Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
12 Months Ended
Sep. 30, 2019
Nov. 15, 2019
Mar. 31, 2019
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Sep. 30, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Entity Registrant Name AMTECH SYSTEMS INC    
Entity Central Index Key 0000720500    
Current Fiscal Year End Date --09-30    
Entity Filer Category Accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Public Float     $ 62,706,022
Entity Common Stock, Shares Outstanding   14,268,797  
Entity Current Reporting Status Yes    
Entity Shell Company false    
Entity File Number 0-11412    
Entity Tax Identification Number 86-0411215    
Entity Address, Address Line One 131 South Clark Drive    
Entity Address, City or Town Tempe    
Entity Address, State or Province AZ    
Entity Address, Postal Zip Code 85281    
City Area Code 480    
Local Phone Number 967-5146    
Entity Interactive Data Current Yes    
Title of 12(b) Security Common Stock, par value $0.01 per share    
Trading Symbol ASYS    
Security Exchange Name NASDAQ    
Entity Incorporation, State or Country Code AZ    
Document Annual Report true    
Document Transition Report false