JPH10261598A - Method for forming plating electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a plating electrode on a plating electrode formation part and reduce the scattering of a film thickness and stabilize a growth rate by providing a conductive plating electrode formation region on the upper surface of a substrate and forming a conductive film that is electrically connected to the electrode formation part at the lower surface side of the substrate and using a conductive film as a cathode. SOLUTION: A resist film is formed on an upper surface 11a of a GaAs substrate 11, a window as an electrode formation region is formed at the resist film, Au is subjected to high-vacuum metal deposition on a front surface, and the resist film is eliminated and an Au electrode 10 is formed. Then, a via hole 15 reaching the Au electrode 10 that is a first plating electrode formation part is formed through the substrate. Then, after the resist film is provided on a lower surface 11b of the substrate 11, a window is provided at the region of the lower surface 11b of the substrate 11, the region of the lower surface 11b being exposed from the window is etched, the via hole 15 where the lower surface 10a of the Au electrode 10 is exposed is formed in the substrate 11, and a conductive film 17 is formed on the lower surface 11b of the substrate 11 and the inner wall of the via hole 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a plated electrode of a semiconductor device, and more particularly to a method for forming a plated electrode using an electrolytic plating method.

[0002]

2. Description of the Related Art Conventionally, a plating electrode such as a wiring electrode is generally formed by using an electrolytic plating method. Particularly in GaAsIC, formation of a wiring electrode by Au plating is well known. The electrolytic plating method is a surface treatment for reducing a metal ion by an electrolysis reaction in an electrolyte solution containing a metal ion to deposit a target metal on a negative conductive material, and the deposited metal becomes a plating electrode.

Literature (Literature: JP-A-63-161646)
In (1), a gold (Au) plated electrode is formed on a metal electrode provided on a substrate by using an electrolytic plating method. In this document, a metal electrode is referred to as a first metal, and a plating electrode is referred to as Au.
It is called plating. A method of forming such a conventionally known plating electrode will be described with reference to the drawings. FIG. 11 and FIG. 12 are process diagrams for explaining a process of forming a plating electrode which has been conventionally used, and each diagram is a diagram schematically showing a cross section of a structure obtained in a main process step. is there. FIG. 13 is an image diagram schematically showing a relationship between a conventional plating apparatus and a structure to be plated.

[0004] First, after a metal electrode 130 is patterned on a substrate 110 (FIG. 11A), the metal electrode 130 is formed.
An insulating coating is formed on the entire upper surface of the substrate 110 and the substrate 110.
Next, a contact hole 160 is formed in the insulating film so as to expose the upper surface of the metal electrode 130 (FIG. 11B),
An insulating film 150 is formed on the remaining insulating film. The conductive film 1 is formed on the insulating film 150, the inner wall 160a of the contact hole, and the upper surface of the exposed metal electrode 130.
70 (also referred to as a current film) (FIG. 11C).

Next, a resist is applied on the conductive film 170, and the resist located on the metal electrode 130 is removed to expose the conductive film 170 on the metal electrode 130, thereby forming a resist pattern 190 ( FIG. 11 (D).

Here, a step of plating Au on the metal electrode 130 of the structure formed in the steps up to now will be described with reference to FIG. The plating apparatus 210 mainly includes a plating tank 230, a DC power supply 250, a cathode pin 270 serving as a cathode, and an anode 290 located at the bottom in the plating tank 230.
And a plating solution circulation pump 310. The pump 310 sucks the electrolytic plating solution 330 from the top and discharges it from the bottom of the conical shape so that the dissolved particles (ions) in the plating solution 330 are uniformly suspended in the solution. It is. As shown in FIG. 13, the cathode pin 270 is provided inside the plating tank 230 with the tip of the pin 270 facing upward.

In performing plating, first, the substrate 110
In order to use the upper conductive film 170 (current film) as a cathode, the resist pattern 1 formed on the conductive film 170
90 and the tip of the cathode pin 270 is
0 (FIG. 12A). Also, at least the exposed conductive film 170 is brought into contact with the liquid surface 330a of the electrolytic plating solution 330 containing Au ions. By applying a negative voltage to the cathode pin 270, the conductive film 170 that is in conduction with the cathode pin 270 becomes a cathode, and therefore, Au deposits on the exposed conductive film 170 on the metal electrode 130. It becomes the Au plating electrode 350 (FIG. 12)
(A)). In this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

After plating is completed, the resist pattern 190 is removed with an organic solvent or the like (FIG. 12B), and the portion of the current film 170 on the insulating film 150 is etched using the deposited Au plating electrode 350 as an etching mask. The electrode 4 finally formed by removing the remaining portion 170a of the current film and the Au plating electrode 350
00 is obtained (FIG. 12C).

[0009]

However, the above-described method for forming a plated electrode has the following problems.

[0010] A current film is provided on the upper surface side of the substrate, and this film must be partially removed after plating electrodes are formed. For this reason, the number of steps for forming the plating electrode is large, and the formation takes time.

Further, in order to bring the cathode pins into contact with the current film, a resist pattern formed on the current film is penetrated. For this reason, the pins are consumed while the cathode pins are used a plurality of times. When a voltage is applied to the cathode pin, the cathode pin itself is also a cathode and is in contact with the electrolytic plating solution, so that plating metal is deposited on the cathode pin. As a result, poor contact or contact with the current film occurs due to deterioration or deterioration of the shape of the cathode pin, which deteriorates the film quality of the plated electrode, increases the variation in the film thickness, or makes the film growth rate unstable. A desired resistance value cannot be obtained with such a plated electrode. Further, when another layer is laminated on the plated electrode, the adhesion to the other layer is deteriorated.

For this reason, there has been a demand for a method capable of easily forming a plated electrode having a good film quality, a small variation in the film thickness and a stable growth rate.

[0013]

Therefore, according to the method of forming a plated electrode of the present invention, when a plated electrode is formed on a substrate by using an electrolytic plating method, (a) conductive plating is formed on the upper surface of the substrate. An electrode forming portion is provided, (b) a conductive film electrically connected to the plating electrode forming portion is formed on the lower surface side of the substrate, and (c) plating is performed on the plating electrode forming portion using the conductive film as a cathode. An electrode is formed.

A conductive film that is conductive from the conductive plating electrode forming portion and the lower surface of the substrate is used as a current film. Therefore, the conductive plating electrode forming portion on the upper surface of the substrate is brought into contact with the electrolytic plating solution, but the current film on the lower surface side of the substrate can be exposed without being brought into contact with the electrolytic plating solution. And a plating electrode can be formed without depositing plating metal on the current film side. Therefore, it is possible to suppress the deterioration of the film quality and the occurrence of the variation in the film thickness due to the deterioration and the deterioration of the shape of the cathode pin as in the related art, and it is possible to further stabilize the film growth rate.

Since the current film (conductive film) is formed on the lower surface of the substrate, there is no need to quickly remove the current film after forming the plating electrode. The current film can be removed together when cutting from the lower surface side to make the substrate thinner in a later step. For this reason,
Since the number of steps can be reduced as compared with the related art, and the manufacturing time can be shortened, the formation of a plated electrode becomes easy.

Preferably, the step (a) includes a step of forming a metal electrode as a plating electrode forming portion on the upper surface of the upper surface of the substrate. When the plating electrode forming portion is a metal electrode, a plating electrode is formed on this metal electrode and can be used as a wiring electrode.

Preferably, the step (a) includes a step of forming an active layer as a plating electrode forming portion in a surface region of the upper surface of the substrate. When the plating electrode forming portion is an active layer, a plating electrode is formed on this active layer and can be used as an ohmic electrode.

Preferably, in the step (a), an active layer is formed as a plating electrode forming portion on a surface region of the upper surface of the substrate, and a metal electrode contacting a part of the active layer is formed on the upper surface of the substrate. And a step of forming on the upper side. When viewed from above, the plated electrode forming portion formed in this way has a metal electrode partially overlapped on the active layer, but the other active layer regions are exposed. When a plating electrode is formed thereon, it can be used as a wiring electrode or an ohmic electrode.

The step (a) includes forming a metal electrode on the upper surface of the substrate as a plating electrode forming portion, and forming an insulating film on the upper surface of the substrate in contact with a part of the metal electrode. And a step of carrying out. When viewed from above, the plating electrode forming portion formed in this manner has an insulating film partially covering the metal electrode, but the other metal electrodes are exposed. When a plating electrode is formed on this,
It can be used as an ohmic electrode.

Preferably, in the step (b), a via hole is formed in the substrate from the lower surface of the substrate to the plating electrode forming portion, and a conductive film is formed on the lower surface of the substrate and the inner wall of the via hole. And a step. A via hole is provided in the substrate, and a conductive film is formed not only on the lower surface side of the substrate but also on the inner wall of the via hole. Since the via hole reaches the plated electrode forming portion, the plated electrode forming portion and the conductive film provided on the lower surface side of the substrate can be electrically connected via the conductive film in the via hole.

Preferably, in the step (b), a conductive film is formed on the entire lower surface of the substrate, and a conductive region electrically connected to the conductive film is formed in the substrate located below the plating electrode forming portion. And the step of performing Thus, the conductive portion formed in the substrate and the conductive film formed on the lower surface side of the substrate can be conducted through the conductive region in the substrate.

Preferably, the conductive region is formed by using ion implantation and annealing techniques. By performing ion implantation and subsequent annealing in the substrate, a conductive region having conductivity can be formed.

Preferably, the plating electrode forming portion in the step (a) and the conductive film in the step (b) are simultaneously formed in one step by forming a conductive layer on the entire surface of the substrate. Good. If a conductive layer is formed including such a step, a part of the conductive layer on the upper surface side of the substrate can be used as a plating electrode formation portion, and the conductive layer on the lower surface side of the substrate can be used as the conductive film described above. . In addition, since the steps (a) and (b) can be performed simultaneously in one step,
The number of steps for forming the plating electrode can be further reduced, and the plating electrode can be easily formed.

Preferably, in the step (c), the step of bringing the cathode pin into contact with the conductive film and the step of bringing the electrolytic plating solution into contact with at least the exposed surface of the plating electrode forming portion without contacting the cathode pin. And applying a negative voltage to the cathode pin. Since the conductive film is exposed on the lower surface side of the substrate, the cathode pin can be brought into direct contact with the conductive film, so that deterioration or deterioration of the shape of the cathode pin can be prevented. Further, since the cathode pins are not in contact with the electrolytic plating solution, plating metal does not deposit on the pins even when a voltage is applied to the cathode pins. For this reason, deterioration in the quality of the plated metal film and variation in the film thickness caused by poor contact between the cathode pin and the conductive film are drastically reduced, and the film growth rate is stabilized.

Preferably, the cathode pin is brought into contact with the conductive film on the lower surface side of the substrate.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings are only schematically shown to the extent that the invention can be understood, and thus the invention is not limited to the illustrated examples. In the drawings, hatching (hatched lines) showing a cross section is omitted except for a part for easy understanding of the drawings.

<First Embodiment> First, referring to FIGS. 1 to 3, as a first embodiment, Au (gold) plating is applied to a metal electrode formed on the upper surface of the upper surface of a GaAs substrate. An example in which the plating electrode is formed by applying the method will be described. 1 and 2 are schematic process diagrams for explaining the first embodiment, and each diagram is shown by a cross-section of a structure obtained in a main process step. FIG. 3 is a schematic image diagram showing a relationship between a plating apparatus used for carrying out the method of forming a plated electrode of the present invention and a structure to be plated.

First, the step of providing a conductive plating electrode forming portion on the upper surface of the substrate is performed by first forming a first electrode on the upper surface 11 a of the substrate 11.
A metal electrode is provided as the plating electrode forming part 10 (FIG. 1).
(A)).

In this example, a GaAs substrate is used as the substrate 11, and the metal electrode is the Au electrode 10. First G
After a resist film is formed on the upper surface 11a of the aAs substrate 11, a window as an electrode formation region is formed in the resist film by photolithography, and then Au is applied to the entire surface of the resist film including the window from above the substrate. Vacuum deposited. Thereafter, the resist film is removed by a lift-off method, and Ga
The Au electrode 10 is formed on the upper surface 11a of the As substrate 11 (FIG. 1A).

Next, the step of forming a conductive film electrically connected to the plating electrode forming portion on the lower surface side of the substrate includes:
A via hole 15 is formed from the lower surface 11b of the substrate 11 to reach the Au electrode 10, which is the first plated electrode formation portion, by penetrating the inside of the substrate (FIG. 1B).

In this example, after a resist film is provided on the lower surface 11b of the substrate 11, a window is provided in the resist film in the region of the lower surface 11b of the GaAs substrate 11 located below the Au electrode 10 by photolithography. . The region of the lower surface 11b exposed from this window is defined as a via hole forming region, and the lower surface 10 of the Au electrode 10 is formed in the GaAs substrate 11 by using both wet etching and dry etching.
A via hole 15 exposing a is formed (FIG. 1).
(B)).

Next, a conductive film 17 is formed on the lower surface 11b of the substrate 11 and the inner wall 15a of the via hole 15.
(C)).

In this example, the lower surface 11 of the GaAs substrate 11
b and Ti / Au are formed as a conductive film 17 (also referred to as a current film) on the entire inner wall 15a of the via hole by using a normal vacuum deposition method. At this time, the thicknesses of Ti and Au are each set to 1000 ° (100 nm) (FIG. 1C).

Next, a resist is applied to the entire upper surface 11a of the GaAs substrate 11, a resist film is formed, and a resist pattern 1 having a window 13 exposing the upper surface 10b of the Au electrode 10 is formed on the resist film by photolithography.
9 is formed (FIG. 2A).

Next, using the conductive film 17 as a cathode,
The plating electrode 3 is formed on the Au electrode 10 which is a plating electrode forming portion.
In the step of forming 5, first, the cathode pin 27 is brought into contact with the conductive film 17 (FIG. 2B).

Here, FIG. 3, FIG. 2 (B) and FIG.
With reference to (C), a method of forming a plating electrode will be described in further detail. The plating apparatus 21 used in the embodiment of the present invention mainly includes a plating tank 23, a DC power supply 25, a cathode pin 27 serving as a cathode, an anode 29 at the bottom of the plating tank 23, and a plating solution circulation pump 31. I have it. This pump 31
This is the same as the conventional configuration in that the electroplating solution 33 is sucked from the top and discharged from the bottom of the conical shape so that the dissolved particles (ions) in the plating solution 33 are uniformly suspended in the solution. In the present invention, the upper surface 11 a of the substrate 11 is brought into contact with the electrolytic plating solution 33 in the plating tank 23.
Side Au electrode 10, as shown in FIG.
The upper surface 11a side of the liquid is the surface of the electrolytic plating solution 33 (FIG. 2B).
In order to make the liquid level easy to understand, it is indicated by a dashed line. ) 33a. In this apparatus 21, the cathode pins 27 are provided above the lower surface 11b side of the substrate 11 with the tips of the pins 27 facing the liquid surface 33a of the plating solution 33 (at this time, the lower surface side of the substrate 11 is the plating solution 33). On the side remote from the liquid level 33). In this example, the cathode pins 27 are brought into contact with the conductive film 17 (current film) formed on the lower surface 11b of the substrate 11.

Next, the electrolytic plating solution 33 is applied to the cathode pins 2.
7, a negative voltage is applied to the cathode pin 27 while being in contact with at least the first plating electrode forming portion, that is, the upper surface 10b of the Au electrode 10.

The plating bath 23 is filled with an electrolytic plating solution 33 containing Au ions having a positive charge, and the electrolytic plating solution 33 is brought into contact with at least the Au electrode 10. Here, since the cathode pin 27 is on the side of the lower surface 11b of the GaAs substrate 11, it does not contact the electrolytic plating solution 33. When a negative voltage is applied to the cathode pin 27, the conductive film 17 (current film) becomes a cathode, and the Au electrode 10 which is electrically connected to the current film 17 also becomes a cathode. Therefore, Au ions in the plating solution 33 are reduced near the Au electrode 10 in contact with the electrolytic plating solution 33, and the Au electrode 1
Au precipitates on 0. At this time, when the voltage was 1.5 V and the time for applying the voltage was 15 minutes, the thickness of the Au plating electrode 35 on the Au electrode 10 became 3 μm (FIG. 2).
(B)).

Thereafter, the resist pattern 1 on the substrate 11
By removing 9 with an organic solvent such as acetone, G
An Au plating electrode 35 can be formed on the aAs substrate 11 via the Au electrode 10 (FIG. 2C).

As a result, the conductive film 17 is formed on the lower surface 1 of the substrate 11.
1b, it is easy to make contact with the cathode pin 27, so that it does not penetrate the resist pattern and make contact with the conductive film. Since there is no possibility of contact with the liquid, deterioration of the cathode pin 27 is small. Further, since the cathode pin 27 is not in contact with the electrolytic plating solution 33, the metal to be plated does not deposit on the pin 27, and the shape of the cathode pin 27 can be prevented from being deteriorated.
Thereby, poor contact with the conductive film 17 can be reduced. Further, since it is not always necessary to remove the conductive film 17, the forming process can be shortened and made easier than before.

The formed Au plating electrode is suitable for use as a wiring electrode.

<Second Embodiment> As a second embodiment, an example in which Au (gold) plating is applied to an active layer formed on a surface region of an upper surface of a GaAs substrate to form a plating electrode will be described. This will be described with reference to FIG. FIG. 4 is a schematic process diagram for explaining the second embodiment, and corresponds to FIGS. 1 and 2. Hereinafter, points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

First, in the step of providing a conductive plating electrode forming portion on the upper surface of the substrate, an active layer is formed as a second plating electrode forming portion 30 in the surface region of the upper surface 11a of the substrate 11.

In this example, the active layer 30 is formed by implanting Si ions into the surface region of the upper surface of the GaAs substrate 11 and performing annealing at a temperature of 800 ° C. to 900 ° C. (FIG. 4A). .

Next, similarly to the first embodiment, the via hole 15 exposing the lower surface 30a of the active layer 30 is
A conductive film 17 (current film) made of Ti / Au is formed on the lower surface 11b of the substrate 11, the inner wall 15a of the via hole 15, and the exposed lower surface 30a of the active layer 30 by a normal vacuum deposition method. (FIG. 4)
(B)).

Next, a resist is applied to the entire upper surface 11a of the GaAs substrate 11 to form a resist film, and the resist film has a window 32 for partially exposing the upper surface 30b of the active layer 30 by photolithography. A resist pattern 19 is formed (FIG. 4C).

Next, the cathode pins 27 are connected to the GaAs substrate 1.
1 while contacting the electrolytic plating solution 33 with the upper surface 30 b of the active layer 30 exposed from the resist pattern 19 while contacting the Ti / Au film 17 on the lower surface side of the cathode pin 2.
7 is applied with a negative voltage. Cathode pin 27 and Ti / A
Since the u film 17 and the active layer 30 are conductive, the active layer 3
Numeral 0 indicates a cathode, and Au ions in the electrolytic plating solution 33 are reduced by the active layer 30 to deposit Au on the upper surface 30b (for details, see the description of the first embodiment and FIG. 1).
(FIG. 4C). Also in this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

By removing the resist pattern 19 with an organic solvent, an Au plating electrode 35 is formed on the active layer 30 (FIG. 4D).

As a result, as in the case of the first embodiment, since the plating solution does not contact the cathode pins 27 or the cathode pins 27 do not penetrate the resist pattern, the deterioration of the cathode pins 27 and the shape of the cathode pins 27 are prevented. Connection failure with the conductive film 17 due to the deterioration of the thickness can be reduced. Also,
Since it is not always necessary to remove the conductive film 17, the number of steps can be reduced, and therefore, the formation of a plated electrode becomes easy.

The formed Au plating electrode 35 is preferably used as an ohmic electrode.

<Third Embodiment> As a third embodiment, an active layer formed on the surface region of the upper surface of a GaAs substrate and a portion formed on the upper surface of the substrate in contact with a part of the active layer are formed. An example in which Au (gold) plating is performed on a metal electrode to form a plated electrode will be described with reference to FIG.
FIG. 5 is a schematic process chart for explaining the third embodiment, and corresponds to FIGS. 1 and 2. Hereinafter, the first
Only the points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

First, a conductive plating electrode forming portion is provided on the upper surface of the substrate. In this example, the third plating electrode forming section 40 is formed by an active tank and a metal electrode. Therefore, the active layer 4
Oa is formed in the surface region of the upper surface 11a of the substrate 11, and a metal electrode 40b is formed on the upper surface 11a of the substrate 11 so as to contact a part of the active layer 40a.

Here, the upper surface 11a of the GaAs substrate 11
After implanting Si ions into the surface region, annealing is performed to form an active layer 40a, and an Au electrode 40b is formed above the upper surface 11a of the substrate 11 (FIG. 5A). In this case, the Au electrode 40b may be appropriately formed depending on the design such that the Au electrode 40b is brought into contact with the peripheral region of the active layer 40a and exposes the central region. This Au electrode 40b
Can be formed using a conventionally known method such as a lift-off method or a vapor deposition method.

Next, a conductive film 17 electrically connected to the active layer 40a, which is a part of the third plated electrode forming portion, is formed on the substrate 1
1 is formed on the side of the lower surface 11b. This step is performed on the substrate 11
A via hole 15 is formed in the substrate 11 from the lower surface 11b of the substrate 11 to the lower surface 40aa of the active layer 40a, which is a part of the plated electrode forming portion, and then the lower surface 11b of the substrate 11, the inner wall 15a of the via hole 15 and the exposed lower surface 40aa A conductive film 17 is formed thereon.

Here, similarly to the second embodiment, a via hole 15 exposing the lower surface 40aa of the active layer 40a is formed in the GaAs substrate 11, and the lower surface 11b of the substrate 11 and the inner wall 15a of the via hole are formed. And a conductive film 17 (current film) made of Ti / Au on the lower surface 40aa
Is formed by a normal vacuum deposition method (FIG. 5B).

Next, a resist is applied to the entire upper surface 11a of the GaAs substrate 11 including the Au electrode 40b to form a resist film, and the active layer 40a and the Au electrode 40b are partially applied to the resist film by photolithography. A resist pattern 19 having an exposed window 42 is formed (FIG. 5C).

Next, in the same manner as in the first embodiment, the cathode pin 27 is connected to the Ti on the lower surface 11b side of the GaAs substrate 11.
/ Au film 17 so that the electroplating solution 33 is exposed from the resist pattern 19 to the active layers 40a and A
A negative voltage is applied to the cathode pin 27 while making contact with the u electrode 40b. Cathode pin 27 and Ti / Au film 1
7 is electrically connected to the active layer 40a and the Au electrode 40b, the active layer 40a and the Au electrode 40b become a cathode, and the Au ions in the electrolytic plating solution 33 are reduced by the active layer 40a and the Au electrode 40b to reduce the Au. Deposits (for details, see the description of the first embodiment and FIG. 1) (FIG. 5)
(C)). Also in this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

By removing the resist pattern 19 with an organic solvent, an Au plating electrode 35 can be formed on the active layer 40a and the Au electrode 40b (FIG. 5D).

As a result, the cathode pin 2
7 does not come into contact with the plating solution, and the cathode pin 27 does not penetrate the resist pattern.
7 and poor connection with the conductive film 17 due to deterioration of the shape can be reduced. Also, the conductive film 17 is not necessarily required.
Because there is no need to remove, the number of steps can be reduced,
Therefore, formation of the plating electrode becomes easy.

The formed Au plating electrode 35 is preferably used as a wiring electrode or an ohmic electrode.

<Fourth Embodiment> As a fourth embodiment, a metal electrode formed on the upper surface of a GaAs substrate and an insulating film formed on the upper surface of the substrate in contact with a part of the metal electrode are described. An example of forming a plated electrode by applying Au (gold) plating on a film will be described with reference to FIG.
FIG. 6 is a schematic process diagram for explaining the fourth embodiment, and corresponds to FIGS. 1 and 2. Hereinafter, the first
Only the points different from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

In this example, the fourth plating electrode forming portion 50
Is formed with the metal electrode 50a and the insulating film 50b.

First, an Au electrode 50a is formed above the upper surface 11a of the GaAs substrate 11 by the same process as in the first embodiment, and then the lower surface 50aa of the Au electrode 50a is formed from the lower surface 11b side of the substrate 11. Is formed (FIG. 6A).

Next, the Au electrode 5 is formed on the upper surface 11a of the substrate 11.
First contact hole 5 exposing upper surface 50ab of Oa
3 is formed (FIG. 6B).

Next, the lower surface 11b of the GaAs substrate 11, the inner wall 15a of the via hole, and the exposed lower surface 50a of the Au electrode 50a are formed in the same steps as in the first embodiment.
A conductive film 17 (current film) is formed on the substrate a (FIG. 6B).

Next, a resist film is formed by applying a resist on the Au electrode 50a and the insulating film 50b on the upper surface 11a side of the substrate 11, and the resist film is formed on the Au electrode 50a and the insulating film 50b by photolithography. A resist pattern 19 having a second contact hole 55 that is partially exposed is formed (FIG. 6C).

Next, in the same manner as in the first embodiment, the cathode pin 27 is brought into contact with the conductive film 17 provided on the lower surface 11b side of the substrate 11, and the Au electrode 50a and the insulating film 50 are formed.
A part of b is brought into contact with the electrolytic plating solution 33, and a negative voltage is applied to the cathode pin 27. In this example, overplating is performed with a longer voltage application time. As a result, A
The Au plating electrode 35 can be formed also on the u electrode 50a and the insulating film 50b (FIG. 6C). Also in this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

Thereafter, the resist pattern 19 is removed (FIG. 6D).

The formed Au plated electrode 35 is suitable for use as an ohmic electrode.

<Fifth Embodiment> As a fifth embodiment, a first electrode in which a metal electrode formed on the upper surface of a GaAs substrate is plated with Au (gold) to form a plated electrode.
An example different from the first embodiment will be described with reference to FIGS. 7 and 8 are schematic process diagrams for explaining the fifth embodiment, and each diagram is shown by a cross-section of a structure obtained in a main process step.

First, on the upper side of the upper surface 11a of the substrate 11, the first
In the same manner as in the embodiment, the fifth plated electrode forming portion 60
Is formed (FIG. 7A).

Next, a conductive film 17 electrically connected to the Au electrode 60 is formed on the lower surface 11b side of the substrate 11. First, the conductive film 17 is formed on the entire lower surface 11b of the substrate 11.
To form

In this example, the lower surface 11 of the GaAs substrate 11
b / Ti / A using an ordinary vacuum deposition method
A u film 17 is formed (FIG. 7B).

Next, the conductive film 17 is formed in the region of the substrate 11 located below the Au electrode 60 as the fifth plated electrode forming portion.
The conductive region 63 is formed to be electrically connected to the conductive region 63.

In this example, after a first resist is applied on the Ti / Au film 17 to form a first resist film,
A first resist pattern 61 having a first opening 61a exposing a portion of the Ti / Au film 17 is formed by removing a region of the first resist film located below the electrode 60. After that, Si ions are implanted from the opening 61a to perform an annealing process, so that the substrate 1 located below the Au electrode 60 is
The above-mentioned conductive region 63 is formed in 1. This conductive region 63 conducts with the Ti / Au film 17 (FIG. 7C).

After that, the first resist pattern 61 is removed (FIG. 8A).

Next, using the conductive film 17 as a cathode,
The plating electrode 35 is formed on the Au electrode 60 as a plating electrode formation part. Since this step is the same as in the first embodiment, a brief description will be given. A second resist film is formed by applying a second resist on the entire upper surface 11a of the substrate 11 and removing the region of the second resist film on the Au electrode 60 to partially expose the Au electrode 60. Opening 6
A second resist pattern 65 having 5a is formed (FIG. 8B). At least the exposed upper surface of the Au electrode 60 is brought into contact with the electrolytic plating solution 33 containing Au ions, and the cathode pin 27 is brought into contact with the Ti / Au film 17 to apply a negative voltage to the cathode pin 27. . As a result, Au precipitates on the Au electrode 60, and the Au plated electrode 35 is formed (FIG. 8B). Also in this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

After the completion of the Au plating on the Au electrode 60, the second resist pattern 65 is removed (FIG. 8).
(C)).

In this embodiment, the fifth plated electrode forming portion 60 may be not only the metal electrode but also the metal electrode 50a and the insulating film 50b used in the fourth embodiment.

The conductive region 63 may be formed in a region of the substrate 11 below the Au electrode 60 within a range not exceeding the region of the upper surface 11a of the substrate 11 on which the Au electrode 60 is formed. 7 (C).

The formed Au plated electrode 35 is
It is suitable for use as an ohmic electrode.

<Sixth Embodiment> As a sixth embodiment, an example in which both a plating electrode forming portion and a current film are simultaneously formed by a conductive layer formed on the entire GaAs substrate will be described with reference to FIGS. This will be described with reference to FIG.
9 and 10 are schematic process diagrams for explaining the sixth embodiment. Each figure shows a cross section of the structure obtained in the main process step.

First, a conductive plating electrode forming portion is provided on the upper surface of the substrate, and a conductive film electrically connected to the plating electrode forming portion is formed on the lower surface side of the substrate. This step is the sixth
The plating electrode forming portion and the conductive film are formed as a continuous integrated layer as a conductive layer. Therefore, by forming this conductive layer on at least the upper surface, the lower surface, and both side surfaces of the surface of the substrate, it can be formed simultaneously in one step.

In this example, first, a Ti / Au layer 71 is formed using a vacuum evaporation method, a sputtering method, or a CVD method so as to cover the entire surface of the GaAs substrate 11 (FIG. 9A).

Next, a resist film is formed by applying a resist on the Ti / Au layer 71 on the side of the upper surface 11a of the GaAs substrate 11, and the size of the sixth plated electrode forming portion 70 is formed on the resist film by photolithography. Is formed with a resist pattern 19 having an opening 73 corresponding to. Thus, the Ti / Au layer 71 is exposed in the opening 73. This exposed portion becomes the sixth plated electrode forming portion 70.
Then, T formed on the lower surface side of the GaAs substrate 11 is formed.
The i / Au layer 71 becomes the conductive film 17. The sixth plating electrode forming portion 70 and the conductive film 17 are electrically connected (FIG. 9).
(B)).

Next, a plating electrode 35 is formed on the sixth plating electrode forming portion 70 using the conductive film 17 as a cathode. Since this step is the same as in the first embodiment,
A brief description will be given.

The cathode pin 27 is brought into contact with the Ti / Au layer 71 formed on the lower surface 11b side of the GaAs substrate 11, and at least the first
The Ti / Au layer 71 exposed in the opening 73 is brought into contact with the electrolytic plating solution 33 containing Au ions, and a negative voltage is applied to the cathode pin 27. Then, Au is deposited on the Ti / Au layer 71 in the first opening 73 of the resist pattern 19, that is, on the sixth plated electrode forming portion 70. And this Au becomes the Au plating electrode 35. (FIG. 9 (C)).
Also in this figure, the level of the plating solution is indicated by a dashed line for easy understanding.

When the deposited Au has a desired film thickness, the plating is finished and the resist 19 is removed (FIG. 10).
(A)). After that, the Ti / Au layer 71 other than the Ti / Au layer 71a located under the Au plating electrode 35 is removed by wet etching and dry etching (FIG. 10B).

As a result, the number of steps can be reduced, and the time for forming the plating electrode 35 can be shortened.
It becomes easy to form a plated electrode. In addition, the cathode pin 2
7 does not come into contact with the plating solution and does not penetrate the resist pattern, so that the shape of the cathode pin 27 is not deteriorated and the contact between the cathode pin 27 and the conductive film 17 is improved.

The Au plated electrode 35 thus formed is suitable for use as a wiring electrode.

[0091]

As is apparent from the above description, in forming a plating electrode on a substrate by using an electrolytic plating method, a conductive plating electrode forming portion, for example, a metal electrode or an active layer is provided on the upper surface of the substrate. A conductive film (current film) electrically connected to the plating electrode forming portion, for example, Ti / Au
A film is formed on the lower surface side of the substrate, a cathode pin as a cathode is brought into contact with the conductive film from the lower surface side of the substrate, and plating is performed by an electroplating method using the conductive film as a cathode. The plating electrode is formed by depositing on the plating electrode forming portion. By providing the conductive film on the lower surface side of the substrate as described above, it is not necessary to remove the conductive film after completion of the plating electrode, so that the manufacturing time can be shortened and the plated electrode can be easily formed.

Also, since the cathode pins of the plating apparatus used to turn the conductive film into a cathode are provided at positions away from the level of the electrolytic plating solution, and are brought into direct contact with the conductive film exposed on the lower surface side of the substrate. The contact can be easily made without penetrating the resist or the like as in the related art. For this reason, deterioration and deterioration of the shape of the cathode pin can be prevented. Further, since the cathode pin does not come into contact with the electrolytic plating solution, plating metal does not deposit at the tip of the pin. Therefore, poor contact between the cathode pin and the conductive film is also reduced.

Accordingly, the variation in the thickness of the plating electrode is reduced, the quality of the film is good, and the growth rate of the film can be stabilized.

The method of forming a plated electrode according to the present invention is preferably applied to a compound semiconductor element using InP or the like, a semiconductor element using Si or the like, an element using an insulating substrate such as sapphire, or the like. is there. The plating metal is Au
Alternatively, Ni, Sn, Cu, or the like may be used.

[Brief description of the drawings]

FIGS. 1A to 1C are schematic process diagrams for explaining a first embodiment;

FIGS. 2A to 2C are schematic process diagrams following FIG. 1 for explaining the first embodiment;

FIG. 3 is a schematic image diagram showing a relationship between a plating apparatus used for carrying out a method of forming a plated electrode of the present invention and a structure to be plated.

FIGS. 4A to 4D are schematic process diagrams for explaining a second embodiment;

FIGS. 5A to 5D are schematic process diagrams for explaining a third embodiment; FIGS.

FIGS. 6A to 6D are schematic process diagrams used for describing a fourth embodiment;

FIGS. 7A to 7C are schematic process diagrams used to explain a fifth embodiment;

FIGS. 8A to 8C are schematic process diagrams following FIG. 7 for describing a fifth embodiment;

FIGS. 9A to 9C are schematic process diagrams for explaining a sixth embodiment; FIGS.

FIGS. 10A and 10B are schematic process diagrams following FIG. 9 for explaining the sixth embodiment; FIGS.

FIGS. 11A to 11D are schematic process diagrams for explaining a conventional technique.

12 (A) to 12 (C) are schematic process diagrams subsequent to FIG. 11 for explaining a conventional technique.

FIG. 13 is a schematic image diagram showing a relationship between a conventional plating apparatus and a structure to be plated.

[Description of Signs] 10: First plating electrode forming portion, metal electrode, Au electrode 10a: Lower surface 10b: Upper surface 11, 110: Substrate, GaAs substrate 11a: Upper surface 11b: Lower surface 13: Window 15: Via hole 15a: Inner wall 17 , 170: conductive film, current film, Ti / Au
Film 19, 190: resist pattern 21, 210: plating apparatus, apparatus 23, 230: plating tank 25, 250: DC power supply 27, 270: cathode pin, pin 29, 290: anode 30: second plating electrode forming section, active Layer 30a: lower surface 30b: upper surface 31, 310: plating solution circulation pump 32: window 33, 330: electrolytic plating solution, plating solution 33a, 330a: liquid surface 35, 350: plating electrode, Au plating electrode 40: third plating electrode Forming part 40a: Active layer 40b: Metal electrode, Au electrode 40aa: Lower surface 42: Window 50: Fourth plating electrode forming part 50a: Metal electrode, Au electrode 50b: Insulating film 50aa: Lower surface 50ab: Upper surface 53: First contact hole 55: second contact hole 60: fifth plating electrode forming portion, Au electrode 61: first resist pattern 61a: First opening 63: Conductive region 65: Second resist pattern 65a: Second opening 70: Sixth plating electrode forming portion 71: Conductive layer, Ti / Au layer 71a: Ti located below Au plating electrode / Au layer 73: Opening 130: Metal electrode 150: Insulating film 160: Contact hole 160a: Inner wall 170a: Rest of current film 400: Electrode

Claims (11)

[Claims] When forming a plating electrode on a substrate by using an electrolytic plating method, (a) providing a conductive plating electrode forming portion on an upper surface of the substrate; and (b) electrically connecting with the plating electrode forming portion. A method for forming a plated electrode, comprising: forming a conductive film to be connected on the lower surface side of the substrate; and (c) forming the plated electrode on the plated electrode forming portion using the conductive film as a cathode. 2. The plating method according to claim 1, wherein the step (a) includes a step of forming a metal electrode as the plating electrode forming portion on an upper side of an upper surface of the substrate. Method of forming electrodes. 3. The method for forming a plated electrode according to claim 1, wherein the step (a) includes a step of forming an active layer as the plated electrode forming portion in a surface region of an upper surface of the substrate. The method of forming the plating electrode. 4. The method for forming a plating electrode according to claim 1, wherein the step (a) comprises: forming an active layer as a plating electrode forming part in a surface region of an upper surface of the substrate; Forming a metal electrode in contact with a part of the active layer on the upper side of the substrate. 5. The method for forming a plated electrode according to claim 1, wherein the step (a) comprises: forming a metal electrode above the upper surface of the substrate as the plated electrode forming portion; Forming an insulating film in contact with a part of the metal electrode on the upper side. 6. The method for forming a plated electrode according to claim 1, wherein in the step (b), a via hole reaching the plated electrode formation portion from a lower surface of the substrate is formed by penetrating through the substrate. Forming the conductive film on the lower surface of the substrate and the inner wall of the via hole. 7. The method for forming a plated electrode according to claim 1, wherein the step (b) comprises: forming the conductive film on the entire lower surface of the substrate; and a substrate located below the plated electrode forming portion. Forming a conductive region in the conductive film, the conductive region being electrically connected to the conductive film. 8. The method for forming a plated electrode according to claim 7, wherein the conductive region is formed using an ion implantation and annealing technique. 9. The method for forming a plating electrode according to claim 1, wherein the plating electrode forming portion in the step (a) and the conductive film in the step (b) are formed by forming a conductive layer on the entire surface of the substrate. And a method of forming a plated electrode, characterized in that they are formed simultaneously in one step. 10. The method of forming a plated electrode according to claim 1, wherein in the step (c), a step of contacting a cathode pin with the conductive film is performed, and an electrolytic plating solution is contacted with the cathode pin. Applying a negative voltage to the cathode pin while at least contacting the exposed surface of the plating electrode formation portion. 11. The method for forming a plated electrode according to claim 10, wherein the cathode pin is brought into contact with the conductive film on the lower surface side of the substrate.