JP5294944B2 - Substrate cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve cleaning with enhanced cleaning capability by effectively using two-liquid jet cleaning even when residues tightly sticks on a substrate and sufficient cleaning performance cannot be obtained only by merely applying existent two-liquid jet cleaning in the case of cleaning after CMP etc. <P>SOLUTION: The method of cleaning the substrate, in which contaminants sticking on the substrate are cleaned, includes: performing processing for increasing the absolute value of a zeta potential of the substrate and the contaminants sticking on the substrate; and then carrying out contact cleaning for cleaning a surface of the substrate with a cleaning tool in contact with the surface of the substrate; and carrying out two-liquid jet cleaning for cleaning the substrate surface by jetting a gas and a liquid to the substrate surface simultaneously. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for cleaning a substrate such as a semiconductor wafer, and more particularly to a method for cleaning a substrate used in a post-CMP cleaning process.

A CMP (Chemical Mechanical Polishing) technique is widely used in a semiconductor wafer flattening process, a buried wiring forming process, and the like in a semiconductor device manufacturing process. In the CMP technique of a semiconductor wafer, various films to be polished such as SiO ₂ film and metal film formed on the semiconductor wafer are polished by using an abrasive containing abrasive grains called slurry. For this reason, abrasive grains, solutions, and polishing residues contained in the slurry remain on the semiconductor wafer after polishing. In order to remove these residues on the semiconductor wafer, post-CMP cleaning is performed. As the post-CMP cleaning, contact cleaning is generally used in which a cleaning tool such as a sponge brush (PVA sponge) made of PVA (polyvinyl alcohol) is brought into contact with a semiconductor wafer while using ultrapure water or a chemical solution as a cleaning solution. It is used.

  The post-CMP cleaning is generally performed by dividing into first-stage cleaning, second-stage cleaning, and further. In the first stage cleaning by the contact cleaning method, for example, as shown in FIG. The roll type PVA sponge 40 is pressed against the substrate W with an appropriate pressure while being supplied to the front and back surfaces. The substrate W and the roll type PVA sponge 40 are each rotated by being held by a holder (not shown).

  FIG. 9 shows a cleaning machine 70 suitable for performing the second stage cleaning by the contact cleaning method. The cleaning machine 70 is disposed above the substrate W by being suspended from a cleaning cup 72 that surrounds the periphery of the rotating substrate W held by a chuck (not shown) or the like and a free end of the swing arm 74. A rotatable pencil-type PVA sponge (cleaning tool) 76 and a cleaning liquid nozzle 80 for supplying a cleaning liquid 78 to the surface of the substrate W are provided. A control unit 82 such as a mass flow controller is installed in the cleaning liquid supply line that supplies the cleaning liquid to the cleaning liquid nozzle 80.

  As a result, the pencil-type PVA sponge (cleaning tool) 76 is brought into contact with the surface of the substrate W held and rotated via a chuck (not shown) with a predetermined pressing force, and is swung while rotating. By supplying a cleaning liquid such as pure water or a chemical solution to the surface of the substrate W, the second stage cleaning (contact cleaning) of the surface of the substrate W is performed in the cleaning cup 72. After cleaning, the substrate W is dried by high speed spin or IPA (isopropyl alcohol) vapor.

  However, when a substrate such as a semiconductor wafer is cleaned by the conventional contact cleaning method as described above, contaminants such as a CMP residue are accumulated inside a cleaning tool such as a PVA sponge while the substrate is repeatedly cleaned, and is transferred onto the substrate. The problem is that reverse contamination occurs. This problem is a universal issue regardless of the shape of the PVA sponge, the type of cleaning liquid, and the supply method.

  When observing and analyzing the minute foreign matter remaining on the substrate with a scanning electron microscope or the like, most of them are abrasive grains contained in the slurry, and it is highly possible that the abrasive grains are accumulated in a large amount in the PVA sponge. I understand. Furthermore, when the contamination on the substrate is measured by the foreign substance inspection device, a lot of deposits may be detected at the place where the PVA sponge contacts the semiconductor wafer at the end of the contact cleaning, which confirms the occurrence of the reverse contamination. It turns out that it is.

In response to such problems of contact cleaning, so-called two-fluid jet cleaning has been proposed in which liquid and gas are supplied into an ejection nozzle and two substrates are ejected at high speed from the ejection nozzle toward the substrate to clean the substrate. (See Patent Document 1). In the two-fluid jet cleaning, for example, as shown in FIG. 4, a cleaning liquid such as pure water or CO ₂ gas-dissolved water and a gas such as N ₂ gas or dry air are jetted at high speed in the jet nozzle section 54. A two-fluid jet flow 52 in which the cleaning liquid is present as minute mist is generated, and the two-fluid jet flow 52 is sprayed on the surface of the substrate W at a high speed to remove foreign matters on the substrate W by the pressure at the time of mist collision. . Two-fluid jet cleaning is expected as a next-generation cleaning technology from the viewpoint of non-contact type, stable cleaning performance without electrostatic damage.

  In addition, as a method using the two-fluid jet cleaning method, the first chemical solution is supplied to the substrate to fill the substrate surface with the first chemical solution, and the second chemical solution is applied to the substrate surface filled with the first chemical solution. A cleaning method has been proposed in which the substrate surface is cleaned by a two-fluid cleaning method (see Patent Document 2).

Japanese Patent No. 3504023 JP 2008-226900 A

  By replacing some or all of the cleaning steps using the contact cleaning method with the cleaning steps using the two-fluid jet cleaning, cleaning without back-contamination can be expected. However, in the post-CMP cleaning, the abrasive grains contained in the slurry in the CMP process are pressed against the substrate with a strong pressure, so that the residue adheres more firmly to the substrate than in the case of being removed by a general cleaning process. It has been found that sufficient cleaning performance cannot be obtained simply by applying the two-fluid jet cleaning to the post-CMP cleaning.

In Table 1, the TEOS film formed on the surface of a semiconductor wafer having a diameter of 300 mm is CMPed with a slurry containing SiO ₂ abrasive grains or CeO ₂ abrasive grains, and the number of residual particles after cleaning by conventional contact cleaning is similar to that of CMP. Table 1 shows the results of the measurement of the number of residual particles when the two-fluid jet cleaning is performed after the above.

For the measurement of the number of particles, the number of particles of 80 nm or more was detected excluding the edge 2 mm of the semiconductor wafer. The cleaning step of the contact cleaning includes a first stage cleaning using the first cleaning machine 16 shown in FIG. 3 and a second stage cleaning using the cleaning machine 70 shown in FIG. used. Then, two evaluations were performed immediately after the pencil-type PVA sponge (cleaning tool) 76 of the cleaning machine 70 shown in FIG. 9 was replaced with a new one and after being used for cleaning processing of 600 semiconductor wafers. The two-fluid jet cleaning, after the first-stage cleaning using the first cleaning machine 16 shown in FIG. 3, by using the second cleaning machine 18 shown in FIG. 4, CO ₂ gas dissolved water (flow rate 200ml / min) and N ₂ gas (flow rate: 100 L / min).

As can be seen from Table 1, in contact cleaning, the number of particles of 80 nm or more is 26,000 or more regardless of whether the PVA sponge is used or not, and even if the particle size is limited to 120 nm or more, 1,500 to 2,000 particles are generated. was detected. On the other hand, in the two-fluid jet cleaning, the number of particles is slightly reduced by 80 nm or more, and although it can be seen that the cleaning performance is slightly better than the contact cleaning, many particles still remain. The reason why the contact cleaning has a larger number of residual particles than the two-fluid jet cleaning is thought to be that contamination is accumulated in the PVA sponge and reverse contamination occurs. Even if ultrapure water was used in place of the CO ₂ gas-dissolved water, no difference was observed in the tendency shown in Table 1.

  The present invention has been made in view of the above circumstances. For example, in the case of post-CMP cleaning, the residue adheres firmly to the substrate, and sufficient cleaning performance is obtained simply by applying the existing two-fluid jet cleaning. It is an object of the present invention to provide a method for cleaning a substrate that can perform cleaning with improved cleaning capability by more effectively using two-fluid jet cleaning even if it cannot be obtained.

The substrate cleaning method of the present invention is a substrate cleaning method for cleaning contaminants attached to a substrate. The zeta potential of contaminants attached on a substrate having the same polarity as the zeta potential of the substrate and the data potential. A process to increase both absolute values is performed, and then the substrate surface is cleaned by bringing a cleaning tool into contact with the substrate surface to clean the substrate surface and simultaneously jetting gas and liquid toward the substrate surface. Two-fluid jet cleaning is performed.

Thus, by performing the processing together to increase the absolute value of the zeta potential of the contaminants adhering on the substrate having the same polarity as the zeta potential and the data potential of the substrate, between the substrate and the contaminants Increases the electric repulsive force, so that, for example, abrasive grains firmly pressed against the substrate surface during CMP can also be detached from the substrate surface, and then cleaning performance by contact cleaning and two-fluid jet cleaning Can be increased.

It is preferable that both the zeta potential of the substrate after the increase in the absolute value of the zeta potential and the zeta potential of the contaminant attached on the substrate are −50 mV or less or +50 mV or more.

  The treatment for increasing the absolute value of the zeta potential can be performed by supplying a cleaning liquid containing a surfactant to the substrate surface. The treatment for increasing the absolute value of the zeta potential may be performed by supplying an alkaline cleaning liquid to the substrate surface.

  The cleaning tool is made of, for example, PVA sponge. Thereby, it is possible to prevent the contamination from being accumulated in the PVD sponge.

  The treatment for increasing the absolute value of the zeta potential is preferably performed on the substrate immediately after CMP. This enhances the cleaning effect on the substrate even in the case of post-CMP cleaning in which the residue adheres firmly to the substrate and sufficient cleaning performance cannot be obtained simply by applying the existing two-fluid jet cleaning. be able to.

At least one of the contact cleaning and the two-fluid jet cleaning, it is carried out while both increasing the absolute value of the zeta potential of the contaminants adhering on the substrate having the same polarity as the zeta potential and the data potential of the substrate preferable. Accordingly, even in the contact cleaning or the two-fluid jet cleaning, the electric repulsive force between the substrate and the contaminant can be increased to further enhance the cleaning effect.

According to the present invention, by performing the processing together to increase the absolute value of the zeta potential of the contaminants adhering on the substrate having the same polarity as the zeta potential and the data potential of the substrate, the substrate and the contaminants By increasing the electric repulsive force between them, for example, abrasive grains firmly pressed against the substrate surface during CMP can also be detached from the substrate surface, and then contact cleaning and two-fluid jet cleaning are performed. The cleaning ability can be increased.

1 is an overall layout view of a CMP apparatus used in a substrate cleaning method of the present invention. It is a figure which shows the outline | summary of the grinding | polishing part with which the CMP apparatus shown in FIG. 1 is equipped. It is a figure which shows the outline | summary of the 1st washing machine with which the CMP apparatus shown in FIG. 1 is equipped. It is a figure which shows the outline | summary of the 2nd grinding machine with which the CMP apparatus shown in FIG. 1 is equipped. It is a processing flowchart of the washing | cleaning method of the board | substrate of embodiment of this invention. It is a processing flowchart of the washing | cleaning method of the board | substrate of other embodiment of this invention. It is a processing flowchart of the washing | cleaning method of the board | substrate of other embodiment of this invention. It is a processing flowchart of the washing | cleaning method of the board | substrate of other embodiment of this invention. It is a figure which shows the outline | summary of the conventional washing machine.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the following examples, it applied to the post-CMP cleaning of the substrate for cleaning a substrate such as a semiconductor wafer immediately after performing CMP using a slurry containing abrasive grains such as SiO ₂ abrasive grains or CeO ₂ abrasive grains. An example is shown. Needless to say, the present invention can be widely applied to substrate cleaning in general other than post-CMP cleaning.

  FIG. 1 is an overall layout view of a CMP apparatus used in the substrate cleaning method of the present invention. As shown in FIG. 1, the CMP apparatus includes a polishing unit 10, a load / unload unit 12, two transporters 14 a and 14 b, a first cleaning machine 16 that performs first-stage cleaning by contact cleaning of the substrate, A second cleaning machine 18 and a reversing machine 20 that perform the second stage cleaning by the two-fluid jet cleaning are provided, and a substrate delivery table 22 is disposed between the polishing unit 10 and the transfer machine 14a.

  The polishing unit 10 performs polishing (CMP) processing of the substrate W such as a semiconductor wafer, and the absolute value of the zeta voltage of the substrate W immediately after CMP and contaminants (abrasive grains contained in the slurry) adhering to the substrate W. As shown in FIG. 2, a rotatable polishing table 26 having a polishing pad 24 attached to the upper surface and a pressing force against the polishing table 26 while holding the substrate W as shown in FIG. A rotatable substrate holder 28, a slurry nozzle 32 that supplies a slurry (abrasive) 30 onto the polishing pad 24, and a cleaning liquid nozzle 36 that supplies a cleaning liquid 34 onto the polishing pad 24 are provided.

As a result, the substrate W held by the substrate holder 28 is pressed against the polishing pad 24 while rotating the substrate holder 28 and the polishing table 26, and at the same time, the slurry 30 is supplied from the slurry nozzle 32 onto the polishing pad 24. Polish. After the polishing of the substrate W, the substrate W held by the substrate holder 28 is pressed against the polishing pad 24 while rotating the substrate holder 28 and the polishing table 26 , respectively, and the cleaning liquid nozzle 36 is placed on the polishing pad 24. By supplying the cleaning liquid 34 containing the surfactant, the absolute value of the zeta voltage of the contaminants such as abrasive grains contained in the slurry 30 attached to the surface of the substrate W and the substrate W is increased. Instead of the cleaning liquid 34 containing the interfacial temporary agent, an alkaline cleaning liquid may be used.

  As shown in FIG. 3, the first cleaning machine 16 that performs first-stage cleaning by contact cleaning of the substrate W grips the outer peripheral portion with, for example, a roller and rotates both the front and back surfaces of the substrate W as the roller rotates. And a pair of roll-type PVA sponges (cleaning tools) 40 that are movable in a direction that allows them to move toward and away from each other, and a cleaning liquid nozzle 44 that supplies the cleaning liquid 42 to both the front and back surfaces of the substrate W. A control unit 46 such as a mass flow controller for controlling the flow rate is installed in the cleaning liquid supply line for supplying the cleaning liquid.

  As a result, a pair of roll-type PVA sponges (cleaning tools) 40 are rotated on the front and back surfaces of the substrate W while rotating with a predetermined pressing force between the front and back surfaces of the substrate W rotating with the rotation of the roller or the like. By supplying the cleaning liquid 42 from the cleaning liquid nozzle 44, the front and back surfaces of the substrate W are cleaned (first-stage cleaning).

As shown in FIG. 4, the second cleaning machine 18 that performs the second stage cleaning by the two-fluid jet cleaning of the substrate W holds the substrate W by a chuck (not shown) or the like and rotates the substrate W as the chuck rotates. A cleaning cup 50 that surrounds the periphery and a substrate W held by the chuck or the like are arranged in a freely movable manner, and a cleaning fluid and a gas are jetted toward the substrate W at a high speed to generate a two-fluid jet flow 52. And an ejection nozzle 54 for spraying at high speed. The jet nozzle 54 is connected to a cleaning liquid supply line 56 for supplying a cleaning liquid such as pure water or CO ₂ gas-dissolved water, and a gas supply line 58 for supplying a gas such as N ₂ gas or dry air. 58 includes control units 60 and 62 for adjusting the flow rates of the cleaning liquid and the gas, respectively.

Thereby, the cleaning liquid such as pure water or CO ₂ gas-dissolved water and the gas such as N ₂ gas or dry air are ejected from the ejection nozzle 54 at a high speed, so that the cleaning liquid exists in the gas as a minute mist. A fluid jet flow 52 is generated, and the two-fluid jet flow 52 is sprayed at high speed toward the rotating substrate W held by a chuck or the like, so that foreign matters on the substrate W are removed by the pressure at the time of mist collision. Is done. As a result, the substrate W is cleaned (second stage cleaning).

Next, a substrate cleaning method according to an embodiment of the present invention will be described with reference to the processing flow of FIG.
First, the substrate W stored in a storage case such as a substrate cassette is set in the load / unload unit 12. The substrate W is, for example, a semiconductor wafer having a diameter of 300 mm and a TEOS film formed on the surface. One substrate W is taken out from the storage case set in the load / unload unit 12 by the transfer device 14b and transferred to the reversing device 20. The substrate W whose surface is inverted downward by the reversing machine 20 is transported to the substrate delivery table 22 by the transporting machine 14 a and is held by the substrate holder 28 of the polishing unit 10.

  After the substrate holder 28 holding the substrate W is moved above the polishing table 26, the substrate holder 28 is lowered and the substrate W is pressed with a predetermined pressing force while rotating the substrate holder 28 and the polishing table 26, respectively. At the same time, the slurry 30 is supplied from the slurry nozzle 32 onto the polishing pad 24 to polish the substrate W (TEOS film polishing). After the polishing of the substrate W, the substrate W held by the substrate holder 28 is pressed against the polishing pad 24 while rotating the substrate holder 28 and the polishing table 26, respectively, and the cleaning liquid nozzle 36 is placed on the polishing pad 24. By supplying the cleaning liquid 34 containing a surfactant, the absolute value of the zeta voltage of the substrate W and contaminants such as abrasive grains contained in the slurry attached to the substrate W is increased. The supply time of the cleaning liquid 34 containing the surfactant is required to be several seconds or more, and is preferably 10 seconds or more. The pressing force for pressing the substrate W toward the polishing pad 24 while supplying the cleaning liquid 34 containing the surfactant may be smaller than the pressing force for pressing the substrate W toward the polishing pad 24 during polishing.

  Next, the substrate W held by the substrate holder 28 is transferred to the substrate transfer table 22 and transferred, and the substrate received by the substrate transfer table 22 is transferred to the first cleaner 16 by the transfer device 14a. With this cleaning machine 16, a pair of roll-type PVA sponges (cleaning tools) 40 are rotated while contacting with a predetermined pressing force on both the front and back surfaces of the substrate W rotating with the rotation of a roller or the like. By supplying the cleaning liquid 42 made of pure water from the cleaning liquid nozzle 44 to both the front and back surfaces, the front and back surfaces of the substrate W are contact cleaned (first stage cleaning).

The substrate W after the first stage cleaning is transferred to the reversing machine 20 by the transfer machine 14a, and the substrate whose surface is turned upside down by the reversing machine 20 is transferred to the second cleaning machine 18 by the transfer machine 14a. With this cleaning machine 18, for example, two fluids consisting of N ₂ gas 100 L / min and CO ₂ dissolved water 200 ml / min are sprayed from the ejection nozzle 54 onto the surface of the substrate W at a high speed to perform two-fluid jet cleaning (second stage cleaning )I do.

  Next, the substrate W is dried by the high-speed spin by the cleaning machine 18, and the dried substrate W is returned to the storage case (substrate cassette) of the load / unload unit 12 by the transport device 14b.

Table 2 shows the results of measuring the number of residual particles on the substrate (wafer) when the above treatment is performed, as two-fluid jet cleaning. For comparison, instead of the two-fluid jet cleaning by the second cleaning machine 18, the cleaning machine 70 shown in FIG. 9 is used, and the residue on the substrate (wafer) is cleaned using pure water as the cleaning liquid. The results of measuring the number of particles are also shown in Table 2 as contact cleaning.

  From Table 2, by adding a treatment with a cleaning solution containing a surfactant (a treatment that increases the absolute value of the zeta voltage of the substrate and contaminants on the substrate), 9,601 particles, 80 It can be seen that the number of fluid jet cleaning is 6,400, which is a significant improvement compared to 20,000-36,000 remaining in the conventional cleaning method. Furthermore, when compared with the larger number of particles with a size of 120 nm or more, which is likely to affect the yield of semiconductor devices, the number is 1,905 after contact cleaning, but it is reduced to 717 after two-fluid jet cleaning. You can see that

The following reasons can be considered as a mechanism that can reduce the number of residual particles by supplying a cleaning liquid containing a surfactant before the two-fluid jet cleaning process. That is, when the zeta potential in the cleaning liquid of the substrate surface film (SiO ₂ film) and abrasive grains (SiO ₂ particles or CeO ₂ particles) to be CMP is compared, when the cleaning liquid is ultrapure water (pH 7), SiO 2 ₂ and CeO ₂ have a weak negative potential of −20 to −50 mV, but in the case of ultrapure water to which a surfactant is added, a strong negative potential of −50 mV or more is shown, and the SiO ₂ film and abrasive grains The electric repulsive force between is increasing. As a result, abrasive grains firmly pressed against the surface of the substrate surface film (SiO ₂ film) during CMP can be detached, and re-adhesion can be suppressed. At the same time, the pressure at the time of micro mist collision generated by the two-fluid jet exceeds the contact cleaning by the pencil type PVA sponge, and it is easy to remove foreign matters, and the two-fluid jet cleaning is non-contact cleaning and there is no back contamination, It is considered that excellent cleaning performance as shown in Table 2 was achieved.

The results in Table 2 are for the conditions where the N ₂ gas flow rate is 100 L / min and the CO ₂ gas dissolved water flow rate is 200 ml / min, but the N ₂ gas flow rate is reduced to 75 L / min, 50 L / min or less. However, it has been confirmed that substantially the same cleaning performance can be obtained even if the flow rate of the CO ₂ gas dissolved water is reduced to 100 ml / min or less. In addition, CO ₂ gas-dissolved water is effective for preventing electrification at the time of cleaning, but for the purpose of removing particles only, the same effect can be obtained even if ultra pure water is used instead of CO ₂ gas-dissolved water. It has been confirmed that

  In the above embodiment, the surfactant is used as a means for giving an electric repulsive force between the substrate surface film and the abrasive grains, but an equivalent effect can be obtained even with an alkaline chemical solution. In addition, the number of times the cleaning liquid containing the surfactant or the alkaline chemical liquid is supplied onto the polishing pad is not limited to one time, and may be supplied several times after the CMP. Slurry or another chemical may be supplied to the polishing pad. In the above embodiment, the first stage cleaning and the second stage cleaning are performed by two cleaning machines. However, the number of cleaning machines is three or more, and the third stage cleaning or more is performed. May be. Furthermore, the installation position and direction of the roll type PVA sponge 40 and the substrate W in the first cleaning machine 16 that performs the first stage cleaning can be arbitrarily set. For example, the substrate may be installed vertically so that the roll type PVA sponge contacts at least the surface of the substrate. The drying method in the second cleaning machine 18 that performs the second stage cleaning is not limited to high-speed spin rotation, and may be IPA drying or another drying means. The same applies to the following examples.

  FIG. 6 shows a processing flow of another embodiment of the present invention. This example is different from the example shown in FIG. 5 in that the cleaning liquid 34 used for contact cleaning by the first cleaning machine 16 shown in FIG. The point is that water is used. Thus, contact cleaning by the roll type PVD sponge (cleaning tool) 40 is performed while increasing the absolute value of the contaminants such as abrasive grains adhering to the substrate W and the substrate W.

Table 3 shows the results of measuring the number of residual particles on the substrate (wafer) when the above treatment is performed, as two-fluid jet cleaning. For comparison, instead of the two-fluid jet cleaning by the second cleaning machine 18, the cleaning machine 70 shown in FIG. 9 is used, and the residue on the substrate (wafer) is cleaned using pure water as the cleaning liquid. The results of measuring the number of particles are also shown in Table 3 as contact cleaning.

  In the two-fluid jet cleaning, as compared with Table 2, there is an effect of reducing about 1,100 particles at 80 nm or more, and the number of particles at 120 nm or more is halved. In the contact cleaning, there is no effect of adding the surfactant, and conversely, the number of particles is larger than the cleaning result with pure water shown in Table 2. This phenomenon is because some of the particles removed by contact cleaning are accumulated inside the sponge, but the sponge itself is also cleaned by the addition of the surfactant, and the accumulated particles are released and remain on the substrate. It is believed that there is.

Table 4 shows the results obtained by measuring the number of residual particles on the substrate (wafer) when the surfactant concentration of the cleaning liquid used for the first stage cleaning is changed stepwise to 0.5 to 8%.

From Table 4, there is a tendency for the number of residual particles to be large when the surfactant concentration in the cleaning liquid is 2% and 4%, and the number of particles is small when the surfactant concentration is 0.5% and 8%. I understand. Therefore, the surfactant concentration in the cleaning liquid is more preferably less than 2% or higher than 4%. The reason why the number of particles slightly increases in the region where the surfactant concentration of the cleaning liquid is 2 to 4% is presumed as follows. That is, as long as the abrasive grains are aggregated from several to several tens of fine abrasive grains and exist in the slurry, and there is no change in the electrical repulsion between the abrasive grains, the surface of the polished substrate (SiO ₂ ) However, it remains in this aggregated state. When the amount of the surfactant added is increased by post-cleaning, the electrical repulsion between the abrasive grains increases, the aggregation of the abrasive grains weakens, the abrasive grains are scattered, and the total surface area of the abrasive grains increases. However, in a state where the amount of the surfactant is halfway (in this case, corresponding to a region having a concentration of 2 to 4%), although the surfactant is adsorbed on the increased abrasive grain surface, the substrate surface film (SiO ₂ film) The amount of surfactant adsorbed on the surface will be insufficient. For this reason, the electric repulsive force between the substrate surface film (SiO ₂ film) and the abrasive grains becomes insufficient, and is detected as an increase in the number of residual particles. When the surfactant concentration in the cleaning liquid is higher than 4%, for example, 8%, a sufficient amount of the surfactant can be adsorbed on the substrate surface film (SiO ₂ surface), so the number of residual particles decreases again.

  FIG. 7 shows a process flow of a substrate cleaning method according to still another embodiment of the present invention. 5 and 6 of this example is different from the example shown in FIG. 5 and FIG. 6 as a cleaning liquid 52 used for two-fluid jet cleaning by the second cleaning machine 18 shown in FIG. The point is that water is used. Thus, the two-fluid jet cleaning is performed while increasing the absolute value of the contaminants such as abrasive grains adhering to the substrate W and the substrate W.

In this case, for example, a surfactant may be added to the CO ₂ gas-dissolved water. However, when a surfactant that easily foams is used, the surfactant foams at the time of mist formation and hinders cleaning. In that case, it is preferable to add an antifoaming agent as appropriate together with the surfactant. For example, a two-fluid jet composed of N ₂ gas and CO ₂ gas-dissolved water is sprayed onto the substrate surface, and simultaneously with FIG. A cleaning liquid containing a surfactant may be supplied to the substrate surface from another cleaning liquid nozzle (not shown). The timing at which the cleaning liquid containing the surfactant is supplied to the substrate surface may not be the entire time during which the two-fluid jet is ejected, but only a part of the time, for example, the initial time during which the two-fluid jet is ejected.

  FIG. 8 shows a processing flow of still another embodiment of the present invention. 7 is different from the example shown in FIG. 7 in that, when the two-fluid jet cleaning is performed by the second cleaning machine 18 shown in FIG. 4, a cleaning liquid containing a surfactant is first supplied from the cleaning liquid nozzle not shown in FIG. However, after that, the two-fluid jet is jetted onto the substrate surface. As described above, even when the cleaning liquid containing the surfactant is supplied to the substrate surface before the two-fluid jet cleaning, the same cleaning effect as described above can be obtained. Further, a higher cleaning effect can be obtained by alternately repeating the step of supplying the cleaning liquid containing the surfactant to the substrate surface and the step of performing the two-fluid jet cleaning.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 10 Polishing part 12 Load / unload part 14a, 14b Conveyor 16, 18 Cleaning machine 24 Polishing pad 26 Polishing table 28 Substrate holder 30 Slurry 32 Slurry nozzle 34, 42 Cleaning liquid 36, 44 Cleaning liquid nozzle 40 Roll type PVA sponge (cleaning tool )
50 Washing cup 52 Two-fluid jet 54 Spray nozzle 56 Cleaning liquid supply line 58 Gas supply line

Claims (7)

In the substrate cleaning method for cleaning contaminants adhering to the substrate,
It performs a process of both increasing the absolute value of the zeta potential of the contaminants adhering on the substrate having the same polarity as the zeta potential and the data potential of the substrate, thereafter,
A substrate characterized by performing contact cleaning in which a cleaning tool is brought into contact with the surface of the substrate to clean the surface of the substrate, and two-fluid jet cleaning in which gas and liquid are simultaneously jetted toward the substrate surface to clean the substrate surface. Cleaning method. The zeta potential of the substrate after the increase in the absolute value of the zeta potential and the zeta potential of the contaminant adhering to the substrate are both -50 mV or less or +50 mV or more. Item 4. A method for cleaning a substrate according to Item 1.   3. The substrate cleaning method according to claim 1, wherein the treatment for increasing the absolute value of the zeta potential is performed by supplying a cleaning liquid containing a surfactant to the substrate surface.   3. The substrate cleaning method according to claim 1, wherein the treatment for increasing the absolute value of the zeta potential is performed by supplying an alkaline cleaning liquid to the substrate surface.   The substrate cleaning method according to claim 1, wherein the cleaning tool is made of PVA sponge.   6. The method for cleaning a substrate according to claim 1, wherein the processing for increasing the absolute value of the zeta potential is performed on the substrate immediately after CMP. At least one of the contact cleaning and the two-fluid jet cleaning, to be performed while both increasing the absolute value of the zeta potential of the contaminants adhering on the substrate having the same polarity as the zeta potential and the data potential of the substrate The substrate cleaning method according to claim 1, wherein the substrate is cleaned.

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