JP-7856014-B2 - Semiconductor equipment

Inventors

• 坂根 宏樹

Assignees

• 株式会社デンソー

Dates

Publication Date

20260511

Application Date

20230110

Claims (7)

1. A semiconductor device, A semiconductor substrate (12) having a trench (14) on its upper surface, A gate insulating film (16) covering the inner surface of the trench, A gate electrode (18) is disposed within the trench and is insulated from the semiconductor substrate by the gate insulating film, The upper electrode (22) in contact with the upper surface of the semiconductor substrate, A lower electrode (24) in contact with the lower surface of the semiconductor substrate, It has, The aforementioned semiconductor substrate A first n-type region (32) is in contact with the upper electrode and is in contact with the gate insulating film on the side surface of the trench, The lower side surface of the first n-type region is a p-type upper body region (34) that is in contact with the gate insulating film, An n-type barrier region (36) in contact with the gate insulating film on the lower side surface of the upper body region, A p-shaped lower body region (38) is in contact with the gate insulating film on the lower side surface of the barrier region and is separated from the upper body region by the barrier region, A connection portion (40) that electrically connects the barrier region and the upper electrode, An n-type drift region (42) in contact with the gate insulating film on the lower side surface of the lower body region, A second n-type region (46, 144) having a higher n-type impurity concentration than the drift region, positioned below the drift region, and in contact with the lower electrode, It has, The lower portion (16b) of the gate insulating film, which is the part that is in contact with the lower body region, is thicker than the upper portion (16a) of the gate insulating film, which is the part that is in contact with the upper body region. Semiconductor equipment.
2. The gate insulating film has a thickness-changing portion (16c) in which the thickness increases from the upper portion toward the lower portion. The thickness-changing portion is located within the range in contact with the barrier region. The semiconductor device according to claim 1.
3. The semiconductor device according to claim 1 or 2, wherein the p-type impurity concentration in the lower body region is lower than the p-type impurity concentration in the upper body region.
4. The semiconductor device according to claim 1 or 2, wherein the semiconductor substrate is disposed below the drift region and has a p-type collector region (44) in contact with the lower electrode.
5. The semiconductor device according to claim 1 or 2, wherein the connecting portion is made of an n-type semiconductor and is in Schottky contact with the upper electrode.
6. The semiconductor device according to claim 5, wherein the Schottky barrier between the connection portion and the upper electrode is 0.7 eV or less.
7. The semiconductor device according to claim 1 or 2, wherein the upper portion is made of a different material from the lower portion.

Description

The technology disclosed herein relates to semiconductor devices. The semiconductor device disclosed in Patent Document 1 has an IGBT (insulated gate bipolar transistor) and a diode. An n-type drift region is distributed across the IGBT region and the diode region. Within the IGBT region, a p-type body region is provided above the drift region. The body region is separated into an upper body region and a lower body region by an n-type barrier region. The barrier region is electrically connected to the upper electrode by a connection portion (more specifically, an n-type connection region). Within the diode region, a p-type anode region is provided above the drift region, and an n-type cathode region is provided below the drift region. The anode region is in contact with the upper electrode, and the cathode region is in contact with the lower electrode. When the diode is turned on, holes flow from the anode region to the cathode region via the drift region. At this time, holes also flow from the body region within the IGBT region to the cathode region via the drift. When holes are injected from the body region to the cathode region in this way, losses are likely to occur when the diode subsequently performs reverse recovery operation. In the semiconductor device described in Patent Document 1, a barrier region and a connection portion are provided to suppress the flow of holes from the body region within the IGBT region to the drift when the diode is ON. This suppresses reverse recovery losses. While Patent Document 1 describes a semiconductor device having an IGBT and a diode with a barrier region and connection portion, a barrier region and connection portion can also be provided in a MOSFET (metal-oxide-semiconductor field effect transistor). Providing a barrier region and connection portion in a MOSFET can suppress losses during the reverse recovery operation of the MOSFET's body diode. International Publication No. WO2015/029116 Cross-sectional view of the semiconductor device 10 of the embodiment.Enlarged cross-sectional view of the area around the trench of the semiconductor device 10 in the embodiment.Enlarged cross-sectional view of the trench area of the comparative semiconductor device.A graph showing the rise characteristics of the current Ic of the comparative semiconductor device.A graph showing the rise characteristics of current Ic for normal and abnormal IGBTs that do not have a barrier region or connection.Diagram illustrating the method for forming the gate insulating film.Enlarged cross-sectional view of the area around the trench in the semiconductor device of modification 1.Cross-sectional view of the semiconductor device of modified example 2.Cross-sectional view of the semiconductor device of modified example 3. In one example of a semiconductor device disclosed herein, the gate insulating film may have a thickness-changing portion in which the thickness increases from the upper portion toward the lower portion. In this case, the thickness-changing portion may be located within a range adjacent to the barrier region. If the thickness-changing portion is located within the upper or lower body region, the variation in gate thresholds will increase during mass production of semiconductor devices. As described above, if the thickness-changing portion is located within the range adjacent to the barrier region, the variation in gate thresholds can be suppressed. In one example of a semiconductor device disclosed herein, the p-type impurity concentration in the lower body region may be lower than the p-type impurity concentration in the upper body region. To suppress electric field concentration around trenches in the off state of a semiconductor device, the p-type impurity concentration in the lower body region can be made lower than that in the upper body region. In this case, channels are more likely to form in the lower body region, making leakage current problems more pronounced. Even in this case, however, as described above, leakage current can be suppressed by making the lower portion of the gate insulating film thicker than the upper portion. In one example of a semiconductor device disclosed herein, the semiconductor substrate may be located below the drift region and may have a p-type collector region in contact with the lower electrode. In one example of a semiconductor device disclosed herein, the connection portion is made of an n-type semiconductor and may be in Schottky contact with the upper electrode. This configuration allows for further suppression of leakage current by the Schottky barrier. The Schottky barrier between the connection portion and the upper electrode may be 0.7 eV or less. In one example of a semiconductor device disclosed herein, the upper portion may be made of a different material than the lower portion. The semiconductor device 10 in the embodiment shown in Figure 1 has a semiconductor substrate 12 made of silicon. The semiconductor substrate 12 may be