TW494489B - Extrusion-free wet cleaning process for copper-dual damascene structures - Google Patents

Abstract

An extrusion-free wet cleaning process for post-etch Cu-dual damascene structures is developed. The process includes the following steps: (1) providing a wafer having a silicon substrate and at least one post-etch Cu-dual damascene structure, the post-etch Cu-dual damascene structure having a via structure exposing a portion of a Cu wiring line electrically connected with an N+ diffusion region of the silicon substrate, and a trench structure formed on the via structure; (2) applying a diluted H202 solution on the wafer to slightly oxidize the surface of the exposed Cu wiring line; (3) washing away cupric oxide generated in the oxidation step by means of an acidic cupric oxide cleaning solution containing diluted HF, NH4F or NH20H; and (4) providing means for preventing Cu reduction reactions on the Cu wiring line.

Description

494489 V. Description of the invention (1) Field of the invention The present invention relates to an improved wet copper cleaning method, especially a two-stage (tw 〇- step) wet cleaning method, combined with an extrusion inhibition method. step), especially for copper-low dielectric constant (1 ow-k) dielectric layer process systems. This two-stage wet cleaning method includes a mild oxidation step and a subsequent oxide etching step. The method of the present invention can effectively suppress the phenomenon of protrusions caused by the presence of large copper ions in the cleaning solvent. ^ Background note In the early days of the development of integrated circuits, aluminum metal and silicon dioxide dielectric materials have been the standard materials used in the industry in the design of metal interconnects. This combination of materials has always been welcomed because of its proven etching technology. However, in recent years, with the shrinking of the process line width, the integrated circuit technology has evolved to the deep sub-micron generation, coupled with the realistic factors such as the speed requirements of the product, the traditional ILu / Stone dioxide is connected intraday. The system (A 1 / S i 0 2 interc ο η nectsystem) has clearly no longer met the new process requirements and product specifications. In its place, the copper process technology, which has flourished in recent years, is matched with a low dielectric constant material as an insulating layer between metals. Because copper metal has about 40% lower resistivity than Ming metal,

Page 5 V. Description of the invention (2) " " "-If ¥ 4 is used, the capacitance effect between the metal wires can be reduced.

de ^ 卩 can reduce the RC delay caused by the transmission of electronic signals (RC performance and perf rmance). Common low-secondary materials such as FLAREtm, SiLKTM, and BCB (—species Porous media] materials 1). Although the copper process combined with low dielectric constant gas materials have many electrical advantages', however, there are also many process problems to be solved. The first * deposit of money will accompany the process of engraving the dual mosaic structure Some complex organometallic polyniers are attached to the canals of the dual damascene structure and the contact window walls. These components of unknown organometallic polymers are not easy to remove by dry etching. In addition, the double damascene junction is etched. In the process of raising, 'Since copper does not have the same oxide film as aluminum, it can form an oxide film to avoid being attacked by the external environment. Therefore, the copper pollution problem of contact windows has also been an urgent need for improvement. After the structure is etched, a double mosaic structure needs to be cleaned to effectively remove the residue during the engraving process. One method is to use dilute Release of hydrofluoric acid-containing solution treatment. In addition, another method developed by United Microelectronics Corp. (UMC) and Mattson Technology Wet Process Division (Exton, Pa.) Uses a The two-stage wet cleaning process treats the residues in the etching process. The first step of this two-stage wet cleaning is to use a mild 3 6: 1 (v / v) diluted hydrogen peroxide solution to complete the etching of the dual damascene structure. , Combined with the ultrasonic vibration (megasonics irradiati ο η) technology. This diluted hydrogen peroxide solution can additionally contain

494489 V. Description of the invention (3) A surfactant (surf actant), or a surfactant which does not contain any type, may be used. This first step is used to slightly oxidize the surface of the copper wire, and to remove a portion of the southern molecular residue 'and to remove copper atoms sputtered onto the contact window wall. The second step of this two-stage wet cleaning is to use a mild copper emulsion post-treatment step to completely strip and remove the thin oxide layer on the surface of the copper wire (the bean components are CuO ^ and Cu (OH) 2), while removing all Polymer residues. The surname solution used in this second step generally contains H F, * ΝΗ, or ΝΗ 20Η in an acidic environment. Please refer to Figure 1. Figure 1 shows a schematic cross-section of a post-e ~ tch dual damascene struct ιθθ30 after cleaning on a silicon substrate 姓 〇. Taking the aforementioned two-stage cleaning process as an example, the mosaic structure 30 in Fig. 1 exposes a part of the area of the first layer of copper metal wires 22 and 24, where the first layer of metal wires 22 is passed through a The tungsten plug 16 is electrically connected to the P-doped region 12 formed in the silicon substrate 10, and the first metal wire 24 is passed through a tungsten plug 18 to the n + doped in the silicon substrate 10. Miscellaneous areas 1 4 are electrically connected. In this way, due to the difference in p_n potential in the silicon substrate 10, in the cleaning solution containing ions, the first metal wire 24 plays the role of a cathode, and the first metal wire 22 plays the role An anode role. The result is a copper oxide, such as Cu (0H) 2, which is oxidized in an acidic environment and dissociates a large amount of copper ions in the cleaning solution (see formula 1 in Figure 1) to form a copper wire depression 1 3. The role of cathode _ The reduction reaction occurs on the surface of the first layer of metal wire 24 (see Figure 2 in Equation 1), and is deposited on the surface of the second layer of metal wire 24, forming a steel protrusion (copper 11 111 11 II · 第 7 Page 494489 V. Description of the invention (4) extrusi〇n) 15o It can be seen that although the conventional two-stage copper process cleaning method can effectively remove the residue, it has another problem, which is the phenomenon of copper protrusions. This phenomenon is due to the redox reaction in the solution in the second step in the two-stage cleaning process, and the first layer of metal wires 24 electrically connected to the silicon substrate 10 plays a cathode in this redox reaction ( cath 〇de) · role. · Summary of the invention "# Therefore, the main object of the present invention is to provide an improved method for cleaning after etching of a dual damascene structure to solve the above-mentioned phenomenon of protrusions on the copper wire. According to a preferred embodiment of the present invention, the method of the present invention includes the following main steps: (1) Provide a semiconductor wafer including a silicon substrate and a post-etch dual damascene structure. The dual damascene structure includes a via structure and a trench structure formed on the contact window structure, wherein the contact window structure exposes a portion of the area of the first layer of copper metal wires, and the first A layer of copper metal wire is electrically connected to an N-doped region formed on the silicon substrate; > (2). Washing the semiconductor wafer with a diluted hydrogen peroxide solution to slightly

Page 8 494489 V. Description of the invention (5) Emulsify the exposed layer of copper metal surface, (3) Wash the copper formed on the surface of the first layer of copper metal wire with a copper oxide cleaning solvent An oxide, wherein the copper oxide cleaning solvent comprises I1F, NH4F or NH2OH; and (4) providing a protrusion suppression means to suppress a copper reduction reaction occurring on the surface of the first copper metal wire. According to the purpose of the present invention, the protrusion suppressing means utilizes an inert gas purging method to deliver an inert gas to the abundance of the conductor crystal. The surface of the wafer is used to clean the semiconductor wafer with the diluted peroxide solution. In the process, it can be in an environment with low oxidation power. ^ According to the purpose of the present invention, the protrusion inhibiting means is to add a copper rot # inhibitor (C uc 〇rr 〇si ο η inhibitor) to the diluted hydrogen peroxide solution, such as be η ζ ο tria ζ ο 1 e (Β Τ A) to achieve the effect of inhibiting the formation of copper protrusions on the surface of the first layer of copper metal wires. According to the purpose of the present invention, the protrusion suppressing means is to reduce the hydrogen peroxide concentration of the diluted hydrogen peroxide solution to 100: 1 (v / v), so as to achieve the suppression of the occurrence of the first copper metal wire. The effect of copper protrusions on the surface. According to the purpose of the present invention, the protrusion inhibiting means is to reduce the temperature of the dilute hydrogen peroxide solution to less than 15 ° C, so as to achieve inhibition in the

Page 9 494489 V. Description of the invention (6) The effect of the formation of copper protrusions on the surface of the first layer of copper metal wire. According to the object of the present invention, the protrusion suppresses the pH of the copper oxide cleaning solvent to 7 or more, and, *.丨 4 Use the copper protrusions on the surface of the first layer of copper metal wire to form 1] the emperor suppressor ^ Occurred in the detailed description of the invention = the following describes the details of the method of the present invention by using Figures 2 and 3 : Significant :: A schematic diagram of the double mosaic structure 9 0 used to evaluate the effect of an improved button-down wet depuration effect of the present invention. The dual damascene structure is formed by a dual damascene process, with a low dielectric constant; the first layer of copper metal wire layers 92 and 94 is generally the same. The so-called low dielectric $ # == generally refers to dielectric materials with a dielectric constant (k) of less than 3, which covers charter dielectric materials and inorganic dielectric materials, which can be spin-on or chemical Vapor deposition (chemical vapor dep siti CVD) technology is formed. Among them, inorganic low-dielectric constant materials include doped oxide: fluorine atom doped (F-doped) is called fluorine; fluorinated silicon glass (FSG); hydrogen atom doped is called HSQ Hydrocarbon doping (C and H doped) is called MSQ (methyl silsesquioxane), black diamond (black diamond) material, Coral and porous silica glass (p0r0Us si 1 ica) and so on. Organic low-dielectric constant materials include amorphous fluorocarbon polymers (am〇rph〇us fluorocarbon polymers) and poly Si imine polymers.

Page 10 494489 V. Description of the invention (7) (fluorinated po: lyimide), Teflon (PTFE), poly (arylene ether) 'benzocyclobutene, SilkT ^ & FLAREn, etc. As shown in FIG. 2, the special feature of the dual damascene structure 90 is the application of the silicon nitride etch stop layer 82 and the silicon oxide mask 84 used to define the low dielectric constant material layer 72. Each double-inlaid structure includes a ditch and a pile: formed under the ditch. The contact window exposes a portion of the area of the wires 92 and 94. After finishing the etching of the dual damascene structure, U ^ 'and the trench sidewalls will leave metal polymer residues that may contain C, 〇, si, (: _ | touch 1 ^', need to be cleaned in a wet manner. 2 夂 疋 ' Ingredients A > The problem with washability is that a pound of moxibustion is ordered with Shi Xi's base. This is the first copper metal wire 94 electrically connected by a tungsten plug 68, and a heterozygous area 64. The copper wire protrusion was found. On the other hand, the p-doped metal wire 92 in the silicon substrate 60 that is electrically connected to the silicon substrate 60 via the tungsten plug 66 after the first steel washing process plays an anode-like role in the cleaning process. Τ area 62, and In addition, in the process of engraving the contact window, C Η 〆 rA r / 0 Α is required to dry the engraving gas to remove the contact window and the silicon nitride etching stop layer 82 containing a bottom). In this way, the via (charge) valley accumuiate is on the passing surface and the position of the charge forming portion, so that the subsequent wet cleaning process is performed, and the redox reaction of the copper wire is accelerated at the bottom of the contact window of the second. In order to form a conductive and sexual environment, the phenomenon of w depression ~ protrusion is now 494489. V. Description of the invention (8) In order to solve the problem of the copper wire protrusion caused by the reduction reaction, the method of the present invention provides a protrusion suppression method to suppress A copper reduction reaction may occur on the surface of the first layer of copper metal wire 94. The improved two-stage wet copper process cleaning method includes the following main steps: (1) an oxidation step; (2) a copper oxide etching step ; And (3) Means for suppressing protrusions. ^ Among them, the oxidation step is cleaned with a mildly diluted hydrogen peroxide solution: forming an etched double-mosaic structure, which can be combined with megasonics irradiation technology. This dilution In the hydrogen peroxide solution, j may further include a surfactant, or it may not include any type of surfactant. The copper oxide etching step is to use a mild copper oxide etching step to completely strip and remove the thin oxide layer (its components are CuO # and Cu (0H) 2) on the surface of the copper wire, while removing all the molecular residues. The etching solution used in this step generally contains HF, NH4F, MAH or diluted HF / HC1. The protrusion suppression method of the method of the present invention can be performed for the oxidation step, or can be performed for the copper oxide etching step, or both. The oxidation step and the copper oxide etching step are performed. The main purpose of the protrusion suppression method is to prevent copper metal from accumulating on the surface of the first copper metal wire 94 through a reduction reaction. 〇 Please refer to FIG. 3, which is a schematic flow chart showing the present invention Method for inhibiting protrusions. As shown in FIG. 3, in a preferred embodiment of the present invention

Page 12 494489 5. In the description of the invention (9), there are four options for the protrusion suppression method for the oxidation step. These four options can be used alone or in combination. There is one protrusion suppression method for the copper oxide etching step, which can be performed simultaneously with four kinds of protrusion suppression methods for the oxidation step. The four protrusion suppression methods for the oxidation step include: (1) using an inert gas purging method to send an inert gas to the surface of the semiconductor wafer, so that the semiconductor is cleaned by using the diluted superemulsified rat solution In the process of the wafer, it can be in an environment with low oxidizing power; (2) adding a copper rot #inhibitor (Cu cor ros i on inh bit 〇r) in diluted hydrogen peroxide solution, such as benz 〇triaz 〇 1 e (BTA); (3) reduce the hydrogen peroxide concentration of the diluted hydrogen peroxide solution to below 100: 1 (v / v); and (4) reduce the temperature of the diluted hydrogen peroxide solution to below 1. The protrusion suppression method for the copper oxide etching step is to increase the pH value of the copper oxide cleaning solvent to above 7 to achieve the effect of suppressing the copper reduction reaction on the surface of the first copper metal wire. Compared with the conventional copper wet cleaning technology, the method of the present invention utilizes a protrusion suppression method to inhibit dissociated copper ions from accumulating on the surface of the first copper metal wire 94 through a reduction reaction, thereby effectively preventing the occurrence of copper protrusions. At the same time, the double-mosaic structure after etching can be cleaned and cleaned to improve the reliability of the product. The above description is only a preferred embodiment of the present invention. Any equal changes and modifications made in accordance with the scope of the patent application for the present invention should be covered by the present invention patent.

Page 13 494489

Page 14 494489 Simple illustration of the diagram Simple illustration of the diagram Figure 1 is a schematic cross-section showing a double mosaic structure cleaned by conventional methods. Fig. 2 is a schematic cross-sectional view showing a double-embedded structure for evaluating the method of the present invention. Fig. 3 is a schematic flow chart showing the protrusion restraining means of the method of the present invention. Explanation of Symbols

10 Silicon substrate 12 P doped 1 N ′, domain 13 Wire recess 14 N doped region 15 Copper protrusions 16, 18 Crane plug 11, 24 First layer of copper metal wire 30 Double damascene structure 60 Silicon substrate 62 P doped Miscellaneous region 64 Doped domain 6 6 λ 68 Tungsten plug 72 Low-dielectric constant material layer 82 Silicon nitride 1 Insect stop layer 84 Silicon oxide mask: Cover 90 Double damascene structure 92 ^ 94 15 pages

Claims (1)

494489 VI. Application Patent Scope 1. A wet cleaning method with no protrusion formation (e X trusi ο η-free), used for cleaning copper-dual inlaid enemy structure after one etch, the The method includes the following steps: Provide a semiconductor wafer including a silicon substrate and a etched dual damascene structure. The etched dual damascene structure includes a via structure and a trench structure formed on the contact window. On the structure, the contact window structure exposes a part of the area of the first layer of copper metal wire, and the first layer of copper metal wire is electrically connected to an N-doped region formed on the silicon substrate, and a dilution process is used. A hydrogen oxide solution is used to clean the semiconductor wafer to lightly and slightly oxidize the exposed surface of the first layer of copper metal; and use a copper oxide cleaning solvent to wash away the copper oxide formed on the surface of the first layer of copper metal wire, Wherein the copper oxide cleaning solvent contains HF, NH4F or NH20H; and a protrusion suppression means is provided to suppress the occurrence of the first copper metal wire The reduction reaction of the copper surface. 2. The method according to item 1 of the patent application, wherein the first layer of copper metal wire is electrically connected to an N-doped region of the silicon substrate, and has a cathode-like function in a copper oxide cleaning solvent. 3. The method according to item 1 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to use inertness in the process of cleaning the semiconductor wafer with the diluted hydrogen peroxide solution. gas Page 16 494489 6. Scope of patent application Blowing off the surface of the semiconductor wafer to reduce the oxidizing power of the diluted hydrogen peroxide solution. 4. The method according to item 1 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to add a copper rot I insect inhibitor to the diluted hydrogen peroxide solution. 5. The method according to item 4 of the patent application, wherein the copper corrosion inhibitor comprises benzotriazo1e (BTA). 6. The method according to item 1 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to reduce the hydrogen peroxide concentration of the diluted hydrogen peroxide solution to 100: 1 ( V / V) or less. 7. The method according to item 1 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to lower the temperature of the diluted hydrogen peroxide solution to less than 15 ° C. 8. The method according to item 1 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to raise the pH of the copper oxide cleaning solvent to 7 or more. 9. A wet cleaning method for a copper process, comprising: an oxidation step; Page 17 494489 6. The scope of the patent application is a copper oxide etching step, using a copper oxide cleaning solution to wash away the copper oxide generated in the oxidation step; and at least one protrusion suppression means to suppress the occurrence of Copper reduction on the surface of a layer of copper metal wire. 10. The method of claim 9 in the scope of patent application, wherein the oxidation step is used to slightly oxidize the surface of the first layer of copper metal wire, and the oxidation step includes the use of a diluted hydrogen peroxide solution. I 1 1. The method according to item 9 of the patent application, wherein the copper oxide cleaning solution contains HF, NH4F, NH2OH, or diluted HF / HC. 1 2. The method according to item 9 of the patent application, wherein The copper oxide system is CuOCu (OH) 2. Article the. The domain and area are mixed with N items. The 1st base base Fan Fanli is a special one. Please apply for the power line. Line 3 1 is a gold-copper layer 1 4. If the method of item 9 of the scope of patent application, The method for inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to blow off with an inert gas in the oxidation step to reduce the oxidizing power of the diluted hydrogen peroxide solution. 1 5. The method according to item 9 of the scope of patent application, wherein the inhibition occurs in the item Page 18 494489 VI. Scope of patent application The method for reducing copper on the surface of a layer of copper metal wire is to add a copper rot I insect inhibitor to the diluted hydrogen peroxide solution. 16. The method of claim 15 in the scope of patent application, wherein the copper corrosion inhibitor comprises benzotatriaz 1e (BTA). _ 1 7. The method according to item 9 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to reduce the hydrogen peroxide concentration of the diluted, hydrogen oxide solution to 1 0 0: 1 (v / v) or less. : 1 8. The method according to item 9 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to lower the temperature of the diluted hydrogen peroxide solution to less than 15 ° C . 19. The method according to item 9 of the scope of patent application, wherein the method of inhibiting the copper reduction reaction occurring on the surface of the first layer of copper metal wire is to raise the pH of the copper oxide cleaning solvent to 7 or more.