Currently, more than 98% of electronic component materials use single crystal silicon. Among them, the CZ method accounts for about 85%, and the other part is the flotation method and the FZ growth method. Single crystal silicon grown by the CZ method is used to produce low-power integrated circuit components. Single crystal silicon grown by the FZ method is mainly used in high-power electronic components. The CZ method is more commonly used in the semiconductor industry than the FZ method, mainly because its high oxygen content provides the advantage of wafer strengthening. Another reason is that the CZ method is easier to produce large-sized single crystal silicon rods than the FZ method.

At present, the CZ method is mainly used in China

The main equipment of the CZ method: CZ growth furnace

The components of the CZ method growth furnace can be divided into four parts

(1) Furnace body: including quartz crucible, graphite crucible, heating and insulation components, furnace walls

(2) Crystal rod and crucible lifting and rotating mechanism: including seed crystal chuck, hanging wire and Pull up the rotating component

(3) Atmospheric pressure control: including gas flow control, vacuum system and pressure control valve

(4) Control system: including detection sensor and computer control System

Processing technology:

Feeding → Melting → Neck growth → Shoulder growth → Equal diameter growth → Tail growth

(1) Feeding: Polycrystalline silicon The raw materials and impurities are put into the quartz crucible. The type of impurities depends on the N or P type of the resistor. Impurity types include boron, phosphorus, antimony, and arsenic.

(2) Melting: After adding polysilicon raw materials into the quartz crucible, the crystal growth furnace must be closed and evacuated, then filled with high-purity argon gas to maintain it within a certain pressure range, and then turn on the graphite heating Turn on the power supply of the device and heat it to above the melting temperature (1420°C) to melt the polysilicon raw material.

(3) Neck growth: When the temperature of the silicon melt is stable, the seed crystal is slowly immersed in the silicon melt. Due to the thermal stress when the seed crystal is in contact with the silicon melt field, dislocations will occur in the seed crystal, and these dislocations must be eliminated by shrinkage growth. Neck growth is to quickly lift the seed crystal upward, so that the diameter of the grown seed crystal is reduced to a certain size (4-6mm). Since the dislocation line forms an angle with the growth axis, as long as the necking is long enough, the dislocation can grow. out of the crystal surface, producing a crystal with zero dislocations.

(4) Shoulder-free growth: After the thin neck is grown, the temperature and pulling speed must be reduced so that the diameter of the crystal gradually increases to the required size.

(5) Equal-diameter growth: After the thin neck and shoulders are grown, the diameter of the ingot can be maintained between plus and minus 2mm by continuously adjusting the pulling speed and temperature. This diameter is fixed. The part is called the equal diameter part. Single crystal silicon wafers are taken from equal diameter sections.

(6) Tail growth: If the crystal rod is separated from the liquid surface immediately after growing the equal-diameter part, the effect force will cause dislocations and slip lines to appear in the crystal rod. Therefore, in order to avoid this problem, the diameter of the crystal rod must be slowly reduced until it becomes a sharp point separated from the liquid surface. This process is called tail growth. The grown ingot is raised to the upper furnace chamber and cooled for a period of time before being taken out, thus completing a growth cycle.

Single crystal silicon rods are processed into single crystal silicon polished silicon wafers

Processing process:

Single crystal growth → cutting → outer diameter rolling → flat edge or V-groove processing→slicing

Beveling→grinding and etching-polishing→cleaning→packaging

Cutting: the purpose is to cut off the head and tail of the single crystal silicon rod and those that exceed customer specifications The single crystal silicon rod is segmented into lengths that can be processed by the slicing equipment, and test pieces are cut to measure the resistivity and oxygen content of the single crystal silicon rod.

Cutting equipment: inner garden cutting machine or outer garden cutting machine

Main imported materials for cutting: blade

Outer diameter grinding: due to single crystal silicon The outer diameter surface of the rod is not flat and the diameter is larger than the diameter specification specified for the final polished wafer. A more accurate diameter can be obtained by rolling the outer diameter.

Outer diameter roller grinding equipment: grinder

Flat edge or V-groove processing: refers to the orientation and designated processing, used to flatten or flat edge the specific crystallization direction on the single crystal silicon holder V shape.

Processing equipment: grinder and X-RAY diffractometer.

Slicing: refers to cutting a single crystal silicon rod into thin wafers with precise geometric dimensions.

Slicing equipment: inner cutting machine or wire cutting machine

Chamfering: refers to trimming the edge of the cut wafer into an arc shape to prevent the edge of the wafer from cracking and crystal lattice Defects are generated and the flatness of the epitaxial layer and photoresist layer is increased.

The main equipment for chamfering: chamfering machine

Grinding: refers to the ability to remove saw marks and surface damage layers caused by slicing and wheel grinding through grinding, effectively improving the single crystal silicon wafer The curvature, flatness and parallelism reach specifications that can be handled by a polishing process.

Grinding equipment: grinder (double-sided grinding)

Main raw materials: grinding slurry (main ingredients are alumina, chromium sand, water), slip fluid.

Corrosion: refers to the damage layer formed on the surface of the wafer due to processing stress after mechanical processing such as slicing and grinding. It is usually removed by chemical etching.

Corrosion methods: (A) Acid corrosion is the most commonly used.

Acidic corrosive fluid consists of nitric acid (HNO3), hydrofluoric acid (HF), and some buffer acids (CH3COCH, H3PO4).

(B) Alkaline corrosion, the alkaline corrosion solution consists of KOH or NaOH plus pure water.

Polishing: refers to the polishing of single crystal silicon wafers that need to improve micro-defects on the surface to obtain high flatness wafers.

Polishing equipment: multi-chip polishing machine, single-chip polishing machine.

Polishing method: Coarse polishing: mainly used to remove the damaged layer, generally the removal amount is about 10-20um;

Fine polishing: mainly used to improve the micro-roughness of the wafer surface, generally The removal amount is less than 1um

Main raw materials: The polishing slurry is composed of finely suspended silicic acid gel with SiO2 and NaOH (or KOH or NH4OH). It is divided into coarse polishing slurry and fine polishing slurry.

Cleaning: Many steps require cleaning during the processing of single crystal silicon wafers. The cleaning here is mainly the final cleaning after polishing. The purpose of cleaning is to remove all sources of contamination from the wafer surface.

Cleaning method: Mainly traditional RCA wet chemical cleaning technology.

Main raw materials: H2SO4, H2O2, HF, NH4HOH, HCL

(3) Causes of loss

A. Polycrystalline silicon - single crystal silicon rod< /p>

In the process of processing polycrystalline silicon into monocrystalline silicon rods: if losses occur due to re-doped crucible bottom materials, head and tail materials, they cannot be reused and can only be used as additives in the metallurgical industry such as iron smelting, aluminum smelting, etc.; If the loss is caused by non-redoped crucible bottom materials, head and tail materials, which can be used to make low-grade silicon products, this part should be taxed as scraps.

Heavy doping refers to putting polysilicon raw materials and impurities close to saturation (types include boron, phosphorus, antimony, arsenic. The type of impurity depends on the N or P type of resistance) into a quartz crucible and melting it. Ingredients.

Heavy doping is mainly used to produce silicon wafers with low resistivity (resistivity <0.011 ohm/cm).

Loss: about 15% of the bottom material of the pot after the single crystal is drawn.

The head and tail materials in the shaping process of single crystal silicon rods are about 20%.

During the single crystal shaping process (outer diameter grinding process), since the outer diameter surface of the single crystal silicon rod is not flat and the diameter is larger than the diameter specification specified for the final polished wafer, the outer diameter grinding process A more accurate diameter can be obtained. The loss is about 10%-13%.

Hope it helps!