JPH073577B2 - Substrate cleaning method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a substrate on which a pattern having minute unevenness steps is formed, particularly a photomask (or reticle) used in a photolithography process during semiconductor manufacturing, and a semiconductor. The present invention relates to a method for cleaning a wafer or the like.

(Background of the Invention) In a photolithography process for manufacturing a semiconductor element, a circuit pattern image on a photomask or reticle is usually printed on a semiconductor wafer by an optical exposure transfer device. In this case, if foreign matter adheres to the photomask or reticle, it becomes a defect on the transferred circuit pattern,
This causes the manufactured semiconductor device to be defective.

Therefore, the presence or absence of foreign matter on the mask or reticle is automatically detected, and when the foreign matter is detected, the foreign matter is removed by a cleaning device. Various types of cleaning devices have been proposed and commercialized as this cleaning device, but brush cleaning has attracted attention as a system with high foreign matter removal efficiency (cleaning efficiency). Brush cleaning is a method of pressing a rotating brush against the surface of a mask or reticle (substrate) and removing foreign matter by friction. There are roughly two types of cleaning methods using a rotating brush. One is to rotate and brush the brush in a plane parallel to the substrate surface, and the other is to rotate the roller brush. The substrate and the roller brush are moved relative to each other to rub the entire surface of the substrate.

However, in any method, when the brush collides with the edge of the substrate, a minute brush piece (a few microns or less) is generated from the bristles of the brush. In brush cleaning, the cleaning liquid is sprayed onto the substrate at the same time as friction with the brush (or brushing), or the substrate is immersed in the cleaning liquid to wash away the foreign matter. There is a defect that it is caught at the edge part of and cannot be completely removed.

Therefore, the present invention reduces foreign matter generated from the scrubbing material itself that rubs the substrate when cleaning the substrate by friction,
An object of the present invention is to provide a cleaning method with improved cleaning effect.

(Summary of the Invention) According to the present invention, when rubbing a substrate with a scrubbing material such as a brush (or sponge), the scrubbing material on the surface of the substrate is cleaned so as to prevent the scrubbing material from colliding with the end face portion of the substrate. It has a technical gist to limit.

(Embodiment) FIG. 2 is an overall schematic view of an automatic cleaning apparatus to which an embodiment of the present invention is applied.

A glass substrate 5 such as a reticle or a mask is stored in the storage unit 1, a brush cleaning tank 2 to which the method of the present invention is applied is disposed at a position farthest from the storage unit 1, and the storage unit 1 is adjacent to the brush cleaning tank 2. A rinse tank 3 for washing the glass substrate 5 with alcohol is arranged at the sandwiched position, and the rinse tank 3 is further provided.
A vapor drying tank 4 for drying the glass substrate 5 using Freon vapor is arranged at a position sandwiched between the storage portions 1. The storage unit 1, the brush cleaning tank 2, the rinse tank 3, and the steam drying tank 4 (hereinafter, simply referred to as the steam tank 4) are arranged along a linear transfer path 6 of the glass substrate 5. The glass substrate 5 to be cleaned stored in the storage unit 1 is positioned above the brush cleaning tank 2 while jumping over the steam tank 4 and the rinse tank 3 along the path 6 while being held vertically. Inside the brush cleaning tank 2, a pure water jetting portion (water washing means) 7 for jetting pure water onto the glass substrate 5 and a washing liquid jetting portion (washing liquid applying means) for jetting a washing liquid such as an aqueous ammonia solution are sequentially provided from the top. 8 and a brush (scrubbing material) 11 that rotates so as to rub the surface of the glass substrate 5 are arranged by being divided by the shatterproof plates 9 and 10, respectively. The bottom of the brush cleaning tank 2
12 has a pyramidal shape, which improves the collection efficiency of drainage.

In order to replace pure water with isopropyl alcohol liquid (hereinafter referred to as IPA) or the like inside the rinse tank 3, there is provided an IPA jet part 13 for jetting the IPA, and both surfaces of the glass substrate 5 are rinsed with IPA. To do. Further, the bottom portion 14 of the rinse tank 3 is also formed in the shape of a cone to enhance the drainage liquid recovery efficiency. The Freon liquid 16 is supplied to the bottom of the steam tank 4 from the supply line 18 by a predetermined amount and heated by the heater 19. As a result, Freon vapor is filled in the tank 4, and the glass substrate 5 is dried by vapor. The Freon liquid condensed and dropped by the glass substrate 5 has low purity and is contaminated.
It is received by the receiving tray 17a so as not to be mixed with the Freon liquid 16 and recovered through the recovery line 17b. A cooling pipe 15 is provided around the upper part of the steam tank 4 to prevent Freon steam from flowing out of the tank.

FIG. 3 is an enlarged perspective view of the brush cleaning tank 2. The glass substrate 5 is sandwiched by the arms 20 from both ends,
In the vertical state, the glass substrate 5 is conveyed in the y direction and the z direction parallel to the surface of the glass substrate 5.

The upper part of this brush cleaning tank 2 has a glass substrate 5 and an arm 20.
An opening 21 is provided for advancing and retreating, and is sealed. This structure is effective in preventing dust from entering the tank 2 and preventing mist (spray) of various liquids inside from going out. Now, the pure water injection part 7
Are the pipes 7a, 7b arranged parallel to both surfaces of the glass substrate 5 coming in downward from the opening 21, and the pipes 7a, 7b.
Jet puzzles 22,23,2 provided at two locations in 7b
It consists of 4,25. Pure water having a constant pressure is supplied to the pipes 7a and 7b, and the injection nozzles 22 to 25 jet the pure water into a fan-shaped liquid film by the pressure. The nozzles 22 to 25 are arranged so that the pure water spreads out in a fan shape in the lateral direction of the surface of the glass substrate 5 (in the y direction in the figure) and at the same time, it sprays so as not to spread in the up-down direction. It has a simple structure.

Below the pipes 7a and 7b, shatterproof plates 9a and 9b are provided facing each other in a state of being inclined downward toward the center of the tank 2. The lower ends of the shatterproof plates 9a and 9b are separated by an appropriate distance so that the glass substrate 5 and the arm 20 can pass through. The anti-scattering plates 9a, 9b prevent the pure water from the nozzles 22 to 25 or the pure water once sprayed on the glass substrate 5 from splashing again and splashing upward.

When the glass substrate 5 passes between the scattering prevention plates 9a and 9b and moves further downward, the glass substrate 5 reaches the cleaning liquid ejecting portion 8. The cleaning liquid jetting portion 8 is composed of pipes 8a, 8b positioned in parallel with the glass substrate 5 like the pure jetting portion 7, and jetting nozzles 26, 27, 28, 29 provided in each of the pipes 8a, 8b. It The arrangement of the pipes 8a and 8b and the nozzles 26 to 29 is the same as that of the pure water jetting unit 7 described above. A pressurized cleaning liquid, for example, an ammonia aqueous solution is supplied to the pipes 8a and 8b, and the ammonia aqueous solution is sprayed from the nozzles 26 to 29 on both sides of the glass substrate 5 in a fan shape. In this case, the aqueous ammonia solution does not necessarily have to be in the form of a liquid film. Below these pipes 8a, 8b,
Similar to the shatterproof plates 9a and 9b, shatterproof plates 10a and 10b are provided so as to be inclined downward toward the center of the tank 4. Like the scattering prevention plates 9a and 9b, the functions of the scattering prevention plates 10a and 10b also prevent the aqueous ammonia solution from the nozzles 26 to 29 from splashing upwards, but not only that. Splashes from the rotating brush 11 placed below it,
It also has the function of preventing jumping out.

The rotating brush 11 includes a cylindrical brush 11a having a rotation axis O ₁ arranged parallel to the surface of the glass substrate 5, and a rotation axis O ₂
And a cylindrical brush 11b having That brush 11
a and 11b are arranged such that when the glass substrate 5 comes down through the gap between the shatterproof plates 10a and 10b, the space 35 between the rotation axes O ₁ and O ₂ is determined so that the glass substrate 5 is narrowed. Has been. The bristles of the brushes 11a and 11b are, for example, a nylon material, and are bristled so as to extend in the radial direction with respect to the rotation axes O ₁ and O ₂ . The brush 11a rotates clockwise about the rotation axis O ₁ as indicated by the arrow 50a in FIG. 3, and the brush 11b rotates counterclockwise about the rotation axis O ₂ as indicated by the arrow 50b. That is, the glass substrate 5 sandwiched between the brushes 11a and 11b is rotated by the brushes 11a and 11b so that the bottom portion 1 of the tank 4 is
The second side is rubbed so that it is tucked in (downward). Therefore, foreign matters (dust, stains, etc.) attached to both surfaces of the glass substrate 5 are scraped off toward the bottom 12 by the bristles of the brushes 11a and 11b. The axial lengths of the cylindrical brushes 11a and 11b are in contact with the glass substrate 5 in the lateral direction as wide as possible, and an arm that holds both end surfaces of the glass substrate 5 is provided.
The length is set so as not to touch the vertical left end face portion of the glass substrate 5 and the glass substrate 5. This is extremely effective in preventing abrasion of the bristles of the brushes 11a and 11b, that is, generation of brush pieces. Further, the interval between the meshing portions of the brushes 11a and 11b and the position where the pure water from the pure water spouting portion 7 hits the glass substrate is set to be larger than at least the vertical width (height) of the glass substrate.

In FIG. 3, the brush cleaning tank 4 is configured to be separable into an upper side portion and a lower side portion with a joint portion 34 with packing as a boundary, and a pure water jetting portion 7, a cleaning liquid jetting portion 8 and The shatterproof plates 9 and 10 are provided on the upper side and fixed to the entire apparatus, and the lower side provided with the brushes 11a and 11b can be removed downward from the upper side. This is to facilitate replacement of the brushes 11a and 11b. Brushes 11a, 11 on the lower side
A motor for individually rotating b is integrally provided as shown in FIG. FIG. 4 is a plan view showing only the lower part thereof, and here, only the motor 40a for rotating the brush 11a and the belt drive mechanism 41a for transmitting the rotation of the motor 40a to the rotation axis O ₁ of the brush 11a are shown. Also for the brush 11b, the motor 40b and the belt drive mechanism 41b are integrally provided on the lower side of the tank 4.

FIG. 5 is a circuit block diagram of a control system for controlling the drive of the transfer arm 20 and the drive of the brush cleaning tank 4. The entire device is integrally controlled by a main control unit (hereinafter referred to as MCU) 60.
Various commands from the MCU60 are interface circuits (hereinafter, IF
Called 61) to each drive. Drive circuit 62
Drives a solenoid valve 63 that switches whether to supply pressurized pure water to the pipes 7a and 7b according to a command from the MCU 60. Drive circuit 64
Drives a solenoid valve 65 that switches whether to supply pressurized cleaning liquid (ammonia aqueous solution) to the pipes 8a and 8b in response to a command from the MCU 60. The drive circuit 66 receives a command from the MCU 60, and the brush 11
The motors 40a and 40b for rotating a and 11b are individually driven.

Drive unit including power sources such as motors (hereafter called ZACT) 67
Moves the arm 20 up and down (moves in the Z direction) in response to a command from the MCU 60. The amount of movement is also commanded by the MCU 60. Similarly, a drive unit including a power source (hereinafter referred to as YACT) 6
8 moves the arm 20 in the y direction, that is, the direction along the surface of the glass substrate 5, in response to a command from the MCU 60. The amount of movement in the y direction is also commanded by the MCU 60.
In this way, by holding the glass substrate 5 in a vertical state and transporting it in a direction parallel to the surface thereof, it is possible to obtain the effect of reducing the adhesion of minute dust floating in the atmosphere to the surface of the glass substrate 5.

Next, the brush cleaning operation of this embodiment will be described. Opening 21
The glass substrate 5 descending from the surface is rinsed with pure water at the position of the pure water jetting portion 7 shown in FIG. 3 to wet both surfaces of the glass substrate 5, and in some cases weakened by the pure water spray pressure. Foreign matter that has adhered is also washed away. Next, the glass substrate 5 further descends and is brushed by the rotating brush 11 while receiving the injection of the aqueous ammonia solution from the nozzles 26 to 29. The operation at this time will be described in detail with reference to FIG.

First, as shown in FIG. 1, the glass substrate 5 is placed at a position a where the aqueous ammonia solution AQ is not injected and the upper end surface of the substrate
Positioned so that 5a is located. The position a is also the initial position during brushing. The aqueous ammonia solution AQ is supplied from the nozzle 26 (27) and the nozzle 28 above the position c where the two rotating brushes 11a and 11b are in contact (or closest to each other).
It is jetted so as to collide with the aqueous solution from (29).

Now, the glass substrate 5 in the initial position a has its upper end surface 5a
Is lowered at a constant speed until it reaches the position b in FIG. 1, that is, the position below the two rotating brushes 11a, 11b. The next glass substrate 5 is raised at a constant speed until the upper end surface 5a reaches the initial position a again. The above is the end of one brushing operation, but the MCU 60 repeats this brushing operation, that is, the reciprocating operation of the position a, the position b, and the position a of the glass substrate 5 any number of times depending on the adhered state of the foreign matter. To order. Of course, only one brushing operation is required, and if the glass substrate 5 is not so dirty, the operation of cleaning up to the peripheral portion that is not originally exposed (positions a, b
The same effect can be obtained by omitting the round trip between. Next, in the glass substrate 5, the upper end surface 5a thereof is located at a position d above the position c.
It descends until it is located at and then rises again to position a. The reciprocating operation between the position a and the position d is repeated at least once or plural times. Therefore, during brushing between the positions a and d, the rotating brushes 11a and 11b do not collide with the upper end surface 5a, and the generation of brush pieces is almost eliminated.

Here, how the brush pieces are generated will be described with reference to FIG. FIG. 6 shows a state in which the upper end surface 5a is located at the position c in FIG. In such a state, the upper end surface 5a
Can occur while descending from position a to position b or rising from position b to position a. In particular, in the process of rising from the position b, the rotating brushes 11a and 11b move the glass substrate 5
Since both sides 5b, 5c of the brush are rotated so as to rub from top to bottom, and the glass substrate 5 is raised, the uppermost surface 5a of the bristles of the brush will collide most violently. When the tips of the bristles of the brush hit the corners formed by the upper end surface 5a and the surfaces 5b, 5c, the tips of the bristles become minute pieces and scatter. However, in this embodiment, since the brush rubs from the top to the bottom, the substrate 5 rises, and the aqueous ammonia solution AQ is sprayed from the top to the bottom, the generated brush pieces are generated on the glass substrate 5. Flowed from top to bottom along the surfaces 5b and 5c, and from the bottom surface 5d shown in Fig. 1 to the tank 2
Will be washed off at the bottom. In general, one surface 5c of the glass substrate 5 is a simple glass surface having no unevenness, so that the brush pieces are washed off from the lower end surface 5d without remaining on the surface 5c. However, since a thin film PT of chromium or the like is patterned and vapor-deposited on the other surface 5b as shown in FIG. 7, a brush is attached to the edge portion of the thin film PT extending in the y direction parallel to the upper end surface 5a. There is a high possibility that a piece of Br will remain. Therefore,
If the upper end surface 5a of the glass substrate 5 is simply brushed so as to reciprocate between the position a and the position b, the brush piece Br remains on the surface 5b as shown in FIG. Therefore, by reciprocating the upper end surface 5a between the position a and the position d as in the present embodiment, even if the brush piece Br adheres to the step edge portion of the thin film PT, the brush piece Br does not contact the end surface 5a.
Since it does not occur, the number is small and it will be washed away when brushing multiple times. For this reason,
The distance between the position c and the position d shown in FIG. 1 is set to be approximately the same as the distance from the region where the thin film PT is formed on the surface 5b to the upper end surface 5a. In a normal mask or reticle, the periphery of the glass substrate 5 is not patterned, and there is a margin of several mm to several tens of mm in the periphery. Since this margin portion is not a region that contributes to the original exposure or inspection, the slight residual foreign matter due to insufficient brushing does not pose a serious problem. The tips of the rotating brushes 11a and 11b may collide with the lower end surface 5d of the glass substrate 5, but the lower end surface 5d
Since the brush piece generated in step 2 is washed off downward from the rotating direction of the rotating brush and the injection direction of the aqueous ammonia solution AQ, there is no possibility of adhering to the thin film forming region on the surface 5b.

In addition, in the case of accurately cleaning the surface of the glass substrate 5 as large as possible, the dimension information of the marginal area around the reticle or mask is input to the MCU 60, and the arm 20
It is also possible to lower the glass substrate 5 until it reaches a bare position such that the upper end surface 5a does not collide with the brush based on the dimensional information when the glass substrate 5 is moved up and down.

Now, when the brushing between the positions a and d is completed, the injection of the aqueous ammonia solution AQ is stopped and the glass substrate 5 is moved to the position a.
After being rinsed with pure water again, it is drawn out from the opening 21 to above the tank 2.

In the above embodiment, the gap 35 (see FIG. 2) between the two rotary brushes 11a and 11b is constant, but the gap is several mm.
With a configuration that can be varied to some extent, when the upper end surface 5a of the substrate 5 reaches the position c, the gap 35 can be widened so that the brush does not collide with the upper end surface 5a. Also in this case, the same effect can be obtained in that the cleaning surface of the substrate 5 is limited.
Further, the same applies to a configuration in which the axes O ₁ and O ₂ of the rotating brushes 11a and 11b are set upright and the substrate 5 is moved horizontally in an upright state. In this case, brush pieces are generated from the vertical end of the substrate 5.

It should be noted that how to combine the reciprocal brushing between the positions a and b of the glass substrate 5 and the reciprocal brushing between the positions a and d may be stored in the MCU 60 in advance. At that time, it is desirable to take into consideration the dust adhesion information from a known foreign substance inspection device.

Next, a brushing method according to the second embodiment of the present invention will be described with reference to FIG. In this embodiment, the aqueous ammonia solution AQ is sprayed from both sides of the glass substrate 5 substantially horizontally along the surfaces 5b and 5c. Therefore, as a device,
Nozzles 32a, 32b, 33a, 33b for injecting the aqueous ammonia solution AQ are provided so that they hardly spread. Nozzle 32a, 3
2b is the upper side of the rotating brush 11a and the ammonia solution A on the substrate 5
The nozzles 33a and 33b are arranged so as to inject the aqueous ammonia solution AQ onto the substrate 5 below the rotary brush 11a. When the aqueous solution AQ is sprayed substantially parallel to the rotation axis of the rotating brush in this way, the effect of washing off the brush piece Br adhering to the step edge on the surface 5b is improved. As is clear from the above description, the step edge on which the brush piece Br is caught is an edge that is substantially parallel to the rotation axes O ₁ and O _{2 of} the brush, so the brush piece Br is pushed away by the jet pressure along the edge. It will be.

Although the respective embodiments of the present invention have been described above, a cup-shaped brush may be used as another embodiment. in this case,
Since the cup-shaped brush rotates in a plane parallel to the surface of the glass substrate 5, the diameter of the cup-shaped brush may be set so that the thin film forming region on the substrate rubs and the end face does not rub. Further, when the diameter of the cup-shaped brush is considerably smaller than the thin film forming region, it is necessary to relatively move the substrate and the brush two-dimensionally while rotating the cup-shaped brush. The same effect can be obtained by limiting the range of the two-dimensional movement so as not to collide with the end face portion.

The same effect can be obtained by using sponge or the like as the scrubbing material in addition to the brush. Further, in the case of a rotating brush, the same is true even when the rotation is forcibly stopped when the brush reaches a position where it comes into contact with the end surface of the substrate.

(Effects of the Invention) As described above, according to the present invention, the scrubbing material is prevented from colliding with the end portion of the substrate, so that minute foreign matter (brush pieces, sponge pieces, etc.) generated from the scrubbing material itself is extremely reduced, and scrubbing The material itself does not become a pollution source, and the cleaning efficiency of the substrate is improved step by step.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the state of the brushing process according to the first embodiment of the present invention, FIG. 2 is a layout diagram schematically showing the overall structure of an automatic cleaning device, and FIG. 3 is a structure of a brush cleaning tank. FIG. 4 is a perspective view showing the rotary brush drive mechanism, FIG. 5 is a circuit block diagram of the control system, FIG. 6 is a plan view showing an example of the arrangement of the rotary brush and the glass substrate, and FIG. Is a sectional view showing a partial section of the glass substrate, and FIG. 8 is a plan view showing another embodiment of the present invention. [Explanation of symbols for main parts] 2 …… Brush cleaning tank 5 …… Glass substrate, 5a, 5b …… End surface 11a, 11b …… Rotating brush (scrub material) PT …… Thin film, Br …… Brush piece

Claims (5)

[Claims] 1. A method of cleaning a surface of a substrate by friction by relatively moving a plate-shaped substrate and a scrubbing member, wherein the scrubbing member collides with an end portion of the substrate in the relative moving direction. In order not to do so, the scrubbing material is separated from the surface of the substrate in the vicinity of the end portion, and the cleaning surface of the substrate surface with the scrubbing material is limited. 2. The scrubbing member is a pair of rotating brushes radially planted on a cylindrical roller, and the rotating brush and the substrate are opposed to each other so that the substrate is located between the pair of rotating brushes. The method according to claim 1, wherein the distance between the rotating brushes is increased near the edge of the substrate so that the rotating brush does not collide with the edge of the substrate when moving. 3. The rotating brush rotates in a scraping direction with respect to the substrate, and when the rotating brush and the substrate are relatively moved, in the vicinity of an end portion of the substrate on the rear side with respect to the scraping direction of the rotating brush, The method according to claim 2, wherein the distance between the rotating brushes is increased. 4. The method according to claim 1, wherein the cleaning liquid is sprayed onto the surface of the substrate from at least two directions when the scrubbing material is rubbed. 5. The scrubbing material is a brush that rotates in a plane parallel to the surface of the substrate, and the scrubbing material of the brush is adjusted so that the area rubbed by the rotation of the brush becomes smaller than the size of the substrate. Method according to claim 1, characterized in that it is of limited size.