Phenomenon and Analysis of Quartz Crucible in Single Crystal

1. Quartz crucible on the wall after the use of brown small circle phenomenon: the brown wall on the wall of small circle.

Explanation: The quartz crucible itself is amorphous, the quartz crucible itself is amorphous state energy, in the appropriate conditions, he will phase change and the formation of a stable square quartz crystal state. The formation of the crystalline form of the cristobalite includes two stages of nucleation and growth, which are structural defects or impurities (especially some alkaline metals or heavy metals) that usually occur on the walls of the quartz crucible. The initial fenched quartz crystal is spherical, and further growth is along the crucible wall into a dendritic to the lateral development, this is because the quartz crucible and the reaction of the solution when the vertical direction of the growth is suppressed. Between the square quartz crystal and the amorphous quartz crucible wall is usually mixed with a layer of silicon solution, while the edge of the quartz crystal, usually covered with brown sio bubbles. Sio gas is brown, brown little circle is sio crystal. The fundamental reason is that the impurities on the crucible wall or silicon material cleaning is not clean caused by the acid or heavy metal residues, so that crucible instability at high temperatures, resulting in appeals.

Note: The physical and chemical properties of silicon oxide (sio) Sio: black brown to loess colored amorphous powder. Melting point> 1702 ° C. Boiling point 1880 ° C, the purity of 99.5% of the silica powder and coal tar pitch powder (or silica powder) to C / SiO2 = 1.3 or Si / SiO2 = 1.2 ratio of mixed into the electric heating of the vacuum furnace, into the non-oxidizing Gas (such as argon, hydrogen and other gases), high temperature reaction, the preparation of ultra-fine (0.1 / μm below) amorphous silicon oxide. In general it can be obtained by the rapid cooling of silicon dioxide with pure silica at high temperature: SiO2 + Si → 2SiO Sio is the product of si and sio2 heating under vacuum conditions. At the time of seeding, there is a layer of brown Smoke around, this is sio.

Pathways:

1. Cleaning of silicon material need to ensure that no acid residue or heavy metal

2. Crucible its own quality clearance

3. Improve the process, use a coating or spray the crucible.

2. Crystallization of quartz crucible: Quartz crucible at high temperature has become the trend into silica crystals (square quartz). This process is called recrystallization, also known as "devastation", often referred to as "crystallization". Explain: Crystallization usually occurs in the surface of quartz crucible, in accordance with the provisions of China's quartz glass industry standard, the semiconductor industry with quartz glass at 1400 ℃ ± 5 ℃ for 6 hours, the average thickness of the crystal layer should be <100μm, 100μm Within the crystallization is normal. Serious crystallization has a great influence on the single crystal, and the crystallization of the inner wall of the quartz crucible may break the original coating of the inner wall of the crucible, which will cause the bubble layer below the coating to react with the molten silicon, causing part of the particles Silica into the molten silicon, making the growth of the crystal structure is mutated and can not be normal long crystal. Crystallization will reduce the original thickness of the quartz crucible, reducing the strength of the crucible easily lead to deformation of the quartz crucible.

possible reason:

(K) Sodium (Na) Lithium (Li) and alkaline earth metal ions Calcium (Ca) Magnesium (Mg) The presence of these ions is the presence of quartz in the crucible of all the quartz crucibles. Crucible produced

The main factors of crystallization.

2 during the operation, due to improper operation method will produce crystallization such as in the prevention of quartz crucible and loading silicon material in the process, into the sweat, saliva, oil, dust and so on.

3 The new graphite crucible is not completely calcined or contaminated to put into use is the main reason for the crystallization of quartz crucible.

4 for the crystallization of raw materials, low purity, too much impurities or cleaning process problems.

5 when the temperature is too high melt, will also increase the degree of crystallization.

6 quartz crucible production, cleaning, packaging process by being contaminated.

Solutions:

1 quartz crucible manufacturers to ensure that the production of crucible from the use of materials to all aspects of production are in line with quality requirements.

2 in the whole process of single crystal production should be strictly in accordance with the procedures to seriously operate.

3 crystal used in the purity of raw materials must meet the production requirements, if the raw material itself contains more impurities in the process of soldering will also cause crystallization. Especially the presence of alkali metal ions, will reduce the crystallization temperature of 200 ~ 300 ℃.

4 raw material cleaning must meet the technological requirements, into the acid or alkali treatment of raw materials if not acid and alkali residue rinse thoroughly, easily lead to crystallization.

5 new graphite devices, such as graphite crucible contains a certain amount of ash and other impurities, put into use before going through thorough high temperature calcination can be used.

6 melt should be selected at the appropriate melt temperature to reduce the crystallization or reduce the degree of crystallization.

3. The deformation of the quartz crucible

Phenomenon: quartz crucible deformation after use

influences:

1. After the deformation of the quartz crucible, in the process of pulling the crystal with the rise of the pot, the quartz crucible deformation of the protruding part will crash to the guide tube, affecting or can not continue the normal pull crystal.

2. The quartz crucible deformed by the hook in the soldering, and the inner surface of the crucible protrudes inwardly. When the dissolved material reaches the normal seeding position, it has collided with the draft tube, which leads directly to The serious consequences of pulling crystal.

3 bag in the drum and drums larger, in the process of pulling the crystal with the decline in the level, the drum will gradually exposing the liquid surface, then the crystal bar has been pulled out of the drum package, if not stop A serious accident occurred.

possible reason:

1. improper loading method. The contact between the material on the liquid level line and the quartz crucible is in contact with the surface, which is liable to occur during the melting process. The uppermost part of the crucible is filled with small pieces of fine material, which is prone to dissolve in the lower part of the melt, the upper part of the crystalline state caused by crucible deformation.

2. Improper melting method.

3. The temperature is too high. As the melting point of silicon 1420 ℃, the general melt temperature of 1550 ~ 1600 ℃ or so, if the melt temperature is too high, in the melt process is prone to deformation.

4. The temperature is too low. When the temperature of the molten material is low, the upper part of the crucible is in contact with the wall of the crucible, so that the quartz material is deformed by the quartz crucible.

5. The quality of raw materials is uneven, Qi contains impurities much higher than the original polycrystalline, pickling process is not perfect, the crucible of the normal use of the impact is also very large, mainly in the prone to serious crystallization.

6. Quartz itself has quality problems. Quartz crucible in the production, cleaning, packaging contamination caused by crystallization (including the liquid level above the part) so that the original thickness of the quartz crucible will be thin, the strength also decreases, prone to deformation.

Note: Deutsche single crystal workshop quartz crucible quality inspection standard diameter height curvature wall thickness bottom transparent layer 18 "456-458 321 +2 / -2 ≥9 7.5-9 9.0-10.5 3 20" 504-508 356 ≥10 9-10 10-12 4 Appearance indicators

Less than 0.8mm below the black point in the sandwich allowed 1, straight wall less than 1.0mm black spots in the sandwich allows 1

Less than 0.3mm below the curvature of the bubble in the sandwich allows one, straight wall less than 0.5mm bubble in the sandwich allows an impurity content

The total content of 13 impurity elements of Al, Fe, Ca, Mg, Cu, Co, Ni, Mn, Ti, Na, K, Li and B is not more than 30 * 10-6.