Semiconductor device manufacturing: process – Gettering of substrate – By implanting or irradiating
Reexamination Certificate
2000-04-06
2002-05-21
Mulpuri, Savitri (Department: 2812)
Semiconductor device manufacturing: process
Gettering of substrate
By implanting or irradiating
Reexamination Certificate
active
06391746
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to methods of forming gettering regions within silicon semiconductor wafers and to gettering regions formed by such methods.
BACKGROUND OF THE INVENTION
Impurity contamination of Si semiconductor wafers is a problem within the semiconductor industry. Of particular concern are metallic contaminants, such as iron, nickel and copper. When such impurities are present in a Si semiconductor device, the impurities degrade the characteristics and reliability of the device. As integration in semiconductor devices becomes increasingly dense, the tolerance for metallic contaminants becomes increasingly stringent.
Among the methods for decreasing metallic contamination in semiconductor wafers are methods for improving cleanliness in plants which manufacture such semiconductive devices. However, regardless of how many steps are taken to insure clean production of semiconductor devices, some degree of contamination by metals is inevitable. Accordingly, it is desirable to develop methods and structure for isolating metallic contaminants present in semiconductor wafers from devices which are ultimately formed within and upon such wafers. The act of isolating these contaminants is generally referred to as gettering, as the contaminants are gathered, or gettered, to specific areas within a semiconductor wafer.
Conventional processes for gettering metallic contaminants often focus on creating defects or damage within a semiconductor wafer in a region where gettering is sought to occur. Generally, such gettering regions are formed well below the regions of a wafer where device formation will ultimately occur and separated from such regions by an expanse of substrate. Two embodiments of such prior art methods are shown with reference to
FIGS. 1 and 2
. Referring to these figures, a semiconductor wafer
10
comprises a front-side surface
12
and a back-side surface
14
. Front-side surface
12
is defined as a surface where device formation will ultimately occur. A damage region
16
is formed beneath front-side surface
12
and is placed deep enough within the substrate that later devices formed on front-side surface
12
are isolated from the damage region
16
. Damage region
16
is typically formed by introducing impurities into the lattice of the semiconductor material of wafer
10
. In
FIG. 1
, damage region
16
is a layer within the middle of substrate
10
, while in
FIG. 2
, damage region
16
is a layer along back-side
14
of wafer
10
. After damage region
16
is formed, wafer
10
is heated to drive metallic contaminants into the damage region.
A problem of increasing concern as semiconductor devices become increasingly smaller is substrate-background current, or diffusion current. Such diffusion current is function of device temperature and increases exponentially with temperature. Thus, if the temperature of a semiconductor wafer increases, such as typically occurs during operation of semiconductor devices, the diffusion current generally also increases. At a given temperature, more diffusion current will generally form from a defect region of a semiconductor wafer than from a region without defects. Thus, damage regions
16
tend to generate more diffusion current at a given temperature than do other regions of a semiconductor wafer
10
.
The diffusion current electrons formed in damage region
16
will generally drift away from damage region
16
, potentially toward front-side surface
12
. Such electrons at front-side surface
12
may degrade the performance of devices that are later formed on surface
12
.
For the above-described reasons, it would be desirable to develop a gettering region which could collect diffusion current electrons. Also, since hole counterparts of the diffusion current electrons can also be generated as the diffusion current electrons are generated, it would also be desirable to develop a gettering region which could collect such holes.
REFERENCES:
patent: 4116719 (1978-09-01), Shimizu et al.
patent: 4144100 (1979-03-01), MacIver et al.
patent: 4178191 (1979-12-01), Flatley
patent: 4665425 (1987-05-01), Piotrowski
patent: 4717680 (1988-01-01), Piotrowski
patent: 4960731 (1990-10-01), Spitz et al.
patent: 4986841 (1991-01-01), Oyoshi et al.
patent: 5126278 (1992-06-01), Kodiara
patent: 5145794 (1992-09-01), Kase et al.
patent: 5162241 (1992-11-01), Mori et al.
patent: 5183767 (1993-02-01), Baratte et al.
patent: 5198371 (1993-03-01), Li
patent: 5244819 (1993-09-01), Yue
patent: 5272373 (1993-12-01), Baratte et al.
patent: 5389563 (1995-02-01), Kuroi et al.
patent: 5453385 (1995-09-01), Shinji
patent: 5561072 (1996-10-01), Saito
patent: 5578507 (1996-11-01), Kuroi
patent: 5731637 (1998-03-01), Hori et al.
patent: 5757063 (1998-05-01), Tomita et al.
patent: 5773356 (1998-06-01), Gonzalez et al.
patent: 4218685 (1993-04-01), None
McHugo, S.A. et al., “Copper in Silicon: Quantitative Analysis of Internal and Proximity Gettering”, Materials Science Forum, vols. 258-263 (1997), pp. 461-466.
Kuroi, T. et al., Highly Reliable 1.15&mgr;m MOSFETs with Surface Proximity Gettering (SPG) and Nitrided Oxide Spacer Using Nitrogen Implantation, 1995 Sympos. On VLSI Tech. Digest of Technical Papers, pp. 19-20.
Kuroi, T. et al., “Proximity Gettering of Heavy Metals by High Energy Ion Implantation”, Extended Abstracts of the 1992 Internatl. Conference on Solid State Devices and Materials, Tsukuba, pp. 398-400.
Kuroi, T. et al., “Proximity Gettering of Micro-Defects by High Energy Ion Implantation”, Extended Abstracts of the 1991 Internatl. Conference on Solid State Devices and Materials, Yokohama, pp. 56-58.
Overwijk, M.H.F. et al., “Proximity Gettering of Transition Metals in Silicon by Ion Implantation”, Nuclear Instruments and Methods in Physics Research B96 (1995), pp. 257-260.
Shimizu, S. et al., “Impact of Surface Proximity Gettering and Nitrided Oxide Side-Wall Spacer by Nitrogen Implantation on Sub-Quarter Micron CMOS LDD FETs”, IEEE (1995), pp. 859-862.
Skorupa, W. et al., “Proximity Gettering of Iron in Separation-By-Implanted-Oxygen Wafers”, IEEE (1997), pp. 737-739.
Skorupa, W. et al., “Proximity Gettering by MeV-Implantation of Carbon: Microstructure and Carrier Lifetime Measurements”, Nuclear Instruments and Methods in Physics Research B55 (1991), pp. 224-229.
Skorupa, W. et al., “Proximity Gettering of Transition Metals in Separation by Implanted Oxygen Structures”, Appl. Phys. Lett. 67 (20), Nov. 13, 1995, pp. 2992-2994.
Wong, H., “Proximity Gettering With Mega-Electron-Volt Carbon and Oxygen Implanations”, Appl. Phys. Lett. 52 (12), Mar. 21, 1988, pp. 1023-1025.
Yankov, R.A., “Proximity Gettering of Copper in Separation-By-Implanted-Oxygen Structures”, Nuclear Instruments and Methods in Physics Research B120 (1996), pp. 60-63.
Handout, 2ndannual “Smart and Economic Device and Process Designs for ULSI Using MeV Technology” Seminar, sponsored by Genus, Inc., Jul. 20, 1994, 10 pages.
Gonzalez Fernando
Honeycutt Jeffrey W.
Micro)n Technology, Inc.
Mulpuri Savitri
Wells St. John P.S.
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