JP3518486B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for controlling current switching in a thickness direction and a method of manufacturing the same, and more particularly to a semiconductor device having improved turn-off response and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a so-called insulated gate bipolar transistor (IGBT) in which a bipolar transistor and a field effect transistor are integrated has been used for applications requiring high input impedance and low output impedance.

FIG. 9 shows a general structure of such an IGBT. The n epitaxial layer 14 is formed on the p-type silicon substrate 12, and the n epitaxial layer 14 is formed.
An n + source region 26, ap body region 22 and ap + body region 24 are formed on the surface by ion implantation or the like. A portion of the n epitaxial layer 14 that is not the p body region 22 becomes an n drift region. On the surface of the n-epitaxial layer 14, the gate electrode 18 insulated from the n-epitaxial layer 14 by the gate insulating films 16, 20 and 30.
Is formed. Gate electrode 18 covers a portion of the n drift region, a portion of p body region 22, and a portion of n + source region 26 of the surface of n epitaxial layer 14. Further, a source electrode 28 which is electrically connected to the n + source region 26 and the p + body region 24 is provided on the front surface side, and a drain electrode 10 which is electrically connected to the substrate 12 is provided on the back surface side. .

In such a structure, the basic operation of the IGBT is to control switching of the current from the drain electrode 10 to the source electrode 28 by the voltage of the gate electrode 18. That is, the drain electrode 10 with respect to the source electrode 28 in a state where no voltage is applied to the gate electrode 18.
Even if a voltage is applied such that the voltage is high, the current does not flow because the pn junction between the p body region 22 and the p + body region 24 and the n drift region is in the opposite direction. However, when a positive voltage is applied to the gate electrode 18, electrons are attracted to the surface of the p body region 22 to form an n channel, the field effect transistor is turned on, and the n + source region 26 passes through the n channel. Electrons flow into the n drift region. As a result, the carrier concentration in the n drift region increases and the resistance decreases, and the diode formed of the n drift region and the substrate 12 becomes conductive to inject holes from the substrate 12 into the n drift region. Therefore, the bipolar transistor is turned on, and a current flows in the thickness direction from the drain electrode 10 to the source electrode 28.

When the application of the positive voltage to the gate electrode 18 is stopped, the IGBT is turned off again, but the n drift region in the on state is filled with electrons and holes at a high concentration, and the gate voltage is reduced. Is turned off, the carrier concentration in the n drift region does not immediately decrease even if the injection of electrons from the n + source region 26 is cut off. Therefore, the IGBT
The transient characteristics when the switch is turned off do not suddenly become zero and become smooth, and it is an important issue to prevent such an increase in turn-off time.

For example, in Japanese Unexamined Patent Publication No. 10-199894, the back side of the IGBT (drain electrode 1 in FIG.
(0 side) to perform ion irradiation to form a lattice defect in a region near the substrate 12 in the n drift region, and carriers are recombined by the lattice defect to improve turn-off response. There is.

[0007]

However, in recent years,
From the viewpoint of reducing the element size and improving the element performance, A
heavy metals such as Cu instead of light metals such as l
Attempts have been made to reduce the resistance value by using such as an electrode, and it is necessary to form a lattice defect region in the IGBT having such a heavy metal electrode.

When ion irradiation is performed through a light metal electrode such as Al to form a lattice defect region, irradiation ions and A
Although the interaction with the 1 atom is not so problematic, when a heavy metal electrode such as Cu is irradiated with high energy ions,
The heavy metal atom is activated by the interaction between the ion and the heavy metal atom, and the interfacial rank density of the IGBT is increased by the gamma ray or the neutron beam from the activated heavy metal atom, and especially the threshold voltage is lowered. It was happening. Such a problem arises even when a light metal such as Al is used for the electrode itself, when a barrier layer made of a heavy metal such as TiN or TiC is formed on the periphery of the electrode in order to suppress the reaction between the electrode and silicon. Can occur as well. That is, when high-energy ions are irradiated through the barrier layer, the barrier metal is activated and the radiation changes the threshold voltage.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is to provide an element such as a threshold voltage fluctuation even in a semiconductor device having a heavy metal electrode (including a case where a heavy metal barrier layer is included). It is an object of the present invention to provide a method and an apparatus capable of forming a lattice defect region by ion irradiation without causing characteristic deterioration and thereby improving turn-off response characteristics.

[0010]

In order to achieve the above object, the present invention provides a switching element on the front surface side of a semiconductor layer, and controls switching of the current in the thickness direction of the semiconductor layer by turning on / off the switching element. The semiconductor device according to claim 1, wherein the heavy metal electrode and 1.
And a lattice defect region formed by implanting ions with a dose of 0 × 10 ¹¹ / cm ² or less. In the case of a light metal such as Al, the amount of radiation is relatively small even when irradiated with ions, which is not a problem, but when a heavy metal that is heavier than Al is used, the amount of radiation increases and the threshold voltage is lowered. Therefore, in the case of irradiating ions through the heavy metal electrode, it is less than or equal to a predetermined value, specifically 1.
By setting it to 0 × 10 ¹¹ / cm ² or less, the generated radiation dose is suppressed, the increase in interface order density due to radiation is prevented, and the threshold voltage is maintained constant.

Here, the heavy metal electrode may be a multi-layer metal electrode having a heavy metal layer for barrier at least on the semiconductor layer side. As the heavy metal electrode, for example, Ti or Ni,
Au or the like is used, and TiN, TiC, or the like is used as the barrier heavy metal layer.

Further, according to the present invention, a switching element is provided on the front surface side of the semiconductor layer and heavy metal electrodes are provided on the front surface side and the back surface side of the semiconductor layer, and a current in the thickness direction of the semiconductor layer is supplied by turning on / off the switching element. Provided is a method for manufacturing a semiconductor device that performs switching control. This method has a step of forming a lattice defect region by implanting ions with a dose of 1.0 × 10 ¹¹ / cm ² or less into a part of the semiconductor layer through the heavy metal electrode. And

Here, it is preferable that the ions are implanted a plurality of times by changing their irradiation positions. As a result, it is possible to reduce the irradiation amount per time.

Further, it is preferable that the ions are implanted a plurality of times by shifting the center position of the irradiation beam by the half width of the irradiation beam. As a result, it is possible to reduce the amount of ion irradiation per time, level the implanted ion amount regardless of the position, and form uniform lattice defect regions.

Further, it is preferable that the dose of the ions is changed according to the thickness of the heavy metal electrode. When the film thickness of the electrode is small, the total amount of radiation generated by the ion irradiation is small, and the influence on the threshold value is small. Therefore, by increasing the ion irradiation amount as the electrode film thickness becomes smaller, it becomes possible to reliably form the lattice defect region while suppressing the fluctuation of the threshold value. Note that this means that when manufacturing a plurality of semiconductor devices having different electrode film thicknesses, the ion irradiation dose is made different for each semiconductor device.

Further, according to the present invention, a switching element is provided on the front surface side of the semiconductor layer and heavy metal electrodes are provided on the front surface side and the back surface side of the semiconductor layer, and a current in the thickness direction of the semiconductor layer is supplied by turning on / off the switching element. A method of manufacturing a semiconductor device in which switching control is performed, characterized in that a lattice defect region is formed by implanting ions into a part of the semiconductor layer before forming the heavy metal electrode. By implanting ions prior to the formation of the heavy metal electrode, the lattice defect region can be formed without causing activation of the heavy metal electrode.

Further, according to the present invention, a switching element is provided on the front surface side of the semiconductor layer, and heavy metal electrodes are provided on the front surface side and the back surface side of the semiconductor layer, and a current in the thickness direction of the semiconductor layer is supplied by turning on / off the switching element. A method of manufacturing a semiconductor device in which switching control is performed, wherein after the heavy metal electrode is formed on one of the front surface side and the back surface side of the semiconductor layer and before the heavy metal electrode is formed on the other side, the other A lattice defect region is formed by implanting ions into a part of the semiconductor layer from the side. Even if the heavy metal electrode is formed on one side of the semiconductor device, the lattice defect region can be formed without inducing activation of the heavy metal electrode by implanting ions from the other side where the heavy metal electrode is not yet formed.

In each of the above methods, the heavy metal electrode may be a multi-layer metal electrode having a heavy metal layer for barrier at least on the semiconductor layer side.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the IGBT according to this embodiment. The basic configuration is the IGBT shown in FIG.
The n epitaxial layer 14 is formed on the p-type silicon substrate 12, and the n + source region 26, the p body region 22, and the p + body region 24 are formed on the surface of the n epitaxial layer 14. Further, the gate electrode 18 insulated by the gate insulating films 16, 20, 30 is formed on the surface of the n epitaxial layer 14, the source electrode 28 is formed on the front surface side, and the drain electrode 10 is formed on the rear surface side.

Here, in this embodiment, the drain electrode 10 and the source electrode 28 are made of Ti, Ni, Au, AuS.
It is made of heavy metals such as b and V, and its wiring has C
Heavy metals such as u are used. Unlike the case of using a light metal such as Al, the resistance value can be reduced by using such a heavy metal. On the other hand, when such a heavy metal is used as the electrode material and the wiring material, when ion irradiation is performed to form the lattice defect region 32 for promoting carrier recombination in the vicinity of the substrate 12 in the n drift region as described above, There is a possibility that the heavy metal reacts with the high-energy ions and the heavy metal is activated to reduce the threshold voltage of the IGBT, that is, the breakdown voltage of the pn junction.

Therefore, in the present embodiment, the dose of the ions to be irradiated when forming the lattice defect region 32 is controlled, thereby suppressing the activation of the heavy metal and suppressing the fluctuation of the threshold voltage.

FIG. 2 shows changes in the threshold voltage before and after the irradiation when the ion irradiation amount when the ions are irradiated through the drain electrode 10 is changed. The amount of ion irradiation is set to 1.0 × 10 ¹¹ / cm ² or less and 1.0 × 10 ¹² / cm ² . In addition, 1.
0 × 10 ¹¹ / cm ² or less means, for example, 4.2 × 10 ¹⁰ / cm ^2.
cm ² and 7.5 × 10 ¹⁰ / cm ² are shown. As can be seen from the figure, when the dose is 1.0 × 10 ¹¹ / cm ² or less, there is almost no change in the threshold voltage before and after the irradiation, but the ion dose is 1.0 × 10 ¹² / cm ²
Reaches about 6.0V before irradiation to about 5.0 after irradiation.
It has fallen to V.

As described above, when the lattice defect region 32 is formed by irradiating the ions through the heavy metal electrode (and the heavy metal wiring), the ion irradiation amount is set to 1.0 × 10 ¹¹ / cm ² or less, and the heavy metal is The activation of
The turn-off time can be shortened by suppressing the threshold voltage drop (breakdown voltage drop) of the GBT and recombining the carriers remaining in the n drift region due to the existence of the lattice defect region 32.

The ion irradiation dose is preferably as small as possible as long as a sufficient lattice defect region 32 is formed. For example, when a high voltage is applied to the source gas at the center of the cyclotron to obtain an ion source. , 1.0
It may be possible to obtain a dose of about 10 ⁷ / cm ² . Of course, this does not preclude the use of smaller ion doses.

Ions to be irradiated are, for example, ³ He ²⁺ , ⁴ He
²⁺ , ¹ H ⁺ , ² H ^{+ and the} like can be used, and when the ions are irradiated, the lattice defect region 32 is formed not by one irradiation but by two or more irradiations. It is also preferable to do. By thus irradiating the ions in a plurality of times, it is possible to reduce the amount of ion irradiation per time and to more reliably prevent the heavy metal from being activated. When the ion irradiation is performed a plurality of times, it is preferable to perform irradiation with the center positions of the ion beams to be irradiated displaced from each other, and specifically, it is desirable to perform irradiation with the center of the ion beam shifted by a half width. This makes it possible to form the lattice defect region 32 uniformly over almost the entire n drift region while reducing the amount of ion irradiation per time.

In this embodiment, 1.0 × 10
Ions are irradiated through the heavy metal electrode at an irradiation dose of ¹¹ / cm ² or less, but it is also preferable to appropriately set the ion irradiation dose according to the film thickness of the heavy metal electrode. As the thickness of the heavy metal electrode decreases, the probability of collision between high-energy ions and heavy metal atoms decreases, and the probability of activation also decreases, so that the ion irradiation dose can be increased as compared with the case where the film thickness is large. It can also be said that the smaller the film thickness of the heavy metal electrode, the smaller the number of activated heavy metal atoms, and thus the smaller the total amount of radiation, and thus the lowering of the threshold value is less likely to occur.

FIG. 3 shows the relationship between the thickness of the heavy metal electrode and the maximum ion irradiation dose that does not cause the threshold fluctuation.
As shown in the figure, the smaller the film thickness of the heavy metal electrode, the larger the maximum ion irradiation dose that does not cause the threshold fluctuation. In this way, by changing the ion irradiation amount according to the film thickness of the heavy metal electrode, the lattice defect region 32 is reliably formed in the n drift region while suppressing the threshold voltage drop due to activation of the heavy metal electrode. The turn-off time can be shortened. For example, when the thickness of the drain electrode 10 is 100 nm, the ion irradiation dose is 5.0 × 10 5.
^When the film thickness of the drain electrode 10 is 10 nm / cm ² and the film thickness is 50 nm, the ion irradiation dose is 1.0 × 10 ¹¹ / cm ² .

FIG. 4 shows a method of manufacturing an IGBT according to another embodiment. In the embodiment described above, after the drain electrode 10 and the source electrode 28 are formed, ion irradiation is performed through the heavy metal electrode to form the lattice defect region 3.
2 is formed in the n drain region, but in the present embodiment, the ion irradiation is performed before forming the heavy metal electrode,
The lattice defect region 32 is formed in the drain region. That is, as shown in FIG. 4A, prior to forming the drain electrode 10 on the back surface side of the substrate 12, ion irradiation is performed from the back surface side of the substrate 12 to form a lattice defect region near the substrate 12 in the n drift region. 32 is formed, and as shown in FIG. 4B, the drain electrode 10 is formed on the back surface side of the substrate 12 after the lattice defect region 32 is formed.

By thus forming the lattice defect region 32 before forming the heavy metal electrode, the activation of the heavy metal electrode is surely prevented, and the turn-off time is shortened without lowering the threshold voltage. be able to.

The ion irradiation amount at this time does not necessarily have to be 1.0 × 10 ¹¹ / cm ² or less as in the above-described embodiment, and the ion irradiation amount can be larger than that.

FIG. 5 shows a flowchart of the method for manufacturing the IGBT in this embodiment. First, the n epitaxial layer 14 is formed on the p substrate 12 (S10).
1). After forming the n epitaxial layer 14, the n epitaxial layer 14 is thermally oxidized to form the insulating film 16, and the gate electrode 18 is formed on the insulating film 16 (S102).
Next, a donor element is ion-implanted into a part of the n epitaxial layer 14 to form the n + source region 26 (S10).
3). Further, an acceptor element such as boron is ion-implanted into a part of the n epitaxial layer 14 to form the p body region 22 at a position deeper than the n + source region 26 (S).
104). After forming the p body region 22, the insulating films 20 and 30 are formed of silicon oxide or the like, and the acceptor element is ion-implanted into a part of the n epitaxial layer 14 to form the p + body region 24 (S105). And
A source electrode 28 for electrically connecting the p + body region 24 and the n + source region is formed (S106).

In the conventional IGBT manufacturing method, after the source electrode 28 is formed, the drain electrode 10 is subsequently formed on the back surface side of the substrate 12, and further ³ He ²⁺ is formed via the drain electrode 10 or the source electrode 28. While the lattice defect region 32 is formed by irradiating high-energy ions such as the above, in the present embodiment, after the source electrode 28 is formed and before the drain electrode 10 is formed, ions are emitted from the back surface side of the substrate 12. Irradiation is performed and ions are implanted into the n drift region to form the lattice defect region 32 (S107). And
After forming the lattice defect region 32, the drain electrode 10 is formed on the back surface side of the substrate 12 (S108).

As described above, by performing the ion irradiation before forming the heavy metal electrode to form the lattice defect region 32, the lattice defect region 32 can be formed without particularly limiting the ion irradiation amount. The turn-off time can be surely shortened without changing the threshold voltage.

In this embodiment, the lattice defect region 32 is formed by irradiating ions from the back surface side of the substrate 12, but the lattice defect region 32 is formed by irradiating ions from the source electrode 28 side. Is also possible.

FIG. 6 shows an IGBT manufacturing method in such a case. As shown in FIG. 6A, p
Before forming the source electrode 28 for establishing conduction between the + body region 24 and the n + source region 26, ion irradiation is performed from the surface side to form the lattice defect region 32 in the n drift region. Then, the source electrode 28 is formed as shown in FIG.

Also by this method, as in the case of FIG. 4, activation of the heavy metal electrode can be prevented, fluctuation of the threshold voltage can be prevented, and turn-off time can be shortened.

In the embodiments described above, heavy metals such as Ti, Ni, Au, etc. are used as the material of the electrodes. However, as the material itself of the electrodes, light metals such as Al are used, and the chemical reaction between the electrodes and the silicon compound is performed. The same can be applied to the case where a heavy metal barrier layer is used at the interface between the electrode and the silicon compound for prevention.

FIG. 7 shows a method of manufacturing an IGBT using such a barrier layer. As shown in FIG. 7A, TiN, TiC, Ti-Si-N, and I are formed between the gate insulating films 20 and 30 and the source electrode 28.
r-Ta, TaC, TaN, Ta-Si, Ta-Si-
A barrier layer 34 made of a metal or a metal compound that is heavier than Al, such as N, W, WN, WSiN, and WReB, is formed. Ion irradiation is performed before the drain electrode 10 is formed on the back surface side to form the lattice defect region 32. Form. afterwards,
As shown in FIG. 7B, the drain electrode 10 is formed on the back surface side of the substrate 12 to form an IGBT.

Also in this embodiment, since ion irradiation is not performed through the heavy metal barrier layer 34, activation of the barrier layer 34 can be prevented and fluctuations in the threshold voltage can be suppressed.

FIG. 8 shows an IG according to another embodiment.
A method of manufacturing BT is shown. Also in this embodiment, the barrier layer 34 is formed on the electrode periphery similarly to the manufacturing method shown in FIG. 7, but before the barrier layer 34 is formed, ion irradiation is performed from the surface side to form the n drift region. The lattice defect region 32 is formed (FIG. 8A). After that, FIG.
As shown in (b), the barrier layer 34 and the source electrode 2
8 is formed.

Even with this method, since the ion irradiation is not performed through the barrier layer 34, the lattice defect region 32 is formed and the turn-off time is shortened without causing the threshold voltage fluctuation due to activation. You can

Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications and uses are possible within the scope of the technical idea of the present invention. For example, the gate electrode 18 may be of a trench type,
Further, the conductivity type of the semiconductor in each region of the IGBT may be the complementary type (if it is p-type, it is n-type). In addition, a buffer region may be appropriately provided in the configuration of the IGBT, and the semiconductor may be made of a material other than silicon.

[0044]

As described above, according to the present invention, the turn-off characteristic can be improved without causing the characteristic variation of the semiconductor device, especially the decrease of the threshold voltage.

[Brief description of drawings]

FIG. 1 is a sectional view of an IGBT according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an ion irradiation dose and a threshold voltage fluctuation in the embodiment.

FIG. 3 is a graph showing a relationship between a heavy metal electrode film thickness and an ion irradiation dose in the embodiment.

FIG. 4 is an explanatory diagram of an IGBT manufacturing method according to another embodiment.

5 is a flowchart of the manufacturing method shown in FIG.

FIG. 6 is an explanatory diagram showing an IGBT manufacturing method according to another embodiment.

FIG. 7 is an explanatory diagram showing an IGBT manufacturing method according to still another embodiment.

FIG. 8 is an explanatory view showing an IGBT manufacturing method according to still another embodiment.

FIG. 9 is an explanatory diagram of a conventional IGBT manufacturing method.

[Explanation of symbols]

10 drain electrode, 12 substrate, 14 n epitaxial layer, 16 gate insulating film, 18 gate electrode, 22
p body region, 24 p + body region, 26 n + source region, 28 source electrode, 32 lattice defect region.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/78 H01L 21/336

Claims (8)

(57) [Claims] 1. A semiconductor device in which a switching element is provided on a front surface side of a semiconductor layer, and a current in a thickness direction of the semiconductor layer is switching-controlled by turning on / off the switching element, wherein a heavy metal electrode and one of the semiconductor layers are provided. A lattice defect region formed by implanting ions at a dose of 1.0 × 10 ¹¹ / cm ² or less, and the heavy metal electrode has a barrier defect at least on the semiconductor layer side.
A semiconductor device comprising a multi-layer metal electrode provided with a heavy metal for a rear . 2. A switching element is provided on the front surface side of the semiconductor layer.
In addition to the provision of heavy metal electrodes on the front and back sides of the semiconductor layer,
A pole is provided, and the switching element is turned on / off to
Semiconductor for switching current control in the thickness direction of a semiconductor layer
A method for manufacturing a body device, comprising: applying 1.0 × to a part of the semiconductor layer through the heavy metal electrode.
Ion implantation at a dose of 10 ¹¹ / cm ² or less
Forming a lattice defect region further, wherein the heavy metal electrode is formed on at least the semiconductor layer side,
Semi-conductor characterized by being a multi-layer metal electrode with metal
Body device manufacturing method. 3. The method according to claim 2, wherein the io
Is a method for manufacturing a semiconductor device, characterized in that the irradiation positions are mutually changed and a plurality of times are injected . 4. The method according to claim 2, wherein the io
Is the center position of the irradiation beam by the half width of the irradiation beam
A method for manufacturing a semiconductor device, which comprises implanting a plurality of times by shifting the implantation . 5. The method according to claim 2, wherein the io
A method of manufacturing a semiconductor device, comprising: changing the amount of ion irradiation according to the thickness of the heavy metal electrode . 6. A switching element is provided on the front surface side of the semiconductor layer.
In addition to the provision of heavy metal electrodes on the front and back sides of the semiconductor layer,
A pole is provided, and the switching element is turned on / off to
Semiconductor for switching current control in the thickness direction of a semiconductor layer
A method for manufacturing a body device, comprising:
By implanting ions in a part of the semiconductor layer,
A method for manufacturing a semiconductor device, which comprises forming a recessed region . 7. A switching element is provided on the surface side of the semiconductor layer.
In addition to the provision of heavy metal electrodes on the front and back sides of the semiconductor layer,
A pole is provided, and the switching element is turned on / off to
Semiconductor for switching current control in the thickness direction of a semiconductor layer
A method of manufacturing a body device, comprising: a front surface side of the semiconductor layer;
Or after the heavy metal electrode is formed on one of the back side
Before the heavy metal electrode is formed on the other side, the other side
By implanting ions into part of the semiconductor layer from
A method of manufacturing a semiconductor device, comprising forming a lattice defect region . 8. The method according to claim 6,
In addition, the heavy metal electrode has a bar at least on the semiconductor layer side.
A method of manufacturing a semiconductor device, comprising a multilayer metal electrode having a heavy metal layer for a rear .