Gas flow process control system and method using crystal microbalance(s)

Patent metadata

Field	Value
Publication number	US-10256126-B2
Application number	US-201615272924-A
Country	US
Kind code	B2
Filing date	Sep 22, 2016
Priority date	Sep 22, 2016
Publication date	Apr 9, 2019
Grant date	Apr 9, 2019

Abstract

Disclosed are process control systems and methods incorporating a crystal microbalance (CM) (e.g., a quartz crystal microbalance (QCM)) into gas flow line(s) entering and/or exiting a processing chamber. A CM measures the resonance of a quartz crystal sensor contained therein as gas flows over that crystal sensor and can, thereby be used to accurately monitor, in real time, the mass flow rate of the gas. The mass flow rate may indicate that gas contamination has occurred and, in response, a controller can cause the gas flow to stop. Additionally, the mass flow rate may indicate the desired result will not be achieved within the processing chamber and, in response, advanced process control (APC) can be performed (e.g., the controller can adjust the gas flow). CM(s) incorporated into gas flow lines entering and/or exiting a processing chamber can provide precise measurements for process monitoring at minimal cost.

First claim

What is claimed is:

1. A system comprising:
a processing chamber having an inlet;
a gas source;
a tube connecting the gas source to the inlet;
a single valve regulating flow of a gas from the gas source through the tube and into the processing chamber where a surface of a work piece is exposed to the gas;
a crystal microbalance integrated into the tube outside the processing chamber, wherein the crystal microbalance determines an actual mass flow rate of the gas flowing from the gas source through the tube and into the processing chamber; and
a controller in communication with the crystal microbalance and operably connected to the valve,
wherein the controller determines a difference between the actual mass flow rate and a target mass flow rate,
wherein the target mass flow rate is an optimal mass flow rate for achieving a desired composition and concentration of the gas within the processing chamber in order to further achieve specific results on the surface of the work piece during the processing, and
wherein the controller adjusts the valve given the difference in order to meet the target mass flow rate.

2. The system of claim 1 ,
wherein the tube comprises a first portion connecting the gas source to the crystal microbalance and a second portion connecting the crystal microbalance to the inlet of the processing chamber, and
wherein the gas flows from the gas source through the first portion, through the crystal microbalance, through the second portion and through the inlet into the processing chamber.

3. The system of claim 1 , wherein adjusting of the valve by the controller comprises:
at least one of increasing a pulse period for opening the valve and increasing a size of an aperture of the valve, when the actual mass flow rate is below the target mass flow rate; and
at least one of decreasing a pulse period for opening the valve and decreasing a size of an aperture of the valve, when the actual mass flow rate is above the target mass flow rate.

4. The system of claim 1 , wherein adjusting of the valve by the controller comprises closing the valve when a difference between the actual mass flow rate and a target mass flow rate is greater than a threshold difference.

5. The system of claim 1 , the crystal microbalance comprising a quartz crystal microbalance.

6. The system of claim 1 , the crystal microbalance comprising:
an oscillating circuit with an integrated crystal sensor and a pair of series connected inverters,
wherein the pair of series connected inverters comprises a first inverter and a second inverter,
wherein the integrated crystal sensor has a front side and a back side opposite the front side, the front side having a sensing surface and a front side electrode and the back side having a back side electrode, and
wherein an input of the first inverter is connected to the front side electrode and an output of the first inverter is connected to the back side electrode and to an input of the second inverter;

a frequency counter connected to an output of the second inverter and monitoring frequency shifts at the output of the second inverter as a result of changes in resonance of the crystal sensor in response to changes in mass of the gas flowing over the sensing surface while passing through the tube; and,
a processor in communication with the frequency counter and determining the mass flow rate of the gas based on the frequency shifts, wherein the actual mass flow rate is the mass of the gas that flows through the tube passed the crystal microbalance per unit time at a known pressure and temperature.

7. A system comprising:
a processing chamber for processing a surface of a semiconductor wafer, the processing chamber having a first inlet, a second inlet and an outlet;
a first gas source;
a first tube connecting the first gas source to the first inlet;
a single first valve regulating flow of a first gas from the first gas source through the first tube and into the processing chamber where the surface of the semiconductor wafer is exposed to the first gas;
a first crystal microbalance integrated into the first tube outside the processing chamber, wherein the first crystal microbalance determines a first actual mass flow rate of the first gas flowing from the first gas source through the first tube into the processing chamber;
a second gas source;
a second tube connecting the second gas source to the second inlet;
a single second valve regulating flow of a second gas from the second gas source through the second tube and into the processing chamber where the surface of the semiconductor wafer is exposed to the second gas;
a second crystal microbalance integrated into the second tube outside the processing chamber, wherein the second crystal microbalance determines a second actual mass flow rate of the second gas flowing from the second gas source through the second tube into the processing chamber;
a third valve at the outlet;
a controller in communication with the first crystal microbalance and the second crystal microbalance and operably connected to the first valve, the second valve and the third valve,
wherein the controller controls the processing of the surface of the semiconductor wafer in the processing chamber by:
causing the first valve and the second valve to alternatingly pulse the first gas and the second gas into the processing chamber through the first tube and the second tube, respectively, and further causing the third valve to purge any gas from the processing chamber between pulses such that discrete self-limiting reactions occur at the surface of the semiconductor wafer;
during a first pulse of the first gas by the first valve, determining a first difference between the first actual mass flow rate and a first target mass flow rate;
during a second pulse of the second gas by the second valve, determining a second difference between the second actual mass flow rate and a second target mass flow rate; and
during subsequent pulses of the first gas and the second gas, adjusting at least one of the first valve given the first difference to meet the first target mass flow rate and the second valve given the second difference to meet the second target mass flow rate,
wherein the first target mass flow rate is a first optimal mass flow rate for achieving a first desired composition and concentration of the first gas within the processing chamber with each first pulse,
wherein the second target mass flow rate is a second optimal mass flow rate for achieving a second desired composition and concentration of the second gas within the processing chamber with each second pulse, and
wherein the first desired composition and concentration of the first gas and the second desired composition and concentration of the second gas are predetermined in order to achieve specific results on the surface of the semiconductor wafer during the processing.

8. The system of claim 7 ,
wherein the first tube comprises a first portion connecting the first gas source to the first crystal microbalance and a second portion connecting the first crystal microbalance to the first inlet of the processing chamber,
wherein the first gas flows from the first gas source through the first portion of the first tube, through the first crystal microbalance, through the second portion of the first tube and into the first inlet of the processing chamber,
wherein the second tube comprises a first portion connecting the second gas source to the second crystal microbalance and a second portion connecting the second crystal microbalance to the second inlet of the processing chamber, and
wherein the second gas flows from the second gas source through the first portion of the second tube, through the second crystal microbalanc

Assignees

• Globalfoundries Inc

Inventors

• Finlay Robert B
• Conerney Brian

Classifications

• H10P50/283

  by chemical means · CPC title

• H10P14/6339

  deposition by cyclic CVD, e.g. ALD, ALE or pulsed CVD · CPC title

• H10P72/0604 Primary

  Process monitoring, e.g. flow or thickness monitoring · CPC title

• G01F1/80

  operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted · CPC title

• H01J2237/006

  Details of gas supplies, e.g. in an ion source, to a beam line, to a specimen or to a workpiece, (H01J37/3244 takes precedence; environmental cells for electron microscopes H01J2237/2003; microscopes with environmental specimen chamber H01J2237/2608) · CPC title