JPH0444235A - Manufacture of high-speed bipolar transistor - Google Patents

Abstract

PURPOSE:To enable a narrower base width to be achieved by doping impurities whose diffusion coefficient is larger than that at other parts onto a part which is directly below a genuine base of a buried layer when forming a buried layer and by utilizing the plenomenon that the impurities with a larger diffusion coefficient are raised by later heat treatment. CONSTITUTION:When doping impurities of an N<+> buried layer 2a for a P sub strate 1, impurities with a larger diffusion coefficient than that at other parts are doped at a part which is directly below a genuine base and an epitaxial layer 4 is allowed to grow on it, thus forming a separation diffusion layer 3 for element separation. The impurities with a larger diffusion coefficient which are doped directly below the genuine base of the N<+> buried layer 2a is raised as shown in figure by later heat treatment, thus suppressing diffusion of boron ion at the genuine base part of a base diffusion layer 5 due to implanta tion of boron ion, enabling impurity distribution to be sharp, and helping to achieve a narrow base width.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing high-speed bipolar transistors, and in particular to a method for realizing a narrower base diffusion layer.

[Prior Art] FIG. 2 shows the structure of an example of a conventional bipolar transistor.

In the figure, l is the P substrate, 2 is the N buried layer, and 3
4 is an isolation diffusion layer, 4 is an epitaxial layer, 5 is a base diffusion layer, 6 is an emitter diffusion layer, and 7 is a collector diffusion layer.

Narrowing the base width is an absolute prerequisite for increasing the speed of bipolar transistors.

On the other hand, boron ion implantation is used to form the base diffusion layer of high-speed bipolar transistors, but due to channeling, the impurity distribution deviates from the Gaussian distribution, resulting in an impurity profile as shown in the example of the boron profile in Figure 3. As a result, a steep distribution cannot be achieved, and this has been an obstacle to narrowing the base width.

[Problem to be solved by the invention]

Conventionally, in the manufacture of high-speed bipolar transistors, as described above, due to channeling, the impurity distribution in the base diffusion layer deviates from the Gaussian distribution, making it impossible to realize a steep impurity distribution, which has been an obstacle to narrowing the base width.
The present invention was made to solve the above problems.
It is an object of the present invention to provide a manufacturing method that can realize a narrower base width.

[Means to solve the problem]

In the manufacturing method of the present invention, when forming a buried layer, a portion of the buried layer directly below the intrinsic base is doped with an impurity having a higher diffusion coefficient than other portions, and it is possible to prevent the impurity having a high diffusion coefficient from rising during subsequent heat treatment. By utilizing this, a narrow base diffusion layer with a steep impurity distribution can be realized.

〔Example〕

FIG. 1 shows the structure of an example of a high-speed bipolar transistor produced by the manufacturing method of the present invention.

In the figure, 1, 3, 4, 5, 6, 7 indicate the same or corresponding parts as the same reference numerals in FIG. 2, and 2a.

When doping the P substrate 1 with impurities for the N buried layer, the part directly below the intrinsic base is doped with an impurity that has a higher diffusion coefficient than other parts, and the epitaxial layer 4 is grown on top of it to form an element isolation layer. Separation diffusion layer 3 for
form.

The impurity with a large diffusion coefficient doped directly under the intrinsic base of the N buried layer 2 rises up as shown in the figure by heat treatment, and prevents the diffusion of boron ions in the intrinsic base portion of the base diffusion layer 5 due to boron ion implantation. It works to suppress impurity distribution, steepen the impurity distribution, and help realize a narrow base width.

The following formation of the emitter diffusion layer 6, collector diffusion layer 7, electrode wiring, etc. is performed by conventional methods.

C. Effects of the Invention] As explained above, according to the present invention, it is possible to realize a narrower base width, and there is an effect that the speed of the bipolar transistor can be increased.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of an example of a high-speed bipolar transistor manufactured by the manufacturing method of the present invention, FIG. 2 is a cross-sectional view showing the structure of an example of a conventional bipolar transistor, and FIG. 3 is an explanation showing an example of a boron profile. It is a diagram. 1...P substrate, 2a...N buried layer, 3
... Separation diffusion layer, 4... Epitaxial layer, 5...
- Base diffusion layer, 6... Emitter diffusion layer, 7... Collector diffusion layer Note that the same reference numerals in the drawings indicate the same or corresponding i. Patent applicant: New Japan Radio Co., Ltd.-xJ(u) Surface depth Figure 3

Claims (1)

[Claims] When forming the buried layer, the portion directly below the intrinsic base of the buried layer is doped with an impurity having a higher diffusion coefficient than other portions, and the impurity distribution is adjusted by utilizing the rise of the impurity having a large diffusion coefficient in the buried layer. A method for manufacturing a high-speed bipolar transistor characterized by forming a steep and narrow base diffusion layer.