JPH10209090A - Polishing method and polishing equipment of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable effectively flatening the surface of a work wherein step- differences are generated on the surface, with a small working amount and a short working time, by polishing the surface while electric field is generated between the abrasive cloth and the work to electrically attract abrasive grains to the abrasive cloth side. SOLUTION: The surface of a silicon wafer (work) 1 having protrusion patterns 1d on the surface is polished by supplying colloidal silica 8 in the sate of suspension to a gap between the surface and an abrasive cloth 5 which is relatively moved coming into contact with the wafer 1 and composed of polyurethane form. The colloidal silica 8 is charged to negative polarity in suspension 7 whose PH is adjusted, stably separated and levitated. Since the colloidal silica 8 is forcibly attracted to the abrasive cloth 5 with electrostatic force by a voltage applying means 22, the colloidal silica 8 does not act on the bottom of a recessed part 1e on the surface of the wafer 1, and protruding parts 1d are selectively worked. Thereby the surface of the wafer 1 on which step-differences are generated can be flatened with small working amount and short working time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for forming a laminated wiring on a semiconductor wafer surface, and polishing and flattening a convex pattern or the like generated on the surface of an intermediate layer laminated on a circuit by wiring or the like. And a polishing apparatus for semiconductors.

[0002]

2. Description of the Related Art In recent years, integrated circuits formed on the surface of a semiconductor wafer have been increasingly densified, and three-dimensional laminated wirings for forming circuits have been formed on the integrated circuits.

In the step of performing the laminated wiring, as shown in FIG. 4, the upper layer 1 formed on the circuit 1b by wiring or the like on the surface 1a of the silicon wafer (work) 1 is formed.
On the surface of c, a convex pattern 1d is formed according to the thickness and arrangement of the circuit 1b. Now, because of the step H caused by the convex pattern 1d, a very fine and high-density circuit cannot be formed when a circuit is formed on the surface of the upper layer 1c. Is polished and flattened.

An example of a conventional semiconductor polishing apparatus used for this purpose is shown in FIGS. 5 and 6. The polishing method is such that a silicon wafer 1 having a convex pattern 1d on its surface is rotated by a rotation axis L. This is held around by a chuck 42 to which a load W is applied while being rotated around, and is uniformly pressed against a foamed polyurethane polishing cloth 41 held by a platen 43 which is rotated around a rotation axis M that is offset from the rotation axis L. The suspension 7 of polishing abrasive grains 8 such as colloidal silica is appropriately supplied between the polishing cloth 41 and the silicon wafer 1 to polish and flatten the surface of the silicon wafer 1. Abrasive paper or the like on which abrasive grains are adhered and fixed is generally used because of problems such as a change in polishing action force due to abrasion of the abrasive grains and damage to the silicon wafer 1 due to poor removability of polishing debris. Is not used.

[0005]

In order to efficiently flatten the surface of a work such as the silicon wafer 1, only the convex pattern 1d on the surface of the silicon wafer 1 needs to be selectively removed. In the polishing method and the semiconductor polishing apparatus, as shown in FIGS.
Also causes a processing action on the lower part 1e of the surface of the silicon wafer 1, so that the processing amount and the processing time are considerably longer than the removal amount of only the step H of the convex pattern 1d before the surface of the silicon wafer 1 becomes flat. This is disadvantageous in terms of cost, and at the end of polishing, since the difference in the processing amount between the portions of the silicon wafer 1 becomes large, problems such as short-circuiting of the upper and lower layer circuits 1b are likely to occur depending on the portion. There is such a problem.

The present invention has been made in view of the above problems, and provides a polishing method and a semiconductor polishing apparatus capable of efficiently planarizing the surface of a work having a step on the surface with a small processing amount and processing time. The purpose is to:

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a polishing method in which abrasive grains are supplied between a polishing cloth and a workpiece which relatively moves while contacting the workpiece with the workpiece. In the polishing method, the polishing is performed while generating an electric field between the polishing cloth and the work so that the polishing grains are electrically attracted toward the polishing cloth.

Further, the present invention provides a polishing cloth which moves a surface of a semiconductor as a work relative to the semiconductor while contacting the semiconductor, a charged polishing abrasive supplied in a suspended state between the polishing cloth and the semiconductor. In a semiconductor polishing apparatus for polishing using a, a work holding means for holding a semiconductor, a tool holding means for holding the polishing cloth, the work holding means capable of generating a potential difference between the polishing cloth and the work, and An electrode provided on the tool holding means and a voltage applying means for applying a DC voltage between the pair of electrodes are provided.

According to the polishing method and the semiconductor polishing apparatus of the present invention, the charged polishing abrasive grains supplied in a suspended state are forcibly sucked into the polishing cloth by the electrostatic force of the voltage applying means. The abrasive grains do not act on the bottom of the concave portion on the work surface, and the convex portion on the work surface is selectively processed. Therefore, the surface of the work having a step on the surface can be efficiently planarized with a small processing amount and processing time.

[0010] In the polishing method of the present invention, the polishing cloth is held on the opposite side of the work side of the bag-like elastic member having an internal pressure, and the work surface is polished while urging the elastic member against the work surface. With this configuration, the surface can be polished while applying a uniform contact pressure to the entire surface of the work by the bag-shaped elastic member having an internal pressure, so that the convex portions of the surface can be simultaneously selected over the entire surface of the work. Even if the held work is warped, only the protrusions on the entire surface of the work can be efficiently removed with a small processing amount and processing time.

In the polishing method of the present invention, the surface of the workpiece is polished while rotating the workpiece about a workpiece rotation axis perpendicular to the workpiece surface and rotating the polishing cloth about a tool rotation axis away from the workpiece rotation axis. With such a configuration, in any part on the surface of the work, the part on the polishing cloth corresponding to the part, the movement direction and the movement speed are almost randomized, and the same processing action can be given, so that Even for a work having a large size, the surface of the work can be polished uniformly and flattened efficiently.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

In one embodiment of the semiconductor polishing apparatus of the present invention, as shown in FIGS. 1 to 3, the surface of a silicon wafer (work) 1 having a convex pattern 1d on its surface is The present invention relates to a polishing pad 5 made of foamed polyurethane that moves relatively while contacting with it, and a method of supplying suspended colloidal silica 8 between the polishing pad 5 and the silicon wafer 1 for polishing. In addition, this colloidal silica 8 is
In the pH-adjusted suspension 7, the negative electrode is spontaneously and stably charged to the negative electrode, and is therefore stably dispersed and suspended in the suspension 7.

As shown in FIG. 1, the semiconductor polishing apparatus comprises a work holding means 2 for holding a silicon wafer 1;
Tool holding means 3 for holding the polishing cloth 5, support means 20 for supporting the tool holding means 3 so as to be able to retract upward,
A moving means 21 for moving the supporting means 20 in a position controllable manner in the horizontal direction Q, and a voltage applying means (DC power supply) 22 for generating a potential difference between the polishing pad 5 and the work 1 are provided.

The work holding means 2 comprises a metal chuck 4 for adsorbing the silicon wafer 1, a rotary table 28 for supporting the chuck 4, and a rotary table 28 for rotating the rotary table 28 around a work rotation axis L via a belt 29. And a motor 26 for driving. The chuck 4 is provided with a pan 9 for holding a suspension 7 of colloidal silica 8 so that the silicon wafer 1 is immersed therein. The negative electrode power supply brush 24 of the voltage applying means 22 is in contact with the chuck 4 at one position on the side surface of the cylindrical portion.
“a” also serves as the electrode surface on the silicon wafer 1 side.

The tool holding means 3 has a rubber-made hemispherical shell-like elastic member 10 having an abrasive cloth 5 adhered to the outer surface facing the silicon wafer 1 side, and holds the opening of the elastic member 10 in an airtight manner. A holder 11 made of resin, a spindle 6 made of metal for supporting the holder 11, and a motor 27 for rotating the spindle 6 around a tool rotation axis M via a belt 30 are provided.

The elastic member 10 and the holder 11 are both insulating and form a space 14 filled with oil 15 therebetween, and the electrode surface 23a of the electrode 23 is connected to the elastic member 10 and the holder 11. Stored without contact.

A positive electrode power supply brush 25 of a voltage applying means 22 is in contact with the spindle 6 at one position on the side surface of the cylindrical portion. I have. The spindle 6 is located in the space 14
The space 15 is filled with the oil 15 together with the space 14, and the upper end opening of the hollow part 19 is provided with a pressure setting means 13 through a rotary joint 12.
Is connected, and a desired contact pressure P is applied to the surface of the silicon wafer 1 via the elastic member 10 by adjusting the internal pressure of the space 14.

The support means 20 includes an air cylinder 31 for retracting the tool holding means 3 upward along the guide 32 when the silicon wafer 1 and the polishing cloth 5 are replaced, a guide 32, and the tool holding means 3 for polishing. And a lower end stopper 33 for positioning the lower end at the lower end.

The moving means 21 includes a horizontal guide 16 for holding the supporting means 20 so as to be movable in the horizontal direction Q, and a supporting means 2.
And a servomotor 18 for controlling the position of the horizontal direction Q of 0 through a ball screw 17.

The voltage applying means 22 uses the power supply brush 24, which is in contact with the chuck 4 on the silicon wafer 1 side, as a negative electrode,
Power supply brush 25 abutting on spindle 6 on polishing cloth 5 side
And a DC power supply 22 for applying a DC voltage between the pair of power supply brushes 24 and 25.

The polishing method according to the above-described structure includes the following S1
This is performed in step S8.

S1: The tool holding means 3 is retracted upward by the air cylinder 31 of the support means 20, and the silicon wafer 1 is attracted to the upper surface 4a of the chuck 4.

S 2: The suspension 7 of the colloidal silica 8 whose pH has been adjusted is poured into the pan 9 above the polished surface of the silicon wafer 1.

S3: The tool holding means 3 is positioned at the lower end by the stopper 33 of the support means 20.

S4: The pressure of the oil 15 in the elastic member 10 is adjusted by the pressure setting means 13 so that the polishing cloth 5 applies a desired contact pressure P to the surface of the silicon wafer 1.

S5: A DC voltage is applied between the chuck 4 and the spindle 6 by the voltage applying means 22 so that the colloidal silica 8 repels the silicon wafer 1 and is attracted to the polishing cloth 5 side.

S6: The silicon wafer 1 is rotated about the rotation axis L by the motor 26, the polishing pad 5 is rotated about the rotation axis M by the motor 27, and the tool holding means 3 is previously moved in the horizontal direction Q by the moving means 21. The surface of the silicon wafer 1 is polished while being moved based on the set movement pattern.

S7: When one polishing is completed, the above S1
Steps S6 to S6 are repeated. These procedures may be automatically operated by a robot (not shown), and the above steps S2 and S4 may be performed only when necessary.

According to the above-described embodiment, the charged colloidal silica 8 supplied in the suspended state is forcibly sucked into the polishing pad 5 by the electrostatic force of the voltage applying means 22, so that it is on the surface of the silicon wafer 1. The colloidal silica 8 does not act on the bottom of the concave portion 1e, and the convex portion 1d on the surface of the silicon wafer 1 is selectively processed. Therefore, the surface of the silicon wafer 1 having the step H on the surface can be efficiently planarized with a small processing amount and processing time.
In addition, the polishing pad 5 applies a uniform contact pressure P to the surface of the silicon wafer 1 by the pressure of the oil 15 via the elastic member 10.
Is added, even if the held silicon wafer 1 is warped, it can be efficiently flattened. Since the silicon wafer 1 is rotated around the work rotation axis L and the polishing pad 5 is polished while being rotated about the tool rotation axis M away from the work rotation axis L, the polishing is performed at any position on the surface of the silicon wafer 1. Also, every part on the polishing pad 5 comes into contact in every direction of movement to give the same level of processing action, and even the silicon wafer 1 having a large area can be efficiently flattened.

In the above-described embodiment, the colloidal silica 8 is used as the abrasive grains. However, the present invention is not limited to this, and can be charged in the suspension and electrically attracted to the polishing cloth 5 side. Any effect can be obtained, for example, with cerium oxide abrasive grains, and the same operation and effect as described above can be obtained.

Further, in the above embodiment, the work is the silicon wafer 1, but as is clear from the above description, the present invention is not limited to this, and the surface may have a step regardless of the conductor or the insulator. The same operation and effect as described above can be obtained for a certain work. When the work is a conductor, the work itself also functions as a work-side electrode.

In the above embodiment, the electrode 23 on the side of the polishing pad 5 is disposed above the elastic member 10 via the space 14. However, the present invention is not limited to this.
It is sufficient that an electric field can be efficiently generated therebetween. For example, a flexible electrode may be attached to the outer surface of the elastic member 10, and the polishing cloth 5 may be attached to this electrode via a flexible insulating member. .

[0034]

According to the polishing method and the semiconductor polishing apparatus of the present invention, the charged polishing abrasive grains supplied in the suspended state are forcibly sucked into the polishing cloth by the electrostatic force of the voltage applying means. The abrasive grains do not act on the bottom of the concave portion on the surface of the work such as a semiconductor, and the convex portion on the work surface is selectively processed. Therefore, the surface of the work having a step on the surface can be efficiently planarized with a small processing amount and processing time.

In the polishing method of the present invention, the polishing cloth is held on the opposite side of the work side of the bag-like elastic member having an internal pressure, and the work surface is polished while urging the elastic member against the work surface. With this configuration, the surface can be polished while applying a uniform contact pressure to the entire surface of the work by the bag-shaped elastic member having an internal pressure, so that the convex portions of the surface can be simultaneously selected over the entire surface of the work. Even if the held work is warped, only the protrusions on the entire surface of the work can be efficiently removed with a small processing amount and processing time.

In the polishing method of the present invention, the surface of the workpiece is polished while rotating the workpiece about a workpiece rotation axis perpendicular to the workpiece surface and rotating the polishing cloth about a tool rotation axis away from the workpiece rotation axis. With such a configuration, in any part on the surface of the work, the part on the polishing cloth corresponding to the part, the movement direction and the movement speed are almost randomized, and the same processing action can be given, so that Even for a work having a large size, the surface of the work can be polished uniformly and flattened efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a semiconductor polishing apparatus according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view illustrating one embodiment of the polishing method of the present invention.

FIG. 3 is an enlarged schematic view showing a partial cross section of a workpiece after polishing according to the present invention is completed.

FIG. 4 is an enlarged schematic view showing a partial cross section of an example of a work.

FIG. 5 is a schematic diagram showing a conventional example.

FIG. 6 is a partially enlarged cross-sectional view illustrating a conventional example upside down.

FIG. 7 is an enlarged schematic diagram showing a partial cross section of a work after polishing according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer (work) which has a convex pattern on the surface 2 Work holding means 3 Tool holding means 5 Polishing cloth 8 Colloidal silica (polishing abrasive) 10 Elastic member 22 DC power supply (voltage applying means) L Work rotation axis M Tool rotation axis

Claims (4)

[Claims] In a polishing method for supplying and polishing abrasive grains between a polishing cloth and a work, the surface of the work relatively moving while being in contact with the work, the polishing is performed between the polishing cloth and the work. A polishing method characterized in that polishing is performed while generating an electric field such that abrasive grains are electrically attracted to the polishing cloth side. 2. The polishing cloth according to claim 1, wherein the polishing cloth is held on a work-side surface of a bag-shaped elastic member having an internal pressure, and polishes the work surface while urging the elastic member against the work surface. Method. 3. The work surface is polished while rotating the work around a work rotation axis perpendicular to the work surface and rotating the polishing cloth about a tool rotation axis away from the work rotation axis. The polishing method as described above. 4. Using a polishing cloth which relatively moves the surface of a semiconductor as a workpiece while contacting the semiconductor, and charged polishing abrasive grains supplied in a suspended state between the polishing cloth and the semiconductor. In a semiconductor polishing apparatus for polishing, a work holding means for holding a semiconductor, a tool holding means for holding the polishing cloth, and the work holding means and the tool holding means capable of generating a potential difference between the polishing cloth and the work. And a voltage applying means for applying a DC voltage between the pair of electrodes.