JP6663525B2 - Polishing head, CMP polishing apparatus having polishing head, and method of manufacturing semiconductor integrated circuit using the same - Google Patents

Description

  The present invention relates to a structure of a polishing head of a CMP polishing apparatus for evenly planarizing a wafer surface, a CMP polishing apparatus having the same, and a method of manufacturing a semiconductor integrated circuit using the same.

  2. Description of the Related Art In recent years, a new fine processing technology has been developed in accordance with high integration and high performance of a semiconductor integrated circuit (hereinafter, referred to as LSI). A chemical mechanical polishing (abbreviation to CMP) method is one of the methods, and is frequently used in the LSI manufacturing process, particularly, in the flattening of the interlayer insulating film, the formation of metal plugs, and the formation of embedded wiring in a multilayer wiring forming process. This is the technology used for The basic structure of a CMP polishing apparatus includes a rotating platen to which a polishing pad is attached, a wafer holding head, a slurry supply nozzle, and a pad reproducing device (conditioner). The polishing pad side is not necessarily a rotating platen, and there are a plurality of cases for a head, and conversely, there is a polishing pad having a plurality of heads for one pad. The parameters for controlling the CMP polishing apparatus include, in addition to the polishing method, polishing load, platen rotation speed, head rotation speed, slurry selection / supply method, conditioning condition / frequency, etc. As described above, there is a method in which an air bag is pressurized on a head portion for fixing a wafer (for example, see Patent Document 1).

JP 2005-268566 A

  However, the head structure shown in Patent Document 1 for fixing a wafer by pressure using an air bag has the following problems. That is, the pressure of the pressurized airbag becomes locally high at the outer peripheral portion of the airbag, and the wafer region in contact with that portion is more strongly pressed against the polishing pad than other regions, and the other region is pressed down. The polished insulating material is more removed than the wafer area. When the polished insulating material in a part of the wafer is excessively shaved, the polishing uniformity in the wafer surface varies, and as a result, the thickness of the insulating material in the wafer surface varies. In the wafer region where the film thickness variation occurs, the electrical characteristics vary, and in some cases, abnormalities occur in the electrical characteristics.

FIG. 14 shows a schematic diagram thereof. As shown in FIG. 14, in the prior art, compressed air is introduced to hold down the wafer, and a high pressure 6 of air is locally applied to the outer peripheral portion of the airbag, and the pressure is higher than the central portion. The wafer 1 pressed by the high pressure portion from above has an increased polishing rate of the insulating film in a region where the pressure is high, that is, the high pressure region X, and is scraped more than the central portion where the pressure pressed down from above is low. In the region X, the in-plane uniformity of the wafer 1 after the planarization of the insulating film material has been deteriorated.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a CMP polishing apparatus that improves polishing uniformity.

  In order to solve the above problems, a polishing head of a CMP polishing apparatus has the following features. That is, a polishing head of a CMP polishing apparatus, wherein a first airbag and a second airbag which contact a polishing pad and a back surface of a wafer mounted on a surface of the polishing pad and press the surface of the wafer against the polishing pad. A first airbag having an airbag and a top ring surrounding the airbag and the wafer, wherein the first airbag is in contact with a central portion of the wafer and the second airbag is in contact with an outer peripheral portion of the wafer. A second film thickness of the second airbag is larger than a first film thickness of the first airbag.

  By using the above-mentioned means, a method of manufacturing a semiconductor integrated circuit in which an air bag for holding down a wafer is uniformly pressed, the entire surface of the wafer can be held down uniformly, and a variation in thickness of a wafer insulating material in a wafer surface is reduced. Can be provided.

FIG. 1 is a schematic sectional view of a polishing head of a CMP polishing apparatus showing a first embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing a second embodiment of the present invention. It is a schematic plan view and a sectional view of an air bag in a polishing head of a CMP polishing apparatus showing a third embodiment of the present invention. It is a schematic plan view and a sectional view of an air bag in a polishing head of a CMP polishing apparatus showing a fourth embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing a fifth embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing a sixth embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing a seventh embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing an eighth embodiment of the present invention. It is a schematic plan view and a sectional view of an airbag in a polishing head of a CMP polishing apparatus showing a ninth embodiment of the present invention. It is a schematic plan view and a sectional view of an air bag in a polishing head of a CMP polishing apparatus showing a tenth embodiment of the present invention. It is a schematic plan view and a sectional view of an air bag in a polishing head of a CMP polishing apparatus showing an eleventh embodiment of the present invention. FIG. 16 is a schematic sectional view of a polishing head structure of a CMP polishing apparatus showing a twelfth embodiment of the present invention. It is a schematic plan view and a schematic sectional view of a polishing head of a conventional CMP polishing apparatus. It is a schematic diagram which shows the dispersion | variation in the residual film in a wafer surface after grinding | polishing by the conventional CMP polishing apparatus. 1 is a plan view showing a semiconductor integrated circuit manufactured according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view showing a first embodiment of the present invention, and particularly shows a CMP polishing apparatus schematically showing a sectional structure of a polishing head portion. As described above, in the prior art shown in FIG. 14, when compressed air is introduced to press the wafer, a high pressure 6 is locally applied to the outer peripheral portion due to the influence of the shape of the air bag and the like, so that The pressure will be high. The wafer 1 pressed by the high pressure portion from above increases the polishing rate of the insulating film in the high pressure region X where the pressure is strong, and is more polished than the central portion where the pressure pressed down from above is small. As a result, the in-plane uniformity of the surface of the wafer after the planarization of the insulating film material is deteriorated.

  In the CMP polishing apparatus of FIG. 1, an airbag 101 is arranged on the back surface of a wafer 1 placed on a polishing pad 5 with the front surface facing downward, and compressed air is sent into the airbag 101. The wafer 1 is pressed down from above, and the surface of the wafer 1 is fixed to be pressed against the polishing pad 5. A retainer ring 3 is arranged so as to surround the wafer 1 and the airbag 101 from the side, and a top ring 2 is arranged so as to surround them. A polishing pad 5 is arranged below the wafer 1, and a top ring 2 including the wafer 1 rotates on the polishing pad 5 to polish an insulating material on a surface of the wafer 1 to flatten the surface.

  Here, the airbag 101 has a structure in which the thickness of the bag body constituting the airbag 101 is increased as the constituent material of the airbag goes outward from the center. At this time, the range in which the thickness is provided is determined by checking the polishing rate of the entire wafer according to the configuration of the CMP polishing apparatus and the shape of the wafer 1. It is good to design to have. At this time, it is preferable to use the actually measured value of the region width where the polishing rate is increased by pressing with a high pressure obtained by the conventional technique. The pressure on the wafer 1 is dispersed in the thick portion as compared with the conventional thickness.

  In the case of the conventional thickness, a high pressure is locally applied to the outer peripheral portion of the airbag, the polishing rate is increased, and there is a problem that the insulating material is excessively shaved. By increasing the thickness, the high pressure locally applied only to the outside of the airbag 101 is dispersed, and the pressure of the airbag 101 that presses the wafer 1 becomes uniform at the central portion and the outer peripheral portion. There is an advantage that the wafer 1 is uniformly formed with high quality over the entire surface.

  As described above, the first embodiment of the present invention is characterized in that the air pressure is uniformly distributed by making the thickness of the airbag 101 outwardly optimum, and the wafer 1 can be uniformly pressed. have.

  Next, FIG. 2 is a schematic sectional view showing a second embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. First, as shown in FIG. 14, in the prior art, it is possible to grasp the region where the polishing rate of the insulating film material is increased in the region where the high pressure of air is locally applied and the uniformity of the planarization is deteriorated. Further, factors that increase the pressure of the airbag toward the outside include a point that the airbag is formed of one member and a point that a centrifugal force acts because the head rotates.

  For this reason, in the embodiment of FIG. 2, the airbag is divided into two bags. A circular inner airbag 201 and a donut-shaped outer airbag 202 arranged so as to surround the inner airbag. As described above, since the area where the polishing rate is increased is known from the outer high-pressure area in the prior art, the width of the outer airbag may be set so as to cover the width of this area. The inner airbag 201 and the outer airbag 202 can be individually pressure-controlled. As described above, in the second embodiment, the airbag is composed of two individually controllable pressures, and the pressure applied to the central portion of the wafer 1 from the airbag and the pressure applied to the outer peripheral portion from the airbag. It has the feature that the pressure can be evenly distributed and the wafer can be held down uniformly.

  Next, FIG. 3 is a schematic sectional view showing a third embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. As described in the second embodiment, the outer airbag 302 is arranged around the inner airbag 301, but the shape of the outer airbag 302 is made small. By making the shape of the outer air bag 302 small, the air pressure is applied more uniformly than the donut shape of the second embodiment, and as a result, there is an advantage that the wafer 1 is uniformly pressed. As described above, in the third embodiment, the air bag is formed of two types of circles, and the pressure for pressing the central portion of the wafer 1 from the air bag and the pressure for pressing the outer peripheral portion from the air bag are set to the second values. It has a feature that the pressure can be more uniformly dispersed and the wafer can be uniformly pressed as compared with the embodiment. Here, the inner large circular airbag and the outer small airbag can be individually pressure-controlled.

  Next, FIG. 4 is a schematic sectional view showing a fourth embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. Compared to the arrangement of the outer airbag 302 around the inner airbag 301 described in the third embodiment, all the inner airbags 301 made up of one were arranged in the same size as the outer airbag 302, The structure is constituted by the small airbag 401. Compared to the third embodiment, since all are configured with small airbags 401, there is an advantage that the air pressure is evenly applied as compared to a large airbag. Here, each airbag can be individually pressure-controlled. It is.

  As described above, in the fourth embodiment, since the airbags are all constituted by the small airbags 401, the air pressure is applied more uniformly than the large airbags, and as a result, the pressure for pressing the wafer 1 is reduced over the entire surface of the wafer 1. It has the feature that it can be held down more uniformly.

  Next, FIG. 5 is a schematic sectional view showing a fifth embodiment of the present invention, in which only an air bag of a CMP polishing apparatus is simply shown. As described in the prior art FIG. 13 or the first embodiment, when one large air bag is used, the air pressure is locally dispersed, and the pressure for pressing the wafer becomes uneven. there were. Therefore, as shown in FIG. 5, a hose-shaped airbag spiral type 501 in which the shape of the airbag is formed into a hose shape and arranged in a spiral shape. For the direction of the spiral, you can select the best one, left or right. There is an advantage that the air pressure is uniformly applied by reducing the size of the airbag into a hose shape. As described above, in the fifth embodiment, the air bag is constituted by the hose-shaped air bag spiral type 501, so that air is applied more uniformly than in the prior art FIG. 13 or the first embodiment, and as a result, the pressure for pressing down the wafer 1 is reduced. It has the feature that the entire surface of the wafer 1 can be made more uniform and pressed. Further, in the present embodiment, it is possible to make the pressure for holding down the wafer even more uniform by making the thickness of the hose-shaped air bag contacting the outer peripheral portion of the wafer smaller than the thickness of the hose-shaped air bag contacting the central portion of the wafer. it can.

  Next, FIG. 6 is a schematic sectional view showing a sixth embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. The inner air bag 601 has the features of both the first and second embodiments. The inner air bag 601 is formed in a circular shape, and the donut-shaped outer air bag 602 is arranged so as to surround the inner air bag 601. The outer airbag 602 has a thicker constituent material. Since the head of the CMP polisher rotates, the airbag disposed outside due to the circumferential force is applied more pressure than the airbag at the center. By making the material of the airbag thicker than that of the central portion, there is an advantage that the air pressure is applied uniformly and the wafer 1 is pressed down uniformly. As described above, in the sixth embodiment, the outer airbag 602 having a thicker material is used, so that air is applied more uniformly than in the second embodiment, and as a result, the pressure for pressing the wafer 1 becomes more uniform over the entire surface of the wafer 1. It has a feature that can be held down.

  Next, FIG. 7 is a schematic cross-sectional view showing a seventh embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. It has features of both the first and third embodiments, and a small circular outer airbag 702 is arranged so as to surround the circular inner airbag 701. The outer airbag 702 has a thicker constituent material. Since the head of the CMP polisher rotates, the airbag disposed outside due to the circumferential force is applied more pressure than the airbag at the center. By making the material of the airbag thicker than that of the central portion, there is an advantage that the air pressure is applied uniformly and the wafer 1 is pressed down uniformly. As described above, in the sixth embodiment, the outer airbag 702 having a thicker material is used, so that air is applied more uniformly than in the third embodiment. As a result, the pressure for pressing the wafer 1 is more uniform over the entire surface of the wafer 1. It has a feature that can be held down.

  Next, FIG. 8 is a schematic sectional view showing an eighth embodiment of the present invention, and simply shows only an air bag of a CMP polishing apparatus. It has the features of both the first embodiment and the fourth embodiment, and a small airbag 801 is arranged. The small airbag thick 802 disposed on the outermost periphery makes the constituent material thick. Since the head of the CMP polisher rotates, the airbag disposed outside due to the circumferential force is applied more pressure than the airbag at the center. By making the material of the airbag thicker than that of the central portion, there is an advantage that the air pressure is applied uniformly and the wafer 1 is pressed down uniformly. As described above, in the sixth embodiment, the outer airbag 802 having a thicker material is used, so that air is applied more uniformly than in the fourth embodiment, and as a result, the pressure for pressing the wafer 1 becomes more uniform over the entire surface of the wafer 1. It has a feature that can be held down.

  Next, FIG. 9 is a schematic sectional view showing a ninth embodiment of the present invention, in which only an air bag of a CMP polishing apparatus is simply shown. It has the features of both Embodiment 2 and Embodiment 5, and a hose-shaped airbag spiral type 902 is arranged so as to surround the circular inner airbag 901. For the spiral of the hose-shaped airbag spiral type 902, the optimal one may be selected on the right or the left. As described in the related art 13, if the airbag is composed of one airbag, the air pressure at the outer peripheral portion is higher than that at the center of the airbag, and the polishing rate of the outer peripheral portion is reduced by pressing the wafer 1 at a high pressure. However, there is a problem that the uniformity of the flattening is deteriorated due to the increase in the thickness of the insulating film, but the region where the polishing rate of the outer peripheral portion obtained by the conventional technique is increased is formed by the hose-shaped airbag spiral type 902. By using two airbags, there is an advantage that the pressure at the center and the pressure at the outer periphery become uniform, and the pressure for pressing the wafer 1 becomes uniform over the entire surface of the wafer 1. As described above, the ninth embodiment has a configuration in which the hose-shaped airbag spiral type 902 is arranged so as to surround the circular inner airbag 901, so that air is more uniformly applied than in the second embodiment. As a result, the pressure for pressing the wafer 1 is characterized in that the entire surface of the wafer 1 can be pressed more uniformly.

  Next, FIG. 10 is a schematic sectional view showing a tenth embodiment of the present invention, in which only an air bag of a CMP polishing apparatus is simply shown. It has the features of both Embodiment 3 and Embodiment 5, and is formed of a small outer hose-shaped airbag spiral type 1102 so as to surround a circular hose-shaped inner hose-type airbag spiral type 1001. . The spiral of the inner hose-shaped air bag spiral type 1001 and the outer hose-shaped air bag spiral type 1102 may be selected from the right and left. As described in the related art 13, if the airbag is composed of one airbag, the air pressure at the outer peripheral portion is higher than that at the center of the airbag, and the polishing rate of the outer peripheral portion is reduced by pressing the wafer 1 at a high pressure. However, there is a problem that the uniformity of the flattening is deteriorated due to the increase in the thickness of the insulating film. Forming the hose-shaped spiral airbag of the mold 1001 and the outer hose-shaped airbag spiral mold 1102 has an advantage that the uniformity of the air pressure at the center portion and the outer peripheral portion is improved as compared with the fifth embodiment. As described above, the tenth embodiment is more uniform than the third embodiment by forming a small outer-hose airbag spiral mold 1102 so as to surround a circular hose-shaped inner hose airbag spiral mold 1001. Then, air is applied to the central portion and the outer peripheral portion, and as a result, the pressure for pressing the wafer 1 is characterized in that the entire surface of the wafer 1 can be pressed more uniformly.

  Next, FIG. 11 is a schematic sectional view showing an eleventh embodiment of the present invention, in which only an air bag of a CMP polishing apparatus is simply shown. It has the features of both the fourth and fifth embodiments, and is formed by a small hose-shaped airbag spiral type 1101. You can choose the best spiral right or left. As described in the fourth embodiment, in the case of an airbag composed of one, the air pressure in the outer peripheral portion becomes higher than the central portion of the airbag, and the polishing rate in the outer week portion is reduced by pressing the wafer 1 at a high pressure. Increased, the insulating film was excessively shaved, and the uniformity of flattening was degraded. The use of the spiral air bag spiral mold 1101 has an advantage that the uniformity of the air pressure at the center portion and the outer peripheral portion is improved as compared with the fourth embodiment. As described above, in the eleventh embodiment, by forming the small hose-shaped air bag spiral type 1101, air is uniformly applied to the central portion and the outer peripheral portion compared to the fourth embodiment, and as a result, the pressure for pressing the wafer 1 is reduced. It has the feature that the entire surface can be made more uniform and pressed.

  Next, FIG. 12 is a schematic sectional view showing a twelfth embodiment of the present invention, and schematically shows the structure of a head portion of a CMP polishing apparatus. A feature of the first embodiment is that a shock absorbing (gel-like) sheet 1201 is provided between the wafer 1 and the airbag 101.

  The shock absorbing (gel-like) sheet 1201 sandwiched between the wafer 1 and the airbag 101 relaxes and disperses the pressure even when local pressure is generated from the airbag 101, and uniformly applies the pressing pressure to the wafer 1. There are advantages that can be conveyed. As described above, in the twelfth embodiment, the shock absorbing (gel) sheet 1201 sandwiched between the wafer 1 and the airbag 101 relaxes and disperses the pressure from the airbag, thereby uniformly disposing the wafer 1. It has the feature of being able to transmit the pressing pressure.

  Although illustration is omitted, in the second to eleventh embodiments, the same effect as in the twelfth embodiment can be expected by providing the shock absorbing (gel-like) sheet 1201 on the wafer 1. Although the present embodiment has been described and described with an air bag, by replacing the air bag with a water-resistant and pressure-resistant one, the application from a pressure application method using air gas to a pressure application method using liquid can be sufficiently expected.

  FIG. 15 is a plan view showing the semiconductor integrated circuit 8 manufactured according to the embodiment described above. The plurality of semiconductor integrated circuits 8 are two-dimensionally arranged on the surface of the wafer 1 except for a slight margin. In the manufacturing process of the semiconductor integrated circuit 8, the CMP polishing apparatus flattens the surface of the semiconductor integrated circuit 8 by chemically and mechanically polishing the surface, and a metal film or an insulating film to be formed next is disposed on the flat surface. Like that. Depending on the structure of the semiconductor integrated circuit 8, the CMP polishing apparatus may be used many times in the manufacturing process, and it is natural that the flatness of the entire surface of the wafer is required to be good.

DESCRIPTION OF SYMBOLS 1 Wafer 2 Top ring 3 Retainer ring 4 Air bag 5 Polishing pad 6, X Local high pressure place 7 Abnormal wafer quality area due to local high pressure place 8 Semiconductor integrated circuit 101 Air bag 201 Inner air bag 202 Outer air bag 301 Inner air bag 302 Outer air bag 401 Small air bag 501 Hose-shaped air bag spiral type 601 Inner air bag 602 Outer air bag 701 Inner air bag 702 Outer air bag 801 Small air bag 802 Small air bag thick 901 Inner air Bag 902 Hose-shaped air bag spiral type 1001 Inner hose-shaped air bag spiral type 1002 Outer hose-shaped air bag spiral type 1101 Small hose type Ah bag spiral 1201 shock absorber (gel-like) sheet

Claims (10)

A polishing head of a CMP polishing apparatus,
A polishing pad,
A first airbag and a second airbag that abut against a back surface of a wafer placed on a surface of the polishing pad and press a surface of the wafer against the polishing pad;
A top ring surrounding the first airbag and the second airbag and the wafer;
With
The first airbag contacting the central portion of the wafer and the second airbag contacting the outer peripheral portion of the wafer are different bags, and the first airbag has a thickness greater than the first film thickness of the first airbag. (2) A polishing head, wherein the second film thickness of the airbag is large. 2. The air bag according to claim 1, wherein the first air bag is a circular air bag, and the second air bag is an annular air bag provided around the circular air bag. The polishing head as described.   In plan view, the first airbag is a circular airbag, and the second airbag is provided around the first airbag, and is a collection of a plurality of circular airbags smaller than the circular airbag. The polishing head according to claim 1, wherein the polishing head is a body.   In a plan view, the first airbag is an aggregate of a plurality of circular airbags, and the second airbag is an aggregate of a plurality of circular airbags provided around the first airbag. The polishing head according to claim 1, wherein:   The planar airbag, wherein the first airbag is a circular airbag, and the second airbag is a spiral hose-shaped airbag provided around the circular airbag. 2. The polishing head according to 1.   In a plan view, the first airbag is a first spiral-hose-shaped airbag, and the second airbag is provided around the first spiral-hose-shaped airbag, and the first spiral is formed. The polishing head according to claim 1, wherein the polishing head is an aggregate of a plurality of second spiral hose-shaped airbags smaller than the hose-shaped airbag.   In a plan view, the first airbag is an aggregate of a plurality of spiral hose-shaped airbags, and the second airbag is an aggregate of a plurality of spiral hose-shaped airbags provided around the first airbag. The polishing head according to claim 1, wherein the polishing head is a body.   The polishing head according to any one of claims 1 to 7, wherein an impact absorbing sheet is provided between the wafer and the first airbag and the second airbag.   A CMP polishing apparatus comprising the polishing head according to claim 1.   A method for manufacturing a semiconductor integrated circuit, comprising a step of flattening a wafer surface using the CMP polishing apparatus according to claim 9.

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