JP2757112B2 - Wafer polishing equipment - Google Patents

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 polishing apparatus suitable for application to a planarization processing technique for improving the flatness of a semiconductor device.

[0002]

2. Description of the Related Art With the progress of high integration and large scale of semiconductor devices, miniaturization of wirings and multi-layering of wirings have become more and more important. When the wiring is miniaturized, the end face must be sharpened, and the covering property of the insulating film or the wiring to be deposited thereon is reduced. Also, when wiring is multi-layered,
Since the unevenness of the lower wiring or the insulating film is piled up, the unevenness of the surface becomes severe. Even if an attempt is made to form the wiring on the surface, the stepper becomes out of focus and the processing accuracy of the wiring is reduced. In any case, disconnection of the wiring is likely to occur, and the reliability of the semiconductor device is reduced.

In order to solve this problem, various flattening techniques have been developed. For example, there is a glass flow method in which a glass film such as PSG or BPSG is formed by CVD, and then heated to 800 to 1100 ° C. to make it viscous flow to flatten. This method is simple in process, but has the drawback that the wiring material is limited, such as the use of Al wiring because it is heated to a high temperature. In addition, various methods have been developed, but each has its advantages and disadvantages, and there is no decisive technology.

In recent years, in order to overcome this situation, a flattening method using a wafer polishing technique has been developed. That is, in the process of manufacturing a semiconductor device, planarization processing technology for improving the flatness of the wafer, specifically, a means for flattening a projection portion of a silicon oxide film generated corresponding to wiring on the wafer, It is intended to apply polishing technology. Conventionally, this wafer polishing technique has been developed in order to equalize the thickness over the entire surface of the wafer and to preferentially remove a thick portion of the wafer.

However, in the planarization processing technology for manufacturing semiconductor devices, the cross-sectional shape of a wafer (hereinafter, referred to as a wafer W) in the processing process is different from the thick portion of the wafer W shown in FIG. Even if there is a difference between the thin portion and the thin portion, it is necessary to develop a technique for polishing a wafer W having a sectional shape shown in FIG.

This polishing technique specifically removes a step, that is, an oxide film projection 53 in an oxide film 52 (interlayer insulating film) on a wafer 51 shown in FIG.
2 is to maintain a uniform thickness. 6 and 7
In the figure, 54 is an element, and 55 is a wiring. In these figures, the global unevenness of the wafer W is exaggerated for convenience of explanation (the same applies to FIG. 5).

[0007] The removal amount of the surface layer during wafer polishing strongly depends on the polishing pressure. Therefore, in the above surface-based polishing technique, as shown in FIGS.
It is extremely important to make the polishing pressure distribution D on the surface of the wafer W uniform (uniformly distributed load), thereby preventing problems such as sagging around the wafer (not shown). For this reason, as disclosed in Japanese Patent Application Laid-Open No. 5-69310 and the like, the wafer is polished by bringing the back surface of the wafer into contact with the wafer holding plate and holding it, and supplying a pressurized fluid to the back side of the wafer holding plate. Various proposals have been made for a polishing apparatus for performing mirror polishing by pressing against a board.

[0008]

However, in the conventional polishing apparatus, although uniformity of the polishing pressure distribution is taken into consideration, it is difficult to avoid the inferior assembly accuracy of the polishing machine, the inferior processing accuracy of the polishing machine, or the wafer holding plate. However, there is a problem that the polishing pressure distribution is not sufficiently equalized due to the imperfect function.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a polishing apparatus capable of easily performing a surface reference polishing without generating peripheral sagging or peripheral protrusion of a wafer. It is in.

[0010]

According to a first aspect of the present invention, there is provided a wafer polishing apparatus in which a back surface of a wafer is brought into contact with a wafer holding plate to hold the wafer holding plate, and a pressurized fluid is supplied to the back side of the wafer holding plate. By doing so, in an apparatus for polishing a wafer by pressing the wafer against a polishing cloth surface, a cylindrical body having one end opened, and a housing provided with a ring-shaped projection on the inner periphery thereof, and an annular holding ring are provided. A wafer holding member provided concentrically on a lower end surface thereof, a wafer holding member provided with a template surrounding the wafer on a lower surface side of the wafer holding plate, and a ring-shaped projection of the housing; and a wafer holding member. A closed chamber is formed by connecting a holding ring to the housing via an elastic tubular member, and the holding ring is connected to a body of the housing via a highly flexible support member. , Said sealed chamber, characterized by comprising contact to a source of pressurized fluid.

According to a second aspect of the present invention, in the wafer polishing apparatus according to the first aspect, the wafer holding plate is formed of a flexible hard thin plate, and the flexibility of an annular portion of the wafer holding plate around the wafer holding region is reduced. The annular portion is made a movable region by making the flexibility higher than that of the wafer holding region.

According to a third aspect of the present invention, in the first aspect of the present invention, the cross-sectional shape and the size of the closed chamber substantially match the cross-sectional shape and the size of the wafer on both the wafer holding member side and the housing side. It is characterized by the following. -Polishing equipment.

As the hard thin plate constituting the flexible wafer holding plate, for example, a thin plate of hard plastic, hard rubber, metal or the like is used. As the hard plastic, a thermosetting resin such as an epoxy resin and a phenol resin, a heat-resistant hard resin such as polyethylene terephthalate, polybutylene terephthalate, polyimide, and polysulfone are preferably used. Fibers, synthetic fibers, or those reinforced with woven or nonwoven fabrics thereof may be used. In the case of a hard plastic or a hard rubber (including the case where it is reinforced with the above-mentioned fiber or the like), the plate thickness is preferably 0.1 mm to 1.0 mm in order to secure flexibility as a plate. As the metal, steel typified by stainless steel is preferably used. In this case, in order to secure flexibility as a plate, 0.05 mm is used.
Preferably, the thickness is about 0.2 mm.

[0014]

The wafer polishing apparatus of the present invention (see FIGS. 1 and 4)
In, the wafer W is held on the wafer holding plate 2,
If the wafer W is positioned directly above the polishing cloth 41 provided on the polishing platen 42 and compressed air of, for example, an appropriate pressure is supplied from the pressurized fluid supply source to the closed chamber 7, the wafer W is displaced by the pressure and the wafer W is moved. Since the polishing pad 41 is pressed against the polishing cloth 41 at a predetermined pressure, polishing can be performed in a usual manner. In this case, the wafer holding member 4 includes an elastic tubular member 5 and
Since it is hung from the housing 6 by the highly flexible support member 8, it is difficult to avoid a polishing machine of the order of several μm to several tens μm inferior in assembly accuracy, in inferior processing accuracy, or in thermal / mechanical deformation due to use. Is absorbed, and the wafer W can be reliably pressed against the polishing pad 41.

Further, the wafer W is held by a flexible wafer holding plate 2, and the back surface of the holding plate 2 is pressed by compressed air, so that the warp of the wafer is corrected and the thickness of the wafer is varied. Accordingly, the wafer holding plate 2 itself is deformed, so that the surface of the wafer can be brought into close contact with the polishing pad 41. That is, the wafer holding plate 2 is shown in FIGS.
As shown in the figure, the wafer polishing plate has a uniform polishing pressure distribution over the entire back surface of the wafer W, and the region to which the polishing pressure is applied does not spread outside the wafer back surface, and the wafer holding plate 2 has a shape adapted to the global unevenness of the wafer W. Polishing is performed by bending. In the wafer holding member 4, the outer peripheral portion of the wafer holding plate 2 is fixed to a highly rigid holding ring 1, and the flexibility of the movable region 2 b (see FIGS. 1 to 3) outside the wafer holding region 2 a of the wafer holding plate 2. Is higher than the wafer holding area 2a, so that the distortion and deformation of the supporting member 8 generated due to the holding force acting on the highly flexible supporting member 8 are not transmitted to the wafer holding area 2a. Can be.

The vertical component acting on the holding ring 1 due to the holding force acting on the support member 8 and the weight of the holding ring 1 are received by the template 3 surrounding the wafer, and therefore act on the wafer holding area 2a. The pressing force can be only the air pressure, and the pressing force on the wafer surface can be kept uniform.

Further, the balance of the force when the inside of the closed chamber 7 is pressurized with the compressed air will be described in connection with the case where the sectional area of the closed chamber 7 on the housing 6 side is larger than the wafer holding member 4 side, that is, the sectional area of the wafer. Considering that the air pressure in the closed chamber 7 is uniform, the force acting on the wafer holding member 4 side from the housing side is larger than the force pressing the wafer against the polishing cloth 41 from the back side of the wafer by the air. The difference is transmitted to the template via the retaining ring and simultaneously from the wafer retaining plate to the wafer. Then, the load applied to the template becomes too large, causing not only deterioration of the polishing cloth, but also a hindrance to the supply of the abrasive to the wafer surface, and at the same time, the load transmitted to the wafer holding plate has an uneven contact pressure of the wafer. Cause. Similar inconvenience is caused when the sectional area on the housing side is smaller than the sectional area on the holding member side. However, when the cross-sectional area and the cross-sectional shape of the two are the same as in the present invention (claim 3), the force acting on the wafer is only the air pressure acting on the back surface of the wafer. It can be uniform. By these actions, the polishing pressure in the wafer surface becomes uniform, so that the amount of wafer removal during polishing becomes uniform, and surface-based polishing becomes possible.

[0018]

Next, the present invention will be described more specifically with reference to embodiments shown in the drawings. Example 1 FIG. 1 is a sectional view of a main part of a polishing apparatus, FIG. 2 is a plan view of a wafer holding plate, and FIG. 3 is a sectional view thereof. As shown in FIG.
A wafer polishing apparatus is constructed by providing a wafer suction / rotation device 21 directly above and below a polishing platen 42 on which a polishing cloth 41 is provided. In the suction / rotation device 21, a cylindrical body 6 a having an open end and a ring-shaped protrusion 6 on the inner periphery thereof are provided at the tip of the rotating shaft 13 having the flow paths 11 and 12 formed therein.
The wafer holding member 4 having the following configuration is provided on the housing 6 provided with the wafer b.

That is, a wafer holding plate (hereinafter, simply referred to as a holding plate) 2 which is a vacuum suction plate is provided on a lower end surface of an annular holding ring 1, and an annular template 3 is provided on a lower surface of the holding plate 2. A wafer holding member 4 is formed, and an inner peripheral surface of the holding ring 1 of the wafer holding member 4 is connected to an inner peripheral surface of the ring-shaped protrusion 6b by an elastic tubular member 5 in a sealed state to form a closed chamber 7. I do. In addition, the retaining ring 1
A plurality of high-flexible metal rods are radially arranged, or a lower portion of the body 6a is provided via a support member 8 made of a thin annular, highly-flexible rubber, plastic, or metal plate. connect. By doing so, the wafer holding member 4
Is suspended from the housing 6 and can be three-dimensionally displaced.

The flow path 11 is connected to a vacuum pump (both not shown) through a pipe and an on-off valve, and as shown in FIGS. A) 31 communicates with the flow channel 11 via the connector 16, the flexible hose 14, and the connector 15 as described below. The flow path 12 communicates with a compressor (neither is shown) through a pipe and an opening / closing valve so that compressed air can be supplied to the closed chamber 7.

A large number of suction holes 31 formed in the holding plate 2
In this case, one is formed at the center of the holding plate 2 and a plurality of holes are formed on concentric circles around the center. In addition, all the suction holes are formed by bonding a thin, narrow, soft rod-shaped rubber (or belt-shaped rubber) 33 having a long groove 32 formed on one surface to the back surface of the holding plate 2, that is, a surface opposite to the wafer suction surface. At the same time, the central suction hole 31c is communicated with all the other suction holes 31, and the connector 16 is protruded from the central suction hole 31c. On the other hand, as shown in FIG.
And the flexible hose 14 such as a rubber hose is attached between the connector 15 and the connector 16.

The holding plate 2 is entirely made of hard plastic,
It is made of a thin plate made of hard rubber or metal to provide flexibility. The wafer holding region 2a where the holding plate 2 is in contact with the back surface of the wafer, and the portion fixed to the holding ring 1 are made of these materials. The flexibility of the movable region 2b, which is an annular portion (see FIGS. 1 to 3) of the remaining portion, that is, the portion receiving the pressure of the compressed air except for the wafer holding region 2a, is made of a material. Preferably, it is higher than the above. In FIGS. 1 to 3, m indicates a boundary line for dividing the wafer holding region 2a and the movable region 2b, and n indicates a boundary line for dividing the movable region 2b and a portion fixed to the holding ring 1 outside the movable region 2b. Further, if the width of the movable region 2b is large, the force acting on the wafer surface will be uneven, so it is preferable to make the movable region 2b as narrow as possible and increase the flexibility.

The rigid plastic thin plate constituting the holding plate 2 has a flexural modulus or a tensile modulus of 5%.
A thermosetting resin or a heat-resistant thermoplastic resin of 000 kf / cm ² or more, having a wall thickness of 0.1 to 1.0 mm is used. As a thin plate made of hard rubber, ebonite or a wall having a hardness equivalent to that of ebonite and having a thickness of 0.1 to 1.8 is used.
mm. The metal thin plate is made of stainless steel and has a thickness of 0.05 to 0.1 mm.
20 mm can be used.

The movable area 2b is preferably kept as narrow as possible. In order to make the flexibility of the movable region 2b higher than that of the wafer holding region 2a, for example, the movable region 2b
b may be made thinner than the wafer holding region 2a,
Thereby, the movable region 2b can be easily formed. As the elastic tubular member 5, for example, a soft rubber sheet or a soft rubber sheet reinforced with synthetic fibers is used. As the highly flexible support member 8, a thin metal rod radially arranged as described above, or a thin plate made of rubber, plastic, or metal is used. Further, it is preferable that the shape and size of the closed chamber 7 substantially match the shape and size of the wafer on the wafer holding member 4 side and the housing 6 side.

Next, the operation of the above polishing apparatus will be described with reference to FIG.
This will be described with reference to FIGS. First, by operating the vacuum pump, the wafer W whose sectional structure is shown in FIG.
Adsorb to. When the entire holding plate 2 is made of a hard plastic or the like, the wafer W may be suctioned at an appropriate interval between the wafer W and the inner peripheral surface of the template 3, and the suction position is not particularly limited. Wafer holding area 2a
When the movable region 2b having higher flexibility is formed, it is important that the outer peripheral edge of the wafer W is matched with the outer peripheral edge of the wafer holding region 2a. Next, compressed air of a predetermined pressure is supplied to the closed chamber 7 by the operation of the compressor to press the back surface of the holding plate 2, displace the wafer holding member 4, and move the wafer W to the polishing cloth 41 of the polishing platen 42.
And polished by a normal method.

In this polishing apparatus, the wafer holding member 4 is suspended from the housing 6 by elastic and highly flexible members (5, 8), and a rod-shaped member is used as a member for communicating the suction holes 31 of the holding plate 2 with each other. The rubber 33 is used to prevent the flexibility of the holding plate 2 from being impaired, and the load applied to the wafer holding member 4 is received by the template 3 provided on the lower surface of the holding plate 2. 2a is made flexible and the flexible hose 14 is provided as a member for connecting the suction hole 31 to the vacuum flow path 11, so that the wafer holding member 4 responds to the pressure of the compressed air as shown in FIG. As shown in FIG. 5, the oxide film 52 on the surface of the wafer W is displaced freely by the pressure from the holding plate 2.
Is brought into contact with the surface of the polishing cloth 41, the holding plate 2 is bent in a form conforming to global irregularities on the back surface of the wafer W, and the polishing pressure distribution D on the back surface of the wafer W is uniform over the entire surface.

As a result, the oxide film projection 53 corresponding to the portion where the wiring 55 is provided in FIG. 6 is preferentially applied over the entire polished surface of the wafer without causing peripheral sagging due to excessive polishing or peripheral projection due to insufficient polishing. Polishing and removal can be performed with a constant polishing amount, and as shown in FIG.
The wafer W having a uniform thickness can be obtained.

The holding plate 2 has a wafer holding area 2a.
And the movable region 2b having a higher flexibility than the above, and polishing the outer peripheral edge of the wafer W so as to match the outer peripheral edge of the wafer holding region 2a, the entire holding plate 2 is uniformly flexible. The polishing pressure at the outer peripheral edge of the wafer can be easily controlled to be the same as the polishing pressure at other portions as compared with the case where the polishing film is formed of a hard plastic or the like, so that a polishing wafer having a more uniform thickness of the oxide film 52 can be obtained. Can be. Further, as the wafer holding plate, a backing pad fixing type holding plate (non-wax method) can be applied instead of the vacuum suction type holding plate 2 in the above embodiment. In this case, an annular template is fixed to the outer periphery of the lower surface of the wafer holding plate.

[0029]

As is apparent from the above description, according to the wafer polishing apparatus of the present invention, the holding plate is three-dimensionally freely displaced integrally with the wafer holding member in accordance with the pressure of the pressurized fluid. At the same time, the wafer can be polished under uniform polishing pressure distribution over the entire back surface of the wafer W and bent into a form adapted to the global unevenness of the wafer, so that the polished wafer without peripheral sagging and peripheral projections can be formed. Thus, there is an effect that a surface-based polishing apparatus having excellent performance can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a plan view of a holding plate in the embodiment of FIG.

FIG. 3 is a sectional view of FIG. 2;

FIG. 4 is a sectional view for explaining the operation of the embodiment in FIG. 1;

FIG. 5 is a sectional view for explaining the operation of the embodiment in FIG. 1,
FIG. 5 is an enlarged schematic view of a part of FIG. 4.

FIG. 6 is a sectional view of a wafer before polishing.

FIG. 7 is a sectional view of a polished wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holding ring 2 Wafer holding plate 2a Wafer holding area 2b Movable area 3 Template 4 Wafer holding member 5 Cylindrical member 6 Housing 6a Body 6b Ring-shaped projection 7 Sealed chamber 8 Support member 11, 12 Channel 13 Rotating shaft 14 Flexible hose 15, 16 Connector 21 Suction / rotation device 31 Vacuum suction hole 32 Long groove 33 Bar-shaped rubber 41 Polishing cloth 42 Polishing platen 51 Wafer 52 Oxide film 53 Oxide film protrusion 54 Element 55 Wiring D Polishing pressure distribution W (Process for manufacturing semiconductor device (In) wafer m, n boundary

────────────────────────────────────────────────── ─── Continuing on the front page (72) Fumio Suzuki Inventor 150 Odakura Odakura, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Shin-Etsu Semiconductor Co., Ltd. Semiconductor Shirakawa Research Laboratories (56) References JP-A-5-69310 (JP, A) JP-A-64-45566 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24B 37/04

Claims (3)

(57) [Claims] 1. A wafer is brought into contact with a polishing cloth surface and polished by bringing a back surface of a wafer into contact with a wafer holding plate and holding the wafer holding plate, and supplying a pressurized fluid to a back side of the wafer holding plate. In the apparatus, a cylindrical body having one end opened, a housing provided with a ring-shaped projection on the inner periphery thereof, and a wafer holding plate provided concentrically on a lower end surface of an annular holding ring; A wafer holding member provided with a template surrounding the wafer on a lower surface side of the wafer holding plate, wherein the ring-shaped projection of the housing and the holding ring of the wafer holding member are connected via an elastic tubular member. And forming a closed chamber by connecting the holding ring to the body of the housing via a highly flexible support member, and connecting the closed chamber to a supply source of a pressurized fluid. Wafer polishing apparatus according to claim and. 2. The wafer holding plate is made of a flexible hard thin plate, and the flexibility of an annular portion around the wafer holding region in the wafer holding plate is higher than the flexibility of the wafer holding region. 2. The wafer polishing apparatus according to claim 1, wherein the annular portion is a movable area. 3. The wafer polishing apparatus according to claim 1, wherein the cross-sectional shape and dimensions of the closed chamber substantially match the cross-sectional shape and dimensions of the wafer on both the wafer holding member side and the housing side. apparatus.