JP2770087B2 - Wafer polishing method and polishing top ring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method for precisely polishing the surface of a wafer such as a silicon semiconductor to a mirror surface, and a polishing top ring.

[0002]

2. Description of the Related Art Conventionally, in order to precisely polish the surface of a wafer to be polished into a mirror surface, a polishing apparatus as shown in FIG. 6 is used, which is mounted on a turntable a which is driven to rotate horizontally at a constant speed. A polishing cloth b is adhered, and a rotatable top ring c is provided above the outer peripheral portion so as to be vertically movable.
A concave portion is formed in the lower portion of the top ring c, and an inverted dish-shaped pressing box d is housed therein, and the lower surface thereof is closed by a pressing plate e to form a sealed space f. Has a structure in which a fluid supply pipe h and a fluid discharge pipe i having a double cylindrical structure are opened via a pressure adjusting mechanism g.

In this case, a plate j to which a plurality of wafers W to be polished are attached is placed on the polishing cloth b with the surface to be polished to be attached down, and a top ring c is lowered from above to push the plate. e is brought into contact with the upper surface of the plate j. Next, when compressed air is supplied into the closed space f from the fluid supply pipe h, the pressure of the compressed air acts on the plate j via the push plate e to press the plate j.

Accordingly, if the pressure of the compressed air is adjusted by the pressure adjusting mechanism g and the pressure is uniformly applied to the upper surface of the plate j via the push plate e, a state in which the plate j is not bent and deformed is obtained. Thus, the wafer W to be polished adhered to the lower surface of the plate j can be polished so as to have a parallel and flat surface with high precision (Japanese Patent Application Laid-Open No. Sho 64-64).
No. 2857).

[0005]

In the above-mentioned prior art, a uniform pressure is applied to the upper surface of the plate by supplying compressed air into the closed space of the top ring, so that the wafer to be polished can be precisely formed. Although the mirror surface can be machined, the pressing force becomes relatively large on the entry side of the turntable rotation due to the polishing resistance of the lower end surface of the polished wafer rubbed against the polishing cloth. There is a problem that high-precision polishing cannot be performed due to uneven surface run-out or uneven pressing of the wafer due to uneven thickness of the wafer to be polished.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and is intended to prevent the pressing force on the wafer to be polished from relatively increasing on the entry side of the rotation of the turntable. Provided is a method for polishing a wafer and a top ring for the polishing, wherein a uniform pressing force is always applied to the entire surface even when a slight surface runout occurs or the thickness of the wafer to be polished is uneven. That is the task.

[0008]

SUMMARY OF THE INVENTION As a means for technically solving this problem, the present invention provides a method of polishing a wafer by polishing a wafer to be polished to a mirror surface by pressing a wafer to be polished against a polishing surface of a turntable with a top ring. At the lower end of the top ring, a pressure plate is suspended via an elastic sheet so as to be freely movable independently of the top ring, and a closed space is formed between the top ring and the top ring. On the lower surface side of the pressure plate, a wafer chuck is attached via a fixture formed of an elastically deformable material. The wafer chuck is sucked and held by the wafer chuck, and a pressure fluid is supplied to the closed space. However, even if a slight runout occurs during the rotation of the turntable, it can be easily followed by the free movement of the pressurizing plate, and the turntable can be rotated. Also act a large grinding resistance on the lower surface of the polished wafer in the entering side, and constantly gist polishing method of the wafer holding constant the pressing force never rotational moment is generated in the fixture.

Further, according to the present invention, a pressure plate holding portion provided at a lower end portion of a top ring which rotates axially, and a wafer chuck for sucking and holding a wafer to be polished on a lower surface side are formed of elastically deformable materials. A pressure plate attached via a fixture is suspended in the pressure plate holding portion so that the pressure plate can freely move independently of the top ring and does not generate a rotational moment. A ring-shaped elastic sheet that forms a sealed space between the pressure plate and the pressure plate holding portion; a mechanism that supplies a pressurized fluid into the sealed space; and a mechanism that sucks and discharges compressed air to and from the wafer chuck. And a top ring for wafer polishing. In the wafer polishing top ring, a plurality of wafer chucks are disposed on the pressing plate, and the inner peripheral portion of the ring-shaped elastic sheet is fixed to the mounting fixture, and the outer peripheral portion is mounted on the pressing plate holding portion. The vertical holding shaft of the top ring has a suction through-hole communicating with the through-hole of the wafer chuck via a connection pipe, and a pressure fluid supply path communicating with the enclosed space in parallel. It is characterized by being provided.

[0010]

According to the present invention, since the center of the elastic sheet suspending the pressure plate is attached to the pressure plate and is located substantially at the center of the fixture, the rotation of the turntable enters. Even if polishing resistance acts on the lower surface of the wafer to be polished rubbed against the polishing cloth on the side, no rotational moment is generated in the fixture and the pressing force is constant. Since the pressure plate is suspended from the pressure plate holding portion via the elastic sheet, it can freely move independently of the pressure plate holding portion, and is surrounded by the elastic sheet. Since pressurized fluid is supplied to the enclosed space,
Even if a slight runout occurs during the rotation of the turntable, this can be easily followed and a uniform pressing force can be maintained. Further, by forming the pressure plate and the fixture for attaching the wafer chuck to the pressure plate with an elastically deformable material, it is possible to prevent the pressing force from being varied due to uneven thickness of the wafer to be polished. .

[0011]

[0012]

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a top ring formed so as to be rotatable and vertically movable, and has a vertical holding shaft 1a and a reverse plate-shaped pressure plate holding portion 1b attached to a flange at a lower end thereof. .

A pressure plate 2 has a plurality of wafer chucks 3 fitted and fixed to the lower surface thereof by fixtures 4. Each wafer chuck 3 has a flat open end and sucks the rear side of the wafer to be polished. A plurality of suction pores 3a are uniformly arranged vertically in the open end, and these suction pores 3a are opened to a recess 2a provided in the pressure plate 2 and communicate with each other. 2a is a pressure plate 2
Communicates with the through-hole 2b formed at the bottom.

Reference numeral 5 denotes a substantially ring-shaped elastic sheet made of rubber or the like, and the pressing plate 2 is connected to the pressing plate holding portion 1 of the top ring 1 via the elastic sheet.
b. That is, a ring-shaped fixture 6 is fixed to the pressure plate 2 so as to surround the fixture 4. The inner peripheral portion of the elastic sheet 5 is fixed to the fixture 6, and the elastic sheet 5 Is fixed to a ring-shaped holding member 7 attached to the pressure plate holding portion 1b. Thereby, the pressure plate 2 can freely move via the elastic sheet 5 independently of the top ring 1, and a closed space 8 is formed between the pressure plate 2 and the pressure plate holding portion 1b. Is done. The pressure plate 2
The fixture 4 for attaching the wafer chuck 3 to the pressure plate 2 is made of a material that can be elastically deformed as compared with the pressure plate holding portion 1b.

Reference numeral 9 denotes a pressure fluid supply passage, which is provided at the center of the top ring 1 in the vertical holding shaft 1a along the axial direction, and the lower end of which is open in the closed space 8 and is not shown. A pressure adjusting fluid can be supplied into the closed space 8 from the pressurized fluid supply device.

Reference numeral 10 denotes a plurality of suction holes provided in parallel with the periphery of the pressure fluid supply passage 9 in the vertical holding shaft 1a, and a connecting pipe 11 is connected to the lower end thereof. 11
Is a connecting member attached to the upper part of the pressure plate 2.
The introduction holes 12a are connected to the recesses 2a through the through holes 2b. Therefore, the suction through hole 10 communicates with each suction fine hole 3a of the wafer chuck 3 through the connection pipe 11, the introduction hole 12a, the through hole 2b, and the concave portion 2a.

The thus constructed top ring 1 according to the present invention is incorporated in a known wafer polishing apparatus as shown in FIG. 4, and in this case, the wafer W to be polished is attracted and fixed by the wafer chuck 3. Then, a pressurized fluid is supplied into the closed space 8 and the wafer W to be polished is pressed against the polishing cloth C on the turntable T to perform polishing.

The operation of the polishing process will be described. First, the top ring 1 is lowered in a state where the wafer W to be polished is not sucked, and the position of the turntable T is determined by determining the space between the top ring 1 and the processed surface.

Next, after the top ring 1 is raised, the top ring 1 is moved to a position for attracting a wafer to be polished (not shown).

Thereafter, the top ring 1 is lowered to a predetermined position, and the wafer W to be polished is held by suction. The suction of the wafer W to be polished is performed by applying suction force to the wafer chuck 3 by sucking air through the suction holes 10. According to such an adsorption method, it is not necessary to fix the wafer W to be polished by the bonding means as in the related art.

Each wafer chuck 3 has a wafer W to be polished.
Then, the top ring 1 is raised and moved to the position above the turntable T.

Thereafter, the top ring 1 is lowered to the position where it was first positioned.

A pressure fluid such as compressed air is supplied from a pressure fluid supply passage 9 into the closed space 8 of the top ring 1 to adjust the internal pressure.

Next, a polishing slurry (not shown) is supplied to the center of the turntable T.

The turntable T and the top ring 1 are rotated while adjusting the fluid pressure so that the pressure inside the closed space 8 is kept constant. At this time, the turntable T is rotated by forcible driving, but the top ring 1 may be either forcibly driven or free-rotated (co-rotation by rotation of the turntable).

Thus, the wafer W to be polished is polished into a mirror surface, and the center of the ring-shaped elastic sheet 5 suspending the pressure plate 2 is attached to the pressure plate 2 as described above. Since the fixing tool 4 is located at substantially the center of the fixing tool 4, even if a large polishing resistance acts on the lower surface of the wafer W to be polished against the polishing cloth C on the side of the rotation of the turntable T, the fixing tool No pressing moment is generated at 4 and the pressing force is constant. Since the pressure plate 2 is suspended by the pressure plate holding portion 1b via the elastic sheet 5, the pressure plate 2 can freely move independently of the pressure plate holding portion 1b, and Since the pressurized fluid is supplied into the enclosed space 8 surrounded by 5, even if a slight runout occurs when the turntable T rotates, it can easily follow the runout and maintain a uniform pressing force. can do. Accordingly, uneven polishing of the wafer W to be polished can be prevented. Further, since the pressure plate 2 and the fixture 4 for attaching the wafer chuck 3 to the pressure plate 2 are made of a material that can be elastically deformed as compared with the pressure plate holding portion 1b, the polishing target wafer W It is possible to prevent the pressing force from varying due to the thickness unevenness.

In this case, a uniform pressure can be applied to the entire surface of the wafer W to be polished, and even if the wafer W to be polished has some thickness unevenness, the thickness unevenness can be absorbed. In other words, since the pressing force applied to all the polished wafers W can be kept constant at all times, no irregularities such as uneven polishing and uneven polishing occur, and all the polished wafers W are formed with a highly accurate parallel and flat surface. It becomes possible to polish precisely to have. Further, the pressing force at the time of processing can be easily adjusted by the pressurized fluid supplied into the closed space 8, which is convenient for work.

After the completion of the polishing, the operation of each part is stopped and the top ring 1 is raised.

Finally, the top ring 1 is lowered to approach a wafer take-out portion (not shown), and the suction of the wafer W to be polished is released. The suction release of the wafer W to be polished
This can be easily performed by stopping the suction operation and supplying compressed air to the suction through-hole 10 to blow out from the suction hole 3a of the wafer chuck 3. This eliminates the need for a step of peeling off the polished wafer as in the related art, thereby preventing the wafer from being damaged.

In this way, the polishing process for one batch is completed, the polishing process for the next batch is started, and the operation is sequentially repeated.

Since the pressure plate 2 has low rigidity, it is expected that the wafer will be deformed during polishing and cannot be polished flat. However, as shown in FIG. If the center G of the load of the portion (W) and the center of the wafer W (the center of the first moment) are made to coincide with each other, such a problem can be prevented.

[0032]

As described above, according to the present invention,
Since the center of the ring-shaped elastic sheet that suspends the pressure plate is located substantially at the center of the fixture attached to the pressure plate, the ring-shaped elastic sheet slides on the polishing cloth on the side where the turntable rotates. Even if a large polishing resistance acts on the lower surface of the polished wafer to be polished, no rotational moment is generated in the fixture and the pressing force is constant. Further, since the pressure plate is suspended by the pressure plate holding portion via the elastic sheet, it can freely move independently of the pressure plate holding portion, and is surrounded by the elastic sheet. Since the pressurized fluid is supplied inside the closed space,
Even if a slight runout occurs during the rotation of the turntable, this can be easily followed and a uniform pressing force can be maintained. Therefore, the entire surface of the wafer to be polished can always be uniformly pressed against the turntable, and the polishing accuracy of the wafer to be polished can be significantly improved by preventing inclination polishing or uneven polishing of the wafer to be polished.

[0033]

Further, since the pressure plate and the fixture for attaching the wafer chuck to the pressure plate are formed of a material which can be elastically deformed as compared with the pressure plate holding portion, a plurality of sucked substrates are formed. Even if there is some thickness unevenness in the polished wafer, the thickness unevenness can be absorbed by the free movement, and the pressing force applied to all the polished wafers can be always kept constant. Therefore, all the wafers to be polished can be precisely polished so as to have parallel and flat surfaces with high precision. Further, the pressing force at the time of processing can be easily adjusted by the pressurized fluid supplied into the closed space of the top ring, which is convenient for work.

[Brief description of the drawings]

FIG. 1 is a sectional view of a top ring according to the present invention.

FIG. 2 is a bottom view of the top ring.

FIG. 3 is an enlarged sectional view taken along line AA of FIG. 1;

FIG. 4 is an explanatory view showing a use state of a top ring.

FIG. 5 is an explanatory diagram showing a positional relationship between a load applied to a wafer and a wafer.

FIG. 6 is an explanatory diagram of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Top ring 1a ... Vertical holding shaft 1b ... Pressing plate holding part 2: Pressing plate 2a ... Recess
2b: Through hole 3: Wafer chuck 3a: Suction hole 4: Fixing member 5: Elastic sheet 6: Mounting member 7: Ring-shaped holding member 8: Sealed space 9: Pressure fluid supply path 10: Suction hole 11 … Connection pipe 12…
Connection member 12a: introduction hole W: wafer to be polished
T: Turntable C: Polishing cloth

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Makoto Tsukada 150 Odakura Osaikura, Nishishiro-mura, Nishishirakawa-gun, Fukushima Prefecture Inside Shirakawa Plant, Shin-Etsu Semiconductor Co., Ltd. 150, Ohira Shin-Etsu Semiconductor Co., Ltd. Shirakawa Plant (56) References JP-A-2-232158 (JP, A) JP-A 5-69310 (JP, A) (58) Fields studied (Int. Cl. ⁶ , (DB name) B24B 37/04 B24B 37/00

Claims (3)

(57) [Claims] 1. A wafer polishing method in which a wafer to be polished is pressed against a polishing surface of a turntable by a top ring and polished into a mirror surface, and a lower end of the top ring is pressurized.
The plate is not connected to the top ring via the elastic sheet
It is suspended so that it can move freely in the relationship,
Between the pressure plate and the pressure plate.
On the lower side, the wafer chuck is made of a material that can be elastically deformed.
This wafer is attached via the formed fixture
The wafer to be polished is sucked and held by the chuck, and the
Supply pressure fluid to the closed space and rotate the turntable
Free movement of the pressure plate even when slight runout occurs
Therefore, it is easy to follow and the turntable
Large polishing resistance on the lower surface of the wafer to be polished on the entry side
Even if it acts, a rotational moment is generated in the fixture.
A wafer polishing method, wherein the pressing force is always kept constant . 2. A et provided at the lower end of the top ring for axial rotation
The pressurized plate holding part and the wafer chuck that sucks and holds the wafer to be polished on the lower side are made of an elastically deformable material.
And a pressure plate attached through the formed fastener, preparative this pressure plate to the pressure plate holding part
So that it can move freely regardless of
Mento with Jisuru suspended so as not to cause, Li to form a closed space between the pressure plate and the pressure plate holding unit
A top ring for polishing a wafer, comprising: a ring-shaped elastic sheet; a mechanism for supplying a pressurized fluid into the closed space; and a mechanism for sucking and discharging compressed air to and from the wafer chuck. 3. A plurality of wafer chucks are arranged on a pressure plate.
The inner peripheral part of the ring-shaped elastic sheet is fixed to the fixture
And the outer periphery is attached to the pressure plate holder.
To the top ring
The holding shaft is connected to the through hole of the wafer chuck through a connection tube.
And a pressure fluid supply that communicates with the enclosed space.
3. A feed line is provided in parallel.
The top ring for wafer polishing according to the above.