Method for controlling plating rate in an electroless plating system

Claim 1

A method for controlling plating in an electroless plating process for plating with an additive bath, said bath having a replenishment control for establishing a replenishment rate of a selected bath component comprising: continuously monitoring the plating rate of said additive bath and generating an electrical current representing said monitored rate; comparing said monitored rate with a desired rate; deriving a control voltage from the difference between said measured rate and desired rate; and replenishing said additive bath with said selected bath component as a function of said control voltage.

Claim 2

A method for controlling plating in an electroless plating process for plating with an additive bath, said bath having a replenishment control for establishing a replenishment rate of a selected bath component comprising: continuously monitoring the plating rate of said additive bath and generating an electrical current representing said monitored rate; comparing said monitored rate with a desired rate; deriving a control voltage from the difference between said measured rate and desired rate; and replenishing said additive bath with said selected bath component as a function of said control voltage.

Claim 5

A method for controlling plating in an electroless plating process for copper plating with an additive bath, said bath having a replenishment control for establishing a concentration of a selected bath component comprising: continuously monitoring the present plating rate of said additive bath and generating an electric current representing said monitored plating rate; generating a first feedback control term from said electrical current proportional to the difference between the present plating rate and a desired rate; generating a second feedback control term proportional to the integral of said first feedback control term; generating a third feedback term proportional to minus the time derivative of said first feedback control term; generating a control voltage from said first, second and third feedback control terms; and applying said control voltage to said replenishment control, whereby said concentration is maintained at a predetermined level.

Claim 6

A method for controlling plating in an electroless plating process for copper plating with an additive bath, said bath having a replenishment control for establishing a concentration of a selected bath component comprising: continuously monitoring the present plating rate of said additive bath and generating an electric current representing said monitored plating rate; generating a first feedback control term from said electrical current proportional to the difference between the present plating rate and a desired rate; generating a second feedback control term proportional to the integral of said first feedback control term; generating a third feedback term proportional to minus the time derivative of said first feedback control term; generating a control voltage from said first, second and third feedback control terms; and applying said control voltage to said replenishment control, whereby said concentration is maintained at a predetermined level.

Claim 9

A method for controlling the concentration of a chemical constituent replenished from a reservoir to an electroless plating bath, comprising: measuring at regular intervals the plating rate of said plating bath; computing over a plurality of said intervals a running average of a plurality of plating rate measurements; subtracting a predetermined plating rate set point from the running average plating rate to obtain a plating rate deviation; forming the summation of said plating rate deviations whereby an integral of said plating rate deviation is obtained; subtracting the previous value of a determined deviation to a present value of said deviation whereby a derivative of said deviation is determined; combining said present deviation, integral of said plating rate deviations and derivative of said deviation to obtain a control parameter for said chemical constituent of an electroless plating bath; generating a control signal proportional to said control parameter; and replenishing said electroless plating bath with said chemical constituent at a rate controlled by said control signal.

Claim 10

A method for controlling the concentration of a chemical constituent replenished from a reservoir to an electroless plating bath, comprising: measuring at regular intervals the plating rate of said plating bath; computing over a plurality of said intervals a running average of a plurality of plating rate measurements; subtracting a predetermined plating rate set point from the running average plating rate to obtain a plating rate deviation; forming the summation of said plating rate deviations whereby an integral of said plating rate deviation is obtained; subtracting the previous value of a determined deviation to a present value of said deviation whereby a derivative of said deviation is determined; combining said present deviation, integral of said plating rate deviations and derivative of said deviation to obtain a control parameter for said chemical constituent of an electroless plating bath; generating a control signal proportional to said control parameter; and replenishing said electroless plating bath with said chemical constituent at a rate controlled by said control signal.