JP3278935B2 - Resist removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing a resist. The present invention can be used, for example, as a photoresist stripping method in a semiconductor manufacturing process. In particular, even for a resist which is difficult to remove, such as a photoresist after ion implantation at a high dose, a residue or the like is generated. Therefore, it can be applied as a method of peeling well.

[0002]

2. Description of the Related Art For example, in a conventional resist stripping process in a semiconductor process, an O ₂ plasma or the like is used instead of a wet process using fuming nitric acid or sulfuric acid and hydrogen peroxide (a mixed solution of nitric acid and hydrogen peroxide). The so-called dry ashing method used has been widely adopted even in mass production sites.

In this dry ashing process, the photoresist composed of an organic polymer is basically removed by a combustion reaction of CO and CO ₂ by the contribution of O radicals and O ₂ radicals generated in plasma. With a simple mechanism, the peeling of the ordinary photoresist material itself is relatively easy.

However, there are cases where it is difficult to remove the photoresist material. For example, resist stripping after ion implantation is not always easy. This is particularly problematic when a high dose ion implantation process is required, for example, in the case of forming source / drain regions for the manufacture of VLSI.

[0005] When a photoresist is used as a mask for ion implantation, ion implantation with a high dose and high energy is naturally performed in this resist. At this time, the heat caused by the ion bombardment is considered to be the main cause, but the surface of the resist is hardened. For example, it is not easy to remove the hardened layer only with ordinary O ₂ plasma, and the peelability of the resist is reduced. It will significantly deteriorate.

For example, more specifically, popping (Po
Residues may be produced by a phenomenon called pping). At the time of resist ashing, a process is usually performed while heating the semiconductor wafer to a high temperature of 200 ° C. or higher in order to increase the ashing rate. At this time, the solvent of the resist remaining inside the resist is naturally vaporized and discharged, but since the hardened layer is present on the resist surface after the high dose ion implantation, ashing does not easily proceed, and the solvent is not easily removed. Cannot be released after being vaporized, the internal pressure of the vaporized portion of the solvent increases rapidly inside the resist, and the resist is destroyed at a certain point. This phenomenon is called popping, and the surface hardened layer scattered by this rupture,
Inevitably becomes a residue and is difficult to remove.

Further, the hardened layer of the surface is not only intended to be formed by thermal, ion implanted dopants, causing a substitution to a crosslinking reaction in the molecular structure of the resist material, this portion O ₂ Since it is oxidized by plasma, it may be a residue as a difficult-to-etch layer as it is. If these remain, they become a source of contamination by particles, and may significantly reduce the yield of LSIs and the like.

As a countermeasure for this, a cured layer as described above is used.
A so-called two-step ashing method has been proposed in which an RIE process in which an H ₂ -based gas is added is removed by adding ion bombardment, and then normal ashing is performed (Proceedings of the Spring Meeting of the Japan Society of Applied Physics, 1989, 1P-). 13,
Fujimura et al. 574). However, this method requires additional steps and requires a large-scale apparatus. Further, there is a problem that the processing time of the H ₂ RIE takes a long time, and the throughput decreases. Therefore, a further improvement process is desired.

[0009]

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method of removing a resist which can easily remove and remove a resist which has been difficult to remove conventionally without causing contamination. It is something to offer.

[0010]

According to the invention of claim 1 of the present application, a hardened layer is formed on the surface by using it as a mask for ion implantation for forming source / drain regions of a semiconductor device. In the method of removing the resist by ashing, the used resist is treated with a resist solvent prior to the ashing to form a hole for degassing, and then ashing is performed to remove the resist. And then clean the remaining hardened layer
More physically removed or decomposed by plasma
A resist removal wherein the Rukoto, thereby is to achieve the above object.

The invention of claim 2 of the present application is directed to a semiconductor device.
Ion implantation mask for source / drain region formation
Used as a hardened layer on the surface
A resist removal method that removes dist by ashing
Before use by the ashing process
By treating the resist with a resist solvent,
A hole for punching holes is formed, and then ashing is performed to remove
And the ion implantation direction of the ion implantation.
Is tilted from the direction perpendicular to the surface to be ion-implanted.
The implantation hardens the resist on both side walls.
Ashing layer, and the ashing 2
Resist removal characterized by performing step ashing
The above-mentioned method achieves the above object.

According to a third aspect of the present invention, the liquid treatment is performed by using ultrasonic waves.
3. The method according to claim 1, wherein the step is performed while applying a voltage.
The resist removal method described above achieves the above object.

For example, the present invention can be implemented in an embodiment as shown in FIG. That is, a resist pattern is formed on a workpiece such as a semiconductor wafer or the like (Ia), and a base is patterned using the resist pattern as a mask (I).
Thereafter, liquid treatment is performed with a resist solvent or the like (II), and the resist after the treatment is removed by ashing (III).

[0014] As the liquid for liquid treatment in the present invention, such as by attack the vulnerable parts of the hardened resist as described later, resist solvent capable of dissolving here
Any agent can be used. For example, various solvents generally used as resist solvents can be used.

Table 1 below shows typical resist solvents and their physical properties.

[0016]

[Table 1]

[0017]

According to the present invention, a vulnerable portion of a hardened resist layer, for example, which has become difficult to be stripped after high dose ion implantation, is dissolved by liquid treatment, for example, treatment with a resist solvent. This prevents popping during ashing. As described above, the popping phenomenon at the time of resist ashing of high dose ion implantation is caused by the presence of the surface hardened layer by increasing the internal pressure of the solvent or the like in the resist, and therefore, the hardening occurs as in the case of gas removal. You can make holes in the layers. Liquid processing is performed as a means for forming the gas holes. It is a preferable embodiment to use a solvent originally used for dissolving the resin and the photosensitive agent in the resist.

Of course, since the resist surface is hardened by the high dose ion implantation, it is impossible to completely remove the resist even by using a resist solvent. However, the cured layer itself is not evenly formed over the entire patterned surface, but naturally has a weak portion depending on the injection angle and the like. Therefore, if only the vulnerable part is dissolved with a liquid (solvent), the part becomes a hole without gas, so that the occurrence of popping in the ashing process can be prevented.

If the cured layer finally left is physically removed by washing in a later step or is decomposed and removed by post-treatment with plasma, good resist ashing with no residue can be realized.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. Needless to say, the present invention is not limited by the embodiments.

Embodiment 1 In this embodiment, the present invention is applied to the manufacture of a semiconductor device.
It was used to remove the photoresist after ion implantation at a high dose. More specifically, as shown in FIG.
As ⁺ 1E16, 60 keV, ion implantation angle 0 ° o
ff, that is, ion implantation was performed perpendicularly to the surface of the substrate 1, and the present invention was applied to a photoresist stripping process after ion implantation was performed without forming an angle. In the figure, the ion implantation is schematically indicated by an arrow, and the cured layer 4 of the resist 3 is schematically indicated by hatching. Reference numeral 2 denotes an insulating material such as SiO ₂ which is a portion to be etched.

The sample after ion implantation was immersed in ethyl lactate, which is said to be relatively easy to dissolve the photosensitive agent, as a processing liquid. At this time, the ion implantation was originally performed at 0 °
The hardened layer 4 is also thin near the bottom of the pattern due to the shadow effect, and a part of the hardened layer is melted by the ethyl lactate treatment (FIG. 3). The portion removed by dissolution is indicated by reference numeral 5.

Thereafter, the sample was transferred to a microwave downstream type ashing apparatus, and ashing was performed under the following conditions. (Ashing condition) Gas used: O ₂ / N ₂ = 950/50 SCCM Pressure: 133 Pa μ wave power: 1 kWatt Wafer temperature: 250 ° C. In normal ashing, the resist during peeling is popping at this high temperature processing of 250 ° C. However, in this embodiment, since a part of the hardened layer is melted and a hole for degassing is formed, popping does not occur, and ashing is performed while leaving only the hardened layer 4. You can end (Fig. 4).

Thereafter, when the sample was washed with, for example, sulfuric acid / hydrogen peroxide using a spin processor, the cured layer 4 was successfully removed as shown in FIG. 5 due to the effect of the physical rotation of the spin processor. .

Example 2 A resist having the same structure as in Example 1 was peeled off under the following conditions.

In this embodiment, the ion implantation is performed by P ⁺ 1E1
The ion implantation was performed under the condition of 6,60 keV and at an angle of 7 ° off, that is, at an angle of 7 ° from the direction perpendicular to the substrate surface (FIG. 6). In FIG. 6, the direction of ion implantation is clearly indicated by an arrow that is extremely angled.

Since the wafer is generally ion-implanted while being rotated, the side walls of the resist are also attacked by ion implantation (see the ion implantation directions from both sides in FIG. 6).

The sample after use of the resist was immersed in cyclohexanone. By this treatment, the vulnerable part of the hardened layer 4 is dissolved in cyclohexanone. Of course, compared to resins, ordinary photosensitizers are harder to dissolve in such solvents, but they do not mean to dissolve them all, but only to make gas holes to prevent popping. Therefore, it is sufficient to melt only a weak part and make a minute hole as the dissolution removal part 5 (FIG. 7).

The sample was then transferred to a microwave downstream type ashing apparatus, and two-step ashing was performed under the following conditions.

Step I Gas system used: O ₂ / N ₂ = 950/5
0SCCM pressure: 133 Pa μ wave power: 1 kWatt Wafer temperature: 250 ° C. Step II Gas used: O ₂ / S ₂ F ₂ = 950
/ 50 SCCM Pressure: 133 Pa Microwave power: 1 kWatt Wafer temperature: 250 ° C. Since a gas vent hole is formed by the solvent treatment, the ashing is performed by the treatment in Step I without popping, leaving only the cured layer 4. The process ends (FIG. 8).

The decomposition of the hardened layer proceeds in the S ₂ F ₂ adding ashing process of the next step II, so that the hardened layer can be removed to some extent (FIG. 9).

Finally, all the residues were removed through a cleaning step using fuming nitric acid or the like, and clean ashing was realized (FIG. 10).

Example 3 In this example, the same process as in Example 2 was performed.
However, the immersion treatment using cyclohexanone was performed while applying ultrasonic waves. As a result, more efficient resist stripping was realized. In this embodiment, an arbitrary ultrasonic wave applying device can be used, and the conditions are also arbitrary. Here, specifically, ultrasonic vibration is added by applying DC power (for example, applying 200 W) to the crystal ultrasonic vibrator. The ultrasonic vibration can be given, for example, at a frequency of 15 to 1 MHz at 1 to 10 W.

Example 4 In this example, the cured layer remaining after the liquid (solvent) treatment was
The decomposition treatment is performed by a plasma treatment in which an F system or a gas system containing any of CO, NO, and SO molecules is added.

In this embodiment, a gas to which at least CO is added is used as an ashing gas.
The ashing may be divided into two steps, and the residue resulting from the first step may be removed by CO-adding ashing at the time of over-ashing, and at least CO may be H ₂ or H ₂ O, NH ₃ or the like. A gas system obtained by adding a source gas may be used, or an F-based gas may be added to the gas.

In this embodiment, As ⁺ is set to 1E16, 60k
A photoresist sample (photoresist is TSMR-V3) after ion implantation with eV was subjected to the same liquid treatment as in Example 1, and the sample was set on a plasma asher utilizing microwave discharge. Ashing was performed under the following conditions. Gas: O ₂ / CO = 800/200 sccm Pressure: 266 Pa Microwave power: 1 kW Susceptor temperature: 250 ° C.

According to the present embodiment, good ashing without residue can be realized.

Example 5 In Example 4, the liquid treatment was performed while applying ultrasonic waves as in Example 3. Others were the same as in Example 4, and good results were obtained.

[0039]

According to the resist removing method of the present invention, it is possible to easily remove and remove the resist which has been conventionally difficult to remove without causing contamination.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration example of the present invention.

FIG. 2 is a cross-sectional view of a material to be processed, showing a process of Example 1 (1).

FIG. 3 is a cross-sectional view of a process target material, illustrating a process of Example 1 (2).

FIG. 4 is a cross-sectional view of the material to be processed, illustrating the process of Example 1 (3).

FIG. 5 is a cross-sectional view of the material to be processed, illustrating the process of Example 1 (4).

FIG. 6 is a cross-sectional view of a material to be processed, illustrating a process of Example 2 (1).

FIG. 7 is a cross-sectional view of a process target material, illustrating a process of Example 2 (2).

FIG. 8 is a cross-sectional view of the material to be processed, illustrating the process of Example 2 (3).

FIG. 9 is a cross-sectional view illustrating the process of the second embodiment of the material to be processed (4).

FIG. 10 is a cross-sectional view of a process target material, illustrating the process of Example 2 (5).

[Explanation of symbols]

 I Use of resist II Liquid (solvent) treatment III Ashing 1 Substrate 3 Resist 4 Hardened layer 5 Dissolution remover

Continuation of front page (56) References JP-A-3-174723 (JP, A) JP-A-4-111308 (JP, A) JP-A-4-242920 (JP, A) JP-A-2-18931 (JP) JP-A-1-101633 (JP, A) JP-A-4-28219 (JP, A) JP-A-3-261128 (JP, A) JP-A-61-162045 (JP, U) JP-A 61-164030 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (3)

(57) [Claims] 1. A method for forming a source / drain region of a semiconductor device.
In a resist removal method of removing a resist having a hardened layer on its surface by using ashing by using it as a mask for ion implantation, the used resist is treated with a resist solvent prior to the ashing treatment. A hole for degassing is formed, then ashing is performed to remove and remove
After that, the remaining hardened layer is physically removed by washing.
Or a method for removing resist by plasma . 2. A method for forming a source / drain region of a semiconductor device.
By using it as a mask for ion implantation
Remove the resist with a hardened layer on the surface by ashing.
In the method of removing the resist, the used resist is used prior to the ashing process.
For degassing by treating with a resist solvent
And then ashing is performed to remove and remove
Rutotomoni, the ion implantation direction of the ion implantation, the row Ukoto ion implantation is inclined from the vertical direction with respect to the ion implanted surface
The resist has a hardened layer on both side walls
, And the and resist removal method and performing in the ashing 2 step ash. 3. A resist removal method according to claim 1 or 2 liquid processing, and performs while ultrasound was marked pressure.