JPH02191353A - Inspection of semiconductor substrate - Google Patents

Abstract

PURPOSE:To detect a void formed in an adhesive bond with ease by irradiating a bond surface of a semiconductor substrate which is yielded by bonding semiconductor substrates or by doing the same through an oxide layer with specific wavelength infrared rays. CONSTITUTION:Any void of a bonded silicon semiconductor substrate 4 is inspected by irradiation thereof with 2.0mum or less infrared rays, the silicon semiconductor substrate portion 4 is displaced substantially as a black image on a monitor of a video device 10. On the contrary, the void 11 is displaced on the monitor as a black interference fringe, and hence it is clearly detachable. Thus, the yield of void detection in a silicon semiconductor substrate bonded surface is sharply improved and yields of a dicing process and a polishing process as manufacturing processes thereafter are also increased.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a method for inspecting semiconductor substrates, and in particular, the present invention relates to a method for inspecting semiconductor substrates, and in particular, the present invention relates to a method for inspecting semiconductor substrates that are arranged facing each other, or one or more of the semiconductor substrates. This method is suitable for inspecting a bonded semiconductor substrate obtained by forming an oxide film on both sides and then bonding mirror surfaces formed on the oxide films or a mirror surface formed on the oxide film and a mirror surface formed on the surface of the semiconductor substrate.

(Prior art) A mirror surface obtained by polishing the surface of a single-crystal silicon semiconductor substrate is brought into close contact with the surface in a clean atmosphere and heat-treated. Strength is obtained, and furthermore, it has been determined that this bonding surface does not have any negative electrical effects on the PN junction that is formed. Therefore, a semiconductor device in which an active element or a passive element is formed by introducing impurities into a bonded semiconductor substrate has been developed and is now in the stage of practical use.

Bonded semiconductor substrates include not only silicon semiconductor substrates, but also oxide layers coated on their surfaces, oxide layers and silicon semiconductor substrates, silicon semi-semiconductor substrates and polysilicon layers formed thereon, and polysilicon substrates. Adhesive structures between layers are known.

If dust or the like adheres to the adhesive surface formed by such a combination of silicon semiconductor substrates through the above processing steps, unbonded portions, or voids, will be formed, which will not only deteriorate the electrical characteristics of the semiconductor element, but also cause the semiconductor to deteriorate. This causes cracks to occur during the dicing process, polishing process, and other manufacturing processes necessary for the device. For this,
After the bonded silicon semiconductor substrate passes through a void inspection process, it is transferred to the semiconductor element manufacturing process.

5L-8IO (X-0<X≦2)-8t or 5t-8
The inspection process for bonded silicon semiconductor substrates with a structure of
．． A method is adopted in which the intensity of transmitted infrared rays is measured by irradiating infrared rays with a wavelength of 0 μm to 5.6 μm, and the incident infrared rays are reflected in the voids created by voids and are not transmitted.

FIG. 4 is a curve diagram showing the relationship between the infrared transmittance of the bonded silicon semiconductor substrate and the infrared wavelength (μm) on the horizontal axis and the vertical axis, respectively.

On the other hand, 5i by infrared rays with a wavelength of 2.0 μm to 5.6 μm
-8iO (X-0 < It consists of a mechanism.

The outline of this inspection device will be explained with reference to FIGS. 8 and 9. Figure 8 shows parallel infrared rays emitted from a light source 50 such as a halogen lamp. It is equipped with a method of irradiating the Ii measurement adhesive silicon semiconductor substrate 51, and in FIG. 9, it is a type of inspection device that simply uses infrared rays.

In FIG. 8, which uses parallel infrared rays, a light source 50 such as a halogen lamp is followed by a filter 52 and a reflecting mirror 5.
3 and a convex mirror 54 are installed to bond the silicon semiconductor substrate 5.
Investigate the adhesive surface of No.1.

On the other hand, the inspection apparatus shown in FIG. wi9 employs a method in which infrared rays emitted from a light source 50 such as a halogen lamp are incident on a bonded silicon semiconductor substrate 51 to be measured via a convex mirror 54. In both apparatuses, an image pickup tube 5B is attached to a column 55 so as to be vertically movable, and a monitor 57 directly connected to the image pickup tube 56 is installed so as to correspond to the bonded silicon semiconductor substrate 5I to be measured.

The result of this re-inspection device, that is, the presence or absence of voids, is used as information in the subsequent dicing process.

(Problem to be solved by the invention) The method for measuring the intensity of transmitted infrared rays is described in Patent Association Publication Technical Report 8.
5-8424, as shown in the curve diagram in FIG. 4, 5t-SLOx (0<X≦2)-S
For a bonded silicon semiconductor substrate with a t structure, the wavelength is 2.0 μm ~
When 5.6 μm infrared light irradiates a void, it is reflected and attenuated. When an image of the bonded surface taken by the inspection device's camera is displayed on a monitor, the silicon semiconductor substrate appears white, but voids also appear whitish, and interference fringes may not be discernible.

As described above, void inspection is not only inaccurate as information for the guising process, but also quite difficult. Therefore, there have been problems such as cracking or chipping defects occurring in the semiconductor device manufacturing process or polishing process, and furthermore, the electrical characteristics of the semiconductor device using the adhesive wafer deteriorate.

The present invention was made under these circumstances, and in particular,
An object of the present invention is to provide a method for inspecting a silicon semiconductor substrate having a silicon oxide layer formed on an adhesive surface.

[Structure of the invention]

(Means for Solving the Problems) A feature of the present invention is that the transmitted intensity of infrared rays of less than 2.0 μm generated from a light source is measured on the adhesive surface of semiconductor substrates that are adhered to each other or through an oxide layer. There is.

(Function) As is clear from Figure 4, when the silicon oxide layer formed on the adhesive surface of the silicon semiconductor substrate is irradiated with infrared rays with a wavelength of less than 2.0 μm, even if voids exist, the infrared transmittance decreases. It has been found that there is no change in , and it is clear that similar results can be obtained between silicon semiconductor substrates.

When this phenomenon is utilized to inspect voids in a bonded silicon semiconductor substrate by irradiating it with infrared rays of less than 2.0 μm, the silicon semiconductor substrate portion appears as a nearly black image on the monitor of the imaging device.

In contrast, voids appear on the monitor as black interference fringes, making them clearly detectable.

Therefore, the yield of detecting voids on the bonding surface of the silicon semiconductor substrate is greatly improved, and the yield of subsequent manufacturing steps such as dicing and polishing steps also increases.

By the way, the adhesive layer produced in the silicon semiconductor substrate bonding process is the bulk (B) that constitutes the silicon semiconductor substrate.
It is formed from an oxide layer or a silicon layer having a structure that is somewhat different from that of Ulk). It is not clear why the intensity of transmitted infrared rays with a wavelength of less than 2.0 μm is not attenuated when detecting voids formed in this adhesive layer.

(Example) An example according to the present invention will be described with reference to FIGS. 1 to 7.

(1) P-type silicon semiconductor substrate 100 with a resistance ratio of 9 to 12 Ω, a thickness of 525 μm, and a mirror-polished surface
After preparing the sheet, it is kept in an H210 atmosphere maintained at 1100° C. for 100 minutes to form a thermal oxide film of 7000 Å on a mirror surface.

In terms of cleanliness, for example, a P-type silicon semiconductor substrate coated with a thermal oxide layer placed in a clean room maintained at about class 1O, and a thermal oxide layer coated on the surface of another P (N)-type silicon semiconductor substrate are placed in a clean room maintained at about class 1O. Hold the two in close contact with each other. If heat treatment is performed as it is, 5L-SLO (0<X
<2) Fifty bonded silicon semiconductor substrates 4 to be inspected having a structure of /SL are obtained.

The bonded silicon semiconductor substrate 4 thus formed is placed in the measuring apparatus shown in FIG. The measuring device cuts infrared rays 6 emitted from a light source 5 made of a halogen bulb to a wavelength of 2.0 μm or more.
Wavelength 2. is passed through the installed band pass filter 7.
After cutting off the infrared rays 8 with a wavelength of 0 μm or more, the bonded silicon semiconductor substrate 4 to be inspected is irradiated and the transmitted intensity of the infrared rays 9 with a wavelength of less than 2.0 μm is measured.

As the measuring device, those shown in FIGS. 8 and 9 are generally used, but the system configuration diagram shown in FIG. 2 will be used for explanation. That is, an imaging device 10 equipped with a camera for photographing and a monitor for displaying images is installed at a distance of 50 cm to 100 cm from the bonded silicon semiconductor substrate 4 to be inspected, and the voids determined from the images on this monitor are determined as follows. It is used as information for the dicing process and polishing process.

That is, the dicing process is stopped for dicing lines where voids exist to prevent a decrease in yield due to the occurrence of defects.

FIG. 3 shows a monitor image when a void exists in the bonded silicon semiconductor substrate 4 to be inspected. That is, as described above, the infrared rays 9 with a wavelength of less than 2.0 μm that irradiated the void...the transmittance is not attenuated and the interference fringes 11 appear on the monitor.
, and even areas with gaps can be easily and reliably detected.

On the other hand, Fig. 3a shows a monitor image of the sample shown in Fig. 3, through which infrared rays 9 with a wavelength of 2.0 μm or more are transmitted by the conventional method without installing the bandpass filter 7. is not shown at all, and it is judged that the entire bonding surface is glued.

In addition, the 50 bonded silicon semiconductor substrates to be inspected that had undergone the void inspection were subjected to the dicing process, and then their compatibility with the fracture caused by dicing into 0.5 squares was investigated, and the results are shown in Figure 5. . This figure compares the detection rate of voids confirmed by destructive inspection between the conventional method and the present invention.The detection rate of the method of the present invention is about 90%, while the detection rate of the conventional method is only 10%.
%, which is clear from the effectiveness of the present invention.

For this inspection device, those shown in FIGS. 8 and 9 are used.

(2) As a second embodiment, an example will be shown in which another silicon semiconductor substrate is bonded to an oxide layer formed on the surface of the silicon semiconductor substrate. Both silicon semiconductor substrates have a specific resistance of 9
A surface of a silicon semiconductor substrate exhibiting P or N conductivity type and having a thickness of 12Ω·(2) and a thickness of 525 μm is prepared.

50 of them were clean H21 sheets maintained at 1100℃.
A thermal oxide film of 70 GOA is formed by holding the film in an atmosphere of 0□ for ioo minutes. A pair taken out from each is adhered using the method and conditions described above.

That is, when a bonded silicon semiconductor substrate to which a semiconductor substrate was bonded via an oxide layer was subjected to a void detection process to check for the presence or absence of voids, the same results as in the first example were obtained, so the details will be omitted. . Further, the apparatus shown in FIGS. 8 and 9 is used to inspect the voids on the bonding surface of the bonded silicon semiconductor substrate.

(3) The third embodiment is an example in which silicon semiconductor substrates are bonded together and then the bonded surface is investigated. That is, both silicon semiconductor substrates have a specific resistance of 9 to 12 as in the second embodiment.
Ω・(to), 525 μm thick P or N conductor 1! A silicon semiconductor substrate surface exhibiting an i-type is prepared, a mirror surface is formed on this surface, and then bonded. The apparatus shown in FIGS. 8 and 9 is used to inspect the bonding surface of this bonded silicon semiconductor substrate for voids.

Note that this bonded silicon semiconductor substrate can be measured with infrared rays at wavelengths of less than 2 μm, as in the first and second embodiments, so work efficiency is improved because there is no need to use infrared rays with different wavelengths as in the past. There are advantages.

〔Effect of the invention〕

In the present invention, the accuracy of detecting voids in a bonded silicon semiconductor substrate with an oxide layer interposed therebetween is considerably improved compared to conventional methods.

FIG. 6 shows the incidence of cracking and chipping defects that occur in the polishing process after void inspection and in the semiconductor device manufacturing process in which active or passive devices are formed by introducing impurities. Furthermore,
FIG. 7 shows the manufacturing yield of semiconductor devices manufactured using the bonded silicon semiconductor substrate that has undergone the void inspection process.

In other words, the occurrence rate of cracks is only 10% or less compared to 50% in the conventional case, and the manufacturing yield of semiconductor devices is also 20% of the conventional rate.
This is a significant improvement from 80% to 80%.

As described above, the present invention has a large effect on the mass production of bonded silicon semiconductor devices, and can also improve the reliability of the semiconductor devices.

Since voids in the bonded semiconductor substrate are detected as interference fringes, the resolution depends on the wavelength of infrared rays, so λ/2
determined by Therefore, the conventional test method 2.0 to 5.6μ
In the case of m, the detection limit for voids was 1 to 2.8 μm, whereas in the present invention, voids smaller than 1 μm can be detected, which has the advantage of improving detection accuracy.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the semiconductor substrate integrated through the bonding process, Figure 2 is a configuration diagram of the system used in the method of the present invention, and Figures 3a and b are images shown on the monitor after bond inspection. Figure 4 shows the transmittance of infrared rays irradiating a silicon semiconductor substrate, Figure 5 shows the detection rate of voids confirmed by demolition inspection, and Figure 6 shows chips and cracks. Figure 7 is a diagram showing the manufacturing yield of semiconductor devices.
FIGS. 8 and 9 are cross-sectional views showing the outline of a conventional inspection device. 1.3; 81 2: SiO 4: Adhesive silicon semiconductor substrate 5: Light source 6: Infrared rays 7: Filter 8: Transmitted infrared rays M1 Figure 2 Figure to: Eo I3≧aCt Noriji Senji Patent attorney Norio Ogo Figure 3

Claims (1)

[Claims] 1. A method for inspecting semiconductor substrates, comprising measuring the transmitted intensity of infrared rays of less than 2.0 μm emitted from a light source through the adhesive surface of semiconductor substrates that are adhered to each other or through an oxide layer.