JPH0413848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a semiconductor body equipped with a type of isolation region and a method of manufacturing the same.

The insulation isolation method has traditionally been a very important technology for semiconductor devices, and is positioned as a technology that will become even more important in the future, especially in bipolar devices and the like, as speeds and densities increase. Conventionally, the first
As shown in FIG. 1A, an insulating separation layer 12 is formed in a semiconductor substrate 11 from the surface, and the remaining region between them is used as an active layer 13 to incorporate an element. At this time, when the distance between the separation layers 12 is shortened in order to increase the density, large stress begins to act between them, causing crystal defects and deteriorating device characteristics.
As shown in FIG. 1A, bird's beaks 14 are formed, and the distance between the separation layers 12 cannot be reduced. In response to this, an attempt has been made to form an insulating separation layer 12 inside 11, as shown in FIG. 1b. For example, the structure shown in Figure 1b is formed by deeply implanting oxygen by ion implantation to form an oxide, but this method has the drawback that implantation defects remain and a large amount of oxygen must be implanted. It has the drawback of being too realistic and unrealistic.

Other attempts have also been made to achieve complete insulation isolation using anodic oxidation, but there are various problems and the technology is still incomplete.

The present invention aims to provide a new method for forming such an insulating separation layer, and to realize a high-speed bipolar device using the method.

In the method of the present invention, a single crystallization method is applied to a semiconductor polycrystalline film or an amorphous film in which at least a part is on an insulating film and the other part is in direct contact with a semiconductor substrate.

Various proposals have been made regarding this single crystallization method over the past few years. The proposed technology will be briefly explained below.

Polycrystalline islands left on an insulating substrate (e.g. SiO ₂ or Si ₃ N ₄ ) by etching are made into single crystals or large crystals by so-called beam annealing methods such as CW, pulse laser annealing, and electron beam annealing. There is a technology to granulate it. Although fairly good single-crystal islands can be obtained using this method, it is impossible to control the crystal orientation, and since seed crystals are scattered around the islands, complex islands consisting of large crystal grains are likely to occur. Major shortcomings have been recognized.

In addition, the grapho-epikitacy method is the same as the above-mentioned method in that it attempts to form a single crystal thin film on an amorphous insulating film by beam annealing. By preparing corresponding very fine grooves in advance, it is possible to control the crystal orientation, which was impossible with the above-mentioned methods. However, although it seems that some success has been achieved in growing single crystals from an aqueous solution of KCl, satisfactory results have not been achieved with semiconductor films such as Si. In other words, this method does not have a size large enough to form semiconductor devices (several μm square), and it is not possible to analyze device characteristics, crystal defects, small-angle grain boundaries, twin crystals, etc. , it is not a usable technique.

In bridging epitaxy and seeded beam annealing, the crystal orientation is controlled to some extent because the substrate is used as a seed crystal. However, as is well known, crystal defects begin to occur at the point where crystals grow from the seed crystal portion to the insulating layer, and after 1 to 3 μm growth, phenomena such as polycrystalization occur. In particular, in seeded beam annealing, single crystals grow from the opening to the periphery, so the area where the crystal orientation of the substrate continues accurately and grows does not reach 1 μm around the periphery, and grows as a polycrystal with a large grain size of 1 to 5 μm. Therefore, it is observed like a chrysanthemum. It is thought that such a symmetrical shape corresponds to a concentric temperature distribution with the opening serving as a heat sink.

On the other hand, in bridging epitaxy, single crystals are grown from both sides using seed crystals on both sides as bridge piers. The seed crystal part and the insulating part on which polycrystalline material is placed alternately form lines and spaces in parallel, and a total of about 3 μm from both sides is almost single crystallized. However, grain boundaries such as small-angle grain boundaries and large defects remain in the central portion where both sides collide. Furthermore, it has the disadvantage that bridging wider than that is difficult. The reason why a somewhat larger single crystal can be obtained with bridging epitaxy is probably because the symmetry of the heat distribution is closer to uniaxiality than with seeded beam annealing. This means that single crystallization using CW laser annealing, which has a slow cooling rate and strong temperature distribution anisotropy due to heat conduction, is better than single crystallization using pulsed laser annealing, which has very little temperature distribution anisotropy. This can be seen from the fact that better results were obtained than in crystallization. That is, it can be seen that when the cooling rate is slow, heat flows to the seed crystal portions that are linearly arranged heat sinks, so it is easy to realize a substantially uniaxial temperature distribution. However, since the beam diameter of a laser or the like is small, this uniaxiality naturally breaks down in the peripheral area of the beam, which is considered to be the cause of poor crystallinity. This means that the growth area of a single crystal with good crystallinity and orientation is almost limited to the central part of the laser beam, and even if the overlap of the scanning laser beams is increased, the crystallinity cannot be improved. This is probably due to the fact that it is rarely done.

The present invention improves the uniaxiality of temperature distribution as discussed above, realizes a structure suitable for single crystal growth that takes into account crystal growth habits, and overcomes various drawbacks of conventional methods. The present invention provides an isolated single-crystal substrate with improved crystallinity, and at the same time provides excellent semiconductor devices such as high-speed bipolar devices and MOS devices.

The present invention uses the shape and arrangement of both the so-called relief, which serves as both electrical insulation and thermal insulation (low thermal conductivity), and the opening, which is both a heat sink and a seed crystal, to achieve uniformity as close to uniaxial as possible. It has the characteristics of causing heat flow and crystal growth at the same time, and has an auxiliary crystal orientation control effect by the relief of the opening with sharp corners.
This is a unique method that has the effect of improving the crystallinity of areas where defects are likely to occur, and can be called insulation separation heat flow control and relief complementary epitaxy.

First, the method on which the present invention is based will be explained using FIG. a shows a cross section taken along the line -' of the plan view b. b' in FIG. 2b is a portion excluding the laminated portion. A first insulating film 22 is formed in the shape of parallel strips on a substrate 21, and second insulating films 23 and 24 are formed above and orthogonally to form a window 25 consisting of a rectangular insulating part. There is. A rectangular opening 26 is formed by the second insulating film 23 and the first insulating film 22. Normally, no matter how advanced the etching method is used, or when an insulating film is formed at once by nitriding or oxidizing through a protective film, the corners of the opening 26 are not rounded. take on In the structure shown in FIG. 2, since the insulating films 22, 23, and 24 are formed twice in a rectangular shape in a straight line,
The corner portion of the opening 26 is formed very sharply. As mentioned above, this exhibits a useful effect as a so-called relief, which accurately maintains the orientation of the crystal grown from the seed crystal.

In the case of this embodiment, the two sides of the opening 26 made up of the insulating films 22 and 23 are not only parallel to the insulating film 23 (part of the rectangular insulating section 25) but also completely coincident with each other.

Inside the window 25 of the rectangular insulating part, in contact with the opening 26, there is a single crystallized region, that is, the substrate extension part 2.
7 is formed so as to partially protrude above the first insulating film 22 . The substrate extension portion 27 and the substrate 26 are used as a region for fabricating currently used semiconductor devices, that is, a device substrate. The opening 26 in FIG. 2 has the feature of serving not only as a seed crystal but also as a conductive path connecting the substrate 26 and the substrate extension 27.

In addition, the board extension part 27 can be
1, an opening can be formed in this portion, and the same type of structure can be further laminated.

In the example shown in FIG. 2, the opening 26 and the window 25 of the insulating part are both rectangular, but they may also be configured in a rhombus shape according to the orientation of the substrate and the orientation of crystal growth, as will be described later. You can get the same effect. Further, although a part of the periphery of the opening 26 and the window 25 of the insulating part is common, it does not necessarily have to be the same, and it is sufficient that they are approximately parallel to each other even if there is a slight gap. .

Next, the production of an insulated single crystal substrate having the structure shown in FIG. 2 will be explained.

First, using a strip-shaped mask A on the substrate 21,
LOCOS oxidation is performed using a conventional method to form lines and spaces between the insulating film 22 and the opening 28 which will serve as a seed crystal, as shown in FIG. Insulating film 22
The thickness may be 0.3 to 1.0 μm, which is commonly used. On top of this, an amorphous layer or a polycrystalline layer (thickness 0.2 to 1.0 μm) to be converted into a single crystal is laminated on the entire surface.

Next, using a mask B that leaves a rectangular window with a #-shaped pattern, the polycrystalline layer is subjected to a process such as oxidation or nitriding, leaving a portion corresponding to the opening portion 25 of the insulating portion. Form 24. At this time, by etching this portion in advance to reduce the thickness to about 1/2, the surface can be made almost flat.

Also, before or after this step, the state of the interface between the opening 26, which will serve as a seed crystal, and the substrate extension 27 is improved by ion implantation or the like. Crystal growth is improved when the interface is dirty.

Further, since the opening 26 is formed by the end face of the insulating film 22 and the end face of the window 25 of the insulating part, for example, one side of the opening 26 is
Even at 0.5 μm, the edges are not round and a rectangular shape is well formed. Such small openings cannot be created using current conventional photolithography;
Usually it becomes a round shape. It is believed that the rectangular opening with such precise corners exhibits an effective relief effect as recognized in grapho-epitaxy, and contributes to the good crystallinity according to the present invention.

Next, an energy beam is irradiated to convert the amorphous or polycrystalline substrate extension 27 into a single crystal.
The beam to be irradiated can be pulsed laser, CW laser,
Any method such as an electron beam, infrared rays, or ultraviolet rays may be used, as long as the energy can be absorbed by the substrate extension portion 27 and melted in a short time. According to studies by the present inventors, the required irradiation energy varies depending on the quality and type of the laminated films, the state of the overlying protective film, etc., and also varies depending on the substrate temperature. However, according to the inventors' study, although there are problems such as instability of the CW-Ar laser annealing equipment and poor reproducibility of the fine laminated structure,
At 300 to 500℃, the incident energy to the board is 3 to 500℃.
11W, and the scanning speed was in the range of 30 mm/sec to 3 m/sec. At this time, the melt width was approximately 30 μm.

The time during which the rectangular substrate extension portion 27 is irradiated with this beam is about 0.01 to 1 msec, and it was found that melting and crystal growth were performed in this short time. Even in pulsed laser annealing or electron beam annealing, it is estimated that if melting and crystal growth are performed in approximately this time, a single crystal with the same quality as the single crystal recrystallized by the above-mentioned CW-Ar laser can be obtained.

Furthermore, as a result of a simple experiment conducted by the present inventors, in order to obtain a good crystal with few crystal defects, the radius of the irradiated beam should be set approximately at the loading area of the substrate extension part 27 extending above the first insulating film 22. It was necessary that the length be greater than 29. This means that the surrounding insulation area 2
This can be understood by considering the heat distribution in the substrate extension portion 27 surrounded by 3 and 24. That is, the seed crystal 28 and the insulating layer 2
The center of the beam is at the boundary between 2 and 2, and even if it is a heat sink, sufficient energy is irradiated.
A portion of the boundary surface of the seed crystal melts and crystal growth begins from within the seed crystal, followed by a uniform uniaxial flow of heat to the heat sink, i.e. perpendicular to the lines of the seed crystal 28. Therefore, it is thought that crystal growth also uniformly proceeds in the opposite direction to the heat flow. If the beam diameter is sufficiently smaller than the window 25 of the insulation, melting will occur in the form of a spot and the heat flow will be directed towards the center of the spot and uniaxiality will be lost. Furthermore, in this case, the substrate extension 27 within the same window 25 is scanned many times, and partial melting and crystal growth are repeated within the same window, resulting in minute differences in crystal orientation. It is understandable that the experimental results show that heating and cooling increase the generation of distortion and defects.

Although the crystallinity of the substrate extension 27 thus obtained is good, considerable thermal stress remains. It is also considered that thermal stress remains between the surrounding insulating film and the surrounding insulating film. To leave this, 700
Annealing at ~1000℃ for about 30 minutes is very effective.

In FIG. 2, the opening 26 is located approximately at the center of the window 25 of the insulating portion, but it goes without saying that it may be located closer to either side. It is also possible, of course, to completely oxidize the recrystallized portion directly above the opening 26 to completely insulate and separate the substrate extension 27 into two. Furthermore, it is clear from the above discussion that even if the recrystallized portion directly above the opening 26 is used as a channel and the substrate extensions 27 extending on both sides are used for the source and drain, a great effect of insulation isolation can be obtained.

The present invention implements the following steps based on the above method. i.e. (100) to (110)
A first insulating film in a strip shape is selectively formed on a single crystal semiconductor substrate having a main surface, leaving a part of the substrate, and a non-single crystal silicon layer is formed on the substrate and the first insulating film. By selectively insulating a part of the silicon layer to form a second insulating film, an island shape with a straight periphery is formed over a part of the substrate and the first insulating film at both ends thereof. A silicon layer is formed, and the peripheral surface of the island-shaped silicon layer is formed to be approximately parallel or perpendicular to the (100) to (110) plane of the substrate, and an energy beam is applied to the silicon layer. Irradiate to crystallize.

Alternatively, the main surface of the substrate may be the (111) plane, and the peripheral surface of the silicon layer may be approximately parallel or perpendicular to the (100) to (211) planes.

Figure 3 shows another example. A first insulating film 32 is formed on a semiconductor substrate 31 by, for example, the LPCVD method. The insulating film 32 is formed into a strip shape as described above.
A polycrystalline layer is further placed on the entire surface, and an insulating section 33 is formed to surround the opening 35 of the insulating section in the same manner as described above. The subsequent steps are the same as the method described above. A feature of this example is that it is relatively easy to form elements in advance under the insulating film 32, so that the area of the semiconductor substrate can be used effectively.

Next, the orientation of the opening and the window of the insulating part in the method of the present invention will be explained using FIGS. 4 and 5.

In the present invention, recrystallization occurs from a seed crystal, so orientation is controlled. However, as mentioned above,
It has a great auxiliary effect as a relief. Therefore, it is natural that a material having a symmetry similar to that of the seed crystal has excellent crystallinity. In FIGS. 4 and 5, an Si crystal having a cubic crystal structure will be explained as an example.
For the sake of simplicity, for example, speaking of (100) plane,
Let the equivalence of 100, 010, 001 refer to any of the three sides. Furthermore, the <110> direction in the figure is a direction perpendicular to the (110) plane in the following explanation.

According to the studies of the present inventors, as shown in two examples in FIG. 4a, when using a substrate whose principal plane is approximately the (100) plane, the rectangular opening 26 in FIG.
And the periphery of the window 25 of the insulation part is in the <110> direction or in the <100> direction, that is, in the (110) plane or in the (100) direction.
The best crystallinity was obtained when each plane was approximately perpendicular to the other. This can be seen especially from the fact that the symmetry of the rectangular opening 26 serving as a relief matches the crystal orientation of the seed crystal.

As shown in FIG. 4b, when using a substrate whose main plane is approximately the (110) plane, the peripheries of the rectangular opening 26 and the window 25 of the insulating part in FIG. 2 are each (100).
Particularly good crystallinity was obtained when the crystallinity was approximately perpendicular or parallel to the (110) plane.

FIG. 5 shows three examples of orientations that have particularly excellent crystallinity when using a substrate whose main plane is approximately the (111) plane. As shown in the figure, in either case, the periphery of the opening 26 in Figure 2 is (110).
It is almost perpendicular or parallel to either the (211) plane or the (211) plane. Among these, the shape with particularly excellent crystallinity is shown in FIG. It was at the time when the

The one shown in FIGS. 5b and 5c consists of a periphery parallel to only one of the (110) and (211) planes, and as can be seen from the figures, it is rhombic. Second
The end of the first insulating layer 22 and the second insulating layer 2 in the figure
The ends of 3 intersect at a 60° angle instead of at a right angle. Therefore, considering the heat flow, the symmetry is slightly broken and there is little uniformity, so it seems that the crystallinity is not very good, but the effect of the relief is large and as a result, it is good. It is thought that it became crystalline. As shown in the above embodiment, since the first and second insulating layers are formed in two parts, this 60 degree angle may be formed sharply.
This seems to be the reason why the relief is so effective. At this time, if the first and second insulating layers are formed at the same time, the edges will naturally become rounded and the relief effect will be lost.

The reason why much better crystals are obtained in the present invention than in conventional bridging epitaxy or seeded beam annealing is due to the relief effect and the crystal growth by the heat flow control introduced by the present invention. It is clear that this is due to control. Moreover, it is an excellent product in which the crystal orientation is accurately controlled.

The following are non-limiting examples of the invention.

Example 1 Using mask A, the first oxide layer (see Fig. 2
2) Width 15 μm, width of seed crystal (Fig. 2 28)
Alternating lines and spaces of 1.5 μm were formed. On top of this, polycrystalline silicon was laminated to a thickness of about 0.5 μm using the LPCVD method. At this time, the substrate temperature was maintained at 500°C. Next, a window with a width of 4 μm and a length of 10 μm, a window with a width of 4 μm and a length of 14 μm, and a window with a width of 4 μm and a length of 10 μm.
Mask B with three different types of 18μm windows
2 to oxidize the polycrystalline portion surrounding the substrate extension 27 as shown in FIG. 2, forming a completely oxidized layer in the arrangement shown in FIG. 4a. The sizes of the obtained windows are approximately 3 × 9 μm, 3 × 13 μm, and 3 ×
It was 17μm. At this time, the lengths of the loading portion (FIG. 2 29) on the first insulating film are approximately 3 μm, 5 μm, and 5 μm, respectively.
It was 7μm.

CW-Ar laser irradiation was continued. The substrate temperature was approximately 350°C, the scanning speed was 30 mm/sec, the laser energy was approximately 5 W, and the width of the melted polycrystalline Si was approximately 25 μm.

The obtained single crystal layer was lightly etched with Seco etchant and then examined with a dark field optical microscope. It was found that single crystallization using the above three types of windows was successfully carried out. However, for the 3 x 17 μm window, which has a loading area that is more than 10 times as thick as 0.5 μm, small crystals on the other side were partially observed at about 2 μm at the edge. In other parts, almost no crystal defects were observed, indicating that the crystal was excellent.

Note that the microcrystalline portion formed at the end is a very small portion, so if this portion is used, for example, as a source, drain, or contact, it is possible to avoid adverse effects due to disordered crystal orientation. Therefore, it has been found that if the crystals are used in this way, the crystals will no longer be of poor quality and cannot be used.

Example 2 A laminated single crystal substrate having a similar structure was created through the same steps as in Example 1. However, at this time,
As a result of rotating mask B by 15 degrees from Example 1, the opening is not rectangular but diamond-shaped. The crystallinity of the obtained substrate extension was good for the 3 x 9 μm window, but was not satisfactory for the other two large windows, and the
Considerable defects and polycrystalline formation were observed from the 4 μm position.

Example 3 The same treatment as in Example 1 was carried out. However, in this example, CW-Ar laser irradiation was performed at approximately 10W and scanning speed.
It was set to 3000mm/sec. The melting width of the polycrystalline silicon at this time was about 30 μm. The crystallinity of the obtained single crystal was almost the same as that of Example 1.

Example 4 The same treatment as in Example 2 was carried out. However, CW-
The Ar laser irradiation was approximately 4 W and the scanning speed was 3000 mm/sec. The melting width of polycrystalline silicon at this time is approximately
It was 20μm. The crystallinity of the obtained single crystal had many defects and many grain boundaries were observed for all windows.

Example 5 The same process as in Example 1 was carried out using a substrate whose main plane was approximately the (111) plane. The arrangement of the windows is in the orientation shown in Figure 5a. The crystallinity of the obtained single crystals was as excellent as in Example 1.

Example 6 The same study as in Example 5 was conducted. However, in this embodiment, the windows were arranged in the orientations shown in FIGS. 5b and 5c. The crystallinity of the obtained single crystals was all quite good, but was somewhat inferior to that of Example 5. However, it was better than that of Example 2.

Example 7 An experiment similar to Example 1 was conducted. However, in this study, polycrystalline silicon was formed using plasma CVD to a thickness of approximately 0.3 μm. The substrate temperature at this time was approximately 320°C.
After further forming an oxide layer window, Si ⁺ was implanted at 5×10 ¹⁵ /cm ² at an acceleration energy of 150 Kev, and electron beam annealing was performed. The irradiation conditions are acceleration energy 5Kev, current 3mA, and substrate temperature.
The temperature was 500°C and the scanning speed was 2000mm/sec. The melting width of the silicon layer at this time was approximately 50 μm. The obtained single crystal layer had almost the same crystallinity as that obtained in Example 1, and it was found that almost the same results could be obtained with a laser beam or an electron beam.

[Brief explanation of drawings]

Figures 1a and b are cross-sectional views showing conventionally manufactured or proposed insulation isolation structures, Figures 2a and b
3 is a cross-sectional view of another semiconductor substrate according to the present invention, and FIGS. 4a and 5 are cross-sectional views of another semiconductor substrate according to the present invention. FIG. 3 is a diagram schematically showing the orientation of an opening and a window of an insulating part in a method of one embodiment. 21, 31...Substrate, 22, 23, 24, 33
... Insulating film, 25 ... Window of insulating section, 26 ... Opening, 27, 37 ... Substrate extension part.

Claims (1)

[Claims] 1. A first insulating film in the form of a strip is selectively formed on a single crystal semiconductor substrate having a (100) to (110) principal surface, leaving a part of the substrate, and A non-single crystal silicon layer is formed on the first insulating film, and a part of the silicon layer is selectively insulated to form a second insulating film, so that a part of the substrate and both ends of the first insulating film are formed. An island-shaped silicon layer with a straight periphery is formed over the insulating film of the substrate, and the peripheral surface of the island-shaped silicon layer is (100) of the substrate.
A method of manufacturing a semiconductor substrate, characterized in that the silicon layer is formed substantially parallel or perpendicular to the (110) plane, and crystallized by irradiating the silicon layer with an energy beam. 2. On a single crystal semiconductor substrate having a (111) main surface,
A strip-shaped first insulating film is selectively formed leaving a part of the substrate, a non-single crystal silicon layer is formed on the substrate and the first insulating film, and a part of the silicon layer is selectively formed. A part of the substrate and both ends of the first insulating film are insulated to form a second insulating film.
An island-shaped silicon layer with a straight periphery is formed over the insulating film, and the peripheral surface of the island-shaped silicon layer is substantially parallel or perpendicular to the (110) or (211) plane of the substrate. Form it so that it becomes
A method for manufacturing a semiconductor substrate, characterized in that the silicon layer is crystallized by irradiating the silicon layer with an energy beam.