Surface treatment method of compound semiconductor substrate, fabrication method of compound semiconductor, compound semiconductor substrate, and semiconductor wafer

Abstract

A surface treatment method of a compound semiconductor substrate, a fabrication method of a compound semiconductor, a compound semiconductor substrate, and a semiconductor wafer are provided, directed to reducing the impurity concentration at a layer formed on a substrate by reducing the impurity concentration at the surface of the substrate formed of a compound semiconductor. The compound semiconductor substrate surface treatment method includes a substrate preparation step and a first washing step. The substrate preparation step includes the step of preparing a substrate formed of a compound semiconductor containing at least 5 mass % of indium. In the first washing step, the substrate is washed for a washing duration of at least 3 seconds and not more than 60 seconds using washing liquid having a pH of at least −1 and not more than 3, and an oxidation-reduction potential E (mV) satisfying the relationship of −0.08333x+0.750≦E≦−0.833x+1.333, where x is the pH value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a substrate surface treatment method according to a first embodiment of the present invention.

FIG. 2 represents the relationship between pH and oxidation-reduction potential E (mV).

FIG. 3 is a schematic sectional view of a compound semiconductor substrate subsequent to a first washing step (S20) of the first embodiment.

FIG. 4 is a schematic sectional view of a semiconductor wafer according to a modification of the first embodiment.

FIG. 5 is a flowchart of a compound semiconductor substrate surface treatment method according to a second embodiment of the present invention.

FIG. 6 is a schematic sectional view of a washing device used in a rinsing step.

FIG. 7 represents the relationship between the ratio of In/P at the substrate surface and impurity concentration subsequent to epitaxial growth.

FIG. 8 represents the haze at the substrate surface subsequent to epitaxial growth.

Claims

1. A surface treatment method of a compound semiconductor substrate comprising: a substrate preparation step of preparing a substrate formed of a compound semiconductor containing at least 5 mass % of indium, anda first washing step of washing said substrate for a washing duration of at least 3 seconds and not more than 60 seconds using washing liquid having a pH of at least −1 and not more than 3, and an oxidation-reduction potential E (mV) satisfying a relationship of −0.08333x+0.750≦E≦−0.833x+1.333, where x is a pH value.

2. The surface treatment method of a compound semiconductor substrate according to claim 1, wherein the pH of said washing liquid is adjusted to at least −1 and not more than 1.5 in said first washing step.

3. The surface treatment method of a compound semiconductor substrate according to claim 1, wherein said first washing step includes a first rinsing step of rinsing said substrate with deionized water.

4. The surface treatment method of a compound semiconductor substrate according to claim 3, wherein ultrasonic waves are applied to said deionized water in said first rinsing step.

5. The surface treatment method of a compound semiconductor substrate according to claim 1, further comprising a second washing step of washing said substrate using washing liquid with the pH adjusted to acidity of at least 2 and not more than 6.3, and having an oxidizing agent added, after said first washing step.

6. The surface treatment method of a compound semiconductor substrate according to claim 5, wherein the washing duration in said second washing step is at least 5 seconds and not more than 60 seconds.

7. The surface treatment method of a compound semiconductor substrate according to claim 5, wherein said second washing step includes a second rinsing step of rinsing said substrate with deionized water.

8. The surface treatment method of a compound semiconductor substrate according to claim 7, wherein ultrasonic waves are applied to said deionized water in said second rinsing step.

9. The surface treatment method of a compound semiconductor substrate according to claim 1, comprising a pre-washing step of washing said substrate using alkaline washing liquid, prior to said first washing step.

10. The surface treatment method of a compound semiconductor substrate according to claim 9, wherein said pre-washing step includes a wet-cleaning step of rinsing said substrate with deionized water.

11. A fabrication method of a compound semiconductor comprising the steps of: conducting the surface treatment method of a compound semiconductor substrate defined in claim 1, anda post-treatment step of conducting film deposition on a surface of said substrate after said step of conducting the surface treatment method.

12. A compound semiconductor substrate processed by the surface treatment method of a compound semiconductor substrate defined in claim 1, wherein (a proportion of Group III atoms)/(a proportion of Group V atoms) is below 1.5 based on XPS analysis with a photoelectron take-off angle of 10° for a surface of said compound semiconductor substrate.

13. A semiconductor wafer comprising: a substrate of a different type, andthe compound semiconductor substrate defined in claim 12, formed on said substrate of a different type.