JPH0758049A - Method of introduction of hydrogen atom into silicon substrate - Google Patents

Abstract

PURPOSE:To obtain maximum concentration of H gas in a short time by introducing H atoms without causing any damage on the surface of an Si wafer by introducing the H gas into the Si wafer by joining an Si layer containing H atoms to the Si wafer and heating the same. CONSTITUTION:H2 is employed as a carrier and monosilane is employed as reaction gas, and a hydrogenated amorphous Si layer 8 is grown by about 5mum on the surface and the back surface of the Si wafer using a plasma CVD process. Then, the sample is annealed in the Ar atmosphere to diffuse H atoms over the entire region, and thereafter it is gradually cooled to about 100 deg.C to inactivate an acceptor and then the sample is quickly cooled to room temperature for keeping the state. Hereby, H atoms are introduced without damaging in the Si wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for introducing hydrogen atoms without damaging the surface of a silicon substrate (hereinafter referred to as Si wafer).

Silicon (hereinafter referred to as Si) is a typical single semiconductor, and an integrated circuit such as an IC or an LSI is made by using this. That is, an ingot made of Si single crystal is made by the pulling method (Czochralski method) and
After slicing to a thickness of around 500 μm, polishing and making a wafer, various devices are formed on this wafer by using thin film forming technology, photolithography technology (photolithography), impurity element implantation technology, etc. . Here, the Si single crystal produced by the pulling method is extremely high in purity.
An impurity element is selectively introduced into a Si wafer to form an n-type or p-type semiconductor region, and device formation is performed using this semiconductor region. There are active and inactive.

Here, the active element is an element which exists in the Si crystal and forms a donor level or an acceptor level, and the inactive element is oxygen (O) or nitrogen (N). It is an element that is difficult to ionize. The O element is Si
Since the crucible used for pulling the single crystal is made of quartz (SiO ₂ ) and the partial pressure of O ₂ gas in the atmosphere is high, about 10 ¹⁸ atoms / cm ³ is contained in the crystal. When this content is high, precipitates are generated when the wafer is heat-treated, and secondary defects such as stacking faults and transitions occur around it, degrading the quality. The amount of O contained therein is measured.

Next, hydrogen (H) atoms easily diffuse in the Si single crystal, interact with impurity atoms contained in the single crystal to form a complex, and easily react with crystal defects. It has a feature called. That is, although an impurity element is often intentionally introduced into a high-purity Si crystal to form a semiconductor region, an H atom forms a complex with these impurity atoms to change electrical properties. It is known that there is a property of causing it, and that the introduction of H atom has a property of accelerating the diffusion of O atom existing in the Si crystal and deteriorating the mechanical property of the Si single crystal. Therefore, if H atoms can be introduced into the Si single crystal with good controllability, various properties including electrical properties can be controlled.

[0005]

2. Description of the Related Art As described above, in forming a semiconductor device, an impurity atom is intentionally introduced into a Si wafer to form a semiconductor region, and the H atom is combined with the contained impurity atom. Body formation is used to control electrical properties.

Heretofore, the introduction of H atoms into a Si wafer has mainly been performed by using a plasma generator or an ion implanter. FIG. 4 is a configuration diagram showing a method of introducing H atoms by plasma. A Si wafer 1 is placed on a graphite susceptor 2 and placed in a quartz tube 4 equipped with a second induction coil 3. Then, the exhaust system of the plasma generator is operated to evacuate the inside of the quartz tube 4 to a high vacuum. Next, hydrogen gas (H ₂ ) is supplied at 10 ³ cm / min through a needle valve (not shown).
The gas is evacuated while being supplied at a flow rate of about 3 to maintain the degree of vacuum in the quartz tube 4 at 0.1 to 0.3 torr, and by applying high frequency power of 13.65 MHz to the first induction coil 5, H ₂ gas is supplied. Turn into plasma.

On the other hand, the second induction coil 3 has, for example, 440
Applying KHz power to the Si wafer 1 through the susceptor 2
When heated to 0 to 400 ° C., H ions are introduced by attaching H ions generated by plasmaization. In addition, the ion implantation method is performed after ionizing the target element (H _{2 in} this case) in a vacuum, and then 50 to 500 KeV
It is introduced by giving the energy of the and making it collide with the substrate (Si wafer).

However, according to these methods, damage such as stacking faults and dislocations is likely to occur on the surface of the Si crystal. There is no problem if the depth of introducing H atoms is as shallow as 1 to 2 μm, or if the H concentration is low, but if the depth of the region where H atoms are introduced reaches several hundreds of μm or high concentration is introduced. In that case, there is a problem that it takes a long time to introduce and the damage on the crystal surface increases.

[0009]

The introduction of H atoms in order to adjust the electrical behavior of impurity atoms contained in a Si wafer is generally carried out by using a plasma generator or an ion implanter. It is a method. However, these methods tend to cause damage to the Si crystal, and require long-time treatment when the introduction depth is large, and a plasma generator when high-concentration introduction is required. Since it is difficult to increase the partial pressure of H ₂ , it is difficult to increase the maximum concentration of H atoms. Therefore, the problem is to solve these problems.

[0010]

The above problem is that the introduction of H atoms into a Si substrate is performed by growing a Si layer containing H, for example, hydrogenated amorphous silicon, hydrogenated polysilicon or H ₂ atmosphere in the Si substrate. This can be solved by introducing H atoms into the Si wafer, which is characterized in that the formed Si is bonded and heated.

[0011]

In the present invention, a solid containing H atoms of 10 ¹³ / cm ³ or more is used as Si.
Bonded to a wafer in which a diffusion source of H atoms, is intended to diffuse the H atoms in the Si wafer by only annealing (annealing) time required at a suitable temperature, 10 ¹³ /
The reason why it is limited to ³ cm ³ or more is that the concentration of impurities that normally affect the device characteristics is higher than this, and therefore the H atom concentration must also be higher than this.

Here, the introduction depth and concentration of H atoms into the Si wafer can be adjusted by the annealing temperature, the thickness of the solid containing H atoms, the H atom concentration in the solid, and the like. Then, if necessary, the solid finally used as the diffusion source is removed by means such as etching.

[0013]

[Examples] O atoms contained in a Si wafer exist in the form of interstitial atoms, and the presence of these O atoms causes oxygen precipitates, secondary stacking faults, and dislocation formation. , O
The measurement of concentration is one of the important items in the evaluation of crystals.

There is no problem if the content of the active impurity atoms forming the donor level and the acceptor level is small, but a low resistance containing active impurity atoms of 10 ¹⁷ atoms / cm ³ or more is obtained. When measuring the O atom concentration of a Si wafer using an infrared spectrophotometer, a large number of free carriers are generated by active impurity atoms. Accurate measurement is not possible because it overlaps with the peak (1136 cm ^-1 ), and especially when the concentration of active impurities is high, the infrared absorption due to impurity atoms completely obscures the absorption peak due to vibration of interstitial O atoms Can not.

Therefore, if H atoms are introduced into the Si wafer to inactivate active impurity atoms, the peak intensity of infrared absorption of O atoms can be measured. Hereinafter, an example in which the H atom introduction method of the present invention is applied to this inactivation will be described. Example 1 (using hydrogenated amorphous Si, see FIG. 1) The Si wafer 7 used for measurement had a thickness of 500 μm and contained boron (B) atoms at a concentration of 10 ¹⁹ atoms / cm ^3. There is.
(A in the same figure) As a method for measuring the concentration of interstitial O contained in the Si wafer 7, monosilane (SiH ₄ ) is used as a reaction gas with H ₂ as a reaction gas, and the temperature is 400 ° C. at a vacuum degree of 0.1 to 1 torr. Hydrogenated amorphous on the front and back by the following plasma CVD method
The Si layer 8 was grown to a thickness of 5 μm. The hydrogenated amorphous Si layer 8 thus produced contains H atoms in an amount of about 10% of the total number of atoms, which is a sufficient amount to inactivate B atoms. Next, this sample in Ar atmosphere
After annealing at 400 ℃ for 40 hours to diffuse H atoms all over the Si wafer, it is slowly cooled to 100 ℃ to inactivate the acceptor. Quenched in 2 minutes. (The above B in the same figure) Next, the amorphous Si layer 8 was dissolved and removed by immersion in a mixed solution of hydrofluoric acid (HF) and nitric acid (HNO ₃ ). (As shown in the same figure C) As a result of investigating the infrared absorption of the Si wafer 7 thus processed using an infrared spectrophotometer, the infrared absorption intensity of O atom is accurately measured without being affected by the impurity atom. We were able to. Example 2 (using poly-Si, see FIG. 2) The Si wafer 7 used for measurement has a thickness of 500 μm.
(A in the same figure) As a method for measuring the concentration of interstitial O contained in the Si wafer 7, the Si wafer is used at a vacuum degree of 0.1 to several torr using H ₂ as a carrier and monosilane (SiH ₄ ) as a reaction gas. 7
Polycarbonate is applied to the surface by the low pressure CVD method of heating at 550 to 650 ℃
Si9 was grown to a thickness of 0.5 μm. The poly-Si9 thus produced contains H atoms in an amount of several percent of the total number of atoms. Next, this sample was annealed at 900 ° C. for 90 minutes in an Ar atmosphere to diffuse H atoms all over the Si wafer, then gradually cooled to 450 ° C., and then cooled to room temperature.
As a result, deep impurity levels were inactivated due to the transition metal impurities that penetrated into the Si wafer as contamination during the semiconductor manufacturing process. (Above figure B) Next, the amorphous Si layer 8 was immersed in a mixed solution of HF and HNO _3.
Was removed by dissolution. As a result, it was possible to eliminate the adverse effect of the transition metal impurities on the electrical characteristics of the crystal. Example 3: (Using Si grown in H ₂ atmosphere, see FIG. 3) The Si wafer 10 used for measurement has a thickness of 300 μm.
(A in the same figure above) Another Si wafer 11 grown in an H ₂ atmosphere was bonded to this Si wafer 10. The thickness of the Si wafer 11 is 500
μm, and the surfaces of the two Si wafers 10 and 11 are mirror-like, but they are superposed and 850 ° C in Ar atmosphere.
After placing it on the heater that has been heated to 1 minute to temporarily bond it and then heat it at 1100 ° C for 30 minutes, two Si wafers 1
0 and 11 were completely bonded, but during this bonding process, H
Atomic diffusion occurs, and the H atoms in the Si wafer 11 become Si.
It has diffused to the back surface of the wafer 10.

Next, by cooling this sample to room temperature, a deep impurity level was inactivated due to a transition metal impurity that entered the Si wafer as a contaminant during the semiconductor manufacturing process. (Above figure B)

[0017]

According to the present invention, H atoms can be introduced without damaging the Si wafer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method for carrying out the present invention.

FIG. 2 is another cross-sectional view showing a method for carrying out the present invention.

FIG. 3 is yet another cross-sectional view showing a method for carrying out the present invention.

FIG. 4 is a configuration diagram showing introduction of H atoms by plasma.

[Explanation of symbols]

 1, 7, 10, 11 Si wafer 8 Hydrogenated amorphous Si layer 9 Poly Si

Claims (2)

[Claims] 1. A method for introducing hydrogen atoms into a silicon substrate, wherein the introduction of hydrogen atoms into the silicon substrate is performed by bonding a silicon layer containing hydrogen to the silicon substrate and heating. 2. The hydrogen for the silicon substrate according to claim 1, wherein the silicon containing hydrogen is any one of hydrogenated amorphous silicon, hydrogenated polysilicon, and silicon grown in a hydrogen atmosphere. How to introduce atoms.