JP2007242652A - Process for fabricating semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for fabricating a semiconductor device in which parasitic capacitance can be reduced at a T-shaped electrode. <P>SOLUTION: A semiconductor crystal layer 12 is formed on a substrate 11, a first SiO<SB>2</SB>film 13 having a thickness of 50 nm is formed on the semiconductor crystal layer 12, a second SiO<SB>2</SB>film 14 having a thickness of 100 nm is formed on the SiO<SB>2</SB>film 13, and resist 15 having an opening 15a is formed. The SiO<SB>2</SB>films 14 and 13 directly under the opening 15a are then etched by first reactive ion etching, etching of the SiO<SB>2</SB>film 13 is not advanced, but etching of the SiO<SB>2</SB>film 14 is advanced in the lateral direction by second reactive ion etching to form a T-shaped opening in the SiO<SB>2</SB>films 13 and 14. After removing the resist 15, a T-shaped electrode 16 is formed in the T-shaped opening of the SiO<SB>2</SB>films 13 and 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device having a T-type electrode, for example, a semiconductor device for manufacturing a Schottky junction field effect transistor (FET).

A conventional method for manufacturing a semiconductor device for manufacturing a field effect transistor having a T-type electrode will be described with reference to FIGS. First, as shown in FIG. 6A, a semiconductor crystal layer (Schottky barrier layer) 2 is formed on a substrate 1, a cap layer 3 is formed on the semiconductor crystal layer 2, and an SiO ₂ film is formed on the cap layer 3. 4 is formed. Next, as shown in FIG. 6B, a SiN film 5 is formed on the SiO ₂ film 4. Next, as shown in FIG. 6C, a resist 6 having an opening 6 a is formed on the SiN film 5. Next, as shown in FIG. 6 (d), the etching is isotropically advanced to remove the SiN film 5, and then the etching is anisotropically advanced to remove the SiO ₂ film 4. T-shaped openings are formed in the SiO ₂ film 4 and the SiN film 5. Next, as shown in FIG. 7A, the resist 6 is removed. Next, as shown in FIG. 7B, the cap layer 3 is recess-etched. Next, as shown in FIG. 7C, a gate electrode, that is, a T-type electrode 7 is formed in the T-type opening of the SiO ₂ film 4 and the SiN film 5.

In this semiconductor device manufacturing method, recess etching of the cap layer 3 is performed through the T-type openings of the SiO ₂ film 4 and the SiN film 5, and the T-type electrode 7 is brought into contact with the exposed semiconductor crystal layer 2. By forming this, both reduction of parasitic capacitance and reduction of parasitic resistance are achieved.
T. Enoki, H. Ito, K. Ikuta and Y. Ishii: Proc. Int. Conf. Indium Phosphideand Related Materials, 1995, pp. 81-84

  However, in such a method for manufacturing a semiconductor device, since the SiN film 5 has a high relative dielectric constant (˜7.5), the contribution of parasitic capacitance becomes relatively large at the time of gate miniaturization, and the field effect Improvement of the high-frequency performance of the type transistor is hindered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device that can reduce the parasitic capacitance of a T-type electrode portion.

In order to achieve this object, in the present invention, a first SiO ₂ film is formed on a semiconductor layer, and a _second chemical composition different from that of the first SiO ₂ film is formed on the first SiO ₂ film. An SiO ₂ film is formed, a resist having an opening is formed on the second SiO ₂ film, a first reactive ion etching is performed to anisotropically proceed, and the opening of the resist is formed. The second SiO ₂ film and the first SiO ₂ film immediately below the first SiO ₂ film are removed, and then a second reactive ion etching isotropically performed to perform etching of the second SiO ₂ film. Etching proceeds in the lateral direction to form T-shaped openings in the first and second SiO ₂ films, and to form T-shaped electrodes in the T-shaped openings.

In addition, a first SiO ₂ film is formed on the semiconductor layer, a _second SiO ₂ film having a chemical composition different from that of the first SiO ₂ film is formed on the first SiO ₂ film, and the first SiO ₂ film is formed. Forming a resist having the opening of the SiO ₂ film 2 and performing a third reactive ion etching for isotropically proceeding to remove the second SiO ₂ film immediately below the opening; Then, etching of the second SiO ₂ film is performed in the lateral direction, and then fourth reactive ion etching is performed in which the etching proceeds anisotropically, and the first SiO ₂ film immediately below the opening is performed. Is removed to form T-shaped openings in the first and second SiO ₂ films, and T-shaped electrodes are formed in the T-shaped openings.

In these cases, the first SiO ₂ film may be formed on the semiconductor crystal layer of the field effect transistor, and the T-type electrode as the gate electrode may be formed in the T-type opening.

Further, a cap layer is formed on the semiconductor crystal layer of the field effect transistor, the first SiO ₂ film is formed on the cap layer, and the T-type opening is formed in the first and second SiO ₂ films. After forming the portion and recess-etching the cap layer, the T-type electrode, which is a gate electrode, may be formed in the T-type opening.

In the method for manufacturing a semiconductor device according to the present invention, since the relative dielectric constant of the SiO ₂ film is smaller than the relative dielectric constant of the SiN film, the parasitic capacitance of the T-type electrode portion can be reduced, and the T-type electrode can be reduced. There is no need to form different types of insulating films to form.

A method of manufacturing a semiconductor device for manufacturing a field effect transistor having a T-type electrode according to the present invention will be described with reference to FIGS. First, as shown in FIG. 1A, a semiconductor crystal layer (crystal layer composed of a Schottky barrier layer, a carrier supply layer, and a channel layer) 12 which is a semiconductor layer is formed on a substrate 11, and the semiconductor crystal layer 12 is formed. A first SiO ₂ film 13 having a thickness of 50 nm is formed (deposited) on the SiO ₂ film 13 by sputtering, and continuously changes the film forming conditions (sputtering power, pressure in the chamber, etc.) on the SiO ₂ film 13. A second SiO ₂ film 14 having a thickness of 100 nm is formed (deposited). As a result, the SiO ₂ film 14 has oxygen deficiency in its composition, and the SiO ₂ film 14 and the SiO ₂ film 13 have different chemical compositions and different reactive ion etching (RIE) resistance. Next, as shown in FIG. 1B, a resist is applied onto the SiO ₂ film 14, and the gate pattern is transferred by photolithography or electron beam drawing to form a resist 15 having an opening 15a. The gate length dimension at this time is set to 50 nm, for example. Next, as shown in FIG. 1 (c), first reactive ion etching is performed in which the etching proceeds anisotropically (in the vertical direction) to remove the SiO ₂ films 14 and 13 immediately below the opening 15a. To do. Next, as shown in FIG. 2 (a), by changing the etching gas and the pressure inside the chamber, (laterally) isotropically etching performs second reactive ion etching to proceed, SiO ₂ film Etching 14 proceeds laterally. That is, by utilizing the fact that the reactive ion etching resistance of the SiO ₂ film 14 and the reactive ion etching resistance of the SiO ₂ film 13 are different from each other, the etching of the SiO ₂ film 13 does not proceed and the SiO ₂ film 14 is not etched. Etching is advanced in the lateral direction to form T-shaped openings in the SiO ₂ films 13 and 14. Next, as shown in FIG. 2B, the resist 15 is removed. Next, as shown in FIG. 2C, a gate electrode made of metal, that is, a T-type electrode 16 is formed in the T-type openings of the SiO ₂ films 13 and 14 by, for example, vapor deposition or lift-off.

In this semiconductor device manufacturing method, the SiO ₂ film 14 is formed on the SiO ₂ film 13, and the relative dielectric constant of the SiO ₂ film is about 4, which is about half the relative dielectric constant of the SiN film. As a result, the parasitic capacitance of the T-type electrode 16 can be reduced, and the contribution of the parasitic capacitance does not increase even when the gate is miniaturized, which hinders the improvement of the high-frequency performance of the field effect transistor. There is nothing to do. Further, since the SiO ₂ film 13 and the SiO ₂ film 14 are formed in order to form the T-type electrode 16 and it is not necessary to form different types of insulating films, the number of devices required for manufacturing is reduced and the manufacturing time is reduced. Can be easily achieved. In addition, by using the T-type electrode 16 as a gate electrode, a gate electrode capable of reducing both parasitic capacitance and parasitic resistance can be obtained, and characteristics of a miniaturized field effect transistor can be improved. it can.

Next, a method for manufacturing a semiconductor device for manufacturing a field effect transistor having another T-type electrode according to the present invention will be described with reference to FIG. First, after performing the process described in FIG. 1A, a resist 15 having an opening 15a is formed on the SiO ₂ film 14 as shown in FIG. 3A. Next, as shown in FIG. 3B, the third reactive ion etching isotropically progressed to remove the SiO ₂ film 14 immediately below the opening 15a and the SiO ₂ film 14 Etching is performed in the lateral direction. Next, as shown in FIG. 3C, the fourth reactive ion etching is performed to change the etching gas and the pressure in the chamber to cause the etching to proceed anisotropically, and SiO ₂ immediately below the opening 15a. By removing the film 13, T-shaped openings are formed in the SiO ₂ films 13 and 14. Next, the steps described in FIGS. 2B and 2C are performed.

Next, a method of manufacturing a semiconductor device for manufacturing a field effect transistor having another T-type electrode according to the present invention will be described with reference to FIGS. First, as shown in FIG. 4A, the semiconductor crystal layer 12 is formed on the substrate 11, the cap layer 21 is formed on the semiconductor crystal layer 12, and the SiO 2 is formed on the cap layer 21 (on the semiconductor crystal layer 12). _Two films 13 are formed, and a SiO ₂ film 14 is formed on the SiO ₂ film 13. Next, as shown in FIG. 4B, a resist 15 having an opening 15 a is formed on the SiO ₂ film 14. Next, as shown in FIG. 4C, third reactive ion etching is performed to anisotropically advance the etching, and the SiO ₂ films 14 and 13 immediately below the opening 15a are removed. Next, as shown in FIG. 5 (a), the etching gas and the pressure in the chamber are changed, and the fourth reactive ion etching isotropically advanced to perform etching of the SiO ₂ film 14 laterally. By proceeding in the direction, T-shaped openings are formed in the SiO ₂ films 13 and 14. Next, as shown in FIG. 5B, after removing the resist 15, the cap layer 21 is recess-etched. Next, as shown in FIG. 5C, a T-type electrode 16 is formed so as to be in contact with the semiconductor crystal layer 12 exposed in the T-type openings of the SiO ₂ films 13 and 14.

In the above-described embodiment, the case where the gate length is 50 nm has been described. However, the contribution of the parasitic capacitance is constant regardless of the gate length, so that the shorter the gate length, the more the present invention. Since the effect becomes more remarkable, it is desirable that the gate length be 200 nm or less. In addition, the thickness of the first and second SiO ₂ films can be made as thin as possible considering that the filling state of the opening of the metal for the T-type electrode depends on the aspect ratio with the gate length. Although it is desirable, since the parasitic capacitance increases when the thickness is reduced, the thickness is required to be as thick as the electrode embedding technique allows, from the viewpoint of improving the device performance. Considering the actual filling of the metal for the T-type electrode into the opening, the thickness of the first SiO ₂ film is about the same as the gate length, and the thickness of the second SiO ₂ film is about three times the gate length. It is desirable to set it as the film thickness. In the above-described embodiment, the cap layer 21 is recess-etched after removing the resist 15, but the resist 15 may be removed after the cap layer 21 is recess-etched.

It is explanatory drawing of the manufacturing method of the semiconductor device which concerns on this invention. It is explanatory drawing of the manufacturing method of the semiconductor device which concerns on this invention. It is explanatory drawing of the manufacturing method of the other semiconductor device which concerns on this invention. It is explanatory drawing of the manufacturing method of the other semiconductor device which concerns on this invention. It is explanatory drawing of the manufacturing method of the other semiconductor device which concerns on this invention. It is explanatory drawing of the manufacturing method of the conventional semiconductor device. It is explanatory drawing of the manufacturing method of the conventional semiconductor device.

Explanation of symbols

11 ... substrate 12 ... semiconductor crystal layer 13 ... first SiO ₂ film 14 ... second SiO ₂ film 15 ... resist 15a ... opening 16 ... T-type electrode 21 ... cap layer

Claims (4)

The first SiO ₂ film is formed on the semiconductor layer, the above first SiO ₂ film to form a different second SiO ₂ film having a chemical composition in the first SiO ₂ film, the second A resist having an opening is formed on the SiO ₂ film, and first reactive ion etching is performed to anisotropically advance the second SiO ₂ film immediately below the opening of the resist. The first SiO ₂ film is removed, and then the second reactive ion etching for isotropically proceeding etching is performed, and the etching of the second SiO ₂ film is proceeded in the lateral direction, whereby the first 1. A method of manufacturing a semiconductor device, comprising: forming a T-type opening in the first SiO ₂ film; and forming a T-type electrode in the T-type opening. The first SiO ₂ film is formed on the semiconductor layer, the above first SiO ₂ film to form a different second SiO ₂ film having a chemical composition in the first SiO ₂ film, the second A resist having the opening of the SiO ₂ film is formed, a third reactive ion etching isotropically proceeding to remove the second SiO ₂ film immediately below the opening, and the above Etching of the second SiO ₂ film is performed in the lateral direction, and then the fourth reactive ion etching is performed to anisotropically proceed to remove the first SiO ₂ film immediately below the opening. Thus, a T-type opening is formed in the first and second SiO ₂ films, and a T-type electrode is formed in the T-type opening. 3. The first SiO ₂ film is formed on a semiconductor crystal layer of a field effect transistor, and the T-type electrode which is a gate electrode is formed in the T-type opening. The manufacturing method of the semiconductor device of description. A cap layer is formed on the semiconductor crystal layer of the field effect transistor, the first SiO ₂ film is formed on the cap layer, and the T-shaped opening is formed in the first and second SiO ₂ films. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the T-type electrode which is a gate electrode is formed in the T-type opening after forming and recess-etching the cap layer. 4.

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