JP2001237229A - Substrate treatment method, substrate treatment equipment and device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize plasma ashing wherein treatment time is short and the etching amount of base substance is small in ashing treatment of resist. SOLUTION: Mixed gas whose main component is water vapor and fluorine based gas like SF6 is introduced from a gas supply tube 14 into a plasma generating chamber 10. Decomposition is performed by using microwave supplied from a waveguide 12, and resist on a wafer W is eliminated by using generated mixed gas plasma. In the case of resist having a cured layer which is formed by ion implantation, peeling is effectively performed by fluorine radical, and the etching amount of a base substance oxide layer can be restrained to be at most several Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist ashing step, and more particularly, to a substrate processing method capable of effectively ashing a resist hardened by ion implantation in a processing step of a semiconductor wafer or the like. The present invention relates to a substrate processing apparatus and a device manufacturing method.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a photoresist applied to a substrate such as a wafer is frequently removed and removed. In the stripping of the resist, ashing using oxygen plasma which can realize safety and low cost is mainly used.

FIG. 5 illustrates a conventional substrate processing method. As shown in FIG.
On top, a pattern of a resist 102 is formed,
The substrate 10 using the pattern of the resist 102 as a mask
For example, phosphorus ions P are implanted with an ion acceleration energy of 80 KeV and an implantation amount of 1 × 10 ¹⁶ ions.
/ Cm ² (see FIG. 5B). At the time of this ion implantation, the kinetic energy of the ions is converted to heat energy to cause a thermal change, and a hardened layer 103 is formed as shown in FIG.

Conventionally, when removing the resist 102 on which the cured layer 103 is formed, the cured layer 103 is removed by using oxygen plasma and the cured layer 103 is removed.
The non-hardened resist layer existing underneath was also removed by oxygen plasma.

When an oxygen plasma containing oxygen as a main gas is used, the ion implanted species contained in the hardened layer 103 are
Since a large amount of phosphorus, dirt and the like remains on the substrate 101 as the oxide M, this is removed by a chemical process after ashing.

[0006]

However, in the conventional ashing using oxygen plasma, it takes 5 minutes to perform ashing of a resist cured layer which has been cured by ion implantation.
There is a problem that it takes as long as 10 minutes. This is the "Japanese Journal of App"
led Physics Vol. 28, No. 1
0, October, 1989, pp. 100-150. 2130-21
36 Ashing of Ion-Implant
As disclosed in “d Resist Layer”, the structure of the cured layer is such that the methyl group of the main chain of the benzene ring of the novolak resin, which is the main component of the resist, is replaced with phosphorus, lime, etc., and forms a firm bond It is thought to be.

In order to remove the cured layer, Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 275326, a method of ashing a hardened layer by fluorine radicals using oxygen plasma obtained by adding about 0.1 to 5% of CF ₄ to a gas containing O ₂ as a main component. Has been proposed. The use of fluorine radicals in the step of removing the ion-implanted resist is concerned with etching of the gate oxide film of the exposed substrate by the fluorine radicals.
According to -275,326 No. technique to suppress in order to dispel this concern, the base etching amount of 10 Å or less by the amount of CF ₄ in a small amount of 0.1% to 5%, of 16MDRAM level It is said to adapt to manufacturing technology.

However, recently, as the fine processing is further advanced, it is necessary to keep the etching amount of the base oxide film at a level of several angstroms or less.

Further, as a new problem, in ashing with high reactivity by fluorine radicals, there is a problem that the etching amount of the base oxide film cannot be controlled with good reproducibility. This is presumably because the fluorine radical itself has a relatively long life, and unreacted atomic fluorine is adsorbed onto a substrate such as a wafer, thereby etching the base even after ashing.

[0010] JP-A-5-275326 is to remove the hardened layer in the first step, (O ₂ + CF ₄₎ ashing the second step, stripping the lower resist that is not cured (O ₂ + N ₂ ), in which ashing is performed with an underlayer etching amount of 10 angstroms or less and a high peeling speed. However, in this case, it took 10 seconds to switch between the first step and the second step, and the present inventors have confirmed that, when this time was approached to almost 0 second, the etching amount of the base oxide film was reduced. There was a tendency to increase from several angstroms to several hundreds of angstroms. It is known that fluorine radicals generally do not react with organic substances by themselves, but experiments conducted by the present inventors have revealed that the supply of oxygen radicals is likely to contribute to the reaction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unresolved problems of the prior art, and is intended to improve the releasability in a plasma ashing step of removing a resist having a cured layer formed by ion implantation. It is an object of the present invention to provide a substrate processing method, a substrate processing apparatus, and a device manufacturing method that can further reduce the amount of etching of a base by fluorine radicals while using fluorine radicals, and that can be controlled with good reproducibility. .

[0012]

In order to achieve the above-mentioned object, a substrate processing method according to the present invention uses a plasma of a mixed gas mainly containing water vapor and a fluorine-based gas in an ashing step of an ion-implanted resist. And removing the resist.

Further, the substrate processing apparatus of the present invention has a chamber having an exhaust means, a substrate holding means for holding a substrate in the chamber, and a gas introducing means for introducing water vapor and a fluorine-based gas into the chamber. A plasma generating means for generating plasma in the chamber.

[0014]

[Function] Plasma is generated by using water vapor having an ashing ability by itself and a mixed gas containing SF ₆ or NF ₃ as a main component, which is a fluorine-based gas which is considered to be capable of supplying a fluorine radical effective for removing a cured layer of a resist. The generation supplies an appropriate amount of fluorine radicals and vaporizes or eliminates atomic fluorine which is considered to remain on the substrate in a small proportion. As a result, the amount of base etching can be suppressed to several angstroms or less with good reproducibility, and the ion-implanted resist can be quickly and effectively removed.

Unlike in the case where oxygen plasma is used, a large amount of residue due to the oxidation of the ion-implanted species contained in the cured layer of the resist does not remain.

In order to further reduce the oxide residue of the ion-implanted species, hydrogen containing no oxygen seems to be more advantageous than water vapor having oxygen as a constituent molecule.
When a hydrogen gas or a hydrogen compound containing no oxygen is used, the ashing rate becomes extremely low, and the speed is almost the same as that of plasma ashing using a gas containing only oxygen. Therefore, water vapor and SF ₆ or NF ₃
Is desirable.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a microwave plasma ashing processing apparatus which is a substrate processing apparatus according to an embodiment, which includes a plasma generation chamber 10 which is a chamber having an exhaust port 10a, and a plasma generation chamber 10 inside the plasma generation chamber 10. A wafer holder 11 as a substrate holding means for holding a wafer W as a substrate, and a microwave oscillator 12 as a plasma generating means
a, a waveguide 12 for supplying microwaves into the plasma generation chamber 10 from the a and a microwave transmission made of flat-plate quartz having a relative permittivity ε = 3.8 or alumina having a relative permittivity ε = 9.7. Water vapor and SF in the window 13 and the plasma generation chamber 10
₆ or a gas supply pipe 14 as a gas introduction means for introducing a mixed gas containing a fluorine-based gas such as NF ₃ as a main component.
And a mass flow controller 15 for controlling the supply amount of the mixed gas.

The inside of the plasma generation chamber 10 is evacuated by a vacuum pump 16 which is an exhaust means connected to an exhaust port 10a, and an adjustment valve 17 for controlling an exhaust amount and a mass flow controller 15 for controlling a supply amount of a mixed gas are provided. By adjusting, the inside of the plasma generation chamber 10 is maintained at a predetermined pressure, microwaves are introduced from the waveguide 12 into the plasma generation chamber 10,
The mixed gas of the water vapor and the fluorine-based gas supplied from the gas supply pipe 14 is decomposed by microwave energy and turned into plasma.

This plasma causes the wafer holder 11
Ashing processing of the upper wafer W is performed.

FIG. 2 illustrates the ashing of a substrate such as a wafer, which is a substrate processing method using the above-described substrate processing apparatus. As shown in FIG. In order to ion-implant the substrate 1 using the pattern of the resist 2 as a mask, for example, phosphorus ions P are ion-accelerating energy of 80 Ke.
V is implanted under the conditions of an implantation amount of 1 × 10 ¹⁶ ions / cm ² (see FIG. 2B). At the time of this ion implantation, the kinetic energy of the ions is converted into thermal energy to cause a thermal change, and a cured layer 3 is formed as shown in FIG. As described above, the resist 2 having the cured layer 3 is removed by ashing using plasma of a proper amount of water vapor and a mixed gas containing SF ₆ or NF ₃ as a main component.

Compared to the case of using a mixed gas plasma of O ₂ and CF ₄ as in the conventional example, the amount of etching of the base oxide film on the surface of the substrate 1 is smaller, and the ashing time is 1/3 to 2 times. / 3, and the residue after ashing is reduced to about 1/3 of the conventional example.

The mechanism by which such an effect appears is that fluorine radicals cut the polymer main chain and side chains of the cured layer 3 altered by ion implantation, and hydrogen,
Alternatively, it is considered that the resist is efficiently removed by bonding and volatilization of oxygen or fluorine.

At this time, the ion-implanted species such as phosphorus and whisker that have entered the hardened layer 3 by ion implantation include fluorine F,
It is thought that it combines with hydrogen H and evaporates.

Further, since the absolute number of oxygen is smaller than that of oxygen plasma ashing mainly composed of oxygen, as shown in FIG. 2D, oxides M such as phosphorus and lime remaining on the surface of the substrate 1 are formed. And the burden on post-treatment chemical treatment is small.

Further, since water vapor traps fluorine F, it is easy to control a very small concentration of fluorine.
The amount of etching of the base oxide film by atomic fluorine, which is considered to be adsorbed to the surface of the substrate 1 at a small ratio, is always stably suppressed to several angstroms or less.

Usually, when ashing an ion-implanted resist, ashing is performed at a low temperature of 150 ° C. or less in order to avoid burst of the ion-implanted resist. In the mass production process, ashing may be performed at a temperature equal to or higher than 150 ° C. by setting the ashing temperature to another ashing process in view of the management of the apparatus. In this case, due to the difference in thermal expansion coefficient between the cured layer and the non-cured layer, the resist pattern may cause a burst,
The burst resist fragments may overlap, and a residue containing a hardened layer component may remain after ashing.

If the wafer temperature is the same, the substrate processing method according to the present embodiment is considered to be superior to the prior art because the ashing rate is high and the amount of etching of the underlying oxide film is small.

In the plasma ashing according to this embodiment, in addition to microwave plasma, parallel plate plasma using high frequency, ECR plasma, helicon plasma, plasma using ICP, or downstream (downflow) of these plasmas The ashing method performed in step (1) is used.

Further, as the mixed gas used for the plasma ashing according to the present embodiment, it is desirable to use a mixed gas of steam and SF ₆ or a mixed gas of steam and NF ₃ .
If the fluorine concentration is too high, the exposed base oxide film may be etched more than necessary. Therefore, the gas mixture ratio is adjusted to an appropriate range according to the etching amount.

(Embodiment 1) Processing is performed at a wafer temperature of around 130 ° C. where no resist burst occurs. A wafer such as a glass substrate or a quartz substrate is placed on a wafer holder in the plasma generation chamber of the microwave plasma processing apparatus shown in FIG. 1, an adjustment valve is opened, and the plasma generation chamber is exhausted from an exhaust port. Next, a processing gas is introduced from a gas supply pipe. A mass flow controller provided in communication with the exhaust port is adjusted to introduce a predetermined flow rate of the mixed gas. In this embodiment, steam, that is, H ₂ O gas is supplied at about 400 sccm, and SF ₆ is supplied at about 80 sccm. In this way, the plasma generation chamber is maintained at a predetermined pressure lower than the atmospheric pressure. Specifically, it is desirable to maintain the pressure at about 65.5 Pa. The wafer temperature is kept at 130 ° C. Then, the microwave is generated by operating the microwave oscillator having the adjusting means for adjusting the intensity of the microwave output. The generated microwave is propagated along the waveguide and supplied into the plasma generation chamber through a microwave transmission window made of alumina or quartz. By the supplied microwave energy, the processing gas is decomposed to be in a plasma state. As a result, ashing as shown in FIG. 2 was performed, and the ashing time was 100 seconds. When the etching rate of the thermal oxide film was examined under the same conditions, the etching amount of the base oxide film was about 3 Å. When the number of residues was measured with a particle counter to measure the number of residues at this time, about 70 particles of 0.2 μm or more were found.

(Comparative Example 1) Processing is performed at a wafer temperature around 130 ° C. where no resist burst occurs. A wafer such as a glass substrate or a quartz substrate is placed on a wafer holder in the plasma generation chamber of the microwave plasma processing apparatus shown in FIG. 1, an adjustment valve is opened, and the plasma generation chamber is exhausted from an exhaust port. Next, a processing gas is introduced from a gas supply pipe. The mass flow controller provided in communication with the exhaust port was adjusted so that O ₂ gas was about 500 sccm and CF ₄ was 1 s.
Ccm was supplied. In this way, the plasma generation chamber is maintained at a predetermined pressure lower than the atmospheric pressure. Specifically, 6
It is desirable to keep it at about 5.5 Pa. The wafer temperature is kept at 130 ° C. Then, the microwave is generated by operating the microwave oscillator having the adjusting means for adjusting the intensity of the microwave output. The generated microwave is propagated along the waveguide and supplied to the plasma generation chamber through a microwave transmission window made of alumina or quartz. By the supplied microwave energy, the processing gas is decomposed to be in a plasma state. As a result, ashing was performed, and the ashing time was 300 seconds. When the etching rate of the thermal oxide film was examined under the same conditions, the etching amount of the base oxide film was about 50 angstroms. In order to measure the number of residues at this time, when the number of residues was checked with a particle counter,
The number of particles having a size of 0.2 μm or more was about 150.

(Embodiment 2) Processing is performed at a wafer temperature of 130 ° C. or more where a burst of resist occurs. A wafer such as a glass substrate or a quartz substrate is placed on a wafer holder in the plasma generation chamber of the microwave plasma processing apparatus shown in FIG. 1, an adjustment valve is opened, and the plasma generation chamber is exhausted from an exhaust port. Next, a processing gas is introduced from a gas supply pipe. A mass flow controller provided in communication with the exhaust port is adjusted to introduce a predetermined flow rate of the mixed gas. In this embodiment, about 400 sccm of water vapor, that is, H ₂ O gas,
SF ₆ was supplied at about 80 sccm. In this way, the plasma generation chamber is maintained at a predetermined pressure lower than the atmospheric pressure. Specifically, it is desirable to maintain the pressure at about 65.5 Pa. The wafer temperature is kept at 200 ° C. Then, the microwave is generated by operating the microwave oscillator having the adjusting means for adjusting the intensity of the microwave output. The generated microwave is propagated along the waveguide and supplied into the plasma generation chamber through a microwave transmission window made of alumina or quartz. By the supplied microwave energy, the processing gas is decomposed to be in a plasma state. As a result, ashing as shown in FIG. 2 was performed, and the ashing time was 50 seconds. When the etching rate of the thermal oxide film was examined under the same conditions, the etching amount of the base oxide film was about 6 angstroms. When the number of residues was measured with a particle counter to measure the number of residues at this time, about 3000 particles having a size of 0.2 μm or more were found.

(Comparative Example 2) Processing is performed at a wafer temperature of 130 ° C. or higher at which a resist burst occurs. A wafer such as a glass substrate or a quartz substrate is placed on a wafer holder in the plasma generation chamber of the microwave plasma processing apparatus shown in FIG. 1, an adjustment valve is opened, and the plasma generation chamber is exhausted from an exhaust port. Next, a processing gas is introduced from a gas supply pipe. The mass flow controller provided in communication with the exhaust port was adjusted so that O ₂ gas was about 500 sccm and CF ₄ was 1 s.
Ccm was supplied. In this way, the plasma generation chamber is maintained at a predetermined pressure lower than the atmospheric pressure. Specifically, 6
It is desirable to keep it at about 5.5 Pa. The wafer temperature is kept at 200. Then, the microwave is generated by operating the microwave oscillator having the adjusting means for adjusting the intensity of the microwave output. The generated microwave is propagated along the waveguide and supplied into the plasma generation chamber through a microwave transmission window made of alumina or quartz. With the supplied microwave energy,
The processing gas is decomposed into a plasma state. As a result, ashing was performed, and the ashing time was 100 seconds. When the etching rate of the thermal oxide film was examined under the same conditions, the etching amount of the base oxide film was about 100 angstroms. In order to measure the number of residues at this time,
When the number of residues was checked using a particle counter,
The number of particles having a size of 2 μm or more was about 10,000.

The number of particles of Example 2 was 3000.
Although the number of pieces appears to be a relatively large number, in the case of ashing using only oxygen, since the number is generally several tens of thousands, it can be seen that the peelability is good. In addition, the hardware and process specialized in the stripping of the ion-implanted resist described in the abstract of the 50th Autumn Meeting of the Japan Society of Applied Physics (1988) Hydrogen ions are used to destroy the cured layer polymer, supply hydrogen to the slices, and combine the organic component and ion-implanted species with hydrogen to completely vaporize them.) The number of particles is on the order of 2,000 particles, and in the present invention, the same level of peeling performance is obtained with a normal plasma device without using a dedicated plasma device.

By the way, the addition amount of SF ₆ is about 16% in the above embodiment, but if it is less than this range, the ashing time is slightly longer, but the etching amount of the underlying oxide film is smaller. Therefore, it can be said that the process has a wide margin with respect to the addition amount and the prevention of the etching of the base oxide film.

Next, a device manufacturing method using the above-described substrate processing method will be described. FIG. 3 shows a manufacturing flow of a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern designed. In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon.
Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. Step 5
(Assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in Step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 4 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development)
Then, the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed.
In step 19 (resist removal), unnecessary resist after etching is removed by the above-described substrate processing method. By repeating these steps, multiple circuit patterns are formed on the wafer. By using the device manufacturing method of the present invention, it is possible to manufacture a highly integrated semiconductor device which has been conventionally difficult to manufacture.

[0039]

Since the present invention is configured as described above, the following effects can be obtained.

In plasma ashing using a gas containing fluorine, the amount of etching of the underlying oxide film can be kept to several angstroms, the ashing time of the ion-implanted resist can be greatly reduced, and the removability of the resist can be improved. As a result, it is possible to reduce the cost of the chemical solution treatment following the ashing, reduce the cost, and contribute to improving the yield of semiconductor devices and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a substrate processing apparatus according to one embodiment.

FIG. 2 is a diagram illustrating a substrate processing method according to one embodiment.

FIG. 3 is a flowchart showing a semiconductor manufacturing process.

FIG. 4 is a flowchart showing a wafer process.

FIG. 5 is a diagram illustrating a substrate processing method according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Resist 3 Hardened layer 10 Plasma generation chamber 11 Wafer holder 12 Waveguide 14 Gas supply pipe 15 Mass flow controller 16 Vacuum pump 17 Adjustment valve

Continued on the front page (72) Inventor Keisuke Shinagawa 3-11-28 Mita, Minato-ku, Tokyo Canon Sales Co., Ltd. (72) Inventor Jin 3-11-28 Mita, Minato-ku, Tokyo Canon Sales Co., Ltd. F term (reference) 2H096 AA25 HA30 JA04 LA08 5F004 AA16 BA20 BD01 DA00 DA01 DA17 DA18 DA25 DA26 DB26 FA02 5F046 MA05 MA12

Claims (4)

[Claims] 1. A method of processing a substrate, comprising: in an ashing step of an ion-implanted resist, the resist is removed by using plasma of a mixed gas mainly composed of water vapor and a fluorine-based gas. 2. The substrate processing method according to claim 1, wherein the fluorine-based gas contains SF ₆ or NF ₃ . 3. A chamber having an exhaust means, a substrate holding means for holding a substrate in the chamber, a gas introducing means for introducing water vapor and a fluorine-based gas into the chamber, and generating a plasma in the chamber. A substrate processing apparatus having a plasma generating means for causing the plasma processing means. 4. A device manufacturing method comprising a step of processing a wafer by the substrate processing method according to claim 1.