JP7539520B2 - CMP Equipment - Google Patents

Description

The present invention relates to a CMP apparatus for CMP polishing of wafers.

In the field of semiconductor manufacturing, CMP apparatuses are known for planarizing semiconductor wafers (hereafter referred to as "wafers") such as silicon wafers.

The polishing apparatus described in Patent Document 1 is a polishing apparatus that applies chemical mechanical polishing, or so-called CMP (Chemical Mechanical Polishing) technology. As shown in FIG. 8, a polishing head 71 of a CMP apparatus 70 supplies compressed air via an air supply line 76 to an air chamber 75 formed in the gap between a carrier 72 and a membrane sheet 74 whose periphery is held by a retainer ring holder 73, and the wafer W is pressed against a polishing cloth 77 by the pressure of the compressed air to be polished. In addition, a membrane sheet 74 is attached to the upper surface of a retainer ring 78 that is pressed against the polishing cloth 77 during polishing, and a backing film 79 of urethane foam is interposed between the membrane sheet 74 and the wafer W.

As shown in FIG. 9, in this type of polishing device 70, the polishing head 71 vacuums the air chamber 75 via the air supply line 76, deforming the wafer W so that it adheres closely to the carrier 72, and then adsorbs and holds the wafer W while transporting it.

JP 2016-159385 A

However, the CMP apparatus described above can only supply positive pressure to the air chamber and polish based on the surface of the wafer, which may make it difficult to handle a wide variety of wafers.

As a result, technical problems arise that must be solved in order to perform CMP polishing on a wide variety of wafers, and the present invention aims to solve these problems.

In order to achieve the above-mentioned object, the CMP apparatus of the present invention comprises a polishing head capable of accommodating a wafer on a polishing pad in a non-adsorbed state, the polishing head comprising a porous chuck having an adsorption surface facing the upper surface of the wafer, a compressed air source supplying compressed air through the porous chuck to an air chamber formed between the wafer and the porous chuck, and an air layer forming means for gradually discharging the compressed air in the air chamber to the outside and adjusting the pressure with which the wafer is pressed against the polishing pad by an air layer of the compressed air retained in the air chamber , the air layer forming means corresponding to a second gap relatively smaller than a first gap between the wafer and the porous chuck, and gradually discharging the compressed air retained in the air chamber to the outside .

With this configuration, compressed air is supplied to the porous chuck, and the air layer formed between the wafer and the porous chuck presses the back surface of the wafer evenly, and the polishing head presses the wafer against the polishing pad, allowing air float polishing to be performed based on the front surface of the wafer.

In addition, in the CMP apparatus of the present invention, it is preferable that the air layer forming means is formed between a carrier that houses the porous chuck and a retainer that surrounds the carrier, and that the compressed air remaining in the air chamber is gradually discharged to the outside so that the upper surface of the wafer is uniformly pressed.

In addition, it is preferable that the polishing head of the CMP apparatus according to the present invention further comprises a negative pressure source that supplies a negative pressure for adsorbing the wafer to the porous chuck, and a switching means for selectively switching between the connection of the porous chuck and the negative pressure source and the connection of the porous chuck and the compressed air source.

In addition, it is preferable that the CMP apparatus according to the present invention performs at least one of air float polishing, in which the polishing head presses the wafer against the polishing pad with the air layer, or suction polishing, in which negative pressure is supplied to the air chamber to suction the wafer to the porous chuck and then press the wafer against the polishing pad.

With this configuration, in addition to air float polishing, the wafer is held by suction on the porous chuck due to the negative pressure supplied to the porous chuck, and the polishing head presses the wafer against the polishing pad, allowing suction polishing based on the back surface of the wafer. Then, by switching the switching valve, it is possible to switch between suction polishing and air float polishing as desired.

The present invention can handle a wide variety of wafers with a single polishing head.

FIG. 1 is a perspective view showing a CMP apparatus according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view showing a schematic view of a main part of a polishing head. FIG. 1 is a schematic diagram showing a process in which a wafer is adsorbed and held on a porous chuck and polished. FIG. 1 is a schematic diagram showing a state in which a wafer is polished while being pressed by air pressure. 13 is an enlarged view showing slurry residue adhered to the outer peripheral edge of the carrier. FIG. 13 is a schematic diagram showing a carrier provided with a water supply pipe. FIG. 4 is a schematic diagram showing how the surface of the carrier is cleaned. FIG. 1 is a schematic diagram showing air float polishing performed in a conventional CMP apparatus. 9 is a schematic diagram showing a state in which a wafer is suction-held in the CMP apparatus shown in FIG. 8 .

The embodiment of the present invention will be described with reference to the drawings. Note that in the following, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, it is not limited to that specific number, and it may be more or less than the specific number.

In addition, when referring to the shape or positional relationship of components, etc., this includes things that are substantially similar or similar to that shape, etc., unless otherwise specified or considered in principle to be clearly different.

In addition, drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional ratios of components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

Figure 1 is a perspective view showing a schematic diagram of a CMP apparatus 1 according to one embodiment of the present invention. The CMP apparatus 1 polishes one surface of a wafer W to a flat surface. The CMP apparatus 1 includes a platen 2 and a polishing head 10.

The platen 2 is formed in a disk shape and is connected to a rotating shaft 3 arranged below the platen 2. When the rotating shaft 3 is rotated by the drive of a motor 4, the platen 2 rotates in the direction of the arrow D1 in FIG. 1. A polishing pad 5 is attached to the upper surface of the platen 2, and CMP slurry, which is a mixture of an abrasive and a chemical agent, is supplied onto the polishing pad 5 from a nozzle (not shown).

The polishing head 10 is formed in a disk shape with a smaller diameter than the platen 2, and is connected to a rotating shaft 10a disposed above the polishing head 10. When the rotating shaft 10a is rotated by a motor (not shown), the polishing head 10 rotates in the direction of the arrow D2 in FIG. 1. The polishing head 10 can be raised and lowered in the vertical direction V by a lifting device (not shown). When polishing the wafer W, the polishing head 10 descends to press the wafer W against the polishing pad 5. The wafer W polished by the polishing head 10 is transferred by a wafer transport mechanism (not shown).

The operation of the CMP apparatus 1 is controlled by a control means (not shown). The control means controls each of the components that make up the CMP apparatus 1. The control means is, for example, a computer, and is composed of a CPU, memory, etc. The functions of the control means may be realized by control using software, or may be realized by something that operates using hardware.

Next, the polishing head 10 will be described. Figure 2 is a vertical cross-sectional view showing the main parts of the polishing head 10.

The polishing head 10 comprises a head body 20, a carrier 30, and a retainer 40.

The head body 20 is connected to the rotating shaft 10a and rotates together with the rotating shaft 10a. The head body 20 is connected to a dense body carrier 30 arranged below the head body 20 via a rotating part 21, and the head body 20 and the carrier 30 rotate in unison.

A storage section 32 is formed on the surface of the carrier 30 to store a porous chuck 31 made of a porous material. The lower surface (adsorption surface) 31a of the porous chuck 31 is formed to be approximately flat. Note that the adsorption surface 31a of the porous chuck 31 is not limited to being formed to be approximately flat, and may be, for example, one with a convex bulge or a concave depression in the center depending on the desired wafer shape after polishing. A small gap is secured between the porous chuck 31 and the wafer W, forming an air chamber A.

The storage section 32 is formed with a conduit 33 that opens into the storage section 32, and the conduit 33 is arranged coaxially with the rotation axis 10a of the polishing head 10 and is connected to a vacuum source and a compressed air source via a rotary joint (not shown).

A switching valve 33a is provided in the pipeline 33. The switching valve 33a can selectively switch between the connection between the porous chuck 31 and the vacuum source and the connection between the porous chuck 31 and the compressed air source. Note that the switching between the connection between the porous chuck 31 and the vacuum source and the connection between the porous chuck 31 and the compressed air source is not limited to a configuration using the switching valve 33a. For example, a pipeline 33 for supplying compressed air and a pipeline 33 for supplying negative pressure may be provided, and each pipeline 33 may be controlled to open and close as necessary.

A carrier pressing means 34 is provided between the head body 20 and the carrier 30. The carrier pressing means 34 is an air bag or the like that is inflated by air supplied from an air supply source (not shown). The pressure of the air supplied from the air supply source is adjusted by a regulator (not shown). The carrier pressing means 34 presses the wafer W against the polishing pad 5 via the carrier 30 according to the pressure of the supplied air.

The retainer 40 is arranged so as to surround the periphery of the carrier 30. The retainer 40 includes a retainer ring 41 that can contact the polishing pad 5, and a retainer ring holder 45. The retainer ring 41 is arranged so that the gap between the retainer ring 41 and the carrier 30 is relatively small compared to the gap between the porous chuck 31 and the wafer W. The retainer ring 41 is arranged with a small gap between it and the carrier 30, forming an air layer forming means 50.

The retainer ring 41 is made of a resin such as glass epoxy, polyether ether ketone (PEEK), or polyphenylene sulfide (PPS). The retainer ring 41 is formed in an annular shape and has a storage pocket 41a in the center for storing the wafer W. The retainer ring 41 and the retainer ring holder 45 are attached to a retainer pressing member 43 via a snap ring 42. A retainer pressing means 44 is provided between the head body 20 and the retainer pressing member 43. Reference numeral 45 denotes a cover that covers the top of the snap ring 42.

The retainer pressing means 44 is an air bag or the like that is inflated by air supplied from an air supply source (not shown). The pressure of the air supplied from the air supply source is adjusted by a regulator (not shown). The retainer pressing means 44 presses the retainer 40 against the polishing pad 5 via the retainer pressing means 44 according to the pressure of the air supplied.

Next, the operation of the CMP apparatus 1 will be described. First, the polishing (adsorption polishing) performed by adsorbing and holding the wafer W on the porous chuck 31 will be described with reference to FIG. 3.

When the vacuum source is activated, negative pressure is supplied through the porous chuck 31 into the air chamber A between the wafer W contained in the storage pocket 41a and the porous chuck 31, and the wafer W is adsorbed to the porous chuck 31 in a substantially flat manner.

When the wafer W is held by suction on the porous chuck 31, the carrier pressing means 34 is activated to press the carrier 30, and the wafer W is polished by pressing the front surface W2 of the wafer W against the polishing pad 5 with the back surface W1 facing the porous chuck 31 as a reference.

Next, we will explain polishing (air float polishing) performed while pressing the wafer W with compressed air, with reference to Figure 4.

When the compressed air source is activated, compressed air is supplied through the porous chuck 31 into the air chamber A between the wafer W contained in the storage pocket 41a and the porous chuck 31.

The compressed air supplied to the air chamber A is retained in the air chamber A by the air layer forming means 50, forming an air layer of compressed air, which presses the back surface W1 of the wafer W with uniform pressure. Specifically, the compressed air is gradually discharged to the outside through the air layer forming means 50, which is a small gap between the carrier 30 and the retainer ring 41, so that the air layer of compressed air retained in the air chamber A presses the back surface W1 of the wafer W with uniform pressure.

Then, the carrier pressing means 34 is activated to press the carrier 30, and the wafer W is pressed against the polishing pad 5 with the surface W2 facing the polishing pad 5 as a reference, and is polished.

The CMP apparatus 1 may perform either the suction polishing or the air float polishing described above, or may perform both in sequence.

For example, when only suction polishing is performed, the polishing head 10 suction-holds the wafer W and transports the wafer W to the polishing pad 5, and then the wafer W can be quickly moved to CMP polishing while maintaining the suction-hold state of the wafer W.

In suction polishing, the wafer W rotates together with the polishing head 10 and is polished, so objects suitable for suction polishing are, for example, thin objects that are prone to break and whose edges may be damaged if they come into contact with the retainer ring 41.

When only air float polishing is performed, the polishing head 10 holds the wafer W by suction and transports the wafer W to the polishing pad 5, then releases the suction hold of the wafer W and places the wafer W on the polishing pad 5. Then, the process moves to air float polishing, and the wafer W is polished by CMP.

In air float polishing, polishing is performed based on the surface W2 of the wafer W, so objects suitable for air float polishing are, for example, relatively thick and strong. In this way, since it is possible to freely switch between suction polishing and air float polishing, a single polishing head 10 can be used to handle a wide variety of wafers W.

In addition, if negative pressure is supplied to air chamber A after air float polishing and suction polishing is performed while holding the wafer W flat, the same polishing head 10 can be used to polish the wafer using the wafer's front surface as a reference, and then polish the wafer using the wafer's back surface W1 as a reference.

In addition, after suction polishing, the suction holding of the wafer W is released, the wafer W is placed on the polishing pad 5, and air float polishing is started. In this case, the wafer W can be polished with the back surface of the wafer as a reference using the same polishing head 10, and then polished with the front surface of the wafer W as a reference.

In addition, when performing air float polishing after suction polishing, there is an advantage in that it is easier to suction-hold the back surface W1 of the wafer W flatly, since no slurry is interposed between the porous chuck 31 and the wafer W when the wafer W is suction-held, compared to when suction polishing is performed after air float polishing.

However, in a conventional CMP apparatus 70, as shown in FIG. 8, the wafer W side and the carrier 72 side are separated by a membrane sheet 74, so the slurry does not penetrate into the carrier 72 side.

However, in the CMP apparatus 1 according to this embodiment, it is conceivable that the slurry may pass between the wafer W and the retainer ring 41 and adhere to the carrier 30. If air float polishing is performed as shown in FIG. 4 with the slurry adhered to the carrier 30, the dried slurry residue may adhere to the outer peripheral edge of the carrier 30 as shown in FIG. 5, which may cause leakage when the wafer W is held by suction, resulting in poor suction.

To prevent such slurry residue from adhering to the adsorption surface 31a, it is preferable to adopt the following method.

For example, a water supply source is connected to the pipe 33 via a rotary joint (not shown). Then, instead of supplying dry compressed air, mist air obtained by mixing a small amount of moisture into compressed air is supplied. This makes it possible to prevent the slurry from drying and adhering to the outer periphery of the carrier 30, and to adsorb the wafer W along the adsorption surface 31a of the porous chuck 31, compared to when dry compressed air is supplied.

As shown in FIG. 6, a water supply pipe 35 connected to a water supply source may be provided in addition to the pipe 33, and dry compressed air may be supplied via the pipe 33, while moisture may be supplied via the water supply pipe 35. This prevents the slurry from drying and adhering to the outer peripheral edge of the carrier 30, and allows the wafer W to be adsorbed along the adsorption surface 31a of the porous chuck 31.

As shown in FIG. 7, a cleaning member 60 may be provided to clean the carrier 30 and the adsorption surface 31a of the porous chuck 31. The cleaning member 60 may be, for example, a sponge or a brush.

When cleaning the porous chuck 31 with the cleaning member 60, it is preferable to do so while the polishing head 10 is housed in the cleaning cup 61 in order to prevent the slurry residue from scattering.

It is preferable to perform cleaning with the cleaning member 60 each time one wafer W is polished, but cleaning may be performed after a predetermined polishing time, number of wafers, etc. is completed. This prevents slurry residue from adhering to the adsorption surface 31a of the porous chuck 31, and allows the wafer to be adsorbed along the adsorption surface 31a of the porous chuck 31.

In this way, the CMP apparatus 1 according to this embodiment is capable of performing adsorption polishing based on the back surface W1 of the wafer W by adsorbing and holding the wafer W to the porous chuck 31 through the negative pressure supplied to the porous chuck 31, and by the polishing head 10 pressing the wafer W against the polishing pad 5.

In addition, the compressed air supplied to the porous chuck 31 creates an air layer between the wafer W and the porous chuck 31 that uniformly presses the back surface W1 of the wafer W, and the polishing head 10 presses the wafer W against the polishing pad 5, allowing air float polishing to be performed based on the surface of the wafer W.

And because the suction polishing and air float polishing can be switched between as desired by switching the switching valve 33a, a single polishing head 10 can handle a wide variety of wafers W.

Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention extends to such modifications.

REFERENCE SIGNS LIST 1 CMP apparatus 2 Platen 3 Rotating shaft (of platen) 4 Motor 5 Polishing pad 10 Polishing head 10a Rotating shaft (of polishing head) 20 Head body 21 Rotating section 30 Carrier 31 Porous chuck 31a Adsorption surface 32 Storage section 33 Pipe 33a Switching valve (switching means)
Reference Signs List 34 Carrier pressing means 35 Water supply pipe 40 Retainer 41 Retainer ring 41a Storage pocket 42 Snap ring 43 Retainer pressing member 44 Retainer pressing means 45 Retainer ring holder 50 Air layer forming means 60 Cleaning member 61 Cleaning cup A Air chamber W Wafer

Claims (4)

a polishing head capable of accommodating a wafer on a polishing pad in a non-adsorbed state;
The polishing head includes:
a porous chuck having an adsorption surface facing an upper surface of the wafer;
a compressed air source that supplies compressed air through the porous chuck to an air chamber formed between the wafer and the porous chuck;
an air layer forming means for adjusting a pressure for pressing the wafer against the polishing pad by an air layer of the compressed air remaining in the air chamber ;
The CMP apparatus is characterized in that the air layer forming means corresponds to a second gap that is relatively smaller than the first gap between the wafer and the porous chuck, and gradually discharges the compressed air remaining in the air chamber to the outside. 2. The CMP apparatus according to claim 1, wherein the air layer forming means is formed between a carrier that accommodates the porous chuck and a retainer that surrounds the carrier , and gradually discharges the compressed air remaining in the air chamber to the outside so that the upper surface of the wafer is uniformly pressed. The polishing head includes:
a negative pressure source that supplies a negative pressure for adsorbing the wafer to the porous chuck;
A switching means for selectively switching between a connection between the porous chuck and the negative pressure source and a connection between the porous chuck and the compressed air source;
2. The CMP apparatus of claim 1, further comprising: The CMP apparatus according to claim 3, characterized in that the polishing head performs at least one of air float polishing, in which the air layer presses the wafer against the polishing pad, and suction polishing, in which negative pressure is supplied to the air chamber to press the wafer against the polishing pad while the wafer is suctioned to the porous chuck.