TW525242B - Method for removing carbon-rich particles adhered on a copper surface - Google Patents

Abstract

A method for removing carbon-rich particles adhered on a copper surface, especially on a copper surface of a copper/low k dielectric dual damascene structure is provided. A barrier layer and a barrier-CMP stopping layer are formed between the copper layer and the low k dielectric layer of the dual damascene structure. After a Cu-CMP process and a barrier CMP process, a chemical buffing polishing process using an acidic aqueous solution under a downward force of about 0.5 to 3 psi is performed to remove carbon-rich particles adhered on the exposed copper surface. The carbon-rich particle is generated from the low k dielectric layer with at least 90% carbon element being exposed due to dishing phenomenon of the copper layer, which is then polished during the Cu-CMP process and the barrier CMP process and thus produces many carbon-rich particles. Finally, a post-CMP cleaning step is carried out to remove residual impurities on the exposed copper surface. Alternately, a first chemical buffing polishing process using an acidic aqueous solution is performed after the Cu-CMP process, and a second chemical buffing polishing process using an acidic aqueous solution is performed after the barrier CMP process. These two chemical buffing polishing processes are used to remove the carbon-rich particles on the copper surface.

Description

525242 V. Description of the invention (1) 5-1 Field of invention: The present invention relates to a semiconductor process; in particular, it relates to a method for removing carbon-rich particles on a metal surface, especially a copper / low-k dielectric. Exposed copper surface on double mosaic structure. 5-2 Background of the Invention: After the semiconductor process enters the deep sub-micron field, the copper wire damascene process is used in conjunction with the intermetal dielectric layer to use low-k materials, which can effectively reduce the RC delay time and improve the electron migration (electromigration). characteristic. The first A is a typical copper / low-k dielectric dual damascene structure. A substructure (not shown) having a plurality of elements is formed in a semiconductor substrate 100, and a metal layer (not shown) is formed over the substrate 100. A barrier layer of a nitride stone or a carbide of a chemical mechanical polishing stop layer 104 and a barrier layer of Ta or Ta N 106 are a low-k dielectric layer 1 located above the substrate 1 〇2 and a copper metal layer 108. The barrier layer 106 is used to prevent copper from diffusing into the low-k dielectric layer 102. Referring to FIG. 1B, during this copper / low-k dielectric dual damascene process, a copper chemical mechanical polishing step is first performed to planarize the trenches 1 12 and the dielectric embedded in the low-k dielectric layer. Cu 1 1 0 copper metal layer 1

Page 5 525242 5 〇 Machine 4, the description of the invention (2) 8 to the barrier layer 1 06. Then, a mechanical grinding step is performed to remove the barrier layer 10, and a chemical polishing step is performed to remove the barrier layer 106 until the termination layer. However, the speed of grinding of copper metal with softer materials on Dian Qiu ... other discouragements around the copper metal layer 10 as shown in the first B picture, the copper metal layer 1 after chemical mechanical polishing 1 The upper surface / dish structure will be faster than ______ with the dotted line below the layer 1 〇8 the phenomenon of degeneration, even if the dielectric value is low ~~ to a barrier chemical mechanical polishing During the chemical-mechanical polishing of the stop layer 10 4 and S 1 0 2 丄 barrier layer, the low-k dielectric layer was exposed on the surface of the metal and was polished. This low-k dielectric layer = 1 Q ^ metal layer And also ... ch) layer, containing at least 90% of carbon charcoal in the copper chemical mechanical grinding step and resistance $ t, * is rich in these two chemistries, "the polishing liquid has the opposite 2 science, the J surface will belong to the dagger During the mechanical grinding, there may be X, X: The particles causing the process defects will be adsorbed to the exposed%, and the particles will be absorbed. 7 layers of funeral services, and according to this, the gt method, special 11 in total-can effectively remove the steel surface copper surface 0:-steel / low-k dielectric dual-insertion pole on the jealous low-k value medium Removal method of electrolyte particles. This method teaches ^ upper face <. 、 Chemical-mechanical grinding 赉 Ύ gram version aeration in the town 肷 process

525242 V. Description of the invention (3) 5-3 Purpose and summary of the invention:-The purpose of the present invention is to provide a method for removing carbon-rich particles on the copper surface, especially a steel / low-k dielectric dual inlay Structurally exposed copper surface. After a copper chemical-mechanical polishing step and a barrier chemical-mechanical and polishing step are completed, an acidic aqueous solution is used, under a wafer pressure of about 0.5 to 3 psi, to perform a chemical buffer polishing step (with ㈣丨 ... buffing process) 'in order to effectively remove the vinegar anti-particles adsorbed on the exposed copper surface' The production of these vine carbon particles is due to the discontinuity of the copper metal layer, which results in a low-k dielectric The exposure was caused during these two CMP steps and was caused by the grinding. Another object of the present invention is to provide a method for removing carbon-rich particles on a copper surface ', in particular, an exposed copper surface on a steel / low-k dielectric dual damascene structure. After the copper chemical mechanical polishing step is completed, an acidic aqueous solution is used for a first chemical buffer polishing step, followed by a barrier layer chemical mechanical polishing step, and then an acidic aqueous solution is used for a second chemical buffer polishing step; Two chemical buffer grinding steps remove carbon-rich particles adsorbed on the steel surface. Yet another object of the present invention is to provide a method for effectively removing carbon-rich particles on a copper surface; this method is suitable for low-k dielectric mechanical polishing r £, 〇

Page 7 525242 V. Description of the invention (4) According to the above-mentioned object, the present invention provides a method for removing carbon-rich particles on a copper surface, in particular, a copper / low-k dielectric dual-mosaic structure is exposed. Of copper surface. First, a semiconductor substrate is provided. A primary structure (s u b s tr u c t u r e) including a plurality of elements is formed in the substrate, and a metal layer is formed on the substrate. A low-k dielectric layer is formed on the substrate, and then a termination layer is formed on the low-k dielectric layer. The pattern etches the termination layer and the low-k dielectric layer to form a plurality of via holes for interconnections. Pattern # Carves this termination layer and a low-k dielectric layer to form a plurality of trenches for conducting wires. After that, a uniform blanket layer is formed on the stop layer and the low-k dielectric layer which are pattern-etched for use as a barrier layer. A copper metal layer is formed on the barrier layer / to fill the via hole and trench. Next, a copper chemical mechanical polishing step is performed to planarize the copper metal layer to the barrier layer. Then, a mechanical polishing step of the barrier layer is performed to remove the barrier layer to the stop layer. Using an acidic aqueous solution, a chemical buffing polishing process is performed at a wafer pressure of about 0.5 to 3 psi to remove the copper metal layer filled in the trench and the via hole. Carbon-rich particles adsorbed on exposed copper surfaces. Finally, a post-chemical mechanical polishing step is performed to remove impurities remaining on the exposed copper surface. In addition, after the copper chemical mechanical polishing step is completed, the present invention can also use an acidic aqueous solution to perform a first chemical buffer polishing step, followed by a barrier layer chemical mechanical polishing step, and then use an acidic aqueous solution to perform a second chemical Buffer grinding step.

Page 8 525242 V. Description of the invention (5) The purpose and many advantages of the present invention will be made clear by the following detailed description of specific embodiments and with reference to the accompanying drawings. 5-4 Detailed description of specific embodiments: The method of the present invention is suitable for removing carbon-rich particles adsorbed on a metal surface. In a specific embodiment of the present invention, a copper / low-k dielectric dual damascene structure is used, as shown in FIG. 1B, as an example of implementing the method of the present invention. FIG. 1B, substrate 1 〇 is a semiconductor substrate, in which a substructure (not shown) having a plurality of elements is formed in the substrate 100, and a metal layer (not shown) is formed in the substrate Above 1 0 0. The low-k dielectric layer 102 may be formed of a spin-on polymer such as an aromatic hydrocarbon, si 1 k, and f 1 a r e. The low-k / {i dielectric layer 102 contains at least 90% of carbon elements and is a carbon-rich layer. A pattern of a trench 1 12 and a via 110 is formed in the low-k dielectric layer 102. The barrier layer 106 is usually a Ta or TaN layer, which is used as a liner layer of the trench 1 1 2 and the via 1 1 0 to prevent copper metal from diffusing into the low-k dielectric layer 1. 0 2 in. A protective layer of silicon nitride (S i 3N 4) or silicon carbide (si 1 ic ο ncarbide) is formed on this low-k dielectric layer 102 for chemical and mechanical use as the barrier layer 106. One of the grinding steps

525242 V. Description of the invention (6) Termination layer 104. The chemical mechanical polishing of the copper metal system forms a dished structure under the dotted line on the top surface of the copper metal layer 108.

The barrier layer 106 of Ta or TaN is a blanket-type layer uniformly covering the area inside and outside the trench 12 and the via hole 110. Based on the considerations of low film stress, good covering ability and good adhesion, the barrier layer 106 of Ta or Ta N is usually formed by physical vapor deposition (PVD). The copper metal layer 108 is filled in the trench 12 and the via hole 110, and can be formed by PVD, CVD, or electroplating. Typically, the thickness of the copper metal layer can be from 1 lum to several microns. In a general dual damascene process, the low-k dielectric layer 102 is pattern-etched twice in a conventional lithography and etching manner. The first pattern etching forms a via hole 1 1 0 for the interconnects in the low-k dielectric layer 1 0 2, and the second pattern etching forms a wire in the low-k dielectric layer 1 0 2 The trenches 1 1 2 for conductive lines, such as trenches for copper lines. Referring to FIG. 2A, in a specific embodiment of the present invention, after the copper metal layer 108 is deposited on the barrier layer 106, a copper chemical mechanical polishing step 2 0 0 is performed on the copper metal layer 108. Plane up to the barrier layer 106. After that, a barrier layer chemical mechanical polishing step 2 02 is performed to

Page 10 j ^ 242 V. Description of the invention (7) " a-", 1, followed by the barrier layer 10 6 to the termination layer 1 04. As shown in FIG. 1B, during this chemical mechanical polishing step, the low-k dielectric layer 2 is easily exposed and polished due to the dishing phenomenon of the copper metal layer 18 as described above. Therefore, many carbon-rich particles are adsorbed on the exposed copper surface, causing defects in the dual damascene process. ^: T, in the present invention, chemical buffing polishing process ^ (chemical buffing polishing process) 2 0 4 = the target pressure of the tablet is about 0.5 to 3 ps.

Pyridine: t: ΐ: ί The carbon-rich particles are removed by an appropriate chemical reaction f: / The solution may be a succinic liquid containing carboxyl ic acid, such as containing citric acid ( … 仏 acid) or oxalic acid (ammonium caAo / i may contain organic carboxylic acid, after chemical-mechanical grinding, the ammonium salt is clear: cattle: = Acidic aqueous solution on the top surface. In order to remove the pots: 1 step is applied to the exposed copper surface to remove residual impurities thereon. During copper chemical mechanical polishing, the low-k dielectric may The parts are exposed and ground, so this s 1 0 2 T is here, 夂 昭 筮 -r with the same, + know Λ In another specific embodiment of the Cang ',,, and brother B picture, in copper chemistry The mechanical polishing step 'use-acid water— & 3 Q Q①After the wafer is pressed at a pressure of about 0.5 to 3 psi, the polishing step 3 〇2,-an appropriate chemical reaction, will suck ... on the copper surface, via, Carry out the chemical mechanical polishing step of the barrier layer to remove the carbon particles. Then 〇6 until the stop layer i 〇4 ... to remove the barrier layer 1 ^ m alkaline aqueous solution

525242 V. Description of the invention (8) The second chemical buffer grinding step 3 0 6 removes carbon-rich particles on the copper surface under a wafer pressure of about 0.5 ^ to 3 p s i. This acidic aqueous solution contains _ an organic pelic acid, such as selective acid or oxalic acid. Alternatively, it may be an acidic aqueous solution containing an ammonium salt of organic ferulic acid. Finally, a chemical mechanical polishing 'post-cleaning step is applied to the exposed copper surface to remove the remaining impurities thereon. The above descriptions are merely preferred embodiments of the present invention, and are not intended to limit the scope of patent application for the present invention; all other equivalent changes or modifications made without departing from the spirit disclosed by the present invention should be included in the following Within the scope of the patent application.

525242 on page 12 is a simple illustration of the first A picture series-a general cross section of the copper / low-k dielectric dual-inlay structure, the first B picture is the copper / low-k dielectric of the A-th picture. Cross-sectional view of the structure after the double-mounting process after a copper chemical mechanical polishing step and a barrier layer chemical mechanical polishing step. Among them, the exposed copper surface has a dishing phenomenon. Figure A shows the steps of the method of a specific embodiment of the present invention. Flowchart J and _—— B are flowcharts of the steps of the method of another specific embodiment of the present invention. The representative symbols of the main part 0; semiconductor substrate 1 0 2 low-k dielectric layer 1 0 4 termination Layer 1 0 6 barrier layer 1 0 8 copper metal layer 1 1 0 via hole 1 1 2 trench 2 0 0 Copper chemical mechanical grinding 2 0 2 Barrier layer chemical mechanical grinding 2 0 4 The first chemical slow grinding

Page 13 525242 Brief description of the drawing 3 0 0 3 0 2 3 0 4 3 0 6 Copper chemical mechanical polishing Second chemical buffer polishing Barrier layer chemical mechanical polishing Chemical buffer polishing

Claims (1)

525242 Case No. 89125963 Amendment 6. The scope of patent application is formed by spin-on polymer low-k material. 3. The method according to item 2 of the patent application range, wherein the above-mentioned low-k dielectric layer is formed of a spin-coated polymer (spi η-ο η ρ ο 1 ymer) with a low-k value material, and the spin-coat type is high The molecular material is selected from the following: aromatic hydrocarbons, silk A f1 are. 4. The method according to item 1 of the patent application, wherein the above-mentioned termination layer is formed of silicon nitride (S i3N4). 5. The method according to item 1 of the scope of patent application, wherein the above-mentioned termination layer is formed of silicon carbide. 6. The method of claim 1 in which the above barrier layer is formed of Ta metal. 7. The method of claim 1 in which the above barrier layer is formed of TaN. 8. The method of claim 1 in which the above-mentioned copper metal layer is formed by a chemical vapor deposition method. 9. The method according to item 1 of the patent application, wherein the copper metal layer is formed by a physical vapor deposition method. Page 16 525242 No. 1 8912MM VI. Scope of Patent Application Month Month Amendment 1 〇 If the scope of patent application No. 1 is formed by a plating method. The method of the item, in which the above-mentioned steel metal layer is 11 · It is carried out according to the method and liquid of item 1 in the scope of patent application. 12. For example, citric acid is used in the scope of patent application. The above-mentioned grinding step is based on the use of the above-mentioned chemistry, but the acidic water-solubility of β-quincunic acid ~~~ %% carboxylic acid organic carboxylic acid 13. As described in the patent application No. 11 is oxalic acid. The method of item 15 above, wherein a method for removing carbon-rich particles on a copper surface at least includes: providing a semiconductor substrate 'a primary structural system including a plurality of elements formed in the substrate' and a metal layer system Formed on the substrate; forming a low-k dielectric layer on the substrate; forming a termination layer on the low-k dielectric layer; patterning the termination layer and the low-k dielectric layer to form a pattern A plurality of vias for interconnection; Page 525242 _ Case No. 89125963 VI. Patent application scope The pattern name is engraved with the termination layer and the low-k dielectric layer to form a plurality of trenches for conducting wires; 'forming a uniform blanket-type layer after pattern etching The termination layer and the low-k dielectric layer are used as a barrier layer; Λ forms a copper metal layer on the barrier layer to fill the via hole and trench; ~ performs a copper chemistry Mechanical polishing step to planarize the copper metal layer to the barrier layer;-using an acidic aqueous solution and a wafer pressure of about 0.5 to 3 psi Force 'to perform a first chemical buffer grinding step to remove carbon particles adsorbed on the exposed copper surface of the copper metal layer filled in the trench and the interlayer hole; @ 进行 一 阻 卩 早 层A chemical mechanical polishing step to remove the barrier layer and the stop layer; using an acidic aqueous solution to perform a second chemical buffer polishing step to remove the copper metal layer filled in the trench and the via hole The carbon-rich particles adsorbed on the exposed copper surface; and a step of cleaning after chemical mechanical polishing. 16 · The method according to item 15 of the patent application range, wherein the above-mentioned low-k dielectric f layer is formed of a spin-on polymer low-k material. 17 · The method according to item 16 of the scope of patent application, wherein the above-mentioned low-k dielectric layer is formed of a low-k material having a spin-on type (spin — 〇on p〇lymer), Page 18 525242 Amendment No. 89125963 VI. Scope of patent application The spin-coated local molecular materials are selected, silk and flare. The following items are listed below: aromatic hydrocarbons 18. If the scope of patent application is No. 15 Method, wherein the above-mentioned termination layer is formed of nitride nitride (Si3N4). 19. The method according to item 15 of the scope of patent application, wherein the above-mentioned termination layer is formed of silicon carbide. 20. The method according to item 15 of the scope of patent application, wherein the above-mentioned barrier layer g is formed of T a metal. 21. The method according to item 15 of the patent application range, wherein the above barrier layer is formed of TaN. 22. The method according to item 15 of the scope of patent application, wherein the above copper metal layer is formed by a chemical vapor deposition method. 23. The method according to item 15 of the scope of patent application, wherein the above-mentioned copper metal layer is formed by a physical vapor deposition method. 24. The method of claim 15 in the scope of patent application, wherein the above copper metal layer is formed by an electroplating method. III m p. 19 525242 Case No. 89125963 _ Amendment VI. Patent application scope 25. For the method of patent application scope item 15, wherein the first chemical buffer grinding step mentioned above uses an organic acid Acidic aqueous solution. 2 6. The method according to item 25 of the scope of patent application, wherein the organic carboxylic acid is citric acid. 27. The method according to item 25 of the patent application, wherein the organic carboxylic acid is oxalic acid. 28. The method of claim 15 in the scope of patent application, wherein the first chemical buffer grinding step is performed using an acidic aqueous solution containing a salt of an organic acid. 29. The method of claim 15 in the scope of patent application, wherein the second chemical buffer grinding step is performed using an acidic aqueous solution containing an organic acid. 30. The method according to item 29 of the patent application range, wherein the organic carboxylic acid is citric acid. 31. The method according to item 29 of the patent application, wherein the organic carboxylic acid is oxalic acid. I! Page 20 525242 Page 21