JP2001068457A - Dry etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate etching velocity or shape uniformity on a wafer surface during treatment by judging proceeding of sample treatment under the conditions that a residence time of molecule ad atom decided by a plasma pressure, a total gas flow rate, a treatment sample, and the length of a region wherein plasma in a vertical direction is generated, is specified. SOLUTION: A sample treatment is carried out while judging proceeding degree of a sample treatment under the conditions that a residence time of molecule and atom decided by a treatment pressure of plasma, a total gas flow rate, a treatment sample and the length of a region wherein a plasma in a vertical direction is generated is within 100 ms. A sample 113 is installed on a sample installation electrode 112 and is constructed to be in contact with a plasma 117. In the process, a sample treatment can be carried out at a fast speed by applying RF wave oscillated by an RF electrode 109 to the electrode 112 by using an RF matching device 110 and a blocking capacitor 111. A light emitting spectroscope 119 is installed as a for measuring change of the number of particles in plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method used for manufacturing semiconductor elements, electronic circuits, and the like, and more particularly to a method and an apparatus for evaluating in-plane uniformity of an etching rate during an etching process.

[0002]

2. Description of the Related Art At present, in etching methods used for manufacturing semiconductor devices and the like, a method using plasma is mainly used in order to realize fineness and anisotropic processing. As a means for generating plasma, a method of irradiating a gas introduced into a vacuum vessel with an electromagnetic wave and dissociating the gas with the energy is generally used. As a plasma source for generating the plasma, a capacitively coupled plasma (CCP: Capa) is used.
citive Coupled Plasma), inductively coupled plasma (IC
P: Inductive Coupled Plasma), ECR (Electron C)
yclotron Resonance) There is a plasma. And recently, E
In CR plasmas, instead of conventional microwaves, U
Systems using HF waves have been developed. The etching apparatus is provided with a mechanism for measuring one or more emission intensities in the plasma, and is used to determine the end point of the etching. For example, C-MO
When etching the gate portion of S, the emission intensity of 391 nm (SiCl) from the plasma is monitored, and it is determined that the gate processing has been completed when the emission intensity has become small. That is, information for automatically switching to the next step or terminating the etching process is obtained by the mechanism for measuring the emission of plasma.

On the other hand, uniformity of the etching rate is one of the important factors for improving the yield of semiconductor manufacturing.
Methods for evaluating the uniformity include a method of extracting a wafer and measuring an etching step, and a method of observing a cross-sectional shape by dividing the wafer, and are mainly performed off-line.

[0004]

As described above, in the conventional method for evaluating in-plane uniformity of etching, it is necessary to take the workpiece once out of the line and measure it with another measuring instrument. This has led to a decrease in throughput.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the throughput and set the conditions by making it possible to evaluate the etching rate or the uniformity of the etching shape in a processing wafer surface during an etching process in an etching processing apparatus using plasma. The goal is to increase the speed. Another object of the present invention is to reduce the non-uniformity of the etching rate, which varies depending on the type of the stacked films, when etching a multilayer film, and finally realize etching with a uniform shape, thereby improving the production yield. It is in.

[0006]

In order to achieve the above object, a method of the present invention comprises the steps of introducing a sample to be processed into a vacuum vessel and fixing the sample; introducing a gas into the vacuum vessel; Generating a plasma in a vacuum vessel, controlling the ion current density distribution of the plasma with respect to the sample to be processed, etching the sample to be processed, and measuring the emission intensity from the plasma during the plasma processing Then, in the plasma processing method including a step of determining the degree of sample processing, the molecule is determined by the processing pressure of the plasma, the total gas flow rate and the length of the region in which plasma in the direction perpendicular to the sample to be processed is generated, The method is characterized in that the sample processing is performed while determining the degree of progress of the sample processing under the condition that the residence time of the atoms is within 100 ms.

Further, the plasma uniformity A with respect to the residence time τ (ms) of molecules and atoms determined by the processing pressure of the plasma, the total gas flow rate, and the length of the region where the plasma is generated in the direction perpendicular to the sample to be processed. The sample processing is performed while determining the degree of progress of the sample processing under the condition that the ratio A / τ of (%) is larger than 0.11.

Further, the above method is characterized in that it comprises a step of calculating the in-plane uniformity of the etching processing and a step of controlling the etching rate distribution based on the result of the determination of the degree of progress of the sample processing.

In the above method, the means for generating plasma includes a UHF or VHF wave generator having a frequency of 80 MHz to 900 MHz and two or more electromagnets. , The etching process is performed while controlling the in-plane distribution of the etching rate.

FIG. 2 is a graph (b) showing the structure of a metal wiring portion (a) in a semiconductor device and the time change of the emission intensity of excited nitrogen (N: 414 nm) when the wiring portion is subjected to plasma etching; (C) is shown. here,
In FIG. 2A, 201 is a resist, 202 is C-TiN,
203 is Al-Cu, 204 is B-TiN, 205 is S
iO ₂ (interlayer insulating film) 206 is a lower wiring. Here, this etching process was performed by a processing apparatus having a configuration shown in FIG. 1 described later.

The etching conditions are as follows: the output of the RF power source is 40 W
The sputtering rate distribution of SiO ₂ is about 12% in both cases, but in FIG.
0mm, while the total gas flow is 400sccm (Fig.
Is pressure 3 Pa, plasma thickness (distance 120 in FIG. 1) 15
0 mm, total gas flow 400 sccm. Where SiO ₂
The sputter rate distribution of
It is generally used as an index for plasma uniformity evaluation.

When comparing FIGS. 2 (b) and 2 (c),
In (c), it can be seen that a uniform fine structure 213 exists near the end point of the etching of the B-TiN 204.
This phenomenon is considered to be related to the residence time of the reaction product. That is, the phenomenon that the same molecule or atom repeatedly emits light in the plasma is reduced due to the reduced residence time of the atom or molecule in the plasma due to the decrease in the plasma thickness. It is considered that the measurement of the information on the uniformity has become possible.

The stay time τ (s) can be generally expressed by Equation 1. Here, P in Equation 1 is the pressure (Pa) of the reaction processing chamber, V is the volume (l) of the reaction processing chamber, and Q is the gas flow rate (Pa · l / s).

[0014]

Τ = PV / Q (1) Therefore, in order to reduce the staying time, the etching is performed under the condition that the pressure is lower, the plasma volume is smaller, and the gas flow rate is larger. There is a need to do. In order to observe the fine structure of this uniformity,
The smaller the O ₂ sputter rate distribution, the shorter the residence time.

Therefore, an apparatus is used in which etching performance is guaranteed even if the stay time of observation particles determined by pressure, volume and gas flow rate is shortened within a range that can satisfy the uniformity required for wafer processing. The first object can be achieved by measuring a time change of the specific light emission intensity at the time of etching.

Further, by measuring the time change of the light emission intensity and feeding back the information to a circuit for controlling the ion current distribution or the RF bias distribution, it becomes possible to correct the distribution during the plasma processing. The second
Can achieve the purpose.

[0017]

(Embodiment 1) FIG. 1 is a sectional view of a UHF wave ECR plasma etching apparatus provided with an electrode (antenna) for emitting a 450 MHz UHF wave and an electromagnet to which the present invention can be applied. In the figure, 101 is a UHF power supply, 102 is a UHF wave matching device, 103 is a dielectric plate, 104
Is an electromagnetic wave radiation electrode, 105 is an antenna grounding part, 106
Is an electromagnet, 107 is a discharge part container, 108 is a vacuum exhaust device, 109 is an RF power supply, 110 is an RF matching device, 111 is a blocking capacitor, 112 is a sample setting electrode, 11
3 is a processing sample, 114 is a gas introduction tube, 115 is a shower plate, 116 is a quartz plate, 117 is plasma, 118
Denotes an emission spectroscope, 119 denotes an ion current density distribution control mechanism, and 120 denotes the thickness of plasma.

Conventional microwave ECR plasma or ICP
In the plasma source, generally, when the plasma thickness 120 is reduced, the in-plane distribution of the plasma density is deteriorated and the uniformity of the gas flow is deteriorated. , It is desirable that the gas flow from just above the wafer.

In this device, the electromagnetic wave radiation electrode 104 is installed on the atmosphere side, but the effect is the same even on the vacuum side. In this case, the plasma thickness 120 is defined as the distance between the sample setting electrode 112 and the shower plate 115.
In this apparatus, after introducing a gas into the discharge unit vessel 107 from the gas introduction pipe 114, the pressure in the vessel can be controlled by a variable opening valve (not shown) attached to the evacuation unit 108.

A UHF wave oscillated from a UHF power supply 101 is transmitted by a coaxial tube or a waveguide, matched with load impedance by a UHF wave matching device 102, and emitted into a discharge vessel 107 by an electromagnetic wave radiation electrode 104. Is done. Due to the energy of the emitted electromagnetic waves, the discharge part container 1
The gas in 07 is dissociated. At that time, the magnetic field generated by the electromagnet 106 causes electrons to move in an electron cyclotron motion, and the plasma 117 is generated in a pressure region of about 0.3 to 3 Pa.
Can be generated.

The processing sample 113 is set on the sample setting electrode 112 and has a structure in contact with the plasma 117. At this time, the sample processing can be performed at high speed by applying the RF wave oscillated from the RF power supply 109 to the sample setting electrode 112 using the RF matching device 110 and the blocking capacitor 111.

An emission spectrometer 119 was installed as a means for measuring the change in the number of particles in the plasma. The above spectroscope 1
By setting the 19 detection wavelengths to a specific wavelength and measuring the time change during the etching process, the end point of the etching can be detected. The ion current density distribution control mechanism 118 controls the ion current density distribution (in this case, changes the current of the electromagnet) based on the measurement result of the change in the emission intensity.

Such a device (chamber inner diameter φ44)
In 0), the plasma thickness 120 was 150 mm, the pressure was 3 Pa, the total gas flow rate was 400 sccm, and the UHF power was 8 mm.
The time change of the light emission intensity when etching was performed at 00 W was measured as shown in FIG. The residence time of the numerator at this time is about 100 ms from the above equation (1). Stay time 1
Since such a structure was not seen in FIG. 2B, which is 20 ms, the uniformity of the emission intensity change as shown in FIG. Can be observed.

According to this, for example, a CM of 0.3 Pa
In the gate etching of the OS, when the plasma thickness is 104 mm, a non-uniform structure of about 12% can be observed when the total gas flow rate is 30 sccm or more.

The SiO ₂ sputtering rate distribution A
(%) And the stay time τ (ms) were varied to summarize the observation of the fine structure 213 of uniformity. The results shown in Table 1 were obtained. It was found that uniformity could be observed. According to this, 5
In order to observe the% uniformity, the etching may be performed under the condition that the dwell time is 46 ms or less.

[0026]

[Table 1]

As described above, as a result of applying the present invention, it is possible to detect the non-uniformity of the etching rate of about 5% in 8 inches in real time, so that the wafer needs to be measured off-line as in the conventional case. And the throughput at the time of setting the etching conditions can be improved.

As an etching apparatus to which the present invention can be applied, as in the UHF wave ECR plasma etching apparatus used in this embodiment, even if the plasma thickness is 100 mm or less in a pressure range of about 0.3 Pa to 3 Pa, the distribution is stable. It goes without saying that a controllable plasma must be generated and the etching process must be possible. As a means for measuring the change in the number of particles in the plasma, QM
The same effect can be obtained by using S (quadrupole mass spectrometer) or the like and fixing the observed mass number and measuring the time change of the signal intensity.

Embodiment 2 An embodiment in which the present invention is used to control the etching rate distribution of a multilayer film in real time is described below. In the pressure region, gas flow region, plasma thickness, and ion current distribution shown in FIG. 3C, the multilayer film is etched as shown in FIG. : 414 nm).

At this time, 3 near the end point of the C-TiN layer 202
03 was found to have a microstructure. This determination is made according to FIG.
Is determined as a criterion when the end point time 303 shown in FIG. At this time, the etching states of the center and the edge of the wafer at the time 306 near the end of the C-TiN etching are as shown in FIGS. 3A and 3B, respectively. It can be seen that the etching reaching surface 302 is different.

Therefore, by applying the present invention, the ion current distribution during the etching time 307 of the Al layer is made to have a distribution with the edge raised as shown in FIG. 3F, so that the etching rate at the edge is increased. . As a result, the etching state of the center and the edge of the wafer at the time 308 near the end of the Al etching is as shown in FIGS. 3D and 3E, and the etching reaching surface of the bottom surface 301 at the center and the bottom surface 302 at the end. Could be aligned.

When the etching is again performed with the B-TiN etching + over-etching time 309 being a flat ion current distribution as shown in FIG. 3 (i), the time change of the emission intensity of excited nitrogen is observed as 305. Figure 3
As shown in (g) and (h), the etching of the uniform shape was finally completed at the center and the end.

When the present invention is not used, the time variation of the emission intensity of the excited nitrogen has a fine structure as shown by a broken line 304, and the final shapes are also the bottom surface 301 at the center and the bottom surface 30 at the end.
2 do not match, resulting in a non-uniform shape.

By using the etching method capable of controlling the uniformity in this manner, it is possible to achieve an improvement in yield and an increase in the speed of condition setting.

[0035]

According to the present invention, in dry etching using plasma, the in-plane uniformity of a processed wafer can be evaluated online. Further, since the etching shape can be finally processed uniformly in the plane in the multilayer film etching, the yield can be improved and the etching conditions can be set at a higher speed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a plasma etching apparatus for carrying out the present invention.

FIG. 2 is a cross-sectional view of a metal wiring portion processed in an example of the present invention and a measurement diagram of a temporal change in emission intensity during etching.

FIG. 3 is an explanatory view of an embodiment in which multilayer film etching is performed by applying the present invention.

[Explanation of symbols]

101: UHF power supply, 102: UHF wave matching device, 103
... Dielectric plate, 104 ... Electromagnetic radiation electrode, 105 ... Antenna ground part, 106 ... Electromagnet, 107 ... Discharge part container
8 vacuum evacuation device, 109 RF power supply, 110 RF matching device, 111 blocking capacitor, 112 sample setting electrode, 113 processing sample, 114 gas introduction pipe, 1
Reference numeral 15: shower plate, 116: quartz plate, 117: plasma, 118: emission spectrometer, 119: ion current density distribution control mechanism, 120: thickness of plasma, 201: resist, 202: C-TiN, 203: Al- Cu, 20
4 ... B-TiN, 205 ... SiO 2 ( interlayer insulating film) 2
06 ... lower wiring, 208 ... C-TiN etching time,
209: Al-Cu etching time, 210: B-Ti
N etching time, 211 ... over etching time, 2
13: Microstructure of uniformity, 301: Etched bottom surface at the center, 302: Etched bottom surface at the end, 303 ... CT
i. The end point time of iN202, 304... time change of the emission intensity of excited nitrogen when the present invention is not applied, 305... time change of the N2 emission intensity when the present invention is applied, 306.
TiN etching end time, 307 ... Al etching time, 308 ... Al etching end time, 309
... B-TiN etching + over-etching time.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazunori Tsujimoto 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. F term in the Central Research Laboratory of the Works (reference) 4K057 DA11 DA14 DA16 DB06 DD03 DD08 DG07 DG16 DG20 DJ02 DM18 DM28 DN01 5F004 AA01 BA14 BB07 BB13 BB14 BB28 CA02 CA03 CA06 CA08 CB02 CB04 CB15

Claims (4)

[Claims] A step of introducing and fixing a sample to be processed into a vacuum vessel; a step of introducing a gas into the vacuum vessel; a step of generating plasma in the vacuum vessel; Controlling the ion current density distribution with respect to, and etching the sample to be processed,
In a plasma processing method including a step of measuring emission intensity from plasma during plasma processing and determining a degree of sample processing, plasma in a direction perpendicular to the processing pressure of the plasma, a total gas flow rate, and a sample to be processed is generated. Dry etching, wherein the sample processing is performed while determining the degree of progress of the sample processing under the condition that the stay time of molecules and atoms determined by the length of the region is within 100 ms. 2. A step of introducing a sample to be processed into a vacuum vessel and fixing the same, a step of introducing the gas into the vacuum vessel, a step of generating plasma in the vacuum vessel, and a step of Controlling the ion current density distribution with respect to, and etching the sample to be processed,
In a plasma processing method including a step of measuring emission intensity from plasma during plasma processing and determining a degree of sample processing, plasma in a direction perpendicular to the processing pressure of the plasma, a total gas flow rate, and a sample to be processed is generated. While the ratio A / τ of the plasma uniformity A (%) to the residence time τ (ms) of molecules and atoms determined by the length of the region to be determined is larger than 0.11, the degree of progress of the sample processing is determined. A dry etching method characterized by performing sample processing. 3. The dry etching method according to claim 1, wherein the determination of the degree of progress of the sample processing is performed based on a result of the determination.
A dry etching method comprising a step of calculating in-plane uniformity of an etching process and a step of controlling an etching rate distribution. 4. A dry etching method according to claim 1, wherein said means for generating plasma includes a UH having a frequency of 80 MHz to 900 MHz.
It is configured to include an F to VHF wave generator and two or more electromagnets, and performs an etching process while controlling an in-plane distribution of an etching rate by changing respective currents flowing through the electromagnets. Dry etching method.