JPH01260856A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of the threshold voltage value of a gate, by adding acceptor impurities such as boron in gate polysilicon, doping phosphorus at the same time, and using movable ions such as alkali metal ions in a gate insulating film as a getter. CONSTITUTION:A polysilicon film 13 which is used as a gate electrode is deposited by a vapor growth method. Boron 13 having the high concentration of 1E15/cm<2>-1E16/cm<2> is doped in the polysilicon film by an ion implanting method. Phosphorus 13'' having the adequate concentration of 5E13/cm<2>-5E14/ cm<2> is doped by an ion implantation method. The boron and the phosphorus are activated 13''' by heat treatment. Since the concentration of the boron is lower than that of the phosphorus, a P<+> polysilicon film whose sheet resistance is sufficiently low is formed. A phosphorus doped P<+> polysilicon film 13''' which has a getter effect for movable ions such as alkali metal ions in a gate insulating film 12 is formed with the phosphorus that is incorporated in the film at the adequate concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a miniaturized semiconductor device.

[Summary of the invention]

This invention is a semiconductor device having a P polysilicon gate, in which phosphorus is doped in addition to acceptor impurities such as boron into a polysilicon film that is a gate electrode material.

[Conventional technology]

Conventionally, when forming a P polysilicon gate, a method has been used in which an acceptor impurity such as boron is doped into a polysilicon film that is a gate electrode material.

[Problem to be solved by the invention]

However, in the conventional method of forming P° borine recongate,
There is a problem in that the gate threshold voltage fluctuates because there is no or little effect of gettering mobile ions such as alkali metal ions in the gate insulating film.

[Means to solve the problem]

In order to solve the above problems, the present invention adds a highly doped acceptor impurity such as boron to the polysilicon film that is the gate electrode material, and has a concentration that does not significantly affect the sheet resistance of the gate electrode. Rin was also doped.

[Effect]

Since mobile ions such as alkali metal ions in the gate insulating film are gettered by the phosphorus doped into the gate 1i, it is possible to suppress fluctuations in the gate threshold voltage. Since phosphorus is lightly doped compared to heavily doped acceptor impurities such as boron, its effect on the polarity and sheet resistance of the P9 polysilicon gate electrode can be ignored.

〔Example〕

FIG. 1 fat to tel are cross-sectional views schematically showing the process order of the method for forming a phosphorus-doped l-P" polysilicon gate of the present invention. In FIG. In FIG. 1(b), 13 represents a state in which a polysilicon film used as a gate electrode is deposited by vapor phase growth. In FIG. This shows that the film is doped with boron at a high concentration of IE15/aII to IE16/-. Figure 1 1d
In l, 13' is 5E13/- by ion implantation method.
~5E14/(ffl) This shows that phosphorus is doped at an appropriate concentration. In Figure 1 1dl, 13'' shows that boron and phosphorus have been activated by heat treatment. Compared to boron, verine is Since the concentration is low, a P polysilicon film with sufficiently low sheet resistance is formed.

Further, due to the phosphorus contained in the film at an appropriate concentration, a phosphorus-doped P° polysilicon film is formed that has a getter effect for mobile ions such as alkali metal ions in the gate insulating film. Thereafter, the polysilicon film was patterned using normal photolithography to form a gate electrode.

〔Effect of the invention〕

As described above in detail, the method for forming a phosphorus-doped P9 polysilicon gate according to the present invention has a gator effect on mobile ions such as alkali metal ions in the gate insulating film in a miniaturized integrated circuit, and It has an excellent feature that enables the formation of a P polysilicon gate electrode with a sufficiently low sheet resistance.

[Brief explanation of the drawing]

FIG. 1 (al to te) is a cross-sectional view schematically showing the process order of the method for forming a phosphorus-doped l-P'' polysilicon gate of the present invention. 11...Semiconductor silicon substrate 12...Gate insulating film 13・ ・ ・Polysilicon film 13'...Boron-doped polysilicon film I3"...Boron & phosphorus-doped polysilicon film 13#'...Phosphorus-doped P0 polysilicon film and above Applicant: Seiko Electronics Co., Ltd. - 1111 1111---------------111111---12"F'"-To body and 9
F'#R further (a)
HA11 Cow nose body 1J consignment KARA Honko January production method [F1 page Fr side view Figure 1

Claims (1)

[Claims] A method for manufacturing a semiconductor device having a P^+ polysilicon gate, the method comprising doping phosphorus in addition to an acceptor impurity such as boron into the gate polysilicon.