U.S. patent application number 09/729068 was filed with the patent office on 2001-05-03 for method of programming a semiconductor memory.
This patent application is currently assigned to Infineon Technologies AG. Invention is credited to Gobel, Holger, Krause, Gunnar.
Application Number | 20010000758 09/729068 |
Document ID | / |
Family ID | 7840515 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000758 |
Kind Code |
A1 |
Gobel, Holger ; et
al. |
May 3, 2001 |
Method of programming a semiconductor memory
Abstract
A method of programming a semiconductor memory includes forming
a multiplicity of fuse links in at least two mutually parallel
planes in a semiconductor body, and separating the fuse links from
one another with an electrical insulator. It also includes
irradiating a selected fuse link with at least two laser beams and
melting the selected fuse link by crossing the laser beams at the
selected fuse link.
Inventors: |
Gobel, Holger; (Hamburg,
DE) ; Krause, Gunnar; (Munchen, DE) |
Correspondence
Address: |
WERNER H. STEMER
P.O. Box 2480
Hollywood
FL
33022
US
|
Assignee: |
Infineon Technologies AG
|
Family ID: |
7840515 |
Appl. No.: |
09/729068 |
Filed: |
December 4, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09729068 |
Dec 4, 2000 |
|
|
|
09143122 |
Aug 28, 1998 |
|
|
|
6180992 |
|
|
|
|
Current U.S.
Class: |
438/466 ;
438/467; 438/601 |
Current CPC
Class: |
G11C 17/14 20130101 |
Class at
Publication: |
438/466 ;
438/467; 438/601 |
International
Class: |
H01L 021/326; H01L
021/479; H01L 021/44 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 1997 |
DE |
197 37 611.8 |
Claims
We claim:
1. A method of programming a semiconductor memory, which comprises:
forming a multiplicity of fuse links in at least two mutually
parallel planes in a semiconductor body, and separating the fuse
links from one another with an electrical insulator; irradiating a
selected fuse link with at least two laser beams and melting the
selected fuse link by crossing the laser beams at the selected fuse
link.
Description
CROSS-REFERENCE TO RELATED APPLICATION
1. This application is a division of U.S. application Ser. No.
09/143,122, filed Aug. 28, 1998.
BACKGROUND OF THE INVENTION
2. Field of the Invention
3. The invention belongs into the semiconductor technology field.
More specifically, the invention pertains to a method of
programming a semiconductor memory, having a multiplicity of fuses
which are provided on a semiconductor body and can each be
programmed individually through the injection of energy to break or
make a conducting connection.
4. It is well-known to use fuses for the permanent storage of data
in semiconductor storage devices and for programming the redundancy
in semiconductor storage devices of this type. In the former case,
the state of the fuse ("conducting" or "nonconducting") establishes
a data value ("0" or "1"), while in the latter case, if there is a
defective storage cell, a redundant storage cell is connected into
the circuit by activating the fuse.
5. Fuses generally consist of, for example, polycrystalline silicon
or a similar suitable material that can be fused or melted through
the action of energy, by means of which a previously existing
conducting connection is broken. It is, however, also conceivable
to use a material which is converted by the action of energy from
the nonconducting state to the conducting state, in order thus to
create a conducting connection. It will nevertheless be assumed
below that a previously existing conducting connection will be
destroyed by the action of energy.
6. The action of energy may be brought about, for example, by
irradiating a fuse with a laser beam, or else simply by passing a
relatively heavy current through a particular fuse, in order to
cause it to melt.
7. Contemporary fuse configurations use fuses which are arranged
next to one another, for example in the form of a matrix, on the
surface of the semiconductor body, or chip, of a semiconductor
storage device. As the number of fuses rises, that is to say as the
storage capacity of the semiconductor storage device increases, the
overall effect is that the required area of the chip becomes ever
greater.
8. In order to keep the required area as small as possible,
attempts have to date been made to design the fuses as small as
possible in geometric terms. However, that procedure is limited by
the fact that, when the fuse is activated or programmed, i.e. for
example when the fuses are illuminated with a laser beam, a minimum
mutual separation of the individual fuses must be respected so that
the desired fuse can deliberately and reliably be melted by the
laser beam.
SUMMARY OF THE INVENTION
9. It is accordingly an object of the invention to provide a method
of programming a semiconductor memory, which overcomes the
above-mentioned disadvantages of the prior art devices and methods
of this general type and which is distinguished by a considerably
reduced area requirement, yet in which individual fuses can be
activated deliberately and reliably.
10. With the foregoing and other objects in view there is provided,
in accordance with the invention, a method of programming a
semiconductor memory, comprising a semiconductor body and a
multiplicity of fuses disposed in the semiconductor body, the fuses
being arranged in at least two planes and being programmable by a
superposition of at least two laser beams crossing at a respective
fuse to be programmed.
11. In other words, the objects of the invention are satisfied with
a fusible link configuration disposed in at least two planes on the
semiconductor body. The fuses may be arranged above one another in
several, say, n planes. The area required by the fuses on the
semiconductor body is therefore reduced approximately by a factor
n, if the wiring for connecting the fuses is disregarded.
12. In accordance with an added feature of the invention, an
insulating layer is disposed between the planes of the fuses. The
insulator is preferably silicon dioxide.
13. In accordance with another feature of the invention, the fuses
consist of polycrystalline silicon. The polycrystalline silicon
links can be melted by passing a current through them or by
superimposed action of at least two laser beams, in order thus to
activate (or deactivate) the fuses. The two acting laser beams then
cross at the fuse to be activated.
14. Accordingly, there is also provided, in accordance with the
invention, a method of programming a semiconductor memory, which
comprises:
15. forming a multiplicity of fuse links in at least two mutually
parallel planes in a semiconductor body, and separating the fuse
links from one another with an electrical insulator;
16. irradiating a selected fuse link with at least two laser beams
and melting the selected fuse link by crossing the laser beams at
the selected fuse link.
17. Where several fuse planes are arranged above one another, the
fuses can be programmed either by a specific current, which causes
the material to melt, or alternatively by the superimposition of
several laser beams. The intensity of the laser beams should be
chosen such that just a single beam will not damage the material;
however, if a plurality of beams are superimposed at one point (the
location of the fuse to be programmed), then the local energy
intensity will become great enough for the fuse to be
destroyed.
18. Other features which are considered as characteristic for the
invention are set forth in the appended claims.
19. Although the invention is illustrated and described herein as
embodied in a method of programming a semiconductor memory, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
20. The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying drawing
figure.
BRIEF DESCRIPTION OF THE DRAWINGS
21. FIG. 1 is a perspective view of a fuse configuration in two
planes, with a separating insulator layer having been omitted for
purposes of clarity; and
22. FIG. 2 is a partial sectional view through a semiconductor body
and the fuse configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
23. Referring now to the figures of the drawing in detail, there is
seen a plurality of polycrystalline silicon fuses 1. The fuses are
arranged in two planes 2, 3 above one another in the z direction on
a surface of a semiconductor body 10. The fuses extend in the x-y
plane, of the semiconductor body 10 and they are separated from one
another by a silicon dioxide insulator layer.
24. A fuse 4 to be programmed is exposed to two laser beams 5, 6
which cross at a point 7 in the region of the fuse 4. The fuse 4 is
thereby melted and thus broken. The energy of the laser beams 5, 6
is adjusted such that one beam alone cannot cause any melting, and
this ensures that only the fuse 4 where the laser beams 5, 6 cross
is deliberately destroyed, while the other fuses 1 remain
undamaged.
25. As an alternative to the intersecting laser beams 5, 6, it is
also possible to pass a current through the fuse 4, such that this
fuse 4 is melted and therefore destroyed.
* * * * *