JPH11102899A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase resist selective ratio by having chemically amplified resist cured. SOLUTION: By introducing phosphorus ions into a chemically amplified photoresist 7 which serves as a mask, the surface layer of the resist 7 cures and its resist selectivity increases. Therefore, effective etching can be performed in simple steps. Especially, when phosphorus ions used as an ion species are implanted into the resist 7 by an ion-implantation method with a dose of 5×10<14> cm<-2> or more, the resist selectivity in an Al interconnection layer 6 is substantially further enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for etching a layer under a mask using a chemically amplified photoresist as a mask.

[0002]

2. Description of the Related Art For miniaturization of a semiconductor device such as a MOS device, it is extremely important to accurately etch a semiconductor layer, a conductive layer or an insulating layer by photolithography and etching. I have. One means is to increase the etching selectivity between a photoresist serving as an etching mask and a layer to be etched. For example, Japanese Patent Application Laid-Open No. Hei 2-177536 (H01L21 / 302) discloses that a photoresist is replaced with a silicon ion ( Cured by injecting Si ⁺ )
A technique of increasing the etching selectivity with respect to a silicon substrate under a resist and then performing dry etching is described.

[0003]

In the conventional example, some effects can be expected, but the higher the etching selectivity, the better, and further improvement is desired. The present invention has been made in view of the above problems, and has as its object to increase the etching selectivity between a chemically amplified resist and a layer thereunder by a simple process.

[0004]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein a layer under a mask is etched using a chemically amplified photoresist into which an impurity is introduced as a mask. The method of manufacturing a semiconductor device according to claim 2 is
A step of exposing the chemically amplified photoresist using laser light, a step of introducing impurities into the resist, and using the chemically amplified photoresist into which the impurities are introduced as a mask,
Etching the layer under the mask.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor device according to the second aspect, a KrF excimer laser beam is used as the laser beam. According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the first to third aspects, wherein phosphorus ions are used as the impurities, and the impurities are introduced into the photoresist by an ion implantation method. is there.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the first to fourth aspects, wherein a metal layer such as aluminum is etched. According to a sixth aspect of the present invention, in the method for manufacturing a semiconductor device according to the fourth or fifth aspect, the dose of the ions is set to 5 × 10 ¹⁴ cm ⁻² or more. That is, by introducing impurities such as phosphorus ions (P ⁺ ) into a chemically amplified photoresist as a mask, the resist is cured and the etching selectivity with a layer under the mask is increased.

The metal layer of aluminum or the like generally has a low selectivity with respect to the resist, but the use of a chemically amplified resist hardened by impurity implantation as a mask increases the selectivity with respect to the resist, thereby controlling the etching. Easier to do. In particular, 5 × 10 ¹⁴ for chemically amplified resist
When ions are implanted at a dose of not less than cm ^{−2, the} degree of increase in the resist selectivity is remarkable.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. 1 to 5 are views for explaining a process embodying the present invention. Step 1 (see FIG. 1): A silicon oxide film 2 (organic-silane-based TEOS oxide film) is deposited on a single-crystal silicon substrate 1 by a low-pressure CVD method to a thickness of 200 nm.
By a sputtering method, a TiN / Ti laminated thin film (thickness 1000/500 (total 1500)) 3, an Al alloy film (Al-Si (1%)-Cu (0.5%)) (thickness 60
A metal wiring layer 6 is formed by laminating a TiN thin film (thickness 200 °) 5 in this order, and a t-BOC-based chemically amplified photoresist (positive type) ( A film thickness of 0.8 μm) 7 is spin-coated.

Step 2 (see FIG. 2): Exposure using a KrF excimer laser, TMAH (Tetramethyl anmonium hyd)
ride) The resist 7 is patterned through a developing operation using a solution. Step 3 (see FIG. 3): Phosphorus ions (P ⁺ ) are implanted into the entire surface of the device by an ion implantation method. Thereby, phosphorus ions are introduced into the resist 7, the surface layer of the resist 7 is hardened, and the selectivity with respect to the resist is increased.

Step 4 (see FIG. 4): The metal wiring layer 6 is dry-etched using the resist 7 as a mask. This dry etching is performed using a normal magnetron RI.
Boron trichloride gas (BCl ₃ ) (flow rate 20 sccm) and chlorine gas (Cl ₂ ) using E (Reactive Ion Etching) method
(Flow rate 45 sccm) using a pressure of 30 mTor
Perform with r.

Step 5 (see FIG. 5): The resist 7 is
It is removed by a downstream ashing method using an amine-based stripping solution. FIG. 6 shows a case where the acceleration energy is 15
The relationship between the dose of phosphorus ions and the selectivity to resist under the condition of 0 KeV is shown.

As shown in the figure, as the ion dose increases, the selectivity with respect to the resist increases. In particular, in any case, the selectivity sharply increases when the dose is set at 5 × 10 ¹⁴ cm ⁻² as a bending point. It has increased. Therefore, in order to obtain a high resist selectivity, a dose amount of 5 ×
It can be seen that it is sufficient to set it to 10 ¹⁴ cm ^-2 or more. In particular, the acceleration energy is 150 KeV and the dose is 1.0 × 10
^{At 16} cm ^-2 , the selectivity to resist becomes 8, which is about 6 when ion implantation is not performed (about 1.3).
Double.

FIG. 7 shows the relationship between the dose of phosphorus ions and the etching rate under the same conditions as in FIG.
1 is shown for each of the alloys (AlSiCu). The etching rate of the Al alloy tends to slightly increase as the dose increases.

On the other hand, the etching rate of the resist rapidly decreases as the dose increases. That is, it can be seen that the amount of the resist hardened and the thickness of the resist reduced by etching is reduced. As described above, in the etching method of this embodiment, a high selectivity with respect to the resist can be obtained, and the amount of decrease in the resist film thickness due to ion implantation can be minimized. The effect can be obtained.

Here, the mechanism by which the selectivity to resist is improved by the method of the present invention will be described below. Four samples were used to analyze the mechanism. Sample (1): t-BOC chemically amplified photoresist without ion implantation Sample (2): acetal chemically amplified photoresist without ion implantation Sample (3): acceleration energy: 150 KeV, dose :
T-BOC-based chemically amplified photoresist implanted with phosphorus ions (P ⁺ ) under the condition of 1.0 × 10 ¹⁶ cm ⁻² Sample (4): acceleration energy: 150 KeV, dose:
Acetal-based chemically amplified photoresist in which phosphorus ions (P ⁺ ) were implanted under the condition of 1.0 × 10 ¹⁶ cm ⁻² FIG. 8 shows a sample (3) evaluated using a laser Raman method (Laser-Raman). 3 shows a Raman spectrum of a resist surface layer. A band can be observed in the range of 800 to 1900 / cm. When this band is analyzed in detail, a main band around 1550 / cm to 1570 / cm (FIG. 8A) and a shoulder band around 1390 / cm (FIG. 8B) ). These two Raman bands are
It is already known that a layered graphite structure (SP ² bond) and a diamond structure (SP ³ bond) are unique to a mixed diamond carbon film. For example, `` M.
Yoshikawa et al., Appl. Phys. Lett., 64 (1988) 6464.
In the diamond-like carbon film formed by the sputtering method, the main band was set at about 1550 / cm at 1400 / cm.
It has been reported that a Raman spectrum having a shoulder band around / cm is observed.
It is considered that the resist surface layer of (3) has a structure similar to the diamond-like carbon film in which SP ² bonds and SP ³ bonds are mixed.

Similar observations were made on sample (4), and the same Raman spectrum was observed as on sample (3). Thus, a diamond-like carbon film was formed on the resist surface layer of sample (4). It is thought that it is. The sample
Similar observations were made for (1) and (2), but no specific band was observed.

FIG.⁺Chemically amplified type implanted with ions
Shows the relationship between photoresist dose and resist thickness.
It is a thing. Ion implantation reduces resist thickness
This indicates that the initial resist film thickness
Acceleration energy: 150 KeV, dose: 1.0
× 10 ¹⁶cm^-23,000 yen (30
0 nm), and when the acceleration voltage is reduced, the film thickness
The amount of reduction is even smaller.

In FIG. 6, FIG. 7, and FIG. 9, the symbols .largecircle. Indicate the values when the t-BOC-based chemically amplified resist used in the present embodiment was used as a sample, and the symbols .circle-solid. Indicate the acetal-based chemically amplified resist. It shows the values when the mold resist was used as a sample. In the present invention, the same functions and effects can be obtained even if the following modifications are made.

1) TiN thin film, A
Although a metal wiring layer made of a 1 alloy film and a Ti / TiN laminated thin film was used, Ti and TiN serve to function as a so-called barrier metal and a cap metal.
An alloy film alone may be used, or a semiconductor layer such as a silicon substrate or an insulating layer such as a silicon oxide film may be used.

2) As an etching method, plasma RIE
Method, an etching method using various plasma sources such as ECR plasma etching, helicon wave plasma etching, ICP plasma etching, a sputter etching method using an inert gas, a reactive gas (for example, CCl
₄ , the same effect can be obtained by performing a reactive ion beam etching method (also called RIBE or reactive ion milling) using SF ₆ ).

[0021]

According to the etching method of the present invention, by introducing impurities such as phosphorus ions (P ⁺ ) into a chemically amplified photoresist as a mask, the resist is cured and the selectivity to the resist is reduced. Since the height is increased, the etching accuracy can be improved by a simple process, which greatly contributes to the advance of fine processing technology.

Particularly, for a chemically amplified resist, 5 × 1
By implanting ions at a dose of 0 ¹⁴ cm ⁻² or more, the selectivity to resist is significantly increased, and the above-described effect can be further promoted.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing an etching process in an embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing an etching process in an example of the present invention.

FIG. 3 is a process cross-sectional view showing an etching process in an example of the present invention.

FIG. 4 is a process sectional view showing an etching process in the example of the present invention.

FIG. 5 is a process sectional view showing an etching process in the example of the present invention.

FIG. 6 is a graph showing a relationship between a phosphorus ion dose and a resist selectivity.

FIG. 7 is a graph showing a relationship between a phosphorus ion dose and an etching rate.

FIG. 8 is a diagram showing a Raman spectrum of a photoresist into which phosphorus ions have been implanted.

FIG. 9 is a graph showing a relationship between a dose amount and a resist film thickness in a photoresist into which phosphorus ions have been implanted.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate (substrate) 4 Al alloy film 6 metal wiring layer 7 photoresist

Claims (6)

[Claims] 1. A method for manufacturing a semiconductor device, comprising etching a layer under a mask using a chemically amplified photoresist into which an impurity is introduced as a mask. 2. A step of exposing a chemically amplified photoresist using a laser beam, a step of introducing an impurity into the resist, and etching a layer under the mask using the chemically amplified photoresist into which the impurity has been introduced as a mask. The process of
A method for manufacturing a semiconductor device, comprising: 3. The method according to claim 2, wherein a KrF excimer laser beam is used as the laser beam. 4. The method of manufacturing a semiconductor device according to claim 1, wherein phosphorus ions are used as said impurities and are introduced into said photoresist by an ion implantation method. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the layer under the mask is a metal layer such as aluminum. 6. The ion dose of 5 × 10 ¹⁴ c
^{6. The} method for manufacturing a semiconductor device according to claim 4, wherein m ^-2 or more.