BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a semiconductor device into which the resistance element of the invention is incorporated;
FIG. 2 is a layout diagram (a) and cross-sectional view (b) of a resistance element according to a first embodiment of the invention;
FIG. 3 is a layout diagram (a) and cross-sectional view (b) of a resistance element according to another embodiment of the invention;
FIG. 4 is an example of a circuit diagram forming a resistance element according to one embodiment of the invention;
FIG. 5 is a diagram showing a flowchart for manufacturing a resistance element according to one embodiment of the invention;
FIG. 6 is a circuit diagram of an active terminator IC using a resistance element according to the prior art;
FIG. 7 is a circuit diagram of an active terminator IC using another resistance element according to the prior art; and
FIG. 8 is a diagram wherein scatter in the resistance value of a resistance element having an identical structure was observed in a wafer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the sake of convenience, the following description is divided into plural sections or embodiments, but unless specified otherwise, these are not mutually unrelated, and one thereof includes part or all of the modifications, details and additions of another.
Also, in the following embodiments, when numbers of elements (including numbers, figures, amounts and ranges) are mentioned, unless otherwise specified or when clearly limited in principle to a specific number, the invention is not limited to that specific number and may include a number which is larger or smaller.
Further, in the following embodiments, it will be understood that the component elements thereof (including elemental steps), unless otherwise specified or when considered to be clearly necessary, are not absolutely indispensable.
Likewise, in the following embodiments, when shape or positional relationships of component elements are mentioned, unless otherwise specified or when considered to be clearly unacceptable, they shall actually include close or approximate shapes or relationships. This is the same also for the aforesaid values and ranges.
Some embodiments of the invention will hereafter be described in detail based on the drawings.
Embodiment 1
A resistance element in a semiconductor device according to this embodiment will now be described referring to the drawings.
FIG. 1 is a schematic diagram of the resistance element in the semiconductor device (semiconductor integrated circuit device) of this invention. The circuit of FIG. 1 is a driver circuit whereof the input which is a minute signal of an ECL, the output is a 15V signal of about 2.5 Gpbs amplitude, and the circuit is connected to a DUT. A high precision 50 Ω termination resistor for impedance matching is connected to the driver circuit. A resistance element 2 which is a dummy resistance has two terminals respectively connected to pads 5, 6 for voltage monitoring and pads 5a, 6a for current application, and the resistance value thereof can be precisely measured without being affected by scatter in the contact resistance of the probe needle. Adjacent to the resistance element 2 which is a dummy resistance, termination resistors 1, 3 connected to the bus line are disposed adjacent to each other, one terminal being connected to the circuit, and one terminal being connected to pads 7, 8 connected to the bus line. The termination resistors 1, 3 which are paired with the dummy resistance element 2, comprise a main resistance R0 and resistance elements R1, R2, . . . , Rn for resistance adjustment connected in parallel therewith, and fuses F1, F2, . . . , Fn respectively connected in series with the resistance elements for resistance adjustment. In order to adjust the resistance of the termination resistors 1 and 3, the fuse to be cut is determined based on the measured resistance of the dummy resistor element 2. The fuse to be cut is connected to resistance elements for resistance adjustment of the same type in the termination resistors 1, 3 and dummy resistance element 2. After the fuse is cut, the resistance value of the dummy resistance element 2 is re-evaluated, and it is verified that it is the desired resistance value. The dummy resistance element 2 and termination resistors 1, 3 have identical structures and are disposed adjacent to each other, so the resistance value of the termination resistors can be estimated identical to that of the dummy resistance element. Due to this construction, the termination resistors 1 and 3 do not have pads for voltage measurement, so parasitic capacitance is not increased, and resistance can be measured and adjusted with high precision. In the diagrams, the resistance element was described as a termination resistor, but it may also be a resistance element for gain adjustment used in an analog IC, or a resistance element for offset cancellation.
Embodiment 2
FIG. 2 shows a layout diagram and a cross-sectional structure of a resistance element in the semiconductor device of the invention. The resistance element 1 and the dummy resistor 2 have identical structures so that they form one pair, and the distance 17 between them is arranged to be within 500 μm. The resistance element is formed by a polySi layer or a metal layer such as TaN, TiN and SiCr. The resistance element comprises RO (9a, 9b) which is the main resistance and resistance elements 10, 11, 12 wherein the resistance itself functions as a fuse connected to interconnection layers 15, 16 in parallel, and whereof the lengths are identical to that of the main resistance RO. Due to this, since the current density flowing into the resistance element is essentially identical for each resistance, the reliability of the termination resistor connected to the driver circuit which requires a large current to flow, can be increased. Further, the width of the resistance elements 10, 11, 12 can be changed, and they are weighted. Due to this, compared to the case where the resistance value is not weighted, the range in which the resistance value can be adjusted is increased, and the surface area of the resistance element can be made small. Also, the insulation film of the upper parts 13, 14 is removed or the film thickness is reduced so that they can be cut by a laser. In this example, to increase laser cutting yield, two holes are provided.
Embodiment 3
FIG. 3 shows a second example of a layout diagram and cross-sectional structure of the resistance element in the semiconductor device of the invention. Although the construction and composition of the resistance element are identical to those of FIG. 2, in FIG. 3, the fuses are formed by an interconnection layer 20 which connects the resistance elements. To increase the laser cutting yield, an insulation film 21 on the interconnection layer is removed or made thinner.
Embodiment 4
FIG. 4 is a circuit diagram wherein a weighting is given to the resistance elements for resistance adjustment R1, R2, . . . Rn described in FIGS. 2 and 3.
The resistance element 1 is designed to have a resistance value of 55 Ω when all the fuses are cut, and 45 Ω when none of the fuses are cut
In this case, there are 32 (25) ways of cutting the fuses, and the precision of the resistance value can be adjusted to within ±0.4%.
Embodiment 5
FIG. 5 shows a manufacturing flow diagram for forming a resistance element in the semiconductor device of the invention. In a wafer which completed a previous process, the resistance of the dummy resistor is measured by a first probe test. Next, to adjust the resistance value to a desired value, a fuse is cut by the laser. Next, in a second probe test, the resistance value of the dummy resistor is measured, it is verified that the resistance value is within a desired resistance adjustment range, e.g., 1%, and wafer manufacture is completed. At this time, if the resistance value is finished to be larger than 1%, another fuse can be cut to adjust the resistance value. Further, the wafer can also be completed omitting the second probe test.
A resistance element with an adjustable resistance value, wherein the resistance value is within 1% or less of a desired design value, having a low parasitic capacitance and which permits a relatively large current to flow, can easily be obtained.
Patent Application
20080036036
