JPS6360517A - Forming method single crystal semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain crystal growing means adapted to form a semiconductor element by utilizing the difference of growth rate due to an impurity concentration by providing a high concentration impurity region near a hole including at least part of the hole. CONSTITUTION:A fine high concentration impurity region 26 is formed in an amorphous semiconductor layer 25 over an insulating film 22 from a hole 23. A single crystallization is started from the hole 23, but since the growth rate of the region 26 is high, the crystallization of this region precedes, and a slender single crystal region having the same crystal orientation as a substrate is formed. The crystallization is advanced in two directions from the hole end of the exposed part of the substrate and from the slender region in a region in which an impurity is not doped. In other words, a wide single crystallized region can be obtained in the amount of secondary growth from the region 26. Such a slender high concentration impurity region is formed by a focused ion beam. Thus, a wasteful area for accelerating the crystallization can be eliminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides sQ I (se+n + co
The present invention relates to a method for forming a structure. More specifically, the present invention relates to a novel method for forming SOI fabrication suitable for high integration of semiconductor devices.

[Conventional technology]

A so-called SOI layered single-crystal semiconductor thin film on an insulating film.
(Semiconductor On In5ula
The tor) structure can replace the conventional semiconductor device's p-n junction in a reverse bias state, which achieves electrical isolation, with isolation by an insulator, improving dielectric strength and reducing parasitic capacitance. It is possible to increase the speed of devices by reducing
This is the second most important basic structure in semiconductor devices. This SOI
Methods to realize this structure include methods using melting and recrystallization using energy beams such as lasers and force beams, and methods using solid-phase Evita kinial growth from amorphous 3i at low temperatures. There is. The latter uses an extremely slow crystallization phenomenon at low temperatures, so the SOI formation rate is about 1 person/individual, but since it does not pass through a molten state, the shape controllability of the formed single crystal film is good. In addition, since impurity diffusion does not substantially occur, highly accurate dopant distribution can be realized, and there are many advantages in forming fine elements.

Formation of SOI by this solid phase growth requires a seed crystal aligned in a constant direction in order to control the crystal orientation, and generally the semiconductor substrate itself is used as the seed crystal, as shown in FIG. That is, in FIG. 2(A), an insulating film 22 is provided on a single crystal semiconductor substrate 21, an amorphous semiconductor layer 24 is formed so as to be in contact with the substrate at an opening 23 of the insulating film, and the opening of the insulating film is That is, the exposed portion of the AAA crystal semiconductor substrate was used as 4. When this structure is heated to around 600C for 3i, the amorphous Si forms a welded part 23 with the semi-crystalline substrate.
Then, phase transition occurs to a single crystal, and first, as shown by the arrow in Fig. 2, crystallization progresses in the direction perpendicular to the substrate. Next, single crystallization progresses along the insulating film 22 in nine directions indicated by arrows in FIG.

The size of the single crystallized region obtained by this solid phase growth depends on the rate of solid phase growth and the rate of crystal nucleation in the instep of the amorphous semiconductor layer, and crystal nuclei are generated at a certain temperature. The limit is 3', which can grow at the same phase growth rate at that temperature and time. Fi is usually produced by solid phase growth of Si at about 600C
It is rejected that it is 4 to 5 μm. However, this growth distance is likely to depend on the concentration of impurities; for example, as shown in Fig. 3, the growth distance is 9 x 3 x 102°C! If it is introduced by means such as ion implantation so that the temperature is 1 degree n-3, the growth rate will increase several times, and the single crystal growth distance will also increase several times, without changing the nucleation rate. be able to. This phenomenon is already known. However, it is not possible to fabricate a semiconductor device in a layer into which impurities have been introduced at such a high concentration in the north, and conventional methods have been used, for example, to provide a region in which impurities are not thoroughly introduced in the direction of crystal growth. Therefore, efforts were made to create a portion that would form the active head of a semiconductor device. However, in this method, the SL grows at a size longer than the growth distance when no gold doping is used.
'l region cannot be formed.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a new crystal growth method that is more suitable for forming semiconductor elements such as LSIs while utilizing the difference in growth rate due to the impurity 4 degree.

[Failure to solve the problem]

The invention is based on the fact that crystal growth is accelerated by impurities and that the crystallization seeds can be small.

[Effect]

This will be explained using FIG. First, as shown in FIG. 1(a), a thin high concentration impurity region 26 is provided in the amorphous semiconductor layer 24 from the opening 23 to the insulating film 22. Single crystallization starts from the opening 23 as in the conventional method, but since the growth rate of the high concentration impurity region 26 is fast,
As shown in Figure 2, crystallization in this region precedes the formation of an elongated single crystal region having the same crystal orientation as the substrate. In the region not doped with impurities, single crystallization progresses at a slow growth rate, but crystallization progresses from two directions: from the open end of the exposed portion of the substrate and from the above-mentioned elongated single crystal region. That is, it is possible to obtain a single crystallized region that is wider by the amount of secondary growth from the thin high concentration region 26. The high concentration region 26 does not need to be wide, and may be thin as long as it can lead to single crystallization, and for the purpose of effectively forming a semiconductor element on SOI, the more the better. Although such an elongated high concentration impurity region can be formed by known phosphorography and ion implantation, it can be formed more easily by using a focused ion beam.

Although the above explanation is about the case where there is a single high concentration region, a plurality of high concentration regions may be formed. This effect will be discussed later.

〔Example〕

Examples of the present invention will be shown below.

FIG. 1 used in the above description is an example of application of the present invention.

The substrate 21 is made of pcedar (100) and 10Ω Si.
An oxide film 22 with a thickness of 5 Qnm was formed by thermal oxidation at 1000C, and a pattern having striped openings 23 with a width of 2 μm was formed by photolithography. Then, after surface cleaning, 8000
, After 30 minutes of heat treatment, lower the substrate temperature to 2000℃,
A 0.3 μm amorphous Si film 24 was formed by electron beam evaporation. After heat treatment at 350C in vacuum for 1 hour, it was taken out into the air, photoresist was applied, a slit with a width of 2 μm perpendicular to the above-mentioned striped opening was formed by etching, and 2×10 phosphorus was ion-implanted at 60 KeV. "crn-2, 3X 10 at 130KeV"
cm-" was implanted to form a high-concentration region 26. After removing the resist '2, this was heat-treated at 600C in a nitrogen atmosphere for 8 hours, and crystal growth of approximately 20 μm was observed in the high-concentration region. Secondary single crystal growth with a width of 2.5 μm was observed on both sides of the high concentration region.Single crystal growth was also observed with a width of about 5 μm from the edge of the striped opening of the oxide film.

Similarly, after forming an amorphous Si layer of 0.3 μm, a focused phosphorus ion beam focused to a diameter of about 0.2 μm was scanned in a direction perpendicular to the oxide film stripe at 160 KeV.

Phosphorus ions were implanted at a line dose of I x 10"cm-' to form a highly concentrated impurity region 26 with an extremely fine line. When this was heat-treated in a nitrogen atmosphere for 600 tll' for 8 hours, phosphorus ions were implanted along the scanned line. width 3~1
A single crystalline region of 0 μm was obtained over a length of 15 μm.

Next, an example will be described in which a plurality of high concentration regions are provided close to each other.

FIG. 4 shows that an oxide film 22 having stripe-shaped openings 23 is formed on a single crystal substrate 21 in the same manner as described above, and an amorphous 8
A structure in which one layer 24 is formed is shown.

The difference from the above example is that linearly provided high concentration impurity regions 26 and 26' are provided at an interval of 6 μm, and K here only shows a part thereof. The narrower the width of the high concentration region, the wider the device formation area, but in general photolithography, the width is about 1 μm. By using a focused ion beam, it is possible to form a narrower high concentration region. Figure 5 is a plan view showing the state of solid phase growth, where (a) shows the early stage of growth and (b) shows the middle stage of growth. Single crystallization begins independently while forming (111) facets in the high concentration region 26.26'.As single crystallization progresses in the high concentration region, the single crystallized portion is then seeded. Then, single crystallization begins in the non-doped region in a direction perpendicular to the direction of single crystallization in the high concentration region, and eventually these regions collide to form a grain boundary 27. This grain boundary 27 has a small inclination angle. This is a grain boundary and is formed near the center between the striped high concentration regions.Crystallization progresses further while maintaining this state, and eventually polycrystalline nuclei are generated and the expansion of the single crystal region stops. Between the high concentration regions, a single crystal having a small tilt grain boundary approximately in the center is obtained in an area of 6 μm×10 μm.

Note that if the interval between the high concentration regions exceeds 10 μm, a region that is not single crystallized remains near the center, so it is desirable that the interval between the high concentration regions is 10 μm or less.

Next, another example utilizing this growth will be described.

In FIG. 6, amorphous Si 24 is formed on a fully formed Si substrate 21 having an island-shaped opening 23, and phosphorus is linearly implanted thereon using a focused ion beam 28.
The figure shows how high concentration regions 26, 26', 26'', etc. are formed. is 18μ
It is m. The spot diameter of the focused ion beam is 0.2 μm, and the phosphorus ion is
It is inserted at μml￥0 intervals.

FIG. 7 shows the shape of the crystal subgrain boundary 27 after solid phase growth. High concentration area 26.26'.

26" etc. are almost single-crystalline, and the shape of regular crystal sub-grain boundaries is observed. For example, if these crystal sub-grain boundaries are included in the active region of a device such as a MO8FET channel region, the device characteristics will be affected. Therefore, in this example, we avoided the sub-grain boundary and
The elements are arranged with a region 29 having a length of 10 μm and a length of 10 μm as an operating region. Furthermore, regions that require high concentration doping due to the structure of the device, such as source/drain regions, are arranged so as to overlap with the high concentration region 26 etc. formed by the focused ion beam.
Care was taken not to waste area for the purpose of crystallization. In addition, if electrical continuity via the high concentration region 26 etc. due to the focused ion beam causes problems in the circuit configuration,
Naturally, this high concentration region on the oxide film was cut by etching or oxidation.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to single-crystallize high-purity amorphous Si, which has a slow crystal growth rate, beyond its growth limit, and realize an expanded SOI structure. By providing a high concentration region of ultra-fine wires using the method described above, it is possible to substantially eliminate wasted area for promoting crystallization.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a bird W & showing an embodiment of the present invention, Fig. 2 is a cross-sectional view of a bird W & showing solid phase growth using the conventional method, Fig. 3 is data showing expansion of the solid phase growth region by doping, FIG. 4 is a detailed cross-sectional view showing another embodiment of the present invention, FIG. 5 is a plan view showing solid phase growth in the structure of FIG. 4, and FIG. 6 is a schematic cross-sectional view of another embodiment of the present invention. 7 is a plan view showing the structure of FIG. 6 after solid phase growth. 21...≠crystalline semiconductor substrate, 22... oxide film, 23
... Oxide film opening (substrate exposed part), 24 ... Amorphous Si layer, 25 ... Solid phase growth region, 26 ... High concentration impurity region, 27 ... Crystal subgrain boundary, 28... Focusing line, 29... Arrangement position of the operating region of the element. Agent: Patent attorney Katsuma Ogawa'. (A) Z3 Aiguchi Figure 1 (B) 25 4 Sensei & I, and the name of the delivery. ■Z Diagram (In Tomi 3 Diagram Heat or Rikanoma (Kanawa Vine) 4 Diagram Z1 Fulong Crystal Unson 4 Substrates 22 Luxurious Membrane Z3 Trowel M Opening Shu 24 Amorphous Hand Il Fuji 5 Diagram (b) Z3 Drunken and Moon-5M40 Part 27 Kakei Akiyoshi

Claims (1)

[Claims] 1. A method for forming a single crystal semiconductor thin film, in which an amorphous semiconductor thin film deposited on a single crystal semiconductor substrate through an insulating film having an opening is successively single-crystallized from the opening, A method for forming a single crystal semiconductor thin film, characterized in that a high concentration impurity region is provided in a region adjacent to the opening including at least a portion of the opening. 2. In the method for forming a single crystal semiconductor thin film as described in claim 1, the high concentration impurity region is used as the wiring region of the semiconductor element, and at least a part of the single crystallized portion of the other region is used as the operating area of the semiconductor element. 1. A method for forming a single crystal semiconductor thin film, which comprises arranging an opening and a high concentration impurity region, as used in the invention. 3. A method for forming a quasi-crystalline semiconductor thin film according to claim 1, characterized in that the high concentration impurity region is formed by drawing with a focused ion beam. 4. The method for forming a single crystal semiconductor thin film according to claim 1, characterized in that a plurality of high concentration regions are formed in a linear shape with a width of 1 μm or less, with an interval not exceeding 10 μm. A method for forming a single crystal semiconductor thin film.