JPS6250974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a planar semiconductor device, and more specifically, to a semiconductor device having a phosphor glass film formed in a silicon oxide film using phosphorus as a diffused impurity source and a plating electrode. Relating to a manufacturing method.

In order to increase the stability of planar semiconductor devices during operation,
It is a widely known technique to leave a phosphorous glass film formed from phosphorus used as an N ⁺ type impurity diffusion source and use it as a final surface stabilizing protective film of a semiconductor device. For example, when obtaining an NPN type silicon transistor, it is common to use phosphorus P as an emitter-forming impurity, but as is well known, when phosphorus is diffused into a substrate having a silicon oxide film on its surface, the phosphorus is It also combines with the silicon oxide film to form a phosphorous glass film on the surface of the silicon oxide film. Since this phosphorus glass film has an extremely effective effect on stabilizing the surface of the transistor, it is desirable to leave it as it is.

However, especially in the process of manufacturing planar plating electrode transistors, etc., when an electroless nickel plating method is used as an electrode forming method, in order to facilitate the formation of nickel electrodes, it is necessary to use a plating pretreatment solution (for example, gold tetrachloride). After dipping the wafer in an electroless nickel plating solution (for example, a mixture of sodium hypophosphite, ammonium chloride, sodium citrate, nickel chloride, and water), the wafer is heated to 80 to 98°C. While doing so, attach the electrodes. This plating pretreatment liquid or electroless nickel plating liquid etches the phosphorous glass film more easily than the silicon oxide film, so the phosphorous glass film formed during the emitter diffusion is removed, and the surface of the semiconductor device is no longer stable. function had been lost. Therefore, as a method for eliminating the above-mentioned defects, a method has been proposed in which the photoresist film used in forming the electrode hole remains and the phosphor glass film is protected during the plating pretreatment step or the plating step.

However, in the method of using the photoresist film to protect the phosphor glass film, the protective effect against the nickel plating pretreatment liquid is great, but in the nickel plating process in which the entire wafer is immersed in the nickel plating liquid, the nickel plating liquid has alkalinity. In addition, the adhesion of the photoresist film to the silicon substrate body deteriorates when exposed to alkaline solutions, and the adhesion further deteriorates because the nickel plating solution is heated to 80 to 98°C. The photoresist film tends to peel off from the silicon substrate body, making it impossible to obtain a stable etching protection effect of the phosphorous glass film. Furthermore, the photoresist film needs to be removed after the nickel plating process, but chemical reactions (e.g. oxidation, corrosion) are likely to occur on the nickel plated surface during the photoresist film removal process, making it difficult to obtain a good nickel plated electrode. It has the following drawbacks. Furthermore, in this manufacturing method, the phosphor glass film is present in the top layer of the semiconductor device, so when operated in a humid atmosphere, the phosphor glass film has the property of easily adsorbing moisture, which affects the characteristics of this semiconductor device. is prone to deterioration.

The present invention has been developed in view of the above-mentioned points, and can be particularly effectively used in the manufacture of planar semiconductor devices having plated electrodes. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can be stabilized and further improve electrical characteristics.

That is, the present invention specifically uses phosphorus as a diffused impurity source to form an N-type region in a semiconductor substrate, and at the same time forms a phosphorous glass film on this semiconductor substrate, and at least one A process of forming a layer of silicon oxide film and heat-treating the semiconductor substrate containing this silicon oxide film in an atmosphere at a temperature of 800 degrees Celsius or higher, or immersing the semiconductor substrate in a plating pretreatment solution containing hydrofluoric acid, or removing the semiconductor substrate for 80 degrees ℃
The etching resistance of the silicon oxide film in the plating process of immersing it in an electroless plating solution heated to a temperature above can be strengthened, and it can be used as an etching protection film for the phosphorous glass film, thereby stabilizing the surface of the phosphorus glass film. without reducing its function as a chemical film.
It is an object of the present invention to provide a simple method for manufacturing a semiconductor device that can improve the adsorption resistance to moisture and stabilize the characteristics of the semiconductor device by leaving the silicon oxide film on the phosphorous glass film.

The present invention will be specifically described below with reference to embodiments shown in the drawings. Figures 1 to 5 show planar NPNs with plated electrodes prepared using the method of the present invention.
FIG. 3 is a cross-sectional view of an element in each manufacturing process when manufacturing a transistor. In FIG. 1, reference numeral 1 denotes a semiconductor substrate, for example, an N-type silicon substrate, which becomes a collector region when a transistor element is manufactured. Reference numeral 2 denotes a silicon oxide film forming an oxide film, which is formed on the surface of the silicon substrate 1 by subjecting it to thermal oxidation treatment. An NPN transistor is formed on the semiconductor substrate formed in this manner. First, as shown in FIG. Region 4 is formed. By using phosphorus as a diffused impurity source for forming the emitter region 4, the silicon oxide film 2 and phosphorus are combined to form a phosphorous glass film 5 (for example, P ₂ O ₅ --SiO ₂ ). This phosphor glass film 5
is used as a surface stabilizing film for a transistor. Next, as shown in FIG. 3, a silicon oxide film 6 is deposited on the phosphorus glass film 5 by chemical vapor deposition.
(CVDSiO ₂ film) is formed. This silicon oxide film 6 forms a protective film for protecting the phosphorus glass film 5 during the nickel electrode process described later, and also prevents the phosphorus glass film from adsorbing moisture, etc. in a humid atmosphere. Subsequently, the silicon substrate 1 including the silicon oxide film 6 is heat-treated in an atmosphere at a temperature of 800° C. or higher. This heat treatment is for the purpose of densifying the silicon oxide film 6 well and improving the etching resistance of the silicon oxide film 6 against a plating pretreatment solution and a nickel plating solution during the subsequent formation of a nickel electrode. Subsequently, as shown in FIG. 4, the silicon oxide film 6, phosphorous glass film 5, and silicon oxide film 2 are etched by photoetching to form an emitter region 4, a base region 3,
Electrode holes 7, 8, and 9 are formed on the collector region 1. Thereafter, the silicon substrate 1 is immersed in a plating pretreatment solution (for example, a mixture of gold tetrachloride, hydrofluoric acid, and water) to facilitate the attachment of nickel electrodes, and then, for example, by an electroless plating method, as shown in FIG. Next, nickel electrodes 10, 11, and 12 are formed as shown in FIG.

This results in a planar type with nickel electrodes.
The NPN transistor was completed,
Protection of the phosphorous glass film of the silicon oxide film 6 against the plating pretreatment liquid and plating liquid will be described in detail. The above-mentioned Nickelmetsuki pre-treatment liquid is more effective than the pre-treatment liquid for forming electrodes (e.g. a mixture of hydrofluoric acid and water at a ratio of 1:50) that is generally used when aluminum is used as an electrode material. The silicon oxide film 6 is etched several hundred times faster. Therefore, in order to use the silicon oxide film 6 as a protective film for the phosphorous glass film 5, it is necessary to devise ways to significantly improve the etching resistance. A measure to achieve this objective is the heat treatment step following the formation of the silicon oxide film 6, as described above. FIG. 6 shows the relationship between the etching rate of the plating pretreatment liquid and the heat treatment temperature during nickel plating. (characteristics) improve,
It can be seen that at temperatures above about 800°C, the etching rate is saturated to a nearly constant level. In the plating pretreatment solution (mixture of gold tetrachloride, hydrofluoric acid, and water) shown in this example, the etching rate of the silicon oxide film 6 is about 1/5 of that without heat treatment, as shown in FIG. has declined to

According to experiments conducted by the present inventors, the degree of reduction in the etching rate varies somewhat by changing the plating pretreatment liquid, but the heat treatment temperature at which the minimum rate is reached is approximately 800°C.

Further, FIG. 7 shows a case in which a phosphorous glass film 5, a silicon oxide film simply formed by chemical vapor deposition, and a silicon oxide film 6 heat-treated at 800° C. or higher are immersed in the plating pretreatment solution. This shows the relationship between the etching thickness of the silicon oxide film and the etching time, and the characteristics A, A, and Etching are shown in order from the former.
They are shown as B and C. In this example, it can be seen that characteristic A has a gradient of about 40 to 100 times that of characteristic C, and characteristic B has a gradient of about 10 times that of characteristic C. Furthermore, as is clear from this characteristic diagram, simply forming the silicon oxide film 6 on the phosphorous glass film 5 has a protective effect;
It can be seen that an even better effect (approximately 10 times greater in this example) can be obtained by the heat treatment described above.

In addition, in FIG. 8, a phosphorous glass film is added to an electroless plating solution (in this example, a mixed solution consisting of sodium hypophosphite, ammonium chloride, sodium citrate, nickel chloride, and water), similar to that in FIG. 7. 5. This shows the relationship between the etching thickness of the silicon oxide film and the etching time when a silicon oxide film and a silicon oxide film 6 heat-treated at 800°C or higher are respectively immersed. They are shown as E and F. This case also shows characteristics almost similar to those shown in FIG. 7, and it can be seen that the etching resistance is significantly improved by heat-treating the silicon oxide film at 800° C. or higher.

In the embodiments described above, the present invention is applied to a method for manufacturing a planar type NPN transistor having a nickel electrode, but it can also be applied to a planar type semiconductor device having a plated electrode such as other types of transistors or diodes. It can be widely used for The present invention can also be applied to other planar type plating electrode semiconductor devices in which the plating pretreatment liquid and the plating liquid can easily etch phosphorous glass films and silicon oxide films.

As described above, according to the manufacturing method of the present invention, a silicon oxide film is formed on the phosphorous glass film on the semiconductor substrate formed during the N-type impurity diffusion treatment, and the semiconductor substrate is heat-treated in an atmosphere at a temperature of 800°C or higher. As a result, this silicon oxide film becomes well densified, and the function of the phosphor glass film as a surface stabilizing film is not deteriorated even during the etching process performed when forming the plating electrode. Since it is present in the uppermost layer of the semiconductor, adsorption of moisture and the like does not occur, and therefore it has the effect of stabilizing the characteristics of the semiconductor element.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views of a semiconductor device in each manufacturing process showing one embodiment of the method of the present invention;
The figure is a characteristic diagram showing the relationship between heat treatment temperature of silicon oxide film and etching rate for plating pretreatment liquid, Figure 7 is a characteristic diagram showing the relationship between etching time and etching film thickness for plating pretreatment liquid, and Figure 8 is a characteristic diagram showing the relationship between etching film thickness and etching time for plating pretreatment liquid. 1 is a characteristic diagram showing the relationship between etching time and etching film thickness for a plating solution. 1... Silicon substrate forming a semiconductor substrate, 2, 6...
Silicon oxide film, 4... Emitter region serving as an N-type region, 5... Phosphorus glass film, 7, 8, 9... Emitter electrode hole and base electrode hole forming electrode extraction holes, respectively.
Collector electrode holes, 10, 11, 12...Nickel electrodes forming plated electrodes.

Claims (1)

[Claims] 1. A method for manufacturing a planar semiconductor device having a plating electrode, the method comprising the steps of forming an N-type region in a semiconductor substrate using phosphorus as a diffusion impurity source and simultaneously forming a phosphorous glass film on the semiconductor substrate. , forming at least one layer of silicon oxide film on the phosphorous glass film; heat-treating the semiconductor substrate including the silicon oxide film in an atmosphere at a temperature of 800° C. or higher; and drilling at least the silicon oxide film. forming an electrode extraction hole;
a step of immersing the semiconductor substrate in a plating pretreatment solution containing hydrofluoric acid; and immersing the semiconductor substrate in an electroless plating solution heated to a temperature of 80° C. or higher to plate the electrode in the electrode extraction hole on the semiconductor substrate. 1. A method of manufacturing a semiconductor device, the method comprising: forming a semiconductor device.