JP2005294707A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device which avoids an occurrence of a defect and has a high reliability when forming a damascene wiring. <P>SOLUTION: The method comprises the steps of acidifying the surface to be processed by processing a surface to be processed provided on a semiconductor substrate 22 on a polishing cloth by an acidifying processing solvent 27, and transferring the semiconductor substrate 22 from on the polishing cloth 21 to a cleaning unit with the surface to be processed kept acidic. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a CMP (Chemical-Mechanical-Planarization) process for forming a Cu damascene wiring of a system LSI or a high-speed LOGIC-LSI.

  The next-generation high-performance LSI requires high integration of elements, and the design rule of damascene wiring formed by CMP is becoming a strict design with a wiring width of 0.07 to 30 μm and a film thickness of 100 nm.

  Usually, CMP using slurry is performed to form a damascene wiring having a thickness of 100 nm. If the cleaning process after the CMP is insufficient and the finished state of the wiring is poor, for example, if there is a local abnormality, the performance of the semiconductor device is drastically deteriorated. Further, since there is a possibility of disconnection during operation, research is being conducted on cleaning of a wafer after CMP (see, for example, Patent Document 1).

  When Cu damascene wiring is formed, it is essential to reduce defects such as Cu corrosion, Cu dissolution, scratches, and dust reattachment (contamination from abrasive particles, polishing products, polishing cloth, etc.) as much as possible after cleaning. It is. Recently, since the miniaturization of semiconductor devices has progressed and the influence of defect yields has become clear, the demand for defect reduction has further increased. By increasing the level of defect evaluation, it has been confirmed that corrosion that occurs only in a special pattern portion and very slight erosion at the end of the wiring have occurred. It has also been found that dust and scratches cannot be ignored.

At present, a method for manufacturing a highly reliable semiconductor device by avoiding such a defect has not yet been obtained.
JP 2001-358111 A

  An object of the present invention is to provide a method for manufacturing a semiconductor device having high reliability by avoiding the occurrence of defects.

  A method of manufacturing a semiconductor device according to one aspect of the present invention includes a step of treating a surface to be processed provided on a semiconductor substrate with an acid treatment liquid on a polishing cloth to make the surface to be treated acidic, and the surface to be processed. A step of moving the semiconductor substrate from the polishing cloth to a cleaning unit while maintaining acidity.

  According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, wherein a surface to be processed provided on a semiconductor substrate is brought into contact with a polishing cloth, a liquid is supplied onto the polishing cloth, and an acid concentration on the polishing cloth is set. The step of processing the surface to be processed while monitoring, and detecting that the acid concentration is less than a predetermined value set in advance, and retracting the semiconductor substrate from the polishing cloth, the cleaning unit It has the process to convey, It is characterized by the above-mentioned.

  According to still another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, wherein a surface to be processed provided on a semiconductor substrate is brought into contact with a polishing cloth, a liquid is supplied onto the polishing cloth, and a pH on the polishing cloth is adjusted. While monitoring, the process of processing the surface to be processed, and detecting that the pH exceeds a predetermined value set in advance, the semiconductor substrate is retracted from the polishing cloth and transported to the cleaning unit It comprises the process.

  According to an aspect of the present invention, a method for manufacturing a highly reliable semiconductor device by avoiding the occurrence of defects is provided.

  Embodiments of the present invention will be described below.

  As a result of intensive investigations on corrosion that occurs only in a special pattern portion or on a very small wiring end, the present inventors have not caused the defect in CMP itself. We found that there is a cause in the method of finishing and cleaning and polishing. For example, in the case of a Cu film, the surface of the Cu film is protected by the complexing agent in the slurry at the stage of polishing with slurry and subsequent polishing with pure water. No excitement occurs. However, if polishing with pure water is performed after polishing using a cleaning liquid, corrosion or scooping of the special pattern portion occurs. In pursuit of this cause, it was found that the protective film on the surface of the Cu film was removed by polishing with the cleaning liquid, and that defects were generated by polishing with pure water after the protective film was removed. I found it.

  We also found that pure water is involved in the increase of dust and scratches. Specifically, during polishing with the cleaning liquid, it is an environment in which any dust on the wafer and the polishing cloth is easily washed away. However, polishing with pure water causes back-contamination from the polishing cloth, resulting in an environment in which dust tends to remain on the surfaces of the wafer and the polishing cloth. Therefore, when pure water is used for final finishing, back-contamination from the polishing cloth occurs, dust increases, and scratches also increase secondarily. Back-contamination due to pure water occurs on the polishing cloth during polishing with pure water after cleaning.

  Based on these findings, avoid polishing with pure water after the pure Cu surface is exposed by polishing with the cleaning liquid. Specifically, the target surface after the Cu surface is exposed by the treatment on the polishing cloth. By making the surface acidic, defects can be reduced. In the method according to the embodiment of the present invention, the surface to be treated must not be cleaned with pure water after the polishing with the cleaning liquid is finished, and generally before being transferred to the cleaning unit. It is necessary to be. Further, in the case of polishing only with the slurry without using the cleaning liquid and transporting it to the cleaning unit, the surface to be processed after the slurry polishing must be in an acidic state. By maintaining the pH or acid concentration of the treated surface after the treatment on the polishing cloth within a predetermined range, the treated surface can be maintained acidic. In the case of pH, it is less than 7, and the acid concentration depends on the acid used, but for example, citric acid is 0.05 wt% or more.

  Specifically, this can be achieved by treating the surface to be treated on an abrasive cloth using an acidic treatment liquid and directly transporting the treated semiconductor substrate to a cleaning unit. The acidic treatment liquid may be either a slurry or a cleaning liquid. When polishing with an acidic slurry, the polished semiconductor substrate may be moved directly to the cleaning unit. When an acidic cleaning solution is used, a neutral or alkaline slurry can also be used. In this case, after polishing with a neutral or alkaline slurry, after washing with pure water, washing with an acidic cleaning solution is performed. May be.

(Embodiment 1)
A method for forming Cu damascene wiring will be described as an example. FIG. 1 is a process cross-sectional view showing Cu-CMP.

  First, as shown in FIG. 1A, an insulating film 11 having a thickness of 6000 mm was deposited on a semiconductor substrate 10 on which an element (not shown) was formed, and a groove 14 was formed. Here, the insulating film 11 is formed using TEOS (tetraethoxysilane).

  A TaN film (100 Å) as the liner material 12 and a Cu film (6000 Å) as the wiring material film 13 were deposited on the entire surface of the insulating film 11 by sputtering and plating.

By removing unnecessary portions of the Cu film 13 and the TaN film 12 by CMP, a Cu damascene wiring is formed. Specifically, as shown in FIG. 2, the top ring 23 holding the semiconductor substrate 22 is applied with a polishing load of 300 gf / cm ² while rotating the turntable 20 to which the polishing cloth 21 is attached at 100 rpm. Touched. The rotational speed of the top ring 23 was 100 rpm, and the slurry as the processing liquid 27 was supplied onto the polishing cloth 21 from the processing liquid supply nozzle 25 at a flow rate of 200 cc / min. Here, polishing was performed for 80 seconds using CMS7401 / CMS7452 (JSR) as the slurry and IC1000 (RODEL) as the polishing cloth. In FIG. 2, the water supply nozzle 24 and the dresser 26 are also shown.

Thereafter, unnecessary portions of the TaN film 12 were removed by CMP to expose the surface of the insulating film 11 as shown in FIG. Here, the same conditions as described above except that the rotational speeds of the top ring 23 and the turntable 20 are both changed to 50 rpm, the polishing load is changed to 400 gf / cm ^2, and CMS8301 (JSR) is used as the slurry. Polishing was performed for 60 seconds. CMS8301 is an alkaline slurry having a pH of 9.5, and a corrosion inhibitor (anticorrosive) is blended therein. Although an acidic slurry is preferable, an alkaline slurry can be used if an anticorrosive agent is added.

  Following this polishing, pure water is supplied from the water supply nozzle 24 to prepare for shifting to the acidic side by polishing for 15 seconds. Further, from the cleaning liquid supply nozzle (not shown), a citric acid aqueous solution 0 as a cleaning liquid is prepared. Polishing was performed for 30 seconds by supplying 2 wt%. The steps so far are continuously performed on one turntable 20 as shown in FIG. 2, and then directly taken over to the next step such as roll cleaning. Since the pH of the citric acid aqueous solution is 3, the surface to be treated is subjected to roll cleaning while being in an acidic state. As the cleaning liquid, an acidic aqueous solution such as citric acid, oxalic acid, maleic acid, malonic acid or the like can be used.

  In FIG. 3, the structure of the grinding | polishing apparatus used for the method concerning embodiment of this invention is shown typically. The illustrated polishing apparatus has a general configuration, and includes a CMP unit 30 that performs polishing in two systems, and a cleaning unit 31 that cleans a wafer transferred from each. The semiconductor wafer 33 is held by the polishing unit 34 after CMP is performed on the turntable 32 in the CMP unit 30. In the example described above, after the polishing with the citric acid aqueous solution is completed, the wafer 33 is transported with the surface remaining acidic. The CMP unit 30 also includes a dressing unit 35.

  In the cleaning unit 31, a wafer hanger (not shown) of the wafer transfer robot 36 receives the semiconductor wafer 33 from the polishing unit 34 and transfers it to the double-sided roll cleaning machine 37. The wafer is cleaned on both sides with water or the like by a double-sided roll cleaning machine 37 and further transferred to a reversing machine 38 by a wafer transfer robot 36. The inverted wafer is cleaned and dried by the pencil cleaner 39 and then accommodated in the cassette 40.

In this embodiment, roll cleaning is performed while the surface to be processed is acidic. There were no defects such as corrosion of Cu or chipping of Cu wiring edges on the surface of the surface to be processed before roll cleaning, and such defects were not confirmed even after roll cleaning. Further, the number of scratches on the Cu film was 10 / cm ² , and as a result of observation with a defect evaluation apparatus, dust was 60 / cm ² .

For comparison, polishing was performed by a conventional method. Specifically, after performing the polishing with a citric acid aqueous solution in the same manner as described above, the polishing was further performed with pure water for 15 seconds. In the insulating film 11 after the pure water polishing, as shown in FIG. 4, a gap 50 is generated at the end of the Cu wiring, and the depth reaches a maximum of 500 mm. Further, the number of scratches on the Cu film was 98 / cm ² and the number of dust was 170 / cm ² , and it was confirmed that defects were increased by pure water polishing.

(Embodiment 2)
As shown in FIG. 5, the insulating film 11 is composed of a first insulating film (thickness 3000 mm) 51 made of LKD5109 (made by JSR) and a second insulating film (thickness 1500 mm) made of LKD27 (made by JSR). Each film was formed on the semiconductor substrate 10 with the same configuration as in FIG. 1A except that the film was changed to a laminated film and the liner 12 was changed to the Ta / TaN film 53. The LKD 27 used for forming the second insulating film 52 is a hydrophobic material.

  Further, CMP is performed under the same conditions as described above to remove unnecessary portions of the Cu film 13 and the surface of the Ta / TaN film 53 is exposed. Then, CMP is performed under the same conditions as described above to perform the second insulating film 52. The surface of was exposed.

  Following this polishing, pure water was supplied from the water supply nozzle 24 and polished for 15 seconds, and then a cleaning liquid was supplied from a cleaning liquid supply nozzle (not shown) to perform polishing for 30 seconds. As the cleaning liquid, CIREX (Wako Pure Chemical Industries) was diluted with pure water, and an aqueous solution having a citric acid concentration of 1 wt% was used. The processing after polishing with the slurry of the Ta / TaN film 53 was performed while monitoring the citric acid concentration on the polishing cloth. Specifically, the acidity was measured using a near-infrared spectrometer, and the citric acid concentration on the polishing cloth was monitored.

  When the cleaning liquid supplied to the surface to be processed was switched to pure water, the citric acid concentration on the polishing cloth became less than 0.1 wt%, so the semiconductor substrate was saved from the polishing cloth and immediately put into the cleaning unit. Moved.

  Such an operation may be controlled to be performed in conjunction with each other. That is, when the concentration of citric acid detected by the sensor falls below a predetermined value (for example, 0.1 wt%) set in advance, the polishing apparatus body is interlocked so as to be interlocked. When cleaning and polishing are performed while monitoring the citric acid concentration on the polishing cloth with a sensor, and the citric acid concentration exceeds a predetermined value, the main body device receives an interlock from the sensor. The top ring is immediately guided to the retracted position, and the semiconductor substrate is transferred to the cleaning unit.

  If the citric acid concentration is slightly lower than 0.1 wt%, it is sufficiently acidic, so that in this embodiment as well, cleaning is performed in the cleaning unit while maintaining the surface to be processed in an acidic state. It is. When the surface after citric acid polishing was observed, no defects were observed as in the case of Embodiment 1, and Cu abnormality was avoided.

  The predetermined value of the acid concentration is a value corresponding to the minimum acid concentration at which the surface to be treated that is in contact with the polishing cloth can be in an acidic state, and can be determined as appropriate according to the acid used. In general, an acid concentration of 0.05 wt% can be said to be in an acidic state, but the predetermined value may be set to about 0.1 wt% in order to reliably maintain the surface to be processed in an acidic state. desired.

  For comparison, polishing with a cleaning liquid was followed by polishing with pure water for 15 seconds. On the surface of the surface to be treated after the pure water polishing, the erosion as shown in FIG. 4 occurred.

  In general, an insulating film made of a hydrophobic material tends to accelerate reverse contamination by pure water. Besides LKD27, Silk (manufactured by Dow Chemical, Co.), Coral (manufactured by Novellus Systems, Inc.), and BD (black diamond, manufactured by Applied Materials) are known as hydrophobic insulating film materials. Yes. As described above, the use of pure water was avoided by maintaining the acid concentration on the polishing cloth within a predetermined range, thereby reducing the back contamination of the insulating film.

(Embodiment 3)
In the same manner as in the second embodiment, the Ta / TaN film 53 was exposed as shown in FIG.

  The slurry for polishing the Ta / TaN film 53 is pure 5% by weight of colloidal silica as abrasive grains, 0.1% by weight of BTA (benzotriazole) as a corrosion inhibitor, and 0.1% by weight of nitric acid as a pH adjuster. Prepared in addition to water. The resulting slurry has a pH of 1.5. Except for using such a slurry, unnecessary portions of the Ta / TaN film 53 were removed under the same conditions as in the first embodiment. In the present embodiment, the Ta / TaN film 53 is polished while monitoring the pH of the surface to be processed by a high resolution sensor around pH 2.5. Specifically, the ion concentration was measured using a conductivity meter, and the pH on the polishing cloth was monitored.

  Following the polishing with the slurry, when pure water was supplied from the water supply nozzle 24, the pH of the surface to be processed exceeded 2.5, so the semiconductor substrate was retracted from the polishing cloth and immediately moved to the cleaning unit. I let you.

  Such an operation may be controlled to be performed in conjunction with each other. That is, when the pH detected by the sensor exceeds a predetermined value (for example, 2.5) set in advance, the polishing apparatus body is interlocked so as to be interlocked. When pure water polishing is performed while monitoring the pH on the polishing cloth with a sensor and the pH exceeds a predetermined value, the main unit receives an interlock from the sensor. The top ring is immediately guided to the retracted position, and the semiconductor substrate is transferred to the cleaning unit.

  If the pH is approximately 2.5 or lower, the acidic state is obtained. Therefore, also in this embodiment, the cleaning unit is cleaned while the surface to be processed is maintained in the acidic state. When the surface of the surface to be treated before roll cleaning was observed, no defects were observed as in the case of Embodiment 1, and Cu anomaly was avoided.

  The predetermined value of pH is the maximum pH at which the surface to be treated that is in contact with the polishing cloth can be in an acidic state. If the pH is less than 7, it can be said to be acidic, but in order to reliably maintain the surface to be treated in an acidic state, it is desirable that the predetermined value of pH is as small as 3 or less.

  For comparison, polishing was performed on a polishing cloth in the same manner as described above except that pure water was supplied until the pH of the surface to be processed exceeded 7.0. On the surface to be processed after the pure water polishing, the erosion as shown in FIG. 4 occurred. Even when the surface to be processed was polished using an acidic slurry, it was confirmed that defects were generated when polishing with pure water until the surface to be processed became neutral in the subsequent process.

  As described above, the formation of Cu damascene wiring has been described as an example. However, the wiring material is not limited to Cu, and when Al or W is used, similarly, by moving to a cleaning unit in an acidic state, Abnormalities after polishing can be avoided.

1 is a process cross-sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. Schematic which shows the state of CMP. Schematic showing the structure of the grinding | polishing apparatus used for the method concerning embodiment of this invention. Sectional drawing which shows the state of the insulating film after grinding | polishing by the conventional method. Sectional drawing showing the manufacturing method of the semiconductor device concerning other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate; 11 ... Insulating film; 12 ... Liner material; 13 ... Wiring material film 14 ... Groove; 20 ... Turntable; 21 ... Polishing cloth; 22 ... Semiconductor substrate 23 ... Top ring; ... Processing liquid supply nozzle 26 ... Dresser; 27 ... Processing liquid; 30 ... CMP unit; 31 ... Cleaning unit 32 ... Turntable; 33 ... Semiconductor wafer; 34 ... Polishing unit 35 ... Dressing unit; 36 ... Wafer transfer robot 37 ... Double-sided Roll cleaning machine; 38 ... reversing machine; 39 ... pencil cleaning machine 40 ... cassette; 50 ... punch; 51 ... first insulating film; 52 ... second insulating film 53 ... Ta / TaN film.

Claims (5)

Treating the surface to be treated provided on the semiconductor substrate with an acidic treatment liquid on a polishing cloth to make the surface to be treated acidic;
And a step of moving the semiconductor substrate from the polishing cloth to a cleaning unit while keeping the surface to be processed acidic.   The surface to be treated is a surface of a conductive film deposited on an insulating film having a recess provided on the semiconductor substrate, the acidic treatment liquid is a slurry, and the treatment polishes the conductive film. The method for manufacturing a semiconductor device according to claim 1, wherein the surface of the insulating film is exposed by being selectively left in the recess.   The said to-be-processed surface is a surface of the insulating film which has the electroconductive film embedded in the recessed part provided on the said semiconductor substrate, The said acidic process liquid is a washing | cleaning liquid. A method for manufacturing a semiconductor device. Contacting the surface to be processed provided on the semiconductor substrate with a polishing cloth, supplying a liquid onto the polishing cloth, and monitoring the acid concentration on the polishing cloth, and processing the surface to be processed; and A method for manufacturing a semiconductor device, comprising: detecting that the acid concentration is less than a predetermined value set in advance, retracting the semiconductor substrate from the polishing cloth, and transporting the semiconductor substrate to a cleaning unit. . Contacting the surface to be processed provided on the semiconductor substrate with a polishing cloth, supplying a liquid onto the polishing cloth, and monitoring the pH on the polishing cloth, and processing the surface to be processed; and the pH A method of manufacturing a semiconductor device, comprising: detecting that a predetermined value exceeds a predetermined value, retracting the semiconductor substrate from the polishing cloth, and transporting the semiconductor substrate to a cleaning unit.

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