JP2006100735A - Cleaning method of cover glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method which attains high cleaning performance and a low cost, in cleaning the cover glass of a solid-state image pickup device. <P>SOLUTION: The cleaning method of the cover glass is employed when the solid-state image pickup device is manufactured, wherein a solid-state image pickup element chip with a solid-state image pickup element formed on its surface, and the cover glass joined to the solid-state image pickup element chip, are provided between the solid-state image pickup element chip and the cover glass. Then the device is sealed by a spacer of a predetermined thickness of a shape surrounding the solid-state image pickup element. The cleaning method includes a first wet cleaning process in which the cover glass with the spacer formed on the surface is cleaned by deionized water, a dry cleaning process in which ashing of the cover glass is carried out by oxygen plasma, and a second wet cleaning process in which the cover glass is cleaned by APM liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for cleaning a cover glass, and more particularly, to a method for cleaning a cover glass when manufacturing a chip size package (CSP) type solid-state imaging device.

  A solid-state imaging device made of a CCD or a CMOS used for a digital camera or a mobile phone is increasingly required to be downsized. For this reason, the conventional large package, in which the entire solid-state image sensor chip is hermetically sealed in a ceramic package or the like, has recently moved to a chip size package (CSP) type, which is approximately the same size as the solid-state image sensor chip. I am doing.

  Under such circumstances, a spacer is formed on the transparent glass plate so as to correspond to the position surrounding the light receiving portion of each solid-state image sensor formed on the wafer (semiconductor substrate). A method has been proposed in which a gap is formed between the wafer and the wafer, and then the transparent glass plate and the wafer are diced along a scribe line and separated into individual solid-state imaging devices ( For example, see Patent Documents 1 to 3.)

  As a method for forming a spacer on such a transparent glass plate, photoetching is generally used. FIG. 6 is a cross-sectional view of the step of forming this spacer. In FIG. 6A, a wafer serving as a spacer 13 is bonded to the surface of a cover glass 12 corresponding to a transparent glass plate via an adhesive 13A, and then a pattern of a photoresist R is formed on the surface of the wafer.

  As a wafer to be the spacer 13, for example, a silicon wafer can be used. The pattern of the photoresist R is formed through processes such as resist coating, exposure using a photomask, development, and post baking.

  Next, in FIG. 6B, anisotropic etching is performed on the wafer (silicon wafer) to be the spacer 13 by dry etching to form a pattern of the spacer 13. At this time, the adhesive 13A is not removed because it has etching resistance.

Next, in FIG. 6C, ashing is performed to remove the pattern of the photoresist R and the exposed adhesive 13A. In this way, the pattern of the spacers 13 is formed on the surface of the cover glass 12.
JP-A-7-202152 JP 2002-231921 A JP 2004-6834 A

  However, such a method for forming a spacer has a high probability of causing the following problems (defects 1 to 3).

  Defect 1 is insufficient cleanliness. In the cover glass 12 having the pattern of the spacers 13 formed on the surface, it is necessary to remove all foreign matters having a size of 5 μm or more that affect the image to be captured. However, in the above processing method, dry etching residues, foreign matters due to the environment and the like cannot be sufficiently removed, and the cleanness tends to be insufficient as a cover glass of the solid-state imaging device.

  As a defect 2, an adhesive trace is mentioned. FIG. 7 is a flowchart for explaining a mechanism that causes such a problem. FIG. 7 is a partial cross-sectional view showing an enlarged portion of each solid-state imaging device chip in the cover glass 12 shown in FIG.

  7A is an enlarged view of a portion where the pattern of the spacer 13 of FIG. 6B is not formed. In FIG. 7A, foreign substances 30, 30 such as particles are present on the surface of the layer of the adhesive 13A.

  In FIG. 7B, ashing (oxygen plasma ashing) for removing the pattern of the photoresist R (see FIG. 6B) and the layer of the adhesive 13A is performed. However, as shown in FIG. 7C, if there are foreign substances 30 and 30 such as particles, the foreign substances 30 and 30 act as a mask for ashing, and the removal of the adhesive 13A at this portion is insufficient. It becomes.

  Then, the remaining adhesive 13 </ b> A remains as an adhesive trace even after the cleaning that is the next step. Although this adhesive trace greatly deteriorates the quality of the solid-state imaging device, it must be removed, but it is difficult to remove it later by a general cleaning method, which is a serious problem.

Defect 3 includes peeling of the spacer 13. The dry etching residue and the foreign matters resulting from the environment in the above-described defect 1 are organic substances. On the other hand, when the conventional general wet cleaning that acts on the organic substance, for example, cleaning with an SPM liquid (a liquid in which the ratio of H ₂ SO ₄ : H ₂ O ₂ is 4: 1) is performed, the organic substance is caused by the action of the chemical solution. This damages the adhesive of the spacer and causes the spacer 13 to peel off.

  The present invention has been made in view of such circumstances, and is a solid-state imaging device composed of a solid-state imaging device chip (wafer) and a cover glass, such as a chip size package (CSP) type solid-state imaging device. In cleaning the cover glass, an object of the present invention is to provide a method for cleaning the cover glass that eliminates the above-mentioned drawbacks and has high cleaning performance and low cost.

  In order to achieve the above object, the present invention provides a process of forming a large number of solid-state image sensors on the upper surface of a wafer, and individual solid-states at locations corresponding to the solid-state image sensors on the lower surface of a cover glass bonded to the wafer. A step of forming a frame-shaped spacer having a predetermined thickness surrounding the image sensor; a step of aligning the wafer and the cover glass and bonding the spacer through the spacer; and the bonded wafer and the cover Dividing the glass into individual solid-state imaging devices, and a method of cleaning the cover glass of the solid-state imaging device manufactured by the first wet cleaning of the cover glass having the spacer formed on the surface with pure water A cleaning step, a dry cleaning step of ashing the cover glass after wet cleaning with oxygen plasma, and the cover glass after dry cleaning A second wet cleaning step of cleaning with APM solution, provides a cleaning method of the cover glass, characterized in that it comprises a.

  Further, according to the present invention, a solid-state image sensor chip having a solid-state image sensor formed on a surface and a cover glass bonded to the solid-state image sensor chip are provided between the solid-state image sensor chip and the cover glass. In the method for cleaning a cover glass when manufacturing a solid-state imaging device sealed with a spacer having a predetermined thickness surrounding the solid-state imaging element, the cover glass having the spacer formed on the surface is purified water. A first wet cleaning step for cleaning with, a dry cleaning step for ashing the cover glass after wet cleaning with oxygen plasma, and a second wet cleaning step for cleaning the cover glass after dry cleaning with an APM solution. A cover glass cleaning method is provided.

  According to the present invention, since a cleaning process is provided before and after ashing, high cleaning performance can be obtained. In particular, by using the APM liquid, the zeta potential on the glass surface takes a large negative value, so that the reattachment of foreign matters is small.

  In the present invention, it is preferable to apply ultrasonic vibration of 50 kHz or less in the first wet cleaning step. By applying such low-frequency ultrasonic vibration, the cleaning property is improved and the effects of the present invention can be further exhibited.

  Moreover, in this invention, it is preferable to manage an APM liquid at 40-90 degreeC and to apply an ultrasonic vibration of 950 kHz or more in the said 2nd wet cleaning process. By managing the APM liquid at such a temperature and applying ultrasonic vibration, the etching rate can be increased and the cleaning time can be shortened.

  Moreover, in this invention, it is preferable that the volumetric compounding ratio of ammonia of APM liquid and hydrogen peroxide shall be 0.10-0.34 in the said 2nd wet cleaning process. Moreover, in this invention, it is preferable that the volumetric compounding ratio of the hydrogen peroxide of APM liquid and water shall be 0.05-0.34 in the said 2nd wet washing process. By setting it as such a mixture ratio, the etching rate of the silicon | silicone as a spacer can be made low, and, thereby, the undercut of a spacer can be made small.

  Moreover, in this invention, it is preferable to wash | clean the said cover glass with the pure water which applied the ultrasonic vibration of 50 kHz or less after the washing | cleaning by APM liquid in the said 2nd wet washing process. By adding such a process, it is possible to easily remove foreign matters that could not be removed by cleaning with the APM liquid.

  As described above, according to the method for cleaning a cover glass of the present invention, since a cleaning process is provided before and after ashing, high cleaning performance can be obtained. In addition, by using the APM liquid, the zeta potential on the glass surface takes a large negative value, so that there is little reattachment of foreign matter.

  Hereinafter, preferred embodiments of a cover glass cleaning method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 and FIG. 2 are a perspective view and a cross-sectional view showing a main part of a chip size package (CSP) type solid-state imaging device to which a cover glass cleaning method according to the present invention is applied.

  The solid-state imaging device 21 includes a solid-state imaging device 11A and a rectangular solid-state imaging device chip 11C provided with pads 11B, 11B, which are a plurality of connection terminals for electrical connection with the solid-state imaging device 11A. The frame-shaped spacer 13 is mounted on the solid-state image sensor chip 11C so as to surround the image sensor 11A, and the cover glass 12 is mounted on the spacer 13 and seals the solid-state image sensor 11A.

  The solid-state imaging device chip 11C is obtained by dividing a semiconductor substrate (wafer) described later. Further, the spacer 13 is joined to the cover glass 12 via the adhesive 13A and the solid-state imaging device chip 11C via the adhesive 13B.

  A general semiconductor element manufacturing process is applied to manufacture of the solid-state imaging element 11A. The solid-state imaging device 11A includes a photodiode that is a light-receiving device formed on a wafer (solid-state imaging device chip 11C), a transfer electrode that transfers excitation voltage to the outside, a light-shielding film having an opening, an interlayer insulating film, and an interlayer insulating film. An inner lens formed on the upper part, a color filter provided on the upper part of the inner lens via an intermediate layer, a micro lens provided on an upper part of the color filter via an intermediate layer, and the like.

  Since the solid-state imaging device 11A is configured in this way, light incident from the outside is condensed by the microlens and the inner lens and irradiated to the photodiode, so that the effective aperture ratio is increased.

  The pads 11B, 11B,... Are formed by printing on the solid-state image sensor chip 11C using, for example, a conductive material. Similarly, wiring is provided between the pad 11B and the solid-state imaging device 11A by printing.

  Further, a through wiring 24 penetrating the solid-state imaging element chip 11C is provided, and conduction between the pad 11B and the external connection terminal 26 is established.

  As a wafer to be divided into a large number of solid-state imaging device chips 11C, a single crystal silicon wafer is generally used.

  The spacer 13 is made of an inorganic material such as silicon. That is, the material of the spacer 13 is preferably a material similar in physical properties such as a thermal expansion coefficient to the wafer (solid-state imaging device chip 11C) and the cover glass 12. For this reason, the material of the spacer 13 is preferably silicon.

  The cover glass 12 is made of a transparent α-ray shielding glass in order to prevent the destruction of the CCD photodiode.

  Next, the cover glass cleaning method according to the present invention will be described. FIG.6 (c) is sectional drawing of the cover glass 12 with a spacer, as already stated. FIG. 3 is a flow chart of the cover glass cleaning method according to the present invention and a cross-sectional view of the cover glass 12 at that time. Each of the cover glass 12 with a spacer in FIG. It is a figure which expands and shows the part corresponding to 11A. FIG. 4 is a table showing conditions for dry cleaning and second wet cleaning.

  In FIG. 3A, dry etching is performed. As shown in FIG. 4, the dry etching apparatus and conditions employ an ICP type ashing method, the oxygen flow rate is adjusted to 99.0 sccm, and the platen power is set to 100 W. The cross-section of the cover glass 12 after dry etching is in a state where large foreign matters D, D... And small foreign matters d, d.

  Next, in FIG. 3B, the first wet cleaning is performed. The first wet cleaning is a process of removing large (about several tens of μm) foreign matters D, D... On the adhesive 13A layer, that is, dry etching residues, environmental foreign matters, and the like. And it aims at preventing the production | generation of an adhesive trace demonstrated in FIG.

This first wet cleaning is pure water ultrasonic cleaning. That is, room temperature (room temperature) pure water (ultra pure water) is used as the cleaning liquid. The ultrasonic frequency is 38 kHz, and the ultrasonic density is 0.5 W / cm ² or more. The washing time is 2 minutes. The cross section of the cover glass 12 after the first wet cleaning is in a state in which large foreign matters D, D.

  Subsequently, in FIG.3 (c), it draws up with warm water (warm pure water) and performs drying. As another known drying method, there is a solvent vapor drying method, which is not preferable because the adhesive 13A is easily dissolved by the solvent.

  Next, in FIG. 3D, dry cleaning (ashing) using oxygen plasma is performed. This ashing is a process of removing the photoresist R on the spacer 13 and the adhesive 13A on the cover glass 12. Since it is difficult to remove the adhesive 13A on the cover glass 12 in a subsequent process (second wet cleaning process), it is necessary to completely remove the adhesive 13A in the dry cleaning (ashing).

  As the ashing apparatus and conditions, various known apparatuses and conditions applicable to semiconductor manufacturing and the like can be adopted. Thereby, the pattern of the photoresist R and the exposed layer of the adhesive 13A are removed, and the cross section of the cover glass 12 is in the state shown in FIG.

  Next, in FIG. 3E, cleaning (APM cleaning) using the APM liquid, which is the second wet cleaning process, is performed. The purpose of this second wet cleaning process is to lift dry etching residues that could not be removed in the previous process (dry cleaning), foreign matters caused by the environment, and the like from the surface of the cover glass 12. That is, the surface of the cover glass 12 is light-etched with the APM liquid.

  The APM liquid (Ammonia-Hydrogen Peroxide Mixture) is a cleaning liquid used in the Si wafer cleaning method (RCA cleaning) proposed by the US RCA, and the volume ratio of ammonia: hydrogen peroxide: water is a predetermined value. It is a liquid. This cleaning method is considered to be an excellent cleaning method for removing organic dirt and adhered particles.

An example of suitable cleaning conditions is shown in FIG. That is, the volume ratio of ammonia: hydrogen peroxide: water = 1: 4: 20 as the APM liquid, and the temperature is controlled around 70 ° C. The frequency of the applied ultrasonic wave is 950 kHz, and the density of the ultrasonic wave is 0.3 W / cm ² . The washing time is 8 minutes.

  As described above, one of the features of the present invention is that the volume ratio of ammonia and hydrogen peroxide in the APM liquid is 0.10 to 0.34 (ammonia: hydrogen peroxide = 10 to 34: 100). The volume mixing ratio of hydrogen peroxide and water in the APM solution is 0.05 to 0.34 (ammonia: water = 5 to 34: 100).

  The volume ratio of ammonia: hydrogen peroxide: water = 1: 1 to 2: 5 to 7 is used for the APM liquid in normal RCA cleaning, but the above values are adopted in the present invention. By setting it as such a mixture ratio, the etching rate of the silicon as the spacer 13 can be lowered, and thereby the undercut of the spacer 13 can be reduced. Details of this will be described later.

  In the second wet cleaning step, as described above, an effect of removing a relatively small foreign substance d having a size of about several μm can be obtained by applying ultrasonic waves.

  Next, in FIG. 3F, this pure water ultrasonic cleaning in which pure water ultrasonic cleaning is performed is a process of removing small foreign matter d that could not be removed by cleaning with the APM liquid.

An example of this suitable cleaning condition is shown in FIG. That is, room temperature (room temperature) pure water (ultra pure water) is used as the cleaning liquid. The ultrasonic frequency is 38 kHz, and the ultrasonic density is 0.9 W / cm ² . The washing time is 2 minutes. Such low-frequency ultrasonic vibrations are effective in removing small foreign matter d having strong adhesion. Further, by using pure water (ultra pure water), a rinsing step can be eliminated after this.

  By adding such a process, it is possible to easily remove the small foreign matter d that could not be removed by the cleaning with the APM liquid.

  Next, in FIG. 3G, pull-up drying is performed by hot pure water drying. The state at the end of cleaning is shown in FIG. In this state, various foreign substances D, D..., D, d.

  Next, the operation of the cover glass cleaning method according to the present invention will be described. In particular, foreign matter D, D..., D, d affected by the volume ratio of ammonia: hydrogen peroxide: water as the APM liquid and the presence or absence of pure water ultrasonic cleaning (FIG. 3 (f)) after APM cleaning. The relationship between the removability and the adhesive strength of the spacer 13 will be described.

  FIG. 5 is an enlarged cross-sectional view of the cover glass 12 shown in FIG. 3 (h) after the drying process, and corresponds to FIG. 6 (c) described above.

  Among these, FIG. 5A shows the volume ratio of ammonia: hydrogen peroxide: water = 1: 1: 5 as the APM solution, and omits the pure water ultrasonic cleaning after the APM cleaning (FIG. 3F). Of the conditions.

  FIG. 5B is a diagram in which the volume ratio of ammonia: hydrogen peroxide: water = 1: 4: 20 as the APM liquid, and pure water ultrasonic cleaning (FIG. 3F) after APM cleaning is performed. And the conditions of FIG.

  In FIG. 5A, since the etching rate of the spacer 13 (silicon) by the APM liquid is large, the amount of undercut of the spacer 13 is also large. The etching rate of the cover glass 12 by the APM liquid is not as high as that of silicon, but is a predetermined amount, and the cover glass 12 has a predetermined amount of undercut.

  As a result, the spacer side substantial adhesive width and the glass side substantial adhesive width are the widths indicated by the arrows in FIG. Therefore, such an undercut of the spacer 13 reduces the adhesion area between the spacer 13 and the adhesive 13 </ b> A and easily causes a defect due to the separation of the spacer 13.

  It should be noted that the foreign substances d, d.

  In FIG. 5B, the etching rate of the spacer 13 (silicon) by the APM liquid is reduced, and the amount of undercut of the spacer 13 is also reduced. Further, the etching rate of the cover glass 12 by the APM liquid is smaller than the condition of FIG. 5A, but the processing time is increased accordingly, and the etching amount is substantially the same as the condition of FIG. It is. Therefore, the amount of undercut of the cover glass 12 is also substantially the same as the condition of FIG.

  As a result, the spacer-side substantial adhesive width and the glass-side substantial adhesive width are the widths indicated by the arrows in FIG. 5B, and are wider than the conditions in FIG. Therefore, the undercut of the spacer 13 reduces the adhesion area between the spacer 13 and the adhesive 13 </ b> A, and does not cause a problem that a defect due to the separation of the spacer 13 easily occurs. It is important that the substantial adhesive width between the spacer 13 and the adhesive 13A is larger than the glass-side substantial adhesive width.

  In addition, since the etching amount of the cover glass 12 by the APM liquid is equivalent to the condition of FIG. 5A, the level of the effect that the foreign matter d, d... Is removed (lifted off) from the surface of the cover glass 12 is also equivalent. is there.

  Furthermore, under the conditions of FIG. 5B, foreign matter d, d... Is removed (lifted off) from the surface of the cover glass 12 by introducing pure water ultrasonic cleaning (FIG. 3F) after APM cleaning. The level of effectiveness is improving.

  5B, the undercut of the cover glass 12 is equivalent to the condition of FIG. 5A. However, by reducing the etching amount of the cover glass 12 with the APM liquid, the undercut of the cover glass 12 is performed. The amount of cut can also be reduced from the condition shown in FIG. Thereby, the adhesion area between the cover glass 12 and the adhesive 13A does not decrease. Therefore, there is no problem that defects due to peeling of the spacers 13 are likely to occur.

  In this case, since the etching rate of the cover glass 12 by the APM liquid is smaller than the condition of FIG. 5A, the level of the effect of removing foreign matter d, d... From the surface of the cover glass 12 (lift-off) is also achieved. The level of the effect of removing pure water ultrasonic cleaning after APM cleaning (FIG. 3 (f)) and removing foreign matter d, d... From the surface of the cover glass 12 (lift-off) is shown. It can be substantially equivalent to the condition of 5 (a).

  According to the condition of FIG. 5B described above (the flow of FIG. 3 and the condition of FIG. 4), both maintenance of the cleaning performance and maintenance of the adhesive strength of the spacer 13 can be achieved.

  As described above, according to the method for cleaning a cover glass of the present invention, before the dry cleaning (ashing process), the cover glass 12 having the spacer 13 formed on the surface is cleaned with pure water to which ultrasonic waves are applied. Therefore, the foreign matters D, D... On the surface of the adhesive 13A can be removed. Since the APM cleaning is performed after the dry cleaning (ashing process), the foreign matters d, d... Are removed (lifted off) from the surface of the cover glass 12. Further, since the cover glass 12 is cleaned with pure water to which ultrasonic waves are applied after the APM cleaning, foreign matters d, d... That cannot be removed by the APM cleaning are removed from the surface of the cover glass 12.

  In addition, according to the method for cleaning a cover glass of the present invention, it is possible to easily remove the needle-like protrusions on the side wall of the spacer 13 generated during dry etching. Thereby, while the shape of the side wall of the spacer 13 becomes favorable, the effect of preventing dust generation from the spacer 13 is also obtained.

  As mentioned above, although embodiment of the cleaning method of the cover glass which concerns on this invention was described, this invention is not limited to the said embodiment, Various aspects can be taken.

  For example, in the above embodiment, the volume ratio of ammonia: hydrogen peroxide: water is set to 1: 4: 20 as the APM liquid, but a predetermined effect can be obtained even if a ratio other than this is adopted.

  That is, as described above, the volume mixing ratio of ammonia and hydrogen peroxide in the APM liquid is set to 0.10 to 0.34, and the volume mixing ratio of hydrogen peroxide and water in the APM liquid is set to 0.05 to 0. .34, the undercut of the spacer 13 can be reduced.

  Moreover, the conditions for applying ultrasonic waves are not limited to the values shown in FIG. 4, and various other conditions (frequency, ultrasonic density, cleaning time, etc.) can be adopted.

The perspective view of the solid-state imaging device to which the cleaning method of the cover glass concerning the present invention is applied Sectional drawing of the principal part of the solid-state imaging device to which the cleaning method of the cover glass which concerns on this invention is applied FIG. 2 is a flowchart of a cover glass cleaning method according to the present invention, and a cross-sectional view of the cover glass at that time. Table showing conditions for first wet cleaning and post-ashing cleaning Cross-sectional view of the cover glass showing the effect of the APM liquid mixing ratio Cross-sectional view of the process of forming the spacer Flow diagram explaining the mechanism that causes defects in the formation of spacers

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Wafer (substrate), 11A ... Solid-state image sensor, 11B ... Pad, 11C ... Solid-state image sensor chip, 12 ... Cover glass, 13 ... Spacer, 13A ... Adhesive, 21 ... Solid-state image sensor, 30, D, d ... Foreign matter, R ... photoresist

Claims (7)

Forming a large number of solid-state image sensors on the upper surface of the wafer;
Forming a frame-shaped spacer of a predetermined thickness in a shape surrounding each solid-state image sensor at a position corresponding to the solid-state image sensor on the lower surface of the cover glass bonded to the wafer;
Aligning the wafer and the cover glass and bonding via the spacer;
Dividing the bonded wafer and the cover glass into individual solid-state imaging devices;
In the method for cleaning the cover glass of the solid-state imaging device manufactured by:
A first wet cleaning step of cleaning the cover glass having the spacer formed thereon with pure water;
A dry cleaning step of ashing the cover glass after wet cleaning with oxygen plasma;
A second wet cleaning step of cleaning the cover glass after dry cleaning with an APM solution;
A method for cleaning a cover glass, comprising: A solid-state image sensor chip having a solid-state image sensor formed on the surface;
A cover glass bonded to the solid-state imaging device chip,
In the method of cleaning the cover glass when manufacturing a solid-state imaging device provided between the solid-state imaging element chip and the cover glass and sealed with a spacer having a predetermined thickness surrounding the solid-state imaging element. ,
A first wet cleaning step of cleaning the cover glass having the spacer formed thereon with pure water;
A dry cleaning step of ashing the cover glass after wet cleaning with oxygen plasma;
A second wet cleaning step of cleaning the cover glass after dry cleaning with an APM solution;
A method for cleaning a cover glass, comprising:   The cover glass cleaning method according to claim 1 or 2, wherein an ultrasonic vibration of 50 kHz or less is applied in the first wet cleaning step.   The cover glass cleaning method according to any one of claims 1 to 3, wherein in the second wet cleaning step, the APM liquid is managed at 40 to 90 ° C and ultrasonic vibration of 950 kHz or more is applied.   The cover glass cleaning method according to any one of claims 1 to 4, wherein in the second wet cleaning step, a volume ratio of ammonia and hydrogen peroxide in the APM liquid is set to 0.10 to 0.34.   The cover glass cleaning method according to any one of claims 1 to 5, wherein in the second wet cleaning step, a volume ratio of hydrogen peroxide to water in the APM liquid is set to 0.05 to 0.34. The cover glass cleaning according to any one of claims 1 to 6, wherein in the second wet cleaning step, after the cleaning with the APM liquid, the cover glass is cleaned with pure water to which ultrasonic vibration of 50 kHz or less is applied. Method.

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