JPH07171757A - Wafer grinding device - Google Patents

Abstract

PURPOSE:To provide a wafer grinding device capable of the planarization grinding without peripheral sag of a wafer or the like, and capable of the multilayer interconnection and high integration of the wafer. CONSTITUTION:A wafer W is sucked and supported on a flexible and thin wafer sucking and holding plate 3 to be arranged at a lower opening part 13 of a wafer holding member 2, the wafer holding member 2 is supported in a suspended manner on a housing 4 by an expandable cylindrical member 6 and a highly flexible supporting member 7, and the compressed air of the pressure P to satisfy the expression pi/4(d1<2>-d2<2>).P=M is introduced into a sealed chamber 12 to eliminate effect of the self weight of the wafer holding member 2 and to grind the wafer W only by the uniform air pressure. Where, d1 is the outer diameter of the wafer, d2 is the inner diameter of an upper opening part 14 of the wafer holding member 2 of d2<d1, and M is the self weight of the wafer holding member 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus, and more particularly to a wafer polishing apparatus suitable for application to a planarization processing technique for improving the flatness of semiconductor devices.

[0002]

2. Description of the Related Art With the progress of high integration and large scale of semiconductor devices, miniaturization of wiring and multilayering of wiring have become more and more important. When the wiring is miniaturized, the end face is inevitably sharpened, and the covering property of the insulating film or the wiring to be deposited thereon is deteriorated. Also, when the wiring is multi-layered,
Since unevenness of the underlying wiring or insulating film is piled up, the unevenness of the surface becomes severe, and even if an attempt is made to form a wiring on the surface, the stepper cannot focus and the processing accuracy of the wiring deteriorates. In either case, the wiring is likely to be broken, and the reliability of the semiconductor device is reduced.

Various flattening techniques have been developed to solve this problem. For example, there is a glass flow method in which a glass film of PSG, BPSG, or the like is formed by CVD and then heated to 800 to 1100 ° C. to cause viscous flow for flattening. Although this method is simple in process, it has a drawback that the wiring material is limited such that Al wiring cannot be used because it is heated to a high temperature. Other than this, various methods have been developed, but each method has advantages and disadvantages, and there is no deciding technique.

In recent years, in order to overcome this situation, a flattening method applying a wafer polishing technique is being developed. That is, in the process of manufacturing a semiconductor device, a planarization processing technique for improving the flatness thereof, specifically, as a means for flattening the protruding portion of the silicon oxide film generated corresponding to the wiring on the wafer, It is intended to apply polishing technology.

However, in the planarization processing technique for manufacturing a semiconductor device, the cross-sectional shape of the wafer (hereinafter, referred to as wafer W) in the processing process is the same as the thick portion of the wafer W shown in FIG. Even if there is a difference with the thin portion, it is necessary to develop a technique for polishing the wafer W whose sectional shape is the same as the polishing amount of the surface oxide film shown in FIG. The reason for this is that conventionally, this wafer polishing technique has been developed in the direction of preferentially removing a large-thickness portion of the wafer for the purpose of equalizing the thickness on the entire surface of the wafer.

This surface reference polishing technique is specifically shown in FIG.
Oxide film 52 (interlayer insulating film) on the silicon substrate 51 shown in FIG.
The step, that is, the oxide film protrusion 53 is removed, and the thickness of the oxide film 52 is maintained uniform. In FIGS. 8 and 9, 54 is an element and 55 is a wiring.
Further, in these drawings, the global unevenness of the wafer W is exaggerated for convenience of explanation.

By the way, the removal amount of the surface layer at the time of polishing a wafer strongly depends on the polishing pressure. Therefore, in the above-mentioned surface reference polishing technique, as shown in FIG. 7, the polishing pressure distribution D on the surface of the wafer W is made uniform (uniform load distribution), thereby preventing the occurrence of defects such as sagging around the wafer (not shown). It is extremely important to do so. Therefore, in Japanese Patent Laid-Open No. 5-69310, the back surface of the wafer is brought into contact with the wafer holding plate to hold it, and a pressurized fluid is supplied to the back surface side of the wafer holding plate to polish the wafer. Various proposals have been made for a polishing device that presses against a board and performs mirror polishing.

[0008]

However, in the conventional polishing apparatus, although the polishing pressure distribution is considered to be uniform, it is difficult to avoid, such as poor assembly accuracy of the polishing machine, poor processing accuracy of parts, or wafer holding plate. However, there is a problem that the uniformization of the polishing pressure distribution is insufficient due to the incomplete function.

The present invention solves the above-mentioned problems. A wafer polishing apparatus capable of planarizing polishing without causing sagging around the wafer and improving reliability and high integration of multilayer wiring of the wafer. The purpose is to provide.

[0010]

A wafer polishing apparatus according to claim 1 has a lower opening having a diameter slightly larger than the outer diameter d _{1 of the} wafer on the lower end side, and d ₂ <d ₁ on the upper end side.
A wafer holding member of weight M forming an upper opening of
A wafer suction holding plate made of a flexible hard thin plate that closes the lower opening and sucks and supports the wafer, a cylindrical body portion that is hung and supported on the stationary side of the device and that opens at the lower end side, and inside the A housing having a formed ring-shaped protrusion having an inner diameter d ₂ , an expandable tubular member bridged between the ring-shaped protrusion of the housing and the wafer holding member, the tubular member and the wafer suction member. A closed chamber formed by a holding plate between the ring-shaped protrusion of the housing and the wafer holding member, and a highly flexible support member that is installed between the body of the housing and the wafer holding member,
A polishing apparatus comprising: a vacuum passage that connects the wafer suction holding plate and a vacuum source; and a compressed air supply passage that connects the closed chamber and a compressed air source that supplies compressed air having a pressure P to the closed chamber. It is characterized in that the pressure P satisfies the relational expression of π / 4 (d ₁ ² −d ₂ ² ) P = M.

In the wafer polishing apparatus according to a second aspect of the present invention, the highly flexible support member provided between the body of the housing and the wafer holding member is located at the center of the wafer surface where the wafer and the polishing cloth are in contact with each other. It is characterized in that it is arranged in a downward slope.

[0012]

The wafer is supported by the wafer holding member via a wafer suction holding plate having a diameter slightly larger than the outer diameter d ₁ of the wafer. This wafer holding member is suspended and supported by a housing supported on the stationary side of the device via an elastic tubular member and a highly flexible supporting member. The inner diameter d ₂ of the tubular member is smaller than the outer diameter d _{1 of the} wafer. When the compressed air is introduced into the closed chamber from the compressed air source, the upper air supporting force that receives the weight M of the wafer holding member on the stepped portion of the wafer holding member formed between the upper opening and the lower opening of the wafer holding member. Works. By adjusting the compressed air pressure P and setting the pressure P that satisfies the relational expression of π / 4 (d ₁ ² −d ₂ ) ² · P = M, the influence of the weight M of the wafer holding member is eliminated and the wafer adsorption The wafer comes into full contact with the holding plate, and the air pressure of pressure P acts uniformly. The wafer is pressed against the polishing cloth with a constant pressure, but the unevenness of the shape of the wafer itself is absorbed by the deformation of the wafer suction holding plate made of a flexible hard thin plate. Further, the wafer holding member is stably supported at the center position by the supporting member.

Further, since the supporting member is arranged so as to be inclined toward the center point of the wafer surface in contact with the polishing cloth, the wafer does not move or rotate during polishing. Therefore, highly accurate and stable polishing can be performed, and the polishing work efficiency can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view illustrating the overall configuration of an embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing the detailed structure around a wafer suction holding plate of the present embodiment, and FIG. 3 is a support member support of the present embodiment. FIG. 4 is a partial sectional view for explaining the shape and its action.
Is a partial cross-sectional view showing the correct polishing posture of this embodiment, FIG. 5 is a partial cross-sectional view showing the case where the value of the pressure P exceeds the appropriate pressure value, and FIG. 6 shows the case where the value of the pressure P is less than the appropriate pressure value. It is a partial sectional view showing each.

As shown in FIG. 1, the wafer polishing apparatus 1 of the present embodiment is roughly classified into a wafer holding member 2 and a flexible structure which is fixed to the wafer holding member 2 by closing the lower opening 13 thereof. Wafer suction holding plate 3 made of hard thin plate
And a housing 4 having a body portion 15 and a ring-shaped protrusion portion 16 projecting downward and supported by a stationary side 17 of the apparatus via a rotary shaft 18, and a diameter smaller than the outer diameter d ₁ of the wafer W. A stretchable tubular member 6 installed between the upper opening 14 of the wafer holding member 2 having an inner diameter d ₂ and the ring-shaped projection 16 of the housing 4, and a high flexure installed between the wafer holding member 2 and the housing 4. Support member 7 and vacuum source 8
A compressed air source 9, a polishing cloth 10 and a rotating mechanism 11 for driving the rotating shaft 18. As shown in the figure, a closed chamber 12 is formed between the wafer holding member 2 and the housing 4 by the wafer suction holding plate 3 and the tubular member 6.

The wafer holding member 2 has a wafer 5 on the lower side.
A hollow cylindrical member having a lower opening 13 having an inner diameter slightly larger than the outer diameter d _{1 of} the above and an upper opening 14 having an inner diameter d ₂ smaller than the outer diameter d ₁ above.
A stepped portion 19 is provided between the lower opening 13 side and the upper opening 14 side.
Is formed.

The wafer adsorption / holding plate 3 is made of a flexible hard thin plate, specifically, for example, hard plastic, hard rubber or a metal thin plate. As the hard plastic, epoxy resin, thermosetting resin such as phenol resin, heat-resistant hard resin such as polyethylene terephthalate, polybutylene terephthalate, polyimide, polysulfone are preferably used, and these are glass fiber, carbon. It may be reinforced with fibers, synthetic fibers, or woven or non-woven fabrics thereof. In the case of hard plastic or hard rubber (including the case of being reinforced with the above fibers or the like), the plate thickness is preferably 0.1 mm to 1.0 mm in order to ensure flexibility as a plate body. As the metal, steel typified by stainless steel is preferably used, but in this case, 0.05 mm in order to ensure flexibility as a plate body.
It is preferable that the thickness is about 0.2 mm.

As shown in FIG. 2, the wafer suction holding plate 3
Has a large number of suction holes 20 formed therethrough. Each suction hole 20 has a central hole 2 through a passage 21 in the connector 33.
Connect to 2. The center hole 22 communicates with the inside of the flexible hose 23. In this case, a large number of suction holes 20 formed in the wafer suction holding plate 3 are formed in the central portion of the wafer suction holding plate 3 and a plurality of through holes are formed in concentric circles centered on the suction holes. Further, by adhering a thin, narrow and soft rod-shaped rubber (or band-shaped rubber) 32 having a long groove 31 on one surface to the back surface of the wafer suction holding plate 3, that is, the surface opposite to the wafer suction surface, all The suction hole is sealed, the central hole 22 is made to communicate with all the other suction holes 20, and the connector 33 is projectingly provided in the central hole 22. Although the rod-shaped rubber is exemplified as the material forming the gas passage on the back surface of the wafer suction holding plate 3, any material that is the same material as the wafer suction holding plate 3 and can be bent like the wafer suction holding plate can be used. Needless to say.

On the other hand, the housing 4 comprises a cylindrical body surrounded by a body portion 15 projecting downward in a flange shape on the outer periphery of the disk-shaped member 24, and has a ring shape projecting downward inside thereof. The protrusion 16 is formed. The inner diameter of the ring-shaped protrusion 16 is formed to have a size substantially equal to the above d ₂ . One end side of the rotary shaft 18 is fixed to the center of the disc-shaped member 24. In addition, the other end side of the rotating shaft 18 has the rotating mechanism 1
Connected to 1.

The tubular member 6 is made of an elastic material,
It is installed between the upper opening of the wafer holding member 2 and the ring-shaped protrusion 16 of the housing 4. On the other hand, a highly flexible support member 7 is installed between the wafer holding member 2 and the body portion 15 of the housing 4. The support member 7 is made of, for example, a plurality of highly flexible metal thin rods arranged in a radial pattern, an annular highly flexible rubber, a plastic, a metal thin plate, or the like.

As shown in FIG. 3, the support member 7 has a body portion 15
Is arranged in a downward slope from and the extension point thereof coincides with the center point O of the wafer W surface in contact with the polishing cloth. The reason for this is that the friction force F acts on the wafer W due to the contact between the wafer W and the polishing cloth 10, but the rotation moment is applied to the wafer holding member 2 by the support member 7 being arranged with the center point O oriented. This is to prevent it from working. When the rotational moment acts, the polishing pressure between the wafer W and the polishing pad 10 becomes non-uniform, which makes high-precision polishing difficult.

The wafer holding member 2 is suspended and supported by the housing 4 via the tubular member 6 and the supporting member 7. Further, the space between the wafer holding member 2 and the housing 4 is surrounded by the wafer suction holding plate 3, the tubular member 6 and the disc-shaped member 24 of the housing 4 to form a closed chamber 12.

A vacuum passage 25 and a compressed air supply passage 26 are formed in the rotary shaft 18 fixed to the housing 4. The vacuum passage 25 is connected to a flexible hose 23 arranged in the closed chamber 12, and the vacuum source 8 is connected via an opening / closing valve 27.
Connected to. On the other hand, the compressed air supply passage 26 has the closed chamber 12
It communicates with the inside and is connected to the compressed air source 9 via the on-off valve 28.

Next, the operation of this embodiment will be described. First,
The wafer W is brought into contact with substantially the center of the wafer suction holding plate 3, and the vacuum source 8 is operated. Open / close valve 27, vacuum passage 25,
Vacuum is applied to each suction hole 20 through the flexible hose 23 and the center hole 22 of the wafer suction holding plate 3 and the passage 21, so that the wafer W is uniformly sucked and supported by the wafer suction holding plate 3. Next, the compressed air of pressure P is supplied from the compressed air source 9 through the on-off valve 28 and the compressed air supply passage 26 to the closed chamber 12.
Introduce inside.

FIG. 4 shows an operating state of the compressed air having the pressure P in the closed chamber 12. A compression pressure of P acts uniformly in the closed chamber 12. Of these, the stepped portion 19 has π
/ 4 (d ₁ ² −d ₂ ² ) · P upward supporting force acts on the wafer W, and the wafer W has a uniform pressure P within the range of its diameter d _1.
Acts and receives a reaction force of the same pressure from the polishing cloth 10 side. The pressure is balanced in the upper and lower parts and the left and right parts of the wafer holding member 2 other than the above.

The adjusted value of the pressure _{P, π / 4 (d 1} 2 -d
_If the supporting force of ₂ ² ) · P is made equal to the own weight M of the wafer holding member 2, the influence of the own weight of the wafer holding member 2 disappears, and only the total pressure of π / 4d ₁ ² · P acts on the wafer W. On the other hand, since the wafer suction holding plate 3 is formed of a flexible hard thin plate, it deforms following the large irregularities of the wafer W, and does not follow the irregularities of the small wafer W without following it. Therefore, planarization polishing becomes possible.

Even if the thickness of the wafer W is not uniform, it is absorbed by the flexible wafer suction holding plate 3 and the highly flexible support member 7 (FIG. 1), and the wafer W and the polishing cloth 10 are absorbed. Are polished while contacting with uniform pressure. As described above, uniform and highly accurate polishing is performed. Further, as described above, since the supporting member 7 is arranged so as to be inclined downwardly toward the center point O of the wafer W surface in contact with the polishing cloth, no rotational moment acts on the wafer holding member 2 during polishing. Therefore, high precision polishing is possible.

FIG. 5 and FIG. 6 are views showing a state of defective polishing in this embodiment. When the pressure P ₁ in the closed chamber 12 is larger than the pressure P satisfying the above formula of π / 4 (d ₁ ² −d ₂ ² ) · P = M, as shown in FIG. 2, the wafer suction holding plate 3 is deformed into a convex shape. Therefore, the wafer W and the polishing pad 10 tend to come into strong contact with each other on the central side of the wafer W. Therefore, the contact between the wafer W and the polishing cloth 10 becomes non-uniform, and high-precision polishing becomes difficult.

On the other hand, as shown in FIG.
When the internal pressure P ₂ becomes P ₂ <P, the wafer holding member 2
A part of its own weight M acts on the wafer W side, and the wafer suction holding plate 3 is deformed into a concave shape. Therefore, the peripheral side of the wafer W is pressed against the polishing cloth 10 and becomes slightly rough, causing sagging around the periphery.
As with the above, high precision polishing becomes difficult. From the above, adjustment work for adjusting the pressure P of the compressed air supplied into the closed chamber 12 to an appropriate value is required in this embodiment, but by adjusting the pressure to an appropriate value, high precision polishing is stable. Done.

[0030]

According to the present invention, the following remarkable effects are obtained. 1) Adjusting the pressure of the compressed air supplied into the closed chamber inside the wafer holding member to a value that satisfies the relational expression of π / 4 (d ₁ ² −d ₂ ² ) P = M, The influence of the self-weight M disappears, and only the uniform air pressure of the pressure P acts on the wafer W. As a result, the wafer surface and the polishing cloth are in uniform contact with each other. 2) Even if the thickness of the wafer W is uneven, the wafer suction holding plate and the supporting member absorb the uneven acting force, so that the wafer surface and the polishing cloth are in uniform contact with each other. Therefore, highly accurate polishing can be performed. 3) Since the wafer adsorption / holding plate is made of a flexible hard thin plate, the large irregularities of the wafer W are deformed accordingly.
Planarization polishing is possible without following small irregularities. 4) Since the support member is arranged so as to be inclined downward toward the center point of the wafer W surface where the wafer surface and the polishing cloth are in contact with each other, there is no effect of a rotation moment during polishing, and high precision polishing can be performed. 5) By the above, the wafer W can be highly precisely planarized and polished, and the reliability and the integration of the multilayer wiring of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall structure of an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a detailed structure around a wafer suction holding plate of the present embodiment.

FIG. 3 is a partial cross-sectional view for explaining a disposition form of a support member of the present embodiment.

FIG. 4 is a partial cross-sectional view illustrating a proper polishing state in the present embodiment.

FIG. 5 is a partial cross-sectional view illustrating an improperly polished state in the present embodiment.

FIG. 6 is a partial cross-sectional view illustrating an improperly polished state in the present embodiment.

FIG. 7 is a cross-sectional view illustrating the action of planarization polishing.

FIG. 8 is a cross-sectional view of a wafer W before polishing.

FIG. 9 is a cross-sectional view of a wafer W after polishing.

[Explanation of symbols]

 1 Wafer Polishing Device 2 Wafer Holding Member 3 Wafer Adsorption Holding Plate 4 Housing 6 Cylindrical Member 7 Supporting Member 8 Vacuum Source 9 Compressed Air Source 10 Polishing Cloth 11 Rotating Mechanism 12 Sealed Chamber 13 Lower Opening 14 Upper Opening 15 Body 16 ring-shaped protrusion 17 stationary side 18 rotary shaft 19 stepped portion 20 adsorption hole 21 passage 22 center hole 23 flexible hose 24 disk member 25 vacuum passage 26 compressed air supply passage 27 on-off valve 28 on-off valve 31 long groove 32 rod-shaped rubber 33 Connector 41 Polishing cloth 42 Polishing surface plate 51 Silicon substrate 52 Oxide film 53 Oxide film protrusion 54 Element 55 Wiring D Polishing pressure distribution W (in the process of manufacturing a semiconductor device) Wafer

Claims (2)

[Claims] 1. A lower opening having a diameter slightly larger than the outer diameter d _{1 of the} wafer is provided, and d ₂ <d _{1 is provided at the} upper end.
A wafer holding member of weight M forming an upper opening of
A wafer suction holding plate made of a flexible hard thin plate that closes the lower opening and sucks and supports the wafer, a cylindrical body portion that is hung and supported on the stationary side of the device and that opens at the lower end side, and inside the A housing having a formed ring-shaped protrusion having an inner diameter d ₂ , an expandable tubular member bridged between the ring-shaped protrusion of the housing and the wafer holding member, the tubular member and the wafer suction member. A closed chamber formed by a holding plate between the ring-shaped protrusion of the housing and the wafer holding member, and a highly flexible support member that is installed between the body of the housing and the wafer holding member,
A polishing apparatus comprising: a vacuum passage that connects the wafer suction holding plate and a vacuum source; and a compressed air supply passage that connects the closed chamber and a compressed air source that supplies compressed air having a pressure P to the closed chamber. A wafer polishing apparatus, wherein the pressure P satisfies the following formula. π / 4 (d ₁ ² −d ₂ ² ) · P = M 2. A highly flexible support member, which is provided between the body of the housing and the wafer holding member, is arranged so as to be inclined downward toward the center point of the wafer surface where the wafer and the polishing cloth are in contact with each other. The wafer polishing apparatus according to claim 1, wherein: