CONDUCTIVITY CONTROL OF WATER CONTENT IN SOLVENT STRIP BATHS

• US 20080023045A1
• Filed: 06/20/2007
• Published: 01/31/2008
• Est. Priority Date: 07/27/2006
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Johnson, Michael R., O'Connor, John J., Joseph, Martin, Miller, Greg P.
• Granted Patent: US 8,545,636 B2
• Time in Patent Office: Days
• US Class Current: 134/27
• CPC Class Codes: G05D 21/02 characterised by the use of electric means
• CPC Class Codes: H01L 21/02068 during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
• CPC Class Codes: H01L 21/67057 with the semiconductor substrates being dipped in baths or vessels
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A system and method for control of water content in a strip bath. The method to control water content in a solvent bath used for cleaning of semiconductor parts in the back end of semiconductor manufacturing requires addition of water to replace evaporated water. This is done by periodically adjusting a conductivity setpoint at least in part based on the elapsed chemical bathlife and at least in part based on the number of semiconductor parts that have been processed in the bath. The conductivity of the strip bath solution is then continuously measured (as by using an electrodeless conductivity probe). Water is added (as by a DI water injection system) into the bath solution whenever the solvent conductivity falls below the conductivity set point.

Claims

1. A method for control of water content in a solvent strip bath used to clean semiconductor parts, the method comprising:

a) periodically automatically adjusting a conductivity set point for a solvent solution in a solvent strip bath at least in part based on chemical bathlife interval and at least in part based on number of lots that have been processed in said strip bath;

b) substantially continuously measuring bath solvent conductivity; and

c) automatically injecting water into said solvent solution whenever measured bath solvent conductivity falls below said conductivity set point.

2. The method of claim 1, wherein step b is effected using an electrodeless conductivity sensor.

3. The method of claim 1 wherein step a is performed by a controller, step b includes sending a conductivity signal to said controller, and step c is effected by a signal sent from said controller.

4. The method of claim 3, further including sending from said controller an alarm signal if measured conductivity is outside of a selected range, said alarm signal preventing any further injection of water and preventing any further loads of semiconductor materials from being placed in said solvent strip bath.

5. The method of claim 3, further including sending from said controller an alarm signal if total water injected for a selected time interval exceeds a user-defined amount, said alarm signal preventing any further injection of water and preventing any further loads of semiconductors from being placed in said solvent strip bath.

6. A method to maintain a more uniform solvent composition in a solvent bath, said solvent solution containing volatile compounds comprising:

a) periodically determining a conductivity set point for a solvent solution in said solvent bath at least in part based upon hours of bath life and at least in part based on amount of semiconductor material processed during said hours of bathlife;

b) measuring solution conductivity of said solvent solution;

c) measuring solvent level in said strip bath;

d) adding water into said solvent solution whenever measured strip bath conductivity falls below said conductivity set point; and

e) adding solvent into said strip bath whenever solvent level falls below a user-defined fill level.

7. The method of claim 6, wherein step b is effected using an electrodeless conductivity sensor.

8. The method of claim 6, further including triggering an alarm signal if total water added for a selected time interval exceeds a user-defined amount, said alarm signal preventing any further addition of water or solvent and preventing any additional semiconductor materials from being placed in said bath.

9. A device for cleaning semiconductor parts comprising:

a solvent bath tank;

at least one level sensor positioned such that it may monitor fluid level in said solvent bath tank;

a solvent source;

a water source;

a conductivity probe configured to monitor conductivity of solvent in said solvent bath tank; and

a controller configured to receive signals from said conductivity probe, said controller configured to calculate a conductivity set point at least in part based on a controller-calculated chemical bathlife and at least in part on an amount of semiconductor material processed during said bathlife, said controller further regulating flow from said solvent source into the solvent bath tank and flow from said water source into said solvent bath tank such that water is added to said solvent bath tank when measured conductivity falls below said conductivity set point and solvent is added from said solvent source when said level monitor falls below a preset threshold.

10. The device of claim 9, wherein said tank is made of stainless steel.

11. The device of claim 9, wherein said conductivity probe is an electrodeless conductivity probe.

12. The device of claim 9, wherein said controller includes an alarm that signals if a system parameter is outside of a selected specification.

13. The device of claim 9, wherein said at least one level monitor includes an overfill level sensor, a low level sensor and a process level sensor, each configured to send a signal to the controller.

14. The device of claim 13, wherein said overfill level sensor and low level sensor are configured to send an alarm signal to the controller, said alarm signal causing said controller to prevent further addition of liquid from said solvent source and said water source, said controller additionally sending an inhibition signal to a product load station.