JPH1015789A - Method and apparatus for polishing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for polishing a semiconductor wafer which can gain sufficient efficiency without producing any flaws on the surface of the semiconductor wafer. SOLUTION: A wafer supporting board supporting a semiconductor wafer 12 is inserted into an opening part 42A of a polishing liquid vessel 42 to immerse the semiconductor wafer 12 in polishing liquid 44. Next, a combined piston and wafer supporting board 14 is forced further into a combined cylinder and opening part 42A to increase the static pressure of the polishing liquid 44. The wafer supporting board 14 is rotated to move the semiconductor wafer 12 relatively to the polishing liquid and polish the surface 12A of the semiconductor wafer 12. According to this method, only the polishing liquid contacts the surface 12A, so that any flaws are produced on the surface 12A. Further, the viscosity of the polishing liquid 44 is raised by increasing the static pressure of the polishing liquid 44 to improve the holding property of grsins, so that the sufficient polishing efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a semiconductor wafer, and more particularly to a method for polishing a semiconductor wafer by a relative movement between a polishing liquid and the semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, the density of semiconductor devices has been increased and the number of layers has been increased, and a technique of polishing a semiconductor wafer with high precision in a manufacturing process thereof has been regarded as important. Conventionally, a chemical mechanical polishing method has been used as one of the methods for that. This is a polishing method in which a polishing liquid is supplied dropwise onto the surface of a polisher, and the polisher and the semiconductor wafer are relatively moved while being pressed. In this method, polishing proceeds by wiping the surface of the semiconductor wafer with a polishing liquid or a polisher.

On the other hand, a float polishing method has been conventionally used. This is a polishing method in which a polishing liquid is poured into a container in which a polisher is fixed, and a semiconductor wafer is immersed therein so as to be opposed to the polisher, and the polisher and the semiconductor wafer are relatively moved without contacting each other. In this method, a flow occurs in the polishing liquid between the polisher and the semiconductor wafer due to the relative movement between the two. Then, the polishing proceeds as the surface of the semiconductor wafer is rubbed by this flow.

[0004]

However, in the conventional chemical mechanical polishing method, polishing is performed by pressing a polisher against the surface of the semiconductor wafer. And there is a disadvantage that excessive polishing is likely to occur. Furthermore, if the semiconductor wafer has a large diameter,
Although the polishing liquid permeates to some extent into the outer peripheral portion of the semiconductor wafer, the polishing liquid hardly permeates up to the central portion of the semiconductor wafer. Therefore, there is a difference in the amount of the supplied polishing liquid between the central portion and the outer peripheral portion of the semiconductor wafer, and there is a disadvantage that the polishing is not performed uniformly.

On the other hand, the conventional float polishing method has a drawback that the polishing efficiency is extremely low because the polishing is performed simply by rubbing the surface of the semiconductor wafer with the flow of the polishing liquid. The present invention has been made in view of such circumstances, and it is possible to perform polishing with high in-plane uniformity without causing scratches on the surface of a semiconductor wafer, and to obtain sufficient polishing efficiency. It is an object of the present invention to provide a method and an apparatus for polishing a semiconductor wafer which can be performed.

[0006]

In order to achieve the above object, the present invention provides a method for polishing a semiconductor wafer in which a polishing liquid is brought into contact with a semiconductor wafer and the two are relatively moved to polish the semiconductor wafer. The semiconductor wafer is immersed in the polishing liquid filled in the container, the container is sealed, and polishing is performed while controlling the static pressure of the polishing liquid in the container.

In the polishing method of the present invention, first, a polishing liquid is filled in a container, and a semiconductor wafer is immersed in the polishing liquid to seal the container. Next, the static pressure of the polishing liquid in the container is controlled, and the semiconductor wafer and the polishing liquid are relatively moved to polish the semiconductor wafer. According to this method, no surface other than the polishing liquid comes into contact with the surface of the semiconductor wafer, so that no scratch occurs. Also, since the polishing liquid is uniformly supplied to the entire surface of the semiconductor wafer,
Polishing with high in-plane uniformity can be performed. Further, by increasing the static pressure of the polishing liquid, the viscosity of the polishing liquid can be increased, and when the abrasive particles are suspended in the polishing liquid, the retention of the abrasive particles can be improved. Therefore, sufficient polishing efficiency can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method and an apparatus for polishing a semiconductor wafer according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a main structure of a polishing apparatus 10 according to a first embodiment of the present invention. The polishing apparatus 10 mainly includes a wafer support mechanism, a polishing liquid container, and a cylinder / piston mechanism.

First, the wafer support mechanism will be described.
This mechanism is for holding, rotating, and moving the semiconductor wafer 12, and is composed of a wafer support board 14, a motor 16 for rotating the wafer support board 14, and a hydraulic cylinder 18 for moving the whole of the board vertically in the drawing. I have. The lower surface of the wafer support plate 14 is held by air suction with the surface 12A on which the semiconductor wafer 12 is polished facing downward. The wafer support plate 14 is also used as a piston in a cylinder / piston mechanism described later, and a packing 20 is attached to the peripheral surface. Further, a rotary shaft 22 is fixed to the center of the upper part of the wafer support plate 14, and the rotary shaft 22 is connected to a spindle of the motor 16 mounted on a base 28 via gears 24 and 26. Therefore, when the motor 16 is driven to rotate, the wafer support board 14 is rotated at a predetermined speed in the direction indicated by the arrow a in the figure.

The rotary shaft 22 is supported by a base 28 via a bearing 29. This base 28
Is vertically movably supported by a guide 32 installed on the column 30 via a linear motion bearing (not shown). Further, a rod 34 of the hydraulic cylinder 18 is provided above the rotating shaft 22 with the coupling 36 and the load cell 3.
8 are fixed. This load cell 38
This is for detecting a compressive stress between the rotating shaft 22 and the rod 34. The hydraulic cylinder 18 is attached to the column 30 via the arm 40. Therefore, when the rod 34 expands and contracts by the hydraulic cylinder 18, the rotating shaft 22 moves up and down, and the wafer support board 14 moves up and down as shown by the arrow b in the figure.

Next, the polishing liquid container will be described. The polishing liquid 44 is filled in the polishing liquid container 42 and the airbag 4
6, a propeller 48, a heater 50 and a temperature sensor 52 are immersed in the polishing liquid 44 and arranged. The polishing liquid 44
Is a colloidal suspension of abrasive grains in an alkaline solution.

The airbag 46 is provided for controlling the static pressure of the polishing liquid 44. The airbag 46 is
It is expandable and contractable, and is connected to an air pump 56 via an air regulator 54. Therefore, the inside of the airbag 46 is pressurized by sending the pressurized air by the air pump 56. The pressure of the sent air is adjusted by the air regulator 54, so that the internal pressure of the airbag 46 is adjusted and the static pressure of the polishing liquid 44 is controlled.

The propeller 48 is provided to stir the polishing liquid 44 and is connected to a motor 60 via a shaft 58. Therefore, when the motor 60 is driven to rotate, the propeller 48 is rotated, and the polishing liquid 44 is stirred. The heater 50 and the temperature sensor 52
4 for controlling the temperature, and is connected to a temperature controller 62. Temperature controller 62
The heater 50 maintains the polishing liquid 44 at a predetermined temperature while the temperature sensor 52 detects the temperature of the polishing liquid 44.

An opening 42A into which the wafer support board 14 is inserted is formed in an upper portion of the polishing liquid container 42. The opening 42A is also used as a cylinder in a cylinder / piston mechanism to be described later.
The inner wall of 2A is formed so as to circumscribe the packing 20 of the wafer support board 14. Next, the cylinder / piston mechanism will be described. This mechanism is for controlling the static pressure of the polishing liquid 44. As described above, in the polishing apparatus 10, the cylinder is connected to the opening 42 of the polishing liquid container 42.
A, the piston also serves as the wafer support board 14. Then, the wafer support board 14 is inserted into the opening 42A by the operation of the hydraulic cylinder 18 and further moved up and down, so that the polishing liquid 44 in the polishing liquid container 42 is
Is controlled.

Here, a method for polishing the semiconductor wafer 12 by the polishing apparatus 10 configured as described above will be described. First, the semiconductor wafer 12 is mounted on the wafer support plate 14 with the surface 12A to be polished down. Further, the polishing liquid 44 is filled in the polishing liquid container 42. Next, the hydraulic cylinder 18 is operated to set the wafer support plate 1
4 is inserted into the opening 42A, and the semiconductor wafer 12 is immersed in the polishing liquid 44. At this time, the packing 20 of the wafer support plate 14 is inscribed in the inner wall of the opening 42A, so that the polishing liquid container 42 is sealed. And the wafer support board 1
4 is further pressed into the opening 42A to increase the static pressure of the polishing liquid 44, and at the same time, the semiconductor wafer 12 and the polishing liquid 44 are caused to move relative to each other by rotating the wafer support plate 14, thereby performing polishing.

According to this polishing method, the surface 12A has
Since there is no contact other than the polishing liquid 44, no scratch is caused. In addition, since the polishing liquid 44 is uniformly supplied to the entire surface 12A, polishing with high in-plane uniformity can be performed. Now, when the static pressure of the polishing liquid 44 is increased, the polishing liquid 4
Since the viscosity of No. 4 increases and the retention of abrasive grains increases, the polishing efficiency increases. Therefore, the polishing efficiency can be controlled by controlling the static pressure of the polishing liquid 44.

The static pressure of the polishing liquid 44 can be controlled by vertically moving the wafer support plate 14 inserted into the opening 42A. At this time, the static pressure of the polishing liquid 44 can be detected through the load cell 38. The control of the static pressure of the polishing liquid 44 can also be performed by adjusting the internal pressure of the airbag 46. At this time, the static pressure of the polishing liquid 44 can be detected through the air regulator 54. According to this method, since it is not necessary to move the wafer support plate 14 during polishing, control is easy.

Further, the polishing liquid 44 is
Is agitated to make the semiconductor wafer 12 uniform. In addition, by controlling the temperature of the polishing liquid 44 by the temperature controller 62, the reactivity between the polishing liquid 44 and the semiconductor wafer 12 can be controlled, and the polishing efficiency can be controlled.

Next, FIG. 2 shows a main structure of a polishing apparatus 70 according to a second embodiment of the present invention. In FIG. 2, FIG.
The same reference numerals as in FIG. 1 denote the same or similar members as in the polishing apparatus 10 of the first embodiment shown in FIG. 1, and a description thereof will be omitted. In this polishing apparatus 70, the polishing liquid container 4
A lid 72 is provided to seal 2. The lid 72 has a bearing 7 on the rotating shaft 22 passing through the center thereof.
4 and is moved up and down integrally with the wafer support plate 14.

In order to control the static pressure of the polishing liquid 44, a cylinder 76 communicating with the polishing liquid container 42 and a piston 78 inscribed in the cylinder 76 are provided. In this polishing apparatus 70, the lid 72 is
The polishing liquid container 42 is hermetically closed by being brought into close contact with the upper end of A. The piston 78 is moved by a mechanism (not shown).
The piston 78 is expanded and contracted so that the piston 78
By moving in and out of 6 as shown by arrow c in the figure,
The static pressure of the polishing liquid 44 is controlled.

Next, FIG. 3 shows a main structure of a polishing apparatus 90 according to a third embodiment of the present invention. In FIG. 3, FIG.
The same reference numerals as those in FIGS. 1 and 2 denote the same or similar members as those of the polishing apparatus 10 of the first embodiment shown in FIG. 2 and the polishing apparatus 70 of the second embodiment shown in FIG. The description is omitted. In this polishing apparatus 90, the wafer support board 14 is also used as a lid for the opening 42A. A rod 92 is fixed to the upper center of the wafer support board 14, and the rod 92 is fixed to the base 28.

A stirrer 94 as a magnet is immersed in the polishing liquid 44 in order to stir the polishing liquid 44. Further, a bar magnet 96 and a motor 98 connected to the bar magnet 96 are provided outside the polishing liquid container 42 at a position facing the stirrer 94.
Is arranged. The stirrer 94, the bar magnet 96 and the motor 98 constitute a magnetic stirrer. Accordingly, when the rod magnet 96 is rotated in the direction of arrow d in the figure by the motor 98, the stirrer 94 is rotated in the same direction, and the polishing liquid 44 is stirred.

In the polishing apparatus 90, the polishing liquid container 42 is sealed by bringing the wafer support plate 14 into close contact with the upper end of the opening 42A. Then, the wafer support plate 14 is not rotated, and the polishing liquid 44 is
Is stirred, whereby the semiconductor wafer 12 and the polishing liquid 44 are moved relative to each other to perform polishing. In the above-described embodiment of the present invention, a polishing liquid 44 in which abrasive grains are dispersed in a colloidal form in an alkaline solution is used. However, without being limited to this, an appropriate polishing liquid may be selected according to the purpose of polishing.

Further, the wafer support board 14 holds the semiconductor wafer 12 by sucking air. However, without being limited to air suction, it may be held by other appropriate means. In addition, since the movement of the wafer support plate 14 and the polishing liquid container 42 may all be relatively performed, for example, the wafer support plate 14 may be fixed and the polishing liquid container 42 may be moved.

Although the hydraulic cylinder 18 is used to move the wafer support board 14 up and down, another moving device such as a screw feeder may be used. Also,
An air bag 46 and an air regulator 54 serve as a bag for controlling the static pressure of the polishing liquid 44 and a pressure control device in the bag.
Although a device using air as a pressure medium is used, the device including the air pump 56 and the air pump 56 may be used.

As a method of stirring the polishing liquid 44,
Although the method using the propeller 48 and the stirrer 94 is used,
Other methods may be used. For example, a method in which a magnetic fluid or magnetic abrasive grains are mixed with the polishing liquid 44 and the polishing liquid 44 is moved by changing an external magnetic field may be used. Further, the polishing liquid 44 may be vibrated using ultrasonic waves. Further, a heater 50 and a temperature sensor 5 serving as temperature control means are provided.
The installation place of 2 is not limited to the inside of the polishing liquid container 42, but may be any place where the temperature of the polishing liquid 44 can be controlled. For example, it may be embedded in the wall of the polishing liquid container 42.

[0027]

As described above, according to the method for polishing a semiconductor wafer of the present invention, since the surface other than the polishing liquid does not come into contact with the surface of the semiconductor wafer, no scratch is generated. Further, since the polishing liquid is uniformly supplied to the entire surface of the semiconductor wafer, it is possible to perform polishing with high in-plane uniformity. Further, since the viscosity of the polishing liquid is increased by increasing the static pressure of the polishing liquid, and the retention of the abrasive grains is increased, sufficient polishing efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a main part structural diagram of a polishing apparatus according to a first embodiment of the present invention.

FIG. 2 is a main part structural view of a polishing apparatus according to a second embodiment of the present invention.

FIG. 3 is a main part structural view of a polishing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Polishing apparatus 12 ... Semiconductor wafer 14 ... Wafer support board 42 ... Polishing liquid container 44 ... Polishing liquid 46 ... Airbag 48 ... Propeller 50 ... Heater 70 ... Polishing apparatus 76 ... Cylinder 78 ... Piston 90 ... Polishing apparatus 94 ... Stirrer

Claims (8)

[Claims] 1. A semiconductor wafer polishing method for polishing a semiconductor wafer by bringing a polishing liquid into contact with a semiconductor wafer and causing the two to move relative to each other, wherein the semiconductor wafer is immersed in the polishing liquid filled in a container, A method for polishing a semiconductor wafer, comprising sealing the container and performing polishing while controlling the static pressure of the polishing liquid in the container. 2. A semiconductor wafer polishing apparatus for polishing a semiconductor wafer by bringing a polishing liquid into contact with a semiconductor wafer and causing the two to move relative to each other, wherein: a support portion for supporting the semiconductor wafer; A polishing liquid container having a receiving port formed so that a wafer can be inserted therein, and relatively inserting the semiconductor wafer into the receiving port,
An insertion mechanism for immersing the semiconductor wafer in the polishing liquid filled in the polishing liquid container; sealing means for sealing the polishing liquid container; and controlling a static pressure of the polishing liquid in the polishing liquid container. A semiconductor wafer polishing apparatus, comprising: a pressure control mechanism; and a polishing movement mechanism that relatively moves the semiconductor wafer and the polishing liquid. 3. The semiconductor wafer polishing apparatus according to claim 2, wherein said pressure control mechanism is a cylinder / piston mechanism communicating with said polishing liquid container. 4. The semiconductor according to claim 3, wherein the cylinder part of the cylinder / piston mechanism is also used by the polishing liquid container, and the piston part of the cylinder / piston mechanism is also used by the support part. Wafer polishing equipment. 5. The pressure control mechanism controls a static pressure of the polishing liquid by variably controlling an inner pressure of the bag, which is immersed and arranged in the polishing liquid. 3. The semiconductor wafer polishing apparatus according to claim 2, comprising: a pressure control device in the bag. 6. The semiconductor wafer polishing apparatus according to claim 2, wherein said polishing movement mechanism is a rotating mechanism for rotating said semiconductor wafer and said polishing liquid container relatively. 7. The semiconductor wafer polishing apparatus according to claim 2, wherein said polishing movement mechanism is a stirring mechanism for stirring said polishing liquid. 8. A polishing apparatus according to claim 2, further comprising temperature control means for controlling a temperature of said polishing liquid in said polishing liquid or adjacent to said polishing liquid container. 8. The semiconductor wafer polishing apparatus according to 6 or 7.