Browse Prior Art Database

OPTIMIZATION OF WAFER RINSING

IP.com Disclosure Number: IPCOM000008359D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-10
Document File: 4 page(s) / 212K

Publishing Venue

Motorola

Related People

Thomas Roche: AUTHOR [+2]

Abstract

This work describes the experiments which have been done relating the amount of chemical remaining on the wafers with variables of the rinse such as temperature, flow rate, dump rinsing and the cycling of the rinse valves. We have found that the efftciency of water use can be improved by simply cycling the water flow on and off, with up to an order of magnitude less chemical remaining on the wafer with pulsing compared with the same amount of water used without pulsing. The reasons for this result are still being investigated.

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MOTOROLA Technical Developments

OPTIMIZATION OF WAFER RINSING

by Thomas Roche, Thomas Peterson

ABSTRACT

  This work describes the experiments which have been done relating the amount of chemical remaining on the wafers with variables of the rinse such as temperature, flow rate, dump rinsing and the cycling of the rinse valves. We have found that the efftciency of water use can be improved by simply cycling the water flow on and off, with up to an order of magnitude less chemical remaining on the wafer with pulsing compared with the same amount of water used without pulsing. The reasons for this result are still being investigated.

EXPERIMENTAL

Equipment

  All experiments were carried out in an SCP Global Technologies Model 9400 wet process tool. The chemical concentrations were measured in the rinse baths with Thornton Resistivity probes which recorded resistivities in the range of 0. I to about
18.00 MOhms. The resistivity was recorded every 5 seconds using a computer attached to.the readout function of the tool and converted from resistivity to conductivity.

Experimental Procedure

The experiments were carried out by adjusting

the flow rate of the water going into each rinse bath (the primary bath and the final rinse bath) and, in some cases, adjusting the flow program (percentage and period of time on and off, dump rinse, hot and cold water valve operation if available, dump rinse or overflow rinse) of the primary rinse bath only. The water in both baths was then allowed to flow until it reached the highest resistivity possible, and then the recipe was begun to treat the wafers with the chemicals of interest, 2 minutes for our 12: I HF bath and 10 minutes for the Piranha solution. After the chemical process, the wafers were moved robot- ically to the primary rinse bath and treated with the

rinse process of interest. The wafers were then moved robotically to the final rinse bath and the resistivity recorded in this bath to determine the amount of chemical remaining on the wafers after the first rinse.

Analysis of Data

  The resistivity readings of the water in the final rinse bath were converted to conductivity readings and integrated over the time of the rinse. The water in this rinse bath was always allowed to return to its maximum value during the experiment so we are mainly concerned with the change in resistivity during the experiment.

RESULTS AND DISCUSSION

Experimental Results

  In comparison with theoretical predictions, the results we have seen show that simple addition of chemicals to a rinse bath result in a performance much like that predicted by the theory. The rinse baths appear to operate like CSTRs. The addition of a boat with wafers and residual chemical shows a similar response in these experiments but it is diffr- cult to say that the model describes these results adequately. It should be noted that the experiments described here helped us standardize the results we present here. We ran experiments using either sul...