Positive oblique angle contact type metal tungsten field plate LDMOS (Laterally Diffused Metal Oxide Semiconductor) device
By introducing positive bevel silicon and contact metal tungsten field plate structures in LDMOS devices, the problems of large size and low switching performance of existing devices are solved, and higher breakdown voltage, lower on-resistance and faster switch speed.
Patent Information
- Application Number
- CN202411395978.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2025-02-14
AI Technical Summary
The device size of existing polysilicon field plate type LDMOS devices is relatively large, especially the distance between the drain to the source and the polysilicon gate above the field plate is too long, which affects the breakdown voltage and switching performance of the device. At the same time, the polysilicon gate charge is over Large results in degradation of switching performance.
The contact metal tungsten field plate LDMOS device adopts a positive bevel angle to form a positive bevel structure on the drift region to assist depletion and reduce the length on the polysilicon gate. The contact metal tungsten field plate is used to replace the traditional polysilicon field field. plate.
Reduce device size, increase breakdown voltage, increase drift area doping concentration, reduce on-resistance, and increase the switching speed of the device by reducing the polysilicon gate length.
Smart Images
Figure CN119451174A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor integrated circuits, in particular to a positive-angle contact-type metal tungsten field plate LDMOS device. Background Art
[0002] Power semiconductor devices are the core devices responsible for power conversion and control in integrated circuits. Among them, LDMOS is one of the most critical devices. Due to its excellent switching performance, small area, and most importantly, its compatibility with chip integration processes, it is widely used in consumer electronics, new energy vehicles and other fields with significant economic benefits. The field plate type LDMOS covers a dielectric layer in the drift region and applies a voltage bias through the gate to assist the depletion of the drift region, effectively increasing the breakdown voltage of the LDMOS device, and can further increase the doping concentration of the drift region, so that the device on-resistance is further reduced.
[0003] like Figure 1 As shown, taking the traditional N-type field plate structure LDMOS as an example, Figure 1 Its structure is as follows: N-type drift region: composed of an N-type low-doped drift region 101 . P-type body region: consists of the P-type well region 102 in the figure. Polysilicon gate: composed of polysilicon 103 in the figure. Field plate dielectric layer: composed of the thicker silicon dioxide 104 in the figure. Thin gate oxide dielectric layer: composed of the thinner silicon dioxide 105 in the figure. Sidewall: Made of 106 silicon nitride sidewalls Drain region: consists of an N-type heavily doped region 107 . Drain electrode: The drain of LDMOS is connected through electrode 108 . Gate electrode: The gate of LDMOS is connected through electrode 109 . Source region: consists of a heavily N-doped region 110 . Body region: consists of heavily P-doped region 111. Source / body electrode: The source region 110 and the body region 111 are short-circuited and then connected to the output electrode 112 . For a P-type structure LDMOS, it is only necessary to invert all the above-mentioned doping regions. Existing polysilicon field plate type LDMOS devices are usually lateral structures, and their device size is relatively large, especially the distance between the drain and the source and the distance between the polysilicon gate above the field plate. The long distance between the two will have an adverse effect on the breakdown voltage and gate charge of the device. In addition, the use of polysilicon field plates will cause excessive gate charge, causing the switching performance of LDMOS devices to deteriorate. Summary of the invention
[0004] The present invention aims at the deficiencies of the prior art and provides a positive-angle contact-type metal tungsten field plate LDMOS device.
[0005] The present invention comprises a drift region, a body region, a drain region, a source region and a body region. The drift region on one side of the body region is a positive bevel drift region, so that the depletion region in the drift region extends toward the drain region, thereby realizing auxiliary depletion of the drift region; The drain region is located at a side of the drift region away from the body region, and leads to a drain electrode; The source region and the body region are located on the other side of the body region, leading out the source electrode; The positive bevel drift region is covered with a field plate dielectric layer, and a contact metal tungsten field plate is located above the field plate dielectric layer; One side of the field plate dielectric layer is a drain region, and the other side is a gate region.
[0006] Furthermore, the gate region includes a gate oxide dielectric layer connected to the drift region and the body region and a polysilicon gate located on the gate oxide dielectric layer.
[0007] Furthermore, the field plate dielectric layer is a silicon dioxide dielectric layer.
[0008] Furthermore, the contact-type metal tungsten field plate reduces the length of the polysilicon gate while assisting the depletion of the polysilicon gate, thereby reducing the gate charge and improving the switching speed of the device.
[0009] Beneficial effects of the present invention: The present invention reduces the device size and assists in depletion of the drift region by introducing positive bevel silicon and a contact field plate structure, thereby increasing the breakdown voltage of the device and increasing the concentration of the drift region to reduce the on-resistance. In addition, the contact field plate can effectively reduce the length of the polysilicon gate, thereby reducing the gate charge and increasing the switching speed of the device. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 It is a structural diagram of an LDMOS device in the prior art; Figure 2 This is a structural diagram of the LDMOS device in an embodiment of the present application. DETAILED DESCRIPTION
[0011] The present invention is further described below in conjunction with the accompanying drawings and embodiments.
[0012] The embodiment of the present application provides a positive bevel contact metal tungsten field plate LDMOS device. The LDMOS described in the present embodiment is called Lateral Diffused Metal Oxide Semiconductor, which is a power semiconductor device that uses double diffusion technology to perform two diffusions of boron and phosphorus in the same window, and the difference in the lateral junction depth of the two impurity diffusions can accurately determine the channel length. The LDMOS device has a large breakdown voltage, a low on-resistance, and a fast switching speed.
[0013] The positive bevel structure described in this embodiment refers to that the diameter of the device is shortened from the high-doped area to the low-doped area. This bevel is called a positive bevel. The positive bevel can extend the depletion region to the area with a shorter diameter, thereby assisting surface depletion and increasing the breakdown voltage of the PN junction.
[0014] Taking n-type devices as an example, Figure 2 As shown, the structure provided by this embodiment at least includes: Positive-bevel N-type drift region: a certain angle is formed on silicon by etching, and then N-type low-doped ion implantation is performed to form a positive-bevel N-type drift region 201 . P-type body region: composed of a P-type well region 202 . Polysilicon gate: composed of polysilicon 203. Field plate dielectric layer: composed of thick silicon dioxide 204, covering the positive bevel drift region. Thin gate oxide dielectric layer: composed of thinner silicon dioxide 205. Contact field plate: It is composed of a contact field plate 206, and its material is metal tungsten. Drain region: consists of an N-type heavily doped region 207 . Drain electrode: The drain of the LDMOS is connected through the electrode 208 . Gate electrode: The gate of LDMOS is connected through electrode 209 . Source region: consists of a heavily N-doped region 210 . Body region: consists of heavily P-doped region 211. Source / body electrode: The source region 210 and the body region 211 are short-circuited and then connected to the output electrode 212. For a P-type structure LDMOS, it is only necessary to invert all the above-mentioned doping regions. The process flow for preparing the structural device is as follows: 1. Photolithography and etching of the positive bevel area to form a positive bevel structure. 2. Ion implantation and annealing in the drift region and body region to form the drift region and body region. 3. Deposition and etching of thin gate oxide dielectric layer. 4. Polysilicon deposition and etching. 5. Side wall deposition and etching. 6. Ion implantation and annealing of heavily doped regions of drain, source and lead. 7. Deposition and etching of thick silicon dioxide dielectric layer. 8. Drain electrode, source / body electrode and gate electrode are led out. 9. Contact metal tungsten field plate deposition and etching. Combined with the structural features and manufacturing process of this embodiment, this embodiment has the following significant effects: 1) The LDMOS structure of this embodiment uses a positive bevel structure. Compared with the LDMOS structure, the positive bevel structure used in the LDMOS structure of this embodiment shortens the diameter of the device from the highly doped body region to the low-doped drift region, which allows the depletion region in the drift region to extend toward the drain, thereby achieving auxiliary depletion of the drift region. In this way, the doping of the drift region can be further improved while maintaining the same breakdown voltage, thereby reducing the on-resistance of the device and improving the performance of the LDMOS device. In addition, the positive bevel structure can effectively reduce the horizontal distance between the source and drain while maintaining the same length of the current conduction path, thereby reducing the device size and improving the integration of the LDMOS device. 2) The LDMOS structure of this embodiment also uses a contact field plate structure. Compared with the traditional polysilicon-silicon dioxide structure field plate, the contact field plate structure can effectively reduce the polysilicon gate length while assisting gate depletion, thereby reducing the gate charge and improving the switching speed of the device. 3) When manufacturing the device of the present invention, metal tungsten is selected as the contact field plate material. This is because metal tungsten is also usually used for the contact electrode lead-out of the LDMOS device. Therefore, the metal field plate and contact electrode processes can be integrated without adding a new mask, saving manufacturing and process development costs. The above are preferred embodiments of the present invention. It should be noted that a person skilled in the art may make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications are also considered to be within the protection scope of the present invention.
Claims
1. A positively beveled contact metal tungsten field plate LDMOS device, comprising a drift region, a body region, a drain region, a source region and a body region, characterized in that: The drift region on one side of the body region is a positive bevel drift region, so that the depletion region in the drift region extends toward the drain region, thereby realizing auxiliary depletion of the drift region; The drain region is located at a side of the drift region away from the body region, and leads to a drain electrode; The source region and the body region are located on the other side of the body region, leading out the source electrode; The positive bevel drift region is covered with a field plate dielectric layer, and a contact metal tungsten field plate is located above the field plate dielectric layer; One side of the field plate dielectric layer is a drain region, and the other side is a gate region.
2. The positive-angle contact metal tungsten field plate LDMOS device according to claim 1, characterized in that: The gate region includes a gate oxide dielectric layer connected to the drift region and the body region and a polysilicon gate located on the gate oxide dielectric layer.
3. The positive-angle contact metal tungsten field plate LDMOS device according to claim 1, characterized in that: The field plate dielectric layer is a silicon dioxide dielectric layer.
4. The positive-angle contact metal tungsten field plate LDMOS device according to claim 2, characterized in that: The contact-type metal tungsten field plate reduces the length of the polysilicon gate while assisting the depletion of the polysilicon gate, thereby reducing the gate charge and improving the switching speed of the device.