KR101928395B1 - Power semiconductor device and manufacturing method thereof - Google Patents

Abstract

A power semiconductor device and a manufacturing method thereof are disclosed. The power semiconductor device includes a drift layer of a first conductivity type; A first field stop layer of a first conductivity type formed in a lower portion of the drift layer to have a first peak ion concentration that is relatively larger than an ion concentration of the drift layer; A second field stop layer of a first conductivity type formed below the first field stop layer to have a second peak ion concentration that is relatively larger than the first peak ion concentration; And a second conductive type collector region formed under the second field stop layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a power semiconductor device and a manufacturing method thereof,

The present invention relates to a power semiconductor device and a manufacturing method thereof.

2. Description of the Related Art An insulated gate bipolar transistor (IGBT) (hereinafter referred to as an IGBT) which is a switching device of a high breakdown voltage and a high speed is a power semiconductor which can reduce the operating resistance as compared with a MOS field effect transistor Device.

The IGBT is a type of switching that controls the turn-on and turn-off of the element by controlling the ON / OFF state of the element by flowing a voltage to the gate to form a channel, flowing electrons of the N conductive emitter and holes of the P conductive collector, Device. Here, the maximum collector voltage that can withstand the switch-off state is defined as the breakdown voltage, and the breakdown voltage is mainly determined by the area divided by the maximum electric field concentrated in the P-conductivity type base and the N drift layer.

IGBTs have been improved to reduce the voltage drop at switch-on, improve the breakdown voltage indicating the stopping voltage at switch-off, and improve the switching time at switch-on / off, and are expected to be applied to high voltage and high current applications such as inverter or motor drive Is widely used in the field.

In addition, the IGBT has a high resistance and a thin layer of the drift layer, which is the most resistant layer, to reduce the conduction loss, and the field stop (FS , Field Stop) layer.

Since the field stop layer is provided, the depletion layer expanded in the drift layer having a high resistance at the time of off is suppressed. Therefore, punch-through can be prevented even if the drift layer is made relatively thin.

However, a field stop (FS) IGBT having a thin-thickness drift layer and a field stop layer has a depletion region formed between the P-conductivity-type well and the N-conductivity-type drift layer as the voltage Vce increases, When the voltage Vce is further increased, the punchthrough breakdown voltage BV must be generated.

In order to solve this problem, it is possible to consider a method of increasing the thickness or concentration of the field stop layer. However, such a solution may deteriorate the switching and static characteristics, There is a problem to increase.

The above-described background technology is technical information that the inventor holds for the derivation of the present invention or acquired in the process of deriving the present invention, and can not necessarily be a known technology disclosed to the general public prior to the filing of the present invention.

Korean Patent No. 10-0902848 (Insulated Gate Bipolar Transistor for High Voltage and Method of Manufacturing the Same)

The present invention forms a plurality of field stop layers each having a different doping peak between a N-type drift layer and a P-type conductivity collector layer in a simple and inexpensive process, so that even when a thin drift layer is formed, And a method of manufacturing the power semiconductor device.

Other objects of the present invention will become readily apparent from the following description.

According to an aspect of the present invention, there is provided a drift layer of a first conductivity type; A first field stop layer of a first conductivity type formed in a lower portion of the drift layer to have a first peak ion concentration that is relatively larger than an ion concentration of the drift layer; A second field stop layer of a first conductivity type formed below the first field stop layer to have a second peak ion concentration that is relatively larger than the first peak ion concentration; And a collector region of a second conductivity type formed under the second field stop layer.

The first field stop layer may be formed by proton irradiation and heat treatment, and the second field stop layer may be formed by ion implantation and heat treatment of the first conductivity type.

The first peak ion concentration is 1e ¹⁵ / cm ³ or less random value, the second peak ion concentration may be any less than 1e ¹⁶ / cm ^3.

The second field stop layer may be formed to have a relatively thin thickness as compared with the first field stop layer.

The drift layer may be formed to have any thickness that is 3/4 or less of the depletion region width (Wpp, BV) at the breakdown voltage.

The collector region may be formed only in a predetermined region of the lower region of the second field stop layer.

Other aspects, features, and advantages will become apparent from the following drawings, claims, and detailed description of the invention.

According to embodiments of the present invention, by forming a plurality of field stop layers each having a different doping peak between the N conductive drift layer and the P conductive collector layer in a simple and inexpensive process, a thin drift layer It is possible to secure an excellent withstand voltage characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a cross-sectional configuration of a field stop IGBT according to the prior art;
FIG. 2 illustrates a doping concentration profile and a depletion region expansion state of the field stop IGBT shown in FIG. 1; FIG.
3 is a diagram illustrating a cross-sectional configuration of a field-stop IGBT according to an embodiment of the present invention.
FIG. 4 illustrates a doping concentration profile and a depletion region expansion state of the field stop IGBT shown in FIG. 3; FIG.
5 is a flowchart illustrating a process for manufacturing a field stop IGBT according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Where an element such as a layer, region or substrate is described as being "on" or "onto" another element, the element may be directly on top of another element or may extend directly over it , Or an intervening element may exist. On the other hand, if one element is referred to as being "directly on" another element or "directly onto" another element, there are no other intermediate elements. Also, when an element is described as being "connected" or "coupled" to another element, the element may be directly connected to or directly coupled to another element, or an intermediate intervening element may be present have. On the other hand, if one element is described as being "directly connected" or "directly coupled" to another element, there are no other intermediate elements.

The terms "below" or "above" or "upper" or "lower" or "horizontal" or "lateral" Relative terms such as " vertical "may be used herein to describe a relationship to another element, layer or region of an element, layer or region, as shown in the figures. It should be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Although an insulating gate bipolar transistor (IGBT) is mainly described in the present specification, it is natural that the technical idea of the present invention can be applied to and extended to various types of semiconductor devices such as power MOSFETs.

FIG. 1 is a view illustrating a cross-sectional structure of a field stop IGBT according to the prior art. FIG. 2 illustrates a doping concentration profile and a depletion region expansion state of the field stop IGBT shown in FIG. Fig.

1, the field-stop IGBT includes a P-type well 20 formed on an N-drift region formed on an N-type semiconductor substrate and a P- A plurality of N-conductivity-type wells 40 which are impurity regions are formed. In addition, a P conductive type ion region 30 having a high concentration can be further formed in the P conductive type well 20.

A gate oxide film 51 is formed on the upper part of the adjacent P conductive well 20 and a gate poly electrode 52 is formed on the gate oxide film 51. The gate oxide film 51 and the gate poly electrode 52 And an emitter metal electrode 70 is formed on the interlayer insulating film so that active cells are included therein and are electrically connected to N-type wells 40, which are source regions.

A N conductive type field stop layer 90 is formed below the drift region and a P conductive type collector region 95 is formed below the field stop layer 90. A P conductive type collector region 95 is formed under the field stop layer 90, A collector metal electrode 80 is formed.

An IGBT is a minority carrier element through which a current flows by a hole carrier. That is, since the hole current injected from the lower P-type collector region 95 moves past the drift region of low ion concentration, the length of the drift region is minimized to reduce the power consumption in the forward operation There is a need.

However, in order to ensure the required breakdown voltage in the application circuit, a sufficient drift region (N Drift) is required to prevent the extended depletion region from reaching the collector region 95. That is, since a drift region having a sufficient thickness is required for securing the breakdown voltage, there is a limitation in reducing the forward power consumption.

1, a field stop layer 90, which is an N-conduction type region having an ion concentration higher than the ion concentration of the drift region, is formed by using a field stop IGBT formed in the upper portion of the collector region 95 .

In the case of the illustrated field-stop IGBT, since the depletion region expanded when the reverse voltage is applied is blocked by the field stop layer 90, a high breakdown voltage can be obtained with only a relatively small-thickness drift region, There is an advantage that operation characteristics are ensured.

2 is a diagram illustrating a doping concentration profile and a depletion region expansion state in the Y direction section of the field stop IGBT.

As shown by the solid line in FIG. 2, the ion concentration is varied in each section such as P-type well 20, drift region, field stop layer 90, and collector region 95. As compared with the drift region, Layer 90 is configured to have a high ion concentration. The field stop layer 90 may be formed by thermal annealing after proton irradiation so as to have a relatively high concentration and a predetermined thickness as compared with the drift region.

With the above-described configuration, the field stop IGBT is capable of blocking the depletion region extended when the reverse voltage is applied, by the field stop layer 90.

However, when the voltage Vce is increased, the depletion region formed between the P-type well 20 and the drift region reaches the field stop layer 90, and when the voltage Vce is continuously increased in this state, When the depletion region expands and the depletion region expands beyond the thickness of the field stop layer 90, a punch-through breakdown voltage (Punch-through BV) is generated to conduct current. The punch-through breakdown voltage generation state due to the extension of the depletion region is shown by a dotted line in Fig.

To prevent the depletion region from expanding beyond the thickness of the field stop layer 90, a solution to further increase the thickness or concentration of the field stop layer 90 may be considered. However, such a solution has a problem of deteriorating switching and static characteristics of the field stop IGBT.

Also, a solution of conducting the proton irradiation for forming the field stop layer 90 at a high concentration may be considered, but this poses a problem of increasing the difficulty of the process and the manufacturing cost.

FIG. 3 is a view illustrating a cross-sectional structure of a field-stop IGBT according to an embodiment of the present invention, FIG. 4 is a diagram illustrating a doping concentration profile and a depletion region expansion state of the field- 5 is a flowchart showing a process for manufacturing a field stop IGBT according to an embodiment of the present invention

Referring to FIG. 3, the field stop IGBT according to the present embodiment has a structure in which a plurality of field stop layers 310 and 320 are stacked between a drift region and a collector region 95.

The first field stop layer 310 may be formed, for example, by irradiating protons that can be implanted to a depth of at least 10 um with a light mass. A peak ion concentration in the first field stop layer 310 may be set to a value of 1e ¹⁵ / cm ³ or less.

In contrast, the second field stop layer 320 can be formed by implanting ions (e.g., phosphorus) that are implanted to a relatively shallow depth with a relatively heavy mass relative to the protons. The peak ion concentration of the second field stop layer 320 may be set to a value of 1e ¹⁶ / cm ³ or more and may be formed to be relatively thin compared to the first field stop layer 310.

That is, the peak ion concentration of the second field stop layer 320 is formed to be relatively higher than the peak ion concentration of the first field stop layer 310, as illustrated by the solid line in FIG.

This is because, if the peak ion concentration of the first field stop layer 310 is increased, the extension of the depletion region can be effectively suppressed. However, since the formation of the first field stop layer 310 of high concentration is not easy, The thickness of the layer 310 must be increased.

However, when the thickness of the first field stop layer 310 is increased, there is a problem that the thickness of the drift layer becomes thinner and a desired level of breakdown voltage can not be obtained in the case of a chip having the same thickness.

Thus, instead of thinning the thickness of the first field stop layer 310, a relatively high concentration of the second field stop layer 320 may be applied to the first field stop layer 310 to effectively block the field field passing through the first field stop layer 310, Is formed between the field stop layer (310) and the collector region (95).

For example, an electric field that causes breakdown in a typical power semiconductor device is 2 x 10 ⁵ V / cm and is presented as a design reference value. In this case, according to the Poisson equation, Lt; ¹² > / cm < ^{2 &} gt ;.

Referring to this, it can be confirmed that the ion concentration of the first and second field stop layers 310 and 320 is sufficiently high enough to block expansion of the depletion region even in the extreme case (see the dotted line in Fig. 4 See also

As described above, since the first and second field stop layers 310 and 320 can effectively block expansion of the depletion region, the field stop IGBT according to the present embodiment can reduce the drift layer to the depletion region width Wpp , BV) of less than 3/4 of the thickness of the first and second electrodes, thereby minimizing switching and conduction losses.

5 shows a manufacturing process of the field stop IGBT according to the present embodiment.

Referring to FIG. 5, in step 510, N-conductive ions (e.g., phosphrus, etc.) are implanted through the backside of the semiconductor substrate to a predetermined depth to form a second field stop layer 320 of high concentration . The N conductive type ions to be implanted are implanted such that the peak ion concentration of the second field stop layer 320 to be formed has a value of 1e ¹⁶ / cm ³ or more.

The step of forming the P conductive well 20 or the like, which is the upper structure shown in FIG. 3, may be preceded by the step of step 510, and the step of grinding the semiconductor substrate to a predetermined thickness may be preceded. Although a planar gate IGBT is illustrated in FIG. 3 and the like, it is natural that the present embodiment can be variously applied to a trench gate IGBT and the like.

In step 520, P conductive ions (e.g., P) are implanted through the backside of the semiconductor substrate to form a P conductive type collector region 95 below the second field stop layer 320 (i.e., close to the back surface of the semiconductor substrate) For example, Boron or the like is implanted to a predetermined depth.

Annealing is then performed at a first temperature (e.g., 500 degrees Celsius) (step 530) to activate the N and P conductivity ions implanted in step 510 and 520, respectively.

Proton irradiation is then performed in step 540 to form a first field stop layer 310 on top of the second field stop layer 320 (i.e., away from the back surface of the semiconductor substrate), and step 550 Annealing is performed at a second temperature (about 400 degrees) for the formation of the first field stop layer 310. [ Here, the first temperature and the second temperature for the heat treatment may be set to the same temperature.

Then, in step 560, a collector metal electrode 80 is formed under the collector region 95.

Referring to FIG. 5, ion implantation for forming the collector region 95, ion implantation for forming the second field stop layer 320, and proton irradiation for forming the first field stop layer 310 are performed in this order The order of the ion implantation and the proton injection is not limited thereto, but it is natural that the ion implantation and the proton implantation can be variously modified.

In order to illustrate the method of manufacturing a power semiconductor device according to the present invention, a method of manufacturing an IGBT adopting a field stop structure has been described. However, the present invention is not limited to a diode or a field- It may be applied to various semiconductor devices such as a MOS-driven thyristor. For example, when a diode is fabricated using a thin wafer fabrication process, in a process of forming an N-type buffer to prevent the depletion layer from extending to the N + conductive region of the lower cathode region, The technical ideas proposed by the present invention can be applied.

As described above, in the method of manufacturing a power semiconductor device according to the present invention, an electrode region (for example, a P-type collector region) is formed by an ion implantation and diffusion process through the backside of a semiconductor substrate, (For example, a field stop layer, N-conductivity type buffer, etc.) of N-conductivity type ions need to be formed at arbitrary positions between the electrodes.

In the case where the power semiconductor device fabricated by the method of manufacturing a power semiconductor device according to the present invention is an IGBT (shorted anode) having a diode one-chip structure, the collector region 95 described above for forming a diode structure, May be formed locally.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims And changes may be made without departing from the spirit and scope of the invention.

20: P conductivity type well 30: P conductivity type ion region
40: N conductivity type well 51: Gate oxide film
52: gate poly electrode 70: emitter metal electrode
80: collector metal electrode 90: field stop layer
95: collector region 310: first field stop layer
320: second field stop layer

Claims (6)

A drift layer of a first conductivity type;
A first field stop layer of a first conductivity type formed in a lower portion of the drift layer to have a first peak ion concentration that is relatively larger than an ion concentration of the drift layer;
A second field stop layer of a first conductivity type formed to be disposed directly below the first field stop layer so as to have a second peak ion concentration that is relatively larger than the first peak ion concentration; And
And a collector region of a second conductivity type formed under the second field stop layer ,
The first field stop layer is formed by irradiation of proton and heat treatment, and the second field stop layer is formed by ion implantation and heat treatment of a first conductivity type having a mass relatively larger than that of the proton, ,
The ion concentration peak position formed by the irradiation and the heat treatment of the proton for forming the first field stop layer and the ion concentration peak position formed by the ion implantation and the heat treatment of the first conductivity type for forming the second field stop layer are Are positioned so that they do not coincide with each other,
Wherein the first field stop layer has an ion concentration distribution that decreases with a relatively steep slope towards the emitter and with a relatively gentle slope toward the collector and the second field stop layer has a relatively gentle slope toward the emitter and is directed toward the collector And has an ion concentration distribution decreasing at a relatively steep slope .
delete The method according to claim 1,
The first peak ion concentration is 1e ¹⁵ / cm ³ or less random value, the power semiconductor device of the second peak ion concentration is characterized in that any value greater than 1e ¹⁶ / cm ^3.
The method according to claim 1 or 3,
Wherein the second field stop layer is formed to have a relatively thin thickness as compared to the first field stop layer.
The method according to claim 1 or 3,
Wherein the drift layer is formed to have an arbitrary thickness that is 3/4 or less of the depletion region width (Wpp, BV) at the breakdown voltage.
The method according to claim 1,
Wherein the collector region is formed only in a predetermined region of the lower region of the second field stop layer.

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