JPH01200628A - Dry etching - Google Patents

Abstract

PURPOSE:To remove a resist in a short time without the occurrence ot a residual substance by a method wherein, in addition to an ashing operation of the resist by using a fluorine-based gas, a substrate is cooled in order to suppress a carbonization reaction of the resist. CONSTITUTION:When a substrate to be processed where an organic compound film such as a resist or the like has been formed on the surface is arranged inside a reaction container 1 and the organic compound film is removed by instroducing a prescribed gas into said container, the substrate to be processed is cooled to a temperature at which a carbonization reaction ot the organic compound film is not caused; as the gas to be introduced into the container 1, a gas containing a halogen element (e.g., NH3, CF4) or a mixed gas of the gas containing the halogen element and other gases (e.g., O2, H2, H2O) is to be used. By this setup, it is possible to remove the organic compound film at high speed without leaving a residual substance on the substrate to be processed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a dry etching method used for surface cleaning, photoresist removal, etc. among semiconductor device manufacturing processes.

(Prior art) Microfabrication technology in the manufacturing process of semiconductor elements, and processing technology in other fields (for example, printed circuit board processing,
In the processing process of compact discs, laser discs, etc.), the photoetching process (Ph
oto EtchingProcess; P E
P) is an important and essential process. Using this organic resist as a mask, it is removed after the underlying treatment (etching, ion implantation, etc.) is completed. The method is to remove it in a solution such as a mixed solution of H2SO4 and H20□ or a solution in which H2O is added, or dry ashing (iodination) in an oxygen (0□) gas discharge. The method of removal is currently mainly used.

However, the former process using a solution has problems such as solution management and work safety.

In particular, it is unsuitable for semiconductor device manufacturing processes, etc., which do not require processes using liquids. In addition, when an organic compound film photoresist is used for patterning aluminum (AI) metal, etc., which is an electrode material used in semiconductor device manufacturing processes, in a mixed solution of H2SO4 and H20□,
There is a problem that the metal is corroded and its uses are limited.

In addition, in the latter dry ashing method, a sample on which an organic compound film is formed is placed in a barrel-type or parallel plate-type reaction vessel that generates an electric discharge, and, for example, 02 gas or 0
This is a method of discharging a mixed gas of two gases and an F-based gas to peel off an organic compound film. According to this method, compared to the method using a solution described above, it is simpler and the base material may be metal or the like, and there is no need to limit the base material. However, this dry ashing method has the problem of causing damage or resist residue on the surface of the sample because the sample is placed during the discharge necessary to obtain a practical predetermined removal rate.

A specific example of a photoetching process using 0.02 plasma will be explained using the schematic diagram of FIG.

FIG. 7 is a cross-sectional perspective view showing a step of forming a gate electrode of an MO8 type device on a substrate such as silicon.

First, as shown in FIG. 7(a), a polycrystalline silicon film that will become a gate electrode is formed on a semiconductor substrate 70 via a gate oxide film 71, and then phosphorous is added by implanting ions such as phosphorus (P). A crystalline silicon film 72 is formed. Subsequently, a resist 73, which is an organic compound film, is applied to the entire surface. after that,
As shown in FIG. 7(b), pattern exposure is performed and development is performed so that a resist 73a remains on a desired portion of the polycrystalline silicon film 72 that will become the gate electrode.

Next, as shown in FIG. 7E, using the resist 73a as a mask, the rest of the polycrystalline silicon film 72 is removed except for the gate electrode 72a by reactive ion etching (RIE) or the like. Thereafter, the resist 73a is removed using the aforementioned 0□ plasma, but at this time, a residue 74 remains on the surface of the gate electrode 72a or the gate oxide film 71, as shown in FIG. 7(d). Furthermore, due to the incidence of charged particles in the plasma. Irradiation damage is induced in SiO2 or its underlying layer. Even if an MO8 type device is formed through such a process, there is a problem that the residue may have an adverse effect on the characteristics of the semiconductor element, such as the residue may have an adverse effect on the subsequent process or the dielectric breakdown voltage of the oxide film may be lowered.

Such problems of damage or residue on the sample surface occur when either barrel type or parallel plate type associating devices are used; in the latter case, charged particles during discharge are incident on the sample surface. , and the damage caused is more noticeable than the former. In addition, in the photo soching process using 0□ plasma dry etching, as described in Fig. 7, an organic resist exposed to discharge as in the case of etching a sample by the RIE method, or a mask for ion implantation is used. When removing an organic resist that has been exposed to ion bombardment, there is a problem in that it is more difficult to remove and a residue is more likely to remain than when these process steps are not performed.

In order to completely remove the residue of the organic compound film, it is necessary to perform long-time ashing for about 1 hour or more.
When ashing is performed for such a long time, a problem arises in that damage to the sample increases.

Further, the fact that the treatment for removing the organic compound film takes time is disadvantageous in terms of the manufacturing process. In order to remove organic compounds at high speed, a method in which the temperature of the sample is raised to 100° C. or higher is also used, but residues are more likely to be generated at high temperatures. Furthermore, in some cases, there are residues that cannot be removed even with a long ashing process.

As a method to solve these problems, there is a down-flow type resist ashing method using F-based gas, or
Ashing methods using F-based active species and H2O, H2, etc. have been reported. Although these methods are more advantageous than 02 Ashing in terms of damage and residue, they pose problems such as corrosion of the substrate during or after the treatment. Furthermore, although these methods can remove the residue, it still takes time to remove the residue. That is, although most of the resist to be removed can be removed in a short time, most of the processing time must be used to remove any remaining residue.

(Problems to be Solved by the Invention) Conventionally, when a solution is used to remove an organic compound film such as a resist, it is difficult to manage the solution, it is difficult to ensure safety, and there are limitations on the underlying material. There is a problem of being exposed. Furthermore, the method using dry 0□ ashes causes damage to the sample, and if the sample has undergone a certain process, a residue is formed that is difficult to remove, and in that case, there are problems such as a long processing time. Furthermore, even in the downflow type method using F-based gas, most of the processing time is used to remove residues, and it is industrially extremely effective to shorten this time.

The present invention has been made in consideration of the above circumstances, and its purpose is to remove organic compound films at high speed and without producing any residue, and to provide a dry film suitable for resist removal, surface treatment, etc. The object of the present invention is to provide an etching method.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to cool a substrate to be processed when removing an organic compound film using a fluorine-based gas.

That is, the present invention provides a dry etching method in which a substrate to be processed having an organic compound film such as a resist formed on its surface is placed in a reaction vessel, and a predetermined gas is introduced into the vessel to remove the organic compound film. The substrate to be treated is cooled to a temperature at which no carbonization reaction of the organic compound film occurs, and a gas containing at least a halogen element (for example, NF, CF, etc.) or at least a halogen element is introduced into the container. containing gas and other gases (e.g. 02°H2
, H2O).

(Function) First, the generation of a residue during the removal of an organic compound film will be explained using a method of iodizing a photoresist as an example.

In the method of removing photoresist using 0-based active species (0 radicals, ozone, etc.), the reaction between the active species and the resist does not proceed at a practical speed unless the temperature is raised to about 1009C or higher. Therefore, in the resist ashing method using only 0-based active species, ashing cannot be performed unless the sample is placed in plasma and receives heat or alternative energy from the plasma. Furthermore, when plasma is not used, a method such as heating the sample is used. By the way, this heating of the resist causes a thermal change in the texture of the resist, causing the inside of the resist to become carbonized. This carbonized resist structure is difficult to remove with O-based active species.
It becomes a residue. As described above, the carbonization phenomenon caused by heating of the resist is a major cause of the residue during ashing.

That is, ashing using 0-based active species is essentially disadvantageous in terms of residue.

On the other hand, when a mixture of F-based active species (for example, F radicals) and 0-based active species is used, the ashing speed of the resist is faster than when using 0-based active species, and The generation of residue is also reduced.

This is because F-based active species (eg, F radicals) efficiently advance resist ashing and also serve to remove residues. That is, F in an O radical atmosphere
By first reacting the radicals with the resist, there is an effect of promoting the reaction between the 0 radicals and the resist. In addition, the residue generated by 0 radical ashing is
Due to the fact that the residue can be removed by exposing it to radicals,
The effect of F is clear.

However, even in this system, once the cyst iodization reaction progresses, the temperature of the resist increases due to the reaction heat. FIG. 5 shows the change in resist temperature rise with respect to resist iodization treatment time. Note that this resist iodization is C
Active species generated by microwave discharge of FJ 10□ gas were supplied into a container containing a substrate to be processed.

It can be seen from FIG. 5 that as resist iodization begins to progress, the resist temperature rises to 150° C. or more. This increase in resist temperature causes the formation of a residue (carbonization of the resist) as described above (in the 0-based iodization method).

However, in ashing using F-based active species, increasing the temperature of the resist is not the essence of iodization, and iodization can be performed even at low temperatures. For example, in the iodization method in which F radicals generated by microwave discharge of NF3 and H2O are separately supplied to the substrate to be processed, the relationship between the temperature of the substrate to be processed and the resist ashing rate is measured. Figure 6 shows the results. show. It is clear that the iodization rate of the resist maintains a practical value even when the substrate temperature is lowered to below room temperature. In addition, -40
The reason why the iodization rate suddenly becomes 0 at temperatures below .degree. C. is related to the dew point of H2O and is because water condenses on the surface of the substrate to be treated.

Now, looking at the generation of residues, there are two cases: when the resist is iodized without controlling the temperature of the substrate to be processed and the temperature is raised due to reaction heat, and when the resist is iodized while being controlled to below room temperature. The iodization time without residue is reduced by approximately half. That is, by lowering the temperature of the substrate to be treated and performing iodization while removing the reaction heat of iodization, the generation of residue can be extremely effectively suppressed. It has been confirmed that the same effect can be obtained by the method using the CFJ + O2 gas described above and the method using other F-based gases.

Therefore, according to the present invention, by cooling the substrate in addition to iodizing the resist with a fluorine-based gas, it is possible to suppress the carbonization reaction of the resist and remove the resist in a short time without generating any residue. becomes possible.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing a dry etching apparatus used in the first embodiment of the present invention.

Reference numeral 11 in the figure is a chamber (reaction container), and the object to be processed 2 is accommodated in the chamber 1 . A first vibe 4 is connected to the chamber 1 for supplying active species containing a halogen element such as fluorine (F). To supply the active species into the chamber 1, a gas containing a halogen element such as fluorine is introduced from the other end 7 of the vibrator 4, and a discharge tube 6 connected to the microwave power source 5 is connected to the vibrator 4. It is done through. Further, the inside of the chamber 1 is evacuated through an exhaust port 3.

Further, the chamber 1 is provided with a second vibe 8 that introduces water vapor, hydrogen gas, or a compound gas containing hydrogen element. This vibrator 8 is connected to a vessel 9 storing water (H20) via a flow rate control valve 11, and a vibrator 10 is connected to the vessel 9-. When introducing water vapor, a carrier gas is introduced from a vibrator 10 into water in a vessel 9 storing water (H2O), and hydrogen and hydrogen gas are sent into the chamber 1 by bubbling the water. When introducing a gas with a low vapor pressure such as H20, it is particularly effective to introduce it using a carrier gas. Further, when introducing hydrogen gas or a gas containing hydrogen element, the gas may be introduced directly without going through the vessel 9.

12 is a sample stage for mounting the object 2 to be processed. 13 is a pipe through which a refrigerant is sent to cool the sample stage. As the refrigerant, for example, a liquid such as water, ethylene glycol, or oil, or a gas may be used. In this way, the temperature of the sample stage 12 is cooled, and thereby the substrate 2 to be processed is also cooled.

Next, a method for removing a photoresist as an organic compound film formed on a semiconductor substrate will be described. Here, NF3 gas was used as the gas containing F (fluorine), which is a halogen element, no carrier gas was used, and H20
to be introduced directly.

FIG. 2 is a perspective sectional view showing the etching process of the substrate to be processed 2 accommodated in the chamber 1 of the apparatus shown in FIG. The substrate to be processed used here is a semiconductor substrate 2 in the MO3IC manufacturing process as shown in FIG. 2(a).
A gate electrode 23 is formed on the gate electrode 1 through a gate insulating film 22, and is etched by RIE using a photoresist 24, which is an organic compound film, formed on the gate electrode 23 as a mask.

The substrate to be processed shown in FIG. 2(a) is housed in the chamber 1 of the apparatus shown in FIG.
This gas is excited by the discharge tube 6, and the fluorine (F) radicals generated thereby are introduced into the chamber 1. Inside the chamber 1, a second
H20 in the vessel 9 is directly supplied as gas through the pipe 8. Here, the partial pressures of NF3 and H2O are:
Although each pressure was kept constant at 0.1 Torr, the partial pressures of NF3 gas and H20 can be changed as appropriate within a range that provides the required etching rate and selectivity.

Under the above conditions, the method of this example was actually used as an electrode material.
I (or A1 compound) as a resist (0FPI?-80
0, Tokyo Ohka Type) was used as a mask to remove the resist after RIH. When the substrate is not cooled, the resist temperature rises to 100° C. or more in about one minute after the reaction gas is introduced and iodization of the resist begins. Although most of the resist is removed by processing for about 1 minute, a residue as shown at 74 in FIG. 7 remains in the center of the Al line pattern.

In order to completely remove this residue, a processing time of 5 minutes or more is required.

On the other hand, in the method of this embodiment, when resist ashing is performed by cooling the sample stage 12 and keeping the temperature of the substrate 2 to be processed at 0° C. and flowing a reactive gas, the processing time is approximately 3 minutes. It was confirmed that ashing can be performed without any residue. By cooling the sample temperature in this manner, the processing time can be approximately halved.

Thus, according to the method of this embodiment, the organic resist formed as a mask on the gate electrode made of A1 etc. is
Since the resist is removed by ashing using F, +H20, the resist can be removed at high speed without increasing the substrate temperature. Furthermore, since the rise in temperature of the substrate due to ashing is suppressed, carbonization of the resist can be suppressed and the generation of residue can be eliminated, thereby further shortening the time required for resist removal. Also, unlike dry 02 ashing, the effect of damage is extremely small.

Although the method of this embodiment did not use a carrier gas for introducing H20, the same can be said of a method using a carrier gas. For example, H as a carrier gas
There is a method using two gases.

In addition, carrier gases such as Ar and N2 may be used, and instead of water vapor and H2, only water vapor, alcohols such as CH30H and C2H50H, or CH
Even if a gas containing at least hydrogen element, such as a hydrocarbon gas such as 41C2H6, is used, the organic compound film can be removed without leaving any residue and at high speed. In addition, fluorine (F
) and other gases that generate active species containing halogen elements include CD E (Chemical Dry Etc.
For example, in addition to NF3, SF6. CF4. C2F6. C3Fg
, CF4 +02・C2F6 +02・C3F2+
02.) (The gas may be any gas containing a fluorine element such as CF2.F2 or a gas containing a halogen element other than fluorine.

Next, a second embodiment method of the present invention will be described. Although the above-mentioned embodiment used an active species containing F and a gas containing H such as F20, the present invention can also be applied to an ashing method in which a gas containing F and a gas containing O are mixed. FIG. 3 shows a schematic configuration of an apparatus for carrying out this method. The basic structure is the same as that in FIG. 1, and the same reference numerals indicate the same structure, so the explanation thereof will be omitted.

A method of removing the resist on the AI pattern similar to that described above using the apparatus shown in FIG. 3 and using CF4 + O2 gas as the gas will be described. The structure of the sample is the same as that shown in FIG. 2(a), and in this case, 24 is a resist mask for RIE (0FPR-800, manufactured by Tokyo Ohka).
is used. Furthermore, 23 is AI, 22 is the underlying Si
O2 and 21 are St substrates. CF4 10800M,
O□ was mixed at a flow rate of 11005CC, and the pressure was 0.2
Torr and microwave discharge. The active species generated therein are supplied into the container 1.

Here, if the temperature of the sample stage 12 is not controlled,
The temperature of the resist rises to over 150°C after approximately one minute of processing. When resist is ashed under these conditions, it only takes about 1 minute to remove most of the resist, but a residue remains on the AI pattern, and the residue is
It cannot be removed even after treatment for more than a minute. In this case, Si
Although the etching speed of O2 is extremely slow, long-term processing will also remove a significant amount of SiO2, which poses a problem in the case of a thin 5in2 base. Further, although this is good in the case of AI, when attempting to ash a resist on a polycrystalline Si pattern, polycrystalline Si is etched faster than SiO□, so long-term processing cannot be performed. .

Therefore, if the sample stage 12 is cooled to about 0° C. and the same process is performed, the resist can be ashed without any residue in about 3 minutes. By cooling the substrate, 5in2. Since the etching speed of the polycrystalline SL is also reduced, the selectivity is also improved and the etching damage to them during processing is reduced.

In this example, CF4 is used as the F-containing gas, but NF3. C2Fb, Cs F8+XeF
2. Any gas containing F, such as SF6, is fine.
The cooling effect is similar.

Next, a third embodiment method of the present invention will be described. Although the above-mentioned 24 examples used a down-flow type device, the method of the present invention can also be applied to an ashing method in which a sample is placed in plasma. FIG. 4 shows a schematic configuration of a parallel plate type ashing device used in this embodiment method.

Reference numerals 61 and 62 are electrodes for generating discharge, and the sample 2 is placed on the lower ground electrode 62.

This ground electrode 62 is fixed on the sample stage 12 and is cooled. The upper electrode 61 is an excitation electrode and is connected to a high frequency power source 63 of, for example, Li2S MHz. Further, 64 is a gas introduction port.

Using the apparatus shown in FIG. 4, resist ashing was performed on the same sample as described above. The gas is 02+CFa (
High frequency (13,5 (iMH)
z) Generate a discharge by excitation (power 500V).

When the temperature of the sample stage 12 is not controlled, the sample temperature rises to nearly 200° C. and a residue is generated after resist ashing, but when the temperature is lowered to 0° C., ashing can be performed without any residue.

In this device, the F-based gas is generally added to the 02 gas as a base. However, in order to supply the F-containing gas, not only the F-containing gas but also the F-containing solid such as fluororesin can be supplied to the plasma. By installing it inside, a gas containing F is released from it, and similar ashing can be performed. A similar cooling effect can be obtained in this case as well. Another method for placing a sample in plasma is to use a barrel-type device, and similar effects can be obtained using this device.

Further, in the above-mentioned embodiment 1.2.3, NF3 and CF4 were used as the fluorine-containing gas, but other fluorine-containing gases mentioned in the first embodiment may be used, or chlorine may be used. Containing gas C12, CCl4゜5iC14, PCl3. BCI
, etc. and a gas containing bromine Br2. CBr, , CBrF
3. Gas I2 or CFC13 further containing elements.

CF2Cl□, CF3Cl, etc. may also be used.

[Effects of the Invention] As detailed above, according to the present invention, when removing an organic compound film using a fluorine-based gas, a residue is left on the substrate by cooling the substrate. The organic compound film can be removed at high speed without any problems. Therefore, it exhibits great effects when applied to resists, surface treatments, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a dry etching apparatus used in the method of the first embodiment of the present invention, FIG. 2 is a perspective view showing the resist ashing process according to the method of the first embodiment, and FIG. A schematic configuration diagram showing the apparatus used in the method of the second embodiment, and FIG. 4 shows the apparatus used in the method of the third embodiment of the present invention. For detailed explanation, Figure 5 is a characteristic diagram showing the relationship between ashing time and resist temperature, Figure 6 is a characteristic diagram showing the relationship between substrate temperature and etching rate, and Figure 7 is a problem with the conventional method. It is a process diagram for explaining the points. 1... Reaction container, 2... Sample, 3... Exhaust port, 4
...First pipe, 5...Microwave power supply, 6...
・Discharge tube, 8... second pipe, 9... vessel,
12... Sample stand, 13... Cooling pipe, 21...
Si substrate, 22...gate oxide film, 23...gate electrode, 24...) first resist. Applicant's representative Patent attorney Takehiko Suzue 2nd diagram Figure 4 Poetry (Public) - Figure 5 148- On L ("C) - Figure 6 Figure 7

Claims (4)

[Claims] (1) In a dry etching method, a substrate to be processed having an organic compound film formed on its surface is placed in a reaction container, and a predetermined reactive gas is introduced into the container to remove the organic compound film. The substrate to be treated is cooled to a temperature at which the carbonization reaction of the organic compound film does not occur, and the gas introduced into the container is a reactive gas containing at least a halogen element, or a reactive gas containing at least a halogen element and another gas. A dry etching method characterized by using a mixed gas with. (2) The reactive gas containing the halogen element is CF_4
, C_2F_6, C_3F_8, F_2, NF_3, X
eF_2, F_3Cl, FCI_3, ClF_5, SF
_6, SiF_4, or a mixture of these gases or a mixture of these gases and other gases is excited with heat, light, discharge, or a charged beam in a region other than the inside of the container, and the reaction occurs there. 2. The dry etching method according to claim 1, wherein the dry etching method is one in which a toxic gas is generated and introduced into the container. (3) The gas containing the halogen element is CF_4, C_
2F_6, C_3F_8, F_2, NF_3, XeF_
2, F_3Cl, FCl_3, ClF_5, SF_6,
It is characterized by being a reactive gas produced by exciting any of SiF_4, mixed gases thereof, or mixed gases of these gases and other gases by performing gas discharge in the container. The dry etching method according to claim 1. (4) A substrate to be treated with an organic compound film formed on its surface is placed in a reaction vessel, the substrate to be treated is cooled to a temperature at which no carbonization reaction of the organic compound film occurs, and a gas containing fluorine is introduced into the vessel. Dry etching characterized by introducing a mixed gas of F active species generated by excitation in a region other than the container and oxygen or hydrogen, iodizing the organic compound film and removing the organic film. Method.