Effect of H₂ Carrier Gas on CVD Growth Rate for 4H-SiC Trench Filling

Abstract

The effect of H2 carrier gas on the growth rate during the trench filling using CVD epitaxial growth was investigated in a wide pressure range (10∼38 kPa). It is found that, in the entire pressure range, reducing H2 flow rate can increase the filling rate (the growth rate inside trench) and the filling efficiency (the thickness ratio between epilayer on trench bottom and mesa top), which means a high productivity and a low risk of void defects. The filling rate and efficiency of ∼1.5 μm/h and ∼18 respectively was achieved at 38 kPa.

Strong impact of slight trench direction misalignment from $[11\bar{2}0]$ on deep trench filling epitaxy for SiC super-junction devices

“…As an alternative, a trench-filling epitaxy technique is expected to be used in higher voltage applications. A trench-filling process for SiC has been developed, [14][15][16][17][18][19][20][21][22][23][24] and we previously reported 7-µm-deep trench-filling by chemical vapor deposition using SiH 4 =C 3 H 8 =H 2 precursor gases, 18) but the reproducibility of the trench-filling growth process 18) was poor. Subsequently, addition of HCl etchant gas to the gas mixture in a 5-µm-deep trench-filling process was found to produce significantly higher growth stability.…”

An empirical growth window concerning the input ratio of HCl/SiH4gases in filling 4H-SiC trench by CVD

“…4(a), which is in accord with a previous report, owing to an enhanced partial pressure of source species, e.g., SiCl 2 , whereas a doubled R G on the mesa in that report was not observed because of a proportionally increased HCl pressure in the reactor. 14) In general, the results in Fig. 4 demonstrate that the input ratio of HCl=SiH 4 = 50 yields well-proportioned deposition and etching reactions, even in a wide range of H 2 from 40 to 80 slm, and provides further evidence for the effectiveness of the empirical growth window.…”

“…These techniques applied together produce R G ∼1.5 µm=h for 5-µm-deep trenches. 14) From an economic viewpoint, further improvement of the filling rate in an ordinary manner using high source flows is worth performing. However, in the CVD trench-filling process, the defective growth of voids usually occurs when using high source flow rates, i.e., the trench closes prior to complete filling owing to mesa overgrowth.…”

“…To improve the filling rate, increasing the concentration of Si-and C-containing species in the reactor, e.g., SiCl 2 , and simultaneously enhancing the HCl partial pressure to counteract the potential overgrowth around the mesa are thought to be feasible. Since lowering the amount of H 2 carrier gas has been proven to efficiently increase the partial pressure of source species and filling rates, 14) filling growth was carried out with half the amount of H 2 carrier gas (H 2 = 40 slm) while keeping other conditions the same as those in the case of Fig. 4(a).…”

A Study of CVD Growth Parameters to Fill 50-μm-Deep 4H-SiC Trenches

“…On commercial n + wafers (4 o off, Si-face), stripe 4H-SiC trenches with depths (D) of 45∼55 μm were formed by reactive ion etching along the direction of wafer's primary orientation, [11][12][13][14][15][16][17][18][19][20]. The line (L) and space (S) of patterns on the lithography mask are equal to each other in the pitch (L+S) of 15∼20 μm.…”