shovel. The commonly available method is base plating. However, due to the high aspect ratio of the forging method, the comformality is not sufficient. Therefore, in this application, Becht learns to replace it by CVD.

Christine Whitman et al. Have published a combined mocvd_w process that can produce a good seeding rate and a low repair rate_seed layer. Its domain force on shame 2 can also be combined with electrochemical deposition to form MOCVD-plated steel. However, the cost of the vapor deposition method is high and it is not easy to reduce the ULSI manufacturing cost. For its problem.

Robert Mikkda et al. Once published Ta (200A) as the adhesion layer, and then the clothes -------- order --------- line-(Please read the precautions on the back before filling (This page) A7

472378 V. Description of the invention (>) A method for depositing Cu (1,000A) as a seed layer on the plating method by de-plating method 'Through experimental results, when the thickness of the sidewall copper is 1' GGGA, the diameter α25_ can be filled, deep and wide Holes with a ratio of 4. The resistivity of the prepared as-deposit is 2,22 / ζ Ω-cm, and after self-annealing at room temperature for 40 hours or 80 ° C for 20 minutes 'The resistivity can be reduced to 1.85 // Ω-cm. (See R. d. Mikkola et al., "Copper electroplating for advanced interconnect technology", Plating and Surfice Finishing 'March 2000, p. 81.) However, when the physical deposition method has a high depth to width ratio, its coverage is high. Poor, it's a problem.

YuriLantasov et al. Proposed using Ti as the adhesion layer and replacing the surface of the activated Pd with electrodeless copper as the seed layer, which can fill holes with a diameter of 0.35 ym ′ and an aspect ratio of 3. However, since the Pd seed layer is plated using the bullying method, it is still not suitable for high aspect ratio holes. (See Yuri Lantasov et al., "New plotting bath for electroless copper deposition on sputtered barrier layers", Microelectronic Engineering, 50, 2000, p. 441.) Xiao Mingjun uses Cu (hfac) 2 as a reactant and uses photodecomposition chemical vapor phase The deposition method (photo-CVD) can directly deposit a copper film on a silicon substrate at a temperature of 240 ° C under normal pressure. (See MJ Shaw, "Study on selective deposition of Cu films 4 This paper size applies to China National Standard (CNS) A4 specifications (210 X 297 mm) ------------: installed --- ----- Order --------- Line · (Please read the notes on the back before filling this page) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs

47237B Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of Invention (9) onSi (100) substrates ofambient pressure "" Master of Electronic Engineering Thesis of National Chiao Tung University, MSECG, 1998 "pt 1: 2. ) However, the resistivity of the copper film obtained by this process is as high as 8.88mΩ-αη, which is not applicable. M. tC Lee et al. Also proposed a chemical replacement method for directly replacing a deposited copper film on silicon 'to perform the reaction at room temperature. When the copper film thickness is 5,000 people, a low resistivity of 2.16 μ Ω-cm can be obtained. (See KM K. Lee et al., "Deposition of Copper films on silicon for cupric sulfate and hydrofluoric acid", Journal of Electrochemical Society, May 1997.) But this method does not take into account the existence of diffusion barriers 'The inability to solve the problem of copper diffusion is its shortcoming. Therefore, it is really necessary to provide a novel method for producing a copper seed layer in a metal process. It is also necessary to provide a method for producing a copper seed layer in a metal process with low cost and easy operation. It is also necessary to provide a method for producing a copper seed layer that can be applied to metal processes with high aspect ratio holes. At the same time, it is necessary to provide a method for preparing a copper seed layer in a metal manufacturing process which can solve problems caused by reaction by-products. 5 This paper size applies to China National Standard (CNS) A4 (21〇X 297 public love) I — 丨 — 111 ------ ^ II I ---— Order — III --- -1 (please first (Read the notes on the back and fill out this page)

47237B Printed clothing by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the Invention (4) [Objective of the Invention] The purpose of the present invention is to provide a novel method for producing a copper seed layer in a metal process. The object of the present invention is also to provide a method for producing a copper seed layer in a metal process with low cost and easy operation. The object of the present invention is also to provide a method for producing a copper seed layer which can be used in a metal process for high aspect ratio holes. The object of the present invention is also to provide a method for producing a copper seed layer in a metal process which can solve the problems caused by reaction by-products. [Brief description of the invention] According to the method for manufacturing the copper seed layer of the metal process towel according to the present invention, a diffusion barrier layer is firstly deposited on a dream wafer, and a polycrystalline fracture, amorphous stone or Tasix film with a considerable thickness is applied thereon. Secondly, the polycrystalline silicon, amorphous silicon, or Tasix film is replaced by copper by chemical substitution method to form 1: a copper seed layer with good coverage, and finally, the copper seed layer is electroplated. The chemical replacement reaction solution produced by the county is composed of one or more etching solutions, which can effectively reduce reaction by-products and obtain excellent effects. The above and other objects and advantages of the present invention can be described in detail below with reference to 6 ------------. (Please read the notes on the back before filling out this page) steins A7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs V. Description of the Invention (f) The following drawings are more clear. [Explanation of the drawing] FIG. 7F is a light diagram of the plating process of the copper seed layer in the metal manufacturing process of the present invention. Figure 2 shows the Auger vertical composition distribution of the copper seeds after the replacement of the copper seeds on the diffusion barrier layer in the metal fabrication process in the month of this issue. Figure 3 shows the SEM image of the finished surface of the copper seed layer on the polycrystalline stone short structure. Fig. 4 shows the results of inspection of the finished product produced by the process of the present invention under xrd. Fig. 5 shows a SEM cross-sectional photograph of the present invention-Example after being filled with electrodeposited copper. Figure 6 shows the capacitor voltage characteristic curve of the finished product. [Detailed description of the invention] The following is a description of the hybrid metal needle layer made of this material. The method of the present invention can be applied to various kinds of metal needles. In the case of the method of the present invention, the method of the present invention is applied to a damagcence technique as an example. However, this example cannot be used to limit the patent scope of the present invention. FIG. 1 is a flowchart showing the bonding of the copper seed layer in the metal process of the present invention. If this paper size applies the Chinese national standard (& oil specification_ (ϋ 297 公 楚) --------------. Clothing -------- order ----- ---- line 丨 -------------- ——————————— (Please read the notes on the back before filling this page) ns Intellectual Property Bureau of the Ministry of Economic Affairs Printed by employee consumer cooperative A7 V. Description of the invention (dagger) As shown in the figure, in step (a), firstly, micro-holes and trenches are formed on the substrate. Under the trenches of the fox, there is Jin Lin The substrate can be any dielectric material suitable for metal manufacturing process, usually silicon oxide material can be used. As for the method of forming holes and trenches, it can be the commonly used method of engraving. Of course, other applicable methods, It can also be used in the present invention. At the same time, there are different choices of methods for forming holes and grooves for substrates made of different materials, all depending on their purpose and effect. Since such methods are conventional techniques, they are not added In step (b), a barrier layer is plated on the substrate forming the holes and trenches by a suitable method. The barrier layer may be TiN TaN or Ta, and the thickness is about It is 50A. If 为 N is used as the barrier layer, it can be plated by LPCVD; if it is Ta, it can be deposited by sputtering or CVD. Other applicable technologies and processing methods can also be applied. In the present invention, polycrystalline silicon is then grown on the barrier layer. A more suitable method includes plating polycrystalline silicon on the surface of the diffusion barrier layer with a thickness of about 650 A in an LPCVD furnace under a 5 lean 'HOmtorr. In addition, PECVD can also be used The method bonds amorphous stone on the surface of the diffusion barrier layer. In step (c), the formed product is placed in a replacement solution, and the replacement solution should contain copper ions to replace the polycrystalline silicon layer. Suitable replacement solutions include CuS04 · 5H20 And its 8 paper sizes are applicable to China National Standard (CNS) A4 (210 X 297 mm) ------------ ^ -------- Order ------ --- Line · (Please read the notes on the back before filling out this page) 472378 Printed on the consumer cooperation board of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the invention (7) His solution containing copper ions. Copper replaced on silicon The electrochemical reaction mechanism of the seed layer is the oxidation-redu ction, redox). Its half reaction is as follows: Anode:

Si ° + 6F — ^ SiF62_ + 4e · (chlorination reaction) Cathode: 2Cu2 + + 4e— > 2Cu ° (metal reduction reaction) The total reaction is:

Si ° + 2Cu2 + + 6F- — ^ SiF62 '+ 2Cu0 In the above reaction, the secondary reactions that may be accompanied are:

Si4 + + 202 · — ^ Si02 Because the presence of this SiCb by-product is not conducive to the adhesion of copper, at this time, one or more etching solutions can be used to contact the Si02 produced by etching, so that Si02 is not on the interface, and this seed layer can be successful. Replacement also has good adhesion. Therefore, the replacement liquid used in the present invention is preferably a composition containing a steel ion solution and an etching solution. Suitable examples include CuS04-5H2O and HF, each of which is formed by a solution of 1.5 g / L and 7 cc / L. In this t / i reduction reaction, the polycrystalline stone yield was about 7 Wmin, and the copper deposition rate was about 155 A / min. At this time, the thickness of polycrystalline silicon and the concentration of HF should be matched, otherwise, the Chinese national standard (CNS> A4 specification (210 X 297 public love) applies) (Please read the precautions on the back before filling this page) Order ------- --Line — 472378 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of Invention (10,000)

After Cu replacement, there is still polycrystalline silicon remaining on the diffusion barrier layer, which reduces the adhesion of the Cu seed layer. After this reaction, a complete copper seed layer can be plated on the surface. Fig. 2 is a diagram showing a copper seed layer according to an embodiment of the present invention, and the presence of Si and Si02 is hardly seen on the interface. The resistivity of the steel seed layer plated in the above example can reach U, and the surface particle size is about 360A. Figure 3 shows the SEM image of the surface of the finished product where the copper seed layer was replaced on a group of polycrystalline structures. In order to improve the adhesion at the interface between Cu and the diffusion barrier, rapid heating annealing at 350 ° C for 8 minutes in nitrogen (step (c)), this resistance value decreases, and the Cu film structure is more dense. In step (d), metal plating is performed. Copper plating can usually be performed in a plating bath at a current density of 2.0 ASD at room temperature. After 15 minutes, the copper film can reach 5000A. Its resistivity is 1.85 / z. The obtained product was examined under XRD, and it was found that the crystal phase had (111) as the largest. Figure 4 shows the results. Table I

Additive dosage CuS04 · 5H20 25g / L 10 This paper size is applicable to China National Standard (CNS) A4 (210 X 297 public love) ------------: Packing ------ --Order -------- · 1 (Please read the notes on the back before filling this page) 472378 A7 V. Description of the invention (B7 h2s〇4 200g / L HC1 0.15cc / L Additive 5c.c / L Electrochemical method to replace the deposited copper seed layer to obtain good step coverage. After electrodeposited copper deposition, the hole can be completely filled with 0.35, 2 aspect ratio holes printed by the Intellectual Property Bureau employee consumer cooperative of the Ministry of Economic Affairs. Fig. 5 shows a SEM cross-section photograph of an embodiment of the present invention after the electrode is filled with copper. If the test piece uses tantalum as a diffusion barrier layer, it can be plated by chemical vapor deposition to improve its step coverage And the uniformity can make the electrodeposited copper be completely deposited in the holes with smaller aperture and higher aspect ratio, and have better resistance to copper ion diffusion. MOS capacitors made by the method of the present invention, with different heating temperatures 300 ℃, 4〇 () C, 450 ° C and 500oC 'Measured Vfb movement, found this seed Wei Chengzhi's copper has a good effect and can heat up to 45. (:, for low dielectric layer / copper in the coffee process. Figure 6 shows the capacitor voltage characteristic curve of the finished product. The above is the process of the metal process of the present invention. For the description of the forged embodiment of the steel seed layer, it is not difficult for those skilled in Siyi to understand the spirit of the present invention and make different extensions and changes. As long as it does not exceed the spirit of the present invention, it should include Within the scope of its patent application. (Please read the notes on the back before filling this page) 衮 -------- Order --------- line. 11 @ (CNS) A4 (210 X 297 ^ 5 "

Claims (1)

472378 A8 B8 C8 D8 6. Scope of patent application. A method for plating a copper metal layer on a substrate, including the following steps: preparing a substrate; plating a diffusion barrier layer on the substrate; applying a wait on the surface of the substrate A replacement layer; replacing the layer to be replaced with a copper thin layer with a replacement liquid; and plating a copper film on the copper thin layer; characterized in that the replacement liquid includes at least one chemical component capable of providing active copper ions and at least A chemical that can reduce silicon oxide. 2. The method according to item 1 of the patent application, wherein the layer to be replaced includes a polycrystalline stone layer, an amorphous broken layer or a TaSix layer. 3. The method of claim 1 in which the material of the barrier layer is selected from TiN, Ta or TaN. 4. A method for plating a copper metal layer on a substrate, comprising the following steps: preparing a substrate; applying a diffusion barrier layer on the surface of the substrate; replacing the surface layer of the diffusion barrier layer with a thin copper layer with a replacement liquid ; And a copper film is plated on the copper thin layer; characterized in that 'the replacement liquid includes at least one chemical capable of providing active copper ions 12 paper standards are applicable to Chinese National Standards (CNS) M specifications (210X297 mm) (please (Please read the notes on the back before filling this page) -0. Shovel, printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 472378 A8 B8 C8 D8 The scope of patent application and at least one chemical component that can reduce silicon oxide. 5. For the method in the fourth item of the patent application, in which the diffusion barrier layer is TaSix. 6. The method of claim 1 or 4, wherein the surface of the substrate has a large number of fine holes and / or fine grooves. 7. The method of claim 1 or 4, wherein the chemical composition of the replacement liquid includes CuS04 · 5H20 and HF. SNI C: \ MY DOCUMENTSaTRI \ OCSP-1213 (Please read the notes on the back before filling out this page), 1T Printed by the Consumers' Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 13 This paper size applies to Chinese national standards (CNS> 8 4 specifications U10X297 Mm)