JP2000133640A - Measurement of pressure in plasma etching chamber in semiconductor device manufacturing process and synchronous measurement of both of pressure therein and efficiency of etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor accurately the real pressure in a plasma etching chamber by a method wherein a plasma having plasma molecules is fed in the chamber and the luminous intensity of one kind of the plasma molecule of the fed plasma is measured to convert the luminous intensity into the pressure in the chamber. SOLUTION: When an etching process for manufacturing a semiconductor device in a plasma etching chamber is executed, a semiconductor wafer is arranged in the plasma etching chamber. A plasma having plasma molecules selected from among plasma molecules of F, a CF2, a CO and the like is fed in the chamber. The luminous intensity of one kind of the plasma molecule of the fed plasma in the case of a prescribed wavelength having a prescribed relation with the plasma molecule is measured. The measured luminous intensity is converted into the pressure in the chamber. As a result, the real pressure in the chamber can be accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method for effectively monitoring the pressure and the etching efficiency in an etching chamber when manufacturing a semiconductor device in a plasma etching chamber. In particular, when manufacturing a semiconductor device in a plasma etching chamber, it is possible to obtain excellent product quality by effectively monitoring the pressure and the etching efficiency in the etching chamber, and to improve the production efficiency. A method for achieving an effect of reducing costs is provided. A major advantage of the present invention is that it can be easily implemented in existing plasma etching chambers, and boasts that there is no need to purchase extra equipment or additional equipment for remodeling.

[0002]

2. Description of the Related Art In performing an etching process for manufacturing a semiconductor device, a semiconductor wafer is placed in a plasma etching chamber. This etching chamber is usually a kind of a half-closed production chamber, having an extraction airflow that is repeatedly suctioned by a vacuum pump. The extraction stream has one or more components. In order to balance the air flow, one spacer or one exhaust plate is provided horizontally in the etching chamber. The separating chamber or the exhaust plate divides the etching chamber into upper and lower portions.

FIG. 1A is a sectional view showing a conventional plasma etching chamber. The conventional plasma etching chamber 11 is divided into an upper etching chamber 13 and a lower etching chamber 14 by a horizontally arranged separator (or exhaust plate) 12. The etching chamber 11 further includes a cathode 15, a focus ring 16, and an electrostatic holding plate 17. One wafer 18 is fixed by the electrostatic holding plate 17. Further, the etching chamber 11 is sealed by the etching chamber partition wall 19.

FIG. 1A further shows a turbine pump 22 and a throttle valve 23. With these devices, a gas having one or more components is extracted out of the etching chamber 11. FIG. 1B is a plan view of a conventional separation plate 12. The spacing plate 12 is usually a ring-shaped plate. There are a plurality of radially formed holes 24 thereon. An insulating ring 21 for isolating the cathode 15 is formed on the spacer plate 12.

In order to control the pressure and air flow in the production chamber, a pressure sensor 2 is connected to the throttle valve 23.
5, and is controlled by one CPU (not shown). The analog signal output from the pressure sensor 25 is converted into a digital signal by an analog / digital converter by comparing with a predetermined value stored in the CPU. Throttle valve 2 more than the CPU
By outputting a control signal to 3, the pressure of the gas in the production chamber is maintained at the predetermined value.

The pressure sensor 25 is usually a capacitor type pressure sensor and has a thin film attached to a condenser coil. When a pressure difference is created between the upper and lower etching chambers, the thin film on the pressure meter (which may be calibrated by the manufacturer) is moved, changing the capacitor value in the sensor coil. This minute change in the capacitor value is immediately converted into a pressure value and output.

[0007]

The above-mentioned pressure sensor 25
Due to having a plurality of precision electrical components therein, the pressure sensor is typically located at a predetermined location separated by a predetermined distance from the etching chamber, as shown generally in FIG. 1A. If the pressure sensor is located close to or inside the etching chamber, the sensor coil may be subject to electromagnetic interference when the plasma is generated, and in severe cases may cause permanent damage. May occur. Moreover, charged particles (electrons or ions) still remain in the plasma, no matter how perfect grounding and shielding are applied.
Inevitable interference. This interference can lead to severe instability of the signal.

In consideration of the influence of plasma and electromagnetic interference, the pressure sensor 25 must be located far from the etching chamber as shown in FIG. 1A. It is generally located near the pump and is separated from the etching chamber by a separator. The main function of the diaphragm is to prevent organic molecules and other by-products generated during the plasma etching step from entering the pump. These extraneous particles have the effect of greatly reducing the service quality and service life of expensive pumps.

As can be seen from research, repeated use of the plasma etch chamber produces a significant amount of organic deposits on the surface of the separator plate. These deposits may fill the holes of the separator plate and may interfere with the flow of the etching gas flow extracted by the vacuum pump, so that it affects the measurement of the pressure difference between the inside and outside of the etching chamber, and the true pressure The difference value cannot be obtained. When the types and properties of the etching chambers are different, the pressure tolerances are also different. For example, if the standard pressure in the etching chamber is between 40 and 70 mTorr, the pressure tolerance is typically on the order of 20 mTorr. Generally, such clogging problems are discovered when inspections are performed with the etching chamber opened. Most clogging problems can be eliminated while performing the example inspections, but they do occur in these cases because abnormalities in the etch chamber can double the situation of organic deposition. Frequently, the severity of the deposition problem is greater than one might imagine.

US Pat. No. 5,694,207 discloses a method for monitoring the etching efficiency in an etching chamber by measuring the emission intensity when the wavelength is 388.5 to 443.7 nm. In order to solve the problem that a severe noise interference phenomenon is caused by a measurement error of light emission intensity, the present invention has proposed a method of measuring light emission intensity of four kinds of wavelengths. The severe noise interference problem and the pressure measurement of the '569,207 need to be based on one invariant molecule may negate the possibility of measuring the pressure in the etching chamber by optical methods. Give a conclusion.

Inaccurate control of the pressure in the etching chamber may lead to an increase in the rejection rate of the semiconductor device. Therefore, it is necessary to improve the product success rate by proposing a better method. As devices become more and more popular and the benefits of manufacturing peripheral equipment for semiconductor devices are increasingly enhanced, there is a keen need for it. Therefore, it is important to reduce production costs by modifying parameters in numerous manufacturing processes that cause each failure or result in rejects. In order to provide more precise etching conditions by monitoring the pressure in the etching chamber more precisely, the present invention solves the above problems by submitting an important method.

[0012]

SUMMARY OF THE INVENTION It is a main object of the present invention to provide an improved process for manufacturing a semiconductor device, thereby achieving the effect of precisely controlling the pressure in an etching chamber. In other words, significantly improving the product success rate by controlling the etching process more precisely by providing a more accurate method of monitoring the true pressure in the etching chamber during the semiconductor manufacturing process. That is its purpose.

The present invention has proposed a non-destructive method that can control the true pressure in the etching chamber. This method has a more economical effect. To elaborate,
The inventors have discovered that certain plasma molecules can produce a predetermined wavelength during the plasma etching process, and that the intensity of this predetermined wavelength has the effect of accurately measuring the pressure in the etching chamber. In general, the emission intensity of plasma molecules is largely shielded by background noise interference, which does not lead to practical applications. Moreover, since the plasma molecules are consumed one after another during the etching process, the emission intensity is also reduced one after another, and the predetermined intensity cannot be maintained.

However, in the present invention, the inventor
By measuring any one of the F, CF ₂ , and CO molecules, it was discovered that its unique emission wavelength intensity had a clear and close relationship with the pressure in the etching chamber. Thus, by utilizing the unique wavelength of one or more of the above molecules, the pressure in the etching chamber may be increased, as the emission intensity may increase when more molecules are stimulated by the increased collision frequency. Can be manufactured for measuring However, these theories must first solve the problems such as the noise interference described in the case of the prior art and the fact that plasma molecules are consumed one after another and cannot maintain a predetermined intensity. These two issues make it very difficult to use the emission intensity as a means of measurement in a complex environment during a semiconductor etching process. Therefore, submitting a method of measuring success as in the present invention must first overcome a variety of penances.

When fluorine (F) is used as a pressure measurement tool, the wavelength of the measured emission intensity is 686 nm, which indicates that the F atoms skip from 3s ⁴ P ₃ to 3p ⁴ P _3. This is to respond. If CF ₂ is used as a pressure measurement tool, the wavelength of the measured emission intensity is generally 269 or 239 nm, and these two are CF 2 respectively.
Two atoms skip from A ¹ B ₁ (v '= 0) to X ¹ A ₁ (v ”= 0), and two atoms skip from A ¹ B ₁ (v' = 9) to X ¹ A ₁ (v” = 0). ). If CO atoms are used in pressure measurement tools, there are generally two wavelengths of emission intensity that can be measured, which are 693 and 505 nm. Respectively
The case where the CO atom skips from d ³ II (v ′ = 2) to a ³ II (v “= 2) and the case that the CO atom skips from d ³ II (v ′ = 7) to a ³ II (v” = 2) Corresponding to

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present invention, by using a kind of appropriate plasma molecules as the measuring means, a simple method can be obtained in which the pressure in the etching chamber can be measured at the original position. The method uses the intensity of a predetermined wavelength emitted by plasma molecules during a plasma etching process as a tool for accurately measuring the pressure in an etching chamber. Optical emission spectra were once proposed to be a tool for measuring the etching efficiency of fluorine / SOG systems, but large amounts of noise interference and plasma molecules become unstable during the etching process For two reasons, the prior art has never proposed to use the same method for measuring pressure. The present invention is intended to accurately measure the pressure in an etching chamber while the true pressure inside the etching chamber and the measured pressure value of a pressure sensor shielded by a spacer plate outside the etching chamber have a considerable difference. In view of the importance of the method, the present inventors have studied the method of the present invention, and have intended to precisely control the etching process and improve the success rate of the manufacture of the semiconductor device.

In the present invention, a direct and clear relationship between the pressure in the etching chamber and the emission intensity of any molecule can be obtained by measuring the emission spectrum of F, CF ₂ , CO, or the like. Therefore, the spectrum of the emission intensity of a certain molecule can be used as a tool for measuring the pressure in the etching chamber. When the pressure increases, the mean free path between the molecules decreases and the frequency of collisions increases. However, as discussed above, a large amount of noise interference is generated, and the amount of plasma molecules is consumed one after another, so that a predetermined value cannot be maintained. It did not employ optical intensity as a pressure measurement tool in complex environments.

FIG. 1A is a sectional view showing a conventional plasma etching chamber, and FIG. 1B is a plan view of a separation plate. As explained above, the accumulation of polymeric impurities in the separator plate may result in the filling of some holes, which may impede the flow of gas entering the vacuum pump, The accuracy of the measurement result for the pressure in the etching chamber of the pressure sensor may be adversely affected.

When fluorine is used as a pressure measurement tool,
The emission intensity can be measured at 686 nm. This is because the fluorine atom corresponds to radiation that skips from 3s ⁴ P ₃ to 3p ⁴ P ₃ . FIG. 2 is a diagram showing the correspondence with the pressure when the plasma molecule F has an emission intensity of 686 nm. By determining one measurement curve, it is possible to proceed with the subsequent pressure measurement. When CF ₂ is used as a pressure measurement tool, the wavelength of the measured emission intensity is 269 or 239 nm, and these two are CF 2 respectively.
_Two atoms skip from A ¹ B ₁ (v '= 0) to X ¹ A ₁ (v ”= 0), and _two atoms skip from A ¹ B ₁ (v' = 9) to X ¹ A ₁ (v” = 0). ). FIG. 3 shows that the plasma molecules CF ₂ are 269 and 23.
It is a corresponding figure corresponding to the pressure of the light emission intensity in the case of 9 nm.

When CO atoms are used in a pressure measurement tool, there are also two emission wavelengths that can be measured, which are 693 and 505 nm. Each CO atom is d ³ II
(v '= 2) to skip to a ³ II (v “= 2) and d ³ II
This corresponds to the case of skipping from (v ′ = 7) to a ³ II (v ″ = 2). FIG. 4 is a correspondence diagram corresponding to the emission intensity pressure when the plasma molecules CO are 693 and 505 nm. Table 1 below shows each plasma molecule of the present invention and their corresponding emission wavelengths.

[0021]

[Table 1]

In some etching processes, there is a direct close relationship between the efficiency of the etching and the pressure in the etching chamber. In such a case, the method disclosed in the present invention can also be used for measuring the etching efficiency. FIG. 5 is a correspondence diagram corresponding to the pressure of the etching efficiency at each different position in the etching chamber. Since the etching efficiency differs at each position, a typical etching efficiency can be obtained by selecting an appropriate plasma molecule and an appropriate position and applying the non-destructive in-situ technique of the present invention. When an appropriate position is selected and the method of the present invention is applied, the measurement results shown in FIG. 6 can be obtained. FIG. 6 is a correspondence diagram between the etching efficiency and the pressure.

FIG. 7 is a diagram showing the measured intensity of the etching efficiency and the pressure when the molecule is F. By utilizing the method of the present invention, the etching efficiency and the pressure in the etching chamber can be measured simultaneously.

An advantage of the present invention is that only the emission intensity of one plasma molecule needs to be measured. According to the present invention, the pressure and the etching efficiency can be obtained from the intensity ratio. FIG. 8 is a diagram showing the ratio between the etching efficiency and the pressure when CO is 505 nm and 639 nm.
However, the intensity ratio is only one preferred embodiment of the present invention, and the present invention is not limited thereto.

[0025]

According to the present invention, the effect of measuring the pressure of the plasma etching chamber in the semiconductor device manufacturing process and the effect of the synchronous measurement of both the pressure of the plasma etching chamber and the etching efficiency in the semiconductor device manufacturing process are obtained. I can do it.

In the preferred embodiment described above, the branch point between the present invention and the prior art has been described in detail. However, the preferred embodiment, the technology disclosed in the drawings, and Table 1 can be applied to the present invention. It is merely an example which is given by way of example, and others pre-state that any modifications should be included in the scope of the present invention based on the gist of the present invention.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a cross section of a conventional etching chamber. B is a plan view showing a separation plate.

FIG. 2 is a correspondence diagram corresponding to pressure of light emission intensity in the case of F;

FIG. 3 is a correspondence diagram corresponding to the pressure of the emission intensity in the case of CF ₂ at 269 and 239 nm, respectively.

FIG. 4 is a correspondence diagram corresponding to the pressure of the emission intensity in each of 693 and 505 nm in the case of CO.

FIG. 5 is a diagram showing a relationship between etching efficiency and pressure at different positions in an etching chamber.

FIG. 6 is a correspondence diagram of the balance between etching efficiency and pressure.

FIG. 7 is a diagram showing the relationship between the light emission intensity, the etching efficiency, and the pressure in the case of F.

FIG. 8 is a graph showing the relationship between the emission intensity, the etching efficiency, and the pressure in the case of 505 nm and 639 nm in the case of CO, respectively.

DESCRIPTION OF SYMBOLS 11 Plasma etching chamber 12 Separator 13 Upper etching chamber 14 Lower etching chamber 15 Cathode 16 Focus ring 17 Electrostatic holding plate 18 Wafer 19 Wall of etching chamber 21 Insulating ring 22 Turbine pump 23 Throttle valve 24 Hole 25 Pressure sensor

 ────────────────────────────────────────────────── 54 Continuing from the front page (54) [Title of the Invention] Method of measuring pressure in plasma etching chamber in semiconductor device manufacturing process and synchronous measurement of both plasma etching chamber pressure and etching efficiency in semiconductor device manufacturing process Setting method

Claims (8)

[Claims] 1. A method for measuring the pressure of a plasma etching chamber in a semiconductor device manufacturing process, comprising: supplying a plasma having plasma molecules selected from F, CF ₂ , CO, and the like to the plasma etching chamber; Measuring the emission intensity of the plasma molecule at a predetermined wavelength having a predetermined relationship with the molecule, and converting the measured emission intensity to the pressure of the etching chamber. Of measuring the pressure of a plasma etching chamber in a semiconductor device manufacturing process. 2. The plasma molecule is F, and the emission intensity is measured at a wavelength of 686 nm,
Alternatively, the plasma is CF ₂ and the emission intensity is measured when the wavelength is 269 or 239 nm, or the plasma molecule is CO and the emission intensity is measured when the wavelength is 693 or 505 nm. 2. The method for measuring the pressure of a plasma etching chamber in a semiconductor device manufacturing process according to claim 1, wherein: 3. The etching chamber according to claim 1, wherein the pressure in the chamber is obtained from a measurement curve for the emission intensity, and the etching chamber has a separating plate for separating the chamber from a vacuum pump. The method for measuring the pressure of the plasma etching chamber in the semiconductor device manufacturing process. 4. The method of measuring the light emission intensity at two or more kinds of wavelengths and the pressure in an etching chamber is performed based on a light emission intensity ratio of a predetermined wavelength. 2. The method according to claim 1, wherein the two or more kinds of predetermined wavelengths belong to the same plasma molecule. 5. A method for synchronously measuring both the pressure of a plasma etching chamber and the etching efficiency in a semiconductor device manufacturing process, wherein a plasma having plasma molecules selected from F, CF ₂ , CO, etc. is supplied to the plasma etching chamber. Supplying (a), measuring the luminescence intensity of at least one kind of plasma molecule at a predetermined wavelength having a predetermined relationship with the molecule, and (b) measuring the measured luminescence intensity in the etching. A method for synchronously measuring both the pressure and the etching efficiency of a plasma etching chamber in a semiconductor device manufacturing process, comprising the step (c) of converting the pressure into a chamber pressure and an etching efficiency. 6. The plasma molecule is F, and the emission intensity is measured at a wavelength of 686 nm,
Alternatively, the plasma is CF ₂ and the emission intensity is measured when the wavelength is 269 or 239 nm, or the plasma molecule is CO and the emission intensity is measured when the wavelength is 693 or 505 nm. 6. A method according to claim 5, wherein both the pressure of the plasma etching chamber and the etching efficiency are measured in the semiconductor device manufacturing process. 7. The etching chamber according to claim 5, wherein the pressure in the chamber is obtained from a measurement curve for the emission intensity, and the etching chamber has a separating plate for separating the chamber from a vacuum pump. A synchronous measurement method for both the pressure of a plasma etching chamber and the etching efficiency in the semiconductor device manufacturing process. 8. The method of measuring the light emission intensity in the case of two or more kinds of wavelengths and the pressure in the etching chamber is performed based on a light emission intensity ratio of a predetermined wavelength. The two or more kinds of predetermined wavelengths belong to the same plasma molecule, and the plasma molecule is CO, and the predetermined wavelength is 505 or 639 nm. A method for synchronously measuring both the pressure of an etching chamber and the etching efficiency in the semiconductor device manufacturing process according to claim 5.