JP3106197B2 - Method for manufacturing high resistance compound semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to OEIC, HEMT,
The present invention relates to a method for manufacturing a high-resistance compound semiconductor used for an electronic device such as an ion-implanted FET, and more particularly to a technique for increasing resistance by heat treatment.

[0002]

2. Description of the Related Art A group III-V compound semiconductor having a resistivity of 10 ⁶
For increasing the resistance to Ω · cm or more (ie, semi-insulating), in the case of a crystal containing Si or S as a shallow donor, a method of adding Fe, Co or Cr as a deep acceptor is industrially used. Have been. This increase in resistance is due to a mechanism that compensates for a shallow donor with a deep acceptor. Therefore, it is said that the resistance cannot be increased unless an element serving as a deep acceptor is added so as to be higher than the concentration of a shallow donor contained in the crystal.

However, when the resistance is increased by doping with Fe, Co, Cr or the like, it is desirable that their concentrations be as low as possible. Because Fe, Co, Cr, etc.
Since it acts as a deep acceptor, it lowers the activation rate of ion-implanted shallow donor-type impurities in an ion-implanted electronic device (such as an FET), and epitaxially grows in a device operated at a high frequency (such as an OEIC or HEMT). This is because these elements diffuse into the film and act as traps to hinder high frequency and high speed. Further, these elements such as Fe are easily segregated, and the concentration of Fe and the like is different between the upper and lower portions of the crystal, so that the above-mentioned activation rate is not uniform, and the yield is reduced.

Conventionally, for example, as semi-insulating InP, F
e-doped InP is mainly used. But F
If the concentration of e is less than 0.2 ppmw, the resistivity becomes 10%.
It will be lower than ⁶ Ω · cm, and the semi-insulating property will be reduced. In order to make this a semi-insulating crystal, the concentration of Fe or the like had to be higher than a certain concentration (0.2 ppmw). In general, the lower the concentration of Fe, Cr, etc. in a III-V compound semiconductor, the lower the resistivity is,
It has been considered that the impurity element serving as a shallow donor exists in the crystal as a residual impurity up to that level. However, the present inventor believes that the mechanism of increasing the resistance of the InP single crystal involves not only compensation by a shallow donor and a deep acceptor, but also an electrically active point defect. By controlling the concentration of point defects by heat-treating the crystal, it has been found that a semi-insulating III-V compound semiconductor can be obtained even if the impurity element concentration of the deep acceptor is much lower than the conventional one. .

Accordingly, the present inventor has previously determined that the total concentration of any one or more of Fe, Co and Cr is 0.2 ppmw.
The present invention has proposed a technique for manufacturing a compound semiconductor having a resistivity of 10 ⁷ Ω · cm or more (Japanese Patent Laid-Open No. 2-69307).
issue). That is, as shown in FIG. 1, an InP wafer (compound semiconductor) 1 cut from a single crystal manufactured by, for example, a melt growth method and containing 0.2 ppmw or less of Fe, Co or Cr is vacuum-sealed in a quartz ampule 2. At the same time, for example, red phosphorus 3 is arranged in the quartz ampoule 2 so that the phosphorus partial pressure in the ampoule 2 is set to a pressure higher than the dissociation pressure of InP, and the quartz ampule 2 is heated at 400 to 640 ° C.
According to our research,
It was found that undoping or heat treatment of an InP single crystal having a concentration of one or more impurity elements of at least 0.05 ppmw of Fe, Co, or Cr did not provide semi-insulating properties.

The present inventor has further studied and, as an improvement plan, first, as shown in FIG. 1, together with red phosphorus 3 in a quartz ampoule 2 without intentionally adding impurities and remaining. Fe, Co existing as impurities
Or the total content of any one or more of Cr is 0.05
By performing a heat treatment on the InP wafer 1 having a ppmw or less in an atmosphere having a phosphorus partial pressure exceeding 6 kg / cm ² , the total concentration of the impurity elements is 0.05 ppmw or less, and the resistivity at 300 K is not more than 0.05 ppmw. A technique for producing a semi-insulating group III-V compound semiconductor (InP) having a mobility of at least 10 ⁶ Ω · cm and exceeding 3000 cm ² / V · s has been proposed (Japanese Patent Application Laid-Open No. 3-279299). The semi-insulating group III-V compound semiconductor (InP) to be obtained by the above-mentioned technique is composed of impurities contained in the crystal, particularly any one of Fe, Co and Cr.
By making the total concentration of the contents of the species or more to be 0.05 ppmw or less, a decrease in the mobility due to the contained impurities is suppressed, and the mobility is set to a desired value or more. Conventionally, considerable attention has been paid to impurity contamination in the above-described heat treatment process. For example, a vapor source material (red phosphorus) used to generate a group V element (phosphorus) vapor has a purity of at least 99.
A material having a purity of about 9999%, in most cases, a purity called "6N" was used. Those having the purity “6N” have a purity of 99.9999%, that is, a concentration of an impurity element (an element other than the group V element phosphorus) contained therein exceeding 0.1 ppmw and 1 ppmw. For example, a compound semiconductor with sufficiently high purity can be obtained even when the material (red phosphorus) having the above-mentioned purity “6N” is used for the synthesis of a compound semiconductor (InP) in which red phosphorus is changed to phosphorus vapor. Can be done.

[0007]

However, in the invention proposed in Japanese Patent Application Laid-Open No. 3-279299 based on our research, the reproducibility of electrical characteristics excluding resistivity as described below is poor. I understood. That is, 900
In an atmosphere having a phosphorus partial pressure of 15 atm (about 15 kg / cm ² ) at 6 ° C., six sets (one set) of InP wafers having a concentration of at least one of Fe, Co or Cr of at least 0.05 ppmw or less are contained. (Several wafers) were prepared and subjected to 6 heat treatments for 20 hours per run (Run). After the treatment, the mobility, which is one of the electrical characteristics of the wafer, was as shown in FIG. Not only did it fluctuate between the runs, but also in the same run. Furthermore, there were quite a few of them whose mobility did not exceed the desired value of 3000 cm ² / V · s.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a high-resistance compound semiconductor having excellent reproducibility of electric characteristics.

[0009]

In order to investigate the cause of the above-mentioned variation in the mobility, the present inventor cut out an InP or GaP single crystal without any doping treatment or heat treatment, and cut out the single crystal from the single crystal. Elemental analysis of the wafer obtained by the heat treatment as described above was performed by the GDMS method (glow discharge mass spectrometry). As a result, as shown in Table 1, in the case of InP, the concentration of Fe element was 0.1 mm before heat treatment.
Less than 002 ppmw (lower detection limit) was 0.008 to 0.089 ppmw after heat treatment, and GaP was less than 0.005 ppmw before heat treatment after heat treatment 0.68 to 1.89 ppmw.
It was as high as 4 ppmw, and in any case, it was found that the Fe element was mixed into the crystal from the outside during the heat treatment.

[Table 1]

The contaminant that generated the Fe element is located in the vicinity of the crystal, for example, a quartz jig 4 such as a quartz ampoule 2 or a spacer, a heater 5, a furnace member 6, and a quartz ampoule 2 shown in FIG. Various types of experiments described below were carried out in order to identify the source of red phosphorus 3 and to identify the source of the contamination. Using red phosphorus having a purity of 99.9999% (concentration of an impurity element contained is 1 ppmw; hereinafter abbreviated as “6N”), the concentration of Fe element contained before heat treatment is less than 0.002 ppmw. 5 atm of InP crystal
At each of the phosphorus partial pressures of 15 atm and 25 atm, heat treatment was performed at 985 ° C. for 40 hours, which is a heat treatment condition capable of promoting the incorporation of Fe into the crystal by diffusion, and elemental analysis was performed. , The higher the phosphorus partial pressure, the more F
e It was found that the concentration was high. Further, the purity is 99.99999% (the concentration of the contained impurity element is 0.9%).
1 ppmw. Hereinafter, it is abbreviated as “7N”. As a result of elemental analysis by performing a heat treatment at 985 ° C. and a phosphorus partial pressure of 25 atm for 40 hours using red phosphorus as shown in Table 3), as shown in Table 3, the lower the purity of red phosphorus, the higher the Fe concentration in the crystal. It turned out that it was.

[Table 2]

[Table 3]

From these results, it was presumed that the source of Fe element contamination was red phosphorus 3. Further, elemental analysis was performed on a GaAs single crystal and a wafer obtained by heat treatment without red phosphorus at an arsenic pressure higher than the dissociation pressure of GaAs cut out from the single crystal. As a result, as shown in Table 1,
The element concentrations were all lower than the analytical detection lower limit, and no Fe element was mixed into the crystal during the heat treatment. Therefore, it was found that there was no contamination by the Fe element under the condition without red phosphorus, and there was contamination by the Fe element only under the condition with red phosphorus, and it was found that the contamination source of the Fe element was red phosphorus 3. That is, it was found that the Fe element was included in the red phosphorus 3 as an impurity. Moreover, in such a heat treatment for making the crystal semi-insulating, the crystal is contaminated with red phosphorus having a purity of 6N (concentration of the impurity element contained is 1 ppwm) which has been considered to be sufficient conventionally. I knew it would be done.

The present invention has been made on the basis of the above findings. In producing a high-resistance compound semiconductor by heat treatment, the crystal of the compound semiconductor and the highest element among the plurality of elements constituting the compound semiconductor are contained in an ampoule. When performing a heat treatment by encapsulating a vapor source material that maintains a partial pressure of the element having a saturated vapor pressure in the ampoule at a predetermined pressure higher than the dissociation pressure of the compound semiconductor, the vapor source material contains an impurity element. It is proposed to use one or more materials selected from the group consisting of allotropes of the element having the highest saturated vapor pressure among the plurality of elements constituting the compound semiconductor having a content of 0.1 ppmw or less. Is what you do. Further, the present invention provides the compound semiconductor, wherein the compound semiconductor is III-V
In the case of a group V compound semiconductor, the vapor source material sealed in the ampoule to maintain the partial pressure of the group V element constituting the group III-V compound semiconductor at a predetermined pressure may be an impurity element (the V group compound). It is proposed to use a material consisting of an allotrope of the group V element having a concentration of 0.1 ppmw or less (an element other than the element). That is, specifically, when the group V element constituting the III-V group compound semiconductor is phosphorus, the purity of 6N and the concentration of the impurity element (element other than phosphorus) which have been considered to be sufficient conventionally are 0%. Over 1 ppmw
In place of red phosphorus which is ppmw, the concentration of impurities (elements other than phosphorus) is 0.1 ppmw or less, ie, the purity is 7N.
The above-described red phosphorus is sealed in an ampoule together with a compound semiconductor crystal made of InP, GaP, or the like, and heat treatment is performed. Note that the above-mentioned allotrope is a simple substance of the same element and different in properties from each other. For example, phosphorus includes red phosphorus and yellow phosphorus.

[0013]

According to the above means, the partial pressure of the element having the highest saturated vapor pressure among the plurality of elements constituting the compound semiconductor, which is sealed in the ampoule together with the compound semiconductor, is determined by the partial pressure of the compound semiconductor. For the vapor source material kept at a predetermined pressure higher than the dissociation pressure, the allotrope of the element having the highest saturated vapor pressure among the plurality of elements constituting the compound semiconductor in which the content of the impurity element is 0.1 ppmw or less Is used, the amount of contaminant vapor (a gas containing an impurity element for the compound semiconductor) generated from the vapor source material can be suppressed to a small amount.
Therefore, the amount of the impurity element mixed into the crystal of the compound semiconductor during the heat treatment can be reduced. For example,
When manufacturing a high-resistance III-V compound semiconductor, a material consisting of an allotrope of a group V element having an impurity element content such as Fe element of 0.1 ppmw or less, that is, a material having a purity of the group V element of 7N or more is used. Since it is used, the concentration of impurities such as Fe element contained in the vapor source material composed of a Group V element having a purity of 7N or more is lower than that of the 6N purity element, and thus contains Fe and Fe elements generated during heat treatment. The amount of the contaminant vapor composed of the compound is much smaller than in the past, and the crystal of the group III-V compound semiconductor is prevented from being contaminated by the Fe element. Therefore, the increase in the Fe element concentration in the crystal after the heat treatment can be suppressed to an extremely low level. By applying a predetermined partial pressure of a group V element and performing a heat treatment, the resistance of the crystal can be increased. For example, according to the invention proposed by the present applicant in Japanese Patent Application Laid-Open No. 3-279299,
e, a predetermined phosphorus partial pressure, that is, a phosphorus partial pressure of 6 kg / cm ² or more, using an InP single crystal having a total content of one or more impurity elements of at least one of Co and Cr less than 0.05 ppmw as a starting material. And heat treatment, the total concentration of the content of any one or more of Fe, Co or Cr is 0.05 ppmw or less, and the mobility is 3000
A high-resistance InP single crystal exceeding cm ² / V · s and having a resistivity at 300 K of 10 ⁶ Ω · cm or more can be manufactured.

[0014]

EXAMPLES Hereinafter, the features of the present invention will be clarified with reference to examples and comparative examples. (Example) A thickness 0 cut out from a single crystal in which the content of Fe, Co, and Cr is less than or equal to the lower limit of analysis detection (0.002 ppmw), which is pulled up from the raw material polycrystal of InP by the liquid-sealed Czochralski method. .5mm InP wafer (thin plate)
As shown in FIG. 1, a plurality of 1, 1,... Were arranged in a quartz ampule 2 at intervals using a quartz jig 4 serving as a spacer. Subsequently, red phosphorus 3 having a purity of 7N is placed in the quartz ampule 2, and the inside of the quartz ampule 2 is evacuated to 1 × 10 ⁻⁶ torr (about 1.3 × 10 ⁻⁹ kg / cm ² ). The opening of the quartz ampule 2 was sealed with an oxyhydrogen burner. At this time, according to the invention proposed in Japanese Patent Application Laid-Open No. 3-279299, the amount of red phosphorus 3 is adjusted so that the phosphorus partial pressure is 6 kg / cm ² (about 6 atm) or more, for example, the phosphorus partial pressure in the quartz ampoule 2. Was adjusted to 25 atm at the heat treatment temperature. Next, the quartz ampoule 2 was placed in a horizontal heating furnace, heated and maintained at a heat treatment temperature of 985 ° C. for 40 hours, and then cooled at a rate of about 30 ° C./min. The above horizontal heating furnace is 100kg in closed type
/ cm ² pressure can be used.
An argon gas having a pressure corresponding to the phosphorus partial pressure corresponding to the temperature was introduced into the heating furnace to maintain a balance between the pressure inside and outside the quartz ampule 2 and prevent the quartz ampule 2 from being broken.

(Comparative Example) For comparison, a heat treatment was carried out in the same manner as in the above example using red phosphorus having a purity of 6N.
Other conditions were the same as those in Example 1.

With respect to the wafers obtained in the above Examples and Comparative Examples, the concentration of Fe element contained in the wafer was examined by elemental analysis. Table 3 shows the results. From the table,
As a result of setting the purity of phosphorus to 7N, the concentration of the Fe element contained in the wafer is about ３ to の of the case of the purity of 6N. It turns out that it is very effective to use red phosphorus.

In the above embodiment, the present invention is applied to
Although the example applied to the heat treatment of nP has been described, GaP
It is needless to say that the present invention can be applied to heat treatment of a compound semiconductor having a group V element of P (including a mixed crystal composition).
Furthermore, the heat treatment conditions such as temperature, group V element partial pressure (phosphorous pressure), and treatment time are not limited to the conditions in the above-described embodiment. A high-resistance III-V compound semiconductor can be manufactured with high reproducibility. Further, for example, in a II-VI compound semiconductor, the partial pressure of a group II element having the highest saturated vapor pressure among a plurality of elements constituting the II-VI compound semiconductor is set to a dissociation pressure of the II-VI compound semiconductor. As a vapor source material used for a higher predetermined pressure, by using a material composed of a group II element alone having an impurity element content of 0.1 ppmw or less, contaminated vapor generated from the vapor source material during heat treatment can be reduced. The amount can be suppressed to a small amount, and contamination by an impurity element which causes a decrease in mobility can be suppressed.

[0018]

According to the method of manufacturing a high-resistance compound semiconductor according to the present invention, the crystal of the compound semiconductor and the ampoule of the element having the highest saturated vapor pressure among the plurality of elements constituting the compound semiconductor are contained in the ampoule. And a vapor source material for maintaining a partial pressure in the inside at a predetermined pressure higher than the dissociation pressure of the compound semiconductor, when performing heat treatment by encapsulation, the content of the impurity element in the vapor source material is 0.1 ppmw
A trowel using one or more materials selected from the group consisting of allotropes of the element having the highest saturated vapor pressure among the plurality of elements constituting the compound semiconductor,
Contaminant vapor (a gas containing an impurity element for the compound semiconductor) generated from the vapor source material during the heat treatment can be suppressed to a small amount. For example, high resistance III-V
When manufacturing a Group III compound semiconductor, by using a material consisting of an allotrope of a Group V element having a concentration of an impurity element of 0.1 ppmw or less, a contaminant vapor of Fe or a compound containing the Fe element generated during heat treatment is used. The amount is much smaller than that of the conventional vapor source material having a purity of 6N, and the heat treatment of the crystal can be performed while suppressing the contamination by the Fe element.
To produce a high-resistance III-V compound semiconductor having a concentration of impurities such as elements of 0.05 ppmw or less, a mobility of not less than a desired value, and a resistivity of 10 ⁶ Ω · cm or more with good reproducibility. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which a wafer is installed in a heating furnace used for manufacturing a high-resistance compound semiconductor.

FIG. 2 is a characteristic diagram showing the mobility of a wafer obtained by a conventional manufacturing method.

[Explanation of symbols]

 Reference Signs List 1 wafer (crystal of III-V compound semiconductor) 2 quartz ampule (ampule) 3 red phosphorus (vapor source material)

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/324 C30B 29/00 C30B 33/00 H01L 21/205 H01L 21/31

Claims (2)

(57) [Claims] 1. A compound semiconductor crystal in an ampoule and a predetermined partial pressure in an ampoule of an element having the highest saturated vapor pressure among a plurality of elements constituting the compound semiconductor, higher than a dissociation pressure of the compound semiconductor. When the heat treatment is performed by enclosing the vapor source material and keeping the pressure of the vapor source material, the concentration of the impurity element in the vapor source material is 0.1 pp.
a high-resistance compound semiconductor characterized by using one or more materials selected from the group consisting of allotropes of elements having the highest saturated vapor pressure among a plurality of elements constituting the compound semiconductor having a mw or less. Manufacturing method. 2. When the compound semiconductor is a III-V group compound semiconductor, the III-V compound is used for the vapor source material.
2. The method for producing a high-resistance compound semiconductor according to claim 1, wherein a material comprising an allotrope of a group V element constituting the group III compound semiconductor is used.