Source: http://www.google.com/patents/US4982090?dq=6,411,947
Timestamp: 2017-11-25 08:14:02
Document Index: 699414312

Matched Legal Cases: ['§3', '§2', '§3', '§7', '§7', '§7']

Patent US4982090 - Method and apparatus for the quantitative, depth differential analysis of ... - Google Patents
A method and an apparatus for the quantitative depth analysis of a solid sample by backscatter analyzing the sample with the light ions, removing a thin layer of the sample by sputter etching, using a beam of medium-mass or high-mass ions to bombard the sample, backscatter analyzing the sputter etched...http://www.google.com/patents/US4982090?utm_source=gb-gplus-sharePatent US4982090 - Method and apparatus for the quantitative, depth differential analysis of solid samples with the use of two ion beams
Publication number US4982090 A
Application number US 07/305,693
Also published as DE3803424A1, DE3803424C2
Publication number 07305693, 305693, US 4982090 A, US 4982090A, US-A-4982090, US4982090 A, US4982090A
Inventors Klaus Wittmaack
Original Assignee Gesellschaft Fur Strahlen- Und Umweltforschung Mbh (Gsf)
Patent Citations (6), Referenced by (93), Classifications (11), Legal Events (4)
Method and apparatus for the quantitative, depth differential analysis of solid samples with the use of two ion beams
US 4982090 A
1. A method for the quantitative depth differential analysis of a solid sample, comprising the steps of:
(a) backscatter analyzing the sample with light ions;
(b) removing a thin layer of the sample by sputter etching, using a beam of medium-mass or high-mass ions to bombard the sample;
(c) backscatter analyzing the sputter etched sample; and
(d) repeatedly performing said steps (b) and (c).
2. A method as in claim 1, wherein each backscatter analyzing step includes a step of directing said light ions onto the sample at a glancing incidence and each said step of removing includes the step of directing the beam of medium-mass or high-mass ions onto the sample at low ion energy and so as to have a glancing incidence on the sample, whereby both shallow and deep lying regions of the sample are exposable for analysis with high depth resolution.
6. An apparatus for the quantitative depth differential analysis of a solid sample, comprising:
analysis chamber for holding therein the sample to be analyzed;
first accelerator means for generation a beam of fast, light ions with an energy in a range from about 0.1 MeV to about 5 MeV and directing the beam of fast ions into said chamber onto a predetermined region of the sample at a desired bombardment angle so that the fast ions are scattered by the atoms of the sample in the predetermined region thereof; and
second accelerator means for generating a beam of slow, medium-mass or high-mass ions with an energy of about 0.5 to about 10 keV and directing the beam of slow ions onto the predetermined region of the sample at a second desired predetermined bombardment angle, said analysis chamber having a sample manipulator means for manipulating the sample and means for determining the energy of the fast ions scattered by the atoms of the sample.
7. An apparatus as in claim 6, wherein the fast ions are selected from the group of ions consisting of H+, He+, He2+ and Li+.
The backscattering spectrometry method employs a beam of fast, light ions (i.e. He+ or He2+) which is directed onto a sample. The desired information about the composition of the sample is obtained by measuring the energy spectrum of the primary particles which are scattered into the solid angle ΔΩ around angle θ. If an atom of mass M2 is located at a depth z of the sample, with z being measured perpendicularly to the surface of the sample, a primary particle of mass M1 and an initial energy E0, after being scattered off M2, exhibits the energy E1 when leaving the sample. This energy can be expressed as follows (Chu et al, §§3.2.1 and 3.2.2):
E.sub.1 =KE.sub.0 -[ε]Nz                           (1)
[ε]=Kε.sub.in /cosθ.sub.in)=(ε.sub.out /cosθ.sub.out)                                      (2)
where K is the so-called kinematic factor which, for a given scattering angle θ (the angle between the directions of the incoming particle, and the exiting particle after scattering), depends only on the mass ratio M2 /M1 (Chu et al, §2.2 as well as Tables II to V). The value ε indicates the mean stopping cross section of the sample for the primary particle along its path between the surface and the scattering center. Subscripts `in` and `out` designate the incoming and exiting particle, respectively. The symbols θin and θout signify the angles between the surface normal and the propagation directions of the incoming and exiting particle bundle. N is the density of the sample in atoms/cm3 (See Chu et al. §§3.2.l and 3.2.2).
ΔE.sub.1,j =[ε]NΔz.sub.j               ( 3)
K(M.sub.2 *)=E.sub.1 (z'=0)/E.sub.0                        ( 5)
z.sub.i,m =(K.sub.i -K.sub.m)E.sub.0 /N[ε]         (6)
z.sub.max =KE.sub.0 /N[ε]                          (7)
Δz.sub.j =βz.sub.max                            (8)
0.2<β≦0.7
A third advantage of the method according to the invention relates to the possibility of performing backscattering analyses (see Chu et al, §§7.4, 7.5) with great depth resolution not only in the vicinity of the surface but also at a greater depth. According to Equation (1), the depth resolution δz can be represented as follows
|δz|=δE.sub.1 /N[ε]  (9)
It follows from Equation (9) that δz becomes smaller, i.e. the depth resolution becomes better, the smaller is δE1 and the larger is [ε]. The energy width δE1 is composed of two parts, the given energy resolution δEr of the backscattering arrangement and the energy straggling δEs (Chu et al, §7.4) which, in the Gaussian approximation, is given by:
δE.sub.1 ={(δE.sub.r).sup.2 +(δE.sub.s).sup.2 }.sup.1/2(10)
Energy straggling increases in proportion to the square root of the path length traversed by the beam in the sample. A good energy resolution δEr can thus be utilized fully only if δEs <δEr, i.e. the depth range that can be analyzed with a narrow energy width δE1 is limited. This applies particularly if, for the purpose of high depth resolution δz, the backscattering measurement is performed at a glancing angle of incidence and/or exit of the analyzing beam so that [ε]becomes large (see Equations 2 and 9 as well as Chu et al, §7.5). The region covered with high depth resolution then becomes very narrow. According to the present invention one can analyze the sample with high depth resolution also at a greater depth if sample material is removed in steps by way of sputtering. In this case it is useful to perform the sputtering with heavy ions (e.g. Xe+) of an energy of less than 1 keV and by bombarding at a glancing angle of incidence (θsputtering >60°). In this way the region 21, which was radiation damaged during sputtering, will extend only to a small depth from the instantaneous surface (see FIG. 2).
For analyses of bombardment at a glancing angle of incidence, i.e. at 80°<θin <90°, it is appropriate to give one or several of apertures 4 to 6 a slit shape so that the slit width bu is much less than the slit height bv. With a sufficiently small divergence of beam 1, it is possible, in the case of bu =bv cos θin, to give Ar a square shape with edges of a length bv.
US3916190 * Mar 1, 1974 Oct 28, 1975 Minnesota Mining & Mfg Depth profile analysis apparatus
US4088895 * Jul 8, 1977 May 9, 1978 Martin Frederick Wight Memory device utilizing ion beam readout
US4670651 * Sep 25, 1985 Jun 2, 1987 Leybold-Heraeus Gmbh Apparatus for performing the SNMS method
US4860224 * May 21, 1986 Aug 22, 1989 501 Tekscan Limited Surface analysis spectroscopy apparatus
US6255662 * Oct 27, 1998 Jul 3, 2001 Axcelis Technologies, Inc. Rutherford backscattering detection for use in Ion implantation
US20130320209 * Apr 30, 2013 Dec 5, 2013 Hitachi High-Technologies Corporation Ion beam processing apparatus
WO1998052216A1 * May 11, 1998 Nov 19, 1998 Silicon Genesis Corporation A controlled cleavage process
U.S. Classification 850/10, 250/305, 850/17, 250/306, 250/288
International Classification H01J37/252, G01N23/203, G01Q30/04, G01Q30/18
Cooperative Classification G01N23/203
European Classification G01N23/203
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WITTMAACK, KLAUS;REEL/FRAME:005037/0832