JPH01272153A - Manufacture of guard ring - Google Patents

Abstract

PURPOSE:To form a deep guard ring in a short thermal diffusion time by evaporating a second conductivity type impurity onto the surface of a semiconductor substrate, shaping a first conductivity type epitaxial growth layer, diffusing the second conductivity type impurity up to the buried region of the epitaxial growth layer from a section just above the buried region and forming the guard ring. CONSTITUTION:An oxide film 6 is shaped onto the surface of an N<-> type low- concentration impurity semiconductor substrate 3, impurity evaporating windows are bored, and a P-type impurity is evaporated onto the surface of the semiconductor substrate 3. The oxide film 6 is removed, an epitaxial growth 3 layer 8 having the same type and the same resistivity as the substrate 3 is deposited, and P<+> type buried regions 1 are formed. The surface of the epitaxial growth layer 8 is oxidized, an oxide film 9 is shaped, and impurity evaporating windows 10 are bored to sections just above the previously formed P<+> type buried regions 1. A P-type impurity is evaporated to the epitaxial growth layer 8 through the impurity evaporating windows 10, and the P-type impurity is diffused up to the buried regions 1 through a thermal diffusion process, thus forming guard rings 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a guard ring used for increasing the voltage resistance of semiconductor devices.

[Prior Art] Conventionally, in order to achieve a high breakdown voltage of a semiconductor element, as shown in FIG. Widely adopted. This is because the presence of the guard ring 2 widens the depletion region 4 to bring it closer to a planar junction, thereby eliminating areas where electric field concentration is likely to occur.

[Problems to be Solved by the Invention] However, in the guard ring structure formed by a general thermal diffusion process, the guard ring 2 consisting of the P-type high concentration impurity diffusion region extends to the N-type low concentration impurity semiconductor substrate 3. There is a problem in that a portion with a small curvature is generated in the depletion region 4, and when a voltage is applied, an electric field is concentrated in this portion, easily causing breakdown of the junction and lowering the withstand voltage. Furthermore, in order to form a deep guard ring 2, a long thermal diffusion process is usually required.
When the diffusion depth of the guard ring 2 is 10 to 20 μm at 50° C., the required diffusion time is 1 to 2 days. If such a long thermal diffusion process is performed, the insulating oxide film etc. will be contaminated due to the redistribution of impurities, causing a decrease in breakdown voltage. Furthermore, there is also the problem that the semiconductor substrate 3 is warped due to the long-term high-temperature treatment, resulting in a decrease in mask alignment accuracy.

The present invention has been made in view of these points, and its purpose is to increase the curvature of the depletion layer near the guard ring region to increase the breakdown voltage, and to form the depletion layer in a short diffusion time. An object of the present invention is to provide a method for manufacturing a guard ring that enables the following.

[Means for Solving the Problems] In order to solve the above problems, in the method for manufacturing a guard ring according to the present invention, as shown in FIG. In the method of manufacturing a high voltage semiconductor device, the semiconductor substrate 3 includes a guard ring 2 of a second conductivity type (P medium type) on the outer periphery of the main bonding region 5 on the front surface of the semiconductor substrate 3,
As shown in FIGS. 1 to 5, after impurities of the second conductivity type (P medium type) are deposited on the surface of the semiconductor substrate 3, an epitaxial growth layer 8 of the first conductivity type (N'''' type) is formed. By forming the second conductivity type (P medium type) buried region 1
is formed in advance, and an impurity of the second conductivity type (N- type) is diffused from directly above the buried region 1 until it reaches the buried region 1 to form the guard ring 2. It is.

[Function] In the present invention, as described above, before the guard ring 2 is formed on the surface of the semiconductor substrate 3 of the first conductivity type by the impurity diffusion process of the second conductivity type, the second conductivity type is The buried region 1 of the second conductivity type is formed in advance on the surface of the semiconductor substrate 3 of the first conductivity type by performing the impurity vapor deposition step and the epitaxial growth step of the first conductivity type. The second impurity diffusion region formed by the diffusion process is connected to the second conductivity type buried region 1, forming a deep guard ring 2.
can be formed in a short thermal diffusion time.

[Example] Figure 1 is a cross-sectional view of a guard ring manufactured by the manufacturing method of the present invention, and Figures 2 to 5 are cross-sectional views for explaining each step of the manufacturing method of the present invention. . Each step will be explained below.

First, as shown in FIG. 2, the surface of an N-type low-concentration impurity semiconductor substrate 3 is oxidized to form an oxide film 6 made of silicon dioxide, and then the impurity is etched through a well-known photolithography process and an etching process. The vapor deposition window 7 is opened. A P-type impurity is deposited on the surface of the semiconductor substrate 3 through the impurity deposition window 7 .

Next, after removing the oxide film 6, an epitaxial growth layer 8 having the same type and resistivity as the semiconductor substrate 3 is deposited to form a P medium-sized buried region 1, as shown in FIG. The surface of the epitaxial growth layer 8 is oxidized to form an oxide film 9 made of silicon dioxide, and then a well-known photolithography process and an etching process are performed to form a P layer with an impurity vapor deposition window 10 previously formed, as shown in FIG. It opens directly above the medium-sized buried region 1. A P-type impurity is deposited on the epitaxial growth layer 8 through this impurity deposition window 10, as shown in FIG. Then, through a thermal diffusion process, the P-type impurity is diffused so as to sufficiently reach the lower buried region 1, thereby forming a guard ring 2 as shown in FIG.

Since the guard ring 2 formed in this way has its deepest part spread planarly in a direction parallel to the surface of the semiconductor substrate 3, the curvature of the formed depletion region 4 is large and the breakdown voltage of the junction is high. . In addition, when forming the guard ring 2 with the same diffusion depth, the diffusion time is shorter than when forming it only by a thermal diffusion process as in the conventional example. Therefore, the main bonding region 5 shown in FIG. If the diffusion conditions for the P10 region and the guard ring 2 during formation are the same,
These diffusion steps can be performed simultaneously.

[Effects of the Invention] As described above, in the guard ring manufacturing method of the present invention, before forming the guard ring on the surface of the first conductivity type semiconductor substrate by the second conductivity type impurity diffusion step. To,
A buried region of the second conductivity type is formed in advance on the surface of the semiconductor substrate of the first conductivity type by performing an impurity deposition step of the second conductivity type and an epitaxial growth step of the first conductivity type. Therefore, there is an advantage that the second impurity diffusion region formed by the thermal diffusion process is connected to the buried region of the second conductivity type, and a deep guard ring can be formed in a short thermal diffusion time. Furthermore, by shortening the thermal diffusion time required to form the guard ring, problems such as contamination due to redistribution of impurities and warping of the semiconductor substrate can be improved. Furthermore, since the shape of the deepest part of the guard ring formed by the method of the present invention extends in a direction parallel to the surface of the semiconductor substrate, the curvature of the depletion region becomes large and the breakdown voltage of the junction increases. There is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a guard ring manufactured by the manufacturing method of the present invention, FIGS. 2 to 5 are sectional views for explaining each step of the manufacturing method of the present invention, and FIG. 6 is a sectional view of a guard ring manufactured by the conventional method. FIG. 3 is a cross-sectional view of the manufactured guard ring. 1 is a buried region, 2 is a guard ring, 3 is a semiconductor substrate, 4 is a depletion region, 5 is a main junction region, 6°9 is an oxide film, 7
．． 10 is an impurity vapor deposition window, and 8 is an epitaxial growth layer.

Claims (1)

[Claims] (1) In a method for manufacturing a high-voltage semiconductor device including a guard ring of a second conductivity type on the outer periphery of a main bonding region on a surface of a semiconductor substrate of a first conductivity type, a guard ring of a second conductivity type is provided on the surface of the semiconductor substrate. After depositing the type impurity, a buried region of the second conductive type is formed in advance by forming an epitaxial growth layer of the first conductive type, and a buried region of the second conductive type is formed directly above the buried region. A method for manufacturing a guard ring, which comprises forming a guard ring by diffusing impurities until it reaches a buried region.