GB2349742A

GB2349742A - Method and apparatus for processing a wafer to remove an unnecessary substance therefrom

Info

Publication number: GB2349742A
Application number: GB0007920A
Authority: GB
Inventors: Kaori Watanabe
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1999-04-01
Filing date: 2000-03-31
Publication date: 2000-11-08
Anticipated expiration: 2020-03-31
Also published as: GB2349742B; GB0007920D0; JP2000294527A

Abstract

A method for processing a wafer 3, comprises, soaking, in a processing fluid 6, at least a portion of the wafer 3 while maintaining in an upward direction a first surface having elements formed thereon. A gas is then blown onto the first surface of the wafer, whereby an unnecessary substance adhering to the wafer is thereby removed. The processing fluid 6 preferably penetrates around and into a predetermined end portion area of the front surface from an edge portion of the wafer. The area of penetration may be controlled by the flow rate of the gas having a radial component extending radially outward on the wafer. The gas may be nitrogen or dry air. Apparatus for processing the wafer may include an ultrasonic wave generating source 7 placed at a bottom portion of a processing bath 2 which is used to contain the processing fluid. The wafer may be held in place by a wafer-holding portion 5 whilst a gas spouting outlet 16 blows gas onto the first surface.

Description

METHOD AND APPARATUS FOR PROCESSING A WAFER TO REMOVE AN UNNECESSARY SUBSTANCE THEREFROM Field of the Invention The present invention relates generally to a method and apparatus for processing particular portions of a wafer to remove unnecessary substances therefore. More particularly, the present invention relates to cleaning or removing film forming materials or substances and the like adhered on the rear surface and on an end portion area of the front surface of a wafer after forming circuit elements on the wafer.

Background of the Invention According to an increase in an integration degree of a semiconductor device, more and more strict reliability is required in the manufacturing process thereof. For example, in a process of forming circuit elements on a substrate, many process steps for forming film8 are performed, and therefore a danger of cross-contamination by materials used in the process steps for forming film. becomes large. Therefore, it is strongly required to establish a processing technology for correctly and completely removing materials or substances used for forming films, ie., film forming materials or substances, adhered or deposited on areas which are other than an element forming area and on which films are not to be formed, before and after each process step for forming a film.

For example, when a ferroelectric film is formed on the surface of an element or when a metal circuit such as aluminum wiring and the like is formed on an element, a sputtering method or a CVD method is used to form such ferroelectric film or metal film. In this case, however, since a wafer is placed in an atmosphere including the film-forming material, the film-forming material deposits or adheres on the rear surface, that is, a surface on which elements are not formed, of a wafer and on an end portion area of the front surface where elements are not formed, as well as on an element forming area of the front surface of the wafer.

Also, when copper circuits are formed on the side of the wafer surface on which circuit elements are formed, since copper is apt to diffuse into silicon of the wafer, a silicon oxide film is often formed beforehand on the rear surface of the wafer as a protective film. After performing a process of forming a copper film, the silicon oxide film on the rear surface of the wafer into which copper has diffuse is now removed.

When the wafer is stored in a carrier and transported, these film-forming materials adhered or deposited on the rear surface of the wafer or on the edge areas of the front surface of the wafer often come off from the wafer due to the friction with the carrier and become a contamination source. Also, when the wafer is held at the end portions thereof and transported, or when the wafer is supported at the rear surface thereof, there is a possibility that the film-forming materials adhered on the rear surface or the edge areas of the front surface of the wafer come off and become a contamination source.

Until now, as disclosed in Japanese patent laid-open publication No. 10-223593 and Japanese patent laid-open publication No. 5-347289, a cleaning method for a wafer and a cleaning apparatus therefor have been developed in which the front surface or both surfaces of a wafer are cleaning processed uniformly. However, a technology is not disclosed heretofore in which only edge areas of the front surface of a wafer and the rear surface thereof are precisely processed while avoiding application of a chemical solution or fluid to an element forming area on the front surface of the wafer.

In order to perform cleaning of a wafer, the inventor of this application heretofore has been using a method called a spin cleaning. With reference to Fig. 7, a cleaning apparatus for this method will be described. Fig. 7 is a cross-sectional view showing a schematic structure of such cleaning apparatus.

A wafer 61 on which semiconductor elements are formed is supported on a wafer support 62 in a processing bath 70, while keeping the side of the front surface 61A, i. e., the surface on which circuit elements are formed, downward, and is fixed by wafer holding pins 63. The wafer support 62 has a mechanism for rotating around a rotating shaft 65 by a rotational drive portion or a rotational drive mechanism 64. At the same time, the rotating shaft 65 constitute an N2 gas supply inlet 67 for supplying nitrogen gas to the side of the front surface 61A of the wafer 61. Also, there is provided a chemical solution/pure water supply inlet 66 over the rear surface of the wafer 61, and, from the chemical solution/pure water supply inlet 66, it is possible to supply a chemical solution for removing film-forming materials and pure water for removing the chemical solution thereafter. The apparatus further has a discharging outlet 68 for discharging processing solutions after performing a cleaning or removing process.

Steps of processing are performed as follows. Chemical solution 69 most suitable for removing Simbrming materials is supplied from the chemical solution/pure water supply inlet 66 while rotating the wafer 61 by the rotational drive portion or rotational drive mechanism 64. Then, pure water is supplied from the chemical solution/pure water supply inlet 66 and cleaning of the wafer 61 is performed. Further, the wafer 61 is s rotated in a condition where the supply of the chemical solution and pure water from the chemical solution/pure water supply inlet 66 is stopped ; therebythe wafer 61 is dried. In this processing, in order to clean the rear surface of the wafer 61 and the end portion area on the front surface of the wafer 61 at the same time, nitrogen gas is blown from the N2 gas supply inlet 67 onto the wafer 61, and the wafer 61 is slightly floated from the wafer support 62. Also, the wafer 61 is rotated at a low speed of 200 rpm. Thereby, the chemical solution slightly penetrates around into the end portion on the front surface 61A of the wafer 61.

However, in this method, since the quantity of penetration of the chemical solution is controlled by balancing the penetration of the chemical solution with centrifugal force applied to the chemical solution, the area which can be processed is limited to the whole portion of the rear surface and only a small portion of the end portion area of the front surface of the wafer, that is, the area from the outer edge inwardly for approximately 2 mm in the direction of radius.

However, the depth ofeachgroove of a carrier for holding a wafer is, for example, usually 8-10 mm, and therefore there is a possibility that, in particular, an edge portion of the groove contacts the area from the outer edge inwardly for more than 2 mm in the direction of radius. Thus, it is impossible to completely avoid a possibility that contamination of a wafer occurs when the wafer is stored and carried by the carrier.

Also, nitrogen gas introduced from the N2 gas supply inlet 67 to float the wafer also plays a role of preventing the chemical solution from intruding into the element forming area of the front surface 61A of the wafer 61 and thereby preventing an element surface from being scarred. Therefore, nitrogen gas must be supplied at a large flow rate, for example, 180 L/min, i. e., liter/minute, when a 6-inch wafer is to be processed, and 300 L/min, when an 8-inch wafer is to be processed.

Further, with respect to the chemical solution and the like material supplied form the chemical solution/pure water supply inlet 66, since these solutions are flicked outwardly away by the centrifugal force simultaneously with the processing, a large quantity of chemical solution, for example, 1-2 L/min, must be supplied, so that these solutions and the like are changed after being reused several times, that is, after recycling is performed.

Therefore, once they are contaminated, there is a possibility that the wafer or wafers processed thereafter are also contaminated.

Still further, since the size of a pipe for supplying the chemical solution cannot be made too thick, it was impossible to use a sparkling chemical solution, for example, HaO2 and the like. For such reason, the kind of usable chemical solution was limited.

Summary of the Invention It is an object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which an area on a wafer surface contacting a chemical solution can be controlled precisely, so that only a necessary portion or portions of a wafer can be completely processed.

It is another object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which an area on a wafer surface contacting a chemical solution can be controlled precisely.

It is still another object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which a processing area in an end portion region on the front surface of the wafer can be enlarged.

It is still another object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which an end portion area on the front surface of the wafer and the rear surface of the wafer can be simultaneously processed, thereby improving efficiency of processing.

It is still another object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which quantity of chemical solution required for processing the wafer can be reduced and the cost of the chemical solution can be reduced.

It is still another object of the preferred embodiments of the present invention to provide a processing method and processing apparatus for a wafer in which cross-contamination caused by the recycling of chemical solution can be decreased.

It is still another object of the preferred embodiments of the present invention to obviate the disadvantages of the conventional processing method and processing apparatus for a wafer.

According to an aspect of the present invention, there is provided a method for processing a wafer comprising: soaking at least a portion of said wafer in a processing fluid while e keeping an element forming surface of said wafer upward, in a condition in which a gas is blown onto said element-forming surface of said wafer, thereby removing unnecessary substance adhered to said wafer.

In this case, it is preferable that unnecessary substance adhered to at least a predetermined end portion area of the element forming surface of the wafer are removed by making the processing fluid penetrate around into a predetermined end portion area of the element forming surface of the wafer from an edge portion of the wafer.

It is also preferable that the direction of blowing the gas has a direction component along a radial direction from the center of the wafer toward the end portion area.

It is further preferable that the at least a portion of the wafer is soaked in the processing fluid while keeping the element forming surface of the wafer upward, in a condition in which a gas is blown onto the element-forming surface of the wafer and the wafer is rotated at a predetermined rotational speed.

It is advantageous that the gas is nitrogen gas.

It is also advantageous that the gas is dry air.

It is further advantageous that unnecessary substance adhered to a predetermined end portion area of the element forming surface of the wafer and unnecessary substance adhered to the rear surface of the wafer are simultaneously removed.

It is preferable that, when the wafer is processed, an ultrasonic wave is generated into the processing fluid.

It is also preferable that the unnecessary substance comprises a material used for forming elements on the wafer According to another aspect of the present invention, there is provided an apparatus for processing a wafer comprising : a processing bath for storing processing fluid ; at least one wafer holding portions each of which holds the wafer and has a gas spouting outlet for blowing a gas onto an element forming surface of the wafer held by the wafer holding portion; and a gas supplying apparatus for supplying the gas blown onto the element forming surface of the wafer from the gas spouting outlet; wherein unnecessary substance adhered to the wafer is removed by soaking at least a portion of the wafer in a processing fluid in the processing bath, while keeping the element forming surface of the wafer upward, in a condition in which a gas is blown onto the element-forming surface of the wafer held by the wafer holding portion.

In this case, it is preferable that unnecessary substance adhered to at least a predetermined end portion area of the element forming surface of the wafer is removed by making the processing fluid penetrate around into a predetermined end portion area of the element forming surface of the wafer from an edge portion of the wafer by soaking at least a portion of the wafer in a processing fluid in the processing bath, while keeping the element forming surface of the wafer upward, in a condition in which a gas is blown onto the element-forming surface of the wafer held by the wafer holding portion.

It is also preferable that each wafer holding portion is movable up or down with respect to the liquid surface of the processing fluid.

It is further preferable that a flow rate of the gas blown from the gas spouting outlet onto the element forming surface of the wafer is controllable.

It is advantageous that the direction of the gas blown from the gas spouting outlet onto the element forming surface of the wafer has a direction component along a radial direction from the center of the element forming surface of the wafer toward the end portion.

It is also advantageous that the apparatus further comprises a rotational drive portion for rotating the wafer holding portion in the direction of the circumference of the wafer held by the wafer holding portion.

It is further advantageous that the apparatus further comprises an ultrasonic wave generating source at the bottom portion of the processing bath It is preferable that the ultrasonic wave generating source generates an ultrasonic wave of 0.1 through 2 MHz.

It is also preferable that the gas blown from the gas spouting outlet onto the element forming surface of the wafer is nitrogen gas.

It is further preferable that the gas blown from the gas spouting outlet onto the element forming surface of the wafer is dry air.

It is advantageous that the unnecessary substance comprises a material used for forming elements on the wafer Brief Description of the Drawings Preferred features of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross sectional view illustrating a processing apparatus for a wafer according to an embodiment of the present invention ; Fig. 2A through Fig. 2C are schematic cross sectional views each showing an example of a wafer support portion which can be used in the processing apparatus for a wafer according to the present invention ; Fig. 3A through Fig. 3D are plan views each showing a wafer support portion used in the processing apparatus according to the present invention when viewed from the front surface of a wafer, and each particularly showing directions of gas spouting schematically; Fig. 4 is a plan view illustrating a manner in which a wafer support portion used in the processing apparatus according to the present invention holds a wafer; Fig. 5 is a table showing examples of film forming substances to be processed and kinds of chemical solutions, and typical processing times by the chemical solutions; Fig. 6A and Fig. 6C are a schematic cross sectional view and a plan view, respectively, illustrating a structure of a processing apparatus for wafers which can process a plurality of sheets of wafers according another embodiment of the present invention; and, Fig. 7 is a schematic cross sectional view of a conventional spin processing apparatus.

Description of a Preferred Embodiment With reference to the drawings, embodiments of the present invention will now be described in detail. Fig. 1 is a schematic cross sectional view showing a structure of a processing apparatus for a wafer, i. e., a wafer processing apparatus, according to an embodiment of the present invention.

As shown in Fig. 1, chemical solution/pure water 6, that is, a processing solution or processing fluid, is stored in a processing bath 2 constituting a wafer processing portion. A substrate or a wafer 3 is soaked in the processing solution and processed, while keeping a surface of the wafer 3 on which circuit elements are formed, i. e., the front surface 3A, upward.

Quantity of the chemical solution/pure water 6 is determined based on the rear surface of the wafer 3 not contacting the bottom of the bottom of the processing bath, for example, such that approximately 100 mL of processing solution is stored in the processing bath. Also, there is disposed an ultrasonic wave generating portion 7 on the bottom of the processing bath 2.

Further, the processing solution, that is, chemical solution or pure water, is supplied from a chemical solution supply tank 9 or from a pure water supply tank 10, and discharged from a discharging outlet 13. Control of the supply and discharge of these processing solution is performed by controlling valves 15 by a valve control portion 14.

The processing 1uid discharged from the discharging outlet 13, that is, waste fluid, can be discarded as a disposable solution to avoid cross-contamination, or can be reused by collecting it into a waste fluid processing apparatus not shown in the drawing and by performing a filtering process to remove contaminant in the waste fluid.

Also, there is provided a heater not shown in the drawing, and thereby it is possible to heat the processing solution 6 if necessary.

The wafer 3 is fixed to a wafer holding portion 5, by using pins 4 which are wafer holding tools, while keeping the element forming surface 3A, i. e., the front surface, upward. Fig. 4 is a plan view showing a manner of holding a wafer by the wafer holding tools. In this drawing, the wafer 3 is chucked by using 6 (six) wafer holding tools (pins) 4, i. e., three holding tools 4A at A positions and three holding tools 4B at B positions. Fig. 4 also shows that, during the processing, it is possible to move three holding tools 4A in A positions to A'positions, while the wafer is chucked by three holding tools 4B in B positions. Also, it is possible to move the holding tools 4B in B positions, while chucking the wafer by the holding tools 4A in A'positions. By making the chucking positions of the wafer holding tools movable, it is possible to avoid leaving unprocessed portions of the wafer chucked by the wafer holding tools 4.

The wafer holding tools 4 are not particularly limited to any particular shape, or to any particular way of holding a wafer. Each of the wafer holding tools 4 can be, for example, a rod-like member which holds the tools 4 can be, for example, a rod like member which holds the wafer from the side thereof, or can be an L-shaped member which holds the wafer from the side and bottom thereof. In any case, it is only necessary that the wafer does not come off when the wafer is rotated at between several hundred and several thousandrpm.

The wafer holding portion or wafer support 5 has a gas jet or gas spouting outlet 16 from which a gas is blown onto the surface of a wafer 3, and, in the apparatus shown in Fig. 1, nitrogen gas is supplied into the wafer holding portion 5 from a nitrogen gas supply apparatus 8 while controlling a flow rate thereof, so that the nitrogen gas is blown onto the front surface of the wafer 3 via the gas jet 16. The nitrogen gas after use is exhausted from a vent 12.

Fig. 2A through Fig. 2C are schematic cross sectional views each showing an example of the wafer holding portion which can be used in the wafer processing apparatus of Fig. 1.

For example, as shown in Fig. 2A, the wafer holding portion 5 may have a cone shape. In this case, the gas jet 16 is provided above the peripheral area of the wafer 3, and nitrogen gas flow 17 is delivered along an inner wall of the cone, so that the gas flow 17 is blown onto an end portion area on the front surface of the wafer 3.

Also, as another shape, the wafer holding portion 5 may have a disc shape as shown in Fig. 2B. In this case, the gas jet 16 is disposed at the central upper portion of the wafer 3, and nitrogen gas 17 is blown onto the wafer 3 such that the nitrogen gas 17 skims from approximately the central portion toward the end portion thereof.

As a variation from the shape of Fig. 2B, as shown in Fig.

2C, the gas jet 16 may be disposed at a higher position from the wafer 3, and the wafer holding portion may have a tapered shape. By such constitution, it is possible to smoothly deliver nitrogen flow 17.

Fig. 3A through 3D schematically show a view of the gas jet 16 and show spouting directions of the nitrogen gas flow 17, when the wafer holding portion 5 is viewed from the side of the front surface of the wafer 3. Fig. 3A and Fig. 3B correspond to the wafer holding portion shown in Fig. 2A, and Fig. 3C and Fig.

3D correspond to the wafer holding portion shown in Fig. 2B.

The spouting directions of the nitrogen gas from the gas jet 16 may be in a radial direction as shown by arrows of the nitrogen gas flow 17 in Fig. 3A and Fig. 3C, or may be along a spiral shape having a component of direction along the circumference of the wafer as shown in Fig. 3B and Fig. 3D.

The spouting direction of the gas can be easily controlled, for example, by forming grooves along radial directions at an inner wall portion, i. e., gas flow path, of the wafer holding portion 5, or by forming grooves each having a spiral shape.

Since the object of blowing a gas onto a wafer is to avoid intrusion of a chemical solution into an element forming area of the wafer, it is necessary that, in any case, the spouting direction of the gas has a direction component in the radial direction from the center of the wafer toward the end portion thereof.

The wafer holding portion 5 is coupled with a rotational drive portion 11, and is driven to rotate the wafer around a shaft of the wafer holding portion 5 (a helve portion of the wafer holding portion 5). By using such structure, the wafer holding portion 5 can rotate at a rotational velocity from a low speed rotation, for example, several ten rpm through a high speed rotation, for example, several thousand rpm, with the wafer 3 chucked by the wafer holding portion 5.

Now, with reference to Fig. 1, an explanation will be given of processing of a wafer.

First, a chemical solution or fluid as a processing fluid is introduced into a processing bath 2. The chemical solution is for dissolving, etching, decomposing or resolving flm forming g materials or substances adhered to the wafer 3, and is appropriately selected depending on the materials or substances to be processed, that is the kinds of film-forming materials or substances adhered to the wafer 3.

Next, the wafer 3 is fixed to the wafer holding portion 5.

While supplying nitrogen gas to the wafer holding portion 5 by the N2 gas supplying apparatus 8 and blowing the nitrogen gas onto the wafer 3 via the gas spouting outlet 16, the wafer holding portion 5 is gradually lowered. The height of the wafer holding portion 5 is controlled in a range approximately from 0.1 to 1.0 mm from the bottom of me cleaning bath or processing bath 2.

After the rear surface of the wafer contacts the processing fluid, the flow rate of the nitrogen gas is controlled such that the chemical solution penetrates around into a predetermined end portion area on the front surface of the wafer but the chemical solution does not penetrate around into an element forming area on the front surface of the wafer. In this case, the height of the front surface of the wafer 3 is slightly lower than the height of the fluid surface of the processing fluid. However, on the front surface of the wafer 3, since nitrogen gas is blown thereto, the processing fluid penetrates around only into the end portion area of the front surface of the wafer 3. The quantity of nitrogen gas supplied in this case is in a range approximately from 10.0 to 100.0 L/min, although it depends on the size of the wafer. It is possible to relatively easily control the area of the chemical solution penetrating around into the end portion area of the front surface of the wafer, by balancing the surface tension of the chemical solution at the wafer surface and the pressure of nitrogen gas. In this case, the wafer holding portion 5 may be rotated at a low speed, for example, at several ten rpm.

However, it is also possible to process the wafer without rotating it.

It is possible to control the area of the chemical solution penetrating around into the end portion area of the front surface of the wafer, with high precision, by the flow rate of nitrogen gas and the relationship of height between the wafer and the fluid surface of the chemical solution. Therefore, according to the present invention, it is possible to control the area of the processing fluid penetrating around into the end portion area of the front surface of the wafer more easily and more correctly than the conventional spin processing.

The end portion area of the front surface of the wafer is an end portion of the front surface of the wafer where elements are not formed. In such area, an area which especially needs to be cleaned is an area which contacts other substances, in a storing or stocking, transporting, or manufacturing process.

For example, when the wafer is stored and transported by using the above-mentioned carrier, an area from the edge portion inwardly for approximately 2 mm on the front surface of the wafer becomes a contacted area. When a quartz boat or a shield ring in a sputtering apparatus is used, an area from the edge portion inwardly for approximately 10 mm on the front surface of the wafer becomes a contacted area.

In this way, the end portion area of the front surface of the wafer which needs to be cleaned varies depending on a film forming process after cleaning, a wafer size, an area of an element forming area, and like factors. According to the present invention, it is possible to appropriately select the area of the end portion area to be cleaned depending on the circumstances and necessity.

When the penetration of the chemical solution reaches a predetermined location or area, an ultrasonic wave of 0.1 through 2 MHz is generated into the processing fluid in the processing bath 2 by the ultrasonic wave generating apparatus 7, while the gas flow rate of nitrogen and the height of the wafer are controlled to maintain the condition of the penetration. By generating the ultrasonic wave, processing efficiency of the wafer can be improved.

With respect to the above-mentioned processing by the chemical solution, it is also possible to perform processing of several sheets of wafers by using the same chemical solution.

Further, it is possible to perform processing of several kinds of film forming substances by changing the kinds of the chemical solution.

After a predetermined time has elapsed, generation of the ultrasonic wave is halted and the chemical solution in the processing bath 2 is discharged from the discharging outlet 13.

Also, pure water or deionized water is introduced into the processing bath 2 from the pure water tank 10, and the flow rate of nitrogen gas and the height of the wafer holding portion 5 are controlled in a manner similar to the case of the abovementioned processing by the chemical solution to perform processing of the wafer by pure water. In this processing, it is preferable that the ultrasonic wave is generated when the processing is performed so as to improve an efficiency of processing the wafer. The processing by pure water is performed to replace with pure water the chemical solution attached to the rear surface of the wafer 3 and the end portion area of the front surface of the wafer 3, and it is preferable that the processing is performed while controlling the gas flow rate such that the processing fluid does not intrude into the element forming area on the front surface of the wafer 3. It is also possible to repeat the processing by pure water several times while replacing the pure water.

After performing the processing by pure water for a predetermined time period, generation of the ultrasonic wave is halted and the pure water in the processing bath 2 is discharged from the discharging outlet 13. Also, the wafer holding portion 5 is rotated at 1000 rpm, and the wafer 3 is dried. In this case, it is also possible to supply a gas, for example, nitrogen gas or dry air, from the gas spouting outlet 16 onto the element forming surface of the wafer 3 to enhance an efficiency of dring.

It should be noted that the kind of the chemical solution can be selected depending on the film forming substance as an object of the processing, here, an object of cleaning. Fig. 5 shows examples of the substances to be processed and the kinds of the chemical solutions, and typical processing times by the chemical solutions.

Although Fig. 5 shows typical examples, the present invention can be applied to any kind of processing solutions, such as acid, alkali, organic solvent, peroxide (H202 and the like) and the like, because, in the present invention, processing is performed as a soaking process.

Also, when one sheet of wafer is processed in one processing bath, it is sufficient that the quantity of the chemical solution is in a range approximately from 10 to 200 mL. Therefore, when compared with the conventional apparatus, the quantity of the chemical solution used can be very smalL In the above-mentioned embodiment, nitrogen gas is used as the gas to be blown onto the wafer surface. However, the gas is not particuarly limited to nitrogen, and any gas may be used which does not have an influence on semiconductor elements at a temperature around the room temperature.

When economy is considered, dry air, for example, is also a preferable kind of gas.

In the above-mentioned embodiment, the apparatus is constituted such that one sheet of wafer is processed in one processing bath. However, as shown in Fig. 6A and Fig. 6B, it is also possible to simultaneously perform processing of a plurality of wafers, by providing a plurality of wafer holding portions in one processing bath.

Fig. 6A is a cross sectional view of a processing g apparatus for wafers according to another embodiment of the present invention which is viewed from a lateral direction, and Fig. 6B schematically shows an example of disposal of wafers which is viewed from the upper side of a processing bath.

The wafer processing apparatus according to this embodiment has a structure substantially the same as that of the wafer processing apparatus of Fig. 1, except that, in the wafer processing apparatus of this embodiment, a plurality of wafer holding portions 55 are provided and a plurality of wafers can be processed at the same time. As shown in Fig. 6A, chemical solution/pure water 56, that is, processing fluid, is stored in a processing bath 52 constituting a wafer processing portion. Five sheets of wafers 53 respectively held by the & ve wafer holding portions 55 are soaked in such processing fluid 56, and are processed. Each of the plurality of wafer holding portions 55 is substantially the same structure as that of the wafer holding portion 5 of the wafer processing apparatus of Fig. 1. At the bottom portion of the processing bath 52, there is disposed an ultrasonic wave generating apparatus 57. The structure of other portions such as a rotation drive portion 511, a nitrogen gas supplying apparatus 58, a vent 512 corresponding to the vent 12 of Fig. 1, supply system of the processing fluid, not shown in Fig. 6A, discharge system of waste fluid can be the same as that of the processing apparatus of Fig. 1, and therefore description thereof is omitted here.

In this embodiment, it is possible to perform the processing of a plurality of sheets of wafers in a lump, by providing a plurality of wafer holding portions 55 in one processing bath.

The kmd of wafer as an object of the processing according to the present invention is not limited to a particular kind of wafer, as long as it has a wafer-like shape such as a silicon wafer, a semiconducting compound or compound semiconductor wafer and the like.

The processing method and the processing apparatus of the present invention can be mainly used for cleaning the rear surface and the end portion area of the front surface of a wafer.

However, they can also be used for stripping a resist film on these portions and for etching processing of these portions.

As mentioned above, according to the present invention, first, the area in the end portion area of the front surface of a wafer contacting a processing fluid can be controlled with high precision and, therefore, a wafer processed by using the processing apparatus and the processing method according to the present invention does not cause the cross-contamination.

Second, according to the present invention, since both the end portion area of the front surface and the rear surface of the wafer can be processed simultaneously, the processing of a wafer can be quite efficiently performed.

Third, quantity of processing fluid such as chemical solution and pure water used in the processing can be extremely small, when compared with the conventional method, so that cost of the chemical solution in the wafer processing can be reduced.

In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative sense rather than a restrictive sense, and all such modifications are to be included within the scope of the present invention. Therefore, it is intended that this invention encompasses all of the variations and modifications as fall within the scope of the appended claims.

Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of other disclosed and/or illustrated features.

. The text of the abstract filed herewith is repeated here as part of the specification.

A method and apparatus for removing an unnecessary substance adhering to a wafer after circuit elements have been formed on the wafer.

The unnecessary substance, such as material used for forming a film, is simultaneously and precisely cleaned or removed from the whole rear surface and from an end portion area of the front surface of the wafer.

At least a portion of the wafer is soaked in a processing fluid while the front surface, on which the circuit elements are located, is maintained in an upward direction while gas is blown thereonto. The processing fluid penetrates around into a predetermined end portion area of the front surface from an edge portion of the wafer. The area of penetration of the processing fluid is controlled by a flow rate of the gas.

Claims

CLAIMS:

1. A method for processing a wafer, comprising the steps of: soaking, in a processing fluid, at least a portion of said wafer while maintaining in an upward direction a first surface having elements formed thereon; and, blowing a gas onto said first surface of said wafer; whereby an unnecessary substance adhering to said wafer is thereby removed.

2. A method as set forth in claim 1, wherein a portion of the unnecessary substance adhering to a predetermined end portion area of said first surface of said wafer is removed by causing said processing fluid to penetrate around into the predetermined end portion area from an edge portion of said wafer.

3. A method as set forth in claim 1, wherein the gas is blown onto said first surface so as to have a radial component extending radially outward on said wafer.

4. A method as set forth in claim 1, and also comprising the simultaneous step of rotating said wafer at a predetermined rotational speed.

5. A method as set forth in claim 1, wherein said gas is nitrogen gas.

6. A method as set forth in claim 1, wherein said gas is dry air.

7. A method as set forth in claim 1, wherein a portion of the unnecessary substance adhering to a predetermined end portion area of said first surface and a portion of the unnecessary substance adhering to an opposite surface of said wafer are simultaneously removed.

8. A method as set forth in claim 1, and also comprising the simultaneous step of generating an ultrasonic wave into said processing fluid.

9. A method as set forth in claim 1, wherein said unnecessary substance comprises a material used for forming elements on said wafer.

10. An apparatus for processing a wafer, comprising: a processing bath for storing processing fluid; at least one wafer-holding portion, each of which holds said wafer and has a gas-spouting outlet for blowing a gas onto a first surface of said wafer while said wafer is held, said first surface having elements formed thereon; and, a gas-supplying apparatus for supplying said gas blown onto said first surface; wherein an unnecessary substance adhering to said wafer is removed by soaking at least a portion of said wafer in a processing fluid in said processing bath, while said first surface of said wafer is maintained in an upward direction and while gas is blown onto said first surface.

11. An apparatus as set forth in claim 10, wherein an unnecessary substance adhering to at least a predetermined end portion area of said first surface of said wafer is removed by causing said processing fluid to penetrate around into a predetermined end portion area of said first surface from an edge portion of said wafer by soaking at least a portion of said wafer in a processing fluid in said processing bath while said first surface of said wafer is maintained in an upward direction and while gas is blown onto said first surface.

12. An apparatus as set forth in claim 10, wherein each of said wafer-holding portions is movable up or down with respect to a surface of said processing fluid.

13. An apparatus as set forth in claim 10, wherein a flow rate of said gas blown from said gas-spouting outlet onto said first surface of said wafer is controllable.

14. An apparatus as set forth in claim 10, wherein the gas is blown onto said first surface so as to have a radial component extending radially outward on said wafer.

15. An apparatus as set forth in claim 10, further comprising a rotational drive portion for rotating said wafer held by said wafer-holding portion.

16. An apparatus as set forth in claim 10, further comprising an ultrasonic wave generating source at a bottom portion of said processing bath.

17. An apparatus as set forth in claim 16, wherein said ultrasonic wave generating source generates an ultrasonic wave of from 0.1 MHz to 2 MHz.

18. An apparatus as set forth in claim 10, wherein said gas blown from said gas-spouting outlet onto said first surface of said wafer is nitrogen gas.

19. An apparatus as set forth in claim 10, wherein said gas blown from said gas-spouting outlet onto said first surface of said wafer is dry air.

20. An apparatus as set forth in claim 10, wherein said unnecessary substance comprises a material used for forming elements on said wafer.

21. A method for processing a wafer, the method being substantially as herein described with reference to and as shown in Figures 1 to 6 of the accompanying drawings.

22. An apparatus for processing a wafer, the apparatus being substantially as herein described with reference to and as shown in Figures 1 to 6 of the accompanying drawings.