JPH1197520A - Method of insulation and isolation semiconductor devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a conductive semiconductor layer insulative over specified depth by limiting the boron element implantation dose within specified range. SOLUTION: The method comprises forming a heavily doped semiconductor layer 12 on the top face of a semiconductor substrate 11, forming a semi- insulative semiconductor layer 13 having a lower impurity concn. than that of the layer 12 on the top of this layer 12, and etching to form an active layer 13' of a Schottky diode 18, after forming a resist layer at a part for forming the active layer 13' and diode 18 and implanting the boron element B<+> ions at an accelerating voltage of about 400 keV and dose of 1×10<12> /cm<2> -1×10<14> /cm<2> , using the resist layer 14 as a mask, thereby uniformly implanting the B<+> ions over the thickness direction of the conductive semiconductor layer 12 to make this layer 12 insulative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrically isolating semiconductor devices from each other when a plurality of semiconductor devices are formed in the same semiconductor layer.

[0002]

2. Description of the Related Art Conventionally, a high-concentration epitaxial layer having high conductivity (a high-concentration semiconductor layer made of gallium arsenide) is formed on a semiconductor substrate made of gallium arsenide by, for example, 1 μm.
There is a method of manufacturing a semiconductor device in which a semiconductor device such as a Schottky diode or a hetero-bipolar transistor is formed using this epitaxial layer to form a device capable of high-speed operation.

[0003]

When a plurality of semiconductor elements are formed on a conductive semiconductor layer made of gallium / arsenic, each semiconductor element is electrically connected by the conductive semiconductor layer. It is necessary to electrically isolate each other. Conventionally, a method of removing a conductive semiconductor layer existing between semiconductor elements by etching and electrically isolating the semiconductor elements from each other is disclosed.
For example, a method of ion-implanting a boron element into a semiconductor layer made of arsenic and converting the semiconductor layer into an insulator by this ion implantation, or a method of ion-implanting oxygen or hydrogen to convert the semiconductor layer into an insulator can be considered. ing.

[0004] A method of insulatingly separating semiconductor elements from each other by etching is called a mesa etching method or the like. According to the mesa etching method, a groove equal to the thickness (about 1 μm) of the semiconductor layer is formed in the semiconductor layer. Since it is formed, there is a disadvantage that unevenness is formed on the surface of the semiconductor layer. That is, since the wiring layer must be formed on the uneven surface, the wiring layer is disadvantageously formed with a high rate of being formed in a disconnected state and a high incidence of defects.

On the other hand, according to a method of ion-implanting a boron element and converting the ion-implanted portion into an insulator or a method of ion-implanting oxygen, no irregularities are formed on the surface of the semiconductor layer. Conventionally, there is a disadvantage that only a thickness of about 0.1 μm from the surface can be converted into an insulator. In the case where hydrogen ions are used, there is an application example up to a depth of about 1 μm, but there are drawbacks that thermal stability is poor and a large amount of implantation is required.

For this reason, a semiconductor layer for forming a semiconductor element such as a Schottky diode or a hetero-bipolar transistor needs to have a thickness of at least about 1 μm. Cannot be electrically insulated stably. SUMMARY OF THE INVENTION An object of the present invention is to propose an insulation separation method capable of converting a semiconductor layer having a thickness of about 1 μm into an insulator by an ion implantation method.

[0007]

According to a first aspect of the present invention, a boron semiconductor is ion-implanted into a conductive semiconductor layer made of gallium arsenide having a thickness of 0.2 μm or more, and the dose is 1 × 10 ^12. Another object of the present invention is to provide a method of insulating and separating a semiconductor layer having conductivity by injecting it in the range of / cm ² to 1 × 10 ¹⁴ / cm ² .

According to the method for insulating and isolating a semiconductor device proposed in claim 1, the implantation dose of boron element is 1 ×.
The semiconductor layer having conductivity can be formed into an insulator over a depth of 0.2 μm or more only by limiting the range to 10 ¹² / cm ² to 1 × 10 ¹⁴ / cm ² . According to a second aspect of the present invention, a conductive semiconductor layer made of gallium arsenide is ion-implanted with a divalent boron element at a dose of 1 ×.
The present invention proposes a method for insulating and isolating a semiconductor element in which a semiconductor layer having conductivity is made into an insulator by injecting it in the range of 10 ¹² / cm ² to 1 × 10 ¹⁴ / cm ² .

According to the invention proposed in claim 2, by selecting the ion-implanted element as the divalent boron element, the acceleration voltage at the time of ion implantation is reduced to about one of the acceleration voltage for accelerating the monovalent boron element. / 2. As a result, the conductive semiconductor layer can be made into an insulator by an inexpensive ion implantation apparatus. According to the method of insulating and separating a semiconductor device proposed in claim 3 of the present invention, a plurality of masks, for example, a resist layer are formed in an island shape on the upper surface of a conductive semiconductor layer, and a boron element is dosed using the mask. 1x
The present invention proposes a method of insulating and separating a semiconductor element in which ions are implanted in a range of 10 ¹² / cm ² to 1 × 10 ¹⁴ / cm ² to electrically insulate mask forming portions from each other.

According to the third aspect of the present invention, a semiconductor element can be formed using the island-shaped conductive semiconductor layer covered by the resist layer. The semiconductor elements thus formed can be electrically separated from each other by implanting boron. Therefore, according to the method for insulating and separating a semiconductor element proposed in claim 3, the semiconductor elements formed on each island-shaped conductive layer can be insulated and separated from each other while keeping the planar shape. Therefore, a wiring conductor for electrically connecting the semiconductor elements can be formed on a plane. Therefore, the formation of the wiring conductor can be reliably performed, and an advantage that the production with a good yield can be realized is obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the method for insulating and separating a semiconductor device according to the present invention is applied to the formation of a Schottky diode. Reference numeral 11 shown in FIG. 1A indicates a semiconductor substrate made of, for example, gallium arsenide (GaAs). The upper surface of the semiconductor substrate 11 has an impurity concentration of, for example, 1 × 10 ¹⁸
The semiconductor layer 12 having a high concentration of about / cm ^{3 is} formed by an epitaxial growth method. That is, the semiconductor layer 12 is a conductive semiconductor layer and has a thickness of about 1 μm. On the upper surface of the conductive semiconductor layer 12, the impurity concentration is slightly lower than that of the semiconductor layer 12, for example, 1 × 10
^The semiconductor layer 13 having a semi-insulating property is selected to be about ¹⁷ / cm ^3.
By the epitaxial growth method.
The thickness is about m.

A photoresist is applied on the upper surface of the semiconductor layer 13 and is exposed to light so as to leave the semiconductor layer 13 substantially at the center of the area where the Schottky diode is to be formed. The process is called a photolithography process.) An active layer 13 'of the Schottky diode shown in FIG. 1B is formed. The portion where the active layer 13 'and the Schottky diode are to be formed is subjected to a photolithographic process through
As shown in C, a resist layer 14 is formed, and boron is ion-implanted using the resist layer 14 as a mask. In this example, a case where a monovalent boron element B ⁺ is implanted will be described. When monovalent boron is ion-implanted, an acceleration voltage of about 400 keV is required as an implantation condition, and an implantation dose is 1 × 10 ¹² / cm ² .
By implanting in the range of 1 × 10 ¹⁴ / cm ² , the boron element can be implanted uniformly throughout the thickness direction (thickness of 1 μm) of the semiconductor layer 12 having conductivity, and the semiconductor layer 12 becomes an insulator. can do. A portion 15 shown in FIG. 1D shows an insulating separation layer made into an insulator.

After forming the insulating separation layer 15, the resist layer 14 is removed, a Schottky electrode 16 of, for example, titanium is formed on the upper surface of the active layer 13 ', and AuGe or the like is formed on the upper surface of the conductive semiconductor layer 12. The ohmic electrode 17 is formed. The activation layer 13 'and the Schottky electrode 16
And the ohmic electrode 17, the Schottky diode 18 can be formed.

Although the above description has been made on the case where monovalent boron is ion-implanted, the present invention proposes a case where divalent boron is further ion-implanted. When ion implantation of divalent boron element B ²⁺ is performed, the accelerating voltage is increased to about 1 when ion implantation of monovalent boron B ⁺ is performed.
/ 2, for example, 200 keV is sufficient. That is, since the divalent boron element B ²⁺ has twice the charge of the monovalent boron element, the acceleration voltage is 200
Even if the energy is reduced to keV, sufficient acceleration energy can be given, and ions can be implanted into the semiconductor layer 12 to a depth of 1 μm or more. In order to uniformly implant the boron element in the thickness direction of the semiconductor layer 12, the dose amount is 1 × 10 ¹²
/ Cm ² to 1 × 10 ¹⁴ / cm ² .

For ion implantation of the divalent boron element B ²⁺ , a filter that allows only the divalent boron element to pass therethrough is arranged in the ion implantation apparatus, and only the divalent boron element is extracted and ion-implanted. FIG. 2 shows an example of an experiment for evaluating how much the insulating separation layer 15 is converted into an insulator. FIG.
As shown in A, a semiconductor layer 12 having an impurity concentration of 1 × 10 ¹⁸ / cm ³ and a thickness of 1 μm is formed on one surface of a semiconductor substrate 11 by an epitaxial growth method.

In FIG. 2B, for example, A
An electrode 21 made of uGe / Ni / Au is deposited.
In the state where the electrode 21 is formed, FIG.
C, boron element is ion-implanted, and the semiconductor layer 1 is implanted.
In FIG. 2, the insulating separation layer 15 shown in FIG. 2D is formed. In this example, a case is illustrated in which divalent boron element B ²⁺ is ion-implanted by accelerating at 200 keV. A resistance measuring device 22 between the electrodes 21
Was measured by

FIG. 3 shows a change in the resistance value between the electrodes 21 when the dose is varied in this evaluation experiment.
As shown in FIG. 3, when the dose exceeds 1 × 10 ¹² / cm ² , the resistance R between the electrodes 21 sharply increases, and the resistance R increases until the dose reaches 1 × 10 ¹⁴ / cm ^2. Is 1
Maintain × 10 ⁶ Ω / mouth or more. Therefore, the dose amount is 1 ×
By selecting the range of 10 ¹² / cm ² to 1 × 10 ¹⁴ / cm ² , the resistance value of the insulating separation layer 15 can be maintained at a high resistance, and the semiconductor elements can be insulated and separated. I understand.

FIGS. 4 to 6 show experimental examples in which the temperature stability was measured when the dose of ion implantation was changed. FIG. 4 shows the temperature stability of the insulating separation layer 15 at each temperature when the divalent boron element B ²⁺ is accelerated at 200 keV and the dose is 2 × 10 ¹² / cm ² . 2 × 10 dose
^{In the case of 12} / cm ² , as can be seen from the curves C, D and E, when the temperature is heated to 100 ° C. or more, the insulation resistance is deteriorated. It is practical if the use conditions are limited to 100 ° C. or less.

FIG. 5 shows the temperature stability of the insulating separation layer 15 with respect to each temperature when the dose is 1 × 10 ¹³ / cm ² . In this case, the resistance value R increases with the application time of the temperature at any temperature (63 ° C. to 243 ° C.), and a high insulation resistance is obtained. FIG. 6 shows a dose amount of 5 × 10 ¹³ / cm ^2.
It shows the temperature stability in the case of. In this case as well, it can be seen that the resistance value R increases with the lapse of the application time at any temperature, and a high insulation resistance can be obtained.

[0020]

As described above, according to the present invention, the dose at the time of ion implantation of boron element is 1 × 10 ¹²
1μm by simply selecting the ^{/ cm 2 ~1 × 10 14 /} cm 2
A conductive semiconductor layer having a moderate thickness can be converted into an insulator having high resistance. Therefore, the semiconductor elements formed in the conductive semiconductor layer can be insulated and separated from each other in a planar shape.

Therefore, since the wiring conductor for electrically connecting the semiconductor elements can be formed on a plane, a highly reliable wiring conductor can be formed. Further, there is obtained an advantage that the rate of occurrence of defects can be reduced and manufacturing can be performed with good yield.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining an embodiment of the present invention.

FIG. 2 is a process chart for explaining an experimental example performed to prove the effect of the present invention.

FIG. 3 is a graph for explaining the effect of the present invention.

FIG. 4 is a graph showing an example of actually measuring the temperature stability of an insulating separation layer obtained by the insulating separation method according to the present invention.

FIG. 5 is a view similar to FIG. 4;

FIG. 6 is a view similar to FIG. 4;

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 12 conductive semiconductor layer 13 'active layer 14 resist layer 15 insulating separation layer 16 Schottky electrode 17 ohmic electrode 18 Schottky diode

Claims (3)

[Claims] 1. A gallium alloy having a thickness of 0.2 μm or more.
Boron element for conductive semiconductor layers of arsenic
Dose of 1 × 10 by ion implantation¹²/ Cm ^Two~ 1 × 1
0¹⁴/ Cm^TwoInjection in the range of
Insulation of a semiconductor device that makes a semiconductor layer with insulation an insulator
Construction method. 2. A conductive half made of gallium arsenide.
Doping a divalent boron element into the conductor layer by ion implantation
1 × 10¹²/ Cm^Two~ 1 × 10¹⁴/ Cm ^TwoIn the range
Insulation converts conductive semiconductor layers into insulators
Method for insulating and separating semiconductor elements. 3. A plurality of mask layers are selectively formed on an upper surface of a conductive semiconductor layer made of gallium and arsenic, and boron is ion-implanted using the mask to form a dose of 1: 1.
A method of insulating and isolating a semiconductor element, wherein the implantation is performed in a range of × 10 ¹² / cm ² to 1 × 10 ¹⁴ / cm ² to electrically insulate the mask-forming portions from each other.