WO2003107408A1

WO2003107408A1 - Polisher

Info

Publication number: WO2003107408A1
Application number: PCT/JP2003/007555
Authority: WO
Inventors: 荒井　一尚; 宮崎　一弥; 石川　和則; 津曲　昭男; 三井　義則
Original assignee: 株式会社ディスコ
Priority date: 2002-06-17
Filing date: 2003-06-13
Publication date: 2003-12-24
Also published as: AU2003242400A1; JP2004022804A

Abstract

A polisher (10) for polishing the surface of a semiconductor wafer (W) has at least a polishing pad (11) containing abrasive grains. A polishing solution supply unit (14) is composed of a first storage tank (17) where a first liquid is stored, a second storage tank (18) where a second liquid is stored, a mixing section (19) connected to the first and second tanks (17, 18) and adapted for producing a polishing solution by mixing the first and second liquids, and a supply section (20) for supplying the polishing solution to the contact portion where the polishing pad (11) is in contact with the semiconductor wafer (W) directly after the polishing solution is produced at the mixing section (19). Thus, foreign matters are not mixed, and the semiconductor wafer is polished without being adversely influenced by them.

Description

Specification

Technical field

The present invention relates to a polishing apparatus used for CMP (Chemical Mechanical Polishing) of semiconductor wafers. Background art

The semiconductor wafer is sliced from a silicon ingot, both surfaces are flattened by a double-side grinder or a lapping device, and then mirror-polished using a polishing device, so that an integrated circuit can be formed on the surface.

Also, in the process of forming an integrated circuit on the surface of the semiconductor device 8, polishing with a polishing device is performed in flattening an interlayer insulating film in forming a multilayer wiring, forming a metal plug, and forming a buried metal wiring. Will be As described above, the polishing apparatus is an important apparatus that is indispensable in the process of processing a semiconductor wafer.

In general, a polishing apparatus is composed of a polishing pad formed of a filter or the like, a polishing pad made of silica, alumina, zirconia, manganese dioxide, ceria, and the like, and an oxidizing agent such as hydrogen peroxide solution or ammonia. Slurry supply means for generating and supplying a slurry by mixing the additive of the above-mentioned slurrying agent, and a holding portion for holding the semiconductor wafer and acting on the polishing pad, and comprising: Polishing is performed by the mechanical action of the polishing pad.

In the slurry generating means for generating the above-mentioned slurry, since the abrasive grains and the additives are put into a tank at a predetermined ratio and stirred and mixed, there is a problem that the characteristics of the re-slurry change with time in the tank. is there. Therefore, such a problem In order to solve this problem, for example, in Japanese Patent Application Laid-Open No. 2000-200274, polishing abrasive grains and additives are separately stored, and the two are mixed immediately before use to form a polishing pad. A technology for supplying a contact portion with a semiconductor wafer has been proposed.

However, by mixing the abrasive grains and the additive immediately before use, it is possible to prevent the change in the characteristics of the slurry due to aging, but the inside of the mixing means is polished by the abrasive power of the abrasive grains. For this reason, there is a new problem that polishing debris is mixed into the slurry as an impurity and adversely affects the polishing of semiconductor wafers.

Therefore, when polishing is performed by mixing abrasive grains and additives with a mixing means, it is an object to prevent impurities from being mixed and to have no adverse effect on the polishing of the semiconductor device. have. Disclosure of the invention

The present invention relates to a polishing apparatus for polishing a surface of a semiconductor wafer, a polishing pad containing abrasive grains, a polishing pad supporting portion for supporting the polishing pad, and an action portion for causing the surface of the semiconductor wafer to act on the polishing pad. A polishing pad and a semiconductor: at least a polishing liquid supply unit for supplying a polishing liquid to a contact portion between the polishing pad and the semiconductor, the polishing liquid supply unit comprising: a first storage tank for storing a first liquid; A second storage tank that stores the second liquid, and a mixing unit that is connected to the first storage tank and the second storage tank and mixes the first liquid and the second liquid to generate a polishing liquid. The present invention also provides a polishing apparatus including a supply unit for supplying a polishing liquid immediately after being generated in a mixing unit to a contact portion between a polishing pad and a semiconductor wafer.

And in this polishing apparatus, the working part is a semiconductor. : A holding portion for holding the wafer; and an approaching / separating portion for moving the holding portion toward and away from the polishing pad relatively. The action portion is disposed facing the polishing pad and the abrasive grains are provided. A second polishing pad containing: a second polishing pad supporting portion for supporting the second polishing pad; and a second polishing pad. The semiconductor wafer is sandwiched between the polishing pad and the second polishing pad, and the first liquid is an aqueous ammonia solution. The additional requirement is that the second liquid is an aqueous solution of ethylenediaminetetraacetic acid.

In the polishing apparatus configured as described above, the polishing pad is made to contain abrasive grains and the polishing liquid is not mixed with the abrasive grains, so that the mixing portion is not polished and the polishing liquid contains impurities. And the polishing liquid is generated immediately before it is supplied to the contact area between the semiconductor wafer and the polishing pad, so that the polishing liquid immediately after generation can be used, preventing the polishing liquid from changing over time. can do. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory view showing a first embodiment of a polishing apparatus according to the present invention. FIG. 2 is an explanatory view showing a second embodiment of the polishing apparatus.

FIG. 3 is a cross-sectional view showing a configuration of a mixing unit according to the second embodiment. FIG. 4 is a perspective view showing a third embodiment of the polishing apparatus according to the present invention. FIG. 5 is a perspective view showing a polishing pad and a second polishing pad according to the third embodiment.

FIG. 6 is a plan view showing a planetary gear and a semiconductor ゥ: c-ha according to the third embodiment.

FIG. 7 is a cross-sectional view showing how the semiconductor wafer is polished in the third embodiment.

FIG. 8 is a perspective view showing a polishing apparatus according to a fourth embodiment of the present invention. FIG. 9 is a front view showing a state in which semiconductor ゥ: E-8 is polished in the fourth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION A polishing apparatus 10 shown in FIG. 1 will be described as a first embodiment of the present invention. The polishing apparatus 10 includes a polishing pad 11 containing abrasive grains, a polishing pad support 12 for supporting the polishing pad 11, and a semiconductor wafer W holding a semiconductor wafer W. A polishing liquid supply unit 14 for supplying a polishing liquid to a contact portion between the polishing pad 11 and the semiconductor wafer W is provided. The polishing pad 11 is a material in which abrasive grains are dispersed and contained in a material such as urethane. Boehmite, bayerite, diamond and the like can be used.

For example, 80% by weight of polyol, 52.4% by weight of isocyanate, 0.2% by weight of water, 0.7% by weight of catalyst, 0.5% by weight of silicone foaming agent, and 90% by weight of silica The mixture is formed, poured into a mold, and left at room temperature of 20 ° C. to 30 ° C. for 24 hours. Thus, a polishing pad 11 having a thickness of 9 mm can be manufactured. The inventor of the present invention has confirmed that a polishing pad having a long life can be formed by mixing abrasive particles, such as colloidal silica, fumed silica, boehmite, and bayerite, to which a hydroxyl group is attached, into a urethane material.

A polishing pad 11 is adhered to the upper surface of the polishing pad support portion 12, and is rotatable by being driven by a motor. On the other hand, the working portion 13 is rotatable while holding the semiconductor する: c-W to be polished from above, and the holding portion 15 for holding the semiconductor ゥ m-c W, and the holding portion 15 An approaching / separating portion 16 for vertically moving the semiconductor wafer W relatively to and away from the polishing pad 11;

The polishing liquid supply unit 14 includes a first storage tank 17 for storing a first liquid, for example, an aqueous ammonia solution, and a second storage tank 18 for storing a second liquid, for example, an aqueous solution of ethylenediaminetetraacetic acid. A mixing unit 19 connected to the first storage tank 17 and the second storage tank 18, and a supply unit 20 connected to the mixing unit 19. It is.

In the mixing section 19, the first liquid and the second liquid can be pumped by the pumps 21 and 22 and mixed at an appropriate ratio, and the polishing liquid generated by the mixing is supplied to the supply section 20. Can be supplied to the contact area between the polishing pad 11 and the semiconductor ゥ: L-ha W. The pH of the polishing solution was adjusted to 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, and 13.5, respectively, and the polishing amount of the silicon wafer per minute [ m / min] was measured as 0.01 m / min at pH 9.5, 0.1 / m / min at pH 10.0, 0.15 m / min at pH 10.5, and 0.2 μm at pH 11.0 / Min, 0.3 / mZ min at pH 1 1 55, 0.4 mZ min at PH 12.0, 0.45 m / min at pH 12.5, 0.47 m at pH 13.0, 0.48 m Z at pH 13.5 It was found that the polishing result of pH 12.5 was optimal from both the viewpoints of polishing efficiency and the amount of aqueous ammonia solution used.

When the polishing solution is generated by mixing an aqueous ammonia solution and an aqueous ethylenediaminetetraacetic acid solution, the mixing ratio is set to 9: 1. For example, the aqueous ammonia solution is 9 Om I / min, and the aqueous ethylenediaminetetraacetic acid solution is 1 OmI / min. Stir and mix in proportions. Here, the ammonia aqueous solution is, for example, a solution obtained by diluting an ammonia stock solution (28%) with a volume of 2 with respect to a volume of 1, and has a pH of 2.5 or more. On the other hand, the aqueous solution of ethylenediaminetetraacetic acid has a concentration of 0.01 moI / liter. The ethylenediaminetetraacetic acid aqueous solution plays a role of preventing metal such as copper from adhering to the semiconductor I: L-ha W.

The polishing liquid having a pH of 12.5 generated by mixing is discharged from the supply unit 20 at a flow rate of 100 ml / min. Also, since the polishing liquid is generated immediately before the polishing liquid is supplied to the contact portion between the semiconductor wafer I and the polishing pad 11, the generated polishing liquid is reduced to a necessary minimum amount. The pumps 21 and 22 are adjusted so that the generated polishing liquid 23 immediately flows out of the supply unit 20 without staying in the mixing unit 19. Then, while the polishing pad 11 fixed to the polishing pad support portion 12 rotates, When the approaching / separating portion 16 descends and comes into contact with the lower surface of the semiconductor wafer L-W, the semiconductor wafer W rotates with the rotation of the polishing pad 11 and the polishing pad 11 containing abrasive grains and the supply section 2 The lower surface of the semiconductor wafer W is polished by the polishing liquid flowing out from zero. At this time, for example, the polishing pressure is set to 300 g / cm ² , and the rotation speed of the polishing pad 11 is set to 40 rpm.

The mixing unit 19 is provided with a pH sensor 24, and the controller 25 reads the value of pH, and can adjust the supply amount of ethylenediaminetetraacetic acid according to the value.

When the polishing is performed in this manner, since the generated polishing liquid 23 does not contain abrasive grains and the inside of the mixing section 19 is not polished by stirring, impurities may be mixed into the polishing liquid. Absent. Further, since the polishing liquid 23 is generated immediately before the polishing liquid is supplied to the contact portion between the semiconductor wafer W and the polishing pad 11, the polishing liquid immediately after the generation can be supplied. However, it is possible to prevent the polishing liquid 23 from changing over time. Therefore, polishing can be performed satisfactorily and stably.

Next, a polishing apparatus 30 shown in FIG. 2 will be described as a second embodiment of the present invention. The polishing apparatus 3 0, the polishing pad 3 1 containing the abrasive grains, the polishing pad support 3 2 for supporting the polishing pad 3 1, semiconductor polishing pad ₃ 1 holds semiconductor © X- wafer W It is composed of a working part 33 that acts on the surface of the wafer W, and a polishing liquid supply part 34 that supplies a polishing liquid to a contact part between the polishing pad 11 and the semiconductor wafer W.

The polishing pad 31, the polishing pad support portion 32, and the action portion 33 are configured in the same manner as in the example of FIG. 1, and the action portion 33 includes a holding portion 35 and an approach / separation portion 36. On the other hand, the polishing liquid supply unit 34 includes a first storage tank 37 for storing a first liquid such as an aqueous ammonia solution, and a second storage tank 38 for storing a second liquid such as an aqueous solution of ethylenediaminetetraacetic acid. And a mixing section 39 connected to the first storage tank 37 and the second storage tank 38, and a supply section 40 connected to the mixing section 39. You.

In the mixing section 39, the first liquid and the second liquid can be pumped out by the pumps 41 and 42 and mixed at an appropriate ratio, and the polishing liquid generated by the mixing is supplied. It can be supplied from the part 40 to the contact part between the polishing pad 31 and the semiconductor wafer W.

As shown in FIG. 3, the mixing section 39 has a substantially conical rotator 44 driven by a motor 43 and rotatable, and a lid 45 having an open lower end to constitute a supply section 40. The first liquid and the second liquid are supplied to the inside of the lid 45.

A plurality of grooves 46 are provided on the outer peripheral surface of the rotator 44, and inside the lid 45, the first liquid and the second liquid that have flowed in descend along the grooves 46. Then, during the downward movement, the first liquid and the second liquid are mixed with the rotation of the rotating body 44, and the generated polishing liquid 47 is dropped downward from the supply unit 40.

In the polishing apparatus 30 configured as shown in FIG. 2, the polishing pad 31 fixed to the polishing pad support section 32 rotates, and the approaching / separating section 36 descends. When the semiconductor wafer W comes into contact with the lower surface of the wafer W, the semiconductor wafer W rotates with the rotation of the polishing pad 31, and the semiconductor wafer W is polished by the polishing pad 31 containing abrasive grains and the polishing liquid 47 flowing out of the supply part 40. C The lower surface of W is polished.

When the polishing is performed in this manner, no abrasive is contained in the polishing liquid 47 and the inside of the mixing section 39 is not polished, so that no impurities are mixed in the polishing liquid. Further, since the polishing liquid 47 is generated immediately before being supplied to the contact portion between the semiconductor wafer W and the polishing pad 31, the polishing liquid 47 can be supplied immediately after the polishing liquid is generated. The liquid 47 can be prevented from changing over time. Therefore, the polishing can be performed satisfactorily and stably.

Next, a polishing apparatus 50 shown in FIG. 4, FIG. 5, and FIG. 6 will be described as a third embodiment of the present invention. As shown in FIG. 5, the polishing apparatus 50 includes a polishing pad. A pad 51 and a second polishing pad 52 are provided, both of which contain abrasive grains such as silica, alumina, zirconia, manganese dioxide, ceria, colloidal silica, and diamond.

The polishing pad 51 is supported by a polishing pad support 53, and a center gear 54 and an outer peripheral gear 55 are formed on the upper surface of the polishing pad 51. And the central gear

As shown in FIG. 6, a ring-shaped planetary gear 56 holding the semiconductor wafer W on the inner peripheral surface 56a is combined with the outer gear 54 and the outer gear 55. The outer peripheral gear 55 is rotatable. On the other hand, the second polishing pad 52 is fixedly supported on the lower surface of the second polishing pad support portion 57.

As shown in FIG. 4, the second polishing pad supporting portion 57 is fixed to a rotating shaft 58, and the rotating shaft 58 is connected to the elevating portion 59 so as to be freely rotatable. The elevating unit 59 is guided by the rerail 61 by driving by the motor 60 and is capable of ascending and descending. That is, the rotating shaft 58, the elevating part 59, the motor 60, and the rail 61 constitute an approaching / separating part, and this, the second polishing pad 52, and the second polishing pad support part 57, An action section is configured.

Further, a polishing liquid supply unit 62 is connected to the elevating unit 59. This polishing liquid supply section

6 2 is a first storage tank 6 3 for storing the first liquid, a second storage tank 6 4 for storing the second liquid, and a mixture of the first liquid and the second liquid. And a mixing section 65 for generating a polishing liquid. The mixing section 65 is configured like the mixing section 19 shown in FIG. 1 or the mixing section 39 shown in FIG. 2, and generates a polishing liquid containing no abrasive grains.

As shown in FIG. 7, the generated polishing liquid flows into the flow passage 66 formed inside the rotating shaft 58, flows out from the second polishing pad 52, and is supplied to the semiconductor wafer W. You. That is, in this case, the second polishing pad 52 becomes a supply unit for supplying the polishing liquid. The center gear 54 is fixed to a fixed shaft 67. On the other hand, the polishing pad support portion 53 is configured to rotate by a rotation transmitted from the polishing pad drive motor 68 via the drive transmission belt 69. It rotates while being supported by the bearing 70 by force.

Then, as the polishing pad 51 rotates at a rotation speed of, for example, about 40 rpm, the second polishing pad 52 rotates freely as the polishing pad supporting portion 53 rotates at, for example, about 40 rpm. When the polishing liquid is supplied, the semiconductor wafer W is sandwiched between the first polishing pad 51 and the second polishing pad 52, and a pressure of, for example, about 300 g Z cm ² is applied to the first polishing pad 51 and the first polishing pad 51. The polishing pad 51, the second polishing pad 52 and the polishing liquid polish both surfaces of the semiconductor ゥ: L-ha W. The used polishing liquid is drained from the drain hole 72 after being received in the drain receiving portion 71. Note that the first polishing pad 52 may be fixed.

When polishing is performed in this manner, no impurities are mixed into the polishing liquid, and the polishing liquid is supplied without causing a change with time, so that polishing can be performed satisfactorily and stably.

Next, a polishing apparatus 80 shown in FIG. 8 will be described as a fourth embodiment of the present invention. In this polishing apparatus 80, the semiconductor wafers L to C before polishing are housed in a cassette 81, carried out by carrying-in / out means 82, and placed on a positioning table 83. Then, after the center position is adjusted, the first transfer means 84 places the chuck on a chuck table 86 that can move in the horizontal direction with the expansion and contraction of the bellows 85 and can rotate. By the movement of the table 86, it is positioned immediately below the polishing means 87.

The polishing means 87 is connected to a support plate 90 slidably engaged with a pair of guide rails 89 provided vertically on the inner surface of the wall portion 88, and A nut (not shown) provided inside is screwed into a ball screw 92 connected to the pulse motor 91, and the support plate 9 is rotated as the ball screw 92 rotates by the driving of the pulse motor 91. 0 and the polishing means 87 connected to it move up and down.

In the vicinity of the polishing means 87, a first storage tank 93 for storing a first liquid, a second storage tank 94 for storing a second liquid, a first liquid and a second liquid Mixed with A polishing liquid supply unit 97 including a mixing unit 95 for generating a polishing liquid and a supply unit 96 for supplying the generated polishing liquid is provided. The mixing section 95 is configured like the mixing section 19 shown in FIG. 1 or the mixing section 39 shown in FIG. 2, and generates a polishing liquid containing no abrasive grains.

The polishing means 87 is fixed to a spindle 98 having a vertical axis, a motor 99 for rotating and driving the spindle 98, a mounter 100 formed at the lower end of the spindle, and a mounter 100. Polishing pad support 101 and a polishing pad 102 fixed to the lower surface of the polishing pad support 101. The polishing is performed as the spindle 98 rotates by being driven by the motor 99. The pad 102 is configured to rotate.

The polishing pad 102 contains abrasive particles dispersed in a material such as urethane. The abrasive particles include silica, alumina, zirconia, manganese dioxide, seria, colloidal silica, fumed silica, boehmite. , Bayerite, diamond and the like can be used.

At the time of polishing, as shown in FIG. 9, while the chuck table 86 rotates, the polishing liquid 103 immediately after being generated is supplied from the supply unit 96 to the semiconductor —: n-c and rotates together. When the polishing pad 102 descends and comes into contact with the semiconductor wafer W to apply pressure, polishing is performed by the polishing pad 102 and the polishing liquid 103.

At this time, for example, the polishing pressure is 300 g / cm ² , the rotation speed of the polishing pad 102 is 40 rpm, and the rotation speed of the chuck table 86 is 10 rpm.

After the polishing is completed, the chuck table 86 moves to be positioned near the second transport means 104, and the polished semiconductor ゥ: c-ha W is cleaned by the second transport means 104. Conveyed to the means 105. And the semiconductor wafer A washed here is transported. It is stored in the cassette 106 by the access means 82. Industrial applicability

As described above, in the polishing apparatus according to the present invention, the polishing pad is made to contain the abrasive grains, and the polishing liquid is not mixed with the abrasive grains. The polishing liquid is not mixed with the impurities, and the polishing liquid is generated immediately before the polishing liquid is supplied to the contact portion between the semiconductor wafer and the polishing pad. It can prevent the liquid from changing over time. Therefore, good and stable polishing can be efficiently performed.

Claims

The scope of the claims

1. A polishing apparatus for polishing a surface of a semiconductor ゥ x—c,

A polishing pad containing abrasive grains, a polishing pad supporting portion for supporting the polishing pad, an operating portion for causing the surface of the semiconductor wafer to act on the polishing pad, and a contact portion between the polishing pad and the semiconductor wafer. A polishing liquid supply unit for supplying a polishing liquid, the polishing liquid supply unit includes: a first storage tank that stores a first liquid;

A second storage tank for storing a second liquid;

A mixing unit connected to the first storage tank and the second storage tank and mixing the first liquid and the second liquid to generate a polishing liquid;

A supply unit that supplies a polishing liquid immediately after being generated in the mixing unit to a contact portion between the polishing pad and the semiconductor X-C;

Polishing device composed of

2. The working part is a holding part for holding the semiconductor wafer: L-ha,

2. The polishing apparatus according to claim 1, further comprising: an approaching / separating portion that relatively moves the holding portion toward and away from the polishing pad.

3. The working unit is a second polishing pad that is disposed to face the polishing pad and contains abrasive grains, a second polishing pad support that supports the second polishing pad, and the second polishing. An approaching / separating portion for relatively moving the pad toward or away from the polishing pad, wherein the semiconductor pad is sandwiched between the polishing pad and the second polishing pad. The polishing apparatus according to claim 1.

4. The polishing apparatus according to claim 1, wherein the first liquid is an aqueous ammonia solution, and the second liquid is an aqueous solution of ethylenediaminetetraacetic acid.