JP2017195379A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device and a method of manufacturing the same capable of preventing oxidation of an electrode containing Ni and thereby preventing deterioration in wettability with solder, and of achieving good electrical contact between the semiconductor substrate and the electrode at low cost.SOLUTION: A semiconductor device 1 comprises: a semiconductor substrate 2; and a rear face electrode 4 formed by sequentially laminating a first metal electrode 41, a second metal electrode 42, and a third metal electrode 43, on the semiconductor substrate 2. The first metal electrode 41 is formed of Ti or a Ti alloy. The second metal electrode 42 is formed of Ni or a Ni alloy. The third metal electrode 43 is an alloy of Ag and at least one or more of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi. A metal film formed of Ag is further provided between the second metal electrode and the third metal electrode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor device including a metal electrode formed by stacking a plurality of metal films and a method for manufacturing the same.

  In many semiconductor devices used for power conversion or the like, metal electrodes are formed on the front and back surfaces of a semiconductor substrate in order to pass a current in the vertical direction of the semiconductor device. As a method of mounting such a semiconductor device on a circuit board, soldering is used as a simple method. For mounting a semiconductor device by soldering, for example, it is necessary to join the semiconductor device and the circuit board by forming an alloy layer with a back electrode of the semiconductor device and solder.

  A Ni electrode that forms a stable alloy with Sn, which is a main component of solder, is used for the back electrode of the semiconductor device. However, Ni is easily oxidized in the air, and the oxidized Ni has a very poor bondability with the solder. Therefore, conventionally, various methods for suppressing oxidation of the surface of the Ni electrode (hereinafter also referred to as surface oxidation) have been proposed.

  For example, a Ti electrode, a Ni electrode, and an Au electrode are sequentially stacked on a semiconductor substrate, and are electrically connected to the semiconductor substrate by the Ti electrode so that the Ni electrode does not oxidize by direct contact with air by the Au electrode. (See, for example, Patent Documents 1 and 2).

  Further, a method for preventing oxidation of the Ni electrode by forming a Pd / Au laminated electrode on the surface of the Ni electrode is disclosed (for example, see Patent Document 3).

  In addition, a method for preventing oxidation of the Ni electrode by forming an AuSi electrode, a Ti electrode, a Ni electrode, and an Ag electrode on the semiconductor substrate in order is disclosed (for example, see Patent Document 4).

JP-A-6-77262 JP 2011-233643 A JP 2007-63042 A JP-A-61-220344

  In Patent Documents 1 and 2, an Au electrode is formed on the surface of the Ni electrode, and has a function of preventing oxidation of the Ni electrode. However, Au has a problem that the price is very high (high cost) due to the recent increase in demand.

  In Patent Document 3, the Pd / Au electrode is formed on the surface of the Ni electrode, and has the function of preventing the oxidation of the Ni electrode as in the case of forming only the Au electrode. However, compared with the case where only the Au electrode is used, the amount of Au used can be reduced, but the consumption of Au remains unchanged, and high cost becomes a problem. Moreover, although Pd is cheaper than Au, the price is high.

  Further, in Patent Document 4, an Ag electrode is formed on the surface of a Ni electrode, and if soldering is performed immediately after the formation of the Ag electrode, the minimum necessary effect on the surface oxidation of the Ni electrode can be obtained ( The oxidation of the Ni electrode can be suppressed to some extent). However, in the case where the outermost surface of each laminated electrode is an Ag electrode, if the time for leaving (exposed) in an environment with a high sulfur concentration is long, Ag is easily sulfided. As a result, the wettability with the solder is deteriorated. Further, since Ag has poor barrier performance against oxygen, it is known that when heat treatment is performed in an atmosphere in which oxygen exists after the formation of the Ag electrode, the surface of the Ni electrode is oxidized by oxygen that has passed through the Ag electrode. As a result, there is a problem that the wettability of the solder deteriorates.

  The present invention has been made to solve these problems, and prevents oxidation of the electrode containing Ni without deteriorating the wettability with the solder, and electrically between the semiconductor substrate and the electrode. The present invention relates to a semiconductor device capable of realizing good contact at low cost and a method for manufacturing the same.

  In order to solve the above problems, a semiconductor device according to the present invention includes a semiconductor substrate, a metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate. The first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag, Pd, Ni, Cu, Mg, Zn, Nd, It is an alloy with at least one of Sn and Bi, and further includes a metal film made of Ag between the second metal electrode and the third metal electrode.

  A semiconductor device according to the present invention includes a semiconductor substrate, and a metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate, the first metal electrode Is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag and at least one of Pd, Ni, Mg, Zn, Nd, Sn, and Bi It is an alloy mainly composed of Ag as described above.

  The semiconductor device according to the present invention includes a semiconductor substrate, a metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate, and a metal electrode via solder. And the first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag, Pd, Ni, Mg , Zn, Nd, Sn, and Bi.

  Further, the method of manufacturing a semiconductor device according to the present invention includes (a) a step of preparing a semiconductor substrate, (b) a step of forming a surface electrode on the surface of the semiconductor substrate, and (c) on the back surface of the semiconductor substrate. A step of sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode to form a back electrode; and (d) a temperature from 0 ° C. to 180 ° C. in the atmosphere by bringing a probe into contact with the front electrode. In the step (b), the first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is An alloy of Ag and at least one or more of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi.

  According to another aspect of the present invention, there is provided a semiconductor device manufacturing method comprising: (a) preparing a semiconductor substrate; and (b) sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate. Forming a metal electrode, and in step (b), the first metal electrode is Ti or a Ti alloy, the second metal electrode is Ni or a Ni alloy, and the third metal electrode is Ag. And an alloy of at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi, and further comprising a metal film made of Ag between the second metal electrode and the third metal electrode. Form.

  According to another aspect of the present invention, there is provided a semiconductor device manufacturing method comprising: (a) preparing a semiconductor substrate; and (b) sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate. Forming a metal electrode, and in step (b), the first metal electrode is Ti or a Ti alloy, the second metal electrode is Ni or a Ni alloy, and the third metal electrode is Ag. And at least one of Pd, Ni, Mg, Zn, Nd, Sn, and Bi.

  According to the present invention, a semiconductor device includes a semiconductor substrate, and a metal electrode formed by sequentially stacking a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate. Is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag and Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi It is an alloy of at least one or more, and further includes a metal film made of Ag between the second metal electrode and the third metal electrode, so that oxidation of the electrode containing Ni is prevented and wettability with the solder is deteriorated. In addition, it is possible to achieve an electrical good contact between the semiconductor substrate and the electrode at a low cost.

  The semiconductor device includes a semiconductor substrate, and a metal electrode formed by sequentially stacking a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate, and the first metal electrode includes Ti Or a Ti alloy, the second metal electrode is Ni or a Ni alloy, and the third metal electrode is made of Ag and at least one of Pd, Ni, Mg, Zn, Nd, Sn, and Bi. Since it is an alloy containing Ag as a main component, oxidation of the electrode containing Ni is prevented, wettability with the solder is not deteriorated, and good electrical contact is obtained between the semiconductor substrate and the electrode. It can be realized at low cost.

  Further, the semiconductor device is joined to the metal electrode via a semiconductor substrate, a metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate, and solder. The first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag, Pd, Ni, Mg, Zn, Since it is an alloy with at least one of Nd, Sn, and Bi, oxidation of the electrode containing Ni is prevented, so that the wettability with the solder is not deteriorated, and electrical property between the semiconductor substrate and the electrode is reduced. It is possible to achieve good contact at low cost.

  In addition, a method for manufacturing a semiconductor device includes: (a) a step of preparing a semiconductor substrate; (b) a step of forming a surface electrode on the surface of the semiconductor substrate; and (c) a first metal on the back surface of the semiconductor substrate. A step of laminating an electrode, a second metal electrode, and a third metal electrode in order to form a back electrode; and (d) contacting the probe with the front electrode to conduct electricity in the temperature range from 0 ° C. to 180 ° C. in the atmosphere. A step of performing characteristic inspection, wherein in step (b), the first metal electrode is Ti or a Ti alloy, the second metal electrode is Ni or a Ni alloy, and the third metal electrode is Ag. Since it is an alloy with at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi, oxidation of the electrode containing Ni is prevented and wettability with the solder is not deteriorated, and Electrically good between semiconductor substrate and electrode It is possible to realize a low cost to obtain a Do contact.

  In addition, the semiconductor device manufacturing method includes: (a) a step of preparing a semiconductor substrate; and (b) a first metal electrode, a second metal electrode, and a third metal electrode stacked on the semiconductor substrate in order. In the step (b), the first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag and Pd. , Ni, Cu, Mg, Zn, Nd, Sn, and Bi, in order to further form a metal film made of Ag between the second metal electrode and the third metal electrode In addition, it is possible to realize at low cost that the electrode containing Ni is prevented from being oxidized and the wettability with the solder is not deteriorated and that an electrical good contact is obtained between the semiconductor substrate and the electrode. .

  In addition, the semiconductor device manufacturing method includes: (a) a step of preparing a semiconductor substrate; and (b) a first metal electrode, a second metal electrode, and a third metal electrode stacked on the semiconductor substrate in order. In the step (b), the first metal electrode is Ti or Ti alloy, the second metal electrode is Ni or Ni alloy, and the third metal electrode is Ag and Pd. , Ni, Mg, Zn, Nd, Sn, and Bi, which is an alloy mainly composed of Ag and at least one of Bi, prevents oxidation of Ni-containing electrodes and deteriorates wettability with solder. In addition, it is possible to achieve an electrical good contact between the semiconductor substrate and the electrode at a low cost.

It is a figure which shows an example of the cross section of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the cross section of the back surface electrode part of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 1 of this invention. It is a figure which shows an example of the result of the solder wettability test by Embodiment 1 of this invention. It is a figure which shows an example of the cross section of the back surface electrode part of the semiconductor device by Embodiment 2 of this invention. It is a figure which shows an example of the cross section of the semiconductor device by Embodiment 3 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 3 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 3 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 3 of this invention. It is a figure which shows an example of the manufacturing process of the semiconductor device by Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
First, the configuration of the semiconductor device according to the first embodiment of the present invention will be described.

  FIG. 1 is a diagram showing an example of a cross section of the semiconductor device 1 according to the first embodiment. FIG. 2 is an enlarged cross-sectional view of the back electrode 4 portion of the semiconductor device 1. In the first embodiment, the case where the semiconductor device 1 is a diode is shown as an example. Hereinafter, the surface of the semiconductor substrate 2 refers to the surface on the side where the surface electrode 3 is formed, and the back surface of the semiconductor substrate 2 refers to the surface on the side where the back electrode 4 is formed. .

  As shown in FIGS. 1 and 2, the semiconductor device 1 includes a semiconductor substrate 2, a surface electrode 3, a back electrode 4, and an insulating film 5. The back electrode 4 is formed by sequentially laminating a first metal electrode 41, a second metal electrode 42, and a third metal electrode 43 on the back surface of the semiconductor substrate 2.

  As the semiconductor substrate 2, a Si substrate or a SiC substrate is used. When the semiconductor device 1 is a diode or MOSFET (Metal Oxide Semiconductor Field Effect Transistor), the layer on the main surface (back surface) side that forms the back electrode 4 in the semiconductor substrate 2 is an n-type semiconductor layer, and IGBT (Insulated Gate Bipolar). Transistor) is a p-type semiconductor layer.

  Next, the 1st metal electrode 41, the 2nd metal electrode 42, and the 3rd metal electrode 43 which comprise the back surface electrode 4 are demonstrated in detail.

  The first metal electrode 41 is made of Ti or a Ti alloy, and is provided for obtaining ohmic contact between the semiconductor substrate 2 and the back electrode 4. Further, the first metal electrode 41 is configured such that when the second metal electrode 42 and the solder 9 (see FIG. 7) form an alloy over the entire area of the second metal electrode 42, the solder 9 comes into contact with the semiconductor substrate 2. It also has a function as a barrier layer to prevent. That is, since an alloy layer is not formed between the semiconductor substrate 2 and the solder 9, the semiconductor substrate 2 and the solder 9 come into contact with each other, and the adhesion between the semiconductor substrate 2 and the solder 9 is reduced. It is possible to prevent the semiconductor substrate 2 from peeling off.

  Here, the thickness of the first metal electrode 41 is preferably 20 nm or more and 1000 nm or less. When the thickness of the first metal electrode 41 is thinner than 20 nm, the function as a barrier layer may not be exhibited. Further, when the thickness of the first metal electrode 41 is thicker than 1000 nm, the vertical resistance in the semiconductor device 1 increases and the electrical characteristics deteriorate.

  The second metal electrode 42 is Ni and is provided for the purpose of forming an alloy with Sn contained in the solder 9. That is, the second metal electrode 42 forms an alloy with the solder 9 to electrically connect the back electrode 4 and the circuit board 8 (see FIG. 7), and also generates heat generated in the semiconductor device 1. A route to escape is formed.

  Here, the thickness of the second metal electrode 42 is preferably 200 nm or more and 7000 nm or less. When the thickness of the second metal electrode 42 is less than 200 nm, the second metal electrode 42 is entirely alloyed during soldering, and when a defect occurs during soldering and it becomes necessary to perform soldering again, The second metal electrode 42 does not exist, and it becomes impossible to join the solder 9 (an alloy cannot be formed with the solder 9). When the thickness of the second metal electrode 42 is greater than 7000 nm, the warp of the semiconductor device 1 increases due to the difference between the Ni expansion coefficient of the semiconductor substrate 2 and the second metal electrode 42, and the transport of the semiconductor device 1. Or soldering work may be hindered.

  The third metal electrode 43 is an alloy of Ag and at least one element of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi. The third metal electrode 43 is provided in order to prevent surface oxidation of the second metal electrode 42 and improve wettability with the solder 9 in the back electrode 4. Further, when at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi is added to Ag, Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi are added. At least one or more of the above is concentrated on the surface of the third metal electrode 43 and exhibits a function of preventing oxygen from permeating.

  Here, the thickness of the third metal electrode 43 is preferably 20 nm or more and 500 nm or less. When the thickness of the third metal electrode 43 is thinner than 20 nm, the function of preventing the surface oxidation of the second metal electrode 42 cannot be sufficiently exhibited. Moreover, when the thickness of the third metal electrode 43 is thicker than 500 nm, it is difficult to manufacture the semiconductor device 1 at low cost.

  The content of one or more elements selected from Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi in the third metal electrode 43 is preferably 0.1 wt% to 20 wt%. If it is the said content, the conditions for implement | achieving both prevention of the surface oxidation of the 2nd metal electrode 42 and cost reduction are satisfy | filled.

  Next, a method for manufacturing the semiconductor device 1 will be described with reference to FIGS. Below, especially the manufacturing method of the back surface electrode 4, and the joining method of the semiconductor device 1 and the circuit board 8 are demonstrated.

  The diode, bipolar transistor, MOSFET, or IGBT formed in the semiconductor substrate 2 can be formed by a known method. Similarly, the surface electrode 3 can be formed by a known method.

  In FIG. 3, a semiconductor element such as a diode, bipolar transistor, MOSFET, or IGBT is formed in a semiconductor substrate 2 by using an n-type semiconductor, a p-type semiconductor, an insulating film, polysilicon, or the like.

  Next, the surface electrode 3 is formed on the surface of the semiconductor substrate 2 on which the semiconductor element is formed. The surface electrode 3 is made of Al, Al—Si, Al—Si—Cu, Al—Cu, or the like, and is formed by a sputtering method, a vacuum evaporation method, or the like.

  In FIG. 4, the back surface of the semiconductor substrate 2 is ground until the semiconductor substrate 2 has a desired thickness. As a grinding method, there are a method of physically shaving with a grindstone, a method of chemically shaving with an acid, or a method of combining these two methods.

  In FIG. 5, the first metal electrode 41, the second metal electrode 42, and the third metal electrode 43 are sequentially stacked on the back surface of the semiconductor substrate 2 to form the back electrode 4. Here, “continuous lamination” means that the first metal electrode 41, the second metal electrode 42, and the third metal electrode are not taken out of the semiconductor substrate 2 from the film forming apparatus (the apparatus for forming the back electrode 4). 43 is formed in order.

  Before the back electrode 4 is formed, hydrofluoric acid treatment, ammonia hydrogen peroxide / hydrochloric acid hydrogen peroxide / sulfuric acid hydrogen peroxide treatment is performed in order to remove a natural oxide film or foreign matters formed on the surface of the semiconductor substrate 2. Alternatively, a sputter etching process is performed.

  The back electrode 4 is formed by sputtering or vacuum deposition. At this time, in order to form the above-described laminated structure (a laminated structure composed of the first metal electrode 41, the second metal electrode 42, and the third metal electrode 43), a sputter target or a vapor deposition source corresponding to each metal electrode is used. It arrange | positions beforehand in one vacuum apparatus (same as said film-forming apparatus). By doing so, the above laminated structure can be formed without exposing to the atmosphere when forming each metal electrode. If each metal electrode is formed and exposed to the atmosphere, a natural oxide film is formed on the surface of each metal electrode, resulting in a decrease in adhesion between each metal electrode, deterioration in electrical characteristics, and bonding during soldering. Defects occur.

  The first metal electrode 41 may form a silicide layer with the semiconductor substrate 2 when the temperature rises during the formation of the first metal electrode 41, but there is no particular problem here.

  The second metal electrode 42 uses Ni in the first embodiment, but may use, for example, a Ni-V alloy. Since the Ni-V alloy is a non-magnetic material, it is easy to increase the thickness of the sputtering target. In addition, there is a merit that a magnetic circuit mechanism of a sputtering apparatus dedicated to a magnetic material becomes unnecessary.

  The third metal electrode 43 is an alloy layer mainly composed of Ag, and is formed by using a sputtering target configured with a predetermined impurity ratio as the third metal electrode 43. In addition, by preparing a sputter target or vapor deposition source of the impurity metal constituting the third metal electrode 43 and adjusting the film formation rate so as to have a predetermined impurity ratio, simultaneous multi-source sputtering or multi-source vapor deposition is performed. The third metal electrode 43 may be formed.

  Heat treatment may be performed in a vacuum or an inert gas during or after the back electrode 4 is formed. By performing the heat treatment, it is possible to improve the adhesion between the metal electrodes, and to release moisture contained in a minute amount in the metal electrode that causes bonding failure during soldering.

  Note that an Ag layer (a metal film made of Ag) may be formed between the second metal electrode 42 and the third metal electrode 43. In this case, the thickness of the third metal electrode 43 can be reduced, which contributes to cost reduction of the back electrode 4.

  In FIG. 6, an electrical characteristic inspection of the semiconductor device 1 is performed. The electrical characteristic inspection is performed by placing the semiconductor device 1 on the stage 6 connected to an inspection circuit (not shown) and bringing the probe 7 connected to the inspection circuit into contact with the surface electrode 3. In addition, the electrical characteristic inspection is performed under the condition that the temperature of the stage 6 is changed from room temperature to about 200 ° C. in consideration of the situation where the semiconductor device 1 is actually used. In this case, the electrical property inspection is often performed in the atmosphere.

  After the electrical characteristic inspection, an appearance inspection of the semiconductor device 1 is performed. The appearance inspection is performed by visual inspection by an operator or image processing by an appearance inspection apparatus.

  In FIG. 7, the semiconductor device 1 and the circuit board 8 are joined using solder 9.

  For example, paste solder (paste-like solder 9) may be applied on the circuit board 8, and the semiconductor device 1 may be placed on the applied paste solder, and then bonded by heating and cooling. Alternatively, the solder 9 may be placed on the preheated circuit board 8 and melted, and then the semiconductor device 1 may be placed on the melted solder 9 and cooled to join. Alternatively, the molten solder 9 may be applied on the preheated circuit board 8 and then the semiconductor device 1 may be placed and bonded.

  The solder 9 is mainly composed of Sn and contains Ag, Cu, Bi, Sb, P, and the like.

  When Ag is used for the third metal electrode 43 (see, for example, Patent Document 4), when high-temperature heat treatment is performed in the atmosphere at the time of electrical property inspection, the surface of Ni as the second metal electrode 42 is oxidized, and the subsequent solder In some cases, bonding failure occurred during attachment. In addition, the grain growth during the appearance inspection of the back electrode 4 causes the electrode surface to become clouded, and there is a problem that a defect is determined in the appearance inspection.

  On the other hand, in the first embodiment, the third metal electrode 43 is made of an alloy of Ag and at least one element of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi. Since at least one or more of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi is concentrated on the surface of the third metal electrode 43, the permeation of oxygen is suppressed, and after the film formation (first The heat resistance performance after the formation of the three metal electrodes 43 is improved.

  FIG. 8 is a diagram illustrating an example of a result of the solder wettability test performed on the semiconductor device 1 manufactured through the structural steps shown in FIGS. 3 to 7.

  The solder wettability test shown in FIG. 8 is an evaluation of the bonding performance of the back electrode 4 of the semiconductor device 1 to the solder 9 using solder balls. As an evaluation sample, the semiconductor device 1 and the back electrode 4 heated at 180 ° C. for 30 minutes in the air immediately after forming the back electrode 4 were used. Further, a solder ball is placed on the evaluation sample with the back electrode 4 as the upper surface, heated to 200 ° C. in a formic acid atmosphere to reduce the surface, heated to 280 ° C. to melt the solder ball, and after cooling The area where the solder ball spreads out was calculated.

  In FIG. 8, “◯” indicates the third metal electrode 43 according to the first embodiment, that is, the third metal electrode 43 is made of Ag, Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi. The results in the case of an alloy with at least one of these elements are shown. In addition, “x” indicates a result when the third metal electrode 43 according to the first embodiment is Ag (conventional example).

  As shown in FIG. 8, it can be seen that the third metal electrode 43 according to the first embodiment has a larger solder wetting and spreading area than the conventional example even when the high temperature heat treatment is performed. That is, it was confirmed that the third metal electrode 43 according to the first embodiment has better solder wettability than the conventional example.

  From the above, according to the first embodiment, the surface of Ni that is the second metal electrode 42 is oxidized even when the stage 6 is at a high temperature of about 200 ° C. in the atmosphere during the electrical property inspection. I will not let you. Accordingly, when soldering to the circuit board 8 thereafter, the probability that a bonding failure will occur is significantly reduced (the wettability with the solder does not deteriorate). Moreover, when the back surface electrode 4 is visually inspected, discoloration (white turbidity) of the back surface electrode 4 can be suppressed, so that the semiconductor device 1 can be transferred to the solder bonding step without being judged as defective during the appearance inspection. . Further, the first metal electrode 41 forms an ohmic contact (electrically good contact) with the semiconductor substrate 2, so that the semiconductor device 1 that does not cause a loss (loss) in the current flowing in the vertical direction of the semiconductor device 1. Is obtained. Further, since the back electrode 4 does not contain Au, the semiconductor device 1 can be realized at low cost.

  Note that an insulating film 5 as shown in FIG. 1 may be formed before FIG.

<Embodiment 2>
FIG. 9 is a diagram showing an example of a cross section of the back electrode 4 portion of the semiconductor device 1 according to the second embodiment of the present invention.

  The semiconductor device 1 according to the second embodiment is characterized in that a fourth metal electrode 44 is provided between the semiconductor substrate 2 and the first metal electrode 41. Other configurations are the same as those in the first embodiment, and thus description thereof is omitted here. FIG. 9 shows a state in which the back electrode 4 is formed after passing through FIGS. 3 and 4 of the first embodiment. In the following, the description will be given focusing on the difference from the first embodiment.

  As shown in FIG. 9, the fourth metal electrode 44, the first metal electrode 41, the second metal electrode 42, and the third metal electrode 43 are sequentially stacked on the back surface of the semiconductor substrate 2 to form the back electrode 4. .

  The first metal electrode 41 includes at least one of Ti, V, Cr, and Mo. The first metal electrode 41 is in contact with the fourth metal electrode 44 when the second metal electrode 42 and the solder 9 (see FIG. 7) form an alloy throughout the entire area of the second metal electrode 42. It also has a barrier layer function to prevent this.

  When the back side layer of the semiconductor substrate 2 is a p-type semiconductor layer, the fourth metal electrode 44 is Al, or Al—Si, Al—Si—Cu, Al—Cu (of Al, Si and Cu). Alloy with any one or more). The fourth metal electrode 44 is made of Ni or Ni—Si when the back side layer of the semiconductor substrate 2 is an n-type semiconductor layer. With such a configuration, it is possible to obtain good ohmic performance with the semiconductor substrate 2 (the fourth metal electrode 44 forms ohmic contact (electrically good contact) with the semiconductor substrate 2. can do).

  Here, the thickness of the fourth metal electrode 44 is preferably 10 nm or more and 1000 nm or less. When the thickness of the fourth metal electrode 44 is thinner than 10 nm, good ohmic performance cannot be sufficiently exhibited with the semiconductor substrate 2. In addition, when the thickness of the fourth metal electrode 44 is thicker than 1000 nm, there is a possibility that the vertical resistance in the semiconductor device 1 increases and the electrical characteristics deteriorate.

  Second metal electrode 42 and third metal electrode 43 are formed by the same method and material (composition) as in the first embodiment.

  In the case where the back electrode 4 is formed, in the first embodiment, it is preferable to form the semiconductor device 1 without taking it out of the film forming apparatus.

  On the other hand, in the second embodiment, after the fourth metal electrode 44 is formed, the semiconductor device 1 is once taken out from the film forming apparatus, and after being subjected to heat treatment, is again put into the film forming apparatus, and then the first metal electrode 41 and the second metal electrode 42. The third metal electrode 43 may be formed continuously. As described above, by performing the heat treatment after the formation of the fourth metal electrode 44, the ohmic performance between the semiconductor substrate 2 and the fourth metal electrode 44 is stabilized, and thus the electrical characteristics of the semiconductor device 1 are stabilized.

  From the above, according to the second embodiment, even if the back side layer of the semiconductor substrate 2 is either a p-type semiconductor layer or an n-type semiconductor device, it is between the semiconductor substrate 2 and the back electrode 4. Since good ohmic contact can be formed, the electrical characteristics of the semiconductor device 1 can be improved.

<Embodiment 3>
First, the configuration of the semiconductor device according to the third embodiment of the present invention will be described.

  FIG. 10 is a diagram showing an example of a cross section of the semiconductor device 1 according to the third embodiment.

  The semiconductor device 1 according to the third embodiment is characterized in that not only the back surface electrode 4 but also the front surface electrode 3 are laminated. That is, the front electrode 3 and the back electrode 4 formed by stacking are provided on the front and back surfaces of the semiconductor substrate 2.

  As shown in FIG. 10, the semiconductor device 1 includes a semiconductor substrate 2, a front electrode 3, a back electrode 4, and an insulating film 5.

  The surface electrode 3 is formed by sequentially stacking an eighth metal electrode 34, a fifth metal electrode 31, a sixth metal electrode 32, and a seventh metal electrode 33 on the surface of the semiconductor substrate 2.

  The back electrode 4 is formed by sequentially laminating a first metal electrode 41, a second metal electrode 42, and a third metal electrode 43 on the back surface of the semiconductor substrate 2.

  The first metal electrode 41 and the fifth metal electrode 31 include at least one of Ti, V, Cr, and Mo.

  The second metal electrode 42 and the sixth metal electrode 32 are Ni.

  The third metal electrode 43 and the seventh metal electrode 33 are an alloy of Ag and at least one element of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi.

  The eighth metal electrode 34 is made of Al, Al-Si, Al-Si-Cu, Al-Cu, or the like.

  Note that the laminated structure for forming the front electrode 3 and the laminated structure for forming the back electrode 4 do not have to have the same thickness and composition, and the soldering conditions in each of the front electrode 3 and the back electrode 4 Any structure that is optimal for the circuit board 8 may be used.

  Next, a method for manufacturing the semiconductor device 1 will be described with reference to FIGS. Below, the manufacturing method of the laminated structure of the surface electrode 3 is demonstrated especially.

  The diode, bipolar transistor, MOSFET, or IGBT formed in the semiconductor substrate 2 can be formed by a known method. The back electrode 4 can be formed by the same method as in the first embodiment.

  Unlike the back electrode 4, the front electrode 3 needs to form a metal electrode pattern. This is because it is necessary to form a structure other than the surface electrode 3 on the surface of the semiconductor substrate 2.

  In FIG. 11, a semiconductor element such as a diode, a bipolar transistor, a MOSFET, or an IGBT is formed in a semiconductor substrate 2 using an n-type semiconductor, a p-type semiconductor, an insulating film, polysilicon, or the like.

  Next, an eighth metal electrode 34 is formed on the surface of the semiconductor substrate 2 on which the semiconductor element is formed. The eighth metal electrode 34 is formed by a sputtering method, a vacuum evaporation method, or the like.

  In FIG. 12, the back surface of the semiconductor substrate 2 is ground until the semiconductor substrate 2 has a desired thickness.

  Next, the first metal electrode 41, the second metal electrode 42, and the third metal electrode 43 are sequentially stacked on the back surface of the semiconductor substrate 2 to form the back electrode 4.

  In FIG. 13, a resist 10 is applied on the surface of the semiconductor substrate 2, and a pattern for removing the resist 10 is formed by exposure and development so that a desired metal electrode pattern is obtained. Here, the extraction pattern of the resist 10 means a pattern of the resist 10 formed so that a desired metal pattern can be obtained when the resist 10 is dissolved and removed in a subsequent process.

  After the formation of the resist removal pattern, the fifth metal electrode 31, the sixth metal electrode 32, and the seventh metal electrode 33 are stacked and formed.

  In FIG. 14, the resist 10 is dissolved using an organic solvent, and the fifth metal electrode 31, the sixth metal electrode 32, and the seventh metal electrode 33 formed on the resist 10 are peeled off to obtain a desired metal electrode pattern. Form.

  From the above, according to the third embodiment, it is possible to join to the circuit board 8 by soldering on either the front surface side or the back surface side of the semiconductor device 1. Therefore, the electrical characteristics of the semiconductor device 1 can be improved and the reliability can be improved.

  In the third embodiment, the back electrode 4 is described as being the same as that in the first embodiment, but the back electrode 4 according to the second embodiment may be adopted. In this case, the back electrode 4 can be formed by the same method as in the second embodiment.

  Further, after FIG. 14, an insulating film 5 as shown in FIG. 10 may be formed.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Semiconductor device, 2 Semiconductor substrate, 3 Front electrode, 4 Back electrode, 5 Insulating film, 6 Stage, 7 Probe, 8 Circuit board, 9 Solder, 10 Resist, 31 5th metal electrode, 32 6th metal electrode, 33 1st 7 metal electrode, 34 8th metal electrode, 41 1st metal electrode, 42 2nd metal electrode, 43 3rd metal electrode, 44 4th metal electrode.

Claims (10)

A semiconductor substrate;
A metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate;
With
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The third metal electrode is an alloy of Ag and at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi;
The semiconductor device further comprising a metal film made of Ag between the second metal electrode and the third metal electrode. A semiconductor substrate;
A metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate;
With
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The semiconductor device, wherein the third metal electrode is an alloy mainly composed of Ag and at least one of Pd, Ni, Mg, Zn, Nd, Sn, and Bi. A semiconductor substrate;
A metal electrode formed by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate;
A circuit board joined to the metal electrode via solder;
With
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The third metal electrode is an alloy of Ag and at least one of Pd, Ni, Mg, Zn, Nd, Sn, and Bi.   The semiconductor device according to claim 3, further comprising a metal film made of Ag between the second metal electrode and the third metal electrode.   5. The semiconductor device according to claim 1, wherein the main surface side layer forming the metal electrode in the semiconductor substrate is an n-type semiconductor layer. 6.   6. The semiconductor device according to claim 1, wherein a content of Sn in the third metal electrode is 0.1 wt% to 20 wt%. (A) preparing a semiconductor substrate;
(B) forming a surface electrode on the surface of the semiconductor substrate;
(C) forming a back electrode by sequentially stacking a first metal electrode, a second metal electrode, and a third metal electrode on the back surface of the semiconductor substrate;
(D) a step of performing an electrical property test in a temperature range from 0 ° C. to 180 ° C. in the atmosphere by bringing a probe into contact with the surface electrode;
With
In the step (b),
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The method of manufacturing a semiconductor device, wherein the third metal electrode is an alloy of Ag and at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi. After the step (d),
(E) The method of manufacturing a semiconductor device according to claim 7, further comprising a step of joining the back electrode and the circuit board via solder. (A) preparing a semiconductor substrate;
(B) forming a metal electrode by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate;
With
In the step (b),
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The third metal electrode is an alloy of Ag and at least one of Pd, Ni, Cu, Mg, Zn, Nd, Sn, and Bi;
A method of manufacturing a semiconductor device, further comprising forming a metal film made of Ag between the second metal electrode and the third metal electrode. (A) preparing a semiconductor substrate;
(B) forming a metal electrode by sequentially laminating a first metal electrode, a second metal electrode, and a third metal electrode on the semiconductor substrate;
With
In the step (b),
The first metal electrode is Ti or a Ti alloy,
The second metal electrode is Ni or Ni alloy,
The third metal electrode is an alloy mainly composed of Ag and at least one or more of Pd, Ni, Mg, Zn, Nd, Sn, and Bi. Production method.

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