Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2000-09-13
2002-11-19
Nguyen, Tuan H. (Department: 2813)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S633000, C438S626000, C438S691000
Reexamination Certificate
active
06482743
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P11-259098 filed Sep. 13, 1999, which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor device and its manufacturing method, especially suitable for application to a semiconductor integrated circuit device having multi-layered wiring.
2. Description of the Related Art
Along with progressively high integration of elements for semiconductor integrated circuit devices, wiring techniques are moving, toward further microminiaturization and multi-layered structures. It is said, for example, that logical LSI having the design rule of 0.18 micron class requires multi-layered wiring of six or more layers. Therefore, multi-layered wiring processes are getting more and more important in manufacturing processes of semiconductor integrated circuit devices.
However, developments of microminiaturization and multi-layered structures of wiring invited a new problem. That is, since developments of microminiaturization and multi-layered structures of wiring make level differences of inter-layer insulating films large and sharp, it is difficult to make a metal wiring pattern thereon freely from breakage at different levels or other faults.
To solve this problem, chemical mechanical polishing (CMP) has been introduced and used in a wiring process. This method is configured to smooth the surface of an inter-layer insulating film completely by CMP and thereafter make metal wiring thereon. Alternatively, the method is configured to make a via hole in the inter-layer insulating film for electrically connecting upper and lower wiring layers. The method then buries a metal film in the via hole, and subsequently polishes and smooths the metal film by CMP to make a plug in the via hole.
Here is explained a conventional chemical mechanical polishing unit. An example thereof is shown in FIG.
1
. As shown in
FIG. 1
, the chemical mechanical polishing unit includes, as its major components, an abrasive plate
103
which has an abrasive cloth
101
fixed to it and rotates in the arrow-marked direction
102
in
FIG. 1
with an external driving force; a carrier
106
which holds a substrate
104
, such as a wafer, to be polished and urges it onto the abrasive cloth
101
with a polishing pressure, and rotates in the arrow-marked direction
105
in
FIG. 1
with an external driving force. The chemical mechanical polishing unit also includes a slurry supply system
107
which supplies an abrasive agent, i.e. slurry, prepared by suspending abrasive particles of silica or alumina, for example, in water containing a pH adjusting agent. From one end of a slurry supply opening
108
attached to the slurry supply system
107
, slurry
109
is poured down to near the rotation center of the abrasive plate
103
, and the poured slurry
109
is spread over the abrasive cloth
101
due to a centrifugal force produced by rotation of the abrasive plate
103
. Then, while supplying the slurry
109
in this manner, both the abrasive plate
103
and the carrier
106
are rotated to rub the substrate
104
with the abrasive cloth
101
and thereby grind the surface of the substrate
104
. At that time, depending upon the material to be polished, namely, insulating film or metal film, chemical mechanical polishing is effected in a basic or acidic atmosphere.
Chemical mechanical polishing is currently the most effective smoothing method, but it still involves various problems. One problem is the difficulty of burying a metal in via holes by sputtering that has been used for making a metal film, because of progressive reduction of the diameter of the via holes due to microminiaturization. Recently, therefore, electrolytic plating or CVD is often used for making metal films instead of sputtering. On the other hand, there is an active trial to use copper (Cu) having a low specific resistance, high resistance to electro migration and high reliability as wiring metal instead of aluminum (Al) alloys heretofore used. However, when Cu is used to make a film by electrolytic plating, post-plating configuration is not yet satisfactory. More specifically, as shown in
FIG. 2A
, in the case where a Cu film
204
is made by electrolytic plating after via holes
203
are made in an inter-layer insulating film
202
stacked to cover a base-layer wiring
201
of a substrate, not shown, an unevenness is produced on its surface, reflecting the density of the via holes
203
made in the inter-layer insulating film
202
. Therefore, if the Cu film
204
is polished by using slurry of a suspension type normally used for chemical mechanical polishing, the liquid of the slurry forms a thin liquid film between the substrate to be polished and the abrasive cloth, and cause a so-called hydro plane phenomenon. This is similar to the phenomenon that, when a car runs on a highway in rain, rain makes a thin liquid film between the road surface and tires and makes tires liable to slip. Here is remarked the problem that, due to this hydro plain phenomenon, a kind of gap is produced between the abrasive cloth and the substrate and disturbs smoothing by polishing, and the surface configuration of plugs
205
of the Cu film left in the via holes
203
after polishing remain uneven without being smoothed sufficiently. As a result, if an overlying inter-layer insulating film is formed after the plugs
205
are made, undesirable configuration of the plugs
205
and failure to bury the upper plug material in the via holes, for example, might decrease the production yield of semiconductor integrated circuit devices.
Under the circumstances, active studies are being made toward CMP not using slurry. Since this method does not use slurry, the above-mentioned problem does not occur. However, in simple words, this method is similar to grind a surface with a file, and it has the drawback that the evenness of the surface after polishing is inferior to that by CMP using slurry.
Under the above-explained background, for the next-generation semiconductor integrated circuit devices, there has been a demand for chemical mechanical polishing capable of accomplishing global surface evenness while accomplishing local surface evenness as well.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a semiconductor device and its manufacturing method capable of accomplishing global surface evenness while also accomplishing local evenness by removing defects of local surface configuration.
A more general object of the invention is to provide a semiconductor device and its manufacturing method capable of optimizing polishing and obtaining well-smoothed configuration.
To solve the above-indicated problems involved in the conventional techniques, the Inventor made a hard study. Its outline is explained below.
Today's chemical mechanical polishing uses suspension-type slurry for polishing from its starting process. Therefore, if the workpiece to be polished has an unevenness on its surface when polishing is started, the suspension-type slurry causes the above-indicated hydro plain phenomenon between the surface to be polished and the abrasive cloth, and polishing progresses while uneven portions particularly requiring polishing on the workpiece to be polished does not contact the abrasive cloth sufficiently. As a result, the surface configuration after polishing remains insufficient in evenness. Thus, the Inventor made various researches, and found that the surface after polishing was made more compact and smooth by conducting rough smoothing by using non-suspension-type slurry in the first step of polishing so as to remove projecting portions only by physical motions of abrasive particles and thereafter executing polishing by using suspension-type slurry.
The inventor made further studies, and realized, as a result of again reviewing the above-mentioned suspension-type slurry and non-suspension-type slurry from the standpoint of the d
Nguyen Tuan H.
Pham Thanhha
Sonnenschein Nath & Rosenthal
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