Pressure control method for process chamber and pressure control device for process chamber

A device for controlling pressure in a treatment chamber, for regulating the pressure of gas inside a treatment chamber in a semiconductor production step, via a valve situated between the treatment chamber and a suction pump for suctioning gas from within the treatment chamber, the device for controlling pressure in a treatment chamber characterized by comprising:

• outflow rate computing means for computing a predicted outflow rate (Qo) at which gas is discharged from the treatment chamber via the suction pump by the suction of the suction pump;
• required inflow rate computing means for calculating, on the basis of the expression Qi=Qo+(P/Δt)V, a required inflow rate (Qi) at which it is necessary for gas to flow into the treatment chamber in order to reach a preset target pressure (Psp) within the treatment chamber, from a known volume (V) of the treatment chamber and a pressure change rate (ΔP/Δt) required for the current pressure (P1) within the treatment chamber to reach the target pressure (Psp), the rate being derived from the difference between the current pressure (P1) and the target pressure (Psp);
• and inflow rate regulating means for regulating the inflow rate at which gas is to flow into the treatment chamber, to the required inflow rate (Qi) calculated on the basis of the required inflow rate computing means;
• and when inflow of the required inflow rate (Qi) into the treatment chamber is brought about by the inflow rate regulating means and the pressure within the treatment chamber is controlled to the target pressure (Psp), in calculation by the outflow rate computing means of a current predicted outflow rate (Qo(n)) at which gas is discharged from the treatment chamber on the basis of the expression Qo(n)=P2*f1(P2), using a current pressure (P2) within the suction pump and a known characteristic suction rate (Sp=f1(P2)) of the suction pump under prescribed pressure, the current pressure (P2) within the suction pump is calculated according to the expression P2=P1−(Qo(n−1)/f2(θ, P)) from an accurate conductance (Cv(θ, P)=f2(θ, P)) calculated by adding the error between the current pressure (P1) actually measured within the treatment chamber and a known specified pressure (P) within the treatment chamber at the characteristic conductance (Cv=f2(θ)) of the valve at the opening/closing angle (θ) associated with the current position of the switching plate of the valve to the known characteristic conductance (Cv=f2(θ)) of the valve at the opening/closing angle (θ) associated with the current position of the switching plate of the valve, and the current predicted outflow rate Qo(n) at which gas is discharged from the treatment chamber is calculated.