JPH02106942A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and in particular, after bonding an electrode pad of a semiconductor element and an external lead wire with a metal conducting wire, a protective layer is applied to the surface of the semiconductor element. The present invention relates to a method for manufacturing a semiconductor device in which a film is formed.

[Conventional technology]

In general, semiconductor devices are subject to external thermal, chemical, and physical influences, causing reliability problems such as fluctuations in the electrical characteristics of semiconductor elements. In particular, corrosion of electrode pads at the connection portions between electrode pads of semiconductor elements (chips) and metal conductive wires (bonding wires) in resin-sealed semiconductor devices causes regular problems. Therefore, after bonding the electrode pad of the semiconductor element and the external lead wire (lead) with a metal conductor wire, an insulating film is formed on the surface of the semiconductor element at a low temperature of 400 degrees Celsius or less to cover and protect the surface of the semiconductor element. The inventor filed a separate patent application (for example, Japanese Patent Application No. 62-167264.
-242113).

[Problem to be solved by the invention]

The coating protection technique using an insulating film described above can only be effective in corroding when the surface of the semiconductor element is clean. However, in reality, when manufacturing a semiconductor device, various impurities may adhere to the surface of the semiconductor element. For example, in the diffusion process for manufacturing semiconductor devices, impurities (especially fluorine) may remain on the electrode Au pads formed on the semiconductor devices during dry etching, etc. (for example, Nikkei Micro Devices 1986, Vol. 1). Monthly issue, page 96). Furthermore, it has been reported that there is contamination by various impurities in the assembly process for packaging semiconductor devices (Monthly Sewicondu
ctor World September 1987 263-69
page). Therefore, the conventional insulating film coating protection technology has the drawback that stable corrosion protection cannot be reproduced.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention provides a method for manufacturing a semiconductor device in which a surface of a semiconductor element in which an electrode pad of a semiconductor element and an external lead wire are connected by a metal conducting wire is coated and protected with an insulating film. The method includes a step of cleaning the surface of the semiconductor element.

Specifically, this cleaning step includes a method of sputter etching the surface of the semiconductor element using an inert gas discharge, or a method of sputter etching the surface of the semiconductor element using an inert gas discharge. There are methods such as exposing the surface of the semiconductor element in a gas atmosphere.

According to the present invention, a semiconductor device with high moisture resistance can be manufactured with good reproducibility by forming an insulating film after forming a clean semiconductor element surface.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of an argon sputtering apparatus used in a first embodiment of the present invention. 101 is a reactor, 1
02 is a sample, and 103 is a lower electrode. Lower electrode 103
is connected to a high frequency power source 105 via a blocking capacitor 104. 106 is the upper electrode, 107
108 is an argon gas introduction pipe, and 108 is a vacuum exhaust pipe.

Lower electrode 10 in the reactor 101 of the sputtering device
By placing the sample 102 on the sample 3 and discharging argon gas, the surface of the sample 102 is sputtered with argon ions. For example, set the Ar gas pressure to 8mTo
When a sample on which an aluminum thin film was grown is placed in a discharge argon atmosphere formed by applying a high frequency of 300 W while keeping the temperature at
It is etched at a speed of n. As a result, it is possible to obtain a clean aluminum surface in 1-2 minutes.

FIGS. 2(a) to 2(d) show the main steps of the first embodiment of the present invention. FIG. 2(a) is a cross-sectional view of the sample 102 to be placed in the reactor 101 of FIG.
A semiconductor element (chip) 203 is mounted on 2 and bonded with a gold wire 205. 2
Reference numerals 01 and 202 are lead frames, 201 is a portion serving as an external lead line (lead), and 202 is a portion for mounting a semiconductor element. 203 is a semiconductor element (chip), 204 is an aluminum electrode pad formed on the semiconductor element 203, and 205 is a protective film. Also,
206 is a gold wire (ponding wire) connecting the electrode 204 and the external lead wire 201.

FIG. 2(b) shows the reactor 101 in FIG. 1 and FIG. 2(a).
This figure shows the sample shown in Fig. 3 being placed and the surface being sputter-etched with argon. In the figure, 207 indicates discharge argon. For example, by exposing argon at a pressure of 0.8 mTorr to discharge argon formed by applying a high frequency voltage of 300 W for 1 minute, the electrode pad 204. Protective film 205. Also, the surfaces of the gold wire 206 and the like can be cleaned.

FIG. 2(c) shows an insulating film 208 formed on a semiconductor element 203 by chemical vapor deposition (CVD) at a growth temperature of 200 to 250°C.
This shows how it is coated. As the insulating film 208, a silicon oxide film (Sin2), a silicon nitride film (SiN), and a silicon oxynitride film (SiON) are suitable.

Finally, FIG. 2(d) shows a semiconductor device completed as a product by resin sealing, cutting and shaping the lead frame 201. Here, 209 is an encapsulating resin.

Generally, the moisture resistance failure mode of a resin-sealed semiconductor device is caused by the metal electrode (pad) 20 formed on the semiconductor element 203.
4, and this corrosion is significantly accelerated by the presence of ionic impurities and moisture.

As shown in FIGS. 2(a) to 2(d) above, according to the method of manufacturing a semiconductor device of the present invention, the surface of the semiconductor element 203 and the surface of the electrode pad 204 are sputter-etched with discharge argon to form a clean surface. and then the insulating film 20
8 is covered and protected.

Since the surface of the electrode pad 204 is covered with an insulating film 208, it does not come into direct contact with the encapsulating resin 207 and is always clean. As a result, it becomes possible to manufacture a semiconductor device with dramatically improved moisture resistance.

As is clear from the above description, the process of cleaning the surface of the semiconductor element 203 shown in FIG. 2(b) is important. The reason is that if ionic impurities adhere to the surface of the semiconductor element 203, even if the insulating film 208 covers and protects the surface of the semiconductor element 203 and the electrode pad 204 to prevent impurities from entering from the outside. This is because corrosion of the electrode pad 204 progresses due to ionic impurities adhering to the surface of the semiconductor element 203.

Usually, the surface of the electrode 204 is contaminated with impurities from the etching gas due to dry etching of the metal wiring including the electrode pad 204 and the protective film on the electrode pad. In many cases, fluorine carbon and the like are detected on the surface of the electrode pad 204 by Auger electron spectroscopy, but by using the argon sputter etching process of this example, it was confirmed that these were completely detected.

FIG. 3 shows a schematic diagram of an ozone cleaning device used in a second embodiment of the present invention. 301 is the reactor, 302 is sample 10
303 is a heater for heating the sample 102, 304 is an ozone introduction pipe, and 305 is an exhaust pipe. Further, 306 is an oxygen gas supply pipe, and 307 is an ozone generator. Oxygen (02) introduced from the oxygen gas supply pipe 306 is converted into ozone (Ol), and the ozone introduction pipe 3
Sent to 04. 308 is a low pressure mercury lamp that irradiates ultraviolet light to promote the reaction.

A sample 102 heated to 200° C. or lower by a heater 303 is placed in the reactor 301 of such an ozone cleaning device, and ozone (Ol) with a concentration of 200 g/Nm is introduced to remove impurities on the sample surface. Can be removed by reaction. At this time, by irradiating ultraviolet light, the reaction with ozone (O5) on the surface of the sample 102 is promoted and the cleaning effect is improved.

In the method for manufacturing a semiconductor device shown in FIG. 2, the cleaning step shown in FIG. 2(b) can be performed by cleaning using the above-mentioned ozone cleaning device, thereby making it possible to manufacture a semiconductor device with improved moisture resistance.

FIG. 4 shows the results of a moisture resistance experiment conducted on a semiconductor device manufactured according to the present invention. The samples include (1) a conventional semiconductor device sealed with resin without covering with an insulating film after bonding, and (2) a 5in2 semiconductor device without cleaning after bonding.
(3) A semiconductor device according to a first embodiment of the present invention in which a semiconductor device is coated with a film and sealed with a resin; (3) a semiconductor device is cleaned by argon sputter etching after bonding, and then covered with an insulating film (SiO2) and sealed with a resin; (4) Cleaning with ozone after bonding, then insulating film (S
100 pieces of each of four types of semiconductor devices according to the second embodiment of the present invention coated with iO□ and sealed with resin were examined.

For the moisture resistance test, after immersing the sample in solder at 240°C,
An RCT (Pressure Kutzker Test) was conducted by placing the sample in a steam oven at 150°C and 2 atm pressure to determine the number of defects.

In contrast to conventional semiconductor devices that do not coat with an insulating film (SiO2) after bonding, the semiconductor device of the present invention, in which the surface of the semiconductor element is cleaned and coated with an insulating film (SiO2) after bonding, has excellent moisture resistance. It is shown that there is.

The above moisture resistance test was repeated using semiconductor devices manufactured at different times to confirm reproducibility.

Insulating film (SiO2) after bonding without cleaning process
There is no clear reproducibility in the moisture resistance test results of the semiconductor device in which the semiconductor device was formed (the shaded area in FIG. 4). In contrast, the results of the semiconductor device according to the present invention have good reproducibility.

This fact indicates that there are variations in the amount of impurities that adhere to the surface of the semiconductor element during the manufacturing process (diffusion process and assembly process) of the semiconductor device. This shows that these impurities can be removed by the cleaning process according to the present invention.

〔Effect of the invention〕

As explained above, the present invention provides a method for manufacturing a semiconductor device in which an electrode pad of a semiconductor element and an external lead wire are connected by a metal conductive wire, and at least the electrode pad portion is covered with an insulating film. By providing a step of cleaning the surface of the semiconductor element beforehand, a semiconductor device with improved moisture resistance can be realized with good reproducibility.

Further, in the above embodiments, the cleaning process according to the present invention was performed after the bonding process, but the invention is not limited to this. For example, when the assembly process is performed on a clean assembly line, the cleaning process according to the present invention can be performed at any location in the assembly process before the coating process with the insulating film.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an argon sputtering apparatus used in the first embodiment of the present invention, and FIGS. 2(a) to (d)
) is a cross-sectional view for explaining the main steps of the first and second embodiments of the present invention, FIG. 3 is a cross-sectional view of the ozone cleaning device used in the second embodiment, and FIG. 4 is a cross-sectional view of the ozone cleaning device used in the second embodiment. FIG. 3 is a diagram showing the results of a reliability test to show the effect of the method. 101... Reactor, 102... Sample,
103...Lower electrode, 104...Blocking capacitor 105...High frequency power supply, 10
6... Upper electrode, 107... Argon gas introduction pipe, 108... Vacuum exhaust pipe, 201...
...Lead frame (lead part), 202...
...Lead frame (guibat part), 203...
... Semiconductor element (chip), 204 ... Electrode pad, 205 ... Protective film, 206 ...
・Gold wire, 207... Argon discharge or ozone,
208...Insulating film.

Claims (3)

[Claims] (1) In a method for manufacturing a semiconductor device in which an electrode pad of a semiconductor element and an external lead wire are connected by a metal conductive wire, and at least the electrode pad is covered with an insulating film, at least the electrode pad is A method for manufacturing a semiconductor device, comprising a step of cleaning the surface. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the step of cleaning the surface of the electrode pad is a sputter etching step by exposing the surface of the electrode pad to an inert gas discharge atmosphere. (3) Claim 1, wherein the step of cleaning the surface of the electrode pad is a step of leaving the semiconductor element in an ozone gas atmosphere.
Method for manufacturing the described semiconductor device