JP2898725B2 - Pattern formation method - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a pattern, for example, a pattern of an insulating thin film.

(Prior Art) In a method of manufacturing a semiconductor integrated circuit, a step of forming a pattern of an insulating layer or a conductive layer or a resist pattern occupies an important position as a step of forming an important component of an element.

However, the process of forming this pattern has various problems.

Hereinafter, pattern formation of an insulating layer will be described as an example.

In general, the pattern of the insulating layer is widely used for an element isolation region (field insulating film) for isolating elements formed on a silicon substrate and an interlayer insulating film for electrically insulating each wiring. I have.

For example, when a silicon oxide film is used as an interlayer insulating film, first, a silicon oxide film is formed on a substrate to be processed on which a lower wiring is formed by a vapor phase growth method (CVD method) or the like.
This is patterned by lithography and dry etching, and an upper wiring is formed thereon. Also, as a device isolation method using a silicon oxide film as a field insulating film, a LOCOS method of selectively forming a thermal oxide film of silicon is generally used. When patterning a film, lithography and dry etching are required. Thus, in the conventional method of patterning an insulating layer, both use lithography and dry etching in combination, so that the entire process is complicated and
There is a problem that a dimensional conversion difference easily occurs during dry etching, and it is difficult to control a pattern dimension with high accuracy. Further, since the above-described vapor phase growth method and thermal oxidation method require high-temperature heat treatment, there have been problems such as distortion of the substrate due to thermal stress and adverse effects on elements.

In view of the above background, a patterning method based on a completely new concept of forming a resist pattern on a substrate to be processed and selectively growing a silicon oxide film or the like in a liquid phase using the resist pattern as a mask has recently attracted attention. When a silicon oxide film is formed by this method, for example, hydrofluoric acid (H ₂
Using SiF ₆ ), immerse the substrate on which the resist pattern has been formed in an aqueous solution in which the reaction formula H ₂ SiF ₆ + 2H ₂ O6HF + SiO ₂ is in an equilibrium state. Is formed at a relatively low temperature (40 ° C. or less). In this reaction, by utilizing the property that silicon oxide (SiO ₂ ) hardly precipitates on the resist surface, a silicon oxide film can be selectively grown using the resist pattern as a mask. According to this method, since the pattern of the silicon oxide film can be formed without performing dry etching, not only the processing step is significantly shortened, but also the problem of the prior art that a dimensional conversion difference easily occurs during dry etching is solved. Is done.

However, this method has the following problems, and has not yet been put to practical use. That is, simply patterning a normal resist as it is does not always provide sufficient selectivity between the resist and the substrate to be processed with respect to the growth rate of the silicon oxide film, and a small amount of silicon oxide is deposited on the resist pattern surface. I will. For this reason, it is not only impossible to form a silicon oxide film in a desired region, but it is extremely difficult to remove an unnecessary resist pattern after forming the silicon oxide film.

The above-mentioned problem is not limited to the pattern formation of the insulating layer, but is a problem that can be generally applied to the formation of a pattern made of another material.

(Problems to be Solved by the Invention) As described above, a pattern formation method by selective film growth using a liquid phase has attracted attention in order to shorten the processing steps and avoid dry etching and high-temperature heat treatment. However, this conventional pattern formation method cannot ensure sufficient film growth selectivity, and cannot not only form a film in a desired region, but also makes an unnecessary mask pattern such as a resist pattern unnecessary. Was extremely difficult to remove.

The present invention has been made in view of the above circumstances, and has as its object to provide a pattern forming method which solves the above-described problems and enables high-precision control of pattern dimensions.

[Configuration of the invention]

(Means for Solving the Problems) In order to solve the above-described problems, a first invention is to form a thin film on a substrate to be processed, pattern the thin film, and then flow down to the surface of the patterned thin film. Forming a first pattern containing a halogen atom on the surface by a mold etching method, and selectively forming a second pattern on a portion of the substrate to be processed other than the first pattern. And forming a pattern in a liquid phase.

In a second aspect, a thin film containing a halogen atom is formed on a substrate to be processed, and the thin film is patterned to form a first pattern containing a halogen atom. And selectively forming a second pattern in a liquid phase on a portion on the substrate to be processed other than the above.

(Operation) According to the pattern forming method of the present invention, since the surface of the first pattern formed on the substrate to be processed contains a halogen atom, the surface energy of the first pattern is reduced. The second pattern is not formed on the surface of the pattern. That is, the selectivity between the first pattern and the substrate to be processed with respect to the growth rate of the second pattern is greatly improved as compared with the conventional pattern forming method using a liquid phase, and the second pattern is formed only on the substrate to be processed. Can be formed. As a result, if the first pattern becomes unnecessary after these steps, this pattern can be easily removed.

(Example) Hereinafter, an example of a pattern forming method according to the present invention will be described in detail with reference to the drawings.

First Embodiment FIG. 1 is a process sectional view showing a pattern forming method according to a first embodiment of the present invention.

First, a novolak positive resist is spin-coated on a flat silicon substrate 1 using a spinner,
By baking at 90 ° C. for 1 minute on a hot plate, a 1.2 μm-thick resist thin film 2 was formed (FIG. 1A).

Next, on the resist thin film, a desired pattern is collectively transferred using an exposure apparatus using a mercury lamp as a light source,
By developing in a 2.38 wt% aqueous solution of tetramethylammonium hydroxide for 50 seconds, a resist pattern 3 was formed as a first pattern (FIG. 1 (b)).

Next, using a down-flow type etching apparatus used in the dry etching step, the resist pattern 3
(FIG. 1 (c)). Here, the configuration of the etching apparatus includes a reaction vessel equipped with a sample stage on which a sample is placed, a gas inlet for introducing a predetermined gas into the vessel, and a discharge tube for discharging the introduced gas. And an exhaust port for exhausting the inside of the reaction vessel. The inside of the reaction vessel was sufficiently exhausted in advance, and the silicon substrate 1 was placed on the sample stage. Further carbon tetrafluoride (CF ₄₎ as well as introducing a gas and a nitrogen (N ₂₎ gas at a flow rate per minute 50cc and 100cc, respectively, by applying a microwave frequency 2.45GHz to the discharge tube, the CF ₄ Plasma discharge was induced in the gas to generate fluorine radicals 4. From the start to the end of the reaction, the amount of evacuation from the exhaust port was adjusted so that the pressure inside the reaction vessel was 10 Torr.

In order to examine the state of the surface 3a of the resist pattern 3, the fluorine concentration on the surface 3a of the resist pattern after the introduction of fluorine atoms was measured by X-ray photoelectron spectroscopy. As a result, about 95% of hydrogen atoms were replaced by fluorine atoms. It was confirmed that.

Next, the SiO ₂ is dissolved and saturated aqueous hydrofluoric acid
A 0.5 mol / l aqueous solution of boric acid (H ₃ BO ₃ ) was added to adjust the processing solution for liquid phase growth, and the temperature of this processing solution was adjusted using a thermostat provided with a water supply and drainage mechanism. The substrate 1 is immersed in the substrate 1 for 10 hours while maintaining the temperature at 35 ° C. to form a second pattern having a thickness of 0.4 μm on the substrate 1.
The silicon oxide film 5 was formed (FIG. 1 (d)). At this time, the treatment liquid in the constant temperature bath was circulated and a new treatment liquid was successively supplied, so that the SiO ₂ concentration in the vicinity of the substrate to be treated was adjusted to be always constant in a supersaturated state. As a result, as shown in this figure, the silicon oxide film 5 could be selectively formed with high dimensional accuracy only on the substrate where silicon was exposed.

Next, the silicon substrate 1 is placed in a resist incinerator equipped with an oxygen (O ₂ ) gas plasma generating mechanism, and the substrate is treated in an oxygen gas plasma atmosphere at an oxygen gas flow rate of 300 cc / min and an applied voltage of 800 W. The resist pattern 3 which was no longer needed was ashed and removed by exposing the resist pattern 20 for 20 minutes. At this time, the resist pattern 3 was completely removed as shown in FIG. 1 (e), and no residue or the like was generated.

Next, for comparison with the method of the above-described embodiment, FIG. 2 is a process sectional view showing a pattern forming method by a conventional film growth method using a liquid phase. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description will be omitted.

1 (a) and 1 (b) show the conventional method shown in FIG.
This is the same as the steps up to the stage after the step of FIG. 1, and the steps after FIG. 1 (d) are performed without passing through the step of introducing fluorine atoms shown in FIG. 1 (c).

After the steps of FIGS. 1A and 1B, when the substrate 1 is immersed in the above-described processing liquid, a pattern is formed in a desired region as shown in FIG. 2A. Then, a small amount of silicon oxide 21 was also deposited on the surface of the resist pattern 3.

Further, the resist pattern 3 is removed. However, at this time, the resist pattern 3 cannot be completely removed, and as shown in FIG.
The residue 22 mainly composed of SiO ₂ has adhered.

As described above, according to the present invention, it has become clear that the selectivity between the resist pattern and the substrate to be processed with respect to the growth rate of the silicon oxide film can be greatly improved as compared with the conventional method. Further, it has been proved that an unnecessary resist pattern after the formation of the silicon oxide film can be easily and completely removed.

Second Embodiment Next, as a second embodiment of the present invention, an example in which the present invention is applied to a step of separating an element formation region will be described. FIG. 3 is a sectional view of the process.

First, the surface of a p-type silicon wafer 31 having a specific resistance of 10 Ωcm is thermally oxidized to form a silicon oxide film 32 on the surface. Further, on the oxide film 32, a negative resist 32 made of a cyclized rubber and a bisazide compound is coated with a film thickness of 1.1.
Spin coating to a thickness of μm. At this time, silicon oxide film
Numeral 32 prevents the surface of the silicon wafer 31 from being contaminated by contact with the resist 32. Next, using photolithography technology, a line width of 0.8, which is finally an element formation region, is used.
A μm resist pattern 33 was formed as a first pattern (FIG. 3A). Note that this resist pattern 33
And the portion of the silicon oxide film 34 thereunder ultimately become an element formation region.

Next, using the same down-flow type etching apparatus as in the first embodiment, under the conditions of a CF ₄ gas flow rate of 60 cc / min, a N ₂ gas flow rate of 70 cc / min, and an O ₂ gas flow rate of 30 cc / min, Radicals A were generated to introduce fluorine atoms into the surface 33a of the resist pattern 33 (FIG. 3 (d)). Here, the silicon oxide film 32 prevents the underlying silicon wafer 31 from being damaged by fluorine radicals A.

Next, using the resist pattern 33 as a mask, boron (B) atoms are ion-implanted into the silicon wafer 31 at an acceleration voltage of 30 keV and a dose of 5 × 10 ¹³ cm ⁻² to form a p-type inversion prevention layer.
34 was formed (FIG. 3 (c)).

Next, the surface side of the silicon wafer 31 is immersed in an aqueous solution of hydrosilicofluoric acid in which SiO ₂ is dissolved and saturated, and a small amount of aluminum (Al) pieces are added. A 0.8 μm thick silicon oxide film (second pattern, element isolation oxide region) on the silicon oxide film 32 except where the resist pattern 33 is formed
35 was formed with high dimensional accuracy (FIG. 3 (d)). Here, since the aluminum piece reacts with HF in the reaction formula H ₂ SiF ₆ + 2H ₂ O ₆ HF + SiO ₂ , this equilibrium reaction is shifted to the right side, whereby it is possible to deposit SiO ₂ efficiently.

Thereafter, using the same resist ashing apparatus as in the first embodiment, the unnecessary resist pattern 33 was ashed and removed (FIG. 3 (e)). In the present embodiment, a negative resist using a cyclized rubber as a base resin was used for the resist. However, such a rubber-based resin generally has a lower surface free energy than a novolak-based resin, and silicon oxide is used. Since it was difficult to adhere, the resist pattern 33 could be removed more easily than in the first embodiment.

Next, after selectively removing the portion of the silicon oxide film 32 not covered with the silicon oxide film 35, a process of cleaning the surface portion of the silicon wafer 31 under the silicon oxide film 32 was performed.
Further, an element formation region 36 was formed by selectively epitaxially growing the surface of the silicon wafer 31 at a portion not covered with the silicon oxide films 35 and 32 (FIG. 3 (f)). The conventional LOCOS element isolation method has a problem in that an oxide film penetrates beneath a nitride film that serves as a mask for oxidation during field oxidation, thereby narrowing a portion that can be actually used as an element formation region. However, according to the method of the present embodiment, since the element isolation oxide region 35 can be formed perpendicular to the surface of the silicon wafer 31, the above-described problem does not occur.

Third Embodiment Next, as a third embodiment of the present invention, an example in which the present invention is applied to a step of performing wiring between electrodes via a silicon oxide film (interlayer insulating film) will be described. FIG. 4 is a sectional view of the process.

First, on a silicon wafer 41 of p-type specific resistance 10Ωcm,
A gate portion 44 of polysilicon, a gate oxide film 43 and n ⁺
A substrate to be processed was prepared on which a MOS transistor comprising a source 45a and a drain 45b of the type and a field oxide film 42 were formed (FIG. 4 (a)).

Further, a silicon oxide film 46 was formed on the source 45a, the drain 45b, and the gate portion 44 by oxidizing the entire surface of the substrate to be processed (FIG. 4B).

Next, using a photolithography technique, a resist pattern 47 which finally becomes an opening for connecting the wiring to the n ⁺ -type source 45a and drain 45b diffusion layers was formed as a first pattern (FIG. 4). (C)).

Next, using a down-flow type etching apparatus similar to that of the first embodiment, fluorine radicals were produced under the conditions of a CF ₄ gas flow rate of 80 cc / min, a N ₂ gas flow rate of 100 cc / min and an O ₂ gas flow rate of 20 cc / min. B was generated to introduce fluorine atoms into the surface 47a of the resist pattern 47 (FIG. 4 (d)).

Next, the surface side of the substrate to be processed is immersed in an aqueous solution of hydrosilicofluoric acid in which SiO ₂ previously adjusted to 5 ° C. is dissolved and saturated, and then the temperature of the aqueous solution is gradually increased to 60 ° C. By using the resist pattern 47 as a mask, a 0.6 μm-thick silicon oxide film (second pattern, interlayer insulating film) 48 is formed with high dimensional accuracy on the substrate to be processed except where the resist pattern 47 is formed. (4th
Figure (e). In the present embodiment, in order to allowed to deposit efficiently SiO ₂ allowed migrate equilibrium reaction of the reaction formula _{H 2 SiF 6 + 2H 2 O6HF} + SiO 2 of precipitating SiO ₂ in the liquid phase on the right side, of SiO ₂ due to a difference in temperature Since the difference in solubility is used, mixing of metal impurities and the like can be prevented, and as a result, the reliability of the device is greatly improved.

Next, using the same resist ashing apparatus as in the first embodiment, the unnecessary resist pattern is ashed and removed, and the portion of the silicon oxide film 46 formed thereunder is selectively removed. Removed. As a result, the n ⁺ type source 45
Openings 49a and 49b for making contact with a and the drain 45b, respectively, were formed (FIG. 4 (f)).

Next, an aluminum vapor-deposited thin film was formed on the entire surface using a magnetron-type sputtering device so as to fill the opening.
50 was formed (FIG. 4 (g)).

Thereafter, a wiring was formed by patterning the deposited thin film 50, and a silicon oxide film was further deposited thereon as a passivation film 51 by a vapor deposition method (FIG. 4 (h)).

In this embodiment, the silicon oxide film 46 is also used.
Prevents contamination of the wafer by the resist and damage to the wafer by fluorine radicals as in the second embodiment described above.

Fourth Embodiment In the first to third embodiments, as a step of forming a first pattern having a fluorine atom on the surface, a method of forming a resist pattern and then exposing the pattern surface to fluorine radicals is used. In this fourth embodiment, a method is used in which fluorine atoms are initially contained in the resist material. FIG. 5 is a sectional view of the process.

First, an acrylate polymer having a perfluoroalkyl group in the side chain was dissolved in xylene to form a solution. Here, the chemical formula of the acrylate-based polymer is shown by the following formula.

Next, the solution was spin-coated on a flat silicon substrate 61 with a thickness of 1.0 μm using a spooner, and baked at 100 ° C. for 1 minute on a hot plate to form a resist thin film 62 ( Fifth (a)).

Further, a desired pattern was collectively transferred onto the resist thin film 62 using a reduction projection exposure apparatus using a KrF excimer laser (wavelength: 248 nm) as a light source, and then developed for 2 minutes using isoamyl acetate as a developing solution. As a result, a resist pattern 63 was formed as a first pattern as shown in FIG.

Next, FIGS. 1 (d) and 1 (e) shown in the first embodiment.
As a result, a silicon oxide film 64 was formed as a second pattern as shown in FIG. 5 (c), and the resist pattern 63 was removed as shown in FIG. 5 (d).

Further, as a method of including fluorine atoms in the resist material from the beginning, there is a method of adding a fluorine-based additive to the resist material in addition to the method of the above embodiment.

That is, in this method, first, about 300 ppm of a polyethylene oxide surfactant containing a fluorine atom is mixed into a novolak positive resist. Next, a silicon oxide film is formed by the same steps as those shown in FIGS. 5A to 5D shown in the above embodiment method. Here, the chemical formula of the above-mentioned surfactant is as shown in the following formula.

In the method according to the fourth embodiment described above, since the resist surface contains fluorine, the step of exposing this surface to fluorine radicals is not performed, and the substrate to be processed, for example, a silicon substrate is not damaged by fluorine radicals. Can be prevented.

Although a fluorine atom is used as a halogen atom in the first to fourth embodiments, other halogen atoms, for example, a chlorine atom, a bromine atom, and an iodine atom can be used.

Further, it goes without saying that the materials of the first pattern and the second pattern are not limited to those in the above-described embodiment, but can be changed as appropriate.

Further, various modifications can be made without departing from the spirit of the present invention.

〔The invention's effect〕

According to the pattern forming method of the present invention, it is possible to sufficiently secure film growth selectivity and to form a film in a desired region with high dimensional accuracy. Further, when removing an unnecessary mask pattern, for example, a resist pattern, it can be easily and completely removed.

[Brief description of the drawings]

FIGS. 1, 3, 4 and 5 are sectional views showing the first, second, third and fourth embodiments of the pattern forming method according to the present invention, respectively, and FIG. FIG. 7 is a process cross-sectional view showing a pattern forming method by a conventional film growth method using a liquid phase, for comparison with the method according to the example of FIG. In the figure, 1,61 ... silicon processing substrate, 2, 62 ... resist thin film,
3,33,47,63 ... resist pattern (first pattern),
3a, 33a, 47a ... Surface of resist pattern 3, 4, A, B ...
Fluorine radicals, 5, 35, 48, 64: silicon oxide film (second pattern), 21: silicon oxide, 22: residues mainly composed of SiO ₂ , 31, 41: silicon wafer, 32 ... resist, 34 ... p-type inversion prevention layer, 36 ... element formation region, 42 ... field oxide film, 43 ... gate oxide film, 44
... gate part, 45a ... n ⁺ type source, 45b ... n ⁺ type drain, 46 ... silicon oxide film, 49a, 49b ... opening, 5
0: Aluminum deposited thin film, 51: Passivation film.

Claims (5)

(57) [Claims] A thin film is formed on a substrate to be processed, and after patterning the thin film, a halogen atom is contained on the surface of the patterned thin film by a downflow etching method, and the halogen atom is contained on the surface. Forming a first pattern and selectively forming a second pattern in a liquid phase on a portion other than the first pattern on the substrate to be processed. . 2. A step of forming a thin film containing halogen atoms on a substrate to be processed, patterning the thin film to form a first pattern containing halogen atoms, and a process other than the first pattern. Selectively forming a second pattern in a liquid phase on a portion on the substrate to be processed. 3. The pattern forming method according to claim 1, wherein said halogen atom is a fluorine atom. 4. The pattern forming method according to claim 1, wherein said second pattern is made of silicon oxide. 5. The step of forming in the liquid phase of the second pattern, the step of forming a portion on the substrate other than the formation of the first pattern in a solution containing hydrofluoric acid. 3. The pattern forming method according to claim 1, further comprising the step of selectively forming a silicon oxide.