Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
2001-08-23
2002-10-22
Booth, Richard (Department: 2812)
Semiconductor device manufacturing: process
With measuring or testing
C438S424000, C438S692000
Reexamination Certificate
active
06468817
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for manufacturing a semiconductor integrated circuit device, and particularly, to a technique which can effectively be used for manufacturing a semiconductor integrated circuit device, including a step of polishing a thin film formed on a surface of a semiconductor wafer with use of CMP (Chemical Mechanical Polishing).
BACKGROUND OF THE INVENTION
The chemical mechanical polishing is a new micro processing technique involved by high integration and high performance of a semiconductor integrated circuit device (LSI). For example, this technique is adopted to formation of an element separation groove called SGI (Shallow Groove Isolation) and flattening of an interlayer insulating film in a multi-layered wire forming step and forming of an imbedded metal wiring. This chemical mechanical polishing is described, for example, in U.S. Pat. No. 4,944,836.
The chemical mechanical polishing is a method in which the surface of a wafer is polished while supplying polishing slurry onto a surface plate to which a polishing pad made of hard resins is adhered. Used as the polishing slurry is a resultant obtained by dispersing micro grains of a polishing agent such as silica (silicon oxide) or the like in pure water and by adding alkali for adjusting pH thereto. Known as silica contained in the polishing slurry are fumed silica (aerosol silica) obtained by burning silicon tetrachloride (SiCl
4
) and colloidal silica obtained from sodium silicate as a raw material (“The Science of CMP”, pages 128 to 142, issued from Kabushiki-Kaisha Science Forum, Jul. 19, 1999).
Japanese Patent Laid-Open Publication No. 10-163284 discloses a wafer surface inspection method for determining whether the number of particles is the number of actual particles or the number including a scratch when particles remaining on the wafer surface after chemical mechanical polishing and cleaning processing are counted by a particle counter.
SUMMARY OF THE INVENTION
Recently, chemical mechanical polishing for LSI is carried out through a plurality of steps in a wafer process, in order to promote downsizing of elements and multi-layering. For example, in a step of forming an element separation groove in the main surface of a wafer, firstly, the main surface of the wafer is dry-etched, using an oxidation resistant insulating film as a mask, thereby to form a groove in the element separation region. Subsequently, a silicon oxide film having a greater film thickness than the depth of the groove is formed on the main surface of the wafer, and thereafter, the silicon oxide film is subjected to chemical mechanical polishing, using the oxidation-resistant insulating film as a stopper for polishing, so that the silicon oxide film selectively remain inside the groove. An element separation groove is thus formed. Also, in a step of flattening an inter-layer insulating film between a gate electrode and a wire above the gate electrode or between multi-layered wires, a method based on chemical mechanical polishing of a silicon oxide film has come to be used frequently in place of a flattening method using a conventional spin-on-glass (SOG) film.
When the chemical mechanical polishing is adopted to a step of manufacturing an LSI, the quality of the wafer after polishing is an important problem. Representative problems for qualities of wafers after polishing are (1) Scratch, (2) Sticking foreign materials (particles), (3) Uniformity (flatness), and the like.
The (1) scratch is roughly classified into macro scratch and micro scratch. The former is considered to be caused by fall of grinder particles from a diamond dresser used for dressing the polishing pad. The latter is mainly caused by a large agglomerate contained in polishing slurry or clogging of the polishing pad.
In addition, particles contained in the polishing slurry such as grinder particles and a large amount of alkali metal ions remain on the wafer surface after polishing. Therefore, cleaning processing (post cleaning) after polishing must be carried out under sufficient management to remove (2) sticking foreign materials (particles).
In the step of polishing a silicon oxide film as described above, polishing slurry obtained by dispersing silica particles in water is used generally. A hydrophilic silanol group (Si—OH) exists on the surface of silica. Therefore, when silica particles are dispersed in water, cohesion of particles (primary particles) occurs due to the hydrogen bond between particles and the force of van der Waals, so that agglomerates (secondary particles) having a greater grain diameter than a single particle are formed. Therefore, in case of polishing slurry obtained by dispersing silica particles (dispersoid) in water (dispersion medium), the agglomerates constitute components of grinder particles.
The agglomerates do not cause any problem if they have a relatively small grain diameter. However, since some huge agglomerates having a grain diameter of 1 &mgr;m or more exist in the polishing slurry in practice, they cause a very small scratch called a micro scratch on the surface of the wafer, thereby to cause lowering of the yield and reliability. Particularly, in the step of forming an element separation groove described above, a thin oxidation-resistant insulating film formed on the wafer surface is used as a stopper for polishing, to polish the silicon oxide film. Therefore, if a micro scratch occurs on the surface of the oxidation-resistant insulating film, it reaches the silicon substrate as a ground layer, causing deterioration in characteristics of the transistor and etching residues during processing of a gate.
As has been described above, micro scratches are mainly caused by agglomerates in polishing slurry. Therefore, the number of agglomerates is reduced, for example, by a method in which an interface acting agent is added to polishing slurry to improve dispersibility of silica particles, a method in which polishing slurry is filtered to remove agglomerates, or the like. However, even this kind of countermeasure is taken, micro scratches may be caused when the polishing condition is changed, e.g., when the lot of the polishing slurry is changed or when the polishing pad is repapered.
As a countermeasure against micro scratches, a proposal has been made of a grinding grain free polishing method which does not contain grinding particles as a component such as silica or the like or the concentration of the grinding component is lowered very much (for example, Japanese Patent Application No. 10-317233). However, since the range to which this method is applicable is limited, polishing slurry containing grinding particles as a component must be used in the current mass-production wafer process.
Consequently, in order to prevent deterioration of the yield and reliability due to micro scratches, occurrence of a micro scratch must be found in a stage which is as early as possible after the chemical mechanical polishing processing, the factor causing the occurrence of the micro scratch must be found, and appropriate polishing conditions must be selected.
However, since micro scratches have a very small size, it is very difficult to detect and check occurrence of a micro scratch immediately after polishing. In most cases, abnormality caused by a micro scratch is found only after several steps or at the time of an inspection on a cross-section which is carried out in the final inspection step of a wafer process. Therefore, there is a problem that a large number of wafers have become defective when a defect caused by a micro scratch is found in the mass-production wafer process in which chemical mechanical polishing is carried out.
An object of the present invention is to provide a technique capable of detecting occurrence of micro scratches in a stage which is as early as possible after chemical mechanical polishing processing in a mass-production wafer process.
Another object of the present invention is to provide a technique capable of detecting micro scratches, without performing a brea
Abe Hisahiko
Katsumura Yoshiteru
Kenbo Yukio
Nakabayashi Shinichi
Tsuchiyama Hirofumi
Antonelli Terry Stout & Kraus LLP
Booth Richard
Hitachi , Ltd.
Roman Angel
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