Purification method of high-purity n-tetrasilane

Abstract

A high-purity n-tetrasilane purification method includes: introducing a tetrasilane (Si.sub.4H.sub.10) isomeric mixture into a solidifying purification tank, cooling the tetrasilane (Si.sub.4H.sub.10) to a predetermined temperature with refrigerant in the solidifying purification tank, maintaining the predetermined temperature between the freezing temperature of the n-tetrasilane (n-Si.sub.4H.sub.10) and of the i-tetrasilane (i-Si.sub.4H.sub.10), solidifying the n-tetrasilane (n-Si.sub.4H.sub.10) in the tetrasilane (Si.sub.4H.sub.10) isomeric mixture into solid state, and vacuuming the i-tetrasilane (i-Si.sub.4H.sub.10) from the mixture for separation.

Claims

1. A purification method for high-purity n-tetrasilane comprising: introducing a tetrasilane (Si.sub.4H.sub.10) isomeric mixture into a solidifying purification tank, cooling the tetrasilane (Si.sub.4H.sub.10) isomeric mixture to a predetermined temperature by flowing a refrigerant through a jacket of the solidifying purification tank, maintaining the predetermined temperature between the freezing temperature of n-tetrasilane (n-Si.sub.4H.sub.10) and the freezing temperature of i-tetrasilane (i-Si.sub.4H.sub.10) to freeze the n-tetrasilane (n-Si.sub.4H.sub.10) into a solid form within the tetrasilane (Si.sub.4H.sub.10) isomeric mixture, and removing liquid i-tetrasilane (i-Si.sub.4H.sub.10) in the tetrasilane (Si.sub.4H.sub.10) isomeric mixture.

2. The purification method for high-purity n-tetrasilane as claimed in claim 1 further comprising: warming n-tetrasilane (n-Si.sub.4H.sub.10) in solid form to a liquid form, and then distilling the liquid form n-tetrasilane (n-Si.sub.4H.sub.10).

3. The purification method for high-purity n-tetrasilane as claimed in claim 2, further comprising: flowing the refrigerant in the jacket of the solidifying purification tank but not directly adding the refrigerant to the solidifying purification tank, wherein the solidifying purification tank is connected to an extraction tube for extraction of liquid i-tetrasilane (i-Si.sub.4H.sub.10) and trace amounts of trisilane (Si.sub.3H.sub.8).

4. The purification method for high-purity n-tetrasilane as claimed in claim 3 further comprising: reducing pressure within the solidifying purification tank to a pressure of −1.0 kg/cm.sup.2G to extract i-tetrasilane (i-Si.sub.4H.sub.10) and lower silane residues.

5. The purification method for high-purity n-tetrasilane as claimed in claim 3 further comprising: cooling the solidifying purification tank to a temperature that is between −90° C. to −99° C.

6. The purification method for high-purity n-tetrasilane as claimed in claim 3 further comprising: cooling the solidifying purification tank to −95° C.

7. The purification method for high-purity n-tetrasilane as claimed in claim 3, wherein: the solidifying purification tank is connected to an output tube connected to a distillation tower, and the output tube is configured to send the liquid form n-tetrasilane (n-Si.sub.4H.sub.10) to the distillation tower; wherein pentasilanes (Si.sub.5H.sub.12) and heavier silanes in the distillation tower are separated from a bottom of the distillation tower, and trisilane (Si.sub.3H.sub.8) and i-tetrasilane (i-Si.sub.4H.sub.10) are vented through a top of the distillation tower.

8. The purification method for high-purity n-tetrasilane as claimed in claim 7, wherein a solidifying tank is connected to the solidifying purification tank, and the solidifying tank comprises a refrigeration jacket, an an extraction channel, and a discharge pipe; wherein when the solidifying purification tank is liquifying the solid n-tetrasilane (n-Si.sub.4H.sub.10), the solidifying tank is cools a tetrasilane (Si.sub.4H.sub.10) isomeric mixture introduced into the solidifying tank to separate out unsolidified i-tetrasilane (i-Si.sub.4H.sub.10) and trace trisilane (Si.sub.3H.sub.8) from solidified n-tetrasilane (n-Si.sub.4H.sub.10) using the extraction channel.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a process flow chart of the purification method of high-purity n-tetrasilane according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) Please refer to FIG. 1 for the purification method of high-purity n-tetrasilane, a tetrasilane (Si.sub.4H.sub.10) isomeric mixture is introduced into a solidifying purification tank 10 and cooled to a predetermined temperature with a refrigerant, and a jacket 11 is flowed with the refrigerant on the solidifying purification tank 10 but not directly added to the solidifying purification tank 10. The predetermined temperature needs to be lower than the freezing temperature of n-tetrasilane (n-Si.sub.4H.sub.10), which is −89.9° C., and higher than the freezing temperature of i-tetrasilane (i-Si.sub.4H.sub.10), which is −99.4° C. In other words, the solidifying purification tank 10 needs to be cooled down to a predetermined temperature range from −90° C. to −99° C. with the refrigerant, and −95° C. is the best predetermined set temperature. With the proceeding, the n-tetrasilane (n-Si.sub.4H.sub.10) in the tetrasilane (Si.sub.4H.sub.10) isomeric mixture is frozen into its solid form. Furthermore, the solidifying purification tank 10 is connected with an extraction tube 12 for vacuuming to extract the liquid i-tetrasilane (i-Si.sub.4H.sub.10) and trace amount of trisilane (Si.sub.3H.sub.8) in the tetrasilane (Si.sub.4H.sub.10) mixture for separation and purification.

(3) The solidifying purification tank 10 is evacuated until the pressure in the tank reaches −1.0 kg/cm.sup.2G, and with the degree of vacuum pressure, it indicates that the liquid and vapor substances are all removed from the mixture. The solidifying purification tank 10 is then warmed up to the ambient state to convert the remaining solid n-tetrasilane (n-Si.sub.4H.sub.10) to its liquid state. Furthermore, the solidifying purification tank 10 is connected with an output tube 13 to a distillation tower 20. The output tube 13 is used to discharge the liquid n-tetrasilane (n-Si.sub.4H.sub.10) to the distillation tower 20 by filling the pressurized helium to shove all of the n-tetrasilane (n-Si.sub.4H.sub.10) to the distillation tower 20 without consuming any energy. At the distillation tower 20, the pentasilanes (Si.sub.5H.sub.12) and heavier silanes, with boiling point higher than 130˜153° C., contained in the tetrasilane mixture are further separated from the n-tetrasilane (n-Si.sub.4H.sub.10) through the bottom of the distillation tower 20, and the remaining PPM-graded of silanes, trisilane (Si.sub.3H.sub.8) and i-tetrasilane (i-Si.sub.4H.sub.10), with boiling temperatures lower than 101.7° C., are removed through the top of the distillation tower 20 by differences in their boiling temperatures. Since most of i-tetrasilane (i-Si.sub.4H.sub.10) and lower silanes are removed in the earlier process at the solidifying purification tank 10, the residual i-tetrasilane (i-Si.sub.4H.sub.10) in the distillation tower 20 is rare, and it does not affect the boiling temperature (108.1° C.) of the n-tetrasilane (n-Si.sub.4H.sub.10) for the fractional distillation purification. With the above proposed purification method, the n-tetrasilane (n-Si.sub.4H.sub.10) with a purity of 99.99% is then carried out by the final distillation purification at low cost in combined with simple equipment and low energy-consuming process.

(4) Please refer to FIG. 1 again. A solidifying tank 30 is connected to the solidifying purification tank 10. The solidifying tank 30 is comprised of a refrigerant jacket 31, an extracting channel 32, and a discharge pipe 33. The configuration of the solidifying tank 30 is resembled to the solidifying purification tank 10, and it can be implemented for purifying the n-tetrasilanes (n-Si.sub.4H.sub.10) alternatively. When the solidifying purification tank 10 is in the process of warning up to liquefy the n-tetrasilane (n-Si.sub.4H.sub.10), the refrigerant jacket 31 of the solidifying tank 30 is flowed with the refrigerant for cooling the introduced tetrasilanes (Si.sub.4H.sub.10) within. Then, the unsolidified tetrasilane (i-Si.sub.4H.sub.10) and trace trisilane (Si.sub.3H.sub.8) are separated and extracted out through the extracting channel 32 to only retain the solidified n-tetrasilane (n-Si.sub.4H.sub.10) in the solidify tank 30. Afterward, the n-tetrasilane (n-Si.sub.4H.sub.10) in the solidifying tank 30 is warmed up to the ambient temperature while the liquid n-tetrasilane (n-Si.sub.4H.sub.10) in the solidifying purification tank 10 is shoved into the distillation tower 20 for final purification. Rotationally, the tetrasilanes (Si.sub.4H.sub.10) (raw material) is again brought into the empty solidifying purification tank 10 for cooling, while the n-tetrasilane (n-Si.sub.4H.sub.10) in the solidifying tank 30 is warming up and discharging to the distillation tower 20 through the discharge pipe 33. With the two resembling settings in the purification system for alternative and/or rotational practices, the n-tetrasilane (n-Si.sub.4H.sub.10) is efficiently separated and obtained from the tetrasilane (Si.sub.4H.sub.10) isomeric mixture.

(5) Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of invention as hereinafter claimed.