JP2004200654A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To be capable of realizing a micropattern without causing a resist break. <P>SOLUTION: A silicon oxide film 2 is formed on a semiconductor wafer 1 which consists of silicon. After a resist film including carbon is formed on the silicon oxide film 2, a resist pattern 3 is formed by patterning the formed resist film. Subsequently, the resist pattern 3 is exposed to sulfer dioxide gas. After this, the silicon oxide film 2 is dry-etched with the resist pattern 3 exposed to the sulfer dioxide gas as a mask. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device capable of preventing a resist from falling down in a dry etching process using a resist pattern.

  A conventional method for manufacturing a semiconductor device will be described with reference to the drawings.

  3A to 3D show cross-sectional configurations in the order of steps of a conventional method for manufacturing a semiconductor device.

  First, as shown in FIG. 3A, a thermal oxide film 102 is formed on a semiconductor substrate 101 made of silicon. Subsequently, a resist film is applied on the formed thermal oxide film 102, and thereafter, the resist film is patterned by a lithography method to form a resist pattern 103.

Next, as shown in FIG. 3B, dry etching is performed on the thermal oxide film 102 using the resist pattern 103 as a mask. For example, when a capacitively coupled plasma etching apparatus is used, tetrafluorocarbon (CF ₄ ) is supplied at a flow rate of 50 ml / min, and trifluoromethyl (CHF ₃ ) is supplied at a flow rate of 30 ml / min. Oxygen (O ₂ ) is supplied at a flow rate of 5 ml / min, the gas pressure is 5 Pa, the upper discharge power is 1000 W, and the lower discharge power is 1500 W. Here, the flow rate of each gas is a standard state, that is, 0 ° C. and 1 atm.

  In recent years, the processing dimensions of semiconductor devices have been increasingly miniaturized, and thus smaller pattern dimensions have been required for the resist pattern 103 which is a mask for patterning a film to be etched. Therefore, the physical strength of the resist pattern 103 is becoming smaller and smaller (for example, see Patent Document 1).

  In addition, since the thickness of the film to be etched hardly changes even when the semiconductor device is miniaturized, the resist pattern 103 can be made thinner because it is necessary to secure a selectivity with respect to the resist during dry etching. Instead, the value of the aspect ratio (the height of the resist pattern / the line width of the resist pattern) of the resist pattern 103 at the time of pattern formation is becoming larger.

  On the other hand, in the dry etching process, the resist pattern 103 is etched not only in a direction perpendicular to the main surface of the semiconductor substrate 101 but also in a direction horizontal thereto, so that the line width of the resist pattern 103 is further reduced during the etching. . Further, heat stress and stress accompanying deterioration are generated in the resist pattern 103 due to heat and ultraviolet rays from plasma used for dry etching. As a result, as the processing size becomes finer, the upper portion of the resist pattern 103 falls, that is, a so-called resist fall 103a occurs as shown in FIG. The resist pattern 103 in which the resist collapse 103a has occurred functions as an etching mask as it is, and etching of the thermal oxide film 102 below the resist collapse 103a is inhibited. As a result, as shown in FIG. An abnormal pattern portion 102a is formed in the pattern 102.

Therefore, as shown in FIG. 3D, even if the ashing process and the cleaning process are performed to remove the resist pattern 103, the abnormal pattern portion 102a remains in the thermal oxide film 102 as it is.
WO 98/32162 pamphlet

  As described above, the conventional method of manufacturing a semiconductor device has a problem in that the resist pattern 103 has a resist fall 103a when etching the film to be processed.

  SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to realize a fine pattern without causing the resist to collapse.

  As a result of various studies, the present inventors have found that exposing a patterned resist pattern to a gas containing sulfur increases the strength of the side wall of the resist pattern.

  Specifically, a resist pattern made of a commonly used organic material such as novolak and containing carbon is exposed to a gas made of, for example, sulfur dioxide, and measured by Auger electron spectroscopy (AES). Confirm the atom. Further, it has been confirmed by X-ray photoelectron spectroscopy (XPS) that a bond between carbon (C) and sulfur (S) (hereinafter, referred to as a CS bond) is present. Since the compound containing a CS bond has a relatively low vapor pressure, it remains without being detached from the side wall of the resist pattern. In addition, the bond energy of the CS bond is 175 kcal / mol, which is larger than the value of the bond energy of the carbon-carbon bond (CC bond) of 144 kcal / mol. The strength is increased, and as a result, resist collapse can be prevented.

  Specifically, the method for manufacturing a semiconductor device according to the present invention includes the steps of forming a thin film made of an inorganic material, forming a resist film containing carbon on the thin film, and then patterning the formed resist film. Performing a step of forming a resist pattern from a resist film, a step of exposing the resist pattern to a gas containing sulfur, and a step of performing dry etching on the thin film using the resist pattern exposed to the gas containing sulfur as a mask. Have.

  According to the method for manufacturing a semiconductor device of the present invention, after forming a resist pattern from a carbon-containing resist film, the resist pattern is exposed to a gas containing sulfur. Since the containing compound is generated, the strength of the side wall of the resist pattern is increased. As a result, it is possible to prevent the resist from falling down in the miniaturized resist pattern, so that a desired fine pattern can be obtained on a thin film made of an inorganic material.

  Note that the sulfur dioxide gas in Patent Document 1 is used for etching a thin film made of an organic material, and is different from the case where the etching target of the present invention is made of an inorganic material.

  In the method for manufacturing a semiconductor device of the present invention, the inorganic material preferably contains silicon, and the etching gas used for dry etching is preferably a fluorocarbon gas.

  In the method for manufacturing a semiconductor device according to the present invention, the gas containing sulfur is preferably sulfur dioxide.

  In the method for manufacturing a semiconductor device according to the present invention, the gas containing sulfur is preferably in a plasma state.

  In the method of manufacturing a semiconductor device according to the present invention, the step of exposing the resist pattern to a gas containing sulfur and the step of performing dry etching are preferably the same steps. This eliminates the need to provide a step of merely exposing the resist pattern to a gas containing sulfur, thereby improving the throughput of the manufacturing process.

  In the method of manufacturing a semiconductor device according to the present invention, the line width of the resist pattern is preferably 200 nm or less.

  Further, in the method of manufacturing a semiconductor device according to the present invention, it is preferable that the value of the ratio between the height and the line width in the resist pattern is 2.8 or more.

  As described above, when the resist pattern is fine and has a high aspect ratio, the effects of the present invention become more remarkable.

  ADVANTAGE OF THE INVENTION According to the manufacturing method of the semiconductor device concerning this invention, since the intensity | strength of the side wall of a resist pattern increases and it becomes possible to prevent resist fall, it becomes possible to obtain a desired fine pattern in a thin film made of an inorganic material. .

(1st Embodiment)
A first embodiment of the present invention will be described with reference to the drawings.

  1A to 1D show cross-sectional configurations in the order of steps of a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

  First, as shown in FIG. 1A, an inorganic silicon oxide film 2 is formed on a semiconductor substrate 1 made of silicon (Si) by, for example, a thermal oxidation method. Subsequently, a resist film is applied on the formed silicon oxide film 2, and thereafter, the resist film is patterned by lithography to form a resist pattern 3.

Next, as shown in FIG. 1B, the resist pattern on the semiconductor substrate 1 is exposed to plasma-like sulfur dioxide (SO ₂ ), so that the side wall of the resist pattern 3 has a C—S bond containing a C—S bond. The reaction part 3a is formed. Specifically, the plasma is generated by using, for example, an inductively coupled plasma etching apparatus, the flow rate of sulfur dioxide is set to 50 ml / min (0 ° C., 1 atm), the gas pressure is set to 1 Pa, and the upper discharge power is set to 200 W. And the lower discharge power is 30 W. Due to this plasma irradiation, sulfur generated by decomposition (plasmaization) of sulfur dioxide is C—S bonded to carbon contained in the resist pattern 3 to form a C—S reaction part 3 a on each side wall of the resist pattern 3. I do. The formed CS reaction portion 3a protects each side wall of the resist pattern 3 and improves the strength of the resist pattern 3. At this time, since the silicon oxide film 2 hardly reacts with sulfur, it hardly adheres to the surface of the silicon oxide film 2 and does not affect the subsequent dry etching process for the silicon oxide film 2.

Next, as shown in FIG. 1C, the silicon oxide film 2 is etched using the resist pattern 3 as a mask by using a fluorocarbon gas as an etching gas. As the fluorocarbon gas, for example, tetrafluorocarbon (CF ₄ ) and trifluoromethyl (CHF ₃ ) are used. At this time, since each side wall of the resist pattern 3 is protected by the CS reaction portion 3a, the etching can be performed without the resist pattern 3 falling down.

  Next, as shown in FIG. 1D, the resist pattern 3 is removed by ashing and cleaning.

  Thereafter, the semiconductor device is completed by a usual method.

  As described above, according to the first embodiment, by exposing the formed resist pattern 3 to a gas containing sulfur, each side wall of the resist pattern 3 is protected by the CS reaction portion 3a and its strength is increased. Therefore, it is possible to prevent the resist from falling down in the resist pattern 3, so that a desired shape can be obtained in the silicon oxide film 2.

(Second embodiment)
2A to 2C show cross-sectional configurations in the order of steps of a method for manufacturing a semiconductor device according to the second embodiment of the present invention.

  First, as shown in FIG. 2A, an inorganic silicon oxide film 2 is formed on a semiconductor substrate 1 made of silicon by, for example, a thermal oxidation method. Subsequently, a resist film is applied on the formed silicon oxide film 2, and thereafter, the resist film is patterned by lithography to form a resist pattern 3.

Next, as shown in FIG. 2B, the silicon oxide film 2 is etched using the resist pattern 3 as a mask while supplying a sulfur dioxide gas using a fluorocarbon gas as an etching gas. Specifically, for example, using a capacitively coupled plasma etching apparatus, the flow rate of tetrafluorocarbon (CF ₄ ) is set to 50 ml / min, the flow rate of trifluoromethyl (CHF ₃ ) is set to 30 ml / min, and a carrier gas composed of argon is used. Is 500 ml / min, the flow rate of sulfur dioxide is 30 ml / min, the pressure of all gases is 5 Pa, the upper discharge power is 1000 W, and the lower discharge power is 1500 W. Here, the flow rate of each gas is a standard state, that is, 0 ° C. and 1 atm.

  In this etching step, the sulfur dioxide added to the etching gas is converted into plasma and decomposed, and the sulfur generated by the decomposition is C—S bonded to the carbon contained in the resist pattern 3, and carbon dioxide is formed on each side wall of the resist pattern 3. -S reaction part 3a is formed. The formed CS reaction part 3a protects each side wall of the resist pattern 3 and improves the strength of the resist pattern 3. At this time, since the sulfur hardly reacts with the silicon oxide film 2, it does not affect the etching of the silicon oxide film 2.

  Next, as shown in FIG. 2C, the resist pattern 3 is removed by ashing and cleaning.

  Thereafter, the semiconductor device is completed by a usual method.

  As described above, according to the second embodiment, when dry etching is performed on the silicon oxide film 2 using the formed resist pattern 3 as a mask, a gas containing sulfur is added to the etching gas, so that the resist pattern 3 Are protected by the CS semi-recess 3a and the strength thereof is increased. Therefore, it is possible to prevent the resist from falling down in the resist pattern 3, so that a desired shape can be obtained in the silicon oxide film 2.

  In addition, since there is no need to provide a step of merely exposing the resist pattern 3 to a gas containing sulfur, the throughput of the manufacturing process is improved.

  In the first and second embodiments, the silicon oxide film 2 is used as the film to be etched. However, silicon oxide such as TEOS (tetra-ethyl-ortho-silicate) or BPSG (boron-doped phospho-silicate glass) is used. A similar effect can be obtained with an oxide film, a silicon nitride film, a silicon oxynitride film, polysilicon, or amorphous silicon.

  It is also effective for etching metal wiring made of copper (Cu) or aluminum (Al).

  Further, although tetrafluorocarbon and trifluoromethyl are used as the etching gas, another etching gas may be used.

  Although sulfur dioxide is used as the sulfur-containing gas, sulfur monoxide (SO) may be used.

  Further, the line width in the resist pattern 3 is preferably 200 nm or less, and the value of the ratio (aspect ratio) between the height and the line width in the resist pattern 3 is preferably 2.8 or more. As described above, when the resist pattern is fine and has a high aspect ratio, the effect of the present invention becomes more remarkable.

3A to 3D are cross-sectional views illustrating a method of manufacturing the semiconductor device according to the first embodiment of the present invention in the order of steps. 4A to 4C are cross-sectional views illustrating a method of manufacturing a semiconductor device according to a second embodiment of the present invention in the order of steps. 3A to 3D are cross-sectional views illustrating a conventional method for manufacturing a semiconductor device in the order of steps.

Explanation of reference numerals

Reference Signs List 1 semiconductor substrate 2 silicon oxide film 3 resist pattern 3a CS reaction section

Claims (7)

Forming a thin film made of an inorganic material;
After forming a carbon-containing resist film on the thin film, patterning the formed resist film, forming a resist pattern from the resist film,
Exposing the resist pattern to a gas containing sulfur,
Performing dry etching on the thin film using the resist pattern exposed to a gas containing sulfur as a mask.   2. The method according to claim 1, wherein the inorganic material includes silicon, and an etching gas used for the dry etching is a fluorocarbon gas.   3. The method according to claim 1, wherein the gas containing sulfur is sulfur dioxide.   The method for manufacturing a semiconductor device according to claim 1, wherein the gas containing sulfur is in a plasma state.   5. The manufacturing of the semiconductor device according to claim 1, wherein the step of exposing the resist pattern to a gas containing sulfur and the step of performing the dry etching are the same step. 6. Method.   6. The method according to claim 1, wherein a line width of the resist pattern is 200 nm or less. 7. 7. The method according to claim 1, wherein a value of a ratio between a height and a line width in the resist pattern is 2.8 or more. 8.

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