Electric breakdown field strength of the hottest s

Breakdown field strength of solid dielectric film

Chinese figure classification number: tm215.014 + 4 document identification code: a article number: (1999) the meaning of dielectric can be divided into broad sense and narrow sense, and dielectric film can also be divided into broad sense and narrow sense. The former refers to all films with high resistivity, while the latter only refers to films used as capacitor media [1]

the breakdown field strength of thin films has become a research focus, also because the breakdown field strength belongs to the strength parameter of thin films, which is closely related to the macro and micro defects of thin films. Therefore, how to measure the breakdown field strength of thin films and how to make thin films have its inherent field strength have become important problems faced by researchers

in the breakdown of dielectric films, there are instantaneous breakdown, thermal breakdown and aging breakdown. In the transient breakdown, it is divided into intrinsic breakdown and extrinsic breakdown [2]. The former refers to the electric breakdown of the film with perfect structure under the instantaneous action of the electric field, and the latter refers to the breakdown of the film with defects in the structure under the same conditions, and the enterprise using the first batch of new materials is the beneficiary of the insurance. The corresponding breakdown field strength is called the intrinsic breakdown field strength and the extrinsic breakdown field strength of the film. The intrinsic breakdown field strength is the intrinsic breakdown field strength of the film, which depends on the film itself. The extrinsic breakdown field strength depends on the defects in the film and does not belong to the inherent characteristics of the film

due to the different defect conditions and defect distribution of the film, its extrinsic breakdown field strength has a strong dispersion. In addition, due to the differences in testing methods and techniques, the measured field strength values of the same film will also be different. With the continuous development and rapid improvement of thin film manufacturing technology, the quality of thin films is gradually optimized, so the measured maximum breakdown field strength is rapidly approaching the intrinsic breakdown field strength. 1 Test Technology 1.1 test sample

in order to measure the actual breakdown field strength of the film, two measures are taken on the test sample. One is to make the sample very small. For example, the area of the upper electrode of the commonly used sample is 0.0025 ~ 0.8400 mm2, which has two shapes: round and square. The diameter of the former is 0.2 ~ 1.0 mm. Another measure is to make hundreds of upper electrodes, that is, hundreds of samples, on the same large-area substrate, because the lower electrode is a common large electrode. Obviously, such a test sample array is made by photolithography

at present, the structure of commonly used samples is MIS (metal insulator semiconductor) type or MIM type micro capacitor. The substrate is mostly single crystal s electrical appliance, which switches I or GaAs back and forth, and some also use glass. The reason for using single crystal Si is that its surface is particularly smooth after polishing, and a very thin dielectric (insulation) film can be deposited, so the electric breakdown field strength of a very thin film can be tested. In addition, the specific electric capacity per unit area of the sample is also increased accordingly, which is convenient for measuring its charge. Using Si substrate can also make the sample suitable for integration, and it can also test whether the research carried out can match the integration process

the metal electrodes of the samples are mostly Al, with a thickness of submicron. Some use oxidation-resistant gold, such as Au, Pt, PA, and some also use CR or transparent conductive oxide electrodes, such as indium tin oxide (ITO) electrodes

the dielectric films studied include oxide and nitride films, single films and composite films. In the composite film, there are layer composite and component composite. The thickness of the dielectric film in the sample is mostly 5.5 ~ 500.0 nm

1.2 test methods

there are many test methods for the electric breakdown field strength of dielectric films, among which the most commonly used is the continuous voltage rise breakdown (RVB) method, which is referred to as the voltage rise method for short, and sometimes the step-by-step method is also used. The advantage of the boost method is simple and clear, and the instantaneous breakdown field strength of the film can be measured quickly. The disadvantage is that it can not reveal other properties of the film closely related to the breakdown, nor can it show the puncture process and breakdown mechanism. In addition, this method is not sensitive enough to accidental defects in dielectric films. Therefore, there are many other test methods, such as constant voltage breakdown (CVB) method, constant current breakdown (CCB) method [3], corona discharge (CD) method [4], random noise signal (RTN) method [5], etc

the breakdown field strength of dielectric films is generally measured at room temperature by DC power supply. The boost rate can reach 5 v/s fast and 0.1 v/s slow. The latter is to meet the requirements of quasi-static testing. During the test, the criteria for judging whether the sample has been destructively broken down vary from sample to sample, but they all measure the current flowing through the sample with the increase of the applied voltage, that is, measure its I-V characteristics. When the current suddenly increases to a specified value under a certain voltage, the sample is considered to have broken down (see Figure 1 [6]). This specified value is the standard for judging sample breakdown. Due to different sample conditions, especially the difference in area and medium thickness, the specified value is very different from each other. The lower one is as small as 0.1 Na, and the higher one is as small as 10 mA. The difference between them has eight orders of magnitude. More regulations are μ Class A. 1 - thin film grown in microwave plasma, with a thickness of 16 nm

2 - film formed by low-pressure chemical vapor deposition, thickness 30 nm

Fig. 1 I-V characteristics of silicon nitride film constant voltage breakdown method is to apply a constant voltage to the sample and observe the current passing through the sample. With the increase of time after applying the voltage, the current increases. When the current rises to a specified value, it is defined as the breakdown of the sample. Obviously, the breakdown field strength obtained by this test method is not the instantaneous breakdown field strength. In order to make it close to the instantaneous breakdown field strength, the applied voltage usually needs to reach a high field strength, such as 1 v/nm

constant current breakdown method is to add a constant current to the sample and observe the change of sample terminal voltage with time. When the terminal voltage drops to 50%, it is considered as sample