JP2000042883A - Mirror finishing method for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mirror finish the of a chamfered part and outer peripheral surface of a wafer with uniform machining surface pressure and to positively eliminate a grinding mark on the outer peripheral surface. SOLUTION: In a semiconductor wafer mirror finishing method for the chamfered part and outer peripheral surface of a semiconductor wafer chamfered at the angular part of the outer peripheral edge, by polishing drums 4, the chamfered part of the semiconductor wafer to be mirror finished is made to abut the polishing surface of one polishing drum 4 out of a pair of polishing drums 4 that can be elevated by a drum elevating driving means, and the outer peripheral surface of the semiconductor wafer is made to abut the polishing surface of the other polishing drum 4. As to at least the outer peripheral surface of the semiconductor wafer, the polishing drum 4 and the semiconductor wafer are rotated so that a speed vector based on the rotation of the polishing drum 4 and a speed vector based on the rotatory feed of the semiconductor wafer intersect each other, and the chamfered part and the outer peripheral surface are specularly machined individually and simultaneously by the respective polishing drums 4, so that a grinding mark and the like formed in a pre-process can be positively eliminated to improve mirror finished quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mirror-finishing a peripheral edge of a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, a semiconductor wafer (hereinafter, referred to as a wafer) used for an integrated circuit or the like is manufactured by thinly slicing an ingot made of a silicon single crystal. After the edge is chamfered, the edge is mirror-finished in order to prevent particles and increase the strength.

As a method for mirror-finishing a chamfered portion of a semiconductor wafer, for example, a method described in Japanese Patent Publication No. 7-61601 is known. The mirror polishing method disclosed in the above publication includes a step of holding a disc-shaped wafer having a chamfered peripheral edge on a chuck table, a step of rotating the wafer around an axis of the wafer, and a step of linearly moving the wafer. A process in which the polishing drum supported so as to freely contact the wafer with the urging force of a vertically suspended weight, and polishing the peripheral portion of the wafer with the rotating polishing drum;
Changing the contact position with the wafer by moving the polishing drum in the axial direction of the polishing drum, whereby the entire peripheral portion of the wafer can be mirror-polished. Has an effect.

On the other hand, the outer peripheral portion of the wafer is often subjected to a lapping process in a previous process, and is processed in a carrier at this time. Therefore, the outer peripheral portion of the wafer comes into contact with the carrier during processing and is larger than the chamfered portion. Irregularities occur on the outer periphery. In addition, since the outer peripheral portion of the wafer frequently comes into contact with the transfer jig and the like during the transfer between processes, the outer peripheral portion of the wafer has many irregularities, and it is necessary to remove the irregularities when performing mirror finishing. .

Recently, the number of epi-wafers has been increased in order to improve the performance of wafers. However, in the manufacturing process of epi-wafers, polysilicon and oxide films may be formed on the periphery of the wafer, and these are completely removed during mirror polishing. Otherwise, during the heat treatment in a later step, problems such as abnormal growth of the polysilicon and oxide film at the peripheral portion occur.

[0006]

However, in the mirror polishing method disclosed in the above publication, the outer peripheral portion of the wafer a is brought into contact with the outer peripheral surface of the cylindrical polishing drum b as shown in FIG. And the outer peripheral surface d are mirror-finished at the same time, so that the cloth for polishing the chamfered portion c and the outer peripheral surface d does not uniformly contact the entire surface of the processing surface, and as a result, the processing surface pressure e of the processing surface varies. Therefore, there is a problem that the mirror surface cannot be efficiently machined.

FIG. 1 shows a velocity vector f due to the rotation of the polishing drum b and a direction of a circumferential grinding mark g generated on the outer peripheral surface of the wafer a by the grinding in the previous step (a velocity vector due to the rotation of the wafer a). Since they do not cross each other in the same direction as shown in FIG.
There were problems such as difficulty in reliably removing grinding marks c generated on the outer peripheral surface d of the wafer and irregularities generated during transportation.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem. The chamfered portion and the outer peripheral surface of the wafer can be mirror-finished with a uniform processing surface pressure, and the speed vector of the polishing drum and the outer peripheral surface of the wafer can be improved. It is an object of the present invention to provide a method for mirror-finishing a semiconductor wafer, in which the direction of grinding marks is crossed, whereby grinding marks on the outer peripheral surface can be reliably removed.

[0009]

According to the first aspect of the present invention, there is provided a wafer for which a chamfered portion of a wafer whose outer peripheral edge is chamfered and the outer peripheral surface are mirror-polished by a polishing drum. In the mirror polishing method, the chamfered portion of the semiconductor wafer to be mirror-polished is brought into contact with the polishing surface of one polishing drum of a pair of polishing drums that can be raised and lowered by the drum lifting drive means, and the polishing surface of the other polishing drum The outer peripheral surface of the semiconductor wafer is brought into contact with at least the outer peripheral surface of the semiconductor wafer, and the polishing drum and the semiconductor wafer are rotated at least so that the velocity vector due to the rotation of the polishing drum and the velocity vector due to the rotational feed of the semiconductor wafer intersect each other. Is rotated so that the chamfered portion and the outer peripheral surface are simultaneously mirror-finished from the respective polishing drums.

According to the above method, since the chamfered portion and the outer peripheral surface of the wafer are evenly brought into contact with the polished surface of the polishing drum, the chamfered portion and the outer peripheral surface can be mirror-finished with an appropriate surface pressure. As a result, the chamfered portion and the outer peripheral surface can be efficiently mirror-finished at the same time, so that the productivity is improved, and irregularities and the like generated on the chamfered portion during processing and transport of the wafer can be reliably removed. Thus, a processed surface with good quality can be obtained.

Further, even if grinding marks are formed on the outer peripheral surface of the wafer in the previous step, the polished surface grinds the outer peripheral surface of the wafer so that the velocity vector due to the rotation of the polishing drum intersects the grinding marks. The grinding marks and the oxide film formed on the outer peripheral surface can be surely removed, so that a mirror-finished surface with good quality can be obtained.

According to a second aspect of the present invention, there is provided a method for mirror-finishing a wafer in which a chamfered portion of an outer peripheral edge is chamfered and the outer peripheral surface is mirror-polished by a polishing drum. The chamfered portion of the semiconductor wafer to be mirror-finished is brought into contact with the polishing surface of one of the pair of polishing drums which can be raised and lowered by means of urging means, and the semiconductor wafer is brought into contact with the polishing surface of the other polishing drum. The outer peripheral surface is brought into contact with the urging means, and at least the outer peripheral surface of the semiconductor wafer is swung around the support shaft parallel to the rotation center of each polishing drum. The polishing drum and the semiconductor wafer are rotated so that the velocity vectors generated by the rotational feed of the semiconductor wafer intersect with each other, and the surfaces of the respective polishing drums are rotated. Ri portion and the outer peripheral surface is at the same time that so as to mirror polishing.

According to the above method, the chamfered portion and the outer peripheral surface of the wafer can be polished on separate polishing surfaces by a pair of polishing drums, so that the productivity is further improved and the chamfered portion and the outer peripheral surface of the wafer are polished by the respective polishing surfaces. Since the drum is brought into contact with the polishing surface of the drum at an appropriate angle, the surface pressure on each polishing surface is equalized, thereby obtaining a high quality processed surface.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail with reference to the drawings shown in FIGS. 2 is a plan view of the mirror finishing device, FIG. 3 is a front view of the same, FIG. 4 is a view from the X direction in FIG. 3, FIG. 5 is a view from the Y direction in FIG. 2, and FIG. 7 is a detailed view of the chuck driving means, and FIGS. 8 to 10 are operation explanatory views.

In these figures, reference numeral 1 denotes an apparatus main body, which comprises a polishing drum driving means 2 and two wafer driving means 3 installed so as to face each other with the polishing drum driving means 2 interposed therebetween. The polishing drum driving means 2 has a vertically movable member 2a supported on a guide rail 1b laid vertically on the base 1a. The rotating shafts 4a of the pair of polishing drums 4 are vertically attached to the vertically movable member 2a. It is supported in the direction.

In each of the polishing drums 4, a polishing cloth 4c is wound around an outer peripheral surface of a drum body 4b formed in a cylindrical shape, and the rotating shafts 4a of the polishing drum 4 are parallel to each other with an interval therebetween. The rotating shaft 4a is rotatably supported by the lifting member 2a, and a lower end of one of the rotating shafts 4a has a drum driving source 5 composed of an electric motor mounted on the lifting member 2a.
It is connected to the.

The rotating shafts 4a of the respective polishing drums 4 are linked to each other by interlocking means (not shown) such as gears, and the respective drums 4 are rotated in the same direction at the same speed by a drum driving source 5. In addition, each of the polishing drums 4 is moved up and down (oscillated) by the drum up / down driving means 6. As shown in FIG. 4, the drum lifting / lowering driving means 6 is a ball screw 6 rotated by a lifting / lowering driving source 7 composed of an electric motor mounted on the base 1a side.
a and a ball nut 6 screwed into the ball screw 6a
The ball nut 6b is attached to the lifting member 2a side, and the polishing screw 4a is rotated forward and reverse by the lifting drive source 7, so that each polishing drum 4 can be vertically oscillated.

On the other hand, the wafer driving means 3 has a slide table 3a supported by a guide rail 1c laid on the base 1a and movable in the direction of contact and separation, and these slide tables 3a are biased. It is urged by means 8 in the approaching direction. The urging means 8 includes a rope 8a having one end connected to the slide table 3a and a weight W attached to the other end, and a pulley 8b having a middle part of the rope 8a bypassed. with and urges the biasing force W ₁ direction toward the slide table 3a one another by the weight of the weight W, between the base 1a and the slide table 3a, the slide table 3a to urge the direction opposite to the direction An evacuation cylinder 8c for evacuation is provided.

[0019] The aforementioned slide table 3a, the center _{O 1} of the abrasive drum 4, the center O of the chuck 15 to be described later
_The swing table 3b has one end pivotally supported on a support shaft 20 installed on a center line O ₁ -O ₂ connecting the _two swing tables _{2 and 2} , and a swing end side bottom surface of the swing table 3b has Motion table 3
a slider 3c for supporting b from below.
The slider 3c slides on an arc-shaped guide rail 1d centered on the support shaft 20. The swing table 3b is urged by an urging means 9 in a direction orthogonal to the urging direction of the urging means 8.

The urging means 9 has one end connected to the swing table 3b at one end and the other end to which the weight W 'is connected at the other end, and a middle part of the line 9a. Pulley 9
consists b, the biasing force W ₂ around the oscillating table 3b support shaft 20 by the weight of the weight W ', together with being urged in the direction perpendicular to the urging direction of the urging means 8, the slide table Between the swing table 3a and the swing table 3b.
retraction cylinder 9c for retracting b in the direction opposite to the biasing direction
Is provided. A chuck driving means 13 is provided above the support member 3e provided on the swing table 3b, and can be freely inclined at an arbitrary angle about a horizontal axis 12 by an angle changing means 11.

The horizontal axis 12 is located at the center O of the polishing drum 4.
₁ and a center line O ₁ -O ₂ passing through the center O _{2 of the} chuck 15.
And a rocking member 13 a that constitutes a chuck driving means 13 on the horizontal shaft 12.
The angle varying means 11 has a link 11a whose one end is pivotally supported by the horizontal shaft 12, as shown in FIG.

A proximal end of an actuator 11b composed of a pneumatic cylinder is pivotally connected to the other end of the link 11a.
The distal end of the actuator 11b is pivotally attached to the swinging member 13a, and by expanding and contracting the actuator 11b, the chuck driving means 13 is rotated about the horizontal axis 12 to a mirror surface processing position indicated by a virtual line from a solid line position in FIG. It can be tilted up to. The chuck driving means 13 includes:
It has a chuck driving source 14 composed of an electric motor attached to the bottom of the swinging member 13a, and the chuck driving source 14 is a rotating shaft 13 vertically supported by the swinging member 13a.
b is connected to the lower end via a gear 13c. A chuck 15 for holding the wafer 10 to be mirror-finished is attached to the upper end of the rotating shaft 13b, and the angle varying unit 11 and the chuck driving unit 13
It is housed in a case 13d attached to 3a.

Next, a description will be given of a method of simultaneously mirror-etching the chamfered portion 10a and the outer peripheral surface 10b of the wafer 10 using the above-structured mirror-etching apparatus. Wafer 1 to be mirror-finished
0 in advance corners of the outer peripheral edge are chamfered at a predetermined angle alpha _0, the mirror finishing method according to the embodiment of the present invention, the chamfered portion 10a and the outer peripheral surface 10b of the separate polishing drum 4 Mirror processing at the same time. In mirror processing of the wafer 10, first, the chuck driving unit 13 is stopped at a position where the chuck 15 is horizontal, and the wafer 10 is suction-held on the upper surface of the chuck 15 in this state.

Next, in this state, the chamfer angle α of the wafer 10 is set.
_In response to ₀ , the chuck driving means 13 is inclined by the angle α about the horizontal axis 12 by the angle varying means 11. The two polishing drums 4 are simultaneously rotated in the same direction by the drum driving source 5 of the polishing drum driving means 2, and the two chucks 15 are driven by the chuck driving source 14 of the chuck driving means 13.
While the simultaneously rotate in the same direction, by contracting the retraction cylinder 8c of the urging means 8, it is moved to the polishing drum four directions each chuck 15 by the urging force W _1, the chuck 1
5 is brought into contact with the biasing force W _A chamfered portion 10a of the wafer 10 held the outer peripheral surface of one polishing drum 4 as shown in FIG. 2 (polishing point A), the simultaneous retraction cylinder 9c of the biasing means 9 Is also contracted, and the chuck 15 is biased by the urging force W _2.
In by urging direction perpendicular to the biasing force W _1, the outer peripheral surface of the wafer 10 is brought into contact with the biasing force W _B to the outer surface of the other of the abrasive drum 4 (grinding point B).

As a result, the chamfered portion 10a and the outer peripheral surface 10b of the wafer 10 held by each chuck 15 are
As shown in FIG. 6, the polishing surface is simultaneously brought into contact with the outer peripheral surface of each of the polishing drums 4, so that mirror polishing is started at two polishing points A and B, and the urging forces WA and
WB is as follows.

[0026] _{W 1:} weight W biasing force of the W of the wafer drive means _2: by the weight W of the wafer drive means', urging force to urge the direction perpendicular to the biasing force _{W 1} WA: biasing force _W 1, w ₂ biasing force in the grinding point a by WB: biasing force _w 1, the biasing force on the abrasive point B by _{w 2 w 1 = WAcosθA + WAcosθB} ... (1) w 2 = WAsinθA + WBsinθB ... (2) As a result WA ₌ w 1 sinθB −W ₂ cos θB / sin (θA−θB) (3) WB = W ₁ sin θA + W ₂ cos θA / sin (θA + θB) (4)

That is, the chamfered portion 10a of the wafer 10
Is the urging force WA, and the outer peripheral surface 10b is the urging force WB.
Since the mirror polishing is performed by simultaneously pressing the individual polishing drums 4, the polishing efficiency is greatly improved as compared with the conventional method in which the chamfered surface 10 a and the outer peripheral surface 10 b are separately polished.

FIG. 8 shows the relationship between the inclination angle α _{0 of the} wafer 10 and the contact angle θ with respect to the polishing drum 4 depending on the contact position.
It becomes as shown in. That is, when the wafer 10 is tilted by the tilt angle α and the chamfered portion 10a is brought into contact with the polishing drum 4, the contact angle θ at the polishing point A at which the chamfered portion 10a of the wafer 10 is polished is represented by ( The contact angle θ at the polishing point B at which the outer peripheral surface 10b of the wafer 10 is polished decreases as shown in FIG. 9B. As a result, the polishing points A and B of the pair of polishing drums 4 allow the chamfered portion 10 of the wafer 10 to be formed.
a and mirror finishing of the outer peripheral surface 10b can be performed simultaneously.

At this time, the outer peripheral surface 10b of the wafer 10
Is polished in contact with the outer peripheral surface of the polishing drum 4 at a polishing point B near the point R shown in FIG. 8, so that the grinding marks 10c generated on the outer peripheral surface 10b of the wafer 10 in the previous process and the polishing drum 4 As shown in FIG. 10, the speed vector 4d due to the rotation causes the cloth 4c of the polishing drum 4 to polish the outer peripheral surface 10b of the wafer 10 while intersecting as shown in FIG. The film layer can be reliably and efficiently removed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a conventional method for mirror-finishing a semiconductor wafer.

FIG. 2 is a plan view of a mirror processing apparatus for performing a mirror processing method for a semiconductor wafer according to an embodiment of the present invention;

FIG. 3 is a front view of a mirror processing apparatus for performing a method of mirror processing a semiconductor wafer according to an embodiment of the present invention;

FIG. 4 is an arrow view from the X direction in FIG. 3;

FIG. 5 is a view as seen from the Y direction in FIG. 2;

FIG. 6 is an arrow view from the Z direction in FIG. 2;

FIG. 7 is a detailed view of chuck driving means of the mirror processing apparatus for performing the mirror processing method of the semiconductor wafer according to the embodiment of the present invention;

FIG. 8 is an explanatory diagram showing a method for mirror-finishing a semiconductor wafer according to an embodiment of the present invention.

FIGS. 9A and 9B are explanatory views showing a method for mirror-finishing a semiconductor wafer according to an embodiment of the present invention; FIGS.

FIG. 10 is an explanatory diagram illustrating a method for mirror-finishing a semiconductor wafer according to an embodiment of the present invention.

[Explanation of symbols]

4 ... center of O 2 _... semiconductor wafer polishing drum 6 ... Drum lifting drive means 8, 9 ... energizing means 10 ... semiconductor wafer 10a ... chamfered portion 10b ... outer circumferential surface 20 ... support shaft O 1 _... polishing drum

Claims (3)

[Claims] 1. A chamfered portion (10a) and an outer peripheral surface (10b) of a semiconductor wafer (10) whose outer peripheral edge is chamfered.
In a method for mirror-finishing a semiconductor wafer with a polishing drum (4), the polishing surface of one of the pair of polishing drums (4), which can be raised and lowered by a drum lifting drive means (6), is mirror-finished. Semiconductor wafer to be processed (1
0), the outer peripheral surface (10b) of the semiconductor wafer (10) is brought into contact with the polishing surface of the other polishing drum (4), and at least the semiconductor wafer (10) The outer peripheral surface (10b) of the polishing drum (4)
The polishing drum (4) and the semiconductor wafer (10) are rotated so that the velocity vector due to the rotation of the semiconductor wafer and the velocity vector due to the rotational feed of the semiconductor wafer (10) cross each other,
A mirror polishing method for a semiconductor wafer, wherein a chamfered portion (10a) and an outer peripheral surface (10b) are simultaneously mirror-polished from respective polishing drums (4). 2. A chamfered portion (10a) and an outer peripheral surface (10b) of a semiconductor wafer (10) whose outer peripheral edge is chamfered.
In a method for mirror-finishing a semiconductor wafer (10) by polishing a wafer with a polishing drum (4), the polishing surface of one of the pair of polishing drums (4) that can be raised and lowered by a drum lifting drive means (6). Then, the chamfered portion (10a) of the semiconductor wafer (10) to be mirror-finished is biased by the urging means (8).
The outer peripheral surface (10b) of the semiconductor wafer (10) is brought into contact with the polishing surface of the other polishing drum (4) by the urging means (9), and the rotation of each polishing drum (4) is performed. While oscillating the semiconductor wafer (10) about the support shaft (20) parallel to the center, at least the outer peripheral surface (10b) of the semiconductor wafer (10) has a velocity vector due to the rotation of the polishing drum (4) and a semiconductor. The polishing drum (4) and the semiconductor wafer (10) are rotated so that the velocity vectors of the rotational feed of the wafer (10) cross each other, and the chamfered portion (10a) and the outer peripheral surface (10b) are rotated from the respective polishing drums (4). ), A mirror surface processing method for a semiconductor wafer, characterized by simultaneously performing mirror surface processing. 3. A support shaft (20) is provided on a center line O ₁ -O ₂ connecting the center O ₁ of the polishing drum (4) and the center O ₂ of the semiconductor wafer (10). 3. The method for mirror-finishing a semiconductor wafer according to claim 2, wherein the surface is swung.