Does cracking of the target material affect the glow? Analysis of three key factors and countermeasures

Does cracking of the target material affect the glow? Analysis of three key factors and countermeasures

1. Causes and types of cracking of target material

1.1 Internal factors of target material cracking

The internal factors of target cracking mainly include the crystal structure defect of the material itself, the internal stress distribution and the unequal heat treatment. The defects in the crystal structure of the material, such as dislocation, vacancy and grain boundary, are easy to become the starting point of cracks in the case of stress concentration. The uneven distribution of internal stress may be caused by the different cooling rate during the manufacturing process or the change of the thermal expansion coefficient of the material, and these stresses will gradually accumulate and release under certain conditions, forming cracks. In addition, the uneven cooling during the heat treatment process can also lead to thermal stresses inside the material, which, if not released in time, may lead to cracks on the surface or inside the material.

1.2 External factors of target material cracking

The external factors mainly include mechanical stress, thermal shock and chemical corrosion. Mechanical stress is the most common external factor, especially in the process of high-energy particle bombardment, the surface of the target to bear the instantaneous stress is very large, easy to form cracks. Thermal shock is due to the rapid temperature changes experienced by the target during use, such as rapid cooling from a high temperature environment, resulting in a large thermal stress inside the material. Chemical corrosion is due to the exposure of the target to a corrosive environment, resulting in micro-cracks on the surface of the material, which gradually expand with the corrosion process.

1.3 Different types of cracks

According to the size and shape of the crack, the crack of the target can be divided into micro crack and macro crack. Microcracks usually refer to cracks in the nanometer to micron scale, which may not be easily observed by the naked eye or conventional microscopy, but their effect on material properties is very significant. Macroscopic cracks refer to larger cracks, which can usually be directly observed by the naked eye or an ordinary microscope. These cracks not only significantly reduce the mechanical properties of the material, but also affect its electrical and thermal properties.

2. Theoretical analysis of the effect of target cracking on brightening

2.1 Effect of target material cracking on surface energy of materials

2.1.1 The change of energy distribution on the surface of the material by crack formation

The energy distribution on the surface of the material is significantly different in the absence of cracks and in the presence of cracks. The formation and propagation of cracks will lead to the redistribution of energy on the surface of the material, which is manifested in:

1.Stress concentration area: The crack tip is a stress concentration area with extremely high energy density. The stress concentration effect makes the atoms and molecules in the crack tip region in a high energy state, which is easier to be excited.

2.Increase in surface energy: The creation of cracks increases the surface area of the material, thereby increasing the total surface energy. The increase of surface energy will affect the stability of the material, making local areas more prone to flaring.

3.Uneven energy distribution: The uneven distribution of energy caused by cracks makes some regions in a high energy state, while other regions are in a low energy state. This energy gradient will affect the intensity and uniformity of the luminous phenomenon.

2.1.2 Stress concentration effect at crack tip

Stress concentration at the crack tip is one of the main reasons for the change of energy distribution on the surface of the material:

1.High Stress concentration: The Stress Intensity Factor (K) in the crack tip region is very high, usually much higher than the average stress level of the material. The spacing of the atoms in this region is widened, and the atoms are in a high energy unstable state, which is easier to excite and ionize.

2.Local energy accumulation: High energy accumulation in areas of stress concentration makes these areas more prone to brightening under high-energy particle bombardment, because the concentration of energy makes the excitation and transition of electrons easier.

3.Crack propagation: The further propagation of cracks will continuously change the surface energy distribution of the material, resulting in a dynamic change of the brightening phenomenon. In the process of crack propagation, new stress concentration areas are formed constantly, which makes the flaring phenomenon more complicated and unstable.

2.2 Effect of target cracking on charge transfer

2.2.1 Effect of cracks on the conductivity of materials

Conductivity is an important parameter to measure the ability of a material to transfer charge, and the presence of cracks will significantly affect the conductivity of the target:

1.Conductivity reduction: Cracks can disrupt the continuity of the material, resulting in the interruption of the migration path of charge carriers, thereby reducing the overall conductivity of the material. Especially in semiconductors or conductive materials, the presence of cracks can form a resistive barrier that prevents the free flow of charge.

2.Local resistance increases: The crack tip and nearby areas may form local high resistance areas due to structural fracture and stress concentration. These high resistance regions will hinder the migration of charge carriers and affect the uniformity and intensity of the luminous phenomenon.

2.2.2 Effect of cracks on the migration path of charge carriers

The migration path of charge carriers will change significantly under the influence of cracks:

1.Migration path interruption: The formation of cracks will interrupt the original continuous charge carrier migration path, especially in metal or semiconductor targets, the presence of cracks will cause charge carriers to be trapped near the crack during the migration process and cannot pass smoothly.

2.Charge accumulation effect: In the vicinity of the crack, the local accumulation of charge may be caused by the obstruction of charge carrier migration. This charge accumulation effect will cause the enhancement of local electric field, and further affect the intensity and distribution of the luminous phenomenon.

3.Increased carrier recombination rate: High energy states and stress concentration effects in the cracked region can lead to increased charge carrier recombination rates, especially in semiconductor materials, where the recombination of electrons and holes can significantly affect the efficiency of the luminous phenomenon.

2.3 Effect of target cracking on thermodynamic conditions

2.3.1 Local temperature change due to crack

The process of crack formation and propagation is usually accompanied by local temperature changes, which have important effects on the brightening phenomenon:

1.Local temperature increase: The effect of high stress concentration at the crack tip will cause a local area of temperature increase. The increase in temperature increases the kinetic energy of the atoms, making the excitation and transition of electrons easier, thus increasing the intensity of the brightening phenomenon.

2.Thermal diffusion path change: The presence of cracks will change the thermal diffusion path inside the material, causing the heat to be unevenly distributed inside the material. The change of thermal diffusion path will affect the overall thermal properties of the material, thus affecting the stability of the luminous phenomenon.

2.3.2 Local temperature change due to crack

Thermal stress concentration is an important phenomenon in the process of crack formation and propagation, and has a significant effect on the brightening phenomenon:

1.Thermal stress concentration effect: The crack tip area will form a significant thermal stress concentration due to the difference in thermal expansion coefficient. This thermal stress concentration effect will cause the temperature of the local area to rise sharply, affecting the intensity and stability of the shining phenomenon.

2.Thermal cycle effects: In practical applications, the target may undergo multiple thermal cycles. The existence of cracks will make the thermal stress concentration effect accumulate continuously during each thermal cycle, and eventually affect the overall thermal properties and the performance of the brightening phenomenon of the material.

3.Local thermal effect: The local thermal effect at the crack tip causes a change in the structure of the material in the region, such as a phase transition or recrystallization. These structural changes will further affect the electrical and thermal properties of the material, thus affecting the performance of the luminous phenomenon.

3. Practical application of the effect of target cracking on brightening

3.1 Target cracking challenges in industrial applications

In industrial applications, target cracking is a significant challenge. The cracking of the target will not only reduce its service life, but also affect the stability of the flaring phenomenon during sputtering. When the cracked target is bombarded with high-energy particles, the shining phenomenon will become uneven, resulting in a decline in the quality of the sputtered film and affecting the performance of the final product. For example, in semiconductor manufacturing, uniform film thickness and consistent electrical properties are critical to the performance of the device, and the instability of brightening caused by cracking of the target directly affects these key parameters.

3.2 Material design to improve crack resistance of target

In order to deal with the problem of cracking of the target, improving the cracking resistance of the target has become one of the important directions of material design. The development of new high toughness target material is the key to solve this problem. These high-toughness materials can significantly improve their cracking resistance by optimizing the crystal structure and chemical composition of the material. For example, the addition of alloying elements or the use of nanocomposites can enhance the toughness and crack resistance of the material. In addition, surface treatment technology is also widely used to improve the crack resistance of the target. By surface hardening, coating and nano-structured treatment, the formation and spread of cracks on the surface of the target can be effectively reduced, thus improving its service life and performance stability.

3.3 Process improvement for controlling flare phenomenon

The technology method to control the shining phenomenon is also the key to solve the problem of cracking of target material. The effect of target cracking on sputtering process can be reduced to a certain extent by improving the technology of brightening control. For example, optimizing sputtering parameters, such as sputtering power, air pressure, and temperature, can reduce stress concentration on the surface of the target and reduce the probability of crack formation. In addition, combined with a comprehensive solution for target cracking control, such as real-time monitoring of the surface state of the target during sputtering and timely adjustment, can also significantly improve the stability of the brightening phenomenon and the quality of the sputtered film.