JPS61191026A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent precipitation of Si to Al wiring by a method wherein concerning an electrode wiring whose laminated structure is constituted of polysilicon, titanium and Al polysilicon surface layer is oxidated by aqua regina boil. CONSTITUTION:An electrode window is made to an SiO2 film 22 formed on a surface of a semiconductor substrate 21, and an electrode window, whose laminated structure is constituted of polysilicon films 27, 28, a titanium film 29 and an Al film 30, is formed. At that time, the surface of the polysilicon films 27, 28 are oxidated by aqua regina boil, after the polysilicon films 27, 28. Thereby, oxide films are formed on a surface of each grain made of polysilicon. Precipitation of polysilicon is prevented since the oxide film restricts movement of polysilicon grains.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and more specifically, a method for manufacturing a semiconductor device, in which a polycrystalline silicon (polysilicon) surface layer is made of aluminum (Al).
This invention relates to a method for preventing silicon precipitation on Al wiring by oxidizing it in an aqua regia boil before growth.

[Conventional technology]

There is a technology in which an electrode window is opened in an insulating film formed on the surface of a semiconductor substrate, a polysilicon film is grown in the electrode window, a barrier metal film is formed on top of the polysilicon film, and an AIt wiring is formed on this barrier metal. being researched.・Referring to the cross-sectional view of FIG. 2, a silicon dioxide (5iO2) film 22 is formed on the surface of a semiconductor substrate 21, and a base region 23, an emitter region 24, a collector region 25, and a Schottky barrier diode (SBD) are formed on the substrate 21. ) 26 are formed. In the figure, 27 is a doped polysilicon film, 28 is an undoped polysilicon film, 29 is a titanium (Ti) film, and 30 is a pure Alt.
doped polysilicon film 27
is provided in relation to emitter diffusion.

[Problem that the invention seeks to solve]

For the device shown in Figure 2, for example, phosphorus and
A film of silicate glass (PSG) is formed, and heat of about 450° C. is applied at that time. As a result, polysilicon and Al react, and silicon is precipitated in a lump shape in the Aj2 wiring. The polysilicon thus deposited is called a polysilicon flower, and it has been confirmed that undoped polysilicon reacts more easily with i than doped polysilicon.

Referring to the plan view of FIG. 3 (Al), when a black polysilicon flower 31a appears on the surface of the Al wiring 31, the resistance of the AJ wiring 31 increases because it is silicon. If it is deposited completely across the area, no current will be applied.

Furthermore, even if no polysilicon flower is observed when observing the surface, if a cross section is examined, a polysilicon flower 32c that does not reach the surface may be deposited as shown in FIG. 3 (cl).

On the other hand, the thickness of the titanium film 29 is a factor that determines the forward voltage vF value of the SBD, and must be set so as to ensure its function as a barrier metal that suppresses the reaction between 1 and silicon. There is also the problem that the degree of freedom in setting the thickness of the titanium film is reduced due to the precipitation of titanium.

[Means for Solving the Problems] The present invention provides a method for forming an electrode wiring that eliminates the above problems, and the means includes a laminated wiring of a polycrystalline silicon film and an aluminum film taken out from the surface of a semiconductor substrate. The method for manufacturing a semiconductor device is characterized in that after a polycrystalline silicon film is formed, its surface layer is oxidized by aqua regia boiling.

[Effect]

Due to the aqua regia boiling of the polysilicon described above, an oxide film (SiO+ film) is formed not only on the surface layer of the polysilicon but also on the surface of each grain of the polysilicon inside, and this oxide film controls the movement of the polysilicon grains. Because it restricts
Even if a temperature of 450° C. is applied to create an environment where polysilicon grains can easily move, the movement of polysilicon grains is restricted and precipitation of polysilicon flowers is prevented.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

In the method of the present invention, after forming a polysilicon film on the electrode part, aqua regia boiled (HCe: )lNO3-
3:1. The polysilicon surface is oxidized at a liquid temperature of 80±10°C. In this case, as shown in the schematic cross-sectional view of Fig. 1(a), one grain of polysilicon is
The state in which only polysilicon grains 1 are arranged (as shown on the left in the same figure) changes to the state in which the 5i02 film 12 is formed between the grains as shown on the right in the same figure, and the movement of the polysilicon grains 11 changes. is suppressed. In the figure, the arrow indicates that aqua regia has been boiled.

In manufacturing the device shown in FIG. 2, after aqua regia boiling, only the SiO2 film on the surface layer of polysilicon is removed, and then a titanium film is formed. As a result, the polysilicon film and the titanium film are in close contact with each other with good adhesion, while the inside of the polysilicon film is in the state shown in FIG. Precipitation of flowers is prevented.

The inventor of the present application conducted an experiment to determine the relationship between the presence or absence of aqua regia boil and the outside of the SBD, and the results are shown in the following Table 1 on the next page.

In order to satisfy the SBD vF in the device shown in Figure 2, the titanium film thickness should be 70 mm, the alloy conditions should be set at 450°C for 20 minutes,
Argon (Ar) pressure to 2011 Torr or 25 m
Torr is optimal, but under all conditions, polysilicon flowers appeared throughout without aqua regia boiling. On the other hand,
No polysilicon flowers were observed with aqua regia boiling.

Table ■ Titanium Ar pressure Alloy SVD Vp (mV) Polysilicon Aqua regia film thickness (A) (m Torr) ('C/
minutes (at 10μA) Konhana Boil 707400/
30300-3070 707450/20304-3
120 Yes 7015400/30296-3090 No 70
15450/20297~321△No 7020400/
30295~3190 No 7020450/20311~
340×No 7025400/30310~3230No 7
025450/20303~333×No807400/
30290-3200 No note: ○ means no polysilicon flower,
△ indicates that the polysilicon flower is present around the polysilicon flower, and × indicates that the polysilicon flower is present throughout the flower.

The present inventor conducted an experiment to determine whether the presence or absence of aqua regia boil had any effect on the V7- of the SBD, and confirmed that even if aqua regia boiled, it had almost no effect on the Vf of the SBD. . The results of the experiment are shown in graph 1 in Figure 1(b), in which the Δ mark,
In the case of 0μ, the 0 mark and the 0 mark indicate the observation results for other elements when the current was 1 mA and 10 μA, respectively.

〔Effect of the invention〕

As explained above, according to the present invention, in an electrode wiring having a laminated structure of polysilicon, titanium, and ^l, A
Silicon no longer precipitates in the l wiring, improving the reliability of the U' wiring, and the barrier metal is formed without considering silicon precipitation (if the titanium film is too thin, the characteristics of titanium as a barrier metal will deteriorate, (The reaction between Al and Si cannot be prevented), but it can be determined by the vF value and transistor characteristics of SBDs fabricated on the same semiconductor substrate (increasing the degree of freedom).

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing the arrangement of polysilicon grains before and after aqua regia boiling for explaining the present invention;
The same figure (bl is a graph showing the experimental value of vF of SBD, Figure 2 is a cross-sectional view of the semiconductor device to show the electrode wiring, Figure 3 is a graph showing the experimental value of vF of SBD,
Figures (al and (bl) are a plan view and a cross-sectional view showing silicon precipitation in Al wiring. In the figure, 11 is a polysilicon grain, 12 is an oxide film (5
iOz film), respectively. figure

Claims (1)

[Claims] A method for manufacturing a semiconductor device, the method of forming a layered wiring of a polycrystalline silicon film and an aluminum film taken out from the surface of a semiconductor substrate, the method comprising: forming a polycrystalline silicon film and then oxidizing its surface layer by aqua regia boiling.