JPH11126769A - Method and apparatus for chemical-mechanical polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an art for improving adjustment of a polishing pad in a chemical-mechanical polishing operation. SOLUTION: A semiconductor substrate provided with a thin film to be polished is prepared (step 201). Before polishing, a mixture of polishing slurry is directly injected onto the polishing surface (step 203). A tungsten thin film is polished by a polishing apparatus and art (step 205). A residual by-product is formed by polishing (step 207). Before a large amount of tungsten oxide is adhered to the polishing surface, the polishing surface is adjusted (step 209). The operation returns to the step 201 (step 211).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical mechanical polishing method and apparatus, and more particularly, to a tungsten interconnect using a chemical mechanical polishing technique.
And a method and apparatus for manufacturing a plug / via. The method and apparatus of the present invention have wide applicability, such as being applied to different integrated circuit devices using other metals, such as aluminum, copper, or dielectric materials, such as silicon dioxide, silicon nitride, etc. ing.

[0002]

2. Description of the Related Art Chemical mechanical polishing is a technique for polishing a semiconductor substrate and a material such as a thin film formed on the substrate to impart a high degree of uniformity and flatness. It has been used in the process of manufacturing circuit components to remove portions protruding from the thin film or to remove the thin film layer to expose the circuit portion under the thin film. This technique has also been applied to the planarization of semiconductor pieces before microelectronic circuits are fabricated on a substrate.

In conventional chemical mechanical polishing, polishing is performed by using a polishing pad on a flat table, on which a substrate is placed. When the polishing pad is rotated, the substrate positioned or inclined with respect to the polishing pad is polished, and the polishing characteristics of the polishing pad are improved by using the polishing characteristics of the chemical polishing slurry stored on the polishing pad. Polishing was promoted.

[0004]

However, in this conventional chemical mechanical polishing, for example, in a polishing step, by-products remaining on a polishing pad are deposited, resulting in a decrease in polishing efficiency in a polishing operation. As a result, there has been a problem that the polishing process becomes unstable and causes unevenness of the surface of the thin film or the substrate. To solve this problem, the polishing pad had to be constantly cleaned or adjusted.

In recent years, many techniques have been proposed for cleaning or adjusting such residual by-products deposited on the polishing pad. One is simply replacing the polishing pad, which increases the downtime of the equipment and requires that the polishing pad be replaced over an off-rated time. In addition, since the replacement frequency is high, there is a problem that the manufacturing cost is increased and the cost of the integrated circuit is further increased.

Therefore, at present, many techniques for adjusting the surface of the polishing pad have been proposed as a measure against this. One is to often use a rotating wheel to clean the surface of the polishing pad, or to remove a thin film on the polishing pad,
An adjustment technique for restoring the performance of the polishing pad has been proposed. One example is the use of a rotating diamond wheel to remove by-products remaining on the surface of the polishing pad.In this removal process, deionized water was used as a by-product removal medium. . However, these techniques have insignificantly consumed production time to remove by-products, and have increased the cost of manufacturing integrated circuits. Further, these techniques can be used only a limited number of times before replacing the polishing pad, and are only temporary remedies for the above problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for improving the adjustment of a polishing pad in a chemical mechanical polishing process.

Another object of the present invention is to provide a chemical mechanical polishing method for polishing using a conditioning solution during the manufacture of an integrated circuit.

Yet another object of the present invention is to provide a chemical mechanical polishing apparatus having improved conditioning resources.

It is still another object of the present invention to provide a method of manufacturing an integrated circuit for preparing a polishing pad coated with an insoluble metal oxide in a chemical mechanical planarization apparatus.

[0011]

According to an improved technique of the present invention, for example, ammonium hydroxide or the like is used as a polishing pad adjustment solution in a tungsten manufacturing process, and insoluble residual by-products attached to the polishing pad surface are dissolved to form a polishing pad. It is to adjust.

A chemical mechanical polishing method for manufacturing an integrated circuit according to the present invention includes the steps of preparing a semiconductor substrate coated with a thin film containing a tungsten material, polishing the thin film using a polishing pad and a polishing slurry, Producing a plurality of semiconductor substrates by repeating the preparation and polishing steps,
Thereby forming a by-product containing a tungsten oxide material and leaving it on the polishing pad, adjusting the polishing pad with a chemical solution such as ammonium hydroxide,
Removing most of the tungsten oxide material from the polishing pad, thereby extending the life of the polishing pad.

A chemical mechanical polishing apparatus for manufacturing an integrated circuit according to the present invention includes a flat table having a polishing pad, wherein a polishing surface of the polishing pad rotates around a fixed axis.
A carrier head that grips a wafer having a surface containing a tungsten thin film with respect to the polishing surface, and a polishing slurry is applied to the tongue thin film to form an insoluble tungsten oxide, which is placed on the polishing pad. A slurry source containing an acid solution to be adhered, and an adjusting element positioned near the polishing pad and connected to an adjusting solution source that is an ammonium hydroxide solution to dissolve insoluble tungsten oxide, whereby polishing is performed. The life of the pad is extended, and the quality of the device is improved.

Further, the method of manufacturing an integrated circuit is a method of adjusting a polishing pad coated with an insoluble metal oxide in chemical mechanical planarization, the adjustment being performed by using an aqueous solution of an ammonium hydroxide compound on an upper portion. Attaching an adjustment pad containing an adjustment solution to the polishing pad surface, using the adjustment solution and the adjustment pad,
Removing most of the insoluble metal oxide, thereby extending the life of the polishing pad and controlling variables in the manufacturing process.

[0015] The polishing pad contains a polyurethane material, the pH value of the conditioning solution is greater than 7, and the conditioning pad is a brush-like pad or a diamond pad.

Thus, according to the above means of the present invention,
The service life of the polishing pad is extended, and the use of the chemical mechanical polishing tool can reduce the time required for maintenance and replacement of the pad in advance. In addition, the number of fine scratches that have conventionally been caused by residual by-products is reduced, and a process outside the rating can be omitted.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A preferred embodiment of the present invention will be described in detail.

FIG. 1 is a top view of a chemical mechanical polishing apparatus according to an embodiment of the present invention. In the figure, the chemical mechanical polishing apparatus 10 includes a casing 11, and includes at least a polishing area 25, an index table area 27, and a wafer loading and unloading area 35.
The polishing area 25 is provided with a flat table that supports a disk-shaped rotatable polishing pad 19 and has a polishing surface 26 that rotates about a fixed plane and a fixed axis. The polished surface 26 is preferably made of a polyurethane material. For example, a product sold by Rodel (IC-1000) has a polished surface made of polyurethane, and a polished surface made of this product. May be. In addition, the carrier head (not shown) is provided in FIG.
Circle indicated by five thicker lines shown in FIG.
, And has a surface that includes a tungsten thin film with respect to the polished surface.

Above the polishing surface 26 is provided a regulator handle 13 which rotates about the axis 17 and moves the regulator head 15 above the polishing surface in the direction of rotation φ. The adjuster handle 13 gradually moves in the rotation direction φ along the outer periphery of the polishing pad, and adjusts a relatively large polishing area corresponding to the outer surface portion. When the adjuster handle 13 moves toward the center of the polishing pad relative to a relatively small polishing area, the adjuster handle 13 moves toward the center of the polishing pad at a relatively high speed.

As another example, the adjuster handle may be fixed in one location, but with an adjuster head traversing from the outer periphery of the polishing surface to the center of the polishing surface, and in the rotational direction. Instead, it moves radially from the outer periphery to the center of the polishing surface. Of course, the application determines which type of regulator handle is used.

The adjuster head 15 holds a rotatable adjustment pad such as a ring-shaped diamond wheel or a brush, and is rotated with respect to the surface of the polishing pad to perform adjustment. When rotating, the rotating surface of the adjusting pad of the adjuster head 15 presses the surface of the polishing pad with a predetermined pressing force, and adjusts the surface of the polishing pad at a predetermined speed.

FIGS. 2A and 2B are a top view and a side view schematically showing the adjustment pad of the present invention. In FIG. 2A, the adjustment pad 48 in which diamond is buried includes an inner portion 55 and an outer portion 53 extending from the inner portion 55. The outer portion 53 has a surface coated with an abrasive material, such as diamond or alumina, which serves to remove the polishing pad material during the conditioning process.

FIG. 2B is a modified example of FIG. 2A, and is a top view and a side view schematically showing the brush-like adjustment pad 46. In the figure, a brush-like adjustment pad 46 is shown.
Comprises an inner portion 56 and an outer portion 54 having metal bristles extending from the inner portion 56, which contact the polishing pad during the conditioning process.

In these examples, the rotating surface of the adjusting pad has an inner hole (not shown) through which the adjusting solvent is supplied to the surface of the adjusting pad during the adjusting process. In particular, the bore may be connected to a source of the conditioning solvent, and the conditioning solvent may be selectively injected into the conditioning pad using a fluid control tool, such as a pump. This conditioning solvent is used to promote the dissolution of by-products remaining on the polishing pad after the manufacturing process. Of course, other methods may be used to inject the conditioning solvent into the conditioning pad.

Further, the chemical mechanical polishing apparatus 10 includes an adjusting element 21 for adjusting a residual by-product adhered to the polishing pad during the manufacturing process. The type of this residual by-product is determined by the manufacturing process and includes, for example, a silicon dioxide material (or a dielectric layer) for chemical mechanical polishing, and a metal (for example, tungsten, aluminum, copper) for chemical mechanical polishing. In the tungsten manufacturing process, a residual by-product that hinders the tungsten manufacturing process is tungsten oxide.

As an example of using a solvent to remove residual by-products on the adjustment pad in the adjustment element, in the example of a tungsten manufacturing process, a tungsten oxide formed during the manufacturing process using a solvent having a pH greater than 7 It can be removed. Also, in another embodiment of the tungsten manufacturing process, a boric acid solution may be used as the solvent. Also, in a preferred embodiment of the tungsten manufacturing process, an ammonium hydroxide solution may be used as a solvent.

The adjustment element 21 can also be used as a place for the adjustment pad. That is, when the adjustment pad is not used, it is necessary to move from the process area, and this area is outside the main polishing area, and is suitable as a place for the adjustment pad when not used. When the conditioning pad is placed in this location, the conditioning solution is injected into the conditioning pad and melts residual by-products therein.

The chemical mechanical polishing apparatus 10 has a loading stage 31 at which the wafer 1 is placed.
2 is placed in the clamp holder 45 and processed, and the wafer 12 is moved from the clamp holder 45 to the flipper arm 47 by the mechanical arm 29. Then, after the wafer 12 is transferred to the index table by the flipper arm 47 and processed, the wafer 12 is transported by the carrier to the rotating polishing pad and polished, and is washed inside the index table 24. Thereafter, the wafer 12 is transferred from the index table to the brushing tank 37 by the flipper arm 41 in the unloading station 33, where the wafer 12 is cleaned. Finally, the wafer 12 is transferred from the brushing tank 37 to one of the two clamp holders 43 of the unloading station 33 by an unloading transfer device (not shown).

Next, the chemical mechanical polishing process used for manufacturing the integrated circuit of the present invention will be described.

(1) Prepare a semiconductor substrate and (2) LOC
Forming a field oxide layer using OS technology, (3)
P-type wells and N-type wells are formed, (4) a gate oxide layer is grown, (5) a channel region is implanted to adjust the pulse voltage, and (6) a gate polysilicon layer is deposited and doped. (7) A polysilicon gate region is formed by limiting the gate polysilicon layer by the photomask 1, (8) An N-type LDD region is implanted by the photomask 2 by limitation, and (9) P is implanted by the photomask 3. (10) Sidewall spacers are formed in the polysilicon gate region, (11) N + type source / drain regions are implanted by photomask 4 and (12) Photomask 5 to implant the P + type source / drain regions in a limited manner, (13) annealing, and (14) BPSG on the semiconductor substrate. To form, covering the source / drain regions and the gate polysilicon regions, and polished BPSG layer by (15) the chemical mechanical polishing and adjustment method, (1
6) The opening for contacting the source / drain region is limited by the photomask 6, (17) the metal layer is formed in the contact region, (18) the metal layer is limited by the photomask 7, and (19) (20) defining a contact region with the polysilicon gate layer by defining an opening of the dielectric layer by using the photomask 8;
(21) forming a barrier metal layer on the polysilicon layer,
(22) A tungsten metal layer is formed on the metal layer, and (2)
3) Polishing and adjusting the tungsten metal layer, and (24) performing other manufacturing processes.

These manufacturing processes are used when forming a semiconductor integrated circuit, and at least two chemical mechanical polishing processes (ie, processes (15) and (23)) are used. A chemical mechanical polishing process utilizing these conditioning techniques is an essential requirement for dissolving residual by-products generated by polishing using a solution, and one of the solutions is that ammonium hydroxide is used to remove tungsten in a polishing pad. Used for dissolving oxides. As a result, the life of the polishing pad is greatly extended, and the chemical mechanical polishing apparatus is greatly improved.

FIG. 3 is a flowchart of a chemical mechanical polishing process according to the present invention.

First, a semiconductor substrate having a thin film to be polished is prepared (Step 201), and a polishing slurry mixture is directly injected into a polishing surface before polishing (Step 203), and the tungsten thin film is polished by a polishing apparatus and technique. (Step 205), this polishing forms residual by-products (Step 207), and the polishing surface is adjusted by the technique of the present invention (Step 209) before much tungsten oxide adheres to the polishing surface (Step 209). Return (step 211).

In these steps, the thin film is formed of a dielectric layer, for example, silicon dioxide, silicon nitride, borophosphosilicate glass, fluorinated phosphosilicate glass (f).
luorophosphosilicate glass) and other materials. Further, the thin film may be a metal, for example, tungsten, aluminum, copper, or the like, and is determined according to its use.

The tungsten metal layer is used for interconnection in a manner as shown in the schematic cross-sectional view of FIG. The cross-sectional view shown in FIG. 4 shows a semiconductor substrate 31 including a field effect transistor 32, an active region, and a patterned metal layer 3.
3 and other elements. This tungsten is usually deposited by sputtering or chemical vapor deposition techniques.

The metal layer 33 is sandwiched between two dielectric layers 37, which are currently polished by this polishing technique. Application-specific integrated circuits (ASICs), microprocessors (MPs)
U), memory circuits, and integrated circuits in other devices. Many other structures using sub-micron sized design rules also have polishing processes, such as chemical mechanical polishing, applied in part.

The polishing technique used in step 205 employs a rotatable polishing pad applied to the surface of the tungsten thin film. Polishing pads with a polishing surface include, for example, polyurethane, polyester, acrylic,
Acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly 4-methylpentene, cellulose, cellulose ester, polyamide such as nylon and aramid, polyimide, polyimide amide, polysiloxane copolymer, polycarbonate,
It is composed of an oxirane compound, a phenol resin and the like, but the required material is determined depending on the use.

In step 203, the polishing slurry mixture is injected directly into the polishing surface prior to polishing, and
Transferred to the polishing pad via sharp holes connected to a source of polishing slurry. The polishing slurry usually contains abrasive particles and an oxidizing agent. Hydrogen peroxide, K
IO ₃ , iron nitrate solution or the like is used. Abrasive particles are usually borosilicate glass, titanium dioxide, titanium nitride, aluminum oxide, aluminum trioxide, iron nitrate, cerium oxide, silicon dioxide, silicon nitride, silicon carbide, graphite, diamond, or a mixture thereof, Preferably, an acid solution is used.

The tungsten metal of the tungsten thin film to be removed during the polishing process reacts with the acid solution to form, for example, insoluble tungsten oxide particles, which adhere to the polishing surface and gradually reduce the efficiency of the polishing process. However, there is a problem that the removal of the tungsten thin film is affected.

Therefore, before the tungsten oxide adheres to the polishing surface, the polishing surface is adjusted based on step 209. That is, the tungsten oxide particles adhered to the adjustment pad are dissolved and removed using an adjustment solution of ammonium hydroxide.

[0041] In general, ammonium hydroxide, as shown in the following equation, ammonium ion (NH ₄ ⁺⁾ and hydroxide ions - are dissociated into ^(OH).

The ^{_{NH 4 OH → NH 4 + +}} OH - The hydroxide ions dissolve the tungsten trioxide insoluble as shown in the following equation.

[0043] ^{_{WO 3 + 2OH - → WO 4}} 2- + H 2 O That is, soluble tungsten oxide ions (WO ₄
^2- ) and water are dissociated and removed, and at the same time, insoluble tungsten trioxide on the polished surface can be removed. In addition, insoluble tungsten trioxide can be removed by the following manufacturing process.

That is, the polishing process of tungsten uses a polishing pad of polyurethane, for example, a polishing pad of IC-1000 (trade name) manufactured by Rodel, which rotates at a speed higher than a speed of 30 rpm, and a carrier of a carrier. 2p on back of semiconductor substrate by head
Apply a pressure greater than si to 8 psi, preferably greater than 4 psi. Further, the steps of repeating the preparation of the semiconductor substrate and the polishing of the thin film are performed at a thickness of about 4,000 to 7000,
It is preferably performed to form a 6000 ° tungsten thin film.

In this embodiment, the adjustment is performed by injecting an ammonium hydroxide solution having a concentration of 2% or more into the adjustment pad, and the solution is injected into the adjustment pad through a sharp hole in the adjustment pad. I do. That is, the conditioning solution is injected into the conditioning pad from a solution source through a sharp hole in the conditioning pad. In addition, it is also possible to inject the solution into the adjustment pad by the adjustment device.

The adjustment pad is preferably a brush-like unit made of a PVA material (polyvinyl alcohol), and the brush has sufficient hardness to remove tungsten oxide. Then, it is rotated at a speed of 45 rpm by a rotating wheel, and a pressure in the range of 0 to 2 psi is applied on the polishing pad. During the reconciliation process,
20 ° C. to 50 ° C. to improve the removal ability of the conditioning solution
Although the adjustment is performed at a temperature of ° C., it is preferable to remove the tungsten oxide from the polishing pad at a temperature higher than 30 ° C.

Separately, the rotating wheel impregnated with abrasive acts on the polishing surface and removes insoluble tungsten trioxide and other substances present on the polishing surface with the conditioning solution. The rotating wheel impregnated with the abrasive is more likely to break the polishing pad than the brush-shaped unit, so the brush-shaped unit is preferable.

In a particularly preferred embodiment, any wafer having a tungsten thin film is processed by a chemical mechanical polishing apparatus. According to the adjustment technique of the present invention, at least 1000 wafers can be processed before the polishing pad is replaced, whereas according to other adjustment techniques, the length of processing time is unknown, so the polishing surface material is It is already completely worn before replacement. Conventionally, when the manufacturing process cannot overcome the limitations of, for example, time, removal efficiency, and the like, it is responded by replacing the polishing surface.

The acidity or pH value of the conditioning solution has a significant effect on the formation of insoluble tungsten oxide. For example, p
When the H value is greater than 4, a soluble tungsten oxide is formed, and when the H value is less than 4, an insoluble tungsten oxide is formed. FIG. 5 shows the effect of the pH value on the formation of insoluble tungsten oxide, which appears when the pH value is less than 4. However, if the pH value is high,
Tungsten becomes corrosive and forms soluble tungsten oxide.

[0050]

As described above, according to the present invention, a relatively uniform polishing surface can be obtained and the life of the polishing pad can be extended. The present invention also reduces the time required to maintain and replace pads in advance using chemical mechanical polishing tools. Furthermore, the process of removing these scars can be omitted because the fine scars due to the residual conventional by-products are reduced. Other effects are as described above.

[Brief description of the drawings]

FIG. 1 is a top view of a chemical mechanical polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a top view and a side view schematically showing an adjustment pad according to the present invention.

FIG. 3 is a schematic flowchart of a tungsten chemical mechanical polishing process according to the present invention.

FIG. 4 is a sectional view of a semiconductor device manufactured according to the present invention.

FIG. 5 is a graph for explaining a theoretical state of tungsten in a chemical mechanical polishing process according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 chemical mechanical polishing apparatus 13 adjuster handle 15 adjuster head 19 polishing pad 21 adjusting element 25 polishing area 26 polishing surface

Claims (8)

[Claims] A step of preparing a semiconductor substrate coated with a thin film containing a tungsten material; a step of polishing the thin film using a polishing pad and a polishing slurry; Forming a by-product containing a tungsten oxide material and leaving it on the polishing pad, adjusting the polishing pad with an ammonium hydroxide solution, and removing most of the tungsten oxide from the polishing pad. A chemical mechanical polishing method comprising: a step of removing a material; and a step of repeatedly performing the above steps to a satisfactory degree. 2. The polishing pad contains a polyurethane material, the tungsten oxide material is formed by the action of a tungsten-containing material and a polishing slurry, and the tungsten-containing material is chemically vapor-deposited tungsten. The chemical mechanical polishing method according to claim 1, wherein the chemical mechanical polishing method is sputtering tungsten. 3. The step of forming the by-product is performed to form a tungsten thin film having a thickness of about 4000 to 7000 °, wherein the tungsten oxide material is tungsten trioxide, and the pH of the ammonium hydroxide solution is The chemical mechanical polishing method according to claim 1, wherein the value is greater than 7. 4. The chemical mechanical polishing method according to claim 1, wherein the pH value of the ammonium hydroxide solution is larger than 4, and the polishing slurry is an oxidizing agent or an acidic oxide. 5. The chemical mechanical polishing method according to claim 1, wherein the step of adjusting the polishing pad is performed by a rotating diamond wheel or a brush-like adjuster, and wherein the adjusting step supplies deionized water to the polishing pad. 6. A method for preparing a polishing pad coated with an insoluble metal oxide in chemical mechanical planarization, comprising: a rotatable adjustment pad containing an adjustment solution, which is an aqueous solution of an ammonium hydroxide compound, on an upper part thereof. A method of manufacturing an integrated circuit, comprising: attaching to a polishing pad surface; and removing a majority of the insoluble metal oxide using the conditioning solution and the conditioning pad. 7. The polishing pad according to claim 6, wherein the polishing pad contains a polyurethane material, the pH value of the conditioning solution is greater than 7, and the conditioning pad is a brush-like pad or a diamond pad. the method of. 8. A flat table having a polishing pad, wherein a polishing surface of the polishing pad rotates around a fixed axis, and a wafer having a surface containing a tungsten thin film with respect to the polishing surface. A carrier head, a slurry source containing an acid solution for causing a polishing slurry to act on the tongue thin film to form an insoluble tungsten oxide, and depositing the insoluble tungsten oxide on the polishing pad; A conditioning element connected to a conditioning solution source that is an ammonium oxide solution to dissolve insoluble tungsten oxide.