CN101178328A - Gas flow rate control device verify method - Google Patents

Abstract

The invention discloses a calibrating method of a gas flow controller used for calibrating the error of a gas flow controller MFC on line. The gas flow controller is arranged on a gas passage which supplies process gas to a reaction chamber and the method includes the following steps that firstly the reaction chamber is vacuumized, then the flow of the calibrated MFC is set as Qv, the process gas is pumped in the reaction chamber and simultaneously the referenced gas of fixed flow Qs is pumped in the reaction chamber; the pressure change of the reaction chamber is determined then and total flow Q of the gas entering the reaction chamber is deduced according to the perfect gas equation PV=nRT; then the flow Qp of the process gas entering the reaction chamber is obtained according to the formula Qp=Q-Qs and then the Qp is compared with the Qv so as to calibrate the flow error of the MFC. The invention has the advantages of accurate calibrating, high precision and short calibrating time. The invention is not influenced by environment temperature and the chamber volume and is especially suitable for the calibrating of a MFC with small flow.

Description

The method of gas flow control device verification

Technical field

The present invention relates to a kind of method of gas flow control device verification, relate in particular to a kind of method of the gas flow control device of silicon chip process equipment being carried out verification.

Background technology

In the semi-conductor silicon chip process, the deposit of film, etch rate all relies on the mass rate of the process gas that enters reaction chamber and the conditions such as pressure of reaction chamber.Every kind of semi-conductor silicon chip process equipment, different technology all needs the flowrate proportioning of different gas.

At present, generally adopt high-precision MFC (mass flow controller) to measure flow with CONTROL PROCESS gas, but mass flow controller in use for some time, because zero point drift may take place a variety of causes.Mass flow controller zero point drift meeting causes the technology instability, and then influences the entire chip yield.Therefore the verification of mass flow controller is most important in semiconductor equipment.

The method of the gas flow calibration that now often has generally has two kinds:

A kind ofly be, at first reaction chamber vacuumized, the gas flow of MFC is set then, gas feeds in the reaction chamber by MFC, waits gas flow to close the pendulum valve after stable, measures entire reaction chamber step-up ratio within a certain period of time by CM1 (vacuum gauge).Can instead push away the flow Q that obtains gas by the voltage rise rate by formula 1.Attention needs to keep reaction chamber temperature invariable in whole process.

$Q=\frac{1\mathrm{StdAtm}}{760\mathrm{torr}}\×\frac{V\left(\mathrm{cc}\right)}{\mathrm{\Δt}\left(\min \right)}\×\frac{273.15K}{\mathrm{StdTemp}}\×\left[\frac{\mathrm{\ΔP}\left(\mathrm{Torr}\right)}{T\left(K\right)}\right]\mathrm{sccm}$ (formula 1)

In the formula: the StdAtm-standard atmospheric pressure; The V-chamber volume; The Δ t-time period;

Δ P-gas pressure intensity changes; T-gas absolute temperature.

Compare with gas flow value of setting of MFC with calculated value, MFC is carried out verification.

The advantage of this method be calculate simpler relatively, but the verification degree of accuracy is subjected to reaction chamber volume, temperature effect bigger, precision is lower.

For the verification of the MFC of low discharge, the checking time of this technology is long, and precision is poorer.

Another kind method is, according to desirable equation of gaseous state formula:

PV=nRT (formula 2)

In the formula, P is a gas pressure intensity; V is a gas volume; N is the amount of gaseous matter; T is the absolute temperature of gas; R is a gas constant.

Can obtain:

$\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C$ (formula 3)

In the formula 3, for specific reaction chamber, at a certain temperature, Kc is a constant.Generally, utilize inert gas can determine constant K c.

To formula 3 differentiates, can get:

$K_C=\frac{P^{\′}}{n^{\′}}$ (formula 4)

Feed process gas toward reaction chamber, measure the step-up ratio in the set time, by step-up ratio, according to formula 4 push away the flow of gas $Q=n^{,}=\frac{P^{\′}}{\mathrm{Kc}},$

Compare with gas flow value of setting of MFC with calculated value then, MFC is carried out verification.

This method checking precision is higher, but for the verification of the MFC of low discharge, still has the long problem of checking time.

Summary of the invention

The method that the purpose of this invention is to provide the gas flow control device verification that a kind of verification is accurate, precision is high, checking time is short.

The objective of the invention is to be achieved through the following technical solutions:

The method of gas flow control device verification of the present invention is used for the error of on-line testing gas flow control device MFC, and described gas flow controller is installed on the gas circuit of reaction chamber supply process gas.

May further comprise the steps:

A, reaction chamber is extracted into vacuum state;

B, the gas flow Qv of MFC is set, and feeds process gas to reaction chamber, feed the reference gas of firm discharge Qs simultaneously to reaction chamber by MFC;

Total flow Q of the gas that enters reaction chamber is derived in C, the variation by the assaying reaction chamber pressure according to desirable equation of gaseous state formula: PV=nRT,

Wherein, P is a gas pressure intensity; V is a gas volume; N is the amount of gaseous matter; T is the absolute temperature of gas; R is a gas constant;

D, try to achieve the flow Qp of the process gas that enters reaction chamber, and Qp and set MFC gas flow Qv are compared, with the measuring error of verification MFC according to formula Qp=Q-Qs.

Described step C comprises step:

C1, according to desirable equation of gaseous state formula: PV=nRT obtains formula: $\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C$

Wherein, V is the volume of reaction chamber, and T is a steady temperature, and Kc is a constant;

C2, to formula $\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C$ Differentiate can get: $K_C=\frac{P^{\′}}{n^{\′}},$ Can get $Q=n^{,}=\frac{P^{\′}}{\mathrm{Kc}}.$

Described constant K c utilizes inert gas to feed reaction chamber, and passes through formula $K_C=\frac{P^{\′}}{n^{\′}}$ Determine.

In the described steps A, reaction chamber is extracted into vacuum state after, need detection reaction chamber leak rate, and make described leak rate smaller or equal to 1mT/min.

Described reference gas is an inert gas.

As seen from the above technical solution provided by the invention, the method of gas flow control device verification of the present invention, owing to when reaction chamber feeds process gas, feed the reference gas of firm discharge during verification to reaction chamber, can carry out verification to gas flow control device accurately and rapidly, be particularly useful for the verification of low discharge MFC.

Description of drawings

Fig. 1 is the air supply system synoptic diagram of the reaction chamber of semi-conductor silicon chip process equipment;

Fig. 2 is in the verification gas flow control device process of the present invention, the chamber pressure change curve.

Embodiment

The method of gas flow control device verification of the present invention is used for the error of on-line testing MFC (gas flow control device), and MFC is installed on the gas circuit of reaction chamber supply process gas.The reaction chamber here mainly is meant the reaction chamber of semi-conductor silicon chip process equipment, also can be other chamber.

As shown in Figure 1, be the air supply system synoptic diagram of the reaction chamber of semi-conductor silicon chip process equipment:

Gas 11,12,13,14 can enter in the reaction chamber by MFC1, MFC2, MFC3, MFC4, molecular pump, and valve is taken out on the side, the molecular pump exhaust valve, and dried pump has been formed the vacuum acquiring system of entire equipment.Can control vacuum tightness in the reaction chamber by the folding degree of control pendulum valve, the vacuum tightness in the reaction chamber is read by CM1 (vacuum gauge).

Now, suppose gas the 11,12, the 13rd, process gas; And gas 14 is inert gas.

As shown in Figure 2, preferable embodiment comprises,

Step 21, at first reaction chamber is extracted into vacuum state.

In this steps A, reaction chamber is extracted into vacuum state after, preferably detect the leak rate of reaction chamber, and make leak rate, in the hope of the accuracy of check results smaller or equal to 1mT/min.

Step 22, selection need MFC1, MFC2 or the MFC3 of verification, if will carry out verification to MFC1, the gas flow Qv of MFC1 at first is set, and feed process gas 11 to reaction chamber by MFC1, by the reference gas 14 of MFC4 to reaction chamber feeding firm discharge Qs, reference gas 14 is an inert gas simultaneously.

The MFC4 that reference gas 14 passes through is the gas flow control device of new clothes, and the flow value Qs of its setting can think the actual flow of reference gas 14.

Step 23, after the flow of process gas 11 and reference gas 14 reaches balance, close the pendulum valve, the reaction chamber internal pressure begins to rise, variation by CM1 assaying reaction chamber pressure, press P1 from base, measure the changes delta P of Δ t time internal pressure, derive total flow Q of the gas that enters reaction chamber according to desirable equation of gaseous state formula: PV=nRT.

In the formula, P is a gas pressure intensity; V is a gas volume; N is the amount of gaseous matter; T is the absolute temperature of gas; R is a gas constant;

Concrete method of deriving is, according to desirable equation of gaseous state formula: PV=nRT

Obtain formula: $\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C,$ To this formula differentiate, can get: $K_C=\frac{P^{\′}}{n^{\′}},$

Wherein, V is the volume of specific reaction chamber, and T is a steady temperature, and Kc is a constant, but since step-up ratio the P '=Δ P/ Δ t of CM1 assaying reaction chamber can get $Q=n^{,}=\frac{P^{\′}}{\mathrm{Kc}},$

Step 24, can try to achieve the flow Qp of the process gas that enters reaction chamber, and Qp and set MFC1 gas flow Qv are compared, with the measuring error of verification MFC1 according to formula Qp=Q-Qs.

In step 23, described constant K c can utilize reference gas 14 (inert gas) to be set flow and fed reaction chamber by MFC4 before carry out step 21, by the step-up ratio of CM1 assaying reaction chamber, and passed through formula $K_C=\frac{P^{\′}}{n^{\′}}$ Determine.For specific reaction chamber, Kc is constant at a certain temperature, and Kc does not generally need to redeterminate after determining again, other MFC of available Kc verification has only when the volume of reaction chamber or temperature parameter change, and just need redefine Kc.

The present invention is specially adapted to the verification of low discharge MFC.Employing the method can be fast and is not subjected to external condition to influence (as temperature, reaction chamber volume etc.).

For the verification of low discharge MFC, key is to feed the reference gas of firm discharge when verification, be generally inert gas, and its MFC4 is verified as no zero shift.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims (5)

1. the method for a gas flow control device verification is used for the error of on-line testing gas flow control device MFC, and described gas flow controller is installed on the gas circuit of reaction chamber supply process gas, it is characterized in that, may further comprise the steps:

A, reaction chamber is extracted into vacuum state;

B, the gas flow Qv of MFC is set, and feeds process gas to reaction chamber, feed the reference gas of firm discharge Qs simultaneously to reaction chamber by MFC;

Total flow Q of the gas that enters reaction chamber is derived in C, the variation by the assaying reaction chamber pressure according to desirable equation of gaseous state formula: PV=nRT,

Wherein, P is a gas pressure intensity; V is a gas volume; N is the amount of gaseous matter; T is the absolute temperature of gas; R is a gas constant;

D, try to achieve the flow Qp of the process gas that enters reaction chamber, and Qp and set MFC gas flow Qv are compared, with the measuring error of verification MFC according to formula Qp=Q-Qs.

2. the method for the gas flow control device verification of stating according to claim 1 is characterized in that described step C comprises step:

C1, according to desirable equation of gaseous state formula: PV=nRT obtains formula: $\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C$

Wherein, V is the volume of reaction chamber, and T is a steady temperature, and Kc is a constant;

C2, to formula $\frac{\mathrm{RT}}{V}=\frac{P}{n}=K_C$ Differentiate can get: $K_C=\frac{P^{\′}}{n^{\′}}$ , can get $Q=n^{,}=\frac{P^{\′}}{\mathrm{Kc}}.$

3. the method for the gas flow control device verification of stating according to claim 2 is characterized in that, described constant K c utilizes inert gas to feed reaction chamber, and passes through formula $K_C=\frac{P^{\′}}{n^{\′}}$ Determine.

4. the method for the gas flow control device verification of stating according to claim 1 is characterized in that, in the described steps A, reaction chamber is extracted into vacuum state after, need detection reaction chamber leak rate, and make described leak rate smaller or equal to 1mT/min.

5. the method for the gas flow control device verification of stating according to claim 1 is characterized in that described reference gas is an inert gas.

Images