JP3469955B2 - Etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method.

[0002]

2. Description of the Related Art ITO (Indium tin) used in LCDs
oxide) film, the demand for which is increasing more and more today
-While it plays an important role as a transparent pixel electrode of LCD, the etching of this ITO film requires a strong acid system such as hydrochloric acid or nitric acid rather than a so-called dry etching method which does not involve immersion in a treatment liquid. Further, conventionally, a wet etching method in which a substrate to be processed on which an ITO film is formed is immersed in a strong acid-based processing solution in which an acid such as hydrofluoric acid, hydrobromic acid, or hydroiodic acid is appropriately mixed has been generally used. This is because the currently proposed dry etching method cannot achieve a high etching rate, and therefore has a lower throughput than the wet etching method capable of batch processing.

However, in the wet etching method, since it is difficult to control the processing shape and continuously etch the multilayer film, it is a problem how to improve the throughput by the dry etching method which does not use such a processing solution. Become. In this regard, for example, CH in the processing container
_{When 4} gas and H ₂ gas are introduced to generate high-density plasma in the processing container, a high etching rate can be obtained, and the selectivity with respect to the underlying silicon nitride (SiN) film can be sufficiently obtained. Is known.

[0004]

However, for example, when the above-mentioned CH ₄ is dissociated in plasma, C ₂ H ₂ and C ₂
Hydrocarbons such as H ₃ are generated in the processing container and adhere to the substrate to be processed and the processing container.

Hydrocarbons adhering to the substrate to be processed can be removed by the subsequent ashing treatment, but those adhering to the inside of the processing container cause contamination as they are, and the hydrocarbons themselves are electrically conductive. Therefore, when the next substrate to be processed is processed, the input energy may decrease and the plasma may become unstable. Therefore, it is necessary to take some measures, but simply mix oxygen in the process gas,
It was found that when the oxygen and the hydrocarbon are combined to be removed, the etching rate is lowered this time.

Therefore, it is an object of the present invention to solve the above problems by providing an etching method which removes such hydrocarbons and does not reduce the etching rate.

[0007]

In order to achieve the above object, according to claim 1, an ITO (Indi
um Tin Oxide), the substrate to be processed is loaded into a processing container, and H ₂ , He, Cl ₂ ,
A processing gas selected from each gas of HCl and the like is introduced into the processing container, and high frequency power is applied to a spiral, coil or loop antenna provided outside the processing container. A first step of etching the ITO of the substrate for use, and when the etching treatment is completed, the introduction of the processing gas in the first step is stopped, and further O ₂ gas is introduced into the processing container. And a second step of treating the LCD substrate with plasma.

According to a second aspect, the gas is introduced into the processing container.
The flow rate of the O ₂ gas used is the same as that of the gas introduced in the first step.
The feature is that the flow rate is higher than the flow rate of the natural gas.

The shape of the antenna according to claims 1 and 2 may be a single spiral shape, a coil shape, or a loop shape, and in any case, an electric field induced by applying radio frequency power causes Any material that generates plasma may be used. In addition, the outside of the processing container, which is the location of the arrangement, is not limited to the outside of the top plate portion of the processing container,
It may be outside the upper side of the substrate to be processed in the processing container.

Further, in the second step, the degree of pressure reduction in the processing container may be increased . Increase the degree of decompression
Is to further reduce the pressure in the processing vessel.
It

In the second step, the output of radio frequency power applied to the antenna may be increased .

[0012]

[0013]

According to the present invention , dry etching is performed without using a strong acid type etching treatment liquid. According to the etching method of claim 1, after the completion of the etching in the first step, O ₂ gas is introduced into the processing container instead of the processing gases while plasma is being generated in the processing container. The resulting oxygen radicals combine with the hydrocarbons to form CO and CO.
_{2 and} H ₂ O are discharged from the processing container.

[0014] Note that after etching, when plasma by introducing O ₂ gas in place of the bias side of the high-frequency stop and process gas application, oxygen radicals easily diffused by the process vessel, the result processing Oxygen radicals spread to every corner of the container, and hydrocarbons in the processing container can be effectively removed. Then , even if the degree of pressure reduction in the processing container is increased after the etching in the first step, the oxygen radicals are more likely to diffuse into the processing container, and the same effect as described above can be obtained.

[0015] During the O ₂ gas introduction, since increasing the output of the radio-frequency power applied to the antenna for generating plasma, it is possible to more generate oxygen radicals, the removal of hydrocarbon thereby at a high speed can. The flow rate of O ₂ gas introduced into the processing barber device, when more than the flow rate of the introduced processing gas in etching,
It is possible to generate more oxygen radicals, which enables the removal of hydrocarbons at high speed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 schematically shows a cross section of an etching apparatus 1 configured to carry out this embodiment. The processing container 2 in the apparatus 1 is made of a conductive material, for example, aluminum whose surface is oxidized, and is formed into a substantially rectangular prismatic shape as a whole, and is grounded.

A susceptor 4 is provided in the processing container 2 via a susceptor support 3 made of an insulating material such as ceramics. The susceptor support 3 itself is an elevating device installed outside the processing container 2. 5, it is configured to be vertically movable.

On the other hand, an insulating material 6 made of, for example, quartz glass or ceramic is installed above the processing container 2 substantially facing the susceptor 4 so as to hermetically close the inside of the processing container 2.

A cooling jacket 11 is provided between the susceptor support 3 and the susceptor 4, and the processing container 2 is provided.
Cooling water introduced from a cooling water supply source (not shown) provided outside through the cooling water introducing pipe 12 circulates in the cooling jacket 11 and is discharged from the cooling water discharging pipe 13. Is configured.

A heater 14 for heating is housed in the lower portion of the susceptor 4, and the power supplied from a power source 15 installed outside the processing container 2 is adjusted to adjust the power supplied from the cooling jacket 11. The temperature of the surface to be processed of the LCD glass substrate P can be adjusted by controlling the conduction of cold heat.

Further, inside the susceptor 4, a flow passage 17 for flowing a heat transfer gas (back cooling gas) such as He supplied from a gas source 16 provided outside the processing container 2 is formed. The heat transfer gas that has passed through the flow path 17 is stored in a large number of gas reservoirs 18 in the susceptor 4.
Flow through the gas reservoir 18 and the discharge passage 19 having a smaller diameter, and then discharged onto the back surface of the glass substrate P for LCD mounted on the susceptor 4, and the processed surface of the glass substrate P for LCD is processed. The temperature control is performed.

The LCD glass substrate P on the susceptor 4
By itself, a mechanical clamping mechanism (not shown)
The peripheral portion is clamped and held on the susceptor 4.

A high frequency power source 32 is connected to the susceptor 4 through a matching device 31, and a high frequency power having a frequency of several tens of kHz to 10 MHz, preferably 2 MHz, for example, is applied to the susceptor 4 during an etching process. As a result, a bias potential is generated between the plasma and the etchant ions, and the etchant ions can be effectively attracted to the processed surface of the LCD glass substrate P.

On the other hand, on the outer wall surface of the above-mentioned insulating material 6, there is arranged a high frequency antenna 33 for applying a radio frequency of 1 MHz to 100 MHz, which is formed by spirally forming a conductor such as a copper plate, aluminum or stainless steel. The high frequency antenna 33 may have a function of exhibiting an antenna action for generating plasma, and its shape is a coil shape,
It may be looped, or may be one turn when the frequency is high.

Both terminals of the high frequency antenna 33,
That is, the terminals 33a and 33b are connected to the radio frequency power source 35 for plasma generation through the matching device 34. Therefore, for example, by adjusting the current value with the matching device 34 or the like, it is possible to adjust the alternating electric field, that is, the plasma density according to the magnitude of the current flowing through the high frequency antenna 33. In the present embodiment, the frequency of the radio frequency power source 35 is 13.5.
A 6 MHz one was used. Of course, the frequency of the high-frequency power source for plasma generation is not limited to this frequency and can be appropriately selected as needed.

Next, air supply in the etching apparatus 1
Explaining the exhaust system, a gas supply pipe 41 made of quartz glass or ceramics is attached to the upper side surface of the susceptor 4 in the processing container 2, and the gas supply pipe 41 further includes valves 42, 43, 44 and corresponding ones. Through the mass flow controllers 45, 46 and 47, the processing gas supply sources 48, 49 and 50 are connected, respectively. CH ₄ gas is supplied from the processing gas supply source 48, H ₂ gas is supplied from the processing gas supply source 49, and the processing gas supply source 5 is supplied.
O ₂ gas can be supplied from 0, and the valves 42, 43, 44 and the mass flow controller 4 can be supplied.
By controlling 5, 46 and 47, it is possible to introduce a desired gas into the processing container 2 through the gas supply pipe 41 at a desired flow rate.

At the bottom of the processing container 2, an exhaust pipe 5 communicating with an exhaust means (not shown) such as a turbo molecular pump.
1 is provided, and the inside of the processing container 2 can be evacuated to a predetermined degree of decompression by the exhaust means.

A gate valve (not shown) is provided on the side wall of the central portion of the processing container 2, and the glass substrate P for LCD, which is the substrate to be processed, is carried in and out through the gate valve. Has been done. The vertical movement of the susceptor 4 during the process of carrying in and carrying out is performed by the vertical movement of the front lifting mechanism 5.

Next, the control system of the etching apparatus 1 configured as described above will be described. A transmission window 52 made of a transparent material such as quartz glass is attached to one side wall of the processing container 2. The optical sensor 54 detects the light in the processing container 2 through an appropriate optical system device 53, and sends a signal relating to the emission spectrum generated from the processing container 2 to the controller 55. Has been done. Further, a sensor 56 for detecting changes in various conditions such as the pressure inside the processing container 2 is attached to the processing container 2, and a signal regarding the pressure inside the processing container 2 can be sent to the controller 55. Is configured.

The controller 55 uses the feedback signals from these sensors or preset values to set a radio frequency power source 35 for plasma generation, a high frequency power source 32 for biasing, and a cooling water supply source (not shown). ), The power source 15 of the heater 14, the gas source 16 for back cooling, the valves 42, 43 and 44 of the gas supply system, the mass flow controllers 45, 46 and 47, and the exhaust means (not shown) of the exhaust system. It is configured so that various desired conditions for sending and etching can be created.

Next, the etching method according to this embodiment will be described using the etching apparatus 1 configured as described above. First, the LCD glass substrate P is placed on the susceptor 4 by a transporting means (not shown) such as a separately provided transporting arm, and after the transporting means is retracted, the LCD glass substrate P is held by the clamp mechanism described above. Are held on the susceptor 4. Then, the inside of the processing container 2 is evacuated to a predetermined degree of reduced pressure, and while the back cooling gas for heat transfer is supplied to the back surface of the glass substrate P for LCD and each bonding portion of the susceptor 4, the cooling jacket 11 cools the heat. Is supplied to set the processing surface of the LCD glass substrate P to a desired temperature.

Then, CH ₄ gas and H ₂ gas are introduced into the processing container 2 from the gas supply pipe 41 at a rate of 20 sccm and 80 sccm, respectively, and the degree of pressure reduction in the processing container 2 is set to 20 mTorr. After that is detected by the sensor 56, the radio frequency power supply 35 applies high frequency power of 13.56 MHz and power of, for example, 500 W to the high frequency antenna 33, and at the same time, the bias high frequency power supply 32 outputs a frequency of 2 MHz. When high frequency power of, for example, 300 W is applied to the susceptor 4, etchant ions CH ₃ generated by the dissociation of the CH ₄ gas become IT on the surface of the glass substrate P for LCD.
O is etched. That is, In + 3CH ₃ → In (CH ₃ ) ₃ is obtained, and the ITO is etched. As the etching progresses, inside the processing container 2,
In the reaction process, hydrocarbon-based reactive products such as CH ₃ , C ₂ H ₂ , C ₂ H ₃ , and C ₂ H ₄ are generated.

However, when the predetermined etching is completed, the introduction of CH ₄ gas and H ₂ gas is stopped, and at the same time, the type of gas introduced into the processing container 2 is changed to turn the O ₂ gas into the processing container 2 this time. Is introduced, for example, at 100 sccm. At the same time, the application of the high frequency power supply 32 for bias is stopped, while the application of the radio frequency power supply 35, which is responsible for plasma generation, to the high frequency antenna 33 is left unchanged. The application of such high-frequency power and the switching of the introduced gas type are shown in a time chart as shown by the solid line in FIG. The switching should be as short as possible. Therefore, the valves 42, 43, and 44 should be installed as close to the processing container 2 as possible.

After the above process, the O ₂ gas introduced after the etching is dissociated by the plasma, and the O ^* (oxygen radical) generated thereby is combined with the above-mentioned hydrocarbon, resulting in CO and CO. ₂ , H ₂ O
Then, the gas is exhausted from the exhaust pipe 51 to the outside of the processing container 2.

In order to compare this with the case where O ₂ gas is not introduced, the data actually experimented by the inventors are shown in FIGS. 3 and 4. In addition, plasma generation conditions, that is, the power of 13.56 MHz for plasma generation is 500 W, the power of 2 MHz for bias is 300 W, and the degree of pressure reduction is 20 mT.
The flow rates of orr and CH ₄ gas were set to 20 sccm, and the flow rate of H ₂ gas was set to 80 sccm.

First, FIG. 3 shows the analysis results of the residual substances in the processing container 2 when the underlayer was etched with respect to the ITO of SiN under the plasma generation conditions. The vertical axis shows the amount by the amplitude value.
According to this, hydrocarbons such as CH ₃ , C ₂ H
_It can be seen that ₂ , C ₂ H ₃ and C ₂ H ₄ remain in the processing container 2.

Next, under the same plasma generation conditions, the application of a high frequency of 2 MHz for biasing was stopped after the etching was completed, and the power of the high frequency power of 13.56 MHz for plasma generation was reduced to 170 W. the switch to O ₂ gas, and the O ₂ gas was introduced 33Sccm, for example, cleaning for 20 seconds, the results shown in FIG. 4 were obtained.

According to this, the above-mentioned CH ₃ , C ₂ H ₂ ,
Hydrocarbons such as C ₂ H ₃ and C ₂ H ₄ were not detected,
H ₂ O, CO, CO ₂ , O _2, etc. Hydrocarbon and O
A large amount of substances bound with and were detected. Therefore, this confirms that the hydrocarbons in the processing container 2 have been removed.

In the process shown by the solid line in the time chart of FIG. 2 described above, after the etching is completed,
The output of the radio frequency power for plasma generation was unchanged, but the output of the radio frequency power for plasma generation applied to the high frequency antenna 33 after the etching was completed was shown as indicated by the broken line in the time chart of FIG. If it is increased, the plasma density will be increased accordingly, and the amount of oxygen radicals generated as a result will also be increased, so that the introduction time of O ₂ gas can be shortened as shown by the broken line in the time chart of FIG. . Therefore, the throughput can be improved.

From the same viewpoint, the amount of oxygen radicals can be increased even if the amount of O ₂ gas introduced is increased, so that the throughput can be improved. Of course, by using both methods together, it is possible to further shorten the cleaning time and further improve the throughput.

Further in the process of the embodiment described above, CH ₄ gas, the process gas of the H ₂ gas without introducing simultaneously with the O ₂ gas, CH ₄ gas, and stopping the introduction of the H ₂ gas processing vessel Since the introduction of the internal gas is switched to O ₂ gas, the essential etching rate can be maintained at a high level.

The inventors also conducted experiments on this point, and obtained the following results. That is, first, when etching ITO on SiN under the same plasma generation conditions as described above, in addition to CH ₄ gas and H ₂ gas, O ₂
When the flow rate of the O ₂ gas was changed by introducing the gas at the same time, the generation of hydrocarbons such as CH ₃ , C ₂ H ₂ , C ₂ H ₃ and C ₂ H ₄ was reduced, but FIG. The results shown in are obtained. According to this, it can be seen that the etching rate greatly decreases with the introduction amount of O ₂ gas. With this, high throughput cannot be obtained.

On the other hand, using the etching apparatus 1, CH
_{When 4} gas and H ₂ gas were introduced and etching was performed without introducing O ₂ gas, the etching rate characteristics shown in FIGS. 6 to 10, for example, were obtained.

That is, the bias dependence characteristic of the etching rate is as shown in the graph of FIG. 6, in which the high frequency power of 13.56 MHz for plasma generation is fixed at 500 W, the CH ₄ gas is 20 sccm, and the H ₂ gas is H ₂ gas. 80sc
cm, the degree of pressure reduction is set to 20 mTorr, and the output of the high frequency power of 2 MHz for generating the bias potential is increased, the etching rate is increased substantially linearly with it, and at 500 W, it is about 1200 minutes per minute. Angstrom high speed etching has been obtained.

Next, CH ₄ gas was set to 20 sccm, H ₂ gas was set to 80 sccm, and the degree of pressure reduction was set to 20 mTorr, and a high frequency of 2 MHz for generating a bias potential was set to 30.
13.5 for plasma generation this time with fixed at 0W
As the output of high-frequency power of 6 MHz is increased, the etching rate is improved accordingly, and at 1000 W, high-speed etching of about 900 angstroms per minute is obtained.

Next, regarding the dependence of process pressure, CH ₄ gas is 60 sccm and H ₂ gas is 120 sccc.
m, the high frequency power of 13.56 MHz for plasma generation is set to 150 W, the output of high frequency power of 2 MHz to generate the bias potential is set to 600 W, and the degree of pressure reduction of the process pressure is changed. Like 20mT
It becomes the maximum near orr, and the high-speed etching of about 900 angstroms per minute is obtained.

Next, regarding the partial pressure characteristics of the CH ₄ gas and the H ₂ gas, a high frequency power of 13.56 MHz for plasma generation of 150 W and a bias voltage of 2 for generating a bias potential are used.
When the partial pressure ratio of CH ₄ gas and H ₂ gas is changed while the process pressure is set to 30 mTorr while setting the frequency to 30 MHz, as shown in FIG. A high etching rate of over 1000 Å has been obtained.

Then, the partial pressure ratio of the CH ₄ gas was set to 30%, the high frequency power of 13.56 MHz for plasma generation was set to 150 W, and the high frequency power of 2 MHz for generating the bias potential was set, and the process pressure was fixed at 30 mTorr. , The total flow rate of CH ₄ gas and H ₂ gas was increased, and as shown in FIG. 10, the higher the flow rate, the higher the etching rate obtained.

As described above, it was confirmed that a high etching rate can be obtained without introducing O ₂ gas when CH ₄ gas and H ₂ gas are introduced. Therefore, according to the present invention, CH ₄ gas, H ₂ gas and O
_{Since the} gas is introduced by switching between the _two gases, it is possible to perform high-speed etching, and it is possible to remove the hydrocarbon in the processing container.

In the above-described etching apparatus 1, the controller 55 controls the high frequency power source 32 based on the feedback signals from the optical sensors 54 and 56 monitoring the environment inside the processing container 2 or preset values. , 35
Since it is possible to control these by sending a control signal to, it is possible to always obtain optimum processing conditions according to the recipe. Moreover, since the plasma state is monitored by the sensor optics 54, the end of etching is automatically judged to stop the high frequency power source on the bias side, increase the output of the radio frequency power source 35 for plasma generation, and further process. The type of gas introduced into the container 2 can be switched and the flow rate can be adjusted automatically and suitably.

[0051]

Since the etching method of the present invention is dry etching that does not use an etching treatment solution,
The processing shape can be controlled and the multilayer film can be continuously etched. Moreover, after the etching is completed, the substrate to be processed as well as the hydrocarbon in the processing container can be continuously removed without carrying out the substrate to be processed from the processing container. Therefore, it is possible to prevent the contamination in the processing container while maintaining a high throughput and a high etching rate. Also every corner in the processing vessel, the removal of the hydrocarbon can be effectively carried out, since it carried out in high- <br/> mud decoking itself faster,
Throughput is even higher.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a cross section of an etching apparatus for carrying out an embodiment of the present invention.

FIG. 2 is a timing chart of the process of the example.

FIG. 3 is a graph showing a spectrum of a residual substance in a processing container when O ₂ gas is not introduced.

FIG. 4 is a graph showing a spectrum of a residual substance in a processing container when O ₂ gas is introduced at the end of etching.

FIG. 5 is a graph showing O ₂ dependence characteristics of the etching rate of ITO.

FIG. 6 is a graph showing the bias power dependence of the etching rate of ITO.

FIG. 7 is a graph showing the high frequency power dependence characteristics of the etching rate of ITO for plasma generation.

FIG. 8 is a graph showing the process pressure dependency of the etching rate of ITO.

FIG. 9: CH ₄ / (CH ₄ + of etching rate of ITO
Is a graph showing the H ₂₎ partial pressure dependence.

FIG. 10 is a graph showing the total flow rate dependence of the etching rate of ITO on CH ₄ + H ₂ O.

[Explanation of symbols]

1 Etching equipment 2 processing vessels 4 susceptor 6 insulation 32 high frequency power supply 35 radio frequency power supply 33 high frequency antenna 42, 43, 44 valves 45, 46, 47 Mass flow controller 48, 49, 50 Process gas supply source 51 Exhaust pipe 55 Controller Glass substrate for P LCD

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-1-164038 (JP, A) JP-A-6-283472 (JP, A) JP-A-3-77209 (JP, A) JP-A-6- 151383 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (4)

(57) [Claims] 1. An ITO (Indium Tin O 2) on an LCD substrate
In the method for etching xide), the substrate to be processed is loaded into a processing container, and a processing gas selected from H ₂ , He, Cl ₂ , and HCl gases is introduced into the processing container, and the processing is performed. The high-frequency power is applied to a spiral, coil, or loop antenna provided outside the container, and the LC
A first step of etching the ITO of the D substrate; and, when the etching treatment is completed, the introduction of the processing gas in the first step is stopped and further an O ₂ gas is introduced into the processing container. And a second step of treating the LCD substrate by plasma treatment. 2. The etching method according to claim 1, wherein the flow rate of the O ₂ gas introduced into the processing container is higher than the flow rate of the processing gas introduced in the first step. 3. The etching method according to claim 2, wherein the degree of pressure reduction in the processing container is set to be higher in the second step than in the first step. 4. ITO (Indium Tin O) on a substrate for LCD
In the method of etching xide), the substrate to be processed is loaded into a processing container and selected from H ₂ , He, Cl ₂ and HCl gases.
Introducing a natural gas into the processing container, and providing a spiral shape, a coil shape or
Applying high frequency power to the loop antenna, the LC
First step of etching ITO on the D substrate
Then, when the etching process is completed, the first step is performed.
The introduction of the processing gas in the
O that is higher than the flow rate of the processing gas introduced in the first step
Introduce ₂ gases and adjust the degree of pressure reduction in the processing vessel to the first step.
To make the O ₂ gas into plasma
And a second step of processing the LCD substrate.
An etching method characterized by the above.