JPH044752B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a stacked structure of a stacked semiconductor device, and particularly relates to a method for avoiding stress (thermal stress) generated in the stacking process. be.

[Conventional technology]

Figure 3 shows the SOI of a conventional stacked semiconductor device.
(Silicon on Insulator) structure, in which a non-conductive material is placed on the nth active layer 1.
An SOI layered structure is realized by forming the first interlayer insulating layer 3 and further forming the (n+1)th active layer 2 thereon.

The stacked semiconductor device shown in FIG.
2, a circuit is formed using FETs (Field Effect Transistors) or other electric components such as resistors and capacitors, and the upper and lower circuits are further wired through an interlayer insulating film 3, and the circuit is arranged three-dimensionally. A circuit is formed. In the stacked semiconductor device according to the prior art described above, in order to form the active layer 2, the deposited polysilicon is recrystallized using a laser beam or an electron beam.

[Problem that the invention seeks to solve]

A conventional stacked semiconductor device is constructed as shown in FIG. 3, and an active layer 2 is formed on an interlayer insulating film 3. During the formation of this active layer 2, the deposited polysilicon is exposed to a laser beam or an electron beam. It is necessary to perform recrystallization using a beam, and at this time stress (thermal stress) is generated due to the difference in the thermal expansion coefficients of the two layers 2 and 3, causing problems such as warping of the substrate.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a stacked semiconductor device that can avoid warping of the substrate.

[Means for solving problems]

A stacked semiconductor device according to the present invention has a buffer of a thin film multilayer structure in which a plurality of thin silicon layers and thin silicon oxide layers or silicon nitride layers are alternately stacked between an interlayer insulating layer and an active layer thereon. It is designed to incorporate layers.

[Effect]

In this invention, the buffer layer absorbs the stress (thermal stress) that occurs during recrystallization due to the difference in thermal expansion coefficient between the upper and lower active layers and the interlayer insulating layer, thereby avoiding the occurrence of warping of the substrate. At the same time, the crystallinity of the active layer during recrystallization is improved.

〔Example〕

Hereinafter, one embodiment of the present invention will be illustrated and explained.

FIG. 1 shows a stacked semiconductor device according to an embodiment of the present invention, in which 1 is the nth active layer in the stacked semiconductor device, 2 is the (n+1)th active layer, and 3 is the nth active layer. active layer 1 and (n+
1) This is an interlayer insulating layer that separates the active layer (2), and 4 is a buffer layer.

FIG. 2 shows an enlarged view of the buffer layer 4. This buffer layer 4 is a thin silicon layer 4 with a thickness of 10 to 100 Å.
Like a, it has a thin film multilayer structure in which thin silicon oxide layers (or silicon nitride layers) 4b having a thickness of 10 to 100 Å are stacked alternately. Here, the lower limit of the above film thickness of 10 Å means that the thickness of one atomic layer is 5 Å, which is approximately 2 to 3 atomic layers, and the upper limit of 100 Å.
This is because if Å is thicker than this, the effect of absorbing heat stress, which will be described later, cannot be exhibited.

In the process of forming a stacked semiconductor device as shown in FIG. 1, the deposited polysilicon is recrystallized in order to form the active layer 2. In this example, the polysilicon is deposited, Before performing the recrystallization process, a buffer layer 4 is formed, so that the thermal stress generated during the recrystallization process of the active layer 2 is absorbed by the buffer layer 4, thereby avoiding warpage of the substrate. can do. Furthermore, by being able to avoid warping of the substrate, it can be expected that the precision of subsequent wafer processes will be improved.

Note that in the above embodiments, the buffer layer of the thin film multilayer structure was formed by overlapping a silicon layer and a silicon oxide (or silicon nitride) layer;
It is also possible to form a buffer layer by laminating three or more types of materials such as a silicon nitride layer and PSG.

〔Effect of the invention〕

As described above, according to the present invention, since the buffer layer is formed between the interlayer insulating film and the active layer, warping of the substrate due to thermal stress can be avoided, and a high-quality silicon layer can be used as the active layer. There are benefits to be gained. Furthermore, since warpage of the substrate can be avoided, it is expected that the accuracy of subsequent wafer processes will be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a stacked semiconductor device according to an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of the buffer layer in FIG. 1, and FIG. 3 is a conventional stacked semiconductor device. FIG. 1... nth active layer, 2... (n+1)th active layer, 3... nth interlayer insulating layer, 4... buffer layer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a stacked semiconductor device having an SOI layer, a thin silicon layer and a thin silicon oxide layer or a silicon nitride layer are provided between a silicon layer as an active layer and a silicon oxide layer as an interlayer insulating film. 1. A stacked semiconductor device comprising a buffer layer having a thin film multilayer structure formed by alternately stacking a plurality of layers.