Static information storage and retrieval – Addressing – Particular decoder or driver circuit
Reexamination Certificate
2000-06-26
2001-08-21
Phan, Trong (Department: 2818)
Static information storage and retrieval
Addressing
Particular decoder or driver circuit
C365S225700
Reexamination Certificate
active
06278651
ABSTRACT:
BACKGROUND
1. Technical Field
This disclosure relates to semiconductor devices and more particularly, to a semiconductor device employing wordline boost voltages (VPP) for programming electrical fuses.
2. Description of the Related Art
For redundancy activation and trimming purposes, semiconductor memory devices include a plurality of fuses. Typically, these fuses are programmed by a laser beam at the wafer-level; however, new types of fuses are electrically programmable and permit programming in a packaged chip.
The level of the programming voltage for the fuses is typically far above the external supply voltage or any internally generated voltage (e.g., 9.0V-12.0V).
The maximum voltage level that can be achieved by a high voltage pump circuit depends on the pump circuit type and the available supply voltage from which the programming voltage is generated by the pump. A formula for a typical pump circuit is:
V
FUSE
=3
×V
SUP
−3.0V.
This means that the maximum achievable fuse programming voltage is three times the supply voltage from which it is generated minus a constant voltage drop of 3.0V, due to internal losses in the pump circuit.
Usually the voltage pump is supplied by the external chip supply voltage, V
DD
. For current semiconductor technologies V
DD
is about 2.5V. During the burn-in phase of the chip, this voltage is raised by a certain factor (e.g., 1.5). This leads to a 150% increase of all internal voltages on the chip for increased stress of all circuits in order to accelerate early defects.
According to the above formula this permits a fuse programming voltage of:
V
FUSE
=3×(1.5×2.5V)−3.0V×8.25V.
This voltage level is not high enough for programming the fuses. Raising V
DD
to a higher level would permit the pump circuit to reach a higher output level, but would also expose all other circuits on the chip to a voltage stress that is above their reliability.
Therefore, a need exists to achieve a voltage level for programming electrical fuses in a memory device with an on-chip pump circuit without raising the external supply voltage (e.g., V
DD
) above a level which would affect the reliability of circuits which employ the external supply voltage.
SUMMARY OF THE INVENTION
A voltage pump system for programming fuses on a semiconductor chip, in accordance with the present invention, includes a first pump system employing a supply voltage of the semiconductor chip as an input. The first pump system supplies an output voltage higher than the supply voltage on a first output line without raising the supply voltage of the semiconductor chip. A second pump system includes an input connected to the first output. The second pump system supplies an output voltage sufficient for programming electrical fuses on the semiconductor chip.
In alternate embodiments, the first pump system may include a wordline boost voltage pump and the first output includes a wordline boost voltage (V
PP
). V
PP
may be about 3.1 volts. The output voltage for fuse programming may be between about 9 and about 12 volts. The semiconductor chip may include a dynamic random access memory. The voltage pump may include other circuits to which the supply voltage provides power, and the supply voltage may include a threshold value above which reliability problems are experienced in the other circuits. The threshold value may be about 2.5 volts.
Another voltage pump system for programming fuses on a semiconductor chip, in accordance with the present invention, includes a wordline boost pump system employing a supply voltage of the semiconductor chip as an input. The wordline boost pump system supplies a wordline boost voltage, which is higher than the supply voltage on a first output line without raising the supply voltage of the semiconductor chip. A fuse voltage pump system includes an input connected to the first output. The fuse voltage pump system supplies an output voltage sufficient for programming electrical fuses on the semiconductor chip. A plurality of electrical fuses are disposed on the semiconductor chip and programmed on-chip by the output voltage of the fuse voltage pump system in accordance with addressing information.
In alternate embodiments, the wordline boost voltage is about 3.1 volts. The output voltage for fuse programming may be between about 9 and about 12 volts. The semiconductor chip preferably includes a dynamic random access memory. The voltage pump system may include other circuits to which the supply voltage provides power, and the supply voltage may include a threshold value above which reliability problems are experienced in the other circuits. The threshold value may be about 2.5 volts. The addressing information may include redundancy calculation results. The voltage pump system may include a fuse line coupled to the output line of the fuse programming pump for providing the output voltage sufficient for programming electrical fuses to program the fuses in accordance with the addressing information.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
REFERENCES:
patent: 5293386 (1994-03-01), Muhmenthaler et al.
patent: 5410510 (1995-04-01), Smith et al.
patent: 5933374 (1999-08-01), Weinfurtner
Mueller Gerhard
Weinfurtner Oliver
Braden Stanton C.
Infineon - Technologies AG
Phan Trong
Tran M.
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