JP2005268598A - Etching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical etching apparatus that prevents an unwanted oxide film from being formed at an etching target and a light transmission window, also prevents an etching rate from decreasing even if the optical etching device is applied to the etching of Si, and makes etching with high machining precision. <P>SOLUTION: The etching device comprises: at least a treatment chamber for retaining the inside of the chamber in vacuum; a gas inlet for introducing treatment gas without containing O<SB>2</SB>into the treatment chamber; a light source for generating light having photon energy that is larger than the binding energy of CF<SB>4</SB>; and a light transmission window for introducing light from the light source into the treatment chamber. A thin film formed by Si on at least one layer formed on an object to be treated is etched by using radical generated by applying light to the treatment gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an etching apparatus.

  Dry etching is a processing technique for removing unnecessary portions of a thin film or a substrate using ion radicals. Conventionally known as such dry etching are reactive ion etching (RIE) and etching using high-density plasma generated by microwaves.

  However, since RIE is a technique in which accelerated ions are incident on the substrate and etching is performed, for example, when the method is applied to the manufacture of a thin film transistor (TFT), the substrate is damaged by the ions, and the obtained TFT is obtained. There is a problem that the electrical characteristics of the battery deteriorate. Even in an etching apparatus using high-density plasma generated by microwaves, it is difficult to completely avoid damage to the substrate due to ions present in the plasma, and the deterioration of the electrical characteristics of the TFT is completely prevented. Can not do it.

Therefore, it is known that photoetching, which is dry etching that does not contain ions, is applied to the manufacture of TFTs. As an example, for example, Patent Document 1 discloses that an etching gas containing at least a compound O ₂ having sulfur and fluorine as constituent elements is irradiated with light, and a silicon oxide-based material layer is etched using the generated chemical species. A photo-etching method characterized by this is disclosed. However, when etching a Si thin film, which is widely used in the semiconductor field and the liquid crystal field, is performed by the method described in Patent Document 1, since a processing gas containing oxygen gas is used, undesired oxidation is caused on the object to be etched. There was a problem that a film was formed. Further, since the photon energy of the light source is absorbed by O ₂ , there is a problem that the generation efficiency of F radicals is lowered and the etching rate is lowered. In order to maintain the etching rate, it is conceivable to increase the output of the light source, but this leads to an increase in power consumption and a problem that the cost is increased.

Photoetching is usually performed using an etching apparatus having a configuration in which a processing gas is introduced into a processing chamber in which an object to be etched is placed, and light is irradiated through the processing gas. However, when the etching method described in Patent Document 1 is performed using such a conventional etching apparatus, an oxide film is formed on the light transmission window, and the light transmittance decreases due to this oxide film. As a result, the generation efficiency of F radicals is lowered, and the etching rate is lowered. In addition, since the composition and thickness of the oxide film formed on the light transmission window changes with the etching time, the light transmittance also changes with the etching time, making it difficult to irradiate the etching target with a constant transmittance. Met. Furthermore, since the etching rate also changes with time due to this, it is difficult to maintain the processing accuracy. The thin film material Si to be etched is used as a TFT channel that requires high-precision processing, and it has been difficult to apply the photoetching to the etching of these thin films.
Japanese Patent Laid-Open No. 10-32176 JP-A-5-21397 JP 2001-351909 A JP 2002-212739 A JP 2003-297816 A

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to apply it to Si etching without forming an undesired oxide film on the etching object and the light transmission window. However, it is an object of the present invention to provide an etching apparatus capable of preventing the etching rate from being lowered and performing etching with high processing accuracy.

The etching apparatus of the present invention emits light having photon energy larger than the binding energy of CF ₄ , a processing chamber capable of keeping the chamber in a vacuum, a gas introduction port for introducing a processing gas not containing O ₂ into the processing chamber, and the like. A light source and at least a light transmission window for introducing light from the light source into the processing chamber, and at least one or more layers of Si formed on the object to be processed using radicals generated by irradiating the processing gas with light The thin film formed in (1) is etched.

  Here, it is preferable to use a xenon excimer lamp, a krypton excimer lamp, or an argon excimer lamp as a light source.

The etching apparatus of the present invention preferably uses at least one selected from F ₂ , Cl ₂ , SF ₆ and CF ₄ as the processing gas.

Furthermore, in the etching apparatus of the present invention, the light transmission window is preferably formed of LiF, MgF ₂ , CaF ₂ or quartz.

  According to the etching apparatus of the present invention, the processing gas is irradiated with light from a light source having photon energy larger than the binding energy of the processing gas, and the object to be processed is etched using the generated radicals. As a result, no ions are present during etching, so that no ion damage occurs on the substrate.

In the etching apparatus of the present invention, a processing gas not containing O ₂ is used, and a thin film formed of at least one layer of Si formed on an object to be processed is to be etched. Therefore, etching can be performed without forming an undesired oxide film on the thin film formed of Si. In addition, since the processing gas not containing O ₂ is used, the photon energy of the light source is not absorbed by O ₂ and the generation efficiency of F radicals is not lowered, thereby preventing the etching rate from being lowered. .

Furthermore, in the etching apparatus of the present invention, since the oxide film is not formed in the light transmission window by using the processing gas not containing O ₂ , the thin film can be irradiated with light with a stable light transmittance. Therefore, etching can be performed with high processing accuracy.

  As described above, according to the etching apparatus of the present invention, since an undesired oxide film is not formed on the object to be etched and the light transmission window, a decrease in the etching rate is prevented even when applied to Si etching, and high processing accuracy is achieved. Can be etched. Such an etching apparatus of the present invention is useful for etching Si used as a channel of a TFT gate that requires high precision processing, and the use of the etching apparatus of the present invention does not cause deterioration of electrical characteristics. A TFT can be manufactured.

FIG. 1 is a diagram schematically showing an outline of an etching apparatus 1 according to the present invention. The etching apparatus 1 of the present invention has a processing chamber 2 capable of maintaining a vacuum in the chamber, a gas inlet 3 for introducing a processing gas not containing O ₂ into the processing chamber, and a photon energy larger than the binding energy of CF _4. At least a light source 4 that emits light and a light transmission window 5 for introducing light from the light source 4 into the processing chamber 2 are provided.

  The processing chamber 2 in the etching apparatus 1 of the present invention is not particularly limited as long as it is realized so that the chamber can be kept in a vacuum. Here, “holding in a vacuum” does not necessarily mean a strict vacuum, but includes one that can be held in a room in a substantially airtight manner. In the etching apparatus 1 of the example shown in FIG. 1, the processing chamber 2 has an internal space in which an object to be processed (substrate) 7 can be placed, and a gas introduction for introducing a processing gas into the processing chamber 2. A mouth 3 is provided in communication with the internal space. A vacuum pump 10 is connected to the processing chamber 2 so that the inside of the processing chamber 2 can be kept in vacuum. Further, a light transmission window 5 for irradiating light from the light source 4 into the processing chamber 2 when the processing gas is introduced into the processing chamber 2 with the workpiece 7 placed on the susceptor 6 in the internal space. Is attached.

The light source 4 used in the etching apparatus 1 of the present invention can be used without particular limitation as long as it emits light having photon energy larger than the binding energy of CF ₄ (5.6 eV). Even when a light source that emits light having a photon energy of 5.6 eV or less is used, when CF ₄ is used as a processing gas, there is a problem that etching cannot be performed because F radicals cannot be generated by dissociating CF ₄ . As such a light source, since it is commercialized, it can be easily obtained, and since F radicals can be generated by dissociating the processing gas, a xenon excimer lamp (photon energy: 7.2 eV), krypton excimer A lamp (photon energy: 8.5 eV) and an argon excimer lamp (photon energy: 9.8 eV) are preferable. In the etching apparatus 1 shown in FIG. 1, a lamp that is a light source 4 is accommodated in a lamp house 11, and the lamp house 11 receives light from the light source 4 through a light transmission window 5 in a processing chamber 2. It is attached to the processing chamber 2 so that the object 7 can be irradiated. Further, the lamp house 11 is provided with a nitrogen gas inlet 12 communicating with the internal space thereof, and when irradiating light, the nitrogen gas is introduced into the lamp house 11 from the nitrogen gas inlet 12. The inside of the lamp house 11 is maintained in a nitrogen atmosphere, whereby the light from the light source 4 can be prevented from being attenuated by air.

In the etching apparatus 1 of the present invention, a processing gas not containing O ₂ is introduced into the processing chamber 2 from the gas inlet 3. As long as the processing gas used in the present invention is a gas not containing O ₂ and uses a component having a binding energy smaller than that of CF ₄ , an appropriate processing gas conventionally used in this field is used. Can be used without limitation. Here, as the processing gas not containing O ₂ , the processing gas using a component having a binding energy smaller than that of CF ₄ is used because the photon energy is the smallest among the above-described xenon excimer lamp, krypton excimer lamp and argon excimer lamp. This is because F radicals can be generated by irradiation with light from a xenon excimer lamp.

The processing gas that can be used in the present invention is not particularly limited as long as it has a binding energy smaller than that of CF ₄ , and any conventionally known appropriate gas can be used. However, a xenon excimer lamp, a krypton excimer lamp, and an argon excimer can be used. In order to generate F radicals by irradiating light from a xenon excimer lamp having the smallest photon energy among the lamps, F ₂ (binding energy 1.6 eV), Cl ₂ (binding energy 2.5 eV), SF ₆ (bonding) It is preferable to use at least one selected from energy 3.8 eV), CF ₄ (binding energy 5.6 eV), and the like.

The light transmission window 5 in the etching apparatus 1 of the present invention can irradiate light from the light source 4 into the processing chamber 2 through this, and for example, LiF, MgF ₂ , CaF ₂ , quartz can be used as a forming material. Etc. are exemplified. Since the light transmission window 5 in the etching apparatus 1 of the present invention needs to have an excellent transmittance with respect to the light of the light source, the above exemplified materials are preferable. Furthermore, the light transmission window 5 is more preferably formed of a material having a high transmittance with respect to the wavelength of the light source to be used.

  In the etching apparatus of the present invention, at least one layer formed on the object to be processed (substrate) 7 disposed on the susceptor 6 using radicals generated by irradiating the processing gas with light using the above-described configuration. The thin film formed of Si is etched. As described above, the present invention irradiates the processing gas with light from a light source having a photon energy larger than the binding energy of the processing gas, and etches the processing object using the generated radicals. As a result, unlike conventional etching apparatuses that use reactive ion etching and conventional etching apparatuses that use high-density plasma generated by microwaves, ions are not present during etching, causing ion damage to the workpiece. Absent. FIG. 3 is a diagram comparing the electrical characteristics of a TFT manufactured using the etching apparatus of the present invention and a TFT manufactured using a conventional etching apparatus. As shown in FIG. 3, it can be seen that when the conventional etching apparatus is used, the Id-Vg curve is shifted in the negative direction due to ion damage.

In the present invention, a thin film formed of at least one layer of Si is to be etched. In the present invention, since photo-etching is performed using a processing gas not containing O ₂ , etching can be performed without forming an undesired oxide film on a thin film formed of Si. In addition, since the processing gas not containing O ₂ is used, the photon energy of the light source is not absorbed by O ₂ and the generation efficiency of F radicals is not lowered, thereby preventing the etching rate from being lowered. . Furthermore, in the etching apparatus of the present invention, since the oxide film is not formed in the light transmission window by using the processing gas not containing O ₂ , the thin film can be irradiated with light with a stable light transmittance. Therefore, etching can be performed with high processing accuracy.

  As described above, the etching apparatus of the present invention does not form an undesired oxide film on the object to be etched and the light transmission window, prevents a decrease in the etching rate even when applied to Si etching, and has high processing accuracy. It can be etched. The effect of preventing a decrease in the etching rate by the etching apparatus of the present invention can be evaluated by confirming that the etching amount of Si obtained is the same if many substrates are etched and the etching conditions are the same. it can. Such an etching apparatus of the present invention is useful for etching Si used as an insulating film of a TFT gate that requires high precision processing, and the use of the etching apparatus of the present invention causes deterioration of electrical characteristics. This makes it possible to manufacture a TFT without any.

Hereinafter, the present invention will be described more specifically, but the present invention is not limited to these examples.
<Example 1>
In the etching apparatus 1 of the present invention configured as shown in FIG. 1, a TFT is manufactured using, for example, CF ₄ as a processing gas, a xenon excimer lamp as a light source 4 and a light transmission window 5 formed of LiF, for example. did. 2A and 2B are schematic views of an example of a TFT formed by using the etching apparatus 1 of the present invention. FIG. 2A shows a state before etching, and FIG. 2B shows a state after etching. . In FIG. 2A, a structure in which a SiN layer 22, an amorphous silicon layer 23, and an n ⁺ silicon layer 24 are stacked on a gate electrode 21, and a source electrode 25 and a drain electrode 26 are formed thereon. (Substrate) is shown.

First, such a substrate was placed in the processing chamber 2 of the etching apparatus 1 of the present invention as shown in FIG. 1, and the substrate temperature was kept at 20 ° C. Next, CF ₄ was introduced into the processing chamber 2 from the processing gas inlet 3 at a flow rate of 200 sccm, and the pressure was controlled to 1200 Pa. Then, the light from the xenon excimer lamp 4 was irradiated into the processing chamber 2 through the light transmission window 5. As a result, F radicals were generated because the photon energy was larger than the binding energy of the processing gas. Using this F radical, the n ⁺ silicon layer 24 and part of the amorphous silicon layer 23 were etched to obtain a TFT in the state shown in FIG. Thus, by using the etching apparatus 1 of the present invention, it was possible to obtain a TFT in which the amorphous silicon layer 23 was not damaged by ions and the electrical characteristics were not deteriorated.
<Example 2>
Except that a krypton excimer lamp was used as the light source, the TFT was fabricated by etching in the state shown in FIG. 2A in the same manner as in Example 1. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 3>
Except that an argon excimer lamp was used as a light source, the TFT shown in FIG. 2A was etched in the same manner as in Example 1 to produce a TFT. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 4>
Except for using F ₂ as the processing gas, the TFT was fabricated in the same manner as in Example 1 by etching the state shown in FIG. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 5>
Except for using Cl ₂ as a processing gas, the TFT was fabricated in the same manner as in Example 1 by etching the state shown in FIG. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 6>
Except that SF ₆ was used as the processing gas, the TFT was fabricated by etching in the state shown in FIG. 2A in the same manner as in Example 1. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 7>
Except that F ₂ was used as the processing gas, the TFT was fabricated by etching in the state shown in FIG. 2A in the same manner as in Example 2. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 8>
Except for using Cl ₂ as the processing gas, the TFT was fabricated in the same manner as in Example 2 by etching the state shown in FIG. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 9>
Except that SF ₆ was used as the processing gas, the TFT was fabricated by etching in the state shown in FIG. 2A in the same manner as in Example 2. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 10>
Except that F ₂ was used as a processing gas, the TFT was fabricated by etching in the state shown in FIG. 2A in the same manner as in Example 3. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 11>
Except for using Cl ₂ as a processing gas, a TFT was fabricated in the same manner as in Example 3 by etching the state shown in FIG. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Example 12>
Except that SF ₆ was used as the processing gas, the TFT was fabricated in the same manner as in Example 3 by etching the state shown in FIG. As a result, as in Example 1, ion damage was not caused in the amorphous silicon layer 23, and a TFT in which the electrical characteristics were not deteriorated was obtained (FIG. 2B).
<Examples 13 to 24>
Except for using a light transmissive window formed of MgF ₂ , the TFT shown in FIG. 2A was etched in the same manner as in Examples 1 to 12 to produce TFTs. As a result, as in Example 1, it was possible to obtain TFTs in which the amorphous silicon layer 23 was not damaged by ions and the electrical characteristics were not deteriorated (FIG. 2B).
<Examples 25 to 36>
Except for using a light-transmitting window formed of CaF ₂ , the TFT shown in FIG. 2A was etched to produce TFTs in the same manner as in Examples 1-12. As a result, as in Example 1, it was possible to obtain TFTs in which the amorphous silicon layer 23 was not damaged by ions and the electrical characteristics were not deteriorated (FIG. 2B).
<Examples 37 to 48>
Etching was performed on the state shown in FIG. 2A in the same manner as in Examples 1 to 12 except that a light-transmitting window formed of quartz was used, and TFTs were respectively produced. As a result, as in Example 1, it was possible to obtain TFTs in which the amorphous silicon layer 23 was not damaged by ions and the electrical characteristics were not deteriorated (FIG. 2B).

  Table 1 shows combinations of Examples 1 to 48.

<Comparative Example 1>
A TFT was fabricated in the same manner as in Example 1 except that a mixed gas of CF ₄ and O ₂ was used as the processing gas. As a result, the etching rate decreased. As a result of examination, it was found that an oxide film was formed on the object 7 to be processed and the light transmission window 5, and this oxide film attenuated light from the light source.
<Comparative example 2>
A TFT was produced in the same manner as in Example 1 except that a light source having a photon energy lower than that of CF ₄ was used. As a result, the etching rate was significantly reduced. This was thought to be because F radicals could not be generated because the process gas could not be dissociated.

It is a figure which shows the outline of the etching apparatus 1 of this invention typically. It is a figure which shows typically an example of TFT formed using the etching apparatus 1 of this invention. It is a figure which compares and shows the electrical property of TFT produced using the etching apparatus of this invention, and TFT produced using the conventional etching apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Etching apparatus, 2 processing chamber, 3 gas inlet, 4 light source, 5 light transmission window, 6 susceptor, 7 to-be-processed object, 10 vacuum pump, 11 lamp house, 12 nitrogen gas inlet.

Claims (4)

A processing chamber capable of maintaining a vacuum in the chamber, a gas introduction port for introducing a processing gas not containing O ₂ into the processing chamber, a light source that emits light having photon energy greater than the binding energy of CF ₄ , and light from the light source Etching a thin film formed of at least one layer of Si formed on the object to be processed using radicals generated by irradiating the processing gas with light at least with a light transmission window for introducing a gas into the processing chamber An etching apparatus characterized by:   2. The etching apparatus according to claim 1, wherein a xenon excimer lamp, a krypton excimer lamp or an argon excimer lamp is used as the light source. The etching apparatus according to claim 1, wherein at least one selected from F ₂ , Cl ₂ , SF ₆ and CF ₄ is used as the processing gas. The etching apparatus according to claim 1, wherein the light transmission window is made of LiF, MgF ₂ , CaF ₂ or quartz.

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