Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
3 Months Ended
Dec. 31, 2020
Feb. 05, 2021
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Dec. 31, 2020  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q1  
Entity Registrant Name AMTECH SYSTEMS, INC.  
Entity Central Index Key 0000720500  
Current Fiscal Year End Date --09-30  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   14,141,122
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  
Entity Incorporation, State or Country Code AZ  
Document Quarterly Report true  
Document Transition Report false  
Trading Symbol ASYS  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Security Exchange Name NASDAQ