CN101342679A - A polishing head for chemical mechanical polishing - Google Patents

Abstract

The invention discloses a polishing head for chemical mechanical polishing, comprising: a base, an annular groove in the lower edge region of the base; a retaining ring diaphragm, fixed under the base, and the ring A retaining ring chamber is formed by a groove shaped like a retaining ring; the retaining ring is floated below the retaining ring chamber through the retaining ring diaphragm, and the retaining ring is provided with a pocket area directly below the base to accommodate crystal Circle; multi-chamber diaphragm, the multi-chamber diaphragm has a disc-shaped plane on which a plurality of concentric annular ribs are integrated, and the disc-shaped plane, concentric annular ribs and the lower surface of the base form a plurality of Independent concentric annular chambers. In the polishing process of the present invention, different low down pressures can be applied to different regions of the backside of the wafer through the concentric annular chamber, thereby obtaining better uniformity.

Description

A polishing head for chemical mechanical polishing

technical field

The invention relates to the technical field of integrated circuit manufacturing, in particular to a polishing head for chemical mechanical polishing.

Background technique

In the manufacturing process of integrated circuits, due to the continuous reduction of feature size and the continuous increase of the number of metal interconnection layers, the depth of focus of pattern exposure becomes smaller and smaller. To realize multi-layer wiring, the surface of the wafer must have high uniformity, and CMP (Chemical-Mechanical Polish, chemical mechanical polishing) technology is currently the most effective global planarization technology.

CMP technology is to hold the wafer to be polished by the polishing head and press it on the polishing pad with a certain pressure. During the polishing process, the polishing head drives the wafer to rotate along the rotation axis, and the polishing pad rotates along the other rotation axis. The polishing liquid composed of abrasive grains and chemical solution flows between the wafer and the polishing pad, and the surface is planarized through the joint action of chemical and mechanical. During the polishing process, the polishing head plays the role of clamping the wafer and exerting a downforce on its backside, which is the key to achieving surface planarization.

In the existing CMP technology, it is known that there are various reasons that can cause the non-uniformity of the wafer surface. These reasons include: non-uniform down force applied to the backside of the wafer, edge effects due to the typical difference in the action of the polishing pad at the edge and center of the wafer, non-uniform deposition of the metal/oxide layer, etc. Efforts to address these issues simultaneously have so far been unsuccessful.

At the same time, with the continuous shrinking of the feature size, in order to reduce the RC (resistance capacitance) delay, the introduction of copper interconnection and low-k materials has become inevitable. However, the porous structure of low-k materials makes its mechanical properties very poor. The conventional downforce (2.0-6.0psi) in the CMP process can no longer meet the requirements, and low downforce (<2.0psi) must be used, which requires the polishing head Make corresponding improvements.

Contents of the invention

The problem to be solved by the embodiments of the present invention is to provide a polishing head for chemical mechanical polishing, so as to achieve better uniformity in the polishing process.

In order to achieve the above object, the technical solution of the embodiment of the present invention provides a polishing head for chemical mechanical polishing, the polishing head includes:

a base with an annular groove in the lower edge area of the base;

The retaining ring diaphragm is fixed under the base and forms a retaining ring chamber with the annular groove;

a retaining ring floating below the retaining ring chamber through the retaining ring diaphragm, and the retaining ring is provided with a pocket area directly below the base for accommodating wafers;

A multi-chamber diaphragm, the multi-chamber diaphragm has a disc-shaped plane on which a plurality of concentric annular ribs are integrated, and the disc-shaped plane, concentric annular ribs and the lower surface of the base form a plurality of mutually independent concentric annular chambers.

Wherein, the retaining ring chamber contains gas or liquid, and the pressure of the gas or liquid is transmitted to the retaining ring through the retaining ring diaphragm to form a downward force.

Wherein, the multiple independent concentric annular chambers contain gas or liquid, and the pressure of the gas or liquid is transmitted to the wafer through the multi-chamber diaphragm to form a downward force.

Wherein, the pressure of the gas or liquid in the retaining ring chamber can be adjusted.

Wherein, the pressure of the gas or liquid in the plurality of mutually independent concentric annular chambers can be adjusted separately.

Wherein, the end of the concentric annular rib has an annular flat plate perpendicular to the concentric annular rib for fixing with the base.

Wherein, the plurality of mutually independent concentric annular chambers is 3-5.

Wherein, the materials of the retaining ring diaphragm and the multi-chamber diaphragm are elastic materials, and the elastic materials include fluorine rubber, silicon rubber or polyurethane rubber.

Wherein, the fixing method of the retaining ring diaphragm and the base and the fixing method of the multi-chamber diaphragm and the base are pasting and/or mechanical connection.

Wherein, the lower part of the retaining ring has a plurality of radially opened and uniformly distributed grooves, and the grooves are used for liquid and grinding discharge in/out channels during the polishing process.

Compared with the prior art, the technical solution of the present invention has the following advantages:

In the embodiment of the present invention, during the polishing process, the polishing head can adjust the downforce acting on different regions on the wafer according to the multi-chamber diaphragm, and can adjust the downforce acting on the retaining ring according to the retaining ring diaphragm, while the multi-chamber diaphragm The design of the diaphragm and retaining ring enables low downforce polishing, thereby improving planarization of the wafer surface.

Description of drawings

Fig. 1 is the cross-sectional structure schematic diagram of a kind of polishing head of the embodiment of the present invention;

Fig. 2 is another sectional structural schematic diagram of a kind of polishing head of the embodiment of the present invention;

Fig. 3 is a schematic cross-sectional structure diagram of a retaining ring according to an embodiment of the present invention;

Fig. 4 is a schematic bottom view of a retaining ring according to an embodiment of the present invention;

5 is a schematic cross-sectional structure diagram of a multi-chamber diaphragm according to an embodiment of the present invention;

Fig. 6 is a schematic top view of a multi-chamber membrane according to an embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

1 and 2 are schematic cross-sectional structural views of a polishing head 100 according to a preferred embodiment of the present invention. The polishing head 100 includes an upper shell 10 , a base 20 , a retaining ring diaphragm 30 , a retaining ring 40 and a multi-chamber diaphragm 50 .

The upper housing 10 can be connected with a driving shaft, and the driving shaft drives the wafer 200 to rotate along the axis 90 in a fixed direction during the polishing process. The driving shaft is perpendicular to the polishing pad 300 during the polishing process. The upper housing 10 is cylindrical, and its outer diameter is about 250mm for a 200mm wafer, and about 350mm for a 300mm wafer. In addition, there are through holes passing through the upper housing 10 for gas or liquid pipelines to pass through, so that the polishing head 100 can be controlled by air pressure or hydraulic pressure to exert downward pressure on the wafer 200 . Considering its structural characteristics and working conditions, the upper casing 10 should be made of high strength, good toughness, and corrosion-resistant materials, such as 304# steel, 316# steel, aluminum titanate ceramics, etc.

The base 20 is cylindrical, and its outer diameter is consistent with that of the upper casing 10 . It has an annular groove for forming a retaining ring cavity. The base 20 is connected with the upper housing 10 on the upper side, and connected with the retaining ring 40 and the multi-chamber diaphragm 50 on the lower side. The base 20 should also be made of materials with high strength, good toughness and corrosion resistance.

The retaining ring diaphragm 30 is an annular membrane that completely covers the annular groove of the base 20 and is secured by clamping rings 74 , 75 to form the retaining ring chamber 66 . The retaining ring diaphragm 30 is fixed through the clamping rings 74, 75 by adhesive or mechanical connection or both. Considering its structural features and working conditions, the material of the retaining ring diaphragm 30 should be elastic materials such as fluororubber, silicon rubber or polyurethane rubber, with a thickness of 0.2-3mm.

The retaining ring 40 is an annular flat plate, which is connected with the retaining ring diaphragm 30 in some way, and floats below the retaining ring chamber 66 through the retaining ring diaphragm 30, thereby defining a pocket area directly below the base 20 , which is just sized to hold the wafer 200. During the polishing process, the inner ring surface of the holding ring 40 engages the wafer 200 to prevent the wafer 200 from slipping out from the bottom of the polishing head 100 . During the polishing process, the retaining ring 40 is in direct contact with the polishing pad 200, and its wear and corrosion are very serious. Therefore, the retaining ring 40 should be made of a material with high strength, good elasticity, wear resistance, corrosion resistance, and small deformation due to temperature difference, PPS ( Polyphenylene Sulfide (polyphenylene sulfide), PEEK (Poly Ether Ether Ketone, polyether ether ketone) and other engineering plastics are the best choices.

3 and 4, there is an annular step 41 on the upper part of the retaining ring 40, and the retaining ring 40 is fixed to the retaining ring diaphragm 30 through the upper surface of the annular step 41, thus ensuring that the retaining ring 40 has enough floating space. The lower part of the retaining ring 40 has a plurality of grooves 42 opened radially and evenly distributed, and the grooves 42 are used as discharge in/out channels for liquid and grinding during the polishing process. The depth of the grooves 42 is between 2-5mm, and the number is preferably between 6-12.

Referring back to FIG. 1 and FIG. 2 , the multi-chamber diaphragm 50 is in the shape of a disc with multiple concentric annular ribs integrated thereon. The multi-chamber diaphragm 50 and the lower surface of the base 20 together form a plurality of mutually independent concentric annular chambers 61 , 62 , 63 , 64 , 65 . During the polishing process, the lower surface of the multi-chamber diaphragm 50 is in contact with the backside of the wafer 200, and gas is applied to the backside of the wafer through a plurality of mutually independent concentric annular chambers 61, 62, 63, 64, 65 Or liquid pressure, forming downforce. For a wafer with a specification of 200mm, three concentric annular chambers are preferred, and for a wafer with a specification of 300mm, five concentric annular chambers are preferred. There are five concentric annular chambers in this preferred embodiment.

See Fig. 5 and Fig. 6, five concentric annular ribs 51, 52, 53, 54, 55 are integrated on the disk-shaped plane of the multi-chamber diaphragm 50, and the ends of these concentric annular ribs respectively have a Annular flat plates 51a, 52a, 53a, 54a, 55a of annular ribs. Through these ring-shaped flat plates and clamping rings 71, 72, 73, the multi-chamber diaphragm 50 is fixed on the base 20 by pasting or mechanical connection or both, forming a plurality of mutually independent concentric ring-shaped chambers 61, 62, 63, 64, 65. Considering its structural characteristics and working conditions, the material of the multi-chamber diaphragm 50 should be elastic materials such as fluororubber, silicon rubber or polyurethane rubber, with a thickness of 0.2-3 mm.

Returning to Fig. 1 and Fig. 2, according to the preferred embodiment of the present invention, the base 20 has through holes 61a, 62a, 63a, 64a, 65a, 66a, etc. , 64 , 65 and the retaining ring chamber 66 are fed with gas or liquid, so as to exert a downward force on the wafer 200 and the retaining ring 40 . The pressure of different chambers can be changed by changing the amount of gas or liquid introduced, and thus the pressure applied to the corresponding area on the wafer 200 and the retaining ring 40 can be changed.

As mentioned earlier, one of the main factors affecting the non-uniformity of the wafer surface is the uneven deposition of the metal/oxide layer resulting in a drop in height on the wafer surface. However, the multi-chamber design of the polishing head can apply different pressures to different areas on the backside of the wafer, that is, apply a little higher pressure to the high area, so that the polishing rate will be faster, and apply less pressure to the low area. Some pressure, so that the polishing rate will be slower, so that the height difference caused by the non-uniform deposition of the metal/oxide layer can be eliminated, so that the polished wafer surface can achieve better uniformity. The reason why the multi-chamber design is distributed in a concentric ring is because the deposition of the metal/oxide layer in the previous process is generally carried out by spin coating, etc., and the height difference formed by these processes is often distributed in a concentric ring.

At the same time, the downforce acting on the retaining ring 40 can be changed by changing the amount of gas or liquid that passes into the retaining ring chamber 66, so that the degree of compression of the retaining ring 40 to the polishing pad 300 can be adjusted to improve the polishing performance. Edge effects caused by the typical difference in action of the pads in the edge region of the wafer and in the center region.

The polishing head of the present invention can improve the non-uniformity of the wafer edge; can adjust the removal profile of the wafer surface material to compensate for the non-uniform deposition of the structural layer on the wafer; can realize low down pressure polishing, and then can obtain excellent flatness effect.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1, a kind of rubbing head that is used for chemically mechanical polishing is characterized in that, described rubbing head comprises:

Pedestal, there is annular recess in described pedestal lower edge zone;

The retaining ring barrier film is fixed on the below of described pedestal, forms the retaining ring chamber with described annular recess;

Retaining ring floats on the below of described retaining ring chamber by described retaining ring barrier film, and described retaining ring is provided with pocket area under described pedestal, be used for holding wafer;

Multi-cavity chamber barrier film, described multi-cavity chamber barrier film has the plate-like plane, is integrated with a plurality of concentric circular ribs on it, and the lower surface of described plate-like plane, concentric circular ribs and described pedestal forms a plurality of separate concentric annular chambers.

2, the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that, described retaining ring chamber housing has gas or liquid, and the pressure of described gas or liquid is passed to described retaining ring by described retaining ring barrier film, forms downforce.

3. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1, it is characterized in that, described a plurality of separate concentric annular chamber housing has gas or liquid, and the pressure of described gas or liquid is passed to wafer by described multi-cavity chamber barrier film, forms downforce.

4. the rubbing head that is used for chemically mechanical polishing as claimed in claim 2 is characterized in that, the gas in the described retaining ring chamber or the pressure of liquid can be regulated.

5. the rubbing head that is used for chemically mechanical polishing as claimed in claim 3 is characterized in that, the gas in described a plurality of separate concentric annular chambers or the pressure of liquid can be regulated respectively.

6. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that the end of described concentric circular ribs has the annular plate perpendicular to described concentric circular ribs, is used for fixing with described pedestal.

7. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that, described a plurality of separate concentric annular chambers are 3-5.

8. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that, the material of described retaining ring barrier film and multi-cavity chamber barrier film is an elastomeric material, and described elastomeric material comprises fluorubber, silicon rubber or polyurethane rubber.

9. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that, the fixed form of the fixed form of described retaining ring barrier film and described pedestal and described multi-cavity chamber barrier film and described pedestal is for adopting the mode of stickup and/or mechanical connection.

10. the rubbing head that is used for chemically mechanical polishing as claimed in claim 1 is characterized in that, the bottom of described retaining ring have a plurality ofly radially get through, equally distributed groove, described groove is used for entering/passing away in polishing process liquid and grinding.

Images