Composition for chemical mechanical polishing

Details Composition for chemical mechanical polishing Composition for chemical mechanical polishing

2000-06-22

2002-09-10

Kunemund, Robert (Department: 1765)

Compositions

Etching or brightening compositions

C438S692000, C510S176000

Reexamination Certificate

active

06447694

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing composition which can be used in the semiconductor industry. More particularly, the present invention relates to use of Al
2
O
3
/SiO
2
composite particles as an essential abrasive so as to improve the removal rate without causing microscratches.
2. Description of the Prior Art
Nowadays, the increase in the density of integrated circuits makes their producers aware of the importance of the global planarization of wafers. Under the circumstance, intensive and extensive attention has been given to CMP (Chemical Mechanical Polishing) as a planarization method.
Typically, highly integrated semiconductor devices are manufactured by alternately depositing conducting materials and insulating materials and thus forming patterns. If a surface is not flat, it is very difficult to form a new pattern on the surface. To highly integrate semiconductor devices, it is required to minimize feature sizes and to perform multilevel interconnections. Global planarization is one of the most important prerequisites to achieve this.
As the structures of microprocessors and DRAMs become multileveled, for instance, as the metal layer for the third generation version of 64 MDRAM becomes of a triply structure, problems may occur owing to the process complexity if the films are deposited onto the layers which are not flat. Particularly as for the photolithography process, when it is carried out over a non-planar layer, an incident light will reflect diffusely, which will result in an imprecise photoresist pattern. Thus, there remains a need to make the structure between layers simpler. For this, the surface is planarized by polishing unnecessarily deposited parts thereon, so as to effectively deposit more film layers.
Of the planarization methods ever known, CMP is the most effective. The other planarization methods which have been developed thus far, such as SOG/Etch Back/ECR Depo & Etch, are very complicated in process procedure, requiring 2-5 process steps, but the CMP process can be finished simply by polishing and cleaning.
Conventional polishing compositions or slurries for use in semiconductor CMP processes commonly comprise metallic oxide. According to the materials to be polished, the conventional polishing compositions or slurries can be largely classified into three kinds: polishing compositions for monosilicon, for insulating layers, and for metal lines and plugs.
Abrasives which are most extensively used in the semiconductor CMP process are silica (SiO
2
), alumina (Al
2
O
3
), ceria (CeO
2
), zirconia (ZrO
2
), and titania (TiO
2
), which can be produced by a fuming or a sol-gel method, as described in U.S. Pat. Nos. 4,959,113, 5,354,490, and 5,516,346 and WO 97/40,030. There has recently been reported a composition or a slurry comprising mangania (Mn
2
O
3
) (European Pat. No. 816,457) or a silicon nitride (SiN) (European Pat. No. 786,504). These metal oxides are independently used in the patent references and determine the properties and performance of their polishing slurries. With a relatively unstable dispersed state under an acidic condition, for example, a polishing slurry comprising silica causes less microscratches compared with a polishing slurry comprising alumina, but shows a low removal rate against barrier material when being applied as a metal slurry. On the other hand, a polishing slurry comprising alumina is advantageous in terms of being more stable in a dispersed state compared with a polishing slurry comprising silica and high in the removal rate against barrier materials, but suffers from a serious disadvantage of causing a quantity of microscratches after polishing.
Improved as they are to some extent in physical properties and polishing performance, recently developed polishing slurries comprising ceria, zirconia, titania, mangania or silicon nitride have not yet been stably established in the production processes on a commercial scale and are expensive compared with ones comprising silica or alumina.
Also, there have been reported attempts to use two or more metal oxides in combination with the aim of improving polishing performances. For example, U.S. Pat. No. 5,084,071 discloses that the presence of alumina (Al
2
O
3
) particles brings the slurry comprising silica as a main abrasive to an improved level of polishing reproductivity. Another combined polishing slurry can be referred to WO 97/13889, which discloses the uses of alumina (a type) in combination with a relatively soft metal oxide. Such composite polishing slurries exhibit better results in removal rate and selectivity than do the polishing slurries comprising single metal oxides, but have much to be improved. For example, when a great quantity of alumina (a type) coexists with a small quantity of silica in a polishing slurry, the oxide particles are in a simple mixed state so that poor dispersion stability appears on the slurry, giving rise to particle coagulation during storage. In result, the polishing slurry suffers sedimentation.
SUMMARY OF THE INVENTION
Leading to the present invention, the intensive and thorough research on a polishing composition, repeated by the present inventors, resulted in the finding that fine Al
2
O
3
/SiO
2
composite particles increase a removal rate on semiconductor wafers as well as are superior in polishing selectivity without causing microscratches after polishing.
Therefore, it is an object of the present invention to overcome the above problems encountered in prior arts and to provide a polishing composition which is superior in removal rate and polishing selectivity and free of causing microscratches.
In accordance with the present invention, there is provided a polishing composition comprising fine Al
2
O
3
/SiO
2
composite-based metal oxide particles, deionized water and additives.
The polishing composition of the present invention is suitable for use in polishing various industrial products, including semiconductors, photomasks, glassdiscs, and synthetic resins, especially, in surface planarization of device wafers. In detail, with superiority in removal rate and polishing selectivity for thin films and low incidence of microscratches after polishing, the polishing composition of the present invention can find numerous applications in CMP fields, especially in highly integrated device fabrication fields, including the polishing of silicon, interlayer insulating films, metal lines and plug, and barrier materials.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention contemplates use of an Al
2
O
3
/SiO
2
composite as an essential metal oxide ingredient of a CMP composition suitable for use in fabricating semiconductor devices.
The Al
2
O
3
/SiO
2
composite, a feature of the present invention, can be prepared from AlCl
3
and SiCl
4
by a Co-Fuming method as follows:
AlCl
3
+
SiCl
4
⁢
→
Heat
⁢
 
⁢
(
≥
 
⁢
1000
⁢
°
⁢
 
⁢
C
.
)
air
⁢
Al
2
⁢
O
3
/
SiO
2
+
HCl
.
The metal oxide particles thus obtained are not in a simple mixed state of Al
2
O
3
and SiO
2
, but in a composite state in which Al
2
O
3
is linked to SiO
2
. The composite shows characteristic phisycal properties which are quite different from a simple mixture of the two components. Physical properties of the Al
2
O
3
/SiO
2
composite based on ‘VP MOX 90’, a brand name of Degussa, Germany, are summarized in Table 1, below.
TABLE 1
Physical properties of Al
2
O
3
/SiO
2
(based on VP MOX 90)
Specific Surface Area (BET)
100 ± 25 m
2
/g
pH
>3.8
Isoelectric Point
6~7
Al
2
O
3
Content
67 ± 15 wt %
SiO
2
Content
33 ± 15 wt %
Bulk density
60~100 g/l
Cl Content
<0.5 wt %
The contents of each component in the composite can be controlled depending on fed amount and reaction condition. In a typical Co-Fuming method, a composite comprising 67±15 wt % of Al
2
O
3
and 33±15 wt % of SiO
2
is obtained, which is preferable for the present invention.
Any of the conventional dispersion methods, su

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