JP2001358110A - Scrub-cleaning device and manufacturing method for semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent nonconformity of variations in cutting amount of a Cu wiring in the plane of a wafer, when the surface of wafer is scrub-cleaned after the Cu wiring is formed by a CMP(chemical-mechanical polishing) method. SOLUTION: A brush 203 fitted to the scrub-cleaning device is provided with multiple minute cylindrical protrusions 204 with provided at prescribed intervals on a contact surface to the wafer. This number such that it is least at the central part of brush 203, while being maximum at both end parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrub cleaning apparatus and a semiconductor device manufacturing technique using the same, and more particularly, to chemical mechanical polishing (C).
The present invention relates to a technique that is effective when applied to scrub cleaning of a wafer performed after a polishing process using the MP) technique.

[0002]

2. Description of the Related Art In recent years, the increase in wiring resistance has become remarkable due to the miniaturization of wiring width accompanying high integration of LSIs, and this is a major factor that hinders high performance in high-speed logic LSIs.

[0003] Recently, for example, "1993 VMI
As described in "C (VLSI Multilevel Interconnection Conference) Preliminary Proceedings", pp. 15-21, a groove is previously formed in an insulating film on a silicon substrate, and Al (Al) is formed on the insulating film including the inside of the groove. Cu) is to deposit a Cu (copper) film having lower electric resistance than aluminum (Aluminum), and then to polish an unnecessary Cu film outside the groove by a chemical mechanical polishing (CMP) method to leave a Cu film only inside the groove. The introduction of a wiring forming process, a so-called Damascene process, has been promoted.

In the above damascene process, when a Cu film deposited on an insulating film is polished by a CMP method, a slurry in which an oxidizing agent or the like is added to abrasive grains such as alumina is used.
After polishing, a post-cleaning operation is required to clean the surface of the wafer to remove slurry residues and Cu polishing debris.

The post-cleaning is generally a scrub cleaning in which a brush made of a synthetic resin impregnated with a chemical is applied to the surface of the wafer, and the surface of the wafer is cleaned while rotating the brush and the wafer. The above-mentioned chemical solution is for facilitating removal of contaminants from the surface of the wafer by utilizing the action of the zeta potential, and an alkaline solution such as diluted ammonia water is usually used.

[0006] Scrub cleaning performed as post-CMP cleaning is described in, for example, "Monthly Semiconductor World", pp. 62-63, published by Press Journal, September 20, 1998.

[0007]

SUMMARY OF THE INVENTION As described above, CMP
In the post-cleaning process, the surface of the wafer is cleaned while rotating both the brush and the wafer.While the center of the wafer is in constant contact with the brush during cleaning, the brush is intermittent at the periphery of the wafer. Contact.

However, the amount of abrasion (etching amount) on the wafer surface by scrub cleaning using a brush increases in proportion to the product of the time and the area of contact between the brush and the wafer, so that the wiring at the center of the wafer is reduced. It has been found by the present inventor that the shaving amount becomes larger than that in the peripheral portion, and the cross-sectional area of the wiring after the post-cleaning step is different between the central portion and the peripheral portion of the wafer.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a problem in which the amount of metal wiring shaved varies between the central part and the peripheral part of the wafer when the surface of the wafer is scrubbed after forming the metal wiring by the CMP method. It is to provide the technology that can do.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0011]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

A method of manufacturing a semiconductor device according to the present invention includes the following steps (a) and (b). (A) a step of forming metal wiring by polishing a metal film formed on the main surface of the wafer by a chemical mechanical polishing method; (b) bringing a brush into contact with the main surface or both surfaces of the wafer, A scrub cleaning apparatus for cleaning the surface of the wafer while rotating the brush, wherein a large number of protrusions are provided on the surface of the brush, and an area where the protrusions and the wafer are in contact with each other is increased from a central portion of the wafer. By changing along the direction toward the periphery,
Cleaning the surface of the wafer on which the metal wiring is formed, using a scrub cleaning device in which the product of the time and the area of contact between the brush and the wafer is made substantially uniform over the entire surface of the wafer.

The amount of scraping of the wafer surface due to contact with the brush increases in proportion to the time and area of contact between the brush and the wafer. Therefore, according to the above-described means, the amount of shaving on the surface of the wafer becomes substantially uniform over the entire surface of the wafer.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, the same members are denoted by the same reference numerals, and a repeated description thereof will be omitted.

(Embodiment 1) FIG. 1 is a sectional view of a main part of a wafer (substrate) 1 in the middle of a manufacturing process. For example, p
An n-type well 2 and a field oxide film 3 are formed on a main surface of a wafer (substrate) 1 made of single-crystal silicon. In the active region of the n-type well 2 surrounded by the field oxide film 3, a p-channel MISFET (Qp)
Are formed. p-channel type MISFET (Qp)
A gate oxide film 4 formed mainly on the surface of the n-type well 2, a gate electrode 5 formed on the gate oxide film 4, and a pair of n-type wells 2 formed on both sides of the gate electrode 5. It is composed of p-type semiconductor regions 6 and 6 (source and drain). A p-type well is formed in another region of the substrate 1, and an n-channel MISFET is formed in the p-type well, but these are not shown.

A silicon oxide film 7 is formed on the p-channel type MISFET (Qp), and first-layer wirings 9, 10, 11 are formed on the silicon oxide film 7. The first-layer wirings 9, 10, and 11 are made of, for example, W (tungsten), and are formed through a contact hole 8 formed in the silicon oxide film 7 to form a p-channel MI.
It is electrically connected to the p-type semiconductor region 6 of the SFET (Qp).

The first-layer wirings 9, 10, and 11 are formed by, for example, depositing a W film on the silicon oxide film 7 including the inside of the contact hole 8 by a sputtering method, and then performing dry etching using a photoresist film as a mask. Is formed by patterning the W film.

A silicon oxide film 12 is formed above the first-layer wirings 9, 10 and 11. Through holes 13 and 14 are formed in the silicon oxide film 12 above each of the first-layer wirings 9 and 11, and a plug 15 is embedded in the through holes 13 and 14. The plug 15 is formed, for example, by depositing a W film on the silicon oxide film 12 including the inside of the through holes 13 and 14 by the CVD method, and then etching back the W film.

On top of the silicon oxide film 12, a silicon oxide film 16 is formed. Through hole 13, 1
4 are formed in the silicon oxide film 16 on the upper side of the silicon oxide film 16. On the silicon oxide film 16 including the insides of these grooves 17 and 18, the material of the second layer wiring and The Cu film 19 is formed by a sputtering method or the like.

In order to form the Cu wiring by polishing the Cu film 19, for example, a CMP apparatus as shown in FIG. 2 is used. As shown in the figure, the CMP apparatus 100 has a housing 101 having an open top, and a rotating shaft 102 rotatably attached to the housing 101 is rotatably driven by a motor 103. Polishing machine (platen)
104 is attached. A polishing pad 105 formed by uniformly attaching a synthetic resin having a large number of pores is attached to the surface of the polishing board 104.

Further, the CMP apparatus 100
And a wafer carrier 106 for holding the wafer.
A drive shaft 107 to which the wafer carrier 106 is attached is integrated with the wafer carrier 106 to form a motor (not shown).
, And is moved up and down above the polishing plate 104.

The wafer 1 is held on the wafer carrier 106 by a vacuum suction mechanism (not shown) provided on the wafer carrier 106 with its main surface, that is, the surface to be polished facing downward. A concave portion 106a for accommodating the wafer 1 is formed at the lower end portion of the wafer carrier 106. When the wafer 1 is accommodated in the concave portion 106a, the surface to be polished is substantially the same as the lower end surface of the wafer carrier 106 or A slightly protruding state results.

Above the polishing plate 104, a polishing pad 10
A slurry supply pipe 108 for supplying slurry (S) is provided between the surface of the wafer 5 and the surface to be polished of the wafer 1.
Wafer 1 is formed by slurry (S) supplied from the lower end.
Is polished chemically and mechanically.

The CMP apparatus 100 includes a dresser 109 which is a tool for shaping (dressing) the surface of the polishing pad 105. This dresser 10
Numeral 9 is attached to the lower end of a drive shaft 110 which moves up and down above the polishing plate 104, and is driven to rotate by a motor (not shown).

The dressing is performed after the polishing operation for several wafers 1 is completed or every time the polishing operation for one wafer 1 is completed. Alternatively, dressing may be performed simultaneously with polishing. For example, when the wafer 1 is pressed against the polishing pad 105 by the wafer carrier 106 and polished for a predetermined time, the wafer carrier 10
6 is retracted upward. Next, the dresser 109 moves downward and is pressed against the polishing pad 105, and after its surface is dressed for a predetermined time, the dresser 109 is moved.
Is retracted upward. Subsequently, another wafer 1 is mounted on the wafer carrier 106, and the above-described polishing step is repeated. After the predetermined number of wafers 1 have been polished in this manner, the polishing operation is completed by stopping the rotation of the polishing plate 104.

FIG. 3 is a diagram showing the C using the above CMP apparatus 100.
The wafer (substrate) 1 immediately after the Cu wirings 20 and 21 of the second layer are formed inside the grooves 17 and 18 by polishing the u film 19 is shown. At this time, a slurry residue 22 containing particles such as abrasive grains and metal particles such as Cu oxide adheres to the surface of the wafer (substrate) 1.

Therefore, in the present embodiment, both surfaces of the wafer (substrate) 1 after the polishing operation is cleaned using a scrub cleaning device as shown in FIG. As shown in the figure, the scrub cleaning apparatus 200 includes a stage 202 that is rotationally driven by a motor 201.
The wafer 1 held at 02 rotates at a desired speed in a horizontal plane. A cylindrical brush 203 is pressed against the upper and lower surfaces of the wafer 1 rotating on the stage 202. These brushes 203 are rotated at a desired speed in a plane perpendicular to the main surface of the wafer 1 by a rotation drive mechanism (not shown).

FIGS. 5A and 5B are explanatory views showing the rotation direction of the wafer 1 and the rotation direction of the brush 203 positioned on the stage 202 of the scrub cleaning apparatus 200. FIG. As shown, the wafer 1 rotates in a horizontal plane,
The brush 203 rotates in a plane perpendicular to the main surface of the wafer 1. Therefore, the center of the wafer 1 is always
In contrast to the contact with the brush 203, the contact time with the brush 203 becomes shorter at the peripheral portion farther from the center of the wafer 1.

FIG. 6 shows a brush 2 used in the present embodiment.
It is an expansion perspective view of 03. As shown, this brush 2
A large number of minute cylindrical projections 204 are provided at a predetermined interval on the surface of No. 03, that is, the contact surface with the wafer 1. The number of the protrusions 204 of the brush 203 gradually increases from the center toward both ends. That is, the number of the protrusions 204 is arranged such that the number is the smallest at the center of the brush 203 and the number is the largest at both ends. The brush 203 and the projections 204 provided on the surface of the brush 203 are made of, for example, a porous body of a synthetic resin such as PVA (polyvinyl alcohol).

A cleaning liquid such as diluted ammonia water or pure water is supplied to the brush 203 through a pipe (not shown). The cleaning liquid supplied to the brush 203 gradually oozes from the inside of the brush 203 made of a porous body of a synthetic resin to the surface (the surface in contact with the wafer 1), and wets the surface of the wafer 1 in contact with the brush 203. It has become.

Slurry residue 21 attached to the surface of wafer 1
7, brushes 203, 203 are pressed against the upper and lower surfaces of the wafer 1 and the brushes 203, 203 are rotated with respect to the main surface of the wafer 1 while rotating the wafer 1 in a horizontal plane. And rotate in a vertical plane. At this time, the tips of a large number of protrusions 204 (see FIG. 6) provided on the surfaces of the brushes 203 are slightly (for example, 1).
The wafer 1 is pressed against the wafer 1 with a depressing pressure.
The rotation speed of the wafer 1 is about 20 rpm,
Is about 120 rpm. In this way,
The slurry residue 22 (see FIG. 3) attached to the surface of the wafer 1 is removed by scrubbing both surfaces of the wafer 1 with brushes 203 for a predetermined time.

When the surface of the wafer 1 is scrub-cleaned by the above method, the Cu wiring 1
The abrasion amount (etching amount) of the surfaces of 9 and 20
03 increases in proportion to the contact time and area of the wafer 1. When the brush 203 according to the present embodiment shown in FIG. 6 is used, the center of the wafer 1 in contact with the center of the brush 203 is more in contact with the brush 203 than in the peripheral portion in contact with the end of the brush 203. Time gets longer. However, on the other hand, the projection 204 that contacts the wafer 1 is
3 has the smallest number at the center and the largest number at both ends, the contact area between the brush 203 and the wafer 1 is
The peripheral portion is larger than the central portion of the wafer 1. As a result, the value of the time × area of contact between the brush 203 and the wafer 1 becomes substantially uniform over the entire surface of the wafer 1, and the amount of abrasion (etching amount) of the surfaces of the Cu wirings 19 and 20 becomes almost uniform over the entire surface of the wafer 1 Be equal.

According to an experiment conducted by the present inventor, by optimizing the number of projections 204 under the following conditions,
Abrasion amount (etching amount) on the surfaces of Cu wirings 19 and 20
Became almost uniform over the entire surface of the wafer 1.

The diameter of the used wafer is 125 mm, the rotation speed of the wafer is 22 rpm, and the diameter of the brush is 55 mm. The brush was pressed against the wafer with a pressure that depressed the contact surface with the wafer by 1 mm.

When the number of projections in contact with each area is gradually increased from the center of the brush to the end from the center of the wafer to the outermost periphery and divided into ten equal parts. When the rotation number of the brush is 120 rpm, The optimum number of protrusions is 1, 1, 2, 3, 3, 4, 5, 6, 7, 8 from the center side of the wafer.
(Pieces). When the rotation speed of the brush is 30 rpm, the optimum number of protrusions is 3, 3, 8,
8, 8, 8, 8, 8, 8, 8 (pieces).

In order to make the time × area of contact between the brush 203 and the wafer 1 substantially uniform over the entire surface of the wafer 1, as shown in FIG. In addition to reducing the number, for example, the diameter of the protrusion 204 is gradually increased from the center of the brush 203 toward both ends (or the brush 20).
3, the diameter of the protrusion 204 is gradually reduced from the both ends toward the center).
The smaller the contact area with the center of the wafer 1 becomes, the larger the area of contact with the peripheral part of the wafer 1 becomes,
Various means for changing the size, shape, number, and the like of the projections 204 can be employed.

Further, instead of the above-described means for reducing the contact area between the brush 203 and the wafer 1 from the peripheral portion of the wafer 1 toward the central portion, the pressure of the brush 203 pressed against the surface of the wafer 1 is changed. It may be smaller as going from the center to the center (or larger as going from the center to the periphery). In this case, brush 2
Even if the contact area between the wafer 03 and the wafer 1 is substantially the same over the entire surface of the wafer 1, the same effect as described above can be obtained.

Brush 203 for pressing against the surface of wafer 1
In order to reduce the pressure from the peripheral portion toward the center of the wafer 1, for example, the height of the protrusion 204 is reduced from the both ends of the brush 203 toward the center, or the diameter of the brush 203 is reduced. I just need.

FIG. 8 is a graph showing the effect of the present embodiment measured by the inventor. In the figure, “before countermeasures” indicates that the number of protrusions 204 is equal over the entire area (center and both ends) of the brush 203, and “after countermeasure 1” indicates that the number of protrusions 204 at the center of the brush 203 is 48. In the case where the number of protrusions 204 at the center of the brush 203 is reduced by 9.9%, “after the measure 2” is shown. The “cleaning strength” indicates the amount of abrasion of the wafer surface due to contact with the brush.

As shown in the figure, “before countermeasures”, the “cleaning strength” of the central portion of the wafer was remarkably greater than that of the peripheral portion, while “after countermeasures”, the central portion of the wafer and the peripheral portion were not. The difference in “cleaning strength” was significantly reduced.

In the above description, a case was described in which the surface of the wafer was scrubbed while rotating a cylindrical (roll) brush, but the shape of the brush is not limited to this, and for example, a disk (disk) is used. The present invention can also be applied to a case in which a mold brush and a wafer are superimposed and scrub cleaning is performed while rotating both.

(Embodiment 2) In Embodiment 1 described above,
The cleaning uniformity in the wafer surface was realized mainly by changing the number of protrusions at the center and both ends of the brush.
By optimizing the ratio of “wafer rotation speed / brush rotation speed” (hereinafter referred to as W / B ratio), the cleaning uniformity within the wafer surface can be maintained without changing the number of protrusions at the center and both ends of the brush. Can be realized.

The present inventor has provided an apparatus for scrub cleaning the surface of a wafer while rotating a cylindrical (roll) brush,
In both the apparatus and the apparatus that performs scrub cleaning while rotating a disk (disk) type brush, the higher the number of rotations of the wafer and the lower the number of rotations of the brush, the more the “maximum value of wafer cleaning intensity / minimum value of wafer cleaning intensity It has been found that the ratio of the “values” (hereinafter referred to as the cleaning intensity ratio) is reduced, that is, the cleaning uniformity within the wafer surface is improved.

Then, as a result of examining the relationship between the W / B ratio and the cleaning intensity ratio, FIG. 9 (roll type cleaning device) and FIG.
As shown in (Disk type cleaning device), a unique curve was obtained for each cleaning device. After cleaning, the wafer is cross-section SEM (S
When the shaving amount of the wiring was evaluated by using a canning electron microscope, it was confirmed that the wafer surface was uniformly cleaned when the cleaning intensity ratio was 5 or less. Therefore, from FIG. 9 and FIG. 10, when the cleaning condition where the cleaning intensity ratio is 5 or less, that is, the W / B ratio is obtained, the W / B ratio is 1.2 or more in the roll type cleaning device, and
W / B ratio = 2.0 or more is an effective cleaning condition in post-CMP cleaning.

As described above, the invention made by the inventor has been specifically described based on the embodiments of the invention. However, the invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the invention. Needless to say, it can be changed.

The present invention can also be applied to a so-called dual damascene process in which a Cu film is simultaneously buried in a concave groove and a through hole formed in an insulating film to simultaneously form a Cu wiring and a Cu plug. Further, the present invention can be applied to a case where a wiring or a plug is formed of a metal material other than Cu (for example, W).

The present invention can be widely applied not only to post-CMP cleaning but also to general scrub cleaning.

[0048]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

According to the present invention, the amount of scraping of the metal wiring formed on the main surface of the wafer can be made substantially uniform over the entire surface of the wafer. Deterioration of flatness can be prevented, and C
The reliability and manufacturing yield of a semiconductor device having a metal wiring formed by MP are improved.

[Brief description of the drawings]

FIG. 1 is a fragmentary cross-sectional view of a wafer (substrate) in the middle of a manufacturing process.

FIG. 2 is a schematic diagram of a CMP apparatus.

FIG. 3 is a fragmentary cross-sectional view of a wafer (substrate) in the middle of a manufacturing process.

FIG. 4 is a schematic view of a scrub cleaning device.

FIGS. 5A and 5B are explanatory views showing the rotation direction of a wafer and the rotation direction of a brush positioned in the scrub cleaning apparatus shown in FIG. 4;

6 is an enlarged perspective view of a brush of the scrub cleaning device shown in FIG.

FIG. 7 is a schematic perspective view of a scrub cleaning device.

FIG. 8 is a graph showing the effect of the first embodiment of the present invention.

FIG. 9 is a graph showing the effect of the second embodiment of the present invention.

FIG. 10 is a graph showing the effect of the second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 wafer (substrate) 2 n-type well 3 field oxide film 4 gate oxide film 5 gate electrode 6 p-type semiconductor region (source, drain) 7 silicon oxide film 8 contact hole 9, 10, 11 first layer wiring 12 oxidation Silicon film 13, 14 Through hole 15 Plug 16 Silicon oxide film 17, 18 Concave groove 19 Cu film 20, 21 Cu wiring 22 Slurry residue 100 CMP device 101 Housing 102 Rotating shaft 103 Motor 104 Polishing machine (platen) 105 Polishing pad 106 Wafer carrier 106a Recess 107 Drive shaft 108 Slurry supply pipe 109 Dresser 110 Drive shaft 200 Scrub cleaning device 201 Motor 202 Stage 203 Brush 204 Projection S Slurry Qp P-channel MISFET

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Nobuo Owada 3-16, Shinmachi, Shinmachi, Ome-shi, Tokyo 3 Inside the Device Development Center, Hitachi, Ltd. 3 Hitachi, Ltd. Device Development Center (72) Inventor Naofumi Ohashi 6-chome, Shinmachi, Ome-shi, Tokyo 3 Hitachi, Ltd. Device Development Center

Claims (5)

[Claims] 1. A scrub cleaning apparatus for cleaning a surface of a wafer by bringing a brush into contact with the main surface or both surfaces of the wafer and rotating the wafer and the brush, respectively, wherein a plurality of protrusions are formed on the surface of the brush. Is provided, by changing the area of contact between the protrusions and the wafer along the direction from the center to the periphery of the wafer,
A scrub cleaning apparatus, wherein a value of a product of a time and an area of contact between the brush and the wafer is made substantially uniform over the entire surface of the wafer. 2. A scrub cleaning apparatus for bringing a brush into contact with a main surface or both surfaces of a wafer and cleaning the surface of the wafer while rotating the wafer and the brush, wherein a plurality of protrusions are provided on the surface of the brush. The number or area of the protrusions is changed along the direction from the center to the periphery of the wafer, so that the value of the product of the time and area of contact between the brush and the wafer can be changed. A scrub cleaning device characterized by being substantially uniform over the entire surface. 3. A method of manufacturing a semiconductor device comprising the following steps (a) and (b): (a) polishing a metal film formed on a main surface of a wafer by a chemical mechanical polishing method to form a metal wiring; (B) a scrub cleaning apparatus for cleaning a surface of the wafer while rotating the wafer and the brush, respectively, by bringing a brush into contact with the main surface or both surfaces of the wafer; By providing a number of protrusions, by changing the area where the protrusions and the wafer are in contact along the direction from the center of the wafer to the peripheral portion,
Cleaning the surface of the wafer on which the metal wiring is formed, using a scrub cleaning device in which the product of the time and the area of contact between the brush and the wafer is made substantially uniform over the entire surface of the wafer. 4. A method of manufacturing a semiconductor device comprising the following steps (a) to (c): (a) forming an insulating film on a main surface of a wafer and then forming a connection hole in the insulating film; (B) forming a plug inside the connection hole by depositing a metal film on the insulating film including the inside of the connection hole and then polishing the metal film by a chemical mechanical polishing method; A scrub cleaning device for cleaning a surface of the wafer by rotating a brush with the main surface or both surfaces of the wafer and rotating the brush and the wafer, wherein a plurality of protrusions are provided on the surface of the brush; The value of the product of the time and the area of contact between the brush and the wafer is changed by changing the area of contact between the protrusion and the wafer along the direction from the center to the periphery of the wafer. All over Using a scrubbing device was substantially equal, the step of cleaning the surface of said wafer which metal wiring is formed. 5. A step of forming metal wiring by polishing a metal film formed on a main surface of a wafer by a chemical mechanical polishing method, and contacting a brush with the main surface or both surfaces of the wafer, Cleaning the surface of the wafer on which the metal wiring is formed, using a scrub cleaning device that cleans the surface of the wafer while rotating the brush and the brush, respectively. The ratio of the number of revolutions of the brush to the number of revolutions of the brush is optimized, so that the amount of shaving on the surface of the wafer due to contact with the brush is made uniform over the entire surface of the wafer. Production method.