JPH0451514A - Manufacture of semiconductor device - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding a method for manufacturing a semiconductor device, when depositing silicon on a substrate for the purpose of obtaining a silicon deposited layer with good crystallinity and flatness, it is conventional to deposit silicon immediately after deposition. The structure is such that the film is deposited at a temperature used for the film, and then the deposition temperature is further lowered to a constant temperature without removing it from the deposition apparatus, and the film is deposited to a predetermined thickness.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device that allows silicon to be deposited while maintaining good crystallinity and planarization.

[Prior art]

As semiconductors become more integrated in recent years, the dimensions of their devices have been reduced not only in the lateral direction but also in the thickness direction. for example,
It is expected that in the era of mass production of 4MSRAM and 16MSRAM, dozens of atoms will be stacked.

Deposition, etching, and
In order to manufacture semiconductors by combining many processes such as annealing, it is necessary to perform all of these processes at low temperatures. This is a measure to prevent impurity elements from diffusing due to heat.

By the way, the conventional silicon deposition process in the manufacture of semiconductor devices uses the CVD method. As for the conditions, silane (SiH4) is used as the gas, and the temperature is, for example, 6.
It was deposited at 20°C.

However, when deposited at this temperature, the silicon film was already crystallized at the time of deposition, and as a result, the deposited silicon film was uneven. Such a state becomes an obstacle to film thinning (flattening is not achieved). On the other hand, in order to maintain constant product quality, even lower deposition temperatures have been required in the low temperature process.

Therefore, so-called low-temperature deposition techniques, which perform deposition at lower temperatures than conventional techniques, are being studied.

In other words, it is deposited at a temperature lower than the conventional deposition temperature (620 to 630 °C), for example, 550 °C. In some cases.). Furthermore, since the deposited silicon is in an amorphous state as it is, annealing is performed to restore its crystallinity. This annealing is also at the temperature at which solid phase growth occurs (~580℃
) or above is fine.

In this way, recrystallization occurs from an amorphous state, and a silicon film with a uniform crystal grain size of about 5 to 600 nm can be obtained. Furthermore, the silicon film deposited at low temperature has a flat surface and satisfies both the requirements for lowering the temperature and making the film thinner.

[Problem to be solved by the invention]

However, according to X-ray diffraction, the plane orientations of recrystallized grains obtained by conventional silicon low-temperature deposition processes are scattered and inconsistent. This is a factor that causes variations in device characteristics such as mobility when manufacturing transistors.

In order to solve this problem, for example, specific grooves are formed in the base, or SOI structure (silicon
In the case of annealing, there is an attempt to make a hole through the base silicon substrate and use that part as a seed part to control the solid phase growth direction during annealing of the deposited silicon. However, both require some kind of processing on the base. Moreover, these processes are not always possible.

An object of the present invention is to deposit flat polysilicon with uniform surface orientation at a low temperature without particularly requiring processing regardless of the state of the underlying substrate in the process of depositing silicon.

[Means and effects for solving the problem] The present invention has been made to achieve the above object, and includes depositing Si on a semiconductor film or an insulating film at 620 to 630°C to form a polycrystalline Si film. 5 times using the same deposition device.
Depositing Si at a temperature of 20 to 580°C, the polycrystalline Si
An amorphous Si film is formed on the film, and then heat treatment (annealing) is performed to form an 81-plane phase growth layer (
It is characterized by obtaining a Si epitaxial layer).

That is, the method of the present invention attempts to deposit flat polysilicon with uniform surface orientation at a low temperature as described above. To do this, it is first necessary to form a "seed" to align the plane orientation.

As such, silicon deposition at conventional temperatures (620-630°C) is performed. When deposited at conventional temperatures, the surface orientation is (1
11) It is well known that surface-dominated growth occurs. The reason for this is thought to be that the (111) plane is an energetically stable island.

Utilizing this characteristic, first, as shown in FIG. 1, a thin polycrystalline Si film 2 is formed as a seed portion on a semiconductor film or an insulating film 1 by deposition at a conventional temperature. If thickly deposited, unevenness will occur) Then, the temperature is lowered (520 to 580° C.) and deposition is continued to form an amorphous Si film 3 (FIG. 1 (3)). Low temperature deposited silicon is flat and still in an amorphous state at the end of deposition.

Thus, in the method of the present invention, the silicon deposition process is
After the initial deposition process, 520~
51 is deposited at a low temperature of 580°C. In this case, if the temperature exceeds 580° C., silicon will crystallize during deposition, which is disadvantageous. On the other hand, if it is deposited at a temperature below 520° C., the subsequent annealing will cause variations in crystal grain size, which is disadvantageous as it will lead to variations in electrical properties. Therefore, in the present invention, the above self-temperature range is adopted.

Note that in the low-temperature deposition process, if the deposition rate is an issue, the type of gas may be changed.

As mentioned above, after the low-temperature deposition process, the amorphous S on the surface
The i-film is still in an amorphous state, and its crystal planes have not been identified.

After Si deposition is completed, annealing is performed to improve crystallinity. This annealing is performed at a low temperature (580 to 620° C.) or at a high temperature (800° C.) for a short time to an extent that does not cause diffusion of impurities.

The amorphous layer is rapidly crystallized by such annealing. At this time, solid phase growth occurs by continuing the plane orientation of the seed silicon deposited at the conventional temperature (Fig. 1 (4)), resulting in a flat Si plane phase growth layer (Si epitaxial layer) in which the entire amorphous layer is crystallized. ) 4 (Figure 1 (5)). Its crystal grains are large, ranging from 5 to 600 nm, and the device has excellent electrical properties.

The semiconductor device obtained by the above method of the present invention will be further explained using X-ray diffraction data and transmission electron micrographs.

Figure 2 shows Si 6 after forming a thermal oxide film on a silicon substrate.
A sample immediately after deposition is obtained when a polycrystalline Si film is formed by depositing at 20°C, and then the deposition temperature is lowered using the same deposition equipment and Sl is deposited on the polycrystalline Si film to a predetermined thickness at 560°C. This is a transmission micrograph (X30000). As is clear from this photograph, the surface of the Si film is extremely flat. The X-ray line spectrum of this sample is shown in Figure 3 (A
).

As is clear from this spectrum A, no diffraction peak corresponding to the plane orientation appears. That is, it can be seen that the Si film is amorphous immediately after being deposited.

On the other hand, FIG. 3 shows that the conventional deposition temperature of 620
1 is a transmission electron micrograph (X30000) of a deposited silicon film obtained when deposited at .degree. The sample in this case was also immediately deposited and was not heat-treated. As is clear from this photograph, the surface of the deposited silicon film is uneven. The X-ray diffraction spectrum of this film is shown in FIG. 4(B). In this spectrum, a plurality of diffraction peaks indicating predetermined surface orientations appear. This indicates that crystallization has already occurred immediately after deposition. Note that (111) is the priority direction.

The results of heat treating the deposited silicon film in the present invention will be described below. In addition, in order to make the crystallization more clear,
The surface of the acid film is thinly etched using an etching solution and observed using an electron microscope.

As described above, the deposited silicon film after the low-temperature deposition process according to the method of the present invention is heat-treated at, for example, 650° C. for 30 minutes. The X-ray diffraction spectrum of the sample subjected to this heat treatment is shown in FIG. 4(C).

As is clear from the spectrum diagram in Figure 4(C), one very strong diffraction peak indicating a specific plane orientation (111) was observed, indicating that the plane orientation (111) of the seed silicon was inherited. It is confirmed that it is growing.

On the other hand, FIG. 5 shows that the initial deposition was carried out at 560°C without performing the deposition process according to the method of the present invention;
This is an electron microscopic photograph of a sample deposited at 100° C. and heat-treated (annealed) at 650° C. for 30 minutes after the completion of the deposition. As is clear from this photograph, it can be seen that crystallization has been completed by annealing. However, although the surface of the deposited film after annealing is relatively flat, the size and direction of the crystal grains are also non-uniform.

The X-ray diffraction spectrum of the deposited silicon film obtained by such a conventional method is shown in Figure 6 (however, the annealing temperature was 80°C).
). It can be seen that in this X-ray diffraction spectrum, multiple diffraction peaks indicating specific plane orientations appear. Therefore, the crystal grains of this Si crystal film have different plane orientations. The reason for this is thought to be that there was no seed crystal in the deposited film, and each crystal grew using slight irregularities in the underlying substrate as nuclei.

Therefore, it is extremely effective to form a nucleus exhibiting a specific plane orientation in advance in the form of a base substrate for the silicon film deposited thereon to grow using it as a nucleus.

Therefore, in order to obtain a silicon film with a flat surface with uniform plane orientation, it is necessary to set the initial deposition temperature to 620 to 630° C., then lower the deposition temperature to deposit silicon, and then perform annealing.

The method of the present invention can be applied to all steps of depositing polysilicon. Therefore, as a deposition substrate, not only semiconductors such as Si and GaAs, but also 5
ill)2. Si3N4. The target is an insulating film such as PSG.

EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples, but it goes without saying that the present invention is not limited thereto.

〔Example〕

In this example, an SOI structure (si
The case of manufacturing a semiconductor device having a silicon on one insulator will be described based on FIGS. 7(a) to (I).

A thermal oxide film 12 with a thickness of ~5Qnm is formed on a single crystal silicon substrate 11.
FIG. 7(b). Next, about 100 r++n of silicon is deposited on the thermal oxide film 12 at a temperature of 620° C. using silane gas (50 s-cI+) to form a polycrystalline Si film 13. The deposition time is about 15 minutes. , do not remove the sample from the deposition device (5).
The deposition temperature is lowered to 550° C. and silicon deposition is continued for about 40 minutes to continuously form an amorphous Si film 14 with a thickness of 300 nm on the polycrystalline Si film 13 (see FIG. 7(C).
)).

The following steps are carried out according to conventional methods. That is, LOCO3
structure, the element forming portion is covered with an oxide film and a nitride film 1.
5 (Fig. 7(d)). Then, using a furnace, 1050
0□ annealing is performed for 200 minutes at a temperature of °C. By this annealing, a recrystallized 81-plane phase growth layer (epitaxial layer) 16 is obtained (FIG. 7(e)). This Si plane phase growth layer constitutes a polycrystalline Si layer 16a and a field oxide film 16b that form the element.

Next, the oxide film/nitride film 15 is removed (FIG. 7(f)),
Furthermore, a resist 17 is applied to the second region (the right region in the figure), and B+ ions are implanted (FIG. 7(g)).

This forms a P-type region. Next, resist 17
is peeled off, resist 18 is again applied to the first region (the left region in the figure), and P'' ion implantation is performed (FIG. 7(h)).

This forms an n-type region.

Next, the resist 18 is removed, and then the gate oxide film 29 is removed.
An oxide film with a thickness of 3Q nm is formed at 1100°C. A polycrystalline Si film 19 is deposited thereon at a low temperature in the same manner as in the low temperature process described above. In order to further reduce the resistance value, P ion implantation was performed, and then the
Anneal for 0 m1n (Fig. 7 (1)).

The annealing is performed using RT A (Rapid Therm).
high temperature (>800°C) using a
You can also do it for a short time. Next, the crystallized Si film is etched to form a film 20.20'. A /l mask 21 is formed by depositing Al in the first region. Using this as a mask, B- is implanted to form the source and drain (Pa) in the second region (FIG. 7(j)).
Peel off the mask 21 and then apply the β mask 22 to the second region.
is formed, and P- is implanted to form a source and a drain (n+) in the first region (FIG. 7(k)). Finally, AI
The mask 22 is peeled off, PSG 23 is applied to the entire surface, electrode windows are made in this PSG, and wiring (A I-3i) is formed.
24 is formed, and an insulating film (513N-
) 25 is formed, a window is opened, an Al wiring 26 is formed, a protective film (si, N, ) 27 is formed on the entire surface, and [''M[l
Complete SSRAM.

[Effect of Hathu]

As explained above, the present invention deposits Si on a semiconductor film or an insulating film at a temperature of 620 to 630°C to form a polycrystalline Si film, and then uses the same deposition apparatus to deposit Si at a temperature of 520 to 580°C. Then, amorphous Si is deposited on the polycrystalline Si film.
Since the structure is such that a film is formed and then heat treated to obtain a Si plane phase growth layer, a silicon film with uniform plane orientation and a flat surface can be obtained by a low temperature process. Therefore, the electrical characteristics of the device obtained by the method of the present invention are extremely uniform and excellent without any variation.

When carrying out such a method of the present invention, for example, MOSF
In ET, the mobility obtained when using a conventional polysilicon film has been improved by about 10 times.

Furthermore, it was confirmed that the leakage current was significantly reduced, and it was found that the method of the present invention is extremely effective for device-specific devices.

In addition, there is no need to process the underlying substrate as in conventional methods, and polysilicon can be deposited continuously at low temperatures using the same deposition device without taking the sample out of the deposition device, making it extremely easy to process. This makes it possible to improve throughput and reduce costs.

Furthermore, since a flat and thin silicon film can be obtained, the method of the present invention is extremely advantageous in producing devices with three-dimensional structures.

[Brief explanation of the drawing]

Figures 1 (1) to (5) are diagrams of the principle of the present invention, Figure 2 is an electron micrograph showing the crystalline state of the deposited silicon film in the method of the present invention, and Figure 3 is a diagram showing the crystalline state of the silicon film deposited in the method of the present invention. FIG. 4 is an electron micrograph showing the crystalline state of the deposited silicon film obtained by the method of the present invention and the conventional method, and FIG. 5 is the X-ray diffraction pattern of the deposited silicon film obtained by the conventional method. This is an electron micrograph showing the crystalline state of polysilicon obtained by etching and annealing the film, and FIG. 6 is an X-ray diffraction diagram of polysilicon obtained by annealing the deposited silicon film using the conventional method 7(a) to (1) are process diagrams showing one embodiment of the method of the present invention. 1... Semiconductor film or insulating film, 2... Polycrystalline Si film, 3... Amorphous Si film, 4
...Si solid phase growth layer (epitaxial layer), 11...
・Silicon substrate, 13... Polycrystalline Si film, 14.
...Amorphous Si film, 16...Si solid phase growth layer (epitaxial layer), 19
...Polycrystalline Si film. Principle of the present invention Figure 1: Electron micrograph of deposited silicon film in Method 1 of the present invention Figure 2: Electron micrograph of conventional method 1 Opening deposited silicon film Figure 3: Conventional method 1 Etching the deposited silicon film with openings Electron micrograph of annealed at 650℃

Claims (1)

[Claims] 1. Si on the semiconductor film or insulating film at 620 to 630°C
A polycrystalline Si film is formed by depositing the polycrystalline Si film, followed by depositing Si at a temperature of 520 to 580°C using the same deposition apparatus to form an amorphous Si film on the polycrystalline Si film, and then heat treatment. A method for manufacturing a semiconductor device, the method comprising: obtaining a Si solid-phase growth layer.