JP2009021617A - Substrate processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of effectively removing particles and metal contaminants from the surface of a substrate for a short time and preventing increase in the quantity of etching on the substrate surface when cleaning the substrate in a single wafer processing. <P>SOLUTION: Droplets generated by mixing etchant including fluorine containing chlorine with gas are injected to the surface of the substrate W having a natural oxidation film formed on the surface by a two-fluid nozzle 80, to etch and clean the substrate surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates a semiconductor wafer, a glass substrate for a liquid crystal display device, a glass substrate for a photomask, a substrate processing how to clean the surface of the substrate such as substrates for optical disks.

  For example, in various stages of the semiconductor device manufacturing process, particulate particles and various metal contaminants adhere to the surface of the semiconductor wafer. For this reason, it is necessary to clean the surface of the wafer and remove these particles and metal contaminants from the substrate surface. As a wafer cleaning method, conventionally, a batch method is used in which a large number of wafers are immersed in a cleaning solution at a time to perform a cleaning process. In addition, chemical liquids such as a mixed liquid of ammonia water and hydrogen peroxide water or a mixed liquid of hydrochloric acid and hydrogen peroxide water are used as cleaning liquids, and chemical liquids such as hydrofluoric acid are added to those chemical liquids according to the purpose. A combined cleaning solution is also used. In this batch-type immersion cleaning method, the processing time for each lot takes a long time, but since a large number of wafers are processed simultaneously, a certain productivity is ensured.

On the other hand, due to various processing advantages, a single-wafer cleaning method is also performed in which a cleaning liquid is supplied to the surface of the substrate while the wafers are held horizontally one by one and rotated around the vertical axis. It has been broken. A major problem in this single wafer cleaning method is productivity, and how to shorten the processing time per wafer is an important issue. For this reason, various cleaning processes suitable for the single wafer cleaning method have been developed. For example, a method has been proposed in which the use of a combination of ozone water and dilute hydrofluoric acid as the cleaning liquid improves the contamination removal performance and shortens the processing time. In this method, first, ozone water is supplied to the wafer surface to oxidize the wafer surface, and then dilute hydrofluoric acid is supplied to the wafer surface to selectively etch only the oxide layer on the wafer surface. Thereby, the metal contaminant adhering to the wafer surface is removed from the wafer surface together with the oxide layer. Further, since the layer on the wafer surface supporting the particles disappears, the particles are also removed (see, for example, Patent Document 1).
JP-A-10-256211 (page 2-3)

  However, the above-described method using a combination of ozone water and dilute hydrofluoric acid as a cleaning liquid has a problem in terms of particle removal effect because ozone water itself does not have particle removal capability. Further, in the above method, since the metal contaminants and particles are removed from the wafer surface using hydrofluoric acid, it is necessary to etch the wafer surface layer thickly, which increases the amount of etching on the wafer surface. is there.

The present invention has been made in view of the circumstances as described above, and effectively removes particles and metal contaminants from the surface of the substrate in a short time when the substrate is cleaned by a single wafer method. It can be, for the purpose that you provide neither a substrate processing method that etching of the substrate surface is increased.

The invention according to claim 1, in the substrate processing method for cleaning a substrate with single wafer method, the etching solution consisting of hydrofluoric acid, or is produced by mixing the etching solution and a gas consisting of hydrofluoric acid containing an acidic solution The droplet is sprayed onto the surface of the substrate on which a natural oxide film is formed or a thermal oxide film is formed on the surface, and the substrate surface is etched and washed.

The invention according to claim 2 is characterized in that, in the method according to claim 1 , the acidic liquid is hydrochloric acid.

  According to a third aspect of the present invention, in the method according to the first or second aspect, after the surface of the substrate is washed with the etching solution, pure water is discharged onto the surface of the substrate, and the rinse treatment with the pure water is performed. After completion, the substrate is rotated and spin-dried.

  According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, the droplet is generated by mixing an etching solution and a gas with a two-fluid nozzle, and the droplet is the The substrate surface is cleaned by being sprayed from the two-fluid nozzle to the surface of the substrate.

  According to a fifth aspect of the present invention, in the method according to the third aspect, the droplet is generated by mixing an etching solution and a gas with a two-fluid nozzle, and the droplet is generated from the two-fluid nozzle to the surface of the substrate. The substrate surface is washed to clean the substrate surface, and the rinsing process with pure water is performed by discharging pure water from the two-fluid nozzle onto the surface of the substrate.

According to claim 1 engaging Ru inventions of the substrate processing method, the etching solution consisting of hydrofluoric acid, or the droplets produced by mixing the etching solution and a gas consisting of hydrofluoric acid containing an acidic solution such as hydrochloric acid Then, a natural oxide film is formed on the surface or sprayed onto the surface of the substrate on which a thermal oxide film is formed on the surface. At this time, the particles adhering to the surface of the substrate are physically removed by the kinetic energy at the time of collision due to the ejection of droplets onto the substrate surface. Further, the oxide film on the substrate surface is selectively etched by the etchant. As a result, the metal contaminant adhering to the surface of the substrate is removed from the surface of the substrate together with the oxide film, and particles are completely removed (lifted off) by eliminating the layer on the surface of the substrate. In addition, when the etching solution contains an acidic solution such as hydrochloric acid, the solubility of metal contaminants increases, so that the metal contaminants can be removed from the substrate surface by slightly etching the surface of the substrate. . Therefore, the etching amount on the substrate surface can be further reduced.
Therefore, when the substrate processing method of the invention according to claim 1 is used, particles and metal contaminants can be effectively and quickly removed from the surface of the substrate when the substrate is cleaned by the single wafer method. The amount of etching of the substrate surface does not increase, and the amount of chemical used can be reduced.

In the method of the invention according to claim 2, by using a hydrochloric acid solution, since action of the acidic solution described above is surely achieved, locking Ru inventions of the above effects it can be surely obtained in claim 1.

  In the method of the invention according to claim 3, the substrate after the cleaning treatment is rinsed to remove the etching solution from the substrate surface, and then the substrate is dried by spin drying.

  In the method of the invention according to claim 4, since the mixed droplet of the etching liquid and the gas is suitably generated by the two-fluid nozzle, the above-described effect of the invention according to claim 1 can be obtained with certainty.

  In the method of the invention according to claim 5, since the mixed droplet of the etching liquid and the gas is suitably generated by the two-fluid nozzle, the effect of the invention according to claim 1 can be obtained with certainty. In addition, since the cleaning with the etching liquid and the rinsing process with pure water can be performed with one two-fluid nozzle, the configuration of the apparatus is simplified.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment of the present invention will be described below with reference to the drawings.
1 and 2 show an example of the configuration of a substrate processing apparatus used for carrying out the substrate processing method according to the present invention. FIG. 1 is a plan view of the apparatus, and FIG. It is the schematic block diagram which showed the principal part of the apparatus seen from the direction shown by the arrow A in the end surface .

  The substrate processing apparatus includes a disk-shaped spin base 10 that supports a substrate, for example, a semiconductor wafer W in a horizontal posture. A plurality of, for example, six chuck pins 12 for gripping the peripheral edge of the wafer W are implanted in the peripheral area on the upper surface side of the spin base 10 so as to be equally distributed in the circumferential direction. The chuck pins 12 are in contact with the lower surface side peripheral portion of the wafer W to support the wafer W, and a fixing portion that fixes the wafer W by pressing the outer peripheral end surface of the wafer W supported on the support portion 12a. 12b. Although the detailed structure of the fixing portion 12b of the chuck pin 12 is not shown, the state in which the outer peripheral end surface of the wafer W is pressed to fix the wafer W and the wafer W is detached from the outer peripheral end surface of the wafer W to release the wafer W. It is possible to switch between the states to be performed.

  A through hole 14 is formed at the center of the spin base 10, and a cylindrical rotation support shaft 16 is suspended from the lower surface side of the spin base 10 so as to communicate with the through hole 14. A covered cylindrical casing 20 fixed on the base plate 18 is disposed around the cylindrical rotation support shaft 16. The cylindrical rotation support shaft 16 is supported by the base plate 18 and the casing 20 so as to be rotatable around the vertical axis via bearings 22 and 24, respectively. A motor 26 is disposed in the casing 20 so as to be fixed on the base plate 18. A driving pulley 28 is fixed to the rotating shaft of the motor 26, while a driven pulley 30 is fitted to the cylindrical rotating spindle 16, and a belt 32 is attached to the driving pulley 28 and the driven pulley 30. It is laid around. By these mechanisms, the cylindrical rotation support shaft 16 is rotated, and the wafer W held on the spin base 10 fixed to the upper end of the cylindrical rotation support shaft 16 is rotated in a horizontal plane. . In addition, a nozzle 34 that is connected to the cleaning liquid supply channel is inserted into the hollow portion of the cylindrical rotation support shaft 16. The cleaning liquid is discharged from the upper discharge port of the nozzle 34 toward the center of the lower surface of the wafer W held on the spin base 10.

  Around the casing 20, there is a cylindrical wall portion 36 disposed so as to surround the casing 20, and a bottom wall portion 38 formed integrally with the cylindrical wall portion 36 and connected to the lower end portion of the outer peripheral surface of the cylindrical portion of the casing 20. The base plate 18 is fixedly disposed. The collection tank 40 is configured by the cylindrical portion, the cylindrical wall portion 36 and the bottom wall portion 38 of the casing 20. The bottom wall 38 that forms the bottom of the recovery tank 40 has a V-shaped longitudinal section, and a drain hole 42 is formed in the bottom wall 38. Further, the base plate 18 is provided with a drainage port 44 so as to communicate with the drainage hole 42, and although not shown, the drainage port 44 is connected to the cleaning liquid recovery tank through a flow path. The collected recovery pipes are connected in communication.

On the side of the circular cylindrical wall portion 36, as shown in FIG. 2, the supply mechanism 78 of the etchant such as hydrofluoric acid is provided. The etching solution supply mechanism 78 includes a two-fluid nozzle 80 in which an ejection port is disposed above the wafer W held by the spin base 10 so as to face the surface thereof. The two-fluid nozzle 80 is fixed to the distal end portion of the arm 82, and the arm 82 is held in a horizontal posture in a cantilever manner by the arm holding portion 84. The arm holding portion 84 is fixed to the upper end portion of the rotation support shaft 86 disposed in the vertical direction. The rotation support shaft 86 is connected to a nozzle moving mechanism 88, and is rotated by the nozzle moving mechanism 88 and reciprocated in the vertical direction. Then, by driving the nozzle moving mechanism 88, the two-fluid nozzle 80 can be swung in the horizontal plane, and the two-fluid nozzle 80 can be reciprocated between the central portion and the peripheral portion of the wafer W. The two-fluid nozzle 80 can be moved toward and away from the surface of the wafer W. Further, the arm 82 holding the two-fluid nozzle 80 can be rotated from the position indicated by the two-dot chain line in FIG. 1 to the position indicated by the solid line and retracted to the outer position of the circumferential wall portion 36. ing. The nozzle moving mechanism is not limited to the illustrated example, and various mechanisms can be adopted.

As shown in the longitudinal sectional view of FIG . 3 , the two-fluid nozzle 80 is integrally formed so as to surround an air introduction pipe 90 having a through hole 92 that narrows downward in the axial center portion and an outer periphery of the air introduction pipe 90. And a cylindrical liquid introduction tube 94 integrally formed with a liquid introduction tube portion 96 having a through hole 98 in the shaft center portion, and a straight tube having a large diameter at the top and a small diameter at the bottom. An intermediate portion is formed in a taper shape, and an upper end portion is fitted and fixed to a lower portion of the liquid introduction tube 94, and a lower end portion of the air introduction tube 90 is inserted into the upper end portion with a gap provided therebetween. 100. The lower part of the air introduction pipe 90 is formed so that the outer diameter becomes small, and an annular gap is formed between the lower outer peripheral surface of the air introduction pipe 90 and the inner peripheral surface of the liquid introduction tube 94. The gap communicates with the through hole 96 of the liquid introduction pipe portion 96 to form an annular passage 102. Further, a gap formed between the outer peripheral surface of the lower end portion of the air introduction tube 90 and the inner peripheral surface of the upper end portion of the droplet generation tube 100 is connected to the annular passage 102 in a flow path so as to be inside the droplet generation tube 100. The annular discharge path 104 is opened. The lower end of the droplet generation tube 100 is an injection port 101.

  An air supply pipe 106 that is flow-connected to a compressed air source (not shown) is connected to the through hole 92 of the air introduction pipe 90. An open / close control valve 108 is inserted in the air supply pipe 106. In addition, a liquid supply pipe 110 is connected to a through hole 98 of a liquid introduction pipe portion 96 integrally formed with the liquid introduction cylinder 94, and a supply source of an etching solution containing hydrochloric acid is connected to the liquid supply pipe 110 (see FIG. An etchant supply pipe 112 connected to the flow path (not shown) and a pure water supply pipe 114 connected to the pure water supply source (not shown) are connected in communication. Opening / closing control valves 116 and 118 are respectively inserted in the etching solution supply pipe 112 and the pure water supply pipe 114.

  In the two-fluid nozzle 80 configured as described above, the open / close control valve 116 is opened (the open / close control valve 118 is closed at this time), and the liquid is supplied from the etchant supply source through the etchant supply pipe 112 and the liquid supply pipe 110. When an etching liquid, for example, hydrofluoric acid containing hydrochloric acid (etching liquid) is supplied to the liquid introduction pipe portion 96 of the introduction cylinder 94, the etching liquid passes through the annular passage 102 and the annular discharge path 104 from the lower opening of the annular discharge path 104. The ink is discharged obliquely downward into the droplet generation tube 100 toward the axial center. On the other hand, when the open / close control valve 108 is opened and compressed air is supplied from the compressed air source through the air supply pipe 106 to the air introduction pipe 90, the compressed air is liquid directly downward from the lower end discharge port of the air introduction pipe 90. It is discharged into the inside of the droplet generation tube 100. Then, the compressed air collides with the etching solution inside the droplet generation tube 100. Thereby, an etching liquid and compressed air are mixed and a droplet is produced | generated. The droplet 120 generated in the droplet generation tube 100 is imparted with straightness while passing through a straight tube portion formed in a small diameter of the droplet generation tube 100, and the ejection port 101 at the lower end of the droplet generation tube 100. Is ejected straight downward from the surface of the wafer W and sprayed onto the surface of the wafer W.

In this embodiment, the two-fluid nozzle 80 of the ET etching liquid supply mechanism 78 although the two-fluid nozzle of the internal mixing type, may be a two-fluid nozzle 80 as a two-fluid nozzle of an external mixing type.

  Next, an example of a method for cleaning the semiconductor wafer W using the substrate processing apparatus having the above-described configuration will be described.

By driving the motor 26, Ru rotate the wafer W on the spin base 10 in a horizontal plane. Further, the nozzle moving mechanism 88 is driven to move the two-fluid nozzle 80 from the retracted position indicated by the solid line in FIG. 1 to the upper position of the wafer W indicated by the two-dot chain line, and then approaches the surface of the wafer W. It is, swinging the two-fluid nozzle 80 in the horizontal plane. Then, while the two-fluid nozzle 80 is reciprocated between the central portion and the peripheral portion of the wafer W along the surface of the wafer W on the rotating spin base 10, an etching solution (hydrofluoric acid and A droplet of hydrochloric acid and pure water) is sprayed onto the surface of the wafer W. The mixing ratio (volume ratio) of hydrofluoric acid (50% solution), hydrochloric acid (35% solution) and pure water is, for example, HF: HCl: pure water = 1: 25 to 40: 200. The ratio of hydrofluoric acid is preferably in the range of HF: (HCl + pure water) = 1: 50 to 500. The ratio of hydrochloric acid is preferably in the range of HCl: pure water = 1: 5-75. In addition, what is necessary is just to perform a process at normal temperature, without adjusting temperature. At the same time, a cleaning liquid such as pure water is also discharged from the upper end discharge port of the nozzle 34 toward the center of the lower surface of the wafer W held by the spin base 10. The discharge of pure water or the like to the central portion of the lower surface of the wafer W is subsequently performed as necessary.

  When the cleaning process using the etchant is completed, the two-fluid nozzle 80 is moved back and forth between the central portion and the peripheral portion of the wafer W along the surface of the wafer W on the rotating spin base 10. Then, pure water is discharged onto the surface of the wafer W. At this time, the supply of compressed air to the air introduction pipe 90 of the two-fluid nozzle 80 is stopped. In addition, apart from the two-fluid nozzle 80, a discharge nozzle dedicated to pure water may be installed, and pure water may be discharged from the discharge nozzle onto the surface of the wafer W. When the rinsing process is completed, the wafer W is rotated at a high speed and spin-dried.

  This substrate processing method is suitable when a natural oxide film has already been formed on the surface of the wafer, and the oxide film on the wafer surface is selectively etched with an etching solution to adhere to the wafer surface. The contaminated metal contaminant is removed from the wafer surface together with the oxide film, and the layer on the wafer surface is eliminated, so that the particles are completely removed (lifted off). However, in this method, for example, when cleaning the surface of a silicon wafer, it is necessary not to etch until the bare silicon surface is exposed.

Note that only an etching solution made of hydrofluoric acid not containing hydrochloric acid may be used as the etching solution. Further, it other acidic solution in place of hydrochloric acid, such as citric acid, may be used such as oxalic acid.

FIG. 4 shows the etching characteristics when a wafer W is processed by spraying droplets of an etching solution (a mixed solution of hydrofluoric acid, hydrochloric acid and pure water) from the two-fluid nozzle 80 onto the surface of the wafer W. It is a figure compared with the case where wafer W is processed by discharging etching liquid on the surface of wafer W from a nozzle. In the graph shown in the figure, the horizontal axis represents the processing time, and the vertical axis represents the etching depth (nm). The wafer subjected to the experiment has a diameter of 8 inches and a thermal oxide film formed on the surface. The composition of the etching solution used is HF (50% aqueous solution): HCl (35% aqueous solution): pure water = 1: 41: 207. Moreover, the discharge flow rate of the etching liquid from the two-fluid nozzle 80 is 100 cc / min, and the discharge flow rate of the etching liquid from the rod-shaped nozzle is 1500 cc / min. As can be seen from the results shown in the figure, by using the two-fluid nozzle 80, even when the amount of etching solution used is about 1/15 of the conventional rod-shaped nozzle, it is equivalent to the case of using the rod-shaped nozzle. The etching characteristics were obtained. Under this condition, good results were obtained when the discharge flow rate of the etching solution from the two-fluid nozzle 80 was in the range of 50 cc / min to 130 cc / min.

FIG. 5 shows the in-plane uniformity when the wafer W is processed by ejecting droplets of an etching solution (a mixed solution of hydrofluoric acid, hydrochloric acid, and pure water) from the two-fluid nozzle 80 onto the surface of the wafer W. It is a figure which shows the result of having evaluated. In the graph shown in the figure, the horizontal axis is the distance from the center of the wafer, and the vertical axis is the etching depth (nm). The wafer subjected to the experiment has a diameter of 8 inches and a thermal oxide film formed on the surface. The composition of the etching solution used is HF (50% aqueous solution): HCl (35% aqueous solution): pure water = 1: 40: 200. Moreover, the discharge flow rate of the etching solution from the two-fluid nozzle 80 is 100 cc / min. As can be seen from the results shown in the figure, even when the two-fluid nozzle 80 is used, the etching uniformity within the wafer surface is not affected, and even when the etching amount is small, the etching can be performed within a good surface. Uniformity was obtained.

It is a top view which shows an example of a structure of the substrate processing apparatus used in order to implement the substrate processing method concerning this invention. It is the schematic block diagram which showed the principal part of the substrate processing apparatus seen from the direction shown by arrow A in FIG. It is a longitudinal cross-sectional view which shows an example of a structure of the two-fluid nozzle of the etching liquid supply mechanism in the substrate processing apparatus shown in FIG. It is a figure which shows an etching characteristic when wash | cleaning a board | substrate using the substrate processing apparatus shown in FIG. It is a figure which shows the result evaluated about the in-plane uniformity when performing a board | substrate washing | cleaning using the substrate processing apparatus shown in FIG.

Explanation of symbols

W Semiconductor wafer 10 Spin base 12 Chuck pin 16 Cylindrical rotating spindle 20 Casing 26 Motor 36 Cylindrical wall portion 38 Bottom wall portion 40 Collection tank
78 Etching solution supply mechanism 80 Two-fluid nozzle of etching solution supply mechanism
82 arms
84 Arm holding part
86 Rotating spindle
DESCRIPTION OF SYMBOLS 88 Nozzle moving mechanism 90 Air introduction pipe 94 Liquid introduction cylinder 96 Liquid introduction pipe | tube part 100 Droplet production | generation pipe | tube 101 Injection port 102 of droplet production | generation pipe | tube 102 Annular passage 104 Annular discharge passage
106 Air supply piping
108, 116, 118 Open / close control valve 110 Liquid supply piping 112 Etching liquid supply piping 114 Pure water supply piping 120 Etching liquid droplets

Claims (5)

Etchant comprising hydrofluoric acid, or the droplets produced by mixing the etching solution and a gas consisting of hydrofluoric acid containing an acidic solution, to form a thermal oxide film on the natural oxide film is formed or a surface on the surface A substrate processing method characterized by spraying onto the surface of a substrate and etching and cleaning the substrate surface. The substrate processing method according to claim 1, wherein the acidic liquid is hydrochloric acid. 3. The substrate according to claim 1, wherein after cleaning the surface of the substrate with the etching solution, pure water is discharged onto the surface of the substrate, and after rinsing with the pure water is completed, the substrate is rotated and spin-dried. Substrate processing method. 4. The droplets are generated by mixing an etchant and a gas in a two-fluid nozzle, and the droplets are ejected from the two-fluid nozzle to the surface of the substrate to clean the substrate surface. The substrate processing method according to any one of the above. The droplets are generated by mixing an etching solution and gas with a two-fluid nozzle, and the droplets are jetted from the two-fluid nozzle onto the surface of the substrate to clean the substrate surface. The substrate processing method according to claim 3, wherein the substrate processing method is performed by discharging pure water from the two-fluid nozzle to the surface of the substrate.

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