JP4197302B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device manufacturing method and a semiconductor device. The method for manufacturing a semiconductor device of the present invention is suitably used for manufacturing a compound semiconductor device having a front surface and a back electrode that are electrically connected through a through-hole formed in a substrate.

  A semiconductor device such as a transistor that operates at a high frequency and a high output is indispensable for a portable information terminal, particularly a cellular phone. A compound semiconductor device is generally used for such a semiconductor device. The compound semiconductor device employs a structure in which the front and back electrodes are electrically connected through a through hole penetrating the substrate for the purpose of reducing ground inductance and improving heat dissipation characteristics during device operation.

  FIG. 3 shows a process for forming a through hole in a conventional method for manufacturing a semiconductor device (see, for example, Patent Document 1).

  First, the surface electrode 53 is formed on the surface of the substrate 51 to obtain the structure shown in FIG. The surface electrode 53 is electrically connected to an emitter electrode (not shown) such as a hetero bipolar transistor (HBT).

  Next, the substrate 51 is dry-etched from the portion facing the front electrode 53 on the back surface of the substrate 51, thereby forming a through hole 52 that penetrates the substrate 51. Further, wet etching is performed in order to remove a polymer or the like generated during dry etching. During this wet etching, side etch 55 may occur in the surface electrode 53. This state is shown in FIG.

Next, the back electrode 57 is formed on the back surface of the substrate 51 and in the through hole 52 so as to be electrically connected to the front surface electrode 53, and the structure shown in FIG.
JP-A-1-293615

  As shown in FIG. 3C, the side etch 55 generated by wet etching may not be filled in the process of forming the back electrode 57. In this case, a cavity remains below the surface electrode 53. When the semiconductor device is subjected to stress such as heat, this cavity causes various defects.

  The present invention has been made in view of such circumstances, and provides a method for manufacturing a semiconductor device capable of preventing the occurrence of side etching.

  The method for manufacturing a semiconductor device of the present invention includes (1) forming a surface electrode on a substrate surface via a first insulating film, and (2) using the first insulating film as an etching stopper film to form a surface electrode on the back surface of the substrate. Etching the substrate from the opposite part forms a through hole that penetrates the substrate and reaches the first insulating film, and (3) etching the first insulating film through the through hole, And (4) forming a back electrode electrically connected to the front surface electrode on the back surface of the substrate and in the through hole.

  In the method for manufacturing a semiconductor device of the present invention, when the through hole is formed in the substrate, the first insulating film is used as an etching stopper film, so that side etching can be prevented from occurring on the surface electrode.

  The method for manufacturing a semiconductor device of the present invention includes (1) forming a surface electrode on a substrate surface via a first insulating film, and (2) using the first insulating film as an etching stopper film to form a surface electrode on the back surface of the substrate. Etching the substrate from the opposite part forms a through hole that penetrates the substrate and reaches the first insulating film. (3) Etching the first insulating film through the through hole allows the surface electrode to be formed. And (4) forming a back electrode electrically connected to the front surface electrode on the back surface of the substrate and in the through hole.

  First, the step (1), that is, the step of forming the surface electrode on the substrate surface via the first insulating film will be described.

  As the substrate, for example, an elemental semiconductor substrate such as Si or Ge, a compound semiconductor substrate such as GaAs, GaN, GaP, InP, ZnO, or ZnSe can be used. These may be single crystals or polycrystalline.

  The first insulating film is made of a film that functions as an etching stopper film when the substrate is etched. Specifically, the first insulating film is made of an inorganic insulating film such as a silicon nitride film or a silicon oxide film. Since the surface electrode is formed through the insulating film, the surface electrode and the substrate can be insulated. The first insulating film may be formed only in a region on the substrate surface immediately below the surface electrode, or may be formed on the entire substrate surface.

  The surface electrode can be formed using a conductive material such as titanium, platinum, or gold. The surface electrode can be formed by a plating method or a vapor deposition method. The surface electrode can be formed so as to be electrically connected to a semiconductor device (more specifically, any electrode of the semiconductor device) already formed on the substrate. Further, after the surface electrode is formed, a semiconductor device may be formed over the substrate, and the surface electrode and the semiconductor device may be electrically connected. The semiconductor device is made of HBT, MESFET, HEMT, or the like. Since the semiconductor device is connected to the front surface electrode and the front surface electrode is electrically connected to the back surface electrode of the substrate as will be described later, the ground inductance of the semiconductor device can be reduced, and the characteristics of the semiconductor device can be improved. it can. In addition, when the semiconductor device, the front electrode, and the back electrode are connected by a material having high thermal conductivity, the heat generated in the semiconductor device quickly moves to the back electrode, ensuring stable operation of the semiconductor device. can do.

  Next, the step (2), that is, the first insulating film is used as an etching stopper film, and the substrate is etched from a portion facing the surface electrode on the back surface of the substrate, thereby penetrating the substrate and reaching the first insulating film. The process of forming the through hole will be described.

  The “site facing the front electrode on the back surface of the substrate” includes a site on the back surface of the substrate where a through hole can be formed in the substrate by the method of the present invention. That is, the above-mentioned part includes not only a part on the back surface of the substrate corresponding to a position directly below the front electrode but also a part on the back surface of the substrate that is deviated from directly below the surface electrode as long as the object of the present invention can be achieved.

  “Etching” consists of dry etching, wet etching, or a combination thereof. Dry etching can be performed by, for example, reactive ion etching (RIE). The wet etching can be performed using, for example, an organic acid such as citric acid or a mixed solution of an inorganic acid such as phosphoric acid or sulfuric acid and a hydrogen peroxide solution. The wet etching may be performed using a mixed solution of an aqueous ammonia solution and a hydrogen peroxide solution.

  Since the first insulating film is used as an etching stopper film, the margin for setting the conditions for the etching process can be increased, and the processing quality can be improved.

  In this step, for example, (a) a substrate having a predetermined depth is formed by dry etching the substrate from a portion facing the front electrode on the back surface of the substrate, and (b) the substrate is wet etched through the recess. This can be carried out by a method comprising a step of forming a through hole penetrating the substrate and reaching the first insulating film.

  Specifically, for example, first, a recess having a depth corresponding to about 90 to 95% of the thickness of the substrate is formed by dry etching. Next, wet etching can be performed so as to remove the remainder of the substrate and residues such as polymer generated by dry etching. Since the first insulating film functions as an etching stopper film, side etching does not occur on the surface electrode during wet etching.

  Next, the step (3), that is, the step of exposing the surface electrode to the back side of the substrate by etching the first insulating film through the through hole will be described.

  In order to prevent side etching from occurring on the surface electrode, the etching is preferably performed by dry etching. Dry etching can be performed by, for example, the RIE method.

  It is preferable to include a step of forming a side wall insulating film on the side wall of the through hole (side wall insulating film forming step) after the step (2) or (3) and before the step (4).

  For example, (a) the second insulating film is formed on the back surface of the substrate and in the through hole, and (b) the second insulating film is etched from the back surface of the substrate by dry etching such as a reactive ion etching method. Thus, it can be formed by a method including a step of forming a sidewall insulating film on the sidewall of the through hole. The second insulating film is made of an inorganic insulating film such as a silicon nitride film or a silicon oxide film. The first and second insulating films may be formed of different types of materials, or may be formed of the same type of materials.

  When the sidewall insulating film is formed by this method, the sidewall insulating film forming step is particularly preferably performed before the step (3). In this case, dry etching for forming the sidewall insulating film in the step (b) can be performed, and subsequently, dry etching for removing the first insulating film in the step (3) can be performed. A process can be performed. Moreover, when performing a process (b), since the surface electrode is protected by the 1st insulating film, there exists an advantage that a surface electrode is hard to receive a damage. The dry etching in both steps may be performed under the same conditions or different conditions.

  This step can also be performed after step (3). In this case, since the first insulating film has already been removed, dry etching is preferably performed under the condition that damage to the surface electrode is reduced.

  When a side wall insulating film is formed on the side wall of the through hole and a back electrode is formed thereon, the back electrode is insulated from the substrate at least inside the through hole. Further, as described above, the surface electrode is also insulated from the substrate. Therefore, according to the present invention, a substrate having a through hole, an insulating film formed on the substrate so as to have an opening facing the through hole, and a surface electrode formed on the insulating film so as to close the opening; A semiconductor device is provided that includes a sidewall insulating film formed on the sidewall of the through hole, and a back electrode formed on the back surface of the substrate and in the through hole, and the back electrode is electrically connected to the surface electrode. . In this semiconductor device, the front surface electrode and the back surface electrode are insulated from the substrate except for the back surface of the substrate, so that leakage current flowing on the surface of the substrate can be reduced. “Closing the opening” includes a case where a part of the opening is blocked as long as the object of the present invention can be achieved.

  Next, the step (4), that is, a step of forming a back electrode electrically connected to the front electrode on the back surface of the substrate and in the through hole will be described.

“On the back surface of the substrate” includes a part on the back surface of the substrate.
The back electrode can be formed using a conductive material such as titanium, titanium tungsten, platinum, or gold. The back electrode can be formed by a plating method or a vapor deposition method. The back electrode may be formed of the same material as the front electrode, or may be formed of a different material.

  FIG. 1 is a cross-sectional view illustrating the manufacturing process of the semiconductor device according to the first embodiment. Hereinafter, the manufacturing method of the semiconductor device of the present embodiment will be described with reference to FIG.

  First, the surface electrode 5 is formed on the surface of the substrate 1 made of GaAs via the first insulating film 3 made of a silicon nitride film, thereby obtaining the structure shown in FIG. The surface electrode 5 is electrically connected to a ground electrode of a semiconductor device (not shown) such as HBT, MESFET, and HEMT formed on the surface of the substrate 1. The surface electrode 5 is formed by a plating method (plating power supply metal + plating) or a vapor deposition method using a resist mask.

  Next, using the first insulating film 3 as an etching stopper film, the substrate 1 is etched from a portion facing the front surface electrode 5 on the back surface of the substrate 1, thereby penetrating the substrate 1 and reaching the first insulating film 3. 7 is formed to obtain the structure shown in FIG. This step is performed, for example, by performing dry etching (using CL2, BCL3 gas) at a setting of 90 to 95 μm on a GaAs substrate having a thickness of 100 μm and then performing wet etching (setting at 10 μm or more) with sufficient margins taken into consideration. . For wet etching, a mixed solution of an aqueous solution of an organic acid (citric acid) or an inorganic acid (phosphoric acid, sulfuric acid) and a hydrogen peroxide solution can be used. Further, a mixed solution of an aqueous ammonia solution and a hydrogen peroxide solution may be used to remove the polymer after dry etching. In this wet etching, since the first insulating film 3 functions as an etching stopper film, the surface electrode 5 is not damaged when the through hole 7 is formed, and the margin for setting the conditions of the etching process is increased.

  Next, the structure shown in FIG. 1C is obtained by etching the first insulating film 3 by the RIE method.

  Next, the back surface electrode 13 is formed on the back surface of the substrate 1 and in the through hole 7 so as to be electrically connected to the front surface electrode 5 to obtain the structure shown in FIG. Specifically, Ti—Au or the like is formed as a power supply metal for plating on the entire back surface of the substrate 1 by sputtering or vapor deposition, and then Au plating is performed to form the back electrode 13.

  FIG. 2 is a cross-sectional view illustrating the manufacturing process of the semiconductor device according to the second embodiment. Hereinafter, the manufacturing method of the semiconductor device of this embodiment will be described with reference to FIG.

  The process until obtaining the structure of FIG. 2B is the same as the process until obtaining the structure of FIG.

  Next, a second insulating film 9 made of a silicon nitride film is formed on the back surface of the substrate 1 and in the through hole 7 to obtain the structure shown in FIG.

  Next, by etching the second insulating film 9 from the back surface of the substrate 1 by the RIE method, the sidewall insulating film 11 is formed on the side wall of the through hole 7, and further, the first insulating film 3 is etched by the RIE method. As a result, the structure shown in FIG.

  Next, the back electrode 13 is formed on the back surface of the substrate 1 and in the through hole 7 so as to be electrically connected to the front surface electrode 5 to obtain the structure shown in FIG. Specifically, Ti—Au or the like is formed as a power supply metal for plating on the entire back surface of the substrate 1 by sputtering or vapor deposition, and then Au plating is performed to form the back electrode 13.

  In the semiconductor device obtained by the manufacturing method of the present embodiment, the electrodes 5 and 13 do not contact the substrate 1 at any position on the lower side of the surface electrode 5 and the side surface of the through hole 7. Even if the other bonding pad electrode or wiring metal contacts the substrate 1, the problem of leakage current flowing near the surface of the substrate 1 does not occur.

It is sectional drawing which shows the manufacturing process of the semiconductor device which concerns on Example 1 of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor device which concerns on Example 2 of this invention. It is sectional drawing which shows the manufacturing process of the conventional semiconductor device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 51 Substrate 3 1st insulating film 5, 53 Surface electrode 7, 52 Through-hole 9 2nd insulating film 11 Side wall insulating film 13, 57 Back surface electrode 55 Side etch

Claims (2)

(1) via a first insulating film to form a surface electrode on the surface of the substrate, (2) as a first insulating film an etching stopper film, etching the substrate from a portion facing the surface electrode on the back face of the substrate by, through the substrate a through hole is formed to reach the first insulating film, (3) by dry-etching the first insulating film through the through hole, the surface electrode substrate backside exposed to, provided with a (4) forming on said back electrode board rear surface which is electrically connected to the surface electrode and the through hole,
Between the step (2) and the step (3), (a) a second insulating film is formed on the back surface of the substrate and in the through hole, and (b) the second insulating film is etched from the back surface of the substrate by dry etching. it allows manufacturing method of the through hole semiconductor device you further comprising a step of forming a sidewall insulating film on side walls of the. Step (2) is, (a) the substrate from a position facing the surface electrode on the back face of the substrate to form a recess having a predetermined depth by dry etching, (b) a first insulating film etching stopper film as a manufacturing method according to claim 1 through holes is a step of forming a reaching the first insulating film through the substrate by wet etching the substrate through its said recess.

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