Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2003-04-24
2004-09-14
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S648000, C438S627000
Reexamination Certificate
active
06790734
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device having a gate electrode which comprises a SiGe layer.
2. Description of the Related Art
In manufacturing a semiconductor device, patterning of a conductive film or an insulating film is carried out by either forming a resist film on the conductive film or the insulating film which is formed on a semiconductor substrate and thereafter forming a resist pattern by photolithography or forming a hard mask pattern of SiO
2
or the like thereon, and then applying etching to the conductive film or the insulating film with the pattern being used as a mask. For forming a minute pattern, dry etching is normally employed there at. However, when patterning by dry etching, contaminants such as dry etching products and particles are stuck onto the semiconductor substrate. If contaminants of this sort remain stuck thereon in the subsequent steps, decrease in production yield, deterioration of device characteristics and lower reliability may occur. Therefore, cleaning the semiconductor substrate after patterning is required so as to thoroughly remove the contaminants stuck onto the substrate.
In regards to the cleaning performed after patterning the insulating film, there is disclosed, for instance, in Japanese Patent Application Laid-open No. 142741/1992, an apparatus for manufacturing a semiconductor wherein a semiconductor wafer is treated with a cleaning solution. This publication describes that, after using a hydrofluoric acid based agent (a mixed solution of hydrofluoric acid and ammonium fluoride) for the treatment, a silicon oxide film overlying a silicon semiconductor wafer is patterned by means of wet etching. Then the substrate is treated with a mixed solution of sulfuric acid and hydrogen peroxide to remove the photoresist, and the wafer is cleaned with a mixed solution of ammonia, hydrogen peroxide and pure water to remove particles stuck on the wafer surface. Further, the publication mentions that drying the wafer tends to make particles strongly stuck to the wafer surface, and their removal is considerably difficult, and such a problem can be overcome if the treatment for the removal of the photoresist as well as that for the removal of particles are performed consecutively after wet etching of the silicon oxide film. Further, the publication indicates the apparatus for etching treatment of the silicon oxide film can also be used as an apparatus for etching treatment of the polysilicon film.
Meanwhile, with respect to the cleaning performed after patterning the conductive film, there is disclosed, for instance, in Japanese Patent Application Laid-open No. 223464/2000, that after a layered film made of a refractory metal film (WSi film) and a polycrystalline silicon film is laid on a semiconductor substrate, the layered film is patterned by means of dry etching to form a gate electrode. The substrate is then cleaned with a mixed solution of ammonia and hydrogen peroxide at 35° C. or 45° C. to remove etching residues deposited on the substrate.
In Japanese Patent Application Laid-open No. 223464/2000, it is also mentioned that, if cleaning of the substrate with a mixed solution of ammonia and hydrogen peroxide lasts for a long time period, the lateral faces of the WSi film which constitutes the gate electrode may be excessively dissolved, creating a eroded film section. For the purpose of achieving both the prevention of such a film erosion of the WSi film and the substantially thorough removal of the deposit like dry etching residues, this publication proposes that the cleaning of the substrate is performed only for a specific time period, which is predetermined using the dummy substrate. Further, in the publication, it is described that a contact hole is formed by dry etching in an interlayer insulating film made of a plurality of insulating films (a silicon oxide film, a BPSG (Boro-Phospho-Silicate Glass) film, a BSG (Boro-Silicate Glass) film) which have different etching rates for the wet etching treatment, and that etching residues stuck on the surface of this contact hole are removed by cleaning with a mixed solution of ammonia and hydrogen peroxide. Also in this cleaning, if the treatment time period is set too long, the internal wall of the contact hole becomes uneven due to the differences in the etching rate so that, for the purpose of achieving both prevention of creation of such unevenness and removal of etching residues, this publication proposes that the cleaning is performed only for a specific time period, which is predetermined using the dummy substrate.
In recent years, viewed from the point of improving electrical characteristics of the device, the semiconductor device having a gate electrode which comprises a SiGe layer and a polycrystalline silicon layer has been put forward. For example, a semiconductor device having a gate electrode, wherein a lower layer is a SiGe (poly-Si
0.8
Ge
0.2
) layer for controlling the work function, and an upper layer is a polycrystalline silicon (poly-Si) layer was proposed and its device characteristics were also described in detail (Y. V. Ponomarev et al., IEDM' 97, p.829).
Further, a semiconductor device having a gate electrode comprising a SiGe (poly-Si
1−x
Ge
x
) layer which is doped with P or B was reported (Wen-Chin Lee et al., 1998 Symposium on VLSI Technology Digest of Technical Papers, p. 190). There was also described a semiconductor device having a gate electrode (Ni(Si
x
Ge
1−x
)/poly-Si
0.8
Ge
0.2
) which is formed by growing Ni/TiN on a SiGe (poly-Si
0.8
Ge
0.2
) layer and applying the annealing thereto (Ja-Hum Ku et al., 2000 Symposium on VLSI Technology Digest of Technical Papers, p. 114).
A gate electrode pattern made of a SiGe layer and a polycrystalline silicon layer is formed by applying layers of an oxide film, a SiGe film and a polycrystalline silicon film, in this order, over a semiconductor substrate and forming a resist film on this layered film, and thereafter forming a resist pattern by photolithography and then dry etching the layered film with this resist pattern being used as a mask. However, after patterning is made by dry etching in this way and thereby a gate electrode pattern as well as a gate oxide film pattern are formed, dry etching products formed by the chemical reaction between the etching gas and the objects for etching and particles are left stuck onto the semiconductor substrate surface and the gate electrode. Therefore, it is required to clean the semiconductor substrate so as to remove such contaminants.
Yet, for removing dry etching products and particles which are stuck onto the semiconductor substrate and the gate electrode, if cleaning is carried out by the conventional cleaning method using a mixed solution of ammonia and hydrogen peroxide, there may arise a problem of film erosion of the lateral faces (referred to as “side etch”, hereinafter) of the SiGe layer.
Referring to
FIG. 2
, the above problem of the conventional cleaning method is further described below. FIG.
2
(
a
) is a schematic cross-sectional view of a semiconductor substrate after formation of a gate electrode pattern and a gate oxide film pattern but before cleaning, and FIG.
2
(
b
) is a schematic cross-sectional view of a semiconductor substrate after cleaning. In the drawings, referential numeral
1
represents a semiconductor substrate;
2
, a gate oxide film;
3
, a SiGe layer;
4
, a polycrystalline silicon film and
5
, an element isolation region.
As described above, when a layered film comprising a SiGe film is dry etched, using a resist pattern as a mask (FIG.
2
(
a
)), dry etching products and particles (not shown in the drawings) are stuck onto the semiconductor substrate surface and the gate electrode. In order to remove the dry etching products and the particles which are stuck onto the semiconductor substrate, a mixed solution of ammonia and hydrogen peroxide used in the conventional cleaning method may be still employed. But, to achieve sati
Kohno Michihisa
Shimizu Yuji
Hayes & Soloway P.C.
Lindsay Jr. Walter L.
NEC Electronics Corporation
Niebling John F.
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