CN102842604B - Trench gate type insulated gate bipolar transistor and manufacturing method thereof - Google Patents

Abstract

The embodiment of the invention discloses a trench gate type insulated gate bipolar transistor and a manufacturing method thereof. The trench gate type insulated gate bipolar transistor includes: a drift region; an effective base region located in the front face of the drift region; the trench gate is positioned in the front face of the drift region and on two sides of the effective base region; wherein the trench gate includes: an active trench gate adjacent to the active base region and an inactive trench gate remote from the active base region. According to the groove gate type insulated gate bipolar transistor provided by the invention, the total width of the groove gate is increased by increasing the number of the groove gates in the groove gate bipolar transistor, and the ratio of the effective base region width to the single cell width is reduced, so that the hole concentration in the drift region is increased, the conductance modulation effect is enhanced finally, and the on-resistance of the device can be reduced. In addition, the groove gate type insulated gate bipolar transistor can reduce the current density and improve the short-circuit safe working area of the device.

Description

Trench gate type insulated gate bipolar transistor and manufacturing method thereof

technical field

The invention relates to the technical field of manufacturing technology of semiconductor devices, and more specifically relates to a trench gate type insulated gate bipolar transistor and a manufacturing method thereof.

Background technique

Insulated gate bipolar transistor (Insulate Gate Bipolar Transistor, IGBT) has many advantages of power transistor (Giant Transistor, GTR) and field effect transistor (MOSFET), and has good characteristics. As the main representative of new power semiconductor devices, it is widely used in the fields of industry, information, new energy, medicine, transportation, military and aviation.

The initially developed IGBT has a planar gate structure, and later a trench gate structure formed by a dry etching process appeared. Compared with the planar gate structure, the trench gate structure can improve the conduction characteristics of the IGBT device and reduce the conduction resistance. Referring to FIG. 1, FIG. 1 is a schematic structural diagram of a trench gate IGBT commonly used in the prior art. The trench gate IGBT includes: a drift region 1; a base region 2 located in the front of the drift region 1; The emitter region (or source region) 3 in 2; the gate region 4 located in the drift region 1 and on both sides of the base region 2; the buffer region 6 and the collector region (or drain region) arranged in sequence on the back of the drift region 1 5. In the trench gate type IGBT, since the gate region 4 is formed on the premise of forming a trench in the drift region 1, this structure is called a trench gate type IGBT.

When the above-mentioned trench gate IGBT works at high temperature, on the one hand, the temperature rises, the carrier lifetime increases, and the transistor amplification factor becomes larger, resulting in a larger hole current flowing through the base region 2; on the other hand, the temperature The increase will greatly reduce the mobility of holes, and then increase the resistance of the base region 2, and finally increase the on-resistance of the trench gate IGBT.

In addition, when the trench gate type IGBT is in operation, since the current flows directly from the drift region 1 into the vertical channel and enters the emitter region 3, the cell density of the trench gate type IGBT increases and saturates The current density increases, thereby reducing the short-circuit safe operating area (SCSOA) of the device.

Contents of the invention

In view of this, the present invention provides a trench gate type insulated gate bipolar transistor and its manufacturing method. The transistor not only has a small on-resistance, but also has a small current density during operation, so that the device can be broadened. safe work area.

To achieve the above object, the present invention provides the following technical solutions:

A trench gate type insulated gate bipolar transistor comprising:

drift zone;

An effective base zone located within the front of the drift zone;

Trench gates located in the front of the drift region and on both sides of the active base region;

Wherein, the trench gate includes: an effective trench gate adjacent to the effective base region and an ineffective trench gate far away from the effective base region.

Preferably, in one cell of the trench gate type insulated gate bipolar transistor, there are two effective trench gates and two ineffective trench gates.

Preferably, in one cell of the trench gate type insulated gate bipolar transistor, an idle base region is suspended between adjacent effective trench gates and ineffective trench gates.

Preferably, in one cell of the trench gate type insulated gate bipolar transistor, there is a drift region between adjacent effective trench gates and ineffective trench gates.

Preferably, the above-mentioned transistors also include:

an emitter region located within the active base region;

Buffer and collector regions arranged in sequence on the backside of the drift region.

Preferably, the trench-gate IGBT is an N-channel trench-gate IGBT.

The present invention also provides a method for manufacturing a trench gate type insulated gate bipolar transistor, the method comprising:

A lightly doped silicon substrate is used as the drift region of the trench gate type insulated gate bipolar transistor;

forming an effective base region and a trench gate in the front surface of the drift region;

Wherein, the trench gate includes: an effective trench gate adjacent to the effective base region and an ineffective trench gate far away from the effective base region.

Preferably, in the above method, an effective base region and a trench gate are formed in the front of the drift region, specifically including:

forming a base region in the front side of the drift region by an ion implantation process;

A plurality of trenches are formed in the drift region by photolithography and etching processes, and the plurality of trenches divide the base region into a plurality of regions, and among the plurality of regions into which the base region is divided, the middle one The area is called the effective base area, and the areas on both sides are called the invalid base area;

Gate material is filled in the plurality of trenches to form trench gates. Among the trench gates, the trench gates adjacent to the effective base region are called effective trench gates, and the trench gates far away from the effective base region are called effective trench gates. Trench gates are called inactive trench gates.

Preferably, in the above method, an effective base region and a trench gate are formed in the front of the drift region, specifically including:

forming a plurality of trenches in the drift region by photolithography and etching processes;

Filling gate material in the plurality of trenches, thereby forming trench gates;

An effective base region is formed in the drift region between the two trench gates in the middle by ion implantation process, wherein the trench gate adjacent to the effective base region is called the effective trench gate, and the trench far away from the effective base region is called the effective trench gate. The gate is called an inactive trench gate.

Preferably, the above method also includes:

forming an emitter region within the active base region;

forming a buffer zone within the backside of the drift region;

A collector region is formed within the buffer region.

It can be seen from the above technical solutions that the trench gate type insulated gate bipolar transistor provided by the present invention includes: a drift region; an effective base region located in the front of the drift region; trenches located on both sides of the effective base region in the front of the drift region A trench gate; wherein, the trench gate includes: an effective trench gate adjacent to the effective base region and an ineffective trench gate far away from the effective base region. In the trench gate type insulated gate bipolar transistor provided by the present invention, since the trench gate therein includes an effective trench gate and an ineffective trench gate, the existence of the ineffective trench gate increases the total width of the trench gate, Therefore, when the width of the effective base region remains unchanged, the increase in the total width of the trench gate reduces the ratio of the effective base region width to the width of a single cell, thereby enhancing the conductance modulation effect of the effective base region and reducing the on-resistance.

Furthermore, the increase of the total width of the trench gate also increases the width of the adjacent effective base region, thereby reducing the current density, thereby improving the short-circuit safe working area of the device.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a schematic structural diagram of a trench-gate IGBT commonly used in the prior art;

Fig. 2 is a schematic structural diagram of half a cell in the trench gate IGBT shown in Fig. 1;

Figure 3 is a simulation diagram of the hole concentration distribution in the base region and the drift region of the trench gate IGBT;

Fig. 4 is a structural schematic diagram of half a cell of a trench gate IGBT provided by the present invention;

5 is a schematic structural diagram of half a cell of another trench gate IGBT provided by the present invention;

FIG. 6 is a schematic flowchart of a method for manufacturing a trench-gate IGBT provided by the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As mentioned in the background technology section, although the trench gate IGBT has a lower on-resistance compared with the planar gate IGBT, its on-resistance is still large when it works at high temperature, and its saturation current density Larger, so that the short-circuit safe operating area of the device is smaller.

In order to reduce the on-resistance of the trench-gate IGBT, the most effective solution is to achieve it through the conductance modulation effect. The conductance modulation effect is: when the forward current flowing on the PN junction is large, the concentration of the minority carrier holes injected and accumulated in the lightly doped drift region will be very large. In order to maintain the neutral condition of the semiconductor, the concentration of the majority carrier holes will also Correspondingly, the significant increase makes the resistivity decrease obviously, that is, the conductivity increases greatly, which is the conductance modulation effect.

Therefore, if the conductance modulation effect is to be used to reduce the on-resistance of the trench-gate IGBT, the hole concentration in the drift region needs to be increased. The inventors have found that the hole concentration in the drift region is closely related to the base region width and the drift region width ( or unit cell width) are closely related. The specific discovery process is as follows: Referring to Figure 2 and Figure 3, Figure 2 is a schematic structural diagram of half a cell in the trench gate IGBT shown in Figure 1, and the figure shows that the width of the base region 2 in the half cell is Wm, the width of the drift region 1 is Wd. For the trench gate type IGBT with different base region width and/or drift region width in half a cell (or a single cell), the hole concentration distribution diagram in the base region and the drift region is obtained, as shown in Fig. 3 It can be seen from Figure 3 that the hole concentration in the base region and the drift region increases with the increase of Wd/Wm. The increase of the hole concentration in the drift region can enhance the conductance modulation effect and reduce the on-resistance. Therefore, the on-resistance of the trench gate IGBT can be reduced by increasing Wd/Wm.

It can be known from the above that in order to reduce the on-resistance, it is necessary to increase the ratio of the width of the drift region in a single cell (ie, the width of a single cell) to the width of the base region (ie, Wd/Wm). Under the condition that the width of the base region remains unchanged, the increase of Wd/Wm can be achieved by increasing the width of a single cell. Based on this, the present invention provides a new trench gate type IGBT, the trench gate Compared with the existing trench gate type IGBT, the ratio of the base width to the entire cell width becomes smaller.

Referring to FIG. 4, FIG. 4 shows a schematic structural diagram of half a cell of a trench gate IGBT provided by the present invention, the trench gate IGBT includes: a drift region 1; Base region 7 (corresponding to the base region in the prior art); trench gates on both sides of the effective base region 7 in the front of the drift region 1 (only the trench gate on the right side of the effective base region 7 is shown in FIG. 5 ) ; Wherein, the trench gate includes: an effective trench gate 9 adjacent to the effective base region 7 and an ineffective trench gate 10 far away from the effective base region 7 .

FIG. 4 shows the width Wm of the effective base region 7 and the width Wd of the drift region 1 in half a cell. In the embodiment of the present invention, under the condition that the width of the effective base region remains unchanged, by increasing the number of trench gates (the added trench gates no longer function as gates, so they are called invalid trench gates), and then The total width of the trench gate is increased, thereby increasing the width of a single cell, therefore, the ratio of the effective base width to the width of a single cell is reduced, or in other words: Wm/Wd is increased, thereby enhancing the effective The conductance modulation effect of the base area can reduce the on-resistance.

The number of effective trench gates 9 and the number of ineffective trench gates 10 in this embodiment is two, and the number of ineffective trench gates 10 in other embodiments may be four. Figure 4 shows that there is a drift region 1 between adjacent effective trench gates 9 and invalid trench gates 10. In other embodiments, the gap between adjacent effective trench gates 9 and invalid trench gates 10 can It is the floating ineffective base region 12 , referring to FIG. 5 , the floating ineffective base region 12 is formed in the same process step as the effective base region 7 , but it no longer functions as a base region in the trench gate IGBT. If there are 4 or more ineffective trench gates 10 in one cell of a trench gate IGBT, the gap between adjacent ineffective trench gates 10 can be a drift region, or a floating ineffective base. district.

The trench gate type IGBT provided by the present invention also includes: an emitter region 8 located in the effective base region 7, the emitter region 8 is connected to the emitter E through a metal; a buffer zone 6 arranged in sequence on the back of the drift region 1 and collector region 5.

The trench gate IGBT provided by the present invention may be an N-channel trench gate IGBT, or a P-channel trench gate IGBT.

In the trench gate type IGBT provided by the present invention, the ineffective trench gate and the effective trench gate are formed in the same process step, but the ineffective trench gate no longer functions as a trench gate, and the ineffective trench gate The existence of the trench gate only increases the total width of the trench gate, which in turn increases the width of a single cell and reduces the ratio of the effective base width to the width of a single cell, which ultimately enhances the conductance modulation effect and reduces the conductance. on-resistance.

In addition, in the trench gate type IGBT provided by the present invention, since the total width of the trench gate in a single cell increases, this also makes the gap between adjacent effective base regions in the trench gate type IGBT The distance is increased, so that the current density is reduced, that is, the safe operating area of the device is improved.

Of course, instead of increasing the number of trench gates to achieve the purpose of reducing the ratio of the width of the base region to the width of a single cell as described in this embodiment, it is also possible not to increase the number of trench gates, but to The width of the existing trench gate is increased, which can also achieve the purpose of reducing the ratio of the width of the base region to the width of a single cell. However, since the wider trench is filled with polysilicon (or metal material) to form the trench The process of gate is more difficult, therefore, this idea cannot be implemented smoothly.

The trench gate type IGBT provided by the present invention has been described in detail above, and the manufacturing method of the trench gate type IGBT will be described in detail below.

Referring to FIG. 6, FIG. 6 is a schematic flow chart of a method for manufacturing a trench-gate IGBT provided by the present invention. The method specifically includes the following steps:

Step S1: A lightly doped silicon substrate is used as the drift region of the trench gate IGBT.

The existing lightly doped silicon substrate is used as the substrate for manufacturing the trench gate type IGBT, and subsequent process steps are all implemented in or on the silicon substrate.

Step S2: forming an effective base region and a trench gate in the front surface of the drift region; wherein the trench gate includes: an effective trench gate adjacent to the effective base region and an ineffective trench gate far away from the effective base region.

The formation sequence of the effective base region and the trench gate can be changed, therefore, there are two ways to realize this step, which are as follows:

1. A base region is formed in the front of the drift region by an ion implantation process; a plurality of trenches are formed in the drift region by photolithography and etching processes, and the plurality of trenches divide the base region into multiple In the multiple regions where the base region is divided, the middle region is called the effective base region, and the regions on both sides are called the invalid base region; the gate material (the gate material) is filled in the multiple trenches. It can be polysilicon or metal) to form trench gates. Among the trench gates, the trench gates adjacent to the effective base region are called effective trench gates, and the trench gates far away from the effective base region are called effective trench gates. is an inactive trench gate.

In this formation method, an effective base region is first formed in the drift region, and then a trench gate is formed, which makes an inactive base region suspended between adjacent trench gates on the same side of the effective base region.

2. Form a plurality of trenches in the drift region through photolithography and etching processes; fill gate materials in the plurality of trenches to form trench gates; An effective base region is formed in the drift region between the trench gates, wherein a trench gate adjacent to the effective base region is called an effective trench gate, and a trench gate far from the effective base region is called an ineffective trench gate.

In this formation method, trench gates are first formed in the drift region, and then an effective base region is formed. Therefore, a drift region is formed between adjacent trench gates on the same side of the effective base region.

Step S3: forming an emitter region in the effective base region.

A source region, that is, an emitter region, is formed in the effective base region by an ion implantation process. The doping type of the source region is opposite to that of the effective base region, and the doping concentration of the source region is greater than that of the effective base region. doping concentration.

Step S4: forming a buffer zone on the back of the drift region.

A buffer zone is formed by ion implantation on the back of the drift region, and the doping type of the buffer zone is the same as that of the drift region, except that its doping concentration is slightly higher. The existence of the buffer zone can make the trench gate IGBT have a higher reverse breakdown voltage.

Step S5: forming a collector region in the buffer zone.

A collector region is formed in the buffer region by an ion implantation process, and the doping type of the collector region is opposite to that of the buffer region. A metal connection layer may then be formed on the collector region.

In the manufacturing method of the trench gate type IGBT provided in this embodiment, in the process of forming the trench gate, it is necessary to first form a trench in the drift region, and then fill the trench with gate material to form the trench gate. Since the trench gates formed include effective trench gates adjacent to the effective base region and ineffective trench gates far away from the effective base region, the trenches formed in the drift region are also divided into trenches adjacent to the effective base region. Trenches and trenches away from the active base region, ie multiple trenches need to be formed in the drift region. And because the formation of the groove needs to be completed by photolithography and etching process, and a mask plate is needed in the photolithography process, there is only one groove formed in a single cell in the existing process, so the used There is only one groove-shaped pattern on the mask plate (corresponding to the area of a single cell), and the embodiment of the present invention needs to use a mask with multiple groove-shaped patterns on it (corresponding to the area of a single cell) plate, and then multiple trenches can be formed in the drift region after subsequent steps such as exposure, development, and etching.

Filling the gate material in the plurality of trenches forms trench gates. Among these trench gates, the trench gates adjacent to the effective base region are effective trench gates, and the remaining trench gates are ineffective trench gates. Groove gate, the existence of the ineffective trench gate increases the total width of the trench gate, therefore, under the condition that the effective base area width remains unchanged, the increase of the total width of the trench gate makes the effective base area width account for a single cell The proportion of the width is reduced, thereby enhancing the conductance modulation effect of the effective base region and reducing the on-resistance.

Furthermore, the increase in the total width of the trench gate also increases the width of the adjacent effective base region, thereby reducing the current density and increasing the short-circuit safe working area.

In this embodiment, the description of the trench-gate IGBT and its manufacturing method has its own focus, and relevant parts can be referred to each other.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. a trench gate igbt, is characterized in that, comprising:

Drift region;

Be positioned at effective base in front, drift region;

Be positioned at the trench gate of front, drift region, effectively both sides, base;

Also comprise: the emitter region being positioned at effective base;

Wherein, described trench gate comprises: the effective trench gate adjacent with effective base and the invalid trench gate away from effective base.

2. transistor according to claim 1, is characterized in that, in a cellular of described trench gate igbt, the number of effective trench gate and invalid trench gate is 2.

3. transistor according to claim 2, is characterized in that, in a cellular of described trench gate igbt, is unsettled invalid base between adjacent effective trench gate and invalid trench gate.

4. transistor according to claim 2, is characterized in that, in a cellular of described trench gate igbt, is drift region between adjacent effective trench gate and invalid trench gate.

5. transistor according to claim 1, is characterized in that, also comprises:

Be positioned at buffering area and collector area that the back side, drift region sets gradually.

6. the transistor according to any one of Claims 1 to 5, is characterized in that, described trench gate igbt is N Channel Trench grid-type igbt.

7. a trench gate igbt manufacture method, is characterized in that, comprising:

Adopt lightly doped silicon substrate as the drift region of trench gate igbt;

Effective base and trench gate is formed in front, described drift region;

Also comprise: the emitter region being positioned at effective base;

Wherein, described trench gate comprises: the effective trench gate adjacent with effective base and the invalid trench gate away from effective base.

8. method according to claim 7, is characterized in that, forms effective base and trench gate, specifically comprise in front, described drift region:

In front, described drift region, base is formed by ion implantation technology;

In described drift region, form multiple groove by photoetching, etching technics, and base is divided into multiple region by described multiple groove, in multiple regions that base is divided into, a middle region is called effective base, and the region on both sides is called invalid base;

In described multiple groove, fill grid material, thus form trench gate, in described trench gate, the trench gate adjacent with effective base is called effective trench gate, and the trench gate away from effective base is called invalid trench gate.

9. method according to claim 7, is characterized in that, forms effective base and trench gate, specifically comprise in front, described drift region:

In described drift region, multiple groove is formed by photoetching, etching technics;

In described multiple groove, fill grid material, thus form trench gate;

In the drift region between two trench gate of centre, form effective base by ion implantation technology, wherein, the trench gate adjacent with effective base is called effective trench gate, and the trench gate away from effective base is called invalid trench gate.

10. method according to claim 7, is characterized in that, also comprises:

Buffering area is formed in the back side, described drift region;

Collector area is formed in described buffering area.