Wafer chuck cleaning method and device

Abstract

To provide a method and a device for cleaning a wafer chuck that removes fine foreign matters from a surface of a wafer chuck.SOLUTION: A wafer chuck cleaning device 1 includes: a grindstone 3 for grinding a chuck surface 21; and a nozzle 4 for discharging cleaning fluid to the chuck surface 21. The grindstone 3 scrapes off the chuck surface 21 together with foreign matters and rinses out the chuck surface 21 with the cleaning fluid, thereby removing the foreign matters from the chuck surface 21.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for cleaning a wafer chuck that holds a wafer. [Background technology]

[0002] In the field of semiconductor manufacturing, grinding machines are known that grind semiconductor wafers such as silicon wafers (hereinafter referred to as "wafers") into thin films. The grinding machine grinds the wafer thinly by rotating a wafer chuck that holds the wafer by suction and a grinding wheel that is located opposite the wafer chuck, and pressing the grinding wheel against the wafer while both are rotating.

[0003] During grinding, it is unavoidable that foreign matter such as sludge will be generated. If the wafer chuck holds the wafer by suction while grinding is performed with this foreign matter adhering to the surface of the wafer chuck, the foreign matter may get caught in the wafer, causing processing defects such as cracks or dimples.

[0004] Patent Document 1 discloses that the porous ceramic chuck 12 is slid with a brush 31 and a ceramic rod 32 to remove sludge adhering to the surface of the porous ceramic chuck 12. The reference numerals are those in Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-237108 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when recesses such as grooves exist on the surface of the porous ceramic chuck 12 described above, it is difficult to scrape out minute sludge of about several hundred nanometers in size from the recesses using the brush 31 and the ceramic rod 32, and there is a risk that the sludge will re-adhere to the surface of the porous ceramic chuck 12 during wafer grinding.

[0007] Conventional thick BG tape was able to absorb the unevenness caused by tiny sludge particles getting caught in the tape, but as wafers have become thinner in recent years, BG tape has also tended to become thinner. With such thin BG tape, dimples caused by tiny sludge particles getting caught in the tape can occur, which can worsen LTV (Local Thickness Variation) during processing.

[0008] Therefore, a technical problem arises that must be solved in order to remove minute foreign particles from the surface of the wafer chuck, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0009] In order to achieve the above object, a method for cleaning a wafer chuck according to the present invention is a method for cleaning a wafer chuck having an adsorbent made of a porous material embedded in its surface, the method comprising: a cleaning step of grinding the surface of the wafer chuck together with any foreign matter with a grinding stone immediately after grinding the wafer, thereby removing the foreign matter from the surface; Without rotating the wafer chuck, and a rinsing step of discharging a cleaning fluid, which is water or a compressed fluid, onto the ground surface to wash away the foreign matter removed from the surface.

[0010] According to this configuration, the surface of the wafer chuck is scraped off together with the foreign matter with the grindstone, and then the surface of the wafer chuck is washed away with a cleaning fluid, thereby removing the foreign matter from the surface of the wafer chuck.

[0011] In the method for cleaning a wafer chuck according to the present invention, it is preferable that the surface is ground to be approximately flush in the cleaning step.

[0012] With this configuration, the surface of the wafer chuck is ground to be approximately flush, which reduces the amount of foreign matter remaining or being lifted up during the cleaning process compared to when recesses such as grooves are formed.

[0013] In the method for cleaning a wafer chuck according to the present invention, it is preferable that in the rinsing step, the discharge position of the cleaning fluid is moved in the radial direction of the wafer chuck.

[0014] According to this configuration, by moving the ejection position of the cleaning fluid in the radial direction of the wafer chuck, the cleaning fluid can be applied directly to a wide area of ​​the surface of the wafer chuck, thereby efficiently removing foreign matter.

[0015] In order to achieve the above object, the present invention provides a wafer chuck cleaning device for a wafer chuck having an adsorbent made of a porous material embedded in its surface, the device comprising: a grinding wheel for grinding the surface of the wafer chuck together with foreign matter immediately after grinding the wafer, thereby removing the foreign matter from the surface; Let me and a nozzle for discharging a cleaning fluid, which is water or a compressed fluid, onto the surface of the wafer chuck after grinding to wash away any foreign matter removed from the surface.

[0016] According to this configuration, the surface of the wafer chuck is scraped off together with the foreign matter with the grindstone, and then the surface of the wafer chuck is washed away with a cleaning fluid, thereby removing the foreign matter from the surface of the wafer chuck. [Effects of the Invention]

[0017] The present invention can remove foreign matter from the surface of the wafer chuck by scraping off the surface of the wafer chuck, including any foreign matter, with a grinding stone and then rinsing the surface of the wafer chuck with a cleaning fluid, thereby preventing foreign matter from becoming caught between the wafer chuck and the BG tape and improving the LTV. [Brief explanation of the drawings]

[0018] [Figure 1]1 is a schematic diagram showing a wafer chuck cleaning apparatus according to an embodiment of the present invention; [Figure 2] FIG. 4 is a schematic diagram showing a cleaning process. [Figure 3] FIG. [Figure 4] 1A and 1B are an image showing the surface shape of a wafer chuck to which a wafer chuck cleaning method according to an embodiment of the present invention is applied, an image showing the cross-sectional shape in the X-axis direction, and an image showing the cross-sectional shape in the Y-axis direction. [Figure 5] 10 shows an image showing the surface shape of a wafer chuck that has been subjected to only the cleaning process, an image showing the cross-sectional shape in the X-axis direction, and an image showing the cross-sectional shape in the Y-axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described below with reference to the drawings. When referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when the number is clearly limited to a specific number in principle, the number is not limited to the specific number, and may be greater than or less than the specific number.

[0020] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0021] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0022] 1 is a schematic diagram showing a wafer chuck cleaning apparatus 1 according to a first embodiment of the present invention. The wafer chuck cleaning apparatus 1 cleans the chuck surface 21 of a wafer chuck 2 that holds a wafer. The wafer chuck 2 is incorporated into, for example, a grinding apparatus that grinds wafers or a polishing apparatus that polishes wafers.

[0023] The wafer chuck 2 has an adsorbent 22 made of a porous material such as alumina embedded in the chuck surface 21. The chuck surface 21 is formed to be substantially flush. The wafer chuck 2 is configured to be rotatable about a vertical axis 2a passing through the center of the wafer chuck 2 by a motor (not shown).

[0024] The wafer chuck 2 has a conduit (not shown) that passes through the interior and extends to the chuck surface 21. The conduit is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint (not shown). When the vacuum source is activated, the wafer placed on the wafer chuck 2 is sucked and held by the suction body 22. When the compressed air source or the water supply source is activated, the suction between the wafer and the suction body 22 is released.

[0025] The wafer chuck cleaning device 1 includes a grindstone 3 and a nozzle 4.

[0026] The grinding wheel 3 is, for example, a cup-shaped grinding wheel. The grinding wheel 3 is connected to the lower end of a spindle 31. The spindle 31 is configured to be rotatable about a rotation axis 31a by driving a motor (not shown). The spindle 31 is also configured to be able to move up and down in the vertical direction by an elevator (not shown).

[0027] The nozzle 4 is provided above the wafer chuck 2. The nozzle 4 discharges a cleaning fluid onto the surface of the wafer chuck 2. The cleaning fluid may be water, a compressed fluid, or the like. The spray shape of the cleaning fluid discharged by the nozzle 4 may be any shape, such as a line, a fan, or a cone. The nozzle 4 is configured to be movable in the horizontal direction by a traverse mechanism (not shown).

[0028] The operation of the wafer chuck cleaning apparatus 1 is controlled by a control unit 5. The control unit 5 controls each of the components that make up the wafer chuck cleaning apparatus 1. The control unit 5 is, for example, a computer, and is composed of a CPU, memory, etc. The functions of the control unit 5 may be realized by control using software, or may be realized by something that operates using hardware.

[0029] Next, a procedure for cleaning the chuck surface 21 using the wafer chuck cleaning apparatus 1 will be described with reference to the drawings.

[0030] [Cleaning process] First, the grindstone 3 is brought close to the wafer chuck 2. Next, while the wafer chuck 2 and the grindstone 3 are both rotated, the grindstone 3 is pressed against the wafer chuck 2, thereby grinding the chuck surface 21.

[0031] Since the chuck surface 21 is formed to be approximately flush, it is possible to prevent minute foreign matter such as sludge of about 100 to 200 nm from remaining on the chuck surface 21, compared to when recesses such as grooves are formed.

[0032] Furthermore, when the grinding wheel 3 grinds the chuck surface 21, cooling water is supplied to the processing area where the grinding wheel 3 and the wafer chuck 2 come into contact. Fig. 2 shows a configuration in which cooling water is supplied from a water supply source provided in the wafer chuck 2 through a pipeline so that the cooling water overflows from the chuck surface 21. This allows the cooling water to cool the processing area and lift foreign matter from the chuck surface 21.

[0033] When the grindstone 3 has scraped off a predetermined amount of the chuck surface 21 together with the foreign matter, the rotation of the wafer chuck 2 and the grindstone 3 is stopped, and the grindstone 3 is retracted from the wafer chuck 2.

[0034] [Rinse process] First, the nozzle 4 is positioned above the wafer chuck 2. Next, the nozzle 4 ejects a cleaning fluid toward the chuck surface 21. Any foreign matter on the chuck surface 21 is removed by the impact of the cleaning fluid colliding with the chuck surface 21. After colliding with the chuck surface 21, the cleaning fluid changes direction to the horizontal direction and washes the foreign matter away from the wafer chuck 2. Note that the nozzle 4 is not limited to ejecting the cleaning fluid substantially perpendicular to the chuck surface 21, and may be configured to eject the cleaning fluid obliquely relative to the chuck surface 21, for example.

[0035] It is preferable that the nozzle 4 eject the cleaning fluid toward the chuck surface 21 while the wafer chuck 2 is rotating. In this way, when a liquid is used as the cleaning fluid, the cleaning fluid that collides with the chuck surface 21 is scattered toward the outer periphery by the centrifugal force caused by the rotation of the wafer chuck 2, so that the cleaning fluid containing foreign matter can be prevented from remaining on the chuck surface 21.

[0036] The nozzle 4 may be configured to eject the cleaning fluid while moving horizontally using a traverse mechanism. For example, by ejecting the cleaning fluid while moving the nozzle 4 horizontally from one end to the other end of the wafer chuck 2, the cleaning fluid directly hits the entire surface of the wafer chuck 2, and foreign matter adhering to the chuck surface 21 can be efficiently removed by the force of the water flow.

[0037] The operation of the rinsing step will be described with reference to the drawings.

[0038] FIG. 4(a) is a microscope image showing the surface shape of the wafer chuck 2 that has been subjected to a rinsing process, FIG. 4(b) is a graph showing the surface shape of the wafer chuck 2 shown in FIG. 4(a) in the X-axis direction (Y=0), and FIG. 4(c) is a graph showing the surface shape of the wafer chuck 2 shown in FIG. 4(a) in the Y-axis direction (X=0).

[0039] The main conditions for the rinsing step are as follows: Discharge fluid: Water and air Discharge pressure: Water 0.2MPa, Air 0.5MPa Discharge rate: Water 0.5L / min or more, Air 100L / min Discharge time: 3 seconds or more Chuck rotation speed: 100 rpm

[0040] FIG. 5(a) is a microscope image showing the surface shape of a wafer chuck 2 that has not been subjected to a rinsing process, FIG. 5(b) is a graph showing the surface shape of the wafer chuck 2 shown in FIG. 5(a) in the X-axis direction (Y=0), and FIG. 5(c) is a graph showing the surface shape of the wafer chuck 2 shown in FIG. 5(a) in the Y-axis direction (X=0).

[0041] 5(b) and 6(b), the horizontal axis represents the X-axis coordinate with the center of the wafer chuck 2 as the origin, and the vertical axis represents the height of the chuck surface 21. Furthermore, in FIGS. 5(c) and 6(c), the horizontal axis represents the Y-axis coordinate with the center of the wafer chuck 2 as the origin, and the vertical axis represents the height of the chuck surface 21.

[0042] According to Figure 4(a), the height of the chuck surface 21 is within a small range of 0.076 to 1.672 μm, and according to Figures 4(b) and (c), although the center of the wafer chuck 2 is locally higher (approximately 1.3 to 1.6 μm), the surrounding area has a gentle slope (approximately 1.0 to 1.3 μm).

[0043] On the other hand, for the wafer chuck 2 that has not been subjected to the rinsing process, Fig. 5(a) shows that the height of the chuck surface 21 varies widely, from 0.410 to 9.014 μm, and that large convex portions exist locally. Also, Figs. 5(b) and (c) show that the height variation of the chuck surface 21 in the Y direction (approximately 1.6 to 5.3 μm) is greater than the height variation in the X direction (approximately 4.8 to 5.3 μm), and that localized depressions sometimes occur.

[0044] In this way, with the wafer chuck cleaning apparatus 1 according to the embodiment of the present invention, the grindstone 3 scrapes off the chuck surface 21 together with the foreign matter, and the cleaning fluid then washes away the chuck surface 21, thereby removing the foreign matter from the chuck surface 21. This makes it possible to suppress dimples caused by the presence of foreign matter on the chuck surface 21 and improve the LTV.

[0045] Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. [Explanation of symbols]

[0046] 1. Wafer chuck cleaning device 2 Wafer chuck 21 Chuck surface 3. Grindstone 4 Nozzle 5. Control device

Claims

1. 1. A method for cleaning a wafer chuck having an adsorbent made of a porous material embedded in its surface, comprising: a cleaning step in which the surface of the wafer chuck is ground with a grinding stone together with any foreign matter thereon immediately after the wafer is ground, thereby removing the foreign matter from the surface; a rinsing step in which, without rotating the wafer chuck, a cleaning fluid such as water or a compressed fluid is discharged onto the ground surface to wash away the foreign matter removed from the surface; A method for cleaning a wafer chuck, comprising:

2. 2. The method for cleaning a wafer chuck according to claim 1, wherein the surface is ground to a substantially flush surface in the cleaning step.

3. 3. The method for cleaning a wafer chuck according to claim 1, wherein in the rinsing step, a discharge position of the cleaning fluid is moved in a radial direction of the wafer chuck.

4. A cleaning device for a wafer chuck having an adsorbent made of a porous material embedded in its surface, comprising: a grindstone that grinds the surface of the wafer chuck together with any foreign matter immediately after grinding the wafer, thereby removing the foreign matter from the surface; a nozzle for discharging a cleaning fluid, which is water or a compressed fluid, onto the surface of the non-rotating wafer chuck after grinding to wash away foreign matter removed from the surface; A wafer chuck cleaning device comprising:

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