JPH03239973A - Element for measuring dielectric breakdown relating to lapse of time - Google Patents

Abstract

PURPOSE:To measure the dielectric breakdown of an insulating film with lapse of time by forming many capacitors, which are formed by using the insulator thin films same as the insulator thin films to be evaluated as the dielectrics, on a substrate and parallel connecting the respective capacitors via the wiring branch lines cut by shorting currents. CONSTITUTION:A conductor layer 2 as a 1st electrode is formed over the entire surface of the substrate 1 and several tens to several hundred pieces of the dielectrics 3 which of the same insulating material as the insulating material to be evaluated of SiO2, etc., and has the same film thickness are formed on the surface of the conductor layer 2. Further, 2nd electrodes 4 are formed on the surface of the respective dielectrics 3 and the many capacitors are respectively separately constituted on the substrate 1. The respective electrodes 4 are connected via the aluminum wiring branch lines 6a to a common aluminum wiring line 6b. The branch lines 6a have the sectional area to the extent that the lines are cut by the large shorting current flowing in the capacitor when the dielectrics 3 of this capacitor causes the dielectric breakdown. The element for measuring the dielectric breakdown of the thin films with lapse of time constituted in such a manner is housed in a package 7. The large current flows in the capacitors and can be detected by an ammeter 8 when the dielectric breakdown occures by a deterioration of the dielectrics 3 with lapse of time.

Description

Detailed Description of the Invention (Industrial Field of Application)
Dependent Dielectric Brea
The present invention relates to an element for measuring dielectric breakdown over time, and in particular to an element for measuring dielectric breakdown over time, which is suitable for measuring dielectric breakdown over time of thin insulator films used for gate oxide films of MOS devices, etc. .

(Prior Art) The thickness of the gate oxide film of a MOS device tends to become thinner and thinner as VLS (VLSI) becomes more highly integrated. However, the reduction in power supply voltage is progressing relatively slowly due to demands for device compatibility, securing operating margins, and increasing speed. Therefore, it can be said that the electric field strength applied to the gate oxide film of the MOS device is substantially increasing. Furthermore, the lifetime of the gate oxide film itself is thought to be shortened due to thinning of the film, so when evaluating the reliability of gate oxide films, it is necessary to measure breakdown over time in addition to the conventional measurement of dielectric strength. There is.

Conventionally, when evaluating the reliability of such an insulating film over time, a semiconductor device such as a MOSFET was formed on a substrate, this was sealed in a package, and the completed product was sampled and TDDB measurements were performed. was going on. In TDDB measurement, wiring is taken out from the capacitor structure of the semiconductor device housed in each sampled package, and electric field stress is simultaneously applied to them for a certain period of time to check for damage to the insulating film over time. are doing.

(Problem to be solved by the invention) However, since the insulation film breakdown test is a statistical phenomenon, it is necessary to measure a large number of samples in order to increase the reliability of the test. Since the product is sampled and measured after it has been stored in the pan cage, the same number of packages as the number of samples are required for TDDB measurement. However, most of the semiconductor element pancakes are made of ceramic and are expensive, and it takes a lot of effort to hermetically seal the semiconductor device inside the package. Therefore, for TDDB measurement, a large number of expensive and time-consuming ceramic packages are consumed, resulting in an increase in measurement costs.

Furthermore, since there are a large number of samples, it is desirable to automate the measurement, but this requires a dedicated scanner that can measure a large number of samples in a timely manner, and this equipment is also complex and expensive.

The present invention is a TDDB measurement element that can measure the dielectric breakdown over time of a large number of samples with a small number of ceramic packages, and can easily measure the presence or absence of dielectric breakdown without using a complicated and expensive scanner. It provides:

(Means for Solving the Problems) In order to solve the above problems, the element for measuring dielectric breakdown over time of the present invention has a large number of capacitors on a substrate whose dielectric material is the same insulator thin film as the insulator thin film to be evaluated. The wiring was formed so that these capacitors were connected in parallel through branch paths that were cut by the large current flowing when dielectric breakdown occurred in the insulating thin film used as the dielectric. This is a characteristic feature.

(Function) As described above, in the present invention, apart from the insulating thin film to be evaluated, a large number of capacitors using the same insulating thin film as a dielectric are formed on a common substrate, and these many capacitors are integrated into one. The TDDB measurement is carried out by storing it in a separate package. Therefore, TDD of multiple insulator thin films
The number of packages required to measure B can be extremely small. These capacitors are connected in parallel to the common path through branch circuits, and these branch circuits are formed to such a size that they are cut (fused) by the current flowing through the capacitors when the insulating film breaks down. ing. TDD
B measurement is performed by applying a constant voltage to each capacitor and detecting that when dielectric breakdown occurs in the insulating film used as a dielectric, the capacitor electrode becomes conductive and a large current flows through the capacitor. Since the branch path is cut (fused) when a large current flows, this current only flows temporarily.

TDDB measurement can be performed by checking the time and number of times a large current flows. Since many capacitors are connected in parallel, even if dielectric breakdown occurs in one capacitor and the branch circuit is cut off, the measurement voltage can still be applied to the other capacitors, which eliminates the complexity of the conventional method. There is no need to use a scanner.

With this configuration, TDDB measurements of a large number of samples can be performed in a small number of packages, making it possible to significantly reduce the number of packages required for measurement compared to conventional measurement methods, thus reducing packaging costs. can be saved. Furthermore, since it is possible to determine whether dielectric breakdown has occurred by checking the change in current, there is no need to scan each capacitor, and therefore there is no need to use a complex and expensive scanner.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagrammatic cross-sectional view of a TDDB measuring element of the present invention, and FIG. 2 is a circuit diagram showing the structure of an apparatus for performing TDDB measurement using the element of the present invention.

As shown in FIG. 1, a conductive layer 2 acting as a first electrode is formed on the entire surface of a substrate I, and an insulating film to be evaluated, such as silicon oxide (SiO□), is formed on the surface of the conductive layer 2. Several tens to hundreds of dielectrics 3 each made of an insulating film made of the same insulating material and having the same thickness are formed. A second electrode 4 is further formed on the surface of each dielectric 3, and a large number of capacitors are individually configured on the substrate 1. each second
The electrode 4 is connected to a common aluminum wiring path 6b via an aluminum wiring branch 6a. In the present invention, the aluminum wiring branch 6
It is assumed that a has a cross-sectional area large enough to be cut (fused) by a large short-circuit current flowing through the capacitor when dielectric breakdown occurs in the dielectric 3. Note that the first electrode 2 is formed on the entire surface of the substrate 1, constitutes a common electrode for all capacitors, and is connected to a common aluminum wiring path 6C.

The element for measuring TDDB constructed in this way is housed in the package 7, and the common aluminum wiring paths 6b and 6c are connected to external contacts to complete the element for measuring dielectric breakdown over time. Second
As shown in the figure, a plurality of these packages 7 are connected in parallel and connected to a constant voltage power source 5. The ambient temperature of the packages 7 is set to approximately 150 to 200''C. An ammeter 8 is disposed between these packages 7 and the constant voltage power supply 5, and the current flowing through the common aluminum wiring paths 6b and 6c of each element is measured. Measure.

FIG. 3 is a graph showing the magnitude of the current flowing through the common aluminum wiring paths 6b and 6c. Dielectric material (insulating film) of the capacitor formed on the substrate 1 housed in the package 7
When dielectric breakdown occurs in the capacitor 3 due to changes over time, a large current flows through the capacitor, and this can be detected by the ammeter 8. As mentioned above, the aluminum wiring branch 6a connected to the second electrode of each capacitor is configured to be cut (fused) by the large current flowing at this time.
As shown in the figure, the large current flowing through the ammeter 8 remains temporary. Since each capacitor is connected in parallel, even if dielectric breakdown occurs in one capacitor, it will not affect the measurement of other capacitors. The current flowing through the ammeter 8 is recorded in a recording device (not shown), and by checking this record, it is possible to know the point at which dielectric breakdown occurred and the number of capacitors in which the insulating film 3 was destroyed.

(Effects of the Invention) As described in detail above, according to the present invention, a large number of capacitors are housed in one package, and the dielectrics of these capacitors are made of the same insulating film whose dielectric breakdown over time is to be measured. Since it is formed from an insulating film, it is possible to save on package, which is expensive and takes time to manufacture. In addition, since each capacitor was connected in parallel via a wiring branch that was cut by a short-circuit current, it was possible to measure the dielectric breakdown of the insulating film over time by simply checking the change in current measured with an ammeter. There is no need to use complicated scanners.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic cross-sectional view of a TDDB measurement element according to the present invention, FIG. 2 is a circuit diagram of an apparatus for performing TDDB measurement according to the present invention, and FIG. 3 is a diagram shown in FIG. It is a graph showing the measured value of the current flowing in the circuit. 1... Substrate 2... First electrode 3...
Insulating film 4... Second electrode 5... Constant voltage power supply 6a... Aluminum wiring branch paths 6b, 6C... Common aluminum wiring path

Claims (1)

[Claims] 1. A large number of capacitors whose dielectric material is the same insulating thin film as the insulating thin film to be evaluated is formed on a substrate, and when dielectric breakdown occurs in the insulating thin film using these capacitors as the dielectric material, the current flows. 1. An element for measuring dielectric breakdown over time, characterized in that wiring is formed so as to be connected in parallel via branch paths that are cut by a large current.