JP2010171395A - Method and apparatus for cleaning semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for cleaning a semiconductor wafer wherein even when a defect is generated in a cleaned object, its growth can be suppressed, and miscellaneous defects with the cleaning apparatus can be detected by visual inspection when performing a cleaning operation. <P>SOLUTION: In the method of cleaning the semiconductor wafer W, the surface of the semiconductor wafer W is cleaned by a cleaning unit while dipping the semiconductor wafer W in a cleaning vessel 40 having a filled cleaning liquid 3. In the method, only the light in a predetermined short wavelength range out of visible lights is irradiated to the semiconductor wafer W at least while dipping the wafer W in the cleaning liquid 3 and while keeping the cleaning liquid 3 stuck on the surface of the wafer W after pulling it up from the cleaning vessel 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cleaning method and a cleaning apparatus for an object to be cleaned such as a semiconductor wafer, and more particularly, cleaning of a semiconductor wafer capable of suppressing the growth of mirror-finished surface defects such as a semiconductor wafer generated during cleaning. The present invention relates to a method and a cleaning device.

Conventionally, RCA cleaning is generally used for cleaning a wafer such as a mirror-finished semiconductor wafer (silicon wafer). This RCA cleaning is basically
(1) A cleaning operation (referred to as “SC1 cleaning”) for cleaning particles adhering to the wafer surface with a cleaning liquid composed of ammonia water, hydrogen peroxide water, and pure water;
(2) From a combination of a cleaning operation (referred to as “SC2 cleaning”) for cleaning heavy metals (Fe, Ni, Cr, Cu, etc.) adhering to the wafer surface with a cleaning liquid composed of dilute hydrochloric acid, hydrogen peroxide water, and pure water. And if necessary,
(3) A cleaning operation (referred to as “SPM cleaning”) for cleaning organic substances adhering to the wafer surface with a cleaning liquid composed of sulfuric acid and hydrogen peroxide.
(4) A cleaning operation (referred to as “DHF cleaning”) for cleaning and removing an unnecessary natural oxide film on the silicon surface, which is the wafer surface, with a diluted hydrofluoric acid cleaning solution;
May be added.

  Moreover, as a cleaning apparatus used for this RCA cleaning, a manual type in which wafers are carried into, immersed in, and taken out from a plurality of cleaning tanks containing the above-described cleaning liquid, and a robot ( And an automatic conveyance and cleaning device that is operated by an arm). In recent years, automation of semiconductor manufacturing related equipment has progressed, and most of the cleaning devices are also automatic transport cleaning devices. In such cleaning devices as well, the inside of the cleaning device is used for visual confirmation of the cleaning state by the operator. Measures were taken, such as attaching lighting fixtures and providing a viewing window.

  In such an automatic transfer cleaning apparatus, usually, a robot arm provided above the cleaning tank is used to carry in, immerse, and carry out a wafer as a cleaning object into the cleaning tank. Further, in this automatic transfer cleaning apparatus, in order to detect a chuck error (unloading of an object to be cleaned) at the time of carrying in / out of the wafer, for example, as shown in FIG. It has been generally performed to detect a chucking error by irradiating light of a red light emitting diode (101) 101, detecting whether or not light is blocked by an object to be cleaned (for example, a silicon wafer) 103 by the light receiving element 102. In many cases, a liquid level sensor having the same configuration is attached to check the level of the liquid level.

  However, when the above-described conventional cleaning apparatus is used to clean a mirror-finished silicon wafer with a cleaning liquid that involves etching like SC1 cleaning, the wafer being cleaned is irradiated with light such as illumination. It has been found that the following defects are generated and grow on the mirror surface of the silicon wafer and have a serious adverse effect on the quality of the silicon wafer.

  That is, an impurity metal such as copper deposited in the polishing process or the like, which is the previous process, forms a local battery with silicon (Si), and the surface of the silicon wafer 200 to which the copper atoms are deposited is dissolved by SC1 cleaning, and is not visible to the naked eye. This is a phenomenon in which defects 201 such as invisible fine grooves are formed and grow (see, for example, FIGS. 7A to 7C).

  When a silicon wafer having such a groove is cleaned particularly in SC1, the above-mentioned groove is etched by some action of light emitted from a fluorescent lamp illuminating the cleaning chamber or a heater for heating installed in the cleaning tank. Promoted. For this reason, a defect such as a groove grows, and for example, as shown in FIG. 8, an aggregate of non-negligible pits having a size of about several tens of nm (diameter of about several tens to several hundred atoms) (hereinafter, This is referred to as a “large pit”).

  Regarding the growth of defects on the surface of the silicon wafer due to the light described above, the conventional cleaning method or apparatus could not sufficiently prevent the generation. Therefore, development of a cleaning method or a cleaning apparatus that can suppress the occurrence and growth of defects on the surface of the silicon wafer has been awaited.

  As an example, even in a cleaning solution that involves etching, the silicon wafer is not irradiated with light during immersion, cleaning, or unloading and transporting after the cleaning. A cleaning method and a cleaning apparatus that can be prevented have been proposed (see, for example, Patent Document 1).

  In this cleaning method, at least one surface is mirror-finished or an epitaxial layer is laminated on the surface, and a mirror surface roughness (micro roughness) of a silicon wafer having a PV value of 10 nm or less is cleaned with a plurality of cleaning solutions filled with a cleaning solution. In the wafer cleaning method of sequentially immersing and cleaning in a bath, the irradiation of light is cut off to the silicon wafer at least during the immersion cleaning of the silicon wafer and during the movement between the cleaning baths.

JP-A-11-330030

On the other hand, in such a cleaning method or apparatus with light irradiation blocked, since the cleaning operation is performed in a completely dark environment, the following serious problems could not be found.
(I) A chuck error occurs in the chuck that holds the silicon wafer that is being cleaned, and the silicon wafer that has been immersed in the cleaning tank cannot be completely pulled up, or the chuck is displaced and the silicon wafer that is being cleaned is gripped. Things impossible.
(Ii) A pinhole or the like is generated due to breakage of the heater in the cleaning tank, and the chemical solution penetrates from it to corrode the heater wire and the heater metal is eluted in the solution.

  The present invention has been made in view of the above problems, and can suppress the growth even if a defect occurs in the wafer, and can visually detect various abnormalities of the cleaning apparatus when performing a cleaning operation. An object of the present invention is to provide a cleaning method and a cleaning apparatus for a semiconductor wafer.

As a result of earnest research and development to solve the above problems, the present inventors have obtained the following knowledge. That is, the relationship between the wavelength of light such as illumination used when performing the cleaning operation and the growth of defects formed on the cleaning wafer was investigated in each of the SC1 cleaning, SC2 cleaning, SPM cleaning, and DHF cleaning operation steps. As a result, the following knowledge was obtained.
i) The wavelength dependence of the irradiation light was found only in the SC1 cleaning, and ii) was particularly noticeable in the light of a specific wavelength. That is,
λ _G <β ≦ λ _R (1)
(Where λ _{R is} the boundary wavelength between visible light and infrared light)
λ _G ; green wavelength)
Visible light (hereinafter referred to as “forbidden wavelength band light”) was particularly involved in defect growth.

Based on this knowledge, the following short-wavelength visible light is used as the illumination light in the cleaning work, the work immersed in at least the SC1 cleaning liquid, or the work with the SC1 cleaning liquid attached to the wafer surface, that is,
λ _V ≦ γ ≦ λ _G (2)
(Where λ _{V is} the boundary wavelength between ultraviolet light and visible light)
The present invention has been completed with the conclusion that it is preferable to limit the wavelength to use only visible light (hereinafter referred to as “allowable wavelength band light”).
Further, it was also confirmed that the allowable wavelength band light within the range of the above-described formula (2) does not particularly depend on the light intensity.

That is, the cleaning method according to the present invention includes:
In the silicon semiconductor wafer cleaning method of cleaning the surface by immersing in the cleaning liquid in the cleaning tank,
The cleaning liquid is composed of at least one of ammonia, tetramethylammonium hydroxide, and choline, a hydrogen peroxide solution, and pure water. Further, the cleaning liquid is immersed on the cleaning liquid and pulled up from the cleaning tank, and then is cleaned on the surface of the wafer. While the film is adhered, the wafer is irradiated with short-wavelength visible light.
Moreover, the cleaning method of the present invention comprises:
The wavelength range of the short wavelength visible light is
The wavelength is 580 nm from the boundary wavelength between visible light and ultraviolet light.
Furthermore, the apparatus for cleaning the surface of a semiconductor wafer according to the present invention comprises:
A housing,
A cleaning tank that immerses a silicon semiconductor wafer installed in the housing,
An illuminating device is disposed in the housing, and the illuminating device irradiates the wafer with short-wavelength visible light while the wafer is immersed in the cleaning solution and while the cleaning solution is attached to the wafer surface after being pulled up from the cleaning tank. And the cleaning liquid comprises at least one of ammonia, tetramethylammonium hydroxide, and choline, a hydrogen peroxide solution, and pure water.
It is characterized by that.
Moreover, the cleaning apparatus according to the present invention comprises:
Furthermore, a heating heater, a circulation pump, a communication pipe for communicating the pump and the cleaning tank, and a means for transmitting only the short wavelength visible light to the heating heater and the cleaning tank are provided. To do.
In addition, while the cleaning liquid is attached to the surface after being dipped in the cleaning liquid and after being lifted from the cleaning tank, only the light on a predetermined short wavelength side of the visible light is irradiated to the silicon semiconductor wafer. Is preferred.
Moreover, the cleaning apparatus according to the present invention comprises:
The wavelength range of the short wavelength visible light is
The wavelength is 580 nm from the boundary wavelength between visible light and ultraviolet light.
In the method and apparatus according to the present invention, the wavelength range of the short wavelength visible light is preferably in the range of 380 to 580 nm, more preferably in the range of 480 to 580 nm, and most preferably in the range of 480 to 520 nm. Light having a shorter wavelength than the wavelength range is not preferable because it is outside the visible region and cannot serve as illumination for visual inspection. A wavelength longer than the above wavelength range is not preferable because the generation and growth of defects on the wafer surface are promoted.

  The cleaning method of the present invention provides a predetermined amount of visible light to the object to be cleaned while the cleaning liquid is attached to the surface of the silicon semiconductor wafer, which is the object to be cleaned, during immersion in the cleaning liquid and after being pulled up from the cleaning tank. By performing illumination so that only light on the short wavelength region side is irradiated, growth of defects generated in the object to be cleaned can be suppressed. In addition, the cleaning method of the present invention uses visible light in a predetermined short wavelength region, so that an abnormality in the cleaning process or the cleaning apparatus can be detected visually.

1 is a schematic configuration diagram illustrating a semiconductor wafer cleaning apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the illuminating device which comprises the washing | cleaning apparatus of the semiconductor wafer shown in FIG. 1, the automatic conveyance apparatus which carries out a semiconductor wafer carrying out, the washing | cleaning unit of a to-be-cleaned object, etc. It is a graph which shows the wavelength characteristic regarding the light source of the illuminating device used for the cleaning apparatus of the semiconductor wafer shown in FIG. It is a graph which shows the permeation | transmission characteristic of the filter used for the illuminating device of the cleaning apparatus of the semiconductor wafer shown in FIG. It is a graph which shows the ratio of the large pit formed in the wafer in the environment using the illumination light which concerns on this invention, and the illumination light generally used. (A)-(C) are explanatory drawings which show the effect | action of the liquid level sensor attached to the conventional washing | cleaning unit. It is explanatory drawing explaining the state in which a pit is formed in a silicon substrate. It is a microscope picture which shows the state in which the large pit was image | photographed with the scanning electron microscope.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 show a semiconductor wafer cleaning apparatus 1 according to the present invention. The semiconductor wafer cleaning apparatus 1 is provided inside a semi-enclosed box-shaped housing 2 having a transparent window 60. Illumination device 10 that emits only visible light in the predetermined short wavelength region (the above-described allowable wavelength band (γ)) as an illumination lamp, automatic transfer device 20 that immerses and unloads semiconductor wafer W, and cleaning of semiconductor wafer W And a cleaning unit 30 that performs the cleaning. The housing 2 is installed in a clean room 50.

  The clean room 50 is provided with a lighting fixture 70 for illuminating the interior of the ceiling 50A. The lighting fixture 70 uses a general white fluorescent lamp as a light source. For example, in the present embodiment, the same wavelength distribution characteristic as that of the illumination device 10 installed in the housing 2 of the semiconductor wafer cleaning device 1 described later (see FIG. 3; however, only visible light is emitted). The fluorescent lamp which has is used. For this reason, as will be described in detail later, similar to the illumination device 10, a filter film (not shown) that removes light with a wavelength in an unnecessary band (forbidden wavelength band light) out of light with a wavelength in the visible light range is provided on the outer surface of the light source. It is fixed.

  In the case of this embodiment, the semiconductor wafer W is sliced from an ingot-like silicon crystal to a predetermined thickness, for example, about several hundred microns, by a slicer and mirror-processed by, for example, a CMP (Chemical Mechanical Polishing) method. About several tens of sheet-like pieces immediately after being stored are accommodated in a necessary container (for example, cassette C) such as a fluorine resin, and the cleaning operation is performed.

  In the housing 2, a plurality of types of the above-described cleaning tanks 40 are arranged on a work table placed on the floor surface, and a single or a plurality of the above-described cleaning tanks 40 are provided on the ceiling surface (not limited to this). The illuminating device 10 is installed. In addition, the casing 2 is provided with a window 60 in a part of a wall or the like, and illumination light emitted from the lighting fixture 70 provided on the ceiling 50A of the clean room 50 is inserted into the casing 2 from the window 60. Since there exists a possibility, the filter film F mentioned later is adhere | attached also on the window 60 (vapor deposition).

  The filter film F absorbs visible light in a long wavelength band (forbidden wavelength band light). For example, a band interference filter such as a dichroic filter (two-color filter), a bandpass filter, or a dielectric edge filter is used. Can be configured to have a function of transmitting only the wavelength band. In the filter film F of the present embodiment, for example, a film having wavelength transmission characteristics as shown in FIG. The filter film F has a characteristic of transmitting a relatively broad band of visible light having a wavelength in the above-described allowable wavelength band (γ), but within the allowable wavelength band (γ). If there is, for example, it may be composed of a dielectric multilayer filter having a narrow transmission wavelength and a steep dielectric layer or an appropriate color filter.

  In this way, the fluorescent lamp having the wavelength characteristics shown in FIG. 3 (for example, a fluorescent lamp manufactured by the current Panasonic Corporation (former name: Matsushita Electric Industrial Co., Ltd.)) is used as the light source 11 constituting the illumination device 10. Therefore, in the light after passing through the filter film F, only light having a short wavelength, for example, an allowable wavelength band (γ) from blue to green is emitted into the housing 2 from the visible light described above. Illuminated.

  If the illumination light from the luminaire 70 installed in the clean room 50 does not include visible light in the forbidden wavelength band (β) described above, it is of course unnecessary to deposit the filter film F on the window 60. is there. Further, when the illumination light from the lighting fixture 70 includes infrared light such as near infrared light in addition to the visible light in the forbidden wavelength band (β) described above, light in that wavelength band can also be cut. It is necessary to provide a filter.

  In the SC1 cleaning using the SC1 cleaning liquid, the illuminating device 10 has a long wavelength light in the visible light wavelength band, that is, a light on a long wavelength band side excluding a short wavelength band from blue to green. Based on the inventor's knowledge that it is greatly involved, the inside of the housing 2 is illuminated with visible light (allowable wavelength band light (γ)) consisting only of the wavelength on the short wavelength band side.

Since visual inspection is possible by illuminating with visible light having such a wavelength (allowable wavelength band light (γ)), in the cleaning operation of the semiconductor wafer W, various troubles associated with the cleaning operation can be prevented in advance. A reliable and highly reliable cleaning operation can be performed. Therefore, the following inspection work can be performed under such illumination light. That is,
(I) When a failure such as a chuck error occurs in the chuck of the robot arm 24 that holds the semiconductor wafer W during the cleaning operation, the operator can directly confirm this with the naked eye. Therefore, the cleaning operation can be stopped immediately to repair the failure.
(Ii) Furthermore, when the heater 32 installed in the cleaning tank 40 is damaged and a pinhole or the like is formed, the presence or absence of this damage can be confirmed with the naked eye by visually checking the bubbles. The heater 32 can be replaced quickly.

  In the illumination device 10 of the present embodiment, a normal white fluorescent lamp (the fluorescent lamp described above) having a wavelength distribution characteristic (provided that only visible light is emitted) as shown in FIG. Yes. For this reason, a filter film F, which will be described later, is removed from the light having a wavelength in the visible light range and is removed from the light emission surface of the light source 11. If a light source that emits only visible light of any wavelength other than the wavelength band, that is, only the allowable wavelength band light, is used, for example, a blue light emitting diode, the filter film F is not necessary.

  In the present embodiment, the light source 11 that emits only light in the visible light region is used. However, when the light source 11 includes long-wavelength infrared light that exceeds the visible light region such as near infrared light. Is expected to have a negative effect of growing near-infrared light and infrared light against defects as well as visible light on the long wavelength side (forbidden wavelength band light). is necessary. Therefore, in this case, a filter that cuts light such as near infrared light as well as visible light in the forbidden wavelength band described later may be used. Note that there is no particular problem even if near ultraviolet light or ultraviolet light is present.

  In the illumination device 10 of the present embodiment, the illumination light from the light source 11 using the above-described normal white fluorescent lamp passes through the filter F provided on the outer peripheral surface of the light source 11 to be described later. However, the illumination light from the light source 11 (which may include a part of the light from the luminaire 70 inserted through the window 60) is the minimum necessary for visual inspection. In order to ensure the limited brightness, the light intensity (Cd: candela) of the light source 11 is adjusted. Thereby, as described above, by confirming various troubles associated with the cleaning work with the eyes, those troubles can be prevented in advance.

  That is, in the present embodiment, the abnormal state of the automatic transfer device 20 and the cleaning unit 30, for example, the abnormal decrease or increase in the liquid level in the cleaning tank 40 of the cleaning unit 30, the breakage of the heater 32, and further the automatic transfer device 20. In order to ensure a minimum light intensity (or light quantity) that enables an operator to directly check and check for chuck mistakes or the like in the machine, by adjusting the light intensity (Cd; candela) of the light source 11, the automatic transport device 20 and the cleaning unit 30 are near. The illuminance (Lx; lux) is kept at a minimum brightness of, for example, 1 lux.

  In general, a fluorescent lamp has a total luminous flux of, for example, a 40 W straight tube type and about 2800 to 3500 lumens, and an illuminance of about 400 lux is secured during normal (conventional) operation. On the other hand, in the present invention, the light intensity of the light source 11 of the lighting device 10 is adjusted, and by ensuring the minimum illuminance (1 lux) as described above in the vicinity of the automatic conveyance device 20 and the cleaning unit 30, these It has been confirmed that various abnormalities can be detected visually.

  The automatic transfer device 20 sequentially transfers the semiconductor wafers W constituting the object to be cleaned to the plurality of cleaning tanks 40 containing the cleaning liquids 3, and the semiconductor wafers W transferred in the cleaning tanks 40 to the cleaning liquid 3. It is configured to be immersed and perform necessary cleaning, and to be removed from the cleaning tank 40 after the cleaning operation is completed.

  The automatic conveyance device 20 of the present embodiment includes, for example, a slide shaft 21 that is arranged in parallel along the ceiling surface in the housing 2, a slider 22 that is screwed to the slide shaft 21, and the slider 22 that hangs down from the slider 22. A guide shaft 23 and a robot arm 24 that can freely move up and down along the guide shaft 23 are provided.

  The robot arm 24 can move the semiconductor wafer W to the next cleaning tank 40 by moving in the horizontal direction while holding the semiconductor wafer W. Further, the robot arm 24 moves up and down while gripping the semiconductor wafer W to start the gripping operation and cancels the gripping operation, thereby performing operations of loading, dipping, and unloading of the semiconductor wafer W.

  The cleaning unit 30 is provided with a cleaning unit used for RCA cleaning. Specifically, as shown in FIG. 2, fine particles or the like are mixed in the circulation pump 31, the heater 32, and the cleaning liquid 3. In this case, the filter 34 is removed during the passage, and the communication pipe 33 is attached to the filter 34 and connected to the cleaning tank 40 (described later). Furthermore, in the present embodiment, the outer peripheral surfaces of the heater 32, the communication pipe 33, the filter 34, and the cleaning tank 40 are allowed to transmit visible light (allowable wavelength band light) in a predetermined short wavelength region and have a long wavelength. Cover with a filter film F that absorbs visible light in the band (forbidden wavelength band light). In the present embodiment, the heater 32 is installed outside the cleaning tank 40 via the communication pipe 33, but may be installed inside the cleaning tank 40.

  The pump 31 takes in the cleaning liquid 3 in the cleaning tank 40 from the upper part of the communication pipe 33 and discharges the cleaning liquid 3 from the lower part of the communication pipe 33 into the cleaning tank 40 to circulate the cleaning liquid 3 in the cleaning tank 40. Therefore, the cleaning liquid 3 passing through the communication pipe 33 is heated by the heater 32.

  The heater 32 includes a quartz tube as an outer tube and a nichrome wire (or a platinum wire, a Kanthal wire, or the like) as a heat source provided in the quartz tube, and energizes the nichrome wire from the outside. As a result, the entire quartz tube is heated, and the cleaning liquid 3 inside the communication tube 33 passing therethrough is heated.

  The heater 32 emits light of various wavelengths along with heat generation of the nichrome wire as a heat source, and in particular, visible light on the long wavelength side such as red is simultaneously emitted during the SC1 cleaning operation of the semiconductor wafer W in the present invention. (Near-infrared light may be emitted depending on the luminaire used). Therefore, in the present embodiment, in order to prevent light in such a wavelength band (forbidden wavelength band light) from reaching the cleaning liquid, the filter film F described above is disposed on the entire outer peripheral surface of the heater or the box in which the heater unit is accommodated. Etc. are provided by vapor deposition. In addition, when the surface heating temperature of the heater 32 is high, it may be appropriately surrounded by means without vapor deposition.

In the case of this embodiment, the cleaning tank 40 is a multilayer batch cleaning type, and is used for rinsing together with at least two types of cleaning liquids (chemical solutions), particularly in this embodiment, four types of cleaning liquids (SC1, SC2, SMP, DHF). Are comprised of a plurality of cleaning tanks 40 each containing pure water. In addition, the cleaning liquid is not limited to this. For example, at least one kind of chemical liquid of ammonia, tetramethylammonium hydroxide, and choline, a hydrogen peroxide solution, and pure water are mixed. It may be a washed liquid.
The cleaning unit 30 of the present invention is not limited to the multi-layer batch cleaning type as in the present embodiment, and can be applied to, for example, a single tank batch cleaning type or a single wafer cleaning type.

  In the case of the present embodiment, at least the convenience of two types of cleaning liquids (SC1, SC2) 3 used for SC1 cleaning and SC2 cleaning and two types of cleaning liquids (SMP, DHF) 3 used for SPM cleaning and DHF cleaning In addition to using the four types of cleaning liquids 3, immediately after cleaning with these cleaning liquids 3, the residual cleaning liquid adhering to the surface of the semiconductor wafer W is immersed in the cleaning liquid 3 in the subsequent cleaning operation. It is configured to be removed by rinsing with pure water. For this reason, in this embodiment, in addition to the cleaning tank in which the cleaning liquid 3 is stored, a dedicated rinsing tank (not shown) in which pure water is stored is also installed.

As shown in FIG. 2, the cleaning tank 40 of the present embodiment includes a main body 41 formed of a liquid-resistant material such as quartz glass that is not eroded by each cleaning liquid (chemical liquid), and an opening of the main body 41. And a lid 42 formed of a transparent material that can be closed if necessary. Among these, the outer surface of the main body 41, that is, the four side surfaces and the bottom surface is approximately 380 to 760 (nm) (however, the wavelength band of visible light may be slightly shifted depending on individual differences). Of the total visible light region, light having a wavelength satisfying the expression (1), which is the above-described forbidden wavelength band (β), that is, a wavelength (λ ₀ ) exceeding 580 (nm) in this embodiment is cut. A filter film F, which will be described later, is directly deposited or attached to the periphery. Therefore, even if the light from the heater 31 is leaked, the light can be prevented from entering the cleaning tank 40 from the main body 41 of the cleaning tank 4.

  In addition, in order to prevent the cleaning liquid in the cleaning tank 40 from evaporating, the opened upper portion of the main body 41 is closed with a lid 42 as necessary when the semiconductor wafer W is not carried in or out. Since the lid body 42 is formed of a transparent material, occurrence of various troubles in the cleaning tank 40 during immersion of the semiconductor wafer W can be visually confirmed. In this embodiment, leakage of external light from the outside of the housing 2 is prevented as much as possible. However, for the sake of convenience, the filter film F is also directly deposited on the lid 42 or pasted around it. It is preferable to keep it.

According to the lid 32 on which such a filter film F is deposited, the above-mentioned allowable wavelength band λ _V ≦ γ ≦ λ _G among the light in the visible light range, that is, the limit wavelength (λ _V ; approximately on the short wavelength side) 380 nm) to the limit wavelength (λ _G ; approximately 580 nm) on the long wavelength side can be transmitted, so that the illumination light can show the state of the semiconductor wafer W immersed in the cleaning tank and the level of the cleaning liquid. Direct visual confirmation is possible.
It is more preferable that an appropriate light absorbing material that absorbs visible light in the wavelength band as described above is attached to the inner wall surface, ceiling surface, floor surface, and the like of the housing 2.

  In the case of the present embodiment, as described above, the cleaning liquid 3 uses four types of cleaning liquids, that is, two types of cleaning liquids used for SC1 cleaning and SC2 cleaning and two types of cleaning liquids used for SPM cleaning and DHF cleaning. These cleaning liquids are stored in the four cleaning tanks 40, respectively. Further, in the case of the present embodiment, as described above, immediately after cleaning with these cleaning liquids 3, the residue adhering to the surface of the semiconductor wafer W prior to being immersed in the cleaning liquid 3 in the next cleaning operation. In order to completely remove the cleaning liquid, rinsing with pure water is also performed.

Next, a semiconductor wafer cleaning method using the semiconductor wafer cleaning apparatus 1 according to the present embodiment will be described.
It is used by operating the light source 11 of the illumination device 10 to illuminate the inside of the housing 2 with illumination light in an allowable wavelength band (γ; where λ _V ≦ γ ≦ λ _G ). Λ _V was 380 to 480 nm, and λ _G was 520 to 580 nm.
Next, the required number of semiconductor wafers W are stored in the cassette C and set in a wafer loader at a predetermined position.

Then, the cassette C containing the semiconductor wafer W is held by the robot arm 24 of the automatic transfer device 20 and transferred to the position immediately above the first cleaning tank 40A, and the cassette C is lowered at a position immediately above the first cleaning tank 40A. It is carried into the cleaning tank 40A.
Next, the robot arm 24 is lifted to a position where it is retracted from the cleaning liquid 3 in the cleaning tank 40 after releasing the gripping operation of the cassette C containing the semiconductor wafer W. Immediately after this, when the robot arm 24 holds the lid 42 and moves to the upper part of the cleaning tank 40A and closes the cleaning tank 40A with the lid 42, the circulation pump 31 and the heating heater of the cleaning unit 30 are closed. 32 starts operation.

  As a result, the cleaning operation of the semiconductor wafer W in the cleaning tank is performed for a predetermined time, and the robot arm 24 performs the removal of the lid 42 and the subsequent unloading operation of the cassette C as the predetermined time elapses. Then, the robot arm 24 that holds the cassette C moves immediately above the rinse tank in which pure water is stored, and the semiconductor wafer W is immersed in the rinse tank to rinse off the cleaning liquid 3 remaining on the semiconductor wafer W. .

  Next, the same operation as the previous cleaning operation is repeated to perform the cleaning operation and the rinsing operation in the second cleaning tank 40B. In this manner, similarly, when the cleaning and rinsing operations in the final cleaning tank are completed, the drying operation is performed by moving to a drying means (not shown).

  Thus, according to the present embodiment, the light emitted from the light source constituting the illumination device 10 illuminates the inside of the housing 2 using only light in the allowable wavelength band. Therefore, even if a defect such as a fine groove is formed on the surface of the semiconductor wafer W immersed in the cleaning liquid 3 in the cleaning tank 40, the forbidden wavelength band light that promotes the growth of the defect is not irradiated. For example, an aggregate of pits of about 20 to 30 nm, that is, formation of large pits as described above can be suppressed.

Moreover, according to this embodiment, there is no need to perform a cleaning operation in the dark housing 2 in order to avoid the formation of large pits.
(I) A chuck error occurs in the chuck of the robot arm 24 that grips the semiconductor wafer W during the cleaning operation, and the semiconductor wafer W immersed in the cleaning tank cannot be pulled up, or the chuck is displaced and cannot be gripped. It is possible to avoid overlooking and overlooking troubles.
(Ii) Further, even in the case where the heater 32 installed in the cleaning tank 40 is broken and a pinhole or the like is generated, the inside of the housing 2 is illuminated with the allowable wavelength band light in this embodiment. As a result, the operator can directly check the bubbles associated with the occurrence of the pinhole under the illumination light, and the heater 32 can be replaced quickly. As a result, it is possible to avoid oversight and oversight of troubles such as a chemical solution infiltrated from a pinhole generated from a damaged heater in the cleaning tank, corroding the heater wire, and metal eluting into the cleaning solution.

[Example 1]
Next, referring to FIG. 5, when the cleaning operation is performed by using the light of the allowable wavelength band (γ) of the lighting device of the present invention, and by using the light of the prohibited wavelength band (β). A comparative experiment will be described in which the number of large pits generated with the growth of defects is examined for the case where the cleaning operation is performed.

  In the semiconductor wafer cleaning apparatus 1 including the automatic transfer apparatus 20 and the cleaning unit 30 according to the present embodiment, particularly when the illuminating device A or B that emits the allowable wavelength band light is used, and the general practice of emitting the forbidden wavelength band light. In the case of using a typical illumination device C, the growth rate of defects (pits) generated when a predetermined cleaning operation is performed, that is, the ratio of formation of large pits, for example, aggregates of those grown to about 20 to 30 nm I conducted an experiment to investigate. The chemical used here is a mixture of 29% ammonia water, 31% hydrogen peroxide water and ultrapure water at a ratio of 1: 5: 50. The temperature is 80 ° C., and the cleaning time is 80 to accelerate pit formation. Minutes.

  As a result, data as shown in FIG. 5 was obtained. In the same figure, the frequency (occurrence rate) at which the large pits are generated on the entire surface of the semiconductor wafer W as a sample is plotted on the vertical axis, and the illumination light inside the housing 2 (visible light incident on the cleaning tank 40). ) Was set on the horizontal axis.

  According to FIG. 5, when the allowable wavelength band light according to the present invention is used, the occurrence frequency of large pits is larger than that in the case of emitting conventional general illumination light, that is, visible light including prohibited wavelength band light. It was confirmed that it could be greatly suppressed. That is, in the visible light wavelength band, the illumination device B that blocks light in the forbidden wavelength band (β) longer than 580 nm emits light in the forbidden wavelength band longer than 580 nm. It was confirmed that the occurrence frequency can be suppressed to about 40% of the occurrence frequency of large pits when the apparatus C is used.

  On the other hand, the illuminating device A that emits visible light in the short wavelength region close to near-ultraviolet light is less effective than the illuminating device B, but the illuminating device C that emits forbidden wavelength band light having a longer wavelength than 580 nm. It was confirmed that the frequency of occurrence of large pits when used could be reduced to about 60% of the frequency.

  In addition, this invention is not limited to said embodiment, Various aspects are applicable.

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer cleaning apparatus 2 Housing | casing 3 Cleaning liquid 10 Illumination apparatus 11 Light source 20 Automatic conveyance apparatus 24 Robot arm 30 Cleaning unit 31 Circulation pump 32 Heating heater 33 Communication pipe 34 Filter 40 Cleaning tank 41 Main body 42 Lid 50 Clean room 60 Transparent window 70 Lighting equipment F Filter membrane W Semiconductor wafer (object to be cleaned)
γ Allowable wavelength band (However, λ _V ≦ γ ≦ λ _G )

Claims (5)

In the silicon semiconductor wafer cleaning method of cleaning the surface by immersing in the cleaning liquid in the cleaning tank,
The cleaning liquid is composed of at least one of ammonia, tetramethylammonium hydroxide, and choline, a hydrogen peroxide solution, and pure water. Further, the cleaning liquid is immersed on the cleaning liquid and pulled up from the cleaning tank, and then is cleaned on the surface of the wafer. A method for cleaning a semiconductor wafer, wherein the wafer is irradiated with short-wavelength visible light while the substrate is attached. The wavelength range of the short wavelength visible light is
2. The method for cleaning a semiconductor wafer according to claim 1, wherein the wavelength is 580 nm from a boundary wavelength between visible light and ultraviolet light. A cleaning device for a surface of a semiconductor wafer,
A housing,
A cleaning tank that immerses a silicon semiconductor wafer installed in the housing,
An illuminating device is disposed in the housing, and the illuminating device irradiates the wafer with short-wavelength visible light while the wafer is immersed in the cleaning solution and while the cleaning solution is attached to the wafer surface after being pulled up from the cleaning tank. And the cleaning liquid comprises at least one of ammonia, tetramethylammonium hydroxide, and choline, a hydrogen peroxide solution, and pure water.
A semiconductor wafer cleaning apparatus.   Furthermore, a heating heater, a circulation pump, a communication pipe for communicating the pump and the cleaning tank, and a means for transmitting only the short wavelength visible light to the heating heater and the cleaning tank are provided. The apparatus for cleaning a semiconductor wafer according to claim 3. The wavelength range of the short wavelength visible light is
5. The semiconductor wafer cleaning apparatus according to claim 3, wherein the wavelength is 580 nm from a boundary wavelength between visible light and ultraviolet light.