Title of Invention

"A PROCESS FOR THE PREPARATION OF METHANOL FOR SEMICONDUCTORS."

Abstract

This invention relates to a process for the purification of methanoi for semiconductors comprising the steps of distilling commercial grade methanoi wherein impurities like aluminium, boron, calcium, chromium, copper, gold, iron, manganese, nickel, potassium, sodium, tin, titanium, zinc are below 10 ppm and is charged to fractional distillation, heated in a controlled environment as herein described, to get total condensation rate of 2 lit/ hr and refluxing the resulant for 2 hrs with a reflux ratio of 1:1.

Full Text

FIELD OF INVENTION This invention relates to a process for the purification of methanol for semiconductors. BACKGROUND OF INVENTION An important part of electronic product reliability of achievement is to control of contamination. Contaminants from the environment and/or contaminants introduced during the production and testing operations can create problems with circuits and cause costly failures. Material used in Electronic industry covers a wide range of materials such as metal, alloys, semiconductors, photoresists, specially polymers, ceramics, glasses, thick film material, PCB laminators, etc. In the manufacturing process of the component, the cleaning is the most important step to avoid the dust and impurity contamination. The contamination source is from a atmosphere, from existing process or from any other foreign matter. The silicone grease is used in electronic assembles and which needs to clean by specific high purity solvents i.e. polar and non-polar solvents. Oils, facts, resin, waxes are soluble in solvents which are automatically removed by using semiconductor grade solvents. Such foreign contaminants has to be spring-cleaned for better performance of the device. Hydrophilic organic solvents are miscible with water. They are often referred to in the literature as polar solvents. Typical example of hydrophilic organic solvents used in electronic production cleaning are lower aliphatic alcohols. The electronic grade methanol is one of the important solvents used for cleaning the components and is presently being imported by electronic industries in India. Removal of critical impurities from commercial methanol is difficult task but can be achieved by using special purification techniques. Methanol is extensively used for a degreasing, cleaning etc. during semiconductor processing in the electronic industries. The purity of the methanol should be very high because traces of impurities would affect the performance of the semiconductor devices. The impurity level of the trade metals should be less than 1 ppm. The particulate content should meet specifications of the class 0-2 of the SEMI standard classification i.e. maximum number of particles of 1 micron and above per ml should be less than 10 maximum. Because of stringent purity, specifications and limited requirement, semiconductor grade methanol is not manufactured in India. Though the technology for methanol production is available in the country but the purity is not as per specifications of the electronic industries. DESCRIPTION OF INVENTION According to this invention there is provided a process for the purification of methanol for semiconductors comprising the steps of distilling commercial grade methanol wherein impurities like aluminium, boron, calcium, chromium, copper, gold, iron, manganese, nickel, potassium, sodium, tin, titanium, zinc are below 10 ppm and is charged to fractional distillation, heated in a controlled environment as herein described, to get total condensation rate of 2 lit/ hr and re fluxing the resulant for 2 hrs with a reflux ratio of 1:1. In this process cheap commercial grade methanol is used as a starting material. All the metallic impurities like aluminium, boron, calcium, chromium, copper, gold, iron, lead, manganese, nickel, potassium, sodium, tin, titanium, zinc should be below 10 ppm each. The reflux ratio is defined as the ratio between the number of moles of vapor returned as refluxed liquid to the fractionating column and the number of moles of final product (collected as distillate), both per unit time. The reflux ratio should be varied according to the difficulty of fractionation, rather than be maintaining constant. High efficiency of separation requires a high reflux ratio. Optimum i.e. 1:1 reflux is maintained in the distillation process. Heating mantles provide one of the most convenient means of controlled heating of reaction vessels. They consist of a heating element enclosed within a knitted glass-fibre fabric which is usually protected with a safety earth screen. The heating unit is enclosed within an outer rigid housing (often of polypropylene or aluminum) which is appropriately insulated so that the mantle may be handled at a low outer case temperature. Heating is controlled by in-built or external energy regulators. The details of the process would be apparent from the following examples: EXAMPLE 1 4 lit. of commercial grade methanol was charged in the distillation flask. Some porcelain pieces are added in the flask for unilateral heating. Heating started and adjusted for total condensation rate of 2 lit/hr. Total system equilibrated and the material was refluxed for 2 hrs. to saturate lower boiler impurities at the upper side of the distillation column. After 2 hrs. reflux the material was collected at the rate of 1 lit/hr. keeping reflux ratio 1:1 400 ml of the material collected and kept aside as a rejected material. 3.2 lit of the material collected at the rate of 1 lit/hr. in the collector which was totally intact (to avoid the entry of atmospheric moisture in the system). Remaining 400 ml of the material kept at the bottom in the distillation flask as a rejected material. Total time required was approx. 6 hrs. The yield of the process observed was 80%. The final product was chemically analysed using our standard methods as mentioned in testing and evaluation section. The packaging of the final product was done in clean environment i.e. in clean room. EXAMPLE 2 6 lit. of commercial grade methanol was charged in the distillation flask. Some porcelain pieces are added in the flask for unilateral heating. Heating started and adjusted for total condensation rate of 2 lit/hr. Total system equilibrated and the material was refluxed for 2 hrs. to saturate lower boiler impurities at the upper side of the distillation column. After 2 hrs reflux the material was collected at the rate of 1 lit/hr keeping reflux ratio 1:1. 600 ml of the material collected and kept aside as a rejected material. 4.8 lit of the material collected at the rate of 1 lit/hr in the collector which was totally intact (to avoid the entry of atmospheric moisture in the system). Remaining 600 ml of the material kept at the bottom in the distillation flask as rejected material. Total time required was approx. 9 hrs. The yield of process observed was 80%. The final product was chemically analysed using our standard methods as mentioned in testing and evaluation section. The packaging of the final product was done in clean environment i.e in clean room. EXAMPLES 8 lit. of commercial grade methanol was charged in the distillation flask. Some porcelain pieces are added in the flask for unilateral heating. Heating started and adjusted for total condensation rate of 2 lit/hr. Total system equilibrated and the material was refluxed for 2 hrs to saturate lower boiler impurities at the upper side of distillation column. After 2 hrs reflux the material was collected at the rate of 1 lit/hr. keeping reflux ratio 1 :1 800 ml of the material collected and kept aside as a rejected material. 6.4 lit of the material collected at the rate of 1 lit/hr. in the collector which is totally intact (to avoid the entry of atmospheric moisture in the system). Remaining 800 ml of the material kept at the bottom in the distillation flask as a rejected material. Total time required was required was approx. 11 hrs. The yield of the process observed was 80%. The final product was chemically analysed using our standard methods as mentioned in testing and evaluation section. The packaging of the final product was done in clean environment ie. in clean room. WE CLAIM; 1. A process for the purification of methanol for semiconductors comprising the steps of distilling commercial grade methanol wherein impurities like aluminium, boron, calcium, chromium, copper, gold, iron, manganese, nickel, potassium, sodium, tin, titanium, zinc are below 10 ppm and is charged to fractional distillation, heated in a controlled environment as herein described, to get total condensation rate of 2 lit/ hr and refluxing the resulant for 2 hrs with a reflux ratio of 1:1. 2. A process for purification of methanol substantially as herein described and illustrated in the examples.

Documents:

964-del-1999-abstract.pdf

964-del-1999-claims.pdf

964-del-1999-correspondence-others.pdf

964-del-1999-correspondence-po.pdf

964-del-1999-description (provisional).pdf

964-del-1999-form-1.pdf

964-del-1999-form-19.pdf

964-del-1999-form-2.pdf

964-del-1999-form-3.pdf

964-del-1999-form-4.pdf

964-del-1999-form-5.pdf

964-del-1999-gpa.pdf

964-del-1999-petition-138.pdf