Fabrication method for semiconductor integrated circuit device

Details Fabrication method for semiconductor integrated circuit device Fabrication method for semiconductor integrated circuit device

2001-05-15

2003-02-04

Lebentritt, Michael S. (Department: 2824)

Semiconductor device manufacturing: process

Chemical etching

Combined with the removal of material by nonchemical means

C438S691000, C438S693000, C438S694000

Reexamination Certificate

active

06514864

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a technique for fabricating a semiconductor integrated circuit device; and, more particularly, the invention relates to a technique that is applicable to the fabrication of a semiconductor integrated circuit device, including the step of polishing a thin film formed on the surface of a semiconductor wafer by a chemical mechanical polishing (CMP) method.
In the fabrication of a semiconductor integrated circuit device, an insulating film or dielectric film deposited on a silicon wafer is polished by a chemical mechanical polishing method to form an element isolation groove, to planarize an interlayer insulating film or to form a plug or a buried wiring.
In the conventional chemical mechanical polishing method, a polishing slurry is supplied on a lapping plate to which a pad made of a hard resin is attached, and the surface of a wafer is polished. As a polishing slurry, there is usually employed a slurry wherein fine particles of an abrasive, such as silica (silicon oxide), are dispersed in pure water, to which slurry an alkali for pH adjustment is added.
For silica in the polishing slurry, there is used a colloidal silica obtained by using sodium silicate as a starting material, or fumed silica obtained by combusting silicon tetrachloride (SiCL
4
) with an oxyhydrogen flame. The polishing slurry using the former colloidal silica has the problem that it contains sodium (Na) as an impurity. Although a colloidal silica is available whose content of sodium is reduced for overcoming the problem, such colloidal silica is inconveniently higher in production cost than the latter-mentioned fumed silica.
On the other hand, fumed silica is poorer than colloidal silica with respect to the dispersion stability in an aqueous dispersing medium. Accordingly, a problem has been indicated in the use of fumed silica in that, when a wafer is polished using a polishing slurry comprising this type of silica, the wafer surface suffers microscratches caused by coarse coagulations of the silica particles in the slurry. Many techniques for improving the dispersion stability of this type of slurry have been proposed.
It will be noted that the processes for preparing colloidal silica and fumed silica and the physical properties thereof are set out, for example, in Science of CPM, published on Jul. 19, 1999, by Science Forum Co., Ltd., pp. 128 to 142.
Japanese Laid-open Patent Application No. Hei 8(1996)-257 8 98 discloses an aqueous free grain slurry and its preparation. More particularly, abrasive particles, such as diamond, silicon carbide, alumina, silica, zirconia, cerium oxide, iron oxide, chromium oxide or the like, are applied on the surface thereof with plus charges from charge-determining ions, to which a surface active agent is attached so as to render the abrasive particles hydrophobic, thereby establishing a coagulated state. Eventually, the abrasive particles are prevented from settling with time, so that good dispersion stability and re-dispersability can be maintained over a long period of time.
Japanese Laid-open Patent Application No. Hei 11(1999)-246852 discloses a slurry for polishing and its preparation wherein the dispersability of abrasive grains is good. This slurry for polishing is made of a mixture of abrasive grains, an etching aqueous solution made of an alkaline or acidic aqueous solution having the ability of chemically etching a material to be polished, and a polymer material having a hydrophilic group, characterized in that the polymer material having a hydrophilic group is dispersed in the form of fine globules or is dissolved in the etching aqueous solution.
The abrasive grains used include those of oxides, sulfates or carbonates of silicon, aluminum, titanium, manganese, cesium, an alkaline earth metal or an alkali metal. The polymer material having a hydrophilic group includes a polyamide, a polyimide, a polyethylene, a polystyrene, a polyether, a polyurethane, a polycarbonate, a polyvinyl alcohol, a polyvinyl chloride or a polyvinylidene chloride, each having a carboxyl group, a hydroxyl group, a nitro group or an amino group.
With the slurry for polishing, the polymer material having a hydrophilic group is adsorbed on the abrasive grains, thereby imparting to the slurry thixotropic properties and the sedimentation-preventing function of the abrasive particles, under which the abrasive grains are mutually kept in a weakly coagulated state. Individual abrasive grains are kept in a well dispersed condition with the aid of the network structure through uniform secondary bonds of the molecules of the polymer material. As a result, the abrasive grains do not settle upon storage of the slurry; and, thus, the slurry can be used for polishing as it is without resorting to a procedure for recovering the dispersability by agitating the slurry again after long-term storage thereof.
Japanese Laid-open Patent Application No. Hei 10(1998)-193255 proposes a method of storing a slurry for polishing, which contains abrasive grains, such as of cesium oxide, alumina or manganese oxide, that are poor in dispersability in a liquid, so that when allowed to stand, they are coagulated with time and the polishing characteristics, such as the polishing rate or selection ratio of polishing, are changed in relation to time. In this storage method, after application of ultrasonic vibrations to the polishing slurry, the average size of the grains or a redox potential is measured so that the polishing rate is controlled by monitoring the average grain size or redox potential. It is stated that according to this method, because the degree of secular change in polishing rate of the polishing slurry can be confirmed, the polishing rate of the slurry under storage can be readily and reliably controlled, thus resulting in a great throughput and precise polishing.
SUMMARY OF THE INVENTION
In order to promote the scale down of elements and the formation of multi-layered wirings, a recent LSI is subjected to chemical mechanical polishing in a plurality of steps of a wafer process. For instance, in the step of forming an element isolation groove in the main surface of a wafer, the main surface of the wafer is dry etched using an oxidation-resistant film as a mask to form a groove in an element isolation region. Subsequently, a silicon oxide film is deposited on the main surface of the wafer, including the inside of the groove, to a thickness larger than the depth of the groove, followed by subjecting the silicon oxide film to chemical mechanical polishing by use of the oxidation-resistant insulating film as a stopper for polishing, thereby selectively leaving the silicon oxide film inside the groove to form an element isolation groove.
In such a chemical mechanical polishing step as set out above, it is usual to use a polishing slurry wherein silica particles are dispersed in water. Silica has a hydrophilic silanol group (Si—OH) on the surface thereof, so that when silica particles are dispersed in water, coagulation of particles (primary particles) takes place owing to the hydrogen bond among particles through the silanol group and the van der Waals force, thereby forming coagulated particles (secondary particles) having a size (i.e. diameter) larger than a single particle. Accordingly, the coagulated particles constitute a grain component in a polishing slurry where silica particles (dispersoid) are dispersed in water (dispersion medium).
When the coagulated particles are relatively small in size, little or no problem is involved. Nevertheless, an actual polishing slurry has coarse coagulated particles having a size of 1 pm or over (in this specification, coagulated particles having a size of 1 pm or over is especially called “coarse coagulated particles Such coarse coagulated particles cause fine defects, which are called micrO
3
cratche
3
, to occur on the surface of a wafer, thereby bringing about the lowerings of yield and reliability. For instance, in the step of forming such an element isolation groove as set out before, the silicon oxide film is s

Affiliated with

Also associated with

Rating

Fabrication method for semiconductor integrated circuit device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Fabrication method for semiconductor integrated circuit device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fabrication method for semiconductor integrated circuit device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3160242