JPS6054776B2 - Manufacturing method for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In recent years, a method of sintering glass onto a semiconductor substrate to form a surface protective film has become established as a stabilizing technique.

However, the glass used for such purposes has poor resistance to acids and alkalis, that is, chemical resistance, and has the disadvantage that it is corroded when it comes into contact with chemicals used in the manufacture of semiconductor devices, and its effectiveness as a surface protective film is lost. . Therefore, in manufacturing semiconductor devices using glass as a surface protective film,
The manufacturing process is subject to various limitations, particularly the contact formation process. If a contact is formed before the glass sintering process, the contact metal and the semiconductor substrate will undergo an extreme alloy reaction due to the influence of the temperature and atmosphere during glass sintering, causing damage to the pn junction provided in the semiconductor substrate. or the contact metal may be altered to the point that it loses its structure suitable for its purpose.

Therefore, in semiconductor devices in which glass is sintered, contacts must be formed after the glass is sintered.
When forming contacts after glass or sintering, if the semiconductor substrate is subjected to chemical treatment, it is necessary to cover the sintered glass with a chemical-resistant resist. A process without a chemically resistant resist cannot be adopted. Forming a contact requires an operation to shape the contact surface into a predetermined shape, but the etching method traditionally used in the semiconductor industry suffers from the absence of a chemical-resistant resist, lack of precision, and the method itself. Due to some incompatibilities, it has been difficult to apply this method to manufacturing methods for semiconductor devices that involve sintering glass.
For this reason, a method that has been conventionally used is a method called a reverse resist method. In the reverse resist method, a photoresist having an opening at a contact portion is formed on a semiconductor substrate by a known photoetching technique, a contact metal is vacuum-deposited on the opening of the photoresist and the entire surface of the photoresist, and then the photoresist is removed. This is a selective metal deposition method in which the contact metal is removed along with the contact metal on it, leaving the metal only in the areas where the contact will be formed. This shows a method of forming a contact.In step A, 1 is a silicon substrate and SiO22 is deposited on one main surface.
There is. There is mode 3 on one main surface of the silicon substrate,
In mode 3, the glass 4 is sintered. To sinter the glass into a mode, glass powder is first filled into the remote, for example by electrophoresis. As the glass filling method, centrifugal sedimentation method and blade method can also be applied. Although there are some differences with either filling method, glass powder will stick to areas other than the mode. It is difficult to remove all the glass powder from areas other than the mode. If it is removed, there is a risk that the glass powder that has been carefully filled may be scraped out or contaminated, so sintering is performed with a small amount of glass powder remaining. For this reason, there are particles of unnecessary glass 14 in places other than the mode.
It sticks to me. Next, as in step B, a photoresist 5 is applied. 6 is an opening where there is no photoresist.

Next, the SiO23 in the opening 6 is etched using an etching solution containing hydrofluoric acid.
is etched to expose the contact forming surface 7 as in step C. At this time, SiO2l under the unnecessary glass 14
2. Etching is unnecessary SiO2 in areas where there is no glass 14
There is a slight delay compared to the etching time, so the etching time is extended. The adhesion of the photoresist to the SiO2 surface made of sintered glass is already weak, making it necessary to use an adhesion promoter. Furthermore, as the etching time increases, the effectiveness of the adhesion promoter weakens, causing the SiO2 surface under the photoresist to become weaker. Side etching occurs, eventually resulting in peeling of the photoresist 5 and etching of the glass 4. Therefore, it is conceivable to change the method so that the etching is first performed with an acid such as hydrochloric acid that melts the unnecessary glass 14 but does not dissolve the SiO22, and then the SiO23 is etched. However, even in this case, the first etching weakens the photoresist 5 and the adhesion promoter expires, so the subsequent S
One drawback is that it is useless when etching iO23. Therefore, after removing the unnecessary glass, a photoresist process must be performed again to remove the SiO23. After removing the SiO2, the photoresist 5 is left as it is, and a contact metal 8 is vacuum-deposited on the entire surface as in step D, and then heated in an inert gas to decompose and scatter the photoresist 5, and a contact is formed as in step E. Contact 9 is left on surface 7. According to the conventional method, the photoresist etching step shown in step C has to be repeated twice, which causes high costs. An object of the present invention is to eliminate the etching delay in unnecessary glass portions seen in the conventional method, eliminate the need to repeat the photoresist process twice, and reduce manufacturing costs.

A feature of the present invention is that the unnecessary glass portion can be easily etched by exposing it to oxygen plasma before etching the opening SO2.

The present invention will be explained below with reference to Examples.

In process A in Figure 2, 1 is a silicon substrate with a thickness of 250 μm, 2 is a 1.2 μm thick (7) SiO2, 3 is a mode with a depth of 50 μ1 and a width of 70 μm, and mode 3 is a glass 4 (Asahi Glass). ASFl4OO) is sintered. 1
4 is the largest one with a diameter of 0.2? With granular unnecessary glass,
It is firmly attached to SiO22.

5 is a photoresist (0MR83) formed to a thickness of 7 μm.
).

The state of step A may be before or after the post-baking of the photoresist 5, and in this state it is placed in an LTE PDS3Ol type plasma device and the oxygen pressure is 0. Generate plasma with σ0rr output of 100W and reduce photoresist by 0.2~1μ
Select a time to expose the wafer to the plasma. When performing plasma treatment before post-bake, post-bake is performed after this. Next, 6 volumes of ammonium fluoride, 1 volume of hydrofluoric acid
Etching with an etching solution consisting of At this time,
Since there is almost no delay in etching the SiO2l2 under the unnecessary glass 14, a contact formation surface 7 in which nothing remains as unnecessary material appears when the etching of the SiO22 is completed. Since the etching time during this period hardly increases, side etching of the SiO22 and peeling of the photoresist 5 do not occur. The time required for the oxygen plasma treatment in this example is within 5 minutes, and the cost increase due to the addition of this treatment is minimal. By exposing to oxygen plasma, SiO. Although the details of why this can be easily removed are unknown, there are two reasons: the unused glass has changed in quality to be easily etched, and the development residue of the photoresist, which remains on the unused glass and is difficult to remove, has ashed and no longer inhibits etching. When exposed to plasma, the photoresist also loses weight by about 6 μm in the lateral direction parallel to the main surface of the silicon substrate 1, and the contact formation surface 7 becomes larger, but this is not required for this type of semiconductor device. Since the working accuracy is about 10 μm, this amount of weight loss does not affect the characteristics. As described above, according to the present invention, the delay in etching of unnecessary glass portions is eliminated, so there is no need to add a photoresist process, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating the conventional method, and FIG. 2 is a sectional view illustrating the present invention. 1...Semiconductor substrate, 4...Glass, 5
...Photoresist, 7...Contact region, 8...Contact metal, 9...
·contact.

Claims (1)

[Claims] 1 Apply photoresist to a sintered semiconductor substrate with glass powder attached to a portion, expose it to light, develop it, remove the photoresist on the contact area, attach contact metal to the entire surface, and then apply the photoresist. In a method for manufacturing a semiconductor device in which a contact is formed on a contact region by removing the photoresist on the contact region, the exposed surface of the semiconductor substrate is exposed to oxygen plasma to etch the unnecessary glass on the exposed surface of the semiconductor substrate. A method for manufacturing a semiconductor device characterized by facilitating removal.