JP2002141411A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device which realizes the surface protection while controlling the etched shape of a benzocyclobutene layer. SOLUTION: On the surface of the benzocyclobutene layer, a metal layer having a large affinity with oxygen and a resist layer are formed. The metal layer having a large affinity with oxygen is etched by a pattern formed in the resist so that an opening formed in the resist may be enlarged. Thereafter, with the resist as a mask, the layer is etched to form the top edge of the benzocyclobutene layer into a tapered shape. After the etching of the benzocyclobutene layer, following processes are conducted, with the surface of the layer coated with a metal layer having a large affinity with oxygen, preventing the deterioration of benzocyclobutene due to oxidization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a semiconductor using an organic insulating film. More specifically, according to the semiconductor manufacturing method of the present invention, it is possible to prevent the deterioration of the organic insulating film and provide a stable process.

[0002]

2. Description of the Related Art In recent years, in a semiconductor device, a distance between wirings has been reduced with an increase in integration degree, and an electric capacity between wirings has been increased. When the capacitance between wirings increases, problems such as an increase in power consumption and a decrease in signal processing speed occur. Therefore, the interlayer insulating film is formed using a material having a low dielectric constant to reduce the capacitance between wirings. Benzocyclobutene is used as such a material having a low dielectric constant. Benzocyclobutene is a low-dielectric-constant organic material and further has a characteristic of a low dielectric loss, so that it is used as an insulating layer, and particularly, its use at high frequencies is becoming popular.

As a conventional example of a method of manufacturing a semiconductor device using benzocyclobutene as a material of an insulating film, an etching mask made of a metal film and a resist is formed on an insulating film layer of benzocyclobutene to form a benzocyclobutene layer. Is disclosed in Japanese Patent Application Laid-Open No. 10-256234.
Is disclosed. In this method, if a resist is used, an etching selectivity with benzocyclobutene cannot be obtained, and high-precision etching cannot be performed. Therefore, a two-layer film of a metal film and a resist film is used. FIG.
1 shows a cross-sectional view of a conventional example disclosed in 256256. The feature of this method is that the insulating film layer 402 such as benzocyclobutene formed on the substrate and the lower wiring 401 is formed by using a gas obtained by adding 1 to 10% by volume of CF ₄ , He or Ar to oxygen. , WSi, WSiN or Ti or other metal layer 4
That is, dry etching is performed with high accuracy using 03 as a mask. In addition, the shape characteristic here is that the metal layer 403
When the insulating layer is etched using
04 and the insulating layer 402 cannot be selected, and the resist recedes from the metal mask. Before the etching of the insulating layer 402, the metal layer 403 has been etched in advance using the resist 404 as a mask. Insulating layer 402
Then, the resist 404 is removed by an organic solvent or oxygen reactive ion etching (RIE), and the metal layer 403 is removed by dry etching such as SF ₆ .

[0004]

In the prior art, since an etching gas mainly composed of oxygen is used, accurate processing can be performed with a metal mask having a high selectivity, but the cross-sectional shape of the etched portion has a steep angle. Therefore, when the electrodes are contacted via the insulating layer, there is a problem that disconnection or high resistance due to unstable connection occurs. Further, the etching gas mainly composed of oxygen may change the characteristics of the insulating layer. In addition, when the metal of the mask is removed by dry etching using SF ₆ or the like, the surface of the insulating layer is also exposed to SF ₆ , thus causing deterioration. That is, the benzocyclobutene layer is also partially etched by SF ₆ , and the surface state deteriorates. By SF _6, only the silicon component in the benzocyclobutene is subjected to etching, there is a problem of roughening the surface. These rough surface states impair the function of benzocyclobutene as a passivation film.

[0005] In addition, benzocyclobutene is oxidized by oxygen, and the surface state is degraded. Specifically, when the benzocyclobutene film is exposed to oxygen plasma for a long time or is heated in an oxygen atmosphere, the surface peels off, the dielectric constant and the dielectric loss increase, and it is inherently water-repellent. The surface becomes hydrophilic, and does not function as a protective film.

[0006]

Accordingly, in order to solve the above-mentioned problems, the present invention provides a method for manufacturing a semiconductor device without deteriorating a benzocyclobutene layer which is liable to be deteriorated by SF ₆ and oxygen. . Further, the present invention provides a method for manufacturing a semiconductor device capable of forming a contact hole having a low contact resistance and no disconnection.

The present invention provides a method for removing a metal layer by wet etching after using a metal layer formed on the benzocyclobutene layer having a high affinity for oxygen as an etching mask for etching benzocyclobutene. A method for manufacturing a semiconductor device is provided.

According to the method of manufacturing a semiconductor device of the present invention, a metal layer formed on a benzocyclobutene layer and having a high affinity for oxygen is masked with a resist, and the opening of the metal layer is formed by excessive etching. The benzocyclobutene layer is etched from the opening of the resist, and then the benzocyclobutene layer is etched using the resist as a mask, whereby the opening of the benzocyclobutene having a tapered upper end controlled by the opening of the metal layer. It is characterized by forming.

Further, in the method of manufacturing a semiconductor device according to the present invention, the metal layer on the benzocyclobutene comprises a metal having a high affinity for oxygen and a metal layer used for wiring formed thereon. After patterning the metal layer used for wiring by using the layer as a power supply metal for electrolytic plating, the metal layer used for wiring in portions other than the patterned portion is removed by wet etching, and the oxygen on the benzocyclobutene layer is removed with the oxygen. The process proceeds in a state of being covered with a metal having a high affinity, and is finally removed by wet etching.

In a preferred embodiment, the metal layer having a high affinity for oxygen is formed using titanium, aluminum, tungsten, copper or nickel.

In the present invention, phosphoric acid, hydrochloric acid, hydrofluoric acid, sulfuric acid or nitric acid is used as an etchant used for wet etching.

[0012]

FIG. 1 is a sectional view showing a process of the present invention.
(A) and (B). A benzocyclobutene layer 2 formed on a gallium arsenide or silicon substrate 1
It is covered with a layer of a metal having a high affinity for oxygen, for example, a titanium layer 3. The titanium layer can be formed by electron beam evaporation or sputtering. Further, the titanium layer 3 is covered with the resist 4, and from the opening of the resist 4,
The titanium layer 3 is opened by dry etching. When etching the titanium layer 3, etching conditions are set so that an opening larger than the opening of the resist 4 is obtained. Specifically, by performing dry etching using a fluorine-based gas such as SF ₆ containing no carbon,
By performing the etching under the condition that the isotropic etching can be realized and the etching can be performed about three to four times the film thickness, the opening of the titanium layer 3 can be wider than the opening of the resist 4. Further, the opening of the titanium layer 3 can be wider than the opening of the resist 4 by wet etching using an acid such as phosphoric acid or hydrofluoric acid. The size of the opening can be controlled by conditions such as etching time.

The benzocyclobutene layer 2 is opened using the resist 4 as a mask. In the portion where the titanium layer 3 is over-etched, the benzocyclobutene layer 2 is also etched, and the top edge of the benzocyclobutene layer 2 becomes substantially equal to the edge of the titanium layer 3. After that, resist 4
Is removed by an organic solvent or the like.
It is removed by phosphoric acid heated to 0 ° C. to 100 ° C. (FIG. 1B). As a result, the benzocyclobutene layer 2 is exposed, but the surface state is water-repellent as in the initial stage of film formation. In a normal resist stripping step, after cleaning with an organic solvent or the like, a step of removing surface residues by ashing using oxygen plasma (ashing) is included. During this step, the benzocyclobutene layer 2 is When exposed to the surface, benzocyclobutene is degraded by oxygen plasma, and the water repellency, one of the original features of benzocyclobutene, is lost. Here, if wet etching is not used when removing the metal layer, the surface of the benzocyclobutene layer that has been protected is deteriorated.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. Example 1 FIGS. 2A to 2E are process cross-sectional views of a first embodiment of the present invention. 46 of benzocyclobutene prepolymer
% Mesitylene solution on the silicon substrate 101 at 2000 rpm
m at a rotation speed of 90 m.
30 ° C., 10 minutes at 150 ° C., 5 minutes at 280 ° C., then 3
Heat treatment was performed at 00 ° C. for 5 minutes. The thickness of the benzocyclobutene layer 102 thus formed was 5 μm. A titanium layer 103 having a thickness of 500 ° was formed thereon by a sputtering method. In addition, a photoresist 1
04 was applied, and a desired opening pattern was formed by photolithography (FIG. 2A). SF ₆ gas 1
Using RIE under the conditions of 5 Pa and 150 W in 05,
The titanium layer 103 was dry-etched using the resist 104 as a mask. The etching time was 2 to 3 minutes, and an etching shape wider than the opening of the resist 104 could be realized (FIG. 2B). Subsequently, the benzocyclobutene layer 102 was formed using RIE in a mixed gas of SF ₆ and oxygen (volume ratio 4: 3) 106 under the conditions of 7 Pa and 150 W.
Was dry-etched (FIG. 2C). The etching time was 8 minutes. The etched portion of the benzocyclobutene layer 102 showed a shape having a tapered top edge.

The resist was peeled off with an organic solvent, so that the surface of the benzocyclobutene layer 102 was covered with the titanium layer 103 (FIG. 2D). Finally, the titanium layer 103 is removed from the surface of the benzocyclobutene layer 102 by, for example, etching with phosphoric acid kept at a temperature of 60 ° C. to 100 ° C. or by etching with HF (FIG. 2 ( E)).

Example 2 FIGS. 3A to 3D and FIGS. 4E and 4D are cross-sectional views showing the steps of a second embodiment of the present invention. Substrate 201
On top, a 5 μm thick benzocyclobutene 202 is formed,
On top of this, titanium 203 and gold 204 were added for 500
Evaporated to a thickness of {1000}. further,
A photoresist 205 was applied thereon, a desired pattern was formed, and a wiring 206 was formed by gold electroplating (FIG. 3A). Titanium 203 acts as a protective metal layer of benzocyclobutene, and gold 204 acts as a power supply metal during plating. The resist 205 is removed, and the gold layer 204 of the power supply metal for plating is removed with a mixed solution of ammonium iodide and iodine in ethanol / water.
Unnecessary portions were etched. At this time, the surface of the benzocyclobutene 202 is covered with the titanium 203 (FIG. 3B).

A photoresist 207 is applied to this substrate, and a desired pattern is opened by photolithography. From this opening, RIE was performed using a SF ₆ gas 208 at a pressure of 5 Pa and RF power of 150 W.
Is performed, and the opening portion of the titanium 203 layer is etched (FIG. 3C). The etching time was 2 to 3 minutes, and overetching of 0.5 to 1.0 μm on one side from the opening of the resist 207 was realized.

Subsequently, using a mixed gas 209 of SF ₆ and oxygen (volume ratio 4: 3) under a pressure of 7 Pa, 150
RIE was performed with the RF power of W, and the opening of the benzocyclobutene 202 layer was etched (FIG. 3D).
The etching time was 8 minutes, and benzocyclobutene having a thickness of 5 μm could be etched. When the mixing ratio of SF ₆ was small, the surface state of benzocyclobutene was poor, and etching did not proceed when oxygen was the main component. The top edge of the etched benzocyclobutene layer 202 was tapered. Since the resist is hardened in the peeling of the resist after the etching, it is difficult to remove the resist with a solvent. Therefore, the resist residue was removed by ashing using oxygen plasma frequently. However, in the manufacturing method of the present invention, since the surface of benzocyclobutene is covered with the titanium layer 203, the surface of benzocyclobutene was not deteriorated even by oxygen plasma. Furthermore, since the benzocyclobutene expands due to the difference in thermal expansion due to the difference in thermal expansion, the titanium thin film absorbs the expansion and cracks do not occur on the titanium surface. Also, it is superior to the case where the surface is covered with a silicon nitride film because cracks are prevented.

FIG. 4E shows a benzocyclobutene layer 202 formed on a substrate 201 and titanium 2
3 shows a process cross section of gold 204 of a feeding metal of plating formed on titanium 203 and gold wiring 205 formed by plating. Wiring 2
05 and benzocyclobutene, as shown in FIG.
It was removed by wet etching with phosphoric acid at ℃ (FIG. 4 (D)). According to the production method of the present invention, since the surface of the benzocyclobutene 202 is subjected to the process while being protected, no deterioration occurs.

Embodiment 3 FIGS. 5A to 5C and FIGS. 6D to 6F are sectional views showing the steps of the third embodiment of the present invention. The first wiring 302 formed over the substrate 301 is covered with a benzocyclobutene layer 303. A benzocyclobutene protective metal 304 and a plating power supply metal 305 are provided on this substrate.
Was formed. 500 mm thick titanium was used as the protective metal, and 1000 mm thick gold was used as the power supply metal. A photoresist 306 was applied to the substrate, a pattern was formed by photolithography, and a second wiring 307 was formed by electrolytic plating. (FIG. 5
(A)). The resist 306 is peeled off with an organic solvent or the like, and the power supply metal 305 is etched. In particular,
Gold was etched with a mixed solution of iodine and ammonium iodide in ethanol / water. The protective metal 304 remains on the benzocyclobutene layer. A new photoresist 308 is applied, a desired pattern is opened, and RI
E was used to etch the benzocyclobutene protective metal 304. Specifically, using the SF ₆ gas 309, a pressure of 5 Pa, was performed for 1-2 minutes at an RF power of 150 W (FIG. 5 (B)). The size of the resist opening is
It was 1 μm square or 1 μm diameter round. The protective metal 304 is etched larger than the opening of the resist 308, and is
０．５0.5 μm was retracted. 0.2 μm receding by 1 minute etching, 0.5 μm by 2 minute etching
m receded.

Subsequently, the benzocyclobutene 303 was etched by RIE (FIG. 5C). Specifically, a mixed gas of SF ₆ and oxygen (volume ratio 4: 3) 31
Etching was performed at 150 W under a pressure of 7 Pa in 0 ° C. Since the thickness of the benzocyclobutene layer was 5 μm, the etching was completed in about 8 minutes. Benzocyclobutene 30
The etching shape of 3 is that the top edge is the protective metal 3
It was restricted by the edge of No. 04 and had a tapered shape. Next, the resist 308 is peeled off, and the protective metal 304 of benzocyclobutene is also removed by wet etching using phosphoric acid at a portion other than the wiring, whereby FIG.
It becomes a process sectional view shown to (D). In the resist stripping process, the resist exposed to the plasma is hardened, so strong organic cleaning is required, and when benzocyclobutene is exposed, the surface is deteriorated. Leaving the protective metal layer of benzocyclobutene minimizes stress in the process and keeps the surface state of benzocyclobutene water-repellent, which has a great effect on improving the reliability of the device. However, when the protective metal is removed by dry etching, the surface of benzocyclobutene is deteriorated, so that the protective effect does not work. Substrate 301
In addition, a benzocyclobutene layer 302 is formed, and the first wiring 303 has an opening formed in the benzocyclobutene layer 302. Also, on the top of benzocyclobutene,
A second wiring 304 is formed. On this substrate, a protective metal layer of benzocyclobutene using titanium and a multilayer metal layer 305 of a power supply metal layer using gold are formed, a photoresist 306 is applied, a desired pattern is opened, and a first pattern is formed. A lead electrode 307 for the wiring of FIG.
(E)). When forming the multilayer metal layer 305 in the opening,
Since the top of the opening of the benzocyclobutene layer 302 has a tapered and open shape, the contact state of the metal was good even when the thickness of the benzocyclobutene layer was 5 to 10 μm. After that, the photoresist 306 is peeled off with an organic solvent or the like, and the portions of the multilayer metal layer 305 other than the extraction electrodes 307 are removed by wet etching to obtain a structure shown in FIG. Multilayer metal 305
Used a structure in which the upper layer was gold and the lower layer was titanium. In this case, gold etching may be dry etching such as Ar milling, but titanium in contact with benzocyclobutene needs to be subjected to wet etching using heated phosphoric acid or hydrofluoric acid.

Example 4 In Examples 1 to 3, titanium was used as a metal for surface protection. The effect of titanium is not only to improve the adhesion to benzocyclobutene, but also to improve the affinity of titanium with oxygen. Is large, so that it is easily bonded to oxygen and has an effect of preventing surface oxidation of benzocyclobutene. Like titanium,
Aluminum, tungsten, copper, and the like, which have a high affinity for oxygen, also have an effect of protecting the surface of benzocyclobutene. For example, aluminum and copper also serve as a protective layer of benzocyclobutene, and have the advantage of being usable as a wiring material. 50 benzocyclobutene surface
0 mm-thick metal such as platinum (Pt), gold (Au), palladium (Pd), copper (Cu), titanium (Ti), tungsten (W), nickel (Ni), and aluminum (Al). And then in oxygen plasma, 6
After exposing the metal surface for 0 minutes, the metal was removed by wet etching and dry etching, and the result of examining whether the surface of benzocyclobutene had water repellency was shown in Table 1 and FIG. The percentage of the water repellent area occupying the area of the substrate was evaluated. 100% indicates that no deterioration is observed over the entire surface of the substrate.

When removing by wet etching, platinum, gold and palladium were removed by a mixture of nitric acid and hydrochloric acid. Copper was removed with sulfuric acid, titanium was removed with heated phosphoric acid, tungsten was removed with a mixed solution of hydrofluoric acid and hydrogen peroxide, and nickel and aluminum were removed with sulfuric acid or hydrochloric acid. It has been separately confirmed that the acids used here or the mixture of acid and hydrogen peroxide does not change the surface state of benzocyclobutene. In the case of removing by dry etching, these metal layers were removed by RIE using chlorine gas, SF ₆ or the like.

[0024]

[Table 1]

It is considered that if the metal has a strong affinity for oxygen in the state of being exposed to the oxygen plasma, the effect of suppressing a change in the surface state of benzocyclobutene is considered. As an index of the affinity with oxygen, the standard oxidation-reduction potential based on the standard hydrogen electrode of each metal is shown on the horizontal axis. The more the standard oxidation-reduction potential is in the positive direction, the less likely it is to be oxidized, that is, the smaller the affinity with oxygen. From FIG.
In copper, titanium, tungsten, nickel, and aluminum, no change in the surface state was observed, indicating that there was an effect of suppressing oxidative deterioration of benzocyclobutene. But,
These effects are also effective when the metal layer serving as a protective layer is removed by wet etching, and it is clear that even if a metal has an effect of preventing oxidation, the surface state changes when dry etching is used. Is shown in

[0026]

According to the method of manufacturing a semiconductor device of the present invention, the process can be performed without deteriorating the benzocyclobutene layer which is liable to be deteriorated by oxygen. The formation of holes can be realized.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a manufacturing method of the present invention.

FIG. 2 is a process cross-sectional view showing the first embodiment of the present invention.

FIG. 3 is a process sectional view showing the first embodiment of the present invention.

FIG. 4 is a process cross-sectional view showing a second embodiment of the present invention.

FIG. 5 is a process sectional view showing a second embodiment of the present invention.

FIG. 6 is a process cross-sectional view showing a third embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the standard oxidation-reduction potential used for the metal protective film and the water repellency of the benzocyclobutene layer surface.

FIG. 8 is a cross-sectional view showing a process of a conventional example.

[Explanation of symbols]

1 ... substrate, 2 ... benzocyclobutene film, 3 ... titanium layer,
4 resist, 101 substrate, 102 benzocyclobutene layer, 103 titanium layer, 104 resist, 105
... SF ₆ gas, 106 ... SF ₆ + oxygen mixed gas, 201 ...
Substrate, 202: benzocyclobutene layer, 203: titanium layer, 204: gold layer, 205: resist, 206: wiring,
207: photoresist, 208: SF ₆ gas, 209
... SF ₆ + oxygen mixed gas, 301 ... substrate, 302 ... first
Wiring, 303: benzocyclobutene layer, 304: protective metal, 305: power supply metal, 306: resist, 30
7 ... second wiring, 308 ... photoresist, 309 ... S
F ₆ gas, 310: SF ₆ + oxygen mixed gas, 401: substrate and lower wiring, 402: insulating film layer, 403: metal layer,
404 ... resist.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/3213 H01L 21/88 D 21/3205 FF Term (Reference) 4M104 AA01 AA05 BB02 BB04 BB05 BB14 BB18 CC01 DD08 DD12 DD20 DD35 DD37 DD52 DD64 DD65 DD71 EE18 FF07 FF13 FF17 FF22 HH13 HH15 HH20 5F004 AA12 CA02 CA03 DA18 DB23 EA05 EA10 EA28 5F033 GG02 HH07 HH08 HH11 HH13 HH18 HN19 JJ01 JJ07 JJ01 JJ07 JJ01 JJ07 JJ01 JJ07 QQ08 QQ09 QQ13 QQ14 QQ18 QQ19 QQ20 QQ27 QQ30 QQ34 QQ37 RR21 SS22 XX02 XX09 XX17 XX20 XX24 5F043 AA26 BB18 DD15 FF04 GG03

Claims (5)

[Claims] 1. A method according to claim 1, wherein the benzocyclobutene layer is etched by using a metal layer formed on the benzocyclobutene layer and having a high affinity for oxygen as an etching mask, and then the metal layer is removed by wet etching. Manufacturing method of a semiconductor device. 2. A metal layer formed on the benzocyclobutene layer and having a high affinity for oxygen is masked with a resist, and the opening of the metal layer is made wider than the opening of the resist by performing excessive etching. Then, by etching the benzocyclobutene layer using the resist as a mask, an opening of the benzocyclobutene layer having a tapered shape whose upper end is controlled by the opening of the metal layer is formed. The method for manufacturing a semiconductor device according to claim 1. 3. The metal layer on the benzocyclobutene layer comprises a first metal layer having a high affinity for oxygen and a second metal layer used for wiring formed thereon, and these metal layers are formed by electrolysis. After forming a desired wiring patterned as a power supply metal for plating, the second metal layer used for the wiring other than the pattern is removed by etching, and the first metal layer is used as a process protection film. 3. The method for manufacturing a semiconductor device according to claim 1, wherein: 4. The method of manufacturing a semiconductor device according to claim 1, wherein the metal layer having a high affinity for oxygen is titanium, aluminum, tungsten, copper, or nickel. 5. The method for manufacturing a semiconductor device according to claim 1, wherein phosphoric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, or nitric acid is used as a chemical used for said wet etching.