CN104681430A - Preparation method for improving tensile strain of germanium film - Google Patents

Abstract

The invention discloses a preparation method for improving the tensile strain of a germanium film. The preparation method comprises the following steps: (1) preparing materials; (2) performing annealing; (3) performing cooling treatment; (4) taking out comprehensive germanium film materials. According to the preparation method disclosed by the invention, annealing and cooling treatment are performed on germanium materials, so that an appropriate amount of tensile strain can be obtained, the thickness of the germanium film is not limited, and the germanium film has the characteristics of being simple in technology, easy to realize, low in preparation cost, suitable for mass production and the like. The preparation method can be used for the preparation technology processes of germanium channel MOSFET devices and germanium optoelectronic devices, and is compatible with a silicon-based CMOS (complementary metal-oxide-semiconductor transistor) technology.

Description

A kind of preparation method improving germanium film tensile strain

Technical field

The invention belongs to Material Field, relate to a kind of preparation method improving germanium film tensile strain.

Background technology

Be that the microelectric technique indicated has played important effect in the development of information industry with silicon.But along with improving constantly of integrated circuit integrated level, the size of electronic devices and components will be more and more less, and microelectric technique will be faced with the problems such as heat dissipation problem is serious, power consumption is large, technology difficulty is large.Therefore we need a kind of of new generation silica-base material compatible mutually with silicon technology of searching and technology to further develop integrated circuit.

Germanium material has the carrier mobility higher than silicon materials, is one of ideal material preparing high-speed microelectronic and opto-electronic device; The manufacture craft of germanium device is not only completely compatible with silicon CMOS technology, and cost of manufacture is low, and therefore, the exploitation of germanium material obtains the extensive concern of domestic and international expert.

Compared to traditional germanium material, tensile strain germanium material has more advantage, and application prospect is more wide.Such as: in preparation Ge MOSFET element, suitably in Ge material, introduce tensile strain, the mobility of its charge carrier can be improved further, thus improve the performance of device; In opto-electronic device, tensile strain Ge material can improve the direct band gap luminous efficiency of Ge, thus for the preparation of the gain media of laser.Therefore, the preparation of tensile strain Ge material can promote advancing of microelectronic technology and photoelectron technology greatly.

At present, the method improving germanium material tensile strain mainly contains following several: a kind of method is epitaxial growth Ge material on a si substrate, epitaxial growth temperature is 500 DEG C ~ 800 DEG C, when temperature is reduced to room temperature, the tensile strain being about 0.25% can be introduced in germanium, the method is the tensile strain naturally introduced in epitaxial growth Ge materials process, and its tensile strain value is smaller.Another kind method is by applying mechanical stress to improve its tensile strain on Ge thin-film material, and these class methods cannot be compatible with silicon CMOS technology, is unfavorable for the production in enormous quantities of chip.In addition, the In of content gradually variational can also be utilized on gaas substrates _xga _1-xas buffer layer technique epitaxial growth Ge material, obtains the Ge material of tensile strain, but owing to being subject to the restriction of Ge critical thickness, the Ge that the method obtains is thinner, be about about 10nm, and the method and existing silicon CMOS technology are not compatible mutually, are unfavorable for producing in enormous quantities.We can find out thus, and the method for existing raising germanium film tensile strain all exists process conditions and requires high, complex technical process, is difficult to and the traditional silicon CMOS technology shortcoming such as compatible mutually.

Summary of the invention

The invention provides a kind of preparation method improving germanium film tensile strain for overcoming the problems referred to above, with traditional silicon CMOS technology is compatible mutually and technique preparation process simple, can effectively can improve the method for germanium film tensile strain.

Technical scheme of the present invention is for achieving the above object:

Improve a preparation method for germanium film tensile strain, comprise the steps:

Step one) prepare material: prepare a kind of germanium film compound material, described germanium film compound material comprises germanium film and non-germanium base material, described germanium film growth is on non-germanium base material, and the thermal coefficient of expansion of germanium film is different from the thermal coefficient of expansion of non-germanium base material;

Step 2) annealing: germanium film compound material is put into annealing furnace and anneals in atmosphere of inert gases, described annealing temperature >=300 DEG C and lower than the fusing point of germanium and non-germanium base material, annealing time is >=10 minutes;

Step 3) cooling processing: cool under the germanium film compound material after annealing is placed in 77K ~ 300K temperature, cooling time >=10 minutes;

Step 4) take out germanium film compound material.

Further improvement, described step one) in, germanium film compound material is germanium film on silicon base Epitaxial growth germanium film or insulating barrier.

Further improvement, described step 3) in, the germanium film compound material after annealing is placed in the thermos cup that liquid nitrogen is housed, and described thermos cup is the cooling device with temperature control system.

The present invention anneals and cooling processing to germanium material, just can obtain a certain amount of tensile strain, not limit the thickness of germanium film, and have technique simple, easily realize, preparation cost is low, is applicable to the features such as production in enormous quantities.Described preparation method may be used in germanium trench MOSFET device and germanium opto-electronic device preparation technology flow process, mutually compatible with silicon base CMOS technique.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described:

A kind of preparation method's schematic flow sheet improving germanium film tensile strain of Fig. 1;

The tensile strain that in Fig. 2 embodiment 1, germanium film produces and the relation schematic diagram of annealing temperature.

Embodiment:

Embodiment 1

Preparation method's flow chart of germanium film tensile strain is improved as Fig. 1 is a kind of.First prepared silicon substrate Epitaxial growth germanium film material: be that the germanium film that chemical vapor deposition system grows one deck 0.5 μm is put in the Si substrate of the No clean of 800 μm by thickness; Then take out silicon base Epitaxial growth germanium film material, it is put into the annealing furnace being filled with nitrogen, annealing furnace temperature is set to 800 DEG C, and annealing time is set to 20 minutes; Annealing terminates rapidly silicon base Epitaxial growth germanium film material to be taken out the thermos cup cooling 20 minutes of putting into and liquid nitrogen being housed afterwards; Then silicon base Epitaxial growth germanium film material is taken out.Because germanium material is different from the thermal coefficient of expansion of Si material, to the silicon base Epitaxial growth germanium film material of 0.4% tensile strain be obtained after being cooled to 77K by high annealing, than directly on a silicon substrate epitaxial growth Ge obtain 0.25% tensile strain improve 1.6 times.

When silicon base Epitaxial growth germanium film material is put into anneal, germanium material when high temperature is in the state of complete relaxation, annealing terminate rear rapidly material is put into liquid nitrogen environment under cool, from High-temperature cooling to liquid nitrogen (temperature is 77K) process in, because the thermal coefficient of expansion of place's germanium is at the same temperature all large than silicon, therefore the degree that during cooling, the parallel lattice of germanium shrinks will be larger than silicon, but due to the inhibition of base silicon, the parallel lattice of germanium shrinks and will be restricted, show the state be stretched, thus make the parallel lattice cooling rear germanium larger than the parallel lattice of body germanium, namely in germanium film, tensile strain is created.

The thermal vibration that is main and material of thermal coefficient of expansion due to material is closely related, and along with the reduction of temperature, material thermal vibration weakens, thus causes thermal coefficient of expansion to reduce, and that is, the thermal coefficient of expansion of material and the temperature of environment are closely-related.The thermal coefficient of expansion of germanium and silicon materials and the relation of temperature can use formula (1), (2) describe:

α _Ge(T)＝6.050x10 ^-6+3.600x10 ^-9T-0.350x10 ^-12T ²(K ^-1) (1)

α _Si(T)＝[3.725x(1-e ^{[-5.88x10-3(T+149.15)]})+5.548x10 ^-4T]x10 ^-6(K ^-1) (2)

The tensile strain produced for the germanium film under being cooled to low-temperature condition from the condition of high temperature can represent with formula (3), (4): $e_P=\left(\frac{1}{r}\right)\frac{(Y_{\mathrm{Ge}}{h}_{\mathrm{Ge}}^3+Y_{\mathrm{Si}}{h}_{\mathrm{Si}}^3)}{6Y_{\mathrm{Ge}}{h}_{\mathrm{Ge}}(h_{\mathrm{Ge}}+h_{\mathrm{Si}})}---\left(3\right)$

$\frac{1}{r}=\frac{{6Y}_{\mathrm{Ge}}{Y}_{\mathrm{Si}}{h}_{\mathrm{Ge}}{h}_{\mathrm{Si}}(h_{\mathrm{Ge}}+h_{\mathrm{Si}})\underset{T_L}{\overset{T_H}{\∫}}[{\mathrm{\α}}_{\mathrm{Ge}}\left(T\right)-{\mathrm{\α}}_{\mathrm{Si}}\left(T\right)]\mathrm{dT}}{3Y_{\mathrm{Ge}}{Y}_{\mathrm{Si}}{h}_{\mathrm{Ge}}{h}_{\mathrm{Si}}{(h_{\mathrm{Ge}}+h_{\mathrm{Si}})}^2+(Y_{\mathrm{Ge}}{h}_{\mathrm{Ge}}+Y_{\mathrm{Si}}{h}_{\mathrm{Si}})(Y_{\mathrm{Ge}}{h}_{\mathrm{Ge}}^3+Y_{\mathrm{Si}}{h}_{\mathrm{Si}}^3)}---\left(4\right)$

Wherein Y _ge=102.1GPa, Y _si=130.4GPa, is respectively the Young's modulus size of germanium and silicon, h _ge, h _sibe respectively the thickness of epitaxially grown germanium material and silicon substrate material.The relation of the tensile strain that germanium film produces and annealing temperature as shown in Figure 2.

In the present embodiment, the thickness of silicon base and germanium material is respectively 800 μm and 0.5 μm, when annealing temperature is 1073K (namely 800 DEG C), under being then cooled to liquid nitrogen environment, (77K) can obtain the germanium film being about 0.4% tensile strain, than directly on a silicon substrate epitaxial growth Ge obtain 0.25% tensile strain improve 1.6 times.Prepare tensile strain germanium film by the method not only easy to be mutually integrated with ripe silicon base CMOS technique, and it is simple to have technique, preparation cost is low, reduces production difficulty, is applicable to the advantages such as production in enormous quantities.

Embodiment 2

A kind of preparation method improving germanium film tensile strain: prepare germanium film material on insulating barrier: on described insulating barrier germanium film material Si substrate on have the SiO of one deck 1.2 μm ₂material, SiO ₂material there is the germanium film of one deck 0.1 μm.It is put into the annealing furnace being filled with nitrogen, annealing furnace temperature is set to 850 DEG C, and annealing time is set to 20 minutes; Annealing terminates rapidly germanium film material on insulating barrier to be taken out the thermos cup cooling 20 minutes of putting into and liquid nitrogen being housed afterwards; Then germanium film material on insulating barrier is taken out.Because germanium material is different from the thermal coefficient of expansion of Si material, to the silicon base Epitaxial growth germanium film material of 0.5% tensile strain be obtained after being cooled to 77K by high annealing, than directly on a silicon substrate epitaxial growth Ge obtain 0.25% tensile strain improve 2 times.

Embodiment 3

A kind of preparation method improving germanium film tensile strain: prepare germanium film material on insulating barrier: the SiO having one deck 500 μm of germanium film material on described insulating barrier ₂material, SiO ₂material there is the germanium film of one deck 0.2 μm.It is put into the annealing furnace being filled with nitrogen, annealing furnace temperature is set to 600 DEG C, and annealing time is set to 10 minutes; Annealing terminates rapidly germanium film material on insulating barrier to be taken out the thermos cup cooling 10 minutes of putting into and liquid nitrogen being housed afterwards; Then germanium film material on insulating barrier is taken out.Because germanium material is different from the thermal coefficient of expansion of Si material, to the silicon base Epitaxial growth germanium film material of 0.35% tensile strain be obtained after being cooled to 300K by high annealing, than directly on a silicon substrate epitaxial growth Ge obtain 0.25% tensile strain improve 1.4 times.

Embodiment 4

A kind of preparation method improving germanium film tensile strain: prepare germanium film material on insulating barrier: on described insulating barrier germanium film material Si substrate on have the SiO of one deck 800 μm ₂material, SiO ₂material there is the germanium film of one deck 0.2 μm.It is put into the annealing furnace being filled with nitrogen, annealing furnace temperature is set to 900 DEG C, and annealing time is set to 30 minutes; Annealing terminates rapidly germanium film material on insulating barrier to be taken out the thermos cup cooling 30 minutes of putting into and liquid nitrogen being housed afterwards; Then germanium film material on insulating barrier is taken out.Because germanium material is different from the thermal coefficient of expansion of Si material, to the silicon base Epitaxial growth germanium film material of 0.61% tensile strain be obtained after being cooled to 200K by high annealing, than directly on a silicon substrate epitaxial growth Ge obtain 0.25% tensile strain improve 2.4 times.

The above embodiment is only that the preferred embodiment of the present invention is described; not scope of the present invention is limited; under not departing from the present invention and designing the prerequisite of spirit; the various distortion that those of ordinary skill in the art make technical scheme of the present invention and improvement, all should fall in protection range that claims of the present invention determine.

Claims (3)

1. improve a preparation method for germanium film tensile strain, it is characterized in that, comprise the steps:

Step one) prepare material: prepare a kind of germanium film compound material, described germanium film compound material comprises germanium film and non-germanium base material, described germanium film growth is on non-germanium base material, and the thermal coefficient of expansion of germanium film is different from the thermal coefficient of expansion of non-germanium base material;

Step 2) annealing: germanium film compound material is put into annealing furnace and anneals in atmosphere of inert gases, described annealing temperature >=300 DEG C and lower than the fusing point of germanium and non-germanium base material, annealing time >=10 minute;

Step 3) cooling processing: cool under the germanium film compound material after annealing is placed in 77K ~ 300K temperature, cooling time >=10 minutes;

Step 4) take out germanium film compound material.

2. the as claimed in claim 1 preparation method improving germanium film tensile strain, is characterized in that, described step one) in, germanium film compound material is germanium film on silicon base Epitaxial growth germanium film or insulating barrier.

3. the germanium film that improves as claimed in claim 1 is by the preparation method of tensile strain, it is characterized in that, described step 3) in, the germanium film compound material after annealing is placed in the thermos cup that liquid nitrogen is housed, and described thermos cup is the cooling device with temperature control system.