RU2375719C1 - Method for radiation-induced determination of potentially unstable semiconductor products - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention refers to the field of electronics engineering products testing and can be used for quality and reliability evaluation of micro- and nanoelectronics products used in equipment with long-term service life. Essence of invention: to determine potentially unstable semiconductor products (SCP) following is performed: testing parametres of products are measured; SCP are subjected to ionisation radiation; products are annealed at maximum allowable or marginal temperature for given type of product as per technical specifications (TS); in this process the measurement of testing parametres is carried out before subjecting to ionisation radiation, after subjecting and after annealing; "ionisation radiation - annealing" cycle is repeated several times, while number of cycles depends on SCP type; annealing constant is determined and according to its value products are separated by stability level.

EFFECT: increase in reliability and decrease in time of testing.

Description

The invention relates to the field of testing electronic products, mainly micro and nanoelectronics products used in apparatus with long life.

Known methods for assessing compliance with the requirements for the reliability of electronic products according to GOST B 20.57.4004-81 "Products of electronic equipment, quantum electronics and military electrical equipment. Methods of compliance with the requirements for reliability." This standard provides for the identification during testing of catastrophic failures occurring in products due to a violation of their manufacturing technology and design imperfections.

Testing of products is carried out in the maximum permissible electrical operating conditions and at a temperature maximum permissible for this type of product, and the change in the set (criteria) parameters is recorded. The duration of the tests is indicated in the specifications for this product.

However, the results of these tests are not reliable enough due to the presence of hidden structural defects in the products that cannot be detected by these tests, because they do not affect the change in the criterial parameters of the products, therefore, are not subject to measurement and control. As a result, products recognized as having successfully passed tests may not provide the necessary resource under long-term operating conditions and fail before the specified life. The method proposed in US patent No. 4816753 G01R 31/26 from 03/28/89, is designed to accelerate reliability testing of products. For this, the aging of integrated circuits, in particular, MOS integrated circuits, is stimulated by exposure to them with a dose of ionizing radiation (x-rays, neutron flux, etc.) and a correlation dependence of radiation resistance and product life is established. As a result of exposure to a dose of ionizing radiation in the oxide layers of the device, a large number of electron-hole pairs are stimulated, which are captured by traps at the interface, which leads to failure of the device within a relatively short time.

Initially, at the calibration stage, one group of products is subjected to electrical aging, i.e. exposed to electrical loads until the failure of the device, which occurs as a result of degradation of traps at the interface and measure the product life time depending on the substrate current. The measurement of the substrate currents and the lifetime of the products at the stage of their electrical aging is carried out for products manufactured by various technological processes and having different geometric dimensions, in particular a different width. On the basis of the data obtained by the appropriate mathematical formula, taking into account the width of the device, determine the coefficient of radiation resistance.

Then, at the test stage, the integrated circuits of another group are exposed to ionizing radiation to simulate the degradation of traps at the interface. The radiation dose is increased to critical, at which the number of traps at the interface leads to the failure of the integrated circuit. By comparing the measured critical radiation dose with the radiation resistance coefficient, the product life can be predicted in a very short test time. The disadvantage of this method is that it is destructive, because the identification of the empirical dependence of the service life of the device on the level of its radiation resistance suggests the impact on the plate of a destructive dose of ionizing radiation. The closest method is the method proposed in the patent of the Russian Federation No. 2100817 G01R 31/26 from 12/27/97. In the proposed method for testing the reliability of electronic products, the first group of products is first exposed to electrical loads, and then the first and second groups of products are exposed to ionizing radiation, the specified parameters of the products of both groups are measured, which are used to judge the test results. Both groups of products are selected from one test batch. The dose of ionizing radiation for products of both groups is set to the maximum permissible, non-destructive for this type of product, and the electric load for products of the first group is set within the specified operating conditions, the average statistical value of the specified product parameters in each group is calculated, the results of the tests are compared by comparison. The disadvantage of the proposed method is the use of additional electrical loads, which increases the complexity and energy consumption of the method.

The invention is aimed at increasing reliability and reducing test time.

This is achieved by the fact that in order to determine potentially unstable semiconductor products (PPI), the diagnostic parameters of the products are measured, the effect of ionizing radiation on the PPI is measured, products are annealed at the maximum permissible or maximum permissible temperature for this type of product according to technical specifications (TU), while diagnostic parameters are carried out before exposure to ionizing radiation, after exposure and after annealing, the ionizing radiation is repeated several times - annealing, and about cycles depends on the type of PPI, determine the annealing constant and according to its values the products are divided according to the level of stability.

The method is as follows:

Initially, preliminary tests are carried out, during which criteria criteria and time intervals for measuring electrical parameters are determined. Determine the time points of measurements of electrical parameters. Find the value of the dose of ionizing radiation, which must act on this PPI, depending on the type of product. Determine the temperature of annealing of radiation defects and the number of cycles of exposure to radiation - annealing. The curves of the dependence of the criterial parameters on the annealing time vary according to the law of the exponent and are described by the formula:

,

,

where U is the value of the electric parameter at time t;

U ₀ is the initial value of the electric parameter;

R is the constant annealing.

The annealing constant is a quantity that is numerically equal to the time during which the parameter changes e times.

According to the measurement results of the control sample, the PPI find the arithmetic mean and also the standard deviation of the annealing constant according to well-known formulas from mathematical statistics.

The entire batch of PPI is divided by the level of stability or reliability according to the following criteria:

if the value of the constant annealing of PPI falls into the range of values R ± t _{α, m} σR, then the product is potentially reliable;

where t _{α, m} is the student coefficient;

σR is the standard deviation of the annealing constant.

For the control group PPI it is necessary to conduct electrotraining and compare the results of the training with the results of the method.

Example

Integrated microcircuits (ICs) 530IR18, a six-bit parallel register with D flip-flops made by isoplanar technology, and 1804BC1, a microprocessor made by technology with isolation of elements by a p-n junction, were chosen as the object of research.

Initially, preliminary tests were conducted, during which diagnostic parameters and time intervals for their measurement were determined. To do this, integrated circuits (ICs) were irradiated to a dose of 10 ⁷ P and subsequent annealing for 6 hours, with measurements of full functional parametric control every 3 minutes. Annealing temperature was selected + 125 ° C and + 150 ° C (the maximum allowable and maximum permissible operating temperatures of the IC according to the technical specifications, respectively).

During preliminary tests, a parameter was selected that has a maximum deviation - low-level output current. The high information content of this electric parameter is due to the fact that it is proportional to the gain of the output transistor, which has the greatest sensitivity to radiation, because it has maximum dimensions and is therefore most susceptible to radiation.

For studies, samples of 20 pieces of IP of each type-nominal were formed, each of which was tested up to a dose of 1.6 ∙ 10 ⁷ and 10 ⁷ P. One half of each sample was annealed at a temperature of + 125 ° C, the second at a temperature of + 150 ° C, The dependence of the annealing kinetics on the annealing temperature was studied by themselves. The irradiation cycle was applied three and five times.

According to the results of the experiment, the arithmetic mean values of the annealing constants are given in the table.

Table Arithmetic average of the annealing constants Test stage 1804BC1 530IR18 10 ⁷ P 1.6 · 10 ⁷ P 10 ⁷ P 1.6 · 10 ⁷ P 125 ° C 150 ° C 125 ° C 150 ° C 125 ° C 150 ° C 125 ° C 150 ° C one 15.2 14.1 18.4 17.5 11.3 10.3 14.1 13.3 2 11.5 10.5 15.3 14.1 7.6 7.2 11.3 10.5 3 9.6 9.0 13.1 12.0 6.5 6.3 9.3 8.7 four 8.8 8.3 11.6 10.6 6.1 6.0 8.2 7.6 5 8.4 8.1 10.5 9.6 6.0 5.9 7.3 6.9

The table shows that the annealing constant in the general case depends on the IC technology, decreases with an increase in the irradiation factor and tends to a certain constant value, an increase in the annealing temperature leads to a decrease in the annealing constant, and, conversely, an increase in the radiation dose leads to an increase in the annealing constant and vice versa.

Using the results of 4 and 5 test levels, as they are approximately the same, and by calculating the standard deviations for a given sample of ICs from the test results, we can construct a confidence interval for constant annealing in which the IP data will be potentially reliable.

The results of the proposed method can be explained by the following qualitative model. During radiation exposure, complexes of radiation defects accumulate in the active areas of IC transistors, the concentration of which is directly proportional to the radiation dose. Radiation defects have deep levels in the band gap of silicon and, therefore, having high generation and recombination activity, cause degradation of the IP parameters. Annealing at elevated temperature promotes the decay of radiation defects and the restoration of IP parameters before irradiation.

As the annealing temperature increases, the process of defect decomposition increases, the parameters return to their initial value faster, which manifests itself in a decrease in the annealing constant.

Formed in a single technological cycle and containing a number of high-temperature treatments (oxidation, diffusion), the IMS device structure is initially in a nonequilibrium state. This state is characterized by the presence in the IC of structural defects that create deformation of the crystal lattice (dislocations, microdefects, deformation stresses at the SiO ₂ - Si interface), which leads to a change in the processes of radiation defect formation, and the efficiency of radiation defect formation in such structures is higher than in unreliable, cm article by Achkasov V.N., Zolnikov A.N. Modeling of mechanisms of annealing of radiation defects in IP. Bulletin of the Voronezh State Forestry Engineering Academy, 2002, issue 4, part 2.

Claims (1)

A method of radiation-stimulated determination of potentially unstable semiconductor products, including measuring the diagnostic parameters of the products, exposure to semiconductor products by ionizing radiation, annealing the products at the maximum allowable or maximum permissible temperature for this type of product according to technical conditions, characterized in that the diagnostic parameters are measured before exposure ionizing radiation, after exposure and after annealing, repeat the cycle of exposure radiation-annealing ”, the number of cycles depending on the type of semiconductor product, the annealing constant is determined, and the product is divided according to its stability level.